Diamond, Jared M.
1966-01-01
1. The relation between osmotic gradient and rate of osmotic water flow has been measured in rabbit gall-bladder by a gravimetric procedure and by a rapid method based on streaming potentials. Streaming potentials were directly proportional to gravimetrically measured water fluxes. 2. As in many other tissues, water flow was found to vary with gradient in a markedly non-linear fashion. There was no consistent relation between the water permeability and either the direction or the rate of water flow. 3. Water flow in response to a given gradient decreased at higher osmolarities. The resistance to water flow increased linearly with osmolarity over the range 186-825 m-osM. 4. The resistance to water flow was the same when the gall-bladder separated any two bathing solutions with the same average osmolarity, regardless of the magnitude of the gradient. In other words, the rate of water flow is given by the expression (Om — Os)/[Ro′ + ½k′ (Om + Os)], where Ro′ and k′ are constants and Om and Os are the bathing solution osmolarities. 5. Of the theories advanced to explain non-linear osmosis in other tissues, flow-induced membrane deformations, unstirred layers, asymmetrical series-membrane effects, and non-osmotic effects of solutes could not explain the results. However, experimental measurements of water permeability as a function of osmolarity permitted quantitative reconstruction of the observed water flow—osmotic gradient curves. Hence non-linear osmosis in rabbit gall-bladder is due to a decrease in water permeability with increasing osmolarity. 6. The results suggest that aqueous channels in the cell membrane behave as osmometers, shrinking in concentrated solutions of impermeant molecules and thereby increasing membrane resistance to water flow. A mathematical formulation of such a membrane structure is offered. PMID:5945254
Newman, Gregory A.; Commer, Michael
2006-11-17
Software that simulates and inverts electromagnetic field data for subsurface electrical properties (electrical conductivity) of geological media. The software treats data produced by a time harmonic source field excitation arising from the following antenna geometery: loops and grounded bipoles, as well as point electric and magnetic dioples. The inversion process is carried out using a non-linear conjugate gradient optimization scheme, which minimizes the misfit between field data and model data using a least squares criteria. The software is an upgrade from the code NLCGCS_MP ver 1.0. The upgrade includes the following components: Incorporation of new 1 D field sourcing routines to more accurately simulate the 3D electromagnetic field for arbitrary geologic& media, treatment for generalized finite length transmitting antenna geometry (antennas with vertical and horizontal component directions). In addition, the software has been upgraded to treat transverse anisotropy in electrical conductivity.
NASA Astrophysics Data System (ADS)
de Jong, Roelof
2005-07-01
This program incorporates a number of tests to analyse the count rate dependent non-linearity seen in NICMOS spectro-photometric observations. In visit 1 we will observe a few fields with stars of a range in luminosity in NGC1850 with NICMOS in NIC1 in F090M, F110W and F160W and NIC2 F110W, F160W, and F180W. We will repeat the observations with flatfield lamp on, creating artificially high count-rates, allowing tests of NICMOS linearity as function of count rate. To access the effect of charge trapping and persistence, we first take darks {so there is not too much charge already trapped}, than take exposures with the lamp off, exposures with the lamp on, and repeat at the end with lamp off. Finally, we continue with taking darks during occultation. In visit 2 we will observe spectro-photometric standard P041C using the G096 and G141 grisms in NIC3, and repeat the lamp off/on/off test to artificially create a high background. In visits 3&4 we repeat photometry measurements of faint standard stars SNAP-2 and WD1657+343, on which the NICMOS non-linearity was originally discovered using grism observations. These measurements are repeated, because previous photometry was obtained with too short exposure times, hence substantially affected by charge trapping non-linearity. Measurements will be made with NIC1: Visit 5 forms the persistence test of the program. The bright star GL-390 {used in a previous persistence test} will iluminate the 3 NICMOS detectors in turn for a fixed time, saturating the center many times, after which a series of darks will be taken to measure the persistence {i.e. trapped electrons and the decay time of the traps}. To determine the wavelength dependence of the trap chance, exposures of the bright star in different filters will be taken, as well as one in the G096 grism with NIC3. Most exposures will be 128s long, but two exposures in the 3rd orbit will be 3x longer, to seperate the effects of count rate versus total counts of the trap
Non-linearity in clinical practice.
Petros, Peter
2003-05-01
The whole spectrum of medicine consists of complex non-linear systems that are balanced and interact with each other. How non-linearity confers stability on a system and explains variation and uncertainty in clinical medicine is discussed. A major theme is that a small alteration in initial conditions may have a major effect on the end result. In the context of non-linearity, it is argued that 'evidence-based medicine' (EBM) as it exists today can only ever be relevant to a small fraction of the domain of medicine, that the 'art of medicine' consists of an intuitive 'tuning in' to these complex systems and as such is not so much an art as an expression of non-linear science. The main cause of iatrogenic disease is interpreted as a failure to understand the complexity of the systems being treated. Case study examples are given and analysed in non-linear terms. It is concluded that good medicine concerns individualized treatment of an individual patient whose body functions are governed by non-linear processes. EBM as it exists today paints with a broad and limited brush, but it does promise a fresh new direction. In this context, we need to expand the spectrum of scientific medicine to include non-linearity, and to look upon the 'art of medicine' as a historical (but unstated) legacy in this domain.
Gain optimization with non-linear controls
NASA Technical Reports Server (NTRS)
Slater, G. L.; Kandadai, R. D.
1984-01-01
An algorithm has been developed for the analysis and design of controls for non-linear systems. The technical approach is to use statistical linearization to model the non-linear dynamics of a system by a quasi-Gaussian model. A covariance analysis is performed to determine the behavior of the dynamical system and a quadratic cost function. Expressions for the cost function and its derivatives are determined so that numerical optimization techniques can be applied to determine optimal feedback laws. The primary application for this paper is centered about the design of controls for nominally linear systems but where the controls are saturated or limited by fixed constraints. The analysis is general, however, and numerical computation requires only that the specific non-linearity be considered in the analysis.
Non-linear conduction in LaCaMnO 3 thin films: interface tunneling effects
NASA Astrophysics Data System (ADS)
Amaral, V. S.; Araújo, J. P.; Lourenço, A. A. C. S.; Tavares, P. B.; Pogorelov, Yu. G.; Sousa, J. B.; Vieira, J. M.
2001-05-01
Non-linear resistivity in La 0.78Ca 0.25MnO 3 epitaxial thin films is studied using 2-contact dynamic measurements. Non-linear V- I is obtained below Tc (˜220 K). Evaporated gold or direct silver-paste contacts give similar results. d V/d I at high voltages (˜1 V) follows the usual four-point resistance results, but at lower voltages an additional contribution up to 2 orders of magnitude higher develops at low temperatures. These effects are associated with tunneling processes at the metal/manganite interface.
Stability of non-linear integrable accelerator
Batalov, I.; Valishev, A.; /Fermilab
2011-09-01
The stability of non-linear Integrable Optics Test Accelerator (IOTA) model developed in [1] was tested. The area of the stable region in transverse coordinates and the maximum attainable tune spread were found as a function of non-linear lens strength. Particle loss as a function of turn number was analyzed to determine whether a dynamic aperture limitation present in the system. The system was also tested with sextupoles included in the machine for chromaticity compensation. A method of evaluation of the beam size in the linear part of the accelerator was proposed.
Non-linear Post Processing Image Enhancement
NASA Technical Reports Server (NTRS)
Hunt, Shawn; Lopez, Alex; Torres, Angel
1997-01-01
A non-linear filter for image post processing based on the feedforward Neural Network topology is presented. This study was undertaken to investigate the usefulness of "smart" filters in image post processing. The filter has shown to be useful in recovering high frequencies, such as those lost during the JPEG compression-decompression process. The filtered images have a higher signal to noise ratio, and a higher perceived image quality. Simulation studies comparing the proposed filter with the optimum mean square non-linear filter, showing examples of the high frequency recovery, and the statistical properties of the filter are given,
Non-linear cord-rubber composites
NASA Technical Reports Server (NTRS)
Clark, S. K.; Dodge, R. N.
1989-01-01
A method is presented for calculating the stress-strain relations in a multi-layer composite made up of materials whose individual stress-strain characteristics are non-linear and possibly different. The method is applied to the case of asymmetric tubes in tension, and comparisons with experimentally measured data are given.
Possibilities Of Optically Non Linear Thin Films
NASA Astrophysics Data System (ADS)
De Micheli, Marc; Zyss, Joseph; Azema, Alain
1983-11-01
Efficient integrated frequency doubling devices transparent in the visible and near I.R. are demanded by a number of applications. The optimization of both wave interaction configurations and material intrinsic nonlinear susceptibility are successively discussed within this scope. Basic features such as power confinement, interaction length dependence, phase matching techniques, underlying the second harmonic generation conversion rate in bulk and waveguided structures are compared. Undoped Ga As film epitaxied over n+ doped Ga As substrate and TIPE Lithium Lobate waveguides exemplify the possibilities of non linear thin films. The higher non linear susceptibility of certain organic molecular single crys-tals should help raise the efficiency of doubling devices. We report the definition and bulk performances of two non linear organic crystals, namely POM (3-methyl-4 nitropyridine-1-oxyde) and MAP (methyl-(2,4-dinitropheny1)-aminopropanoate) with a figure of merit up to one order of magnitude above that of Li Nb 03. The combination of organic materials and waveguided configuration should lead to a new generation of non linear devices.
Non-linear resonance in relativistic preheating
Underwood, Bret; Zhai, Yunxiao E-mail: zhaiya@plu.edu
2014-04-01
Inflation in the early Universe can be followed by a brief period of preheating, resulting in rapid and non-equilibrium particle production through the dynamics of parametric resonance. However, the parametric resonance effect is very sensitive to the linearity of the reheating sector. Additional self-interactions in the reheating sector, such as non-canonical kinetic terms like the DBI Lagrangian, may enhance or frustrate the parametric resonance effect of preheating. In the case of a DBI reheating sector, preheating is described by parametric resonance of a damped relativistic harmonic oscillator. In this paper, we illustrate how the non-linear terms in the relativistic oscillator shut down the parametric resonance effect. This limits the effectiveness of preheating when there are non-linear self-interactions.
Pharmaceutical applications of non-linear imaging.
Strachan, Clare J; Windbergs, Maike; Offerhaus, Herman L
2011-09-30
Non-linear optics encompasses a range of optical phenomena, including two- and three-photon fluorescence, second harmonic generation (SHG), sum frequency generation (SFG), difference frequency generation (DFG), third harmonic generation (THG), coherent anti-Stokes Raman scattering (CARS), and stimulated Raman scattering (SRS). The combined advantages of using these phenomena for imaging complex pharmaceutical systems include chemical and structural specificities, high optical spatial and temporal resolutions, no requirement for labels, and the ability to image in an aqueous environment. These features make such imaging well suited for a wide range of pharmaceutical and biopharmaceutical investigations, including material and dosage form characterisation, dosage form digestion and drug release, and drug and nanoparticle distribution in tissues and within live cells. In this review, non-linear optical phenomena used in imaging will be introduced, together with their advantages and disadvantages in the pharmaceutical context. Research on pharmaceutical and biopharmaceutical applications is discussed, and potential future applications of the technology are considered.
Non-linear dark energy clustering
Anselmi, Stefano; Ballesteros, Guillermo; Pietroni, Massimo E-mail: ballesteros@pd.infn.it
2011-11-01
We consider a dark energy fluid with arbitrary sound speed and equation of state and discuss the effect of its clustering on the cold dark matter distribution at the non-linear level. We write the continuity, Euler and Poisson equations for the system in the Newtonian approximation. Then, using the time renormalization group method to resum perturbative corrections at all orders, we compute the total clustering power spectrum and matter power spectrum. At the linear level, a sound speed of dark energy different from that of light modifies the power spectrum on observationally interesting scales, such as those relevant for baryonic acoustic oscillations. We show that the effect of varying the sound speed of dark energy on the non-linear corrections to the matter power spectrum is below the per cent level, and therefore these corrections can be well modelled by their counterpart in cosmological scenarios with smooth dark energy. We also show that the non-linear effects on the matter growth index can be as large as 10–15 per cent for small scales.
Non-linear dynamics in parkinsonism.
Darbin, Olivier; Adams, Elizabeth; Martino, Anthony; Naritoku, Leslie; Dees, Daniel; Naritoku, Dean
2013-12-25
Over the last 30 years, the functions (and dysfunctions) of the sensory-motor circuitry have been mostly conceptualized using linear modelizations which have resulted in two main models: the "rate hypothesis" and the "oscillatory hypothesis." In these two models, the basal ganglia data stream is envisaged as a random temporal combination of independent simple patterns issued from its probability distribution of interval interspikes or its spectrum of frequencies respectively. More recently, non-linear analyses have been introduced in the modelization of motor circuitry activities, and they have provided evidences that complex temporal organizations exist in basal ganglia neuronal activities. Regarding movement disorders, these complex temporal organizations in the basal ganglia data stream differ between conditions (i.e., parkinsonism, dyskinesia, healthy control) and are responsive to treatments (i.e., l-DOPA, deep brain stimulation). A body of evidence has reported that basal ganglia neuronal entropy (a marker for complexity/irregularity in time series) is higher in hypokinetic state. In line with these findings, an entropy-based model has been recently formulated to introduce basal ganglia entropy as a marker for the alteration of motor processing and a factor of motor inhibition. Importantly, non-linear features have also been identified as a marker of condition and/or treatment effects in brain global signals (EEG), muscular activities (EMG), or kinetic of motor symptoms (tremor, gait) of patients with movement disorders. It is therefore warranted that the non-linear dynamics of motor circuitry will contribute to a better understanding of the neuronal dysfunctions underlying the spectrum of parkinsonian motor symptoms including tremor, rigidity, and hypokinesia.
Non-linear memristor switching model
NASA Astrophysics Data System (ADS)
Chernov, A. A.; Islamov, D. R.; Pik'nik, A. A.
2016-10-01
We introduce a thermodynamical model of filament growing when a current pulse via memristor flows. The model is the boundary value problem, which includes nonstationary heat conduction equation with non-linear Joule heat source, Poisson equation, and Shockley- Read-Hall equations taking into account strong electron-phonon interactions in trap ionization and charge transport processes. The charge current, which defines the heating in the model, depends on the rate of the oxygen vacancy generation. The latter depends on the local temperature. The solution of the introduced problem allows one to describe the kinetics of the switch process and the final filament morphology.
Non-Linear Dynamics of Saturn's Rings
NASA Astrophysics Data System (ADS)
Esposito, L. W.
2016-12-01
Non-linear processes can explain why Saturn's rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. Stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, that push the system across thresholds that lead to persistent states. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average. Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like `straw' that can explain the halo morphology and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; this requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km).Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing.Ring dynamics and history implications: Moon-triggered clumping explains both small and large particles at resonances. We calculate the stationary size distribution using a cell-to-cell mapping procedure that converts the phase-plane trajectories to a Markov chain. Approximating it as an asymmetric random walk with reflecting boundaries
Non-Linear Dynamics of Saturn's Rings
NASA Astrophysics Data System (ADS)
Esposito, L. W.
2015-10-01
Non-linear processes can explain why Saturn's rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. We find that stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, pushing the system across thresholds that lead to persistent states. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average: 2-10x is possible. Results of driven N-body systems by Stuart Robbins: Even unforced rings show large variations; Forcing triggers aggregation; Some limit cycles and phase lags seen, but not always as predicted by predator-prey model. Summary of Halo Results: A predatorprey model for ring dynamics produces transient structures like 'straw' that can explain the halo structure and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; Surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km); We propose 'straw'. Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing. Ring dynamics and history implications: Moon
Non-Linear Dynamics of Saturn's Rings
NASA Astrophysics Data System (ADS)
Esposito, Larry W.
2015-04-01
Non-linear processes can explain why Saturn's rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. We find that stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, pushing the system across thresholds that lead to persistent states. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average: 2-10x is possible Results of driven N-body systems by Stuart Robbins: Even unforced rings show large variations; Forcing triggers aggregation; Some limit cycles and phase lags seen, but not always as predicted by predator-prey model. Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like 'straw' that can explain the halo structure and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; Surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km); We propose 'straw'. Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing. Ring dynamics and history implications: Moon
Thinking about Non-Linear Smoothers.
1986-05-01
interesting possibilities for future study . These seem at the moment to fall into 3 categories: 1) Do we need the step that works on ends of abutting swooshes...Unear’smoothers to00 31. Recent work at Stanford 100 32. Coments an ocaly-lnear ttu.ng 101 .’ .. 33. Qevelnd’s i.ow 102 34. smelting 103 APPENDIX C: A...limited degree, with "Benchmarks’. We are, in most subareas, early in our study of non-linear smoothers. As as consequence, we often have to emphasize
Non-linear micromechanics of soft tissues
Chen, Huan; Zhao, Xuefeng; Lu, Xiao; Kassab, Ghassan
2013-01-01
Microstructure-based constitutive models have been adopted in recent studies of non-linear mechanical properties of biological soft tissues. These models provide more accurate predictions of the overall mechanical responses of tissues than phenomenological approaches. Based on standard approximations in non-linear mechanics, we classified the microstructural models into three categories: (1) uniform-field models with solid-like matrix, (2) uniform-field models with fluid-like matrix, and (3) second-order estimate models. The first two categories assume affine deformation field where the deformation of microstructure is the same as that of the tissue, regardless of material heterogeneities; i.e., they represent the upper bounds of the exact effective strain energy and stress of soft tissues. In addition, the first type is not purely structurally motivated and hence cannot accurately predict the microscopic mechanical behaviors of soft tissues. The third category considers realistic geometrical features, material properties of microstructure and interactions among them and allows for flexible deformation in each constituent. The uniform-field model with fluid-like matrix and the second-order estimate model are microstructure-based, and can be applied to different tissues based on micro-structural features. PMID:24817769
Controllability of non-linear biochemical systems.
Ervadi-Radhakrishnan, Anandhi; Voit, Eberhard O
2005-07-01
Mathematical methods of biochemical pathway analysis are rapidly maturing to a point where it is possible to provide objective rationale for the natural design of metabolic systems and where it is becoming feasible to manipulate these systems based on model predictions, for instance, with the goal of optimizing the yield of a desired microbial product. So far, theory-based metabolic optimization techniques have mostly been applied to steady-state conditions or the minimization of transition time, using either linear stoichiometric models or fully kinetic models within biochemical systems theory (BST). This article addresses the related problem of controllability, where the task is to steer a non-linear biochemical system, within a given time period, from an initial state to some target state, which may or may not be a steady state. For this purpose, BST models in S-system form are transformed into affine non-linear control systems, which are subjected to an exact feedback linearization that permits controllability through independent variables. The method is exemplified with a small glycolytic-glycogenolytic pathway that had been analyzed previously by several other authors in different contexts.
Non-linear dynamic compensation system
NASA Technical Reports Server (NTRS)
Lin, Yu-Hwan (Inventor); Lurie, Boris J. (Inventor)
1992-01-01
A non-linear dynamic compensation subsystem is added in the feedback loop of a high precision optical mirror positioning control system to smoothly alter the control system response bandwidth from a relatively wide response bandwidth optimized for speed of control system response to a bandwidth sufficiently narrow to reduce position errors resulting from the quantization noise inherent in the inductosyn used to measure mirror position. The non-linear dynamic compensation system includes a limiter for limiting the error signal within preselected limits, a compensator for modifying the limiter output to achieve the reduced bandwidth response, and an adder for combining the modified error signal with the difference between the limited and unlimited error signals. The adder output is applied to control system motor so that the system response is optimized for accuracy when the error signal is within the preselected limits, optimized for speed of response when the error signal is substantially beyond the preselected limits and smoothly varied therebetween as the error signal approaches the preselected limits.
A survey on non-linear oscillations
NASA Astrophysics Data System (ADS)
Atherton, D. P.; Dorrah, H. T.
1980-06-01
This survey paper presents a comprehensive review of work in the field of non-linear oscillations. A brief discussion of second-order systems is followed by a presentation of exact criteria, approximate analytical methods and computational techniques for limit cycles in single variable systems. Multivariable systems are then covered from an analogous viewpoint which allows the reader to clearly identify both how single variable methods have been extended and the possibilities for further research. Particular emphasis is placed on describing function methods since it is believed that, where exact solutions are not possible, the approach may not only give approximate solutions but provides good insight for further computational or simulation studies. The coverage is essentially restricted to continuous lumped parameter systems and includes both free and forced oscillations. Several applications of the theories in various fields of engineering and science are discussed and indicate the broad interest in non-linear oscillatory phenomena. Finally, a detailed bibliography on the subject is provided.
Gaussian tunneling model of c-axis twist Josephson junctions.
Bille, A.; Klemm, R. A.; Scharnberg, K.; Materials Science Division; Univ. Hamburg
2001-01-01
We calculate the critical current density J{sub c}{sup J}({var_phi}{sub 0}) for Josephson tunneling between identical high-temperature superconductors twisted an angle {var_phi}{sub 0} about the c axis. Regardless of the shape of the two-dimensional Fermi surface and for very general tunneling matrix elements, an order parameter (OP) with general d-wave symmetry leads to J{sub c}{sup J}({pi}/4)=0. This general result is inconsistent with the data of Li et al. [Phys. Rev. Lett. 83, 4160 (1999)] on Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (Bi2212), which showed J{sub c}{sup J} to be independent of {var_phi}{sub 0}. If the momentum parallel to the barrier is conserved in the tunneling process, J{sub c}{sup J} should vary substantially with the twist angle {var_phi}{sub 0} when the tight-binding Fermi surface appropriate for Bi2212 is taken into account, even if the OP is completely isotropic. We quantify the degree of momentum nonconservation necessary to render J{sub c}{sup J}({var_phi}{sub 0}) constant within experimental error for a variety of pair states by interpolating between the coherent and incoherent limits using five specific models to describe the momentum dependence of the tunneling matrix element squared. From the data of Li et al., we conclude that the c-axis tunneling in Bi2212 must be very nearly incoherent, and that the OP must have a nonvanishing Fermi-surface average for T<{approx}T{sub c}. We further show that the apparent conventional sum-rule violation observed by Basov et al. [Science 283, 49 (1999)] can be consistent with such strongly incoherent c-axis tunneling.
Pressure dependence of the c-axis resistivity of graphite
Uher, C.; Hockey, R.L.; Ben-Jacob, E.
1987-03-15
The c-axis resistivity of highly oriented pyrolytic graphite has been measured from 2 to 300 K under hydrostatic pressures of up to 40 kbar. A resistivity peak near 40 K, typical for this type of graphite at ambient pressure, rapidly diminishes with increasing pressure but does not shift its position with respect to temperature. This observation suggests that the origin of the resistivity peak is not in a strong electron-phonon interaction but is associated with a particular structural matrix of these artificially produced graphites. A model is proposed, based on tunneling between microcrystallites, which accounts for the peculiar temperature and pressure dependence of the resistivity.
Non-Linear Dynamics of Saturn's Rings
NASA Astrophysics Data System (ADS)
Esposito, L. W.
2015-12-01
Non-linear processes can explain why Saturn's rings are so active and dynamic. Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit, with relative velocity ranging from nearly zero to a multiple of the orbit average: 2-10x is possible. Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like 'straw' that can explain the halo structure and spectroscopy: Cyclic velocity changes cause perturbed regions to reach higher collision speeds at some orbital phases, which preferentially removes small regolith particles; Surrounding particles diffuse back too slowly to erase the effect: this gives the halo morphology; This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km); We propose 'straw', as observed ny Cassini cameras. Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing. Ring dynamics and history implications: Moon-triggered clumping at perturbed regions in Saturn's rings creates both high velocity dispersion and large aggregates at these distances, explaining both small and large particles observed there. This confirms the triple architecture of ring particles: a broad size distribution of particles; these aggregate into temporary rubble piles; coated by a regolith of dust. We calculate the stationary size distribution using a cell-to-cell mapping procedure that converts the phase-plane trajectories to a Markov chain. Approximating the Markov chain as an asymmetric random walk with reflecting boundaries allows us to determine the power law index from
Non-linear optical deformation potentials in uniaxially strained ZnO microwires
NASA Astrophysics Data System (ADS)
Sturm, C.; Wille, M.; Lenzner, J.; Khujanov, S.; Grundmann, M.
2017-02-01
The emission properties of bent ZnO microwires with diameters ranging from 1.5 μm to 7.3 μm are systematically investigated by cathodoluminescence spectroscopy at T ≈ 10 K . We induced uniaxial strains along the c-axis of up to ± 2.9 % . At these high strain values, we observe a non-linear shift of the emission energy with respect to the induced strain, and the magnitude of the energy shift depends on the sign of the strain. The linear and non-linear deformation potentials were determined to be D 1 = - 2.50 ± 0.05 eV and D 2 = - 15.0 ± 0.5 eV , respectively. The non-linearity of the energy shift is also reflected in the observed spectral broadening of the emission peak as a function of the locally induced strain, which decreases with increasing strain on the compressive side and increases on the tensile side.
Non Linear Beam Dynamics Studies at SPEAR
Terebilo, A.; Pellegrini, C.; Cornacchia, M.; Corbett, J.; Martin, D.; /SLAC
2011-09-12
The frequency map analysis of a Hamiltonian system recently introduced to accelerators physics in combination with turn-by-turn phase space measurements opens new experimental opportunities for studying non linear dynamic in storage rings. In this paper we report on the experimental program at SPEAR having the goal of measuring the frequency map of the machine. In this paper we discuss the accuracy of the instantaneous tune extraction from experimental data and demonstrate the possibility of the frequency map measurement. The instantaneous tune extraction technique can be applied to experimental tracking data with reasonable accuracy. Frequency map can be experimentally determined using the existing turn-by-turn phase space measurement techniques and NAFF instantaneous tune extraction.
Non-linear sequencing and cognizant failure
NASA Astrophysics Data System (ADS)
Gat, Erann
1999-01-01
Spacecraft are traditionally commanded using linear sequences of time-based commands. Linear sequences work fairly well, but they are difficult and expensive to generate, and are usually not capable of responding to contingencies. Any anomalous behavior while executing a linear sequence generally results in the spacecraft entering a safe mode. Critical sequences like orbit insertions which must be able to respond to faults without going into safe mode are particularly difficult to design and verify. The effort needed to generate command sequences can be reduced by extending the vocabulary of sequences to include more sophisticated control constructs. The simplest extensions are conditionals and loops. Adding these constructs would make a sequencing language look more or less like a traditional programming language or scripting language, and would come with all the difficulties associated with such a language. In particular, verifying the correctness of a sequence would be tantamount to verifying the correctness of a program, which is undecidable in general. We describe an extended vocabulary for non-linear sequencing based on the architectural notion of cognizant failure. A cognizant failure architecture is divided into components whose contract is to either achieve (or maintain) a certain condition, or report that they have failed to do so. Cognizant failure is an easier condition to verify than correctness, but it can provide high confidence in the safety of the spacecraft. Because cognizant failure inherently implies some kind of representation of the intent of an action, the system can respond to contingencies in more robust and general ways. We will describe an implemented non-linear sequencing system that is being flown on the NASA New Millennium Deep Space 1 Mission as part of the Remote Agent Experiment.
Non-linear Flood Risk Assessment
NASA Astrophysics Data System (ADS)
Mazzarella, A.
The genesis of floodings is very complex depending on hydrologic, meteorological and evapo-transpirative factors that are linked among themselves in a non linear way with numerous feedback processes. The Cantor dust and the rank-ordering statistics supply a proper framework for identifying a kind of a non linear order in the time succession of the floodings and so provide a basis for their prediction. When a catalogue is analysed, it is necessary to test its completeness with respect to the size of the recorded events and results obtained from analysis of catalogues that do not take into account such a test are suspect and possibly wrong, or, at least, unreliable. Floodings have no instrumentally determined magnitude scale, like that conventionally used for earthquakes, and this is why they are generally described in qualitative terms. For this reason, a semi-quantitative index, called ASI (Alluvial Strength Index) has been here developed that combines attributes of alluvial triggering mechanisms and effects on the territorial and hydraulic system.The historical succession of alluvial events occurred at high valley of Po river (Northern Italy), mean valley of Calore river (Southern Italy) and at Sarno, near Naples, have been accurately reconstructed on the basis of old documents and classified according to their ASI. The catalogues have been verified to be complete only for events classified at least as moderate and this probably because many of the lowest energetic events, especially in the past, escaped the detection. The identification of scale-invariances in the time clustering of alluvial events, both on short and long time scales, even if indicative of the complexity of their genesis, might be very helpful for the assessment and reduction of the hazard of future disasters. For example, on the basis of the results of the rank-ordering statistics, the most probable occurrence of an alluvial event at Sarno, classified at least as strong, is predicted to occur
In situ characterisation of non linear capacitors
NASA Astrophysics Data System (ADS)
Laudebat, L.; Bley, V.; Lebey, T.; Schneider, H.; Tounsi, P.
2001-05-01
Multilayers ceramic capacitors (MLCC) presenting non linear behaviours of their C(V) characteristics may have interesting applications in power electronics. Most of them have already been described. Nevertheless, the choice of a particular type instead of another one is all the more so difficult since, on one hand the physical mechanisms able to explain this behaviour is far from being understood. On the other hand, C(V) characteristics are in general obtained for low voltage values different from the ones they are going to be involved in. In this paper, direct in situ characterisations of different BaTiO3 based capacitors commercially available are achieved. The role of the capacitors' type (X7R,Z5U), of the temperature and of the voltage waveform (and more particularly its polarity) is demonstrated. Temperature values up to 200 oC are measured during normal operations in a RCD dissipative snubber without any alterations of the C(V) characteristics. All these results are discussed as regards the main physical properties of the constitutive materials in order to reach an optimisation of their use through an appropriate dimensioning.
Non-Linear Electrohydrodynamics in Microfluidic Devices
Zeng, Jun
2011-01-01
Since the inception of microfluidics, the electric force has been exploited as one of the leading mechanisms for driving and controlling the movement of the operating fluid and the charged suspensions. Electric force has an intrinsic advantage in miniaturized devices. Because the electrodes are placed over a small distance, from sub-millimeter to a few microns, a very high electric field is easy to obtain. The electric force can be highly localized as its strength rapidly decays away from the peak. This makes the electric force an ideal candidate for precise spatial control. The geometry and placement of the electrodes can be used to design electric fields of varying distributions, which can be readily realized by Micro-Electro-Mechanical Systems (MEMS) fabrication methods. In this paper, we examine several electrically driven liquid handling operations. The emphasis is given to non-linear electrohydrodynamic effects. We discuss the theoretical treatment and related numerical methods. Modeling and simulations are used to unveil the associated electrohydrodynamic phenomena. The modeling based investigation is interwoven with examples of microfluidic devices to illustrate the applications. PMID:21673912
Non linear anthropometric predictors in swimming.
Sekulić, Damir; Zenić, Natasa; Zubcević, Nada Grcić
2007-09-01
In this paper we have tried to identify the significance and character of the linear and non-linear relations between simple anthropometric predictors: body height (BH), body weight (BW), and body mass index, and swimming performance: freestyle swimming 50 (FS50) and 400 meters (FS400), in a sample of young (15 years old on average) male (N = 40) and female (N = 28) swimmers. Linear (general model: y = a+bx) and nonlinear regression (general model: y = a+bx+cx2) were calculated simultaneously. Morphological variables are a significantly better predictor of the FS50 in males (BH mostly), and FS400 in females (BW mostly). This study emphasized some of the main advantages in the nonlinear regression calculation (including an interpretation of the relationships at a more superior level), and consequently allowed a precise anthropometric modeling in swimming using simple and easily measurable variables. For example, the best results in FS400 can be expected for the subjects that are average in BW (which guarantees solid muscle mass--the generator of force), but above average in BH (because of the physical law of lever). In conclusion, nonlinear regressions allow one to define the real nature of the relationships between variables, but only if compared with the linear ones. Additionally, this study emphasized one of the most important factors in defining possible specification-equation (e.g. structure of the influence of the different dimensions on the sport achievement) in different sports. In short, it underlines the importance of sampling the appropriate sample of the subject--highly skilled athletes exclusively.
Non-linear behavior of fiber composite laminates
NASA Technical Reports Server (NTRS)
Hashin, Z.; Bagchi, D.; Rosen, B. W.
1974-01-01
The non-linear behavior of fiber composite laminates which results from lamina non-linear characteristics was examined. The analysis uses a Ramberg-Osgood representation of the lamina transverse and shear stress strain curves in conjunction with deformation theory to describe the resultant laminate non-linear behavior. A laminate having an arbitrary number of oriented layers and subjected to a general state of membrane stress was treated. Parametric results and comparison with experimental data and prior theoretical results are presented.
Phonon mean free path of graphite along the c-axis
Wei, Zhiyong; Yang, Juekuan; Chen, Weiyu; Bi, Kedong; Chen, Yunfei
2014-02-24
Phonon transport in the c-axis direction of graphite thin films has been studied using non-equilibrium molecular dynamics (MD) simulation. The simulation results show that the c-axis thermal conductivities for films of thickness ranging from 20 to 500 atomic layers are significantly lower than the bulk value. Based on the MD data, a method is developed to construct the c-axis thermal conductivity as an accumulation function of phonon mean free path (MFP), from which we show that phonons with MFPs from 2 to 2000 nm contribute ∼80% of the graphite c-axis thermal conductivity at room temperature, and phonons with MFPs larger than 100 nm contribute over 40% to the c-axis thermal conductivity. These findings indicate that the commonly believed value of just a few nanometers from the simple kinetic theory drastically underestimates the c-axis phonon MFP of graphite.
Solute transport under non-linear sorption and decay.
Serrano, S E
2001-04-01
Contaminant transport in aquifers is usually represented by a solution to the advective-dispersive differential equation. When the contaminant is subject to non-linear degradation or decay, or it is characterized by a chemical constituent that follows a non-linear sorption isotherm, the resulting differential equation is non-linear. Using the method of decomposition, series solutions were obtained for the non-linear equation. The series were used to derive and test "simulant" solutions that aries using the concept of double decomposition. Simulant solutions are closed-form analytic expressions that approximate part of the series These expression are simple, stable, and flexible. They permit an accurate forecasting of contaminant propagation .under non-linearity in laboratory or field investigations at early or prolonged times after the spill. In this article, the practical scenario of an instantaneous spill, and that of a constant concentration boundary condition, is studied for situations of non-linear decay, non-linear Freundlich isotherm, and non-linear Langmuir isotherm. The solutions are verified with limited well-known analytical solutions of the linear reactive and non-reactive equations with excellent agreement, and with limited finite difference solutions. Plumes undergoing non-linear decay experience a profile re-scaling with respect to that of linear decay, the degree of which is controlled by magnitude of the non-linear parameter b. The direction of the scaling (scaling up or scaling down with respect to the linear decay plume) is controlled by the magnitude of C (whether greater or less than 1) in relation to the magnitude of b (whether greater or less than 1). When C>1, values of b<1 produce plumes that experience less decay (i.e., are scaled up) than that of the linear decay, whereas values of b> 1 produce non-linear plumes that experience more decay (i.e., are scaled down) than that of the linear decay. The opposite effect is observed when
Modeling Non-Linear Material Properties in Composite Materials
2016-06-28
Technical Report ARWSB-TR-16013 MODELING NON-LINEAR MATERIAL PROPERTIES IN COMPOSITE MATERIALS Michael F. Macri Andrew G...REPORT TYPE Technical 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE MODELING NON-LINEAR MATERIAL PROPERTIES IN COMPOSITE MATERIALS ...systems are increasingly incorporating composite materials into their design. Many of these systems subject the composites to environmental conditions
Discriminant power analyses of non-linear dimension expansion methods
NASA Astrophysics Data System (ADS)
Woo, Seongyoun; Lee, Chulhee
2016-05-01
Most non-linear classification methods can be viewed as non-linear dimension expansion methods followed by a linear classifier. For example, the support vector machine (SVM) expands the dimensions of the original data using various kernels and classifies the data in the expanded data space using a linear SVM. In case of extreme learning machines or neural networks, the dimensions are expanded by hidden neurons and the final layer represents the linear classification. In this paper, we analyze the discriminant powers of various non-linear classifiers. Some analyses of the discriminating powers of non-linear dimension expansion methods are presented along with a suggestion of how to improve separability in non-linear classifiers.
Employment of CB models for non-linear dynamic analysis
NASA Technical Reports Server (NTRS)
Klein, M. R. M.; Deloo, P.; Fournier-Sicre, A.
1990-01-01
The non-linear dynamic analysis of large structures is always very time, effort and CPU consuming. Whenever possible the reduction of the size of the mathematical model involved is of main importance to speed up the computational procedures. Such reduction can be performed for the part of the structure which perform linearly. Most of the time, the classical Guyan reduction process is used. For non-linear dynamic process where the non-linearity is present at interfaces between different structures, Craig-Bampton models can provide a very rich information, and allow easy selection of the relevant modes with respect to the phenomenon driving the non-linearity. The paper presents the employment of Craig-Bampton models combined with Newmark direct integration for solving non-linear friction problems appearing at the interface between the Hubble Space Telescope and its solar arrays during in-orbit maneuvers. Theory, implementation in the FEM code ASKA, and practical results are shown.
Non-linear dielectric monitoring of biological suspensions
NASA Astrophysics Data System (ADS)
Treo, E. F.; Felice, C. J.
2007-11-01
Non-linear dielectric spectroscopy as a tool for in situ monitoring of enzyme assumes a non-linear behavior of the sample when a sinusoidal voltage is applied to it. Even many attempts have been made to improve the original experiments, all of them had limited success. In this paper we present upgrades made to a non-linear dielectric spectrometer developed and the results obtained when using different cells. We emphasized on the electrode surface, characterizing the grinding and polishing procedure. We found that the biological medium does not behave as expected, and the non-linear response is generated in the electrode-electrolyte interface. The electrochemistry of this interface can bias unpredictably the measured non-linear response.
Employment of CB models for non-linear dynamic analysis
NASA Technical Reports Server (NTRS)
Klein, M. R. M.; Deloo, P.; Fournier-Sicre, A.
1990-01-01
The non-linear dynamic analysis of large structures is always very time, effort and CPU consuming. Whenever possible the reduction of the size of the mathematical model involved is of main importance to speed up the computational procedures. Such reduction can be performed for the part of the structure which perform linearly. Most of the time, the classical Guyan reduction process is used. For non-linear dynamic process where the non-linearity is present at interfaces between different structures, Craig-Bampton models can provide a very rich information, and allow easy selection of the relevant modes with respect to the phenomenon driving the non-linearity. The paper presents the employment of Craig-Bampton models combined with Newmark direct integration for solving non-linear friction problems appearing at the interface between the Hubble Space Telescope and its solar arrays during in-orbit maneuvers. Theory, implementation in the FEM code ASKA, and practical results are shown.
Computer modeling of batteries from non-linear circuit elements
NASA Technical Reports Server (NTRS)
Waaben, S.; Federico, J.; Moskowitz, I.
1983-01-01
A simple non-linear circuit model for battery behavior is given. It is based on time-dependent features of the well-known PIN change storage diode, whose behavior is described by equations similar to those associated with electrochemical cells. The circuit simulation computer program ADVICE was used to predict non-linear response from a topological description of the battery analog built from advice components. By a reasonable choice of one set of parameters, the circuit accurately simulates a wide spectrum of measured non-linear battery responses to within a few millivolts.
Fourier imaging of non-linear structure formation
NASA Astrophysics Data System (ADS)
Brandbyge, Jacob; Hannestad, Steen
2017-04-01
We perform a Fourier space decomposition of the dynamics of non-linear cosmological structure formation in ΛCDM models. From N-body simulations involving only cold dark matter we calculate 3-dimensional non-linear density, velocity divergence and vorticity Fourier realizations, and use these to calculate the fully non-linear mode coupling integrals in the corresponding fluid equations. Our approach allows for a reconstruction of the amount of mode coupling between any two wavenumbers as a function of redshift. With our Fourier decomposition method we identify the transfer of power from larger to smaller scales, the stable clustering regime, the scale where vorticity becomes important, and the suppression of the non-linear divergence power spectrum as compared to linear theory. Our results can be used to improve and calibrate semi-analytical structure formation models.
Asymptotic Stability of Interconnected Passive Non-Linear Systems
NASA Technical Reports Server (NTRS)
Isidori, A.; Joshi, S. M.; Kelkar, A. G.
1999-01-01
This paper addresses the problem of stabilization of a class of internally passive non-linear time-invariant dynamic systems. A class of non-linear marginally strictly passive (MSP) systems is defined, which is less restrictive than input-strictly passive systems. It is shown that the interconnection of a non-linear passive system and a non-linear MSP system is globally asymptotically stable. The result generalizes and weakens the conditions of the passivity theorem, which requires one of the systems to be input-strictly passive. In the case of linear time-invariant systems, it is shown that the MSP property is equivalent to the marginally strictly positive real (MSPR) property, which is much simpler to check.
Dilatonic non-linear sigma models and Ricci flow extensions
NASA Astrophysics Data System (ADS)
Carfora, M.; Marzuoli, A.
2016-09-01
We review our recent work describing, in terms of the Wasserstein geometry over the space of probability measures, the embedding of the Ricci flow in the renormalization group flow for dilatonic non-linear sigma models.
Non-Linear Dielectrics and Ferrites in ICEPIC
2012-04-10
in-cell code ICEPIC. The non-linear dielectric model includes a relaxation term to account for the physical response time of the material, which may...Andrew D. Greenwood, David M. French, Brad W. Hoff, Susan L. Heidger Air Force Research Laboratory, Directed Energy Directorate, Kirtland AFB, NM 87117...ICEPIC. The non-linear dielectric model includes a relaxation term to account for the physical response time of the material, which may be longer than an
Valuation of financial models with non-linear state spaces
NASA Astrophysics Data System (ADS)
Webber, Nick
2001-02-01
A common assumption in valuation models for derivative securities is that the underlying state variables take values in a linear state space. We discuss numerical implementation issues in an interest rate model with a simple non-linear state space, formulating and comparing Monte Carlo, finite difference and lattice numerical solution methods. We conclude that, at least in low dimensional spaces, non-linear interest rate models may be viable.
Visual discrimination and adaptation using non-linear unsupervised learning
NASA Astrophysics Data System (ADS)
Jiménez, Sandra; Laparra, Valero; Malo, Jesus
2013-03-01
Understanding human vision not only involves empirical descriptions of how it works, but also organization principles that explain why it does so. Identifying the guiding principles of visual phenomena requires learning algorithms to optimize specific goals. Moreover, these algorithms have to be flexible enough to account for the non-linear and adaptive behavior of the system. For instance, linear redundancy reduction transforms certainly explain a wide range of visual phenomena. However, the generality of this organization principle is still in question:10 it is not only that and additional constraints such as energy cost may be relevant as well, but also, statistical independence may not be the better solution to make optimal inferences in squared error terms. Moreover, linear methods cannot account for the non-uniform discrimination in different regions of the image and color space: linear learning methods necessarily disregard the non-linear nature of the system. Therefore, in order to account for the non-linear behavior, principled approaches commonly apply the trick of using (already non-linear) parametric expressions taken from empirical models. Therefore these approaches are not actually explaining the non-linear behavior, but just fitting it to image statistics. In summary, a proper explanation of the behavior of the system requires flexible unsupervised learning algorithms that (1) are tunable to different, perceptually meaningful, goals; and (2) make no assumption on the non-linearity. Over the last years we have worked on these kind of learning algorithms based on non-linear ICA,18 Gaussianization, 19 and principal curves. In this work we stress the fact that these methods can be tuned to optimize different design strategies, namely statistical independence, error minimization under quantization, and error minimization under truncation. Then, we show (1) how to apply these techniques to explain a number of visual phenomena, and (2) suggest the
Non-linear material characterisation using the noncollinear method
NASA Astrophysics Data System (ADS)
Croxford, Anthony J.; Wilcox, Paul D.; Drinkwater, Bruce W.
2010-04-01
Conventional ultrasonic NDT techniques are limited in their ability to detect small defects by the diffraction limit, that is there is much reduced sensitivity to defects smaller than the wavelength of the interrogating ultrasonic wave. While not a major issue for most inspection, this problem becomes particularly significant for the detection of fatigue damage prior to crack formation. In this regime conventional NDT has proven to be inadequate. For this reason significant effort has been expended on the development of non-linear techniques. These techniques rely on deviations of the material from linear stress strain behaviour which create harmonics in the resulting frequency response. Evidence suggests that changes to a materials condition, such as fatigue damage, change this non-linear response. This paper presents a non-linear inspection method using a non-collinear interaction. This technique has several advantages over other harmonic approaches in that there is spatial separation, modal separation and frequency separation of the non-linear signal. This allows the origin of the non-linear signal and underlying noise levels to be well defined. The capability of the technique is demonstrated using plastically strained material and samples subjected to low cycle fatigue.
Isolating Non-Linear Signatures of Two Colliding Black Holes
NASA Astrophysics Data System (ADS)
Garrido, Rita
2012-03-01
The early and late stages of the binary-black-hole collision can be approximated by perturbations to a background, solutions to linearization of the Einstein's equations. However, once the two black holes are within several radii of each other, and ultimately collide, the solution is intrinsically non-linear. The main objective is to intuitively understand the non-linear portion of the solution to the Einstein equation by performing simulations of such mergers. I will identify the non-linear regime through a process of elimination. The early stages of the coalescence are well known by post-Newtonian theory. The end state is approximated very well by perturbation theory, the waveforms decay as a damped sinusoidal with a frequency and decay time uniquely determined by the mass and spin of the final black hole in theory. I will isolate the non-linear portion of the waveform by fitting the early stages to the post-Newtonian solution and the late stages to the perturbative solution. What remains is the non-linear region. Once isolated, we will search through the physics parameter space of the binary black holes for bulk features. These features can then be used to fine-tune the search algorithms hunting for these collisions with LIGO.
The study of microcurrent path of highly c-axis-oriented Bi(2223)/Ag tapes
NASA Astrophysics Data System (ADS)
Sun, Yuping; Xu, Guoyang; Jiang, Liudi; Du, Jiaju; Zhang, Yuheng
1997-08-01
The microcurrent path of highly c-axis-oriented Bi(2223)/Ag tapes has been investigated by in-plane (I//ab plane) and out-of-plane (I//c axis) transport measurements. It includes the dependence of transport critical current on temperatures close to T c at different magnetic fields and the resistance transition broadening for applied fields H parallel to c-axis. It is found that the transport measurement results of in-plane and out-of-plane are quite different. We attribute the differences to the different microcurrent path. We think that the microcurrent path of the highly c-axis-oriented Bi(2223)/Ag tape is correlated with the direction of current injection.
Characterization of reactively sputtered c-axis aligned nanocrystalline InGaZnO{sub 4}
Lynch, David M.; Zhu, Bin; Ast, Dieter G.; Thompson, Michael O.; Levin, Barnaby D. A.; Muller, David A.; Greene, Raymond G.
2014-12-29
Crystallinity and texturing of RF sputtered c-axis aligned crystal InGaZnO{sub 4} (CAAC IGZO) thin films were quantified using X-ray diffraction techniques. Above 190 °C, nanocrystalline films with an X-ray peak at 2θ = 30° (009 planes) developed with increasing c-axis normal texturing up to 310 °C. Under optimal conditions (310 °C, 10% O{sub 2}), films exhibited a c-axis texture full-width half-maximum of 20°. Cross-sectional high-resolution transmission electron microscopy confirmed these results, showing alignment variation of ±9° over a 15 × 15 nm field of view and indicating formation of much larger aligned domains than previously reported. At higher deposition temperatures, c-axis alignment was gradually lost as polycrystalline films developed.
Non-linear system identification in flow-induced vibration
Spanos, P.D.; Zeldin, B.A.; Lu, R.
1996-12-31
The paper introduces a method of identification of non-linear systems encountered in marine engineering applications. The non-linearity is accounted for by a combination of linear subsystems and known zero-memory non-linear transformations; an equivalent linear multi-input-single-output (MISO) system is developed for the identification problem. The unknown transfer functions of the MISO system are identified by assembling a system of linear equations in the frequency domain. This system is solved by performing the Cholesky decomposition of a related matrix. It is shown that the proposed identification method can be interpreted as a {open_quotes}Gram-Schmidt{close_quotes} type of orthogonal decomposition of the input-output quantities of the equivalent MISO system. A numerical example involving the identification of unknown parameters of flow (ocean wave) induced forces on offshore structures elucidates the applicability of the proposed method.
Noise and non-linearities in high-throughput data
NASA Astrophysics Data System (ADS)
Nguyen, Viet-Anh; Koukolíková-Nicola, Zdena; Bagnoli, Franco; Lió, Pietro
2009-01-01
High-throughput data analyses are becoming common in biology, communications, economics and sociology. The vast amounts of data are usually represented in the form of matrices and can be considered as knowledge networks. Spectra-based approaches have proved useful in extracting hidden information within such networks and for estimating missing data, but these methods are based essentially on linear assumptions. The physical models of matching, when applicable, often suggest non-linear mechanisms, that may sometimes be identified as noise. The use of non-linear models in data analysis, however, may require the introduction of many parameters, which lowers the statistical weight of the model. According to the quality of data, a simpler linear analysis may be more convenient than more complex approaches. In this paper, we show how a simple non-parametric Bayesian model may be used to explore the role of non-linearities and noise in synthetic and experimental data sets.
Non-Linear Vibration Characteristics of Clamped Laminated Shallow Shells
NASA Astrophysics Data System (ADS)
ABE, A.; KOBAYASHI, Y.; YAMADA, G.
2000-07-01
This paper examines non-linear free vibration characteristics of first and second vibration modes of laminated shallow shells with rigidly clamped edges. Non-linear equations of motion for the shells based on the first order shear deformation and classical shell theories are derived by means of Hamilton's principle. We apply Galerkin's procedure to the equations of motion in which eigenvectors for first and second modes of linear vibration obtained by the Ritz method are employed as trial functions. Then simultaneous non-linear ordinary differential equations are derived in terms of amplitudes of the first and second vibration modes. Backbone curves for the first and second vibration modes are solved numerically by the Gauss-Legendre integration method and the shooting method respectively. The effects of lamination sequences and transverse shear deformation on the behavior are discussed. It is also shown that the motion of the first vibration mode affects the response for the second vibration mode.
A general non-linear multilevel structural equation mixture model
Kelava, Augustin; Brandt, Holger
2014-01-01
In the past 2 decades latent variable modeling has become a standard tool in the social sciences. In the same time period, traditional linear structural equation models have been extended to include non-linear interaction and quadratic effects (e.g., Klein and Moosbrugger, 2000), and multilevel modeling (Rabe-Hesketh et al., 2004). We present a general non-linear multilevel structural equation mixture model (GNM-SEMM) that combines recent semiparametric non-linear structural equation models (Kelava and Nagengast, 2012; Kelava et al., 2014) with multilevel structural equation mixture models (Muthén and Asparouhov, 2009) for clustered and non-normally distributed data. The proposed approach allows for semiparametric relationships at the within and at the between levels. We present examples from the educational science to illustrate different submodels from the general framework. PMID:25101022
Pattern formation due to non-linear vortex diffusion
NASA Astrophysics Data System (ADS)
Wijngaarden, Rinke J.; Surdeanu, R.; Huijbregtse, J. M.; Rector, J. H.; Dam, B.; Einfeld, J.; Wördenweber, R.; Griessen, R.
Penetration of magnetic flux in YBa 2Cu 3O 7 superconducting thin films in an external magnetic field is visualized using a magneto-optic technique. A variety of flux patterns due to non-linear vortex diffusion is observed: (1) Roughening of the flux front with scaling exponents identical to those observed in burning paper including two distinct regimes where respectively spatial disorder and temporal disorder dominate. In the latter regime Kardar-Parisi-Zhang behavior is found. (2) Fractal penetration of flux with Hausdorff dimension depending on the critical current anisotropy. (3) Penetration as ‘flux-rivers’. (4) The occurrence of commensurate and incommensurate channels in films with anti-dots as predicted in numerical simulations by Reichhardt, Olson and Nori. It is shown that most of the observed behavior is related to the non-linear diffusion of vortices by comparison with simulations of the non-linear diffusion equation appropriate for vortices.
Ghost Dark Energy with Non-Linear Interaction Term
NASA Astrophysics Data System (ADS)
Ebrahimi, E.
2016-06-01
Here we investigate ghost dark energy (GDE) in the presence of a non-linear interaction term between dark matter and dark energy. To this end we take into account a general form for the interaction term. Then we discuss about different features of three choices of the non-linear interacting GDE. In all cases we obtain equation of state parameter, w D = p/ ρ, the deceleration parameter and evolution equation of the dark energy density parameter (Ω D ). We find that in one case, w D cross the phantom line ( w D < -1). However in two other classes w D can not cross the phantom divide. The coincidence problem can be solved in these models completely and there exist good agreement between the models and observational values of w D , q. We study squared sound speed {vs2}, and find that for one case of non-linear interaction term {vs2} can achieves positive values at late time of evolution.
Metal-Insulator Transition of c-Axis-Controlled V2O3 Thin Film
NASA Astrophysics Data System (ADS)
Shimazu, Yuichi; Okumura, Teppei; Tsuchiya, Takashi; Shimada, Atsushi; Tanabe, Kenji; Tokiwa, Kazuyasu; Kobayashi, Masaki; Horiba, Koji; Kumigashira, Hiroshi; Higuchi, Tohru
2015-06-01
We prepared c-axis-controlled V2O3 thin films by RF magnetron sputtering and proved their metal-insulator transition (MIT) in terms of electronic structure. The lattice constant of the c-axis depends on the film thickness and the lattice mismatch of the substrate and V2O3. MIT is observed at a temperature of ˜150 K in the V2O3 thin films with the lattice constants of c = 13.942 and 13.992 Å, although the V2O3 thin film with c = 13.915 Å exhibits metallic conductivity without MIT. The electron correlation energy, which corresponds to the energy difference between the lower Hubbard band and the upper Hubbard band, increases with increasing lattice constant of the c-axis. Bandwidths also depend on the lattice constant of the c-axis. The intensity of the a1g orbital around the Fermi level decreases with increasing lattice constant of the c-axis. These results suggest that the electron correlation interaction and bandwidths play important roles in the MIT of c-axis-controlled V2O3 thin films.
Neural network modelling of non-linear hydrological relationships
NASA Astrophysics Data System (ADS)
Abrahart, R. J.; See, L. M.
2007-09-01
Two recent studies have suggested that neural network modelling offers no worthwhile improvements in comparison to the application of weighted linear transfer functions for capturing the non-linear nature of hydrological relationships. The potential of an artificial neural network to perform simple non-linear hydrological transformations under controlled conditions is examined in this paper. Eight neural network models were developed: four full or partial emulations of a recognised non-linear hydrological rainfall-runoff model; four solutions developed on an identical set of inputs and a calculated runoff coefficient output. The use of different input combinations enabled the competencies of solutions developed on a reduced number of parameters to be assessed. The selected hydrological model had a limited number of inputs and contained no temporal component. The modelling process was based on a set of random inputs that had a uniform distribution and spanned a modest range of possibilities. The initial cloning operations permitted a direct comparison to be performed with the equation-based relationship. It also provided more general information about the power of a neural network to replicate mathematical equations and model modest non-linear relationships. The second group of experiments explored a different relationship that is of hydrological interest; the target surface contained a stronger set of non-linear properties and was more challenging. Linear modelling comparisons were performed against traditional least squares multiple linear regression solutions developed on identical datasets. The reported results demonstrate that neural networks are capable of modelling non-linear hydrological processes and are therefore appropriate tools for hydrological modelling.
Observing (non)linear lattice dynamics in graphite by ultrafast Kikuchi diffraction
Liang, Wenxi; Vanacore, Giovanni M.; Zewail, Ahmed H.
2014-01-01
In materials, the nature of the strain–stress relationship, which is fundamental to their properties, is determined by both the linear and nonlinear elastic responses. Whereas the linear response can be measured by various techniques, the nonlinear behavior is nontrivial to probe and to reveal its nature. Here, we report the methodology of time-resolved Kikuchi diffraction for mapping the (non)linear elastic response of nanoscale graphite following an ultrafast, impulsive strain excitation. It is found that the longitudinal wave propagating along the c-axis exhibits echoes with a frequency of 9.1 GHz, which indicates the reflections of strain between the two surfaces of the material with a speed of ∼4 km/s. Because Kikuchi diffraction enables the probing of strain in the transverse direction, we also observed a higher-frequency mode at 75.5 GHz, which has a relatively long lifetime, on the order of milliseconds. The fluence dependence and the polarization properties of this nonlinear mode are entirely different from those of the linear, longitudinal mode, and here we suggest a localized breather motion in the a-b plane as the origin of the nonlinear shear dynamics. The approach presented in this contribution has the potential for a wide range of applications because most crystalline materials exhibit Kikuchi diffraction. PMID:24706785
Non-linear effects in bunch compressor of TARLA
NASA Astrophysics Data System (ADS)
Yildiz, Hüseyin; Aksoy, Avni; Arikan, Pervin
2016-03-01
Transport of a beam through an accelerator beamline is affected by high order and non-linear effects such as space charge, coherent synchrotron radiation, wakefield, etc. These effects damage form of the beam, and they lead particle loss, emittance growth, bunch length variation, beam halo formation, etc. One of the known non-linear effects on low energy machine is space charge effect. In this study we focus on space charge effect for Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) machine which is designed to drive InfraRed Free Electron Laser covering the range of 3-250 µm. Moreover, we discuss second order effects on bunch compressor of TARLA.
Non-linear analysis of moderately thick sector plates
NASA Astrophysics Data System (ADS)
Nath, Y.; Sharda, H. B.; Sharma, Ashish
2005-10-01
Non-linear static analysis of moderately thick sector plates under uniformly distributed loading is presented. Using the first-order shear deformation theory and Von Karman type non-linearity, the governing equations of equilibrium are developed and expressed in terms of displacement components. The Chebyshev polynomial is used for spatial discretization of the differential equations. An iterative incremental approach based on Newton-Raphson method is used for the solution. Convergence study is carried out. Effects of annularity, thickness ratio, sector angle and boundary conditions are investigated. Results are compared with those available from the literature.
Photocrosslinkable copolymers for non-linear optical applications
Kawatsuki, N.; Pakbaz, K.; Schmidt, H.W.
1993-12-31
New photocrosslinkable copolymers have been synthesized and applied as non-linear optical materials. The copolymers are based on methyl methacrylate, a photo-excitable benzophenone monomer, a non-linear optical active 4`-[(2-hydroxyethyl)ethylamino]-4-nitro-azobenzene (disperse red 1) side chain monomer and a crosslinkable 2-butenyl monomer. These copolymers can be crosslinked by UV light at 366 nm in the poled state and show a stable alignment of NLO chromophore by monitoring the adsorption spectra. The crosslinked and poled film did not change its alignment after storing 4 weeks at room temperature.
Non-Linear Finite Element Modeling of THUNDER Piezoelectric Actuators
NASA Technical Reports Server (NTRS)
Taleghani, Barmac K.; Campbell, Joel F.
1999-01-01
A NASTRAN non-linear finite element model has been developed for predicting the dome heights of THUNDER (THin Layer UNimorph Ferroelectric DrivER) piezoelectric actuators. To analytically validate the finite element model, a comparison was made with a non-linear plate solution using Von Karmen's approximation. A 500 volt input was used to examine the actuator deformation. The NASTRAN finite element model was also compared with experimental results. Four groups of specimens were fabricated and tested. Four different input voltages, which included 120, 160, 200, and 240 Vp-p with a 0 volts offset, were used for this comparison.
Realization of non-linear coherent states by photonic lattices
Dehdashti, Shahram Li, Rujiang; Chen, Hongsheng; Liu, Jiarui Yu, Faxin
2015-06-15
In this paper, first, by introducing Holstein-Primakoff representation of α-deformed algebra, we achieve the associated non-linear coherent states, including su(2) and su(1, 1) coherent states. Second, by using waveguide lattices with specific coupling coefficients between neighbouring channels, we generate these non-linear coherent states. In the case of positive values of α, we indicate that the Hilbert size space is finite; therefore, we construct this coherent state with finite channels of waveguide lattices. Finally, we study the field distribution behaviours of these coherent states, by using Mandel Q parameter.
Proceedings of the Non-Linear Aero Prediction Requirements Workshop
NASA Technical Reports Server (NTRS)
Logan, Michael J. (Editor)
1994-01-01
The purpose of the Non-Linear Aero Prediction Requirements Workshop, held at NASA Langley Research Center on 8-9 Dec. 1993, was to identify and articulate requirements for non-linear aero prediction capabilities during conceptual/preliminary design. The attendees included engineers from industry, government, and academia in a variety of aerospace disciplines, such as advanced design, aerodynamic performance analysis, aero methods development, flight controls, and experimental and theoretical aerodynamics. Presentations by industry and government organizations were followed by panel discussions. This report contains copies of the presentations and the results of the panel discussions.
BEAM-BASED NON-LINEAR OPTICS CORRECTIONS IN COLLIDERS.
PILAT, R.; LUO, Y.; MALITSKY, N.; PTITSYN, V.
2005-05-16
A method has been developed to measure and correct operationally the non-linear effects of the final focusing magnets in colliders, that gives access to the effects of multi-pole errors by applying closed orbit bumps, and analyzing the resulting tune and orbit shifts. This technique has been tested and used during 4 years of RHIC (the Relativistic Heavy Ion Collider at BNL) operations. I will discuss here the theoretical basis of the method, the experimental set-up, the correction results, the present understanding of the machine model, the potential and limitations of the method itself as compared with other non-linear correction techniques.
Non-linear aeroelastic prediction for aircraft applications
NASA Astrophysics Data System (ADS)
de C. Henshaw, M. J.; Badcock, K. J.; Vio, G. A.; Allen, C. B.; Chamberlain, J.; Kaynes, I.; Dimitriadis, G.; Cooper, J. E.; Woodgate, M. A.; Rampurawala, A. M.; Jones, D.; Fenwick, C.; Gaitonde, A. L.; Taylor, N. V.; Amor, D. S.; Eccles, T. A.; Denley, C. J.
2007-05-01
Current industrial practice for the prediction and analysis of flutter relies heavily on linear methods and this has led to overly conservative design and envelope restrictions for aircraft. Although the methods have served the industry well, it is clear that for a number of reasons the inclusion of non-linearity in the mathematical and computational aeroelastic prediction tools is highly desirable. The increase in available and affordable computational resources, together with major advances in algorithms, mean that non-linear aeroelastic tools are now viable within the aircraft design and qualification environment. The Partnership for Unsteady Methods in Aerodynamics (PUMA) Defence and Aerospace Research Partnership (DARP) was sponsored in 2002 to conduct research into non-linear aeroelastic prediction methods and an academic, industry, and government consortium collaborated to address the following objectives: To develop useable methodologies to model and predict non-linear aeroelastic behaviour of complete aircraft. To evaluate the methodologies on real aircraft problems. To investigate the effect of non-linearities on aeroelastic behaviour and to determine which have the greatest effect on the flutter qualification process. These aims have been very effectively met during the course of the programme and the research outputs include: New methods available to industry for use in the flutter prediction process, together with the appropriate coaching of industry engineers. Interesting results in both linear and non-linear aeroelastics, with comprehensive comparison of methods and approaches for challenging problems. Additional embryonic techniques that, with further research, will further improve aeroelastics capability. This paper describes the methods that have been developed and how they are deployable within the industrial environment. We present a thorough review of the PUMA aeroelastics programme together with a comprehensive review of the relevant research
Chapman, Michael J; Godfrey, Keith R; Chappell, Michael J; Evans, Neil D
2003-05-01
Under certain controllability and observability restrictions, two different parameterisations for a non-linear compartmental model can only have the same input-output behaviour if they differ by a locally diffeomorphic change of basis for the state space. With further restrictions, it is possible to gain valuable information with respect to identifiability via a linear analysis. Examples are presented where non-linear identifiability analyses are substantially simplified by means of an initial linear analysis. For complex models, with four or more compartments, this linear analysis can prove lengthy to perform by hand and so symbolic computation has been employed to aid this procedure.
Characterising dynamic non-linearity in floating wind turbines
NASA Astrophysics Data System (ADS)
Lupton, R. C.
2014-12-01
Fully coupled aero-hydro-control-elastic codes are being developed to cope with the new modelling challenges presented by floating wind turbines, but there is also a place for more efficient methods of analysis. One option is linearisation and analysis in the frequency domain. For this to be an effective method, the non-linearities in the system must be well understood. The present study focusses on understanding the dynamic response of the rotor to the overall platform motion, as would arise from wave loading, by using a simple model of a floating wind turbine with a rigid tower and flexible rotor (represented by hinged rigid blades). First, an equation of motion of the blade is derived and an approximate solution for the blade response is found using the perturbation method. Secondly, the full non-linear solution is found by time- domain simulation. The response is found to be linear at lower platform pitching frequencies, becoming non-linear at higher frequencies, with the approximate solution giving good results for weakly non-linear behaviour. Higher rotor speeds have a stabilising effect on the response. In the context of typical floating turbine parameters, it is concluded that the blade flapwise response is likely to be linear.
Non-linear Langmuir waves in a warm quantum plasma
Dubinov, Alexander E. Kitaev, Ilya N.
2014-10-15
A non-linear differential equation describing the Langmuir waves in a warm quantum electron-ion plasma has been derived. Its numerical solutions of the equation show that ordinary electronic oscillations, similar to the classical oscillations, occur along with small-scale quantum Langmuir oscillations induced by the Bohm quantum force.
Non-linear duality invariant partially massless models?
Cherney, D.; Deser, S.; Waldron, A.; ...
2015-12-15
We present manifestly duality invariant, non-linear, equations of motion for maximal depth, partially massless higher spins. These are based on a first order, Maxwell-like formulation of the known partially massless systems. Lastly, our models mimic Dirac–Born–Infeld theory but it is unclear whether they are Lagrangian.
Tunneling control using classical non-linear oscillator
Kar, Susmita; Bhattacharyya, S. P.
2014-04-24
A quantum particle is placed in symmetric double well potential which is coupled to a classical non-linear oscillator via a coupling function. With different spatial symmetry of the coupling and under various controlling fashions, the tunneling of the quantum particle can be enhanced or suppressed, or totally destroyed.
Multispectral face recognition using non linear dimensionality reduction
NASA Astrophysics Data System (ADS)
Akhloufi, Moulay A.; Bendada, Abdelhakim; Batsale, Jean-Christophe
2009-05-01
Face recognition in the infrared spectrum has attracted a lot of interest in recent years. Many of the techniques used in infrared are based on their visible counterpart, especially linear techniques like PCA (Principal Component Analysis) and LDA (Linear Discriminant Analysis). In this work, we introduce non linear dimensionality reduction approaches for multispectral face recognition. For this purpose, the following techniques were developed: global non linear techniques (Kernel-PCA, Kernel-LDA) and local non linear techniques (Local Linear Embedding, Locality Preserving Projection). The performances of these techniques were compared to classical linear techniques for face recognition like PCA and LDA. Two multispectral face recognition databases were used in our experiments: Equinox Face Recognition Database and Laval University Database. Equinox database contains images in the Visible, Short, Mid and Long waves infrared spectrums. Laval database contains images in the Visible, Near, Mid and Long waves infrared spectrums with variations in time and metabolic activity of the subjects. The obtained results are interesting and show the increase in recognition performance using local non linear dimensionality reduction techniques for infrared face recognition, particularly in near and short wave infrared spectrums.
Non-linear dynamic analysis of geared systems, part 2
NASA Technical Reports Server (NTRS)
Singh, Rajendra; Houser, Donald R.; Kahraman, Ahmet
1990-01-01
A good understanding of the steady state dynamic behavior of a geared system is required in order to design reliable and quiet transmissions. This study focuses on a system containing a spur gear pair with backlash and periodically time-varying mesh stiffness, and rolling element bearings with clearance type non-linearities. A dynamic finite element model of the linear time-invariant (LTI) system is developed. Effects of several system parameters, such as torsional and transverse flexibilities of the shafts and prime mover/load inertias, on free and force vibration characteristics are investigated. Several reduced order LTI models are developed and validated by comparing their eigen solution with the finite element model results. Several key system parameters such as mean load and damping ratio are identified and their effects on the non-linear frequency response are evaluated quantitatively. Other fundamental issues such as the dynamic coupling between non-linear modes, dynamic interactions between component non-linearities and time-varying mesh stiffness, and the existence of subharmonic and chaotic solutions including routes to chaos have also been examined in depth.
Evolution equation for non-linear cosmological perturbations
Brustein, Ram; Riotto, Antonio E-mail: Antonio.Riotto@cern.ch
2011-11-01
We present a novel approach, based entirely on the gravitational potential, for studying the evolution of non-linear cosmological matter perturbations. Starting from the perturbed Einstein equations, we integrate out the non-relativistic degrees of freedom of the cosmic fluid and obtain a single closed equation for the gravitational potential. We then verify the validity of the new equation by comparing its approximate solutions to known results in the theory of non-linear cosmological perturbations. First, we show explicitly that the perturbative solution of our equation matches the standard perturbative solutions. Next, using the mean field approximation to the equation, we show that its solution reproduces in a simple way the exponential suppression of the non-linear propagator on small scales due to the velocity dispersion. Our approach can therefore reproduce the main features of the renormalized perturbation theory and (time)-renormalization group approaches to the study of non-linear cosmological perturbations, with some possibly important differences. We conclude by a preliminary discussion of the nature of the full solutions of the equation and their significance.
Using Non-Linear Statistical Methods with Laboratory Kinetic Data
NASA Technical Reports Server (NTRS)
Anicich, Vincent
1997-01-01
This paper will demonstrate the usefulness of standard non-linear statistical analysis on ICR and SIFT kinetic data. The specific systems used in the demonstration are the isotopic and change transfer reactions in the system of H2O+/D2O, H30+/D2O, and other permutations.
Direct measurement of the quartz c-axis using neutron diffraction
NASA Astrophysics Data System (ADS)
Hunter, Nicholas J. R.; Luzin, Vladimir; Wilson, Christopher J. L.
2017-08-01
Quartz c-axis pole figures are widely used across structural geology and geophysics to gain insights into crustal properties, yet their direct measurement using bulk diffraction techniques has hitherto been unsuccessful. In this contribution, we present measurements of the quartz c-axis using neutron diffraction. This has been achieved by combining advances in neutron diffraction instrumentation, high neutron fluxes and fast data acquisition, with carefully performed diffraction pattern analysis to resolve low intensity diffractions on the (003) diffraction peak hidden in the shoulder of the higher intensity (112) peak. These measurements have allowed us to assess 'recalculated' c-axis pole figures (i.e. those predicted from ODF functions) against measured c-axis pole figures, and thus assess the reliability of quartz c-axis pole figures past and present. We find that measured and recalculated pole figures are generally in good agreement in both strongly and weakly textured rocks, and that inclusion of the (003) pole figure into quartz texture analysis routines improves ODF construction.
Theory of coherent c-axis Josephson tunneling between layered superconductors
Arnold, G. B.; Klemm, R. A.
2000-07-01
We calculate exactly the Josephson current for c-axis coherent tunneling between two layered superconductors, each with internal coherent tight-binding intra- and interlayer quasiparticle dispersions. Our results also apply when one or both of the superconductors is a bulk material, and include the usually neglected effects of surface states. For weak tunneling, our results reduce to our previous results derived using the tunneling Hamiltonian. Our results are also correct for strong tunneling. However, the c-axis tunneling expressions of Tanaka and Kashiwaya are shown to be incorrect in any limit. In addition, we consider the c-axis coherent critical current between two identical layered superconductors twisted an angle {phi}{sub 0} about the c axis with respect to each other. Regardless of the order-parameter symmetry, our coherent tunneling results using a tight-binding intralayer quasiparticle dispersion are inconsistent with the recent c-axis twist bicrystal Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} twist junction experiments of Li et al. [Li et al., Phys. Rev. Lett. 83, 4160 (1999)]. (c) 2000 The American Physical Society.
Hori, Shigeo; Takatani, Yasuhiro; Kadoura, Hiroaki; Uyama, Takeshi; Fujita, Satoru; Tani, Toshihiko
2015-10-28
Highly c-axis oriented apatite-type lanthanum silicate (LSO) thin films were fabricated by a simple solution coating method. In the solution coating method, LSO thin films are obtained by crystallization of initially deposited amorphous LSO precursor thin films. The degree of orientation was influenced by the precursor morphologies and a dense LSO precursor led to a high c-axis orientation perpendicular to the substrate. The oriented LSO thin films were composed of columnar grains with a single crystal orientation over the entire film thickness. In-plane orientation was not detected, which indicates that the c-axis orientation of the LSO thin films can be attributed to self-orientation.
Non-linear Young's double-slit experiment.
San Roman, Julio; Ruiz, Camilo; Perez, Jose Antonio; Delgado, Diego; Mendez, Cruz; Plaja, Luis; Roso, Luis
2006-04-03
The Young's double slit experiment is recreated using intense and short laser pulses. Our experiment evidences the role of the non-linear Kerr effect in the formation of interference patterns. In particular, our results evidence a mixed mechanism in which the zeroth diffraction order of each slit are mainly affected by self-focusing and self-phase modulation, while the higher orders propagate linearly. Despite of the complexity of the general problem of non-linear propagation, we demonstrate that this experiment retains its simplicity and allows for a geometrical interpretation in terms of simple optical paths. In consequence, our results may provide key ideas on experiments on the formation of interference patterns with intense laser fields in Kerr media.
Minimax Techniques For Optimizing Non-Linear Image Algebra Transforms
NASA Astrophysics Data System (ADS)
Davidson, Jennifer L.
1989-08-01
It has been well established that the Air Force Armament Technical Laboratory (AFATL) image algebra is capable of expressing all linear transformations [7]. The embedding of the linear algebra in the image algebra makes this possible. In this paper we show a relation of the image algebra to another algebraic system called the minimax algebra. This system is used extensively in economics and operations research, but until now has not been investigated for applications to image processing. The relationship is exploited to develop new optimization methods for a class of non-linear image processing transforms. In particular, a general decomposition technique for templates in this non-linear domain is presented. Template decomposition techniques are an important tool in mapping algorithms efficiently to both sequential and massively parallel architectures.
Non-linear effects in bunch compressor of TARLA
Yildiz, Hüseyin E-mail: huseyinyildiz@gazi.edu.tr; Aksoy, Avni; Arikan, Pervin
2016-03-25
Transport of a beam through an accelerator beamline is affected by high order and non-linear effects such as space charge, coherent synchrotron radiation, wakefield, etc. These effects damage form of the beam, and they lead particle loss, emittance growth, bunch length variation, beam halo formation, etc. One of the known non-linear effects on low energy machine is space charge effect. In this study we focus on space charge effect for Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) machine which is designed to drive InfraRed Free Electron Laser covering the range of 3-250 µm. Moreover, we discuss second order effects on bunch compressor of TARLA.
Non-linear Poisson-Boltzmann theory for swollen clays
NASA Astrophysics Data System (ADS)
Leote de Carvalho, R. J. F.; Trizac, E.; Hansen, J.-P.
1998-08-01
The non-linear Poisson-Boltzmann (PB) equation for a circular, uniformly char ged platelet, confined together with co- and counter-ions to a cylindrical cell, is solved semi-analytically by transforming it into an integral equation and solving the latter iteratively. This method proves efficient and robust, and can be readily generalized to other problems based on cell models, treated within non-linear Poisson-like theory. The solution to the PB equation is computed over a wide range of physical conditions, and the resulting osmotic equation of state is shown to be in semi-quantitative agreement with recent experimental data for Laponite clay suspensions, in the concentrated gel phase.
SSNN toolbox for non-linear system identification
NASA Astrophysics Data System (ADS)
Luzar, Marcel; Czajkowski, Andrzej
2015-11-01
The aim of this paper is to develop and design a State Space Neural Network toolbox for a non-linear system identification with an artificial state-space neural networks, which can be used in a model-based robust fault diagnosis and control. Such toolbox is implemented in the MATLAB environment and it uses some of its predefined functions. It is designed in the way that any non-linear multi-input multi-output system is identified and represented in the classical state-space form. The novelty of the proposed approach is that the final result of the identification process is the state, input and output matrices, not only the neural network parameters. Moreover, the toolbox is equipped with the graphical user interface, which makes it useful for the users not familiar with the neural networks theory.
New non-linear photovoltaic effect in uniform bipolar semiconductor
Volovichev, I.
2014-11-21
A linear theory of the new non-linear photovoltaic effect in the closed circuit consisting of a non-uniformly illuminated uniform bipolar semiconductor with neutral impurities is developed. The non-uniform photo-excitation of impurities results in the position-dependant current carrier mobility that breaks the semiconductor homogeneity and induces the photo-electromotive force (emf). As both the electron (or hole) mobility gradient and the current carrier generation rate depend on the light intensity, the photo-emf and the short-circuit current prove to be non-linear functions of the incident light intensity at an arbitrarily low illumination. The influence of the sample size on the photovoltaic effect magnitude is studied. Physical relations and distinctions between the considered effect and the Dember and bulk photovoltaic effects are also discussed.
Cosmological non-linearities as an effective fluid
Baumann, Daniel; Senatore, Leonardo; Zaldarriaga, Matias; Nicolis, Alberto E-mail: nicolis@phys.columbia.edu E-mail: matiasz@ias.edu
2012-07-01
The universe is smooth on large scales but very inhomogeneous on small scales. Why is the spacetime on large scales modeled to a good approximation by the Friedmann equations? Are we sure that small-scale non-linearities do not induce a large backreaction? Related to this, what is the effective theory that describes the universe on large scales? In this paper we make progress in addressing these questions. We show that the effective theory for the long-wavelength universe behaves as a viscous fluid coupled to gravity: integrating out short-wavelength perturbations renormalizes the homogeneous background and introduces dissipative dynamics into the evolution of long-wavelength perturbations. The effective fluid has small perturbations and is characterized by a few parameters like an equation of state, a sound speed and a viscosity parameter. These parameters can be matched to numerical simulations or fitted from observations. We find that the backreaction of small-scale non-linearities is very small, being suppressed by the large hierarchy between the scale of non-linearities and the horizon scale. The effective pressure of the fluid is always positive and much too small to significantly affect the background evolution. Moreover, we prove that virialized scales decouple completely from the large-scale dynamics, at all orders in the post-Newtonian expansion. We propose that our effective theory be used to formulate a well-defined and controlled alternative to conventional perturbation theory, and we discuss possible observational applications. Finally, our way of reformulating results in second-order perturbation theory in terms of a long-wavelength effective fluid provides the opportunity to understand non-linear effects in a simple and physically intuitive way.
NON-LINEAR MODELING OF THE RHIC INTERACTION REGIONS.
TOMAS,R.FISCHER,W.JAIN,A.LUO,Y.PILAT,F.
2004-07-05
For RHIC's collision lattices the dominant sources of transverse non-linearities are located in the interaction regions. The field quality is available for most of the magnets in the interaction regions from the magnetic measurements, or from extrapolations of these measurements. We discuss the implementation of these measurements in the MADX models of the Blue and the Yellow rings and their impact on beam stability.
Non-Linear Dynamics and Emergence in Laboratory Fusion Plasmas
Hnat, B.
2011-09-22
Turbulent behaviour of laboratory fusion plasma system is modelled using extended Hasegawa-Wakatani equations. The model is solved numerically using finite difference techniques. We discuss non-linear effects in such a system in the presence of the micro-instabilities, specifically a drift wave instability. We explore particle dynamics in different range of parameters and show that the transport changes from diffusive to non-diffusive when large directional flows are developed.
Linear Algebraic Method for Non-Linear Map Analysis
Yu,L.; Nash, B.
2009-05-04
We present a newly developed method to analyze some non-linear dynamics problems such as the Henon map using a matrix analysis method from linear algebra. Choosing the Henon map as an example, we analyze the spectral structure, the tune-amplitude dependence, the variation of tune and amplitude during the particle motion, etc., using the method of Jordan decomposition which is widely used in conventional linear algebra.
Non-linear stochastic growth rates and redshift space distortions
Jennings, Elise; Jennings, David
2015-04-09
The linear growth rate is commonly defined through a simple deterministic relation between the velocity divergence and the matter overdensity in the linear regime. We introduce a formalism that extends this to a non-linear, stochastic relation between θ = ∇ ∙ v(x,t)/aH and δ. This provides a new phenomenological approach that examines the conditional mean <θ|δ>, together with the fluctuations of θ around this mean. We also measure these stochastic components using N-body simulations and find they are non-negative and increase with decreasing scale from ~10 per cent at k < 0.2 h Mpc^{-1} to 25 per cent at k ~ 0.45 h Mpc^{-1} at z = 0. Both the stochastic relation and non-linearity are more pronounced for haloes, M ≤ 5 × 10^{12} M_{⊙} h^{-1}, compared to the dark matter at z = 0 and 1. Non-linear growth effects manifest themselves as a rotation of the mean <θ|δ> away from the linear theory prediction -f_{LT}δ, where f_{LT }is the linear growth rate. This rotation increases with wavenumber, k, and we show that it can be well-described by second-order Lagrangian perturbation theory (2LPT) fork < 0.1 h Mpc^{-1}. Furthermore, the stochasticity in the θ – δ relation is not so simply described by 2LPT, and we discuss its impact on measurements of f_{LT} from two-point statistics in redshift space. Furthermore, given that the relationship between δ and θ is stochastic and non-linear, this will have implications for the interpretation and precision of f_{LT} extracted using models which assume a linear, deterministic expression.
Non-linear stochastic growth rates and redshift space distortions
Jennings, Elise; Jennings, David
2015-04-09
The linear growth rate is commonly defined through a simple deterministic relation between the velocity divergence and the matter overdensity in the linear regime. We introduce a formalism that extends this to a non-linear, stochastic relation between θ = ∇ ∙ v(x,t)/aH and δ. This provides a new phenomenological approach that examines the conditional mean <θ|δ>, together with the fluctuations of θ around this mean. We also measure these stochastic components using N-body simulations and find they are non-negative and increase with decreasing scale from ~10 per cent at k < 0.2 h Mpc-1 to 25 per cent at kmore » ~ 0.45 h Mpc-1 at z = 0. Both the stochastic relation and non-linearity are more pronounced for haloes, M ≤ 5 × 1012 M⊙ h-1, compared to the dark matter at z = 0 and 1. Non-linear growth effects manifest themselves as a rotation of the mean <θ|δ> away from the linear theory prediction -fLTδ, where fLT is the linear growth rate. This rotation increases with wavenumber, k, and we show that it can be well-described by second-order Lagrangian perturbation theory (2LPT) fork < 0.1 h Mpc-1. Furthermore, the stochasticity in the θ – δ relation is not so simply described by 2LPT, and we discuss its impact on measurements of fLT from two-point statistics in redshift space. Furthermore, given that the relationship between δ and θ is stochastic and non-linear, this will have implications for the interpretation and precision of fLT extracted using models which assume a linear, deterministic expression.« less
Non-linear power spectra in the synchronous gauge
Hwang, Jai-chan; Noh, Hyerim; Jeong, Donghui; Gong, Jinn-Ouk; Biern, Sang Gyu E-mail: hr@kasi.re.kr E-mail: jinn-ouk.gong@apctp.org
2015-05-01
We study the non-linear corrections to the matter and velocity power spectra in the synchronous gauge (SG). For the leading correction to the non-linear power spectra, we consider the perturbations up to third order in a zero-pressure fluid in a flat cosmological background. Although the equations in the SG happen to coincide with those in the comoving gauge (CG) to linear order, they differ from second order. In particular, the second order hydrodynamic equations in the SG are apparently in the Lagrangian form, whereas those in the CG are in the Eulerian form. The non-linear power spectra naively presented in the original SG show rather pathological behavior quite different from the result of the Newtonian theory even on sub-horizon scales. We show that the pathology in the nonlinear power spectra is due to the absence of the convective terms in, thus the Lagrangian nature of, the SG. We show that there are many different ways of introducing the corrective convective terms in the SG equations. However, the convective terms (Eulerian modification) can be introduced only through gauge transformations to other gauges which should be the same as the CG to the second order. In our previous works we have shown that the density and velocity perturbation equations in the CG exactly coincide with the Newtonian equations to the second order, and the pure general relativistic correction terms starting to appear from the third order are substantially suppressed compared with the relativistic/Newtonian terms in the power spectra. As a result, we conclude that the SG per se is an inappropriate coordinate choice in handling the non-linear matter and velocity power spectra of the large-scale structure where observations meet with theories.
Non-linear characteristics of Rayleigh-Taylor instable perturbations
NASA Astrophysics Data System (ADS)
Fan, Zhengfeng; Luo, Jisheng
2008-04-01
The direct numerical simulation method is adopted to study the non-linear characteristics of Rayleigh-Taylor instable perturbations at the ablation front of a 200 μm planar CH ablation target. In the simulation, the classical electrical thermal conductivity is included, and NND difference scheme is used. The linear growth rates obtained from the simulation agree with the Takabe formula. The amplitude distribution of the density perturbation at the ablation front is obtained for the linear growth case. The non-linear characteristics of Rayleigh-Taylor instable perturbations are analyzed and the numerical results show that the amplitude distributions of the compulsive harmonics are very different from that of the fundamental perturbation. The characteristics of the amplitude distributions of the harmonics and their fast growth explain why spikes occur at the ablation front. The numerical results also show that non-linear effects have relations with the phase differences of double mode initial perturbations, and different phase differences lead to varied spikes.
Non-linear Oscillations of Compact Stars and Gravitational Waves
NASA Astrophysics Data System (ADS)
Passamonti, Andrea
2006-07-01
This thesis investigates in the time domain a particular class of second order perturbations of a perfect fluid non-rotating compact star: those arising from the coupling between first order radial and non-radial perturbations. This problem has been treated by developing a gauge invariant formalism based on the 2-parameter perturbation theory (Sopuerta, Bruni and Gualtieri, 2004) where the radial and non-radial perturbations have been separately parameterized. The non-linear perturbations obey inhomogeneous partial differential equations, where the structure of the differential operator is given by the previous perturbative orders and the source terms are quadratic in the first order perturbations. In the exterior spacetime the sources vanish, thus the gravitational wave properties are completely described by the second order Zerilli and Regge-Wheeler functions. As main initial configuration we have considered a first order differentially rotating and radially pulsating star. Although at first perturbative order this configuration does not exhibit any gravitational radiation, we have found a new interesting gravitational signal at non-linear order, in which the radial normal modes are precisely mirrored. In addition, a resonance effect is present when the frequencies of the radial pulsations are close to the first axial w-mode. Finally, we have roughly estimated the damping times of the radial pulsations due to the non-linear gravitational emission. The coupling near the resonance results to be a very effective mechanism for extracting energy from the radial oscillations.
Non-linear dynamic analysis of beams with variable stiffness
NASA Astrophysics Data System (ADS)
Katsikadelis, J. T.; Tsiatas, G. C.
2004-03-01
In this paper the analog equation method (AEM), a BEM-based method, is employed to the non-linear dynamic analysis of a Bernoulli-Euler beam with variable stiffness undergoing large deflections, under general boundary conditions which maybe non-linear. As the cross-sectional properties of the beam vary along its axis, the coefficients of the differential equations governing the dynamic equilibrium of the beam are variable. The formulation is in terms of the displacements. The governing equations are derived in both deformed and undeformed configuration and the deviations of the two approaches are studied. Using the concept of the analog equation, the two coupled non-linear hyperbolic differential equations with variable coefficients are replaced by two uncoupled linear ones pertaining to the axial and transverse deformation of a substitute beam with unit axial and bending stiffness, respectively, under fictitious time-dependent load distributions. A significant advantage of this method is that the time history of the displacements as well as the stress resultants are computed at any cross-section of the beam using the respective integral representations as mathematical formulae. Beams with constant and varying stiffness are analyzed under various boundary conditions and loadings to illustrate the merits of the method as well as its applicability, efficiency and accuracy.
Non-linear viscoelastic behavior of abdominal aortic aneurysm thrombus.
van Dam, Evelyne A; Dams, Susanne D; Peters, Gerrit W M; Rutten, Marcel C M; Schurink, Geert Willem H; Buth, Jaap; van de Vosse, Frans N
2008-04-01
The objective of this work was to determine the linear and non-linear viscoelastic behavior of abdominal aortic aneurysm thrombus and to study the changes in mechanical properties throughout the thickness of the thrombus. Samples are gathered from thrombi of seven patients. Linear viscoelastic data from oscillatory shear experiments show that the change of properties throughout the thrombus is different for each thrombus. Furthermore the variations found within one thrombus are of the same order of magnitude as the variation between patients. To study the non-linear regime, stress relaxation experiments are performed. To describe the phenomena observed experimentally, a non-linear multimode model is presented. The parameters for this model are obtained by fitting this model successfully to the experiments. The model cannot only describe the average stress response for all thrombus samples but also the highest and lowest stress responses. To determine the influence on the wall stress of the behavior observed the model proposed needs to implemented in the finite element wall stress analysis.
Can the Non-linear Ballooning Model describe ELMs?
NASA Astrophysics Data System (ADS)
Henneberg, S. A.; Cowley, S. C.; Wilson, H. R.
2015-11-01
The explosive, filamentary plasma eruptions described by the non-linear ideal MHD ballooning model is tested quantitatively against experimental observations of ELMs in MAST. The equations describing this model were derived by Wilson and Cowley for tokamak-like geometry which includes two differential equations: the linear ballooning equation which describes the spatial distribution along the field lines and the non-linear ballooning mode envelope equation, which is a two-dimensional, non-linear differential equation which can involve fractional temporal-derivatives, but is often second-order in time and space. To employ the second differential equation for a specific geometry one has to evaluate the coefficients of the equation which is non-trivial as it involves field line averaging of slowly converging functions. We have solved this system for MAST, superimposing the solutions of both differential equations and mapping them onto a MAST plasma. Comparisons with the evolution of ELM filaments in MAST will be reported in order to test the model. The support of the EPSRC for the FCDT (Grant EP/K504178/1), of Euratom research and training programme 2014-2018 (No 633053) and of the RCUK Energy Programme [grant number EP/I501045] is gratefully acknowledged.
A multi-scale non-linear vessel enhancement technique.
Abdollahi, Behnaz; El-Baz, Ayman; Amini, Amir A
2011-01-01
We present an enhancement method based on nonlinear diffusion filter and statistical intensity approaches for smoothing and extracting 3-D vascular system from Magnetic Resonance Angiography (MRA) data. Our method distinguishes and enhances the vessels from the other embedded tissues. The Expectation Maximization (EM) technique is employed with non-linear diffusion in order to find the optimal contrast for enhancing vessels; therefore, smoothing while dimming the embedded tissues around the vessels and brightening the vessels. The non-linear diffusion filter smooths the homogeneous regions while preserving edges. The EM technique finds the optimal statistical parameters based on the probability distribution of the classes to discriminate the tissues in the image. Our enhancement technique has been applied to 4 3-D MRA-TOF datasets consisting of around 300 images and has been compared to the regularized Perona and Malik filter. Our experimental results show that the proposed method enhances the image, keeping only the vessels while eliminating the signal from other tissues. In comparison, the conventional non-linear diffusion filter keeps unwanted tissues in addition to the vessels.
Validation of a non-linear model of health.
Topolski, Stefan; Sturmberg, Joachim
2014-12-01
The purpose of this study was to evaluate the veracity of a theoretically derived model of health that describes a non-linear trajectory of health from birth to death with available population data sets. The distribution of mortality by age is directly related to health at that age, thus health approximates 1/mortality. The inverse of available all-cause mortality data from various time periods and populations was used as proxy data to compare with the theoretically derived non-linear health model predictions, using both qualitative approaches and quantitative one-sample Kolmogorov-Smirnov analysis with Monte Carlo simulation. The mortality data's inverse resembles a log-normal distribution as predicted by the proposed health model. The curves have identical slopes from birth and follow a logarithmic decline from peak health in young adulthood. A majority of the sampled populations had a good to excellent quantitative fit to a log-normal distribution, supporting the underlying model assumptions. Post hoc manipulation showed the model predictions to be stable. This is a first theory of health to be validated by proxy data, namely the inverse of all-cause mortality. This non-linear model, derived from the notion of the interaction of physical, environmental, mental, emotional, social and sense-making domains of health, gives physicians a more rigorous basis to direct health care services and resources away from disease-focused elder care towards broad-based biopsychosocial interventions earlier in life. © 2014 John Wiley & Sons, Ltd.
Non-linear curve fitting using Microsoft Excel solver.
Walsh, S; Diamond, D
1995-04-01
Solver, an analysis tool incorporated into Microsoft Excel V 5.0 for Windows, has been evaluated for solving non-linear equations. Test and experimental data sets have been processed, and the results suggest that solver can be successfully used for modelling data obtained in many analytical situations (e.g. chromatography and FIA peaks, fluorescence decays and ISE response characteristics). The relatively simple user interface, and the fact that Excel is commonly bundled free with new PCs makes it an ideal tool for those wishing to experiment with solving non-linear equations without having to purchase and learn a completely new package. The dynamic display of the iterative search process enables the user to monitor location of the optimum solution by the search algorithm. This, together with the almost universal availability of Excel, makes solver an ideal vehicle for teaching the principles of iterative non-linear curve fitting techniques. In addition, complete control of the modelling process lies with the user, who must present the raw data and enter the equation of the model, in contrast to many commercial packages bundled with instruments which perform these operations with a 'black-box' approach.
Non-linearities in Holocene floodplain sediment storage
NASA Astrophysics Data System (ADS)
Notebaert, Bastiaan; Nils, Broothaerts; Jean-François, Berger; Gert, Verstraeten
2013-04-01
Floodplain sediment storage is an important part of the sediment cascade model, buffering sediment delivery between hillslopes and oceans, which is hitherto not fully quantified in contrast to other global sediment budget components. Quantification and dating of floodplain sediment storage is data and financially demanding, limiting contemporary estimates for larger spatial units to simple linear extrapolations from a number of smaller catchments. In this paper we will present non-linearities in both space and time for floodplain sediment budgets in three different catchments. Holocene floodplain sediments of the Dijle catchment in the Belgian loess region, show a clear distinction between morphological stages: early Holocene peat accumulation, followed by mineral floodplain aggradation from the start of the agricultural period on. Contrary to previous assumptions, detailed dating of this morphological change at different shows an important non-linearity in geomorphologic changes of the floodplain, both between and within cross sections. A second example comes from the Pre-Alpine French Valdaine region, where non-linearities and complex system behavior exists between (temporal) patterns of soil erosion and floodplain sediment deposition. In this region Holocene floodplain deposition is characterized by different cut-and-fill phases. The quantification of these different phases shows a complicated image of increasing and decreasing floodplain sediment storage, which hampers the image of increasing sediment accumulation over time. Although fill stages may correspond with large quantities of deposited sediment and traditionally calculated sedimentation rates for such stages are high, they do not necessary correspond with a long-term net increase in floodplain deposition. A third example is based on the floodplain sediment storage in the Amblève catchment, located in the Belgian Ardennes uplands. Detailed floodplain sediment quantification for this catchments shows
Long-term cavity closure in non-linear rocks
NASA Astrophysics Data System (ADS)
Cornet, Jan; Dabrowski, Marcin; Schmid, Daniel Walter
2017-08-01
The time dependent closure of pressurized cavities in viscous rocks due to far-field loads is a problem encountered in many applications like drilling, cavity abandonment and porosity closure. The non-linear nature of the flow of rocks prevents the use of simple solutions for hole closure and calls for the development of appropriate expressions reproducing all the dependencies observed in nature. An approximate solution is presented for the closure velocity of a pressurized cylindrical cavity in a non-linear viscous medium subjected to a combined pressure and shear stress load in the far field. The embedding medium is treated as homogeneous, isotropic, and incompressible and follows a Carreau viscosity model. We derive analytical solutions for the end-member cases of the pressure and shear loads. The exact analytical solution for pressure loads shows that the closure velocity vR is given by the implicit expression {Δ p}/{2{μ _0D_{II}^*}} = - 1/2B( {v_R^2}/{RD_{II^* + v_R^2}};1/2, - 1/{2n}} ), where Δp is the pressure load, R is the hole radius, B is the incomplete beta function, and μ0, D_{II}^*, n are, respectively, the threshold viscosity, transition rate and stress exponent of the Carreau model. The closure velocity is dominated by the linear mechanism under pressure loads smaller than 1.8{μ _0}D_{II}^* and by the non-linear one under large pressure loads. In the non-linear regime, pressure variations support an increasing part of the load with increasing degree of non-linearity. The decay of the stress perturbation in the non-linear zone varies as r- 2/n where r is the radial distance to the hole. A solution for the maximum closure velocity at the cavity rim vRmax under far-field shear is given: v_{R\\max} = ( {1 + {\\overline {M_s}}^{-1/2})R\\overline D_{II}, where \\overline M_s = (1 +{\\overline{D_{II}}^2} \\big nD_{II}^*^2} ) \\big ( 1 + {\\overline {D_{II}}^2} \\big D{_{II}^*}^2 ) and \\overline D_{II} is the second invariant of the far
NASA Astrophysics Data System (ADS)
Sasaki, Misao; Wands, David
2010-06-01
In recent years there has been a resurgence of interest in the study of non-linear perturbations of cosmological models. This has been the result of both theoretical developments and observational advances. New theoretical challenges arise at second and higher order due to mode coupling and the need to develop new gauge-invariant variables beyond first order. In particular, non-linear interactions lead to deviations from a Gaussian distribution of primordial perturbations even if initial vacuum fluctuations are exactly Gaussian. These non-Gaussianities provide an important probe of models for the origin of structure in the very early universe. We now have a detailed picture of the primordial distribution of matter from surveys of the cosmic microwave background, notably NASA's WMAP satellite. The situation will continue to improve with future data from the ESA Planck satellite launched in 2009. To fully exploit these data cosmologists need to extend non-linear cosmological perturbation theory beyond the linear theory that has previously been sufficient on cosmological scales. Another recent development has been the realization that large-scale structure, revealed in high-redshift galaxy surveys, could also be sensitive to non-linearities in the primordial curvature perturbation. This focus section brings together a collection of invited papers which explore several topical issues in this subject. We hope it will be of interest to theoretical physicists and astrophysicists alike interested in understanding and interpreting recent developments in cosmological perturbation theory and models of the early universe. Of course it is only an incomplete snapshot of a rapidly developing field and we hope the reader will be inspired to read further work on the subject and, perhaps, fill in some of the missing pieces. This focus section is dedicated to the memory of Lev Kofman (1957-2009), an enthusiastic pioneer of inflationary cosmology and non-Gaussian perturbations.
Effect of strain along C-axis NbS{sub 2}
Singh, Tapender Kumar, Jagdish Sastri, O. S. K. S.
2015-05-15
We have studied electronic properties of double layered hexagonal structure of the Niobium Di-Sulphide (2H-NbS{sub 2}) superconductor for various strains introduced along the c-axis using ab-initio calculations. The DFT calculations based on Full Potential Linearized Augmented Plane Wave (FPLAPW) method are performed using the ELK code. The total energy curve (E vs a), Density of States (DOS) and the Band structure calculations obtained in this work are matching with the earlier reports. The Pressure-Volume (P-V) diagram for 2H-NbS{sub 2} was obtained using the Equation of State(EOS) calculations, which provides the relationship between the pressure and strain applied along the c-axis. The band structures for various strains ranging from 0 percent to 10 percent along c-axis in steps of 2 percent are obtained. We note that there are increasing number of bands crossing over the Fermi energy level with increase in strain. Thus, we conclude that with increasing strain along c-axis, number of conduction bands crossing the E{sub F} increases, which gives rise to more conduction states and hence higher conductivity.
Effect of strain along C-axis NbS2
NASA Astrophysics Data System (ADS)
Singh, Tapender; Kumar, Jagdish; Sastri, O. S. K. S.
2015-05-01
We have studied electronic properties of double layered hexagonal structure of the Niobium Di-Sulphide (2H-NbS2) superconductor for various strains introduced along the c-axis using ab-initio calculations. The DFT calculations based on Full Potential Linearized Augmented Plane Wave (FPLAPW) method are performed using the ELK code. The total energy curve (E vs a), Density of States (DOS) and the Band structure calculations obtained in this work are matching with the earlier reports. The Pressure-Volume (P-V) diagram for 2H-NbS2 was obtained using the Equation of State(EOS) calculations, which provides the relationship between the pressure and strain applied along the c-axis. The band structures for various strains ranging from 0 percent to 10 percent along c-axis in steps of 2 percent are obtained. We note that there are increasing number of bands crossing over the Fermi energy level with increase in strain. Thus, we conclude that with increasing strain along c-axis, number of conduction bands crossing the EF increases, which gives rise to more conduction states and hence higher conductivity.
Vapor-phase growth of transparent zinc oxide ceramics with c -axis orientation
Noritake, F.; Yamamoto, N.; Horiguchi, Y. ); Fujitsu, S.; Koumoto, K. ); Yanagida, H. )
1991-01-01
Large transparent specimens of polycrystalline zinc oxide with c-axis orientation have been prepared by the vapor transport method. Optical transmittance is 80% to 90% at 800 nm. X-ray diffraction peaks from faces other than (001) are negligible.
Spherulitic (c-axis) Growth for Terrestrial (Mauna Kea, Hawaii) and Martian Hematite "blueberries"
NASA Technical Reports Server (NTRS)
Golden, D. C.; Ming, D. W.; Morris, R. V.
2006-01-01
Hematite concentrations observed by Thermal Emission Spectrometer (TES) onboard Mars Global Surveyor were considered a possible indicator for aqueous processes on Mars. Observations made by Opportunity show that the hematite at Meridiani Planum is present as spherules ( blueberries) and their fragments. The internal structure of the hematite spherules is not discernable at the resolution limit (approx.30 m/pixel) of Opportunity s Microscopic Imager (MI). A terrestrial analog for martian hematite spherules are spherules from hydrothermally altered and sulfate-rich tephra from the summit region of Mauna Kea volcano, Hawaii. The objective of this study is to determine the crystal growth fabric of the Mauna Kea hematite spherules using transmission electron microscopy (TEM) techniques and to relate that crystalline fabric to the observed TES signature of Meridiani Planum "blueberries." TEM analysis of Mauna Kea spherules exhibited a radial growth pattern consisting of "fibrous" hematite with the c-axis of hematite particles aligned along the elongation direction of the hematite fibers. The individual fibers appear to be made of coalesced nano-particles of hematite arranged with their c-axis oriented radially to form a spherical structure. Lattice fringes suggest long-range order across particles and along fibers. According to interpretations of thermal emission spectra for Meridian Planum hematite, the absence of a band at approx. 390/cm implies a geometry where c-face emission dominates. Because the c-face is perpendicular to the c-axis, this is precisely the geometry for the Mauna Kea spherules because the c-axis is aligned parallel to their radial growth direction. Therefore, we conclude as a working hypothesis that the martian spherules also have radial, c-axis growth pattern on a scale that is too small to be detected by the MER MI. Furthermore, by analogy with the Mauna Kea spherules, the martian blueberries could have formed during hydrothermal alteration of
In-plane and c-axis optical spectroscopy study on 122 Fe-pnictides
NASA Astrophysics Data System (ADS)
Wang, Nan Lin
2011-03-01
I present the in-plane and the c-axis optical spectroscopy investigations on 122 Fe-pnictides. For the parent compound BaFe 2 As 2 , the in-plane measurement revealed two different energy gaps in the SDW state, whereas for the c-axis polarized measurement only the energy gap at smaller energy scale could be clearly observed. We suggest different driving mechanisms for the formation of the two energy gaps. The large energy gap is caused by the nesting between disconnected 2D cylinder-like electron and hole Fermi surfaces. It is the main driving force for the SDW instability. The small energy gap is the one formed on the 3D Fermi surface due to the presence of reduced magnetic Brillouin zone which crosses the 3D Fermi surface. It is the consequence of the establishment of the magnetic order. For the doped superconducting 122 samples, the in-plane optical measurement revealed a formation of full superconducting energy gap, whereas the c-axis optical measurement indicated a large residual quasiparticle population down to very low temperature. Those quasiparticles contribute specifically to the c-axis transport. We suggest that there exist horizontal nodes in the superconducting gap in regions of the 3D Fermi surface that contribute dominantly to the c-axis optical conductivity. Work done with Z. G. Chen, W. Z. Hu, B. Cheng, G. Li, J. Dong, T. Dong, R. H. Yuan, P. Zheng, G. F. Chen, J. L. Luo, Z. Fang, X. Dai, C. L. Zhang and P. Dai.
Global non-linear effect of temperature on economic production
NASA Astrophysics Data System (ADS)
Burke, Marshall; Hsiang, Solomon M.; Miguel, Edward
2015-11-01
Growing evidence demonstrates that climatic conditions can have a profound impact on the functioning of modern human societies, but effects on economic activity appear inconsistent. Fundamental productive elements of modern economies, such as workers and crops, exhibit highly non-linear responses to local temperature even in wealthy countries. In contrast, aggregate macroeconomic productivity of entire wealthy countries is reported not to respond to temperature, while poor countries respond only linearly. Resolving this conflict between micro and macro observations is critical to understanding the role of wealth in coupled human-natural systems and to anticipating the global impact of climate change. Here we unify these seemingly contradictory results by accounting for non-linearity at the macro scale. We show that overall economic productivity is non-linear in temperature for all countries, with productivity peaking at an annual average temperature of 13 °C and declining strongly at higher temperatures. The relationship is globally generalizable, unchanged since 1960, and apparent for agricultural and non-agricultural activity in both rich and poor countries. These results provide the first evidence that economic activity in all regions is coupled to the global climate and establish a new empirical foundation for modelling economic loss in response to climate change, with important implications. If future adaptation mimics past adaptation, unmitigated warming is expected to reshape the global economy by reducing average global incomes roughly 23% by 2100 and widening global income inequality, relative to scenarios without climate change. In contrast to prior estimates, expected global losses are approximately linear in global mean temperature, with median losses many times larger than leading models indicate.
Global non-linear effect of temperature on economic production.
Burke, Marshall; Hsiang, Solomon M; Miguel, Edward
2015-11-12
Growing evidence demonstrates that climatic conditions can have a profound impact on the functioning of modern human societies, but effects on economic activity appear inconsistent. Fundamental productive elements of modern economies, such as workers and crops, exhibit highly non-linear responses to local temperature even in wealthy countries. In contrast, aggregate macroeconomic productivity of entire wealthy countries is reported not to respond to temperature, while poor countries respond only linearly. Resolving this conflict between micro and macro observations is critical to understanding the role of wealth in coupled human-natural systems and to anticipating the global impact of climate change. Here we unify these seemingly contradictory results by accounting for non-linearity at the macro scale. We show that overall economic productivity is non-linear in temperature for all countries, with productivity peaking at an annual average temperature of 13 °C and declining strongly at higher temperatures. The relationship is globally generalizable, unchanged since 1960, and apparent for agricultural and non-agricultural activity in both rich and poor countries. These results provide the first evidence that economic activity in all regions is coupled to the global climate and establish a new empirical foundation for modelling economic loss in response to climate change, with important implications. If future adaptation mimics past adaptation, unmitigated warming is expected to reshape the global economy by reducing average global incomes roughly 23% by 2100 and widening global income inequality, relative to scenarios without climate change. In contrast to prior estimates, expected global losses are approximately linear in global mean temperature, with median losses many times larger than leading models indicate.
Non-linear structure in modified action theories of gravity
NASA Astrophysics Data System (ADS)
Lima, Marcos V.
We study the effects and carry out a suite of cosmological simulations of modified action f(R) models where cosmic acceleration arises from an alteration of gravity instead of dark energy. These models introduce an extra scalar degree of freedom which enhances the force of gravity below the Compton scale of the scalar. The simulations exhibit the so-called chameleon mechanism, necessary for satisfying local constraints on gravity, where this scale depends on environment, in particular the depth of the local gravitational potential. We find that the chameleon mechanism can substantially suppress the enhancement of power spectrum in the non-linear regime if the background field value is comparable to or smaller than the depth of the gravitational potentials of typical structures. Nonetheless power spectrum enhancements at intermediate scales remain at a measurable level even when the expansion history is indistinguishable from a cosmological constant, cold dark matter model. We also investigate the effects of the modified dynamics on halo properties such as their abundance and clustering. We find that the f(R) effects on the halo mass- function and bias depend mostly on the linear power spectrum modifications, but that the chameleon mechanism suppresses the modifications at high-mass halos with deep potential wells. The f(R) modifications also affect the threshold density for collapse, or similarly the overdensity for virialization and therefore can change halo definitions from those of ACDM. As a result, simple scaling relations that take the linear matter power spectrum into a non-linear spectrum fail to capture the modifications of f(R) due to the change in collapsed structures, the chameleon mechanism, and the time evolution of the modifications. A quantification of these effects, including modifications on halo profiles, is necessary to accurately describe halo properties and potentially construct a halo model of the non-linear power spectrum.
A non-linear UAV altitude PSO-PD control
NASA Astrophysics Data System (ADS)
Orlando, Calogero
2015-12-01
In this work, a nonlinear model based approach is presented for the altitude stabilization of a hexarotor unmanned aerial vehicle (UAV). The mathematical model and control of the hexacopter airframe is presented. To stabilize the system along the vertical direction, a Proportional Derivative (PD) control is taken into account. A particle swarm optimization (PSO) approach is used in this paper to select the optimal parameters of the control algorithm taking into account different objective functions. Simulation sets are performed to carry out the results for the non-linear system to show how the PSO tuned PD controller leads to zero the error of the position along Z earth direction.
Disorder and Quantum Chromodynamics -- Non-Linear σ Models
NASA Astrophysics Data System (ADS)
Guhr, Thomas; Wilke, Thomas
2001-10-01
The statistical properties of Quantum Chromodynamics (QCD) show universal features which can be modeled by random matrices. This has been established in detailed analyses of data from lattice gauge calculations. Moreover, systematic deviations were found which link QCD to disordered systems in condensed matter physics. To furnish these empirical findings with analytical arguments, we apply and extend the methods developed in disordered systems to construct a non-linear σ model for the spectral correlations in QCD. Our goal is to derive connections to other low-energy effective theories, such as the Nambu-Jona-Lasinio model, and to chiral perturbation theory.
Disorder and Quantum Chromodynamics - Non-Linear σ Models
NASA Astrophysics Data System (ADS)
Guhr, Thomas; Wilke, Thomas
The statistical properties of Quantum Chromodynamics (QCD) show universal features which can be modeled by random matrices. This has been established in detailed analyses of data from lattice gauge calculations. Moreover, systematic deviations were found which link QCD to disordered systems in condensed matter physics. To furnish these empirical findings with analytical arguments, we apply and extend the methods developed in disordered systems to construct a non-linear σ model for the spectral correlations in QCD. Our goal is to derive connections to other low-energy effective theories, such as the Nambu-Jona-Lasinio model, and to chiral perturbation theory.
New Exact Solutions in Non-Linear Elasticity.
1984-01-01
possibility of an infinity of exact solutions. AMS (MOS) Subject Classification: 73C99 Key Words: Neo-Hookean material, Mooney - Rivlin material, stored...the case of a neo-Hookean and Mooney - Rivlin material. They also studied the consequence of the non-linearly elastic material being characterized by a...and lower surfaces for fixed values of the co-ordinates .’..’. in the plane normal to the axes of the plates. " In the case of a Mooney - Rivlin material
Non-linear optical titanyl arsenates: Crystal growth and properties
NASA Astrophysics Data System (ADS)
Nordborg, Jenni Eva Louise
Crystals are appreciated not only for their appearance, but also for their unique physical properties which are utilized by the photonic industry in appliances that we come across every day. An important part of enabling the technical use of optical devices is the manufacture of crystals. This dissertation deals with a specific group of materials called the potassium titanyl phosphate (KIP) family, known for their non-linear optical and ferroelectric properties. The isomorphs vary in their linear optical and dielectric properties, which can be tuned to optimize device performance by forming solid solutions of the different materials. Titanyl arsenates have a wide range of near-infrared transmission which makes them useful for tunable infrared lasers. The isomorphs examined in the present work were primarily RbTiOASO4 (RTA) and CsTiOAsO4 (CTA) together with the mixtures RbxCs 1-xTiOAsO4 (RCTA). Large-scale crystals were grown by top seeding solution growth utilizing a three-zone furnace with excellent temperature control. Sufficiently slow cooling and constant upward lifting produced crystals with large volumes useable for technical applications. Optical quality RTA crystals up to 10 x 12 x 20 mm were grown. The greater difficulty in obtaining good crystals of CTA led to the use of mixed RCTA materials. The mixing of rubidium and cesium in RCTA is more favorable to crystal growth than the single components in pure RTA and CTA. Mixed crystals are rubidium-enriched and contain only 20-30% of the cesium concentration in the flux. The cesium atoms show a preference for the larger cation site. The network structure is very little affected by the cation substitution; consequently, the non-linear optical properties of the Rb-rich isomorphic mixtures of RTA and CTA can be expected to remain intact. Crystallographic methods utilizing conventional X-ray tubes, synchrotron radiation and neutron diffraction have been employed to investigate the properties of the atomic
Non-Linear Dynamics of Saturn’s Rings
NASA Astrophysics Data System (ADS)
Esposito, Larry W.
2015-11-01
Non-linear processes can explain why Saturn’s rings are so active and dynamic. Ring systems differ from simple linear systems in two significant ways: 1. They are systems of granular material: where particle-to-particle collisions dominate; thus a kinetic, not a fluid description needed. We find that stresses are strikingly inhomogeneous and fluctuations are large compared to equilibrium. 2. They are strongly forced by resonances: which drive a non-linear response, pushing the system across thresholds that lead to persistent states.Some of this non-linearity is captured in a simple Predator-Prey Model: Periodic forcing from the moon causes streamline crowding; This damps the relative velocity, and allows aggregates to grow. About a quarter phase later, the aggregates stir the system to higher relative velocity and the limit cycle repeats each orbit.Summary of Halo Results: A predator-prey model for ring dynamics produces transient structures like ‘straw’ that can explain the halo structure and spectroscopy: This requires energetic collisions (v ≈ 10m/sec, with throw distances about 200km, implying objects of scale R ≈ 20km).Transform to Duffing Eqn : With the coordinate transformation, z = M2/3, the Predator-Prey equations can be combined to form a single second-order differential equation with harmonic resonance forcing.Ring dynamics and history implications: Moon-triggered clumping at perturbed regions in Saturn’s rings creates both high velocity dispersion and large aggregates at these distances, explaining both small and large particles observed there. We calculate the stationary size distribution using a cell-to-cell mapping procedure that converts the phase-plane trajectories to a Markov chain. Approximating the Markov chain as an asymmetric random walk with reflecting boundaries allows us to determine the power law index from results of numerical simulations in the tidal environment surrounding Saturn. Aggregates can explain many dynamic aspects
Non-linear dynamics of compound sawteeth in tokamaks
NASA Astrophysics Data System (ADS)
Ahn, J.-H.; Garbet, X.; Lütjens, H.; Marx, A.; Nicolas, T.; Sabot, R.; Luciani, J.-F.; Guirlet, R.; Février, O.; Maget, P.
2016-05-01
Compound sawteeth is studied with the XTOR-2F code. Non-linear full 3D magnetohydrodynamic simulations show that the plasma hot core is radially displaced and rotates during the partial crash, but is not fully expelled out of the q = 1 surface. Partial crashes occur when the radius of the q = 1 surface exceeds a critical value, at fixed poloidal beta. This critical value depends on the plasma elongation. The partial crash time is larger than the collapse time of an ordinary sawtooth, likely due to a weaker diamagnetic stabilization. This suggests that partial crashes result from a competition between destabilizing effects such as the q = 1 radius and diamagnetic stabilization.
Non-linear isocurvature perturbations and non-Gaussianities
Langlois, David; Vernizzi, Filippo; Wands, David E-mail: filippo.vernizzi@cea.fr
2008-12-15
We study non-linear primordial adiabatic and isocurvature perturbations and their non-Gaussianity. After giving a general formulation in the context of an extended {delta}N formalism, we analyse in detail two illustrative examples. The first is a mixed curvaton-inflaton scenario in which fluctuations of both the inflaton and a curvaton (a light isocurvature field during inflation) contribute to the primordial density perturbation. The second example is that of double inflation involving two decoupled massive scalar fields during inflation. In the mixed curvaton-inflaton scenario we find that the bispectrum of primordial isocurvature perturbations may be large and comparable to the bispectrum of adiabatic curvature perturbations.
Non-linear dielectric spectroscopy of microbiological suspensions.
Treo, Ernesto F; Felice, Carmelo J
2009-09-22
Non-linear dielectric spectroscopy (NLDS) of microorganism was characterized by the generation of harmonics in the polarization current when a microorganism suspension was exposed to a sinusoidal electric field. The biological nonlinear response initially described was not well verified by other authors and the results were susceptible to ambiguous interpretation. In this paper NLDS was performed to yeast suspension in tripolar and tetrapolar configuration with a recently developed analyzer. Tripolar analysis was carried out by applying sinusoidal voltages up to 1 V at the electrode interface. Tetrapolar analysis was carried on with sinusoidal field strengths from 0.1 V cm(-1) to 70 V cm(-1). Both analyses were performed within a frequency range from 1 Hz through 100 Hz. The harmonic amplitudes were Fourier-analyzed and expressed in dB. The third harmonic, as reported previously, was investigated. Statistical analysis (ANOVA) was used to test the effect of inhibitor an activator of the plasma membrane enzyme in the measured response. No significant non-linearities were observed in tetrapolar analysis, and no observable changes occurred when inhibitor and activator were added to the suspension. Statistical analysis confirmed these results.When a pure sinus voltage was applied to an electrode-yeast suspension interface, variations higher than 25 dB for the 3rd harmonic were observed. Variation higher than 20 dB in the 3rd harmonics has also been found when adding an inhibitor or activator of the membrane-bounded enzymes. These variations did not occur when the suspension was boiled. The lack of result in tetrapolar cells suggest that there is no, if any, harmonic generation in microbiological bulk suspension. The non-linear response observed was originated in the electrode-electrolyte interface. The frequency and voltage windows observed in previous tetrapolar analysis were repeated in the tripolar measurements, but maximum were not observed at the same values
Special Purpose Non-Linear Digital Position Control Algorithm
NASA Astrophysics Data System (ADS)
Knudsen, David W.
1987-10-01
A Position Control Algorithm with interesting features has been used in the design of an electro-mechanical actuator for a particular application where volume and weight limits are extremely tight. Position feedback, non-linear derived rate feedback, a saturable full-time main integrator, an intermittent fast integrator, compensation for mechanical system compliance, and derived acceleration feedback are used in an extension and modification of classical control concepts. The calculating and decision making power of a microcomputer contained in the actuator has been used to significantly improve upon well known control methods for this special case.
Organic-inorganic hybrid glass: non-linear optical properties
NASA Astrophysics Data System (ADS)
Domínguez Cruz, R.; Mendez-Perez, A.; Romero Galván, G.; Mendoza-Panduro, M.; Trejo-Duran, M.; Alvarado-Mendez, E.; Estudillo-Ayala, J. M.; Rojas-Laguna, R.; Martínez-Richa, A.; Castano, V. M.
2008-04-01
In this paper we report the preliminary results about the optical characterization of a new kind of organic-inorganic hybrid glass named 4-((5-dichloromethylsily1)-penty)oxy-cyanobenzene (DCN) synthesized by sol-gel process. We obtain the sign and magnitude of the sample by the Z-scan technique using a low power He-Ne laser at 632 nm in CW operation. The experimental data show that the DNC glass has a negative Kerr optical non-linearity and is estimated a nonlinear coefficient as Δn˜10-6.
Simulation of magnetisation switching by non-linear resonance
NASA Astrophysics Data System (ADS)
Thirion, C.; Wernsdorfer, W.
2004-05-01
The sub-nanosecond dynamics have recently been probed via non-linear resonance on single magnetic nanoparticles using the micro-SQUID technique. In the presence of a magnetic field considerably smaller than the switching field, the magnetisation of a nanoparticle can be reversed by the application of a small RF field. The experimental determination of the most effective frequency is a direct probe of the small oscillations of the magnetisation in the metastable energy well. We present here a simulation of this experiment using the Landau-Lifschitz-Gilbert equation.
8-PSK Signaling over non-linear satellite channels
NASA Technical Reports Server (NTRS)
Horan, Sheila B.; Caballero, Ruben B. Eng.
1996-01-01
Space agencies are under pressure to utilize better bandwidth-efficient communication methods due to the actual allocated frequency bands becoming more congested. Also budget reductions is another problem that the space agencies must deal with. This budget constraint results in simpler spacecraft carrying less communication capabilities and also the reduction in staff to capture data in the earth stations. It is then imperative that the most bandwidth efficient communication methods be utilized. This thesis presents a study of 8-ary Phase Shift Keying (8PSK) modulation with respect to bandwidth, power efficiency, spurious emissions and interference susceptibility over a non-linear satellite channel.
Non-linear dielectric spectroscopy of microbiological suspensions
Treo, Ernesto F; Felice, Carmelo J
2009-01-01
Background Non-linear dielectric spectroscopy (NLDS) of microorganism was characterized by the generation of harmonics in the polarization current when a microorganism suspension was exposed to a sinusoidal electric field. The biological nonlinear response initially described was not well verified by other authors and the results were susceptible to ambiguous interpretation. In this paper NLDS was performed to yeast suspension in tripolar and tetrapolar configuration with a recently developed analyzer. Methods Tripolar analysis was carried out by applying sinusoidal voltages up to 1 V at the electrode interface. Tetrapolar analysis was carried on with sinusoidal field strengths from 0.1 V cm-1 to 70 V cm-1. Both analyses were performed within a frequency range from 1 Hz through 100 Hz. The harmonic amplitudes were Fourier-analyzed and expressed in dB. The third harmonic, as reported previously, was investigated. Statistical analysis (ANOVA) was used to test the effect of inhibitor an activator of the plasma membrane enzyme in the measured response. Results No significant non-linearities were observed in tetrapolar analysis, and no observable changes occurred when inhibitor and activator were added to the suspension. Statistical analysis confirmed these results. When a pure sinus voltage was applied to an electrode-yeast suspension interface, variations higher than 25 dB for the 3rd harmonic were observed. Variation higher than 20 dB in the 3rd harmonics has also been found when adding an inhibitor or activator of the membrane-bounded enzymes. These variations did not occur when the suspension was boiled. Discussion The lack of result in tetrapolar cells suggest that there is no, if any, harmonic generation in microbiological bulk suspension. The non-linear response observed was originated in the electrode-electrolyte interface. The frequency and voltage windows observed in previous tetrapolar analysis were repeated in the tripolar measurements, but maximum were not
Non-linear identification of a squeeze-film damper
NASA Technical Reports Server (NTRS)
Stanway, Roger; Mottershead, John; Firoozian, Riaz
1987-01-01
Described is an experimental study to identify the damping laws associated with a squeeze-film vibration damper. This is achieved by using a non-linear filtering algorithm to process displacement responses of the damper ring to synchronous excitation and thus to estimate the parameters in an nth-power velocity model. The experimental facility is described in detail and a representative selection of results is included. The identified models are validated through the prediction of damper-ring orbits and comparison with observed responses.
Non-linear plasma wake growth of electron holes
Hutchinson, I. H.; Haakonsen, C. B.; Zhou, C.
2015-03-15
An object's wake in a plasma with small Debye length that drifts across the magnetic field is subject to electrostatic electron instabilities. Such situations include, for example, the moon in the solar wind and probes in magnetized laboratory plasmas. The instability drive mechanism can equivalently be considered drift down the potential-energy gradient or drift up the density-gradient. The gradients arise because the plasma wake has a region of depressed density and electrostatic potential into which ions are attracted along the field. The non-linear consequences of the instability are analysed in this paper. At physical ratios of electron to ion mass, neither linear nor quasilinear treatment can explain the observation of large-amplitude perturbations that disrupt the ion streams well before they become ion-ion unstable. We show here, however, that electron holes, once formed, continue to grow, driven by the drift mechanism, and if they remain in the wake may reach a maximum non-linearly stable size, beyond which their uncontrolled growth disrupts the ions. The hole growth calculations provide a quantitative prediction of hole profile and size evolution. Hole growth appears to explain the observations of recent particle-in-cell simulations.
Polycarbonate-Based Blends for Optical Non-linear Applications
NASA Astrophysics Data System (ADS)
Stanculescu, F.; Stanculescu, A.
2016-02-01
This paper presents some investigations on the optical and morphological properties of the polymer (matrix):monomer (inclusion) composite materials obtained from blends of bisphenol A polycarbonate and amidic monomers. For the preparation of the composite films, we have selected monomers characterised by a maleamic acid structure and synthesised them starting from maleic anhydride and aniline derivatives with -COOH, -NO2, -N(C2H5)2 functional groups attached to the benzene ring. The composite films have been deposited by spin coating using a mixture of two solutions, one containing the matrix and the other the inclusion, both components of the composite system being dissolved in the same solvent. The optical transmission and photoluminescence properties of the composite films have been investigated in correlation with the morphology of the films. The scanning electron microscopy and atomic force microscopy have revealed a non-uniform morphology characterised by the development of two distinct phases. We have also investigated the generation of some optical non-linear (ONL) phenomena in these composite systems. The composite films containing as inclusions monomers characterised by the presence of one -COOH or two -NO2 substituent groups to the aromatic nucleus have shown the most intense second-harmonic generation (SHG). The second-order optical non-linear coefficients have been evaluated for these films, and the effect of the laser power on the ONL behaviour of these materials has also been emphasised.
Effects on non-linearities on aircraft poststall motion
Rohacs, J.; Thomasson, P.; Mosehilde, E.
1994-12-31
The poststall maneuverability controlled by thrust vectoring has become one of the important aspects of new fighter development projects. In simplified case, the motion of aircraft can be described by 6DOF nonlinear system. The lecture deals with the longitudinal motion of poststall maneuverable aircraft. The investigation made about the effects of non-linearities in aerodynamic coefficients having considerable non-linearities and hysteresisis an the poststall motions. There were used some different models of aerodynamic coefficients. The results of investigation have shown that the poststall domain of vectored aircraft can be divided into five different pHs in field of thrust - pitch vector angle, and the chaotic motions of aircraft can be found at the different frequencies of thrust deflection. There were defined an unstable right domain with an unstable oscillation and a field of overpulling at poststall motion. The certain frequency chaotic attractors were got at frequencies of Oxitation between the 0.15 and 0.65 rad/sec. The pitching moment derivatives had the big influence on the chaotic motions, while the lift coefficient derivatives bad the reasonable effects, only.
Left-Right Non-Linear Dynamical Higgs
NASA Astrophysics Data System (ADS)
Shu, Jing; Yepes, Juan
2016-12-01
All the possible CP-conserving non-linear operators up to the p4-order in the Lagrangian expansion are analysed here for the left-right symmetric model in the non-linear electroweak chiral context coupled to a light dynamical Higgs. The low energy effects will be triggered by an emerging new physics field content in the nature, more specifically, from spin-1 resonances sourced by the straightforward extension of the SM local gauge symmetry to the larger local group SU(2)L × SU(2)R × U(1)B-L. Low energy phenomenology will be altered by integrating out the resonances from the physical spectrum, being manifested through induced corrections onto the left handed operators. Such modifications are weighted by powers of the scales ratio implied by the symmetries of the model and will determine the size of the effective operator basis to be used. The recently observed diboson excess around the invariant mass 1.8 TeV-2 TeV entails a scale suppression that suggests to encode the low energy effects via a much smaller set of effective operators. J. Y. also acknowledges KITPC financial support during the completion of this work
PV Degradation Curves: Non-Linearities and Failure Modes
Jordan, Dirk C.; Silverman, Timothy J.; Sekulic, Bill; Kurtz, Sarah R.
2016-09-03
Photovoltaic (PV) reliability and durability have seen increased interest in recent years. Historically, and as a preliminarily reasonable approximation, linear degradation rates have been used to quantify long-term module and system performance. The underlying assumption of linearity can be violated at the beginning of the life, as has been well documented, especially for thin-film technology. Additionally, non-linearities in the wear-out phase can have significant economic impact and appear to be linked to different failure modes. In addition, associating specific degradation and failure modes with specific time series behavior will aid in duplicating these degradation modes in accelerated tests and, eventually, in service life prediction. In this paper, we discuss different degradation modes and how some of these may cause approximately linear degradation within the measurement uncertainty (e.g., modules that were mainly affected by encapsulant discoloration) while other degradation modes lead to distinctly non-linear degradation (e.g., hot spots caused by cracked cells or solder bond failures and corrosion). The various behaviors are summarized with the goal of aiding in predictions of what may be seen in other systems.
Non-linear growth of the line-driving instability
NASA Astrophysics Data System (ADS)
Feldmeier, Achim; Thomas, Timon
2017-08-01
Winds from hot massive stars are driven by scattering of continuum radiation in bound-bound transitions. This radiative driving is subject to a strong instability, leading to shocks and X-ray emission. Time-dependent simulations of the instability encounter problems both for absorption and scattering lines, and it is necessary to introduce an artificially low opacity cut-off κm. The non-linear growth of the instability in the inner steeply accelerating wind is, so far, badly resolved. We present simulations with time-dependent Euler and Lagrange codes for pure line absorption at maximum growth rates of the instability in winds with a linear velocity law. This allows us to study the onset of non-linear growth in detail, and to follow unstable growth over orders of magnitude in velocity perturbations and length-scales. We find that distance-stretching in the accelerating wind causes unstable growth to proceed beyond the limit of a few thermal speeds that applies for short-scale perturbations. We increase the opacity cut-off to realistic values and find that the rarefied intershell gas is more strongly accelerated at larger κm, as is expected.
The linear-non-linear frontier for the Goldstone Higgs
NASA Astrophysics Data System (ADS)
Gavela, M. B.; Kanshin, K.; Machado, P. A. N.; Saa, S.
2016-12-01
The minimal SO(5) / SO(4) σ -model is used as a template for the ultraviolet completion of scenarios in which the Higgs particle is a low-energy remnant of some high-energy dynamics, enjoying a (pseudo) Nambu-Goldstone-boson ancestry. Varying the σ mass allows one to sweep from the perturbative regime to the customary non-linear implementations. The low-energy benchmark effective non-linear Lagrangian for bosons and fermions is obtained, determining as well the operator coefficients including linear corrections. At first order in the latter, three effective bosonic operators emerge which are independent of the explicit soft breaking assumed. The Higgs couplings to vector bosons and fermions turn out to be quite universal: the linear corrections are proportional to the explicit symmetry-breaking parameters. Furthermore, we define an effective Yukawa operator which allows a simple parametrization and comparison of different heavy-fermion ultraviolet completions. In addition, one particular fermionic completion is explored in detail, obtaining the corresponding leading low-energy fermionic operators.
Charged relativistic fluids and non-linear electrodynamics
NASA Astrophysics Data System (ADS)
Dereli, T.; Tucker, R. W.
2010-01-01
The electromagnetic fields in Maxwell's theory satisfy linear equations in the classical vacuum. This is modified in classical non-linear electrodynamic theories. To date there has been little experimental evidence that any of these modified theories are tenable. However with the advent of high-intensity lasers and powerful laboratory magnetic fields this situation may be changing. We argue that an approach involving the self-consistent relativistic motion of a smooth fluid-like distribution of matter (composed of a large number of charged or neutral particles) in an electromagnetic field offers a viable theoretical framework in which to explore the experimental consequences of non-linear electrodynamics. We construct such a model based on the theory of Born and Infeld and suggest that a simple laboratory experiment involving the propagation of light in a static magnetic field could be used to place bounds on the fundamental coupling in that theory. Such a framework has many applications including a new description of the motion of particles in modern accelerators and plasmas as well as phenomena in astrophysical contexts such as in the environment of magnetars, quasars and gamma-ray bursts.
The linear -- non-linear frontier for the Goldstone Higgs
Gavela, M. B.; Kanshin, K.; Machado, P. A. N.; ...
2016-12-01
The minimalmore » $SO(5)/SO(4)$ sigma model is used as a template for the ultraviolet completion of scenarios in which the Higgs particle is a low-energy remnant of some high-energy dynamics, enjoying a (pseudo) Nambu-Goldstone boson ancestry. Varying the $$\\sigma$$ mass allows to sweep from the perturbative regime to the customary non-linear implementations. The low-energy benchmark effective non-linear Lagrangian for bosons and fermions is obtained, determining as well the operator coefficients including linear corrections. At first order in the latter, three effective bosonic operators emerge which are independent of the explicit soft breaking assumed. The Higgs couplings to vector bosons and fermions turn out to be quite universal: the linear corrections are proportional to the explicit symmetry breaking parameters. Furthermore, we define an effective Yukawa operator which allows a simple parametrization and comparison of different heavy fermion ultraviolet completions. In addition, one particular fermionic completion is explored in detail, obtaining the corresponding leading low-energy fermionic operators.« less
Non-linear leak currents affect mammalian neuron physiology
Huang, Shiwei; Hong, Sungho; De Schutter, Erik
2015-01-01
In their seminal works on squid giant axons, Hodgkin, and Huxley approximated the membrane leak current as Ohmic, i.e., linear, since in their preparation, sub-threshold current rectification due to the influence of ionic concentration is negligible. Most studies on mammalian neurons have made the same, largely untested, assumption. Here we show that the membrane time constant and input resistance of mammalian neurons (when other major voltage-sensitive and ligand-gated ionic currents are discounted) varies non-linearly with membrane voltage, following the prediction of a Goldman-Hodgkin-Katz-based passive membrane model. The model predicts that under such conditions, the time constant/input resistance-voltage relationship will linearize if the concentration differences across the cell membrane are reduced. These properties were observed in patch-clamp recordings of cerebellar Purkinje neurons (in the presence of pharmacological blockers of other background ionic currents) and were more prominent in the sub-threshold region of the membrane potential. Model simulations showed that the non-linear leak affects voltage-clamp recordings and reduces temporal summation of excitatory synaptic input. Together, our results demonstrate the importance of trans-membrane ionic concentration in defining the functional properties of the passive membrane in mammalian neurons as well as other excitable cells. PMID:26594148
The linear -- non-linear frontier for the Goldstone Higgs
Gavela, M. B.; Kanshin, K.; Machado, P. A. N.; Saa, S.
2016-12-01
The minimal $SO(5)/SO(4)$ sigma model is used as a template for the ultraviolet completion of scenarios in which the Higgs particle is a low-energy remnant of some high-energy dynamics, enjoying a (pseudo) Nambu-Goldstone boson ancestry. Varying the $\\sigma$ mass allows to sweep from the perturbative regime to the customary non-linear implementations. The low-energy benchmark effective non-linear Lagrangian for bosons and fermions is obtained, determining as well the operator coefficients including linear corrections. At first order in the latter, three effective bosonic operators emerge which are independent of the explicit soft breaking assumed. The Higgs couplings to vector bosons and fermions turn out to be quite universal: the linear corrections are proportional to the explicit symmetry breaking parameters. Furthermore, we define an effective Yukawa operator which allows a simple parametrization and comparison of different heavy fermion ultraviolet completions. In addition, one particular fermionic completion is explored in detail, obtaining the corresponding leading low-energy fermionic operators.
Non-linear plasma wake growth of electron holes
NASA Astrophysics Data System (ADS)
Hutchinson, I. H.; Haakonsen, C. B.; Zhou, C.
2015-03-01
An object's wake in a plasma with small Debye length that drifts across the magnetic field is subject to electrostatic electron instabilities. Such situations include, for example, the moon in the solar wind and probes in magnetized laboratory plasmas. The instability drive mechanism can equivalently be considered drift down the potential-energy gradient or drift up the density-gradient. The gradients arise because the plasma wake has a region of depressed density and electrostatic potential into which ions are attracted along the field. The non-linear consequences of the instability are analysed in this paper. At physical ratios of electron to ion mass, neither linear nor quasilinear treatment can explain the observation of large-amplitude perturbations that disrupt the ion streams well before they become ion-ion unstable. We show here, however, that electron holes, once formed, continue to grow, driven by the drift mechanism, and if they remain in the wake may reach a maximum non-linearly stable size, beyond which their uncontrolled growth disrupts the ions. The hole growth calculations provide a quantitative prediction of hole profile and size evolution. Hole growth appears to explain the observations of recent particle-in-cell simulations.
Filtering Non-Linear Transfer Functions on Surfaces.
Heitz, Eric; Nowrouzezahrai, Derek; Poulin, Pierre; Neyret, Fabrice
2013-07-18
Applying non-linear transfer functions and look-up tables to procedural functions (such as noise), surface attributes, or even surface geometry are common strategies used to enhance visual detail. As with any textured or geometric detail, proper filtering is needed to reduce aliasing when viewed across a range of distances, but accurate and efficient transfer function filtering remains an open problem for several reasons: transfer functions are complex and non-linear, especially when mapped through procedural noise and/or geometry-dependent functions. We accurately solve this problem by computing and sampling from specialized filtering distributions on the fly, yielding very fast performance. We investigate the case where the transfer function to filter is a color map applied to surface textures, as well as color maps applied according to (microscale) geometric details. We introduce a novel representation of a (potentially modulated) color map's distribution over pixel footprints using Gaussian statistics and, in the more complex case of high-resolution color mapped microsurface details, our filtering is view- and light-dependent, and capable of correctly handling masking and occlusion effects. Our approach can be generalized to filter other physical-based rendering quantities. Our framework is also compatible with the case of transfer functions used to warp surface geometry.
Noakes, D.R. ); Tindall, D.A. ); Steinitz, M.O. ); Ali, N. )
1990-05-01
Measurements of the magnetic structure of holmium in {ital c}-axis applied magnetic fields were made by neutron diffraction in the ({ital h}0{ital l}) plane. In applied fields of 1.7 and 2.2 T directed along the {ital c}-axis, the overall periodicity of the spiral structure locks into the commensurate superlattice value 4{ital c}{sub 0} over a finite range of temperature (approximately 2 K at 2.2 T) near 98 K, whereas no such effect is seen in the crystal in zero field. The commensurate plateau extends between two transitions bracketing 98 K reported in magnetization and dilatometry by Steinitz {ital et} {ital al}. (Phys. Rev. B {bold 40}, 763 (1989)). No new satellites were found in this temperature range, but the intensities of the fundamental magnetic Bragg peaks exhibited precursor behavior as the commensurate state was approached in temperature both from above and below.
Renormalization and non-linear symmetries in quantum field theory
NASA Astrophysics Data System (ADS)
Velenich, Andrea
Most of the phenomena we experience, from the microscopic world to the universe at its largest scales, are out of equilibrium and their comprehensive formalization is one of the open problems in theoretical physics. Fluids of interacting particles cooled down or compressed quickly enough to become amorphous solids are an example of rich out-of-equilibrium systems with very slow relaxation dynamics. Even though the equilibrium phases are ordered, these systems remain trapped in glassy metastable states, with disordered microscopic structures. As a realistic model of this phenomenology, in the first part of this work I focused on a field theory of particles obeying a Brownian dynamics. The field-theoretic action displays a time-reversal symmetry leading to Fluctuation-Dissipation relations. For non-interacting particles I solved the field theory exactly, providing the explicit form of all the correlation functions, with their space and time dependence. As a non-perturbative result, the distribution of the density field has been proven to be Poissonian and not Gaussian. For interacting particles the field theory presents two major challenges: its apparent non-renormalizability and a non-linear implementation of the time-reversal symmetry. Non-linear field redefinitions can be used to make the symmetry linear and might even lead to the solution of the interacting equations of motion. However they also alter the renormalizability properties of a field theory. These challenges inspired the second part of the work, where a more abstract approach was taken. Using algebraic methods I investigated the effect of non-linear field redefinitions both on symmetry and on renormalization by focusing on simple scalar field theories as toy models. In the formal setting of the Hopf algebra of Feynman diagrams, symmetries take the form of Hopf ideals and enforce relations among scattering amplitudes; such relations can drastically reduce the number of independent couplings in a field
Non-linear dimensionality reduction of signaling networks
Ivakhno, Sergii; Armstrong, J Douglas
2007-01-01
Background Systems wide modeling and analysis of signaling networks is essential for understanding complex cellular behaviors, such as the biphasic responses to different combinations of cytokines and growth factors. For example, tumor necrosis factor (TNF) can act as a proapoptotic or prosurvival factor depending on its concentration, the current state of signaling network and the presence of other cytokines. To understand combinatorial regulation in such systems, new computational approaches are required that can take into account non-linear interactions in signaling networks and provide tools for clustering, visualization and predictive modeling. Results Here we extended and applied an unsupervised non-linear dimensionality reduction approach, Isomap, to find clusters of similar treatment conditions in two cell signaling networks: (I) apoptosis signaling network in human epithelial cancer cells treated with different combinations of TNF, epidermal growth factor (EGF) and insulin and (II) combination of signal transduction pathways stimulated by 21 different ligands based on AfCS double ligand screen data. For the analysis of the apoptosis signaling network we used the Cytokine compendium dataset where activity and concentration of 19 intracellular signaling molecules were measured to characterise apoptotic response to TNF, EGF and insulin. By projecting the original 19-dimensional space of intracellular signals into a low-dimensional space, Isomap was able to reconstruct clusters corresponding to different cytokine treatments that were identified with graph-based clustering. In comparison, Principal Component Analysis (PCA) and Partial Least Squares – Discriminant analysis (PLS-DA) were unable to find biologically meaningful clusters. We also showed that by using Isomap components for supervised classification with k-nearest neighbor (k-NN) and quadratic discriminant analysis (QDA), apoptosis intensity can be predicted for different combinations of TNF, EGF
Non-linear dimensionality reduction of signaling networks.
Ivakhno, Sergii; Armstrong, J Douglas
2007-06-08
Systems wide modeling and analysis of signaling networks is essential for understanding complex cellular behaviors, such as the biphasic responses to different combinations of cytokines and growth factors. For example, tumor necrosis factor (TNF) can act as a proapoptotic or prosurvival factor depending on its concentration, the current state of signaling network and the presence of other cytokines. To understand combinatorial regulation in such systems, new computational approaches are required that can take into account non-linear interactions in signaling networks and provide tools for clustering, visualization and predictive modeling. Here we extended and applied an unsupervised non-linear dimensionality reduction approach, Isomap, to find clusters of similar treatment conditions in two cell signaling networks: (I) apoptosis signaling network in human epithelial cancer cells treated with different combinations of TNF, epidermal growth factor (EGF) and insulin and (II) combination of signal transduction pathways stimulated by 21 different ligands based on AfCS double ligand screen data. For the analysis of the apoptosis signaling network we used the Cytokine compendium dataset where activity and concentration of 19 intracellular signaling molecules were measured to characterise apoptotic response to TNF, EGF and insulin. By projecting the original 19-dimensional space of intracellular signals into a low-dimensional space, Isomap was able to reconstruct clusters corresponding to different cytokine treatments that were identified with graph-based clustering. In comparison, Principal Component Analysis (PCA) and Partial Least Squares - Discriminant analysis (PLS-DA) were unable to find biologically meaningful clusters. We also showed that by using Isomap components for supervised classification with k-nearest neighbor (k-NN) and quadratic discriminant analysis (QDA), apoptosis intensity can be predicted for different combinations of TNF, EGF and insulin. Prediction
C-axis orientated AlN films deposited using deep oscillation magnetron sputtering
NASA Astrophysics Data System (ADS)
Lin, Jianliang; Chistyakov, Roman
2017-02-01
Highly <0001> c-axis orientated aluminum nitride (AlN) films were deposited on silicon (100) substrates by reactive deep oscillation magnetron sputtering (DOMS). No epitaxial favored bond layer and substrate heating were applied for assisting texture growth. The effects of the peak target current density (varied from 0.39 to 0.8 Acm-2) and film thickness (varied from 0.25 to 3.3 μm) on the c-axis orientation, microstructure, residual stress and mechanical properties of the AlN films were investigated by means of X-ray diffraction rocking curve methodology, transmission electron microscopy, optical profilometry, and nanoindentation. All AlN films exhibited a <0001> preferred orientation and compressive residual stresses. At similar film thicknesses, an increase in the peak target current density to 0.53 Acm-2 improved the <0001> orientation. Further increasing the peak target current density to above 0.53 Acm-2 showed limited contribution to the texture development. The study also showed that an increase in the thickness of the AlN films deposited by DOMS improved the c-axis alignment accompanied with a reduction in the residual stress.
C-axis critical current density of second-generation YBCO tapes.
Jia, Y.; Hua, J.; Crabtree, G. W.; Kwok, W. K.; Welp, U.; Malozemoff, A. P.; Rupich, M.; Fleshler, S.; Materials Science Division; American Superconductor Corp.
2010-10-01
We report on measurements of the temperature and field dependence of the c-axis critical current density (J{sub c}{sup c}) obtained on mesa structures that were patterned into the YBCO layer of second-generation HTS tapes. We find the J{sub c}{sup c}-values of {approx}4 kA cm{sup -2} at 77 K and self-field, corresponding to an unexpectedly high anisotropy in the critical current density J{sub c}{sup ab}/J{sub c}{sup c} of 500-600. C-axis current flow is expected to arise in applications such as the helically wound wires in HTS cables. A simple estimate is given of the fraction of tape width for such a c-axis flow; while in our samples this fraction is approximately 5% for a typical geometry, the fraction will grow linearly with increasing current density anisotropy and could affect the current-carrying ability of the tape.
Microstructure dependence of the c-axis critical current density in second generation YBCO tapes
Jia, Y. Welp, U. Crabtree, G.W.; Kwok, W.K.; Malozemoff, A.P.; Rupich, M.W.; Fleshler, S.; Clem, J.R.
2011-10-31
C-axis current flow in high temperature superconductor (HTS) tape-shaped wires arises in configurations where the local wire axis is not perpendicular to the local magnetic field, such as in power cables with helically wound HTS tapes. The c-axis critical current density J{sub c}{sup c} has been recently found to be orders of magnitude lower than the ab-plane critical current density J{sub c}{sup ab}. Here we report on J{sub c}{sup c} (77 K, sf) values of various YBa{sub 2}Cu{sub 3}O{sub 7}-based (YBCO) tapes with different microstructures. Our results show that the value of J{sub c}{sup c} (77 K, sf) decreases significantly with increasing concentration of ab-plane stacking faults in YBCO thin films and that the critical current anisotropy {gamma} = J{sub c}{sup ab}/J{sub c}{sup c} can reach values as high as 2070, implying that in the highest-anisotropy tape, {approx}20% of the tape width carries c-axis current in a helically wound power cable.
Microstructure dependence of the c-axis critical current density in second-generation YBCO tapes.
Jia, Y.; Welp, U.; Crabtree, G. W.; Kwok, W. K.; Malozemoff, A. P.; Rupich, M. W.; Fleshler, S.; Clem, J. R.
2011-10-01
C-axis current flow in high temperature superconductor (HTS) tape-shaped wires arises in configurations where the local wire axis is not perpendicular to the local magnetic field, such as in power cables with helically wound HTS tapes. The c-axis critical current density J{sub c}{sup c} has been recently found to be orders of magnitude lower than the ab-plane critical current density J{sub c}{sup ab}. Here we report on J{sub c}{sup c} (77 K, sf) values of various YBa{sub 2}Cu{sub 3}O{sub 7}-based (YBCO) tapes with different microstructures. Our results show that the value of J{sub c}{sup c} (77 K, sf) decreases significantly with increasing concentration of ab-plane stacking faults in YBCO thin films and that the critical current anisotropy {gamma} = J{sub c}{sup ab}/J{sub c}{sup c} can reach values as high as 2070, implying that in the highest-anisotropy tape, {approx}20% of the tape width carries c-axis current in a helically wound power cable.
C-Axis critical current density of second-generation YBCO tapes
Jia, Y.; Hua, J.; Crabtree, G.W.; Kwok, W.K.; Welp, U.; Malozemoff, A.P.; Rupich, M.; Fleshler, S.
2010-10-21
We report on measurements of the temperature and field dependence of the c-axis critical current density (J_{c}^{c}) obtained on mesa structures that were patterned into the YBCO layer of second-generation HTS tapes. We find the J_{c}^{c}—values of ~ 4 kA cm^{-2} at 77 K and self-field, corresponding to an unexpectedly high anisotropy in the critical current density J_{c}^{ab}/J_{c}^{c} of 500–600. C-axis current flow is expected to arise in applications such as the helically wound wires in HTS cables. A simple estimate is given of the fraction of tape width for such a c-axis flow; while in our samples this fraction is approximately 5% for a typical geometry, the fraction will grow linearly with increasing current density anisotropy and could affect the current-carrying ability of the tape.
Non-linear hydrodynamical simulations of delta Scuti star pulsations
NASA Astrophysics Data System (ADS)
Templeton, M. R.; Guzik, J. A.; McNamara, B. J.
1998-12-01
We present the initial results of non-linear hydrodynamic simulations of the pulsation modes of delta Scuti stars. These models use the Ostlie and Cox (1993) Lagrangian hydrodynamic code, adapted to use the most recent OPAL (1996) opacities, the Stellingwerf (1974) periodic relaxation method of obtaining stable limit cycle pulsations, and time-dependent convection. Initial tests of first- and second-overtone pulsation models are consistent with the models of Bono, et al (1997) showing asymmetric lightcurves for first overtone rather than fundamental pulsations. Future modeling work will test several stellar models with varying masses, ages, metal and helium abundances and envelope abundance gradients. Ultimately, we hope to determine the role that abundances and, more specifically, helium abundance gradients in delta Scuti envelopes play in light curve shape. This work will be applied to a test sample of known radially-pulsating delta Scuti field stars and the newly-discovered delta Scuti/SX Phoenicis variables in the Galactic Bulge.
Image enhancement by non-linear extrapolation in frequency space
NASA Technical Reports Server (NTRS)
Anderson, Charles H. (Inventor); Greenspan, Hayit K. (Inventor)
1998-01-01
An input image is enhanced to include spatial frequency components having frequencies higher than those in an input image. To this end, an edge map is generated from the input image using a high band pass filtering technique. An enhancing map is subsequently generated from the edge map, with the enhanced map having spatial frequencies exceeding an initial maximum spatial frequency of the input image. The enhanced map is generated by applying a non-linear operator to the edge map in a manner which preserves the phase transitions of the edges of the input image. The enhanced map is added to the input image to achieve a resulting image having spatial frequencies greater than those in the input image. Simplicity of computations and ease of implementation allow for image sharpening after enlargement and for real-time applications such as videophones, advanced definition television, zooming, and restoration of old motion pictures.
New holographic dark energy model with non-linear interaction
NASA Astrophysics Data System (ADS)
Oliveros, A.; Acero, Mario A.
2015-05-01
In this paper the cosmological evolution of a holographic dark energy model with a non-linear interaction between the dark energy and dark matter components in a FRW type flat universe is analysed. In this context, the deceleration parameter q and the equation state w Λ are obtained. We found that, as the square of the speed of sound remains positive, the model is stable under perturbations since early times; it also shows that the evolution of the matter and dark energy densities are of the same order for a long period of time, avoiding the so-called coincidence problem. We have also made the correspondence of the model with the dark energy densities and pressures for the quintessence and tachyon fields. From this correspondence we have reconstructed the potential of scalar fields and their dynamics.
Memristive non-linear system and hidden attractor
NASA Astrophysics Data System (ADS)
Saha, P.; Saha, D. C.; Ray, A.; Chowdhury, A. R.
2015-07-01
Effects of memristor on non-linear dynamical systems exhibiting chaos are analysed both form the view point of theory and experiment. It is observed that the memristive system has always fewer number of fixed points than the original one. Sometimes there is no fixed point in the memristive system. But its chaotic properties are retained. As such we have a situation known as hidden attractor because if it is a stable fixed point then the attractor does not evolve from its basin of attraction(obtained from its stable fixed point) or if there is no fixed point, the question of basin of attraction from fixed point does not arise at all [1, 2]. Our analysis gives a detailed accounts of properties related to its chaotic behavior. Important observations are also obtained with the help of electronic circuits to support the numerical simulations.
Attractor reconstruction for non-linear systems: a methodological note
Nichols, J.M.; Nichols, J.D.
2001-01-01
Attractor reconstruction is an important step in the process of making predictions for non-linear time-series and in the computation of certain invariant quantities used to characterize the dynamics of such series. The utility of computed predictions and invariant quantities is dependent on the accuracy of attractor reconstruction, which in turn is determined by the methods used in the reconstruction process. This paper suggests methods by which the delay and embedding dimension may be selected for a typical delay coordinate reconstruction. A comparison is drawn between the use of the autocorrelation function and mutual information in quantifying the delay. In addition, a false nearest neighbor (FNN) approach is used in minimizing the number of delay vectors needed. Results highlight the need for an accurate reconstruction in the computation of the Lyapunov spectrum and in prediction algorithms.
Detector noise statistics in the non-linear regime
NASA Technical Reports Server (NTRS)
Shopbell, P. L.; Bland-Hawthorn, J.
1992-01-01
The statistical behavior of an idealized linear detector in the presence of threshold and saturation levels is examined. It is assumed that the noise is governed by the statistical fluctuations in the number of photons emitted by the source during an exposure. Since physical detectors cannot have infinite dynamic range, our model illustrates that all devices have non-linear regimes, particularly at high count rates. The primary effect is a decrease in the statistical variance about the mean signal due to a portion of the expected noise distribution being removed via clipping. Higher order statistical moments are also examined, in particular, skewness and kurtosis. In principle, the expected distortion in the detector noise characteristics can be calibrated using flatfield observations with count rates matched to the observations. For this purpose, some basic statistical methods that utilize Fourier analysis techniques are described.
Predictability of extremes in non-linear hierarchically organized systems
NASA Astrophysics Data System (ADS)
Kossobokov, V. G.; Soloviev, A.
2011-12-01
Understanding the complexity of non-linear dynamics of hierarchically organized systems progresses to new approaches in assessing hazard and risk of the extreme catastrophic events. In particular, a series of interrelated step-by-step studies of seismic process along with its non-stationary though self-organized behaviors, has led already to reproducible intermediate-term middle-range earthquake forecast/prediction technique that has passed control in forward real-time applications during the last two decades. The observed seismic dynamics prior to and after many mega, great, major, and strong earthquakes demonstrate common features of predictability and diverse behavior in course durable phase transitions in complex hierarchical non-linear system of blocks-and-faults of the Earth lithosphere. The confirmed fractal nature of earthquakes and their distribution in space and time implies that many traditional estimations of seismic hazard (from term-less to short-term ones) are usually based on erroneous assumptions of easy tractable analytical models, which leads to widespread practice of their deceptive application. The consequences of underestimation of seismic hazard propagate non-linearly into inflicted underestimation of risk and, eventually, into unexpected societal losses due to earthquakes and associated phenomena (i.e., collapse of buildings, landslides, tsunamis, liquefaction, etc.). The studies aimed at forecast/prediction of extreme events (interpreted as critical transitions) in geophysical and socio-economical systems include: (i) large earthquakes in geophysical systems of the lithosphere blocks-and-faults, (ii) starts and ends of economic recessions, (iii) episodes of a sharp increase in the unemployment rate, (iv) surge of the homicides in socio-economic systems. These studies are based on a heuristic search of phenomena preceding critical transitions and application of methodologies of pattern recognition of infrequent events. Any study of rare
Neural networks: What non-linearity to choose
NASA Technical Reports Server (NTRS)
Kreinovich, Vladik YA.; Quintana, Chris
1991-01-01
Neural networks are now one of the most successful learning formalisms. Neurons transform inputs (x(sub 1),...,x(sub n)) into an output f(w(sub 1)x(sub 1) + ... + w(sub n)x(sub n)), where f is a non-linear function and w, are adjustable weights. What f to choose? Usually the logistic function is chosen, but sometimes the use of different functions improves the practical efficiency of the network. The problem of choosing f as a mathematical optimization problem is formulated and solved under different optimality criteria. As a result, a list of functions f that are optimal under these criteria are determined. This list includes both the functions that were empirically proved to be the best for some problems, and some new functions that may be worth trying.
Non-linear radial spinwave modes in thin magnetic disks
Helsen, M. De Clercq, J.; Vansteenkiste, A.; Van Waeyenberge, B.; Weigand, M.
2015-01-19
We present an experimental investigation of radial spin-wave modes in magnetic nano-disks with a vortex ground state. The spin-wave amplitude was measured using a frequency-resolved magneto-optical spectrum analyzer, allowing for high-resolution resonance curves to be recorded. It was found that with increasing excitation amplitude up to about 10 mT, the lowest-order mode behaves strongly non-linearly as the mode frequency redshifts and the resonance peak strongly deforms. This behavior was quantitatively reproduced by micromagnetic simulations. Micromagnetic simulations showed that at higher excitation amplitudes, the spinwaves are transformed into a soliton by self-focusing, and collapse onto the vortex core, dispersing the energy in short-wavelength spinwaves. Additionally, this process can lead to switching of the vortex polarization through the injection of a Bloch point.
Transformation matrices between non-linear and linear differential equations
NASA Technical Reports Server (NTRS)
Sartain, R. L.
1983-01-01
In the linearization of systems of non-linear differential equations, those systems which can be exactly transformed into the second order linear differential equation Y"-AY'-BY=0 where Y, Y', and Y" are n x 1 vectors and A and B are constant n x n matrices of real numbers were considered. The 2n x 2n matrix was used to transform the above matrix equation into the first order matrix equation X' = MX. Specially the matrix M and the conditions which will diagonalize or triangularize M were studied. Transformation matrices P and P sub -1 were used to accomplish this diagonalization or triangularization to return to the solution of the second order matrix differential equation system from the first order system.
Computational models of signalling networks for non-linear control.
Fuente, Luis A; Lones, Michael A; Turner, Alexander P; Stepney, Susan; Caves, Leo S; Tyrrell, Andy M
2013-05-01
Artificial signalling networks (ASNs) are a computational approach inspired by the signalling processes inside cells that decode outside environmental information. Using evolutionary algorithms to induce complex behaviours, we show how chaotic dynamics in a conservative dynamical system can be controlled. Such dynamics are of particular interest as they mimic the inherent complexity of non-linear physical systems in the real world. Considering the main biological interpretations of cellular signalling, in which complex behaviours and robust cellular responses emerge from the interaction of multiple pathways, we introduce two ASN representations: a stand-alone ASN and a coupled ASN. In particular we note how sophisticated cellular communication mechanisms can lead to effective controllers, where complicated problems can be divided into smaller and independent tasks.
The mathematics of non-linear metrics for nested networks
NASA Astrophysics Data System (ADS)
Wu, Rui-Jie; Shi, Gui-Yuan; Zhang, Yi-Cheng; Mariani, Manuel Sebastian
2016-10-01
Numerical analysis of data from international trade and ecological networks has shown that the non-linear fitness-complexity metric is the best candidate to rank nodes by importance in bipartite networks that exhibit a nested structure. Despite its relevance for real networks, the mathematical properties of the metric and its variants remain largely unexplored. Here, we perform an analytic and numeric study of the fitness-complexity metric and a new variant, called minimal extremal metric. We rigorously derive exact expressions for node scores for perfectly nested networks and show that these expressions explain the non-trivial convergence properties of the metrics. A comparison between the fitness-complexity metric and the minimal extremal metric on real data reveals that the latter can produce improved rankings if the input data are reliable.
Ferrite core non-linearity in coils for magnetic neurostimulation
Lazzi, Gianluca
2014-01-01
The need to correctly predict the voltage across terminals of mm-sized coils, with ferrite core, to be employed for magnetic stimulation of the peripheral neural system is the motivation for this work. In such applications, which rely on a capacitive discharge on the coil to realise a transient voltage curve of duration and strength suitable for neural stimulation, the correct modelling of the non-linearity of the ferrite core is critical. A demonstration of how a finite-difference model of the considered coils, which include a model of the current-controlled inductance in the coil, can be used to correctly predict the time-domain voltage waveforms across the terminals of a test coil is presented. Five coils of different dimensions, loaded with ferrite cores, have been fabricated and tested: the measured magnitude and width of the induced pulse are within 10% of simulated values. PMID:26609390
Method and system for non-linear motion estimation
NASA Technical Reports Server (NTRS)
Lu, Ligang (Inventor)
2011-01-01
A method and system for extrapolating and interpolating a visual signal including determining a first motion vector between a first pixel position in a first image to a second pixel position in a second image, determining a second motion vector between the second pixel position in the second image and a third pixel position in a third image, determining a third motion vector between one of the first pixel position in the first image and the second pixel position in the second image, and the second pixel position in the second image and the third pixel position in the third image using a non-linear model, determining a position of the fourth pixel in a fourth image based upon the third motion vector.
Black hole hair removal: non-linear analysis
NASA Astrophysics Data System (ADS)
Jatkar, Dileep P.; Sen, Ashoke; Srivastava, Yogesh K.
2010-02-01
BMPV black holes in flat transverse space and in Taub-NUT space have identical near horizon geometries but different microscopic degeneracies. It has been proposed that this difference can be accounted for by different contribution to the degeneracies of these black holes from hair modes, — degrees of freedom living outside the horizon. In this paper we explicitly construct the hair modes of these two black holes as finite bosonic and fermionic deformations of the black hole solution satisfying the full non-linear equations of motion of supergravity and preserving the supersymmetry of the original solutions. Special care is taken to ensure that these solutions do not have any curvature singularity at the future horizon when viewed as the full ten dimensional geometry. We show that after removing the contribution due to the hair degrees of freedom from the microscopic partition function, the partition functions of the two black holes agree.
Model of intermodulation distortion in non-linear multicarrier systems
NASA Astrophysics Data System (ADS)
Frigo, Nicholas J.
1994-02-01
A heuristic model is proposed which allows calculation of the individual spectral components of the intermodulation distortion present in a non-linear system with a multicarrier input. Noting that any given intermodulation product (IMP) can only be created by a subset of the input carriers, we partition them into 'signal' carriers (which create the IMP) and 'noise' carriers, modeled as a Gaussian process. The relationship between an input signal and the statistical average of its output (averaged over the Gaussian noise) is considered to be an effective transfer function. By summing all possible combinations of signal carriers which create power at the IMP frequencies, the distortion power can be calculated exactly as a function of frequency. An analysis of clipping in lightwave CATV links for AM-VSB signals is used to introduce the model, and is compared to a series of experiments.
Non-linear optical crystal vibration sensing device
Kalibjian, R.
1994-08-09
A non-linear optical crystal vibration sensing device including a photorefractive crystal and a laser is disclosed. The laser produces a coherent light beam which is split by a beam splitter into a first laser beam and a second laser beam. After passing through the crystal the first laser beam is counter-propagated back upon itself by a retro-mirror, creating a third laser beam. The laser beams are modulated, due to the mixing effect within the crystal by vibration of the crystal. In the third laser beam, modulation is stable and such modulation is converted by a photodetector into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal. 3 figs.
Non-linear optical crystal vibration sensing device
Kalibjian, Ralph
1994-01-11
A non-linear optical crystal vibration sensing device (10) including a photorefractive crystal (26) and a laser (12). The laser (12 ) produces a coherent light beam (14) which is split by a beam splitter (18) into a first laser beam (20) and a second laser beam (22). After passing through the crystal (26) the first laser beam (20) is counter-propagated back upon itself by a retro-mirror (32), creating a third laser beam (30). The laser beams (20, 22, 30) are modulated, due to the mixing effect within the crystal (26) by vibration of the crystal (30). In the third laser beam (30), modulation is stable and such modulation is converted by a photodetector (34) into a usable electrical output, intensity modulated in accordance with vibration applied to the crystal (26).
DYNAMIC NON LINEAR IMPACT ANALYSIS OF FUEL CASK CONTAINMENT VESSELS
Leduc, D
2008-06-10
Large fuel casks present challenges when evaluating their performance in the accident sequence specified in 10CFR 71. Testing is often limited because of cost, difficulty in preparing test units and the limited availability of facilities which can carry out such tests. In the past, many casks were evaluated without testing using simplified analytical methods. This paper details the use of dynamic non-linear analysis of large fuel casks using advanced computational techniques. Results from the dynamic analysis of two casks, the T-3 Spent Fuel Cask and the Hanford Un-irradiated Fuel Package are examined in detail. These analyses are used to fully evaluate containment vessel stresses and strains resulting from complex loads experienced by cask components during impacts. Importantly, these advanced analytical analyses are capable of examining stresses in key regions of the cask including the cask closure. This paper compares these advanced analytical results with the results of simplified cask analyses like those detailed in NUREG 3966.
Realising traceable electrostatic forces despite non-linear balance motion
NASA Astrophysics Data System (ADS)
Stirling, Julian; Shaw, Gordon A.
2017-05-01
Direct realisation of force, traceable to fundamental constants via electromagnetic balances, is a key goal of the proposed redefinition of the international system of units (SI). This will allow small force metrology to be performed using an electrostatic force balance (EFB) rather than subdivision of larger forces. Such a balance uses the electrostatic force across a capacitor to balance an external force. In this paper we model the capacitance of a concentric cylinder EFB design as a function of the displacement of its free electrode, accounting for the arcuate motion produced by parallelogram linkages commonly used in EFB mechanisms. From this model we suggest new fitting procedures to reduce uncertainties arising from non-linear motion as well as methods to identify misalignment of the mechanism. Experimental studies on both a test capacitor and the NIST EFB validate the model.
Ferrite core non-linearity in coils for magnetic neurostimulation.
RamRakhyani, Anil Kumar; Lazzi, Gianluca
2014-10-01
The need to correctly predict the voltage across terminals of mm-sized coils, with ferrite core, to be employed for magnetic stimulation of the peripheral neural system is the motivation for this work. In such applications, which rely on a capacitive discharge on the coil to realise a transient voltage curve of duration and strength suitable for neural stimulation, the correct modelling of the non-linearity of the ferrite core is critical. A demonstration of how a finite-difference model of the considered coils, which include a model of the current-controlled inductance in the coil, can be used to correctly predict the time-domain voltage waveforms across the terminals of a test coil is presented. Five coils of different dimensions, loaded with ferrite cores, have been fabricated and tested: the measured magnitude and width of the induced pulse are within 10% of simulated values.
Non-linearities in Theory-of-Mind Development
Blijd-Hoogewys, Els M. A.; van Geert, Paul L. C.
2017-01-01
Research on Theory-of-Mind (ToM) has mainly focused on ages of core ToM development. This article follows a quantitative approach focusing on the level of ToM understanding on a measurement scale, the ToM Storybooks, in 324 typically developing children between 3 and 11 years of age. It deals with the eventual occurrence of developmental non-linearities in ToM functioning, using smoothing techniques, dynamic growth model building and additional indicators, namely moving skewness, moving growth rate changes and moving variability. The ToM sum-scores showed an overall developmental trend that leveled off toward the age of 10 years. Within this overall trend two non-linearities in the group-based change pattern were found: a plateau at the age of around 56 months and a dip at the age of 72–78 months. These temporary regressions in ToM sum-score were accompanied by a decrease in growth rate and variability, and a change in skewness of the ToM data, all suggesting a developmental shift in ToM understanding. The temporary decreases also occurred in the different ToM sub-scores and most clearly so in the core ToM component of beliefs. It was also found that girls had an earlier growth spurt than boys and that the underlying developmental path was more salient in girls than in boys. The consequences of these findings are discussed from various theoretical points of view, with an emphasis on a dynamic systems interpretation of the underlying developmental paths. PMID:28101065
Non-linear dynamics of a spur gear pair
NASA Astrophysics Data System (ADS)
Kahraman, A.; Singh, R.
1990-10-01
Non-linear frequency response characteristics of a spur gear pair with backlash are examined in this paper for both external and internal excitations. The internal excitation is of importance from the high frequency noise and vibration control viewpoint and it represents the overall kinematic or static transmission error. Such problems may be significantly different from the rattle problems associated with external, low frequency torque excitation. Two solution methods, namely the digital simulation technique and the method of harmonic balance, have been used to develop the steady state solutions for the internal sinusoidal excitation. Difficulties associated with the determination of the multiple solutions at a given frequency in the digital simulation technique have been resolved, as one must search the entire initial conditions map. Such solutions and the transition frequencies for various impact situations are easily found by the method of harmonic balance. Further, the principle of superposition can be employed to analyze the periodic transmission error excitation and/or combined excitation problems provided that the excitation frequencies are sufficiently apart from each other. Our analytical predictions match satisfactorily with the limited experimental data available in the literature. Using the digital simulation, we have also observed that the chaotic and subharmonic resonances may exist in a gear pair depending upon the mean or design load, mean to alternating force ratio, damping and backlash. Specifically, the mean load determines the conditions for no impacts, single-sided impacts and double-sided impacts. Our results are different from the frequency response characteristics of the conventional, single-degree-of-freedom, clearance type non-linear system. Our formulation should form the basis of further analytical and experimental work in the geared rotor dynamics area.
Primordial black holes in linear and non-linear regimes
NASA Astrophysics Data System (ADS)
Allahyari, Alireza; Firouzjaee, Javad T.; Abolhasani, Ali Akbar
2017-06-01
We revisit the formation of primordial black holes (PBHs) in the radiation-dominated era for both linear and non-linear regimes, elaborating on the concept of an apparent horizon. Contrary to the expectation from vacuum models, we argue that in a cosmological setting a density fluctuation with a high density does not always collapse to a black hole. To this end, we first elaborate on the perturbation theory for spherically symmetric space times in the linear regime. Thereby, we introduce two gauges. This allows to introduce a well defined gauge-invariant quantity for the expansion of null geodesics. Using this quantity, we argue that PBHs do not form in the linear regime irrespective of the density of the background. Finally, we consider the formation of PBHs in non-linear regimes, adopting the spherical collapse picture. In this picture, over-densities are modeled by closed FRW models in the radiation-dominated era. The difference of our approach is that we start by finding an exact solution for a closed radiation-dominated universe. This yields exact results for turn-around time and radius. It is important that we take the initial conditions from the linear perturbation theory. Additionally, instead of using uniform Hubble gauge condition, both density and velocity perturbations are admitted in this approach. Thereby, the matching condition will impose an important constraint on the initial velocity perturbations δh0 = -δ0/2. This can be extended to higher orders. Using this constraint, we find that the apparent horizon of a PBH forms when δ > 3 at turn-around time. The corrections also appear from the third order. Moreover, a PBH forms when its apparent horizon is outside the sound horizon at the re-entry time. Applying this condition, we infer that the threshold value of the density perturbations at horizon re-entry should be larger than δth > 0.7.
Non-linearities in Theory-of-Mind Development.
Blijd-Hoogewys, Els M A; van Geert, Paul L C
2016-01-01
Research on Theory-of-Mind (ToM) has mainly focused on ages of core ToM development. This article follows a quantitative approach focusing on the level of ToM understanding on a measurement scale, the ToM Storybooks, in 324 typically developing children between 3 and 11 years of age. It deals with the eventual occurrence of developmental non-linearities in ToM functioning, using smoothing techniques, dynamic growth model building and additional indicators, namely moving skewness, moving growth rate changes and moving variability. The ToM sum-scores showed an overall developmental trend that leveled off toward the age of 10 years. Within this overall trend two non-linearities in the group-based change pattern were found: a plateau at the age of around 56 months and a dip at the age of 72-78 months. These temporary regressions in ToM sum-score were accompanied by a decrease in growth rate and variability, and a change in skewness of the ToM data, all suggesting a developmental shift in ToM understanding. The temporary decreases also occurred in the different ToM sub-scores and most clearly so in the core ToM component of beliefs. It was also found that girls had an earlier growth spurt than boys and that the underlying developmental path was more salient in girls than in boys. The consequences of these findings are discussed from various theoretical points of view, with an emphasis on a dynamic systems interpretation of the underlying developmental paths.
Non-linear diffusion and pattern formation in vortex matter
NASA Astrophysics Data System (ADS)
Wijngaarden, Rinke J.; Surdeanu, R.; Huijbregtse, J. M.; Rector, J. H.; Dam, B.; Griessen, R.; Einfeld, J.; Woerdenweber, R.
2000-03-01
Penetration of magnetic flux in YBa_2Cu_3O7 superconducting thin films and crystals in externally applied magnetic fields is visualized with a magneto-optical technique. A variety of flux patterns due to non-linear vortex behavior is observed: 1. Roughening of the flux front^1 with scaling exponents identical to those observed in burning paper^2. Two regimes are found where respectively spatial disorder and temporal disorder dominate. In the latter regime Kardar-Parisi-Zhang behavior is found. 2. Roughening of the flux profile similar to the Oslo model for rice-piles. 3. Fractal penetration of flux^3 with Hausdorff dimension depending on the critical current anisotropy. 4. Penetration as 'flux-rivers'. 5. The occurrence of commensurate and incommensurate channels in films with anti-dots as predicted in numerical simulations by Reichhardt, Olson and Nori^4. By comparison with numerical simulations, it is shown that most of the observed behavior can be explained in terms of non-linear diffusion of vortices. ^1R. Surdeanu, R.J. Wijngaarden, E. Visser, J.M. Huijbregtse, J.H. Rector, B. Dam and R. Griessen, Phys.Rev. Lett. 83 (1999) 2054 ^2J. Maunuksela, M. Myllys, O.-P. Kähkönen, J. Timonen, N. Provatas, M.J. Alava, T. Ala-Nissila, Phys. Rev. Lett. 79, 1515 (1997) ^3R. Surdeanu, R.J. Wijngaarden, B. Dam, J. Rector, R. Griessen, C. Rossel, Z.F. Ren and J.H. Wang, Phys Rev B 58 (1998) 12467 ^4C. Reichhardt, C.J. Olson and F. Nori, Phys. Rev. B 58, 6534 (1998)
NASA Astrophysics Data System (ADS)
Shimoi, Norihiro; Tanaka, Yasumitsu
2015-01-01
c-axis alignment in a polymer or crystal structure has drawn attention in numerous scientific and technological applications, including crystals, thin film growth, electro-optic devices, and phase difference optics. We here demonstrate a new approach based on retardation measurement that can obtain the direction of the c-axis alignment. This is employed to visualize the three-dimensional direction of continuous crystals as a thin optical film utilizing a liquid crystal panel, using retardation analysis equipment with high resolution measurement capability. The direction of the c-axis alignment is shown so as to allow a detailed characterization of the direction perpendicular to the plane. In this analysis, the direction of the c-axis alignment is identified, and differences between molecules at inequivalent sites are quantified. The results suggest that the excellent lubrication properties of the c-axis alignment may be due to a significant localization in lateral directions.
State-variable analysis of non-linear circuits with a desk computer
NASA Technical Reports Server (NTRS)
Cohen, E.
1981-01-01
State variable analysis was used to analyze the transient performance of non-linear circuits on a desk top computer. The non-linearities considered were not restricted to any circuit element. All that is required for analysis is the relationship defining each non-linearity be known in terms of points on a curve.
Discriminating Non-Linearity from Linearity: Its Cognitive Foundations in Five-Year-Olds
ERIC Educational Resources Information Center
Ebersbach, Mirjam; Van Dooren, Wim; Goudriaan, Margje N.; Verschaffel, Lieven
2010-01-01
People often have difficulties in understanding situations that involve non-linear processes. Also, the topic of non-linear functions is introduced relatively late in the curriculum. Previous research has nevertheless shown that already children aged 6 years and older are able to discriminate non-linear from linear processes. Within the present…
Discriminating Non-Linearity from Linearity: Its Cognitive Foundations in Five-Year-Olds
ERIC Educational Resources Information Center
Ebersbach, Mirjam; Van Dooren, Wim; Goudriaan, Margje N.; Verschaffel, Lieven
2010-01-01
People often have difficulties in understanding situations that involve non-linear processes. Also, the topic of non-linear functions is introduced relatively late in the curriculum. Previous research has nevertheless shown that already children aged 6 years and older are able to discriminate non-linear from linear processes. Within the present…
Rapid Non-Linear Uncertainty Propagation via Analytical Techniques
NASA Astrophysics Data System (ADS)
Fujimoto, K.; Scheeres, D. J.
2012-09-01
Space situational awareness (SSA) is known to be a data starved problem compared to traditional estimation problems in that observation gaps per object may span over days if not weeks. Therefore, consistent characterization of the uncertainty associated with these objects including non-linear effects is crucial in maintaining an accurate catalog of objects in Earth orbit. Simultaneously, the motion of satellites in Earth orbit is well-modeled in that it is particularly amenable to having their solution and their uncertainty described through analytic or semi-analytic techniques. Even when stronger non-gravitational perturbations such as solar radiation pressure and atmospheric drag are encountered, these perturbations generally have deterministic components that are substantially larger than their time-varying stochastic components. Analytic techniques are powerful because time propagation is only a matter of changing the time parameter, allowing for rapid computational turnaround. These two ideas are combined in this paper: a method of analytically propagating non-linear orbit uncertainties is discussed. In particular, the uncertainty is expressed as an analytic probability density function (pdf) for all time. For a deterministic system model, such pdfs may be obtained if the initial pdf and the system states for all time are also given analytically. Even when closed-form solutions are not available, approximate solutions exist in the form of Edgeworth series for pdfs and Taylor series for the states. The coefficients of the latter expansion are referred to as state transition tensors (STTs), which are a generalization of state transition matrices to arbitrary order. Analytically expressed pdfs can be incorporated in many practical tasks in SSA. One can compute the mean and covariance of the uncertainty, for example, with the moments of the initial pdf as inputs. This process does not involve any sampling and its accuracy can be determined a priori. Analytical
Non-linear evolution of the cosmic neutrino background
Villaescusa-Navarro, Francisco; Viel, Matteo; Peña-Garay, Carlos E-mail: spb@ias.edu E-mail: viel@oats.inaf.it
2013-03-01
We investigate the non-linear evolution of the relic cosmic neutrino background by running large box-size, high resolution N-body simulations which incorporate cold dark matter (CDM) and neutrinos as independent particle species. Our set of simulations explore the properties of neutrinos in a reference ΛCDM model with total neutrino masses between 0.05-0.60 eV in cold dark matter haloes of mass 10{sup 11}−10{sup 15} h{sup −1}M{sub s}un, over a redshift range z = 0−2. We compute the halo mass function and show that it is reasonably well fitted by the Sheth-Tormen formula, once the neutrino contribution to the total matter is removed. More importantly, we focus on the CDM and neutrino properties of the density and peculiar velocity fields in the cosmological volume, inside and in the outskirts of virialized haloes. The dynamical state of the neutrino particles depends strongly on their momentum: whereas neutrinos in the low velocity tail behave similarly to CDM particles, neutrinos in the high velocity tail are not affected by the clustering of the underlying CDM component. We find that the neutrino (linear) unperturbed momentum distribution is modified and mass and redshift dependent deviations from the expected Fermi-Dirac distribution are in place both in the cosmological volume and inside haloes. The neutrino density profiles around virialized haloes have been carefully investigated and a simple fitting formula is provided. The neutrino profile, unlike the cold dark matter one, is found to be cored with core size and central density that depend on the neutrino mass, redshift and mass of the halo, for halos of masses larger than ∼ 10{sup 13.5}h{sup −1}M{sub s}un. For lower masses the neutrino profile is best fitted by a simple power-law relation in the range probed by the simulations. The results we obtain are numerically converged in terms of neutrino profiles at the 10% level for scales above ∼ 200 h{sup −1}kpc at z = 0, and are stable with
Non-linear processes in the Earth atmosphere boundary layer
NASA Astrophysics Data System (ADS)
Grunskaya, Lubov; Valery, Isakevich; Dmitry, Rubay
2013-04-01
The work is connected with studying electromagnetic fields in the resonator Earth-Ionosphere. There is studied the interconnection of tide processes of geophysical and astrophysical origin with the Earth electromagnetic fields. On account of non-linear property of the resonator Earth-Ionosphere the tides (moon and astrophysical tides) in the electromagnetic Earth fields are kinds of polyharmonic nature. It is impossible to detect such non-linear processes with the help of the classical spectral analysis. Therefore to extract tide processes in the electromagnetic fields, the method of covariance matrix eigen vectors is used. Experimental investigations of electromagnetic fields in the atmosphere boundary layer are done at the distance spaced stations, situated on Vladimir State University test ground, at Main Geophysical Observatory (St. Petersburg), on Kamchatka pen., on Lake Baikal. In 2012 there was continued to operate the multichannel synchronic monitoring system of electrical and geomagnetic fields at the spaced apart stations: VSU physical experimental proving ground; the station of the Institute of Solar and Terrestrial Physics of Russian Academy of Science (RAS) at Lake Baikal; the station of the Institute of volcanology and seismology of RAS in Paratunka; the station in Obninsk on the base of the scientific and production society "Typhoon". Such investigations turned out to be possible after developing the method of scanning experimental signal of electromagnetic field into non- correlated components. There was used a method of the analysis of the eigen vectors ofthe time series covariance matrix for exposing influence of the moon tides on Ez. The method allows to distribute an experimental signal into non-correlated periodicities. The present method is effective just in the situation when energetical deposit because of possible influence of moon tides upon the electromagnetic fields is little. There have been developed and realized in program components
Filtering Non-Linear Transfer Functions on Surfaces.
Heitz, Eric; Nowrouzezahrai, Derek; Poulin, Pierre; Neyret, Fabrice
2014-07-01
Applying non-linear transfer functions and look-up tables to procedural functions (such as noise), surface attributes, or even surface geometry are common strategies used to enhance visual detail. Their simplicity and ability to mimic a wide range of realistic appearances have led to their adoption in many rendering problems. As with any textured or geometric detail, proper filtering is needed to reduce aliasing when viewed across a range of distances, but accurate and efficient transfer function filtering remains an open problem for several reasons: transfer functions are complex and non-linear, especially when mapped through procedural noise and/or geometry-dependent functions, and the effects of perspective and masking further complicate the filtering over a pixel's footprint. We accurately solve this problem by computing and sampling from specialized filtering distributions on the fly, yielding very fast performance. We investigate the case where the transfer function to filter is a color map applied to (macroscale) surface textures (like noise), as well as color maps applied according to (microscale) geometric details. We introduce a novel representation of a (potentially modulated) color map's distribution over pixel footprints using Gaussian statistics and, in the more complex case of high-resolution color mapped microsurface details, our filtering is view- and light-dependent, and capable of correctly handling masking and occlusion effects. Our approach can be generalized to filter other physical-based rendering quantities. We propose an application to shading with irradiance environment maps over large terrains. Our framework is also compatible with the case of transfer functions used to warp surface geometry, as long as the transformations can be represented with Gaussian statistics, leading to proper view- and light-dependent filtering results. Our results match ground truth and our solution is well suited to real-time applications, requires only a few
Linear and Non-Linear Forecasts of Solar Activity
NASA Astrophysics Data System (ADS)
Warren, H.
2016-12-01
Variations in thermospheric density play a major role in perturbing the orbits of objects in low Earth orbit. These variations are strongly influenced by changes in the solar irradiance at extreme ultraviolet (EUV) wavelengths that are ultimately driven by changing levels of solar magnetic activity. Thus predicting the conjunction of operational satellites with orbital debris requires accurate forecasts of solar activity. Current operational models rely on forecasts of proxies for solar activity based on simple linear extrapolation methods. In this poster we present a systematic study of these methods applied to the 10.7 cm solar radio flux, a composite Mg core-to-wing ratio, the total unsigned solar magnetic flux, and the He II 304 irradiance observed by the EVE instrument on the Solar Dynamics Observatory. We find that although RMS errors in these forecasts appear to be small, the corresponding errors in very simple models, such as the persistence of the last measurement, are also small, and the formal skill scores are relatively modest. The use of these proxies and measurements in non-linear methods, such Gaussian process regression and recurrent neural networks, will also be discussed.
Non-linear computer simulation of brain deformation.
Miller, K
2001-01-01
This paper presents realistic computer simulation of deformation of the brain subject to in-vivo indentation. The work presented provides a step towards neurosurgical simulation, with applications to non-rigid registration, virtual reality training and operation planning systems and robotic devices to perform minimally invasive brain surgery. In order to properly analyze experimental data collected in-vivo, a three-dimensional, non-linear finite element model of the brain was developed. Magnetic resonance imaging techniques were used to obtain geometric information needed for the model. The shape of the force-displacement curve obtained using the numerical solution was very similar to the experimental one. The predicted forces were about 31% lower than those recorded during the experiment. Having in mind that the coefficients in the model had been identified based on experimental data obtained in-vitro, and large variability of mechanical properties of biological tissues, such agreement can be considered as very good. By appropriately increasing material parameters describing instantaneous stiffness of the tissue one is able, without changing the structure of the model, to reproduce experimental curve almost perfectly. Numerical studies showed also, that the linear, viscoelastic model of brain tissue is not appropriate for the modeling brain tissue deformation even for moderate strains.
Experimental study of a linear/non-linear flux rope
DeHaas, Timothy; Gekelman, Walter; Van Compernolle, Bart
2015-08-15
Flux ropes are magnetic structures of helical field lines, accompanied by spiraling currents. Commonly observed on the solar surface extending into the solar atmosphere, flux ropes are naturally occurring and have been observed by satellites in the near earth and in laboratory environments. In this experiment, a single flux rope (r = 2.5 cm, L = 1100 cm) was formed in the cylindrical, magnetized plasma of the Large Plasma Device (LaPD, L = 2200 cm, r{sub plasma} = 30 cm, n{sub o} = 10{sup 12 }cm{sup −3}, T{sub e} = 4 eV, He). The flux rope was generated by a DC discharge between an electron emitting cathode and anode. This fixes the rope at its source while allowing it to freely move about the anode. At large currents (I > πr{sup 2}B{sub 0}c/2 L), the flux rope becomes helical in structure and oscillates about a central axis. Under varying Alfven speeds and injection current, the transition of the flux rope from stable to kink-unstable was examined. As it becomes non-linear, oscillations in the magnetic signals shift from sinusoidal to Sawtooth-like, associated with elliptical motion of the flux rope; or the signal becomes intermittent as its current density increases.
Non-linear image scanning microscopy (Conference Presentation)
NASA Astrophysics Data System (ADS)
Gregor, Ingo; Ros, Robert; Enderlein, Jörg
2017-02-01
Nowadays, multiphoton microscopy can be considered as a routine method for the observation of living cells, organs, up to whole organisms. Second-harmonics generation (SHG) imaging has evolved to a powerful qualitative and label-free method for studying fibrillar structures, like collagen networks. However, examples of super-resolution non-linear microscopy are rare. So far, such approaches require complex setups and advanced synchronization of scanning elements limiting the image acquisition rates. We describe theory and realization of a super-resolution image scanning microscope [1, 2] using two-photon excited fluorescence as well as second-harmonic generation. It requires only minor modifications compared to a classical two-photon laser-scanning microscope and allows image acquisition at the high frame rates of a resonant galvo-scanner. We achieve excellent sensitivity and high frame-rate in combination with two-times improved lateral resolution. We applied this method to fixed cells, collagen hydrogels, as well as living fly embryos. Further, we proofed the excellent image quality of our setup for deep tissue imaging. 1. Müller C.B. and Enderlein J. (2010) Image scanning microscopy. Phys. Rev. Lett. 104(19), 198101. 2. Sheppard C.J.R. (1988) Super-resolution in confocal imaging. Optik (Stuttg) 80 53-54.
Non linear processes modulated by low doses of radiation exposure
NASA Astrophysics Data System (ADS)
Mariotti, Luca; Ottolenghi, Andrea; Alloni, Daniele; Babini, Gabriele; Morini, Jacopo; Baiocco, Giorgio
The perturbation induced by radiation impinging on biological targets can stimulate the activation of several different pathways, spanning from the DNA damage processing to intra/extra -cellular signalling. In the mechanistic investigation of radiobiological damage this complex “system” response (e.g. omics, signalling networks, micro-environmental modifications, etc.) has to be taken into account, shifting from a focus on the DNA molecule solely to a systemic/collective view. An additional complication comes from the finding that the individual response of each of the involved processes is often not linear as a function of the dose. In this context, a systems biology approach to investigate the effects of low dose irradiations on intra/extra-cellular signalling will be presented, where low doses of radiation act as a mild perturbation of a robustly interconnected network. Results obtained through a multi-level investigation of both DNA damage repair processes (e.g. gamma-H2AX response) and of the activation kinetics for intra/extra cellular signalling pathways (e.g. NFkB activation) show that the overall cell response is dominated by non-linear processes - such as negative feedbacks - leading to possible non equilibrium steady states and to a poor signal-to-noise ratio. Together with experimental data of radiation perturbed pathways, different modelling approaches will be also discussed.
Non linear inversion of gravity gradients and the GGI gradiometer
NASA Astrophysics Data System (ADS)
Talwani, Manik
2011-12-01
All gradiometers currently operating for exploration in the field are based on Lockheed Martin's GGI gradiometer. The working of this gradiometer is described and a method for robust non linear inversion of gravity gradients is presented. The inversion method involves obtaining the gradient response of a trial body consisting of vertical rectangular prisms. The inversion adjusts the depth to the tops or bases of the prisms. In the trial model all the prisms are not required to have the same area of cross section or the same density (which can also be allowed to vary with depth). The depth to the tops and bottoms of each prism can also be different. This response is compared with the observed values of gradient and through an iterative procedure, the difference is minimized in a least square sense to arrive at a best fitting model by varying the position of the tops or bottoms of the prisms. Each gradient can be individually inverted or one or more gradients can be jointly inverted. The method is extended to invert gravity values individually or jointly with gradient values. The use of Differential Curvature, a quantity which is directly obtained by current gradiometers in use and which is an invariant under a rotation in the horizontal plane, is emphasized. Synthetic examples as well as a field example of inversion are given.
Non-linear optical measurements using a scanned, Bessel beam
NASA Astrophysics Data System (ADS)
Collier, Bradley B.; Awasthi, Samir; Lieu, Deborah K.; Chan, James W.
2015-03-01
Oftentimes cells are removed from the body for disease diagnosis or cellular research. This typically requires fluorescent labeling followed by sorting with a flow cytometer; however, possible disruption of cellular function or even cell death due to the presence of the label can occur. This may be acceptable for ex vivo applications, but as cells are more frequently moving from the lab to the body, label-free methods of cell sorting are needed to eliminate these issues. This is especially true of the growing field of stem cell research where specialized cells are needed for treatments. Because differentiation processes are not completely efficient, cells must be sorted to eliminate any unwanted cells (i.e. un-differentiated or differentiated into an unwanted cell type). In order to perform label-free measurements, non-linear optics (NLO) have been increasingly utilized for single cell analysis because of their ability to not disrupt cellular function. An optical system was developed for the measurement of NLO in a microfluidic channel similar to a flow cytometer. In order to improve the excitation efficiency of NLO, a scanned Bessel beam was utilized to create a light-sheet across the channel. The system was tested by monitoring twophoton fluorescence from polystyrene microbeads of different sizes. Fluorescence intensity obtained from light-sheet measurements were significantly greater than measurements made using a static Gaussian beam. In addition, the increase in intensity from larger sized beads was more evident for the light-sheet system.
Non-linear model for compression tests on articular cartilage.
Grillo, Alfio; Guaily, Amr; Giverso, Chiara; Federico, Salvatore
2015-07-01
Hydrated soft tissues, such as articular cartilage, are often modeled as biphasic systems with individually incompressible solid and fluid phases, and biphasic models are employed to fit experimental data in order to determine the mechanical and hydraulic properties of the tissues. Two of the most common experimental setups are confined and unconfined compression. Analytical solutions exist for the unconfined case with the linear, isotropic, homogeneous model of articular cartilage, and for the confined case with the non-linear, isotropic, homogeneous model. The aim of this contribution is to provide an easily implementable numerical tool to determine a solution to the governing differential equations of (homogeneous and isotropic) unconfined and (inhomogeneous and isotropic) confined compression under large deformations. The large-deformation governing equations are reduced to equivalent diffusive equations, which are then solved by means of finite difference (FD) methods. The solution strategy proposed here could be used to generate benchmark tests for validating complex user-defined material models within finite element (FE) implementations, and for determining the tissue's mechanical and hydraulic properties from experimental data.
Channel Capacity of Non-Linear Transmission Systems
NASA Astrophysics Data System (ADS)
Ellis, Andrew D.; Zhao, Jian
Since their introduction in the late 1970s, the capacity of optical communication links has grown exponentially, fuelled by a series of key innovations including movement between the three telecommunication windows of 850 nm, 1,310 nm and 1,550 nm, distributed feedback laser, erbium-doped fibre amplifiers (EDFAs), dispersion-shifted and dispersion-managed fibre links, external modulation, wavelength division multiplexing, optical switching, forward error correction (FEC), Raman amplification, and most recently, coherent detection, electronic signal processing and optical orthogonal frequency division multiplexing (OFDM). Throughout this evolution, one constant factor has been the use of single-mode optical fibre, whose fundamental principles dated back to the 1800s, when Irish scientist, John Tyndall demonstrated in a lecture to the Royal Society in London that light could be guided through a curved stream of water [1]. Following many developments, including the proposal for waveguides by J.J. Thompson [2], the presentation of detailed calculations for dielectric waveguides by Snitzer [3], the proposal [4] and fabrication [5] of ultra low loss fibres, single-mode fibres were first adopted for non-experimental use in Dorset, UK in 1975, and are still in use today, despite the evolving designs to control chromatic dispersion and non-linearity.
Non Linear Force Free Field Modeling for a Pseudostreamer
NASA Astrophysics Data System (ADS)
Karna, Nishu; Savcheva, Antonia; Gibson, Sarah; Tassev, Svetlin V.
2017-08-01
In this study we present a magnetic configuration of a pseudostreamer observed on April 18, 2015 on southern west limb embedding a filament cavity. We constructed Non Linear Force Free Field (NLFFF) model using the flux rope insertion method. The NLFFF model produces the three-dimensional coronal magnetic field constrained by observed coronal structures and photospheric magnetogram. SDO/HMI magnetogram was used as an input for the model. The high spatial and temporal resolution of the SDO/AIA allows us to select best-fit models that match the observations. The MLSO/CoMP observations provide full-Sun observations of the magnetic field in the corona. The primary observables of CoMP are the four Stokes parameters (I, Q, U, V). In addition, we perform a topology analysis of the models in order to determine the location of quasi-separatrix layers (QSLs). QSLs are used as a proxy to determine where the strong electric current sheets can develop in the corona and also provide important information about the connectivity in complicated magnetic field configuration. We present the major properties of the 3D QSL and FLEDGE maps and the evolution of 3D coronal structures during the magnetofrictional process. We produce FORWARD-modeled observables from our NLFFF models and compare to a toy MHD FORWARD model and the observations.
Studying non-linear dynamics with atom-optics billiards
NASA Astrophysics Data System (ADS)
Davidson, Nir
2002-05-01
The dynamics of particles moving with constant speed in a bounded region and undergoing elastic collisions at the region's boundary (a "billiard") has been extensively investigated both classically and quantum mechanically, since this very simple system exhibits a rich variety of non-linear dynamics phenomena, and is often used as a paradigm for studying the foundations of statistical mechanics. Recently, an "atom-optics billiard" was realized, using a tightly focused laser beam far detuned above the atomic resonance, and rapidly scanning along the desired trap shape(V. Milner, J. L. Hanssen, W. C. Campbell, and M. G. Raizen, Phys. Rev. Lett. 86), 1514 (2001)^,(N. Friedman, A. Kaplan, D. Carasso, and N. Davidson, Phys. Rev. Lett. 86), 1518 (2001). The beam generates a time-averaged potential wall whose shape is varied to create different dynamics of the trapped atoms. Using this system, we demonstrate regular, chaotic and mixed motion, where stickiness close to KAM islands embedded in a chaotic sea yealds Levy flights. We study different mechanisms that affect phase-space structure, e.g. scattering^3, wall softness(A. Kaplan, N. Friedman, M. Andersen, and N. Davidson, Phys. Rev. Lett. 87), 274101 (2001). and external forces(M. Andersen, A. Kaplan, N. Friedman, and N. Davidson, submitted to J. Phys. B (2002).). Exploiting the long atomic coherence times achievable in the billiards, our experimental system also sheds new light on the interplay between dynamics and coherence.
A non linear analytical model of switched reluctance machines
NASA Astrophysics Data System (ADS)
Sofiane, Y.; Tounzi, A.; Piriou, F.
2002-06-01
Nowadays, the switched reluctance machine are widely used. To determine their performances and to elaborate control strategy, we generally use the linear analytical model. Unhappily, this last is not very accurate. To yield accurate modelling results, we use then numerical models based on either 2D or 3D Finite Element Method. However, this approach is very expensive in terms of computation time and remains suitable to study the behaviour of eventually a whole device. However, it is not, a priori, adapted to elaborate control strategy for electrical machines. This paper deals with a non linear analytical model in terms of variable inductances. The theoretical development of the proposed model is introduced. Then, the model is applied to study the behaviour of a whole controlled switched reluctance machine. The parameters of the structure are identified from a 2D numerical model. They can also be determined from an experimental bench. Then, the results given by the proposed model are compared to those issue from the 2D-FEM approach and from the classical linear analytical model.
CMB hemispherical asymmetry from non-linear isocurvature perturbations
Assadullahi, Hooshyar; Wands, David; Firouzjahi, Hassan; Namjoo, Mohammad Hossein E-mail: firouz@mail.ipm.ir E-mail: david.wands@port.ac.uk
2015-04-01
We investigate whether non-adiabatic perturbations from inflation could produce an asymmetric distribution of temperature anisotropies on large angular scales in the cosmic microwave background (CMB). We use a generalised non-linear δ N formalism to calculate the non-Gaussianity of the primordial density and isocurvature perturbations due to the presence of non-adiabatic, but approximately scale-invariant field fluctuations during multi-field inflation. This local-type non-Gaussianity leads to a correlation between very long wavelength inhomogeneities, larger than our observable horizon, and smaller scale fluctuations in the radiation and matter density. Matter isocurvature perturbations contribute primarily to low CMB multipoles and hence can lead to a hemispherical asymmetry on large angular scales, with negligible asymmetry on smaller scales. In curvaton models, where the matter isocurvature perturbation is partly correlated with the primordial density perturbation, we are unable to obtain a significant asymmetry on large angular scales while respecting current observational constraints on the observed quadrupole. However in the axion model, where the matter isocurvature and primordial density perturbations are uncorrelated, we find it may be possible to obtain a significant asymmetry due to isocurvature modes on large angular scales. Such an isocurvature origin for the hemispherical asymmetry would naturally give rise to a distinctive asymmetry in the CMB polarisation on large scales.
Non-linear modulation of short wavelength compressional Alfven eigenmodes
Fredrickson, E. D.; Gorelenkov, N. N.; Podesta, M.; Gerhardt, S. P.; Bell, R. E.; Diallo, A.; LeBlanc, B.; Bortolon, A.; Crocker, N. A.; Levinton, F. M.; Yuh, H.
2013-04-15
Most Alfvenic activity in the frequency range between toroidal Alfven eigenmodes and roughly one half of the ion cyclotron frequency on National Spherical Torus eXperiment [Ono et al., Nucl. Fusion 40, 557 (2000)], that is, approximately 0.3 MHz up to Almost-Equal-To 1.2 MHz, are modes propagating counter to the neutral beam ions. These have been modeled as Compressional and Global Alfven Eigenmodes (CAE and GAE) and are excited through a Doppler-shifted cyclotron resonance with the beam ions. There is also a class of co-propagating modes at higher frequency than the counter-propagating CAE and GAE. These modes have been identified as CAE, and are seen mostly in the company of a low frequency, n = 1 kink-like mode. In this paper, we present measurements of the spectrum of these high frequency CAE (hfCAE) and their mode structure. We compare those measurements to a simple model of CAE and present a predator-prey type model of the curious non-linear coupling of the hfCAE and the low frequency kink-like mode.
Optimum Damping in a Non-Linear Base Isolation System
NASA Astrophysics Data System (ADS)
Jangid, R. S.
1996-02-01
Optimum isolation damping for minimum acceleration of a base-isolated structure subjected to earthquake ground excitation is investigated. The stochastic model of the El-Centro1940 earthquake, which preserves the non-stationary evolution of amplitude and frequency content of ground motion, is used as an earthquake excitation. The base isolated structure consists of a linear flexible shear type multi-storey building supported on a base isolation system. The resilient-friction base isolator (R-FBI) is considered as an isolation system. The non-stationary stochastic response of the system is obtained by the time dependent equivalent linearization technique as the force-deformation of the R-FBI system is non-linear. The optimum damping of the R-FBI system is obtained under important parametric variations; i.e., the coefficient of friction of the R-FBI system, the period and damping of the superstructure; the effective period of base isolation. The criterion selected for optimality is the minimization of the top floor root mean square (r.m.s.) acceleration. It is shown that the above parameters have significant effects on optimum isolation damping.
Amplitude relations in non-linear sigma model
NASA Astrophysics Data System (ADS)
Chen, Gang; Du, Yi-Jian
2014-01-01
In this paper, we investigate tree-level scattering amplitude relations in U( N) non-linear sigma model. We use Cayley parametrization. As was shown in the recent works [23,24], both on-shell amplitudes and off-shell currents with odd points have to vanish under Cayley parametrization. We prove the off-shell U(1) identity and fundamental BCJ relation for even-point currents. By taking the on-shell limits of the off-shell relations, we show that the color-ordered tree amplitudes with even points satisfy U(1)-decoupling identity and fundamental BCJ relation, which have the same formations within Yang-Mills theory. We further state that all the on-shell general KK, BCJ relations as well as the minimal-basis expansion are also satisfied by color-ordered tree amplitudes. As a consequence of the relations among color-ordered amplitudes, the total 2 m-point tree amplitudes satisfy DDM form of color decomposition as well as KLT relation.
Tailored Excitation using Non-Linear B0-Shims
Duan, Qi; van Gelderen, Peter; Duyn, Jeff
2011-01-01
In high field MRI, RF flip angle inhomogeneity due to wavelength effects can lead to spatial variations in contrast and sensitivity. Improved flip angle homogeneity can be achieved through multi-dimensional excitation, but long RF pulse durations limit practical application. A recent approach to reduce RF pulse duration is based on parallel excitation through multiple RF channels. Here, an alternative approach to shorten multi-dimensional excitation is proposed that makes use of non-linear spatial variations in the stationary (B0) magnetic field during a B0-sensitive excitation pulse. As initial demonstration, the method was applied to 2D gradient echo (GE) MRI of human brain at 7T. Using B0 shims with up to second order spatial dependence, it is demonstrated that root-mean-squared flip angle variation can be reduced from 20% to 11% with RF pulse lengths that are practical for general GE imaging applications without requiring parallel excitation. The method is expected to improve contrast and sensitivity in GE MRI of human brain at high field. PMID:22222623
Primordial Black Holes in non-linear perturbation theory
NASA Astrophysics Data System (ADS)
Hidalgo, Juan Carlos
2009-10-01
This thesis begins with a study of the origin of cosmological fluctuations with special attention to those cases in which the non-Gaussian correlation functions are large. The analysis shows that perturbations from an almost massless auxiliary field generically produce large values of the non-linear parameter f_NL. The effects of including non-Gaussian correlation functions in the statistics of cosmological structure are explored by constructing a non-Gaussian probability distribution function (PDF). Such PDF is derived for the comoving curvature perturbation from first principles in the context of quantum field theory, with n-point correlation functions as the only input. The non-Gaussian PDF is then used to explore two important problems in the physics of primordial black holes (PBHs): First, to compute non-Gaussian corrections to the number of PBHs generated from the primordial curvature fluctuations. The second application concerns new cosmological observables. The formation of PBHs is known to depend on two main physical characteristics: the strength of the gravitational field produced by the initial curvature inhomogeneity and the pressure gradient at the edge of the curvature configuration. We account for the probability of finding these configurations by using two parameters: The amplitude of the inhomogeneity and its second radial derivative, evaluated at the centre of the configuration. The implications of the derived probability for the fraction of mass in the universe in the form of PBHs are discussed.
Searching for Non-linearities in Natural Language
NASA Astrophysics Data System (ADS)
Ribarov, Kiril; Smrz, Otakar
2003-08-01
Inspired by wide range of applicability of what is commonly referred to as chaos theories, we explore the nature of energy series of a signal of human speech in the light of nonlinear dynamics. Using the TISEAN software package, analyses on various recordings of the language energy series were carried out (single speaker — different speeches; single speech - different speakers; dialogues; talkshows). Also correlated to other tenths of experiments conveyed on different linguistic inputs as written and morphologically analyzed texts, the presented experiment outputs (up to our knowledge, similar experiments have not been performed yet) reveal the complex and tricky nature of the language and are in favor of certain linguistic hypotheses. However, without further research, they do not encourage us to make explicit claims about the language signal such as dimension estimations (although probably possible) or attractor reconstruction. Our main considerations include: (a) a look into the stochastic nature of the language aiming towards reduction of the currently very large number of parameters present in language models based on Hidden Markov Models on language n-grams; (b) visualization of the behavior of the language and revelation of what could possibly be behind the `noisy' stream of sounds/letters/word-classes observed in our experiments; and last but not least (c) presentation of a new type of signal to the community exploring natural non-linear phenomena.
Passive dynamic controllers for non-linear mechanical systems
NASA Technical Reports Server (NTRS)
Juang, Jer-Nan; Wu, Shih-Chin; Phan, Minh; Longman, Richard W.
1991-01-01
A methodology for model-independent controller design for controlling large angular motion of multi-body dynamic systems is outlined.The controlled system may consist of rigid and flexible components that undergo large rigid body motion and small elastic deformations. Control forces/torques are applied to drive the system, and at the same time suppress the vibrations due to flexibility of the components. The proposed controller consists of passive second-order systems which may be designed with little knowledge of the system parameters, even if the controlled system is non-linear. Under rather general assumptions, the passive design assures that the closed loop system has guaranteed stability properties. Unlike positive real controller design, stabilization can be accomplished without direct velocity feedback. In addition, the second-order passive design allows dynamic feedback controllers with considerable freedom to tune for desired system response, and to avoid actuator saturation. After developing the basic mathematical formulation of the design methodology, simulation results are presented to illustrate the proposed approach applied to a flexible six-degree-of-freedom manipulator.
Organic non-linear optics and opto-electronics
NASA Astrophysics Data System (ADS)
Maldonado, J. L.; Ramos-Ortíz, G.; Rodríguez, M.; Meneses-Nava, M. A.; Barbosa-García, O.; Santillán, R.; Farfán, N.
2010-12-01
π-conjugated organic molecules and polymers are of great importance in physics, chemistry, material science and engineering. It is expected that, in the near future, organic materials will find widespread use in many technological applications. In the case of organic opto-electronic systems, the list of devices includes light emitting diodes (OLEDs), photovoltaic cells (OPVs), field-effect transistors (OFET), photorefractive materials for light manipulation, among others. These materials are also used for photonic applications: all-optical switching, modulators, optical correlators, plastic waveguides, all polymeric integrated circuits, solid-state lasers, and for biophotonic applications as in the case of the development of organic labels for multiphoton microscopy and photodynamic therapy. The advances in the developing of organic compounds with better mechanical, electrical, and optical (linear and non-linear) characteristics are of a great importance for this field. Here, we present the research on this area carried out at the Centro de Investigaciones en Óp-tica (CIO), in collaboration with Chemistry Departments of different institutions. This work focuses on the optical characterization of materials through several techniques such as TOF, FWM, TBC, THG Maker Fringes, HRS, Z-scan, and TPEF. Additionally, some applications, such as dynamic holography by using photorefractive polymers, and OPVs cells will be discussed.
Passive dynamic controllers for non-linear mechanical systems
NASA Technical Reports Server (NTRS)
Juang, Jer-Nan; Wu, Shih-Chin; Phan, Minh; Longman, Richard W.
1991-01-01
A methodology for model-independent controller design for controlling large angular motion of multi-body dynamic systems is outlined.The controlled system may consist of rigid and flexible components that undergo large rigid body motion and small elastic deformations. Control forces/torques are applied to drive the system, and at the same time suppress the vibrations due to flexibility of the components. The proposed controller consists of passive second-order systems which may be designed with little knowledge of the system parameters, even if the controlled system is non-linear. Under rather general assumptions, the passive design assures that the closed loop system has guaranteed stability properties. Unlike positive real controller design, stabilization can be accomplished without direct velocity feedback. In addition, the second-order passive design allows dynamic feedback controllers with considerable freedom to tune for desired system response, and to avoid actuator saturation. After developing the basic mathematical formulation of the design methodology, simulation results are presented to illustrate the proposed approach applied to a flexible six-degree-of-freedom manipulator.
Non-Linear Optical Microscopy Sheds Light on Cardiovascular Disease
Caorsi, Valentina; Toepfer, Christopher; Sikkel, Markus B.; Lyon, Alexander R.; MacLeod, Ken; Ferenczi, Mike A.
2013-01-01
Many cardiac diseases have been associated with increased fibrosis and changes in the organization of fibrillar collagen. The degree of fibrosis is routinely analyzed with invasive histological and immunohistochemical methods, giving a limited and qualitative understanding of the tissue's morphological adaptation to disease. Our aim is to quantitatively evaluate the increase in fibrosis by three-dimensional imaging of the collagen network in the myocardium using the non-linear optical microscopy techniques Two-Photon Excitation microscopy (TPE) and Second Harmonic signal Generation (SHG). No sample staining is needed because numerous endogenous fluorophores are excited by a two-photon mechanism and highly non-centrosymmetric structures such as collagen generate strong second harmonic signals. We propose for the first time a 3D quantitative analysis to carefully evaluate the increased fibrosis in tissue from a rat model of heart failure post myocardial infarction. We show how to measure changes in fibrosis from the backward SHG (BSHG) alone, as only backward-propagating SHG is accessible for true in vivo applications. A 5-fold increase in collagen I fibrosis is detected in the remote surviving myocardium measured 20 weeks after infarction. The spatial distribution is also shown to change markedly, providing insight into the morphology of disease progression. PMID:23409139
Multigrid approaches to non-linear diffusion problems on unstructured meshes
NASA Technical Reports Server (NTRS)
Mavriplis, Dimitri J.; Bushnell, Dennis M. (Technical Monitor)
2001-01-01
The efficiency of three multigrid methods for solving highly non-linear diffusion problems on two-dimensional unstructured meshes is examined. The three multigrid methods differ mainly in the manner in which the nonlinearities of the governing equations are handled. These comprise a non-linear full approximation storage (FAS) multigrid method which is used to solve the non-linear equations directly, a linear multigrid method which is used to solve the linear system arising from a Newton linearization of the non-linear system, and a hybrid scheme which is based on a non-linear FAS multigrid scheme, but employs a linear solver on each level as a smoother. Results indicate that all methods are equally effective at converging the non-linear residual in a given number of grid sweeps, but that the linear solver is more efficient in cpu time due to the lower cost of linear versus non-linear grid sweeps.
Microscopic Study of c-axis Proximity Effect in Cuprate-Manganite Heterostructures
NASA Astrophysics Data System (ADS)
Zhang, H.; Fridman, I.; Gauquelin, N.; Botton, G. A.; Wei, J. Y. T.
2013-03-01
Recent studies have reported long-ranged proximity effect in epitaxial thin-film heterostructures of ferromagnetic manganites and superconducting cuprates, with possible origins in novel spin-triplet correlations. A key evidence for this effect is the suppression of the superconducting Tc observed in multilayer films of La2/3Ca1/3MnO3/YBa2Cu3O7-δ (LCMO/YBCO). However, scanning tunnelling spectroscopy on c-axis LCMO/YBCO bilayers have not seen direct evidence for proximity-induced pairing down to 5nm LCMO thickness. We re-examine the Tc suppression by performing atomically-resolved transmission electron microscopy and resistivity measurements on c-axis YBCO/LCMO films grown by pulsed laser deposition, and relating the microstructure in YBCO with the layer thickness and Tc. The microscopy revealed double CuO-chain intergrowths forming non-stoichiometric YBCO-247 regions that do not appear in x-ray diffraction, but can be related to the Tc suppression. We attribute these intergrowths to heteroepitaxial strain, by comparing all the lattice parameters and symmetries involved. Work supported by NSERC, CFI/OIT and CIFAR
Latest developments of large-diameter c-axis sapphire grown by CHES method
NASA Astrophysics Data System (ADS)
Richard Schwerdtfeger, C.; Ullal, Saurabh; Shetty, Raj; Filgate, Joshua; Dhanaraj, Govindhan
2014-05-01
Large diameter c-axis crystal growth of sapphire boules up to 50 kg is in production at many sites world-wide. It has long been known that c-axis growth of sapphire could be the most cost-effective way to produce large diameter substrates for LED applications compared to a-axis growth with orthogonal coring due to the extremely large size boule required to core large diameter cores from the side of the boule. This paper will discuss the latest improvements, characterization, material utilizations, and crystal quality of boules designed specifically for 6-in., 8-in., and 10-in. wafer production. Improvements and continued R&D in slicing, polishing, and MOCVD of 6-in. and 8-in. sapphire has poised the industry for a rapid shift to larger diameter substrates, if the cores can be cost-effective. ARC Energy's CHES technology can produce 170 mm diameter boules optimized for 6-in. (150 mm) diameter wafer production. Additionally it can produce 8-in. or 10-in. diameter cores directly from 220 mm or 260 mm diameter boules, respectively. The latest developments, both equipment and process, will be discussed along with the resulting boule and core quality. Cost reductions for these large diameter cores will be shown to provide much more cost-effective 6-in. and 8-in. substrates. This low-cost enabling technology is poised to spur stable and long-term LED industry growth.
Synthesis of c-axis oriented AlN thin films on different substrates: A review
Iriarte, G.F.
2010-09-15
Highly c-axis oriented AlN thin films have been deposited by reactive sputtering on different substrates. The crystallographic properties of layered film structures consisting of a piezoelectric layer, aluminum nitride (AlN), synthesized on a variety of substrates, have been examined. Aluminum nitride thin films have been deposited by reactive pulsed-DC magnetron sputtering using an aluminum target in an Ar/N{sub 2} gas mixture. The influence of the most critical deposition parameters on the AlN thin film crystallography has been investigated by means of X-ray diffraction (XRD) analysis of the rocking curve Full-Width at Half Maximum (FWHM) of the AlN-(0 0 0 2) peak. The relationship between the substrate, the synthesis parameters and the crystallographic orientation of the AlN thin films is discussed. A guide is provided showing how to optimize these conditions to obtain highly c-axis oriented AlN thin films on substrates of different nature.
Quartz c-axis texture mapping of a Variscan regional foliation (Malpica Tui Unit, NW Spain)
NASA Astrophysics Data System (ADS)
Llana-Fúnez, Sergio
2002-08-01
Mineral assemblages developed under high pressure and low to intermediate temperature conditions (HP-LIT) are found in eclogites, orthogneisses and metasediments of the Malpica-Tui Unit (MTU), either defining or surrounded by a regional foliation that was mostly re-equilibrated under amphibolite to greenschist facies conditions. This regional tectonic foliation, tracking the exhumation path of the MTU in the context of the Variscan collision in SW Europe, has been studied using the microstructural record in quartz from the different rock types. Most of the quartz c-axis patterns show two distinct asymmetries, contained in perpendicular planes, which are related to two different non-coaxial components of the finite fabric (i.e. the regional foliation and the lineation). The asymmetry of deformation inferred from quartz c-axis textures suggests that fabric accumulation during exhumation occurred under 3-D general flow, departing strongly from the simple shear type. This has significant tectonic implications for the interpretation of regional stretching lineations, which in the present geodynamic setting of irregular collisional tectonics, are not parallel to the direction of general tectonic transport and, ultimately, to the plate convergence direction.
The non-linear initiation of diapirs and plume heads
NASA Astrophysics Data System (ADS)
Bercovici, David; Kelly, Amanda
1997-04-01
A simple theory is devised to describe the non-linear feedback mechanisms involved in the initial growth of a single diapir or plume head from a low viscosity channel overlain by a much more viscous layer. Such feedbacks arise primarily from the relation between the growth of a proto-diapir (i.e. an undulation on the upper boundary of the low viscosity channel) and the draining of the low viscosity channel. In the period of time between its initial exponential growth (characterized by linear stability analysis) and its separation from the low viscosity channel as a fully formed diapir, the proto-diapir can undergo a significant cessation in its development due to deflation of the low viscosity channel; i.e. the proto-diapir's growth can essentially stall for a long period of time before it separates and begins its ascent through the overlying medium. The theory is used to determine a criterion for separation of the diapir from the low viscosity channel that is in terms of the geometrical and mechanical properties of the channel, instead of the ad hoc volume flux widely used in many models of mantle plumes and plume heads (e.g. Whitehead and Luther, 1975; Richards et al., 1989; Olson, 1990; Sleep, 1990; Bercovici and Mahoney, 1994). From this separation criterion, self-consistent scaling laws can be formulated to relate the size of the fully developed diapir and its trailing conduit to the properties of the initial channel, instead of to the ad hoc volume flux. Basic laboratory experiments involving highly viscous fluids are presented and demonstrate that the so-called 'stalling' period between initial growth and separation does indeed occur. These results suggest that nascent mantle plume heads may stall for extended periods at the base of the mantle and thereby contribute to variations in thickness of the D″ layer.
Linear and non-linear bias: predictions versus measurements
NASA Astrophysics Data System (ADS)
Hoffmann, K.; Bel, J.; Gaztañaga, E.
2017-02-01
We study the linear and non-linear bias parameters which determine the mapping between the distributions of galaxies and the full matter density fields, comparing different measurements and predictions. Associating galaxies with dark matter haloes in the Marenostrum Institut de Ciències de l'Espai (MICE) Grand Challenge N-body simulation, we directly measure the bias parameters by comparing the smoothed density fluctuations of haloes and matter in the same region at different positions as a function of smoothing scale. Alternatively, we measure the bias parameters by matching the probability distributions of halo and matter density fluctuations, which can be applied to observations. These direct bias measurements are compared to corresponding measurements from two-point and different third-order correlations, as well as predictions from the peak-background model, which we presented in previous papers using the same data. We find an overall variation of the linear bias measurements and predictions of ˜5 per cent with respect to results from two-point correlations for different halo samples with masses between ˜1012and1015 h-1 M⊙ at the redshifts z = 0.0 and 0.5. Variations between the second- and third-order bias parameters from the different methods show larger variations, but with consistent trends in mass and redshift. The various bias measurements reveal a tight relation between the linear and the quadratic bias parameters, which is consistent with results from the literature based on simulations with different cosmologies. Such a universal relation might improve constraints on cosmological models, derived from second-order clustering statistics at small scales or higher order clustering statistics.
Non-linear pattern formation in bone growth and architecture.
Salmon, Phil
2014-01-01
The three-dimensional morphology of bone arises through adaptation to its required engineering performance. Genetically and adaptively bone travels along a complex spatiotemporal trajectory to acquire optimal architecture. On a cellular, micro-anatomical scale, what mechanisms coordinate the activity of osteoblasts and osteoclasts to produce complex and efficient bone architectures? One mechanism is examined here - chaotic non-linear pattern formation (NPF) - which underlies in a unifying way natural structures as disparate as trabecular bone, swarms of birds flying, island formation, fluid turbulence, and others. At the heart of NPF is the fact that simple rules operating between interacting elements, and Turing-like interaction between global and local signals, lead to complex and structured patterns. The study of "group intelligence" exhibited by swarming birds or shoaling fish has led to an embodiment of NPF called "particle swarm optimization" (PSO). This theoretical model could be applicable to the behavior of osteoblasts, osteoclasts, and osteocytes, seeing them operating "socially" in response simultaneously to both global and local signals (endocrine, cytokine, mechanical), resulting in their clustered activity at formation and resorption sites. This represents problem-solving by social intelligence, and could potentially add further realism to in silico computer simulation of bone modeling. What insights has NPF provided to bone biology? One example concerns the genetic disorder juvenile Pagets disease or idiopathic hyperphosphatasia, where the anomalous parallel trabecular architecture characteristic of this pathology is consistent with an NPF paradigm by analogy with known experimental NPF systems. Here, coupling or "feedback" between osteoblasts and osteoclasts is the critical element. This NPF paradigm implies a profound link between bone regulation and its architecture: in bone the architecture is the regulation. The former is the emergent
Non-Linear Pattern Formation in Bone Growth and Architecture
Salmon, Phil
2014-01-01
The three-dimensional morphology of bone arises through adaptation to its required engineering performance. Genetically and adaptively bone travels along a complex spatiotemporal trajectory to acquire optimal architecture. On a cellular, micro-anatomical scale, what mechanisms coordinate the activity of osteoblasts and osteoclasts to produce complex and efficient bone architectures? One mechanism is examined here – chaotic non-linear pattern formation (NPF) – which underlies in a unifying way natural structures as disparate as trabecular bone, swarms of birds flying, island formation, fluid turbulence, and others. At the heart of NPF is the fact that simple rules operating between interacting elements, and Turing-like interaction between global and local signals, lead to complex and structured patterns. The study of “group intelligence” exhibited by swarming birds or shoaling fish has led to an embodiment of NPF called “particle swarm optimization” (PSO). This theoretical model could be applicable to the behavior of osteoblasts, osteoclasts, and osteocytes, seeing them operating “socially” in response simultaneously to both global and local signals (endocrine, cytokine, mechanical), resulting in their clustered activity at formation and resorption sites. This represents problem-solving by social intelligence, and could potentially add further realism to in silico computer simulation of bone modeling. What insights has NPF provided to bone biology? One example concerns the genetic disorder juvenile Pagets disease or idiopathic hyperphosphatasia, where the anomalous parallel trabecular architecture characteristic of this pathology is consistent with an NPF paradigm by analogy with known experimental NPF systems. Here, coupling or “feedback” between osteoblasts and osteoclasts is the critical element. This NPF paradigm implies a profound link between bone regulation and its architecture: in bone the architecture is the regulation. The former is the
Mechanisms for Non-Linear Optical Behaviour in Molecular Fluids
NASA Astrophysics Data System (ADS)
McEwan, Kenneth J.
Available from UMI in association with The British Library. Requires signed TDF. This thesis describes a study of the non-linear optical mechanisms that allow high power laser radiation to interact and change the optical properties of fluid based media. Attention is focused on understanding the finite time-scale of the microscopic response and its influence on the experimental observation. Two classes of material are studied: liquid crystalline fluids in their isotropic phase and suspensions of particles capable of absorbing the laser radiation. In the former case a quantitative description of the optical transients seen in two experiments, degenerate four wave mixing and "z-scan" (self-focusing), is obtained. This description is based upon an analysis of refractive index changes associated with laser-induced molecular reorientation and with thermal effects, for molecules that absorb the laser radiation. Material parameters for a large range of nematogens are obtained by applying this description to experimental data. In the absorbing colloidal suspensions a novel mechanism for degenerate four wave mixing is identified and studied. The experimental results are suggestive of a mechanism in which vapour bubbles nucleate explosively around the colloidal particles and drive a coherent sound -wave excitation of the fluid. Theoretical studies confirm that rapid bubble nucleation is possible by a process of spinodal decomposition under the experimental conditions and it is shown that this mechanism can be expected to give rise to transient behaviour of the type observed. Finally laser-induced refractive index changes in a colloidal suspension in a solid matrix are studied. The dynamics of the formation of refractive index gratings is examined and correlated with microscopically observed structural changes in the matrix. ftn*Funded by DRA, Electronics Division (formerly RSRE).
Adcock, T. A. A.; Taylor, P. H.
2016-01-15
The non-linear Schrödinger equation and its higher order extensions are routinely used for analysis of extreme ocean waves. This paper compares the evolution of individual wave-packets modelled using non-linear Schrödinger type equations with packets modelled using fully non-linear potential flow models. The modified non-linear Schrödinger Equation accurately models the relatively large scale non-linear changes to the shape of wave-groups, with a dramatic contraction of the group along the mean propagation direction and a corresponding extension of the width of the wave-crests. In addition, as extreme wave form, there is a local non-linear contraction of the wave-group around the crest which leads to a localised broadening of the wave spectrum which the bandwidth limited non-linear Schrödinger Equations struggle to capture. This limitation occurs for waves of moderate steepness and a narrow underlying spectrum.
2007-08-01
Advanced non- linear control algorithms applied to design highly maneuverable Autonomous Underwater Vehicles (AUVs) Vladimir Djapic, Jay A. Farrell...hierarchical such that an ”inner loop” non- linear controller (outputs the appropriate thrust values) is the same for all mission scenarios while a...library of ”outer-loop” non- linear controllers are available to implement specific maneuvering scenarios. On top of the outer-loop is the mission planner
Reduced pressure MOCVD of C-axis oriented BiSrCaCuO thin films
NASA Technical Reports Server (NTRS)
Hamaguchi, Norihito; Vigil, J.; Gardiner, R.; Kirlin, P. S.
1990-01-01
BiSrCaCuO thin films were deposited on MgO (100) single-crystal substrates by metalorganic chemical vapor deposition at 500 C and 2 torr using fluorinated beta-diketonate complexes of Sr, Ca, and Cu and triphenylbismuth. An inverted vertical reaction chamber allowed uniform film growth over large areas (7.7 cm diameter). The as-deposited films were amorphous mixtures of oxides and fluorides; a two-step annealing protocol (750 C + 850-870 C) was developed which gives c-axis oriented films of Bi2Sr2Ca1Cu2O(x). The postannealed films showed onsets in the resistive transition of 110 K, and zero resistivity was achieved by 83 K. Critical current densities as high as 11,000 A/sq cm were obtained at 25 K.
Reduced pressure MOCVD of C-axis oriented BiSrCaCuO thin films
NASA Technical Reports Server (NTRS)
Hamaguchi, Norihito; Vigil, J.; Gardiner, R.; Kirlin, P. S.
1990-01-01
BiSrCaCuO thin films were deposited on MgO (100) single-crystal substrates by metalorganic chemical vapor deposition at 500 C and 2 torr using fluorinated beta-diketonate complexes of Sr, Ca, and Cu and triphenylbismuth. An inverted vertical reaction chamber allowed uniform film growth over large areas (7.7 cm diameter). The as-deposited films were amorphous mixtures of oxides and fluorides; a two-step annealing protocol (750 C + 850-870 C) was developed which gives c-axis oriented films of Bi2Sr2Ca1Cu2O(x). The postannealed films showed onsets in the resistive transition of 110 K, and zero resistivity was achieved by 83 K. Critical current densities as high as 11,000 A/sq cm were obtained at 25 K.
Investigation of the helimagnetic phases of holmium in a c -axis magnetic field
Tindall, D.A. ); Steinitz, M.O.; Kahrizi, M. ); Noakes, D.R. ); Ali, N. )
1991-04-15
Neutron diffraction measurements have been made in the ({ital h}0{ital l}) plane of holmium in a {ital c}-axis magnetic field of 3 T. Thermal expansivity measurements have also been made by capacitance dilatometry. The main focus of our investigation has been a region about 2 K wide near 96 K, where the helimagnetic structure locks into a commensurate state. We have also been able to observe the 2-{tau}'' satellites (at twice the fundamental magnetic ordering {ital q} vector) at temperatures as high as 3 K below the Neel transition. In the region between the lock-in transition and the Neel point, the intensities of these satellites show interesting behavior with temperature and may be showing effects due to the anomalies which have been identified in our magnetization measurements.
Non-Linear Vibrations of a Beam on AN Elastic Foundation
NASA Astrophysics Data System (ADS)
Coskun, I.; Engin, H.
1999-06-01
The non-linear vibrations of an elastic beam resting on a non-linear tensionless Winkler foundation subjected to a concentrated load at the centre is presented in this paper. Since the foundation is assumed to be tensionless, the beam may lift off the foundation and there exists different regions namely contact and non-contact regions. Since the contact regions are not known in advance, the problem appears as a non-linear one even though there is no non-linear term in the foundation model. In this case, the calculation of the roots of a non-linear equation is needed to obtain contact lengths. The perturbation technique is used to solve the non-linear governing equation associated with the problem. Using this technique, the non-linear problem is reduced to the solution of a set of linearized partial differential equations. The lift-off points and the displacements are obtained in linear and non-linear cases, and the variation of these points with respect to various parameters are presented. It is concluded that the contact length varies with the magnitude of the load because of the non-linearity.
C-axis electrical resistivity of PrO1-aFaBiS2 single crystals
NASA Astrophysics Data System (ADS)
Nagao, Masanori; Miura, Akira; Watauchi, Satoshi; Takano, Yoshihiko; Tanaka, Isao
2015-08-01
The high anisotropy in RO1-aFaBiS2 (R denotes a rare-earth element) superconductors demonstrates their potential use as intrinsic Josephson junctions, considering the weak coupling among BiS2-PrO(F)-BiS2 (superconducting-normal-superconducting) layers along the c-axis. We grew PrO1-aFaBiS2 single crystals using CsCl/KCl flux. The superconducting anisotropies of the grown single crystals were estimated to be approximately 40-50 from the effective mass model. The c-axis transport properties were characterized using single-crystal s-shaped intrinsic Josephson junctions with a focused ion beam. Along the c-axis, the crystals showed zero resistivity at 2.7 K and a critical current density of 1.33 × 103 A/cm2 at 2.0 K. The current-voltage curve along the c-axis displayed hysteresis. The c-axis transport measurements under a magnetic field parallel to the ab-plane revealed a “lock-in” state due to the Josephson vortex flow, indicating that BiS2 superconductors are promising candidates for intrinsic Josephson junctions.
Non-Linear Dose-Response Relationships in Biology, Toxicology and Medicine
2007-11-02
The purpose of the conference was to attract researchers from diverse backgrounds who are working in the common area of non-linear dose - response relationships...This unique interdisciplinary conference represents an important step in furthering the understanding of the occurrence, origin, mechanisms, significance and practical applications of non-linear dose - response relationships.
Biomagnetic activity and non linear analysis in obstetrics and gynecology in a Greek population.
Anninos, P; Anastasiadis, P; Adamopoulos, A; Kotini, A
2016-01-01
This article reports the application of non-linear analysis to biomagnetic signals recorded from fetal growth restriction, fetal brain activity, ovarian lesions, breast lesions, umbilical arteries, uterine myomas, and uterine arteries in a Greek population. The results were correlated with clinical findings. The biomagnetic measurements and the application of non-linear analysis are promising procedures in Obstetrics and Gynecology.
Vibration analysis of harmonically excited non-linear system using the method of multiple scales
NASA Astrophysics Data System (ADS)
Moon, Byung-Young; Kang, Beom-Soo
2003-05-01
An analytical method is presented for evaluation of the steady state periodic behavior of non-linear systems. This method is based on the substructure synthesis formulation and a multiple scales procedure, which is applied to the analysis of non-linear responses. A complex non-linear system is divided into substructures, of which equations are approximately transformed to modal co-ordinates including non-linear term under the reasonable procedure. Then, the equations are synthesized into the overall system and the solution of the non-linear system can be obtained. Based on the method of multiple scales, the proposed procedure reduces the size of large-degree-of-freedom problem in solving the non-linear equations. Feasibility and advantages of the proposed method are illustrated by the application of the analytic procedure to the non-linear rotating machine system as a large mechanical structure system. Results obtained are reported to be an efficient approach with respect to non-linear response prediction when compared with other conventional methods.
Rigatos, Gerasimos G
2016-06-01
It is proven that the model of the p53-mdm2 protein synthesis loop is a differentially flat one and using a diffeomorphism (change of state variables) that is proposed by differential flatness theory it is shown that the protein synthesis model can be transformed into the canonical (Brunovsky) form. This enables the design of a feedback control law that maintains the concentration of the p53 protein at the desirable levels. To estimate the non-measurable elements of the state vector describing the p53-mdm2 system dynamics, the derivative-free non-linear Kalman filter is used. Moreover, to compensate for modelling uncertainties and external disturbances that affect the p53-mdm2 system, the derivative-free non-linear Kalman filter is re-designed as a disturbance observer. The derivative-free non-linear Kalman filter consists of the Kalman filter recursion applied on the linearised equivalent of the protein synthesis model together with an inverse transformation based on differential flatness theory that enables to retrieve estimates for the state variables of the initial non-linear model. The proposed non-linear feedback control and perturbations compensation method for the p53-mdm2 system can result in more efficient chemotherapy schemes where the infusion of medication will be better administered.
Yang, Bo; Qin, Gaowu Xiao, Na; Li, Zongbin; Zhao, Xiang; Zuo, Liang; Zhang, Yudong; Esling, Claude
2016-04-14
In the present work, Co-23.0 at. % Pt and Co-23.0 at. % Pt-3.67 at. % P thin films with their c-axis perpendicular to the substrate surface were fabricated on a glass substrate by DC magnetron sputtering. X-ray diffraction and transmission electron microscopic analyses demonstrate that the doping of P improves the c-axis alignment and forms P-rich non-magnetic phase at grain boundary areas, the latter resulting in inter-granular exchange decoupling between Co-Pt grains. The improved c-axis alignment and the inter-granular exchange decoupling give rise to the increase of the out of plane coercivity and the squareness of the Co-Pt-P films.
Single-photon non-linear optics with a quantum dot in a waveguide
Javadi, A.; Söllner, I.; Arcari, M.; Hansen, S. Lindskov; Midolo, L.; Mahmoodian, S.; Kiršanskė, G; Pregnolato, T.; Lee, E. H.; Song, J. D.; Stobbe, S.; Lodahl, P.
2015-01-01
Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon–photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures. PMID:26492951
Investigation of non-linear imaging in high-resolution transmission electron microscopy.
Chang, Yunjie; Wang, Yumei; Cui, Yanxiang; Ge, Binghui
2016-12-01
Transmission cross-coefficient theory and pseudo-weak-phase object approximation theory were combined to investigate the non-linear imaging in high-resolution transmission electron microscopy (HRTEM). The analytical expressions of linear and non-linear imaging components in diffractogram were obtained and changes of linear and non-linear components over sample thickness were analyzed. Moreover, the linear and non-linear components are found to be an odd and even-function of the defocus and Cs, respectively. Based on this, a method for separating the linear and non-linear contrasts in Cs-corrected (non-zero Cs conditions included) HRTEM images was proposed, and its effectiveness was confirmed by image simulations with AlN as an example.
Travelling and standing envelope solitons in discrete non-linear cyclic structures
NASA Astrophysics Data System (ADS)
Grolet, Aurelien; Hoffmann, Norbert; Thouverez, Fabrice; Schwingshackl, Christoph
2016-12-01
Envelope solitons are demonstrated to exist in non-linear discrete structures with cyclic symmetry. The analysis is based on the Non-Linear Schrodinger Equation for the weakly non-linear limit, and on numerical simulation of the fully non-linear equations for larger amplitudes. Envelope solitons exist for parameters in which the wave equation is focussing and they have the form of shape-conserving wave packages propagating roughly with group velocity. For the limit of maximum wave number, where the group velocity vanishes, standing wave packages result and can be linked via a bifurcation to the non-localised non-linear normal modes. Numerical applications are carried out on a simple discrete system with cyclic symmetry which can be seen as a reduced model of a bladed disk as found in turbo-machinery.
Single-photon non-linear optics with a quantum dot in a waveguide.
Javadi, A; Söllner, I; Arcari, M; Hansen, S Lindskov; Midolo, L; Mahmoodian, S; Kiršanskė, G; Pregnolato, T; Lee, E H; Song, J D; Stobbe, S; Lodahl, P
2015-10-23
Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures.
Validation Study of V. I. S. I. O. N.
ERIC Educational Resources Information Center
Elliott, Paul G.
In an attempt to depart from the traditional process of orientating students to career awareness, a new approach is being developed at the Indiana Career Resource Center at South Bend, Indiana. The Basic concept of V. I. S. I. O. N. (Visual Imagery Selector for Indexing Occupational Needs) attempts to utilize a combination of the respondents'…
Aurisano, A.; Backhouse, C.; Hatcher, R.; Mayer, N.; Musser, J.; Patterson, R.; Schroeter, R.; Sousa, A.
2015-12-23
The NOv>A experiment is a two-detector, long-baseline neutrino experiment operating in the recently upgraded NuMI muon neutrino beam. Simulating neutrino interactions and backgrounds requires many steps including: the simulation of the neutrino beam flux using FLUKA and the FLUGG interface, cosmic ray generation using CRY, neutrino interaction modeling using GENIE, and a simulation of the energy deposited in the detector using GEANT4. To shorten generation time, the modeling of detector-specific aspects, such as photon transport, detector and electronics noise, and readout electronics, employs custom, parameterized simulation applications. We will describe the NOv>A simulation chain, and present details on the techniques used in modeling photon transport near the ends of cells, and in developing a novel data-driven noise simulation. Due to the high intensity of the NuMI beam, the Near Detector samples a high rate of muons originating in the surrounding rock. In addition, due to its location on the surface at Ash River, MN, the Far Detector collects a large rate ((˜) 140 kHz) of cosmic muons. Furthermore, we will discuss the methods used in NOv>A for overlaying rock muons and cosmic ray muons with simulated neutrino interactions and show how realistically the final simulation reproduces the preliminary NOv>A data.
NASA Astrophysics Data System (ADS)
Law, Richard D.
2014-09-01
For quartz-rich tectonites two types of deformation thermometer are currently commonly employed: 1) The quartz c-axis fabric opening-angle thermometer that provides an estimate of deformation temperatures when fabrics were ‘locked in' during dislocation creep and dynamic recrystallization. 2) The quartz recrystallization thermometer that indicates a range of likely deformation temperatures based on observed microstructures and inferred mechanisms of dynamic recrystallization. A critically important caveat in applying both thermometers is the assumption that deformation temperature is the primary controlling factor in recrystallization mechanisms and fabric development. However, fabric opening-angles and recrystallization mechanisms are also sensitive to other variables such as strain rate and water weakening. In this paper the development of these thermometers is reviewed, and their potential sensitivities to competing factors such as temperature, strain rate, water weakening and (in the case of opening-angles) 3D strain type are discussed. Examples of the application of these potential thermometers to naturally deformed quartz-rich rocks are given, and case studies of correlations between deformation temperatures estimated by these thermometers and temperatures of synkinematic metamorphism determined by petrology-based thermobarometers are highlighted. In the review, attention is focused on problems associated with applying these thermometers to natural deformation, and examples of such problems are discussed.
Superconductivity in LiOHFeS single crystals with a shrunk c-axis lattice constant
NASA Astrophysics Data System (ADS)
Lin, Hai; Kang, RuiZhe; Kong, Lu; Zhu, XiYu; Wen, Hai-Hu
2017-02-01
By using a hydrothermal ion-exchange method, we have successfully grown superconducting crystals of LiOHFeS with T c of about 2.8 K. Being different from the sister sample (Li1- x Fe x )OHFeSe, the energy dispersion spectrum analysis on LiOHFeS shows that the Fe/S ratio is very close to 1:1, suggesting an almost charge neutrality and less electron doping in the FeS planes of the system. Comparing with the non superconducting LiOHFeS crystal, each peak of the X-ray diffraction pattern of the superconducting crystal splits into two, and the diffraction peaks locating at lower reflection angles are consistent with that of non-superconducting ones. The rest set of diffraction peaks with higher reflection angles is corresponding to the superconducting phase, suggesting that the superconducting phase may has a shrunk c-axis lattice constant. Magnetization measurements indicate that the magnetic shielding due to superconductivity can be quite high under a weak magnetic field. The resistivity measurements under various magnetic fields show that the upper critical field is quite low, which is similar to the tetragonal FeS superconductor.
C-Axis Compression of Magnesium Single Crystals: Multi-Scale Dislocation Dynamics Analyses
NASA Astrophysics Data System (ADS)
Jaber, Wassim; Shehadeh, Mu'tasem
Hexagonal-closed packed materials (HCP) materials has attracted interest recently due to their unique physical and mechanical properties. The low density and the high strength to weight ratio of such materials make them excellent candidates to save structural weight and consequently fuel consumption in both automotive and aircraft fields. However, the deformation behavior of HCP metals hasn't been completely understood as prior work still lack a detailed understanding on the activation of slip planes and twinning. In addition, the work-hardening behavior and the effect of temperature and strain rate are not yet well-established. This work aims at investigating the deformation mechanisms in magnesium single crystals using Multiscale Dislocation Dynamics Plasticity (MDDP) model. In particular, we focus on modeling the deformation behavior under c-axis compression loading. Several Simulations have been carried out to study the effect of dislocation mobility dependence on the dislocation character and its consequences on the evolution of the dislocation density, the dislocation microstructure, and the hardening behavior. Preliminary results show that the experimentally observed hardening behavior can be reproduced by using linear interpolation of the mobility such that screw segments are stationary and edge segments are highly mobile.
Low-bandgap, highly c-axis-oriented Al-doped ZnO thin films
NASA Astrophysics Data System (ADS)
Wen, Long; Kumar, Manish; Cho, Hyung Jun; Leksakul, Komgrit; Geon Han, Jeon
2017-05-01
Low-bandgap transparent conductive oxides will be of interest to researchers who wish to address the health hazards of blue radiation emission from electronic displays. Here, we present a single-step, low-temperature fast enough (throughput > 60 nm min-1) process to grow highly c-axis-oriented crystalline Al-doped ZnO thin films via advanced plasma processing. Dual-power DC-magnetron sputtering plasma was employed for the synthesis of thin films. The addition of top power to a pre-existing rectangular power pushed additional ions to a confined plasma and increased the plasma density and electron temperature. The effect of this additional-ion pushing was systematically studied using the microstructure, surface properties, and electronic properties. As a result, bandgap reduction from 3.35 eV to 3.10 eV and tailoring of electrical resistivity (4.89 × 10-4-8.32 × 10-3 Ω cm) and Seebeck coefficients (21-48 µV K-1) were achieved in addition to excellent transparency. Given their properties, the obtained films show promise for multifunctional applications, such as in UV and near-blue radiation shielding, transparent conductive electrodes and low-temperature thermoelectrics.
Growth of c-axis-oriented superconducting KFe₂As₂ thin films.
Hiramatsu, Hidenori; Matsuda, Shogo; Sato, Hikaru; Kamiya, Toshio; Hosono, Hideo
2014-08-27
KFe2As2, an iron-based superconductor, is expected to exhibit large spin Hall conductivity, and fabrication of high-quality thin films is requisite for evaluation of this effect and application to spintronics devices. Thin-film growth of KFe2As2 is difficult because of two intrinsic properties; its extremely hygroscopic nature and the high vapor pressure of potassium. We solved these issues by combining room-temperature pulsed laser deposition using K-rich KFe2As2 targets with thermal crystallization in KFe2As2 powder after encapsulation in an evacuated silica-glass tube with all of the processes conducted in a vacuum chamber and a dry Ar atmosphere in a glovebox. The optimized KFe2As2 films on (La,Sr)(Al,Ta)O3 single-crystal substrates were obtained by crystallization at 700 °C, and they were strongly c-axis oriented. The electrical measurements were performed with thin films protected by grease passivation to block reaction with the atmosphere. The KFe2As2 films exhibited a superconductivity transition at 3.7 K.
Non-linear modelling and optimal control of a hydraulically actuated seismic isolator test rig
NASA Astrophysics Data System (ADS)
Pagano, Stefano; Russo, Riccardo; Strano, Salvatore; Terzo, Mario
2013-02-01
This paper investigates the modelling, parameter identification and control of an unidirectional hydraulically actuated seismic isolator test rig. The plant is characterized by non-linearities such as the valve dead zone and frictions. A non-linear model is derived and then employed for parameter identification. The results concerning the model validation are illustrated and they fully confirm the effectiveness of the proposed model. The testing procedure of the isolation systems is based on the definition of a target displacement time history of the sliding table and, consequently, the precision of the table positioning is of primary importance. In order to minimize the test rig tracking error, a suitable control system has to be adopted. The system non-linearities highly limit the performances of the classical linear control and a non-linear one is therefore adopted. The test rig mathematical model is employed for a non-linear control design that minimizes the error between the target table position and the current one. The controller synthesis is made by taking no specimen into account. The proposed approach consists of a non-linear optimal control based on the state-dependent Riccati equation (SDRE). Numerical simulations have been performed in order to evaluate the soundness of the designed control with and without the specimen under test. The results confirm that the performances of the proposed non-linear controller are not invalidated because of the presence of the specimen.
Effect of directional distribution on non-linear energy transfer in wind wave spectrum
NASA Astrophysics Data System (ADS)
Lavrenov, I.; Krogstad, H.
2003-04-01
Different directional distribution is investigated from the point of view a non-linear energy transfer in wind wave spectrum. In order to produce a numerical simulation of the non-linear interaction in wind wave spectrum a method of numerical integration of the highest accuracy is used. It is shown that the value of non-linear energy transfer is very sensitive to details of frequency-angular approximation of wave spectrum. The non-linear energy transfer is non-zero in wide frequency - angular range, depending on spectrum angular distribution. The calculation results reveal the presence of non-linear energy transfer to spectral components, which propagation is opposite to wind direction for a wide spectrum angular distribution. It should be noted that neither the discrete interaction approximation (DIA) used in the WAM model (Komen et al., 1994), no diffusive approximation of the non-linear transfer (Pushkarev and Zakharov, 1999) are able not to produce this effect. Numerical results show that the bi-model angular distribution, obtained by Hwang et al. (2000) in field experiments, can be generated by the non-linear energy transfer, sending energy in side direction. Present study has been supported by the INTAS-99-666, INTAS-01-25, INTAS-01-234, INTAS-01-2156, RFBR- 01- 05-64846 Grants.
A New Multi-tanh-Based Non-linear Function Synthesiser
NASA Astrophysics Data System (ADS)
Taher Abuelma'atti, Muhammad; Radhi Al-Abbas, Saad
2016-11-01
A new complementary metal-oxide-semiconductor transadmittance-mode with input voltage and output current, analogue non-linear odd-function synthesiser is presented. The proposed circuit is based on the assumption that a non-linear odd- function can be approximated by the summation of hyperbolic tangent (tanh) functions with different arguments. Each term of the tanh function expansion is realised by exploiting to advantage the inherent non-linearity of a current-controlled current-conveyor (CCCCII) (or an operational transconductance amplifier (OTA)) with a different bias current. The output currents of these CCCCIIs (OTAs) are weighted using the gains of current amplifiers. These weighted currents are algebraically added to form the required non-linear function. The proposed circuit is suitable for integration, can be easily extended to include higher order terms of the tanh-odd-function expansion and can be programmed to realise arbitrary hard non-linear odd-functions that cannot be easily realised using already existing techniques, based on the Taylor-series expansion, for synthesising non-linear functions. PSPICE simulation results, obtained from CCCCII-based realisations of selected hard non-linearities, demonstrating the functionality of the proposed circuit are included.
Freiwald, W A; Valdes, P; Bosch, J; Biscay, R; Jimenez, J C; Rodriguez, L M; Rodriguez, V; Kreiter, A K; Singer, W
1999-12-15
Information processing in the visual cortex depends on complex and context sensitive patterns of interactions between neuronal groups in many different cortical areas. Methods used to date for disentangling this functional connectivity presuppose either linearity or instantaneous interactions, assumptions that are not necessarily valid. In this paper a general framework that encompasses both linear and non-linear modelling of neurophysiological time series data by means of Local Linear Non-linear Autoregressive models (LLNAR) is described. Within this framework a new test for non-linearity of time series and for non-linearity of directedness of neural interactions based on LLNAR is presented. These tests assess the relative goodness of fit of linear versus non-linear models via the bootstrap technique. Additionally, a generalised definition of Granger causality is presented based on LLNAR that is valid for both linear and non-linear systems. Finally, the use of LLNAR for measuring non-linearity and directional influences is illustrated using artificial data, reference data as well as local field potentials (LFPs) from macaque area TE. LFP data is well described by the linear variant of LLNAR. Models of this sort, including lagged values of the preceding 25 to 60 ms, revealed the existence of both uni- and bi-directional influences between recording sites.
NASA Astrophysics Data System (ADS)
Royston, T. J.; Singh, R.
1996-07-01
While significant non-linear behavior has been observed in many vibration mounting applications, most design studies are typically based on the concept of linear system theory in terms of force or motion transmissibility. In this paper, an improved analytical strategy is presented for the design optimization of complex, active of passive, non-linear mounting systems. This strategy is built upon the computational Galerkin method of weighted residuals, and incorporates order reduction and numerical continuation in an iterative optimization scheme. The overall dynamic characteristics of the mounting system are considered and vibratory power transmission is minimized via adjustment of mount parameters by using both passive and active means. The method is first applied through a computational example case to the optimization of basic passive and active, non-linear isolation configurations. It is found that either active control or intentionally introduced non-linearity can improve the mount's performance; but a combination of both produces the greatest benefit. Next, a novel experimental, active, non-linear isolation system is studied. The effect of non-linearity on vibratory power transmission and active control are assessed via experimental measurements and the enhanced Galerkin method. Results show how harmonic excitation can result in multiharmonic vibratory power transmission. The proposed optimization strategy offers designers some flexibility in utilizing both passive and active means in combination with linear and non-linear components for improved vibration mounts.
Uncertainty due to non-linearity in radiation thermometers calibrated by multiple fixed points
Yamaguchi, Y.; Yamada, Y.
2013-09-11
A new method to estimate the uncertainty due to non-linearity is described on the n= 3 scheme basis. The expression of uncertainty is mathematically derived applying the random walk method. The expression is simple and requires only the temperatures of the fixed points and a relative uncertainty value for each flux-doubling derived from the non-linearity measurement. We also present an example of the method, in which the uncertainty of temperature measurement by a radiation thermometer is calculated on the basis of non-linearity measurement.
Some experiences in the estimation of parameters in non-linear differential equations.
Barnes, J G.P.
1969-03-01
The author describes a procedure developed by himself and his colleagues for obtaining estimates of the parameters of rate equations, together with information about confidence regions for the estimates. The program has been used successfully for processing results from the chemical engineering industry, with highly non-linear model systems, particularly since temperature was a variable, and the "rate constants" were non-linear combinations of other constants. In biochemical situations, in which investigations are almost always at constant temperature, the non-linearity should not be so extreme, and the procedure may well be capable of dealing with more than 5 to 7 parameters for which it is recommended.
Rajeswaran, Jeevanantham; Blackstone, Eugene H
2017-02-01
In medical sciences, we often encounter longitudinal temporal relationships that are non-linear in nature. The influence of risk factors may also change across longitudinal follow-up. A system of multiphase non-linear mixed effects model is presented to model temporal patterns of longitudinal continuous measurements, with temporal decomposition to identify the phases and risk factors within each phase. Application of this model is illustrated using spirometry data after lung transplantation using readily available statistical software. This application illustrates the usefulness of our flexible model when dealing with complex non-linear patterns and time-varying coefficients.
A Multiphase Non-Linear Mixed Effects Model: An Application to Spirometry after Lung Transplantation
Rajeswaran, Jeevanantham; Blackstone, Eugene H.
2014-01-01
In medical sciences, we often encounter longitudinal temporal relationships that are non-linear in nature. The influence of risk factors may also change across longitudinal follow-up. A system of multiphase non-linear mixed effects model is presented to model temporal patterns of longitudinal continuous measurements, with temporal decomposition to identify the phases and risk factors within each phase. Application of this model is illustrated using spirometry data after lung transplantation using readily available statistical software. This application illustrates the usefulness of our flexible model when dealing with complex non-linear patterns and time varying coefficients. PMID:24919830
Neural Network Associative Memory Using Non-Linear Holographic Storage Media
1989-12-01
T’,?T Cýy’ ( AFIT/GEO/ENG/89D-3 AD-A214 340 L NEURAL NETWORK ASSOCIATIVE MEMORY USING NON-LINEAR HOLOGRAPHIC STORAGE MEDIA I THESIS I Presented to...order approximations of the required gain were provided. - - -In= unazn A FIT/GEO/ENG/89D-3 NEURAL NETWORK ASSOCIATIVE MEMORY USING NON-LINEAR...approxi- mations of the required gain were provided. vi NEURAL NETWORK ASSOCIATIVE MEMORY USING NON-LINEAR HOLOGRAPHIC STORAGE MEDIA I. Introduction The
Non-linear excitation of quantum emitters in hexagonal boron nitride multiplayers
NASA Astrophysics Data System (ADS)
Schell, Andreas W.; Tran, Toan Trong; Takashima, Hideaki; Takeuchi, Shigeki; Aharonovich, Igor
2016-12-01
Two-photon absorption is an important non-linear process employed for high resolution bio-imaging and non-linear optics. In this work, we realize two-photon excitation of a quantum emitter embedded in a two-dimensional (2D) material. We examine defects in hexagonal boron nitride (hBN) and show that the emitters exhibit similar spectral and quantum properties under one-photon and two-photon excitation. Furthermore, our findings are important to deploy two-dimensional hexagonal boron nitride for quantum non-linear photonic applications.
Origin of the c-Axis Tilt Occurring During the Lateral Epitaxial Overgrowth of GaN
NASA Astrophysics Data System (ADS)
Kuan, T. S.; Inoki, C. K.; Zhang, R.; Gu, S.; Kuech, T. F.
2001-03-01
A large angle c-axis tilt has often been observed in GaN layers grown by lateral epitaxial overgrowth (LEO) through narrow windows defined on a seed layer. The c-axis tilt generates vertical tilt boundaries at the coalescence of growth facets. To investigate the defect mechanisms responsible for the onset of c-axis tilt, a series of GaN LEO samples was grown using the hydride vapor phase epitaxy (HVPE) technique and examined by transmission electron microscopy (TEM). Cross sectional TEM images indicate that as LEO proceeds from triangular-shaped ridges originally grown over the windows, all edge-type threading dislocations propagated from the seed layer bend into screw type and glide on the c plane. Plan-view TEM observations reveal further that to relax the twist/shear strain in the LEO regions, these screw dislocations collectively make another 90^o bend again, forming arrays of edge dislocations parallel to the mask edge. The number of dislocations in the arrays can account for the amount of crystal tilt observed. The c-axis tilt is thus a stress-driven phenomenon dictated by the growth window geometry, and is much less influenced by the growth parameters.
THE SPECTRUM AND TERM ANALYSIS OF V I
Thorne, A. P.; Pickering, J. C.; Semeniuk, J.
2011-01-15
High-resolution spectra of neutral vanadium have been recorded by Fourier transform spectrometry in the region 1492-28600 A (67020-3496 cm{sup -1}) with vanadium-neon and vanadium-argon hollow cathode lamps as sources. Most of the lines exhibit fully or partly resolved hyperfine structure, but the wavenumber uncertainty for the center of gravity of the strongest lines is 0.002 cm{sup -1}. Of the previously published energy levels of V I, 72 have been revised and 37 discarded. In addition, 89 new levels have been found. In total 346 odd levels and 198 even levels are presented. Wavenumbers and classifications are given for 3130 V I lines.
RADIATIVE LIFETIMES OF V I AND V II
Den Hartog, E. A.; Lawler, J. E.; Wood, M. P. E-mail: jelawler@wisc.edu
2014-11-01
New radiative lifetimes are reported for 168 levels of V I ranging in energy from 18086 cm{sup –1} to 47702 cm{sup –1}, and for 31 levels of V II ranging in energy from 34593 cm{sup –1} to 47420 cm{sup –1}. These lifetimes are measured using time-resolved laser-induced fluorescence on a slow atomic/ionic beam as part of an ongoing study of the radiative properties of the iron group elements. All but two of the V II lifetimes have been measured before using modern laser-based methods, but a large fraction of the V I lifetimes are reported here for the first time. Comparison to earlier measurements is discussed. These new lifetimes are, for the most part, accurate to ±5%. They will be combined with branching fraction measurements to produce a large set of transition probabilities for V I and V II which are needed by the astrophysics community for stellar abundance determinations.
Non-Linear Noise Contributions in Highly Dispersive Optical Transmission Systems
NASA Astrophysics Data System (ADS)
Matera, Francesco
2016-01-01
This article reports an analytical investigation, confirmed by numerical simulations, about the non-linear noise contribution in single-channel systems adopting generic modulation-detection formats in long links with both managed and unmanaged dispersion compensation and its impact in system performance. This noise contribution is expressed in terms of a pulse non-linear interaction length and permits a simple calculation of the Q-factor. Results point out the dependence of this non-linear noise on the number of amplifiers spans, N, according to the adopted chromatic dispersion compensation scheme, the modulation-detection format, and the signal baud rate. It is also shown how the effects of polarization multiplexing can be taken into account and how this single-channel non-linear noise contribution can be used in a wavelength-division multiplexing (WDM) environment.
Finite-time H∞ filtering for non-linear stochastic systems
NASA Astrophysics Data System (ADS)
Hou, Mingzhe; Deng, Zongquan; Duan, Guangren
2016-09-01
This paper describes the robust H∞ filtering analysis and the synthesis of general non-linear stochastic systems with finite settling time. We assume that the system dynamic is modelled by Itô-type stochastic differential equations of which the state and the measurement are corrupted by state-dependent noises and exogenous disturbances. A sufficient condition for non-linear stochastic systems to have the finite-time H∞ performance with gain less than or equal to a prescribed positive number is established in terms of a certain Hamilton-Jacobi inequality. Based on this result, the existence of a finite-time H∞ filter is given for the general non-linear stochastic system by a second-order non-linear partial differential inequality, and the filter can be obtained by solving this inequality. The effectiveness of the obtained result is illustrated by a numerical example.
Mathematical Methods in Wave Propagation: Part 2--Non-Linear Wave Front Analysis
ERIC Educational Resources Information Center
Jeffrey, Alan
1971-01-01
The paper presents applications and methods of analysis for non-linear hyperbolic partial differential equations. The paper is concluded by an account of wave front analysis as applied to the piston problem of gas dynamics. (JG)
Non-linear analysis of EEG signals at various sleep stages.
Acharya U, Rajendra; Faust, Oliver; Kannathal, N; Chua, TjiLeng; Laxminarayan, Swamy
2005-10-01
Application of non-linear dynamics methods to the physiological sciences demonstrated that non-linear models are useful for understanding complex physiological phenomena such as abrupt transitions and chaotic behavior. Sleep stages and sustained fluctuations of autonomic functions such as temperature, blood pressure, electroencephalogram (EEG), etc., can be described as a chaotic process. The EEG signals are highly subjective and the information about the various states may appear at random in the time scale. Therefore, EEG signal parameters, extracted and analyzed using computers, are highly useful in diagnostics. The sleep data analysis is carried out using non-linear parameters: correlation dimension, fractal dimension, largest Lyapunov entropy, approximate entropy, Hurst exponent, phase space plot and recurrence plots. These non-linear parameters quantify the cortical function at different sleep stages and the results are tabulated.
Tornøe, Christoffer W; Agersø, Henrik; Jonsson, E Niclas; Madsen, Henrik; Nielsen, Henrik A
2004-10-01
The standard software for non-linear mixed-effect analysis of pharmacokinetic/pharmacodynamic (PK/PD) data is NONMEM while the non-linear mixed-effects package NLME is an alternative as long as the models are fairly simple. We present the nlmeODE package which combines the ordinary differential equation (ODE) solver package odesolve and the non-linear mixed effects package NLME thereby enabling the analysis of complicated systems of ODEs by non-linear mixed-effects modelling. The pharmacokinetics of the anti-asthmatic drug theophylline is used to illustrate the applicability of the nlmeODE package for population PK/PD analysis using the available data analysis tools in R for model inspection and validation. The nlmeODE package is numerically stable and provides accurate parameter estimates which are consistent with NONMEM estimates.
Mathematical Methods in Wave Propagation: Part 2--Non-Linear Wave Front Analysis
ERIC Educational Resources Information Center
Jeffrey, Alan
1971-01-01
The paper presents applications and methods of analysis for non-linear hyperbolic partial differential equations. The paper is concluded by an account of wave front analysis as applied to the piston problem of gas dynamics. (JG)
NASA Astrophysics Data System (ADS)
Wu, Hui; Hu, Liming; Wen, Qingbo
2017-06-01
Electro-osmotic consolidation is an effective method for soft ground improvement. A main limitation of previous numerical models on this technique is the ignorance of the non-linear variation of soil parameters. In the present study, a multi-field numerical model is developed with the consideration of the non-linear variation of soil parameters during electro-osmotic consolidation process. The numerical simulations on an axisymmetric model indicated that the non-linear variation of soil parameters showed remarkable impact on the development of the excess pore water pressure and degree of consolidation. A field experiment with complex geometry, boundary conditions, electrode configuration and voltage application was further simulated with the developed numerical model. The comparison between field and numerical data indicated that the numerical model coupling of the non-linear variation of soil parameters gave more reasonable results. The developed numerical model is capable to analyze engineering cases with complex operating conditions.
Enhanced studies on a composite time integration scheme in linear and non-linear dynamics
NASA Astrophysics Data System (ADS)
Klarmann, S.; Wagner, W.
2015-03-01
In Bathe and Baig (Comput Struct 83:2513-2524, 2005), Bathe (Comput Struct 85:437-445, 2007), Bathe and Noh (Comput Struct 98-99:1-6, 2012) Bathe et al. have proposed a composite implicit time integration scheme for non-linear dynamic problems. This paper is aimed at the further investigation of the scheme's behaviour for use in case of linear and non-linear problems. Therefore, the examination of the amplification matrix of the scheme will be extended in order to get in addition the properties for linear calculations. Besides, it will be demonstrated that the integration scheme also has an impact on some of these properties when used for non-linear calculations. In conclusion, a recommendation for the only selectable parameter of the scheme will be given for application in case of geometrically non-linear calculations.
Non-Linearity in Wide Dynamic Range CMOS Image Sensors Utilizing a Partial Charge Transfer Technique
Shafie, Suhaidi; Kawahito, Shoji; Halin, Izhal Abdul; Hasan, Wan Zuha Wan
2009-01-01
The partial charge transfer technique can expand the dynamic range of a CMOS image sensor by synthesizing two types of signal, namely the long and short accumulation time signals. However the short accumulation time signal obtained from partial transfer operation suffers of non-linearity with respect to the incident light. In this paper, an analysis of the non-linearity in partial charge transfer technique has been carried, and the relationship between dynamic range and the non-linearity is studied. The results show that the non-linearity is caused by two factors, namely the current diffusion, which has an exponential relation with the potential barrier, and the initial condition of photodiodes in which it shows that the error in the high illumination region increases as the ratio of the long to the short accumulation time raises. Moreover, the increment of the saturation level of photodiodes also increases the error in the high illumination region. PMID:22303133
Absolute measurement of ultrasonic non-linearity parameter at contact interface
NASA Astrophysics Data System (ADS)
Yuan, Maodan; Lee, Taekgyu; Kang, To; Zhang, Jianhai; Song, Sung-Jin; Kim, Hak-Joon
2015-10-01
Non-linear interaction of waves with contact interfaces has been widely applied in non-destructive evaluation fields such as bonding quality evaluation, and the detection of closed microcracks and composite delamination. This paper proposes an absolute measurement of the ultrasonic non-linearity parameter using a piezoelectric detection method for two aluminum alloy blocks of different lengths. The results of a two-dimensional finite element method model verified by models for hard and soft contact interfaces, depending on the interface property, were compared with the measured non-linearity parameter. The measured values show good agreement with the modelled results, indicating good potential for measuring the non-linearity parameter at interfaces experimentally and numerically.
Absorption and phase retrieval in phase contrast imaging with non linear Tikhonov regularization
NASA Astrophysics Data System (ADS)
Sixou, B.; Davidoiu, V.; Langer, M.; Peyrin, F.
2012-09-01
The X-ray phase contrast imaging technique relies on the measurement of the Fresnel diffraction intensity patterns associated to a phase shift induced by the object. The simultaneous recovery of the phase and of the absorption is an ill-posed non linear inverse problem. In this work, we investigate the resolution of this problem with non linear Tikhonov regularization and with the Iterative Gauss Newton method. The algorithm is evalutated using simulated noisy data.
NASA Astrophysics Data System (ADS)
Singh, Prince; Sharma, Dinkar
2017-07-01
Series solution is obtained on solving non-linear fractional partial differential equation using homotopy perturbation transformation method. First of all, we apply homotopy perturbation transformation method to obtain the series solution of non-linear fractional partial differential equation. In this case, the fractional derivative is described in Caputo sense. Then, we present the facts obtained by analyzing the convergence of this series solution. Finally, the established fact is supported by an example.
How does non-linear dynamics affect the baryon acoustic oscillation?
Sugiyama, Naonori S.; Spergel, David N. E-mail: dns@astro.princeton.edu
2014-02-01
We study the non-linear behavior of the baryon acoustic oscillation in the power spectrum and the correlation function by decomposing the dark matter perturbations into the short- and long-wavelength modes. The evolution of the dark matter fluctuations can be described as a global coordinate transformation caused by the long-wavelength displacement vector acting on short-wavelength matter perturbation undergoing non-linear growth. Using this feature, we investigate the well known cancellation of the high-k solutions in the standard perturbation theory. While the standard perturbation theory naturally satisfies the cancellation of the high-k solutions, some of the recently proposed improved perturbation theories do not guarantee the cancellation. We show that this cancellation clarifies the success of the standard perturbation theory at the 2-loop order in describing the amplitude of the non-linear power spectrum even at high-k regions. We propose an extension of the standard 2-loop level perturbation theory model of the non-linear power spectrum that more accurately models the non-linear evolution of the baryon acoustic oscillation than the standard perturbation theory. The model consists of simple and intuitive parts: the non-linear evolution of the smoothed power spectrum without the baryon acoustic oscillations and the non-linear evolution of the baryon acoustic oscillations due to the large-scale velocity of dark matter and due to the gravitational attraction between dark matter particles. Our extended model predicts the smoothing parameter of the baryon acoustic oscillation peak at z = 0.35 as ∼ 7.7Mpc/h and describes the small non-linear shift in the peak position due to the galaxy random motions.
Construction of the wave operator for non-linear dispersive equations
NASA Astrophysics Data System (ADS)
Tsuruta, Kai Erik
In this thesis, we will study non-linear dispersive equations. The primary focus will be on the construction of the positive-time wave operator for such equations. The positive-time wave operator problem arises in the study of the asymptotics of a partial differential equation. It is a map from a space of initial data X into itself, and is loosely defined as follows: Suppose that for a solution ψlin to the dispersive equation with no non-linearity and initial data ψ +, there exists a unique solution ψ to the non-linear equation with initial data ψ0 such that ψ behaves as ψ lin as t → infinity. Then the wave operator is the map W+ that takes ψ + to ψ0. By its definition, W+ is injective. An important additional question is whether or not the map is also surjective. If so, then every non-linear solution emanating from X behaves, in some sense, linearly as it evolves (this is known as asymptotic completeness). Thus, there is some justification for treating these solutions as their much simpler linear counterparts. The main results presented in this thesis revolve around the construction of the wave operator(s) at critical non-linearities. We will study the "semi-relativistic" Schrodinger equation as well as the Klein-Gordon-Schrodinger system on R2 . In both cases, we will impose fairly general quadratic non-linearities for which conservation laws cannot be relied upon. These non-linearities fall below the scaling required to employ such tools as the Strichartz estimates. We instead adapt the "first iteration method" of Jang, Li, and Zhang to our setting which depends crucially on the critical decay of the non-linear interaction of the linear evolution. To see the critical decay in our problem, careful analysis is needed to treat the regime where one has spatial and/or time resonance.
Optimal control of a satellite-robot system using direct collocation with non-linear programming
NASA Astrophysics Data System (ADS)
Coverstone-Carroll, V. L.; Wilkey, N. M.
1995-08-01
The non-holonomic behavior of a satellite-robot system is used to develop the system's equations of motion. The resulting non-linear differential equations are transformed into a non-linear programming problem using direct collocation. The link rates of the robot are minimized along optimal reorientations. Optimal solutions to several maneuvers are obtained and the results are interpreted to gain an understanding of the satellite-robot dynamics.
Numerical solution of non-linear dual-phase-lag bioheat transfer equation within skin tissues.
Kumar, Dinesh; Kumar, P; Rai, K N
2017-11-01
This paper deals with numerical modeling and simulation of heat transfer in skin tissues using non-linear dual-phase-lag (DPL) bioheat transfer model under periodic heat flux boundary condition. The blood perfusion is assumed temperature-dependent which results in non-linear DPL bioheat transfer model in order to predict more accurate results. A numerical method of line which is based on finite difference and Runge-Kutta (4,5) schemes, is used to solve the present non-linear problem. Under specific case, the exact solution has been obtained and compared with the present numerical scheme, and we found that those are in good agreement. A comparison based on model selection criterion (AIC) has been made among non-linear DPL models when the variation of blood perfusion rate with temperature is of constant, linear and exponential type with the experimental data and it has been found that non-linear DPL model with exponential variation of blood perfusion rate is closest to the experimental data. In addition, it is found that due to absence of phase-lag phenomena in Pennes bioheat transfer model, it achieves steady state more quickly and always predict higher temperature than thermal and DPL non-linear models. The effect of coefficient of blood perfusion rate, dimensionless heating frequency and Kirchoff number on dimensionless temperature distribution has also been analyzed. The whole analysis is presented in dimensionless form. Copyright © 2017 Elsevier Inc. All rights reserved.
Fault-tolerant control for a class of non-linear systems with dead-zone
NASA Astrophysics Data System (ADS)
Chen, Mou; Jiang, Bin; Guo, William W.
2016-05-01
In this paper, a fault-tolerant control scheme is proposed for a class of single-input and single-output non-linear systems with the unknown time-varying system fault and the dead-zone. The non-linear state observer is designed for the non-linear system using differential mean value theorem, and the non-linear fault estimator that estimates the unknown time-varying system fault is developed. On the basis of the designed fault estimator, the observer-based fault-tolerant tracking control is then developed using the backstepping technique for non-linear systems with the dead-zone. The stability of the whole closed-loop system is rigorously proved via Lyapunov analysis and the satisfactory tracking control performance is guaranteed in the presence of the unknown time-varying system fault and the dead-zone. Numerical simulation results are presented to illustrate the effectiveness of the proposed backstepping fault-tolerant control scheme for non-linear systems.
Bifurcation analysis of a non-linear hysteretic oscillator under harmonic excitation
NASA Astrophysics Data System (ADS)
Il Chang, Seo
2004-09-01
The steady state oscillations of a system incorporating a non-linear hysteretic damper are studied analytically by applying a perturbation technique. The hysteretic damper of the system subject to harmonic resonant force is modelled by combining a Maxwell's model and Kelvin-Voigt's model in series. The non-linearity is imposed by replacing a spring element by a cubic-non-linear spring. The response of the system is described by two coupled second order differential equations including a non-linear constitutive equation. Proper rescaling of the variables and parameters of the equations of motion leads to a set of weakly non-linear equations of motion to which the method of averaging is applied. The bifurcation analysis of the reduced four-dimensional amplitude- and phase-equations of motion shows typical non-linear behaviors including saddle-node and Hopf bifurcations and separate solution branch. By the stability analysis, the saddle-node and Hopf bifurcation sets are obtained in parameter spaces. The software package AUTO is used to numerically study the bifurcation sets and limit cycle solutions bifurcating from the Hopf bifurcation points. It is shown that the limit cycle responses of the averaged system exist over broad parameter ranges.
NASA Astrophysics Data System (ADS)
Aerts, J. R. M.; Dirckx, J. J. J.; Pintelon, R.
2009-03-01
Different methods exist to quantify non-linearity, and recently a new method was proposed that uses multisines to determine output response level, noise level, and level of non-linear distortions simultaneously from one single short experiment. We used heterodyne vibrometry to measure the vibration of a membrane while it is stimulated acoustically, and to determine the non-linear distortions in its response with this new method of analysis. We demonstrate the method on an electrically driven earphone. Analysis of the sound output and optically measured vibration deliver comparable results, and clearly detect non-linear distortions. Next, we apply the method on an acoustically driven elastic membrane. At vibration amplitudes of the same magnitude as on the earphone, non-linear distortions are much smaller, as to be expected on an elastic membrane, but they can still be detected with the vibrometer. This technique can be used to investigate the non-linearity of acoustically driven systems such as the middle ear.
Structural Dynamic Analyses And Test Predictions For Spacecraft Structures With Non-Linearities
NASA Astrophysics Data System (ADS)
Vergniaud, Jean-Baptiste; Soula, Laurent; Newerla, Alfred
2012-07-01
The overall objective of the mechanical development and verification process is to ensure that the spacecraft structure is able to sustain the mechanical environments encountered during launch. In general the spacecraft structures are a-priori assumed to behave linear, i.e. the responses to a static load or dynamic excitation, respectively, will increase or decrease proportionally to the amplitude of the load or excitation induced. However, past experiences have shown that various non-linearities might exist in spacecraft structures and the consequences of their dynamic effects can significantly affect the development and verification process. Current processes are mainly adapted to linear spacecraft structure behaviour. No clear rules exist for dealing with major structure non-linearities. They are handled outside the process by individual analysis and margin policy, and analyses after tests to justify the CLA coverage. Non-linearities can primarily affect the current spacecraft development and verification process on two aspects. Prediction of flights loads by launcher/satellite coupled loads analyses (CLA): only linear satellite models are delivered for performing CLA and no well-established rules exist how to properly linearize a model when non- linearities are present. The potential impact of the linearization on the results of the CLA has not yet been properly analyzed. There are thus difficulties to assess that CLA results will cover actual flight levels. Management of satellite verification tests: the CLA results generated with a linear satellite FEM are assumed flight representative. If the internal non- linearities are present in the tested satellite then there might be difficulties to determine which input level must be passed to cover satellite internal loads. The non-linear behaviour can also disturb the shaker control, putting the satellite at risk by potentially imposing too high levels. This paper presents the results of a test campaign performed in
Influence of non-linear flow on the pumping tests in karstified and fractured aquifers
NASA Astrophysics Data System (ADS)
Farkas-Karay, Gyöngyi; Birk, Steffen; Vasvári, Vilmos; Hajnal, Géza; Mayaud, Cyril
2017-04-01
When evaluating pumping test data in karstified or fractured aquifers remarkable deviations from the theoretically estimated curves can be observed. The assumptions of the commonly used evaluation methods (Theis, Cooper-Jacob, Papadopulus-Cooper) usually do not fit to properties in hard rock aquifers, where often non-linear, heterogeneous and non-isotropic conditions can appear. The analysis of the effect of these conditions helps to better evaluate the pumping test data and to avoid the mistakes caused by the use of traditional methods. In this study the influence of non-linear flow was analysed based on field data and computer-generated time series. Using Non-Linear Flow Process for MODFLOW (Mayaud, C., Walker, P., Hergarten, S. and Birk, S., 2015, Nonlinear Flow Process: A New Package to Compute Nonlinear Flow in MODFLOW. Groundwater, 53: 645-650) allowed the simulation of non-linear flow in aquifers based on the Forchheimer equation. The analysis showed that the detection of non-linear flow can be subserved by separate evaluation of drawdown and recovery time series or by using additional observation wells. Recovery data and data from observation wells far enough from the pumped well are not disturbed by nonlinearity; the comparison with drawdown data of observation wells and the pumped well therefore can show whether or not non-linear flow appears. In particular, proper results of aquifer parameters can be obtained from recovery data. If only drawdown data from the pumped well are available it is helpful to replace the losses caused by non-linear flow by non-linear well losses (see also Mathias, S. A., and L. C. Todman, 2010, Step-drawdown tests and the Forchheimer equation, Water Resour. Res., 46, W07514). The applicability of the Jacob's step-drawdown-test evaluation in Forchheimer-flow cases is demonstrated by comparison with the numerical non-linear flow model. Inaccurate parameter estimates resulting from neglecting non-linear flow demonstrate the
V. I. Lenin and Soviet Military Science (Selected Portion)
1981-12-07
guided by the resolutions of the CC CPSU and Soviet government for military questions, Soviet military science correctly opened the character of modern...character of modern war, the essence of processes and laws governing the revolution in military science , to investigate the most important problems of...r LEVEL F.’.-rv, ,•S)T-14J47-81 I ; i FOREIGN TECHNOLOGY DIVISION 0 N V.I. LENIN AND SOVIET MILITARY SCIENCE (Selected Portion) by N. N. Azovtsev C
2007-10-01
Design and initial in-water testing of advanced non- linear control algorithms onto an Unmanned Underwater Vehicle (UUV) Vladimir Djapic Unmanned...attitude or translating in a direction different from that of the surface. Non- linear controller that compensates for non-linear forces (such as drag...loop” non- linear controller (outputs the appropriate thrust values) is the same for all mission scenarios while an appropriate ”outer-loop” non
NASA Astrophysics Data System (ADS)
Gonçalves Correia, Dayse; Viana Ávila, Kilvia Maria; Cavalcante, Daniel do Nascimento e. Sá; Ferreira Pinto, Paulo Victor; Tadeu de Carvalho Belchior Magalhães, Francisco; Pinheiro de Moura, Lucas; da Conceição Ferreira, Alisson; Mendonça Menezes, Jose Wally; de Freitas Guimarães, Glendo
2016-03-01
In this work, we investigated the optical switching process for three shapes of femtosecond pulses (soliton, Gaussian and super-Gaussian) propagating inside a symmetrical dual-core non-linear directional coupler by simulating their propagation via the coupled non-linear Schrödinger equations. In all simulations, we considered the dispersive effects of second and third order, besides the self-phase modulation and self-steepening non-linear effects. We studied three scenarios for each of the three pulse shapes under investigation. In the first scenario, we added only cross-phase modulation (XPM); in the second approach, we added only Raman scattering; in the third one, we combined both. The study was performed for distinct polarization modes and for different values of the Raman factor, with power range varying from 1 to 300 W. We noted that the XPM non-linear effect results in a decrease in the critical power threshold, whereas the Raman scattering causes an increase. For the first scenario (only XPM effect), the critical power threshold reduced from 113.72 to 104.69 W for the soliton pulse, from 111.49 to 100.77 W for the Gaussian and from 92.79 to 80.47 W for the Super-Gaussian pulse shape. For the second scenario (only Raman scattering), the critical power increased for a Raman factor varying from 1 to 10 fs, and the three pulse shapes reached thresholds above 150 W from a 5 fs factor, reaching more than 200 W for the super-Gaussian pulse as the Raman factor increased. For the third scenario (with both effects combined), we highlight that for a fixed XPM factor of 2, the critical power remained unchanged with the variation of the Raman factor. Hence, we observed that the Super-Gaussian pulse reached lower values for critical power when compared to the other pulse shapes.
Non-linear dual-axis biodynamic response to vertical whole-body vibration
NASA Astrophysics Data System (ADS)
Nawayseh, N.; Griffin, M. J.
2003-11-01
Seated human subjects have been exposed to vertical whole-body vibration so as to investigate the non-linearity in their biodynamic responses and quantify the response in directions other than the direction of excitation. Twelve males were exposed to random vertical vibration in the frequency range 0.25-25 Hz at four vibration magnitudes (0.125, 0.25, 0.625, and 1.25 m s -2 r.m.s.). The subjects sat in four sitting postures having varying foot heights so as to produce differing thigh contact with the seat (feet hanging, feet supported with maximum thigh contact, feet supported with average thigh contact, and feet supported with minimum thigh contact). Forces were measured in the vertical, fore-and-aft, and lateral directions on the seat and in the vertical direction at the footrest. The characteristic non-linear response of the human body with reducing resonance frequency at increasing vibration magnitudes was seen in all postures, but to a lesser extent with minimum thigh contact. Appreciable forces in the fore-and-aft direction also showed non-linearity, while forces in the lateral direction were low and showed no consistent trend. Forces at the feet were non-linear with a multi-resonant behaviour and were affected by the position of the legs. The decreased non-linearity with the minimum thigh contact posture suggests the tissues of the buttocks affect the non-linearity of the body more than the tissues of the thighs. The forces in the fore-and-aft direction are consistent with the body moving in two directions when exposed to vertical vibration. The non-linear behaviour of the body, and the considerable forces in the fore-aft direction should be taken into account when optimizing vibration isolation devices.
Optimization of processing parameters on the controlled growth of c-axis oriented ZnO nanorod arrays
Malek, M. F. Rusop, M.; Mamat, M. H.; Musa, M. Z.; Saurdi, I. Ishak, A.; Alrokayan, Salman A. H. Khan, Haseeb A.
2016-07-06
Optimization of the growth time parameter was conducted to synthesize high-quality c-axis ZnO nanorod arrays. The effects of the parameter on the crystal growth and properties were systematically investigated. Our studies confirmed that the growth time influence the properties of ZnO nanorods where the crystallite size of the structures was increased at higher deposition time. Field emission scanning electron microsope analysis confirmed the morphologies structure of the ZnO nanorods. The ZnO nanostructures prepared under the optimized growth conditions showed an intense XRD peak which reveal a higher c-axis oriented ZnO nanorod arrays thus demonstrating the formation of defect free structure.
NASA Astrophysics Data System (ADS)
Díaz-Azpiroz, Manuel; Fernández, Carlos
2008-05-01
Quartz c-axis fabrics from leucocratic gneisses of the Aracena metamorphic belt (southwestern Variscan Chain) record two different tectonic phases. The first one consists of a predominant flattening component and the local development of shear zones with a normal, top-to-the-north shear sense. The second phase resulted in the reactivation of the first-phase shear zones that subsequently acted with a reverse, top-to-the-south sense of displacement. Accordingly, it is suggested that the imprint of a non-coaxial deformation phase over a previous flattening phase leads to quartz c-axis fabrics defined by asymmetric small circles around the Z-axis of the finite-strain ellipsoid.
NASA Astrophysics Data System (ADS)
Munzar, Dominik
2006-01-01
Changes of the 400 cm-1 peak in the c-axis conductivity of underdoped YBa2Cu3O6.6 upon application of a parallel magnetic field reported by Kojima et al. are shown to be consistent with the model where the peak is due to the superfluid. Results of our calculations of the c-axis response of bilayer compounds with well defined bilayer split bands are presented and discussed. For moderate values of the bilayer splitting (Δɛ comparable to 2Δmax) the spectra of the superconducting state exhibit an additional mode which is due to the condensate and similar to the one of earlier phenonomenological approaches.
Zhang, Haifeng; Bao, Yuanye
2014-03-01
This paper presents a theoretical analysis of a new zigzag C-axis inclined multi-layer ZnO thin-film bulk acoustic wave resonator (FBAR) as a viscosity sensor to monitor the lubrication performance of engine oil and other liquids. Free vibration and forced vibration for the FBAR loaded with liquids are analyzed. Equations necessary to calculate the sensitivity are derived. The numerical analysis shows that as the number of layers increases, the absolute sensitivity increases as well. The influences on the sensitivity of C-axis inclined angle, Q-factor, and thickness are also investigated. The results provide a foundation for further design of multi-layer FBAR viscosity sensors.
NASA Astrophysics Data System (ADS)
Ishii, H.; Hara, T.; Hirano, S.; Figueredo, A. M.; Cima, M. J.
1994-05-01
The magnetic-hysteresis behavior of single-crystal YBCO fibers was investigated below 1 T and in the temperature range 40 to 88 K. The sample was prepared by the laser-heated floating zone method. The magnetization curves exhibited a fairly large asymmetry with respect to the field axis, especially at elevated temperatures. This behavior may be attributed to the surface Meissner current contribution. It was demonstrated for the temperature range examined that the magnetic hysteresis width, Δ M, versus external-field curves were well described by assuming that the critical current density in the c-axis direction Jcc obeys the critical-state model of the form Jc( B)= JcO[1+( B/ B0) n]-1. Then, in turn, the field dependence of the critical current density along the c-axis at field temperatures was deduced using parameters obtained by fitting the Δ M vs. field curves. It was shown that the critical current density in the direction of the c-axis in our sample was over 10 4 A/cm 2 at 77.3 K below 0.3 T. The field and temperature variations of Jcc were discussed in relation to the previous studies on some melt-processed YBCO.
Charge-screening role of c -axis atomic displacements in YBa2Cu3O6 +x and related superconductors
NASA Astrophysics Data System (ADS)
Božin, E. S.; Huq, A.; Shen, Bing; Claus, H.; Kwok, W. K.; Tranquada, J. M.
2016-02-01
The importance of charge reservoir layers for supplying holes to the CuO2 planes of cuprate superconductors has long been recognized. Less attention has been paid to the screening of the charge transfer by the intervening ionic layers. We address this issue in the case of YBa2Cu3O6 +x , where CuO chains supply the holes for the planes. We present a simple dielectric-screening model that gives a linear correlation between the relative displacements of ions along the c axis, determined by neutron powder diffraction, and the hole density of the planes. Applying this model to the temperature-dependent shifts of ions along the c axis, we infer a charge transfer of 5-10% of the hole density from the planes to the chains on warming from the superconducting transition to room temperature. Given the significant coupling of c -axis displacements to the average charge density, we point out the relevance of local displacements for screening charge modulations and note recent evidence for dynamic screening of in-plane quasiparticles. This line of argument leads us to a simple model for atomic displacements and charge modulation that is consistent with images from scanning-tunneling microscopy for underdoped Bi2Sr2CaCu2O8 +δ .
Room temperature sputtering of inclined c-axis ZnO for shear mode solidly mounted resonators
NASA Astrophysics Data System (ADS)
Rughoobur, G.; DeMiguel-Ramos, M.; Mirea, T.; Clement, M.; Olivares, J.; Díaz-Durán, B.; Sangrador, J.; Miele, I.; Milne, W. I.; Iborra, E.; Flewitt, A. J.
2016-01-01
ZnO films with a c-axis significantly inclined away from the surface normal were grown by a remote plasma sputtering technique at room temperature. The films were used to make solidly mounted resonators (SMRs) operating in shear mode at a resonant frequency of 1.35 GHz. Control of the ZnO microstructure was achieved using a polycrystalline AlN seed layer which can be added on top of a sputtered acoustic mirror to give a complete SMR device. The ZnO was reactively sputtered in an atmosphere of argon and oxygen from a zinc target. The c-axis of the ZnO was estimated to be at an angle of ˜45° to the surface normal. SMRs were measured to have quality factors (Q) of up to 140 and effective electromechanical coupling coefficients of up to 2.2% in air. Although an inclined c-axis can be achieved with direct growth onto the acoustic mirror, it is shown that the AlN seed layer provides higher coupling coefficients and narrower inclination angular distribution. The responses of the devices in liquids of different viscosities (acetone, water, and AZ5214E photoresist) were measured. The shear mode Q decreased by 45% in acetone, 72% in water, and 92% in AZ5214E.
Finite element simulation of non-linear acoustic generation in a horn loudspeaker
NASA Astrophysics Data System (ADS)
Tsuchiya, T.; Kagawa, Y.; Doi, M.; Tsuji, T.
2003-10-01
The loudspeaker is an electro-acoustic device for sound reproduction which requires the distortion as small as possible. The distortion may arise from the magnetic non-linearity of the york, the uneven magnetic field distribution, the mechanical non-linearity at the diaphragm suspension and the acoustic non-linearity due to the high sound pressure and velocity in the duct-radiation system. A horn is sometimes provided in front of the vibrating diaphragm radiator, which plays an important role to increase the efficiency by matching the acoustic impedance between the radiator and the ambient medium. The horn is in many cases folded twice or three times to shorten the length, which further degrades the reproduction quality. The sound intensity and velocity are apt to attain very high in the small cross-sectional area in the throat and in the folded regions, which may cause the distortion due to the non-linear effect of the medium. The present paper is to investigate the frequency characteristics of the loudspeaker numerically evaluating the generation of the harmonics and sub-harmonics. An axisymmetric folded horn is considered for which the wave equation with the non-linear term retained is solved by the finite element method. The solution is made in time domain in which the sound pressure calculated at the opening end of the horn is Fourier-transformed to the frequency domain to evaluate the distortion, while the wave marching in the horn is visualized.
NASA Astrophysics Data System (ADS)
Vismara, S. O.; Ricci, S.; Bellini, M.; Trittoni, L.
2016-06-01
The objective of the present paper is to describe a procedure to identify and model the non-linear behaviour of structural elements. The procedure herein applied can be divided into two main steps: the system identification and the finite element model updating. The application of the restoring force surface method as a strategy to characterize and identify localized non-linearities has been investigated. This method, which works in the time domain, has been chosen because it has `built-in' characterization capabilities, it allows a direct non-parametric identification of non-linear single-degree-of-freedom systems and it can easily deal with sine-sweep excitations. Two different application examples are reported. At first, a numerical test case has been carried out to investigate the modelling techniques in the case of non-linear behaviour based on the presence of a free-play in the model. The second example concerns the flap of the Intermediate eXperimental Vehicle that successfully completed its 100-min mission on 11 February 2015. The flap was developed under the responsibility of Thales Alenia Space Italia, the prime contractor, which provided the experimental data needed to accomplish the investigation. The procedure here presented has been applied to the results of modal testing performed on the article. Once the non-linear parameters were identified, they were used to update the finite element model in order to prove its capability of predicting the flap behaviour for different load levels.
The effect of non-linear human visual system components on linear model observers
NASA Astrophysics Data System (ADS)
Zhang, Yani; Pham, Binh T.; Eckstein, Miguel P.
2004-05-01
Linear model observers have been used successfully to predict human performance in clinically relevant visual tasks for a variety of backgrounds. On the other hand, there has been another family of models used to predict human visual detection of signals superimposed on one of two identical backgrounds (masks). These masking models usually include a number of non-linear components in the channels that reflect properties of the firing of cells in the primary visual cortex (V1). The relationship between these two traditions of models has not been extensively investigated in the context of detection in noise. In this paper, we evaluated the effect of including some of these non-linear components into a linear channelized Hotelling observer (CHO), and the associated practical implications for medical image quality evaluation. In particular, we evaluate whether the rank order evaluation of two compression algorithms (JPEG vs. JPEG 2000) is changed by inclusion of the non-linear components. The results show: a) First that the simpler linear CHO model observer outperforms CHO model with the nonlinear components investigated. b) The rank order of model observer performance for the compression algorithms did not vary when the non-linear components were included. For the present task, the results suggest that the addition of the physiologically based channel non-linearities to a channelized Hotelling might add complexity to the model observers without great impact on medical image quality evaluation.
Analysis of non-linear response of the human body to vertical whole-body vibration.
Tarabini, Marco; Solbiati, Stefano; Moschioni, Giovanni; Saggin, Bortolino; Scaccabarozzi, Diego
2014-01-01
The human response to vibration is typically studied using linear estimators of the frequency response function, although different literature works evidenced the presence of non-linear effects in whole-body vibration response. This paper analyses the apparent mass of standing subjects using the conditioned response techniques in order to understand the causes of the non-linear behaviour. The conditioned apparent masses were derived considering models of increasing complexity. The multiple coherence function was used as a figure of merit for the comparison between the linear and the non-linear models. The apparent mass of eight male subjects was studied in six configurations (combinations of three vibration magnitudes and two postures). The contribution of the non-linear terms was negligible and was endorsed to the change of modal parameters during the test. Since the effect of the inter-subject variability was larger than that due to the increase in vibration magnitude, the biodynamic response should be more meaningfully modelled using a linear estimator with uncertainty rather than looking for a non-linear modelling.
Non-Linear Dynamics Tools for the Motion Analysis and Condition Monitoring of Robot Joints
NASA Astrophysics Data System (ADS)
Trendafilova, I.; van Brussel, H.
2001-11-01
Time series from non-damaged and three types of damaged robot joints are considered and analysed from the viewpoint of non-linear dynamics. The embedding spaces for the four types of signals are recovered. The application of surrogate data tests is used to prove the presence of non-linearities in the joints. The results suggest a rise in unstable behaviour due to the introduction of backlash in robot joints. The chaotic behaviour gets stronger with the increase of the backlash extent. This is confirmed by the increase of the embedding dimension as well as by the increase of the Lyapunov exponents and the correlation dimension with the backlash increase. A straightforward method for condition monitoring using non-linear dynamics characteristics, based on a classification procedure, is suggested.
A Signal Transmission Technique for Stability Analysis of Multivariable Non-Linear Control Systems
NASA Technical Reports Server (NTRS)
Jackson, Mark; Zimpfer, Doug; Adams, Neil; Lindsey, K. L. (Technical Monitor)
2000-01-01
Among the difficulties associated with multivariable, non-linear control systems is the problem of assessing closed-loop stability. Of particular interest is the class of non-linear systems controlled with on/off actuators, such as spacecraft thrusters or electrical relays. With such systems, standard describing function techniques are typically too conservative, and time-domain simulation analysis is prohibitively extensive, This paper presents an open-loop analysis technique for this class of non-linear systems. The technique is centered around an innovative use of multivariable signal transmission theory to quantify the plant response to worst case control commands. The technique has been applied to assess stability of thruster controlled flexible space structures. Examples are provided for Space Shuttle attitude control with attached flexible payloads.
Real-Time Monitoring of Non-linear Suicidal Dynamics: Methodology and a Demonstrative Case Report
Fartacek, Clemens; Schiepek, Günter; Kunrath, Sabine; Fartacek, Reinhold; Plöderl, Martin
2016-01-01
In recent years, a number of different authors have stressed the usefulness of non-linear dynamic systems approach in suicide research and suicide prevention. This approach applies specific methods of time series analysis and, consequently, it requires a continuous and fine-meshed assessment of the processes under consideration. The technical means for this kind of process assessment and process analysis are now available. This paper outlines how suicidal dynamics can be monitored in high-risk patients by an Internet-based application for continuous self-assessment with integrated tools of non-linear time series analysis: the Synergetic Navigation System. This procedure is illustrated by data from a patient who attempted suicide at the end of a 90-day monitoring period. Additionally, future research topics and clinical applications of a non-linear dynamic systems approach in suicidology are discussed. PMID:26913016
Non-linear effects of soda taxes on consumption and weight outcomes.
Fletcher, Jason M; Frisvold, David E; Tefft, Nathan
2015-05-01
The potential health impacts of imposing large taxes on soda to improve population health have been of interest for over a decade. As estimates of the effects of existing soda taxes with low rates suggest little health improvements, recent proposals suggest that large taxes may be effective in reducing weight because of non-linear consumption responses or threshold effects. This paper tests this hypothesis in two ways. First, we estimate non-linear effects of taxes using the range of current rates. Second, we leverage the sudden, relatively large soda tax increase in two states during the early 1990s combined with new synthetic control methods useful for comparative case studies. Our findings suggest virtually no evidence of non-linear or threshold effects.
Russell, Steven J.; Carlsten, Bruce E.
2012-06-26
We will quickly go through the history of the non-linear transmission lines (NLTLs). We will describe how they work, how they are modeled and how they are designed. Note that the field of high power, NLTL microwave sources is still under development, so this is just a snap shot of their current state. Topics discussed are: (1) Introduction to solitons and the KdV equation; (2) The lumped element non-linear transmission line; (3) Solution of the KdV equation; (4) Non-linear transmission lines at microwave frequencies; (5) Numerical methods for NLTL analysis; (6) Unipolar versus bipolar input; (7) High power NLTL pioneers; (8) Resistive versus reactive load; (9) Non-lineaer dielectrics; and (10) Effect of losses.
McSharry, P E; He, T; Smith, L A; Tarassenko, L
2002-07-01
The electro-encephalogram is a time-varying signal that measures electrical activity in the brain. A conceptually intuitive non-linear technique, multi-dimensional probability evolution (MDPE), is introduced. It is based on the time evolution of the probability density function within a multi-dimensional state space. A synthetic recording is employed to illustrate why MDPE is capable of detecting changes in the underlying dynamics that are invisible to linear statistics. If a non-linear statistic cannot outperform a simple linear statistic such as variance, then there is no reason to advocate its use. Both variance and MDPE were able to detect the seizure in each of the ten scalp EEG recordings investigated. Although MDPE produced fewer false positives, there is no firm evidence to suggest that MDPE, or any other non-linear statistic considered, outperforms variance-based methods at identifying seizures.
On incremental non-linearity in granular media: phenomenological and multi-scale views
NASA Astrophysics Data System (ADS)
Darve, Félix; Nicot, François
2005-12-01
On the basis of fundamental constitutive laws such as elasticity, perfect plasticity, and pure viscosity, many elasto-viscoplastic constitutive relations have been developed since the 1970s through phenomenological approaches. In addition, a few more recent micro-mechanical models based on multi-scale approaches are now able to describe the main macroscopic features of the mechanical behaviour of granular media. The purpose of this paper is to compare a phenomenological constitutive relation and a micro-mechanical model with respect to a basic issue regularly raised about granular assemblies: the incrementally non-linear character of their behaviour. It is shown that both phenomenological and micro-mechanical models exhibit an incremental non-linearity. In addition, the multi-scale approach reveals that the macroscopic incremental non-linearity could stem from the change in the regime of local contacts between particles (from plastic regime to elastic regime) in terms of the incremental macroscopic loading direction. Copyright
Characterization of non-linear Potassium crystals in the Terahertz frequency domain
NASA Astrophysics Data System (ADS)
Mounaix, P.; Sarger, L.; Caumes, J. P.; Freysz, E.
2004-12-01
Systematic measurements of the dielectric properties of KDP, KNbO3, KTP and KTA non-linear crystals in the Terahertz (THz) spectral range are presented. The index of refraction and the absorption coefficients are measured between 0.1 and 1.5 THz for different crystallographic orientations. The data are deduced from an experimental set-up based on standard Terahertz time domain spectroscopy system at room temperature. These data, key parameters for the optimization of non-linear THz generation by optical rectification as well as electro-optic detection, are analysed in term of non-linear capabilities. We finally review different methods making possible to generate THz wave in these crystals and compare their characteristics.
Non-linear dynamics of a geared rotor-bearing system with multiple clearances
NASA Astrophysics Data System (ADS)
Kahraman, A.; Singh, R.
1991-02-01
Non-linear frequency response characteristics of a geared rotor-bearing system are examined in this paper. A three-degree-of-freedom dynamic model is developed which includes non-linearities associated with radial clearances in the radial rolling element bearings and backlash between a spur gear pair; linear time-invariant gear meshing stiffness is assumed. The corresponding linear system problem is also solved, and predicted natural frequencies and modes match with finite element method results. The bearing non-linear stiffness function is approximated for the sake of convenience by a simple model which is identical to that used for the gear mesh. This approximate bearing model has been verified by comparing steady state frequency spectra. Applicability of both analytical and numerical solution techniques to the multi-degree-of-freedom non-linear problem is investigated. Satisfactory agreement has been found between our theory and available experimental data. Several key issues such as non-linear modal interactions and differences between internal static transmission error excitation and external torque excitation are discussed. Additionally, parametric studies are performed to understand the effect of system parameters such as bearing stiffness to gear mesh stiffness ratio, alternating to mean force ratio and radial bearing preload to mean force ratio on the non-linear dynamic behavior. A criterion used to classify the steady state solutions is presented, and the conditions for chaotic, quasi-periodic and subharmonic steady state solutions are determined. Two typical routes to chaos observed in this geared system are also identified.
Analysis of linear and non-linear genotype × environment interaction.
Yang, Rong-Cai
2014-01-01
The usual analysis of genotype × environment interaction (G × E) is based on the linear regression of genotypic performance on environmental changes (e.g., classic stability analysis). This linear model may often lead to lumping together of the non-linear responses to the whole range of environmental changes from suboptimal and super optimal conditions, thereby lowering the power of detecting G × E variation. On the other hand, the G × E is present when the magnitude of the genetic effect differs across the range of environmental conditions regardless of whether the response to environmental changes is linear or non-linear. The objectives of this study are: (i) explore the use of four commonly used non-linear functions (logistic, parabola, normal and Cauchy functions) for modeling non-linear genotypic responses to environmental changes and (ii) to investigate the difference in the magnitude of estimated genetic effects under different environmental conditions. The use of non-linear functions was illustrated through the analysis of one data set taken from barley cultivar trials in Alberta, Canada (Data A) and the examination of change in effect sizes is through the analysis another data set taken from the North America Barley Genome Mapping Project (Data B). The analysis of Data A showed that the Cauchy function captured an average of >40% of total G × E variation whereas the logistic function captured less G × E variation than the linear function. The analysis of Data B showed that genotypic responses were largely linear and that strong QTL × environment interaction existed as the positions, sizes and directions of QTL detected differed in poor vs. good environments. We conclude that (i) the non-linear functions should be considered when analyzing multi-environmental trials with a wide range of environmental variation and (ii) QTL × environment interaction can arise from the difference in effect sizes across environments.
Analysis of linear and non-linear genotype × environment interaction
Yang, Rong-Cai
2014-01-01
The usual analysis of genotype × environment interaction (G × E) is based on the linear regression of genotypic performance on environmental changes (e.g., classic stability analysis). This linear model may often lead to lumping together of the non-linear responses to the whole range of environmental changes from suboptimal and super optimal conditions, thereby lowering the power of detecting G × E variation. On the other hand, the G × E is present when the magnitude of the genetic effect differs across the range of environmental conditions regardless of whether the response to environmental changes is linear or non-linear. The objectives of this study are: (i) explore the use of four commonly used non-linear functions (logistic, parabola, normal and Cauchy functions) for modeling non-linear genotypic responses to environmental changes and (ii) to investigate the difference in the magnitude of estimated genetic effects under different environmental conditions. The use of non-linear functions was illustrated through the analysis of one data set taken from barley cultivar trials in Alberta, Canada (Data A) and the examination of change in effect sizes is through the analysis another data set taken from the North America Barley Genome Mapping Project (Data B). The analysis of Data A showed that the Cauchy function captured an average of >40% of total G × E variation whereas the logistic function captured less G × E variation than the linear function. The analysis of Data B showed that genotypic responses were largely linear and that strong QTL × environment interaction existed as the positions, sizes and directions of QTL detected differed in poor vs. good environments. We conclude that (i) the non-linear functions should be considered when analyzing multi-environmental trials with a wide range of environmental variation and (ii) QTL × environment interaction can arise from the difference in effect sizes across environments. PMID:25101112
Three-dimensional finite-difference modeling of non-linear ground notion
Jones, E.M.; Olsen, K.B.
1997-08-01
We present a hybrid finite-difference technique capable of modeling non-linear soil amplification from the 3-D finite-fault radiation pattern for earthquakes in arbitrary earth models. The method is applied to model non-linear effects in the soils of the San Fernando Valley (SFV) from the 17 January 1994 M 6.7 Northridge earthquake. 0-7 Hz particle velocities are computed for an area of 17 km by 19 km immediately above the causative fault and 5 km below the surface where peak strike-parallel, strike-perpendicular, vertical, and total velocities reach values of 71 cm/s, 145 cm/s, 152 cm/s, and 180 cm/s, respectively. Selected Green`s functions and a soil model for the SFV are used to compute the approximate stress level during the earthquake, and comparison to the values for near-surface alluvium at the U.S. Nevada Test Site suggests that the non-linear regime may have been entered. We use selected values from the simulated particle velocity distribution at 5 km depth to compute the non-linear response in a soil column below a site within the Van Norman Complex in SFV, where the strongest ground motion was recorded. Since site-specific non- linear material parameters from the SFV are currently unavailable, values are taken from analyses of observed Test Site ground motions. Preliminary results show significant reduction of spectral velocities at the surface normalized to the peak source velocity due to non-linear effects when the peak velocity increases from 32 cm/s (approximately linear case) to 64 cm/s (30-92%), 93 cm/s (7-83%), and 124 cm/s (2-70%). The largest reduction occurs for frequencies above 1 Hz.
The non-linear power spectrum of the Lyman alpha forest
NASA Astrophysics Data System (ADS)
Arinyo-i-Prats, Andreu; Miralda-Escudé, Jordi; Viel, Matteo; Cen, Renyue
2015-12-01
The Lyman alpha forest power spectrum has been measured on large scales by the BOSS survey in SDSS-III at z~ 2.3, has been shown to agree well with linear theory predictions, and has provided the first measurement of Baryon Acoustic Oscillations at this redshift. However, the power at small scales, affected by non-linearities, has not been well examined so far. We present results from a variety of hydrodynamic simulations to predict the redshift space non-linear power spectrum of the Lyα transmission for several models, testing the dependence on resolution and box size. A new fitting formula is introduced to facilitate the comparison of our simulation results with observations and other simulations. The non-linear power spectrum has a generic shape determined by a transition scale from linear to non-linear anisotropy, and a Jeans scale below which the power drops rapidly. In addition, we predict the two linear bias factors of the Lyα forest and provide a better physical interpretation of their values and redshift evolution. The dependence of these bias factors and the non-linear power on the amplitude and slope of the primordial fluctuations power spectrum, the temperature-density relation of the intergalactic medium, and the mean Lyα transmission, as well as the redshift evolution, is investigated and discussed in detail. A preliminary comparison to the observations shows that the predicted redshift distortion parameter is in good agreement with the recent determination of Blomqvist et al., but the density bias factor is lower than observed. We make all our results publicly available in the form of tables of the non-linear power spectrum that is directly obtained from all our simulations, and parameters of our fitting formula.
The non-linear power spectrum of the Lyman alpha forest
Arinyo-i-Prats, Andreu; Miralda-Escudé, Jordi; Viel, Matteo; Cen, Renyue E-mail: miralda@icc.ub.edu E-mail: cen@astro.princeton.edu
2015-12-01
The Lyman alpha forest power spectrum has been measured on large scales by the BOSS survey in SDSS-III at z∼ 2.3, has been shown to agree well with linear theory predictions, and has provided the first measurement of Baryon Acoustic Oscillations at this redshift. However, the power at small scales, affected by non-linearities, has not been well examined so far. We present results from a variety of hydrodynamic simulations to predict the redshift space non-linear power spectrum of the Lyα transmission for several models, testing the dependence on resolution and box size. A new fitting formula is introduced to facilitate the comparison of our simulation results with observations and other simulations. The non-linear power spectrum has a generic shape determined by a transition scale from linear to non-linear anisotropy, and a Jeans scale below which the power drops rapidly. In addition, we predict the two linear bias factors of the Lyα forest and provide a better physical interpretation of their values and redshift evolution. The dependence of these bias factors and the non-linear power on the amplitude and slope of the primordial fluctuations power spectrum, the temperature-density relation of the intergalactic medium, and the mean Lyα transmission, as well as the redshift evolution, is investigated and discussed in detail. A preliminary comparison to the observations shows that the predicted redshift distortion parameter is in good agreement with the recent determination of Blomqvist et al., but the density bias factor is lower than observed. We make all our results publicly available in the form of tables of the non-linear power spectrum that is directly obtained from all our simulations, and parameters of our fitting formula.
Non-linear performance of a three-bearing rotor incorporating a squeeze-film damper
NASA Technical Reports Server (NTRS)
Holmes, R.; Dede, M.
1987-01-01
This paper is concerned with the non-linear vibration performance of a rigid rotor supported on three bearings, one being surrounded by a squeeze-film damper. This damper relies on the pressure built up in the squeeze film to help counter-act external forces arising from unbalance and other effects. As a result a vibration orbit of a certain magnetude results. Such vibration orbits illustrate features found in other non-linear systems, in particular sub-harmonic resonances and jump phenomena. Comparisons between theoretical prediction and experimental observations of these phenomena are made.
Non-linear molecular pattern classification using molecular beacons with multiple targets.
Lee, In-Hee; Lee, Seung Hwan; Park, Tai Hyun; Zhang, Byoung-Tak
2013-12-01
In vitro pattern classification has been highlighted as an important future application of DNA computing. Previous work has demonstrated the feasibility of linear classifiers using DNA-based molecular computing. However, complex tasks require non-linear classification capability. Here we design a molecular beacon that can interact with multiple targets and experimentally shows that its fluorescent signals form a complex radial-basis function, enabling it to be used as a building block for non-linear molecular classification in vitro. The proposed method was successfully applied to solving artificial and real-world classification problems: XOR and microRNA expression patterns. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Zausner, Tobi
Chaos theory may provide models for creativity and for the personality of the artist. A collection of speculative hypotheses examines the connection between art and such fundamentals of non-linear dynamics as iteration, dissipative processes, open systems, entropy, sensitivity to stimuli, autocatalysis, subsystems, bifurcations, randomness, unpredictability, irreversibility, increasing levels of organization, far-from-equilibrium conditions, strange attractors, period doubling, intermittency and self-similar fractal organization. Non-linear dynamics may also explain why certain individuals suffer mental disorders while others remain intact during a lifetime of sustained creative output.
Optimal design of linear and non-linear dynamic vibration absorbers
NASA Astrophysics Data System (ADS)
Jordanov, I. N.; Cheshankov, B. I.
1988-05-01
An efficient numerical method is applied to obtain optimal parameters for both linear and non-linear damped dynamic vibration absorbers. The minimization of the vibration response has been carried out for damped as well as undamped force excited primary systems with linear and non-linear spring characteristics. Comparison is made with the optimum absorber parameters that are determined by using Den Hartog's classical results in the linear case. Six optimization criteria by which the response is minimized over narrow and broad frequency bands are examined. Pareto optimal solutions of the multi-objective decision making problem are obtained.
Free Convective Nonaligned Non-Newtonian Flow with Non-linear Thermal Radiation
NASA Astrophysics Data System (ADS)
Rana, S.; Mehmood, R.; Narayana, PV S.; Akbar, N. S.
2016-12-01
The present study explores the free convective oblique Casson fluid over a stretching surface with non-linear thermal radiation effects. The governing physical problem is modelled and transformed into a set of coupled non-linear ordinary differential equations by suitable similarity transformation, which are solved numerically with the help of shooting method keeping the convergence control of 10-5 in computations. Influence of pertinent physical parameters on normal, tangential velocity profiles and temperature are expressed through graphs. Physical quantities of interest such as skin friction coefficients and local heat flux are investigated numerically.
Influence of shear in the non-linear analysis of RC members
Diotallevi, Pier Paolo; Landi, Luca; Cardinetti, Filippo
2008-07-08
The purpose of this study is to develop an analytical model characterized by a beam-column finite element which is able to reproduce the non-linear flexural-shear behavior of RC structures. The paper shows a brief description of the finite element formulation, the theory used for modeling the constitutive relationship and the scheme of the algorithm, transformed in a computer program, which was developed for implementing the theoretical model. Finally it illustrates a comparison with available experimental results for the calibration and validation of the model and a study on the influence of the non-linear shear response.
Non-linear generalization of the relativistic Schrödinger equations.
NASA Astrophysics Data System (ADS)
Ochs, U.; Sorg, M.
1996-09-01
The theory of the relativistic Schrödinger equations is further developped and extended to non-linear field equations. The technical advantage of the relativistic Schroedinger approach is demonstrated explicitly by solving the coupled Einstein-Klein-Gordon equations including a non-linear Higgs potential in case of a Robertson-Walker universe. The numerical results yield the effect of dynamical self-diagonalization of the Hamiltonian which corresponds to a kind of quantum de-coherence being enabled by the inflation of the universe.
Non-perturbative aspects of particle acceleration in non-linear electrodynamics
Burton, David A.; Flood, Stephen P.; Wen, Haibao
2015-04-15
We undertake an investigation of particle acceleration in the context of non-linear electrodynamics. We deduce the maximum energy that an electron can gain in a non-linear density wave in a magnetised plasma, and we show that an electron can “surf” a sufficiently intense Born-Infeld electromagnetic plane wave and be strongly accelerated by the wave. The first result is valid for a large class of physically reasonable modifications of the linear Maxwell equations, whilst the second result exploits the special mathematical structure of Born-Infeld theory.
Airframe structural damage detection: a non-linear structural surface intensity based technique.
Semperlotti, Fabio; Conlon, Stephen C; Barnard, Andrew R
2011-04-01
The non-linear structural surface intensity (NSSI) based damage detection technique is extended to airframe applications. The selected test structure is an upper cabin airframe section from a UH-60 Blackhawk helicopter (Sikorsky Aircraft, Stratford, CT). Structural damage is simulated through an impact resonator device, designed to simulate the induced vibration effects typical of non-linear behaving damage. An experimental study is conducted to prove the applicability of NSSI on complex mechanical systems as well as to evaluate the minimum sensor and actuator requirements. The NSSI technique is shown to have high damage detection sensitivity, covering an extended substructure with a single sensing location.
[Non-linear rectification of sensor based on immune genetic algorithm].
Lu, Lirong; Zhou, Jinyang; Niu, Xiaodong
2014-08-01
A non-linear rectification based on immune genetic algorithm (IGA) is proposed in this paper, for the shortcoming of the non-linearity rectification. This algorithm introducing the biologic immune mechanism into the genetic algorithm can restrain the disadvantages that the poor precision, slow convergence speed and early maturity of the genetic algorithm. Computer simulations indicated that the algorithm not only keeps population diversity, but also increases the convergent speed, precision and the stability greatly. The results have shown the correctness and effectiveness of the method.
A low emission, low power non-linear frequency modulation based transmitter for implanted devices.
Saraswat, Ruchir; Rodriguez-Villegas, Esther
2013-01-01
The paper proposes a low emission, non linear frequency modulator for transmitting neural signals. With the advent of embedded medical devices, designers need to start developing low Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) devices. We propose a non-phase locked loop based frequency modulator. The modulator utilizes a ramp to encode the bit stream from the neural amplifier. In addition it utilizes a non linear signal to modulate the encoded signal leading to lowering of peak of power spectrum, a measure of electro-magnetic interference. The proposed algorithm has been implemented on 0.18µ AMS technology and results presented.
Solution algorithms for non-linear singularly perturbed optimal control problems
NASA Technical Reports Server (NTRS)
Ardema, M. D.
1983-01-01
The applicability and usefulness of several classical and other methods for solving the two-point boundary-value problem which arises in non-linear singularly perturbed optimal control are assessed. Specific algorithms of the Picard, Newton and averaging types are formally developed for this class of problem. The computational requirements associated with each algorithm are analysed and compared with the computational requirement of the method of matched asymptotic expansions. Approximate solutions to a linear and a non-linear problem are obtained by each method and compared.
On the non-linear attachment characteristics of blood to bacterial cellulose/kaolin biomaterials.
Véliz, Diosángeles Soto; Alam, Catharina; Toivola, Diana M; Toivakka, Martti; Alam, Parvez
2014-04-01
In this communication, we report a non-linear variation in the strength of blood attachment to bacterial cellulose/kaolin biomaterials as the fractions of bacterial cellulose to kaolin are increased. The changes observed for attachment strength are elucidated following both experimental and numerical investigations on both the biomaterial and the blood-biomaterial interface. Our research reveals that the non-linear strength of attachment of blood is related to topographical characteristics on the surface of the biomaterial, the maleability of the biomaterial and the intermolecular strength of attraction between clotted blood proteins (fibrinogen) with the cellulose/kaolin components of the biomaterial.
Non-Linear Structural Dynamics Characterization using a Scanning Laser Vibrometer
NASA Technical Reports Server (NTRS)
Pai, P. F.; Lee, S.-Y.
2003-01-01
This paper presents the use of a scanning laser vibrometer and a signal decomposition method to characterize non-linear dynamics of highly flexible structures. A Polytec PI PSV-200 scanning laser vibrometer is used to measure transverse velocities of points on a structure subjected to a harmonic excitation. Velocity profiles at different times are constructed using the measured velocities, and then each velocity profile is decomposed using the first four linear mode shapes and a least-squares curve-fitting method. From the variations of the obtained modal \\ielocities with time we search for possible non-linear phenomena. A cantilevered titanium alloy beam subjected to harmonic base-excitations around the second. third, and fourth natural frequencies are examined in detail. Influences of the fixture mass. gravity. mass centers of mode shapes. and non-linearities are evaluated. Geometrically exact equations governing the planar, harmonic large-amplitude vibrations of beams are solved for operational deflection shapes using the multiple shooting method. Experimental results show the existence of 1:3 and 1:2:3 external and internal resonances. energy transfer from high-frequency modes to the first mode. and amplitude- and phase- modulation among several modes. Moreover, the existence of non-linear normal modes is found to be questionable.
Interactions between time-varying mesh stiffness and clearance non-linearities in a geared system
NASA Astrophysics Data System (ADS)
Kahraman, A.; Singh, R.
1991-04-01
Frequency response characteristics of a non-linear geared rotor-bearing system with time-varying mesh stiffness k h( overlinet) are examined in this paper. First, the single-degree-of-freedom spur gear pair model with backlash is extended to include sinusoidal or periodic mesh stiffness k h( overlinet) . Second, a three-degree-of-freedom model with k h( overlinet) and clearance non-lineariries associated with gear backlash and rolling element bearings, as excited by the static transmission error overlinee( overlinet) under a mean torque load, is developed. The governing equations are solved using digital simulation technique and only the primary resonances are studied. Resonances of the corresponding linear time-varying system associated with parametric and external excitations are identified using the method of multiple scales and digital simulation. Interactions between the mesh stiffness variation and clearance non-linearities have been investigated; a strong interaction between time-varying mesh stiffness k h( overlinet) and gear backlash is found, whereas the coupling between k h( overlinet) and bearing non-linearities is weak. Finally, our time-varying non-linear formulations yield reasonably good predictions when compared with the benchmark experimental results available in the literature.
Spherically symmetric analysis on open FLRW solution in non-linear massive gravity
Chiang, Chien-I; Izumi, Keisuke; Chen, Pisin E-mail: izumi@phys.ntu.edu.tw
2012-12-01
We study non-linear massive gravity in the spherically symmetric context. Our main motivation is to investigate the effect of helicity-0 mode which remains elusive after analysis of cosmological perturbation around an open Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. The non-linear form of the effective energy-momentum tensor stemming from the mass term is derived for the spherically symmetric case. Only in the special case where the area of the two sphere is not deviated away from the FLRW universe, the effective energy momentum tensor becomes completely the same as that of cosmological constant. This opens a window for discriminating the non-linear massive gravity from general relativity (GR). Indeed, by further solving these spherically symmetric gravitational equations of motion in vacuum to the linear order, we obtain a solution which has an arbitrary time-dependent parameter. In GR, this parameter is a constant and corresponds to the mass of a star. Our result means that Birkhoff's theorem no longer holds in the non-linear massive gravity and suggests that energy can probably be emitted superluminously (with infinite speed) on the self-accelerating background by the helicity-0 mode, which could be a potential plague of this theory.
NASA Astrophysics Data System (ADS)
AMABILI, M.; PELLICANO, F.; PAÏDOUSSIS, M. P.
1999-08-01
The study presented is an investigation of the non-linear dynamics and stability of simply supported, circular cylindrical shells containing inviscid incompressible fluid flow. Non-linearities due to large-amplitude shell motion are considered by using the non-linear Donnell's shallow shell theory, with account taken of the effect of viscous structural damping. Linear potential flow theory is applied to describe the fluid-structure interaction. The system is discretiszd by Galerkin's method, and is investigated by using a model involving seven degrees of freedom, allowing for travelling wave response of the shell and shell axisymmetric contraction. Two different boundary conditions are applied to the fluid flow beyond the shell, corresponding to: (i) infinite baffles (rigid extensions of the shell), and (ii) connection with a flexible wall of infinite extent in the longitudinal direction, permitting solution by separation of variables; they give two different kinds of dynamical behaviour of the system, as a consequence of the fact that axisymmetric contraction, responsible for the softening non-linear dynamical behaviour of shells, is not allowed if the fluid flow beyond the shell is constrained by rigid baffles. Results show that the system loses stability by divergence.
Re-Mediating Classroom Activity with a Non-Linear, Multi-Display Presentation Tool
ERIC Educational Resources Information Center
Bligh, Brett; Coyle, Do
2013-01-01
This paper uses an Activity Theory framework to evaluate the use of a novel, multi-screen, non-linear presentation tool. The Thunder tool allows presenters to manipulate and annotate multiple digital slides and to concurrently display a selection of juxtaposed resources across a wall-sized projection area. Conventional, single screen presentation…
A New Non-Linearity Correction Method for the JWST Near-Infrared Camera
NASA Astrophysics Data System (ADS)
Canipe, Alicia Michelle; Robberto, Massimo; Hilbert, Bryan
2017-06-01
JWST infrared detectors have an intrinsic non-linearity due to the change in PN junction capacitance as charge accumulates in the individual pixel capacitors. Correction of this non-linearity is a fundamental step in the JWST Science Calibration Pipeline. I evaluate a proposed method to calculate a more accurate non-linearity correction for the Near-Infrared Camera (NIRCam) using a function of the ideal linear signal count rate. This algorithm allows the reconstruction of the true linear signal to within 0.2% over ~97% of the full dynamic range, a substantial improvement over the current correction strategy adopted, for example, for the Wide Field Camera 3 infrared channel on Hubble. Using this method, I demonstrate that the coefficients derived to correct a regular ramp (i.e., a sequence of non-destructive samples) are also adequate to reconstruct the true signal in the case of grouped (averaged) samples, characteristic of JWST observations. The robustness of the method is tested using both real data and simulated ramps with different count rates. The new algorithm consistently provides highly accurate non-linearity corrections and can successfully be applied to all 10 NIRCam detectors.
CONSEQUENCES OF NON-LINEAR DENSITY EFFECTS ON BUOYANCY AND PLUME BEHAVIOR
Aquatic plumes, as turbulent streams, grow by entraining ambient water. Buoyant plumes rise and dense ones sink, but, non-linear kinetic effects can reverse the buoyant force in mid-phenomenon. The class of nascent-density plumes begin as buoyant, upwardly accelerating plumes tha...
Testing procedures for non-stationarity and non-linearity in physiological signals.
Popivanov, D; Mineva, A
1999-03-15
Most of the physiological signals (EEG, ECG, blood flow, human gait, etc.) characterize by complex dynamics including both non-stationarities and non-linearities. These time series resemble red noise with long-range correlation and 1/(f beta) power spectrum. A question arises as to how to distinguish the characteristics of the process underlying the signal dynamics from the properties of the observed time series. The classical methods to determine possible non-linear (chaotic) dynamics (e.g. correlation dimension) often fail in such signals because of relatively short data records containing stochastic components and non-stationarities. We report an application of several approaches, aimed at (1) determining of the non-stationarities in the signals and (2) testing whether non-linear dynamics exists. Assessment of the intrinsic correlation properties of the dynamic process and distinguishing the same from external trends was performed using singular spectra and detrended fluctuation analysis. The existence of non-linear dynamics was tested by correlation dimension (modified algorithm of re-embedding) and by correlation integrals of real and surrogate data. The correlation integrals of real signal and surrogate data sets were statistically compared using Kolmogorov-Smirnov (K-S) test. The procedures were tested on EEG and laser-Doppler (LD) blood flow. Our suggestion is that no one approach taken alone is the best for our aims. Instead, a battery of methods should be used.
The Non-Linear Nature of Information and its Implications for Advanced Technology Forces
1998-05-18
anticipated tremendous benefits from the growth of information based technology. It is now axiomatic that the ability to achieve information dominance against...the commercial world are mix. To achieve the information dominance anticipated through advances in technology, military decision makers must understand and accommodate the non-linear nature of the information systems they employ.
NASA Astrophysics Data System (ADS)
Bertolesi, Elisa; Milani, Gabriele; Poggi, Carlo
2016-12-01
Two FE modeling techniques are presented and critically discussed for the non-linear analysis of tuff masonry panels reinforced with FRCM and subjected to standard diagonal compression tests. The specimens, tested at the University of Naples (Italy), are unreinforced and FRCM retrofitted walls. The extensive characterization of the constituent materials allowed adopting here very sophisticated numerical modeling techniques. In particular, here the results obtained by means of a micro-modeling strategy and homogenization approach are compared. The first modeling technique is a tridimensional heterogeneous micro-modeling where constituent materials (bricks, joints, reinforcing mortar and reinforcing grid) are modeled separately. The second approach is based on a two-step homogenization procedure, previously developed by the authors, where the elementary cell is discretized by means of three-noded plane stress elements and non-linear interfaces. The non-linear structural analyses are performed replacing the homogenized orthotropic continuum with a rigid element and non-linear spring assemblage (RBSM). All the simulations here presented are performed using the commercial software Abaqus. Pros and cons of the two approaches are herein discussed with reference to their reliability in reproducing global force-displacement curves and crack patterns, as well as to the rather different computational effort required by the two strategies.
Non-Linear Optical Studies of IR Materials with Infrared Femtosecond Laser
2016-12-15
Final Report APPROVED FOR PUBLIC RELEASE; DISTRIBUTION IS UNLIMITED. AIR FORCE RESEARCH LABORATORY Directed Energy Directorate 3550...matter interaction, Non-linear optics, Laser induced periodic structure, high energy MID-IR short pulse lasers 16. SECURITY CLASSIFICATION OF: 17...SPP) with the incoming light and generate periodic energy density profiles, which results in material removal and forms the LSFL morphology on the
Towards a non-linear theory for induced seismicity in shales
NASA Astrophysics Data System (ADS)
Salusti, Ettore; Droghei, Riccardo
2014-05-01
We here analyze the pore transmission of fluid pressure pand solute density ρ in porous rocks, within the framework of the Biot theory of poroelasticity extended to include physico-chemical interactions. In more details we here analyze the effect of a strong external stress on the non-linear evolution of p and ρ in a porous rock. We here focus on the consequent deformation of the rock pores, relative to a non-linear Hooke equation among strain, linear/quadratic pressure and osmosis in 1-D. We in particular analyze cases with a large pressure, but minor than the 'rupture point'. All this gives relations similar to those discussed by Shapiro et al. (2013), which assume a pressure dependent permeability. Thus we analyze the external stress necessary to originate quick non-linear transients of combined fluid pressure and solute density in a porous matrix, which perturb in a mild (i.e. a linear diffusive phenomenon) or a more dramatic non-linear way (Burgers solitons) the rock structure. All this gives a novel, more realistic insight about the rock evolution, fracturing and micro-earthquakes under a large external stress.
Comments on "arithmetic coding as a non-linear dynamical system"
NASA Astrophysics Data System (ADS)
Pande, Amit; Zambreno, Joseph; Mohapatra, Prasant
2012-12-01
Nagaraj et al. [1,2] present a skewed-non-linear generalized Luroth Series (s-nGLS) framework. S-nGLS uses non-linear maps for GLS to introduce a security parameter a which is used to build a keyspace for image or data encryption. The map introduces non-linearity to the system to add an "encryption key parameter". The skew is added to achieve optimal compression efficiency. s-nGLS used as such for joint encryption and compression is a weak candidate, as explained in this communication. First, we show how the framework is vulnerable to known plaintext based attacks and that a key of size 256 bits can be broken within 1000 trials. Next, we demonstrate that the proposed non-linearity exponentially increases the hardware complexity of design. We also discover that s-nGlS cannot be implemented as such for large bitstreams. Finally, we demonstrate how correlation of key parameter with compression performance leads to further key vulnerabilities.
A Quantitative and Combinatorial Approach to Non-Linear Meanings of Multiplication
ERIC Educational Resources Information Center
Tillema, Erik; Gatza, Andrew
2016-01-01
We provide a conceptual analysis of how combinatorics problems have the potential to support students to establish non-linear meanings of multiplication (NLMM). The problems we analyze we have used in a series of studies with 6th, 8th, and 10th grade students. We situate the analysis in prior work on students' quantitative and multiplicative…
Non-linear controls influence functions in an aircraft dynamics simulator
NASA Astrophysics Data System (ADS)
Guerreiro, Nelson M.; Hubbard, James E., Jr.; Motter, Mark A.
2006-03-01
In the development and testing of novel structural and controls concepts, such as morphing aircraft wings, appropriate models are needed for proper system characterization. In most instances, available system models do not provide the required additional degrees of freedom for morphing structures but may be modified to some extent to achieve a compatible system. The objective of this study is to apply wind tunnel data collected for an Unmanned Air Vehicle (UAV), that implements trailing edge morphing, to create a non-linear dynamics simulator, using well defined rigid body equations of motion, where the aircraft stability derivatives change with control deflection. An analysis of this wind tunnel data, using data extraction algorithms, was performed to determine the reference aerodynamic force and moment coefficients for the aircraft. Further, non-linear influence functions were obtained for each of the aircraft's control surfaces, including the sixteen trailing edge flap segments. These non-linear controls influence functions are applied to the aircraft dynamics to produce deflection-dependent aircraft stability derivatives in a non-linear dynamics simulator. Time domain analysis of the aircraft motion, trajectory, and state histories can be performed using these nonlinear dynamics and may be visualized using a 3-dimensional aircraft model. Linear system models can be extracted to facilitate frequency domain analysis of the system and for control law development. The results of this study are useful in similar projects where trailing edge morphing is employed and will be instrumental in the University of Maryland's continuing study of active wing load control.
Non-Linear Stability of an Electrified Plane Interface in Porous Media
NASA Astrophysics Data System (ADS)
El-Dib, Yusry O.; Moatimid, Galal M.
2004-03-01
The non-linear electrohydrodynamic stability of capillary-gravity waves on the interface between two semi-infinite dielectric fluids is investigated. The system is stressed by a vertical electric field in the presence of surface charges. The work examines a few representative porous media configurations. The analysis includes Rayleigh-Taylor and Kelvin-Helmholtz instabilities. The boundary - value problem leads to a non-linear equation governing the surface evolution. Taylor theory is adopted to expand this equation, in the light of multiple scales, in order to obtain a non-linear Schr¨odinger equation describing the behavior of the perturbed interface. The latter equation, representing the amplitude of the quasi-monochromatic traveling wave, is used to describe the stability criteria. These criteria are discussed both analytically and numerically. In order to identifiy regions of stability and instability, the electric field intensity is plotted versus the wave number. Through a linear stability approach it is found that Darcy's coefficients have a destabilizing influence, while in the non-linear scope these coefficients as well as the electric field intensity play a dual role on the stability.
Fitting and forecasting coupled dark energy in the non-linear regime
Casas, Santiago; Amendola, Luca; Pettorino, Valeria; Vollmer, Adrian; Baldi, Marco E-mail: l.amendola@thphys.uni-heidelberg.de E-mail: v.pettorino@thphys.uni-heidelberg.de
2016-01-01
We consider cosmological models in which dark matter feels a fifth force mediated by the dark energy scalar field, also known as coupled dark energy. Our interest resides in estimating forecasts for future surveys like Euclid when we take into account non-linear effects, relying on new fitting functions that reproduce the non-linear matter power spectrum obtained from N-body simulations. We obtain fitting functions for models in which the dark matter-dark energy coupling is constant. Their validity is demonstrated for all available simulations in the redshift range 0z=–1.6 and wave modes below 0k=1 h/Mpc. These fitting formulas can be used to test the predictions of the model in the non-linear regime without the need for additional computing-intensive N-body simulations. We then use these fitting functions to perform forecasts on the constraining power that future galaxy-redshift surveys like Euclid will have on the coupling parameter, using the Fisher matrix method for galaxy clustering (GC) and weak lensing (WL). We find that by using information in the non-linear power spectrum, and combining the GC and WL probes, we can constrain the dark matter-dark energy coupling constant squared, β{sup 2}, with precision smaller than 4% and all other cosmological parameters better than 1%, which is a considerable improvement of more than an order of magnitude compared to corresponding linear power spectrum forecasts with the same survey specifications.
The Poincaré-Bendixson Theorem and the non-linear Cauchy-Riemann equations
NASA Astrophysics Data System (ADS)
van den Berg, J. B.; Munaò, S.; Vandervorst, R. C. A. M.
2016-11-01
Fiedler and Mallet-Paret (1989) prove a version of the classical Poincaré-Bendixson Theorem for scalar parabolic equations. We prove that a similar result holds for bounded solutions of the non-linear Cauchy-Riemann equations. The latter is an application of an abstract theorem for flows with a(n) (unbounded) discrete Lyapunov function.
NASA Astrophysics Data System (ADS)
Zielnica, J.; Ziółkowski, A.; Cempel, C.
2003-03-01
Design and theoretical and experimental investigation of vibroisolation pads with non-linear static and dynamic responses is the objective of the paper. The analytical investigations are based on non-linear finite element analysis where the load-deflection response is traced against the shape and material properties of the analysed model of the vibroisolation pad. A new model of vibroisolation pad of antisymmetrical type was designed and analysed by the finite element method based on the second-order theory (large displacements and strains) with the assumption of material's non-linearities (Mooney-Rivlin model). Stability loss phenomenon was used in the design of the vibroisolators, and it was proved that it would be possible to design a model of vibroisolator in the form of a continuous pad with non-linear static and dynamic response, typical to vibroisolation purposes. The materials used for the vibroisolator are those of rubber, elastomers, and similar ones. The results of theoretical investigations were examined experimentally. A series of models made of soft rubber were designed for the test purposes. The experimental investigations of the vibroisolation models, under static and dynamic loads, confirmed the results of the FEM analysis.
HOLMES, WILLIAM R.
2014-01-01
Reaction diffusion systems are often used to study pattern formation in biological systems. However, most methods for understanding their behavior are challenging and can rarely be applied to complex systems common in biological applications. I present a relatively simple and efficient, non-linear stability technique that greatly aids such analysis when rates of diffusion are substantially different. This technique reduces a system of reaction diffusion equations to a system of ordinary differential equations tracking the evolution of a large amplitude, spatially localized perturbation of a homogeneous steady state. Stability properties of this system, determined using standard bifurcation techniques and software, describe both linear and non-linear patterning regimes of the reaction diffusion system. I describe the class of systems this method can be applied to and demonstrate its application. Analysis of Schnakenberg and substrate inhibition models is performed to demonstrate the methods capabilities in simplified settings and show that even these simple models have non-linear patterning regimes not previously detected. The real power of this technique however is its simplicity and applicability to larger complex systems where other non-linear methods become intractable. This is demonstrated through analysis of a chemotaxis regulatory network comprised of interacting proteins and phospholipids. In each case, predictions of this method are verified against results of numerical simulation, linear stability, asymptotic, and / or full PDE bifurcation analyses. PMID:24158538
Burau, Viola; Vrangbaek, Karsten
2008-01-01
The paper aims to account for the substance of non-linear governance change by analysing the importance of sector-specific institutions and the pathways of governing they create. The analysis uses recent reforms of the governance of medical performance in four European countries as a case, adopting an inductively oriented approach to comparison. The governance of medical performance is a good case as it is both, closely related to redistributive policies, where the influence of institutions tends to be pertinent, and is subject to considerable policy pressures. The overall thrust of reforms is similar across countries, while there are important differences in relation to how individual forms of governance and the balance between different forms of governance are changing. More specifically, sector-specific institutions can account for the specific ways in which reforms redefine hierarchy and professional self-regulation and for the extent to which reforms strengthen hierarchy and affect the balance with other forms of governance. The recent literature on governance mainly focuses on mapping out the substance of non-linear change, whereas the development of explanations of the substance of governance change is less systematic. In the present paper, therefore, it is suggested coupling the notion of non-linear change with an analysis of sector specific institutions inspired by the historical institutionalist tradition to better account for the substance of non-linear governance change. Further, the analysis offers interesting insights into the complexity of redrawing boundaries between the public and the private in health care.
Non-Linear EMG Parameters for Differential and Early Diagnostics of Parkinson's Disease.
Meigal, Alexander Y; Rissanen, Saara M; Tarvainen, Mika P; Airaksinen, Olavi; Kankaanpää, Markku; Karjalainen, Pasi A
2013-01-01
The pre-clinical diagnostics is essential for management of Parkinson's disease (PD). Although PD has been studied intensively in the last decades, the pre-clinical indicators of that motor disorder have yet to be established. Several approaches were proposed but the definitive method is still lacking. Here we report on the non-linear characteristics of surface electromyogram (sEMG) and tremor acceleration as a possible diagnostic tool, and, in prospective, as a predictor for PD. Following this approach we calculated such non-linear parameters of sEMG and accelerometer signal as correlation dimension, entropy, and determinism. We found that the non-linear parameters allowed discriminating some 85% of healthy controls from PD patients. Thus, this approach offers considerable potential for developing sEMG-based method for pre-clinical diagnostics of PD. However, non-linear parameters proved to be more reliable for the shaking form of PD, while diagnostics of the rigid form of PD using EMG remains an open question.
Phase Structure of the Non-Linear σ-MODEL with Oscillator Representation Method
NASA Astrophysics Data System (ADS)
Mishchenko, Yuriy; Ji, Chueng-R.
2004-03-01
Non-Linear σ-model plays an important role in many areas of theoretical physics. Been initially uintended as a simple model for chiral symmetry breaking, this model exhibits such nontrivial effects as spontaneous symmetry breaking, asymptotic freedom and sometimes is considered as an effective field theory for QCD. Besides, non-linear σ-model can be related to the strong-coupling limit of O(N) ϕ4-theory, continuous limit of N-dim. system of quantum spins, fermion gas and many others and takes important place in undertanding of how symmetries are realized in quantum field theories. Because of this variety of connections, theoretical study of the critical properties of σ-model is interesting and important. Oscillator representation method is a theoretical tool for studying the phase structure of simple QFT models. It is formulated in the framework of the canonical quantization and is based on the view of the unitary non-equivalent representations as possible phases of a QFT model. Successfull application of the ORM to ϕ4 and ϕ6 theories in 1+1 and 2+1 dimensions motivates its study in more complicated models such as non-linear σ-model. In our talk we introduce ORM, establish its connections with variational approach in QFT. We then present results of ORM in non-linear σ-model and try to interprete them from the variational point of view. Finally, we point out possible directions for further research in this area.
Introduction to the Treatment of Non-Linear Effects Using a Gravitational Pendulum
ERIC Educational Resources Information Center
Weltner, Klaus; Esperidiao, Antonio Sergio C.; Miranda, Paulo
2004-01-01
We show that the treatment of pendulum movement, other than the linear approximation,may be an instructive experimentally based introduction to the physics of non-linear effects. Firstly the natural frequency of a gravitational pendulum is measured as function of its amplitude. Secondly forced oscillations of a gravitational pendulum are…
An Assessment of Linear Versus Non-linear Multigrid Methods for Unstructured Mesh Solvers
2001-05-01
problems is investigated. The first case consists of a transient radiation-diffusion problem for which an exact linearization is available, while the...to the Jacobian of a second-order accurate discretization. When an exact linearization is employed, the linear and non-linear multigrid methods
CONSEQUENCES OF NON-LINEAR DENSITY EFFECTS ON BUOYANCY AND PLUME BEHAVIOR
Aquatic plumes, as turbulent streams, grow by entraining ambient water. Buoyant plumes rise and dense ones sink, but, non-linear kinetic effects can reverse the buoyant force in mid-phenomenon. The class of nascent-density plumes begin as buoyant, upwardly accelerating plumes tha...
Introduction to the Treatment of Non-Linear Effects Using a Gravitational Pendulum
ERIC Educational Resources Information Center
Weltner, Klaus; Esperidiao, Antonio Sergio C.; Miranda, Paulo
2004-01-01
We show that the treatment of pendulum movement, other than the linear approximation,may be an instructive experimentally based introduction to the physics of non-linear effects. Firstly the natural frequency of a gravitational pendulum is measured as function of its amplitude. Secondly forced oscillations of a gravitational pendulum are…
Non-Linear Editing for the Smaller College-Level Production Program, Rev. 2.0.
ERIC Educational Resources Information Center
Tetzlaff, David
This paper focuses on a specific topic and contention: Non-linear editing earns its place in a liberal arts setting because it is a superior tool to teach the concepts of how moving picture discourse is constructed through editing. The paper first points out that most students at small liberal arts colleges are not going to wind up working…
Identifying the non-linearities in the period-luminosity relations of Cepheids
NASA Astrophysics Data System (ADS)
Dassa-Terrier, J.
2016-12-01
The period-luminosity relation of Cepheids is essential to characterize the second step of the cosmological distance ladder. However, the possible non-linearity and breaking points around a period of 10 days have important consequences for their use. We review and challenge four different statistical methods on our simulations. We constrain the conditions in which these methods can be applied.
Fitting and forecasting coupled dark energy in the non-linear regime
NASA Astrophysics Data System (ADS)
Casas, Santiago; Amendola, Luca; Baldi, Marco; Pettorino, Valeria; Vollmer, Adrian
2016-01-01
We consider cosmological models in which dark matter feels a fifth force mediated by the dark energy scalar field, also known as coupled dark energy. Our interest resides in estimating forecasts for future surveys like Euclid when we take into account non-linear effects, relying on new fitting functions that reproduce the non-linear matter power spectrum obtained from N-body simulations. We obtain fitting functions for models in which the dark matter-dark energy coupling is constant. Their validity is demonstrated for all available simulations in the redshift range 0z=-1.6 and wave modes below 0k=1 h/Mpc. These fitting formulas can be used to test the predictions of the model in the non-linear regime without the need for additional computing-intensive N-body simulations. We then use these fitting functions to perform forecasts on the constraining power that future galaxy-redshift surveys like Euclid will have on the coupling parameter, using the Fisher matrix method for galaxy clustering (GC) and weak lensing (WL). We find that by using information in the non-linear power spectrum, and combining the GC and WL probes, we can constrain the dark matter-dark energy coupling constant squared, β2, with precision smaller than 4% and all other cosmological parameters better than 1%, which is a considerable improvement of more than an order of magnitude compared to corresponding linear power spectrum forecasts with the same survey specifications.
Re-Mediating Classroom Activity with a Non-Linear, Multi-Display Presentation Tool
ERIC Educational Resources Information Center
Bligh, Brett; Coyle, Do
2013-01-01
This paper uses an Activity Theory framework to evaluate the use of a novel, multi-screen, non-linear presentation tool. The Thunder tool allows presenters to manipulate and annotate multiple digital slides and to concurrently display a selection of juxtaposed resources across a wall-sized projection area. Conventional, single screen presentation…
Gravitational-wave tail effects to quartic non-linear order
NASA Astrophysics Data System (ADS)
Marchand, Tanguy; Blanchet, Luc; Faye, Guillaume
2016-12-01
Gravitational-wave tails are due to the backscattering of linear waves onto the space-time curvature generated by the total mass of the matter source. The dominant tails correspond to quadratic non-linear interactions and arise at the one-and-a-half post-Newtonian (1.5 PN) order in the gravitational waveform. The ‘tails-of-tails’, which are cubic non-linear effects appearing at the 3 PN order in the waveform, are also known. We derive here higher non-linear tail effects, namely those associated with quartic non-linear interactions or ‘tails-of-tails-of-tails’, which are shown to arise at the 4.5 PN order. As an application, we obtain at that order the complete coefficient in the total gravitational-wave energy flux of compact binary systems moving on circular orbits. Our result perfectly agrees with black-hole perturbation calculations in the limit of extreme mass ratio of the two compact objects.
Non-linear dynamic modeling of an automobile hydraulic active suspension system
NASA Astrophysics Data System (ADS)
Mrad, R. Ben; Levitt, J. A.; Fassois, S. D.
1994-09-01
Motived by the strong need for realistically describing the dynamical behaviour of automotive systems through adequate mathematical models, a computer-stimulation-suitable non-linear quarter-car model of a hydraulic active suspension system is developed. Unlike previously available linear models characterised by idealised actuator and component behaviour, the developed model accounts for the dynamics of the main system components, including the suspension bushing, pump, accumulator, power and bypass valves, and hydraulic actuator, while also incorporating preliminary versions of the system controllers. Significant system characteristics, such as non-linear pressure-flow relationships, fluid compressibility, pump and valve non-linearities, leakages, as well as Coulomb friction, are also explicitly accounted for, and the underpinning assumptions are discussed. Simulation results obtained by exercising the model provide insight into the system behavior, illustrate the importance of the actuator/component dynamics and their associated non-linearities and reveal the inadequacy of the idealised linear models in capturing the system behaviour, demonstrate specific effects of valve leakage and fluid bulk modulus, are in qualitative agreement with experimental measurements, and stress the need for proper control law design and tuning. The developed model is particularly suitable for analysis, design, control law optimisation, and diagnostic strategies development.
Non-Gaussian inference from non-linear and non-Poisson biased distributed data
NASA Astrophysics Data System (ADS)
Ata, Metin; Kitaura, Francisco-Shu; Müller, Volker
2014-05-01
We study the statistical inference of the cosmological dark matter density field from non-Gaussian, non-linear and non-Poisson biased distributed tracers. We have implemented a Bayesian posterior sampling computer-code solving this problem and tested it with mock data based on N-body simulations.
Understanding the non-linear clustering of high-redshift galaxies
NASA Astrophysics Data System (ADS)
Jose, Charles; Baugh, Carlton M.; Lacey, Cedric G.; Subramanian, Kandaswamy
2017-08-01
We incorporate the non-linear clustering of dark matter haloes, as modelled by Jose et al. into the halo model to better understand the clustering of Lyman break galaxies (LBGs) in the redshift range z = 3-5. We find that, with this change, the predicted LBG clustering increases significantly on quasi-linear scales (0.1 ≤ r / h-1 Mpc ≤ 10) compared to that in the linear halo bias model. This, in turn, results in an increase in the clustering of LBGs by an order of magnitude on angular scales 5 ≤ θ ≤ 100 arcsec. Remarkably, the predictions of our new model on the whole remove the systematic discrepancy between the linear halo bias predictions and the observations. The correlation length and large-scale galaxy bias of LBGs are found to be significantly higher in the non-linear halo bias model than in the linear halo bias model. The resulting two-point correlation function retains an approximate power-law form in contrast with that computed using the linear halo bias theory. We also find that the non-linear clustering of LBGs increases with increasing luminosity and redshift. Our work emphasizes the importance of using non-linear halo bias in order to model the clustering of high-z galaxies to probe the physics of galaxy formation and extract cosmological parameters reliably.
A Quantitative and Combinatorial Approach to Non-Linear Meanings of Multiplication
ERIC Educational Resources Information Center
Tillema, Erik; Gatza, Andrew
2016-01-01
We provide a conceptual analysis of how combinatorics problems have the potential to support students to establish non-linear meanings of multiplication (NLMM). The problems we analyze we have used in a series of studies with 6th, 8th, and 10th grade students. We situate the analysis in prior work on students' quantitative and multiplicative…
Using the group of non-linear cells design metamaterial bar
NASA Astrophysics Data System (ADS)
Sun, Hongwei; Song, Xin; Hu, Xiaolei; Gu, Jinliang
2016-04-01
The paper presents the wave propagation in one-dimensional metamaterial bar with attached group of non-linear local oscillators by using analytical and numerical models. The focus is on the influence of group of non-linear cells on the filtering properties of the bar in the 1000Hz to 2000Hz range. Group of Periodic cells with alternating properties exhibit interesting dynamic characteristics that enable them to act as filters. Waves can propagate along bars within specific bands of frequencies called pass bands, and attenuate within bands of frequencies called gaps. Gaps in structures with group of periodic cells are located according on the frequency of cells. From the cell, we can yield the effect negative stiffness and effect negative mass. We can also design the gaps from attached oscillators or cells. In the uniform case the gap is located around the resonant frequency of the oscillators, and thus a stop band can be created in the lower frequency range. In the case with group of non-linear cells the results show that the position of the gap can be designed, and the design depends on the amplitude and the degree of non-linear cells.
Design curves for non-linear analysis of simply-supported, uniformly-loaded rectangular plates
NASA Technical Reports Server (NTRS)
Moore, D.
1979-01-01
Design curves for the non-linear analysis of simply-supported rectangular plates subjected to uniform normal pressure loads have been developed. These curves yield the center deflection, center stress and corner stress in non-dimensionalized form plotted against a dimensionless parameter describing the load intensity. The results presented are based on extensive non-linear finite element analysis employing the ARGUS structural analysis program. Plates with length to width ratios of 1, 1.5, 2, 3 and 4 are included. The load range considered extends to 1000 times the load at which the behavior of the plate becomes significantly non-linear. Over the load range considered, the analysis shows that the ratio of center deflection to plate thickness for a square plate is less than 16 to 1, whereas linear theory would predict a center deflection 400 times the plate thickness. Likewise, the stress is markedly lower than would be predicted by linear theory. The present results are shown to be in excellent agreement with the classical linear theory up to a central deflection to plate thickness ratio of about one-half. In the non-linear regime the present results for deflection and stress are in very good agreement with the analytical and experimental work of other investigators.
Non-linear Elasticity and Monitoring of Stress in the Focus of an Earthquake
NASA Astrophysics Data System (ADS)
Bakulin, V.; Bakulin, A.
2001-05-01
Non-linear elasticity proved to give comprehensive framework for relating seismic velocities in rocks to stress. This powerful theory allows attacking the problem of estimating stress state at the focus of earthquakes. Such idea has been proposed long time ago [Kostrov and Nikitin, 1968] however its implementation requires a-priori knowledge of non-linear rock properties. Three non-linear constants needed to describe variation of any velocity with stress are typically estimated from core measurements [Bakulin et al., 2000]. More reliable estimates can be obtained from multi-mode inversions of borehole acoustic data [Sinha, 1996]. Nevertheless database of non-linear formation constants is still very limited. More measurements are required to estimate non-linear rock properties on larger scale and with independent stress constraints. Such measurements can be done in mines [Bakulin and Bakulin, 1999] or in hydrocarbon reservoirs where time-dependent pressure measurements are available. Without knowledge of non-linear rock properties seismic waves can still bring information about directions of tectonic stresses. In particular, shear wave polarizations can deliver directions of principal stresses in the focus of an earthquake, provided the overburden effects were removed. If rock non-linear properties are independently derived then estimation of stress magnitudes becomes feasible. Such techniques were applied in mining environment [Bakulin and Bakulin, 1999]. They may become routine for monitoring stress state in the focus of earthquakes and therefore can be used for forecasting the seismic activity. Bakulin, A. V., Troyan, V. N., and Bakulin, V. N., 2000, Acoustoelasticity of rocks, St. Petersburg (in Russian). Bakulin, V. and Bakulin, A., 1999, Acoustopolarizational method of measuring stress in rock mass and determination of Murnaghan constants: 69th Annual Internat. Mtg., Soc. Expl. Geophys., 1971-1974. Kostrov, B.V., and Nikitin, L.V., 1968, Influence of initial
Metal-organic frameworks as competitive materials for non-linear optics.
Mingabudinova, L R; Vinogradov, V V; Milichko, V A; Hey-Hawkins, E; Vinogradov, A V
2016-09-26
The last five years have witnessed a huge breakthrough in the creation and the study of the properties of a new class of compounds - metamaterials. The next stage of this technological revolution will be the development of active, controllable, and non-linear metamaterials, surpassing natural media as platforms for optical data processing and quantum information applications. However, scientists are constantly faced with the need to find new methods that can ensure the formation of quantum and non-linear metamaterials with higher resolution. One such method of producing metamaterials in the future, which will provide scalability and availability, is chemical synthesis. Meanwhile, the chemical synthesis of organized 3D structures with a period of a few nanometers and a size of up to a few millimeters is not an easy task and is yet to be resolved. The most promising avenue seems to be the use of highly porous structures based on metal-organic frameworks that have demonstrated their unique properties in the field of non-linear optics (NLO) over the past three years. Thus, the aim of this review is to examine current progress and the possibilities of using metal-organic frameworks in the field of non-linear optics as chemically obtained metamaterials of the future. The review begins by presenting the theoretical principles of physical phenomena represented by mathematical descriptions for clarity. Major attention is paid to the second harmonic generation (SHG) effect. In this section we compare inorganic single crystals, which are most commonly used to study the effect in question, to organic materials, which also possess the required properties. Based on these data, we present a rationale for the possibility of studying the non-linear optical properties of metal-organic structures as well as describing the use of synthetic approaches and the difficulties associated with them. The second part of the review explicitly acquaints the reader with a new class of materials
Non-linear modal analysis of structural components subjected to unilateral constraints
NASA Astrophysics Data System (ADS)
Attar, M.; Karrech, A.; Regenauer-Lieb, K.
2017-02-01
In this paper, we present a detailed numerical study of the non-linear dynamics in structural components under unilateral contact constraints. Here, the unilateral term characterises the constitutive law of the restoring force in the constraints as they only sustain elastic reactions in one direction, either compressive or tensile. Thus, the non-differentiability of the contact law at the discontinuity point is the only source of non-linearity. In our approach, the discrete lattice method (DLM) is used to treat the continuous system as a piecewise linear model. Thus, the trajectory of each node in the discrete model would be a sequence of smooth solutions with the switching times between them. The application of the one-step integration scheme allows us to detect the occurrence of contact (i.e. the instants that the lattice nodes cross the discontinuity boundary) and consequently update the active constraints. We also consider embedding the bisection algorithm into the time integration procedure to localise the instants at which the nodes cross the boundary and minimise the accumulative error. Subsequently, the resulting unconditionally stable integration scheme is utilised as the modelling tool in combination with the shooting technique to perform a novel non-smooth modal analysis. In analogy with the smooth non-linear systems, the evolution of non-smooth periodic motions is presented in the frequency-stiffness plots. We apply our method to obtain non-linear normal modes (NNMs) for a number of representative problems, including a bar-obstacle system, a beam-substrate system and a granular chain with tensionless interactions. These numerical examples demonstrate the efficiency of the solution procedure to trace the family of energy-independent non-linear modes across the range of contact stiffnesses. Moreover, the stability analysis of the modes on the plot backbone reveal that they may become unstable due to the interaction with the higher modes or bifurcation of
Images of interlayer vortices and c -axis penetration depth of high- Tc YBa2Cu3O7-y superconductor
NASA Astrophysics Data System (ADS)
Iguchi, Ienari; Takeda, Tomohiro; Uchiyama, Tetsuji; Sugimoto, Akira; Hatano, Takeshi
2006-06-01
The measurements on the magnetic image of interlayer vortices are performed for the high- Tc YBa2Cu3O7-y(110) thin film using a high sensitive scanning SQUID microscopy. Clear images of aligned giant interlayer vortices are observable. For the majority of vortices, using the London model, the c -axis penetration depth is estimated to be about 20μm at 3K . The temperature dependence of λc is obtained from the observed vortex images at different temperatures, whose behavior is in good agreement with those of the microwave cavity measurement.
NASA Astrophysics Data System (ADS)
Munzar, D.; Chaloupka, J.; Bernhard, C.; Dubroka, A.; Vašátko, J.
2010-12-01
The low-temperature spectra of the c-axis infrared conductivity of bilayer high-Tc cuprate superconductors (HTCS) exhibit two superconductivity-induced modes [Li Yu et al., Phys. Rev. Lett. 100 (2008) 177004; and references therein]. Both can be understood in terms of a microscopic theory developed recently [J. Chaloupka, C. Bernhard, D. Munzar, Phys. Rev. B 79 (2009) 184513]. Here we summarize the elements of the theory and report on the temperature dependence (TD) of the low-energy mode and of the total optical spectral weight (SW). The calculated TD of the mode is consistent with experiment but the trends of the SW are not.
NASA Astrophysics Data System (ADS)
Sadakov, A. V.; Romanova, T. A.; Knyazev, D. A.; Chareev, D. A.; Martovitsky, V. P.
We report out-of-plane magnetotransport ρc(B, T) measurements for a high quality superconducting FeSe single crystals in magnetic fields up to 9 Tesla. Samples, grown from the flux under a permanent gradient of temperature with [001] crystallographic orientation were put in magnetic field parallel to ab-plane. The samples were rotated around c-axis, and its superconducting transitions R(H) were measured for each fixed angle in several temperatures. We show that Hc2 is anisotropic in these relatively small fields, with Hc2||a/Hc2||b being ∼1.2 for T=8.3K.
PkANN - I. Non-linear matter power spectrum interpolation through artificial neural networks
NASA Astrophysics Data System (ADS)
Agarwal, Shankar; Abdalla, Filipe B.; Feldman, Hume A.; Lahav, Ofer; Thomas, Shaun A.
2012-08-01
We investigate the interpolation of power spectra of matter fluctuations using artificial neural networks (PkANN). We present a new approach to confront small-scale non-linearities in the power spectrum of matter fluctuations. This ever-present and pernicious uncertainty is often the Achilles heel in cosmological studies and must be reduced if we are to see the advent of precision cosmology in the late-time Universe. We show that an optimally trained artificial neural network (ANN), when presented with a set of cosmological parameters (? and redshift z), can provide a worst-case error ≤1 per cent (for z≤ 2) fit to the non-linear matter power spectrum deduced through N-body simulations, for modes up to k≤ 0.7 h Mpc-1. Our power spectrum interpolator is accurate over the entire parameter space. This is a significant improvement over some of the current matter power spectrum calculators. In this paper, we detail how an accurate interpolation of the matter power spectrum is achievable with only a sparsely sampled grid of cosmological parameters. Unlike large-scale N-body simulations which are computationally expensive and/or infeasible, a well-trained ANN can be an extremely quick and reliable tool in interpreting cosmological observations and parameter estimation. This paper is the first in a series. In this method paper, we generate the non-linear matter power spectra using HALOFIT and use them as mock observations to train the ANN. This work sets the foundation for Paper II, where a suite of N-body simulations will be used to compute the non-linear matter power spectra at sub-per cent accuracy, in the quasi-non-linear regime (0.1 ≤k≤ 0.9 h Mpc-1). A trained ANN based on this N-body suite will be released for the scientific community.
Modelling female fertility traits in beef cattle using linear and non-linear models.
Naya, H; Peñagaricano, F; Urioste, J I
2017-06-01
Female fertility traits are key components of the profitability of beef cattle production. However, these traits are difficult and expensive to measure, particularly under extensive pastoral conditions, and consequently, fertility records are in general scarce and somehow incomplete. Moreover, fertility traits are usually dominated by the effects of herd-year environment, and it is generally assumed that relatively small margins are kept for genetic improvement. New ways of modelling genetic variation in these traits are needed. Inspired in the methodological developments made by Prof. Daniel Gianola and co-workers, we assayed linear (Gaussian), Poisson, probit (threshold), censored Poisson and censored Gaussian models to three different kinds of endpoints, namely calving success (CS), number of days from first calving (CD) and number of failed oestrus (FE). For models involving FE and CS, non-linear models overperformed their linear counterparts. For models derived from CD, linear versions displayed better adjustment than the non-linear counterparts. Non-linear models showed consistently higher estimates of heritability and repeatability in all cases (h(2 ) < 0.08 and r < 0.13, for linear models; h(2 ) > 0.23 and r > 0.24, for non-linear models). While additive and permanent environment effects showed highly favourable correlations between all models (>0.789), consistency in selecting the 10% best sires showed important differences, mainly amongst the considered endpoints (FE, CS and CD). In consequence, endpoints should be considered as modelling different underlying genetic effects, with linear models more appropriate to describe CD and non-linear models better for FE and CS. © 2017 Blackwell Verlag GmbH.
Cremophor EL causes (pseudo-) non-linear pharmacokinetics of paclitaxel in patients.
van Tellingen, O; Huizing, M T; Panday, V R; Schellens, J H; Nooijen, W J; Beijnen, J H
1999-09-01
The non-linear plasma pharmacokinetics of paclitaxel in patients has been well established, however, the exact underlying mechanism remains to be elucidated. We have previously shown that the non-linear plasma pharmacokinetics of paclitaxel in mice results from Cremophor EL. To investigate whether Cremophor EL also plays a role in the non-linear pharmacokinetics of paclitaxel in patients, we have established its pharmacokinetics in patients receiving paclitaxel by 3-, 24- or 96-h intravenous infusion. The pharmacokinetics of Cremophor EL itself was non-linear as the clearance (Cl) in the 3-h schedules was significantly lower than when using the longer 24- or 96-h infusions (Cl175-3 h = 42.8+/-24.9 ml h(-1) m(-2); CI175-24 h = 79.7+/-24.3; P = 0.035 and Cl135-3 h = 44.1+/-21.8 ml h(-1) m(-1); Cl140-96 h = 211.8+/-32.0; P < 0.001). Consequently, the maximum plasma levels were much higher (0.62%) in the 3-h infusions than when using longer infusion durations. By using an in vitro equilibrium assay and determination in plasma ultrafiltrate we have established that the fraction of unbound paclitaxel in plasma is inversely related with the Cremophor EL level. Despite its relatively low molecular weight, no Cremophor EL was found in the ultrafiltrate fraction. Our results strongly suggest that entrapment of paclitaxel in plasma by Cremophor EL, probably by inclusion in micelles, is the cause of the apparent nonlinear plasma pharmacokinetics of paclitaxel. This mechanism of a (pseudo-)non-linearity contrasts previous postulations about saturable distribution and elimination kinetics and means that we must re-evaluate previous assumptions on pharmacokinetics-pharmacodynamics relationships.
Non-linear Frequency Shifts, Mode Couplings, and Decay Instability of Plasma Waves
NASA Astrophysics Data System (ADS)
Affolter, Mathew; Anderegg, F.; Driscoll, C. F.; Valentini, F.
2015-11-01
We present experiments and theory for non-linear plasma wave decay to longer wavelengths, in both the oscillatory coupling and exponential decay regimes. The experiments are conducted on non-neutral plasmas in cylindrical Penning-Malmberg traps, θ-symmetric standing plasma waves have near acoustic dispersion ω (kz) ~kz - αkz2 , discretized by kz =mz (π /Lp) . Large amplitude waves exhibit non-linear frequency shifts δf / f ~A2 and Fourier harmonic content, both of which are increased as the plasma dispersion is reduced. Non-linear coupling rates are measured between large amplitude mz = 2 waves and small amplitude mz = 1 waves, which have a small detuning Δω = 2ω1 -ω2 . At small excitation amplitudes, this detuning causes the mz = 1 mode amplitude to ``bounce'' at rate Δω , with amplitude excursions ΔA1 ~ δn2 /n0 consistent with cold fluid theory and Vlasov simulations. At larger excitation amplitudes, where the non-linear coupling exceeds the dispersion, phase-locked exponential growth of the mz = 1 mode is observed, in qualitative agreement with simple 3-wave instability theory. However, significant variations are observed experimentally, and N-wave theory gives stunningly divergent predictions that depend sensitively on the dispersion-moderated harmonic content. Measurements on higher temperature Langmuir waves and the unusual ``EAW'' (KEEN) waves are being conducted to investigate the effects of wave-particle kinetics on the non-linear coupling rates. Department of Energy Grants DE-SC0002451and DE-SC0008693.
Non-linear scaling of a musculoskeletal model of the lower limb using statistical shape models.
Nolte, Daniel; Tsang, Chui Kit; Zhang, Kai Yu; Ding, Ziyun; Kedgley, Angela E; Bull, Anthony M J
2016-10-03
Accurate muscle geometry for musculoskeletal models is important to enable accurate subject-specific simulations. Commonly, linear scaling is used to obtain individualised muscle geometry. More advanced methods include non-linear scaling using segmented bone surfaces and manual or semi-automatic digitisation of muscle paths from medical images. In this study, a new scaling method combining non-linear scaling with reconstructions of bone surfaces using statistical shape modelling is presented. Statistical Shape Models (SSMs) of femur and tibia/fibula were used to reconstruct bone surfaces of nine subjects. Reference models were created by morphing manually digitised muscle paths to mean shapes of the SSMs using non-linear transformations and inter-subject variability was calculated. Subject-specific models of muscle attachment and via points were created from three reference models. The accuracy was evaluated by calculating the differences between the scaled and manually digitised models. The points defining the muscle paths showed large inter-subject variability at the thigh and shank - up to 26mm; this was found to limit the accuracy of all studied scaling methods. Errors for the subject-specific muscle point reconstructions of the thigh could be decreased by 9% to 20% by using the non-linear scaling compared to a typical linear scaling method. We conclude that the proposed non-linear scaling method is more accurate than linear scaling methods. Thus, when combined with the ability to reconstruct bone surfaces from incomplete or scattered geometry data using statistical shape models our proposed method is an alternative to linear scaling methods.
Bosgra, Sieto; Vlaming, Maria L H; Vaes, Wouter H J
2016-01-01
Microdosing studies allow clinical investigation of pharmacokinetics earlier in drug development, before all high-dose safety concerns have been sorted out. Furthermore, microdosing allows inclusion of target groups that are inadmissible in high-dose phase I trials. A potential concern when considering a microdosing study is that a particular drug candidate may display non-linear pharmacokinetics. Saturation of, for example, membrane transport or metabolism at exposure levels between the microdose and therapeutic dose may limit the predictivity of high-dose pharmacokinetics from microdose observations. Guidance on the likelihood of appreciable non-linear pharmacokinetics based on preclinical information can be helpful in staging the clinical phase and the place of microdosing in it. We present a decision tree that evaluates concerns about non-linearities raised in the preclinical phase and their potential impact on the proportionality between microdose and intended therapeutic dose as predicted from preclinical information. The expected maximum concentrations at relevant sites are estimated by non-compartmental methods. These are compared with dissolution, Michaelis constants for active or enzymatic processes, and binding protein concentrations to assess the potential saturation of the processes below therapeutic doses. The decision tree was applied to ten published cases comparing microdose and therapeutic dose pharmacokinetics, for which concerns about non-linear pharmacokinetics were raised a priori. The decision tree was able to discriminate cases showing substantial non-linearities from cases displaying dose-proportional pharmacokinetics. The recommendations described in this paper may be useful in deciding whether a microdosing study is a sensible option to gain early insight in clinical pharmacokinetics of drug candidates.
Fabrication and Characterization of p-Type SnO Thin Film with High c-Axis Preferred Orientation
NASA Astrophysics Data System (ADS)
Pei, Yanli; Liu, Wuguang; Shi, Jingtao; Chen, Zimin; Wang, Gang
2016-11-01
p-Type tin monoxide (SnO) thin films with high c-axis preferred orientation have been fabricated on quartz substrate via electron-beam evaporation at 280°C. Subsequently, rapid thermal annealing (RTA) was performed in N2 atmosphere at 400°C to 800°C. Their structural, chemical, optical, and electrical properties were investigated by x-ray diffraction analysis, ultraviolet-visible spectroscopy, scanning electron microscopy, x-ray photoelectron spectroscopy, and Hall-effect measurements. The c-axis-oriented films of Sn-rich SnO presented excellent thermal stability up to RTA at 700°C. Both the crystallization and the hole Hall mobility were enhanced with increasing RTA temperature, with Hall mobility of 16 cm2 V-1 s-1 being obtained after RTA at 700°C. It was considered that the presence of defects and low scattering from grain boundaries contributed to this high Hall mobility. RTA annealing temperature above 700°C induced chemical reaction between SnO and the quartz substrate, with a change of the film to amorphous state with Sn4+ formation.
Gu, G.D.; Moon, S.J.; Homes, C.C.; Akrap, A.; Xu,, Z.J.; Wen, J.S.; Lin,, Z.W.; Li, Q.; Basov, D.N.
2011-05-23
We report on the interplane c-axis electronic response of FeTe{sub 0.55}Se{sub 0.45} investigated by infrared spectroscopy. We find that the normal-state c-axis electronic response of FeTe{sub 0.55}Se{sub 0.45} is incoherent and bears significant similarities to those of mildly underdoped cuprates. The c-axis optical conductivity {sigma}{sub c}({omega}) of FeTe{sub 0.55}Se{sub 0.45} does not display well-defined Drude response at all temperatures. As temperature decreases, {sigma}{sub c}({omega}) is continuously suppressed. The incoherent c-axis response is found to be related to the strong dissipation in the ab-plane transport: a pattern that holds true for various correlated materials as well as FeTe{sub 0.55}Se{sub 0.45}.
Yoshida, Shinya; Hanzawa, Hiroaki; Wasa, Kiyotaka; Esashi, Masayoshi; Tanaka, Shuji
2014-09-01
We successfully developed sputter deposition technology to obtain a highly c-axis-oriented monocrystalline Pb(Zr, Ti)O3 (PZT) thin film on a Si wafer by fast cooling (~-180°C/min) of the substrate after deposition. The c-axis orientation ratio of a fast-cooled film was about 90%, whereas that of a slow-cooled (~-40°C/min) film was only 10%. The c-axis-oriented monocrystalline Pb(Zr0.5, Ti0.5)O3 films showed reasonably large piezoelectric coefficients, e(31,f) = ~-11 C/m(2), with remarkably small dielectric constants, ϵ(r) = ~220. As a result, an excellent figure of merit (FOM) was obtained for piezoelectric microelectromechanical systems (MEMS) such as a piezoelectric gyroscope. This c-axis orientation technology on Si will extend industrial applications of PZT-based thin films and contribute further to the development of piezoelectric MEMS.
Iterated non-linear model predictive control based on tubes and contractive constraints.
Murillo, M; Sánchez, G; Giovanini, L
2016-05-01
This paper presents a predictive control algorithm for non-linear systems based on successive linearizations of the non-linear dynamic around a given trajectory. A linear time varying model is obtained and the non-convex constrained optimization problem is transformed into a sequence of locally convex ones. The robustness of the proposed algorithm is addressed adding a convex contractive constraint. To account for linearization errors and to obtain more accurate results an inner iteration loop is added to the algorithm. A simple methodology to obtain an outer bounding-tube for state trajectories is also presented. The convergence of the iterative process and the stability of the closed-loop system are analyzed. The simulation results show the effectiveness of the proposed algorithm in controlling a quadcopter type unmanned aerial vehicle.
Feature Visibility Limits in the Non-Linear Enhancement of Turbid Images
NASA Technical Reports Server (NTRS)
Jobson, Daniel J.; Rahman, Zia-ur; Woodell, Glenn A.
2003-01-01
The advancement of non-linear processing methods for generic automatic clarification of turbid imagery has led us from extensions of entirely passive multiscale Retinex processing to a new framework of active measurement and control of the enhancement process called the Visual Servo. In the process of testing this new non-linear computational scheme, we have identified that feature visibility limits in the post-enhancement image now simplify to a single signal-to-noise figure of merit: a feature is visible if the feature-background signal difference is greater than the RMS noise level. In other words, a signal-to-noise limit of approximately unity constitutes a lower limit on feature visibility.
The quadratically damped oscillator: A case study of a non-linear equation of motion
NASA Astrophysics Data System (ADS)
Smith, B. R.
2012-09-01
The equation of motion for a quadratically damped oscillator, where the damping is proportional to the square of the velocity, is a non-linear second-order differential equation. Non-linear equations of motion such as this are seldom addressed in intermediate instruction in classical dynamics; this one is problematic because it cannot be solved in terms of elementary functions. Like all second-order ordinary differential equations, it has a corresponding first-order partial differential equation, whose independent solutions constitute the constants of the motion. These constants readily provide an approximate solution correct to first order in the damping constant. They also reveal that the quadratically damped oscillator is never critically damped or overdamped, and that to first order in the damping constant the oscillation frequency is identical to the natural frequency. The technique described has close ties to standard tools such as integral curves in phase space and phase portraits.
Theoretically informed entangled polymer simulations: linear and non-linear rheology of melts.
Ramirez-Hernandez, Abelardo; Miller, Marcus; De Pablo, Juan J.
2013-01-02
In recent years, there has been a resurgence in developing models and theories for the non-equilibrium behavior of polymeric liquids. The so-called “tube” models, gradually refined over decades of research, can now provide a description of the linear and non-linear rheology of entangled polymers that is qualitatively consistent with experiments. Such approaches, however, have been limited to homopolymers. Here we present a general formalism that relies on the concept of slip links to describe the dynamics of high polymers. In this work, it is shown to be capable of describing quantitatively the linear response of pure homopolymers and blends, the non-linear rheology of highly entangled systems, and the dynamics of diblock copolymers.
Non-linear approach to the entrainment matrix of superfluid nucleon mixture at zero temperature
NASA Astrophysics Data System (ADS)
Leinson, Lev B.
2017-09-01
The superfluid drag effect, in hydrodynamics of pulsating neutron stars, is conventionally described with the aid of the entrainment matrix relating the mass currents with the velocities of superfluid flows in the system. Equations for the entrainment matrix of a superfluid mixture of neutrons and protons are derived with allowance for the strong dependence of the energy gaps on the velocities of superfluid flows. The calculations are carried out in the frame of the Fermi-liquid theory. The equations obtained are highly non-linear. Numerical solutions to the equations for some typical cases demonstrate that the components of the entrainment matrix possess a highly non-linear dependence on the velocities of the two superflows simultaneously. This effect, previously ignored, can greatly influence the dynamics of neutron stars.
Model predictive control of non-linear systems over networks with data quantization and packet loss.
Yu, Jimin; Nan, Liangsheng; Tang, Xiaoming; Wang, Ping
2015-11-01
This paper studies the approach of model predictive control (MPC) for the non-linear systems under networked environment where both data quantization and packet loss may occur. The non-linear controlled plant in the networked control system (NCS) is represented by a Tagaki-Sugeno (T-S) model. The sensed data and control signal are quantized in both links and described as sector bound uncertainties by applying sector bound approach. Then, the quantized data are transmitted in the communication networks and may suffer from the effect of packet losses, which are modeled as Bernoulli process. A fuzzy predictive controller which guarantees the stability of the closed-loop system is obtained by solving a set of linear matrix inequalities (LMIs). A numerical example is given to illustrate the effectiveness of the proposed method.
Simulation of non-linear rf losses derived from characteristic Nb topography
Reece, Charles E.; Xu, Chen; Kelley, Michael
2013-09-01
A simplified model has been developed to simulate non-linear RF losses on Nb surfaces exclusively due to topographical enhancement of surface magnetic fields. If local sharp edges are small enough, at locations where local surface fields exceed Hc, small volumes of material may become normal conducting without thermal leading to quench. These small volumes of normal material yield increases in the effective surface resistance of the Nb. Using topographic data from typical BCP?d and EP?d fine grain niobium surfaces, we have simulated field-dependent losses and found that when extrapolated to resulting cavity performance, these losses correspond well to characteristic BCP/EP high field Q0 performance differences for fine grain Nb. We describe the structure of the model, its limitations, and the effects of this type of non-linear loss contribution on SRF cavities.
Vuori, Kaarina; Strandén, Ismo; Sevón-Aimonen, Marja-Liisa; Mäntysaari, Esa A
2006-01-01
A method based on Taylor series expansion for estimation of location parameters and variance components of non-linear mixed effects models was considered. An attractive property of the method is the opportunity for an easily implemented algorithm. Estimation of non-linear mixed effects models can be done by common methods for linear mixed effects models, and thus existing programs can be used after small modifications. The applicability of this algorithm in animal breeding was studied with simulation using a Gompertz function growth model in pigs. Two growth data sets were analyzed: a full set containing observations from the entire growing period, and a truncated time trajectory set containing animals slaughtered prematurely, which is common in pig breeding. The results from the 50 simulation replicates with full data set indicate that the linearization approach was capable of estimating the original parameters satisfactorily. However, estimation of the parameters related to adult weight becomes unstable in the case of a truncated data set.
A comparative study of new non-linear uncertainty propagation methods for space surveillance
NASA Astrophysics Data System (ADS)
Horwood, Joshua T.; Aristoff, Jeffrey M.; Singh, Navraj; Poore, Aubrey B.
2014-06-01
We propose a unified testing framework for assessing uncertainty realism during non-linear uncertainty propagation under the perturbed two-body problem of celestial mechanics, with an accompanying suite of metrics and benchmark test cases on which to validate different methods. We subsequently apply the testing framework to different combinations of uncertainty propagation techniques and coordinate systems for representing the uncertainty. In particular, we recommend the use of a newly-derived system of orbital element coordinates that mitigate the non-linearities in uncertainty propagation and the recently-developed Gauss von Mises filter which, when used in tandem, provide uncertainty realism over much longer periods of time compared to Gaussian representations of uncertainty in Cartesian spaces, at roughly the same computational cost.
Manganite-based memristive heterojunction with tunable non-linear I-V characteristics.
Lee, Hong-Sub; Park, Hyung-Ho; Rozenberg, M J
2015-04-21
A resistive random access memory (ReRAM) based on the memristive effect allows high-density integration through a cross-point array (CPA) structure. However, a significant common drawback of the CPA configuration is the crosstalk between cells. Here, we introduce a solution based on a novel heterojunction stack solely made of members of the perovskite manganite family Pr(1-x)Ca(x)MnO3 (PCMO) and CaMnO(3-δ) (CMO) which show electroforming-free bipolar resistive switching. The heterojunction consists of rectifying interfaces and shows a symmetrical and tunable non-linear current-voltage curve. The spectromicroscopic measurements support the scenario of specialized roles, with the memristive effect taking place at the active Al-PCMO interface via a redox mechanism, while non-linearity was achieved by adopting a rectifying double interface PCMO-CMO-PCMO.
Learning from observation, feedback, and intervention in linear and non-linear task environments.
Henriksson, Maria P; Enkvist, Tommy
2016-12-12
This multiple-cue judgment study investigates whether we can manipulate the judgment strategy and increase accuracy in linear and non-linear cue-criterion environments just by changing the training mode. Three experiments show that accuracy in simple linear additive task environments are improved with feedback training and intervention training, while accuracy in complex multiplicative tasks are improved with observational training. The observed interaction effect suggests that the training mode invites different strategies that are adjusted as a function of experience to the demands from the underlying cue-criterion structure. Thus, feedback and the intervention training modes invite cue abstraction, an effortful but successful strategy in combination with simple linear task structures, and observational training invites exemplar memory processes, a simple but successful strategy in combination with complex non-linear task structures. The study discusses adaptive cognition and the implication of the different training modes across a life span and for clinical populations.
Model Order and Identifiability of Non-Linear Biological Systems in Stable Oscillation.
Wigren, Torbjörn
2015-01-01
The paper presents a theoretical result that clarifies when it is at all possible to determine the nonlinear dynamic equations of a biological system in stable oscillation, from measured data. As it turns out the minimal order needed for this is dependent on the minimal dimension in which the stable orbit of the system does not intersect itself. This is illustrated with a simulated fourth order Hodgkin-Huxley spiking neuron model, which is identified using a non-linear second order differential equation model. The simulated result illustrates that the underlying higher order model of the spiking neuron cannot be uniquely determined given only the periodic measured data. The result of the paper is of general validity when the dynamics of biological systems in stable oscillation is identified, and illustrates the need to carefully address non-linear identifiability aspects when validating models based on periodic data.
Linear to non linear analysis for positron acceleration in plasma hollow channel wakefields
NASA Astrophysics Data System (ADS)
Amorim, Ligia Diana; An, Weiming; Mori, Warren B.; Vieira, Jorge
2016-10-01
Plasma wakefield accelerators are promising candidates for future generation compact accelerators. The standard regime of operation, non-linear or blowout regime, is reached when a particle bunch space charge or laser pulse ponderomotive force radially expels plasma electrons forming a bucket of ions that defocus positron bunches, thus preventing their acceleration. To avoid defocusing, hollow plasma channels have been considered. The corresponding wakefields have been examined in the linear and non-linear excitation regimes for electrons. It is therefore important to extend the theory for positron acceleration, particularly in the nonlinear regime where the wakefields strongly differ. In this work we explore the wakefield structure, examine the differences between the electron and positron beam cases, and explore positron acceleration in nonlinear regimes. We support our findings with multi-dimensional particle-in-cell simulations performed with OSIRIS and quasi-3D and QuickPIC.
Sensitivity-based virtual fields for the non-linear virtual fields method
NASA Astrophysics Data System (ADS)
Marek, Aleksander; Davis, Frances M.; Pierron, Fabrice
2017-04-01
The virtual fields method is an approach to inversely identify material parameters using full-field deformation data. In this manuscript, a new set of automatically-defined virtual fields for non-linear constitutive models has been proposed. These new sensitivity-based virtual fields reduce the influence of noise on the parameter identification. The sensitivity-based virtual fields were applied to a numerical example involving small strain plasticity; however, the general formulation derived for these virtual fields is applicable to any non-linear constitutive model. To quantify the improvement offered by these new virtual fields, they were compared with stiffness-based and manually defined virtual fields. The proposed sensitivity-based virtual fields were consistently able to identify plastic model parameters and outperform the stiffness-based and manually defined virtual fields when the data was corrupted by noise.
NASA Astrophysics Data System (ADS)
Vasant, P.; Ganesan, T.; Elamvazuthi, I.
2012-11-01
A fairly reasonable result was obtained for non-linear engineering problems using the optimization techniques such as neural network, genetic algorithms, and fuzzy logic independently in the past. Increasingly, hybrid techniques are being used to solve the non-linear problems to obtain better output. This paper discusses the use of neuro-genetic hybrid technique to optimize the geological structure mapping which is known as seismic survey. It involves the minimization of objective function subject to the requirement of geophysical and operational constraints. In this work, the optimization was initially performed using genetic programming, and followed by hybrid neuro-genetic programming approaches. Comparative studies and analysis were then carried out on the optimized results. The results indicate that the hybrid neuro-genetic hybrid technique produced better results compared to the stand-alone genetic programming method.
A review of non-linear terahertz spectroscopy with ultrashort tabletop-laser pulses
NASA Astrophysics Data System (ADS)
Hwang, Harold Y.; Fleischer, Sharly; Brandt, Nathaniel C.; Perkins, Bradford G., Jr.; Liu, Mengkun; Fan, Kebin; Sternbach, Aaron; Zhang, Xin; Averitt, Richard D.; Nelson, Keith A.
2015-10-01
Over the past decade, breakthroughs in the generation and control of ultrafast high-field terahertz (THz) radiation have led to new spectroscopic methodologies for the study of light-matter interactions in the strong-field limit. In this review, we will outline recent experimental demonstrations of non-linear THz material responses in materials ranging from molecular gases, to liquids, to varieties of solids - including semiconductors, nanocarbon, and correlated electron materials. New insights into how strong THz fields interact with matter will be discussed in which a THz field can act as either a non-resonant electric field or a broad bandwidth pulse driving specific resonances within it. As an emerging field, non-linear THz spectroscopy shows promise for elucidating dynamic problems associated with next generation electronics and optoelectronics, as well as for demonstrating control over collective material degrees of freedom.
Global search of non-linear systems periodic solutions: A rotordynamics application
NASA Astrophysics Data System (ADS)
Sarrouy, E.; Thouverez, F.
2010-08-01
Introducing non-linearities into models contributes towards a better reality description but leads to systems having multiple solutions. It is then legitimate to look for all the solutions of such systems, that is to have a global analysis approach. However no effective method can be found in literature for systems described by more than two or three degrees of freedom. We propose in this paper a way to find all T-periodic solutions—where T is known—of a non-linear dynamical system. This method is compared to three other approaches and is shown to be the most efficient on a Duffing oscillator. As a more complex example, a rotor model including a squeeze-film damper is studied and a second branch of solutions is exhibited.
Local instabilities and the transition to chaos of non-linear waves
NASA Astrophysics Data System (ADS)
1993-03-01
The object of this research contract was to study the singularities of non-linear structures through numerical simulations. The waiting times involved in the use of a Cray II prompted the lab to replace it with an HP 720 work station, which they found to be irreplaceable for the fine analysis of convection, despite the huge amount of calculations involved. The team simulated a fairly large number of two-dimensional phenomenological models, with satisfactory results. Examples described in this report include convection, dislocations in rolled structures, dislocation nucleation using the Landau-Ginzburg equation, the Pesch-Kramer equation (large-scale flows), non-linear wave defects, the optical model, and others.
GA and Lyapunov theory-based hybrid adaptive fuzzy controller for non-linear systems
NASA Astrophysics Data System (ADS)
Roy, Ananya; Das Sharma, Kaushik
2015-02-01
In this present article, a new hybrid methodology for designing stable adaptive fuzzy logic controllers (AFLCs) for a class of non-linear system is proposed. The proposed design strategy exploits the features of genetic algorithm (GA)-based stochastic evolutionary global search technique and Lyapunov theory-based local adaptation scheme. The objective is to develop a methodology for designing AFLCs with optimised free parameters and guaranteed closed-loop stability. Simultaneously, the proposed method introduces automation in the design process. The stand-alone Lyapunov theory-based design, GA-based design and proposed hybrid GA-Lyapunov design methodologies are implemented for two benchmark non-linear plants in simulation case studies with different reference signals and one experimental case study. The results demonstrate that the hybrid design methodology outperforms the other control strategies on the whole.
A new line-of-sight approach to the non-linear Cosmic Microwave Background
Fidler, Christian; Koyama, Kazuya; Pettinari, Guido W. E-mail: kazuya.koyama@port.ac.uk
2015-04-01
We develop the transport operator formalism, a new line-of-sight integration framework to calculate the anisotropies of the Cosmic Microwave Background (CMB) at the linear and non-linear level. This formalism utilises a transformation operator that removes all inhomogeneous propagation effects acting on the photon distribution function, thus achieving a split between perturbative collisional effects at recombination and non-perturbative line-of-sight effects at later times. The former can be computed in the framework of standard cosmological perturbation theory with a second-order Boltzmann code such as SONG, while the latter can be treated within a separate perturbative scheme allowing the use of non-linear Newtonian potentials. We thus provide a consistent framework to compute all physical effects contained in the Boltzmann equation and to combine the standard remapping approach with Boltzmann codes at any order in perturbation theory, without assuming that all sources are localised at recombination.
Non-linear mode coupling and the growth of perturbations in ΛCDM
Enqvist, Kari; Rigopoulos, Gerasimos E-mail: gerasimos.rigopoulos@helsinki.fi
2011-03-01
Cosmic structures at small non-linear scales k > L ∼ 0.2h Mpc{sup −1} have an impact on the longer (quasi-)linear wavelengths with k < L via non-linear UV-IR mode coupling. We evaluate this effect for a ΛCDM universe applying the effective fluid method of Baumann, Nicolis, Senatore and Zaldarriaga. For k < L the ΛCDM growth function for the density contrast is found to receive a scale dependent correction and an effective anisotropic stress sources a shift between the two gravitational potentials, setting φ−ψ≠0. Since such a situation is generically considered as a signature of modified gravity and/or dark energy, these effects should be taken into account before any conclusions on the dark sector are drawn from the interpretation of future observations.
Non-linear mode coupling and the growth of perturbations in ΛCDM
NASA Astrophysics Data System (ADS)
Enqvist, Kari; Rigopoulos, Gerasimos
2011-03-01
Cosmic structures at small non-linear scales k > L ~ 0.2h Mpc-1 have an impact on the longer (quasi-)linear wavelengths with k < L via non-linear UV-IR mode coupling. We evaluate this effect for a ΛCDM universe applying the effective fluid method of Baumann, Nicolis, Senatore and Zaldarriaga. For k < L the ΛCDM growth function for the density contrast is found to receive a scale dependent correction and an effective anisotropic stress sources a shift between the two gravitational potentials, setting phi-ψ≠0. Since such a situation is generically considered as a signature of modified gravity and/or dark energy, these effects should be taken into account before any conclusions on the dark sector are drawn from the interpretation of future observations.
Approximate solutions of non-linear circular orbit relative motion in curvilinear coordinates
NASA Astrophysics Data System (ADS)
Bombardelli, Claudio; Gonzalo, Juan Luis; Roa, Javier
2017-01-01
A compact, time-explicit, approximate solution of the highly non-linear relative motion in curvilinear coordinates is provided under the assumption of circular orbit for the chief spacecraft. The rather compact, three-dimensional solution is obtained by algebraic manipulation of the individual Keplerian motions in curvilinear, rather than Cartesian coordinates, and provides analytical expressions for the secular, constant and periodic terms of each coordinate as a function of the initial relative motion conditions or relative orbital elements. Numerical test cases are conducted to show that the approximate solution can be effectively employed to extend the classical linear Clohessy-Wiltshire solution to include non-linear relative motion without significant loss of accuracy up to a limit of 0.4-0.45 in eccentricity and 40-45° in relative inclination for the follower. A very simple, quadratic extension of the classical Clohessy-Wiltshire solution in curvilinear coordinates is also presented.
A non-linear finite-element model of the newborn ear canal
Qi, Li; Liu, Hengjin; Lutfy, Justyn; Funnell, W. Robert J.; Daniel, Sam J.
2010-01-01
We present a three-dimensional non-linear finite-element model of a 22-day-old newborn ear canal. The geometry is based on a clinical X-ray CT scan. A non-linear hyperelastic constitutive law is applied to model large deformations. The Young’s modulus of the soft tissue is found to have a significant effect on the ear-canal volume change, which ranges from approximately 27% to 75% over the static-pressure range of ±3 kPa. The effects of Poisson’s ratio and of the ratio C10:C01 in the hyperelastic model are found to be small. The volume changes do not reach a plateau at high pressures, which implies that the newborn ear-canal wall would not be rigid in tympanometric measurements. The displacements and volume changes calculated from the model are compared with available experimental data. PMID:17225406
A new line-of-sight approach to the non-linear Cosmic Microwave Background
NASA Astrophysics Data System (ADS)
Fidler, Christian; Koyama, Kazuya; Pettinari, Guido W.
2015-04-01
We develop the transport operator formalism, a new line-of-sight integration framework to calculate the anisotropies of the Cosmic Microwave Background (CMB) at the linear and non-linear level. This formalism utilises a transformation operator that removes all inhomogeneous propagation effects acting on the photon distribution function, thus achieving a split between perturbative collisional effects at recombination and non-perturbative line-of-sight effects at later times. The former can be computed in the framework of standard cosmological perturbation theory with a second-order Boltzmann code such as SONG, while the latter can be treated within a separate perturbative scheme allowing the use of non-linear Newtonian potentials. We thus provide a consistent framework to compute all physical effects contained in the Boltzmann equation and to combine the standard remapping approach with Boltzmann codes at any order in perturbation theory, without assuming that all sources are localised at recombination.
Characterization of memory load in an arithmetic task using non-linear analysis of EEG signals.
Zarjam, Pega; Epps, Julien; Lovell, Nigel H; Chen, Fang
2012-01-01
In this paper, we investigate non-linear analysis of electroencephalogram (EEG) signals to examine changes in working memory load during the performance of a cognitive task with varying difficulty levels. EEG signals were recorded during an arithmetic task while the induced load was varying in seven levels from very easy to extremely difficult. The EEG signals were analyzed using three different non-linear/dynamic measures; namely: correlation dimension, Hurst exponent and approximate entropy. Experimental results show that the values of the measures extracted from the delta frequency band of signals acquired from the frontal and occipital lobes of the brain vary in accordance with the task difficulty level induced. The values of the correlation dimension increased as the task difficulty increased, showing a rise in complexity of the EEG signals, while the values of the Hurst exponent and approximate entropy decreased as task difficulty increased, indicating more regularity and predictability in the signals.
Polynomial elimination theory and non-linear stability analysis for the Euler equations
NASA Technical Reports Server (NTRS)
Kennon, S. R.; Dulikravich, G. S.; Jespersen, D. C.
1986-01-01
Numerical methods are presented that exploit the polynomial properties of discretizations of the Euler equations. It is noted that most finite difference or finite volume discretizations of the steady-state Euler equations produce a polynomial system of equations to be solved. These equations are solved using classical polynomial elimination theory, with some innovative modifications. This paper also presents some preliminary results of a new non-linear stability analysis technique. This technique is applicable to determining the stability of polynomial iterative schemes. Results are presented for applying the elimination technique to a one-dimensional test case. For this test case, the exact solution is computed in three iterations. The non-linear stability analysis is applied to determine the optimal time step for solving Burgers' equation using the MacCormack scheme. The estimated optimal time step is very close to the time step that arises from a linear stability analysis.
Non-linear gauge transformations in D = 10 SYM theory and the BCJ duality
NASA Astrophysics Data System (ADS)
Lee, Seungjin; Mafra, Carlos R.; Schlotterer, Oliver
2016-03-01
Recent progress on scattering amplitudes in super Yang-Mills and super-string theory benefitted from the use of multiparticle superfields. They universally capture tree-level subdiagrams, and their generating series solve the non-linear equations of ten-dimensional super Yang-Mills. We provide simplified recursions for multiparticle superfields and relate them to earlier representations through non-linear gauge transformations of their generating series. Moreover, we discuss the gauge transformations which enforce their Lie symmetries as suggested by the Bern-Carrasco-Johansson duality between color and kine-matics. Another gauge transformation due to Harnad and Shnider is shown to streamline the theta-expansion of multiparticle superfields, bypassing the need to use their recursion relations beyond the lowest components. The findings of this work tremendously simplify the component extraction from kinematic factors in pure spinor superspace.
Sulthana, Ayesha; Latha, K C; Imran, Mohammad; Rathan, Ramya; Sridhar, R; Balasubramanian, S
2014-01-01
Fuzzy principal component regression (FPCR) is proposed to model the non-linear process of sewage treatment plant (STP) data matrix. The dimension reduction of voluminous data was done by principal component analysis (PCA). The PCA score values were partitioned by fuzzy-c-means (FCM) clustering, and a Takagi-Sugeno-Kang (TSK) fuzzy model was built based on the FCM functions. The FPCR approach was used to predict the reduction in chemical oxygen demand (COD) and biological oxygen demand (BOD) of treated wastewater of Vidyaranyapuram STP with respect to the relations modeled between fuzzy partitioned PCA scores and target output. The designed FPCR model showed the ability to capture the behavior of non-linear processes of STP. The predicted values of reduction in COD and BOD were analyzed by performing the linear regression analysis. The predicted values for COD and BOD reduction showed positive correlation with the observed data.
The algebra of physical observables in non-linearly realized gauge theories
NASA Astrophysics Data System (ADS)
Quadri, Andrea
2010-11-01
We classify the physical observables in spontaneously broken non-linearly realized gauge theories in the recently proposed loopwise expansion governed by the Weak Power-Counting (WPC) and the Local Functional Equation. The latter controls the non-trivial quantum deformation of the classical non-linearly realized gauge symmetry, to all orders in the loop expansion. The Batalin-Vilkovisky (BV) formalism is used. We show that the dependence of the vertex functional on the Goldstone fields is obtained via a canonical transformation w.r.t. the BV bracket associated with the BRST symmetry of the model. We also compare the WPC with strict power-counting renormalizability in linearly realized gauge theories. In the case of the electroweak group we find that the tree-level Weinberg relation still holds if power-counting renormalizability is weakened to the WPC condition.
Non-linear dynamics in biological microtubules: solitons and dissipation-free energy transfer
NASA Astrophysics Data System (ADS)
Mavromatos, Nick E.
2017-08-01
I review some recent developments concerning soliton solutions in biological microtubules and their significance in transferring energy without dissipation. I discuss various types of soliton solutions, as well as ‘spikes’, of the associated non-linear Lagrange equations describing the dynamics of a ‘pseudo-spin non-linear σ-model’ that models the dynamics of a microtubule system with dipole-dipole interactions. These results will hopefully contribute to a better understanding of the functional properties of microtubules, including the motor protein dynamics and the information transfer processes. With regards to the latter we also speculate on the use of microtubules as ‘logical’ gates. Our considerations are classical, but the soliton solutions may have a microscopic quantum origin, which we briefly touch upon.
Fully non-linear cosmological perturbations of multicomponent fluid and field systems
NASA Astrophysics Data System (ADS)
Hwang, Jai-chan; Noh, Hyerim; Park, Chan-Gyung
2016-09-01
We present fully non-linear and exact cosmological perturbation equations in the presence of multiple components of fluids and minimally coupled scalar fields. We ignore the tensor-type perturbation. The equations are presented without taking the temporal gauge condition in the Friedmann background with general curvature and the cosmological constant. We include the anisotropic stress. Even in the absence of anisotropic stress of individual component, the multiple component nature introduces the anisotropic stress in the collective fluid quantities. We prove the Newtonian limit of multiple fluids in the zero-shear gauge and the uniform-expansion gauge conditions, present the Newtonian hydrodynamic equations in the presence of general relativistic pressure in the zero-shear gauge, and present the fully non-linear equations and the third-order perturbation equations of the non-relativistic pressure fluids in the CDM-comoving gauge.
Numerical simulation of blood flow through a capillary using a non-linear viscoelastic model.
Shariatkhah, Amin; Norouzi, Mahmood; Nobari, Mohammad Reza Heyrani
2016-01-01
In this article, a periodic developing blood flow in a capillary is simulated using a non-linear viscoelastic model for the first time. Here, the Giesekus model is used as the constitutive equation, and based on the experimental data, the best value for the mobility factor and zero shear rate viscosity are derived. The numerical solution of the problem is obtained using the finite volume method. The algorithm of the solution is pressure implicit with splitting of operators (PISO). The simulation carried out using the Giesekus, Oldroyd-B and Newtonian models and the results indicate that the Giesekus model presents a more accurate solution for the stress and velocity fields than the Newtonian and Oldroyd-B models. The previous studies on this problem were restricted to the linear and quasi-linear viscoelastic models. It is shown that only non-linear viscoelastic models can accurately describe the experimental data of unsteady blood flow in capillaries.
NASA Astrophysics Data System (ADS)
Sabatini, R.; Bailly, C.; Marsden, O.; Gainville, O.
2016-12-01
The long-range atmospheric propagation of explosion-like waves of frequency in the infrasound range is investigated using non-linear ray theory. Simulations are performed for sources of increasing amplitude on rays up to the lower thermosphere and for distances of hundreds of kilometres. A study of the attenuation of the waveforms observed at ground level induced by both the classical mechanisms and the vibrational relaxation of the molecules comprising the atmospheric gas is carried out. The relative importance of classical absorption and vibrational relaxation along the typical atmospheric propagation trajectories is assessed. Non-linear effects are highlighted as well and particular emphasis is placed on their strong interaction with absorption phenomena. A detailed description of the propagation model and of the numerical algorithm used in this work is first reported. Results are then discussed and the importance of the different mechanisms is clarified.
On robustness of constrained non-linear H ∞ predictive controllers with disturbances
NASA Astrophysics Data System (ADS)
He, De-Feng; Ji, Hai-Bo; Zheng, Tao
2010-02-01
This article considers the robustness problem of H ∞ model predictive controllers for constrained non-linear discrete-time systems subject to disturbances, which are dependent on the system state and input. The notions of input-to-state stability and finite L 2-gain of non-linear systems are introduced and exploited to investigate the robustness properties of this predictive controller under the state and input constraints and the disturbance. Moreover, this robustness of the controller is extended to the case of suboptimality of the solution. With its feasibility at initial time, the feasibility of the online optimisation problem is guaranteed for all times in the presence of disturbances and constraints. Finally, an example is employed to illustrate the proposed results.
CMB anisotropies at all orders: the non-linear Sachs-Wolfe formula
NASA Astrophysics Data System (ADS)
Roldan, Omar
2017-08-01
We obtain the non-linear generalization of the Sachs-Wolfe + integrated Sachs-Wolfe (ISW) formula describing the CMB temperature anisotropies. Our formula is valid at all orders in perturbation theory, is also valid in all gauges and includes scalar, vector and tensor modes. A direct consequence of our results is that the maps of the logarithmic temperature anisotropies are much cleaner than the usual CMB maps, because they automatically remove many secondary anisotropies. This can for instance, facilitate the search for primordial non-Gaussianity in future works. It also disentangles the non-linear ISW from other effects. Finally, we provide a method which can iteratively be used to obtain the lensing solution at the desired order.
Learning from Non-Linear Ecosystem Dynamics Is Vital for Achieving Land Degradation Neutrality
Sietz, Diana; Fleskens, Luuk; Stringer, Lindsay C.
2017-02-27
Land Degradation Neutrality is one of the Sustainable Development Goal targets, requiring on-going degradation to be balanced by restoration and sustainable land management. However, restoration and efforts to prevent degradation have often failed to deliver expected benefits,despite enormous investments. Better acknowledging the close relationships between climate, land management and non-linear ecosystem dynamics can help restoration activities to meet their intended goals, while supporting climate change adaptation and mitigation. This paper is the first to link ecological theory of non-linear ecosystem dynamics to Land Degradation Neutrality offering essential insights into appropriate timings, climate-induced windows of opportunities and risks and the financialmore » viability of investments. These novel insights are pre-requisites for meaningful o and monitoring of progress towards Land Degradation Neutrality« less
NASA Astrophysics Data System (ADS)
Orain, François; Bécoulet, M.; Morales, J.; Huijsmans, G. T. A.; Dif-Pradalier, G.; Hoelzl, M.; Garbet, X.; Pamela, S.; Nardon, E.; Passeron, C.; Latu, G.; Fil, A.; Cahyna, P.
2015-01-01
The dynamics of a multi-edge localized mode (ELM) cycle as well as the ELM mitigation by resonant magnetic perturbations (RMPs) are modeled in realistic tokamak X-point geometry with the non-linear reduced MHD code JOREK. The diamagnetic rotation is found to be a key parameter enabling us to reproduce the cyclical dynamics of the plasma relaxations and to model the near-symmetric ELM power deposition on the inner and outer divertor target plates consistently with experimental measurements. Moreover, the non-linear coupling of the RMPs with unstable modes are found to modify the edge magnetic topology and induce a continuous MHD activity in place of a large ELM crash, resulting in the mitigation of the ELMs. At larger diamagnetic rotation, a bifurcation from unmitigated ELMs—at low RMP current—towards fully suppressed ELMs—at large RMP current—is obtained.
Non-Linear System Identification for Aeroelastic Systems with Application to Experimental Data
NASA Technical Reports Server (NTRS)
Kukreja, Sunil L.
2008-01-01
Representation and identification of a non-linear aeroelastic pitch-plunge system as a model of the NARMAX class is considered. A non-linear difference equation describing this aircraft model is derived theoretically and shown to be of the NARMAX form. Identification methods for NARMAX models are applied to aeroelastic dynamics and its properties demonstrated via continuous-time simulations of experimental conditions. Simulation results show that (i) the outputs of the NARMAX model match closely those generated using continuous-time methods and (ii) NARMAX identification methods applied to aeroelastic dynamics provide accurate discrete-time parameter estimates. Application of NARMAX identification to experimental pitch-plunge dynamics data gives a high percent fit for cross-validated data.
Non-Linear Analysis of Mode II Fracture in the end Notched Flexure Beam
NASA Astrophysics Data System (ADS)
Rizov, V.
2016-03-01
Analysis is carried-out of fracture in the End Notched Flex- ure (ENF) beam configuration, taking into account the material nonlin- earity. For this purpose, the J-integral approach is applied. A non-linear model, based on the Classical beam theory is used. The mechanical be- haviour of the ENF configuration is described by the Ramberg-Osgood stress-strain curve. It is assumed that the material possesses the same properties in tension and compression. The influence is evaluated of the material constants in the Ramberg-Osgood stress-strain equation on the fracture behaviour. The effect of the crack length on the J-integral value is investigated, too. The analytical approach, developed in the present paper, is very useful for parametric analyses, since the simple formulae obtained capture the essentials of the non-linear fracture in the ENF con- figuration.
PkANN: Non-Linear Matter Power Spectrum Interpolation through Artificial Neural Networks
NASA Astrophysics Data System (ADS)
Agarwal, Shankar
We investigate the interpolation of power spectra of matter fluctuations using artificial neural networks (ANNs). We present a new approach to confront small-scale non-linearities in the matter power spectrum. This ever-present and pernicious uncertainty is often the Achilles' heel in cosmological studies and must be reduced if we are to see the advent of precision cosmology in the late-time Universe. We detail how an accurate interpolation of the matter power spectrum is achievable with only a sparsely sampled grid of cosmological parameters. We show that an optimally trained ANN, when presented with a set of cosmological parameters (Omh2 , Obh2, ns, w0, sigma8, sum mnu and z), can provide a worst-case error ≤ 1 per cent (for redshift z ≤ 2) fit to the non-linear matter power spectrum deduced through large-scale N-body simulations, for modes up to k ≤ 0.9 hMpc-1 . Our power spectrum interpolator, which we label 'PkANN', is designed to simulate a range of cosmological models including massive neutrinos and dark energy equation of state w 0 ≠ -1. PkANN is accurate in the quasi-non-linear regime (0.1 hMpc-1 ≤ k ≤ 0.9 hMpc -1) over the entire parameter space and marks a significant improvement over some of the current power spectrum calculators. The response of the power spectrum to variations in the cosmological parameters is explored using PkANN. Using a compilation of existing peculiar velocity surveys, we investigate the cosmic Mach number statistic and show that PkANN not only successfully accounts for the non-linear motions on small scales, but also, unlike N-body simulations which are computationally expensive and/or infeasible, it can be an extremely quick and reliable tool in interpreting cosmological observations and testing theories of structure-formation.
Correlation spectroscopy based on non-linear response of silver colloids (including SEHRS)
NASA Astrophysics Data System (ADS)
Brehm, G.; Sauer, G.; Fritz, N.; Schneider, S.; Zaitsev, S.
2005-02-01
The non-linear response (second harmonic generation, SHG, hyper-Rayleigh scattering, HRS, surface-enhanced hyper-Raman scattering, SEHRS, and continuum generation) of two different types of silver colloids is compared by stationary and correlation spectroscopy. Employing a poly-disperse colloid prepared after the protocol of Lee and Meisel we found that the efficiency of all types of non-linear response is greatly enhanced if the colloid is 'activated' by addition of chloride ions. This activation is also necessary to observe SEHRS with both the Lee-Meisel and the mono-disperse colloid prepared by hydrazine reduction. The correlation curves of both types of colloid show one step (τ1/2∼10 ms) which can be associated with lateral diffusion of the individual particles. Its τ1/2-value is larger for the poly-disperse colloid, which contains larger particles. In addition, we find a second step, its relative amplitude being dependent on experimental parameters, whose τ1/2-value is, however, essentially the same for all samples investigated (τ‧1/2∼50 μs). We assign this correlation time to processes that lead to a restructuring of the surface and the formation and destruction of so-called 'hot spots'. Under optimum condition, the efficiency for all non-linear processes connected with one such 'hot spot' is extremely high. 'Hot particles' contain at least one hot spot and can therefore dominate the non-linear signal without the need of aggregation (field enhancement in the gap between particles).
Improving Non-Linear Approaches to Anomaly Detection, Class Separation, and Visualization
2014-12-26
thickness (mm), two-hour serum insulin (mu U/ml), body mass index (weight in kg/(height in m)2), diabetes pedigree function, and age (years). Patients...is O(Nmr + m3) but also requires large m to ensure sufficient sampling [139]. Drineas and Mahoney [67] developed a data- dependent non -uniform...IMPROVING NON -LINEAR APPROACHES TO ANOMALY DETECTION, CLASS SEPARATION, AND VISUALIZATION DISSERTATION Todd J. Paciencia, Major, USAF AFIT-ENS-DS-14
FDATMOS16 non-linear partitioning and organic volatility distributions in urban aerosols
Madronich, Sasha; Kleinman, Larry; Conley, Andrew; Lee-Taylor, Julie; Hodzic, A.; Aumont, Bernard
2015-12-17
Gas-to-particle partitioning of organic aerosols (OA) is represented in most models by Raoult’s law, and depends on the existing mass of particles into which organic gases can dissolve. This raises the possibility of non-linear response of particle-phase OA to the emissions of precursor volatile organic compounds (VOCs) that contribute to this partitioning mass. Implications for air quality management are evident: A strong non-linear dependence would suggest that reductions in VOC emission would have a more-than-proportionate benefit in lowering ambient OA concentrations. Chamber measurements on simple VOC mixtures generally confirm the non-linear scaling between OA and VOCs, usually stated as a mass-dependence of the measured OA yields. However, for realistic ambient conditions including urban settings, no single component dominates the composition of the organic particles, and deviations from linearity are presumed to be small. Here we re-examine the linearity question using volatility spectra from several sources: (1) chamber studies of selected aerosols, (2) volatility inferred for aerosols sampled in two megacities, Mexico City and Paris, and (3) an explicit chemistry model (GECKO-A). These few available volatility distributions suggest that urban OA may be only slightly super-linear, with most values of the sensitivity exponent in the range 1.1-1.3, also substantially lower than seen in chambers for some specific aerosols. Furthermore, the rather low values suggest that OA concentrations in megacities are not an inevitable convergence of non-linear effects, but can be addressed (much like in smaller urban areas) by proportionate reductions in emissions.
FDATMOS16 non-linear partitioning and organic volatility distributions in urban aerosols
Madronich, Sasha; Kleinman, Larry; Conley, Andrew; ...
2015-12-17
Gas-to-particle partitioning of organic aerosols (OA) is represented in most models by Raoult’s law, and depends on the existing mass of particles into which organic gases can dissolve. This raises the possibility of non-linear response of particle-phase OA to the emissions of precursor volatile organic compounds (VOCs) that contribute to this partitioning mass. Implications for air quality management are evident: A strong non-linear dependence would suggest that reductions in VOC emission would have a more-than-proportionate benefit in lowering ambient OA concentrations. Chamber measurements on simple VOC mixtures generally confirm the non-linear scaling between OA and VOCs, usually stated as amore » mass-dependence of the measured OA yields. However, for realistic ambient conditions including urban settings, no single component dominates the composition of the organic particles, and deviations from linearity are presumed to be small. Here we re-examine the linearity question using volatility spectra from several sources: (1) chamber studies of selected aerosols, (2) volatility inferred for aerosols sampled in two megacities, Mexico City and Paris, and (3) an explicit chemistry model (GECKO-A). These few available volatility distributions suggest that urban OA may be only slightly super-linear, with most values of the sensitivity exponent in the range 1.1-1.3, also substantially lower than seen in chambers for some specific aerosols. Furthermore, the rather low values suggest that OA concentrations in megacities are not an inevitable convergence of non-linear effects, but can be addressed (much like in smaller urban areas) by proportionate reductions in emissions.« less
Non-Linear Metamodeling Extensions to the Robust Parameter Design of Computer Simulations
2016-09-15
minimizing the variability about those responses. Two popular combined-array strategies—the response surface model (RSM) approach and the emulator approach...are limited when applied to simulations. In the former case, the mean and variance models can be inadequate due to a high level of non-linearity...Results show that improved prediction models can be attained through the proposed approach at a reduced computational cost. Additionally, a multi
Potential for Terahertz/Optical, Two Color Non-linear Sensing of Liquid Biochemical Agents
2011-05-18
solutions1,2 in the infrared frequency band. To explore the lowest frequency macromo- lecular modes of biomolecules, which occur at terahertz fre- quencies, in...resonant with elec- tronic excitations and macromolecular vibrations . A configuration that optimizes SDFG in the face of strong terahertz absorption by...REPORT Potential for terahertz /optical, two color non-linear sensing of liquid biochemical agents 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: A high
Response statistics of rotating shaft with non-linear elastic restoring forces by path integration
NASA Astrophysics Data System (ADS)
Gaidai, Oleg; Naess, Arvid; Dimentberg, Michael
2017-07-01
Extreme statistics of random vibrations is studied for a Jeffcott rotor under uniaxial white noise excitation. Restoring force is modelled as elastic non-linear; comparison is done with linearized restoring force to see the force non-linearity effect on the response statistics. While for the linear model analytical solutions and stability conditions are available, it is not generally the case for non-linear system except for some special cases. The statistics of non-linear case is studied by applying path integration (PI) method, which is based on the Markov property of the coupled dynamic system. The Jeffcott rotor response statistics can be obtained by solving the Fokker-Planck (FP) equation of the 4D dynamic system. An efficient implementation of PI algorithm is applied, namely fast Fourier transform (FFT) is used to simulate dynamic system additive noise. The latter allows significantly reduce computational time, compared to the classical PI. Excitation is modelled as Gaussian white noise, however any kind distributed white noise can be implemented with the same PI technique. Also multidirectional Markov noise can be modelled with PI in the same way as unidirectional. PI is accelerated by using Monte Carlo (MC) estimated joint probability density function (PDF) as initial input. Symmetry of dynamic system was utilized to afford higher mesh resolution. Both internal (rotating) and external damping are included in mechanical model of the rotor. The main advantage of using PI rather than MC is that PI offers high accuracy in the probability distribution tail. The latter is of critical importance for e.g. extreme value statistics, system reliability, and first passage probability.
Non-linear controls influence functions in an aircraft dynamics simulator
NASA Technical Reports Server (NTRS)
Guerreiro, Nelson M.; Hubbard, James E., Jr.; Motter, Mark A.
2006-01-01
In the development and testing of novel structural and controls concepts, such as morphing aircraft wings, appropriate models are needed for proper system characterization. In most instances, available system models do not provide the required additional degrees of freedom for morphing structures but may be modified to some extent to achieve a compatible system. The objective of this study is to apply wind tunnel data collected for an Unmanned Air Vehicle (UAV), that implements trailing edge morphing, to create a non-linear dynamics simulator, using well defined rigid body equations of motion, where the aircraft stability derivatives change with control deflection. An analysis of this wind tunnel data, using data extraction algorithms, was performed to determine the reference aerodynamic force and moment coefficients for the aircraft. Further, non-linear influence functions were obtained for each of the aircraft s control surfaces, including the sixteen trailing edge flap segments. These non-linear controls influence functions are applied to the aircraft dynamics to produce deflection-dependent aircraft stability derivatives in a non-linear dynamics simulator. Time domain analysis of the aircraft motion, trajectory, and state histories can be performed using these nonlinear dynamics and may be visualized using a 3-dimensional aircraft model. Linear system models can be extracted to facilitate frequency domain analysis of the system and for control law development. The results of this study are useful in similar projects where trailing edge morphing is employed and will be instrumental in the University of Maryland s continuing study of active wing load control.
On the linear and non-linear electronic spectroscopy of chlorophylls: a computational study.
Graczyk, Alicja; Żurek, Justyna M; Paterson, Martin J
2014-01-01
A theoretical analysis of linear and non-linear (two-photon absorption) electronic spectroscopy of all known porphyrinic pigments has been performed using linear and quadratic density functional response theory, with the long-range corrected CAM-B3LYP functional. We found that higher Soret transitions often contain non-Gouterman contributions and that each chlorophyll has the possibility for resonance enhanced TPA in the Soret region, although there is also significant TPA in the Q region.
Finite element modelling of non-linear magnetic circuits using Cosmic NASTRAN
NASA Technical Reports Server (NTRS)
Sheerer, T. J.
1986-01-01
The general purpose Finite Element Program COSMIC NASTRAN currently has the ability to model magnetic circuits with constant permeablilities. An approach was developed which, through small modifications to the program, allows modelling of non-linear magnetic devices including soft magnetic materials, permanent magnets and coils. Use of the NASTRAN code resulted in output which can be used for subsequent mechanical analysis using a variation of the same computer model. Test problems were found to produce theoretically verifiable results.
Dopamine-dependent non-linear correlation between subthalamic rhythms in Parkinson's disease.
Marceglia, S; Foffani, G; Bianchi, A M; Baselli, G; Tamma, F; Egidi, M; Priori, A
2006-03-15
The basic information architecture in the basal ganglia circuit is under debate. Whereas anatomical studies quantify extensive convergence/divergence patterns in the circuit, suggesting an information sharing scheme, neurophysiological studies report an absence of linear correlation between single neurones in normal animals, suggesting a segregated parallel processing scheme. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys and in parkinsonian patients single neurones become linearly correlated, thus leading to a loss of segregation between neurones. Here we propose a possible integrative solution to this debate, by extending the concept of functional segregation from the cellular level to the network level. To this end, we recorded local field potentials (LFPs) from electrodes implanted for deep brain stimulation (DBS) in the subthalamic nucleus (STN) of parkinsonian patients. By applying bispectral analysis, we found that in the absence of dopamine stimulation STN LFP rhythms became non-linearly correlated, thus leading to a loss of segregation between rhythms. Non-linear correlation was particularly consistent between the low-beta rhythm (13-20 Hz) and the high-beta rhythm (20-35 Hz). Levodopa administration significantly decreased these non-linear correlations, therefore increasing segregation between rhythms. These results suggest that the extensive convergence/divergence in the basal ganglia circuit is physiologically necessary to sustain LFP rhythms distributed in large ensembles of neurones, but is not sufficient to induce correlated firing between neurone pairs. Conversely, loss of dopamine generates pathological linear correlation between neurone pairs, alters the patterns within LFP rhythms, and induces non-linear correlation between LFP rhythms operating at different frequencies. The pathophysiology of information processing in the human basal ganglia therefore involves not only activities of individual rhythms, but also
A single-degree-of-freedom model for non-linear soil amplification
Erdik, Mustafa Ozder
1979-01-01
For proper understanding of soil behavior during earthquakes and assessment of a realistic surface motion, studies of the large-strain dynamic response of non-linear hysteretic soil systems are indispensable. Most of the presently available studies are based on the assumption that the response of a soil deposit is mainly due to the upward propagation of horizontally polarized shear waves from the underlying bedrock. Equivalent-linear procedures, currently in common use in non-linear soil response analysis, provide a simple approach and have been favorably compared with the actual recorded motions in some particular cases. Strain compatibility in these equivalent-linear approaches is maintained by selecting values of shear moduli and damping ratios in accordance with the average soil strains, in an iterative manner. Truly non-linear constitutive models with complete strain compatibility have also been employed. The equivalent-linear approaches often raise some doubt as to the reliability of their results concerning the system response in high frequency regions. In these frequency regions the equivalent-linear methods may underestimate the surface motion by as much as a factor of two or more. Although studies are complete in their methods of analysis, they inevitably provide applications pertaining only to a few specific soil systems, and do not lead to general conclusions about soil behavior. This report attempts to provide a general picture of the soil response through the use of a single-degree-of-freedom non-linear-hysteretic model. Although the investigation is based on a specific type of nonlinearity and a set of dynamic soil properties, the method described does not limit itself to these assumptions and is equally applicable to other types of nonlinearity and soil parameters.
NASA Technical Reports Server (NTRS)
Jobson, Daniel J.; Rahman, Zia-Ur; Woodell, Glenn A.; Hines, Glenn D.
2004-01-01
Noise is the primary visibility limit in the process of non-linear image enhancement, and is no longer a statistically stable additive noise in the post-enhancement image. Therefore novel approaches are needed to both assess and reduce spatially variable noise at this stage in overall image processing. Here we will examine the use of edge pattern analysis both for automatic assessment of spatially variable noise and as a foundation for new noise reduction methods.
On removability of singularities on manifolds for solutions of non-linear elliptic equations
Skrypnik, I I
2003-10-31
A precise condition is found for the removability of a singularity on a smooth manifold for solutions of non-linear second-order elliptic equations of divergence form. The condition is stated in the form of a dependence of the pointwise behaviour of the solution on the distance to the singular manifold. The condition obtained is weaker than Serrin's well-known sufficient condition for the removability of a singularity on a manifold.
Dopamine-dependent non-linear correlation between subthalamic rhythms in Parkinson's disease
Marceglia, S; Foffani, G; Bianchi, A M; Baselli, G; Tamma, F; Egidi, M; Priori, A
2006-01-01
The basic information architecture in the basal ganglia circuit is under debate. Whereas anatomical studies quantify extensive convergence/divergence patterns in the circuit, suggesting an information sharing scheme, neurophysiological studies report an absence of linear correlation between single neurones in normal animals, suggesting a segregated parallel processing scheme. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys and in parkinsonian patients single neurones become linearly correlated, thus leading to a loss of segregation between neurones. Here we propose a possible integrative solution to this debate, by extending the concept of functional segregation from the cellular level to the network level. To this end, we recorded local field potentials (LFPs) from electrodes implanted for deep brain stimulation (DBS) in the subthalamic nucleus (STN) of parkinsonian patients. By applying bispectral analysis, we found that in the absence of dopamine stimulation STN LFP rhythms became non-linearly correlated, thus leading to a loss of segregation between rhythms. Non-linear correlation was particularly consistent between the low-beta rhythm (13–20 Hz) and the high-beta rhythm (20–35 Hz). Levodopa administration significantly decreased these non-linear correlations, therefore increasing segregation between rhythms. These results suggest that the extensive convergence/divergence in the basal ganglia circuit is physiologically necessary to sustain LFP rhythms distributed in large ensembles of neurones, but is not sufficient to induce correlated firing between neurone pairs. Conversely, loss of dopamine generates pathological linear correlation between neurone pairs, alters the patterns within LFP rhythms, and induces non-linear correlation between LFP rhythms operating at different frequencies. The pathophysiology of information processing in the human basal ganglia therefore involves not only activities of individual rhythms, but also
NASA Astrophysics Data System (ADS)
Gupta, Rahul Kumar; Shi, Qiongfeng; Dhakar, Lokesh; Wang, Tao; Heng, Chun Huat; Lee, Chengkuo
2017-01-01
Over the years, several approaches have been devised to widen the operating bandwidth, but most of them can only be triggered at high accelerations. In this work, we investigate a broadband energy harvester based on combination of non-linear stiffening effect and multimodal energy harvesting to obtain high bandwidth over wide range of accelerations (0.1 g-2.0 g). In order to achieve broadband behavior, a polymer based spring exhibiting multimodal energy harvesting is used. Besides, non-linear stiffening effect is introduced by using mechanical stoppers. At low accelerations (<0.5 g), the nearby mode frequencies of polymer spring contribute to broadening characteristics, while proof mass engages with mechanical stoppers to introduce broadening by non-linear stiffening at higher accelerations. The electromagnetic mechanism is employed in this design to enhance its output at low accelerations when triboelectric output is negligible. Our device displays bandwidth of 40 Hz even at low acceleration of 0.1 g and it is increased up to 68 Hz at 2 g. When non-linear stiffening is used along with multimodal energy-harvesting, the obtained bandwidth increases from 23 Hz to 68 Hz with percentage increment of 295% at 1.8 g. Further, we have demonstrated the triboelectric output measured as acceleration sensing signals in terms of voltage and current sensitivity of 4.7 Vg-1 and 19.7 nAg-1, respectively.
Gupta, Rahul Kumar; Shi, Qiongfeng; Dhakar, Lokesh; Wang, Tao; Heng, Chun Huat; Lee, Chengkuo
2017-01-01
Over the years, several approaches have been devised to widen the operating bandwidth, but most of them can only be triggered at high accelerations. In this work, we investigate a broadband energy harvester based on combination of non-linear stiffening effect and multimodal energy harvesting to obtain high bandwidth over wide range of accelerations (0.1 g–2.0 g). In order to achieve broadband behavior, a polymer based spring exhibiting multimodal energy harvesting is used. Besides, non-linear stiffening effect is introduced by using mechanical stoppers. At low accelerations (<0.5 g), the nearby mode frequencies of polymer spring contribute to broadening characteristics, while proof mass engages with mechanical stoppers to introduce broadening by non-linear stiffening at higher accelerations. The electromagnetic mechanism is employed in this design to enhance its output at low accelerations when triboelectric output is negligible. Our device displays bandwidth of 40 Hz even at low acceleration of 0.1 g and it is increased up to 68 Hz at 2 g. When non-linear stiffening is used along with multimodal energy-harvesting, the obtained bandwidth increases from 23 Hz to 68 Hz with percentage increment of 295% at 1.8 g. Further, we have demonstrated the triboelectric output measured as acceleration sensing signals in terms of voltage and current sensitivity of 4.7 Vg−1 and 19.7 nAg−1, respectively. PMID:28120924
Darboux Transformation for Coupled Non-Linear Schrödinger Equation and Its Breather Solutions
NASA Astrophysics Data System (ADS)
Feng, Lili; Yu, Fajun; Li, Li
2017-01-01
Starting from a 3×3 spectral problem, a Darboux transformation (DT) method for coupled Schrödinger (CNLS) equation is constructed, which is more complex than 2×2 spectral problems. A scheme of soliton solutions of an integrable CNLS system is realised by using DT. Then, we obtain the breather solutions for the integrable CNLS system. The method is also appropriate for more non-linear soliton equations in physics and mathematics.
Sharp threshold of global existence for non-linear Gross-Pitaevskii equation in RN
NASA Astrophysics Data System (ADS)
Chen, Guanggan; Zhang, Jian
2006-04-01
This paper is concerned with the non-linear Gross-Pitaevskii equation which describes the attractive Bose-Einstein condensate under a magnetic trapE By an intricate variational argument we derive out a sharp threshold of blowing up and global existence by applying the potential well argument and the concavity method. Furthermore, we answer the question: How small are the initial data, the global solutions of the Cauchy problem of the equation exist for [graphic: see PDF
Non-linear regimes in mean-field full-sphere dynamo
NASA Astrophysics Data System (ADS)
Pipin, V. V.
2017-04-01
The mean-field dynamo model is employed to study the non-linear dynamo regimes in a fully convective star of mass 0.3 M⊙ rotating with period of 10 d. For intermediate value of parameter of the turbulent magnetic Prandl number, PmT = 3, we found the oscillating dynamo regimes with period about 40 yr. The higher PmT results to longer dynamo periods. If the large-scale flows is fixed, we find that the dynamo transits from axisymmetric to non-axisymmetric regimes for the overcritical parameter of the α-effect. The change of dynamo regime occurs because of the non-axisymmetric non-linear α-effect. The situation persists in the fully non-linear dynamo models with regards for the magnetic feedback on the angular momentum balance and the heat transport in the star. It is found that the large-scale magnetic field quenches the latitudinal shear in the bulk of the star. However, the strong radial shear operates in the subsurface layer of the star. In the non-linear case, the profile of the angular velocity inside the star become close to the spherical surfaces. This supports the equator-ward migration of the axisymmetric magnetic field dynamo waves. It was found that the magnetic configuration of the star dominates by the regular non-axisymmetric mode m = 1. As a result of the differential rotation, it forms the Yin Yang magnetic polarity pattern with the strong (>500 G) poloidal magnetic field in polar regions.
Non-linear partitioning and organic volatility distributions of urban aerosols.
Madronich, S; Conley, A J; Lee-Taylor, J; Kleinman, L I; Hodzic, A; Aumont, B
2016-07-18
Gas-to-particle partitioning of organic aerosols (OA) is represented in most models by Raoult's law, and depends on the existing mass of particles into which organic gases can dissolve. This raises the possibility of non-linear response of particle-phase OA mass to the emissions of precursor volatile organic compounds (VOCs) that contribute to this partitioning mass. Implications for air quality management are evident: a strong non-linear dependence would suggest that reductions in VOC emission would have a more-than-proportionate benefit in lowering ambient OA concentrations. Chamber measurements on simple VOC mixtures generally confirm the non-linear scaling between OA and VOCs, usually stated as a mass-dependence of the measured OA yields. However, for realistic ambient conditions including urban settings, no single component dominates the composition of the organic particles, and deviations from linearity are presumed to be small. Here we re-examine the linearity question using volatility spectra from several sources: (1) chamber studies of selected aerosols, (2) volatility inferred for aerosols sampled in two megacities, Mexico City and Paris, and (3) an explicit chemistry model (GECKO-A). These few available volatility distributions suggest that urban OA may be only slightly super-linear, with most values of the normalized sensitivity exponent in the range 1.1-1.3, also substantially lower than seen in chambers for some specific aerosols. The rather low exponents suggest that OA concentrations in megacities are not an inevitable convergence of non-linear effects, but can be addressed (much like in smaller urban areas) by proportionate reductions in emissions.
A Family of Ellipse Methods for Solving Non-Linear Equations
ERIC Educational Resources Information Center
Gupta, K. C.; Kanwar, V.; Kumar, Sanjeev
2009-01-01
This note presents a method for the numerical approximation of simple zeros of a non-linear equation in one variable. In order to do so, the method uses an ellipse rather than a tangent approach. The main advantage of our method is that it does not fail even if the derivative of the function is either zero or very small in the vicinity of the…
Non-linear longitudinal compression effect on dynamics of the transcription bubble in DNA.
Shikhovtseva, E S; Nazarov, V N
2016-01-01
The dependence of the dynamics of transcription bubble on the parameters of non-linear longitudinal compression is presented on the base of simple model of soliton-like conformational switchings in two-component bistable polymer molecules with energetically non-equivalent stable states. It has been shown that under certain conditions the longitudinal compression may be a trap for a conformational switching. Copyright © 2016 Elsevier B.V. All rights reserved.
Piezoelectric Non-linear Nanomechanical Temperature and Acceleration Intensive Clocks (PENNTAC)
2014-05-01
overlaid dashed black line represents the fixed point solution of the Duffing resonator. Resonator non-linearities tend to worsen the oscillator PN by...Schematic and Actual implementation of the Oscillator Setup used to demonstrate PN shaping via a Duffing Resonator. (1) AlN CMR mounted on a PCB, (2...exhibited by the Duffing resonator 3.2 1/f Resonator Flicker Noise In order to identify the main noise sources in our oscillators , and
Non-Linear Susceptibility of Spin-Glasses on Frustrated Triangular Cactus Tree
NASA Astrophysics Data System (ADS)
Yasumura, Kaoru; Ono, Ikuo
1984-01-01
In order to explore the frustration effects on a non-linear susceptibility χ2 of spin-glasses, ferro-antiferromagnetic mixtures, diluted antiferromagnets and Mattis model are comperatively investigated in line with a random ordered phase. The jump of χ2 in the vicinity of the transition temperature is common in these models, and the magnitude of the jump is proved to depend strongly on the concentration of antiferromagnetic bond, but weakly on that of frustration.
A Family of Ellipse Methods for Solving Non-Linear Equations
ERIC Educational Resources Information Center
Gupta, K. C.; Kanwar, V.; Kumar, Sanjeev
2009-01-01
This note presents a method for the numerical approximation of simple zeros of a non-linear equation in one variable. In order to do so, the method uses an ellipse rather than a tangent approach. The main advantage of our method is that it does not fail even if the derivative of the function is either zero or very small in the vicinity of the…
Beyond the borders--Biomedical applications of non-linear Raman microscopy.
Winterhalder, Martin Josef; Zumbusch, Andreas
2015-07-15
Raman spectroscopy offers great promise for label free imaging in biomedical applications. Its use, however, is hampered by the long integration times required and the presence of autofluorescence in many samples which outshines the Raman signals. In order to overcome these limitations, a variety of different non-linear Raman imaging techniques have been developed over the last decade. This review describes biomedical applications of these novel but already mature imaging techniques.
Gupta, Rahul Kumar; Shi, Qiongfeng; Dhakar, Lokesh; Wang, Tao; Heng, Chun Huat; Lee, Chengkuo
2017-01-25
Over the years, several approaches have been devised to widen the operating bandwidth, but most of them can only be triggered at high accelerations. In this work, we investigate a broadband energy harvester based on combination of non-linear stiffening effect and multimodal energy harvesting to obtain high bandwidth over wide range of accelerations (0.1 g-2.0 g). In order to achieve broadband behavior, a polymer based spring exhibiting multimodal energy harvesting is used. Besides, non-linear stiffening effect is introduced by using mechanical stoppers. At low accelerations (<0.5 g), the nearby mode frequencies of polymer spring contribute to broadening characteristics, while proof mass engages with mechanical stoppers to introduce broadening by non-linear stiffening at higher accelerations. The electromagnetic mechanism is employed in this design to enhance its output at low accelerations when triboelectric output is negligible. Our device displays bandwidth of 40 Hz even at low acceleration of 0.1 g and it is increased up to 68 Hz at 2 g. When non-linear stiffening is used along with multimodal energy-harvesting, the obtained bandwidth increases from 23 Hz to 68 Hz with percentage increment of 295% at 1.8 g. Further, we have demonstrated the triboelectric output measured as acceleration sensing signals in terms of voltage and current sensitivity of 4.7 Vg(-1) and 19.7 nAg(-1), respectively.
Design and implementation of non-linear image processing functions for CMOS image sensor
NASA Astrophysics Data System (ADS)
Musa, Purnawarman; Sudiro, Sunny A.; Wibowo, Eri P.; Harmanto, Suryadi; Paindavoine, Michel
2012-11-01
Today, solid state image sensors are used in many applications like in mobile phones, video surveillance systems, embedded medical imaging and industrial vision systems. These image sensors require the integration in the focal plane (or near the focal plane) of complex image processing algorithms. Such devices must meet the constraints related to the quality of acquired images, speed and performance of embedded processing, as well as low power consumption. To achieve these objectives, low-level analog processing allows extracting the useful information in the scene directly. For example, edge detection step followed by a local maxima extraction will facilitate the high-level processing like objects pattern recognition in a visual scene. Our goal was to design an intelligent image sensor prototype achieving high-speed image acquisition and non-linear image processing (like local minima and maxima calculations). For this purpose, we present in this article the design and test of a 64×64 pixels image sensor built in a standard CMOS Technology 0.35 μm including non-linear image processing. The architecture of our sensor, named nLiRIC (non-Linear Rapid Image Capture), is based on the implementation of an analog Minima/Maxima Unit. This MMU calculates the minimum and maximum values (non-linear functions), in real time, in a 2×2 pixels neighbourhood. Each MMU needs 52 transistors and the pitch of one pixel is 40×40 mu m. The total area of the 64×64 pixels is 12.5mm2. Our tests have shown the validity of the main functions of our new image sensor like fast image acquisition (10K frames per second), minima/maxima calculations in less then one ms.
Agent based reasoning for the non-linear stochastic models of long-range memory
NASA Astrophysics Data System (ADS)
Kononovicius, A.; Gontis, V.
2012-02-01
We extend Kirman's model by introducing variable event time scale. The proposed flexible time scale is equivalent to the variable trading activity observed in financial markets. Stochastic version of the extended Kirman's agent based model is compared to the non-linear stochastic models of long-range memory in financial markets. The agent based model providing matching macroscopic description serves as a microscopic reasoning of the earlier proposed stochastic model exhibiting power law statistics.
A non-linear homogeneous model for bone-like materials under compressive load.
Mengoni, M; Voide, R; de Bien, C; Freichels, H; Jérôme, C; Léonard, A; Toye, D; Müller, R; van Lenthe, G H; Ponthot, J P
2012-02-01
Finite element (FE) models accurately compute the mechanical response of bone and bone-like materials when the models include their detailed microstructure. In order to simulate non-linear behavior, which currently is only feasible at the expense of extremely high computational costs, coarser models can be used if the local morphology has been linked to the apparent mechanical behavior. The aim of this paper is to implement and validate such a constitutive law. This law is able to capture the non-linear structural behavior of bone-like materials through the use of fabric tensors. It also allows for irreversible strains using an elastoplastic material model incorporating hardening. These features are expressed in a constitutive law based on the anisotropic continuum damage theory coupled with isotropic elastoplasticity in a finite strain framework. This material model was implemented into metafor (LTAS-MNNL, University of Liège, Belgium), a non-linear FE software. The implementation was validated against experimental data of cylindrical samples subjected to compression. Three materials with bone-like microstructure were tested: aluminum foams of variable density (ERG, Oakland, CA, USA), polylactic acid foam (CERM, University of Liège, Liège, Belgium), and cancellous bone tissue of a deer antler (Faculty of Veterinary Medicine, University of Liège, Liège, Belgium).
A review on non-linear aeroelasticity of high aspect-ratio wings
NASA Astrophysics Data System (ADS)
Afonso, Frederico; Vale, José; Oliveira, Éder; Lau, Fernando; Suleman, Afzal
2017-02-01
Current economic constraints and environmental regulations call for design of more efficient aircraft configurations. An observed trend in aircraft design to reduce the lift induced drag and improve fuel consumption and emissions is to increase the wing aspect-ratio. However, a slender wing is more flexible and subject to higher deflections under the same operating conditions. This effect may lead to changes in dynamic behaviour and in aeroelastic response, potentially resulting in instabilities. Therefore, it is important to take into account geometric non-linearities in the design of high aspect-ratio wings, as well as having accurate computational codes that couple the aerodynamic and structural models in the presence of non-linearities. Here, a review on the state-of-the-art on non-linear aeroelasticity of high aspect-ratio wings is presented. The methodologies employed to analyse high aspect-ratio wings are presented and their applications discussed. Important observations from the state-of-the-art studies are drawn and the current challenges in the field are identified.
NASA Astrophysics Data System (ADS)
Singh, Gajbir; Venkateswara Rao, G.; Iyengar, N. G. R.
1995-03-01
The influence of finite amplitudes on the free flexural vibration response of moderately thick laminated plates is investigated. For this purpose, a simple higher order theory involving only four unknowns and satisfying the stress free conditions at the top and bottom surface of the composite plate is proposed. The proposed theory eliminates the use of shear correction factors which are otherwise required in Mindlin's plate theory. A rectangular four-node[formula]continuous finite element is developed based on this theory. The non-linear finite element equations are reduced to two non-linear ordinary differential equations governing the response of positive and negative deflection cycles. Direct numerical integration method is then employed to obtain the periods or non-linear frequencies. The finite element developed and the direct numerical integration method employed are validated for the case of isotropic rectangular plates. It is found that unsymmetrically laminated rectangular plates with hinged-hinged edge conditions oscillate with different amplitudes in the positive and negative deflection cycles. Furthermore, such plates would oscillate with a frequency less than the fundamental frequency for finite small amplitudes of oscillation. It is shown that this behaviour is strongly influenced by the boundary conditions. Results are presented for many configurations of composite plates.
Localization of non-linearly modeled autonomous mobile robots using out-of-sequence measurements.
Besada-Portas, Eva; Lopez-Orozco, Jose A; Lanillos, Pablo; de la Cruz, Jesus M
2012-01-01
This paper presents a state of the art of the estimation algorithms dealing with Out-of-Sequence (OOS) measurements for non-linearly modeled systems. The state of the art includes a critical analysis of the algorithm properties that takes into account the applicability of these techniques to autonomous mobile robot navigation based on the fusion of the measurements provided, delayed and OOS, by multiple sensors. Besides, it shows a representative example of the use of one of the most computationally efficient approaches in the localization module of the control software of a real robot (which has non-linear dynamics, and linear and non-linear sensors) and compares its performance against other approaches. The simulated results obtained with the selected OOS algorithm shows the computational requirements that each sensor of the robot imposes to it. The real experiments show how the inclusion of the selected OOS algorithm in the control software lets the robot successfully navigate in spite of receiving many OOS measurements. Finally, the comparison highlights that not only is the selected OOS algorithm among the best performing ones of the comparison, but it also has the lowest computational and memory cost.
Localization of Non-Linearly Modeled Autonomous Mobile Robots Using Out-of-Sequence Measurements
Besada-Portas, Eva; Lopez-Orozco, Jose A.; Lanillos, Pablo; de la Cruz, Jesus M.
2012-01-01
This paper presents a state of the art of the estimation algorithms dealing with Out-of-Sequence (OOS) measurements for non-linearly modeled systems. The state of the art includes a critical analysis of the algorithm properties that takes into account the applicability of these techniques to autonomous mobile robot navigation based on the fusion of the measurements provided, delayed and OOS, by multiple sensors. Besides, it shows a representative example of the use of one of the most computationally efficient approaches in the localization module of the control software of a real robot (which has non-linear dynamics, and linear and non-linear sensors) and compares its performance against other approaches. The simulated results obtained with the selected OOS algorithm shows the computational requirements that each sensor of the robot imposes to it. The real experiments show how the inclusion of the selected OOS algorithm in the control software lets the robot successfully navigate in spite of receiving many OOS measurements. Finally, the comparison highlights that not only is the selected OOS algorithm among the best performing ones of the comparison, but it also has the lowest computational and memory cost. PMID:22736962
Non-linear direct effects of acid rain on leaf photosynthetic rate of terrestrial plants.
Dong, Dan; Du, Enzai; Sun, Zhengzhong; Zeng, Xuetong; de Vries, Wim
2017-09-12
Anthropogenic emissions of acid precursors have enhanced global occurrence of acid rain, especially in East Asia. Acid rain directly suppresses leaf function by eroding surface waxes and cuticle and leaching base cations from mesophyll cells, while the simultaneous foliar uptake of nitrates in rainwater may directly benefit leaf photosynthesis and plant growth, suggesting a non-linear direct effect of acid rain. By synthesizing data from literature on acid rain exposure experiments, we assessed the direct effects of acid rain on leaf photosynthesis across 49 terrestrial plants in China. Our results show a non-linear direct effect of acid rain on leaf photosynthetic rate, including a neutral to positive effect above pH 5.0 and a negative effect below that pH level. The acid rain sensitivity of leaf photosynthesis showed no significant difference between herbs and woody species below pH 5.0, but the impacts above that pH level were strongly different, resulting in a significant increase in leaf photosynthetic rate of woody species and an insignificant effect on herbs. Our analysis also indicates a positive effect of the molar ratio of nitric versus sulfuric acid in the acid solution on leaf photosynthetic rate. These findings imply that rainwater acidity and the composition of acids both affect the response of leaf photosynthesis and therefore result in a non-linear direct effect. Copyright © 2017 Elsevier Ltd. All rights reserved.
Non-linear partially massless symmetry in an SO(1,5) continuation of conformal gravity
NASA Astrophysics Data System (ADS)
Apolo, Luis; Hassan, S. F.
2017-05-01
We construct a non-linear theory of interacting spin-2 fields that is invariant under the partially massless (PM) symmetry to all orders. This theory is based on the SO(1, 5) group, in analogy with the SO(2, 4) formulation of conformal gravity, but has a quadratic spectrum free of ghost instabilities. The action contains a vector field associated with a local SO(2) symmetry which is manifest in the vielbein formulation of the theory. We show that, in a perturbative expansion, the SO(2) symmetry transmutes into the PM transformations of a massive spin-2 field. In this context, the vector field is crucial to circumvent earlier obstructions to an order-by-order construction of PM symmetry. Although the non-linear theory lacks enough first class constraints to remove all helicity-0 modes from the spectrum, the PM transformations survive to all orders. The absence of ghosts and strong coupling effects at the non-linear level are not addressed here.
Non-linear analysis and calculation of the performance of a shelving protection system by FEM
NASA Astrophysics Data System (ADS)
García Nieto, P. J.; del Coz Díaz, J. J.; Vilán Vilán, J. A.; Suárez Sierra, J. L.
2012-12-01
The aim of this paper consists on the study, analysis and calculation of the efficiency of a shelving protection system by means of the finite element method (FEM). These shelving protection systems are intended to prevent the eventual damage due to the impacts of transport elements in motion, such as: forklifts, dumpers, hand pallet trucks, and so on. The impact loads may threaten the structural integrity of the shelving system. The present structural problem is highly non-linear, due to the simultaneous presence of the following nonlinearities: material non-linearity (plasticity in this case), geometrical non-linearity (large displacements) and contact-type boundary conditions (between the rigid body and the protection system). A total of forty eight different FEM models are built varying the thickness of the steel plate (4, 5 and 6 mm), the impact height (0.1, 0.2, 0.3 and 0.4 meters) and the impact direction (head-on collision and side impact). Once the models are solved, the stress distribution, the overall displacements and the absorbed impact energy were calculated. In order to determine the best shelving protection's candidate, some constraints must be taken into account: the maximum allowable stress (235 MPa), the maximum displacement (0.05 m) and the absorbed impact energy (400 J according to the European Standard Rule PREN-15512). Finally, the most important results are shown and conclusions of this study are exposed.
The non-linear coupled spin 2-spin 3 Cotton equation in three dimensions
NASA Astrophysics Data System (ADS)
Linander, Hampus; Nilsson, Bengt E. W.
2016-07-01
In the context of three-dimensional conformal higher spin theory we derive, in the frame field formulation, the full non-linear spin 3 Cotton equation coupled to spin 2. This is done by solving the corresponding Chern-Simons gauge theory system of equations, that is, using F = 0 to eliminate all auxiliary fields and thus expressing the Cotton equation in terms of just the spin 3 frame field and spin 2 covariant derivatives and tensors (Schouten). In this derivation we neglect the spin 4 and higher spin sectors and approximate the star product commutator by a Poisson bracket. The resulting spin 3 Cotton equation is complicated but can be related to linearized versions in the metric formulation obtained previously by other authors. The expected symmetry (spin 3 "translation", "Lorentz" and "dilatation") properties are verified for Cotton and other relevant tensors but some perhaps unexpected features emerge in the process, in particular in relation to the non-linear equations. We discuss the structure of this non-linear spin 3 Cotton equation but its explicit form is only presented here, in an exact but not completely refined version, in appended files obtained by computer algebra methods. Both the frame field and metric formulations are provided.
Impact of quadratic non-linearity on the dynamics of periodic solutions of a wave equation
NASA Astrophysics Data System (ADS)
Kolesov, Andrei Yu; Rozov, Nikolai Kh
2002-02-01
For the non-linear telegraph equation with homogeneous Dirichlet or Neumann conditions at the end-points of a finite interval the question of the existence and the stability of time-periodic solutions bifurcating from the zero equilibrium state is considered. The dynamics of these solutions under a change of the diffusion coefficient (that is, the coefficient of the second derivative with respect to the space variable) is investigated. For the Dirichlet boundary conditions it is shown that this dynamics substantially depends on the presence - or the absence - of quadratic terms in the non-linearity. More precisely, it is shown that a quadratic non-linearity results in the occurrence, under an unbounded decrease of diffusion, of an infinite sequence of bifurcations of each periodic solution. En route, the related issue of the limits of applicability of Yu.S. Kolesov's method of quasinormal forms to the construction of self-oscillations in singularly perturbed hyperbolic boundary value problems is studied.
Impact of quadratic non-linearity on the dynamics of periodic solutions of a wave equation
Kolesov, Andrei Yu; Rozov, Nikolai Kh
2002-02-28
For the non-linear telegraph equation with homogeneous Dirichlet or Neumann conditions at the end-points of a finite interval the question of the existence and the stability of time-periodic solutions bifurcating from the zero equilibrium state is considered. The dynamics of these solutions under a change of the diffusion coefficient (that is, the coefficient of the second derivative with respect to the space variable) is investigated. For the Dirichlet boundary conditions it is shown that this dynamics substantially depends on the presence - or the absence - of quadratic terms in the non-linearity. More precisely, it is shown that a quadratic non-linearity results in the occurrence, under an unbounded decrease of diffusion, of an infinite sequence of bifurcations of each periodic solution. En route, the related issue of the limits of applicability of Yu.S. Kolesov's method of quasinormal forms to the construction of self-oscillations in singularly perturbed hyperbolic boundary value problems is studied.
A non-linear Granger-causality framework to investigate climate-vegetation dynamics
NASA Astrophysics Data System (ADS)
Papagiannopoulou, Christina; Miralles, Diego G.; Decubber, Stijn; Demuzere, Matthias; Verhoest, Niko E. C.; Dorigo, Wouter A.; Waegeman, Willem
2017-05-01
Satellite Earth observation has led to the creation of global climate data records of many important environmental and climatic variables. These come in the form of multivariate time series with different spatial and temporal resolutions. Data of this kind provide new means to further unravel the influence of climate on vegetation dynamics. However, as advocated in this article, commonly used statistical methods are often too simplistic to represent complex climate-vegetation relationships due to linearity assumptions. Therefore, as an extension of linear Granger-causality analysis, we present a novel non-linear framework consisting of several components, such as data collection from various databases, time series decomposition techniques, feature construction methods, and predictive modelling by means of random forests. Experimental results on global data sets indicate that, with this framework, it is possible to detect non-linear patterns that are much less visible with traditional Granger-causality methods. In addition, we discuss extensive experimental results that highlight the importance of considering non-linear aspects of climate-vegetation dynamics.
Least squares reconstruction of non-linear RF phase encoded MR data.
Salajeghe, Somaie; Babyn, Paul; Sharp, Jonathan C; Sarty, Gordon E
2016-09-01
The numerical feasibility of reconstructing MRI signals generated by RF coils that produce B1 fields with a non-linearly varying spatial phase is explored. A global linear spatial phase variation of B1 is difficult to produce from current confined to RF coils. Here we use regularized least squares inversion, in place of the usual Fourier transform, to reconstruct signals generated in B1 fields with non-linear phase variation. RF encoded signals were simulated for three RF coil configurations: ideal linear, parallel conductors and, circular coil pairs. The simulated signals were reconstructed by Fourier transform and by regularized least squares. The Fourier reconstruction of simulated RF encoded signals from the parallel conductor coil set showed minor distortions over the reconstruction of signals from the ideal linear coil set but the Fourier reconstruction of signals from the circular coil set produced severe geometric distortion. Least squares inversion in all cases produced reconstruction errors comparable to the Fourier reconstruction of the simulated signal from the ideal linear coil set. MRI signals encoded in B1 fields with non-linearly varying spatial phase may be accurately reconstructed using regularized least squares thus pointing the way to the use of simple RF coil designs for RF encoded MRI. Crown Copyright © 2016. Published by Elsevier Inc. All rights reserved.
Stochastic non-linear oscillator models of EEG: the Alzheimer's disease case.
Ghorbanian, Parham; Ramakrishnan, Subramanian; Ashrafiuon, Hashem
2015-01-01
In this article, the Electroencephalography (EEG) signal of the human brain is modeled as the output of stochastic non-linear coupled oscillator networks. It is shown that EEG signals recorded under different brain states in healthy as well as Alzheimer's disease (AD) patients may be understood as distinct, statistically significant realizations of the model. EEG signals recorded during resting eyes-open (EO) and eyes-closed (EC) resting conditions in a pilot study with AD patients and age-matched healthy control subjects (CTL) are employed. An optimization scheme is then utilized to match the output of the stochastic Duffing-van der Pol double oscillator network with EEG signals recorded during each condition for AD and CTL subjects by selecting the model physical parameters and noise intensity. The selected signal characteristics are power spectral densities in major brain frequency bands Shannon and sample entropies. These measures allow matching of linear time varying frequency content as well as non-linear signal information content and complexity. The main finding of the work is that statistically significant unique models represent the EC and EO conditions for both CTL and AD subjects. However, it is also shown that the inclusion of sample entropy in the optimization process, to match the complexity of the EEG signal, enhances the stochastic non-linear oscillator model performance.
Shock formation and non-linear dispersion in a microvascular capillary network.
Pop, S R; Richardson, G; Waters, S L; Jensen, O E
2007-12-01
Temporal and spatial fluctuations are a common feature of blood flow in microvascular networks. Among many possible causes, previous authors have suggested that the non-linear rheological properties of capillary blood flow (notably the Fåhraeus effect, the Fåhraeus-Lindqvist effect and the phase-separation effect at bifurcations) may be sufficient to generate temporal fluctuations even in very simple networks. We have simulated blood flow driven by a fixed pressure drop through a simple arcade network using coupled hyperbolic partial differential equations (PDEs) that incorporate well-established empirical descriptions of these rheological effects, accounting in particular for spatially varying haematocrit distributions; we solved the PDE system using a characteristic-based method. Our computations indicate that, under physiologically realistic conditions, there is a unique steady flow in an arcade network which is linearly stable and that plasma skimming suppresses the oscillatory decay of perturbations. In addition, we find that non-linear perturbations to haematocrit distributions can develop shocks via the Fåhraeus effect, providing a novel mechanism for non-linear dispersion in microvascular networks.
Overgaard, Rune V; Jonsson, Niclas; Tornøe, Christoffer W; Madsen, Henrik
2005-02-01
Pharmacokinetic/pharmacodynamic modelling is most often performed using non-linear mixed-effects models based on ordinary differential equations with uncorrelated intra-individual residuals. More sophisticated residual error models as e.g. stochastic differential equations (SDEs) with measurement noise can in many cases provide a better description of the variations, which could be useful in various aspects of modelling. This general approach enables a decomposition of the intra-individual residual variation epsilon into system noise w and measurement noise e. The present work describes implementation of SDEs in a non-linear mixed-effects model, where parameter estimation was performed by a novel approximation of the likelihood function. This approximation is constructed by combining the First-Order Conditional Estimation (FOCE) method used in non-linear mixed-effects modelling with the Extended Kalman Filter used in models with SDEs. Fundamental issues concerning the proposed model and estimation algorithm are addressed by simulation studies, concluding that system noise can successfully be separated from measurement noise and inter-individual variability.
Spherical collapse, formation hysteresis and the deeply non-linear cosmological power spectrum
NASA Astrophysics Data System (ADS)
Mead, A. J.
2017-01-01
I examine differences in non-linear structure formation between cosmological models that share a z = 0 linear power spectrum in both shape and amplitude, but that differ via their growth history. N-body simulations of these models display an approximately identical large-scale-structure skeleton, but reveal deeply non-linear differences in the demographics and properties of haloes. I investigate to what extent the spherical-collapse model can help in understanding these differences, in both real and redshift space. I discuss how this is difficult to do if one attempts to identify haloes directly, because in that case one is subject to the vagaries of halo-finding algorithms. However, I demonstrate that the halo model of structure formation provides an accurate non-linear response in the power spectrum, but only if results from spherical collapse that include formation hysteresis are properly incorporated. I comment on how this fact can be used to provide per cent level accurate matter power-spectrum predictions for dark energy models for k ≤ 5 h Mpc-1 by using the halo model as a correction to accurate ΛCDM simulations. In the Appendix, I provide some fitting functions for the linear-collapse threshold (δc) and virialized overdensity (Δv) that are valid for a wide range of dark energy models. I also make my spherical-collapse code available at https://github.com/alexander-mead/collapse.
Relativistic weak lensing from a fully non-linear cosmological density field
Thomas, D.B.; Bruni, M.; Wands, D. E-mail: marco.bruni@port.ac.uk
2015-09-01
In this paper we examine cosmological weak lensing on non-linear scales and show that there are Newtonian and relativistic contributions and that the latter can also be extracted from standard Newtonian simulations. We use the post-Friedmann formalism, a post-Newtonian type framework for cosmology, to derive the full weak-lensing deflection angle valid on non-linear scales for any metric theory of gravity. We show that the only contributing term that is quadratic in the first order deflection is the expected Born correction and lens-lens coupling term. We use this deflection angle to analyse the vector and tensor contributions to the E- and B- mode cosmic shear power spectra. In our approach, once the gravitational theory has been specified, the metric components are related to the matter content in a well-defined manner. Specifying General Relativity, we write down a complete set of equations for a GR+ΛCDM universe for computing all of the possible lensing terms from Newtonian N-body simulations. We illustrate this with the vector potential and show that, in a GR+ΛCDM universe, its contribution to the E-mode is negligible with respect to that of the conventional Newtonian scalar potential, even on non-linear scales. Thus, under the standard assumption that Newtonian N-body simulations give a good approximation of the matter dynamics, we show that the standard ray tracing approach gives a good description for a ΛCDM cosmology.
Mayorga, René V; Arriaga, Mariano
2007-10-01
In this article, a novel technique for non-linear global optimization is presented. The main goal is to find the optimal global solution of non-linear problems avoiding sub-optimal local solutions or inflection points. The proposed technique is based on a two steps concept: properly keep decreasing the value of the objective function, and calculating the corresponding independent variables by approximating its inverse function. The decreasing process can continue even after reaching local minima and, in general, the algorithm stops when converging to solutions near the global minimum. The implementation of the proposed technique by conventional numerical methods may require a considerable computational effort on the approximation of the inverse function. Thus, here a novel Artificial Neural Network (ANN) approach is implemented to reduce the computational requirements of the proposed optimization technique. This approach is successfully tested on some highly non-linear functions possessing several local minima. The results obtained demonstrate that the proposed approach compares favorably over some current conventional numerical (Matlab functions) methods, and other non-conventional (Evolutionary Algorithms, Simulated Annealing) optimization methods.
An evaluation of bias in propensity score-adjusted non-linear regression models.
Wan, Fei; Mitra, Nandita
2016-04-19
Propensity score methods are commonly used to adjust for observed confounding when estimating the conditional treatment effect in observational studies. One popular method, covariate adjustment of the propensity score in a regression model, has been empirically shown to be biased in non-linear models. However, no compelling underlying theoretical reason has been presented. We propose a new framework to investigate bias and consistency of propensity score-adjusted treatment effects in non-linear models that uses a simple geometric approach to forge a link between the consistency of the propensity score estimator and the collapsibility of non-linear models. Under this framework, we demonstrate that adjustment of the propensity score in an outcome model results in the decomposition of observed covariates into the propensity score and a remainder term. Omission of this remainder term from a non-collapsible regression model leads to biased estimates of the conditional odds ratio and conditional hazard ratio, but not for the conditional rate ratio. We further show, via simulation studies, that the bias in these propensity score-adjusted estimators increases with larger treatment effect size, larger covariate effects, and increasing dissimilarity between the coefficients of the covariates in the treatment model versus the outcome model.
NASA Astrophysics Data System (ADS)
Zhang, Ruikun; Hou, Zhongsheng; Ji, Honghai; Yin, Chenkun
2016-04-01
In this paper, an adaptive iterative learning control scheme is proposed for a class of non-linearly parameterised systems with unknown time-varying parameters and input saturations. By incorporating a saturation function, a new iterative learning control mechanism is presented which includes a feedback term and a parameter updating term. Through the use of parameter separation technique, the non-linear parameters are separated from the non-linear function and then a saturated difference updating law is designed in iteration domain by combining the unknown parametric term of the local Lipschitz continuous function and the unknown time-varying gain into an unknown time-varying function. The analysis of convergence is based on a time-weighted Lyapunov-Krasovskii-like composite energy function which consists of time-weighted input, state and parameter estimation information. The proposed learning control mechanism warrants a L2[0, T] convergence of the tracking error sequence along the iteration axis. Simulation results are provided to illustrate the effectiveness of the adaptive iterative learning control scheme.
Tewarie, P.; Bright, M.G.; Hillebrand, A.; Robson, S.E.; Gascoyne, L.E.; Morris, P.G.; Meier, J.; Van Mieghem, P.; Brookes, M.J.
2016-01-01
Understanding the electrophysiological basis of resting state networks (RSNs) in the human brain is a critical step towards elucidating how inter-areal connectivity supports healthy brain function. In recent years, the relationship between RSNs (typically measured using haemodynamic signals) and electrophysiology has been explored using functional Magnetic Resonance Imaging (fMRI) and magnetoencephalography (MEG). Significant progress has been made, with similar spatial structure observable in both modalities. However, there is a pressing need to understand this relationship beyond simple visual similarity of RSN patterns. Here, we introduce a mathematical model to predict fMRI-based RSNs using MEG. Our unique model, based upon a multivariate Taylor series, incorporates both phase and amplitude based MEG connectivity metrics, as well as linear and non-linear interactions within and between neural oscillations measured in multiple frequency bands. We show that including non-linear interactions, multiple frequency bands and cross-frequency terms significantly improves fMRI network prediction. This shows that fMRI connectivity is not only the result of direct electrophysiological connections, but is also driven by the overlap of connectivity profiles between separate regions. Our results indicate that a complete understanding of the electrophysiological basis of RSNs goes beyond simple frequency-specific analysis, and further exploration of non-linear and cross-frequency interactions will shed new light on distributed network connectivity, and its perturbation in pathology. PMID:26827811
Are non-linearity effects of absorption important for MAX-DOAS observations?
NASA Astrophysics Data System (ADS)
Pukite, Janis; Wang, Yang; Wagner, Thomas
2017-04-01
For scattered light observations the absorption optical depth depends non-linearly on the trace gas concentrations if their absorption is strong. This is the case because the Beer-Lambert law is generally not applicable for scattered light measurements due to many (i.e. more than one) light paths contributing to the measurement. While in many cases a linear approximation can be made, for scenarios with strong absorption non-linear effects cannot always be neglected. This is especially the case for observation geometries with spatially extended and diffuse light paths, especially in satellite limb geometry but also for nadir measurements as well. Fortunately the effects of non-linear effects can be quantified by means of expanding the radiative transfer equation in a Taylor series with respect to the trace gas absorption coefficients. Herewith if necessary (1) the higher order absorption structures can be described as separate fit parameters in the DOAS fit and (2) the algorithm constraints of retrievals of VCDs and profiles can be improved by considering higher order sensitivity parameters. In this study we investigate the contribution of the higher order absorption structures for MAX-DOAS observation geometry for different atmospheric and ground properties (cloud and aerosol effects, trace gas amount, albedo) and geometry (different Sun and viewing angles).
Sensitivity of wavepackets in jets to non-linear effects: the role of the critical layer
NASA Astrophysics Data System (ADS)
Tissot, Gilles; Zhang, Mengqi; Lajús, Francisco C., Jr.; Cavalieri, André V. G.; Jordan, Peter; Colonius, Tim
2015-11-01
Linear instability waves, or wavepackets, are key building blocks for the jet-noise problem. It has been shown in previous work that linear models correctly predict the evolution of axisymmetric wavepackets up to the end of the potential core of subsonic turbulent jets. Beyond this station linear models fail, and non-linearity is the likely missing piece. The essential underlying nonlinear mechanisms are unknown, and it remains unclear how these should be incorporated in a reduced-order model. The non-linear interactions are considered in this work as an ``external'' harmonic forcing added to the standard linear model. This modelling framework is explored using three complementary problems: a direct forcing, a resolvant analysis and a 4D-Var data assimilation approach. In all of the problems considered, the critical layer is found to be relevant: it is the position where the sensitivity of the linear waves to non-linearity is greatest. Furthermore, forced perturbations are tilted by shear, in a manner that suggests an Orr-like mechanism. The ensemble of results suggest that the critical layer may play a central role in the modelling of wavepackets in subsonic turbulent jets, and indeed may be the key to remedying the shortcomings of linear reduced-order models.
Differential diagnosis of breast lesions by use of biomagnetic activity and non-linear analysis.
Anninos, P A; Kotini, A; Koutlaki, N; Adamopoulos, A; Galazios, G; Anastasiadis, P
2000-01-01
Breast cancer mortality rates have not changed during the past 60 years despite significant advances in screening methods. It is tempting therefore to use novel technology in order to better understand breast oncology. In this study we investigated the biomagnetic activity obtained in benign and malignant breast lesions using a single channel biomagnetometer SQUID (Superconducting Quantum Interference Device) in order to assess the method's efficacy in the differential diagnosis of these two types of lesions and its establishment as a screening technique. Magnetic recordings were obtained from 21 patients with palpable breast lumps. Of these 11 were invasive carcinomas and 10 were benign breast lesions. We used non-linear analysis to investigate whether there is any biological differentiation in the dynamics in these two types of lesions. High amplitudes characterized the waveform of a malignant breast lesion whereas in benign breast lesions the corresponding amplitudes were low. Using the application of non-linear analysis we observed a clear saturation value for the dimension of malignant breast lesions and no saturation for benign ones. Biomagnetic measurements with the SQUID and the application of non-linear analysis are promising procedures in assessing and differentiating breast tumors.
Non-linear dynamic analysis of a flexible rotor supported on porous oil journal bearings
NASA Astrophysics Data System (ADS)
Laha, S. K.; Kakoty, S. K.
2011-03-01
In the present paper, the non-linear dynamic analysis of a flexible rotor with a rigid disk under unbalance excitation mounted on porous oil journal bearings at the two ends is carried out. The system equation of motion is obtained by finite element formulation of Timoshenko beam and the disk. The non-linear oil-film forces are calculated from the solution of the modified Reynolds equation simultaneously with Darcy's equation. The system equation of motion is then solved by the Wilson- θ method. Bifurcation diagrams, Poincaré maps, time response, journal trajectories, FFT-spectrum, etc. are obtained to study the non-linear dynamics of the rotor-bearing system. The effect of various non-dimensional rotor-bearing parameters on the bifurcation characteristics of the system is studied. It is shown that the system undergoes Hopf bifurcation as the speed increases. Further, slenderness ratio, material properties of the rotor, ratio of disk mass to shaft mass and permeability of the porous bush are shown to have profound effect on the bifurcation characteristics of the rotor-bearing system.
PWFSs on GMCAO: a different approach to the non-linearity issue
NASA Astrophysics Data System (ADS)
Viotto, Valentina; Bergomi, Maria; Dima, Marco; Farinato, Jacopo; Greggio, Davide; Magrin, Demetrio; Portaluri, Elisa; Ragazzoni, Roberto; Esposito, Simone; Pinna, Enrico
2016-07-01
In the last years, the Pyramid WFS finally proved itself to be a very powerful tool for wavefront retrieval, in different applications, inside and outside Astronomy, often showing outstanding results. However, being intrinsically a non-linear WFS, the P-WFS non-linearity error starts to play a role when the AO loop is not closed on the sensor zero-WFE point. This led to the need to elaborate new concepts when trying to apply the P-WFS to open (or partially open) loop based techniques, not to trade sensitivity for linearity. This was the case for GMCAO, in which the reference stars are selected on a wide technical area of the sky, outside the FoV to be optimized, limiting the correction experienced by the WFSs to poor Strehl Ratio regime. While, in the recent past, we proposed a solution based on the Very Linear WFS, a sub-system that locally closes the loop on the Pyramid pin to let the sensor operate in its best regime, we now explore a different approach in which the P-WFS non-linearity is continuously measured, injecting a known aberration onto the sensor. In particular, we evaluate in this paper the possibility to apply basic PWFSs to the GMCAO technique, measuring the nonlinearity of the sensor and taking it into account in the wavefront computation, with an approach similar to what already proposed in the LBT AO facility FLAO for the non-common path aberrations correction.
The non-linear analysis of multi-support rotor-bearing systems
Kicinski, J.; Drozdowski, R.
1995-12-31
This paper contains selected parts of the simulation research of large rotor machines (200 MW power turbine-sets). These investigations were based on a non-linear theoretical model and the NLDW computer program, and were carried out in the Institute of Fluid-Flow Machinery of PAS. A trial has been performed of the optimization of system-dynamic properties, through the suitable selection of thermally deformed bearing-bush centers line -- the so called ``hot`` line -- (due to a rotor`s geodesic line), as well as the selection of the external fixing stiffness of bearing supports. Examples are also included of the orbits of selected system nodes for two differently powered turbine-sets. On this basis, an analysis of the stability of those turbines was achieved. A significant objective of this paper is also to point out some possibilities of applying the simulation research, based on a non-linear description of the system, to the diagnostics of rotor-machinery. Non-linear analysis facilitates the possibility of easily generating vibration spectra, as well as creating simulation waterfall graphs. These properties of nonlinear analysis create convenient conditions for gaining specific diagnostic information.
a Frequency Domain Based NUMERIC-ANALYTICAL Method for Non-Linear Dynamical Systems
NASA Astrophysics Data System (ADS)
Narayanan, S.; Sekar, P.
1998-04-01
In this paper a multiharmonic balancing technique is used to develop certain algorithms to determine periodic orbits of non-liner dynamical systems with external, parametric and self excitations. Essentially, in this method the non-linear differential equations are transformed into a set of non-linear algebraic equations in terms of the Fourier coefficients of the periodic solutions which are solved by using the Newton-Raphson technique. The method is developed such that both fast Fourier transform and discrete Fourier transform algorithms can be used. It is capable of treating all types of non-linearities and higher dimensional systems. The stability of periodic orbits is investigated by obtaining the monodromy matrix. A path following algorithm based on the predictor-corrector method is also presented to enable the bifurcation analysis. The prediction is done with a cubic extrapolation technique with an arc length incrementation while the correction is done with the use of the least square minimisation technique. The under determined system of equations is solved by singular value decomposition. The suitability of the method is demonstrated by obtaining the bifurcational behaviour of rolling contact vibrations modelled by Hertz contact law.
Noury, Nima; Hipp, Joerg F; Siegel, Markus
2016-10-15
Transcranial electric stimulation (tES) is a promising tool to non-invasively manipulate neuronal activity in the human brain. Several studies have shown behavioral effects of tES, but stimulation artifacts complicate the simultaneous investigation of neural activity with EEG or MEG. Here, we first show for EEG and MEG, that contrary to previous assumptions, artifacts do not simply reflect stimulation currents, but that heartbeat and respiration non-linearly modulate stimulation artifacts. These modulations occur irrespective of the stimulation frequency, i.e. during both transcranial alternating and direct current stimulations (tACS and tDCS). Second, we show that, although at first sight previously employed artifact rejection methods may seem to remove artifacts, data are still contaminated by non-linear stimulation artifacts. Because of their complex nature and dependence on the subjects' physiological state, these artifacts are prone to be mistaken as neural entrainment. In sum, our results uncover non-linear tES artifacts, show that current techniques fail to fully remove them, and pave the way for new artifact rejection methods.
Schwab, Matthias; Schmidt, Karin; Roedel, Marcus; Mueller, Thomas; Schubert, Harald; Anwar, M Akthar; Nathanielsz, Peter W
2001-01-01
We determined the effects of betamethasone on the fetal sheep electrocorticogram (ECoG) using linear (power spectral) and non-linear analysis. For non-linear analysis we used an algorithm based on the Wolf algorithm for the estimation of the leading Lyapunov exponent which calculates a prediction error based on the course of the time series in the phase space. A high prediction error stands for low predictibility or low regularity and vice versa. After 48 h of baseline recordings, vehicle (n = 6) or betamethasone (n = 7) at 10 μg h−1 was infused over 48 h to the sheep fetus at 128 days gestational age (0.87 of gestation). ECoG spectral analysis revealed no difference in power spectrum between vehicle- and betamethasone-treated fetuses. The prediction error of the ECoG during REM sleep was higher than during non-REM or quiet sleep in both groups (P < 0.0001) revealing lower causality of brain activity during REM sleep. During REM sleep, prediction error significantly decreased 18-24 h after onset of betamethasone treatment (P < 0.05) and returned to baseline values within the following 24 h of continued betamethasone treatment. No ECoG changes were found during quiet sleep. Non-linear ECoG changes during metabolically active REM sleep accompanied the previously described decrease in cerebral blood flow. These results suggest that betamethasone in doses used in perinatal medicine acutely alters complex neuronal activity. PMID:11230525
An effective description of dark matter and dark energy in the mildly non-linear regime
Lewandowski, Matthew; Maleknejad, Azadeh; Senatore, Leonardo
2017-05-18
In the next few years, we are going to probe the low-redshift universe with unprecedented accuracy. Among the various fruits that this will bear, it will greatly improve our knowledge of the dynamics of dark energy, though for this there is a strong theoretical preference for a cosmological constant. We assume that dark energy is described by the so-called Effective Field Theory of Dark Energy, which assumes that dark energy is the Goldstone boson of time translations. Such a formalism makes it easy to ensure that our signatures are consistent with well-established principles of physics. Since most of the informationmore » resides at high wavenumbers, it is important to be able to make predictions at the highest wavenumber that is possible. Furthermore, the Effective Field Theory of Large-Scale Structure (EFTofLSS) is a theoretical framework that has allowed us to make accurate predictions in the mildly non-linear regime. In this paper, we derive the non-linear equations that extend the EFTofLSS to include the effect of dark energy both on the matter fields and on the biased tracers. For the specific case of clustering quintessence, we then perturbatively solve to cubic order the resulting non-linear equations and construct the one-loop power spectrum of the total density contrast.« less
Stochastic non-linear oscillator models of EEG: the Alzheimer's disease case
Ghorbanian, Parham; Ramakrishnan, Subramanian; Ashrafiuon, Hashem
2015-01-01
In this article, the Electroencephalography (EEG) signal of the human brain is modeled as the output of stochastic non-linear coupled oscillator networks. It is shown that EEG signals recorded under different brain states in healthy as well as Alzheimer's disease (AD) patients may be understood as distinct, statistically significant realizations of the model. EEG signals recorded during resting eyes-open (EO) and eyes-closed (EC) resting conditions in a pilot study with AD patients and age-matched healthy control subjects (CTL) are employed. An optimization scheme is then utilized to match the output of the stochastic Duffing—van der Pol double oscillator network with EEG signals recorded during each condition for AD and CTL subjects by selecting the model physical parameters and noise intensity. The selected signal characteristics are power spectral densities in major brain frequency bands Shannon and sample entropies. These measures allow matching of linear time varying frequency content as well as non-linear signal information content and complexity. The main finding of the work is that statistically significant unique models represent the EC and EO conditions for both CTL and AD subjects. However, it is also shown that the inclusion of sample entropy in the optimization process, to match the complexity of the EEG signal, enhances the stochastic non-linear oscillator model performance. PMID:25964756
A Comparison of PDE-based Non-Linear Anisotropic Diffusion Techniques for Image Denoising
Weeratunga, S K; Kamath, C
2003-01-06
PDE-based, non-linear diffusion techniques are an effective way to denoise images. In a previous study, we investigated the effects of different parameters in the implementation of isotropic, non-linear diffusion. Using synthetic and real images, we showed that for images corrupted with additive Gaussian noise, such methods are quite effective, leading to lower mean-squared-error values in comparison with spatial filters and wavelet-based approaches. In this paper, we extend this work to include anisotropic diffusion, where the diffusivity is a tensor valued function which can be adapted to local edge orientation. This allows smoothing along the edges, but not perpendicular to it. We consider several anisotropic diffusivity functions as well as approaches for discretizing the diffusion operator that minimize the mesh orientation effects. We investigate how these tensor-valued diffusivity functions compare in image quality, ease of use, and computational costs relative to simple spatial filters, the more complex bilateral filters, wavelet-based methods, and isotropic non-linear diffusion based techniques.
Comparison of PDE-based non-linear anistropic diffusion techniques for image denoising
NASA Astrophysics Data System (ADS)
Weeratunga, Sisira K.; Kamath, Chandrika
2003-05-01
PDE-based, non-linear diffusion techniques are an effective way to denoise images.In a previous study, we investigated the effects of different parameters in the implementation of isotropic, non-linear diffusion. Using synthetic and real images, we showed that for images corrupted with additive Gaussian noise, such methods are quite effective, leading to lower mean-squared-error values in comparison with spatial filters and wavelet-based approaches. In this paper, we extend this work to include anisotropic diffusion, where the diffusivity is a tensor valued function which can be adapted to local edge orientation. This allows smoothing along the edges, but not perpendicular to it. We consider several anisotropic diffusivity functions as well as approaches for discretizing the diffusion operator that minimize the mesh orientation effects. We investigate how these tensor-valued diffusivity functions compare in image quality, ease of use, and computational costs relative to simple spatial filters, the more complex bilateral filters, wavelet-based methods, and isotropic non-linear diffusion based techniques.
Non-linear magnetization effects within the Kosterlitz-Thouless theory
NASA Astrophysics Data System (ADS)
Benfatto, Lara; Castellani, Claudio; Giamarchi, Thierry
2008-03-01
Recent experiments in cuprate superconductors have attracted the attention on the role of vortex fluctuations. Measurements of the field-induced magnetization showed that the correlation length diverge exponentially, as predicted within the Kosterlitz-Thouless (KT) theory. However, it is somehow puzzling thepersistence of strong non-linear magnetization effects at low field. Here we address this issue by means of a new theoretical approach to the KT transition at finite magnetic field, based on the sine-Gordon model. This approach is particularly useful in two respects. First, it leads to a straightforward definition of the field-induced magnetization as a function of the external magnetic field H instead of the magnetic induction B, which is crucial to get a consistent description of the Meissner phase. Second, it allows us to identify the cross-over field Hcr from linear to non-linear magnetization both below and above the transition. Above TKT Hcr turns out to scale as the inverse correlation length, so that it decreases as the transition is approached. As a consequence, the fact that only the non-linear regime is accessible experimentally should be interpreted as a typical signature of the fast divergence of the correlation length within the KT theory. L.Benfatto, C.Castellani and T.Giamarchi, Phys. Rev. Lett. 99, 207002 (2007)
Non-linear dynamics of a one-way clutch in belt-pulley systems
NASA Astrophysics Data System (ADS)
Zhu, Farong; Parker, R. G.
2005-01-01
One-way clutches are frequently used in the serpentine belt accessory drives of automobiles and heavy vehicles. The clutch plays a role similar to a vibration absorber in order to reduce belt/pulley vibration and noise and increase belt life. This paper analyzes a two-pulley system where the driven pulley has a one-way clutch between the pulley and accessory shaft that engages only for positive relative displacement between these components. The belt is modelled with linear springs that transmit torque from the driving pulley to the accessory pulley. The one-way clutch is modelled as a piecewise linear spring with discontinuous stiffness that separates the driven pulley into two degrees of freedom. The harmonic balance method combined with arclength continuation is employed to illustrate the non-linear dynamic behavior of the one-way clutch and determine the stable and unstable periodic solutions for given parameters. The results are confirmed by numerical integration and the bifurcation software AUTO. At the first primary resonance, most of the responses are aperiodic, including quasiperiodic and chaotic solutions. At the second primary resonance, the peak bends to the left with classical softening non-linearity because clutch disengagement decouples the pulley and the accessory over portions of the response period. The dependence on clutch stiffness, excitation amplitude, and inertia ratio between the pulley and accessory is studied to characterize the non-linear dynamics across a range of conditions.
NASA Astrophysics Data System (ADS)
Danielli, Amos; Maslov, Konstantin; Xia, Jun; Wang, Lihong V.
2012-02-01
Photoacoustic microscopy (PAM) has been shown to be a valuable tool for quantifying hemoglobin oxygenation within single vessels. Recently, optical-resolution PAM was developed to achieve higher resolution by reducing the laser beam diameter, which increased the light intensity. As intensity increases, saturation of the optical absorption and multiphoton/ multi-step absorption can occur, which, together with the temperature dependence of thermal expansion, result in a non-linear dependence of the photoacoustic signal on the excitation pulse fluence. For hemoglobin, the major absorber in tissue for photoacoustic imaging, these non-linear phenomena have strong wavelength dependence. To enable quantitative photoacoustic measurements at different wavelengths in the presence of nonlinearity, a careful wide range analysis of the intensity-dependent absorption is required. Here, we built a photoacoustic spectrometer, using a tunable nanosecond optical parametric oscillator that operates between 410 nm and 2400 nm as our light source. To reduce uncertainty in our measurements due to inhomogeneous spatial distribution of the optical fluence, we used a flat-top beam illumination and a flat transducer which was mounted in reflection mode, effectively reducing quantitative measurements to a one dimensional problem. Intensity-dependent non-linear spectra of the photoacoustic signals of oxyand deoxy-hemoglobin were obtained. These measurements have the potential to contribute significantly to quantitative functional PAM.
Multiphysics modeling of non-linear laser-matter interactions for optically active semiconductors
NASA Astrophysics Data System (ADS)
Kraczek, Brent; Kanp, Jaroslaw
Development of photonic devices for sensors and communications devices has been significantly enhanced by computational modeling. We present a new computational method for modelling laser propagation in optically-active semiconductors within the paraxial wave approximation (PWA). Light propagation is modeled using the Streamline-upwind/Petrov-Galerkin finite element method (FEM). Material response enters through the non-linear polarization, which serves as the right-hand side of the FEM calculation. Maxwell's equations for classical light propagation within the PWA can be written solely in terms of the electric field, producing a wave equation that is a form of the advection-diffusion-reaction equations (ADREs). This allows adaptation of the computational machinery developed for solving ADREs in fluid dynamics to light-propagation modeling. The non-linear polarization is incorporated using a flexible framework to enable the use of multiple methods for carrier-carrier interactions (e.g. relaxation-time-based or Monte Carlo) to enter through the non-linear polarization, as appropriate to the material type. We demonstrate using a simple carrier-carrier model approximating the response of GaN. Supported by ARL Materials Enterprise.
Impulsively Generated Linear and Non-linear Alfven Waves in the Coronal Funnels
NASA Astrophysics Data System (ADS)
Chmielewski, P.; Srivastava, A. K.; Murawski, K.; Musielak, Z. E.
2014-01-01
We present simulation results of the impulsively generated linear and non-linear Alfvén waves in the weakly curved coronal magnetic flux-tubes (coronal funnels) and discuss their implications for the coronal heating and solar wind acceleration. We solve numerically the time-dependent magnetohydrodynamic equations to find the temporal signatures of the small and large-amplitude Alfvén waves in the model atmosphere of open and expanding magnetic field configuration with a realistic temperature distribution. We compute the maximum transversal velocity of both linear and non-linear Alfvén waves at different heights of the model atmosphere, and study their response in the solar corona during the time of their propagation. We infer that the pulse-driven non-linear Alfvén waves may carry sufficient wave energy fluxes to heat the coronal funnels and also to power the solar wind that originates in these funnels. Our study of linear Alfvén waves shows that they can contribute only to the plasma dynamics and heating of the funnel-like magnetic flux-tubes associated with the polar coronal holes.
Non-linear effects on solute transfer between flowing water and a sediment bed.
Higashino, Makoto; Stefan, Heinz G
2011-11-15
A previously developed model of periodic pore water flow in space and time, and associated solute transport in a stream bed of fine sand is extended to coarse sand and fine gravel. The pore water flow immediately below the sediment/water interface becomes intermittently a non-Darcy flow. The periodic pressure and velocity fluctuations considered are induced by near-bed coherent turbulent motions in the stream flow; they penetrate from the sediment/water interface into the sediment pore system and are described by a wave number (χ) and a period (T) that are given as functions of the shear velocity (U(∗)) between the flowing water and the sediment bed. The stream bed has a flat surface without bed forms. The flow field in the sediment pore system is described by the continuity equation and a resistance law that includes both viscous (Darcy) and non-linear (inertial) effects. Simulation results show that non-linear (inertial) effects near the sediment/water interface increase flow resistance and reduce mean flow velocities. Compared to pure Darcy flow, non-linear (inertial) effects reduce solute exchange rates between overlying water and the sediment bed but only by a moderate amount (less than 50%). Turbulent coherent flow structures in the stream flow enhance solute transfer in the pore system of a stream bed compared to pure molecular diffusion, but by much less than standing surface waves or bed forms.
NASA Astrophysics Data System (ADS)
Ouyang, Wei; Mao, Weijian; Li, Wuqun; Zhang, Pan
2017-02-01
An approach for approximate direct quadratic non-linear inversion in two-parameter (density and bulk modulus) heterogeneous acoustic media is being presented and discussed in this paper. The approach consists of two parts: the first is a linear generalized Radon transform (GRT) migration procedure based on the weighted true-amplitude summation of pre-stack seismic scattered data that is adapted to a virtually arbitrary observing system, and the second is a non-iterative quadratic inversion operation, produced from the explicit expression of amplitude radiation pattern that is acting on the migrated data. This ensures the asymptotic inversion can continue to simultaneously locate the discontinuities and reconstruct the size of the discontinuities in the perturbation parameters describing the acoustic media. We identify that the amplitude radiation pattern is the binary quadratic combination of the parameters in the process of formulating non-linear inverse scattering problems based on second-order Born approximation. The coefficients of the quadratic terms are computed by appropriately handling the double scattering effects. These added quadratic terms provide a better amplitude correction for the parameters inversion. Through numerical tests, we show that for strong perturbations, the errors of the linear inversion are significant and unacceptable. In contrast, the quadratic non-linear inversion can give fairly accurate inversion results and keep almost the same computational complexity as conventional GRT liner inversion.
Reservoir computing and extreme learning machines for non-linear time-series data analysis.
Butcher, J B; Verstraeten, D; Schrauwen, B; Day, C R; Haycock, P W
2013-02-01
Random projection architectures such as Echo state networks (ESNs) and Extreme Learning Machines (ELMs) use a network containing a randomly connected hidden layer and train only the output weights, overcoming the problems associated with the complex and computationally demanding training algorithms traditionally used to train neural networks, particularly recurrent neural networks. In this study an ESN is shown to contain an antagonistic trade-off between the amount of non-linear mapping and short-term memory it can exhibit when applied to time-series data which are highly non-linear. To overcome this trade-off a new architecture, Reservoir with Random Static Projections (R(2)SP) is investigated, that is shown to offer a significant improvement in performance. A similar approach using an ELM whose input is presented through a time delay (TD-ELM) is shown to further enhance performance where it significantly outperformed the ESN and R(2)SP as well other architectures when applied to a novel task which allows the short-term memory and non-linearity to be varied. The hard-limiting memory of the TD-ELM appears to be best suited for the data investigated in this study, although ESN-based approaches may offer improved performance when processing data which require a longer fading memory.
NASA Astrophysics Data System (ADS)
Papagiannopoulou, Christina; Decubber, Stijn; Miralles, Diego; Demuzere, Matthias; Dorigo, Wouter; Verhoest, Niko; Waegeman, Willem
2017-04-01
Satellite data provide an abundance of information about crucial climatic and environmental variables. These data - consisting of global records, spanning up to 35 years and having the form of multivariate time series with different spatial and temporal resolutions - enable the study of key climate-vegetation interactions. Although methods which are based on correlations and linear models are typically used for this purpose, their assumptions for linearity about the climate-vegetation relationships are too simplistic. Therefore, we adopt a recently proposed non-linear Granger causality analysis [1], in which we incorporate spatial information, concatenating data from neighboring pixels and training a joint model on the combined data. Experimental results based on global data sets show that considering non-linear relationships leads to a higher explained variance of past vegetation dynamics, compared to simple linear models. Our approach consists of several steps. First, we compile an extensive database [1], which includes multiple data sets for land surface temperature, near-surface air temperature, surface radiation, precipitation, snow water equivalents and surface soil moisture. Based on this database, high-level features are constructed and considered as predictors in our machine-learning framework. These high-level features include (de-trended) seasonal anomalies, lagged variables, past cumulative variables, and extreme indices, all calculated based on the raw climatic data. Second, we apply a spatiotemporal non-linear Granger causality framework - in which the linear predictive model is substituted for a non-linear machine learning algorithm - in order to assess which of these predictor variables Granger-cause vegetation dynamics at each 1° pixel. We use the de-trended anomalies of Normalized Difference Vegetation Index (NDVI) to characterize vegetation, being the target variable of our framework. Experimental results indicate that climate strongly (Granger
Applications of Non-linearities in RF MEMS Switches and Resonators
NASA Astrophysics Data System (ADS)
Vummidi Murali, Krishna Prasad
The 21st century is emerging into an era of wireless ubiquity. To support this trend, the RF (Radio Frequency) front end must be capable of processing a range of wireless signals (cellular phone, data connectivity, broadcast TV, GPS positioning, etc.) spanning a total bandwidth of nearly 6 GHz. This warrants the need for multi-band/multi-mode radio architectures. For such architectures to satisfy the constraints on size, battery life, functionality and cost, the radio front-end must be made reconfigurable. RF-MEMS (RF Micro-Electro-Mechanical Systems) are seen as an enabling technology for such reconfigurable radios. RF-MEMS mainly include micromechanical switches (used in phase shifters, switched capacitor banks, impedance tuners etc.) and micromechanical resonators (used in tunable filters, oscillators, reference clocks etc.). MEMS technology also has the potential to be directly integrated into CMOS (Complementary metal-oxide semiconductor) ICs (Integrated Circuits) leading to further potential reductions of cost and size. However, RF-MEMS face challenges that must be addressed before they can gain widespread commercial acceptance. Relatively low switching speed, power handling, and high-voltage drive are some of the key issues in MEMS switches. Phase noise influenced by non-linearities, need for temperature compensation (especially Si based resonators), large start-up times, and aging are the key issues in Si MEMS Resonators. In this work potential solutions are proposed to address some of these key issues, specifically the reduction of high voltage drives in switches and the reduction of phase noise in MEMS resonators for timing applications. MEMS devices that are electrostatically actuated exhibit significant non-linearities. The origins of the non-linearities are both electrical (electrostatic actuation) and mechanical (dimensions and material properties). The influence of spring non-linearities (cubic and quadratic) on the performance of switches and
Ma, Rongfei
2015-01-01
In this paper, ammonia quantitative analysis based on miniaturized Al ionization gas sensor and non-linear bistable dynamic model was proposed. Al plate anodic gas-ionization sensor was used to obtain the current-voltage (I-V) data. Measurement data was processed by non-linear bistable dynamics model. Results showed that the proposed method quantitatively determined ammonia concentrations. PMID:25975362
Ma, Rongfei
2015-01-01
In this paper, ammonia quantitative analysis based on miniaturized Al ionization gas sensor and non-linear bistable dynamic model was proposed. Al plate anodic gas-ionization sensor was used to obtain the current-voltage (I-V) data. Measurement data was processed by non-linear bistable dynamics model. Results showed that the proposed method quantitatively determined ammonia concentrations.
NASA Astrophysics Data System (ADS)
Wang, Gang; Wang, Chaoli; Du, Qinghui; Cai, Xuan
2016-10-01
In this paper, we address the output consensus problem of tracking a desired trajectory for a group of second-order agents on a directed graph with a fixed topology. Each agent is modelled by a second-order non-linear system with unknown non-linear dynamics and unknown non-linear control gains. Only a subset of the agents is given access to the desired trajectory information directly. A distributed adaptive consensus protocol driving all agents to track the desired trajectory is presented using the backstepping technique and approximation technique of Fourier series (FSs). The FS structure is taken not only for tracking the non-linear dynamics but also the unknown portion in the controller design procedure, which can avoid virtual controllers containing the uncertain terms. Stability analysis and parameter convergence of the proposed algorithm are conducted based on the Lyapunov theory and the algebraic graph theory. It is also demonstrated that arbitrary small tracking errors can be achieved by appropriately choosing design parameters. Though the proposed work is applicable for second-order non-linear systems containing unknown non-linear control gains, the proposed controller design can be easily extended to higher-order non-linear systems containing unknown non-linear control gains. Simulation results show the effectiveness of the proposed schemes.
Non-linear Paradigm for Drift Wave - Zonal Flow interplay: coherence, chaos and turbulence
NASA Astrophysics Data System (ADS)
Zonca, Fulvio
2003-10-01
Non-linear equations for the slow space-time evolution of the radial drift wave (DW) envelope and zonal flow (ZF) amplitude have been self-consistently derived for a model nonuniform tokamak equilibrium within the coherent 4-wave drift wave-zonal flow modulation interaction model of Chen, Lin and White(chen00). For the sake of simplicity, in this work we assume electrostatic fluctuations; but our formalism is readily extended to electromagnetic fluctuations(chen01). In the local limit, i.e. neglecting equilibrium profile variations, the coherent 4-wave DW-ZF modulation interaction model has successfully demonstrated spontaneous generation of ZFs and non-linear DW/ITG-ZF dynamics in toroidal plasmas(chen00). The present work is an extension of previous analyses to allow both (slow) temporal and spatial variations of the DW/ITG radial envelope; thus, it naturally incorporates the effects of equilibrium variations; i.e., turbulence spreading and size-dependence of the saturated wave intensities and transport coefficients(lin99). This approach makes it possible to treat equilibrium profile variations and non-linear interactions on the same footing, assuming that coupling among different DWs on the shortest non-linear time scale is mediated by ZF only. At this level, the competition between linear drive/damping, DW spreading due to finite linear (and nonlinear) group velocity(lin02,chen02,kim02) and non-linear energy transfer between DWs and ZF, determines the saturation levels of the fluctuating fields. Despite the coherence of the underlying non-linear dynamics at this level, this system exhibits both chaotic behavior and intermittency, depending on system size and proximity to marginal stability(chen02). The present model can be further extended to include longer time-scale physics such as 3-wave interactions and collisionless damping of zonal flows. 9 chen00 Liu Chen, Zhihong Lin and Roscoe White, Phys. Plasmas 7, 3129, (2000). chen01 L. Chen, Z. Lin, R.B. White and
Scarneciu, Camelia C.; Sangeorzan, Livia; Rus, Horatiu; Scarneciu, Vlad D.; Varciu, Mihai S.; Andreescu, Oana; Scarneciu, Ioan
2017-01-01
Objectives: This study aimed at assessing the incidence of pulmonary hypertension (PH) at newly diagnosed hyperthyroid patients and at finding a simple model showing the complex functional relation between pulmonary hypertension in hyperthyroidism and the factors causing it. Methods: The 53 hyperthyroid patients (H-group) were evaluated mainly by using an echocardiographical method and compared with 35 euthyroid (E-group) and 25 healthy people (C-group). In order to identify the factors causing pulmonary hypertension the statistical method of comparing the values of arithmetical means is used. The functional relation between the two random variables (PAPs and each of the factors determining it within our research study) can be expressed by linear or non-linear function. By applying the linear regression method described by a first-degree equation the line of regression (linear model) has been determined; by applying the non-linear regression method described by a second degree equation, a parabola-type curve of regression (non-linear or polynomial model) has been determined. We made the comparison and the validation of these two models by calculating the determination coefficient (criterion 1), the comparison of residuals (criterion 2), application of AIC criterion (criterion 3) and use of F-test (criterion 4). Results: From the H-group, 47% have pulmonary hypertension completely reversible when obtaining euthyroidism. The factors causing pulmonary hypertension were identified: previously known- level of free thyroxin, pulmonary vascular resistance, cardiac output; new factors identified in this study- pretreatment period, age, systolic blood pressure. According to the four criteria and to the clinical judgment, we consider that the polynomial model (graphically parabola- type) is better than the linear one. Conclusions: The better model showing the functional relation between the pulmonary hypertension in hyperthyroidism and the factors identified in this study is
Non-Linear Concentration-Response Relationships between Ambient Ozone and Daily Mortality
Bae, Sanghyuk; Lim, Youn-Hee; Kashima, Saori; Yorifuji, Takashi; Honda, Yasushi; Kim, Ho; Hong, Yun-Chul
2015-01-01
Background Ambient ozone (O3) concentration has been reported to be significantly associated with mortality. However, linearity of the relationships and the presence of a threshold has been controversial. Objectives The aim of the present study was to examine the concentration-response relationship and threshold of the association between ambient O3 concentration and non-accidental mortality in 13 Japanese and Korean cities from 2000 to 2009. Methods We selected Japanese and Korean cities which have population of over 1 million. We constructed Poisson regression models adjusting daily mean temperature, daily mean PM10, humidity, time trend, season, year, day of the week, holidays and yearly population. The association between O3 concentration and mortality was examined using linear, spline and linear-threshold models. The thresholds were estimated for each city, by constructing linear-threshold models. We also examined the city-combined association using a generalized additive mixed model. Results The mean O3 concentration did not differ greatly between Korea and Japan, which were 26.2 ppb and 24.2 ppb, respectively. Seven out of 13 cities showed better fits for the spline model compared with the linear model, supporting a non-linear relationships between O3 concentration and mortality. All of the 7 cities showed J or U shaped associations suggesting the existence of thresholds. The range of city-specific thresholds was from 11 to 34 ppb. The city-combined analysis also showed a non-linear association with a threshold around 30-40 ppb. Conclusion We have observed non-linear concentration-response relationship with thresholds between daily mean ambient O3 concentration and daily number of non-accidental death in Japanese and Korean cities. PMID:26076447
Unsteady Solution of Non-Linear Differential Equations Using Walsh Function Series
NASA Technical Reports Server (NTRS)
Gnoffo, Peter A.
2015-01-01
Walsh functions form an orthonormal basis set consisting of square waves. The discontinuous nature of square waves make the system well suited for representing functions with discontinuities. The product of any two Walsh functions is another Walsh function - a feature that can radically change an algorithm for solving non-linear partial differential equations (PDEs). The solution algorithm of non-linear differential equations using Walsh function series is unique in that integrals and derivatives may be computed using simple matrix multiplication of series representations of functions. Solutions to PDEs are derived as functions of wave component amplitude. Three sample problems are presented to illustrate the Walsh function series approach to solving unsteady PDEs. These include an advection equation, a Burgers equation, and a Riemann problem. The sample problems demonstrate the use of the Walsh function solution algorithms, exploiting Fast Walsh Transforms in multi-dimensions (O(Nlog(N))). Details of a Fast Walsh Reciprocal, defined here for the first time, enable inversion of aWalsh Symmetric Matrix in O(Nlog(N)) operations. Walsh functions have been derived using a fractal recursion algorithm and these fractal patterns are observed in the progression of pairs of wave number amplitudes in the solutions. These patterns are most easily observed in a remapping defined as a fractal fingerprint (FFP). A prolongation of existing solutions to the next highest order exploits these patterns. The algorithms presented here are considered a work in progress that provide new alternatives and new insights into the solution of non-linear PDEs.
Towards a non-linear theory for fluid pressure and osmosis in shales
NASA Astrophysics Data System (ADS)
Droghei, Riccardo; Salusti, Ettore
2015-04-01
In exploiting deep hydrocarbon reservoirs, often injections of fluid and/or solute are used. To control and avoid troubles as fluid and gas unexpected diffusions, a reservoir characterization can be obtained also from observations of space and time evolution of micro-earthquake clouds resulting from such injections. This is important since several among the processes caused by fluid injections can modify the deep matrix. Information about the evolution of such micro-seismicity clouds therefore plays a realistic role in the reservoir analyses. To reach a better insight about such processes, and obtain a better system control, we here analyze the initial stress necessary to originate strong non linear transients of combined fluid pressure and solute density (osmosis) in a porous matrix. All this can indeed perturb in a mild (i.e. a linear diffusion) or dramatic non linear way the rock structure, till inducing rock deformations, micro-earthquakes or fractures. I more detail we here assume first a linear Hooke law relating strain, stress, solute density and fluid pressure, and analyze their effect in the porous rock dynamics. Then we analyze its generalization, i.e. the further non linear effect of a stronger external pressure, also in presence of a trend of pressure or solute in the whole region. We moreover characterize the zones where a sudden arrival of such a front can cause micro-earthquakes or fractures. All this allows to reach a novel, more realistic insight about the control of rock evolution in presence of strong pressure fronts. We thus obtain a more efficient reservoir control to avoid large geological perturbations. It is of interest that our results are very similar to those found by Shapiro et al.(2013) with a different approach.
Analysis of non linear partially standing waves from 3D velocity measurements
NASA Astrophysics Data System (ADS)
Drevard, D.; Rey, V.; Svendsen, Ib; Fraunie, P.
2003-04-01
Surface gravity waves in the ocean exhibit an energy spectrum distributed in both frequency and direction of propagation. Wave data collection is of great importance in coastal zones for engineering and scientific studies. In particular, partially standing waves measurements near coastal structures and steep or barred beaches may be a requirement, for instance for morphodynamic studies. The aim of the present study is the analysis of partially standing surface waves icluding non-linear effects. According to 1st order Stokes theory, synchronous measurements of horizontal and vertical velocity components allow calculation of rate of standing waves (Drevard et al, 2003). In the present study, it is demonstrated that for deep water conditions, partially standing 2nd order Stokes waves induced velocity field is still represented by the 1st order solution for the velocity potential contrary to the surface elevation which exhibits harmonic components. For intermediate water depth, harmonic components appear not only in the surface elevation but also in the velocity fields, but their weight remains much smaller, because of the vertical decreasing wave induced motion. For irregular waves, the influence of the spectrum width on the non-linear effects in the analysis is discussed. Keywords: Wave measurements ; reflection ; non-linear effects Acknowledgements: This work was initiated during the stay of Prof. Ib Svendsen, as invited Professor, at LSEET in autumn 2002. This study is carried out in the framework of the Scientific French National Programmes PNEC ART7 and PATOM. Their financial supports are acknowledged References: Drevard, D., Meuret, A., Rey, V. Piazzola, J. And Dolle, A.. (2002). "Partially reflected waves measurements using Acoustic Doppler Velocimeter (ADV)", Submitted to ISOPE 03, Honolulu, Hawaii, May 2003.
Scarneciu, Camelia C; Sangeorzan, Livia; Rus, Horatiu; Scarneciu, Vlad D; Varciu, Mihai S; Andreescu, Oana; Scarneciu, Ioan
2017-01-01
This study aimed at assessing the incidence of pulmonary hypertension (PH) at newly diagnosed hyperthyroid patients and at finding a simple model showing the complex functional relation between pulmonary hypertension in hyperthyroidism and the factors causing it. The 53 hyperthyroid patients (H-group) were evaluated mainly by using an echocardiographical method and compared with 35 euthyroid (E-group) and 25 healthy people (C-group). In order to identify the factors causing pulmonary hypertension the statistical method of comparing the values of arithmetical means is used. The functional relation between the two random variables (PAPs and each of the factors determining it within our research study) can be expressed by linear or non-linear function. By applying the linear regression method described by a first-degree equation the line of regression (linear model) has been determined; by applying the non-linear regression method described by a second degree equation, a parabola-type curve of regression (non-linear or polynomial model) has been determined. We made the comparison and the validation of these two models by calculating the determination coefficient (criterion 1), the comparison of residuals (criterion 2), application of AIC criterion (criterion 3) and use of F-test (criterion 4). From the H-group, 47% have pulmonary hypertension completely reversible when obtaining euthyroidism. The factors causing pulmonary hypertension were identified: previously known- level of free thyroxin, pulmonary vascular resistance, cardiac output; new factors identified in this study- pretreatment period, age, systolic blood pressure. According to the four criteria and to the clinical judgment, we consider that the polynomial model (graphically parabola- type) is better than the linear one. The better model showing the functional relation between the pulmonary hypertension in hyperthyroidism and the factors identified in this study is given by a polynomial equation of second
Mississippi River Delta front loading mechanisms using non-linear wave modeling
NASA Astrophysics Data System (ADS)
Georgiou, I. Y.; Bentley, S. J.; Xu, K.; Maloney, J. M.; Miner, M. D.; Keller, G. P.; Obelcz, J.
2016-02-01
River deltas often exhibit submarine slides caused by the nature of weak unconsolidated clays deposited through rapid fine grained sedimentation. The role of waves as trigger mechanisms has been suggested and studied by many previous efforts, highlighting among others; the effect of cyclic loading from large hurricane waves shoaling on the delta front seafloor, high near-bed orbital velocities resulting from these waves that can exceed 2m/s, and the development of a pressure gradient across a wave crest that can differentially load the seabed. With declines in suspended sediment load over recent time (1700-present) delta front degradation is inevitable, and recent works suggest that the MRDF is nearing that phase. The impacts of delta front degradation and the potential increase in submarine failures pose an important economic and societal risk to delta populations and infrastructure. Here, we revisit the pressure gradient as a possible loading mechanism for triggering submarine slides and failures. We extend previous studies by hindcasting waves from known hurricanes that influenced the delta using a fully non-linear fluid dynamics model. By controlling the wave properties at the seaward boundary (wave height, length, period) and the type of waves that are forced (linear-sinusoidal, and non-linear-cnoidal, higher order stokes) we examine the pressure gradients along a wave crest and compare with measured shear strength of delta front soils. We further our analysis by evaluating the potential increase in pressure gradients near the bed resulting from shoaling waves on the delta front, in combination with variations in delta-front slopes. Results suggest that the presence of non-linear waves creates larger pressure gradients over shorter wave lengths (or periods), which produce differential loading of the seabed due to transient pressures. Furthermore, our results suggest that the resulting transient pressures may be higher than previously reported, due to the rapid
Extracting a common pulse like signal from Time Serie using a non linear Kalman Filter
NASA Astrophysics Data System (ADS)
Gazeaux, J.; Batista, D.; Ammann, C.; Naveau, P.; Jégat, C.; Gao, C.
2009-04-01
To understand the nature and cause of natural climate variability, it is important to attribute past climate variations to particular forcing factors. In this work, our main focus is to introduce an automatic assimilation procedure to estimate the magnitude of strong but short-lived perturbations, such as large explosive volcanic eruptions, using climate/proxies time series. The extraction and decomposition procedure is run on real multivariate time series of sulfate from ice cores drilled at different sites in Greenland. The sulfate ejected by volcanoes is transported through the stratosphere towards the poles and deposited via sedimentation near the pole. Sulfate in Greenland is then a marker of huge volcanic eruptions which occur all over the world. Such pulse-like processes are highly non linear, as much in time as for their intensity. If they are not detected, such pulse-like signals of extreme and rare events can perturb an objective calculation of the trend. This work is then as much an estimation procedure for such signals, as a first step to estimate a posteriori trend in the time series. Our extraction algorithm handles multivariate time series with a common but unknown forcing. This statistical procedure is based on a multivariate multi-state space model and a non linear Kalman Filter. The non linearity is solved using the calculation of a twice conditional expectation and variance. It can provide an accurate estimate of the timing and duration of individual pulse-like events from a set of different series covering the same temporal space. It not only allows for a more objective estimation of its associated peak amplitude and the subsequent time evolution of the signal, but at the same time it provides a measure of confidence through the posterior probability for each pulse-like event. The flexibility, robustness and limitations of our approach are discussed by applying our method to simulated time series and to the Monte-Carlo method to test the
Prediction of Mind-Wandering with Electroencephalogram and Non-linear Regression Modeling.
Kawashima, Issaku; Kumano, Hiroaki
2017-01-01
Mind-wandering (MW), task-unrelated thought, has been examined by researchers in an increasing number of articles using models to predict whether subjects are in MW, using numerous physiological variables. However, these models are not applicable in general situations. Moreover, they output only binary classification. The current study suggests that the combination of electroencephalogram (EEG) variables and non-linear regression modeling can be a good indicator of MW intensity. We recorded EEGs of 50 subjects during the performance of a Sustained Attention to Response Task, including a thought sampling probe that inquired the focus of attention. We calculated the power and coherence value and prepared 35 patterns of variable combinations and applied Support Vector machine Regression (SVR) to them. Finally, we chose four SVR models: two of them non-linear models and the others linear models; two of the four models are composed of a limited number of electrodes to satisfy model usefulness. Examination using the held-out data indicated that all models had robust predictive precision and provided significantly better estimations than a linear regression model using single electrode EEG variables. Furthermore, in limited electrode condition, non-linear SVR model showed significantly better precision than linear SVR model. The method proposed in this study helps investigations into MW in various little-examined situations. Further, by measuring MW with a high temporal resolution EEG, unclear aspects of MW, such as time series variation, are expected to be revealed. Furthermore, our suggestion that a few electrodes can also predict MW contributes to the development of neuro-feedback studies.
Non-linear analyses of heart rate variability during heavy exercise and recovery in cyclists.
Casties, J-F; Mottet, D; Le Gallais, D
2006-10-01
We investigated the time course of RR interval variability during exercise and subsequent 50 minutes of recovery in seven well-trained male cyclists who performed an exercise with 3 successive 8 min stages at 40 %, 70 % and 90 % of their maximal oxygen uptake. The goal of the study was to check whether the decrease in the amplitude of heart rate variability during heavy exercise was accompanied by changes in the chaotic structure of the fluctuations. Heart rate variability was analysed in the temporal and frequency domain using traditional tools and using non-linear methods (Largest Lyapunov Exponent, Detrended Fluctuation Analysis, Minimum Embedding Dimension). When compared to rest, variability at the heaviest exercise intensity was significantly lower (RR: 0.94 +/- 0.22 vs. 0.34 +/- 0.01 ms; SDRR: 0.11 +/- 0.04 vs. 0.01 +/- 0.00 ms) due to a decrease in both LF (2101 +/- 1450 vs. 0.14 +/- 0.09 ms (2) . Hz (-1)) and HF spectral energy (1148 +/- 1126 vs. 7.88 +/- 9.24 ms (2) . Hz (-1)). Non-linear analyses showed that heart rate variability remained chaotic whatever the exercise intensity (the largest Lyapunov exponent was positive at 90 % of the maximal oxygen uptake), with a fractal organisation that tended towards white noise (DFA value close to 0.5) during heavy exercise. During recovery, temporal and spectral variables came back to their rest values within about 30 minutes following an exponential pattern. Non-linear analyses revealed that heartbeat dynamics were disorganised at the beginning of recovery, and involved more regulating systems than at rest, even after 50 minutes of recovery. We concluded that, during heavy exercise, heart rate variability was mainly influenced by other factors than autonomous nervous system, and suggest that mechanical or neurological couplings between the cardiac, locomotor and respiratory systems could play an important part in the observed changes.