WorldWideScience

Sample records for based nonlinear interaction

  1. Visible and ultraviolet light sources based nonlinear interaction of lasers

    DEFF Research Database (Denmark)

    Andersen, Martin Thalbitzer; Tidemand-Lichtenberg, Peter; Jain, Mayank; Pedersen, Christian

    narrow spectrum, high intensities and fast pulsing characteristics. Apart from potential significant reduction in filtration requirements as compared to the LED’s, these characreistics help in accurate examination of different trap parameters. In this poster recent work on a general approach for......Different light sources can be used for optically stimulated luminescence measurements and usually a halogen lamp in combination with filters or light emitting diodes (LED’s) are used to provide the desired stimulation wavelength. However lasers can provide a much more well-defined beam, very...... synthesizing any wavelength in the visible and ultraviolet light based sum frequency generation between two lasers is presented....

  2. Interaction of two strong nonlinearities

    Czech Academy of Sciences Publication Activity Database

    Půst, Ladislav; Szöllös, Ondřej

    Lyngby: TU of Denmark, 2000 - (True, H.; Sorensen, M.), s. 1-9 [Proceedings European nonlinear oscillations conference /3./. Lyngby (DK), 08.08.1999-12.08.1999] R&D Projects: GA ČR GA101/97/0670 Keywords : strong nonlinearity * interaction * nonlinear oscillations Subject RIV: BI - Acoustics http://www.imm.dtu.dk/documents/users/mps/ENOC/proceedings/

  3. Nonlinear interaction between single photons.

    Science.gov (United States)

    Guerreiro, T; Martin, A; Sanguinetti, B; Pelc, J S; Langrock, C; Fejer, M M; Gisin, N; Zbinden, H; Sangouard, N; Thew, R T

    2014-10-24

    Harnessing nonlinearities strong enough to allow single photons to interact with one another is not only a fascinating challenge but also central to numerous advanced applications in quantum information science. Here we report the nonlinear interaction between two single photons. Each photon is generated in independent parametric down-conversion sources. They are subsequently combined in a nonlinear waveguide where they are converted into a single photon of higher energy by the process of sum-frequency generation. Our approach results in the direct generation of photon triplets. More generally, it highlights the potential for quantum nonlinear optics with integrated devices and, as the photons are at telecom wavelengths, it opens the way towards novel applications in quantum communication such as device-independent quantum key distribution. PMID:25379916

  4. Nonlinear interactions in the thalamocortical loop in essential tremor: A model-based frequency domain analysis.

    Science.gov (United States)

    He, F; Sarrigiannis, P G; Billings, S A; Wei, H; Rowe, J; Romanowski, C; Hoggard, N; Hadjivassilliou, M; Rao, D G; Grünewald, R; Khan, A; Yianni, J

    2016-06-01

    There is increasing evidence to suggest that essential tremor has a central origin. Different structures appear to be part of the central tremorogenic network, including the motor cortex, the thalamus and the cerebellum. Some studies using electroencephalogram (EEG) and magnetoencephalography (MEG) show linear association in the tremor frequency between the motor cortex and the contralateral tremor electromyography (EMG). Additionally, high thalamomuscular coherence is found with the use of thalamic local field potential (LFP) recordings and tremulous EMG in patients undergoing surgery for deep brain stimulation (DBS). Despite a well-established reciprocal anatomical connection between the thalamus and cortex, the functional association between the two structures during "tremor-on" periods remains elusive. Thalamic (Vim) LFPs, ipsilateral scalp EEG from the sensorimotor cortex and contralateral tremor arm EMG recordings were obtained from two patients with essential tremor who had undergone successful surgery for DBS. Coherence analysis shows a strong linear association between thalamic LFPs and contralateral tremor EMG, but the relationship between the EEG and the thalamus is much less clear. These measurements were then analyzed by constructing a novel parametric nonlinear autoregressive with exogenous input (NARX) model. This new approach uncovered two distinct and not overlapping frequency "channels" of communication between Vim thalamus and the ipsilateral motor cortex, defining robustly "tremor-on" versus "tremor-off" states. The associated estimated nonlinear time lags also showed non-overlapping values between the two states, with longer corticothalamic lags (exceeding 50ms) in the tremor active state, suggesting involvement of an indirect multisynaptic loop. The results reveal the importance of the nonlinear interactions between cortical and subcortical areas in the central motor network of essential tremor. This work is important because it demonstrates

  5. A Numerical Study of Nonlinear Wave Interactions

    Science.gov (United States)

    de Bakker, A.; Tissier, M.; Ruessink, G.

    2014-12-01

    Nonlinear triad interactions redistribute energy among a wave field, which transforms the shape of the incident short waves (f = 0.05 - 2 Hz) and generates energy at infragravity frequencies (f = 0.005-0.05 Hz). Recently, it has been suggested that infragravity energy may dissipate by energy transfers from infragravity frequencies to either the (former) short-wave spectral peak, or through infragravity-infragravity self-interactions that cause the infragravity waves to steepen and to eventually break. To investigate these infragravity dissipation mechanisms, we use the non-hydrostatic SWASH model. In this study, we first validate the model with the high-resolution GLOBEX laboratory data set and then explore the dependence of the energy transfers, with a focus on infragravity frequencies, on beach slope. Consistent with previous studies we find that SWASH is able to reproduce the transformation and corresponding nonlinear energy transfers of shoreward propagating waves to great detail. Bispectral analysis is used to study the coupling between wave frequencies; nonlinear energy transfers are then quantified using the Boussinesq coupling coefficient. To obtain more detailed insight we divide the nonlinear interactions in four categories based on triads including 1) infragravity frequencies only, 2) two infragravity frequencies and one short-wave frequency, 3) one infragravity frequency and two short-wave frequencies and 4) short-wave frequencies only. Preliminary results suggest that interactions are rather weak on gently beach slopes (1:80) and, in the innermost part of the surf zone, are dominated by infragravity-infragravity interactions. On steeper slopes (1:20), interactions are stronger, but entirely dominated by those involving short-wave frequencies only. The dependence of the transfers on offshore wave conditions and beach shape will be explored too. Funded by NWO.

  6. INFLUENCES OF NONLINEAR INTERACTIONS ON POLARITIONS

    Institute of Scientific and Technical Information of China (English)

    牛家胜; 罗莹; 马本堃

    2001-01-01

    In this paper, we have analysed theoretically the polarization and dielectric constant generated by the nonlinear interactions between ions in ionic crystals. The spectrum of polaritons (coupling modes of photons and optical phonons)under nonlinear interactions has been developed. A new branch of dispersion relations has emerged in the original frequency gap between CTO and ωLO.

  7. Nonlinear Interaction of Convective Cells in Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans; Juul Rasmussen, Jens; Thomsen, Kenneth

    1984-01-01

    The nonlinear interaction of externally excited convective cells was investigated experimentally. Two cells of the same polarity were observed to coalesce into one large cell provided their relative distance was sufficiently short. The nonlinear nature of the interaction was explicitly demonstrat...

  8. Electromagnetic interaction of arbitrary radial-dependent anisotropic spheres and improved invisibility for nonlinear-transformation-based cloaks

    OpenAIRE

    Qiu, Cheng-Wei; Novitsky, Andrey V.; Ma, Hua; Qu, Shaobo

    2009-01-01

    An analytical method of electromagnetic wave interactions with a general radially anisotropic cloak is established. It is able to deal with arbitrary parameters ($\\epsilon_r(r)$, $\\mu_r(r)$, $\\epsilon_t(r)$ and $\\mu_t(r)$) of a radially anisotropic inhomogeneous shell. The general cloaking condition is proposed from the wave relations for the first time. We derive the parameters of a novel class of spherical nonlinear cloaks and examine its invisibility performance by the proposed method at v...

  9. Interaction between two nonlinear Schroedinger solitons

    International Nuclear Information System (INIS)

    The interaction between nonlinear Schroedinger solitons is derived by the least action principle approach as a potential function of the soliton's separation and their initial relative phase, which shows clearly how the solitons interact with each other. Two solitons with the same initial phase always attract each other, while those of opposite phase repel. The method developed in the paper can be extended to deal with interaction between solitons of other nonlinear equations

  10. Nonlinear interaction of the concentrated waves

    International Nuclear Information System (INIS)

    The nonlinear problem of the wave propagation is considered. In addition to Kerr nonlinearity the question of the existence of concentrated solutions is analyzed for the threshold and saturable nonlinearity. It is shown that both in the case of threshold nonlinearity, and in the case of saturable nonlinearity solitary waves – concentrated solutions of the corresponding wave equations exist. For the nonlocal nonlinearity, it is taken into account that the diffusion process transforms the interaction of the electromagnetic field with the environment. This phenomenon is described by the system of differential equations including the equation for the perturbation of the dielectric permittivity. The mathematical problem is reduced to the eigenvalue problem for nonlinear integro-differential equation of Hartree type. The computational procedure is constructed

  11. Nonlinear Interaction of Convective Cells in Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans; Juul Rasmussen, Jens; Thomsen, Kenneth

    1985-01-01

    The nonlinear interaction of externally excited convective cells was investigated experimentally. Two cells of the same polarity coalesced into one large cell provided their relative distance was sufficiently short, while cells of opposite polarity interacted through a mutual perturbation of orbi...... only. The nonlinear nature of the coalescence was explicitly demonstrated. The implications of the observations for interpreting the cascade in a turbulent spectrum in two-dimensional systems are pointed out....

  12. Simulation of 3D parachute fluid–structure interaction based on nonlinear finite element method and preconditioning finite volume method

    Directory of Open Access Journals (Sweden)

    Fan Yuxin

    2014-12-01

    Full Text Available A fluid–structure interaction method combining a nonlinear finite element algorithm with a preconditioning finite volume method is proposed in this paper to simulate parachute transient dynamics. This method uses a three-dimensional membrane–cable fabric model to represent a parachute system at a highly folded configuration. The large shape change during parachute inflation is computed by the nonlinear Newton–Raphson iteration and the linear system equation is solved by the generalized minimal residual (GMRES method. A membrane wrinkling algorithm is also utilized to evaluate the special uniaxial tension state of membrane elements on the parachute canopy. In order to avoid large time expenses during structural nonlinear iteration, the implicit Hilber–Hughes–Taylor (HHT time integration method is employed. For the fluid dynamic simulations, the Roe and HLLC (Harten–Lax–van Leer contact scheme has been modified and extended to compute flow problems at all speeds. The lower–upper symmetric Gauss–Seidel (LU-SGS approximate factorization is applied to accelerate the numerical convergence speed. Finally, the test model of a highly folded C-9 parachute is simulated at a prescribed speed and the results show similar characteristics compared with experimental results and previous literature.

  13. Simulation of 3D parachute fluid-structure interaction based on nonlinear finite element method and preconditioning finite volume method

    Institute of Scientific and Technical Information of China (English)

    Fan Yuxin; Xia Jian

    2014-01-01

    A fluid–structure interaction method combining a nonlinear finite element algorithm with a preconditioning finite volume method is proposed in this paper to simulate parachute tran-sient dynamics. This method uses a three-dimensional membrane–cable fabric model to represent a parachute system at a highly folded configuration. The large shape change during parachute infla-tion is computed by the nonlinear Newton–Raphson iteration and the linear system equation is solved by the generalized minimal residual (GMRES) method. A membrane wrinkling algorithm is also utilized to evaluate the special uniaxial tension state of membrane elements on the parachute canopy. In order to avoid large time expenses during structural nonlinear iteration, the implicit Hil-ber–Hughes–Taylor (HHT) time integration method is employed. For the fluid dynamic simula-tions, the Roe and HLLC (Harten–Lax–van Leer contact) scheme has been modified and extended to compute flow problems at all speeds. The lower–upper symmetric Gauss–Seidel (LU-SGS) approximate factorization is applied to accelerate the numerical convergence speed. Finally, the test model of a highly folded C-9 parachute is simulated at a prescribed speed and the results show similar characteristics compared with experimental results and previous literature.

  14. Soil-structure interaction including nonlinear soil

    OpenAIRE

    Gicev, Vlado

    2008-01-01

    There are two types of models of soil-structure system depending upon the rigidity of foundation: models with rigid and models with flexible foundation. Main features of the soil-structure interaction phenomenon: -wave scattering, -radiation damping, -reduction of the system frequencies. In this presentation, the influence of interaction on the development of nonlinear zones in the soil is studied.

  15. Pulse interaction in nonlinear vacuum electrodynamics

    OpenAIRE

    Ignatov, A. M.; Poponin, V. P.

    2000-01-01

    The energy-momentum conservation law is used to investigate the interaction of pulses in the framework of nonlinear electrodynamics with Lorentz-invariant constitutive relations. It is shown that for the pulses of the arbitrary shape the interaction results in phase shift only.

  16. Nonlinear theory of electroelastic and magnetoelastic interactions

    CERN Document Server

    Dorfmann, Luis

    2014-01-01

    This book provides a unified theory of nonlinear electro-magnetomechanical interactions of soft materials capable of large elastic deformations. The authors include an overview of the basic principles of the classical theory of electromagnetism from the fundamental notions of point charges and magnetic dipoles through to distributions of charge and current in a non-deformable continuum, time-dependent electromagnetic fields and Maxwell’s equations. They summarize the basic ingredients of continuum mechanics that are required to account for the deformability of material and present nonlinear constitutive frameworks for electroelastic and magnetoelastic interactions in a highly deformable material. The equations contained in the book are used to formulate and solve a variety of representative boundary-value problems for both nonlinear electroelasticity and magnetoelasticity.

  17. Nonlinear dynamics of interacting populations

    CERN Document Server

    Bazykin, Alexander D

    1998-01-01

    This book contains a systematic study of ecological communities of two or three interacting populations. Starting from the Lotka-Volterra system, various regulating factors are considered, such as rates of birth and death, predation and competition. The different factors can have a stabilizing or a destabilizing effect on the community, and their interplay leads to increasingly complicated behavior. Studying and understanding this path to greater dynamical complexity of ecological systems constitutes the backbone of this book. On the mathematical side, the tool of choice is the qualitative the

  18. Nonlinear interactions for massive spin-2 fields

    CERN Document Server

    Schmidt-May, Angnis

    2016-01-01

    We give a basic introduction to ghost-free nonlinear theories involving massive spin-2 fields, focussing on bimetric theory. After motivating the construction of such models from field theoretical considerations, we review the linear theories for massive and massless spin-2 fluctuations propagating on maximally symmetric backgrounds. The structure of general nonlinear spin-2 interactions is explained before we specialise to the ghost-free case. We review the maximally symmetric solutions of bimetric theory, its mass spectrum and the parameter limit which brings the theory close to general relativity. Finally we discuss applications of bimetric theory to cosmology with particular emphasis on the role of the general relativity limit.

  19. Nonlinear quantum optics mediated by Rydberg interactions

    Science.gov (United States)

    Firstenberg, O.; Adams, C. S.; Hofferberth, S.

    2016-08-01

    By mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons via electromagnetically induced transparency, it is now possible to realize a medium which exhibits a strong optical nonlinearity at the level of individual photons. We review the theoretical concepts and the experimental state-of-the-art of this exciting new field, and discuss first applications in the field of all-optical quantum information processing.

  20. Polaritons and retarded interactions in nonlinear optical susceptibilities

    NARCIS (Netherlands)

    Knoester, Jasper; Mukamel, Shaul

    1989-01-01

    The role of retarded intermolecular interactions (polariton effects) in the nonlinear optical susceptibilities of condensed phases is studied. A systematic method for calculating these susceptibilities is developed, based on the derivation of reduced equations of motion which couple the electronic v

  1. Non-Linear Interactive Stories in Computer Games

    DEFF Research Database (Denmark)

    Bangsø, Olav; Jensen, Ole Guttorm; Kocka, Tomas

    2003-01-01

    The paper introduces non-linear interactive stories (NOLIST) as a means to generate varied and interesting stories for computer games automatically. We give a compact representation of a NOLIST based on the specification of atomic stories, and show how to build an object-oriented Bayesian network...

  2. Nonlinear lepton-photon interactions in external background fields

    CERN Document Server

    Akal, Ibrahim

    2016-01-01

    Nonlinear phenomena of lepton-photon interactions in external backgrounds with a generalised periodic plane-wave geometry are studied. We discuss nonlinear Compton scattering in head-on lepton-photon collisions extended properly to beyond the soft-photon regime. In addition, our results are applied to stimulated lepton-antilepton pair production in photon collisions with unrestricted energies. Derivations are considered semi-classically based on unperturbed fermionic Volkov representations encoding the full interaction with the background field. Closed expressions for total probabilities considering S-matrix elements have been derived. The general formula is applied to Compton scattering by an electron propagating in an external laser-like background. We obtain additive contributions in the extended unconstrained result which turns out to be stringently required in the highly nonlinear regime. A detailed comparison of contributing harmonics is discussed for various field parameters.

  3. Nonlinear Electromagnetic Interactions in Energetic Materials

    CERN Document Server

    Wood, M A; Moore, D S

    2016-01-01

    We study the scattering of electromagnetic waves in anisotropic energetic materials. Nonlinear light-matter interactions in molecular crystals result in frequency-conversion and polarization changes. Applied electromagnetic fields of moderate intensity can induce these nonlinear effects without triggering chemical decomposition, offering a mechanism for non-ionizing identification of explosives. We use molecular dynamics simulations to compute such two-dimensional Raman spectra in the terahertz range for planar slabs made of PETN and ammonium nitrate. We discuss third-harmonic generation and polarization-conversion processes in such materials. These observed far-field spectral features of the reflected or transmitted light may serve as an alternative tool for stand-off explosive detection.

  4. Nonlinear interactions between gravity waves and tides

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao; XU JiYao; MA RuiPing

    2007-01-01

    In this study, we present the nonlinear interactions between gravity waves (GWs) and tides by using the 2D numerical model for the nonlinear propagation of GWs in the compressible atmosphere. During the propagation in the tidal background, GWs become instable in three regions, that is z = 75-85 km, z =90-110 km and z= 115-130 km. The vertical wavelength firstly varies gradually from the initial 12 km to 27 km. Then the newly generated longer waves are gradually compressed. The longer and shorter waves occur in the regions where GWs propagate in the reverse and the same direction of the horizontal mean wind respectively. In addition, GWs can propagate above the main breaking region (90-110 km). During GWs propagation, not only the mean wind is accelerated, but also the amplitude of tide is amplified. Especially, after GWs become instable, this amplified effect to the tidal amplitude is much obvious.

  5. Nonlinear interactions between gravity waves and tides

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this study, we present the nonlinear interactions between gravity waves (GWs) and tides by using the 2D numerical model for the nonlinear propagation of GWs in the compressible atmosphere. During the propagation in the tidal background, GWs become instable in three regions, that is z = 75―85 km, z = 90―110 km and z = 115―130 km. The vertical wavelength firstly varies gradually from the initial 12 km to 27 km. Then the newly generated longer waves are gradually compressed. The longer and shorter waves occur in the regions where GWs propagate in the reverse and the same direction of the hori-zontal mean wind respectively. In addition, GWs can propagate above the main breaking region (90—110 km). During GWs propagation, not only the mean wind is accelerated, but also the amplitude of tide is amplified. Especially, after GWs become instable, this amplified effect to the tidal amplitude is much obvious.

  6. Nonlinear interactions in renal blood flow regulation

    DEFF Research Database (Denmark)

    Marsh, Donald J.; Sosnovtseva, Olga; Chon, Ki H.;

    2005-01-01

    We have developed a model of tubuloglomerular feedback (TGF) and the myogenic mechanism in afferent arterioles to understand how the two mechanisms are coupled. This paper presents the model. The tubular model predicts pressure, flow, and NaCl concentration as functions of time and tubular length...... vasomotor oscillation. There are nonlinear interactions between TGF and the myogenic mechanism, which include the modulation of the frequency and amplitude of the myogenic oscillation by TGF. The prediction of modulation is confirmed in a companion study ( 28)....

  7. Nonlinear wave-wave interactions and wedge waves

    Institute of Scientific and Technical Information of China (English)

    Ray Q.Lin; Will Perrie

    2005-01-01

    A tetrad mechanism for exciting long waves,for example edge waves,is described based on nonlinear resonant wave-wave interactions.In this mechanism,resonant interactions pass energy to an edge wave,from the three participating gravity waves.The estimated action flux into the edge wave can be orders of magnitude greater than the transfer fluxes derived from other competing mechanisms,such as triad interactions.Moreover,the numerical results show that the actual transfer rates into the edge wave from the three participating gravity waves are two-to three- orders of magnitude greater than bottom friction.

  8. Polaritons and retarded interactions in nonlinear optical susceptibilities

    OpenAIRE

    Knoester, Jasper; Mukamel, Shaul

    1989-01-01

    The role of retarded intermolecular interactions (polariton effects) in the nonlinear optical susceptibilities of condensed phases is studied. A systematic method for calculating these susceptibilities is developed, based on the derivation of reduced equations of motion which couple the electronic variables to the Maxwell (internal) electric field E. The susceptibilities are obtained by iteratively solving these equations in powers of E. Thus, the common introduction of intermediate susceptib...

  9. Dynamical soil-structure interactions: influence of soil behaviour nonlinearities

    International Nuclear Information System (INIS)

    The interaction of the soil with the structure has been largely explored the assumption of material and geometrical linearity of the soil. Nevertheless, for moderate or strong seismic events, the maximum shear strain can easily reach the elastic limit of the soil behavior. Considering soil-structure interaction, the nonlinear effects may change the soil stiffness at the base of the structure and therefore energy dissipation into the soil. Consequently, ignoring the nonlinear characteristics of the dynamic soil-structure interaction (DSSI) this phenomenon could lead to erroneous predictions of structural response. The goal of this work is to implement a fully nonlinear constitutive model for soils into a numerical code in order to investigate the effect of soil nonlinearity on dynamic soil structure interaction. Moreover, different issues are taken into account such as the effect of confining stress on the shear modulus of the soil, initial static condition, contact elements in the soil-structure interface, etc. During this work, a simple absorbing layer method based on a Rayleigh/Caughey damping formulation, which is often already available in existing Finite Element softwares, is also presented. The stability conditions of the wave propagation problems are studied and it is shown that the linear and nonlinear behavior are very different when dealing with numerical dispersion. It is shown that the 10 points per wavelength rule, recommended in the literature for the elastic media is not sufficient for the nonlinear case. The implemented model is first numerically verified by comparing the results with other known numerical codes. Afterward, a parametric study is carried out for different types of structures and various soil profiles to characterize nonlinear effects. Different features of the DSSI are compared to the linear case: modification of the amplitude and frequency content of the waves propagated into the soil, fundamental frequency, energy dissipation in

  10. Enhanced nonlinear interactions in quantum optomechanics via mechanical amplification

    Science.gov (United States)

    Lemonde, Marc-Antoine; Didier, Nicolas; Clerk, Aashish A.

    2016-01-01

    The quantum nonlinear regime of optomechanics is reached when nonlinear effects of the radiation pressure interaction are observed at the single-photon level. This requires couplings larger than the mechanical frequency and cavity-damping rate, and is difficult to achieve experimentally. Here we show how to exponentially enhance the single-photon optomechanical coupling strength using only additional linear resources. Our method is based on using a large-amplitude, strongly detuned mechanical parametric drive to amplify mechanical zero-point fluctuations and hence enhance the radiation pressure interaction. It has the further benefit of allowing time-dependent control, enabling pulsed schemes. For a two-cavity optomechanical set-up, we show that our scheme generates photon blockade for experimentally accessible parameters, and even makes the production of photonic states with negative Wigner functions possible. We discuss how our method is an example of a more general strategy for enhancing boson-mediated two-particle interactions and nonlinearities. PMID:27108814

  11. Nonlinear dynamics of specific DNA-protein interactions

    Science.gov (United States)

    Dwiputra, D.; Hidayat, W.; Khairani, R.; Zen, F. P.

    2016-03-01

    Interactions between DNA binding protein and specific base pairs of nucleic acid is critical for biological process. We propose a new model of DNA-protein interactions to depict the dynamics of specific DNA-protein interactions. Hydrogen bonds (H-bonds) are, among the other intermolecular interactions in DNA, the most distinctive in term of specificity of molecular bonds. As H-bonds account for specificity, we only consider the dynamics affected by H-bonds between DNA base pairs and H-bonds connecting protein side chains and DNA. The H-bonds are modelled by Morse potentials and coupling terms in the Hamiltonian of coupled oscillators resembling a coupling between planar DNA chain and a protein molecule. In this paper we give a perturbative approach as an attempt for a soliton solution. The solution is in the form of nonlinear travelling wave having the amplitudes satisfying coupled nonlinear Schrodinger equations and is interpreted as the mediator for nonlocal transmittance of biological information in DNA.

  12. Nonlinear Growth of Singular Vector Based Perturbations

    Science.gov (United States)

    Reynolds, C. A.

    2002-12-01

    The nonlinearity of singular vector-based perturbation growth is examined within the context of a global atmospheric forecast model. The characteristics of these nonlinearities and their impact on the utility of SV-based diagnostics are assessed both qualitatively and quantitatively. Nonlinearities are quantified by examining the symmetry of evolving positive and negative "twin" perturbations. Perturbations initially scaled to be consistent with estimates of analysis uncertainty become significantly nonlinear by 12 hours. However, the relative magnitude of the nonlinearities is a strong function of scale and metric. Small scales become nonlinear very quickly while synoptic scales can remain significantly linear out to three day. Small shifts between positive and negative perturbations can result in significant nonlinearities even when the basic anomaly patterns are quite similar. Thus, singular vectors may be qualitatively useful even when nonlinearities are large. Post-time pseudo-inverse experiments show that despite significant nonlinear perturbation growth, the nonlinear forecast corrections are similar to the expected linear corrections, even at 72 hours. When the nonlinear correction does differ significantly from the expected linear correction, the nonlinear correction is usually better, indicating that in some cases the pseudo-inverse correction effectively suppresses error growth outside the subspace defined by the leading (dry) singular vectors. Because a significant portion of the nonlinear growth occurs outside of the dry singular vector subspace, an a priori nonlinearity index based on the full perturbations is not a good predictor of when pseudo-inverse based corrections will be ineffective. However, one can construct a reasonable predictor of pseudo-inverse ineffectiveness by focusing on nonlinearities in the synoptic scales or in the singular vector subspace only.

  13. Fluid transport due to nonlinear fluid-structure interaction

    DEFF Research Database (Denmark)

    Jensen, Jakob Søndergaard

    1997-01-01

    This work considers nonlinear fluid-structure interaction for a vibrating pipe containing fluid. Transverse pipe vibrations will force the fluid to move relative to the pipe creating unidirectional fluid flow towards the pipe end. The fluid flow induced affects the damping and the stiffness of the...... pipe. The behavior of the system in response to lateral resonant base excitation is analysed numerically and by the use of a perturbation method (multiple scales). Exciting the pipe in the fundamental mode of vibration seems to be most effective for transferring energy from the shaker to the fluid......, whereas higher modes of vibration can be used to transport fluid with pipe vibrations of smaller amplitude. The effect of the nonlinear geometrical terms is analysed and these terms are shown to affect the response for higher modes of vibration. Experimental investigations show good agreement with...

  14. Anomalous interaction of nonlocal solitons in media with competing nonlinearities

    DEFF Research Database (Denmark)

    Esbensen, B. K.; Bache, Morten; Bang, Ole; Krolikowski, Wieslaw

    2012-01-01

    We theoretically investigate properties of individual bright spatial solitons and their interaction in nonlocal media with competing focusing and defocusing nonlinearities. We consider the general case with both nonlinear responses characterized by different strengths and degrees of nonlocality. We...... employ a variational approach to analytically describe soliton properties. In particular, we prove analytically that the interplay of focusing and defocusing nonlocal nonlinearities leads to attraction or repulsion of solitons depending on their separation distance. We then study the propagation and...

  15. Soil Structure Interaction in Nonlinear Soil

    OpenAIRE

    Gicev, Vlado

    2008-01-01

    A two-dimensional (2-D) model of a building supported by a semi-circular flexible foundation embedded in nonlinear soil is analyzed. The building, the foundation, and the soil have different physical properties. The model is excited by a half-sine SH wave pulse, which travels toward the foundation. The results show that the spatial distribution of permanent, nonlinear strain in the soil depends upon the incident angle, the amplitude, and the duration of the pulse. If the wave h...

  16. Non-linear electromagnetic interactions in thermal QED

    OpenAIRE

    Brandt, Fernando T.; Frenkel, Josif

    1994-01-01

    We examine the behavior of the non-linear interactions between electromagnetic fields at high temperature. It is shown that, in general, the log(T) dependence on the temperature of the Green functions is simply related to their UV behavior at zero-temperature. We argue that the effective action describing the nonlinear thermal electromagnetic interactions has a finite limit as T tends to infinity. This thermal action approaches, in the long wavelength limit, the negative of the corresponding ...

  17. Dynamical and spectral properties of interacting quantum nonlinear resonances

    International Nuclear Information System (INIS)

    While considering nonlinear quantum systems in the quasiclassical occupation region interacting with an external periodical field, the renormalization method is used. In case of interactions of two nonlinear resonances renormalization is associated with occurence of higher order nonlinear resonances. There is a limit in the renormalization pattern related to existence of higher resonances, for which the number of quasienergy levels in the potential pit is small. Analysis of distributions of delocalized quasi-energy functions, corresponding to destroyed resonances, and those of distances between the adjastment quasienergy levels has shown the presence of considerable correlations. The correlations are due to phase space restricted in action and quantum effects leading to classical chaos restriction

  18. Symbolic computation of nonlinear wave interactions on MACSYMA

    International Nuclear Information System (INIS)

    In this paper the use of a large symbolic computation system - MACSYMA - in determining approximate analytic expressions for the nonlinear coupling of waves in an anisotropic plasma is described. MACSYMA was used to implement the solutions of a fluid plasma model nonlinear partial differential equations by perturbation expansions and subsequent iterative analytic computations. By interacting with the details of the symbolic computation, the physical processes responsible for particular nonlinear wave interactions could be uncovered and appropriate approximations introduced so as to simplify the final analytic result. Details of the MACSYMA system and its use are discussed and illustrated. (Auth.)

  19. Ghost Dark Energy with Non-Linear Interaction Term

    Science.gov (United States)

    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.

  20. Nonlinear interaction of meta-atoms through optical coupling

    Energy Technology Data Exchange (ETDEWEB)

    Slobozhanyuk, A. P.; Kapitanova, P. V.; Filonov, D. S.; Belov, P. A. [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Powell, D. A. [Nonlinear Physics Centre and Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Australian National University, Canberra, ACT 0200 (Australia); Shadrivov, I. V.; Kivshar, Yu. S. [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Nonlinear Physics Centre and Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Australian National University, Canberra, ACT 0200 (Australia); Lapine, M., E-mail: mlapine@physics.usyd.edu.au [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), School of Physics, University of Sydney, New South Wales 2006 (Australia); McPhedran, R. C. [Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), School of Physics, University of Sydney, New South Wales 2006 (Australia)

    2014-01-06

    We propose and experimentally demonstrate a multi-frequency nonlinear coupling mechanism between split-ring resonators. We engineer the coupling between two microwave resonators through optical interaction, whilst suppressing the direct electromagnetic coupling. This allows for a power-dependent interaction between the otherwise independent resonators, opening interesting opportunities to address applications in signal processing, filtering, directional coupling, and electromagnetic compatibility.

  1. Enhanced energy transport owing to nonlinear interface interaction.

    Science.gov (United States)

    Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang

    2016-01-01

    It is generally expected that the interface coupling leads to the suppression of thermal transport through coupled nanostructures due to the additional interface phonon-phonon scattering. However, recent experiments demonstrated that the interface van der Waals interactions can significantly enhance the thermal transfer of bonding boron nanoribbons compared to a single freestanding nanoribbon. To obtain a more in-depth understanding on the important role of the nonlinear interface coupling in the heat transports, in the present paper, we explore the effect of nonlinearity in the interface interaction on the phonon transport by studying the coupled one-dimensional (1D) Frenkel-Kontorova lattices. It is found that the thermal conductivity increases with increasing interface nonlinear intensity for weak inter-chain nonlinearity. By developing the effective phonon theory of coupled systems, we calculate the dependence of heat conductivity on interfacial nonlinearity in weak inter-chain couplings regime which is qualitatively in good agreement with the result obtained from molecular dynamics simulations. Moreover, we demonstrate that, with increasing interface nonlinear intensity, the system dimensionless nonlinearity strength is reduced, which in turn gives rise to the enhancement of thermal conductivity. Our results pave the way for manipulating the energy transport through coupled nanostructures for future emerging applications. PMID:26787363

  2. Axial Non-linear Dynamic Soil-Pile Interaction - Keynote

    OpenAIRE

    Holeyman A.; Whenham V.

    2014-01-01

    This keynote lecture describes recent analytical and numerical advances in the modeling of the axial nonlinear dynamic interaction between a single pile and its embedding soil. On one hand, analytical solutions are developed for assessing the nonlinear axial dynamic response of the shaft of a pile subjected to dynamic loads, and in particular to vibratory loads. Radial inhomogeneity arising from shear modulus degradation is evaluated over a range of parameters and compared with those obtained...

  3. Inverse problem for multi-body interaction of nonlinear waves

    CERN Document Server

    Marruzzo, Alessia; Antenucci, Fabrizio; Pagnani, Andrea; Leuzzi, Luca

    2016-01-01

    The inverse problem is studied in multi-body systems with nonlinear dynamics representing, e.g., phase-locked wave systems, standard multimode and random lasers. Using a general model for four-body interacting complex-valued variables we test two methods based on pseudolikelihood, respectively with regularization and with decimation, to determine the coupling constants from sets of measured configurations. We test statistical inference predictions for increasing number of sampled configurations and for an externally tunable {\\em temperature}-like parameter mimicing real data noise and helping minimization procedures. Analyzed models with phasors and rotors are generalizations of problems of real-valued spherical problems (e.g., density fluctuations), discrete spins (Ising and vectorial Potts) or finite number of states (standard Potts): inference methods presented here can, then, be straightforward applied to a large class of inverse problems.

  4. Nonlinear interaction between acoustic gravity waves

    OpenAIRE

    P. Axelsson; J. Larsson; Stenflo, L.

    1996-01-01

    The resonant interaction between three acoustic gravity waves is considered. We improve on the results of previous authors and write the new coupling coefficients in a symmetric form. Particular attention is paid to the low-frequency limit.

  5. Nonlinear dynamic soil-structure interaction in earthquake engineering

    International Nuclear Information System (INIS)

    The present work addresses a computational methodology to solve dynamic problems coupling time and Laplace domain discretizations within a domain decomposition approach. In particular, the proposed methodology aims at meeting the industrial need of performing more accurate seismic risk assessments by accounting for three-dimensional dynamic soil-structure interaction (DSSI) in nonlinear analysis. Two subdomains are considered in this problem. On the one hand, the linear and unbounded domain of soil which is modelled by an impedance operator computed in the Laplace domain using a Boundary Element (BE) method; and, on the other hand, the superstructure which refers not only to the structure and its foundations but also to a region of soil that possibly exhibits nonlinear behaviour. The latter sub-domain is formulated in the time domain and discretized using a Finite Element (FE) method. In this framework, the DSSI forces are expressed as a time convolution integral whose kernel is the inverse Laplace transform of the soil impedance matrix. In order to evaluate this convolution in the time domain by means of the soil impedance matrix (available in the Laplace domain), a Convolution Quadrature-based approach called the Hybrid Laplace-Time domain Approach (HLTA), is thus introduced. Its numerical stability when coupled to Newmark time integration schemes is subsequently investigated through several numerical examples of DSSI applications in linear and nonlinear analyses. The HLTA is finally tested on a more complex numerical model, closer to that of an industrial seismic application, and good results are obtained when compared to the reference solutions. (author)

  6. The Nonlinear Interaction Process in the Wave Assimilation Model and Its Experiments

    Institute of Scientific and Technical Information of China (English)

    杨永增; 纪永刚; 袁业立

    2003-01-01

    This paper presents a composite interaction formula based on the discrete-interactionoperator of wave-wave nonlinear interaction for deriving its adjoint source function in the wave assimilation model. Assimilation experiments were performed using the significant wave heights observed by the TOPES/POSEIDON satellite, and the gradient distribution in the physical space wasalso analyzed preliminarily.

  7. Nanoradar based on nonlinear dimer nanoantenna.

    Science.gov (United States)

    Lapshina, Nadezhda; Noskov, Roman; Kivshar, Yuri

    2012-09-15

    We introduce the concept of a nanoradar based on the operation of a nonlinear plasmonic nanoantenna. The nanoradar action originates from modulational instability occurring in a dimer nanoantenna consisting of two subwavelength nonlinear nanoparticles. Modulation instability causes a dynamical energy exchange between the nanoantenna eigenmodes resulting in periodic scanning of the nanoantenna scattering pattern. Such nanoradar demonstrates a wide scanning sector, low operation threshold, and ultrafast time response being potentially useful for many applications in nanophotonics circuitry. PMID:23041904

  8. Dynamic nonlinear interaction of elastic plates on discrete supports

    International Nuclear Information System (INIS)

    A study on the dynamic nonlinear interaction of elastic plates using the finite element method is presented. The elastic plate is discretized by 4-node isoparametric Mindlin elements. The constitutive relation of the discrete supports can be any nonlinear curve given by pairs of force-displacement points. The nonlinear behaviour is represented by the overlay approach. This model also allows the simulation of a progressive decrease on the supports stiffnesses during load cycles. The dynamic nonlinear incremental movement equations are integrated by the Newmark implicit operator. Two alternatives for the incremental-iterative formulation are compared. The paper ends with a discussion of the advantages and limitations of the presented numerical models. (Author)

  9. Nonlinear wave equation in frequency domain: accurate modeling of ultrafast interaction in anisotropic nonlinear media

    DEFF Research Database (Denmark)

    Guo, Hairun; Zeng, Xianglong; Zhou, Binbin;

    2013-01-01

    further simulations we demonstrate few-cycle compressed solitons in extremely short crystals, where spectral phenomena, such as blue/red shifting, nonstationary radiation in accordance with the nonlocal phase-matching condition, and dispersive-wave generation are observed and marked, which helps improve......We interpret the purely spectral forward Maxwell equation with up to third-order induced polarizations for pulse propagation and interactions in quadratic nonlinear crystals. The interpreted equation, also named the nonlinear wave equation in the frequency domain, includes quadratic and cubic...... nonlinearities, delayed Raman effects, and anisotropic nonlinearities. The full potential of this wave equation is demonstrated by investigating simulations of solitons generated in the process of ultrafast cascaded second-harmonic generation. We show that a balance in the soliton delay can be achieved due to...

  10. Nonlinear interaction involving zero energy wave

    International Nuclear Information System (INIS)

    Three-wave interactions involving one or two modes with non-definite sign of wave energy, treated by second order differential equations in time, are studied. The third mode is assumed to suffer heavy linear damping, and is treated by means of Tang's adiabatic approximation. The possibility of negative pump energy and positive decay mode energy is shown to lead to an explosive situation. Self-similar explosive solutions are derived, and it is shown that almost any solution asymptotically approaches, in some sense, these self-similar solutions

  11. Nonlinear ac conductivity of interacting 1d electron systems

    OpenAIRE

    Rosenow, Bernd; Nattermann, Thomas

    2004-01-01

    We consider low energy charge transport in one-dimensional (1d) electron systems with short range interactions under the influence of a random potential. Combining RG and instanton methods, we calculate the nonlinear ac conductivity and discuss the crossover between the nonanalytic field dependence of the electric current at zero frequency and the linear ac conductivity at small electric fields and finite frequency.

  12. Nonlinear PI Control with Adaptive Interaction Algorithm for Multivariable Wastewater Treatment Process

    Directory of Open Access Journals (Sweden)

    S. I. Samsudin

    2014-01-01

    Full Text Available The wastewater treatment plant (WWTP is highly known with the nonlinearity of the control parameters, thus it is difficult to be controlled. In this paper, the enhancement of nonlinear PI controller (ENon-PI to compensate the nonlinearity of the activated sludge WWTP is proposed. The ENon-PI controller is designed by cascading a sector-bounded nonlinear gain to linear PI controller. The rate variation of the nonlinear gain kn is automatically updated based on adaptive interaction algorithm. Initiative to simplify the ENon-PI control structure by adapting kn has been proved by significant improvement under various dynamic influents. More than 30% of integral square error and 14% of integral absolute error are reduced compared to benchmark PI for DO control and nitrate in nitrogen removal control. Better average effluent qualities, less number of effluent violations, and lower aeration energy consumption resulted.

  13. Nonlinear light-matter interactions in engineered optical media

    Science.gov (United States)

    Litchinitser, Natalia

    In this talk, we consider fundamental optical phenomena at the interface of nonlinear and singular optics in artificial media, including theoretical and experimental studies of linear and nonlinear light-matter interactions of vector and singular optical beams in metamaterials. We show that unique optical properties of metamaterials open unlimited prospects to ``engineer'' light itself. Thanks to their ability to manipulate both electric and magnetic field components, metamaterials open new degrees of freedom for tailoring complex polarization states and orbital angular momentum (OAM) of light. We will discuss several approaches to structured light manipulation on the nanoscale using metal-dielectric, all-dielectric and hyperbolic metamaterials. These new functionalities, including polarization and OAM conversion, beam magnification and de-magnification, and sub-wavelength imaging using novel non-resonant hyperlens are likely to enable a new generation of on-chip or all-fiber structured light applications. The emergence of metamaterials also has a strong potential to enable a plethora of novel nonlinear light-matter interactions and even new nonlinear materials. In particular, nonlinear focusing and defocusing effects are of paramount importance for manipulation of the minimum focusing spot size of structured light beams necessary for nanoscale trapping, manipulation, and fundamental spectroscopic studies. Colloidal suspensions offer as a promising platform for engineering polarizibilities and realization of large and tunable nonlinearities. We will present our recent studies of the phenomenon of spatial modulational instability leading to laser beam filamentation in an engineered soft-matter nonlinear medium. Finally, we introduce so-called virtual hyperbolic metamaterials formed by an array of plasma channels in air as a result of self-focusing of an intense laser pulse, and show that such structure can be used to manipulate microwave beams in a free space. This

  14. An explicit MOT-TDVIE scheme for analyzing electromagnetic field interactions on nonlinear scatterers

    KAUST Repository

    Ulku, Huseyin Arda

    2015-02-01

    An explicit marching on-in-time (MOT) based time domain electric field volume integral equation (TDVIE) solver for characterizing electromagnetic wave interactions on scatterers with nonlinear material properties is proposed. Discretization of the unknown electric field intensity and flux density is carried out by half and full Schaubert-Wilton-Glisson basis functions, respectively. Coupled system of spatially discretized TDVIE and the nonlinear constitutive relation between the field intensity and the flux density is integrated in time to compute the samples of the unknowns. An explicit PE(CE)m scheme is used for this purpose. Explicitness allows for \\'easy\\' incorporation of the nonlinearity as a function only to be evaluated on the right hand side of the coupled system of equations. A numerical example that demonstrates the applicability of the proposed MOT scheme to analyzing electromagnetic interactions on Kerr-nonlinear scatterers is presented. © 2015 IEEE.

  15. Nonlinear modal interactions in parity-time (PT) symmetric lasers.

    Science.gov (United States)

    Ge, Li; El-Ganainy, Ramy

    2016-01-01

    Parity-time symmetric lasers have attracted considerable attention lately due to their promising applications and intriguing properties, such as free spectral range doubling and single-mode lasing. In this work we discuss nonlinear modal interactions in these laser systems under steady state conditions, and we demonstrate that several gain clamping scenarios can occur for lasing operation in the -symmetric and -broken phases. In particular, we show that, depending on the system's design and the external pump profile, its operation in the nonlinear regime falls into two different categories: in one the system is frozen in the phase space as the applied gain increases, while in the other the system is pulled towards its exceptional point. These features are first illustrated by a coupled mode formalism and later verified by employing the Steady-state Ab-initio Laser Theory (SALT). Our findings shine light on the robustness of single-mode operation against saturation nonlinearity in -symmetric lasers. PMID:27143324

  16. Nonlinear oscillations in coriolis based gyroscopes

    Directory of Open Access Journals (Sweden)

    Dag Kristiansen

    1999-01-01

    Full Text Available In this paper we model and analyze nonlinear oscillations which are known to exist in some Coriolis based gyroscopes due to large amplitude excitation in the drive loop. A detailed derivation of a dynamic model for a cylinder gyroscope which includes geometric nonlinearities is given, and energy transfer between the system's modes are analyzed using perturbation theory and by proposing a simplified model. The model is also simulated, and the results are shown to give an accurate description of the experimental results. This work is done in order to gain a better understanding of the gyroscope's dynamics, and is intended to be a starting point for designing nonlinear observers and vibration controllers for the gyroscope in order to increase the performance.

  17. Nonlinear interactions between gravity waves and background winds

    Institute of Scientific and Technical Information of China (English)

    Liu Xiao; Xu Jiyao

    2007-01-01

    Using the nonlinear propagating gravity waves (GW) model in the two-dimensional compressible atmosphere and the linear GW theory, the process of GW propagation in different background winds, e.g. the direction of the background wind is opposite to (dead wind) or the same as (tail wind) the direction of the horizontal phase velocity of GW, is studied. The results show that the dead wind prolongs the vertical wavelength and accelerates GW propagation. Therefore, GW propagates up to a higher height becomes instable in a short time and eventually induces an inverse jet flow. Then, the vertical wavelength is becoming short due to the nonlinear interactions between GW and the inverse jet flow. The vertical wavelength and group velocity decrease after GW propagates into the tail wind. The initial instable time is delayed. Although most of GW is trapped in the instable region, some of GW propagates above the instable region.Compared with GW propagation in the tail wind, the nonlinear interactions between GW and the dead wind are also strong. In contrast,the linear GW theory predicts that GW can propagate freely in the dead wind. The vertical wavelength simulated by the nonlinear numerical model is different from that predicted by the linear theory greatly after GW propagates into the dead wind.

  18. Impact of nonlinear effective interactions on GFT quantum gravity condensates

    CERN Document Server

    Pithis, Andreas G A; Tomov, Petar

    2016-01-01

    We present the numerical analysis of effectively interacting Group Field Theory (GFT) models in the context of the GFT quantum gravity condensate analogue of the Gross-Pitaevskii equation for real Bose-Einstein condensates including combinatorially local interaction terms. Thus we go beyond the usually considered construction for free models. More precisely, considering such interactions in a weak regime, we find solutions for which the expectation value of the number operator N is finite, as in the free case. When tuning the interaction to the strongly nonlinear regime, however, we obtain solutions for which N grows and eventually blows up, which is reminiscent of what one observes for real Bose-Einstein condensates, where a strong interaction regime can only be realized at high density. This behaviour suggests the breakdown of the Bogoliubov ansatz for quantum gravity condensates and the need for non-Fock representations to describe the system when the condensate constituents are strongly correlated. Furthe...

  19. High-order finite difference solution for 3D nonlinear wave-structure interaction

    DEFF Research Database (Denmark)

    Ducrozet, Guillaume; Bingham, Harry B.; Engsig-Karup, Allan Peter;

    2010-01-01

    This contribution presents our recent progress on developing an efficient fully-nonlinear potential flow model for simulating 3D wave-wave and wave-structure interaction over arbitrary depths (i.e. in coastal and offshore environment). The model is based on a high-order finite difference scheme...

  20. Nonlinear Interactions between Slender Structures and Axial Flow

    Science.gov (United States)

    Du, Li

    2015-03-01

    For decades, dynamic behaviors of a slender structure with axial flow have been extensively studied. However, the governing equation based on expansions of small quantities is complicatedly-expressed and can be inappropriate as amplitude becomes considerably large. In this research, we are dedicated to finding an approach to study the nonlinear dynamics of a fluid-conveying slender strcture with arbitrary amplitude. By introducing the Intrinsic Coordinate, we find a concise way to describe the configuration of the system. Differential relations of such coordinate are studied and the rigorous nonlinear equation of motion is derived. Then rather than small-deflection approximation, linear dynamics are studied using Argand Diagram under a weaker condition named low-varying approximation. Nonlinear properties including Hopf bifurcation, limit-cycle motion and vibration frequencies are studied theoretically and experimentally.

  1. Power absorption during nonlinear electron cyclotron wave-particle interaction

    International Nuclear Information System (INIS)

    The linear theory of wave absorption and the quasilinear theory of the evolution of the distribution function are presently the main tools for a quantitative description of ECRH and ECCD in fusion devices. However the applicability of this theories is violated for some ECRH (ECCD) scenarios in typical experimental conditions. In particular this is true for one of the basic scenarios where the 2. harmonic electron cyclotron resonance for the extraordinary mode (X-mode) is used. In this paper a numerical model for ECRH and ECCD which consistently takes into account nonlinear wave-particle interaction has been developed. The results of computations show that the distortion of the particle distribution function from Maxwellian is strong for parameters typical for present day ECRH experiments. These leads to a reduction of the absorption, consequent broadening of the absorption profile and incomplete absorption. The distortion of the particle distribution function is essentially different from what is expected from the quasilinear theory where a Fokker-Planck equation is assumed to be valid. The positive derivative of the distribution function indicates that nonlinear effects of ECRH may cause the electron Bernstein wave instability. The modelling of ECCD at the 2. harmonic X-mode resonance shows that the effect of power redistribution in velocity space can especially be important for current drive. Therefore, for ECCD the absorption should be taken into account correctly by using nonlinear computations. With increasing both magnetic field and size of the beam, the nonlinear effects become more important. Therefore, the proper account of nonlinear effects is ultimate for reactor-scale devices

  2. Nonlinear transient and chaotic interactions in disc brake squeal

    Science.gov (United States)

    Oberst, S.; Lai, J. C. S.

    2015-04-01

    In automotive disc-brake squeal, most numerical studies have been focussed on the prediction of unstable vibration modes in the frequency domain using the complex eigenvalue analysis. However, the magnitude of the positive real part of a complex eigenvalue is an unreliable indicator of squeal occurrence. Although nonlinearities have been shown to play a significant role in brake squeal, transient nonlinear time domain analyses have rarely been applied owing to high computational costs. Here the complex eigenvalue analysis, the direct steady-state analysis and the transient nonlinear time domain analysis are applied to an isotropic pad-on-disc finite element model representing a simple model of a brake system. While in this investigation, in-plane pad-mode instabilities are not detected by the complex eigenvalue analysis, the dissipated energy obtained by the direct steady-state analysis of the model subjected to harmonic contact pressure excitation is negative at frequencies of pad modes, indicating a potential for instabilities. Transient nonlinear time domain analysis of the pad and disc dynamics reveal that in-plane pad vibrations excite a dominant out-of-plane disc mode. For intermittently chaotic pad motion, the disc dynamics is quasi-periodic; and for chaotic motion of the pad, a toroidal attractor is found for the disc's out-of-plane motion. Nonlinear interactions between the pad and the disc highlight that different parts in a brake system display different dynamic behaviour and need to be analysed separately. The type II intermittency route to chaos could be the cause for the experimentally observed instantaneous mode squeal.

  3. Breakdown of modulational approximations in multimode nonlinear interactions

    Science.gov (United States)

    Rizzato, Felipe; Iorra, Paulo; Marini, Samuel; Peter, Eduardo; Pakter, Renato; Chavez, Abraham

    2015-11-01

    The present work investigates the breakdown of the modulational approximation in a multimode extension of the three wave (triplet) nonlinear interaction. The modulational approach is accurate when the nonlinear wave coupling is weak, which causes amplitudes and phases to evolve slowly in time. We examine the types of dynamics arising when the coupling rises from very small to large values. At small couplings, when the modulational approach is valid, amplitude excursions are small and energy remains confined to the most unstable triplet subset of the multimode system. Above a critical value of the coupling, amplitude excursions abruptly become much larger and energy distributes more evenly among the active modes. Estimates for the critical coupling and relaxation times can be obtained with proper analysis of the most unstable triplet. CNPq (BR), FAPERGS (BR), AFOSR (USA, grant FA9550-12-1-0438).

  4. Cluster-based control of nonlinear dynamics

    CERN Document Server

    Kaiser, Eurika; Spohn, Andreas; Cattafesta, Louis N; Morzynski, Marek

    2016-01-01

    The ability to manipulate and control fluid flows is of great importance in many scientific and engineering applications. Here, a cluster-based control framework is proposed to determine optimal control laws with respect to a cost function for unsteady flows. The proposed methodology frames high-dimensional, nonlinear dynamics into low-dimensional, probabilistic, linear dynamics which considerably simplifies the optimal control problem while preserving nonlinear actuation mechanisms. The data-driven approach builds upon a state space discretization using a clustering algorithm which groups kinematically similar flow states into a low number of clusters. The temporal evolution of the probability distribution on this set of clusters is then described by a Markov model. The Markov model can be used as predictor for the ergodic probability distribution for a particular control law. This probability distribution approximates the long-term behavior of the original system on which basis the optimal control law is de...

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

    Science.gov (United States)

    Raychowdhury, Prishati; Singh, Poonam

    2012-12-01

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

  6. Vision-based interaction

    CERN Document Server

    Turk, Matthew

    2013-01-01

    In its early years, the field of computer vision was largely motivated by researchers seeking computational models of biological vision and solutions to practical problems in manufacturing, defense, and medicine. For the past two decades or so, there has been an increasing interest in computer vision as an input modality in the context of human-computer interaction. Such vision-based interaction can endow interactive systems with visual capabilities similar to those important to human-human interaction, in order to perceive non-verbal cues and incorporate this information in applications such

  7. Thermo-mechanical interaction in nonlinear vibrating systems

    Czech Academy of Sciences Publication Activity Database

    Pešek, Luděk; Půst, Ladislav

    Praha : Ústav termomechaniky AV ČR, 2003 - (Dobiáš, I.), s. 147-154 ISBN 80-85918-81-1. [Národní konference s mezinárodní účastí : Dynamika strojů. Praha (CZ), 11.02.2003-12.02.2003] R&D Projects: GA ČR GA101/02/0241 Institutional research plan: CEZ:AV0Z2076919 Keywords : thermo-mechanic interaction * non-linear * response curves Subject RIV: BI - Acoustics

  8. DGFEM for interaction of fluids and nonlinear elasticity

    Czech Academy of Sciences Publication Activity Database

    Feistauer, M.; Hadrava, M.; Kosík, A.; Horáček, Jaromír

    Bratislava: Slovak University of Technology , 2016 - (Handlovičová, A.; Ševčovič, D.), s. 74-83 ISBN 978-80-227-4544-4. [ALGORITMY 2016 Conference on Scientific Computing /20./. Vysoké Tatry - Podbanské (SK), 13.03.2016-18.03.2016] R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : compressible Navier-Stokes equations * ALE method * nonlinear dynamic elasticity * discontinuous Galerkin method * fluid-structure interaction Subject RIV: BI - Acoustics http://www.iam.fmph.uniba.sk/amuc/ojs/index.php/algoritmy/article/view/396/313

  9. Soliton solutions of the nonlinear Schrodinger equation with nonlocal Coulomb and Yukawa interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, Betti [School of Engineering and Science, International University Bremen (IUB), 28725 Bremen (Germany)]. E-mail: b.hartmann@iu-bremen.de; Zakrzewski, Wojtek J. [Department of Mathematical Sciences, University of Durham, Durham DH1 3LE (United Kingdom)]. E-mail: w.j.zakrzewski@durham.ac.uk

    2007-07-09

    We study the nonlinear Schrodinger equation in (1+1) dimensions in which the nonlinear term is taken in the form of a nonlocal interaction of the Coulomb or Yukawa-type. We solve the equation numerically and find that, for all values of the nonlocal coupling constant, and in all cases, the equation possesses solitonic solutions. We show that our results, for the dependence of the height of the soliton on the coupling constant, are in good agreement with the predictions based on an analytic treatment in which the soliton is approximated by a Gaussian.

  10. Soliton solutions of the non-linear Schroedinger equation with nonlocal Coulomb and Yukawa-interactions

    OpenAIRE

    Hartmann, Betti; Zakrzewski, Wojtek J.

    2006-01-01

    We study the non-linear Schroedinger equation in (1+1) dimensions in which the nonlinear term is taken in the form of a nonlocal interaction of the Coulomb or Yukawa-type. We solve the equation numerically and find that, for all values of the nonlocal coupling constant, and in all cases, the equation possesses solitonic solutions. We show that our results, for the dependence of the height of the soliton on the coupling constant, are in good agreement with the predictions based on an analytic ...

  11. Soliton solutions of the nonlinear Schrodinger equation with nonlocal Coulomb and Yukawa interactions

    International Nuclear Information System (INIS)

    We study the nonlinear Schrodinger equation in (1+1) dimensions in which the nonlinear term is taken in the form of a nonlocal interaction of the Coulomb or Yukawa-type. We solve the equation numerically and find that, for all values of the nonlocal coupling constant, and in all cases, the equation possesses solitonic solutions. We show that our results, for the dependence of the height of the soliton on the coupling constant, are in good agreement with the predictions based on an analytic treatment in which the soliton is approximated by a Gaussian

  12. Soliton solutions of the non-linear Schroedinger equation with nonlocal Coulomb and Yukawa-interactions

    CERN Document Server

    Hartmann, B; Hartmann, Betti; Zakrzewski, Wojtek J.

    2006-01-01

    We study the non-linear Schroedinger equation in (1+1) dimensions in which the nonlinear term is taken in the form of a nonlocal interaction of the Coulomb or Yukawa-type. We solve the equation numerically and find that, for all values of the nonlocal coupling constant, and in all cases, the equation possesses solitonic solutions. We show that our results, for the dependence of the height of the soliton on the coupling constant, are in good agreement with the predictions based on an analytic treatment in which the soliton is approximated by a gaussian.

  13. Nonlinear fluid-structure interaction of axisymmetric systems

    International Nuclear Information System (INIS)

    Full text: Various numerical procedures, which each have respective merits and drawbacks, are available for the investigation of fluid-structure interaction problems. This paper concentrates on the coupling of the finite element method (FEM) for modeling the structure and the boundary element method (BEM) used to represent the compressible, inviscid fluid. Both methods are formulated in the time domain and a special algorithm is developed to realize the coupling. In particular, nonlinear effects, such as material nonlinearities, large displacements or unilateral boundary conditions, may be taken into account in the structural model, while on infinite expansion of the fluid region is included in the boundary element formulation. For axisymmetric systems, the number of degrees of freedom can be decreased considerably compared to the full three-dimensional situation. Whereas a suitable FE formulation for axisymmetric elastodynamic problems is well-known, the transient fundamental solution for the scalar wave propagation in the BE domain had to be determined numerically up to now. In this contribution an explicit form of this fundamental solution is developed. The numerical results obtained for a simply-shaped geometry and its analytical solution match very well. With this new approach more complicated nonlinear coupled systems like fluid-filled pipes, submerged structures or cylindrical tanks can be simulated without depending too muck on available computer resources. Refs. 3 (author)

  14. Gradient-based optimization in nonlinear structural dynamics

    DEFF Research Database (Denmark)

    Dou, Suguang

    optimization of nonlinear structural dynamics. In the modelling, nonlinear finite elements are used. In the analysis, nonlinear frequency response and nonlinear normal modes are calculated based on a harmonic balance method with higher-order harmonics. In the characterization, nonlinear modal coupling...... coefficients are calculated directly from a nonlinear finite element model. Based on the analysis and the characterization, a new class of optimization problems is studied. In the optimization, design sensitivity analysis is performed by using the adjoint method which is suitable for large-scale structural......The intrinsic nonlinearity of mechanical structures can give rise to rich nonlinear dynamics. Recently, nonlinear dynamics of micro-mechanical structures have contributed to developing new Micro-Electro-Mechanical Systems (MEMS), for example, atomic force microscope, passive frequency divider...

  15. Modeling of fatigue crack induced nonlinear ultrasonics using a highly parallelized explicit local interaction simulation approach

    Science.gov (United States)

    Shen, Yanfeng; Cesnik, Carlos E. S.

    2016-04-01

    This paper presents a parallelized modeling technique for the efficient simulation of nonlinear ultrasonics introduced by the wave interaction with fatigue cracks. The elastodynamic wave equations with contact effects are formulated using an explicit Local Interaction Simulation Approach (LISA). The LISA formulation is extended to capture the contact-impact phenomena during the wave damage interaction based on the penalty method. A Coulomb friction model is integrated into the computation procedure to capture the stick-slip contact shear motion. The LISA procedure is coded using the Compute Unified Device Architecture (CUDA), which enables the highly parallelized supercomputing on powerful graphic cards. Both the explicit contact formulation and the parallel feature facilitates LISA's superb computational efficiency over the conventional finite element method (FEM). The theoretical formulations based on the penalty method is introduced and a guideline for the proper choice of the contact stiffness is given. The convergence behavior of the solution under various contact stiffness values is examined. A numerical benchmark problem is used to investigate the new LISA formulation and results are compared with a conventional contact finite element solution. Various nonlinear ultrasonic phenomena are successfully captured using this contact LISA formulation, including the generation of nonlinear higher harmonic responses. Nonlinear mode conversion of guided waves at fatigue cracks is also studied.

  16. Seismic response analysis of a nuclear reactor structure considering nonlinear soil-structure interaction

    Energy Technology Data Exchange (ETDEWEB)

    Bhaumik, Lopamudra, E-mail: lbhaumi2@illinois.edu [University of Illinois at Urbana-Champaign (United States); Raychowdhury, Prishati, E-mail: prishati@iitk.ac.in [Indian Institute of Technology Kanpur (India)

    2013-12-15

    Highlights: • Seismic response analysis of an internal shearwall of a reactor is done. • Incremental dynamic analysis is performed with 30 recorded ground motions. • Equivalent viscous damping increases up to twice when nonlinear SSI is considered. • Roof drift demand increases up to 25% upon consideration of foundation nonlinearity. • Base shear, base moment and ductility reduce up to 62%, 40%, and 35%, respectively. - Abstract: This study focuses on the seismic response analysis of an internal shearwall of a typical Indian reactor resting on a medium dense sandy silty soil, incorporating the nonlinear behavior of the soil-foundation interface. The modeling is done in an open-source finite element framework, OpenSees, where the soil-structure interaction (SSI) is modeled using a Beam-on-Nonlinear-Winkler-Foundation (BNWF) approach. Static pushover analysis and cyclic analysis are performed followed by an incremental dynamic analysis (IDA) with 30 recorded ground motions. For performing IDA, the spectral acceleration of each motion corresponding to the fundamental period, S{sub a}(T{sub 1})is incremented from 0.1 g to 1.0 g with an increment step of 0.1 g. It is observed from the cyclic analysis that the equivalent viscous damping of the system increases upto twice upon incorporation of inelastic SSI. The IDA results demonstrate that the average peak base shear, base moment and displacement ductility demand reduces as much as 62%, 40%, and 35%, respectively, whereas the roof drift demand increases up to 25% upon consideration of foundation nonlinearity for the highest intensity motion. These observations indicate the need of critical consideration of nonlinear soil-structure interaction as any deficient modeling of the same may lead to an inaccurate estimation of the seismic demands of the structure.

  17. Seismic response analysis of a nuclear reactor structure considering nonlinear soil-structure interaction

    International Nuclear Information System (INIS)

    Highlights: • Seismic response analysis of an internal shearwall of a reactor is done. • Incremental dynamic analysis is performed with 30 recorded ground motions. • Equivalent viscous damping increases up to twice when nonlinear SSI is considered. • Roof drift demand increases up to 25% upon consideration of foundation nonlinearity. • Base shear, base moment and ductility reduce up to 62%, 40%, and 35%, respectively. - Abstract: This study focuses on the seismic response analysis of an internal shearwall of a typical Indian reactor resting on a medium dense sandy silty soil, incorporating the nonlinear behavior of the soil-foundation interface. The modeling is done in an open-source finite element framework, OpenSees, where the soil-structure interaction (SSI) is modeled using a Beam-on-Nonlinear-Winkler-Foundation (BNWF) approach. Static pushover analysis and cyclic analysis are performed followed by an incremental dynamic analysis (IDA) with 30 recorded ground motions. For performing IDA, the spectral acceleration of each motion corresponding to the fundamental period, Sa(T1)is incremented from 0.1 g to 1.0 g with an increment step of 0.1 g. It is observed from the cyclic analysis that the equivalent viscous damping of the system increases upto twice upon incorporation of inelastic SSI. The IDA results demonstrate that the average peak base shear, base moment and displacement ductility demand reduces as much as 62%, 40%, and 35%, respectively, whereas the roof drift demand increases up to 25% upon consideration of foundation nonlinearity for the highest intensity motion. These observations indicate the need of critical consideration of nonlinear soil-structure interaction as any deficient modeling of the same may lead to an inaccurate estimation of the seismic demands of the structure

  18. Nonlinear behaviour of electrostatically actuated carbon nanotube-based devices

    International Nuclear Information System (INIS)

    In this paper nonlinear behaviour of electrostatically actuated carbon nanotubes (CNTs) is investigated. The model comprises a clamped-clamped CNT suspended over a graphite ground electrode plate from which a potential difference is imposed. The actuation is based on ac and dc applied voltages and it is assumed that the neutral axis of bending is stretched when the beam is deflected, and also, the interatomic interaction forces between CNT and ground plate are considered. The versatile Galerkin's method is employed to reduce the nonlinear integral-partial-differential equation of motion to a nonlinear ordinary differential equation in time, and then, the reduced equation is solved by direct numerical integration. In the dc voltage actuation case, the pull-in/pull-out phenomena, hysteresis characteristic, pull-in time duration and the response of the system are studied. The obtained results are compared with the molecular dynamics method. Eventually, a nano-switch immune to input noise is proposed, which relies on the hysteresis characteristic of the system. In combined ac and dc voltage actuations, the vibrational behaviour and nonlinear frequency response of nano-resonator are studied.

  19. LINEAR AND NONLINEAR AERODYNAMIC THEORY OF INTERACTION BETWEEN FLEXIBLE LONG STRUCTURE AND WIND

    Institute of Scientific and Technical Information of China (English)

    徐旭; 曹志远

    2001-01-01

    In light of the characteristics of the interactions between flexible structure and wind in three directions, and based on the rational mechanical section-model of structure, a new aerodynamic force model is accepted, i. e. the coefficients of three component forces are the functions of the instantaneous attack angle and rotational speed Ci = Ci(β(t),θ),(i = D, L, M). So, a new method to formulate the linear and nonlinear aerodynamic items of wind and structure interacting has been put forward in accordance with "strip theory"and modified "quasi-static theory ", and then the linear and nonlinear coupled theory of super-slender structure for civil engineering analyzing are converged in one model. For the linear aerodynamic-force parts, the semi-analytical expressions of the items so-called "flutter derivatives" corresponding to the one in the classic equations have been given here,and so have the nonlinear parts. The study of the stability of nonlinear aerodynamic-coupled torsional vibration of the old Tacoma bridge shows that the form and results of the nonlinear control equation in rotational direction are in agreement with that of V. F. Bohm's.

  20. Characterizing premixed laminar flame–acoustics nonlinear interaction

    International Nuclear Information System (INIS)

    Highlights: • Premixed flame–acoustics interaction is studied. • Premixed flame is found to respond strongly to lower-frequency perturbations. • Higher-frequency flow disturbances pass through the flame smoothly. • Linear and nonlinear transfer functions are determined. • Hammerstein–Wiener model can provide a better agreement. - Abstract: Self-excited thermoacoustic oscillations, also known as combustion instability is generated by the coupling between unsteady combustion and acoustic perturbations. If such combustion instability occurs, then pressure fluctuations may become so intense that they can cause overheating and/or engine structural damage. Thus it is necessary to understand the dynamic coupling physics between acoustic perturbations and unsteady combustion, and to identify a measure to characterize the interaction between a heat source and oncoming acoustic perturbations. The present work investigates linear and nonlinear responses of a conical premixed laminar flame to oncoming acoustic disturbances. Unsteady heat release from the premixed flame is assumed to be caused by its surface area variation. And the area variation results from the fluctuations of the oncoming acoustic flow velocity. In order to track the flame front variation in real-time, the classical G-equation is applied. Second-order finite difference (FD) method is then used to expand the dynamic flame model. Time evolution of the flame surface under the periodic acoustics forcing is successfully captured. Finally, system identification is then conducted to estimate the linear and nonlinear flame transfer function to quantify the dynamic response of the flame to oncoming acoustic disturbances. Good agreement is obtained

  1. Nonlinear theory of beam-wave interaction for gyroklystron

    International Nuclear Information System (INIS)

    A transient analysis in time domain of beam-wave interaction for gyroklystron is made with self-consistent field theory. A nonlinear theory for gyroklystron with multiple cavities is then established, and corresponding electron motion equations and transient electromagnetic field equations with a complex form are given. For a Ka-band gyroklystron with four cavities, some numerical results of beam-wave interaction are given and analyzed. A saturated output power of 335 kW, corresponding to efficiency of 39.6% and saturated bandwidth of 320 MHz is achieved with a 72.8 kV, 11.8 A electron beam in TE01 mode when the speed spread is 5%. The numerical results agree well with the experimental data. (authors)

  2. Molecular dynamics simulation of complex plasmas: interaction of nonlinear waves

    Science.gov (United States)

    Durniak, Celine; Samsonov, Dmitry

    2008-11-01

    Complex plasmas consist of micron sized microspheres immersed into ordinary ion-electron plasmas. They exist in solid, liquid, gaseous states and exhibit a range of dynamic phenomena such as waves, solitons, phase transitions, heat transfer. These phenomena can be modelled in complex plasmas at the microscopic or ``molecular'' scale, which is almost impossible in ordinary solids and liquids. We simulate a monolayer complex plasma consisting of 3000 negatively-charged particles (or grains) with the help of molecular dynamics computer simulations. The equations of grain motion are solved using a 5^th order Runge Kutta method taking into account interaction of every grain with each other via a Yukawa potential. The grains are confined more strongly in the vertical direction than in the horizontal. After seeding the grains randomly the code is run until the equilibrium is reached as the grain kinetics energy reduces due to damping force equal to the neutral friction in the experiments and a monolayer crystal lattice is formed. Then we investigate interactions between nonlinear waves in a monolayer strongly coupled complex plasma moving in three dimensions. Different excitations are applied during a short time symmetrically on both sides of the lattice. Structural properties and nonlinear waves characteristics are examined as the pulses propagate across the complex plasma in opposite directions.

  3. Structure-based control of complex networks with nonlinear dynamics

    CERN Document Server

    Zañudo, Jorge G T; Albert, Réka

    2016-01-01

    Given the network of interactions underlying a complex system, what can we learn about controlling such a system solely from its structure? Over a century of research in control theory has given us tools to answer this question, which were widely applied in science and engineering. Yet the current tools do not always consider the inherently nonlinear dynamics of real systems and the naturally occurring system states in their definition of "control", a term whose interpretation varies across disciplines. Here we use a new mathematical framework for structure-based control of networks governed by a broad class of nonlinear dynamics that includes the major dynamic models of biological, technological, and social processes. This framework provides realizable node overrides that steer a system towards any of its natural long term dynamic behaviors and which are guaranteed to be effective regardless of the dynamic details and parameters of the underlying system. We use this framework on several real networks, compar...

  4. Hollow Gaussian beam generation through nonlinear interaction of photons with orbital-angular-momemtum

    CERN Document Server

    Chaitanya, N Apurv; Banerji, J; Samanta, G K

    2016-01-01

    Hollow Gaussian beams (HGB) are a special class of doughnut shaped beams that do not carry orbital angular momentum (OAM). Such beams have a wide range of applications in many fields including atomic optics, bio-photonics, atmospheric science, and plasma physics. Till date, these beams have been generated using linear optical elements. Here, we show a new way of generating HGBs by three-wave mixing in a nonlinear crystal. Based on nonlinear interaction of photons having OAM and conservation of OAM in nonlinear processes, we experimentally generated ultrafast HGBs of order as high as 6 and power >180 mW at 355 nm. This generic concept can be extended to any wavelength, timescales (continuous-wave and ultrafast) and any orders. We show that the removal of azimuthal phase of vortices does not produce Gaussian beam. We also propose a new and only method to characterize the order of the HGBs.

  5. Hollow Gaussian beam generation through nonlinear interaction of photons with orbital angular momentum.

    Science.gov (United States)

    Chaitanya, N Apurv; Jabir, M V; Banerji, J; Samanta, G K

    2016-01-01

    Hollow Gaussian beams (HGB) are a special class of doughnut shaped beams that do not carry orbital angular momentum (OAM). Such beams have a wide range of applications in many fields including atomic optics, bio-photonics, atmospheric science, and plasma physics. Till date, these beams have been generated using linear optical elements. Here, we show a new way of generating HGBs by three-wave mixing in a nonlinear crystal. Based on nonlinear interaction of photons having OAM and conservation of OAM in nonlinear processes, we experimentally generated ultrafast HGBs of order as high as 6 and power >180 mW at 355 nm. This generic concept can be extended to any wavelength, timescales (continuous-wave and ultrafast) and any orders. We show that the removal of azimuthal phase of vortices does not produce Gaussian beam. We also propose a new and only method to characterize the order of the HGBs. PMID:27581625

  6. NONLINEAR DATA RECONCILIATION METHOD BASED ON KERNEL PRINCIPAL COMPONENT ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    In the industrial process situation, principal component analysis (PCA) is a general method in data reconciliation.However, PCA sometime is unfeasible to nonlinear feature analysis and limited in application to nonlinear industrial process.Kernel PCA (KPCA) is extension of PCA and can be used for nonlinear feature analysis.A nonlinear data reconciliation method based on KPCA is proposed.The basic idea of this method is that firstly original data are mapped to high dimensional feature space by nonlinear function, and PCA is implemented in the feature space.Then nonlinear feature analysis is implemented and data are reconstructed by using the kernel.The data reconciliation method based on KPCA is applied to ternary distillation column.Simulation results show that this method can filter the noise in measurements of nonlinear process and reconciliated data can represent the true information of nonlinear process.

  7. Nonlinear interaction of kinetic Alfvén waves and ion acoustic waves in coronal loops

    Science.gov (United States)

    Sharma, Prachi; Yadav, Nitin; Sharma, R. P.

    2016-05-01

    Over the years, coronal heating has been the most fascinating question among the scientific community. In the present article, a heating mechanism has been proposed based on the wave-wave interaction. Under this wave-wave interaction, the high frequency kinetic Alfvén wave interacts with the low frequency ion acoustic wave. These waves are three dimensionally propagating and nonlinearly coupled through ponderomotive nonlinearity. A numerical code based on pseudo-spectral technique has been developed for solving these normalized dynamical equations. Localization of kinetic Alfvén wave field has been examined, and magnetic power spectrum has also been analyzed which shows the cascading of energy to higher wavenumbers, and this cascading has been found to have Kolmogorov scaling, i.e., k-5 /3 . A breakpoint appears after Kolmogorov scaling and next to this spectral break; a steeper scaling has been obtained. The presented nonlinear interaction for coronal loops plasmas is suggested to generate turbulent spectrum having Kolmogorov scaling in the inertial range and steepened scaling in the dissipation range. Since Kolmogorov turbulence is considered as the main source for coronal heating; therefore, the suggested mechanism will be a useful tool to understand the mystery of coronal loop heating through Kolmogorov turbulence and dissipation.

  8. Nonlinear Projection-Based Approach for Generating Compact Models of Nonlinear Thermal Networks

    OpenAIRE

    Codecasa, L.; D'Amore, Dario; Maffezzoni, P.

    2006-01-01

    Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/5920) International audience A nonlinear projection-base approach for generating compact models of nonlinear thermal networks is proposed. This approach is an extension of Galerkin's method, based on the theory of kernels. High accuracy for large temperature variations and high compactness of the generated models can be obtained.

  9. Nonlinear Optical Properties of Triphenylalanine-based Peptide Nanostructures

    Science.gov (United States)

    Kudryavtsev, A. V.; Mishina, E. D.; Sigov, A. S.

    2016-05-01

    Nonlinear optical properties of peptide nanobelts and peptide nanospheres, the two types of self-assembled triphenylalanine-based peptide nanostructures, are studied. Nanobelts nonlinear susceptibility tensor components are evaluated, and nanobelts crystal structure and crystallographic orientation are defined on the basis of nonlinear optical mapping and polarization dependences of the second harmonic signal. The results obtained suggest that it is possible to use these materials as biologically compatible nonlinear optical converters.

  10. Multi-ion Mach-Zehnder interferometer with artificial nonlinear interactions

    International Nuclear Information System (INIS)

    We propose a method to implement a Mach-Zehnder interferometry based upon a string of trapped ions with artificial nonlinear interactions. By manipulating the coupling strength between two involved internal states of the ions, we could achieve the beam splitting/recombination with NOON states. Using current techniques for manipulating trapped ions, we discuss the experimental feasibility of our scheme and analyze some undesired uncertainty under realistic experimental environment

  11. Axial Non-linear Dynamic Soil-Pile Interaction - Keynote

    Directory of Open Access Journals (Sweden)

    Holeyman A.

    2014-01-01

    Full Text Available This keynote lecture describes recent analytical and numerical advances in the modeling of the axial nonlinear dynamic interaction between a single pile and its embedding soil. On one hand, analytical solutions are developed for assessing the nonlinear axial dynamic response of the shaft of a pile subjected to dynamic loads, and in particular to vibratory loads. Radial inhomogeneity arising from shear modulus degradation is evaluated over a range of parameters and compared with those obtained by other authors and by a numerical radial discrete model simulating the pile and soil movements from integration of the laws of motion. New approximate non linear solutions for axial pile shaft behaviour developed from general elastodynamic equations are presented and compared to existing linear solutions. The soil non linear behaviour and its ability to dissipate mechanical energy upon cyclic loading are shown to have a significant influence on the mechanical impedance provided by the surrounding soil against pile shaft movement. The limitations of over-simplified modelling of pile response are highlighted.

  12. Theoretical studies of some nonlinear laser-plasma interactions

    International Nuclear Information System (INIS)

    The nonlinear coupling of intense, monochromatic, electromagnetic radiation with plasma is considered in a number of special cases. The first part of the thesis serves as an introduction to three-wave interactions. A general formulation of the stimulated scattering of transverse waves by longitudinal modes in a warm, unmagnetized, uniform plasma is constructed. A general dispersion relation is derived that describes Raman and Brillouin scattering, modulational instability, and induced Thomson scattering. Raman scattering (the scattering of a photon into another photon and an electron plasma wave) is investigated as a possible plasma heating scheme. Analytic theory complemented by computer simulation is presented describing the nonlinear mode coupling of laser light with small and large amplitude, resonantly excited electron plasma waves. The simulated scattering of a coherent electromagnetic wave by low frequency density perturbations in homogeneous plasma is discussed. A composite picture of the linear dispersion relations for filamentation and Brillouin scattering is constructed. The absolute instability of Brillouin weak and strong coupling by analytic and numerical means is described

  13. New holographic dark energy model with non-linear interaction

    CERN Document Server

    Oliveros, A

    2014-01-01

    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 $w_{\\Lambda}$ 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.

  14. Nonlinear laser-plasma interaction in magnetized liner inertial fusion

    Science.gov (United States)

    Geissel, Matthias; Awe, T. J.; Bliss, D. E.; Campbell, M. E.; Gomez, M. R.; Harding, E.; Harvey-Thompson, A. J.; Hansen, S. B.; Jennings, C.; Kimmel, M. W.; Knapp, P.; Lewis, S. M.; McBride, R. D.; Peterson, K.; Schollmeier, M.; Scoglietti, D. J.; Sefkow, A. B.; Shores, J. E.; Sinars, D. B.; Slutz, S. A.; Smith, I. C.; Speas, C. S.; Vesey, R. A.; Porter, J. L.

    2016-03-01

    Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. While magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Key LPI processes are determined, and mitigation methods are discussed. Results with and without improvement measures are presented.

  15. On a class of nonlinear dispersive-dissipative interactions

    Energy Technology Data Exchange (ETDEWEB)

    Rosenau, P. [Tel Aviv Univ. (Israel). School of Mathematical Sciences

    1997-07-29

    The authors study the prototypical, genuinely nonlinear, equation; u{sub t} + a(u{sup m}){sub x} + (u{sup n}){sub xxx} = {mu}(u{sup k}){sub xx}, a, {mu} = consts., which encompasses a wide variety of dissipative-dispersive interactions. The parametric surface k = (m + n)/2 separates diffusion dominated from dissipation dominated phenomena. On this surface dissipative and dispersive effects are in detailed balance for all amplitudes. In particular, the m = n + 2 = k + 1 subclass can be transformed into a form free of convection and dissipation making it accessible to theoretical studies. Both bounded and unbounded oscillations are found and certain exact solutions are presented. When a = (2{mu}3/){sup 2} the map yields a linear equation; rational, periodic and aperiodic solutions are constructed.

  16. Nonvolatile Memory Based on Nonlinear Magnetoelectric Effects

    Science.gov (United States)

    Shen, Jianxin; Cong, Junzhuang; Chai, Yisheng; Shang, Dashan; Shen, Shipeng; Zhai, Kun; Tian, Ying; Sun, Young

    2016-08-01

    The magnetoelectric effects in multiferroics have a great potential in creating next-generation memory devices. We use an alternative concept of nonvolatile memory based, on a type of nonlinear magnetoelectric effects showing a butterfly-shaped hysteresis loop. The principle is to utilize the states of the magnetoelectric coefficient, instead of magnetization, electric polarization, or resistance, to store binary information. Our experiments in a device made of the PMN-PT/Terfenol-D multiferroic heterostructure clearly demonstrate that the sign of the magnetoelectric coefficient can be repeatedly switched between positive and negative by applying electric fields, confirming the feasibility of this principle. This kind of nonvolatile memory has outstanding practical virtues such as simple structure, easy operation in writing and reading, low power, fast speed, and diverse materials available.

  17. Flight Dynamic Simulation with Nonlinear Aeroelastic Interaction using the ROM-ROM Procedure Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes to develop an integrated flight dynamics simulation capability with nonlinear aeroelastic interactions by combining a flight...

  18. Flight Dynamic Simulation with Nonlinear Aeroelastic Interaction using the ROM-ROM Procedure Project

    Data.gov (United States)

    National Aeronautics and Space Administration — ZONA Technology, Inc. proposes to develop an integrated flight dynamics simulation capability with nonlinear aeroelastic interactions by combining a flight dynamics...

  19. Pitch glide effect induced by a nonlinear string-barrier interaction

    Science.gov (United States)

    Kartofelev, Dmitri; Stulov, Anatoli; Välimäki, Vesa

    2015-10-01

    Interactions of a vibrating string with its supports and other spatially distributed barriers play a significant role in the physics of many stringed musical instruments. It is well known that the tone of the string vibrations is determined by the string supports, and that the boundary conditions of the string termination may cause a short-lasting initial fundamental frequency shifting. Generally, this phenomenon is associated with the nonlinear modulation of the stiff string tension. The aim of this paper is to study the initial frequency glide phenomenon that is induced only by the string-barrier interaction, apart from other possible physical causes, and without the interfering effects of dissipation and dispersion. From a numerical simulation perspective, this highly nonlinear problem may present various difficulties, not the least of which is the risk of numerical instability. We propose a numerically stable and a purely kinematic model of the string-barrier interaction, which is based on the travelling wave solution of the ideal string vibration. The model is capable of reproducing the motion of the vibrating string exhibiting the initial fundamental frequency glide, which is caused solely by the complex nonlinear interaction of the string with its termination. The results presented in this paper can expand our knowledge and understanding of the timbre evolution and the physical principles of sound generation of numerous stringed instruments, such as lutes called the tambura, sitar and biwa.

  20. Characterizing the nonlinear interaction of S- and P-waves in a rock sample

    OpenAIRE

    Gallot, Thomas; Malcolm, Alison; Szabo, Thomas L.; Brown, Stephen; Burns, Daniel; Fehler, Michael

    2014-01-01

    The nonlinear elastic response of rocks is known to be caused by the rocks' microstructure, particularly cracks and fluids. This paper presents a method for characterizing the nonlinearity of rocks in a laboratory scale experiment with a unique configuration. This configuration has been designed to open up the possibility the nonlinear characterization of rocks as an imaging tool in a field scenario. The nonlinear interaction of two traveling waves: a low-amplitude 500 kHz P-wave probe and a ...

  1. Nonlinear neutrino-photon interactions inside strong laser pulses

    CERN Document Server

    Meuren, Sebastian; Di Piazza, Antonino

    2015-01-01

    Even though neutrinos are neutral particles and interact only via the exchange of weak gauge bosons, charged leptons and quarks can mediate a coupling to the photon field beyond tree level. Inside a relativistically strong laser field nonlinear effects in the laser amplitude can play an important role, as electrons and positrons interact nonperturbatively with the coherent part of the photon field. Here, we calculate for the first time the leading-order contribution to the axial-vector--vector current-coupling tensor inside an arbitrary plane-wave laser field (which is taken into account exactly by employing the Furry picture). The current-coupling tensor appears in the calculation of various electroweak processes inside strong laser fields like photon emission or trident electron-positron pair production by a neutrino. Moreover, as we will see below, the axial-vector--vector current-coupling tensor contains the Adler-Bell-Jackiw (ABJ) anomaly. This occurrence renders the current-coupling tensor also interest...

  2. Nonlinear neutrino-photon interactions inside strong laser pulses

    Science.gov (United States)

    Meuren, Sebastian; Keitel, Christoph H.; Di Piazza, Antonino

    2015-06-01

    Even though neutrinos are neutral particles and interact only via the exchange of weak gauge bosons, charged leptons and quarks can mediate a coupling to the photon field beyond tree level. Inside a relativistically strong laser field nonlinear effects in the laser amplitude can play an important role, as electrons and positrons interact nonperturbatively with the coherent part of the photon field. Here, we calculate for the first time the leading-order contribution to the axial-vector-vector current-coupling tensor inside an arbitrary plane-wave laser field (which is taken into account exactly by employing the Furry picture). The current-coupling tensor appears in the calculation of various electroweak processes inside strong laser fields like photon emission or trident electron-positron pair production by a neutrino. Moreover, as we will see below, the axial-vector-vector current-coupling tensor contains the Adler-Bell-Jackiw (ABJ) anomaly. This occurrence renders the current-coupling tensor also interesting from a fundamental point of view, as it is the simplest Feynman diagram in an external field featuring this kind of anomaly.

  3. Nonlinear polarization interaction in bacteriorhodopsin films with anisotropically saturating absorption

    Science.gov (United States)

    Korchemskaya, Elena Y.; Soskin, Marat S.; Stepanchikov, Dmitriy A.; Druzhko, Anna B.; Dyukova, Tatyana V.

    1996-06-01

    The effect of protein and matrix modifications on the photoanisotropic properties is studied for developing the concept of impact upon the main optical properties of the dynamic optical material based on bacteriorhodopsin (BR) both interaction of transmembrane protein--chromophore complex BR with matrix and interaction of protein opsin with chromophore retinal. Also possibility of the application of BR-films for the light polarization modulator is proposed.

  4. Nonlinear interactions of electromagnetic waves with the auroral ionosphere

    International Nuclear Information System (INIS)

    The ionosphere provides us with an opportunity to perform plasma experiments in an environment with long confinement times, very large-scale lengths, and no confining walls. The auroral ionosphere with its nearly vertical magnetic field geometry is uniquely endowed with large amount of free energy from electron and ion precipitation along the magnetic field and mega-ampere current across the magnetic field. To take advantage of this giant outdoor laboratory, two facilities HAARP and HIPAS, with frequencies ranging from the radio to optical bands, are now available for active probing of and interaction with this interesting region. The ponderomotive pressures from the self-consistent wave fields have produced significant local perturbations of density and particle distributions at heights where the incident EM frequency matches a plasma resonance. This paper will review theory and experiments covering the nonlinear phenomena of parametric decay instability to wave collapse processes. At HF frequencies plasma lenses can be created by preconditioning pulses to focus what is a normally divergent beam into a high-intensity spot to further enhance nonlinear phenomena. At optical wavelengths a large rotating liquid metal mirror is used to focus laser pulses up to a given height. Such laser pulses are tuned to the same wavelengths of selected atomic and molecular resonances, with resulting large scattering cross sections. Ongoing experiments on dual-site experiments and excitation of ELF waves will be presented. The connection of such basic studies to environmental applications will be discussed. Such applications include the global communication using ELF waves, the ozone depletion and remediation and the control of atmospheric CO2 through the use of ion cyclotron resonant heating

  5. Nonlinear interactions of electromagnetic waves with the auroral ionosphere

    Science.gov (United States)

    Wong, Alfred Y.

    1999-09-01

    The ionosphere provides us with an opportunity to perform plasma experiments in an environment with long confinement times, very large-scale lengths, and no confining walls. The auroral ionosphere with its nearly vertical magnetic field geometry is uniquely endowed with large amount of free energy from electron and ion precipitation along the magnetic field and mega-ampere current across the magnetic field. To take advantage of this giant outdoor laboratory, two facilities HAARP and HIPAS, with frequencies ranging from the radio to optical bands, are now available for active probing of and interaction with this interesting region. The ponderomotive pressures from the self-consistent wave fields have produced significant local perturbations of density and particle distributions at heights where the incident EM frequency matches a plasma resonance. This paper will review theory and experiments covering the nonlinear phenomena of parametric decay instability to wave collapse processes. At HF frequencies plasma lenses can be created by preconditioning pulses to focus what is a normally divergent beam into a high-intensity spot to further enhance nonlinear phenomena. At optical wavelengths a large rotating liquid metal mirror is used to focus laser pulses up to a given height. Such laser pulses are tuned to the same wavelengths of selected atomic and molecular resonances, with resulting large scattering cross sections. Ongoing experiments on dual-site experiments and excitation of ELF waves will be presented. The connection of such basic studies to environmental applications will be discussed. Such applications include the global communication using ELF waves, the ozone depletion and remediation and the control of atmospheric CO2 through the use of ion cyclotron resonant heating.

  6. A test to evaluation non-linear soil structure interaction

    International Nuclear Information System (INIS)

    JNES is planning a new project to study non-linear soil-structure interaction (SSI) effect under large earthquake ground motions equivalent to and/or over a design earthquake ground motion of S2. Concerning the SSI test, it is pointed out that handling of the scale effect of the specimen taking into account the surrounding soil on the earthquake response evaluation to the actual structure is essential issue for the scaled model test. Thus, for the test, the largest specimen possible and the biggest input motion possible are necessary. Taking into account the above issues, new test methodology, which utilizes artificial earthquake ground motion, is considered desirable if it can be performed at a realistic cost. With this motivation, we have studied the test methodology which applying blasting power as for a big earthquake ground motion. The information from a coalmine company in the U.S.A. indicates that the works performed in the surface coalmine to blast a rock covering a coal layer generates a big artificial ground motion, which is similar to earthquake ground motion. Application of this artificial earthquake ground motion for the SSI test is considered very promising because the blasting work is carried out periodically for mining coal so that we can apply artificial motions generated by the work if we construct a building model at a closed point to the blasting work area. The major purposes of the test are to understand (a) basic earthquake response characteristics of a Nuclear Power Plant (NPP) reactor building when a large earthquake strikes the NPP site and (b) nonlinear characteristics of SSI phenomenon during a big earthquake. In the paper of ICONE-13, we will introduce the test method and basic characteristics of measured artificial ground motions generated by the blasting works on an actual site. (authors)

  7. Analysis of electromagnetic wave interactions on nonlinear scatterers using time domain volume integral equations

    KAUST Repository

    Ulku, Huseyin Arda

    2014-07-06

    Effects of material nonlinearities on electromagnetic field interactions become dominant as field amplitudes increase. A typical example is observed in plasmonics, where highly localized fields “activate” Kerr nonlinearities. Naturally, time domain solvers are the method of choice when it comes simulating these nonlinear effects. Oftentimes, finite difference time domain (FDTD) method is used for this purpose. This is simply due to the fact that explicitness of the FDTD renders the implementation easier and the material nonlinearity can be easily accounted for using an auxiliary differential equation (J.H. Green and A. Taflove, Opt. Express, 14(18), 8305-8310, 2006). On the other hand, explicit marching on-in-time (MOT)-based time domain integral equation (TDIE) solvers have never been used for the same purpose even though they offer several advantages over FDTD (E. Michielssen, et al., ECCOMAS CFD, The Netherlands, Sep. 5-8, 2006). This is because explicit MOT solvers have never been stabilized until not so long ago. Recently an explicit but stable MOT scheme has been proposed for solving the time domain surface magnetic field integral equation (H.A. Ulku, et al., IEEE Trans. Antennas Propag., 61(8), 4120-4131, 2013) and later it has been extended for the time domain volume electric field integral equation (TDVEFIE) (S. B. Sayed, et al., Pr. Electromagn. Res. S., 378, Stockholm, 2013). This explicit MOT scheme uses predictor-corrector updates together with successive over relaxation during time marching to stabilize the solution even when time step is as large as in the implicit counterpart. In this work, an explicit MOT-TDVEFIE solver is proposed for analyzing electromagnetic wave interactions on scatterers exhibiting Kerr nonlinearity. Nonlinearity is accounted for using the constitutive relation between the electric field intensity and flux density. Then, this relation and the TDVEFIE are discretized together by expanding the intensity and flux - sing half

  8. Drill-string dynamics with uncertainty in the bit-rock nonlinear interaction model

    OpenAIRE

    Ritto, T. G.; Soize, Christian; Sampaio, R

    2009-01-01

    The stochastic dynamics of a drill-string is analyzed, where the uncertainty is in the bit-rock nonlinear interaction model. The Maximum Entropy Principle is used to construct a probabilistic model for the nonlinear operator related to the bit-rock interaction model. A numerical model is developed using the Timoshenko beam theory and it is discretized by means of the Finite Element Method. The nonlinear dynamics analyzed considers the main efforts that the column is subjected to as, for insta...

  9. Fast and Chaotic Fiber-Based Nonlinear Polarization Scrambler

    CERN Document Server

    Guasoni, M; Gilles, M; Picozzi, A; Fatome, J

    2015-01-01

    We report a simple and efficient all-optical polarization scrambler based on the nonlinear interaction in an optical fiber between a signal beam and its backward replica which is generated and amplified by a reflective loop. When the amplification factor exceeds a certain threshold, the system exhibits a chaotic regime in which the evolution of the output polarization state of the signal becomes temporally chaotic and scrambled all over the surface of the Poincar\\'e sphere. We derive some analytical estimations for the scrambling performances of our device which are well confirmed by the experimental results. The polarization scrambler has been successfully tested on a single channel 10-Gbit/s On/Off Keying Telecom signal, reaching scrambling speeds up to 250-krad/s, as well as in a wavelength division multiplexing configuration. A different configuration based on a sequent cascade of polarization scramblers is also discussed numerically, which leads to an increase of the scrambling performances.

  10. Nonlinear Wave-Currents interactions in shallow water

    CERN Document Server

    Lannes, David

    2015-01-01

    We study here the propagation of long waves in the presence of vorticity. In the irrotational framework, the Green-Naghdi equations (also called Serre or fully nonlinear Boussinesq equations) are the standard model for the propagation of such waves. These equations couple the surface elevation to the vertically averaged horizontal velocity and are therefore independent of the vertical variable. In the presence of vorticity, the dependence on the vertical variable cannot be removed from the vorticity equation but it was however shown in [?] that the motion of the waves could be described using an extended Green-Naghdi system. In this paper we propose an analysis of these equations, and show that they can be used to get some new insight into wave-current interactions. We show in particular that solitary waves may have a drastically different behavior in the presence of vorticity and show the existence of solitary waves of maximal amplitude with a peak at their crest, whose angle depends on the vorticity. We als...

  11. Dual roles of shear flow in nonlinear multi-scale interactions

    Science.gov (United States)

    Hu, Z. Q.; Wang, Z. X.; Wei, L.; Li, J. Q.; Kishimoto, Y.

    2016-01-01

    Effect of shear flow on the multi-scale nonlinear interaction in plasmas is numerically investigated by using a self-consistent Landau-fluid model. Dual roles of shear flow in the process are discovered, significantly suppressing micro-scale fluctuations and dramatically promoting macro-scale fluctuations. Furthermore, its similar dual roles in turbulent transport are also demonstrated. The novel underlying mechanism for the nonlinear promotion is identified as the formation of a large vortex flow inside magnetic island, which as a common phenomenon have been often observed in space and magnetic fusion plasmas. The theoretical prediction on the threshold of shear flow based on an analytical modeling is verified via numerical simulations.

  12. An Efficient Nonlinear Regression Approach for Genome-wide Detection of Marginal and Interacting Genetic Variations.

    Science.gov (United States)

    Lee, Seunghak; Lozano, Aurélie; Kambadur, Prabhanjan; Xing, Eric P

    2016-05-01

    Genome-wide association studies have revealed individual genetic variants associated with phenotypic traits such as disease risk and gene expressions. However, detecting pairwise interaction effects of genetic variants on traits still remains a challenge due to a large number of combinations of variants (∼10(11) SNP pairs in the human genome), and relatively small sample sizes (typically process a large number of SNP pairs, (2) how to distinguish between true signals and SNPs/SNP pairs merely correlated with true signals, (3) how to detect nonlinear associations between SNP pairs and traits given small sample sizes, and (4) how to control false positives. In this article, we present a unified framework, called SPHINX, which addresses the aforementioned challenges. We first propose a piecewise linear model for interaction detection, because it is simple enough to estimate model parameters given small sample sizes but complex enough to capture nonlinear interaction effects. Then, based on the piecewise linear model, we introduce randomized group lasso under stability selection, and a screening algorithm to address the statistical and computational challenges mentioned above. In our experiments, we first demonstrate that SPHINX achieves better power than existing methods for interaction detection under false positive control. We further applied SPHINX to late-onset Alzheimer's disease dataset, and report 16 SNPs and 17 SNP pairs associated with gene traits. We also present a highly scalable implementation of our screening algorithm, which can screen ∼118 billion candidates of associations on a 60-node cluster in <5.5 hours. PMID:27159633

  13. Breather-to-soliton transitions, nonlinear wave interactions, and modulational instability in a higher-order generalized nonlinear Schrödinger equation.

    Science.gov (United States)

    Wang, Lei; Zhang, Jian-Hui; Wang, Zi-Qi; Liu, Chong; Li, Min; Qi, Feng-Hua; Guo, Rui

    2016-01-01

    We study the nonlinear waves on constant backgrounds of the higher-order generalized nonlinear Schrödinger (HGNLS) equation describing the propagation of ultrashort optical pulse in optical fibers. We derive the breather, rogue wave, and semirational solutions of the HGNLS equation. Our results show that these three types of solutions can be converted into the nonpulsating soliton solutions. In particular, we present the explicit conditions for the transitions between breathers and solitons with different structures. Further, we investigate the characteristics of the collisions between the soliton and breathers. Especially, based on the semirational solutions of the HGNLS equation, we display the novel interactions between the rogue waves and other nonlinear waves. In addition, we reveal the explicit relation between the transition and the distribution characteristics of the modulation instability growth rate. PMID:26871080

  14. Breather-to-soliton transitions, nonlinear wave interactions, and modulational instability in a higher-order generalized nonlinear Schrödinger equation

    Science.gov (United States)

    Wang, Lei; Zhang, Jian-Hui; Wang, Zi-Qi; Liu, Chong; Li, Min; Qi, Feng-Hua; Guo, Rui

    2016-01-01

    We study the nonlinear waves on constant backgrounds of the higher-order generalized nonlinear Schrödinger (HGNLS) equation describing the propagation of ultrashort optical pulse in optical fibers. We derive the breather, rogue wave, and semirational solutions of the HGNLS equation. Our results show that these three types of solutions can be converted into the nonpulsating soliton solutions. In particular, we present the explicit conditions for the transitions between breathers and solitons with different structures. Further, we investigate the characteristics of the collisions between the soliton and breathers. Especially, based on the semirational solutions of the HGNLS equation, we display the novel interactions between the rogue waves and other nonlinear waves. In addition, we reveal the explicit relation between the transition and the distribution characteristics of the modulation instability growth rate.

  15. Signal-noise interaction in nonlinear optical fibers: a hydrodynamic approach

    CERN Document Server

    Barletti, Luigi

    2015-01-01

    We present a new perturbative approach to the study of signal-noise interactions in amplified optical fibers. The approach is based on the hydrodynamic formulation of the nonlinear Schr\\"odinger equation that governs the propagation of light in the fiber. Our method is discussed in general and is developed in more details for some special cases, namely the small-dispersion regime, the continuous-wave (CW) signal and the solitonic pulse. The accuracy of the approach is numerically tested in the CW case.

  16. Simulations of energetic particles interacting with nonlinear anisotropic dynamical turbulence

    Science.gov (United States)

    Heusen, M.; Shalchi, A.

    2016-09-01

    We investigate test-particle diffusion in dynamical turbulence based on a numerical approach presented before. For the turbulence we employ the nonlinear anisotropic dynamical turbulence model which takes into account wave propagation effects as well as damping effects. We compute numerically diffusion coefficients of energetic particles along and across the mean magnetic field. We focus on turbulence and particle parameters which should be relevant for the solar system and compare our findings with different interplanetary observations. We vary different parameters such as the dissipation range spectral index, the ratio of the turbulence bendover scales, and the magnetic field strength in order to explore the relevance of the different parameters. We show that the bendover scales as well as the magnetic field ratio have a strong influence on diffusion coefficients whereas the influence of the dissipation range spectral index is weak. The best agreement with solar wind observations can be found for equal bendover scales and a magnetic field ratio of δ B / B0 = 0.75.

  17. A Coupling Model of Nonlinear Wave and Sandy Seabed Dynamic Interaction

    Institute of Scientific and Technical Information of China (English)

    CHENG Yong-zhou; WANG Yong-xue; JIANG Chang-bo

    2007-01-01

    In the paper,a weak coupling numerical model is developed for the study of the nonlinear dynamic interaction between water waves and permeable sandy seabed.The wave field solver is based on the VOF (Volume of Fluid) method for continuity equation and the two-dimensional Reynolds Averaged Navier Stokes (RANS) equations with a k-ε closure.The free surface of cnoidal wave is traced through the PLIC-VOF (Piecewise Linear Interface Construction).Biot's equations have been applied to solve the sandy seabed,and the u-p finite element formulations are derived by the application of the Galerkin weighted-residual procedure.The continuity of the pressure on the interface between fluid and porous medium domains is considered.Laboratory tests were performed to verify the proposed numerical model,and it is shown that the pore-water pressures and the wave heights computed by the VOF-FEM models are in good agreement with the experimental results.It is found that the proposed model is effective in predicting the seabed-nonlinear wave interaction and is able to handle the wave-breakwater-seabed interaction problem.

  18. Accelerated graph-based nonlinear denoising filters

    OpenAIRE

    Knyazev, Andrew; Malyshev, Alexander,

    2015-01-01

    Denoising filters, such as bilateral, guided, and total variation filters, applied to images on general graphs may require repeated application if noise is not small enough. We formulate two acceleration techniques of the resulted iterations: conjugate gradient method and Nesterov's acceleration. We numerically show efficiency of the accelerated nonlinear filters for image denoising and demonstrate 2-12 times speed-up, i.e., the acceleration techniques reduce the number of iterations required...

  19. Nonlinear fault diagnosis method based on kernel principal component analysis

    Institute of Scientific and Technical Information of China (English)

    Yan Weiwu; Zhang Chunkai; Shao Huihe

    2005-01-01

    To ensure the system run under working order, detection and diagnosis of faults play an important role in industrial process. This paper proposed a nonlinear fault diagnosis method based on kernel principal component analysis (KPCA). In proposed method, using essential information of nonlinear system extracted by KPCA, we constructed KPCA model of nonlinear system under normal working condition. Then new data were projected onto the KPCA model. When new data are incompatible with the KPCA model, it can be concluded that the nonlinear system isout of normal working condition. Proposed method was applied to fault diagnosison rolling bearings. Simulation results show proposed method provides an effective method for fault detection and diagnosis of nonlinear system.

  20. The bandwidth of optimized nonlinear vibration-based energy harvesters

    International Nuclear Information System (INIS)

    In an attempt to improve the performance of vibration-based energy harvesters, many authors suggest that nonlinearities can be exploited to increase the bandwidths of linear devices. Nevertheless, the complex dependence of the response upon the input excitation has made a realistic comparison of linear harvesters with nonlinear energy harvesters challenging. In a previous work it has been demonstrated that for a given frequency of excitation, it is possible to achieve the same maximum power for a nonlinear harvester as that for a linear harvester, provided that the resistance and the linear stiffness of both are optimized. This work focuses on the bandwidths of linear and nonlinear harvesters and shows which device is more suitable for harvesting energy from vibrations. The work considers different levels of excitation as well as different frequencies of excitation. In addition, the effect of the mechanical damping of the oscillator on the power bandwidth is shown for both the linear and nonlinear cases. (paper)

  1. Ground states for a system of nonlinear Schrodinger equations with three waves interaction

    OpenAIRE

    Pomponio, Alessio

    2009-01-01

    We consider a system of nonlinear Schrodinger equations with three waves interaction studying the existence of ground state solutions. In particular, we find a vector ground state, namely a ground state with the three components all different from zero.

  2. Nonlinear theory of intense laser-plasma interactions modified by vacuum-polarization effects

    OpenAIRE

    Chen, Wenbo; Bu, Zhigang; Li, Hehe; Luo, Yuee; Ji, Peiyong

    2013-01-01

    The classical nonlinear laser-plasma interaction theory is corrected. Given the effects of vacuum polarization (induced by extreme laser) as nonlinear media response, one-dimensional wave equations of a monochromatic laser field are derived from the Heisenberg-Euler Lagrangian density and a derivative correction with the first order quantum electrodynamic (QED) effects. A more suitable model to formulate the interactions of extreme laser and high-energy-density plasma is developed. In the res...

  3. Application of a nonlinear theory to the relativistic electron beam-plasma interaction

    International Nuclear Information System (INIS)

    The nonlinear theory of the Weibel-type electromagnetic instability developed in a relativistic electron beam-plasma interaction is presented and compared with the results of linear and quasilinear theories. The basic equations for a nonlinear REB-plasma interaction and the dispersion relation for the considered instability are established. The mechanism of the energy transfer from REB to the plasma is studied, finally obtaining the expression for the energy transfer time and the characteristic stopping length. (Author)

  4. Ultrafast and octave-spanning optical nonlinearities from strongly phase-mismatched cascaded interactions

    DEFF Research Database (Denmark)

    Zhou, B. B.; Chong, A.; Wise, F. W.;

    2012-01-01

    Cascaded nonlinearities have attracted much interest, but ultrafast applications have been seriously hampered by the simultaneous requirements of being near phase matching and having ultrafast femtosecond response times. Here we show that in strongly phase-mismatched nonlinear frequency conversion...... crystals the pump pulse can experience a large and extremely broadband self-defocusing cascaded Kerrlike nonlinearity. The large cascaded nonlinearity is ensured through interaction with the largest quadratic tensor element in the crystal, and the strong phase mismatch ensures an ultrafast nonlinear......% efficiency, and upon further propagation an octave-spanning supercontinuum is observed. Such ultrafast cascading is expected to occur for a broad range of pump wavelengths spanning the near- and mid-IR using standard nonlinear crystals....

  5. Bundle structures of stretching-energy and nonlinear interactions among modes in elastic wave turbulence

    International Nuclear Information System (INIS)

    The real-space dynamics and the nonlinear interactions among Fourier modes in elastic wave turbulence are investigated by simulating the Foppl-von Karman equation. We find that the bundle structures of ridges appear intermittently in the time evolution of the stretching energy field. The time-evolution of the nonlinearity indicates the existence of active and moderate phases in turbulent state. Conditional sampling analysis reveals that the bundle structure, which is the embodiment of the strong nonlinear interactions among modes, induces the energy supply from an external force to the system

  6. Bundle structures of stretching-energy and nonlinear interactions among modes in elastic wave turbulence

    Science.gov (United States)

    Takaoka, Masanori; Yokoyama, Naoto

    2015-01-01

    The real-space dynamics and the nonlinear interactions among Fourier modes in elastic wave turbulence are investigated by simulating the Foppl-von Karman equation. We find that the bundle structures of ridges appear intermittently in the time evolution of the stretching energy field. The time-evolution of the nonlinearity indicates the existence of active and moderate phases in turbulent state. Conditional sampling analysis reveals that the bundle structure, which is the embodiment of the strong nonlinear interactions among modes, induces the energy supply from an external force to the system.

  7. On triad nonlinear resonant interactions of deep water waves trapped by jet currents

    Science.gov (United States)

    Shrira, Victor; Slunyaev, Alexey

    2014-05-01

    We derive an asymptotic description of weakly nonlinear wave interactions between waves trapped by opposing jet currents by extending the asymptotic modal approach developed in Shrira & Slunyaev (2014). It is widely believed that to the leading order the nonlinear interactions between water waves in deep water are always quartic and potential. We show that for waves trapped on the jet currents it is not true: triad resonant interactions between trapped modes are always allowed. Moreover, the nonlinear evolution of the wave field is to the leading order determined by these triad interactions if the current is sufficiently strong or wave field nonlinearity is appropriately weak. To the leading order the corresponding interaction coefficients are controlled by the background vorticity due to the jet. More specifically, we consider waves upon a longitudinally uniform jet current; the current is assumed to be stationary and without vertical shear. The approximate separation of variables allows us to find the two-dimensional mode structure by means of one-dimensional boundary value problem (BVP) for wave Fourier harmonics along the current. The asymptotic weakly nonlinear theory taking into account quadratic nonlinearity for broad but not necessary weak currents is developed. The evolution equations for three interacting modes are written explicitly, the nonlinear interaction coefficients are computed. The three-wave interactions weaken when the current is weak. When the ratio of the current magnitude to wave celerity is of order of wave steepness the effects of 3-wave and 4-wave resonances appear at the same asymptotic order. These regimes, as well as the identified regimes where triad resonant interactions between trapped waves are dominant, lead to a qualitatively new wave dynamics which remains to be explored yet. V.I. Shrira, A.V. Slunyaev, Trapped waves on jet currents: asymptotic modal approach. J. Fluid Mech. 738, 65-104 (2014).

  8. Nonlinear Zeno dynamics due to atomic interactions in Bose–Einstein condensate

    International Nuclear Information System (INIS)

    We show that nonlinear interactions induce both the Zeno and anti-Zeno effects in the generalized Bose–Josephson model (with the on-site interactions and the second-order tunneling) describing Bose–Einstein condensate in double-well trap subject to particle removal from one of the wells. We find that the on-site interactions induce only the Zeno effect, which appears at long evolution times, whereas the second-order tunneling leads to a strong decay of the atomic population at short evolution times, reminiscent of the anti-Zeno effect, and destroys the nonlinear Zeno effect due to the on-site interactions at long times

  9. Nonlinear Zeno dynamics due to atomic interactions in Bose–Einstein condensate

    Energy Technology Data Exchange (ETDEWEB)

    Navarro, V.G.; Shchesnovich, V.S., E-mail: valery@ufabc.edu.br

    2014-12-01

    We show that nonlinear interactions induce both the Zeno and anti-Zeno effects in the generalized Bose–Josephson model (with the on-site interactions and the second-order tunneling) describing Bose–Einstein condensate in double-well trap subject to particle removal from one of the wells. We find that the on-site interactions induce only the Zeno effect, which appears at long evolution times, whereas the second-order tunneling leads to a strong decay of the atomic population at short evolution times, reminiscent of the anti-Zeno effect, and destroys the nonlinear Zeno effect due to the on-site interactions at long times.

  10. Nonlinear image processing based on optimization of generalized information methods

    OpenAIRE

    Bajkova, Anisa T.

    2002-01-01

    A range of nonlinear image reconstruction procedures based on extremizing the generalized Shannon entropy, Kullback-Leibler cross-entropy and Renyi information measures and proposed by the author in early papers is presented. The ``generalization'' assumes search for the solution over the space of real bipolar or complex functions. Such an approach allows, first, to reconstruct signals of any type and physical nature and, secondly, to decrease nonlinear intensity image distortions caused by m...

  11. Kernel-Based Nonlinear Discriminant Analysis for Face Recognition

    Institute of Scientific and Technical Information of China (English)

    LIU QingShan (刘青山); HUANG Rui (黄锐); LU HanQing (卢汉清); MA SongDe (马颂德)

    2003-01-01

    Linear subspace analysis methods have been successfully applied to extract features for face recognition. But they are inadequate to represent the complex and nonlinear variations of real face images, such as illumination, facial expression and pose variations, because of their linear properties. In this paper, a nonlinear subspace analysis method, Kernel-based Nonlinear Discriminant Analysis (KNDA), is presented for face recognition, which combines the nonlinear kernel trick with the linear subspace analysis method - Fisher Linear Discriminant Analysis (FLDA).First, the kernel trick is used to project the input data into an implicit feature space, then FLDA is performed in this feature space. Thus nonlinear discriminant features of the input data are yielded. In addition, in order to reduce the computational complexity, a geometry-based feature vectors selection scheme is adopted. Another similar nonlinear subspace analysis is Kernel-based Principal Component Analysis (KPCA), which combines the kernel trick with linear Principal Component Analysis (PCA). Experiments are performed with the polynomial kernel, and KNDA is compared with KPCA and FLDA. Extensive experimental results show that KNDA can give a higher recognition rate than KPCA and FLDA.

  12. Nonlinear control structures based on embedded neural system models.

    Science.gov (United States)

    Lightbody, G; Irwin, G W

    1997-01-01

    This paper investigates in detail the possible application of neural networks to the modeling and adaptive control of nonlinear systems. Nonlinear neural-network-based plant modeling is first discussed, based on the approximation capabilities of the multilayer perceptron. A structure is then proposed to utilize feedforward networks within a direct model reference adaptive control strategy. The difficulties involved in training this network, embedded within the closed-loop are discussed and a novel neural-network-based sensitivity modeling approach proposed to allow for the backpropagation of errors through the plant to the neural controller. Finally, a novel nonlinear internal model control (IMC) strategy is suggested, that utilizes a nonlinear neural model of the plant to generate parameter estimates over the nonlinear operating region for an adaptive linear internal model, without the problems associated with recursive parameter identification algorithms. Unlike other neural IMC approaches the linear control law can then be readily designed. A continuous stirred tank reactor was chosen as a realistic nonlinear case study for the techniques discussed in the paper. PMID:18255659

  13. Nonlinear dynamic analysis of framed structures including soil-structure interaction effects

    International Nuclear Information System (INIS)

    The role of oil-structure interaction on seismic behavior of reinforced concrete structures is investigated in this paper. A finite element approach has been adopted to model the interaction system that consists of the reinforced concrete plane frame, soil deposit and interface which represents the frictional between foundation of the structure and subsoil. The analysis is based on the elasto-plastic behavior of the frame members (beams and columns) that is defined by the ultimate axial force-bending moment interaction curve, while the cap model is adopted to govern the elasto-plastic behavior of the soil material. Mohr-Coulomb failure law is used to determine the initiation of slippage at the interface, while the separation is assumed to determine the initiation of slippage at the interface, while the separation is assumed to occur when the stresses at the interface becomes tension stresses. New-Mark's Predictor-Corrector algorithm is adopted for nonlinear dynamic analysis. The main aim of present work is to evaluate the sensitivity of structures to different behavior of the soil and interface layer when subjected to an earthquake excitation. Predicted results of the dynamic analysis of the interaction system indicate that the soil-structure interaction problem can have beneficial effects on the structural behavior when different soil models (elastic and elasto-plastic) and interface conditions (perfect bond and permitted slip)are considered. (author)

  14. Theoretical and Experimental Study on the Acoustic Wave Energy After the Nonlinear Interaction of Acoustic Waves in Aqueous Media

    Institute of Scientific and Technical Information of China (English)

    兰朝凤; 李凤臣; 陈欢; 卢迪; 杨德森; 张梦

    2015-01-01

    Based on the Burgers equation and Manley-Rowe equation, the derivation about nonlinear interaction of the acoustic waves has been done in this paper. After nonlinear interaction among the low-frequency weak waves and the pump wave, the analytical solutions of acoustic waves’ amplitude in the field are deduced. The relationship between normalized energy of high-frequency and the change of acoustic energy before and after the nonlinear interaction of the acoustic waves is analyzed. The experimental results about the changes of the acoustic energy are presented. The study shows that new frequencies are generated and the energies of the low-frequency are modulated in a long term by the pump waves, which leads the energies of the low-frequency acoustic waves to change in the pulse trend in the process of the nonlinear interaction of the acoustic waves. The increase and decrease of the energies of the low-frequency are observed under certain typical conditions, which lays a foundation for practical engineering applications.

  15. Non-Linearly Interacting Ghost Dark Energy in Brans-Dicke Cosmology

    CERN Document Server

    Ebrahimi, E

    2016-01-01

    In this paper we extend the form of interaction term into the non-linear regime in the ghost dark energy model. A general form of non-linear interaction term is presented and cosmic dynamic equations are obtained. Next, the model is detailed for two special choice of the non-linear interaction term. According to this the universe transits at suitable time ($z\\sim 0.8$) from deceleration to acceleration phase which alleviate the coincidence problem. Squared sound speed analysis revealed that for one class of non-linear interaction term $v_s^2$ can gets positive. This point is an impact of the non-linear interaction term and we never find such behavior in non interacting and linearly interacting ghost dark energy models. Also statefinder parameters are introduced for this model and we found that for one class the model meets the $\\Lambda CDM$ while in the second choice although the model approaches the $\\Lambda CDM$ but never touch that.

  16. Nonlinear system modeling based on experimental data

    Energy Technology Data Exchange (ETDEWEB)

    PAEZ,THOMAS L.; HUNTER,NORMAN F.

    2000-02-02

    The canonical variate analysis technique is used in this investigation, along with a data transformation algorithm, to identify a system in a transform space. The transformation algorithm involves the preprocessing of measured excitation/response data with a zero-memory-nonlinear transform, specifically, the Rosenblatt transform. This transform approximately maps the measured excitation and response data from its own space into the space of uncorrelated, standard normal random variates. Following this transform, it is appropriate to model the excitation/response relation as linear since Gaussian inputs excite Gaussian responses in linear structures. The linear model is identified in the transform space using the canonical variate analysis approach, and system responses in the original space are predicted using inverse Rosenblatt transformation. An example is presented.

  17. Non-linear theory of laser-plasma interactions

    International Nuclear Information System (INIS)

    Research progress on each of the following areas is briefly described: (1) optical ray retracing of Brillouin backscattering from a nonisothermal plasma; (2) electromagnetic oscillating two-stream instability of laser radiation; (3) second harmonic generation of upper hybrid radiation in a plasma; (4) nonlinear scattering of upper hybrid laser radiation by electron Bernstein modes in a plasma; and (5) destructive collisions of supersonic solitons

  18. Seismic response of nuclear reactors in layered liquefiable soil deposits including nonlinear soil-structure interaction

    International Nuclear Information System (INIS)

    Analysis of seismic response of structures located at a site with potential for soil liquefaction has drawn attention of many researchers. The topic is particularly important in the design of critical facilities like nuclear reactors and defense installations. This paper presents the results of a study involving evaluation of coupled seismic response of structures (model nuclear reactors) and characteristics of soil liquefaction at a site. The analysis procedure employed is based on the nonlinear finite element (FE) technique and accounts for the interaction effects due to a neighboring structure. Emphasis is given to the following features: prediction of spatial and temporal variation of pore water pressure; identification of the on-set of liquefaction based on the effective stress approach, and tracing the propagation of the liquefied zones with time and resulting response of the structures

  19. Spectral energy transfer of atmospheric gravity waves through sum and difference nonlinear interactions

    Energy Technology Data Exchange (ETDEWEB)

    Huang, K.M. [Wuhan Univ. (China). School of Electronic Information; Chinese Academey of Sciences, Hefei (China). Key Lab. of Geospace Environment; Embry Riddle Aeronautical Univ., Daytona Beach, FL (United States). Dept. of Physical Science; Ministry of Education, Wuhan (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan (China); Liu, A.Z.; Li, Z. [Embry Riddle Aeronautical Univ., Daytona Beach, FL (United States). Dept. of Physical Science; Zhang, S.D.; Yi, F. [Wuhan Univ. (China). School of Electronic Information; Ministry of Education, Wuhan (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan (China)

    2012-07-01

    Nonlinear interactions of gravity waves are studied with a two-dimensional, fully nonlinear model. The energy exchanges among resonant and near-resonant triads are examined in order to understand the spectral energy transfer through interactions. The results show that in both resonant and near-resonant interactions, the energy exchange between two high frequency waves is strong, but the energy transfer from large to small vertical scale waves is rather weak. This suggests that the energy cascade toward large vertical wavenumbers through nonlinear interaction is inefficient, which is different from the rapid turbulence cascade. Because of considerable energy exchange, nonlinear interactions can effectively spread high frequency spectrum, and play a significant role in limiting wave amplitude growth and transferring energy into higher altitudes. In resonant interaction, the interacting waves obey the resonant matching conditions, and resonant excitation is reversible, while near-resonant excitation is not so. Although near-resonant interaction shows the complexity of match relation, numerical experiments show an interesting result that when sum and difference near-resonant interactions occur between high and low frequency waves, the wave vectors tend to approximately match in horizontal direction, and the frequency of the excited waves is also close to the matching value. (orig.)

  20. Time-varying interaction leads to amplitude death in coupled nonlinear oscillators

    Indian Academy of Sciences (India)

    Awadhesh Prasad

    2013-09-01

    A new form of time-varying interaction in coupled oscillators is introduced. In this interaction, each individual oscillator has always time-independent self-feedback while its interaction with other oscillators are modulated with time-varying function. This interaction gives rise to a phenomenon called amplitude death even in diffusively coupled identical oscillators. The nonlinear variation of the locus of bifurcation point is shown. Results are illustrated with Landau–Stuart (LS) and Rössler oscillators.

  1. The dynamics of interacting nonlinearities governing long wavelength driftwave turbulence

    International Nuclear Information System (INIS)

    Because of the ubiquitous nature of turbulence and the vast array of different systems which have turbulent solutions, the study of turbulence is an area of active research. Much present day understanding of turbulence is rooted in the well established properties of homogeneous Navier-Stokes turbulence, which, due to its relative simplicity, allows for approximate analytic solutions. This work examines a group of turbulent systems with marked differences from Navier-Stokes turbulence, and attempts to quantify some of their properties. This group of systems represents a variety of drift wave fluctuations believed to be of fundamental importance in laboratory fusion devices. From extensive simulation of simple local fluid models of long wavelength drift wave turbulence in tokamaks, a reasonably complete picture of the basic properties of spectral transfer and saturation has emerged. These studies indicate that many conventional notions concerning directions of cascades, locality and isotropy of transfer, frequencies of fluctuations, and stationarity of saturation are not valid for moderate to long wavelengths. In particular, spectral energy transfer at long wavelengths is dominated by the E x B nonlinearity, which carries energy to short scale in a manner that is highly nonlocal and anisotropic. In marked contrast to the canonical self-similar cascade dynamics of Kolmogorov, energy is efficiently passed between modes separated by the entire spectrum range in a correlation time. At short wavelengths, transfer is dominated by the polarization drift nonlinearity. While the standard dual cascade applies in this subrange, it is found that finite spectrum size can produce cascades that are reverse directed and are nonconservative in enstrophy and energy similarity ranges. In regions where both nonlinearities are important, cross-coupling between the nolinearities gives rise to large no frequency shifts as well as changes in the spectral dynamics

  2. Long-term wave growth and its linear and nonlinear interactions with wind fluctuations

    Directory of Open Access Journals (Sweden)

    Z. Ge

    2008-05-01

    Full Text Available Following Ge and Liu (2007, the simultaneously recorded time series of wave elevation and wind velocity are examined for long-term (on Lavrenov's τ4-scale or 3 to 6 h linear and nonlinear interactions between the wind fluctuations and the wave field. Over such long times the detected interaction patterns should reveal general characteristics for the wave growth process. The time series are divided into three episodes, each approximately 1.33 h long, to represent three sequential stages of wave growth. The classic Fourier-domain spectral and bispectral analyses are used to identify the linear and quadratic interactions between the waves and the wind fluctuations as well as between different components of the wave field.

    The results show clearly that as the wave field grows the linear interaction becomes enhanced and covers wider range of frequencies. Two different wave-induced components of the wind fluctuations are identified. These components, one at around 0.4 Hz and the other at around 0.15 to 0.2 Hz, are generated and supported by both linear and quadratic wind-wave interactions probably through the distortions of the waves to the wind field. The fact that the higher-frequency wave-induced component always stays with the equilibrium range of the wave spectrum around 0.4 Hz and the lower-frequency one tends to move with the downshifting of the primary peak of the wave spectrum defines the partition of the primary peak and the equilibrium range of the wave spectrum, a characteristic that could not be revealed by short-time wavelet-based analyses in Ge and Liu (2007. Furthermore, these two wave-induced peaks of the wind spectrum appear to have different patterns of feedback to the wave field. The quadratic wave-wave interactions also are assessed using the auto-bispectrum and are found to be especially active during the first and the third episodes. Such directly detected wind-wave interactions, both linear and

  3. Nonlinear interaction between wave and convective disturbances in the solar corona

    Science.gov (United States)

    Veselovsky, I. S.; Mikhalyaev, B. B.; Bembitov, D. B.

    2015-12-01

    During more than two decades, many non-stationary events have been observed in the solar corona by different ground and space instruments, namely: oscillations and flows. These events play a crucial role in a solving two important problems of the solar physics: coronal heating and solar wind acceleration. Numerous observational data and theoretical works demonstrate the nonlinear interaction between waves and flows in the solar atmosphere. On other hand, nonlinear effects can also be used in coronal seismology, where a significant success leaded to many original works on linear disturbances in the coronal plasma. The nonlinear approach should make it possible to achieve more precise results.

  4. Eluding the Physical Constraints in a Nonlinear Interaction Sound Synthesis Model for Gesture Guidance

    Directory of Open Access Journals (Sweden)

    Etienne Thoret

    2016-06-01

    Full Text Available In this paper, a flexible control strategy for a synthesis model dedicated to nonlinear friction phenomena is proposed. This model enables to synthesize different types of sound sources, such as creaky doors, singing glasses, squeaking wet plates or bowed strings. Based on the perceptual stance that a sound is perceived as the result of an action on an object we propose a genuine source/filter synthesis approach that enables to elude physical constraints induced by the coupling between the interacting objects. This approach makes it possible to independently control and freely combine the action and the object. Different implementations and applications related to computer animation, gesture learning for rehabilitation and expert gestures are presented at the end of this paper.

  5. Demonstration of a Chip-based Nonlinear Optical Isolator

    CERN Document Server

    Hua, Shiyue; Jiang, Xiaoshun; Hua, Qian; Jiang, Liang; Xiao, Min

    2016-01-01

    Despite fundamentally challenging in integrated (nano)photonics, achieving chip-based light nonreciprocity becomes increasingly urgent in signal processing and optical communications. Because of material incompatibilities in conventional approaches based on Faraday effects, alternative solutions have resorted to nonlinear processes to obtain one-way transmission. However, revealed dynamic reciprocity in a recent theoretical analysis has pinned down the functionalities of these nonlinear isolators. To overcome this dynamic reciprocity, we here report the first demonstration of a nonlinear optical isolator on a silicon chip enforced by phase-matched parametric amplification. Using a high-Q microtoroid resonator, we realize highly nonreciprocal transport at the 1,550 nm wavelength when waves are simultaneously launched in both forward and backward directions. Our design, compatible with current CMOS technique, yields convincing isolation performance with sufficiently low insertion loss for a wide range of input ...

  6. Nonlinear beam plasma interaction in plasma with a superthermal electrons

    International Nuclear Information System (INIS)

    The study of plasmas containing superthermal particles is very important to the understanding of space and astrophysical phenomena. The non-Maxwellian plasmas are also crucial to the understanding of space and astrophyisical plasma dynamics. The kappa-type distribution is used to model a high energy tail in the electron/ion distribution function. We have investigated the dynamics of small amplitude electrostatic solitary structures in a plasma consisting of superthermal electrons, ions and an electron beam. Solitary structures is investigated. The effect(s) of ion beam characteristics, as well as of superthermality of the background, have been studied numerically to trace their influence on solitary structures. The results of this investigation may be important for understanding the nonlinear structures in astrophysical and space environments. (author)

  7. Nonlinear Optical Interactions in Bacteriorhodopsin Using Z-Scan

    Science.gov (United States)

    Aranda, Francisco J.; Rao, Devulapalli V. G. L. N.; Wong, Chi L.; Zhou, Ping; Chen, Zhong; Akkara, Joseph A.; Kaplan, David L.; Roach, Joseph F.

    1995-06-01

    Nonlinear refractive index coefficient n2 of bacteriorhodopsin suspensions in water is measured by the Z-scan technique with a low power continuous wave laser at 647.1 manometer wavelength. Our results indicate that both the magnitude and the sign of n2 depend strongly on the light intensity. Negative values for n2 are obtained for on axis laser irradiance at the focus above 3 W/cm2. The observed self-defocusing phenomena can be attributed to the index change due to the light induced transition between the photochromic states. The results elucidate the origin of n2 and offer a plausible explanation for the differences in the reported n2 measurements.

  8. Fluid-structure interaction for nonlinear response of shells conveying pulsatile flow

    Science.gov (United States)

    Tubaldi, Eleonora; Amabili, Marco; Païdoussis, Michael P.

    2016-06-01

    Circular cylindrical shells with flexible boundary conditions conveying pulsatile flow and subjected to pulsatile pressure are investigated. The equations of motion are obtained based on the nonlinear Novozhilov shell theory via Lagrangian approach. The flow is set in motion by a pulsatile pressure gradient. The fluid is modeled as a Newtonian pulsatile flow and it is formulated using a hybrid model that contains the unsteady effects obtained from the linear potential flow theory and the pulsatile viscous effects obtained from the unsteady time-averaged Navier-Stokes equations. A numerical bifurcation analysis employs a refined reduced order model to investigate the dynamic behavior. The case of shells containing quiescent fluid subjected to the action of a pulsatile transmural pressure is also addressed. Geometrically nonlinear vibration response to pulsatile flow and transmural pressure are here presented via frequency-response curves and time histories. The vibrations involving both a driven mode and a companion mode, which appear due to the axial symmetry, are also investigated. This theoretical framework represents a pioneering study that could be of great interest for biomedical applications. In particular, in the future, a more refined model of the one here presented will possibly be applied to reproduce the dynamic behavior of vascular prostheses used for repairing and replacing damaged and diseased thoracic aorta in cases of aneurysm, dissection or coarctation. For this purpose, a pulsatile time-dependent blood flow model is here considered by applying physiological waveforms of velocity and pressure during the heart beating period. This study provides, for the first time in literature, a fully coupled fluid-structure interaction model with deep insights in the nonlinear vibrations of circular cylindrical shells subjected to pulsatile pressure and pulsatile flow.

  9. Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions in Atomic Force Microscopy

    OpenAIRE

    Cantrell, John H.; Cantrell, Sean A.

    2010-01-01

    The various dynamical implementations of the atomic force microscope have become important nanoscale characterization tools for the development of novel materials and devices. One of the most significant factors affecting all dynamical AFM modalities is the cantilever tip-sample surface interaction force. We have developed a detailed mathematical model of this interaction that includes a quantitative consideration of the nonlinearity of the interaction force as a function of the cantilever ti...

  10. Near-field soil-structure interaction analysis using nonlinear hybrid modeling

    International Nuclear Information System (INIS)

    The hybrid modeling method (Gupta and Penzien 1980) and associated analysis procedure for solving a three-dimensional soil-structure interaction problem was developed by Gupta and Penzien (1981) and Gupta et al.(1982). Subsequently, successive modifications have been made to the original modeling method and analysis procedure allowing more general treatment of the SSI problem (Penzien, 1988). Through many correlation studies of field test data obtained under forced-vibration and earthquake-excitation conditions, it has been shown that the HASSI programs can effectively predict the dynamic response of a soil-structure system, if realistic soil parameters are adopted. In the above, the entire structure-foundation system is considered to respond in a linear fashion. Since the reflected three-dimensional waves at the soil-structure interface decays very rapidly with distance away from the structure (Katayama, 1987 (a)), the response of the soil close to the base of the structure may greatly affect its response; therefore, proper modeling of the non-linear soil behavior characteristic is essential. The nonlinear behavior of near-field soil has been taken into consideration in HASSI-7 by the standard equivalent linearization procedures used in programs SHAKE and FLUSH

  11. Electron-phonon interaction and nonlinear transport phenomena in solid Hg point-contacts

    International Nuclear Information System (INIS)

    At cryogenic temperatures the conductivity of Hg point-contacts was studied in both the superconducting and normal state. An original method of fabricating the Hg-based point-contacts directly in liquid 4He was proposed, which guaranteed creation of small-size high-purity ballistic contacts. The resistance of the contacts as well as the current-voltage characteristics along with the voltage dependence of their first and second derivatives were experimentally investigated at 1.5 K. We analyze such characteristics of the contacts as Josephson critical current, excess current, energy gap and the nonlinear part of conductivity caused by electron-phonon interaction (EPI). The point-contact EPI function gpc(ω) for Hg was reconstructed and integral parameters of EPI were calculated. The gpc(ω) was then used as an approximation to the phonon density of states for estimations of the thermodynamic characteristics in Hg. Finally we discuss the results of our calculations of non-linear conductivity caused by manifestation of the frequency dependence of the energy gap function in the elastic current component through the contact.

  12. Dynamical soil-structure interactions: influence of soil behaviour nonlinearities; Interaction Dynamique Sol-Structure: Influence des Nonlinearites de Comportement du Sol

    Energy Technology Data Exchange (ETDEWEB)

    Gandomzadeh, Ali

    2011-02-08

    The interaction of the soil with the structure has been largely explored the assumption of material and geometrical linearity of the soil. Nevertheless, for moderate or strong seismic events, the maximum shear strain can easily reach the elastic limit of the soil behavior. Considering soil-structure interaction, the nonlinear effects may change the soil stiffness at the base of the structure and therefore energy dissipation into the soil. Consequently, ignoring the nonlinear characteristics of the dynamic soil-structure interaction (DSSI) this phenomenon could lead to erroneous predictions of structural response. The goal of this work is to implement a fully nonlinear constitutive model for soils into a numerical code in order to investigate the effect of soil nonlinearity on dynamic soil structure interaction. Moreover, different issues are taken into account such as the effect of confining stress on the shear modulus of the soil, initial static condition, contact elements in the soil-structure interface, etc. During this work, a simple absorbing layer method based on a Rayleigh/Caughey damping formulation, which is often already available in existing Finite Element softwares, is also presented. The stability conditions of the wave propagation problems are studied and it is shown that the linear and nonlinear behavior are very different when dealing with numerical dispersion. It is shown that the 10 points per wavelength rule, recommended in the literature for the elastic media is not sufficient for the nonlinear case. The implemented model is first numerically verified by comparing the results with other known numerical codes. Afterward, a parametric study is carried out for different types of structures and various soil profiles to characterize nonlinear effects. Different features of the DSSI are compared to the linear case: modification of the amplitude and frequency content of the waves propagated into the soil, fundamental frequency, energy dissipation in

  13. Directed momentum current of Bose–Einstein condensate in the presence of spatially modulated nonlinear interaction

    Science.gov (United States)

    Zhao, Wen-Lei; Ding, Cai-Ying; Liu, Jie; Fu, Li-Bin

    2016-06-01

    We investigate the quantum transport dynamics of periodically delta-kicked Bose–Einstein condensate under the effect of spatially modulated nonlinear interactions. The spatial modulation frequency can dramatically affect the transport behaviors of the ultra-cold atoms. For odd frequency, the linear growth of the directed current is close to that of the noninteracting case for not very strong nonlinear interaction. Both the acceleration and the quantum state evolution gradually approach that of the noninteracting case with increasing frequency. For other values of frequency, a very weak nonlinear interaction can dramatically reduce the linear growth of the directed current. The quantum state evolution differs rapidly from that of the noninteracting case. The underlying dynamic mechanism is uncovered and some important implications are addressed.

  14. Statistical Analysis of Nonlinear Processes Based on Penalty Factor

    OpenAIRE

    Zhang, Yingwei; Zhang, Chuanfang; Zhang, Wei

    2014-01-01

    A new process monitoring approach is proposed for handling the nonlinear monitoring problem in the electrofused magnesia furnace (EFMF). Compared to conventional method, the contributions are as follows: (1) a new kernel principal component analysis is proposed based on loss function in the feature space; (2) the model of kernel principal component analysis based on forgetting factor is updated; (3) a new iterative kernel principal component analysis algorithm is proposed based on penalty fac...

  15. Topological charge algebra of optical vortices in nonlinear interactions.

    Science.gov (United States)

    Zhdanova, Alexandra A; Shutova, Mariia; Bahari, Aysan; Zhi, Miaochan; Sokolov, Alexei V

    2015-12-28

    We investigate the transfer of orbital angular momentum among multiple beams involved in a coherent Raman interaction. We use a liquid crystal light modulator to shape pump and Stokes beams into optical vortices with various integer values of topological charge, and cross them in a Raman-active crystal to produce multiple Stokes and anti-Stokes sidebands. We measure the resultant vortex charges using a tilted-lens technique. We verify that in every case the generated beams' topological charges obey a simple relationship, resulting from angular momentum conservation for created and annihilated photons, or equivalently, from phase-matching considerations for multiple interacting beams. PMID:26832066

  16. A Non-smooth Nonlinear Conjugate Gradient Method for Interactive Contact Force Problems

    DEFF Research Database (Denmark)

    Silcowitz, Morten; Niebe, Sarah Maria; Erleben, Kenny

    Interactive rigid body simulation is important for robot simulation and virtual design. A vital part of the simulation is the computation of contact forces. This paper addresses the contact force problem, as used in interactive simulation. The contact force problem can be formulated in the form of...... a nonlinear complementarity problem (NCP), which can be solved using an iterative splitting method, such as the projected Gauss–Seidel (PGS) method. We present a novel method for solving the NCP problem by applying a Fletcher–Reeves type nonlinear nonsmooth conjugate gradient (NNCG) type method. We...

  17. Pulse shape effects on photon-photon interactions in non-linear optical quantum gates

    OpenAIRE

    Hofmann, Holger F.; Nishitani, Hitoshi

    2009-01-01

    Ideally, strong non-linearities could be used to implement quantum gates for photonic qubits by well controlled two photon interactions. However, the dependence of the non-linear interaction on frequency and time makes it difficult to preserve a coherent pulse shape that could justify a single mode model for the time-frequency degree of freedom of the photons. In this paper, we analyze the problem of temporal multi-mode effects by considering the pulse shape of the average output field obtain...

  18. Likelihood-Based Inference in Nonlinear Error-Correction Models

    DEFF Research Database (Denmark)

    Kristensen, Dennis; Rahbæk, Anders

    We consider a class of vector nonlinear error correction models where the transfer function (or loadings) of the stationary relation- ships is nonlinear. This includes in particular the smooth transition models. A general representation theorem is given which establishes the dynamic properties of...... trends and a linear trend in general. Gaussian likelihood-based estimators are considered for the long- run cointegration parameters, and the short-run parameters. Asymp- totic theory is provided for these and it is discussed to what extend asymptotic normality and mixed normaity can be found. A...

  19. Soliton pair generation in the interactions of Airy and nonlinear accelerating beams

    CERN Document Server

    Zhang, Yiqi; Wu, Zhenkun; Zheng, Huaibin; Lu, Keqing; Li, Yuanyuan; Zhang, Yanpeng

    2013-01-01

    We investigate numerically the interactions of two in-phase and out-of-phase Airy beams and nonlinear accelerating beams in Kerr and saturable nonlinear media, in one transverse dimension. We find that bound and unbound soliton pairs, as well as single solitons, can form in such interactions. If the interval between two incident beams is large relative to the width of their first lobes, the generated soliton pairs just propagate individually and do not interact. However, if the interval is comparable to the widths of the maximum lobes, the pairs interact and display varied behavior. In the in-phase case, they attract each other and exhibit stable bound, oscillating, and unbound states, after shedding some radiation initially. In the out-of-phase case, they repel each other and after an initial interaction, fly away as individual solitons. While the incident beams display acceleration, the solitons or soliton pairs generated from those beams do not.

  20. Nonlinear interaction of impulsive gravitational waves for the vacuum Einstein equations

    CERN Document Server

    Luk, Jonathan

    2013-01-01

    In this paper, we study the problem of the nonlinear interaction of impulsive gravitational waves for the Einstein vacuum equations. The problem is studied in the context of a characteristic initial value problem with data given on two null hypersurfaces and containing curvature delta singularities. We establish an existence and uniqueness result for the spacetime arising from such data and show that the resulting spacetime represents the interaction of two impulsive gravitational waves germinating from the initial singularities. In the spacetime, the curvature delta singularities propagate along 3-dimensional null hypersurfaces intersecting to the future of the data. To the past of the intersection, the spacetime can be thought of as containing two independent, non-interacting impulsive gravitational waves and the intersection represents the first instance of their nonlinear interaction. Our analysis extends to the region past their first interaction and shows that the spacetime still remains smooth away fro...

  1. Adaptive Observer-Based Fault Estimate for Nonlinear Systems

    Institute of Scientific and Technical Information of China (English)

    ZONG Qun; LIU Wenjing; LIU Li

    2006-01-01

    An approach for adaptive observer-based fault estimate for nonlinear system is proposed.H-infinity theory is applied to analyzing the design method and stable conditions of the adaptive observer,from which both system state and fault can be estimated.It is proved that the fault estimate error is related to the given H-infinity track performance indexes,as well as to the changing rate of the fault and the Lipschitz constant of the nonlinear item.The design steps of the adaptive observer are proposed.The simulation results show that the observer has good performance for fault estimate even when the system includes nonlinear terms,which confirms the effectiveness of the method.

  2. Dissipative-based adaptive neural control for nonlinear systems

    Institute of Scientific and Technical Information of China (English)

    Yugang NIU; Xingyu WANG; Junwei LU

    2004-01-01

    A dissipative-based adaptive neural control scheme was developed for a class of nonlinear uncertain systems with unknown nonlinearities that might not be linearly parameterized. The major advantage of the present work was to relax the requirement of matching condition, I.e., the unknown nonlinearities appear on the same equation as the control input in a state-space representation, which was required in most of the available neural network controllers. By synthesizing a state-feedback neural controller to nake the closed-loop system dissipative with respect to a quadratic supply rate, the developed control scheme guarantees that the L2-gain of controlled system was less than or equal to a prescribed level. And then, it is shown that the output tracking error is uniformly ultimate bounded. The design scheme is illustrated using a numerical simulation.

  3. Nonlinear geosphere-biosphere interactions and the Cambrian explosion

    Science.gov (United States)

    von Bloh, W.; Bounama, C.; Franck, S.

    2003-04-01

    A conceptual model for the global carbon cycle of the Earth containing the reservoirs mantle, ocean floor, continental crust, continental biosphere, the kerogen , as well as the aggregated reservoir ocean and atmosphere is presented. In this study the evolution of the mean global surface temperature, the biomass, and reservoir sizes over the whole history and future of the Earth under a maturing Sun is investigated. Reasonable values for the present distribution of carbon in the surface reservoirs of the Earth are obtained and a pronounced global minimum of mean surface temperature at the present state of the Earth is found. Furthermore, three different biosphere types are introduced: procaryotes, eucaryotes, and higher metazoa. They all differ in their temperature tolerance interval and their biogenic enhancement of silicate rock weathering. Around 500 Myr in the past we find a rise of higher metazoa caused by the nonlinear feedback between biosphere and climate. Biotic amplifying of weathering provides and maintains the environment of higher life forms. Such a mechanism may explain the so-called Cambrian explosion.

  4. Nonlinear Dynamics Based Digital Logic and Circuits

    OpenAIRE

    Behnam eKia; John Florian Lindner; William eDitto

    2015-01-01

    We discuss the role and importance of dynamics in the brain and biological neural networks, and argue that dynamics is one of the main missing elements in conventional Boolean logic and circuits. We summarize a simple dynamics based computing method, and categorize different techniques that we have introduced to realize logic, functionality, and programmability. We discuss the role and importance of coupled dynamics in networks of biological excitable cells, and then review our simple coupled...

  5. A Cumulant-based Analysis of Nonlinear Magnetospheric Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Jay R. Johnson; Simon Wing

    2004-01-28

    Understanding magnetospheric dynamics and predicting future behavior of the magnetosphere is of great practical interest because it could potentially help to avert catastrophic loss of power and communications. In order to build good predictive models it is necessary to understand the most critical nonlinear dependencies among observed plasma and electromagnetic field variables in the coupled solar wind/magnetosphere system. In this work, we apply a cumulant-based information dynamical measure to characterize the nonlinear dynamics underlying the time evolution of the Dst and Kp geomagnetic indices, given solar wind magnetic field and plasma input. We examine the underlying dynamics of the system, the temporal statistical dependencies, the degree of nonlinearity, and the rate of information loss. We find a significant solar cycle dependence in the underlying dynamics of the system with greater nonlinearity for solar minimum. The cumulant-based approach also has the advantage that it is reliable even in the case of small data sets and therefore it is possible to avoid the assumption of stationarity, which allows for a measure of predictability even when the underlying system dynamics may change character. Evaluations of several leading Kp prediction models indicate that their performances are sub-optimal during active times. We discuss possible improvements of these models based on this nonparametric approach.

  6. Numerical method of studying nonlinear interactions between long waves and multiple short waves

    International Nuclear Information System (INIS)

    Although the nonlinear interactions between a single short gravity wave and a long wave can be solved analytically, the solution is less tractable in more general cases involving multiple short waves. In this work we present a numerical method of studying nonlinear interactions between a long wave and multiple short harmonic waves in infinitely deep water. Specifically, this method is applied to the calculation of the temporal and spatial evolutions of the surface elevations in which a given long wave interacts with several short harmonic waves. Another important application of our method is to quantitatively analyse the nonlinear interactions between an arbitrary short wave train and another short wave train. From simulation results, we obtain that the mechanism for the nonlinear interactions between one short wave train and another short wave train (expressed as wave train 2) leads to the energy focusing of the other short wave train (expressed as wave train 3). This mechanism occurs on wave components with a narrow frequency bandwidth, whose frequencies are near that of wave train 3. (geophysics, astronomy and astrophysics)

  7. A nonlinear interface formulation for soil–structure interaction systems

    OpenAIRE

    Haikal, Ghardir

    2014-01-01

    Finite element simulations of soil–structure interaction systems require the use of nonconfirming meshes (NCM) to increase accuracy in capturing the behavior in each material and along the interface. The use of NCM meshes, however, presents a number of challenges in modeling the soil–structure contact interface. The main issue in modeling contact with NCMs is how to ensure geometric compatibility and a complete transfer of surface tractions through the interface in the presence of large mater...

  8. Ion beam analysis based on cellular nonlinear networks

    OpenAIRE

    Senger, V.; R. Tetzlaff; H. Reichau; Ratzinger, U.

    2011-01-01

    The development of a non- destructive measurement method for ion beam parameters has been treated in various projects. Although results are promising, the high complexity of beam dynamics has made it impossible to implement a real time process control up to now. In this paper we will propose analysing methods based on the dynamics of Cellular Nonlinear Networks (CNN) that can be implemented on pixel parallel CNN based architectures and yield satisfying results even at low re...

  9. Ion beam analysis based on cellular nonlinear networks

    Science.gov (United States)

    Senger, V.; Tetzlaff, R.; Reichau, H.; Ratzinger, U.

    2011-07-01

    The development of a non- destructive measurement method for ion beam parameters has been treated in various projects. Although results are promising, the high complexity of beam dynamics has made it impossible to implement a real time process control up to now. In this paper we will propose analysing methods based on the dynamics of Cellular Nonlinear Networks (CNN) that can be implemented on pixel parallel CNN based architectures and yield satisfying results even at low resolutions.

  10. Nonlinear theory of laser-induced dipolar interactions in arbitrary geometry

    CERN Document Server

    Shahmoon, Ephraim

    2013-01-01

    Polarizable dipoles, such as atoms, molecules or nanoparticles, subject to laser radiation, may attract or repel each other. We derive a general formalism in which such laser-induced dipole-dipole interactions (LIDDI) in any geometry and for any laser strength are described in terms of the resonant dipole-dipole interaction (RDDI) between dipoles dressed by the laser. Our expressions provide a physically clear and technically simple route towards the analysis of LIDDI in a general geometry. This approach can treat both mechanical and internal-state interactions between the dipoles. Our general results reveal LIDDI effects due to nonlinear dipole-laser interactions, unaccounted for by previous treatments of LIDDI. We discuss, via several simple approaches, the origin of these nonlinear effects and their absence in previous works.

  11. Field-matter interaction in atomic and plasma physics, from fluctuations to the strongly nonlinear regime

    International Nuclear Information System (INIS)

    This manuscript provides a theoretical description, sometimes illustrated by experimental results, of several examples of field-matter interaction in various domains of physics, showing how the same basic concepts and theoretical methods may be used in very different physics situations. The issues addressed here are nonlinear field-matter interaction in plasma physics within the framework of classical mechanics (with a particular emphasis on wave-particle interaction), the linear analysis of beam-plasma instabilities in the relativistic regime, and the quantum description of laser-atom interaction, including quantum electrodynamics. Novel methods are systematically introduced in order to solve some very old problems, like the nonlinear counterpart of the Landau damping rate in plasma physics, for example. Moreover, our results directly apply to inertial confinement fusion, laser propagation in an atomic vapor, ion acceleration in a magnetized plasma and the physics of the Reversed Field Pinch for magnetic fusion. (author)

  12. Uranium(IV) Interaction with Aqueous/Solid Interfaces Studied by Nonlinear Optics

    Energy Technology Data Exchange (ETDEWEB)

    Geiger, Franz [Northwestern Univ., Evanston, IL (United States)

    2015-03-27

    This is the Final Technical Report for "Uranium(IV) Interaction with Aqueous/Solid Interfaces Studied by Nonlinear Optics", by Franz M. Geiger, PI, from Northwestern University, IL, USA, Grant Number SC0004101 and/or DE-PS02-ER09-07.

  13. Nonlinear Interactions within the D-Region Ionosphere

    Science.gov (United States)

    Moore, Robert

    2016-07-01

    This paper highlights the best results obtained during D-region modification experiments performed by the University of Florida at the High-frequency Active Auroral Research Program (HAARP) observatory between 2007 and 2014. Over this period, we saw a tremendous improvement in ELF/VLF wave generation efficiency. We identified methods to characterize ambient and modified ionospheric properties and to discern and quantify specific types of interactions. We have demonstrated several important implications of HF cross-modulation effects, including "Doppler Spoofing" on HF radio waves. Throughout this talk, observations are compared with the predictions of an ionospheric HF heating model to provide context and guidance for future D-region modification experiments.

  14. Development of a Generalized Methodology for Soil-Structure Interaction Analysis Using Nonlinear Time-Domain Techniques

    International Nuclear Information System (INIS)

    A generalized time-domain method for Soil-Structure Interaction Analysis is developed, based upon an extension of the Bielak Method. The methodology is combined with the use of a simple hysteretic soil model based upon the Ramberg-Osgood formulation and applied to a notional Small Modular Reactor. These benchmark results compare well with those obtained by using the industry-standard frequency domain code SASSI. The methodology provides a path forward for investigation of other sources of nonlinearity, including those associated with the use of more physically-realistic material models incorporating pore-pressure effects, gap opening/closing, the effect of nonlinear structural elements, and 3D seismic inputs.

  15. Interharmonic modulation products as a means to quantify nonlinear D-region interactions

    Science.gov (United States)

    Moore, Robert

    Experimental observations performed during dual beam ionospheric HF heating experiments at the High frequency Active Auroral Research Program (HAARP) HF transmitter in Gakona, Alaska are used to quantify the relative importance of specific nonlinear interactions that occur within the D region ionosphere. During these experiments, HAARP broadcast two amplitude modulated HF beams whose center frequencies were separated by less than 20 kHz. One beam was sinusoidally modulated at 500 Hz while the second beam was sinusoidally modulated using a 1-7 kHz linear frequency-time chirp. ELF/VLF observations performed at two different locations (3 and 98 km from HAARP) provide clear evidence of strong interactions between all field components of the two HF beams in the form of low and high order interharmonic modulation products. From a theoretical standpoint, the observed interharmonic modulation products could be produced by several different nonlinearities. The two primary nonlinearities take the form of wave-medium interactions (i.e., cross modulation), wherein the ionospheric conductivity modulation produced by one signal crosses onto the other signal via collision frequency modification, and wave-wave interactions, wherein the conduction current associated with one wave mixes with the electric field of the other wave to produce electron temperature oscillations. We are able to separate and quantify these two different nonlinearities, and we conclude that the wave-wave interactions dominate the wave-medium interactions by a factor of two. These results are of great importance for the modeling of transioinospheric radio wave propagation, in that both the wave-wave and the wave-medium interactions could be responsible for a significant amount of anomalous absorption.

  16. Information Fusion Based Decoupling Control for Multivariable Nonlinear System

    OpenAIRE

    2015-01-01

    A decoupling control method based on information fusion estimation for a nonlinear system is presented in the paper. For each main channel and its coupled channels of the system, according to the information fusion theorem, the estimation of the system future state is obtained by fusing the information of the desired output trajectory of the system. Furthermore, approximate optimal control rule is obtained by fusing the system future state information and the control energy soft constraint in...

  17. Nonlinear seismic response analysis of embedded reactor buildings based on the substructure approach in time domain

    International Nuclear Information System (INIS)

    A practical method for elasto-plastic seismic response analysis is described under considerations of nonlinear material law of a structure and dynamic soil-structure interaction. The method is essentially based on the substructure approach of time domain analysis. Verification of the present method is carried out for typical BWR-MARK II type reactor building which is embedded in a soil, and the results are compared with those of the frequency response analysis which gives good accuracy for linear system. As a result, the present method exhibits sufficient accuracy. Furthermore, elasto-plastic analyses considering the soil-structure interaction are made as an application of the present method, and nonlinear behaviors of the structure and embedment effects are discussed. (orig.)

  18. Relative Nonlinear Electrodynamics Interaction of Charged Particles with Strong and Super Strong Laser Fields

    CERN Document Server

    Avetissian, Hamlet

    2006-01-01

    This book covers a large class of fundamental investigations into Relativistic Nonlinear Electrodynamics. It explores the interaction between charged particles and strong laser fields, mainly concentrating on contemporary problems of x-ray lasers, new type small set-up high-energy accelerators of charged particles, as well as electron-positron pair production from super powerful laser fields of relativistic intensities. It will also discuss nonlinear phenomena of threshold nature that eliminate the concurrent inverse processes in the problems of Laser Accelerator and Free Electron Laser, thus creating new opportunities for solving these problems.

  19. Giant Kerr nonlinearity induced by interacting quantum coherences from decays and incoherent pumping

    Institute of Scientific and Technical Information of China (English)

    Bai Yan-Feng; Yang Wen-Xing; Han Ding-An; Yu Xiao-Qiang

    2012-01-01

    A scheme for generating the giant enhancement of the Kerr nonlinearity in a four-level system with the quantum coherences from the decays and the incoherent pumping is proposed.Compared with that generated in a general fourlevel system,the Kerr nonlinearity can be enhanced by several orders of magnitude with vanishing linear absorption.By using the numerical results,we show that the remarkable enhancement should be attributed to the interaction of the quantum coherences from the decays and the incoherent pumping.

  20. Nonlinear Interaction of Elliptical Laser Beam with Collisional Plasma: Effect of Linear Absorption

    Science.gov (United States)

    Keshav, Walia; Sarabjit, Kaur

    2016-01-01

    In the present work, nonlinear interaction of elliptical laser beam with collisional plasma is studied by using paraxial ray approximation. Nonlinear differential equations for the beam width parameters of semi-major axis and semi-minor axis of elliptical laser beam have been set up and solved numerically to study the variation of beam width parameters with normalized distance of propagation. Effects of variation in absorption coefficient and plasma density on the beam width parameters are also analyzed. It is observed from the analysis that extent of self-focusing of beam increases with increase/decrease in plasma density/absorption coefficient.

  1. Nonlinear interaction of two trapped-mode resonances in a bilayer fish-scale metamaterial

    Science.gov (United States)

    Tuz, Vladimir R.; Novitsky, Denis V.; Mladyonov, Pavel L.; Prosvirnin, Sergey L.; Novitsky, Andrey V.

    2014-09-01

    We report on a bistable light transmission through a bilayer "fish-scale" (meander-line) metamaterial. It is demonstrated that an all-optical switching may be achieved nearly the frequency of the high-quality-factor Fano-shaped trapped-mode resonance excitation. The nonlinear interaction of two closely spaced trapped-mode resonances in the bilayer structure composed with a Kerr-type nonlinear dielectric slab is analyzed in both frequency and time domains. It is demonstrated that these two resonances react differently on the applied intense light which leads to destination of a multistable transmission.

  2. Nonlinear interaction of two trapped-mode resonances in a bilayer "fish-scale" metamaterial

    CERN Document Server

    Tuz, Vladimir R; Mladyonov, Pavel L; Prosvirnin, Sergey L; Novitsky, Andrey V

    2014-01-01

    We report on a bistable light transmission through a bilayer "fish-scale" (meander-line) metamaterial. It is demonstrated that an all-optical switching may be achieved nearly the frequency of the high-quality-factor Fano-shaped trapped-mode resonance excitation. The nonlinear interaction of two closely spaced trapped-mode resonances in the bilayer structure composed with a Kerr-type nonlinear dielectric slab is analyzed in both frequency and time domains. It is demonstrated that these two resonances react differently on the applied intense light which leads to destination of a multistable transmission.

  3. Interactive example-based hatching

    NARCIS (Netherlands)

    Gerl, Moritz; Isenberg, Tobias

    2013-01-01

    We present an approach for interactively generating pen-and-ink hatching renderings based on hand-drawn examples. We aim to overcome the regular and synthetic appearance of the results of existing methods by incorporating human virtuosity and illustration skills in the computer generation of such im

  4. Global Spiral Arms Formation by Non-linear Interaction of Wakelets

    CERN Document Server

    Kumamoto, Jun

    2016-01-01

    The formation and evolution of galactic spiral arms is not yet clearly understood despite many analytic and numerical work. Recently, a new idea has been proposed that local density enhancements (waklets) arising in the galactic disk connect with each other and make global spiral arms. However, the understanding of this mechanism is not yet sufficient. We analyze the interaction of wakelets by using N-body simulations including perturbing point masses, which are heavier than individual N-body particles and act as the seeds for wakelets. Our simulation facilitates more straightforward interpretation of numerical results than previous work by putting a certain number of perturbers in a well-motivated configuration. We detected a clear sign of non-linear interaction between wakelets, which make global spiral arms by connecting two adjacent wakelets. We found that the wave number of the strongest non-linear interaction depends on galactic disk mass and shear rate. This dependence is consistent with the prediction...

  5. A quadrature based method of moments for nonlinear Fokker–Planck equations

    International Nuclear Information System (INIS)

    Fokker–Planck equations which are nonlinear with respect to their probability densities and occur in many nonequilibrium systems relevant to mean field interaction models, plasmas, fermions and bosons can be challenging to solve numerically. To address some underlying challenges, we propose the application of the direct quadrature based method of moments (DQMOM) for efficient and accurate determination of transient (and stationary) solutions of nonlinear Fokker–Planck equations (NLFPEs). In DQMOM, probability density (or other distribution) functions are represented using a finite collection of Dirac delta functions, characterized by quadrature weights and locations (or abscissas) that are determined based on constraints due to evolution of generalized moments. Three particular examples of nonlinear Fokker–Planck equations considered in this paper include descriptions of: (i) the Shimizu–Yamada model, (ii) the Desai–Zwanzig model (both of which have been developed as models of muscular contraction) and (iii) fermions and bosons. Results based on DQMOM, for the transient and stationary solutions of the nonlinear Fokker–Planck equations, have been found to be in good agreement with other available analytical and numerical approaches. It is also shown that approximate reconstruction of the underlying probability density function from moments obtained from DQMOM can be satisfactorily achieved using a maximum entropy method

  6. A quadrature based method of moments for nonlinear Fokker-Planck equations

    Science.gov (United States)

    Otten, Dustin L.; Vedula, Prakash

    2011-09-01

    Fokker-Planck equations which are nonlinear with respect to their probability densities and occur in many nonequilibrium systems relevant to mean field interaction models, plasmas, fermions and bosons can be challenging to solve numerically. To address some underlying challenges, we propose the application of the direct quadrature based method of moments (DQMOM) for efficient and accurate determination of transient (and stationary) solutions of nonlinear Fokker-Planck equations (NLFPEs). In DQMOM, probability density (or other distribution) functions are represented using a finite collection of Dirac delta functions, characterized by quadrature weights and locations (or abscissas) that are determined based on constraints due to evolution of generalized moments. Three particular examples of nonlinear Fokker-Planck equations considered in this paper include descriptions of: (i) the Shimizu-Yamada model, (ii) the Desai-Zwanzig model (both of which have been developed as models of muscular contraction) and (iii) fermions and bosons. Results based on DQMOM, for the transient and stationary solutions of the nonlinear Fokker-Planck equations, have been found to be in good agreement with other available analytical and numerical approaches. It is also shown that approximate reconstruction of the underlying probability density function from moments obtained from DQMOM can be satisfactorily achieved using a maximum entropy method.

  7. An Interactive Multimedia Based Instruction in Experimental Modelling

    DEFF Research Database (Denmark)

    Knudsen, Morten; Nielsen, J.N.; Østergaard, J.;

    1997-01-01

    A CD-ROM based interactive multimedia instruction in experimental modelling for Danish Engineering School teachers is described. The content is based on a new sensitivity approach for direct estimation of physical parameters in linear and nonlinear dynamic systems. The presentation is inspired of...... Solomans=s inventory of learning styles. To enhance active learning and motivation by real life problems, the simulation tool Matlab is integrated in the authoring program Medi8or....

  8. Nonlinear Landau-Zener Tunnelling with Two and Three-Body Interactions

    Institute of Scientific and Technical Information of China (English)

    WEI Xiu-Fang; TANG Rong-An; YONG Wen-Mei; XUE Ju-Kui

    2008-01-01

    We investigate the nonlinear Landau-Zener tunnelling of Bose-Einstein condensate (BEC) in an accelerating optical lattice with two- and three-body interactions between the particles. The influence of the three-body interaction on the eigenstates and the transition probability are discussed both analytically and numerically.The analytical eigenstates and the tunnelling probability are obtained,which are verified by numerical methods.It is shown that the eigenstates and the tunnelling probability are modified dramatically by three-body interaction.

  9. Engineering selective linear and nonlinear Jaynes–Cummings interactions and applications

    International Nuclear Information System (INIS)

    We present a framework to engineer nonlinear selective Jaynes–Cummings interactions for one-, two- and three-photon transitions. Higher order transitions are also discussed. Numerical simulations are presented to prove the effectiveness of our scheme. We further analyse how to apply these selective interactions to deterministic step-by-step preparation of number states, even in the non-ideal situation where cavity losses and atomic spontaneous emission are considered. Finally, we present a scheme, derived from the engineered selective interactions, to delay the decoherence process of the prepared Fock state. (paper)

  10. Three-wave interaction in two-component quadratic nonlinear lattices

    DEFF Research Database (Denmark)

    Konotop, V. V.; Cunha, M. D.; Christiansen, Peter Leth;

    1999-01-01

    We investigate a two-component lattice with a quadratic nonlinearity and find with the multiple scale technique that integrable three-wave interaction takes place between plane wave solutions when these fulfill resonance conditions. We demonstrate that. energy conversion and pulse propagation known...... from three-wave interaction is reproduced in the lattice and that exact phase matching of parametric processes can be obtained in non-phase-matched lattices by tilting the interacting plane waves with respect to each other. [S1063-651X(99)15110-9]....

  11. All-optical devices based on carrier nonlinearities for optical filtering and spectral equalization

    Science.gov (United States)

    Burger, Johan Petrus

    InGaAsP-based quantum wells can display nonlinear refractive index changes of ~0.1 near the band-edge for intrawell carrier density changes of 1 × 1018cm-3, due to effects like bandfilling and the plasma effect, which make these materials promising for the realization of all-optical signal processing devices, as demonstrated here. A novel single passband filter with sub-gigahertz bandwidth and greater than 40nm of tunability was experimentally demonstrated. The filter uses the detuning characteristics of nearly degenerate four-wave mixing in a broad area semiconductor optical amplifier to obtain frequency selectivity. The key to this demonstration was the spatial separation of the filtered signal from the input signal, based on their different propagation directions. An analysis of an analogous integrated optic dual-order mode nonlinear mode-converter, with integrated mode sorters which separate the signal from the interacting modes, was also undertaken. This device is promising as a filter, a wavelength converter, notch filter, and a wavelength recognizing switch. Novel ways to prevent carrier diffusion, which washes out the nonlinear grating, were suggested. It is important to have a large mutual overlap to modal overlap ratio of the two interacting modes on the nonlinear medium, because the mixing efficiency scales as the fourth power of this number. Three types of integrated optic limiters (based on Kerr- like nonlinearities) namely an all-optical cutoff modulator, a nonlinear Y-branch and an interferometer with an internal Kerr element, were theoretically investigated. A beam propagation program, which can solve the propagation of an optical field in a semiconductor in the presence of carrier diffusion, was developed for the numerical analysis of these structures. A negative feedback mechanism was identified in the Y-branch devices and a new limiting configuration was discovered in a Y- branch with a selectively placed defocusing nonlinearity. Dichroic

  12. Transient stability improvement by nonlinear controllers based on tracking

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, Juan M. [Centro de Investigacion y Estudios Avanzados, Guadalajara, Mexico. Av. Cientifica 1145. Col. El Bajio. Zapopan, Jal. 45015 (Mexico); Arroyave, Felipe Valencia; Correa Gutierrez, Rosa Elvira [Universidad Nacional de Colombia, Sede Medellin. Facultad de Minas, Escuela de Mecatronica (Colombia)

    2011-02-15

    This paper deals with the control problem in multi-machine electric power systems, which represent complex great scale nonlinear systems. Thus, the controller design is a challenging problem. These systems are subjected to different perturbations, such as short circuits, connection and/or disconnection of loads, lines, or generators. Then, the utilization of controllers which guarantee good performance under those perturbations is required in order to provide electrical energy to the loads with admissible stability margins. The proposed controllers are based on a systematic strategy, which calculate nonlinear controllers for generating units in a power plant, both for voltage and velocity regulation. The formulation allows designing controllers in a multi-machine power system without intricate calculations. Results on a power system of the open research indicate the proposition's suitability. The problem is formulated as a tracking problem. The designed controllers may be implemented in any electric power system. (author)

  13. On the efficacy of friction damping in the presence of nonlinear modal interactions

    Science.gov (United States)

    Krack, Malte; Bergman, Lawrence A.; Vakakis, Alexander F.

    2016-05-01

    This work addresses friction-induced modal interactions in jointed structures, and their effects on the passive mitigation of vibrations by means of friction damping. Under the condition of (nearly) commensurable natural frequencies, the nonlinear character of friction can cause so-called nonlinear modal interactions. If harmonic forcing near the natural frequency of a specific mode is applied, for instance, another mode may be excited due to nonlinear energy transfer and thus contribute considerably to the vibration response. We investigate how this phenomenon affects the performance of friction damping. To this end, we study the steady-state, periodic forced vibrations of a system of two beams connected via a local mechanical friction joint. The system can be tuned to continuously adjust the ratio between the first two natural frequencies in the range around the 1:3 internal resonance, in order to trigger or suppress the emergence of modal interactions. Due to the re-distribution of the vibration energy, the vibration level can in fact be reduced in certain situations. However, in other situations, the multi-harmonic character of the vibration has detrimental effects on the effective damping provided by the friction joint. The resulting response level can be significantly larger than in the absence of modal interactions. Moreover, it is shown that the vibration behavior is highly sensitive in the neighborhood of internal resonances. It is thus concluded that the condition of internal resonance should be avoided in the design of friction-damped systems.

  14. Quantum transport of strongly interacting photons in a one-dimensional nonlinear waveguide

    CERN Document Server

    Hafezi, Mohammad; Gritsev, Vladimir; Demler, Eugene; Lukin, Mikhail

    2009-01-01

    We present a theoretical technique for solving the quantum transport problem of a few photons through a one-dimensional, strongly nonlinear waveguide. We specifically consider the situation where the evolution of the optical field is governed by the quantum nonlinear Schr\\"odinger equation (NLSE). Although this kind of nonlinearity is quite general, we focus on a realistic implementation involving cold atoms loaded in a hollow-core optical fiber, where the atomic system provides a tunable nonlinearity that can be large even at a single-photon level. In particular, we show that when the interaction between photons is effectively repulsive, the transmission of multi-photon components of the field is suppressed. This leads to anti-bunching of the transmitted light and indicates that the system acts as a single-photon switch. On the other hand, in the case of attractive interaction, the system can exhibit either anti-bunching or bunching, which is in stark contrast to semiclassical calculations. We show that the ...

  15. Quantum transport of strongly interacting photons in a one-dimensional nonlinear waveguide

    Science.gov (United States)

    Hafezi, Mohammad; Chang, Darrick E.; Gritsev, Vladimir; Demler, Eugene; Lukin, Mikhail D.

    2012-01-01

    We present a theoretical technique for solving the quantum transport problem of a few photons through a one-dimensional, strongly nonlinear waveguide. We specifically consider the situation where the evolution of the optical field is governed by the quantum nonlinear Schrödinger equation. Although this kind of nonlinearity is quite general, we focus on a realistic implementation involving cold atoms loaded in a hollow-core optical fiber, where the atomic system provides a tunable nonlinearity that can be large even at a single-photon level. In particular, we show that when the interaction between photons is effectively repulsive, the transmission of multiphoton components of the field is suppressed. This leads to antibunching of the transmitted light and indicates that the system acts as a single-photon switch. On the other hand, in the case of attractive interaction, the system can exhibit either antibunching or bunching, which is in stark contrast to semiclassical calculations. We show that the bunching behavior is related to the resonant excitation of bound states of photons inside the system.

  16. Latitudinal dependence of nonlinear interaction between electromagnetic ion cyclotron wave and terrestrial ring current ions

    International Nuclear Information System (INIS)

    Electromagnetic ion cyclotron (EMIC) waves can lead to the rapid decay (on a timescale of hours) of the terrestrial ring current. Such decay process is usually investigated in the framework of quasi-linear theory. Here, both theoretical analysis and test-particle simulation are performed to understand the nonlinear interaction between ring current ions and EMIC waves. In particular, the dependence of the nonlinear wave-particle interaction processes on the ion initial latitude is investigated in detail. These nonlinear processes are classified into the phase trapping and phase bunching, and the phase bunching is further divided into the channel and cluster effects. Compared to the prediction of the quasi-linear theory, the ring current decay rate can be reduced by the phase trapping, increased by the channel effect phase bunching, but non-deterministically influenced by the cluster effect phase bunching. The ion initial latitude changes the occurrence of the phase trapping, modulates the transport direction and strength of the cluster effect phase bunching, and only slightly affects the channel effect phase bunching. The current results suggest that the latitudinal dependence of these nonlinear processes should be considered in the evaluation of the ring current decay induced by EMIC waves

  17. Nonlinear time-series-based adaptive control applications

    Science.gov (United States)

    Mohler, R. R.; Rajkumar, V.; Zakrzewski, R. R.

    1991-01-01

    A control design methodology based on a nonlinear time-series reference model is presented. It is indicated by highly nonlinear simulations that such designs successfully stabilize troublesome aircraft maneuvers undergoing large changes in angle of attack as well as large electric power transients due to line faults. In both applications, the nonlinear controller was significantly better than the corresponding linear adaptive controller. For the electric power network, a flexible AC transmission system with series capacitor power feedback control is studied. A bilinear autoregressive moving average reference model is identified from system data, and the feedback control is manipulated according to a desired reference state. The control is optimized according to a predictive one-step quadratic performance index. A similar algorithm is derived for control of rapid changes in aircraft angle of attack over a normally unstable flight regime. In the latter case, however, a generalization of a bilinear time-series model reference includes quadratic and cubic terms in angle of attack.

  18. Seismic induced nonlinear rotor-bearing-casing interaction of rotating nuclear components

    International Nuclear Information System (INIS)

    The study of the dynamics of turbomachinery during seismic events has been of continuous interest to both researchers and designers of large rotating equipment. Failure in such equipment, especially those associated with nuclear power generation, can lead to catastrophic consequences. Hence, there is a general trend for corporations to overdesign the equipment without any indepth understanding of the dynamical performance of the machine under extreme operating conditions. The overall objective of this paper are fourfold, namely: (1) To study the nonlinear dynamics of rotor-bearing casing system during rub interactions; (2) To examine the effects of suddenly induced imbalance and base motion in the global dynamical behavior of the system; (3) To develop engineering insights through the modal parameters in both time and frequency domain; (4) To generate signature analysis on rub forces for pattern recognition. These goals are achieved through the development of a modal impact model. Accuracy and efficiency of this transient model are maintained using a self-adaptive integration scheme

  19. Nonlinear interaction and propagation of gravitational and electromagnetic waves in plasmas

    OpenAIRE

    Servin, Martin

    2003-01-01

    Gravitational waves and electromagnetic waves are important as carriers of energy and information. This thesis is devoted to the study of the propagation and interaction of these waves in plasmas, with emphasis on nonlinear effects and applications within astrophysics. The physical systems are described by the Einstein-Maxwell-fluid equations or Einstein-Maxwell-Vlasov equations, when a kinetic treatment is required. The small amplitude and high-frequency approximation is employed for the gra...

  20. INAKT--an interactive non-linear regression program for enzyme inactivation and affinity labelling studies.

    Science.gov (United States)

    Christophersen, A; McKinley-McKee, J S

    1984-01-01

    An interactive program for analysing enzyme activity-time data using non-linear regression analysis is described. Protection studies can also be dealt with. The program computes inactivation rates, dissociation constants and promotion or inhibition parameters with their standard errors. It can also be used to distinguish different inactivation models. The program is written in SIMULA and is menu-oriented for refining or correcting data at the different levels of computing. PMID:6546558

  1. Linear and nonlinear aspects of relativistic heavy ion interactions from EMU01 results

    International Nuclear Information System (INIS)

    The recent status of the EMU01 experiment where nuclear emulsions are used as both target/detector material for horizontally exposed stacks and as detector for vertically exposed chamber plates is discussed. An investigation of the behaviour in the number of produced particles per participating nucleon reveal weak nonlinear effects for the most central collisions. Intermittency index can be obtained from the density distributions for S+Au and S+Ag interactions which corresponds to fractal dimensions somewhat smaller than unity

  2. Nonlinear instability and chaos in plasma wave-wave interactions, I., Introduction

    International Nuclear Information System (INIS)

    Conventional linear stability analyses may fail for fluid systems with an indefinite free energy functional. When such a system is linearly stable, it is said to possess negative energy modes. Instability may then occur either via dissipation of the negative energy modes, or nonlinearly via resonant wave-wave coupling, leading to explosive growth. In the dissipationless case, it is conjectured that intrinsic chaotic behavior may allow initially nonresonant systems to reach resonance by diffusion in phase space. In this and a companion paper [submitted to Physics of Plasmas], this phenomenon is demonstrated for a simple equilibrium involving cold counterstreaming ions. The system is described in the fluid approximation by a Hamiltonian functional and associated noncanonical Poisson bracket. By Fourier decomposition and appropriate coordinate transformations, the Hamiltonian for the perturbed energy is expressed in action-angle form. The normal modes correspond to Doppler-shifted ion-acoustic waves of positive and negative energy. Nonlinear coupling leads to decay instability via two-wave interactions, and to either decay or explosive instability via three-wave interactions. These instabilities are described for various (integrable) systems of waves interacting via single nonlinear terms. This discussion provides the foundation for the treatment of nonintegrable systems in the companion paper

  3. Design Intelligent Model base Online Tuning Methodology for Nonlinear System

    Directory of Open Access Journals (Sweden)

    Ali Roshanzamir

    2014-04-01

    Full Text Available In various dynamic parameters systems that need to be training on-line adaptive control methodology is used. In this paper fuzzy model-base adaptive methodology is used to tune the linear Proportional Integral Derivative (PID controller. The main objectives in any systems are; stability, robust and reliability. However PID controller is used in many applications but it has many challenges to control of continuum robot. To solve these problems nonlinear adaptive methodology based on model base fuzzy logic is used. This research is used to reduce or eliminate the PID controller problems based on model reference fuzzy logic theory to control of flexible robot manipulator system and testing of the quality of process control in the simulation environment of MATLAB/SIMULINK Simulator.

  4. Spin–orbit interaction effect on nonlinear optical rectification of quantum wire in the presence of electric and magnetic fields

    International Nuclear Information System (INIS)

    Here we have investigated the influence of external electric field and magnetic field on the nonlinear optical rectification of a parabolic confinement wire in the presence of Rashba spin–orbit interaction. We have used density matrix formulation for obtaining optical properties within the effective mass approximation. The results are presented as a function of quantum wire radius, electric field, magnetic field, Rashba spin–orbit interaction strength and photon energy. Our results indicate an increase of electric field gives the red-shift of the peak positions of nonlinear optical rectification. The role of confinement strength and spin–orbit interaction strength as control parameters on this nonlinear property have been demonstrated.

  5. Nonlinear theory of intense laser-plasma interactions modified by vacuum polarization effects

    International Nuclear Information System (INIS)

    The classical nonlinear theory of laser-plasma interactions is corrected by taking account of the vacuum polarization effects. A set of wave equations are obtained by using the Heisenberg-Euler Lagrangian density and the derivative correction with the first-order quantum electrodynamic effects. A model more suitable to formulate the interactions of ultra-strong lasers and high-energy-density plasmas is developed. In the result, some environments in which the effects of vacuum polarization will be enhanced are discussed

  6. Electromechanically reconfigurable CdS nanoplate based nonlinear optical device.

    Science.gov (United States)

    Yi, Fei; Ren, Mingliang; Zhu, Hai; Liu, Wenjin; Agarwal, Ritesh; Cubukcu, Ertugrul

    2016-06-13

    Here, we report experimental demonstration of dynamic control and enhancement of second harmonic generation and two photon excited photoluminescence in CdS nanoplates via an electromechanically reconfigurable Fabry-Perot (FP) microcavity. Microcavity coupled CdS nanoplates can be configured as a single or dual wavelength nonlinear light source by tuning the pump wavelength while the output intensities can be tuned by the on-chip control voltage. Our work realizes a reconfigurable device platform with insight toward advanced optical devices based on semiconductor nanoplates for next generation on-chip tunable light sources, sensors and optomechanical systems. PMID:27410362

  7. Nonlinear State Estimation with Missing Observations Based on Mathematical Programming

    Czech Academy of Sciences Publication Activity Database

    Pavelková, Lenka

    Praha : ÚTIA AV ČR, 2010 - (Janžura, M.; Ivánek, J.). s. 23-23 [6th International Workshop on Data – Algorithms – Decision Making. 02.12.2010-04.12.2010, Jindřichův Hradec] R&D Projects: GA MŠk 1M0572 Institutional research plan: CEZ:AV0Z10750506 Keywords : state filtering * bounded errors * missing measurements Subject RIV: BC - Control Systems Theory http://library.utia.cas.cz/separaty/2010/AS/pavelkova-nonlinear state estimation with missing observations based on mathematical programming .pdf

  8. Characterizing the nonlinear interaction of S- and P-waves in a rock sample

    CERN Document Server

    Gallot, Thomas; Szabo, Thomas L; Brown, Stephen; Burns, Daniel; Fehler, Michael

    2014-01-01

    The nonlinear elastic response of rocks is known to be caused by the rocks' microstructure, particularly cracks and fluids. This paper presents a method for characterizing the nonlinearity of rocks in a laboratory scale experiment with a unique configuration. This configuration has been designed to open up the possibility the nonlinear characterization of rocks as an imaging tool in a field scenario. The nonlinear interaction of two traveling waves: a low-amplitude 500 kHz P-wave probe and a high-amplitude 50 kHz S-wave pump has been studied on a room-dry 15 x 15x 3 cm slab of Berea sandstone. Changes in the arrival time of the P-wave probe as it passes through the perturbation created by the traveling S-wave pump were recorded. Waveforms were time gated to simulate a semi-infinite medium. The shear wave phase relative to the P-wave probe signal was varied with resultant changes in the P-wave probe arrival time of up to 100 ns, corresponding to a change in elastic properties of 0.2%. In order to estimate the ...

  9. Nonlinear interaction of photons and phonons in electron-positron plasmas

    International Nuclear Information System (INIS)

    Nonlinear interaction of electromagnetic waves and acoustic modes in an electron-positron plasma is investigated. The plasma of electrons and positrons is quite plastic so that the imposition of electromagnetic (EM) waves causes depression of the plasma and other structural imprints on it through either the nonresonant or resonant interaction. Our theory shows that the nonresonant interaction can lead to the coalescence of photons and collapse of plasma cavity in higher (≥ 2) dimensions. The resonant interaction, in which the group velocity of EM waves is equal to the phase velocity of acoustic waves, is analyzed and a set of basic equations of the system is derived via the reductive perturbation theory. We find new solutions of solitary types: bright solitons, kink solitons, and dark solitons as the solutions to these equations. Our computation hints their stability. An impact of the present theory on astrophysical plasma settings is expected, including the cosmological relativistically hot electron-positron plasma. 20 refs., 9 figs

  10. Characterizing the nonlinear interaction of S- and P-waves in a rock sample

    Science.gov (United States)

    Gallot, Thomas; Malcolm, Alison; Szabo, Thomas L.; Brown, Stephen; Burns, Daniel; Fehler, Michael

    2015-01-01

    The nonlinear elastic response of rocks is known to be caused by the rocks' microstructure, particularly cracks and fluids. This paper presents a method for characterizing the nonlinearity of rocks in a laboratory scale experiment with a unique configuration. This configuration has been designed to open up the possibility of using the nonlinear characterization of rocks as an imaging tool in the field. In our experiment, we study the nonlinear interaction of two traveling waves: a low-amplitude 500 kHz P-wave probe and a high-amplitude 50 kHz S-wave pump in a room-dry 15 × 15 × 3 cm slab of Berea sandstone. Changes in the arrival time of the P-wave probe as it passes through the perturbation created by the traveling S-wave pump were recorded. Waveforms were time gated to simulate a semi-infinite medium. The shear wave phase relative to the P-wave probe signal was varied with resultant changes in the P-wave probe arrival time of up to 100 ns, corresponding to a change in elastic properties of 0.2%. In order to estimate the strain in our sample, we also measured the particle velocity at the sample surface to scale a finite difference linear elastic simulation to estimate the complex strain field in the sample, on the order of 10-6, induced by the S-wave pump. We derived a fourth order elastic model to relate the changes in elasticity to the pump strain components. We recover quadratic and cubic nonlinear parameters: β ˜ = - 872 and δ ˜ = - 1.1 × 10 10 , respectively, at room-temperature and when particle motions of the pump and probe waves are aligned. Temperature fluctuations are correlated to changes in the recovered values of β ˜ and δ ˜ , and we find that the nonlinear parameter changes when the particle motions are orthogonal. No evidence of slow dynamics was seen in our measurements. The same experimental configuration, when applied to Lucite and aluminum, produced no measurable nonlinear effects. In summary, a method of selectively determining the

  11. Multi-modal vibration energy harvesting approach based on nonlinear oscillator arrays under magnetic levitation

    Science.gov (United States)

    Abed, I.; Kacem, N.; Bouhaddi, N.; Bouazizi, M. L.

    2016-02-01

    We propose a multi-modal vibration energy harvesting approach based on arrays of coupled levitated magnets. The equations of motion which include the magnetic nonlinearity and the electromagnetic damping are solved using the harmonic balance method coupled with the asymptotic numerical method. A multi-objective optimization procedure is introduced and performed using a non-dominated sorting genetic algorithm for the cases of small magnet arrays in order to select the optimal solutions in term of performances by bringing the eigenmodes close to each other in terms of frequencies and amplitudes. Thanks to the nonlinear coupling and the modal interactions even for only three coupled magnets, the proposed method enable harvesting the vibration energy in the operating frequency range of 4.6-14.5 Hz, with a bandwidth of 190% and a normalized power of 20.2 {mW} {{cm}}-3 {{{g}}}-2.

  12. Neural network-based H∞ filtering for nonlinear systems with time-delays

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A novel H∞ design methodology for a neural network-based nonlinear filtering scheme is addressed.Firstly,neural networks are employed to approximate the nonlinearities.Next,the nonlinear dynamic system is represented by the mode-dependent linear difference inclusion (LDI).Finally,based on the LDI model,a neural network-based nonlinear filter (NNBNF) is developed to minimize the upper bound of H∞ gain index of the estimation error under some linear matrix inequality (LMI) constraints.Compared with the existing nonlinear filters,NNBNF is time-invariant and numerically tractable.The validity and applicability of the proposed approach are successfully demonstrated in an illustrative example.

  13. Ion scale nonlinear interaction triggered by disparate scale electron temperature gradient mode

    International Nuclear Information System (INIS)

    We have observed that the disparate scale nonlinear interactions between the high-frequency (∼0.4 MHz) electron temperature gradient (ETG) mode and the ion-scale low-frequency fluctuations (∼kHz) were enhanced when the amplitude of the ETG mode exceeded a certain threshold. The dynamics of nonlinear coupling between the ETG mode and the drift wave (DW) mode has already been reported [C. Moon, T. Kaneko, and R. Hatakeyama, Phys. Rev. Lett. (2013)]. Here, we have newly observed that another low-frequency fluctuation with f ≃ 3.6 kHz, i.e., the flute mode, was enhanced, corresponding to the saturation of the DW mode growth. Specifically, the bicoherence between the flute mode and the DW mode reaches a significant level when the ∇Te/Te strength exceeded 0.54 cm−1. Thus, it is shown that the ETG mode energy was transferred to the DW mode, and then the energy was ultimately transferred to the flute mode, which was triggered by the disparate scale nonlinear interactions between the ETG and ion-scale low-frequency modes

  14. Nonlinear dynamic behavior of rubbing rotor under interaction between bending and torsional vibrations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The nonlinear dynamic behavior of a rubbing rotor system was studied with a mathematical model established with the eccentricity and interaction between bending and torsional vibrations taken into consideration.The nonlinear vibrational response of a rubbing rotor was analyzed using numerical integral,spectroscopic analysis and Poince mapping method,which made it possible to have better understanding of the vibrational characteristics of partial rubbing and complete circular rubbing rotors.The numerical results reveal the response of torsional vibration mainly takes a form of suporchronous motion,and its frequency decreases as the rotational speed increases when partial rubbing occurs,and the response of torsional vibration is synchronous when complete circular rubbing occurs.The comparison of the dynamics of rubbing rotors with and without the interaction between bending and torsional vibrations shows the interaction between bending and torsional vibrations advances the rotational speed,at which the response of bending vibration changes from a synchronous motion into a quasi-periodic motion,and the interaction between bending and torsional vibrations reduces stability of the rubbing rotor.

  15. Theoretical studies of nonlinear phenomena in high intensity laser matter interaction. Relativistic effects

    International Nuclear Information System (INIS)

    We study the propagation of a linearly polarized travelling wave and the form of a linearly polarized standing wave in a cold electron plasma taking into account the electron relativistic-mass oscillation. The values of the wave amplitude we obtain for different laser intensities are weakened by the relativistic nonlinear terms which also allow propagation in the overdense plasma. We also study the interaction of such a wave with the overdense plasma which is assumed to be homogeneous. Instabilities appear for transverse and longitudinal waves when the pump-field frequency is at the same time below the electron plasma frequency and above but very near the cut-off frequency obtained by KAW and DAWSON with a nonlinear relativistic theory

  16. On Nonlinear Self-interaction of Geodesic Acoustic Mode Driven By Energetic Particles

    International Nuclear Information System (INIS)

    It is shown that nonlinear self-interaction of energetic particle-driven Geodesic Acoustic Mode does not generate a second harmonic in radial electric field using the fluid model. However, kinetic effects of energetic particles can induce a second harmonic in the radial electric field. A formula for the second order plasma density perturbation is derived. It is shown that a second harmonic of plasma density perturbation is generated by the convective nonlinearity of both thermal plasma and energetic particles. Near the midplane of a tokamak, the second order plasma density perturbation (the sum of second harmonic and zero frequency sideband) is negative on the low field side with its size comparable to the main harmonic at low fluctuation level. These analytic predictions are consistent with the recent experimental observation in DIII-D.

  17. On Nonlinear Self-interaction of Geodesic Acoustic Mode Driven by Energetic Particles

    International Nuclear Information System (INIS)

    It is shown that nonlinear self-interaction of energetic particle-driven Geodesic Acoustic Mode does not generate a second harmonic in radial electric field using the fluid model. However, kinetic effects of energetic particles can induce a second harmonic in the radial electric field. A formula for the second order plasma density perturbation is derived. It is shown that a second harmonic of plasma density perturbation is generated by the convective nonlinearity of both thermal plasma and energetic particles. Near the midplane of a tokamak, the second order plasma density perturbation (the sum of second harmonic and zero frequency sideband) is negative on the low field side with its size comparable to the main harmonic at low fluctuation level. These analytic predictions are consistent with the recent experimental observation in DIII-D.

  18. Modulus synchronization in a network of nonlinear systems with antagonistic interactions and switching topologies

    Science.gov (United States)

    Zhai, Shidong

    2016-04-01

    This paper studies the collective behavior in a network of nonlinear systems with antagonistic interactions and switching topologies. The concept of modulus synchronization is introduced to characterize the case that the moduli of corresponding components of the agent (node) states reach a synchronization. The network topologies are modeled by a set of directed signed graphs. When all directed signed graphs are structurally balanced and the nonlinear system satisfies a one-sided Lipschitz condition, by using matrix measure and contraction theory, we show that modulus synchronization can be evaluated by the time average of some matrix measures. These matrices are about the second smallest eigenvalue of undirected graphs corresponding to directed signed graphs. Finally, we present two numerical examples to illustrate the effectiveness of the obtained results.

  19. Probabilistic model identification of the bit-rock-interaction-model uncertainties in nonlinear dynamics of a drill-string

    OpenAIRE

    Ritto, T. G.; Soize, Christian; Sampaio, R

    2010-01-01

    This paper deals with a procedure to perform the identification of the probabilistic model of uncertainties in a bit-rock interaction model for the nonlinear dynamics of a drill-string. The bit-rock interaction model is represented by a nonlinear constitutive equation, whose uncertainties are modeled using the nonparametric probabilistic approach. The identification of the parameter of this probabilistic model is carried out using the maximum likelihood method together with a statistical redu...

  20. Ensemble-based Kalman Filters in Strongly Nonlinear Dynamics

    Institute of Scientific and Technical Information of China (English)

    Zhaoxia PU; Joshua HACKER

    2009-01-01

    This study examines the effectiveness of ensemble Kalman filters in data assimilation with the strongly nonlinear dynamics of the Lorenz-63 model, and in particular their use in predicting the regime transition that occurs when the model jumps from one basin of attraction to the other. Four configurations of the ensemble-based Kalman filtering data assimilation techniques, including the ensemble Kalman filter, ensemble adjustment Kalman filter, ensemble square root filter and ensemble transform Kalman filter, are evaluated with their ability in predicting the regime transition (also called phase transition) and also are compared in terms of their sensitivity to both observational and sampling errors. The sensitivity of each ensemble-based filter to the size of the ensemble is also examined.

  1. Generation and Nonlinear Dynamical Analyses of Fractional-Order Memristor-Based Lorenz Systems

    OpenAIRE

    Huiling Xi; Yuxia Li; Xia Huang

    2014-01-01

    In this paper, four fractional-order memristor-based Lorenz systems with the flux-controlled memristor characterized by a monotone-increasing piecewise linear function, a quadratic nonlinearity, a smooth continuous cubic nonlinearity and a quartic nonlinearity are presented, respectively. The nonlinear dynamics are analyzed by using numerical simulation methods, including phase portraits, bifurcation diagrams, the largest Lyapunov exponent and power spectrum diagrams. Some interesting phenome...

  2. A nonlinear PCA algorithm based on RBF neural networks

    Institute of Scientific and Technical Information of China (English)

    YANG Bin; ZHU Zhong-ying

    2005-01-01

    Traditional PCA is a linear method, but most engineering problems are nonlinear. Using the linear PCA in nonlinear problems may bring distorted and misleading results. Therefore, an approach of nonlinear principal component analysis (NLPCA) using radial basis function (RBF) neural network is developed in this paper. The orthogonal least squares (OLS) algorithm is used to train the RBF neural network. This method improves the training speed and prevents it from being trapped in local optimization. Results of two experiments show that this NLPCA method can effectively capture nonlinear correlation of nonlinear complex data, and improve the precision of the classification and the prediction.

  3. Simulation-based optimal Bayesian experimental design for nonlinear systems

    KAUST Repository

    Huan, Xun

    2013-01-01

    The optimal selection of experimental conditions is essential to maximizing the value of data for inference and prediction, particularly in situations where experiments are time-consuming and expensive to conduct. We propose a general mathematical framework and an algorithmic approach for optimal experimental design with nonlinear simulation-based models; in particular, we focus on finding sets of experiments that provide the most information about targeted sets of parameters.Our framework employs a Bayesian statistical setting, which provides a foundation for inference from noisy, indirect, and incomplete data, and a natural mechanism for incorporating heterogeneous sources of information. An objective function is constructed from information theoretic measures, reflecting expected information gain from proposed combinations of experiments. Polynomial chaos approximations and a two-stage Monte Carlo sampling method are used to evaluate the expected information gain. Stochastic approximation algorithms are then used to make optimization feasible in computationally intensive and high-dimensional settings. These algorithms are demonstrated on model problems and on nonlinear parameter inference problems arising in detailed combustion kinetics. © 2012 Elsevier Inc.

  4. Temperature induced syllable breaking unveils nonlinearly interacting timescales in birdsong motor pathway.

    Directory of Open Access Journals (Sweden)

    Matías A Goldin

    Full Text Available The nature of telencephalic control over premotor and motor circuits is debated. Hypotheses range from complete usurping of downstream circuitry to highly interactive mechanisms of control. We show theoretically and experimentally, that telencephalic song motor control in canaries is consistent with a highly interactive strategy. As predicted from a theoretical model of respiratory control, mild cooling of a forebrain nucleus (HVC led to song stretching, but further cooling caused progressive restructuring of song, consistent with the hypothesis that respiratory gestures are subharmonic responses to a timescale present in the output of HVC. This interaction between a life-sustaining motor function (respiration and telencephalic song motor control suggests a more general mechanism of how nonlinear integration of evolutionarily new brain structures into existing circuitry gives rise to diverse, new behavior.

  5. Non-Linear Interaction of Electromagnetic Waves in a Magneto-Active Plasma

    International Nuclear Information System (INIS)

    1. With a view to constructing a theory of induced scattering of electromagnetic waves on the particles of a magnetoactive plasma, recourse was had to the general method of deriving equations describing the non-linear inter action of waves as used previously by Gorbunov, Pustovalov and Silin for the case of an isotropic plasma. By this means similar equations can also be written for a magnetoactive plasma. The plasma ground state distribution function used for this purpose is regarded as constant in time and space. This means disregarding the effect of oscillations on the distribution of the particles, and in a number of cases this is fully justified; at the same time the equations describing wave interaction can be written in closed form. The spectra of the interacting waves are regarded as linear, that is independent of their energy. 2. The authors have studied the induced scattering of electromagnetic waves on particles of an unbounded homogeneous magnetoactive plasma. Such interaction plays the greatest part, as far as the problem is treated non-linearly, in cases where the expansion spectrum of the interacting waves do not satisfy the decay conditions. In such a case, in obtaining the starting equations terms up to and. including those of the third order must be taken into account for the purpose of expanding the current density in powers of the field. Particular attention was paid to wave interaction in a cold plasma, and also to the interaction of longitudinal waves in non-isothermal and other plasmas with arbitrary electron and ion temperatures. 3. For the case of a cold plasma, general expressions were derived for the tensors determining the matrix elements of interaction, and by means of these expressions equations were obtained describing the evolution in time of the expansion of oscillation energy for Various relationships between the frequencies and directions of propagation of the interacting waves and the parameters of the plasma. On the basis of

  6. Interactions of bright solitons for the (2+1)-dimensional coupled nonlinear Schroedinger equations from optical fibres with symbolic computation

    International Nuclear Information System (INIS)

    In nonlinear optical fibres, the evolution of two polarization envelopes is governed by a system of coupled nonlinear Schroedinger (CNLS) equations. In this paper, with the aid of symbolic computation, the analytical bright one- and two-soliton solutions of the (2+1)-dimensional CNLS equations under certain constraints are presented by employing the Hirota method. We have discussed the head-on and overtaking interactions which include elastic and inelastic collisions between two parallel bright solitons. In the interaction process, the intensities of solitons can exhibit various redistributions. We also point out that these properties have important physical applications in constructing various logic gates and nonlinear optical fibers

  7. Data based identification and prediction of nonlinear and complex dynamical systems

    Science.gov (United States)

    Wang, Wen-Xu; Lai, Ying-Cheng; Grebogi, Celso

    2016-07-01

    The problem of reconstructing nonlinear and complex dynamical systems from measured data or time series is central to many scientific disciplines including physical, biological, computer, and social sciences, as well as engineering and economics. The classic approach to phase-space reconstruction through the methodology of delay-coordinate embedding has been practiced for more than three decades, but the paradigm is effective mostly for low-dimensional dynamical systems. Often, the methodology yields only a topological correspondence of the original system. There are situations in various fields of science and engineering where the systems of interest are complex and high dimensional with many interacting components. A complex system typically exhibits a rich variety of collective dynamics, and it is of great interest to be able to detect, classify, understand, predict, and control the dynamics using data that are becoming increasingly accessible due to the advances of modern information technology. To accomplish these goals, especially prediction and control, an accurate reconstruction of the original system is required. Nonlinear and complex systems identification aims at inferring, from data, the mathematical equations that govern the dynamical evolution and the complex interaction patterns, or topology, among the various components of the system. With successful reconstruction of the system equations and the connecting topology, it may be possible to address challenging and significant problems such as identification of causal relations among the interacting components and detection of hidden nodes. The "inverse" problem thus presents a grand challenge, requiring new paradigms beyond the traditional delay-coordinate embedding methodology. The past fifteen years have witnessed rapid development of contemporary complex graph theory with broad applications in interdisciplinary science and engineering. The combination of graph, information, and nonlinear dynamical

  8. Data based identification and prediction of nonlinear and complex dynamical systems

    Science.gov (United States)

    Wang, Wen-Xu; Lai, Ying-Cheng; Grebogi, Celso

    2016-07-01

    The problem of reconstructing nonlinear and complex dynamical systems from measured data or time series is central to many scientific disciplines including physical, biological, computer, and social sciences, as well as engineering and economics. The classic approach to phase-space reconstruction through the methodology of delay-coordinate embedding has been practiced for more than three decades, but the paradigm is effective mostly for low-dimensional dynamical systems. Often, the methodology yields only a topological correspondence of the original system. There are situations in various fields of science and engineering where the systems of interest are complex and high dimensional with many interacting components. A complex system typically exhibits a rich variety of collective dynamics, and it is of great interest to be able to detect, classify, understand, predict, and control the dynamics using data that are becoming increasingly accessible due to the advances of modern information technology. To accomplish these goals, especially prediction and control, an accurate reconstruction of the original system is required. Nonlinear and complex systems identification aims at inferring, from data, the mathematical equations that govern the dynamical evolution and the complex interaction patterns, or topology, among the various components of the system. With successful reconstruction of the system equations and the connecting topology, it may be possible to address challenging and significant problems such as identification of causal relations among the interacting components and detection of hidden nodes. The "inverse" problem thus presents a grand challenge, requiring new paradigms beyond the traditional delay-coordinate embedding methodology. The past fifteen years have witnessed rapid development of contemporary complex graph theory with broad applications in interdisciplinary science and engineering. The combination of graph, information, and nonlinear dynamical

  9. Parabolized Stability Equations analysis of nonlinear interactions with forced eigenmodes to control subsonic jet instabilities

    International Nuclear Information System (INIS)

    Nonlinear evolution of disturbances in an axisymmetric, high subsonic, high Reynolds number hot jet with forced eigenmodes is studied using the Parabolized Stability Equations (PSE) approach to understand how modes interact with one another. Both frequency and azimuthal harmonic interactions are analyzed by setting up one or two modes at higher initial amplitudes and various phases. While single mode excitation leads to harmonic growth and jet noise amplification, controlling the evolution of a specific mode has been made possible by forcing two modes (m1, n1), (m2, n2), such that the difference in azimuth and in frequency matches the desired “target” mode (m1 − m2, n1 − n2). A careful setup of the initial amplitudes and phases of the forced modes, defined as the “killer” modes, has allowed the minimizing of the initially dominant instability in the near pressure field, as well as its estimated radiated noise with a 15 dB loss. Although an increase of the overall sound pressure has been found in the range of azimuth and frequency analyzed, the present paper reveals the possibility to make the initially dominant instability ineffective acoustically using nonlinear interactions with forced eigenmodes

  10. Parabolized Stability Equations analysis of nonlinear interactions with forced eigenmodes to control subsonic jet instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Itasse, Maxime, E-mail: Maxime.Itasse@onera.fr; Brazier, Jean-Philippe, E-mail: Jean-Philippe.Brazier@onera.fr; Léon, Olivier, E-mail: Olivier.Leon@onera.fr; Casalis, Grégoire, E-mail: Gregoire.Casalis@onera.fr [Onera - The French Aerospace Lab, F-31055 Toulouse (France)

    2015-08-15

    Nonlinear evolution of disturbances in an axisymmetric, high subsonic, high Reynolds number hot jet with forced eigenmodes is studied using the Parabolized Stability Equations (PSE) approach to understand how modes interact with one another. Both frequency and azimuthal harmonic interactions are analyzed by setting up one or two modes at higher initial amplitudes and various phases. While single mode excitation leads to harmonic growth and jet noise amplification, controlling the evolution of a specific mode has been made possible by forcing two modes (m{sub 1}, n{sub 1}), (m{sub 2}, n{sub 2}), such that the difference in azimuth and in frequency matches the desired “target” mode (m{sub 1} − m{sub 2}, n{sub 1} − n{sub 2}). A careful setup of the initial amplitudes and phases of the forced modes, defined as the “killer” modes, has allowed the minimizing of the initially dominant instability in the near pressure field, as well as its estimated radiated noise with a 15 dB loss. Although an increase of the overall sound pressure has been found in the range of azimuth and frequency analyzed, the present paper reveals the possibility to make the initially dominant instability ineffective acoustically using nonlinear interactions with forced eigenmodes.

  11. Nonlinear interaction of a whispering gallery mode with surface waves in a cylindrical plasma resonator

    International Nuclear Information System (INIS)

    Nonlinear interaction is considered between a low-frequency whispering gallery mode and higher-frequency surface waves in a cylindrical plasma-filled cavity. It is shown that the steady-state intensity distribution of the whispering gallery and surface wave modes can depend on the azimuthal angle phi only for a specified cavity radius, and the maximum amplitudes of the whispering gallery mode must also lie in a discrete set. The decay of an intense whispering gallery mode of constant amplitude into two oppositely moving surface electromagnetic waves is discussed, and expressions are derived for the decay rate and threshold

  12. Nonlinear Modeling of Dynamic Interactions within Neuronal Ensembles using Principal Dynamic Modes

    OpenAIRE

    Marmarelis, V. Z.; Shin, D. C.; Song, D.; Hampson, R. E.; Deadwyler, S; Berger, T. W.

    2012-01-01

    A methodology for nonlinear modeling of multi-input multi-output (MIMO) neuronal systems is presented that utilizes the concept of Principal Dynamic Modes (PDM). The efficacy of this new methodology is demonstrated in the study of the dynamic interactions between neuronal ensembles in the Pre-Frontal Cortex (PFC) of a behaving non-human primate (NHP) performing a Delayed Match-to-Sample task. Recorded spike trains from Layer-2 and Layer-5 neurons were viewed as the “inputs” and “outputs”, res...

  13. Quantum optical non-linearities induced by Rydberg-Rydberg interactions: a perturbative approach

    OpenAIRE

    Grankin, A.; Brion, E.; Bimbard, E.; Boddeda, R.; Usmani, I.; Ourjoumtsev, A.; Grangier, P

    2015-01-01

    In this article, we theoretically study the quantum statistical properties of the light transmitted through or reflected from an optical cavity, filled by an atomic medium with strong optical non-linearity induced by Rydberg-Rydberg van der Waals interactions. Atoms are driven on a two-photon transition from their ground state to a Rydberg level via an intermediate state by the combination of a weak signal field and a strong control beam. By using a perturbative approach, we get analytic resu...

  14. Localized excitations in discrete nonlinear Schrodinger systems: Effects of nonlocal dispersive interactions and noise

    DEFF Research Database (Denmark)

    Rasmussen, Kim; Christiansen, Peter Leth; Johansson, Magnus;

    1998-01-01

    with nearest-neighbor coupling we discuss the stability of highly localized, "breather-like", excitations under the influence of thermal fluctuations. Numerical analysis shows that the lifetime of the breather is aln,aps finite and in a large parameter region inversely proportional to the noise......A one-dimensional discrete nonlinear Schrodinger (DNLS) model with the power dependence, r(-s) on the distance r, of dispersive interactions is proposed. The stationary states of the system are studied both analytically and numerically. Two kinds of trial functions, exp-like and sech-like are...

  15. Nonlinear soil-structure interaction calculations simulating the SIMQUAKE experiment using STEALTH 2D

    Science.gov (United States)

    Tang, H. T.; Hofmann, R.; Yee, G.; Vaughan, D. K.

    1980-01-01

    Transient, nonlinear soil-structure interaction simulations of an Electric Power Research Institute, SIMQUAKE experiment were performed using the large strain, time domain STEALTH 2D code and a cyclic, kinematically hardening cap soil model. Results from the STEALTH simulations were compared to identical simulations performed with the TRANAL code and indicate relatively good agreement between all the STEALTH and TRANAL calculations. The differences that are seen can probably be attributed to: (1) large (STEALTH) vs. small (TRANAL) strain formulation and/or (2) grid discretization differences.

  16. ALE Fractional Step Finite Element Method for Fluid-Structure Nonlinear Interaction Problem

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A computational procedure is developed to solve the problems of coupled motion of a structure and a viscous incompressible fluid. In order to incorporate the effect of the moving surface of the structure as well as the free surface motion, the arbitrary Lagrangian-Eulerian formulation is employed as the basis of the finite element spatial discretization. For numerical integration in time, the fraction step method is used. This method is useful because one can use the same linear interpolation function for both velocity and pressure. The method is applied to the nonlinear interaction of a structure and a tuned liquid damper. All computations are performed with a personal computer.

  17. A Boussinesq-type method for fully nonlinear waves interacting with a rapidly varying bathymetry

    DEFF Research Database (Denmark)

    Madsen, Per A.; Fuhrman, David R.; Wang, Benlong

    2006-01-01

    class II Bragg scattering from an undular sea bottom. The computations are verified against measurements, theoretical solutions and numerical models from the literature. Finally, we make a detailed investigation of nonlinear class III Bragg scattering and results are given for the sub-harmonic and super......-harmonic interactions with the sea bed. We provide a new explanation and a prediction of the resulting downshift/upshift of the peak reflection/transmission as a function of wave steepness. (C) 2005 Elsevier B.V. All rights reserved....

  18. Motion of soliton center of interactional solitons in nonlinear media with an exponential nonlocal response

    Science.gov (United States)

    Dai, Zhiping; Yang, Zhenjun; Ling, Xiaohui; Zhang, Shumin; Pang, Zhaoguang; Li, Jianxing

    2016-05-01

    The motion of two interactional solitons is investigated in nonlinear media with an exponential nonlocal response. A differential equation describing the motion trajectories of soliton center is proposed. Some numerical simulations are performed to illustrate the characteristics of the motion trajectories. The results show that the trajectories always oscillate periodically. However, if the two solitons are launched with a relative inclined angle which is larger than a critical value, they do not collide any more but diverge from each other. The critical angle is also given.

  19. Harmonic Propagation and Interaction Evaluation between Small-Scale Wind Farms and Nonlinear Loads

    OpenAIRE

    Cheng-Xiong Mao; Yan Li; Bu-Han Zhang; Guang-Long Xie

    2013-01-01

    Distributed generation is a flexible and effective way to utilize renewable energy. The dispersed generators are quite close to the load, and pose some power quality problems such as harmonic current emissions. This paper focuses on the harmonic propagation and interaction between a small-scale wind farm and nonlinear loads in the distribution grid. Firstly, by setting the wind turbines as P – Q ( V ) nodes, the paper discusses the expanding Newton-Raphson power flow method for the wind far...

  20. Nonlinear Dimensionality Reduction via Path-Based Isometric Mapping.

    Science.gov (United States)

    Najafi, Amir; Joudaki, Amir; Fatemizadeh, Emad

    2016-07-01

    Nonlinear dimensionality reduction methods have demonstrated top-notch performance in many pattern recognition and image classification tasks. Despite their popularity, they suffer from highly expensive time and memory requirements, which render them inapplicable to large-scale datasets. To leverage such cases we propose a new method called "Path-Based Isomap". Similar to Isomap, we exploit geodesic paths to find the low-dimensional embedding. However, instead of preserving pairwise geodesic distances, the low-dimensional embedding is computed via a path-mapping algorithm. Due to the much fewer number of paths compared to number of data points, a significant improvement in time and memory complexity with a comparable performance is achieved. The method demonstrates state-of-the-art performance on well-known synthetic and real-world datasets, as well as in the presence of noise. PMID:26452249

  1. Attenuation, dispersion and nonlinearity effects in graphene-based waveguides

    Directory of Open Access Journals (Sweden)

    Almir Wirth Lima Jr.

    2015-05-01

    Full Text Available We simulated and analyzed in detail the behavior of ultrashort optical pulses, which are typically used in telecommunications, propagating through graphene-based nanoribbon waveguides. In this work, we showed the changes that occur in the Gaussian and hyperbolic secant input pulses due to the attenuation, high-order dispersive effects and nonlinear effects. We concluded that it is possible to control the shape of the output pulses with the value of the input signal power and the chemical potential of the graphene nanoribbon. We believe that the obtained results will be highly relevant since they can be applied to other nanophotonic devices, for example, filters, modulators, antennas, switches and other devices.

  2. Breakpoint Tuning in DCT-Based Nonlinear Layered Video Codecs

    Directory of Open Access Journals (Sweden)

    Pedro Cuenca

    2004-12-01

    Full Text Available Many studies have been conducted to evaluate the benefits of using layered video coding schemes as a means to improve the robustness of video communications systems. In this paper, we study a frame-aware nonlinear layering scheme for the transport of a DCT-based video over packet-switched networks. This scheme takes into account the relevance of the different elements of the video sequence composing the encoded video sequence. Throughout a detailed study over a large set of video streams, we show that by properly tuning the encoding parameters, it is feasible to gracefully degrade or even maintain the video quality while reducing the amount of data representing the video sequence. We then provide the major guidelines to properly tune up the encoding parameters allowing us to set the basis towards the development of more robust video communications systems.

  3. A nonlinear Stein based estimator for multichannel image denoising

    CERN Document Server

    Chaux, Caroline; Benazza-Benyahia, Amel; Pesquet, Jean-Christophe

    2007-01-01

    The use of multicomponent images has become widespread with the improvement of multisensor systems having increased spatial and spectral resolutions. However, the observed images are often corrupted by an additive Gaussian noise. In this paper, we are interested in multichannel image denoising based on a multiscale representation of the images. A multivariate statistical approach is adopted to take into account both the spatial and the inter-component correlations existing between the different wavelet subbands. More precisely, we propose a new parametric nonlinear estimator which generalizes many reported denoising methods. The derivation of the optimal parameters is achieved by applying Stein's principle in the multivariate case. Experiments performed on multispectral remote sensing images clearly indicate that our method outperforms conventional wavelet denoising techniques

  4. Significance of Wave-Particle Interaction Analyzer for direct measurements of nonlinear wave-particle interactions

    Directory of Open Access Journals (Sweden)

    Y. Katoh

    2013-03-01

    Full Text Available In the upcoming JAXA/ERG satellite mission, Wave Particle Interaction Analyzer (WPIA will be installed as an onboard software function. We study the statistical significance of the WPIA for measurement of the energy transfer process between energetic electrons and whistler-mode chorus emissions in the Earth's inner magnetosphere. The WPIA measures a relative phase angle between the wave vector E and velocity vector v of each electron and computes their inner product W, where W is the time variation of the kinetic energy of energetic electrons interacting with plasma waves. We evaluate the feasibility by applying the WPIA analysis to the simulation results of whistler-mode chorus generation. We compute W using both a wave electric field vector observed at a fixed point in the simulation system and a velocity vector of each energetic electron passing through this point. By summing up Wi of an individual particle i to give Wint, we obtain significant values of Wint as expected from the evolution of chorus emissions in the simulation result. We can discuss the efficiency of the energy exchange through wave-particle interactions by selecting the range of the kinetic energy and pitch angle of the electrons used in the computation of Wint. The statistical significance of the obtained Wint is evaluated by calculating the standard deviation σW of Wint. In the results of the analysis, positive or negative Wint is obtained at the different regions of velocity phase space, while at the specific regions the obtained Wint values are significantly greater than σW, indicating efficient wave-particle interactions. The present study demonstrates the feasibility of using the WPIA, which will be on board the upcoming ERG satellite, for direct measurement of wave-particle interactions.

  5. Color image encryption based on Coupled Nonlinear Chaotic Map

    Energy Technology Data Exchange (ETDEWEB)

    Mazloom, Sahar [Faculty of Electrical, Computer and IT Engineering, Qazvin Islamic Azad University, Qazvin (Iran, Islamic Republic of)], E-mail: sahar.mazloom@gmail.com; Eftekhari-Moghadam, Amir Masud [Faculty of Electrical, Computer and IT Engineering, Qazvin Islamic Azad University, Qazvin (Iran, Islamic Republic of)], E-mail: eftekhari@qazviniau.ac.ir

    2009-11-15

    Image encryption is somehow different from text encryption due to some inherent features of image such as bulk data capacity and high correlation among pixels, which are generally difficult to handle by conventional methods. The desirable cryptographic properties of the chaotic maps such as sensitivity to initial conditions and random-like behavior have attracted the attention of cryptographers to develop new encryption algorithms. Therefore, recent researches of image encryption algorithms have been increasingly based on chaotic systems, though the drawbacks of small key space and weak security in one-dimensional chaotic cryptosystems are obvious. This paper proposes a Coupled Nonlinear Chaotic Map, called CNCM, and a novel chaos-based image encryption algorithm to encrypt color images by using CNCM. The chaotic cryptography technique which used in this paper is a symmetric key cryptography with a stream cipher structure. In order to increase the security of the proposed algorithm, 240 bit-long secret key is used to generate the initial conditions and parameters of the chaotic map by making some algebraic transformations to the key. These transformations as well as the nonlinearity and coupling structure of the CNCM have enhanced the cryptosystem security. For getting higher security and higher complexity, the current paper employs the image size and color components to cryptosystem, thereby significantly increasing the resistance to known/chosen-plaintext attacks. The results of several experimental, statistical analysis and key sensitivity tests show that the proposed image encryption scheme provides an efficient and secure way for real-time image encryption and transmission.

  6. Robust global sensitivity analysis of a river management model to assess nonlinear and interaction effects

    OpenAIRE

    Peeters, L. J. M.; G. M. Podger; T. Smith; T. Pickett; Bark, R. H.; S. M. Cuddy

    2014-01-01

    The simulation of routing and distribution of water through a regulated river system with a river management model will quickly result in complex and nonlinear model behaviour. A robust sensitivity analysis increases the transparency of the model and provides both the modeller and the system manager with a better understanding and insight on how the model simulates reality and management operations. In this study, a robust, density-based sensitivity analysis, developed by P...

  7. Nonlinear Dynamics of Cantilever-Sample Interactions in Atomic Force Microscopy

    Science.gov (United States)

    Cantrell, John H.; Cantrell, Sean A.

    2010-01-01

    The interaction of the cantilever tip of an atomic force microscope (AFM) with the sample surface is obtained by treating the cantilever and sample as independent systems coupled by a nonlinear force acting between the cantilever tip and a volume element of the sample surface. The volume element is subjected to a restoring force from the remainder of the sample that provides dynamical equilibrium for the combined systems. The model accounts for the positions on the cantilever of the cantilever tip, laser probe, and excitation force (if any) via a basis set of set of orthogonal functions that may be generalized to account for arbitrary cantilever shapes. The basis set is extended to include nonlinear cantilever modes. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a matrix iteration procedure. The effects of oscillatory excitation forces applied either to the cantilever or to the sample surface (or to both) are obtained from the solution set and applied to the to the assessment of phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) modalities. The influence of bistable cantilever modes of on AFM signal generation is discussed. The effects on the cantilever-sample surface dynamics of subsurface features embedded in the sample that are perturbed by surface-generated oscillatory excitation forces and carried to the cantilever via wave propagation are accounted by the Bolef-Miller propagating wave model. Expressions pertaining to signal generation and image contrast in A-AFM are obtained and applied to amplitude modulation (intermittent contact) atomic force microscopy and resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM). The influence of phase accumulation in A-AFM on image contrast is discussed, as is the effect of hard contact and maximum nonlinearity regimes of A-AFM operation.

  8. Transistor-based metamaterials with dynamically tunable nonlinear susceptibility

    Science.gov (United States)

    Barrett, John P.; Katko, Alexander R.; Cummer, Steven A.

    2016-08-01

    We present the design, analysis, and experimental demonstration of an electromagnetic metamaterial with a dynamically tunable effective nonlinear susceptibility. Split-ring resonators loaded with transistors are shown theoretically and experimentally to act as metamaterials with a second-order nonlinear susceptibility that can be adjusted through the use of a bias voltage. Measurements confirm that this allows for the design of a nonlinear metamaterial with adjustable mixing efficiency.

  9. Comparison of zonal elution and nonlinear chromatography in determination of the interaction between seven drugs and immobilised β(2)-adrenoceptor.

    Science.gov (United States)

    Li, Qian; Wang, Jing; Zheng, Yuqing Yuan; Yang, Lingjian; Zhang, Yajun; Bian, Liujiao; Zheng, Jianbin; Li, Zijian; Zhao, Xinfeng; Zhang, Youyi

    2015-07-01

    Zonal elution and nonlinear chromatography are two mainstream models for the determination of drug-protein interaction in affinity chromatography. This work intended to compare the results by zonal elution with that by nonlinear chromatography when it comes to the analysis of the interaction between seven drugs and immobilised β2-adrenoceptor (β2-AR). The results of the zonal elution showed that clorprenaline, clenbuterol, methoxyphenamine, salbutamol, terbutaline, tulobuterol and bambuterol have only one type of binding site on immobilised β2-AR, while nonlinear chromatography confirmed the existence of at least two types of binding sites between β2-AR and clorprenaline, clenbuterol and bambuterol. On these sites, both zonal elution and nonlinear chromatography presented the same rank order for the association constants of the seven drugs. Compared with the data from zonal elution, the association constants calculated using nonlinear chromatography gave a good linear response to the corresponding values by radio-ligand binding assay. The sampling efficiencies of nonlinear chromatography were clearly higher than zonal elution. Nonlinear chromatography will probably become a powerful alternative for the high throughput determination of drug-protein interaction. PMID:26002106

  10. Nonperturbative spin-boson and spin-spin dynamics and nonlinear Fano interferences: a unified dissipaton theory based study.

    Science.gov (United States)

    Zhang, Hou-Dao; Xu, Rui-Xue; Zheng, Xiao; Yan, YiJing

    2015-01-14

    We consider the hybrid system-bath dynamics, based on the Yan's dissipaton formalism [Y. J. Yan, J. Chem. Phys. 140, 054105 (2014)]. This theory provides a unified quasi-particle treatment on three distinct classes of quantum bath, coupled nonperturbatively to arbitrary quantum systems. In this work, to study the entangled system and bath polarization and nonlinear Fano interference, we incorporate further the time-dependent light field, which interacts with both the molecular system and the collective bath dipoles directly. Numerical demonstrations are carried out on a two-level system, with comparison between phonon and exciton baths, in both linear and nonlinear Fano interference regimes. PMID:25591343

  11. Nonperturbative spin–boson and spin–spin dynamics and nonlinear Fano interferences: A unified dissipaton theory based study

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hou-Dao [Department of Chemistry, Hong Kong University of Science and Technology, Kowloon (Hong Kong); Xu, Rui-Xue, E-mail: rxxu@ustc.edu.cn; Zheng, Xiao [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Yan, YiJing, E-mail: yyan@ust.hk [Department of Chemistry, Hong Kong University of Science and Technology, Kowloon (Hong Kong); Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Collaborative Innovation Center of Chemistry for Energy Materials, University of Science and Technology of China, Hefei, Anhui 230026 (China)

    2015-01-14

    We consider the hybrid system–bath dynamics, based on the Yan’s dissipaton formalism [Y. J. Yan, J. Chem. Phys. 140, 054105 (2014)]. This theory provides a unified quasi-particle treatment on three distinct classes of quantum bath, coupled nonperturbatively to arbitrary quantum systems. In this work, to study the entangled system and bath polarization and nonlinear Fano interference, we incorporate further the time-dependent light field, which interacts with both the molecular system and the collective bath dipoles directly. Numerical demonstrations are carried out on a two-level system, with comparison between phonon and exciton baths, in both linear and nonlinear Fano interference regimes.

  12. Nonperturbative spin–boson and spin–spin dynamics and nonlinear Fano interferences: A unified dissipaton theory based study

    International Nuclear Information System (INIS)

    We consider the hybrid system–bath dynamics, based on the Yan’s dissipaton formalism [Y. J. Yan, J. Chem. Phys. 140, 054105 (2014)]. This theory provides a unified quasi-particle treatment on three distinct classes of quantum bath, coupled nonperturbatively to arbitrary quantum systems. In this work, to study the entangled system and bath polarization and nonlinear Fano interference, we incorporate further the time-dependent light field, which interacts with both the molecular system and the collective bath dipoles directly. Numerical demonstrations are carried out on a two-level system, with comparison between phonon and exciton baths, in both linear and nonlinear Fano interference regimes

  13. Gradiometer Based on Nonlinear Magneto-Optic Rotation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I SBIR project will demonstrate sensitive measurements of magnetic field gradients by nonlinear atomic spectroscopy. The gradients are determined by...

  14. Nonlinear analysis and enhancement of wing-based piezoaeroelastic energy harvesters

    Science.gov (United States)

    Abdelkefi, A.; Ghommem, M.; Nuhait, A. O.; Hajj, M. R.

    2014-01-01

    We investigate the level of harvested power from aeroelastic vibrations for an elastically mounted wing supported by nonlinear springs. The energy is harvested by attaching a piezoelectric transducer to the plunge degree of freedom. The considered wing has a low-aspect ratio and hence three dimensional aerodynamic effects cannot be neglected. To this end, the three dimensional unsteady vortex lattice method for the prediction of the unsteady aerodynamic loads is developed. A strong coupling scheme that is based on Hamming's fourth-order predictor-corrector method and accounts for the interaction between the aerodynamic loads and the motion of the wing is employed. The effects of the electrical load resistance, nonlinear torsional spring and eccentricity between the elastic axis and the gravity axis on the level of the harvested power, pitch and plunge amplitudes are investigated for a range of operating wind speeds. The results show that there is a specific wind speed beyond which the pitch motion does not pick any further energy from the incident flow. As such, the displacement in the plunge direction grows significantly and causes enhanced energy harvesting. The results also show that the nonlinear torsional spring plays an important role in enhancing the level of the harvested power. Furthermore, the harvested power can be increased by an order of magnitude by properly choosing the eccentricity and the load resistance. This analysis is helpful in designing piezoaeroelastic energy harvesters that can operate optimally at specific wind speeds.

  15. Nonlinear analysis and enhancement of wing-based piezoaeroelastic energy harvesters

    KAUST Repository

    Abdelkefi, Abdessattar

    2014-01-01

    We investigate the level of harvested power from aeroelastic vibrations for an elastically mounted wing supported by nonlinear springs. The energy is harvested by attaching a piezoelectric transducer to the plunge degree of freedom. The considered wing has a low-aspect ratio and hence three dimensional aerodynamic effects cannot be neglected. To this end, the three dimensional unsteady vortex lattice method for the prediction of the unsteady aerodynamic loads is developed. A strong coupling scheme that is based on Hamming\\'s fourth-order predictor-corrector method and accounts for the interaction between the aerodynamic loads and the motion of the wing is employed. The effects of the electrical load resistance, nonlinear torsional spring and eccentricity between the elastic axis and the gravity axis on the level of the harvested power, pitch and plunge amplitudes are investigated for a range of operating wind speeds. The results show that there is a specific wind speed beyond which the pitch motion does not pick any further energy from the incident flow. As such, the displacement in the plunge direction grows significantly and causes enhanced energy harvesting. The results also show that the nonlinear torsional spring plays an important role in enhancing the level of the harvested power. Furthermore, the harvested power can be increased by an order of magnitude by properly choosing the eccentricity and the load resistance. This analysis is helpful in designing piezoaeroelastic energy harvesters that can operate optimally at specific wind speeds. © 2013 Elsevier Ltd.

  16. Interaction of oblique dark solitons in two-dimensional supersonic nonlinear Schrödinger flow

    International Nuclear Information System (INIS)

    We investigate the collision of two oblique dark solitons in the two-dimensional supersonic nonlinear Schrödinger flow past two impenetrable obstacles. We numerically show that this collision is very similar to the dark solitons collision in the one-dimensional case. We observe that it is practically elastic and we measure the shifts of the solitons positions after their interaction. -- Highlights: ► We investigate the collision of oblique dark solitons in the 2D supersonic NLS flow past impenetrable obstacles. ► It is very similar to the dark solitons collision in the 1D case. ► It is practically elastic. ► We measure the shifts of the solitons positions after their interaction.

  17. Three-state interactions determine the second-order nonlinear optical response

    CERN Document Server

    Perez-Moreno, Javier

    2016-01-01

    Using the sum-rules, the sum-over-states expression for the diagonal term of first hyperpolarizability can be expressed as the sum of three-state interaction terms. We study the behavior of a generic three-state term to show that is possible to tune the contribution of resonant terms by tuning the spectrum of the molecule. When extrapolated to the off-resonance regime, the three-state interaction terms are shown to behave in a similar manner as the three-level model used to derive the fundamental limits. We finally show that most results derived using the three-level ansatz are general, and apply to molecules where more than three levels contribute to the second-order nonlinear response or/and far from optimization.

  18. A non-linear analytic stress model for the analysis on the stress interaction between TSVs

    Directory of Open Access Journals (Sweden)

    Ming-Han Liao

    2015-06-01

    Full Text Available Thermo-elastic strain is induced by through silicon vias (TSV due to the difference of thermal expansion coefficients between the copper (∼18 ppm/◦C and silicon (∼2.8 ppm/◦C when the structure is exposed to a thermal budget in the three dimensional integrated circuit (3DIC process. These thermal expansion stresses are high enough to induce the delamination on the interfaces between the copper, silicon, and isolated dielectric. A compact analytic model for the strain field induced by different layouts of thermal copper filled TSVs with the linear superposition principle is found to result in large errors due to the strong stress interaction between TSVs. In this work, a nonlinear stress analytic model with different TSV layouts is demonstrated by the finite element method and Mohr’s circle analysis. The stress characteristics are also measured by the atomic force microscope-raman technique at a nanometer level resolution. This nonlinear stress model for the strong interactions between TSVs results in an electron mobility change ~2-6% smaller than that resulting from a model that only considers the linear stress superposition principle.

  19. The nonlinear interaction of two-crossed focussed ultrasonic beams in the presence of turbulence

    Science.gov (United States)

    Rife, Stephen C.

    1988-06-01

    This paper examines the scattering of a nonlinearly generated sum frequency acoustic wave component from a region of turbulence defined by the overlap volume of two mutually perpendicular crossed focussed ultrasonic beams. The scattered sum frequency pressure amplitude is measured at different radial scan positions across the jet flow stream providing conclusions that explain some qualitative results governing the sum frequency scattering mechanism. Information about the instantaneous velocity components of the turbulent field in the sound-sound interaction volume is measured with an electronic spectrum analyzer. Average spectral shapes of the spectrum near the sum frequency represent information about the probability distribution function of the turbulent velocities. Acoustic measurements are correlated with velocity measurements of circular jets. These correlations demonstrate that the focussed crossed beam apparatus is an effective diagnostic tool for the experimental study of turbulent fluid fields in water. The results of the nonlinear crossed beam experiments indicate the apparatus can be utilized as a diagnostic tool to measure some parameters of turbulent velocity. The measured pressure of the radiated sum frequency correlates with turbulent velocities in the interaction region. Measurements of the Doppler shift and sum-frequency broadening are used to determine mean velocity and turbulent rms velocities respectively.

  20. Study of horizontal-vertical interactive Sway Rocking (SR) model for basemat uplift. Part 2: non-linear response analysis and validation

    International Nuclear Information System (INIS)

    Non-linear earthquake response analyses of a BWR MARK-II type nuclear reactor building are conducted by using a Sway Rocking model (SR model) proposed in Part 1 considering the interaction between horizontal and vertical motion. The results are compared with those of accurate mathematical model using the Green Function method. Horizontal response of the SR model agrees very well with that of the Green Function model. The floor response spectra of induced vertical motions by both methods are also corresponding well in periodic characteristics as well as peak-levels. From these results, it is confirmed that the horizontal-vertical interactive SR model is applicable to non-linear response analyses considering basemat uplift. Based on the comparison of the induced vertical motions due to basemat uplift by both methods, an application limit of the horizontal-vertical interactive SR model is set up at the ground contact ratio of about 50%. (author). 4 refs., 8 figs., 1 tab

  1. Few-optical-cycle pulse interactions with plasmas: Models and nonlinear effects

    International Nuclear Information System (INIS)

    We present an analysis of nonlinear optical effects when a high intense ultrashort laser pulse comprising only few field cycles propagates through an ionized medium. We introduce a model for the optical pulse and plasma based on the real electric field representation and the quantum mechanical description of electron dynamics in the ionization process. In the first part, we study the nonlinear atom response to such short driving pulses and the accompanied process of attosecond continuum production. In the second part, we analyze some collective plasma phenomena with ultrashort driving pulses, for which transverse effects are important. Among them, the processes of leaking mode self-channeling at saturable ionization, induced ionization scattering and large blueshifting with pulse shortening to a single-optical-cycle burst are of particular interest

  2. Nonlinear disturbance observer-based control for multi-input multi-output nonlinear systems subject to mismatching condition

    Science.gov (United States)

    Yang, Jun; Li, Shihua; Chen, Wen-Hua

    2012-08-01

    For a multi-input multi-output (MIMO) nonlinear system, the existing disturbance observer-based control (DOBC) only provides solutions to those whose disturbance relative degree (DRD) is higher than or equal to its input relative degree. By designing a novel disturbance compensation gain matrix, a generalised nonlinear DOBC method is proposed in this article to solve the disturbance attenuation problem of the MIMO nonlinear system with arbitrary DRD. It is shown that the disturbances are able to be removed from the output channels by the proposed method with appropriately chosen control parameters. The property of nominal performance recovery, which is the major merit of the DOBCs, is retained with the proposed method. The feasibility and effectiveness of the proposed method are demonstrated by simulation studies of both the numerical and application examples.

  3. Modified time reversal imaging of a closed crack based on nonlinear scattering

    Science.gov (United States)

    Blanloeuil, Philippe; Rose, L. R. Francis; Guinto, Jed A.; Veidt, Martin; Wang, Chun H.

    2016-04-01

    A recent variant of time reversal imaging is used to detect and characterize a closed crack based on both the fundamental and the second harmonic components of the scattered waves in the presence of Contact Acoustic Nonlinearity at the crack interface. A Finite Element model, which includes unilateral contact with Coulomb friction to account for contact between the crack faces, is used to compute the scattered field resulting from the interaction between incident longitudinal plane waves and the crack. The knowledge of the scattering for multiple incident angles constitutes the input for the imaging algorithm. Good reconstruction of the crack is obtained from both harmonic sources, and second harmonic based images also enables one to identify the location of the second harmonic sources along the crack. This first imaging based on the second harmonic also offers potential baseline free detection of closed cracks.

  4. Nonlinear interaction of proton whistler with kinetic Alfvén wave to study solar wind turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Goyal, R.; Sharma, R. P. [Centre for Energy Studies, Indian Institute of Technology, Delhi-110016 (India); Goldstein, M. L. [NASA Goddard Space Flight Centre, Code 673, Greenbelt, Maryland 20771 (United States); Dwivedi, N. K. [Austrian Academy of Sciences, Space Research Institute, Schmiedlstrasse 6, 8042 Graz (Austria)

    2013-12-15

    This paper presents the nonlinear interaction between small but finite amplitude kinetic Alfvén wave (KAW) and proton whistler wave using two-fluid model in intermediate beta plasma, applicable to solar wind. The nonlinearity is introduced by modification in the background density. This change in density is attributed to the nonlinear ponderomotive force due to KAW. The solutions of the model equations, governing the nonlinear interaction (and its effect on the formation of localized structures), have been obtained using semi-analytical method in solar wind at 1AU. It is concluded that the KAW properties significantly affect the threshold field required for the filament formation and their critical size (for proton whistler). The magnetic and electric field power spectra have been obtained and their relevance with the recent observations of solar wind turbulence by Cluster spacecraft has been pointed out.

  5. DG-FEM solution for nonlinear wave-structure interaction using Boussinesq-type equations

    DEFF Research Database (Denmark)

    Engsig-Karup, Allan Peter; Hesthaven, Jan; Bingham, Harry B.; Warburton, T.

    2008-01-01

    equations in complex and curvilinear geometries which amends the application range of previous numerical models that have been based on structured Cartesian grids. The Boussinesq method provides the basis for the accurate description of fully nonlinear and dispersive water waves in both shallow and deep......We present a high-order nodal Discontinuous Galerkin Finite Element Method (DG-FEM) solution based on a set of highly accurate Boussinesq-type equations for solving general water-wave problems in complex geometries. A nodal DG-FEM is used for the spatial discretization to solve the Boussinesq...

  6. The study on the non-linear soil structure interaction for nuclear power plants

    International Nuclear Information System (INIS)

    1. Introduction: JNES is planning a new project to study non-linear soil-structure interaction (SSI) effect under large earthquake ground motions equivalent to and/or over a design earthquake ground motion of S2(The extreme design earthquake). Concerning the SSI test, it is pointed out that handling of the scale effect of the specimen together with the surrounding soil on the earthquake response evaluation of the actual structure is essential issue for the scaled model test. Thus, for the test, the largest specimen possible and the biggest input motion possible are necessary. Taking into account the above issues, new test methodology, which utilizes artificial earthquake ground motion, is considered desirable if it can be performed at a realistic cost. Under this motivation, we have studied the test methodology which applying blasting power as for a big earthquake ground motion. The information from a coal mine company in the U.S.A. indicates that the works performed in the surface coal mine to blast a rock covering a coal layer generates a big artificial ground motion, which is similar to earthquake ground motion. Application of this artificial earthquake ground motion for the SSI test is considered very promising because the blasting work is carried out periodically for mining coal so that we can apply artificial motions generated by the work if we construct a building model at a closed point to the blasting work area. The major purposes of the test will be to understand (a) basic earthquake response characteristics of a Nuclear Power Plant (NPP) reactor building when a large earthquake strikes the NPP site and (b) nonlinear characteristics of SSI phenomenon during a big earthquake. In the paper, we introduce the test method and basic characteristics of measured artificial ground motions generated by the blasting works on an actual site. 2. Conclusion: It was confirmed that the artificial ground motions generated by blasting works have enough acceleration level

  7. Results-Based Interaction Design

    Science.gov (United States)

    Weiss, Meredith

    2008-01-01

    Interaction design is a user-centered approach to development in which users and their goals are the driving force behind a project's design. Interaction design principles are fundamental to the design and implementation of effective websites, but they are not sufficient. This article argues that, to reach its full potential, a website should also…

  8. Nonlinear inverse modeling of sensor based on back-propagation fuzzy logical system

    Institute of Scientific and Technical Information of China (English)

    Li Jun; Liu Junhua

    2007-01-01

    Objective To correct the nonlinear error of sensor output, a new approach to sensor inverse modeling based on Back-Propagation Fuzzy Logical System (BP FS) is presented. Methods The BP FS is a computationally efficient nonlinear universal approximator, which is capable of implementing complex nonlinear mapping from its input pattern space to the output with fast convergence speed. Results The neuro-fuzzy hybrid system, i.e. BP FS, is then applied to construct nonlinear inverse model of pressure sensor. The experimental results show that the proposed inverse modeling method automatically compensates the associated nonlinear error in pressure estimation, and thus the performance of pressure sensor is significantly improved. Conclusion The proposed method can be widely used in nonlinearity correction of various kinds of sensors to compensate the effects of nonlinearity and temperature on sensor output.

  9. Determination of Landau Fermi-liquid parameters of strongly interacting fermions by means of a nonlinear scaling transformation

    OpenAIRE

    Chen, Ji-sheng

    2008-01-01

    A nonlinear transformation approach is formulated for the correlated fermions' thermodynamics through a medium-scaling effective action. An auxiliary implicit variable-effective chemical potential is introduced to characterize the non-Gaussian fluctuations physics. By incorporating the nonlocal correlation effects, the achieved grand partition function is made of coupled highly nonlinear parametric equations. Analytically, the low temperature expansions for the strongly interacting unitary Fe...

  10. A numerical study on the impact of nonlinear interactions on the amplitude of the migrating semidiurnal tide

    Directory of Open Access Journals (Sweden)

    C. M. Huang

    2006-12-01

    Full Text Available To quantitatively study the effects of nonlinear interactions on tide structure, a nonlinear numerical tidal model is developed, and the reliability and convergence of the adopted algorithm and coding are checked by numerical experiments. Under the same conditions as those employed by the GSWM-00 (Global Scale Wave Model 2000, our model provides the nonlinear quasi-steady solution of the migrating semidiurnal tide, which differs from the GSWM-00 result (the linear steady solution in the MLT region, especially above 100 km. Additionally, their amplitude difference displays a remarkable month-to-month variation, and its significant magnitudes occur during the month with strong semidiurnal tide. A quantitative analysis suggests that the main cause for the amplitude difference is that the initial migrating 12-h tide will interact with the mean flow as well as the nonlinearity-excited 6-h tide, and subsequently yield a new 12-h tidal part. Furthermore, our simulations also show that the mean flow/tidal interaction will significantly alter the background wind and temperature fields. The large magnitudes of the tidal amplitude difference and the background alteration indicate that the nonlinear processes involved in tidal propagations should be comprehensively considered in the description of global atmospheric dynamics in the MLT region. The comparisons among our simulations, the GSWMs and some observations of tides suggest that the nonlinearity-induced tidal structure variation could be a possible mechanism to account for some discrepancies between the GSWMs and the observations.

  11. Reduction of nonlinear patterning effects in SOA-based All-optical Switches using Optical filtering

    DEFF Research Database (Denmark)

    Nielsen, Mads Lønstrup; Mørk, Jesper; Skaguchi, J.;

    2005-01-01

    We explain theoretically, and demonstrate and quantify experimentally, how appropriate filtering can reduce the dominant nonlinear patterning effect, which limits the performance of differential-mode SOA-based switches.......We explain theoretically, and demonstrate and quantify experimentally, how appropriate filtering can reduce the dominant nonlinear patterning effect, which limits the performance of differential-mode SOA-based switches....

  12. Rate of non-linearity in DMS aerosol-cloud-climate interactions

    Directory of Open Access Journals (Sweden)

    M. A. Thomas

    2011-11-01

    Full Text Available The degree of non-linearity in DMS-cloud-climate interactions is assessed using the ECHAM5-HAMMOZ model by taking into account end-to-end aerosol chemistry-cloud microphysics link. The evaluation is made over the Southern oceans in austral summer, a region of minimal anthropogenic influence. In this study, we compare the DMS-derived changes in the aerosol and cloud microphysical properties between a baseline simulation with the ocean DMS emissions from a prescribed climatology, and a scenario where the DMS emissions are doubled. Our results show that doubling the DMS emissions in the current climate results in a non-linear response in atmospheric DMS burden and subsequently, in SO2 and H2SO4 burdens due to inadequate OH oxidation. The aerosol optical depth increases by only ~20 % in the 30° S–75° S belt in the SH summer months. This increases the vertically integrated cloud droplet number concentrations (CDNC by 25 %. Since the vertically integrated liquid water vapor is constant in our model simulations, an increase in CDNC leads to a reduction in cloud droplet radius of 3.4 % over the Southern oceans in summer. The equivalent increase in cloud liquid water path is 10.7 %. The above changes in cloud microphysical properties result in a change in global annual mean radiative forcing at the TOA of −1.4 W m−2. The results suggest that the DMS-cloud microphysics link is highly non-linear. This has implications for future studies investigating the DMS-cloud climate feedbacks in a warming world and for studies evaluating geoengineering options to counteract warming by modulating low level marine clouds.

  13. Image-Based Visual Servoing for Robotic Systems: A Nonlinear Lyapunov-Based Control Approach

    International Nuclear Information System (INIS)

    The objective of this project is to enable current and future EM robots with an increased ability to perceive and interact with unstructured and unknown environments through the use of camera-based visual servo controlled robots. The scientific goals of this research are to develop a new visual servo control methodology that: (1) adapts for the unknown camera calibration parameters (e.g., focal length, scaling factors, camera position and orientation) and the physical parameters of the robotic system (e.g., mass, inertia, friction), (2) compensates for unknown depth information (extract 3D information from the 2D image), and (3) enables multi-uncalibrated cameras to be used as a means to provide a larger field-of-view. Nonlinear Lyapunov-based techniques are being used to overcome the complex control issues and alleviate many of the restrictive assumptions that impact current visual servo controlled robotic systems. The potential relevance of this control methodology will be a plug-and-play visual servoing control module that can be utilized in conjunction with current technology such as feature extraction and recognition, to enable current EM robotic systems with the capabilities of increased accuracy, autonomy, and robustness, with a larger field of view (and hence a larger workspace). These capabilities will enable EM robots to significantly accelerate D and D operations by providing for improved robot autonomy and increased worker productivity, while also reducing the associated costs, removing the human operator from the hazardous environments, and reducing the burden and skill of the human operators

  14. Linear and nonlinear optical properties of nucleic acid bases

    Science.gov (United States)

    Alparone, Andrea

    2013-01-01

    Electronic and vibrational (hyper)polarizabilities of neutral nucleic acid bases (uracil, thymine, cytosine, adenine, hypoxanthine and guanine) were determined using Hartree-Fock, correlated MPn (n = 2, 4), CCSD and DFT (B3LYP, B97-1, CAM-B3LYP) methods. The computations were performed in gaseous and aqueous phases for the most stable tautomeric forms. Frequency-dependent second-order hyperpolarizabilities were calculated for the OKE, IDRI, EFISHG and THG nonlinear optical processes at the wavelength of 1064 nm. The results show that the average electronic polarizabilities increase in the order uracil guanine. This order is also maintained for the electronic hyperpolarizabilities, with the inversion between cytosine and thymine. The response electric properties for the tautomers are almost similar to each other, whereas group substitution and solvation effects are much more significant. Among the DFT methods, the long-range corrected CAM-B3LYP functional gives the better performances, reproducing satisfactorily the correlated ab initio (hyper)polarizability data.

  15. Towards modeling of nonlinear laser-plasma interactions with hydrocodes: the thick-ray approach.

    Science.gov (United States)

    Colaïtis, A; Duchateau, G; Nicolaï, P; Tikhonchuk, V

    2014-03-01

    This paper deals with the computation of laser beam intensity in large-scale radiative hydrocodes applied to the modeling of nonlinear laser-plasma interactions (LPIs) in inertial confinement fusion (ICF). The paraxial complex geometrical optics (PCGO) is adapted for light waves in an inhomogeneous medium and modified to include the inverse bremsstrahlung absorption and the ponderomotive force. This thick-ray model is compared to the standard ray-tracing (RT) approach, both in the chic code. The PCGO model leads to different power deposition patterns and better diffraction modeling compared to standard RT codes. The intensity-reconstruction technique used in RT codes to model nonlinear LPI leads to artificial filamentation and fails to reproduce realistic ponderomotive self-focusing distances, intensity amplifications, and density channel depletions, whereas PCGO succeeds. Bundles of Gaussian thick rays can be used to model realistic non-Gaussian ICF beams. The PCGO approach is expected to improve the accuracy of ICF simulations and serve as a basis to implement diverse LPI effects in large-scale hydrocodes. PMID:24730950

  16. Theoretical studies of coherent nonlinear drift wave-zonal flow interactions

    International Nuclear Information System (INIS)

    Full text: We have, employing a slab model, carried out in-depth theoretical studies on the coherent nonlinear interactions between drift waves (DW) and zonal flows (ZF). In this talk, we will first review the four-wave modulational mechanism for the spontaneous excitation of zonal flow by coherent drift waves. As the amplitude of the primary (pump) drift wave attains spatial localization due to plasma non-uniformities and/or initial localized perturbations, the excited zonal flows become localized structures; leading to cascading of drift waves toward shorter (radial) wave numbers.This nonlinearly generated normal cascading and accompanied enhanced (radial) dispersiveness leads to the new novel result that, time asymptotically, coherent drift waves can be trapped by the self-induced zonal flows; similar to the Langmuir wave-density cavity soliton physics. Indeed, both analytical theories and direct numerical calculations demonstrate the formation and, consequently, radial propagation of DW-ZF solitary structures. Additional effects such as linear growth, dissipations, equilibrium non-uniformities and soliton dynamics could further lead to interesting physics; e.g., generation, destruction, collision, and reflection of solitons, as well as turbulence bursting. The propagation of DW-ZF solitons causes significant radial spreading of DW turbulence and ,hence, could qualitatively modify the transport processes. Generalization to the toroidal geometries will also be presented. Research supported by U.S. DoE. (author)

  17. Nonlinear gauge interactions: a possible solution to the "measurement problem" in quantum mechanics

    CERN Document Server

    Hansson, Johan

    2010-01-01

    Two fundamental, and unsolved problems in physics are: i) the resolution of the "measurement problem" in quantum mechanics ii) the quantization of strongly nonlinear (nonabelian) gauge theories. The aim of this paper is to suggest that these two problems might be linked, and that a mutual, simultaneous solution to both might exist. We propose that the mechanism responsible for the "collapse of the wave function" in quantum mechanics is the nonlinearities already present in the theory via nonabelian gauge interactions. Unlike all other models of spontaneous collapse, our proposal is, to the best of our knowledge, the only one which does not introduce any new elements into the theory. A possible experimental test of the model would be to compare the coherence lengths - here defined as the distance over which quantum mechanical superposition is still valid - for, \\textit{e.g}, electrons and photons in a double-slit experiment. The electrons should have a finite coherence length, while photons should have a much ...

  18. Nonlinear modal interactions in parity-time (${\\cal PT}$) symmetric lasers

    CERN Document Server

    Ge, Li

    2016-01-01

    Parity-time ($\\cal PT$) symmetric lasers have attracted considerable attention lately due to their promising applications and intriguing properties, such as free spectral range doubling and single-mode lasing. In this work we discuss nonlinear modal interactions in these laser systems under steady state conditions, and we demonstrate that several gain clamping scenarios can occur for lasing operation in the $\\cal PT$-symmetric and $\\cal PT$-broken phases. In particular, we show that, depending on the system's design and the external pump profile, its operation in the nonlinear regime falls into two different categories: in one the system is frozen in the $\\cal PT$ phase space as the applied gain increases, while in the other the system is pulled towards its exceptional point. These features are first illustrated by a coupled mode formalism and later verified by employing the Steady-state Ab-initio Laser Theory (SALT). Our findings shine light on the robustness of single-mode operation in these lasers against ...

  19. Numerical simulation of nonlinear mode interactions in ridge-waveguide semiconductor lasers

    Science.gov (United States)

    Kalagara, Hemashilpa; Eliseev, Petr G.; Osinski, Marek

    2012-02-01

    Nonlinear perturbation of effective group index is calculated numerically in semiconductor ridge waveguide laser structures under an influence of a strong driving wave (mode). Model of nonlinear interaction of waves is used to obtain conditions for appearance of anomalous dispersion of modal index and also for inversion of the group index of guided waves (modes of the ridge-waveguide laser structures). Ranges around critically anomalous dispersion (CAD) points, where the effective group index passes zero value, are calculated numerically. CAD points form closed loops in graphs of detuning vs. driving wave intensity. These loops define ranges where superluminal propagation, as well as slowed reflection of probe wave can be obtained. Numerical simulations are performed for an InGaAs/AlGaAs/GaAs double quantum well (DQW) laser structure and also for a GaAs/AlGaAs separate confinement heterostructure. The threshold intensities for the appearance of CAD points, as well as the influence of relaxation rate and optical confinement on the appearance of superluminal regime are compared for the DQW and SCH structures.

  20. Nonlinear Adaptive Filters based on Particle Swarm Optimization

    OpenAIRE

    Faten BEN ARFIA; Ben Messaoud, Mohamed; Abid, Mohamed

    2009-01-01

    This paper presents a particle swarm optimization (PSO) algorithm to adjust the parameters of the nonlinear filter and to make this type of the filters more powerful for the elimination of the Gaussian noise and also the impulse noise. In this paper we apply the particle swarm optimization to the rational filters and we completed this work with the comparison between our results and other adaptive nonlinear filters like the LMS adaptive median filters and the no-adaptive rational filter.

  1. Classifying general nonlinear force laws in cell-based models via the continuum limit

    OpenAIRE

    Murray, P.J.; Edwards, C M; Tindall, M.J.; Maini, P.K.

    2012-01-01

    Although discrete cell-based frameworks are now commonly used to simulate a whole range of biological phenomena, it is typically not obvious how the numerous different types of model are related to one another, nor which one is most appropriate in a given context. Here we demonstrate how individual cell movement on the discrete scale modeled using nonlinear force laws can be described by nonlinear diffusion coefficients on the continuum scale. A general relationship between nonlinear force la...

  2. Nonlinear wave-structure interactions with a high-order Boussinesq model

    DEFF Research Database (Denmark)

    Fuhrman, David R.; Bingham, Harry; Madsen, Per A.

    2005-01-01

    This paper describes the extension of a finite difference model based on a recently derived highly accurate Boussinesq formulation to include domains having arbitrary piecewise-rectangular bottom-mounted (surface-piercing) structures. The resulting linearized system is analyzed for stability on a...... system is receptive to dissipation, and these problems can be overcome in practice using high-order filtering techniques. The resulting model is verified through numerical simulations involving classical linear wave diffraction around a semi-infinite breakwater, linear and nonlinear gap diffraction, and...

  3. FOXTAIL: Modeling the nonlinear interaction between Alfv\\'en eigenmodes and energetic particles in tokamaks

    CERN Document Server

    Tholerus, Emmi; Hellsten, Torbjörn

    2016-01-01

    FOXTAIL is a new hybrid magnetohydrodynamic-kinetic code used to describe interactions between energetic particles and Alfv\\'en eigenmodes in tokamaks with realistic geometries. The code simulates the nonlinear dynamics of the amplitudes of individual eigenmodes and of a set of discrete markers in five-dimensional phase space representing the energetic particle distribution. Action-angle coordinates of the equilibrium system are used for efficient tracing of energetic particles, and the particle acceleration by the wave fields of the eigenmodes is Fourier decomposed in the same angles. The eigenmodes are described using temporally constant eigenfunctions with dynamic complex amplitudes. Possible applications of the code are presented, e.g., making a quantitative validity evaluation of the one-dimensional bump-on-tail approximation of the system. Expected effects of the fulfillment of the Chirikov criterion in two-mode scenarios have also been verified.

  4. Non-linear interactions of multi-level atoms with a near-resonant standing wave

    International Nuclear Information System (INIS)

    Using a semiclassical density matrix formalism we have calculated the behavior of multi-level atoms interacting with a standing wave field, and show how complex non-linear phenomena, including multi-photon effects, combine to produce saturation spectra as observed in experiments. We consider both 20-level sodium and 24-level rubidium models, contrasting these with a simple 2-level case. The influence of parameters such as atomic trajectory and the time the atom remains in the beam are shown to have a critical effect on the lineshape of these resonances and the emission/absorption processes. Stable oscillations in the excited state populations for both the two-level and multi-level cases are shown to be limit cycles. These limit cycles undergo period doubling as the system evolves into chaos. Finally, using a Monte Carlo treatment, these processes average to produce saturated absorption spectra complete with power and Doppler broadening effects consistent with experiment. (authors)

  5. Non-linear dynamic interactions of a Jeffcott rotor with preloaded snubber ring

    Science.gov (United States)

    Pavlovskaia, E. E.; Karpenko, E. V.; Wiercigroch, M.

    2004-09-01

    A two-degrees-of-freedom model of a Jeffcott rotor with a preloaded snubber ring subjected to out-of-balance excitation has been developed. The purely impact interactions have been investigated. The rotor makes intermittent contacts with the preloaded snubber ring and as a consequence it can be in one of five different contact regimes, which boundaries have been found analytically. The current location of the snubber ring has been determined using the principle of the minimum elastic energy in the snubber ring. Consequently a non-linear piecewise smooth dynamical system has been obtained and studied numerically. The results in form of bifurcation diagrams, phase portraits and Poincaré maps show significant differences for the cases with and without preloading.

  6. Giant resonances in the relativistic RPA with non-linear interactions

    International Nuclear Information System (INIS)

    Nuclear isoscalar and isovector giant resonances are studied in the framework of the relativistic random phase approximation starting from effective Lagrangians containing meson self-interaction terms. The meson propagators are worked out in momentum space from the second variation of the action of the system. The N anti N excitations are not included to be consistent with the relativistic mean field approximation used for these effective Lagrangians. It turns out that the non-linear models such as TM1, NL-SH, etc., which are of great success in describing nuclear ground state properties in mean field approximation can also well reproduce the isoscalar monopole, quadrupole as well as isovector monopole, dipole resonances of spherical nuclei. (orig.)

  7. Electrostatic potential profile and nonlinear current in an interacting one-dimensional molecular wire

    Indian Academy of Sciences (India)

    S Lakshmi; Swapan K Pati

    2003-10-01

    We consider an interacting one-dimensional molecular wire attached to two metal electrodes on either side of it. The electrostatic potential profile across the wire-electrode interface has been deduced solving the Schrodinger and Poisson equations self-consistently. Since the Poisson distribution crucially depends on charge densities, we have considered different Hamiltonian parameters to model the nanoscale wire. We find that for very weak electron correlations, the potential gradient is almost zero in the middle of the wire but are large near the chain ends. However, for strong correlations, the potential is essentially a ramp function. The nonlinear current, obtained from the scattering formalism, is found to be less with the ramp potential than for weak correlations. Some of the interesting features in current-voltage characteristics have been explained using one-electron formalism and instabilities in the system.

  8. A simple method for wind tunnel balance calibration including non-linear interaction terms

    Science.gov (United States)

    Ramaswamy, M. A.; Srinivas, T.; Holla, V. S.

    The conventional method for calibrating wind tunnel balances to obtain the coupled linear and nonlinear interaction terms requires the application of combinations of pure components of the loads on the calibration body compensating the deflection of the balance. For a six-component balance, this calls for a complex loading system and an arrangement to translate and tilt the balance support about all three axes. A simple method called the least-square method is illustrated for a three-component balance. The simplicity arises from the fact that application of the pure components of the loads or reorientation of the balance is not required. A single load is applied that has various components whose magnitudes can be easily found knowing the orientation of the calibration body under load and the point of application of the load. The coefficients are obtained by using the least-square-fit approach to match the outputs obtained for various combinations of load.

  9. Nonlinear interaction of a Gaussian electromagnetic beam with an electrostatic upper hybrid wave: Stimulated Raman scattering

    International Nuclear Information System (INIS)

    Nonlinear interaction of a Gaussian EM beam with a weak electrostatic (ES) upper hybrid wave in a collisionless magneto plasma is investigated. The EM beam is assumed to be propagating perpendicular to external magnetic field in an ordinary mode. For Gaussian intensity distribution of the incident EM wave in a plane perpendicular to the direction of propagation, a dc component of ponderomotive force becomes finite and leads to modification of background density. This leads to strong coupling between EM beam and upper hybrid ES mode in the plasma and can lead to focusing of the excited upper hybrid mode under appropriate conditions. Thus EM power gets converted into ES power. Pump wave equation is solved within WKB and paraxial ray approximations. Then within perturbation approximation, and equation describing the space-time evolution of density perturbation associated with ES upper hybrid wave is derived and solved using the approach of taking self-focusing effects of pump and upper hybrid mode

  10. Nuclear quadrupole interaction and nonlinear optical property of some borate crystals^*

    Science.gov (United States)

    Choh, S. H.; Kim, I. G.; Shin, H. W.; Park, I.-W.

    2003-03-01

    Borate crystals, like Li_2B_4O_7, LiB_3O_5, and BaB_2O_4, consist of 4-coordinated and/or 3-coordinated boron-oxygen bonds. As reported [1], the principal Z-axis of the electric field gradient (EFG) around the boron in 3-coordinated bonds is perpendicular to the plane containing the boron-oxygen bonds. We calculated the principal Z-direction of the EFG-tensor by employing the simple point charge model for the arbitrary planar triangle configurations, and the results are consistent with experimental ones. Moreover, a strong correlation between the nonlinear optical coefficient and the nuclear quadrupole interactions, such as the quadrupole coupling constant and the asymmetry parameter, was empirically found for these compounds. Details will be presented. * Supported by the National Research Laboratory Program(MOST). [1] I. G. Kim and S. H. Choh, J. Phys.: Condens. Matter, b11, 8283 (1999).

  11. Resonant interactions between discrete phonons in quinhydrone driven by nonlinear electron-phonon coupling

    Science.gov (United States)

    Rury, Aaron S.

    2016-06-01

    This study reports experimental, computational, and theoretical evidence for a previously unobserved coherent phonon-phonon interaction in an organic solid that can be described by the application of Fano's analysis to a case without the presence of a continuum. Using Raman spectroscopy of the hydrogen-bonded charge-transfer material quinhydrone, two peaks appear near 700 cm-1 we assign as phonons whose position and line-shape asymmetry depend on the sample temperature and light scattering excitation energy. Density functional theory calculations find two nearly degenerate phonons possessing frequencies near the values found in experiment that share similar atomic motion out of the aromatic plane of electron donor and acceptor molecules of quinhydrone. Further analytical modeling of the steady-state light scattering process using the Peierls-Hubbard Hamiltonian and time-dependent perturbation theory motivates assignment of the physical origin of the asymmetric features of each peak's line shape to an interaction between two discrete phonons via nonlinear electron-phonon coupling. In the context of analytical model results, characteristics of the experimental spectra upon 2.33 eV excitation of the Raman scattering process are used to qualify the temperature dependence of the magnitude of this coupling in the valence band of quinhydrone. These results broaden the range of phonon-phonon interactions in materials in general while also highlighting the rich physics and fundamental attributes specific to organic solids that may determine their applicability in next generation electronics and photonics technologies.

  12. Optimisation of nonlinear motion cueing algorithm based on genetic algorithm

    Science.gov (United States)

    Asadi, Houshyar; Mohamed, Shady; Rahim Zadeh, Delpak; Nahavandi, Saeid

    2015-04-01

    Motion cueing algorithms (MCAs) are playing a significant role in driving simulators, aiming to deliver the most accurate human sensation to the simulator drivers compared with a real vehicle driver, without exceeding the physical limitations of the simulator. This paper provides the optimisation design of an MCA for a vehicle simulator, in order to find the most suitable washout algorithm parameters, while respecting all motion platform physical limitations, and minimising human perception error between real and simulator driver. One of the main limitations of the classical washout filters is that it is attuned by the worst-case scenario tuning method. This is based on trial and error, and is effected by driving and programmers experience, making this the most significant obstacle to full motion platform utilisation. This leads to inflexibility of the structure, production of false cues and makes the resulting simulator fail to suit all circumstances. In addition, the classical method does not take minimisation of human perception error and physical constraints into account. Production of motion cues and the impact of different parameters of classical washout filters on motion cues remain inaccessible for designers for this reason. The aim of this paper is to provide an optimisation method for tuning the MCA parameters, based on nonlinear filtering and genetic algorithms. This is done by taking vestibular sensation error into account between real and simulated cases, as well as main dynamic limitations, tilt coordination and correlation coefficient. Three additional compensatory linear blocks are integrated into the MCA, to be tuned in order to modify the performance of the filters successfully. The proposed optimised MCA is implemented in MATLAB/Simulink software packages. The results generated using the proposed method show increased performance in terms of human sensation, reference shape tracking and exploiting the platform more efficiently without reaching

  13. Identification of nonlinear multi-degree-of freedom structures based on Hilbert transformation

    Science.gov (United States)

    Wu, ZhiGang; Yang, Ning; Yang, Chao

    2014-09-01

    The modeling method and identified method adapted to multi-degree-of-freedom structures with strucrural nonlinearities are established. The component mode synthesis method is used to establish the nonlinear governing equations by extending the connected relationships. Based on the modeling method, the Hilbert transform method is applied to identify the nonlinear stiffness of multi-degree-of-freedom structures. Nonlinear analysis and identification of a typical folding wing configuration with three freeplay hinges are investigated. The nonlinear governing equation is established based on present methods and the computing results of different stiffness are checked by finite element programming. In order to illustrate the influence of the nonlinearities, the frequency response characteristics of the structure are analyzed and Hilbert transform is performed. The Hilbert transform identification method is utilized to identify the nonlinear stiffness of nonlinear hinges in the time domain and several parametric studies are performed. In addition, the comparison of response is made to illustrate the feasibility of the methods. The results show that the extending component mode synthesis method in the present work can be used to establish the governing equation with structural nonlinearities. Based on the modeling method, the Hilbert transform identified method can be extended to multi-degree-of-freedom structures accurately.

  14. Variance-based interaction index measuring heteroscedasticity

    Science.gov (United States)

    Ito, Keiichi; Couckuyt, Ivo; Poles, Silvia; Dhaene, Tom

    2016-06-01

    This work is motivated by the need to deal with models with high-dimensional input spaces of real variables. One way to tackle high-dimensional problems is to identify interaction or non-interaction among input parameters. We propose a new variance-based sensitivity interaction index that can detect and quantify interactions among the input variables of mathematical functions and computer simulations. The computation is very similar to first-order sensitivity indices by Sobol'. The proposed interaction index can quantify the relative importance of input variables in interaction. Furthermore, detection of non-interaction for screening can be done with as low as 4 n + 2 function evaluations, where n is the number of input variables. Using the interaction indices based on heteroscedasticity, the original function may be decomposed into a set of lower dimensional functions which may then be analyzed separately.

  15. A General Approach for Quantifying Nonlinear Connectivity in the Nervous System Based on Phase Coupling.

    Science.gov (United States)

    Yang, Yuan; Solis-Escalante, Teodoro; Yao, Jun; Daffertshofer, Andreas; Schouten, Alfred C; van der Helm, Frans C T

    2016-02-01

    Interaction between distant neuronal populations is essential for communication within the nervous system and can occur as a highly nonlinear process. To better understand the functional role of neural interactions, it is important to quantify the nonlinear connectivity in the nervous system. We introduce a general approach to measure nonlinear connectivity through phase coupling: the multi-spectral phase coherence (MSPC). Using simulated data, we compare MSPC with existing phase coupling measures, namely n : m synchronization index and bi-phase locking value. MSPC provides a system description, including (i) the order of the nonlinearity, (ii) the direction of interaction, (iii) the time delay in the system, and both (iv) harmonic and (v) intermodulation coupling beyond the second order; which are only partly revealed by other methods. We apply MSPC to analyze data from a motor control experiment, where subjects performed isotonic wrist flexions while receiving movement perturbations. MSPC between the perturbation, EEG and EMG was calculated. Our results reveal directional nonlinear connectivity in the afferent and efferent pathways, as well as the time delay (43 ± 8 ms) between the perturbation and the brain response. In conclusion, MSPC is a novel approach capable to assess high-order nonlinear interaction and timing in the nervous system. PMID:26404514

  16. Switching behaviour of nonlinear Mach–Zehnder interferometer based on photonic crystal geometry

    Indian Academy of Sciences (India)

    Man Mohan Gupta; S Medhekar

    2014-06-01

    Nonlinear Mach–Zehnder interferometer (NMZI) created with photonic crystal waveguides (PCW) and with Kerr-type nonlinearity has been investigated in this paper. The NMZI has been simulated using two-dimensional finite difference time domain (2D-FDTD) method. Input verses output (I/O) characteristics have been obtained for different lengths of the nonlinear arm, nonlinear coefficients of the nonlinear arm, wavelengths of the input beam, sizes of defect rods and NMZI offset. The results obtained are compared with earlier published results of NMZI created with conventional step index waveguides (SIW). It is shown that all useful features of light switching offered by SIW-based NMZIs are also possible with PCW-based NMZIs of extremely small dimensions. Moreover, PCW-based NMZIs offer additional useful feature not available with SIW-based NMZIs.

  17. Non-linear dynamics of a drill-string with uncertain model of the bit-rock interaction

    OpenAIRE

    Ritto, T. G.; Soize, Christian; Sampaio, R

    2009-01-01

    The drill-string dynamics is difficult to predict due to the non-linearities and uncertainties involved in the problem. In this paper a stochastic computational model is proposed to model uncertainties in the bit-rock interaction model. To do so, a new strategy that uses the non-parametric probabilistic approach is developed to take into account model uncertainties in the bit-rock non-linear interaction model. The mean model considers the main forces applied to the column such as the bit-rock...

  18. The nonlinear Dirac equation and the study of effective many-particle interactions in QED

    International Nuclear Information System (INIS)

    The starting point of the discussion was extended Lagrangian density for the classical Dirac field. The considered additional terms we had thereby interpreted as effective interactions because the corresponding field theory was not renormalizable. A scalar coupling as well as a vectorial coupling were put into calculation. The equation of motion for the system was thereby a one-particle equation which separated for s1/2 and p1/2 states and led to a system of coupled differential equations for the radial part. The derived radial equations were studied on three different levels. First we considered ordinary systems from atomic physics with ordinal numbers Z ≤ 110 in order to obtain from precision experiments of quantum electrodynamics upper bounds for the coupling constants. Second we have studied the influence of these additional interactions on the energy levels of the superheavy systems with ordinal numbers 110 ≤ Z ≤ 190. Third we have searched for bound states of a nonlinear Dirac equation which should exist only because of the effective interaction. In the further study we have then changed to a field-quantized consideration because our hitherto analysis was purely classical. In this connection we have studied the (e+e-)2 system with a (anti ΨΓΨ)2 interaction. From the corresponding many-particle equation we have then by means of the Hartree-Fock method derived the one-particle equation of the system. Finally we had studied the electron-positron interaction by exchange of a massive intermediate vector boson. (orig./HSI)

  19. Resonant nonlinear interactions between atmospheric waves in the polar summer mesopause region

    Institute of Scientific and Technical Information of China (English)

    刘仁强; 易帆

    2003-01-01

    Data obtained from the mobile SOUSY VHF radar at And(ya/Norway in summer 1987 have been used to study the nonlinear interactions between planetary waves, tides and gravity waves in the polar mesosphere, and the instability of background atmosphere above the mesopause. It is observed that 35-h planetary wave, diurnal, semidiurnal and terdiurnal tides are the prominent perturbations in the Lomb-Scargle spectra of the zonal wind component. By inspecting the frequency combinations, several triads are identified. By bispectral analysis it is shown that most bispectral peaks stand for quadratic coupling between tidal harmonics or between tide and planetary or gravity wave, and the height dependence of bispectral peaks reflects the variation of wave-wave interactions. Above the mesopause, the occurrence heights of the maximum L-S power spectral peaks corresponding to the prominent wave components tend to increase with their frequencies. This may result from the process in which two low frequency waves interact to generate a high frequency wave. Intensities of the planetary wave and tides increase gradually, arrive at their maxima, and then decay quickly in turn with increasing height. This kind of scene correlates with a "chain" of wave-wave resonant interactions that shifts with height from lower frequency segment to higher frequency segment. By instability analysis, it is observed that above the mesopause, the Richardson number becomes smaller and smaller with height, implying that the turbulent motion grows stronger and stronger and accordingly the background atmosphere more and more instable. It is suggested that the wave-wave sum resonant interaction and the wave dissipation due to instability are two dominant dynamical processes that occur in the mesopause region. The former invokes the energy transfer from lower frequency waves to higher frequency waves. The latter results in the heating of the atmosphere and accelerating of the background flow.

  20. Nonlinear structural joint model updating based on instantaneous characteristics of dynamic responses

    Science.gov (United States)

    Wang, Zuo-Cai; Xin, Yu; Ren, Wei-Xin

    2016-08-01

    This paper proposes a new nonlinear joint model updating method for shear type structures based on the instantaneous characteristics of the decomposed structural dynamic responses. To obtain an accurate representation of a nonlinear system's dynamics, the nonlinear joint model is described as the nonlinear spring element with bilinear stiffness. The instantaneous frequencies and amplitudes of the decomposed mono-component are first extracted by the analytical mode decomposition (AMD) method. Then, an objective function based on the residuals of the instantaneous frequencies and amplitudes between the experimental structure and the nonlinear model is created for the nonlinear joint model updating. The optimal values of the nonlinear joint model parameters are obtained by minimizing the objective function using the simulated annealing global optimization method. To validate the effectiveness of the proposed method, a single-story shear type structure subjected to earthquake and harmonic excitations is simulated as a numerical example. Then, a beam structure with multiple local nonlinear elements subjected to earthquake excitation is also simulated. The nonlinear beam structure is updated based on the global and local model using the proposed method. The results show that the proposed local nonlinear model updating method is more effective for structures with multiple local nonlinear elements. Finally, the proposed method is verified by the shake table test of a real high voltage switch structure. The accuracy of the proposed method is quantified both in numerical and experimental applications using the defined error indices. Both the numerical and experimental results have shown that the proposed method can effectively update the nonlinear joint model.

  1. Effect of a novel nonlinearity, viz., electron temperature dependence of electron-ion recombination on electromagnetic wave. Plasma interaction: Nonlinear propagation in the E-layer

    Science.gov (United States)

    Sodha, Mahendra Singh; Mishra, Rashmi; Srivastava, Sweta

    2016-03-01

    In this paper, we consider the nonlinearity in the propagation of electromagnetic (e.m.) waves in a plasma caused by the electron temperature dependence of the coefficient of recombination of electrons with ions; specifically, the ionospheric E layer has been investigated. The enhancement in electron temperature by an intense electromagnetic wave causes reduction of the electron-ion recombination coefficient and thereby enhancement of electron density, the electron collision frequency also gets enhanced. The equations for number and energy balance of electrons and the wave equation have been used to predict the dependence of electron density/collision frequency and the nonlinear refractive index and absorption coefficient on αE02 (proportional to wave irradiance). The dependence of the propagation parameters on αE02 has been used to investigate the nonlinear electromagnetic wave propagation in the ionosphere. The study concludes that the electron temperature dependence of the recombination coefficient should be considered in all analyses of nonlinear plasma-e.m. wave interaction.

  2. Proposal of all-optical sensor based on nonlinear MMI coupler for multi-purpose usage

    Science.gov (United States)

    Tajaldini, M.; MatJafri, M. Z.

    2015-10-01

    In this study, we propose an all-optical sensor based on consideration the nonlinear effects on modal propagation and output intensity based on ultra-compact nonlinear multimode interference (NLMMI) coupler. The sensor can be tuned to highest sensitivity in the wavelength and refractive index ranges sufficient to detect water- soluble chemical, air pollutions, and heart operation. The results indicate high output sensitivity to input wavelength. This sensitivity guides us to propose a wave sensor both transverse and longitudinal waves such as acoustic and light wave, when an external wave interacts with input waveguide. For instance, this sensor can be implemented by long input that inserted in the land, then any wave could detected from earth. The visible changes of intensity at output facet in various surrounding layer refractive index show the high sensitivity to the refractive index of surrounding layer that is foundation of introducing a sensor. Also, the results show the high distinguished changes on modal expansion and output throat distribution in various refractive indices of surrounding layer.

  3. Generation and Nonlinear Dynamical Analyses of Fractional-Order Memristor-Based Lorenz Systems

    Directory of Open Access Journals (Sweden)

    Huiling Xi

    2014-11-01

    Full Text Available In this paper, four fractional-order memristor-based Lorenz systems with the flux-controlled memristor characterized by a monotone-increasing piecewise linear function, a quadratic nonlinearity, a smooth continuous cubic nonlinearity and a quartic nonlinearity are presented, respectively. The nonlinear dynamics are analyzed by using numerical simulation methods, including phase portraits, bifurcation diagrams, the largest Lyapunov exponent and power spectrum diagrams. Some interesting phenomena, such as inverse period-doubling bifurcation and intermittent chaos, are found to exist in the proposed systems.

  4. Simple nonlinear interferometer-based all-optical thresholder and its applications for optical CDMA.

    Science.gov (United States)

    Kravtsov, Konstantin; Prucnal, Paul R; Bubnov, Mikhail M

    2007-10-01

    We present an experimental demonstration of an ultrafast all-optical thresholder based on a nonlinear Sagnac interferometer. The proposed design is intended for operation at very small nonlinear phase shifts. Therefore, it requires an in-loop nonlinearity lower than for the classical nonlinear loop mirror scheme. Only 15 meters of conventional (non-holey) silica-based fiber is used as a nonlinear element. The proposed thresholder is polarization insensitive and is good for multi-wavelength operation, meeting all the requirements for autocorrelation detection in various optical CDMA communication systems. The observed cubic transfer function is superior to the quadratic transfer function of second harmonic generation-based thresholders. PMID:19550579

  5. TCSC Nonlinear Adaptive Damping Controller Design Based on RBF Neural Network to Enhance Power System Stability

    DEFF Research Database (Denmark)

    Yao, Wei; Fang, Jiakun; Zhao, Ping;

    2013-01-01

    In this paper, a nonlinear adaptive damping controller based on radial basis function neural network (RBFNN), which can infinitely approximate to nonlinear system, is proposed for thyristor controlled series capacitor (TCSC). The proposed TCSC adaptive damping controller can not only have the...

  6. Nonlinear Optical Properties in Bismuth-based Glasses

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jianliang; NIE Qiuhua; DAI Shixun; XU Tiefeng; CHEN Feifei; SHEN Xiang; WANG Xunsi

    2011-01-01

    A series of glasses with high Bi2O3 content of Bi2O3-B2O3-WO3 ternary system were chosen and prepared .Their densities and linear refractive indices increase with increasing WO3 content.The optical band gaps Eopt of glasses obtained from ultraviolet absorption edges decreases with increase of WO3 content. Z-scan technique was carried out to investigate the third-order nonlinear optical properties of the glasses. It is found that the nonlinear refraction γ increases with decreasing the optical band gap Eopt, since an increase of WO3 content can promote the non-bridging oxygen ion content, and the highest γ value of samples is 1.173 × 10-14 cm2/W. The results show that these glasses are potential materials in the application of third-order nonlinear optics field.

  7. Generation of secondary waves arising from nonlinear interaction between the quasi 2 day wave and the migrating diurnal tide

    Science.gov (United States)

    Nguyen, Vu A.; Palo, Scott E.; Lieberman, Ruth S.; Forbes, Jeffrey M.; Ortland, David A.; Siskind, David E.

    2016-07-01

    Theory and past observations have provided evidence that atmospheric tides and other global-scale waves interact nonlinearly to produce additional secondary waves throughout the space-atmosphere interaction region. However, few studies have investigated the generation region of nonlinearly generated secondary waves, and as a result, the manifestation and impacts of these waves are still poorly understood. This study focuses on the nonlinear interaction between the quasi 2 day wave (2dayW3) and the migrating diurnal tide (DW1), two of the largest global-scale waves in the atmosphere. The fundamental goals of this effort are to characterize the forcing region of the secondary waves and to understand how it relates to their manifestation on a global scale. First, the Fast Fourier Synoptic Mapping method is applied to Thermosphere Ionosphere Mesosphere Energetics and Dynamics-Sounding of the Atmosphere using Broadband Emission Radiometry satellite observations to provide new evidence of secondary waves. These results show that secondary waves are only significant above 80 km. The nonlinear forcing for each secondary wave is then computed by extracting short-term primary wave information from a reanalysis model. The estimated nonlinear forcing quantities are used to force a linearized tidal model in order to calculate numerical secondary wave responses. Model results show that the secondary waves are significant from the upper mesosphere to the middle thermosphere, highlighting the implications for the atmosphere-space weather coupling. The study also concludes that the secondary wave response is most sensitive to the nonlinear forcing occurring in the lower and middle mesosphere and not coincident with the regions of strongest nonlinear forcing.

  8. Nonlinear Adaptive Filters based on Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Faten BEN ARFIA

    2009-07-01

    Full Text Available This paper presents a particle swarm optimization (PSO algorithm to adjust the parameters of the nonlinear filter and to make this type of the filters more powerful for the elimination of the Gaussian noise and also the impulse noise. In this paper we apply the particle swarm optimization to the rational filters and we completed this work with the comparison between our results and other adaptive nonlinear filters like the LMS adaptive median filters and the no-adaptive rational filter.

  9. Stability and adaptability of runner peanut genotypes based on nonlinear regression and AMMI analysis

    Directory of Open Access Journals (Sweden)

    Roseane Cavalcanti dos Santos

    2012-08-01

    Full Text Available The objective of this work was to estimate the stability and adaptability of pod and seed yield in runner peanut genotypes based on the nonlinear regression and AMMI analysis. Yield data from 11 trials, distributed in six environments and three harvests, carried out in the Northeast region of Brazil during the rainy season were used. Significant effects of genotypes (G, environments (E, and GE interactions were detected in the analysis, indicating different behaviors among genotypes in favorable and unfavorable environmental conditions. The genotypes BRS Pérola Branca and LViPE‑06 are more stable and adapted to the semiarid environment, whereas LGoPE‑06 is a promising material for pod production, despite being highly dependent on favorable environments.

  10. The late Universe with non-linear interaction in the dark sector: the coincidence problem

    CERN Document Server

    Bouhmadi-López, Mariam; Zhuk, Alexander

    2016-01-01

    We study the Universe at the late stage of its evolution and deep inside the cell of uniformity. At such a scale the Universe is highly inhomogeneous and filled with discretely distributed inhomogeneities in the form of galaxies and groups of galaxies. As a matter source, we consider dark matter (DM) and dark energy (DE) with a non-linear interaction $Q = 3\\mathcal{H}\\gamma \\overline\\varepsilon_{\\mathrm{DE}} \\overline\\varepsilon_{\\mathrm{DM}} / (\\overline\\varepsilon_{\\mathrm{DE}} + \\overline\\varepsilon_{\\mathrm{DM}})$, where $\\gamma$ is a constant. We assume that DM is pressureless and DE has a constant equation of state parameter $w$. In the considered model, the energy densities of the dark sector components present a scaling behaviour with $\\overline\\varepsilon_{\\mathrm{DM}} / \\overline\\varepsilon_{\\mathrm{DE}} \\sim \\left({a_0} / {a} \\right)^{-3(w+\\gamma)}$. We investigate the possibility that the perturbations of DM and DE, which are interacting among themselves, could be coupled to the galaxies with the ...

  11. Optimal bipedal interactions with dynamic terrain: synthesis and analysis via nonlinear programming

    Science.gov (United States)

    Hubicki, Christian; Goldman, Daniel; Ames, Aaron

    In terrestrial locomotion, gait dynamics and motor control behaviors are tuned to interact efficiently and stably with the dynamics of the terrain (i.e. terradynamics). This controlled interaction must be particularly thoughtful in bipeds, as their reduced contact points render them highly susceptible to falls. While bipedalism under rigid terrain assumptions is well-studied, insights for two-legged locomotion on soft terrain, such as sand and dirt, are comparatively sparse. We seek an understanding of how biological bipeds stably and economically negotiate granular media, with an eye toward imbuing those abilities in bipedal robots. We present a trajectory optimization method for controlled systems subject to granular intrusion. By formulating a large-scale nonlinear program (NLP) with reduced-order resistive force theory (RFT) models and jamming cone dynamics, the optimized motions are informed and shaped by the dynamics of the terrain. Using a variant of direct collocation methods, we can express all optimization objectives and constraints in closed-form, resulting in rapid solving by standard NLP solvers, such as IPOPT. We employ this tool to analyze emergent features of bipedal locomotion in granular media, with an eye toward robotic implementation.

  12. Three dimensional, non-linear, finite element analysis of compactable soil interaction with a hyperelastic wheel

    Science.gov (United States)

    Chiroux, Robert Charles

    The objective of this research was to produce a three dimensional, non-linear, dynamic simulation of the interaction between a hyperelastic wheel rolling over compactable soil. The finite element models developed to produce the simulation utilized the ABAQUS/Explicit computer code. Within the simulation two separate bodies were modeled, the hyperelastic wheel and a compactable soil-bed. Interaction between the bodies was achieved by allowing them to come in contact but not to penetrate the contact surface. The simulation included dynamic loading of a hyperelastic, rubber tire in contact with compactable soil with an applied constant angular velocity or torque, including a tow load, applied to the wheel hub. The constraints on the wheel model produced a straight and curved path. In addition the simulation included a shear limit between the tire and soil allowing for the introduction of slip. Soil properties were simulated using the Drucker-Prager, Cap Plasticity model available within the ABAQUS/Explicit program. Numerical results obtained from the three dimensional model were compared with related experimental data and showed good correlation for similar conditions. Numerical and experimental data compared well for both stress and wheel rut formation depth under a weight of 5.8 kN and a constant angular velocity applied to the wheel hub. The simulation results provided a demonstration of the benefit of three-dimensional simulation in comparison to previous two-dimensional, plane strain simulations.

  13. Non-linear interaction of intense CO2 radiation with dense plasma

    International Nuclear Information System (INIS)

    Experimental results of the interaction of short (1.5ns) CO2 laser pulses with solid targets at a flux reaching 1013W/cm2 are presented. An attempt is made to carry out a global series of measurements and interpret them in the light of currently available theory. The absorption, reflection, ion and X-ray emission (line and continuum) and in considerable detail the infra-red emission spectra of the plasma in the vicinity of the incident 10.6μm radiation as well as its harmonics were measured. From the emission spectra the existence of the parametric decay and the stimulated Brillouin backscatter instabilities was indentified. Furthermore, the energy and angular dependence of the reflected-light calorimetry in addition to the X-ray and ion emission results are found to be consistent with the hypothesis that the interaction of high power CO2 lasers with plasmas is dominated by non-linear effects such as the parametric decay instability. (author)

  14. Neurosurgery simulation using non-linear finite element modeling and haptic interaction

    Science.gov (United States)

    Lee, Huai-Ping; Audette, Michel; Joldes, Grand R.; Enquobahrie, Andinet

    2012-02-01

    Real-time surgical simulation is becoming an important component of surgical training. To meet the realtime requirement, however, the accuracy of the biomechancial modeling of soft tissue is often compromised due to computing resource constraints. Furthermore, haptic integration presents an additional challenge with its requirement for a high update rate. As a result, most real-time surgical simulation systems employ a linear elasticity model, simplified numerical methods such as the boundary element method or spring-particle systems, and coarse volumetric meshes. However, these systems are not clinically realistic. We present here an ongoing work aimed at developing an efficient and physically realistic neurosurgery simulator using a non-linear finite element method (FEM) with haptic interaction. Real-time finite element analysis is achieved by utilizing the total Lagrangian explicit dynamic (TLED) formulation and GPU acceleration of per-node and per-element operations. We employ a virtual coupling method for separating deformable body simulation and collision detection from haptic rendering, which needs to be updated at a much higher rate than the visual simulation. The system provides accurate biomechancial modeling of soft tissue while retaining a real-time performance with haptic interaction. However, our experiments showed that the stability of the simulator depends heavily on the material property of the tissue and the speed of colliding objects. Hence, additional efforts including dynamic relaxation are required to improve the stability of the system.

  15. Atom laser based on four-wave mixing with Bose-Einstein condensates in nonlinear lattices

    Science.gov (United States)

    Wasak, T.; Konotop, V. V.; Trippenbach, M.

    2013-12-01

    Optical lattices are typically used to modify the dispersion relation of the matter wave, in particular, to ensure resonant conditions for multiwave interactions. Here we propose an alternative mechanism of wave interactions. It can be implemented using a nonlinear lattice and modifies the momentum conservation law of the interacting atoms, leaving the energy conservation unchanged. We propose to apply this phenomenon to construct an atom laser via a resonant four-wave mixing process.

  16. Final report for DOE-FG02-02ER54688: Study of nonlinear interactions between counterpropagating shear Alfven waves

    Energy Technology Data Exchange (ETDEWEB)

    Carter, T A

    2006-11-16

    Final report for DOE Plasma Physics Junior Faculty Development award DOE-FG02-02ER54688. Reports on research undertaken from 8/1/2002 until 5/15/2006, investigating nonlinear interactions between Alfven waves in a laboratory experiment.

  17. Instanton-anti-instanton interaction in the O(3) non-linear σ model and an exactly soluble fermion theory

    International Nuclear Information System (INIS)

    We calculate the potential energy of weak interacting instanton and anti-instanton quarks in the O(3) non-linear σ model, which leads us to a two-component massive fermion theory. The exact solution for the ground state of the theory is built. (author)

  18. Analytical theory for the dark-soliton interaction in nonlocal nonlinear materials with an arbitrary degree of nonlocality

    DEFF Research Database (Denmark)

    Kong, Qian; Wang, Q.; Bang, Ole;

    2010-01-01

    We investigate theoretically the interaction of dark solitons in materials with a spatially nonlocal nonlinearity. In particular we do this analytically and for arbitrary degree of nonlocality. We employ the variational technique to show that nonlocality induces an attractive force in the otherwise...

  19. Two-dimensional spectroscopy for harmonic vibrational modes with nonlinear system-bath interactions. I. Gaussian-white case

    NARCIS (Netherlands)

    Steffen, T; Tanimura, Y

    2000-01-01

    The quantum Fokker-Planck equation is derived for a system nonlinearly coupled to a harmonic oscillator bath. The system-bath interaction is assumed to be linear in the bath coordinates but quadratic in the system coordinate. The relaxation induced dynamics of a harmonic system are investigated by s

  20. A nonlinear strategy for sensor based vehicle path control

    Science.gov (United States)

    Mayr, R.

    1994-01-01

    A method of transverse control which makes use of nonlinear formulations is presented. The strategy is utilized to stabilize a vehicle. The vehicle is autonomously guided and takes its control inputs from an optical sensing system. Additionally, the velocity of the vehicle is dictated by a longitudinal controller, which is also discussed.

  1. UAV Formation Flight Based on Nonlinear Model Predictive Control

    Directory of Open Access Journals (Sweden)

    Zhou Chao

    2012-01-01

    Full Text Available We designed a distributed collision-free formation flight control law in the framework of nonlinear model predictive control. Formation configuration is determined in the virtual reference point coordinate system. Obstacle avoidance is guaranteed by cost penalty, and intervehicle collision avoidance is guaranteed by cost penalty combined with a new priority strategy.

  2. Vortex-based spatiotemporal characterization of nonlinear flows

    Science.gov (United States)

    Byrne, Gregory A.

    Although the ubiquity of vortices in nature has been recognized by artists for over seven centuries, it was the work of artist and scientist Leonardo da Vinci that provided the monumental transition from an aesthetic form to a scientific tool. DaVinci used vortices to describe the motions he observed in air currents, flowing water and blood flow in the human heart. Five centuries later, the Navier-Stokes equations allow us to recreate the swirling motions of fluid observed in nature. Computational fluid dynamic (CFD) simulations have provided a lens through which to study the role of vortices in a wide variety of modern day applications. The research summarized below represents an effort to look through this lens and bring into focus the practical use of vortices in describing nonlinear flows. Vortex-based spatiotemporal characterizations are obtained using two specific mathematical tools: vortex core lines (VCL) and proper orthogonal decomposition (POD). By applying these tools, we find that vortices continue to provide new insights in the realm of biofluids, urban flows and the phase space of dynamical systems. The insights we have gained are described in this thesis. Our primary focus is on biofluids. Specifically, we seek to gain new insights into the connection between vortices and vascular diseases in order to provide more effective methods for clinical diagnosis and treatment. We highlight several applications in which VCL and POD are used to characterize the flow conditions in a heart pump, identify stenosis in carotid arteries and validate numerical models against PIV-based experimental data. Next, we quantify the spatial complexity and temporal stability of hemodynamics generated by a database of 210 patient-specific aneurysm geometries. Visual classifications of the hemodynamics are compared to the automated, quantitative classifications. The quantities characterizing the hemodynamics are then compared to clinical data to determine conditions that are

  3. Interactive Reliability-Based Optimal Design

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Thoft-Christensen, Palle; Siemaszko, A.;

    1994-01-01

    Interactive design/optimization of large, complex structural systems is considered. The objective function is assumed to model the expected costs. The constraints are reliability-based and/or related to deterministic code requirements. Solution of this optimization problem is divided in four main...... used in interactive optimization....

  4. Optical computation based on nonlinear total reflectional optical switch at the interface

    Indian Academy of Sciences (India)

    Jianqi Zhang; Huan Xu

    2009-03-01

    A new scheme of binary half adder and full adder is proposed. It realizes a kind of all-optical computation which is based on the polarization coding technique and the nonlinear total reflectional optical switches.

  5. Properties of Differential Scattering Section Based on Multi-photon Nonlinear Compton Effect

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Properties of damping electrons in collision with photons based on multi-photon nonlinear Compton effect are investigated. The expressions of the differential scattering section are derived. Several useful conclusions are drawn.

  6. Simultaneous Computation of Two Independent Tasks Using Reservoir Computing Based on a Single Photonic Nonlinear Node With Optical Feedback.

    Science.gov (United States)

    Nguimdo, Romain Modeste; Verschaffelt, Guy; Danckaert, Jan; Van der Sande, Guy

    2015-12-01

    In this brief, we numerically demonstrate a photonic delay-based reservoir computing system, which processes, in parallel, two independent computational tasks even when the two tasks have unrelated input streams. Our approach is based on a single-longitudinal mode semiconductor ring laser (SRL) with optical feedback. The SRL emits in two directional optical modes. Each directional mode processes one individual task to mitigate possible crosstalk. We illustrate the feasibility of our scheme by analyzing the performance on two benchmark tasks: 1) chaotic time series prediction and 2) nonlinear channel equalization. We identify some feedback configurations for which the results for simultaneous prediction/classification indicate a good performance, but with slight degradation (as compared with the performance obtained for single task processing) due to nonlinear and linear interactions between the two directional modes of the laser. In these configurations, the system performs well on both tasks for a broad range of the parameters. PMID:25751880

  7. Nonlinear and non-Gaussian Bayesian based handwriting beautification

    Science.gov (United States)

    Shi, Cao; Xiao, Jianguo; Xu, Canhui; Jia, Wenhua

    2013-03-01

    A framework is proposed in this paper to effectively and efficiently beautify handwriting by means of a novel nonlinear and non-Gaussian Bayesian algorithm. In the proposed framework, format and size of handwriting image are firstly normalized, and then typeface in computer system is applied to optimize vision effect of handwriting. The Bayesian statistics is exploited to characterize the handwriting beautification process as a Bayesian dynamic model. The model parameters to translate, rotate and scale typeface in computer system are controlled by state equation, and the matching optimization between handwriting and transformed typeface is employed by measurement equation. Finally, the new typeface, which is transformed from the original one and gains the best nonlinear and non-Gaussian optimization, is the beautification result of handwriting. Experimental results demonstrate the proposed framework provides a creative handwriting beautification methodology to improve visual acceptance.

  8. A scalable nonlinear domain decomposition based contact solver

    Czech Academy of Sciences Publication Activity Database

    Dobiáš, Jiří; Pták, Svatopluk; Dostál, Z.; Markopoulos, A.; Kozubek, T.

    Sao Paulo : Escola politécnica - Universidade de Sao Paulo, 2012 - (Pimenta, P.). s. 37-37 ISBN 978-85-86686-69-6. [World Congress on Computational Mechanics /10./. 08.07.2012-13.07.2012, Sao Paulo] R&D Projects: GA ČR GA101/08/0574 Institutional research plan: CEZ:AV0Z20760514 Keywords : domain decomposition * non-linear mechanics * contact mechanics Subject RIV: BA - General Mathematics

  9. Observer-based Fault Detection and Isolation for Nonlinear Systems

    OpenAIRE

    Lootsma, T.F.

    2001-01-01

    With the rise in automation the increase in fault detectionand isolation & reconfiguration is inevitable. Interest in fault detection and isolation (FDI) for nonlinear systems has grown significantly in recent years. The design of FDI is motivated by the need for knowledge about occurring faults in fault-tolerant control systems (FTC systems). The idea of FTC systems is to detect, isolate, and handle faults in such a way that the systems can still perform in a required manner. One prefers...

  10. Logical Inference for Model-Based Reconstruction of Ultrasonic Nonlinearity

    OpenAIRE

    Carlos Rus; Guillermo Rus

    2015-01-01

    Quantifying the constitutive nonlinearity parameter β in fluids is of key interest for understanding ultrasonic propagation and its wide implications in medical and industrial applications. However, current methods for ultrasonically measuring it show large limitations in that the signal is only valid at a reduced and unjustified spatial range away from the transducer. This is not consistent with the fact that β should be constant everywhere in the fluid and independently of the ultrasonic ex...

  11. Modeling and Backstepping-based Nonlinear Control Strategy for a 6 DOF Quadrotor Helicopter

    Institute of Scientific and Technical Information of China (English)

    Ashfaq Ahmad Mian; Wang Daobo

    2008-01-01

    In this article,a nonlinear model of an underactuated six degrees of freedom (6 DOF) quadrotor helicopter is derived on the basis of the Newton-Euler formalism.The derivation comprises determining equations of the motion of the quadrotor in three dimensions andapproximating the actuation forces through the modeling of aerodynamic coefficients and electric motor dynamics.The derived modelcomposed of translatioual and rotational subsystems is dynamically unstable,so a sequential nonlinear control strategy is used.The con-trol strategy includes feedback linearization coupled with a PD controller for the translational subsystem and a backstepping-based PID nonlinear controller for the rotational subsystem of the quadrotor.The performances of the nonlinear control method are evaluated by nonlinear simulation and the results demonstrate the effectiveness of the proposed control strategy for the quadrotor helicopter inquasi-stationary flights.

  12. Tunable all-optical plasmonic diode based on Fano resonance in nonlinear waveguide coupled with cavities.

    Science.gov (United States)

    Fan, Cairong; Shi, Fenghua; Wu, Hongxing; Chen, Yihang

    2015-06-01

    Tunable all-optical plasmonic diode is proposed based on the Fano resonance in an asymmetric and nonlinear system, comprising metal-insulator-metal waveguides coupled with nanocavities. The spatial asymmetry of the system gives rise to the nonreciprocity of the field localizations at the nonlinear gap between the coupled cavities and to the nonreciprocal nonlinear response. Nonlinear Fano resonance, originating from the interference between the discrete cavity mode and the continuum traveling mode, is observed and effectively tuned by changing the input power. By combining the unidirectional nonlinear response with the steep dispersion of the Fano asymmetric line shape, a transmission contrast ratio up to 41.46 dB can be achieved between forward and backward transmission. Our all-optical plasmonic diode with compact structure can find important applications in integrated optical nanocircuits. PMID:26030529

  13. Experiments in nonlinear dynamics using control-based continuation: Tracking stable and unstable response curves

    DEFF Research Database (Denmark)

    Bureau, Emil; Schilder, Frank; Santos, Ilmar;

    2014-01-01

    We show how to implement control-based continuation in a nonlinear experiment using existing and freely available software. We demonstrate that it is possible to track the complete frequency response, including the unstable branches, for a harmonically forced impact oscillator.......We show how to implement control-based continuation in a nonlinear experiment using existing and freely available software. We demonstrate that it is possible to track the complete frequency response, including the unstable branches, for a harmonically forced impact oscillator....

  14. Nonlinear observer based fault detection and isolation for a momentum wheel

    DEFF Research Database (Denmark)

    Jensen, Hans-Christian Becker; Wisniewski, Rafal

    2001-01-01

    This article realizes nonlinear Fault Detection and Isolation for a momentum wheel. The Fault Detection and Isolation is based on a Failure Mode and Effect Analysis, which states which faults might occur and can be detected. The algorithms presented in this paper are based on a geometric approach...... toachieve nonlinear Fault Detection and Isolation. The proposed algorithms are tested in a simulation study and the pros and cons of the algorithm are discussed....

  15. Energy dissipation by nonlinear soil strains during soil-structure interaction excited by SH pulse

    OpenAIRE

    Gicev, Vlado; Trifunac, Mihailo

    2012-01-01

    Three variants of a two-dimensional (2-D) model of a building supported by a rectangular, flexible foundation embedded in nonlinear soil are analyzed. The building, the foundation, and soil have different physical properties. The building is assumed to be linear, but the foundation and the soil can experience nonlinear deformations. It is shown that the work spent for the development of nonlinear strains in the soil can consume a significant part of the input wave energy, and thus less energy...

  16. Coulomb interaction effects on nonlinear optical response in C60, C70, and higher fullerenes

    OpenAIRE

    Harigaya, Kikuo

    1998-01-01

    Nonlinear optical properties in the fullerene C$_{60}$ and the extracted higher fullerenes -- C$_{70}$, C$_{76}$, C$_{78}$, and C$_{84}$ -- are theoretically investigated by using the exciton formalism and the sum-over-states method. We find that off-resonant third order susceptibilities of higher fullerenes are a few times larger than those of C$_{60}$. The magnitude of nonlinearity increases as the optical gap decreases in higher fullerenes. The nonlinearity is nearly proportional to the fo...

  17. Challenges for the Sequential Interaction Between Optimal Design of Field Campaigns and Model Calibration for Non-Linear Systems

    Science.gov (United States)

    Geiges, A.; Nowak, W.; Rubin, Y.

    2013-12-01

    Stochastic models of sub-surface systems generally suffer from parametric and conceptual uncertainty. To reduce the model uncertainty, model parameters are calibrated using additional collected data. These data often come from costly data acquisition campaigns that need to be optimized to collect the data with the highest data utility (DU) or value of information. In model-based approaches, the DU is evaluated based on the uncertain model itself and is therefore uncertain as well. Additionally, for non-linear models, data utility depends on the yet unobserved measurement values and can only be estimated as an expected value over an assumed distribution of possible measurement values. Both factors introduce uncertainty into the optimization of field campaigns. We propose and investigate a sequential interaction scheme between campaign optimization, data collection and model calibration. The field campaign is split in individual segments. Each segment consists of optimization, segment-wise data collection, and successive model calibration or data assimilation. By doing so, (1) the expected data utility for the newly collected data is replaced by their actual one, (2) the calibration restricts both conceptual and parametric model uncertainty, and thus (3) the distribution of possible future data values for the subsequent campaign segments also changes. Hence, the model to describe the real system improves successively with each collected data segment, and so does the estimate of the yet remaining data requirements to achieve the overall investigation goals. We will show that using the sequentially improved model for the optimal design (OD) of the remaining field campaign leads to superior and more targeted designs.However, this traditional sequential OD optimizes small data segments one-by-one. In such a strategy, possible mutual dependencies with the possible data values and the optimization of data values collection in later segments are neglected. This allows a

  18. Study on Nonlinear Theory and Code of Beam-Wave Interaction for Gyroklystron

    Science.gov (United States)

    Jianhua, Guo; Sheng, Yu; Xiang, Li; Hongfu, Li

    2011-12-01

    A nonlinear self-consistent theory of beam-wave interaction for gyroklystron with multiple cavities is analyzed in this paper. The electron motion equations and transient electromagnetic field equations in a complex form are deduced in detail. A calculation code including a time-dependent description of the electromagnetic fields and a self-consistent analysis of the electrons is designed and the corresponding software implementation is achieved using Fortran language. An example is presented for the operation of the code, namely a four-cavity, Ka-band gyroklystron operating in the TE011 mode at the fundamental of the cyclotron frequency. The numerical results show that a maximal saturated peak output power of 330 kW, corresponding to 39% efficiency and a saturated 3-dB bandwidth of 325 MHz is achieved with a 72.8 kv, 11.8 A electron beam at a focused magnetic field of 13 kG and a beam velocity ratio of 1.63 when the speed spread is 5%. By comparison, the numerical results agree with the experimental results.

  19. Multirate Simulations of String Vibrations Including Nonlinear Fret-String Interactions Using the Functional Transformation Method

    Directory of Open Access Journals (Sweden)

    R. Rabenstein

    2004-06-01

    Full Text Available The functional transformation method (FTM is a well-established mathematical method for accurate simulations of multidimensional physical systems from various fields of science, including optics, heat and mass transfer, electrical engineering, and acoustics. This paper applies the FTM to real-time simulations of transversal vibrating strings. First, a physical model of a transversal vibrating lossy and dispersive string is derived. Afterwards, this model is solved with the FTM for two cases: the ideally linearly vibrating string and the string interacting nonlinearly with the frets. It is shown that accurate and stable simulations can be achieved with the discretization of the continuous solution at audio rate. Both simulations can also be performed with a multirate approach with only minor degradations of the simulation accuracy but with preservation of stability. This saves almost 80% of the computational cost for the simulation of a six-string guitar and therefore it is in the range of the computational cost for digital waveguide simulations.

  20. Nonlinear dynamic fluid-structure interaction calculations with coupled finite element and finite volume programs

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, M.W.; Kashiwa, B.A.; Meier, R.W. [Los Alamos National Lab., NM (United States); Bishop, S. [US Army Night Vision and Electronic Sensors Directorate, Fort Belvoir, VA (United States)

    1994-08-01

    Two- and three-dimensional fluid-structure interaction computer programs for the simulation of nonlinear dynamics were developed and applied to a number of problems. The programs were created by coupling Arbitrary Lagrangian-Eulerian finite volume fluid dynamics programs with strictly Lagrangian finite element structural dynamics programs. The resulting coupled programs can use either fully explicit or implicit time integration. The implicit time integration is accomplished by iterations of the fluid dynamics pressure solver and the structural dynamics system solver. The coupled programs have been used to solve problems involving incompressible fluids, membrane and shell elements, compressible multiphase flows, explosions in both air and water, and large displacements. In this paper, we present the approach used for the coupling and describe test problems that verify the two-dimensional programs against an experiment and an analytical linear problem. The experiment involves an explosion underwater near an instrumented thin steel plate. The analytical linear problem is the vibration of an infinite cylinder surrounded by an incompressible fluid to a given radius.

  1. Spatial interactions in agent-based modeling

    CERN Document Server

    Ausloos, Marcel; Merlone, Ugo

    2014-01-01

    Agent Based Modeling (ABM) has become a widespread approach to model complex interactions. In this chapter after briefly summarizing some features of ABM the different approaches in modeling spatial interactions are discussed. It is stressed that agents can interact either indirectly through a shared environment and/or directly with each other. In such an approach, higher-order variables such as commodity prices, population dynamics or even institutions, are not exogenously specified but instead are seen as the results of interactions. It is highlighted in the chapter that the understanding of patterns emerging from such spatial interaction between agents is a key problem as much as their description through analytical or simulation means. The chapter reviews different approaches for modeling agents' behavior, taking into account either explicit spatial (lattice based) structures or networks. Some emphasis is placed on recent ABM as applied to the description of the dynamics of the geographical distribution o...

  2. Modelling relativistic solitary wave interactions in over-dense plasmas: a perturbed nonlinear Schr\\"{o}ndinger equation framework

    CERN Document Server

    Siminos, E; Saxena, V; Kourakis, I

    2014-01-01

    We investigate the dynamics of localized solutions of the relativistic cold fluid plasma model in the small but finite amplitude limit, for slightly overcritical plasma density. Adopting a multiple scale analysis, we derive a perturbed nonlinear Schr\\"{o}ndinger equation that describes the evolution of the envelope of circularly polarized electromagnetic field. Retaining terms up to fifth order in the small perturbation parameter, we derive a self-consistent framework for the description of the plasma response in the presence of localized electromagnetic field. The formalism is applied to standing electromagnetic solitary wave interactions and the results are validated by simulations of the full cold-fluid model. To lowest order, a cubic nonlinear Schr\\"{o}ndinger equation with a focusing nonlinearity is recovered. Classical quasiparticle theory is used to obtain analytical estimates for the collision time and minimum distance of approach between solitary waves. For larger solitary wave amplitudes the inclusi...

  3. Periodic Flows to Chaos Based on Discrete Implicit Mappings of Continuous Nonlinear Systems

    Science.gov (United States)

    Luo, Albert C. J.

    This paper presents a semi-analytical method for periodic flows in continuous nonlinear dynamical systems. For the semi-analytical approach, differential equations of nonlinear dynamical systems are discretized to obtain implicit maps, and a mapping structure based on the implicit maps is employed for a periodic flow. From mapping structures, periodic flows in nonlinear dynamical systems are predicted analytically and the corresponding stability and bifurcations of the periodic flows are determined through the eigenvalue analysis. The periodic flows predicted by the single-step implicit maps are discussed first, and the periodic flows predicted by the multistep implicit maps are also presented. Periodic flows in time-delay nonlinear dynamical systems are discussed by the single-step and multistep implicit maps. The time-delay nodes in discretization of time-delay nonlinear systems were treated by both an interpolation and a direct integration. Based on the discrete nodes of periodic flows in nonlinear dynamical systems with/without time-delay, the discrete Fourier series responses of periodic flows are presented. To demonstrate the methodology, the bifurcation tree of period-1 motion to chaos in a Duffing oscillator is presented as a sampled problem. The method presented in this paper can be applied to nonlinear dynamical systems, which cannot be solved directly by analytical methods.

  4. Quantum-dot-based integrated non-linear sources

    DEFF Research Database (Denmark)

    Bernard, Alice; Mariani, Silvia; Andronico, Alessio;

    2015-01-01

    The authors report on the design and the preliminary characterisation of two active non-linear sources in the terahertz and near-infrared range. The former is associated to difference-frequency generation between whispering gallery modes of an AlGaAs microring resonator, whereas the latter is...... granted by parametric generation in a waveguide via modal phase matching. Both devices rely on embedded quantum-dot lasers, which allow for low-threshold currents and unconventional geometries. They also include specific degrees of freedom that open a practical route towards phase matching, either during...

  5. Beam-Based Nonlinear Optics Corrections in Colliders

    CERN Document Server

    Pilat, Fulvia Caterina; Malitsky, Nikolay; Ptitsyn, Vadim

    2005-01-01

    A method has been developed to measure and correct operationally the non-linear effects of the final focusing magnets in colliders, which 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 3 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.

  6. Movement-based Interaction in Camera Spaces

    DEFF Research Database (Denmark)

    Eriksson, Eva; Riisgaard Hansen, Thomas; Lykke-Olesen, Andreas

    2006-01-01

    In this paper we present three concepts that address movement-based interaction using camera tracking. Based on our work with several movement-based projects we present four selected applications, and use these applications to leverage our discussion, and to describe our three main concepts space......, relations, and feedback. We see these as central for describing and analysing movement-based systems using camera tracking and we show how these three concepts can be used to analyse other camera tracking applications....

  7. Analytical and numerical modeling of front propagation and interaction of fronts in nonlinear thermoviscous

    DEFF Research Database (Denmark)

    Rasmussen, Anders Rønne; Sørensen, Mads Peter; Gaididei, Yuri Borisovich;

    2008-01-01

    A wave equation, that governs nite amplitude acoustic disturbances in a thermoviscous Newtonian fluid, and includes nonlinear terms up to second order, is proposed. In contrast to the model known as the Kuznetsov equation, the proposed nonlinear wave equation preserves the Hamiltonian structure...

  8. Flatness-Based Tracking Control and Nonlinear Observer for a Micro Aerial Quadcopter

    Science.gov (United States)

    Rivera, G.; Sawodny, O.

    2010-09-01

    This paper deals with the design of a nonlinear observer and a differential flat based path tracking controller for a mini aerial quadcopter. Taking into account that only the inertial coordinates and the yaw angle are available for measurements, it is shown, that the system is differentially flat, allowing a systematic design of a nonlinear tracking control in open and closed loop. A nonlinear observer is carried out to estimate the roll and pitch angle as well as all the linear and angular velocities. Finally the performance of the feedback controller and observer are illustrated in a computer simulation.

  9. Dynamic Simulations of Nonlinear Multi-Domain Systems Based on Genetic Programming and Bond Graphs

    Institute of Scientific and Technical Information of China (English)

    DI Wenhui; SUN Bo; XU Lixin

    2009-01-01

    A dynamic simulation method for non-linear systems based on genetic programming (GP) and bond graphs (BG) was developed to improve the design of nonlinear multi-domain energy conversion sys-tems. The genetic operators enable the embryo bond graph to evolve towards the target graph according to the fitness function. Better simulation requires analysis of the optimization of the eigenvalue and the filter circuit evolution. The open topological design and space search ability of this method not only gives a more optimized convergence for the operation, but also reduces the generation time for the new circuit graph for the design of nonlinear multi-domain systems.

  10. A strategy for adaptive synchronization of an electrical chaotic circuit based on nonlinear control

    International Nuclear Information System (INIS)

    This paper deals with the adaptive synchronization of an electrical chaotic oscillator through a nonlinear control law. The nonlinear controller is designed to synchronize two identical chaotic systems. Lyapunov stability theory is applied to prove that under some conditions the drive-response system can achieve practical synchronization. The designed controller contains only continuous nonlinear terms existing in the dynamical systems and is easy to implement in practice. As an illustrative example to verify the validity of the proposed method, a hyperbolic tangent-based electrical and chaotic circuit is chosen and its dynamics is briefly investigated to demonstrate its chaotic behavior.

  11. Contribution to concrete modelling towards aging and durability: interactions between creep deformations and non-linear behaviour of the material

    International Nuclear Information System (INIS)

    Concrete structures are examined during their lifetime and often present important cracking states, which can progress with time and lead to change the structural behavior. The civil engineering works that the main function corresponds to protection's wall are very sensitive to this damage and its evolution. The growth of the time - dependent cracks represents an aging pathology linked with interaction between creep mechanism and the non-linear behavior of the material. In this thesis, a modeling for these mechanisms and their coupling are proposed. It based on creep strains analysis under different load levels, on the influence of the rate effect to the mechanical behavior. A stress limit is put on prominent manner, where beyond it, the creep - cracking interaction becomes important with the introduction of the ultimate tertiary creep kinetic. This level of strength is identified for infinitely slow loading rates and is also called intrinsic strength. It defines the limit on this side the viscous behavior of the cement paste limits the irreversibility processes as cracking. Thus, a constitutive law of viscoelastic - viscoplastic behavior with a high coupling between the cracking mechanism and the creep strains is proposed. The developments of the model are built on DUVAUT - LIONS approach integrated a generalized MAXWELL chain model. For one part, the viscoelastic behavior translates the creep mechanism under low stresses. For a second part, it associated with the viscoplastic behavior, which allows introducing both creep effect under high stresses and rate effect acting on micro-cracked zones. The cracking mechanism is described throughout a plasticity theory with multi-criteria, which induce a property of anisotropy for hardening. Qualitatively, ails of the creep kinetics are reproduced. An additional validation is based on experimental tests in compression, traction and flexion where the main parameters of the modeling are detailed. Thus, we can conclude on the

  12. Evidence-Based Interactive Management of Change

    Directory of Open Access Journals (Sweden)

    Albert Fleischmann

    2011-06-01

    Full Text Available Evidence-based interactive management of change means hands-on experience of modified work processes, given evidence of change. For this kind of pro-active organizational development support we use an organisational process memory and a communication-based representation technique for role-specific and task-oriented process execution. Both are effective means for organizations becoming agile through interactively modelling the business at the process level and re-constructing or re-arranging process representations according to various needs. The tool allows experiencing role-specific workflows, as the communication-based refinement of work models allows for executable process specifications. When presenting the interactive processes to individuals involved in the business processes, changes can be explored interactively in a context-sensitive way before re-implementing business processes and information systems. The tool is based on a service-oriented architecture and a flexible representation scheme comprising the exchange of message between actors, business objects and actors (roles. The interactive execution of workflows does not only enable the individual reorganization of work but also changes at the level of the entire organization due to the represented interactions.

  13. Nonlinear stability and ergodicity of ensemble based Kalman filters

    Science.gov (United States)

    Tong, Xin T.; Majda, Andrew J.; Kelly, David

    2016-02-01

    The ensemble Kalman filter (EnKF) and ensemble square root filter (ESRF) are data assimilation methods used to combine high dimensional, nonlinear dynamical models with observed data. Despite their widespread usage in climate science and oil reservoir simulation, very little is known about the long-time behavior of these methods and why they are effective when applied with modest ensemble sizes in large dimensional turbulent dynamical systems. By following the basic principles of energy dissipation and controllability of filters, this paper establishes a simple, systematic and rigorous framework for the nonlinear analysis of EnKF and ESRF with arbitrary ensemble size, focusing on the dynamical properties of boundedness and geometric ergodicity. The time uniform boundedness guarantees that the filter estimate will not diverge to machine infinity in finite time, which is a potential threat for EnKF and ESQF known as the catastrophic filter divergence. Geometric ergodicity ensures in addition that the filter has a unique invariant measure and that initialization errors will dissipate exponentially in time. We establish these results by introducing a natural notion of observable energy dissipation. The time uniform bound is achieved through a simple Lyapunov function argument, this result applies to systems with complete observations and strong kinetic energy dissipation, but also to concrete examples with incomplete observations. With the Lyapunov function argument established, the geometric ergodicity is obtained by verifying the controllability of the filter processes; in particular, such analysis for ESQF relies on a careful multivariate perturbation analysis of the covariance eigen-structure.

  14. Polycarbonate-Based Blends for Optical Non-linear Applications.

    Science.gov (United States)

    Stanculescu, F; Stanculescu, A

    2016-12-01

    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. PMID:26873262

  15. Classification of Asthma Based on Nonlinear Analysis of Breathing Pattern.

    Directory of Open Access Journals (Sweden)

    Mohammad Reza Raoufy

    Full Text Available Normal human breathing exhibits complex variability in both respiratory rhythm and volume. Analyzing such nonlinear fluctuations may provide clinically relevant information in patients with complex illnesses such as asthma. We compared the cycle-by-cycle fluctuations of inter-breath interval (IBI and lung volume (LV among healthy volunteers and patients with various types of asthma. Continuous respiratory datasets were collected from forty age-matched men including 10 healthy volunteers, 10 patients with controlled atopic asthma, 10 patients with uncontrolled atopic asthma, and 10 patients with uncontrolled non-atopic asthma during 60 min spontaneous breathing. Complexity of breathing pattern was quantified by calculating detrended fluctuation analysis, largest Lyapunov exponents, sample entropy, and cross-sample entropy. The IBI as well as LV fluctuations showed decreased long-range correlation, increased regularity and reduced sensitivity to initial conditions in patients with asthma, particularly in uncontrolled state. Our results also showed a strong synchronization between the IBI and LV in patients with uncontrolled asthma. Receiver operating characteristic (ROC curve analysis showed that nonlinear analysis of breathing pattern has a diagnostic value in asthma and can be used in differentiating uncontrolled from controlled and non-atopic from atopic asthma. We suggest that complexity analysis of breathing dynamics may represent a novel physiologic marker to facilitate diagnosis and management of patients with asthma. However, future studies are needed to increase the validity of the study and to improve these novel methods for better patient management.

  16. Polycarbonate-Based Blends for Optical Non-linear Applications

    Science.gov (United States)

    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.

  17. Nonlinear modeling of PEMFC based on neural networks identification

    Institute of Scientific and Technical Information of China (English)

    SUN Tao; CAO Guang-yi; ZHU Xin-jian

    2005-01-01

    The proton exchange membrane generation technology is highly efficient and clean, and is considered as the most hopeful "green" power technology. The operating principles of proton exchange membrane fuel cell (PEMFC) system involve thermodynamics, electrochemistry, hydrodynamics and mass transfer theory, which comprise a complex nonlinear system, for which it is difficult to establish a mathematical model. This paper first simply analyzes the necessity of the PEMFC generation technology, then introduces the generating principle from four aspects: electrode, single cell, stack, system; and then uses the approach and self-study ability of artificial neural network to build the model of nonlinear system, and adapts the Levenberg-Marquardt BP (LMBP) to build the electric characteristic model of PEMFC. The model uses experimental data as training specimens, on the condition the system is provided enough hydrogen. Considering the flow velocity of air (or oxygen) and the cell operational temperature as inputs, the cell voltage and current density as the outputs and establishing the electric characteristic model of PEMFC according to the different cell temperatures. The voltage-current output curves of model has some guidance effect for improving the cell performance, and provide basic data for optimizing cell performance that have practical significance.

  18. Nonlinear Spline Kernel-based Partial Least Squares Regression Method and Its Application

    Institute of Scientific and Technical Information of China (English)

    JIA Jin-ming; WEN Xiang-jun

    2008-01-01

    Inspired by the traditional Wold's nonlinear PLS algorithm comprises of NIPALS approach and a spline inner function model,a novel nonlinear partial least squares algorithm based on spline kernel(named SK-PLS)is proposed for nonlinear modeling in the presence of multicollinearity.Based on the iuner-product kernel spanned by the spline basis functions with infinite numher of nodes,this method firstly maps the input data into a high dimensional feature space,and then calculates a linear PLS model with reformed NIPALS procedure in the feature space and gives a unified framework of traditional PLS"kernel"algorithms in consequence.The linear PLS in the feature space corresponds to a nonlinear PLS in the original input (primal)space.The good approximating property of spline kernel function enhances the generalization ability of the novel model,and two numerical experiments are given to illustrate the feasibility of the proposed method.

  19. Inhomogeneities and nonlinear dynamics of a helical DNA interacting with a RNA-polymerase

    International Nuclear Information System (INIS)

    We have numerically investigated the effects of helicity and inhomogeneities on DNA base pairs opening. The inhomogeneities are due to the site-dependent stacking and hydrogen bonding energies in DNA and protein molecules. We have considered a situation in which the active site of the RNA-polymerase molecule binds onto the promoter site of the spin-like model of the DNA molecule at the physiological temperature and creates a bubble. During the study, we have found that the helical coupling has to be very weak compared to intra-strand coupling in the real DNA molecule. Results show that inhomogeneities do not affect the general pattern of base pair opening, even as the periodic inhomogeneity introduces a train of periodic oscillations on the tail of the bubble; while the height of the bubble is an increasing function of the helical coupling parameter. The basic properties of breather-like modes, obtained here by taking into account helical structure and inhomogeneities, are essential for DNA functioning since such breathing-like modes are considered to be much better candidates for the nonlinear modes responsible for a locally open state where biological functioning takes place. (paper)

  20. An interactive segmentation method based on superpixel

    DEFF Research Database (Denmark)

    Yang, Shu; Zhu, Yaping; Wu, Xiaoyu

    2015-01-01

    This paper proposes an interactive image-segmentation method which is based on superpixel. To achieve fast segmentation, the method is used to establish a Graphcut model using superpixels as nodes, and a new energy function is proposed. Experimental results demonstrate that the authors' method has...... excellent performance in terms of segmentation accuracy and computation efficiency compared with other segmentation algorithm based on pixels....

  1. Nonlinear phonon transport and ballistic thermal rectification in asymmetric graphene-based three terminal junctions

    Science.gov (United States)

    Xie, Zhong-Xiang; Li, Ke-Min; Tang, Li-Ming; Pan, Chang-Ning; Chen, Ke-Qiu

    2012-04-01

    By using the nonequilibrium Green's function and the Landauer transport theory, nonlinear phonon properties in asymmetric graphene-based three terminal junctions (AGTTJs) are investigated. Results show that AGTTJs exhibit pronounced nonlinear thermal rectifying behaviors, and the efficiency is efficiently tuned by increasing the asymmetric degree between the left and right terminals or modulating the central probe. The thermal rectifying mechanism is analytically explained by the schematic diagram. It is suggested that AGTTJs may be served as a good ballistic thermal rectifier.

  2. Non-linear model based control of a propylene polymerization reactor

    OpenAIRE

    Al-haj Ali, M.; Betlem, B.; Weickert, G.; Roffel, B.

    2007-01-01

    A modified generic model controller is developed and tested through a simulation study. The application involves model-based control of a propylene polymerization reactor in which the monomer conversion and melt index of the produced polymer are controlled by manipulating the reactor cooling water flow and the inlet hydrogen concentration. Non-linear control is designed using a simplified non-linear model, in order to demonstrate the robustness of the control approach for modeling errors. Two...

  3. Response analysis of a nuclear containment structure with nonlinear soil-structure interaction under bi-directional ground motion

    Science.gov (United States)

    Kumar, Santosh; Raychowdhury, Prishati; Gundlapalli, Prabhakar

    2015-06-01

    Design of critical facilities such as nuclear power plant requires an accurate and precise evaluation of seismic demands, as any failure of these facilities poses immense threat to the community. Design complexity of these structures reinforces the necessity of a robust 3D modeling and analysis of the structure and the soil-foundation interface. Moreover, it is important to consider the multiple components of ground motion during time history analysis for a realistic simulation. Present study is focused on investigating the seismic response of a nuclear containment structure considering nonlinear Winkler-based approach to model the soil-foundation interface using a distributed array of inelastic springs, dashpots and gap elements. It is observed from this study that the natural period of the structure increases about 10 %, whereas the force demands decreases up to 24 % by considering the soil-structure interaction. Further, it is observed that foundation deformations, such as rotation and sliding are affected by the embedment ratio, indicating an increase of up to 56 % in these responses for a reduction of embedment from 0.5 to 0.05× the width of the footing.

  4. Analysis of the interplay of quantum phases and nonlinearity applied to dimers with anharmonic interactions

    International Nuclear Information System (INIS)

    We extend our analysis of the effects of the interplay of quantum phases and nonlinearity to address saturation effects in small quantum systems. We find that initial phases dramatically control the dependence of self-trapping on initial asymmetry of quasiparticle population and can compete or act with nonlinearity as well as saturation effects. We find that there is a minimum finite saturation value in order to obtain self-trapping that crucially depends on the initial quasiparticle phases and present a detailed phase-diagram in terms of the control parameters of the system: nonlinearity and saturation. (author). 14 refs, 3 figs

  5. Asymmetry of nonlinear soil strains during soil-structure interaction excited by SH pulse

    OpenAIRE

    Gicev, Vlado; Trifunac, Mihailo

    2012-01-01

    A two-dimensional (2D) model of a building supported by a rectangular, flexible foundation embedded in nonlinear soil is analyzed. The model is excited by a half-sine SH wave pulse, which travels towards the foundation. The results show that the spatial distribution of permanent, nonlinear strain in the soil depends upon the incident angle, the amplitude, and the duration of the pulse. If the wave has large amplitude and short duration, the nonlinear zone in the soil appears immediately or af...

  6. Interaction between excitons determines the non-linear response of nanocrystals

    International Nuclear Information System (INIS)

    The non-linear response of semiconductor quantum dots is investigated using three-pulse photon echo peak shift (3PEPS) experiments and simulations. The third-order non-linear response is modeled by a three-level system, utilizing Brownian oscillators to model the line-broadening functions. Our results show that biexciton formation and exciton-exciton scattering significantly influence the non-linear response of quantum dots. The exciton to biexciton excited state absorption pathways are also investigated for quantum dots with different crystal structures. Our calculations suggest that the probability of excited state absorption to the biexcitonic state is higher for zinc-blende structured nanocrystals

  7. Wave-front engineering by Huygens-Fresnel principle for nonlinear optical interactions in domain engineered structures

    OpenAIRE

    Qin, Yi-Qiang; Zhang, Chao; Zhu, Yong-yuan

    2007-01-01

    The wave-front engineering for nonlinear optical interactions was discussed. Using Huygens-Fresnel principle we developed a general theory and technique for domain engineering with conventional quasi-phase-matching structures being the special cases. By Fourier analysis we put forward the concept of local quasi-phase matching, which suggests that the quasi-phase matching is fulfilled only locally not globally. Experiments on focal effect of second-harmonic wave agreed well with the theoretica...

  8. Observer-based Fault Detection and Isolation for Nonlinear Systems

    DEFF Research Database (Denmark)

    Lootsma, T.F.

    -tolerance can be applied to ordinary industrial processes that are not categorized as high risk applications, but where high availability is desirable. The quality of fault-tolerant control is totally dependent on the quality of the underlying algorithms. They detect possible faults, and later reconfigure......With the rise in automation the increase in fault detectionand isolation & reconfiguration is inevitable. Interest in fault detection and isolation (FDI) for nonlinear systems has grown significantly in recent years. The design of FDI is motivated by the need for knowledge about occurring faults in...... fault-tolerant control systems (FTC systems). The idea of FTC systems is to detect, isolate, and handle faults in such a way that the systems can still perform in a required manner. One prefers reduced performance after occurrence of a fault to the shut down of (sub-) systems. Hence, the idea of fault...

  9. Quantitative analysis for nonlinear fluorescent spectra based on edges matching

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel spectra-edge-matching approach is proposed for the quantitative analysis of the nonlinear fluorescence spectra of the air impurities excited by a femtosecond laser.The fluorescence spectra are first denoised and compressed,both by wavelet transform,and several peak groups are then picked from each spectrum according to a threshold of intensity and are used to extract the spectral features through principal component analysis.It is indicated that the first two principle components actually cover up to 98% of the total information and are sufficient for the final concentration analysis.The analysis reveals a monotone relationship between the spectra intensity and the concentration of the air impurities,suggesting that the femtosecond laser induced fluorescence spectroscopy along with the proposed spectra analysis method can become a powerful tool for monitoring environmental pollutants.

  10. Nonlinear model predictive control based on collective neurodynamic optimization.

    Science.gov (United States)

    Yan, Zheng; Wang, Jun

    2015-04-01

    In general, nonlinear model predictive control (NMPC) entails solving a sequential global optimization problem with a nonconvex cost function or constraints. This paper presents a novel collective neurodynamic optimization approach to NMPC without linearization. Utilizing a group of recurrent neural networks (RNNs), the proposed collective neurodynamic optimization approach searches for optimal solutions to global optimization problems by emulating brainstorming. Each RNN is guaranteed to converge to a candidate solution by performing constrained local search. By exchanging information and iteratively improving the starting and restarting points of each RNN using the information of local and global best known solutions in a framework of particle swarm optimization, the group of RNNs is able to reach global optimal solutions to global optimization problems. The essence of the proposed collective neurodynamic optimization approach lies in the integration of capabilities of global search and precise local search. The simulation results of many cases are discussed to substantiate the effectiveness and the characteristics of the proposed approach. PMID:25608315

  11. Non-linear scalable TFETI domain decomposition based contact algorithm

    International Nuclear Information System (INIS)

    The paper is concerned with the application of our original variant of the Finite Element Tearing and Interconnecting (FETI) domain decomposition method, called the Total FETI (TFETI), to solve solid mechanics problems exhibiting geometric, material, and contact non-linearities. The TFETI enforces the prescribed displacements by the Lagrange multipliers, so that all the subdomains are 'floating', the kernels of their stiffness matrices are known a priori, and the projector to the natural coarse grid is more effective. The basic theory and relationships of both FETI and TFETI are briefly reviewed and a new version of solution algorithm is presented. It is shown that application of TFETI methodology to the contact problems converts the original problem to the strictly convex quadratic programming problem with bound and equality constraints, so that the effective, in a sense optimal algorithms is to be applied. Numerical experiments show that the method exhibits both numerical and parallel scalabilities.

  12. Analytical Model of the Nonlinear Dynamics of Cantilever Tip-Sample Surface Interactions for Various Acoustic-Atomic Force Microscopies

    Science.gov (United States)

    Cantrell, John H., Jr.; Cantrell, Sean A.

    2008-01-01

    A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.

  13. The influence of surface roughness on the contact stiffness and the contact filter effect in nonlinear wheel-track interaction

    Science.gov (United States)

    Lundberg, Oskar E.; Nordborg, Anders; Lopez Arteaga, Ines

    2016-03-01

    A state-dependent contact model including nonlinear contact stiffness and nonlinear contact filtering is used to calculate contact forces and rail vibrations with a time-domain wheel-track interaction model. In the proposed method, the full three-dimensional contact geometry is reduced to a point contact in order to lower the computational cost and to reduce the amount of required input roughness-data. Green's functions including the linear dynamics of the wheel and the track are coupled with a point contact model, leading to a numerically efficient model for the wheel-track interaction. Nonlinear effects due to the shape and roughness of the wheel and the rail surfaces are included in the point contact model by pre-calculation of functions for the contact stiffness and contact filters. Numerical results are compared to field measurements of rail vibrations for passenger trains running at 200 kph on a ballast track. Moreover, the influence of vehicle pre-load and different degrees of roughness excitation on the resulting wheel-track interaction is studied by means of numerical predictions.

  14. Localized excitations in discrete nonlinear Schrödinger systems: Effects of nonlocal dispersive interactions and noise

    Science.gov (United States)

    Rasmussen, K. Ø.; Christiansen, P. L.; Johansson, M.; Gaididei, Yu. B.; Mingaleev, S. F.

    1998-03-01

    A one-dimensional discrete nonlinear Schrödinger (DNLS) model with the power dependence, r- s on the distance r, of dispersive interactions is proposed. The stationary states of the system are studied both analytically and numerically. Two kinds of trial functions, exp-like and sech-like are exploited and the results of both approaches are compared. Both on-site and inter-site stationary states are investigated. It is shown that for s sufficiently large all features of the model are qualitatively the same as in the DNLS model with nearest-neighbor interaction. For s less than some critical value, scr, there is an interval of bistability where two stable stationary states exist at each excitation number. The bistability of on-site solitons may occur for dipole-dipole dispersive interaction ( s = 3), while scr for inter-site solitions is close to 2.1. In the framework of the DNLS equation with nearest-neighbor coupling we discuss the stability of highly localized, “breather-like”, excitations under the influence of thermal fluctuations. Numerical analysis shows that the lifetime of the breather is always finite and in a large parameter region inversely proportional to the noise variance for fixed damping and nonlinearity. We also find that the decay rate of the breather decreases with increasing nonlinearity and with increasing damping.

  15. Light-shift-induced photonic nonlinearities

    OpenAIRE

    Brandão, FGSL; Hartmann, M. J.; Plenio, M. B.

    2008-01-01

    We propose a new method to produce self- and cross-Kerr photonic nonlinearities, using light-induced Stark shifts due to the interaction of a cavity mode with atoms. The proposed experimental set-up is simpler than in previous approaches, while the strength of the nonlinearity obtained with a single atom is the same as in the setting based on electromagnetically induced transparency. Furthermore our scheme can be applied to engineer effective photonic nonlinear interactions whose strength inc...

  16. Nonlinear theory of the free-electron laser based upon a coaxial hybrid wiggler

    Science.gov (United States)

    Freund, H. P.; Jackson, R. H.; Pershing, D. E.; Taccetti, J. M.

    1994-04-01

    A three-dimensional nonlinear formulation of a free-electron laser based upon a coaxial hybrid iron (CHI) wiggler is described. The CHI wiggler is created by insertion of a central rod and an outer ring [composed of alternating ferrite and dielectric spacers in which the ferrite (dielectric) spacer on the central rod is opposite to the dielectric (ferrite) spacer on the outer ring] along the axis of a solenoidal. An analytic model of the CHI wiggler is developed which is in good agreement with the Poisson/Superfish group of codes. The free-electron laser (FEL) formulation is a slow-time-scale analysis of the interaction of an annular electron beam with the CHI wiggler in a coaxial waveguide. The electromagnetic field is represented as the superposition of the vacuum transverse electric (TE), transverse magnetic (TM), and transverse electromagnetic (TEM) modes of the waveguide, and a set of nonlinear second-order differential equations is derived for the amplitudes and phases of these modes. These equations are solved simultaneously with the three-dimensional Lorentz force equations for the combined magnetostatic and electromagnetic fields. An adiabatic taper is used to model the injection of the beam, and an amplitude taper is included for efficiency enhancement. Simulations are presented for Ka-, Ku- and W-band operation. Multimode operation is also studied. The results indicate that operation over a wide bandwidth is practical with the CHI wiggler, and that the bandwidth in the tapered-wiggler cases is comparable to that for a uniform wiggler. Therefore, relatively high field strengths can be achieved with the CHI wiggler at shorter wiggler periods than is possible in many other conventional wiggler designs.

  17. Evolutionary algorithm based configuration interaction approach

    CERN Document Server

    Chakraborty, Rahul

    2016-01-01

    A stochastic configuration interaction method based on evolutionary algorithm is designed as an affordable approximation to full configuration interaction (FCI). The algorithm comprises of initiation, propagation and termination steps, where the propagation step is performed with cloning, mutation and cross-over, taking inspiration from genetic algorithm. We have tested its accuracy in 1D Hubbard problem and a molecular system (symmetric bond breaking of water molecule). We have tested two different fitness functions based on energy of the determinants and the CI coefficients of determinants. We find that the absolute value of CI coefficients is a more suitable fitness function when combined with a fixed selection scheme.

  18. Higher order harmonic detection for exploring nonlinear interactions with nanoscale resolution

    OpenAIRE

    Vasudevan, R. K.; M. Baris Okatan; Rajapaksa, I.; Kim, Y.; Marincel, D.; Trolier-McKinstry, S.; Jesse, S.; Valanoor, N.; Kalinin, S. V.

    2013-01-01

    Nonlinear dynamics underpin a vast array of physical phenomena ranging from interfacial motion to jamming transitions. In many cases, insight into the nonlinear behavior can be gleaned through exploration of higher order harmonics. Here, a method using band excitation scanning probe microscopy (SPM) to investigate higher order harmonics of the electromechanical response, with nanometer scale spatial resolution is presented. The technique is demonstrated by probing the first three harmonics of...

  19. Enhanced nonlinear imaging through scattering media using transmission matrix based wavefront shaping

    CERN Document Server

    de Aguiar, Hilton B; Brasselet, Sophie

    2016-01-01

    Despite the tremendous progresses in wavefront control through or inside complex scattering media, several limitations prevent reaching practical feasibility for nonlinear imaging in biological tissues. While the optimization of nonlinear signals might suffer from low signal to noise conditions and from possible artifacts at large penetration depths, it has nevertheless been largely used in the multiple scattering regime since it provides a guide star mechanism as well as an intrinsic compensation for spatiotemporal distortions. Here, we demonstrate the benefit of Transmission Matrix (TM) based approaches under broadband illumination conditions, to perform nonlinear imaging. Using ultrashort pulse illumination with spectral bandwidth comparable but still lower than the spectral width of the scattering medium, we show strong nonlinear enhancements of several orders of magnitude, through thicknesses of a few transport mean free paths, which corresponds to millimeters in biological tissues. Linear TM refocusing ...

  20. Thermo-modulational interband susceptibility and ultrafast temporal dynamics in nonlinear gold-based plasmonic devices

    CERN Document Server

    Marini, Andrea; Della Valle, Giuseppe; Lee, Ho Wai; Tran, Truong X; Chang, Wonkeun; Schmidt, Markus A; Longhi, Stefano; Russell, Philip St J; Biancalana, Fabio

    2012-01-01

    Starting from first principles, we theoretically model the nonlinear temporal dynamics of gold-based plasmonic devices resulting from the heating of their metallic components. At optical frequencies, the gold susceptibility is determined by the interband transitions around the X,L points in the first Brillouin zone and thermo-modulational effects ensue from Fermi smearing of the electronic energy distribution in the conduction band. As a consequence of light-induced heating of the conduction electrons, the optical susceptibility becomes nonlinear. In this paper we describe, for the first time to our knowledge, the effects of the thermo-modulational nonlinearity of gold on the propagation of surface plasmon polaritons guided on gold nanowires. We introduce a novel nonlinear Schroedinger-like equation to describe pulse propagation in such nanowires, and we predict the appearance an intense spectral red-shift caused by the delayed thermal response.

  1. Nuclear matter properties in the non-linear Walecka model at finite temperature with interaction between the σ - ω mesons

    International Nuclear Information System (INIS)

    In this work in contrast to the usual Walecka model [1] we include the interaction between the σ – ω mesons [2,3] with the aim of studying the nuclear matter properties in the relativistic mean-field theory in the regime of high temperatures. Therefore in our work we use the non-linear Walecka model. We investigate whether the phase transition characteristic of other models without these interactions vanishes for a given value of chemical potential μ and baryon density ρN

  2. Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

    Science.gov (United States)

    Berger, N. K.; Zhukov, E. A.; Novokhatskii, V. V.

    1984-04-01

    Nonlinear interactions (including wavefront reversal) of light from CW or pulsed 10.6-micron CO2 lasers at the semiconductor-metal phase transition in a VO2 film are investigated experimentally. The results are presented in graphs and characterized in detail. The intensity reflection coefficients of the three-wave interactions are found to be 0.5 percent for a CW reference wave of intensity 900 mW/sq cm and 42 percent for a pulsed reference wave of threshold density 600-800 microjoule/sq cm.

  3. Pseudo-transient Continuation Based Variable Relaxation Solve in Nonlinear Magnetohydrodynamic Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Jin Chen

    2009-12-07

    Efficient and robust Variable Relaxation Solver, based on pseudo-transient continuation, is developed to solve nonlinear anisotropic thermal conduction arising from fusion plasma simulations. By adding first and/or second order artificial time derivatives to the system, this type of method advances the resulting time-dependent nonlinear PDEs to steady state, which is the solution to be sought. In this process, only the stiffness matrix itself is involved so that the numerical complexity and errors can be greatly reduced. In fact, this work is an extension of integrating efficient linear elliptic solvers for fusion simulation on Cray XIE. Two schemes are derived in this work, first and second order Variable Relaxations. Four factors are observed to be critical for efficiency and preservation of solution's symmetric structure arising from periodic boundary condition: refining meshes in different coordinate directions, initializing nonlinear process, varying time steps in both temporal and spatial directions, and accurately generating nonlinear stiffness matrix. First finer mesh scale should be taken in strong transport direction; Next the system is carefully initialized by the solution with linear conductivity; Third, time step and relaxation factor are vertex-based varied and optimized at each time step; Finally, the nonlinear stiffness matrix is updated by just scaling corresponding linear one with the vector generated from nonlinear thermal conductivity.

  4. SVM with Quadratic Polynomial Kernel Function Based Nonlinear Model One-step-ahead Predictive Control

    Institute of Scientific and Technical Information of China (English)

    钟伟民; 何国龙; 皮道映; 孙优贤

    2005-01-01

    A support vector machine (SVM) with quadratic polynomial kernel function based nonlinear model one-step-ahead predictive controller is presented. The SVM based predictive model is established with black-box identification method. By solving a cubic equation in the feature space, an explicit predictive control law is obtained through the predictive control mechanism. The effect of controller is demonstrated on a recognized benchmark problem and on the control of continuous-stirred tank reactor (CSTR). Simulation results show that SVM with quadratic polynomial kernel function based predictive controller can be well applied to nonlinear systems, with good performance in following reference trajectory as well as in disturbance-rejection.

  5. A Somatosensory Interaction System based on Kinect

    Directory of Open Access Journals (Sweden)

    Liang Xiu Bo

    2016-01-01

    Full Text Available The somatosensory interaction technique is one form of the perceptual user interface which is used in video game and virtual reality more and more widly. In this paper, a somatosensory interaction system based on Kinect is presented. Firstly, the user performances his action in front of a kinect, the sensing data from kinect is preprocessed and the main features of the action are extracted. Secondly, the performaced action is recognized by the matching algorithm based on Dynamic Time Warping Hidden Markov Model. Finally, the recognized motion is employed to interact with the virtual human and virtual environment. A series of experiments have been done to test the availablity of our system. Results show that the recognition rate is high enough to be used in virtual reality applications.

  6. Composite nonlinear structure within the magnetosonic soliton interactions in a spin-1/2 degenerate quantum plasma

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jiu-Ning, E-mail: hanjiuning@126.com; Luo, Jun-Hua; Li, Jun-Xiu [Institute of Theoretical Physics and College of Physics and Electromechanical Engineering, Hexi University, Zhangye 734000 (China); Li, Sheng-Chang [School of Science, Xi' an Jiaotong University, Xi' an 710049 (China); Liu, Shi-Wei; Yang, Yang; Duan, Wen-Shan; Han, Juan-Fang [Joint Laboratory of Atomic and Molecular Physics of NWNU and IMPCAS and College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China)

    2015-06-15

    We study the basic physical properties of composite nonlinear structure induced by the head-on collision of magnetosonic solitons. Solitary waves are assumed to propagate in a quantum electron-ion magnetoplasma with spin-1/2 degenerate electrons. The main interest of the present work is to investigate the time evolution of the merged composite structure during a specific time interval of the wave interaction process. We consider three cases of colliding-situation, namely, compressive-rarefactive solitons interaction, compressive-compressive solitons interaction, and rarefactive-rarefactive solitons interaction, respectively. Compared with the last two colliding cases, the changing process of the composite structure is more complex for the first situation. Moreover, it is found that they are obviously different for the last two colliding cases.

  7. Nonlinear genetic-based simulation of soil shear strength parameters

    Indian Academy of Sciences (India)

    Seyyed Mohammad Mousavi; Amir Hossein Alavi; Amir Hossein Gandomi; Ali Mollahasani

    2011-12-01

    New nonlinear solutions were developed to estimate the soil shear strength parameters utilizing linear genetic programming (LGP). The soil cohesion intercept () and angle of shearing resistance () were formulated in terms of the basic soil physical properties. The best models were selected after developing and controlling several models with different combinations of influencing parameters. Comprehensive experimental database used for developing the models was established upon a series of unconsolidated, undrained, and unsaturated triaxial tests conducted in this study. Further, sensitivity and parametric analyses were carried out. and were found to be mostly influenced by the soil unit weight and liquid limit. In order to benchmark the proposed models, a multiple least squares regression (MLSR) analysis was performed. The validity of the models was proved on portions of laboratory results that were not included in the modelling process. The developed models are able to effectively learn the complex relationship between the soil strength parameters and their contributing factors. The LGP models provide a significantly better prediction performance than the regression models.

  8. Nonlinear observer based fault detection and isolation for a momentum wheel

    DEFF Research Database (Denmark)

    Jensen, Hans-Christian Becker; Wisniewski, Rafal

    2001-01-01

    This article realizes nonlinear Fault Detection and Isolation for a momentum wheel. The Fault Detection and Isolation is based on a Failure Mode and Effect Analysis, which states which faults might occur and can be detected. The algorithms presented in this paper are based on a geometric approach...

  9. Nonlinear Dynamic Response of Concrete Structure with Soil-Structure Interaction

    OpenAIRE

    Talberg, Marte Sørbrøden

    2015-01-01

    A common assumption for a structure that is subjected to an earthquake is that the structure is considered fixed at the base. In this thesis, analyses where the soil is deformed and the foundation may be moved and rotate have been done, and it has been investigated if this can reduce forces or displacements in the structure. This have been done through the use of soil-structure interaction (SSI). In this thesis well known beam-column element formulations will be presented, and the benefi...

  10. Nonlinear-Based MEMS Sensors and Active Switches for Gas Detection.

    Science.gov (United States)

    Bouchaala, Adam; Jaber, Nizar; Yassine, Omar; Shekhah, Osama; Chernikova, Valeriya; Eddaoudi, Mohamed; Younis, Mohammad I

    2016-01-01

    The objective of this paper is to demonstrate the integration of a MOF thin film on electrostatically actuated microstructures to realize a switch triggered by gas and a sensing algorithm based on amplitude tracking. The devices are based on the nonlinear response of micromachined clamped-clamped beams. The microbeams are coated with a metal-organic framework (MOF), namely HKUST-1, to achieve high sensitivity. The softening and hardening nonlinear behaviors of the microbeams are exploited to demonstrate the ideas. For gas sensing, an amplitude-based tracking algorithm is developed to quantify the captured quantity of gas. Then, a MEMS switch triggered by gas using the nonlinear response of the microbeam is demonstrated. Noise analysis is conducted, which shows that the switch has high stability against thermal noise. The proposed switch is promising for delivering binary sensing information, and also can be used directly to activate useful functionalities, such as alarming. PMID:27231914

  11. Nonlinear-Based MEMS Sensors and Active Switches for Gas Detection

    KAUST Repository

    Bouchaala, Adam

    2016-05-25

    The objective of this paper is to demonstrate the integration of a MOF thin film on electrostatically actuated microstructures to realize a switch triggered by gas and a sensing algorithm based on amplitude tracking. The devices are based on the nonlinear response of micromachined clamped-clamped beams. The microbeams are coated with a metal-organic framework (MOF), namely HKUST-1, to achieve high sensitivity. The softening and hardening nonlinear behaviors of the microbeams are exploited to demonstrate the ideas. For gas sensing, an amplitude-based tracking algorithm is developed to quantify the captured quantity of gas. Then, a MEMS switch triggered by gas using the nonlinear response of the microbeam is demonstrated. Noise analysis is conducted, which shows that the switch has high stability against thermal noise. The proposed switch is promising for delivering binary sensing information, and also can be used directly to activate useful functionalities, such as alarming.

  12. Nonlinear-Based MEMS Sensors and Active Switches for Gas Detection

    Directory of Open Access Journals (Sweden)

    Adam Bouchaala

    2016-05-01

    Full Text Available The objective of this paper is to demonstrate the integration of a MOF thin film on electrostatically actuated microstructures to realize a switch triggered by gas and a sensing algorithm based on amplitude tracking. The devices are based on the nonlinear response of micromachined clamped-clamped beams. The microbeams are coated with a metal-organic framework (MOF, namely HKUST-1, to achieve high sensitivity. The softening and hardening nonlinear behaviors of the microbeams are exploited to demonstrate the ideas. For gas sensing, an amplitude-based tracking algorithm is developed to quantify the captured quantity of gas. Then, a MEMS switch triggered by gas using the nonlinear response of the microbeam is demonstrated. Noise analysis is conducted, which shows that the switch has high stability against thermal noise. The proposed switch is promising for delivering binary sensing information, and also can be used directly to activate useful functionalities, such as alarming.

  13. Modeling of Nonlinear Aggregation for Information Fusion Systems with Outliers Based on the Choquet Integral

    Directory of Open Access Journals (Sweden)

    Jin-Tsong Jeng

    2011-02-01

    Full Text Available Modern information fusion systems essentially associate decision-making processes with multi-sensor systems. Precise decision-making processes depend upon aggregating useful information extracted from large numbers of messages or large datasets; meanwhile, the distributed multi-sensor systems which employ several geographically separated local sensors are required to provide sufficient messages or data with similar and/or dissimilar characteristics. These kinds of information fusion techniques have been widely investigated and used for implementing several information retrieval systems. However, the results obtained from the information fusion systems vary in different situations and performing intelligent aggregation and fusion of information from a distributed multi-source, multi-sensor network is essentially an optimization problem. A flexible and versatile framework which is able to solve complex global optimization problems is a valuable alternative to traditional information fusion. Furthermore, because of the highly dynamic and volatile nature of the information flow, a swift soft computing technique is imperative to satisfy the demands and challenges. In this paper, a nonlinear aggregation based on the Choquet integral (NACI model is considered for information fusion systems that include outliers under inherent interaction among feature attributes. The estimation of interaction coefficients for the proposed model is also performed via a modified algorithm based on particle swarm optimization with quantum-behavior (QPSO and the high breakdown value estimator, least trimmed squares (LTS. From simulation results, the proposed MQPSO algorithm with LTS (named LTS-MQPSO readily corrects the deviations caused by outliers and swiftly achieves convergence in estimating the parameters of the proposed NACI model for the information fusion systems with outliers.

  14. Self-adaptive one-dimensional nonlinear finite element method based on element energy projection method

    Institute of Scientific and Technical Information of China (English)

    Si YUAN; Yan DU; Qin-yan XING; Kang-sheng YE

    2014-01-01

    The element energy projection (EEP) method for computation of super-convergent resulting in a one-dimensional finite element method (FEM) is successfully used to self-adaptive FEM analysis of various linear problems, based on which this paper presents a substantial extension of the whole set of technology to nonlinear problems. The main idea behind the technology transfer from linear analysis to nonlinear analysis is to use Newton’s method to linearize nonlinear problems into a series of linear problems so that the EEP formulation and the corresponding adaptive strategy can be directly used without the need for specific super-convergence formulation for nonlinear FEM. As a re-sult, a unified and general self-adaptive algorithm for nonlinear FEM analysis is formed. The proposed algorithm is found to be able to produce satisfactory finite element results with accuracy satisfying the user-preset error tolerances by maximum norm anywhere on the mesh. Taking the nonlinear ordinary differential equation (ODE) of second-order as the model problem, this paper describes the related fundamental idea, the imple-mentation strategy, and the computational algorithm. Representative numerical exam-ples are given to show the efficiency, stability, versatility, and reliability of the proposed approach.

  15. Nonlinear Regression Based Health Monitoring of Hysteretic Structures under Seismic Excitation

    Directory of Open Access Journals (Sweden)

    C. Xu

    2015-01-01

    Full Text Available This paper presents a health monitoring method using measured hysteretic responses. Acceleration and infrequently measured displacement are integrated using a multirate Kalman filtering method to generate restoring force-displacement hysteresis loops. A linear/nonlinear regression analysis based two-step method is proposed to identify nonlinear system parameters. First, hysteresis loops are divided into loading/unloading half cycles. Multiple linear regression analysis is applied to separate linear and nonlinear half cycles. Preyielding stiffness and viscous damping coefficient are obtained in this step and used as known parameters in the second step. Then, nonlinear regression analysis is applied to identified nonlinear half cycles to yield nonlinear system parameters and two damage indicators: cumulative plastic deformation and residual deformation. These values are closely related to structural status and repair costs. The feasibility of the method is demonstrated using a simulated shear-type structure with different levels of added measurement noise and a suite of ground motions. The results show that the proposed SHM method effectively and accurately identifies physical system parameters with up to 10% RMS added noise. The resulting damage indicators can robustly and clearly indicate structural condition over different earthquake events.

  16. Nonlinear Dynamics and Chaos of Microcantilever-Based TM-AFMs with Squeeze Film Damping Effects

    Directory of Open Access Journals (Sweden)

    Jie-Yu Chen

    2009-05-01

    Full Text Available In Atomic force microscope (AFM examination of a vibrating microcantilever, the nonlinear tip-sample interaction would greatly influence the dynamics of the cantilever. In this paper, the nonlinear dynamics and chaos of a tip-sample dynamic system being run in the tapping mode (TM were investigated by considering the effects of hydrodynamic loading and squeeze film damping. The microcantilever was modeled as a spring-mass-damping system and the interaction between the tip and the sample was described by the Lennard-Jones (LJ potential. The fundamental frequency and quality factor were calculated from the transient oscillations of the microcantilever vibrating in air. Numerical simulations were carried out to study the coupled nonlinear dynamic system using the bifurcation diagram, Poincaré maps, largest Lyapunov exponent, phase portraits and time histories. Results indicated the occurrence of periodic and chaotic motions and provided a comprehensive understanding of the hydrodynamic loading of microcantilevers. It was demonstrated that the coupled dynamic system will experience complex nonlinear oscillation as the system parameters change and the effect of squeeze film damping is not negligible on the micro-scale.

  17. A Wavelet Bicoherence-Based Quadratic Nonlinearity Feature for Translational Axis Condition Monitoring

    Directory of Open Access Journals (Sweden)

    Yong Li

    2014-01-01

    Full Text Available The translational axis is one of the most important subsystems in modern machine tools, as its degradation may result in the loss of the product qualification and lower the control precision. Condition-based maintenance (CBM has been considered as one of the advanced maintenance schemes to achieve effective, reliable and cost-effective operation of machine systems, however, current vibration-based maintenance schemes cannot be employed directly in the translational axis system, due to its complex structure and the inefficiency of commonly used condition monitoring features. In this paper, a wavelet bicoherence-based quadratic nonlinearity feature is proposed for translational axis condition monitoring by using the torque signature of the drive servomotor. Firstly, the quadratic nonlinearity of the servomotor torque signature is discussed, and then, a biphase randomization wavelet bicoherence is introduced for its quadratic nonlinear detection. On this basis, a quadratic nonlinearity feature is proposed for condition monitoring of the translational axis. The properties of the proposed quadratic nonlinearity feature are investigated by simulations. Subsequently, this feature is applied to the real-world servomotor torque data collected from the X-axis on a high precision vertical machining centre. All the results show that the performance of the proposed feature is much better than that of original condition monitoring features.

  18. Vector rectangular-shape laser based on reduced graphene oxide interacting with long fiber taper

    CERN Document Server

    Gao, Lei; Zeng, Jing; Huang, Wei; Liu, Min

    2014-01-01

    A vector dual-wavelength rectangular-shape laser (RSL) based on a long fiber taper deposited with reduced graphene oxide is proposed, where the nonlinearity is enhanced due to large evanescent-field-interacting length and strong field confinement of a 8 mm fiber taper with a waist diameter of 4 micronmeters. Graphene flakes are deposited uniformly on the taper waist with light pressure effect, so this structure guarantees both excellent saturable absorption and high nonlinearity. The RSL with a repetition rate of 7.9 MHz exhibits fast polarization switching in two orthogonal polarization directions, and the temporal and spectral characteristics are investigated. The results suggest that the long taper-based graphene structure is an efficient choice for nonlinear devices.

  19. A robust nonlinear semi-active control for base seismically-isolated structures

    OpenAIRE

    Teodorescu, Catalin-Stefan; Diop, Sette; Politopoulos, Ioannis; Benidir, Messaoud

    2013-01-01

    This paper proposes a robust nonlinear semi-active control for base seismically-isolated structures. The control is based upon an extension of works of Leitmann et al. on the stabilization of nonlinear systems with uncertain models. For usual models of structure dynamics it is shown that applying a specific control law drives the state variables into a ball of specified radius in finite time. The radius of the ball may be arbitrarily chosen as long as it is not lower than a limiting value. In...

  20. Interacting wave fronts and rarefaction waves in a second order model of nonlinear thermoviscous fluids : Interacting fronts and rarefaction waves

    DEFF Research Database (Denmark)

    Rasmussen, Anders Rønne; Sørensen, Mads Peter; Gaididei, Yuri Borisovich;

    2011-01-01

    the Hamiltonian structure, in contrast to the Kuznetsov equation, a model often used in nonlinear acoustics. An exact traveling wave front solution is derived from a generalized traveling wave assumption for the velocity potential. Numerical studies of the evolution of a number of arbitrary initial conditions...... is proposed. The dynamics of the rarefaction wave is approximated by a collective coordinate approach in the energy balance equation. © 2010 Springer Science+Business Media B.V....

  1. Non-Linear Time-Domain Simulations of the RF Station-Beam Dynamics Interaction for the LHC

    International Nuclear Information System (INIS)

    Non-linear time-domain simulations have been developed for the Positron-Electron Project (PEP-II) and the Large Hadron Collider (LHC). These simulations capture the dynamic behavior of the RF station-beam interaction and are structured to reproduce the technical characteristics of the system (noise contributions, non-linear elements, and more). As such, they provide useful results and insight for the development and design of future LLRF feedback systems. They are also a valuable tool for the study of diverse longitudinal beam dynamics effects such as coupled-bunch impedance driven instabilities and single bunch longitudinal emittance growth. Results from these studies and related measurements from PEP-II and LHC have been presented in multiple places. This report presents an example of the time-domain simulation implementation for the LHC.

  2. Advanced nonlinear signal processing in silicon-based waveguides

    OpenAIRE

    Petropoulos, P.; Ettabib, M.A.; Bottrill, K.R.H.; Lacava, C.; Parmigiani, F.; Hammani, K.; BRUN, M.; Labeye, P.; Nicoletti, S.; Bogris, A.; Kapsalis, A.; Syvridis, D.

    2015-01-01

    This talk presents recent progress in optical signal processing based on compact waveguides fabricated mainly using silicon germanium alloys. Applications include supercontinuum generation, wavelength conversion and signal regeneration.

  3. On the stability and compressive nonlinearity of a physiologically based model of the cochlea

    International Nuclear Information System (INIS)

    Hearing relies on a series of coupled electrical, acoustical (fluidic) and mechanical interactions inside the cochlea that enable sound processing. A positive feedback mechanism within the cochlea, called the cochlear amplifier, provides amplitude and frequency selectivity in the mammalian auditory system. The cochlear amplifier and stability are studied using a nonlinear, micromechanical model of the Organ of Corti (OoC) coupled to the electrical potentials in the cochlear ducts. It is observed that the mechano-electrical transduction (MET) sensitivity and somatic motility of the outer hair cell (OHC), control the cochlear stability. Increasing MET sensitivity beyond a critical value, while electromechanical coupling coefficient is within a specific range, causes instability. We show that instability in this model is generated through a supercritical Hopf bifurcation. A reduced order model of the system is approximated and it is shown that the tectorial membrane (TM) transverse mode effect on the dynamics is significant while the radial mode can be simplified from the equations. The cochlear amplifier in this model exhibits good agreement with the experimental data. A comprehensive 3-dimensional model based on the cross sectional model is simulated and the results are compared. It is indicated that the global model qualitatively inherits some characteristics of the local model, but the longitudinal coupling along the cochlea shifts the stability boundary (i.e., Hopf bifurcation point) and enhances stability

  4. On the stability and compressive nonlinearity of a physiologically based model of the cochlea

    Energy Technology Data Exchange (ETDEWEB)

    Nankali, Amir [Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan (United States); Grosh, Karl [Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan (United States); Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan (United States)

    2015-12-31

    Hearing relies on a series of coupled electrical, acoustical (fluidic) and mechanical interactions inside the cochlea that enable sound processing. A positive feedback mechanism within the cochlea, called the cochlear amplifier, provides amplitude and frequency selectivity in the mammalian auditory system. The cochlear amplifier and stability are studied using a nonlinear, micromechanical model of the Organ of Corti (OoC) coupled to the electrical potentials in the cochlear ducts. It is observed that the mechano-electrical transduction (MET) sensitivity and somatic motility of the outer hair cell (OHC), control the cochlear stability. Increasing MET sensitivity beyond a critical value, while electromechanical coupling coefficient is within a specific range, causes instability. We show that instability in this model is generated through a supercritical Hopf bifurcation. A reduced order model of the system is approximated and it is shown that the tectorial membrane (TM) transverse mode effect on the dynamics is significant while the radial mode can be simplified from the equations. The cochlear amplifier in this model exhibits good agreement with the experimental data. A comprehensive 3-dimensional model based on the cross sectional model is simulated and the results are compared. It is indicated that the global model qualitatively inherits some characteristics of the local model, but the longitudinal coupling along the cochlea shifts the stability boundary (i.e., Hopf bifurcation point) and enhances stability.

  5. Modelling of nonlinear shoaling based on stochastic evolution equations

    DEFF Research Database (Denmark)

    Kofoed-Hansen, Henrik; Rasmussen, Jørgen Hvenekær

    1998-01-01

    A one-dimensional stochastic model is derived to simulate the transformation of wave spectra in shallow water including generation of bound sub- and super-harmonics, near-resonant triad wave interaction and wave breaking. Boussinesq type equations with improved linear dispersion characteristics a...... experimental data in four different cases as well as with the underlying deterministic model. In general, the agreement is found to be acceptable, even far beyond the region where Gaussianity (Gaussian sea state) may be justified. (C) 1998 Elsevier Science B.V....

  6. Support Vector Machine-Based Nonlinear System Modeling and Control

    Institute of Scientific and Technical Information of China (English)

    张浩然; 韩正之; 冯瑞; 于志强

    2003-01-01

    This paper provides an introduction to a support vector machine, a new kernel-based technique introduced in statistical learning theory and structural risk minimization, then presents a modeling-control framework based on SVM.At last a numerical experiment is taken to demonstrate the proposed approach's correctness and effectiveness.

  7. Implementation of neural network based non-linear predictive

    DEFF Research Database (Denmark)

    Sørensen, Paul Haase; Nørgård, Peter Magnus; Ravn, Ole;

    1998-01-01

    -linear systems. GPC is model-based and in this paper we propose the use of a neural network for the modeling of the system. Based on the neural network model a controller with extended control horizon is developed and the implementation issues are discussed, with particular emphasis on an efficient Quasi...

  8. Blind separation of sources in nonlinear convolved mixture based on a novel network

    Institute of Scientific and Technical Information of China (English)

    胡英; 杨杰; 沈利

    2004-01-01

    Blind separation of independent sources from their nonlinear convoluted mixtures is a more realistic problem than from linear ones. A solution to this problem based on the Entropy Maximization principle is presented. First we propose a novel two-layer network as the de-mixing system to separate sources in nonlinear convolved mixture. In output layer of our network we use feedback network architecture to cope with convoluted mixtures. Then we derive learning algorithms for the two-layer network by maximizing the information entropy. Based on the comparison of the computer simulation results, it can be concluded that the proposed algorithm has a better nonlinear convolved blind signal separation effect than the H.H. Y' s algorithm.

  9. Saturations-based nonlinear controllers with integral term: validation in real-time

    Science.gov (United States)

    Alatorre, A. G.; Castillo, P.; Mondié, S.

    2016-05-01

    Popular saturations-based nonlinear controller usually include proportional and derivative components of the state or output. The fact that in many applications, these components do not suffice to insure the convergence to the desired output values, motivate the addition of an integral term. In this paper, three configurations of nonlinear controllers based on saturation functions are improved with an integral component. The stability of the three algorithms is analysed using the Lyapunov theory. Simulation results validate the proposed control laws when they are applied to nonlinear systems with constant and unknown perturbations. Real-time experiments realised with a quad-rotor aerial vehicle and a hovercraft vehicle show that the proposed scheme can follow autonomously some trajectories, and that it could be robust with respect to delays.

  10. NONLINEAR DYNAMICS OF AXIALLY ACCELERATING VISCOELASTIC BEAMS BASED ON DIFFERENTIAL QUADRATURE

    Institute of Scientific and Technical Information of China (English)

    Hu Ding; Liqun Chen

    2009-01-01

    This paper investigates nonlinear dynamical behaviors in transverse motion of an axially accelerating viscoelastic beam via the differential quadrature method. The governing equa-tion, a nonlinear partial-differential equation, is derived from the viscoelastic constitution relation using the material derivative. The differential quadrature scheme is developed to solve numeri-cally the governing equation. Based on the numerical solutions, the nonlinear dynamical behaviors presented in the case that the mean axial speed and the amplitude of the speed fluctuation are respectively varied while other parameters are fixed. The Lyapunov exponent and the initial value sensitivity of the different points of the beam, calculated from the time series based on the numer-ical solutions, are used to indicate periodic motions or chaotic motions occurring in the transverse motion of the axially accelerating viscoelastic beam.

  11. Support vector machine based nonlinear model multi-step-ahead optimizing predictive control

    Institute of Scientific and Technical Information of China (English)

    ZHONG Wei-min; PI Dao-ying; SUN You-xian

    2005-01-01

    A support vector machine with guadratic polynomial kernel function based nonlinear model multi-step-ahead optimizing predictive controller was presented. A support vector machine based predictive model was established by black-box identification. And a quadratic objective function with receding horizon was selected to obtain the controller output. By solving a nonlinear optimization problem with equality constraint of model output and boundary constraint of controller output using Nelder-Mead simplex direct search method, a sub-optimal control law was achieved in feature space. The effect of the controller was demonstrated on a recognized benchmark problem and a continuous-stirred tank reactor. The simulation results show that the multi-step-ahead predictive controller can be well applied to nonlinear system, with better performance in following reference trajectory and disturbance-rejection.

  12. Function Based Nonlinear Least Squares and Application to Jelinski--Moranda Software Reliability Model

    CERN Document Server

    Liu, Jingwei

    2011-01-01

    A function based nonlinear least squares estimation (FNLSE) method is proposed and investigated in parameter estimation of Jelinski-Moranda software reliability model. FNLSE extends the potential fitting functions of traditional least squares estimation (LSE), and takes the logarithm transformed nonlinear least squares estimation (LogLSE) as a special case. A novel power transformation function based nonlinear least squares estimation (powLSE) is proposed and applied to the parameter estimation of Jelinski-Moranda model. Solved with Newton-Raphson method, Both LogLSE and powLSE of Jelinski-Moranda models are applied to the mean time between failures (MTBF) predications on six standard software failure time data sets. The experimental results demonstrate the effectiveness of powLSE with optimal power index compared to the classical least--squares estimation (LSE), maximum likelihood estimation (MLE) and LogLSE in terms of recursively relative error (RE) index and Braun statistic index.

  13. IMAGE-BASED VISUAL SERVOING FOR ROBOTIC SYSTEMS: A NONLINEAR LYAPUNOV-BASED CONTROL APPROACH

    Science.gov (United States)

    The objective of this project is to enable current and future EM robots with an increased ability to perceive and interact with unstructured and unknown environments through the use of camera-based visual servo controlled robots. The scientific goals of this research are to devel...

  14. Leveraging nonlinear saturation-based phenomena in an L-shaped vibration energy harvesting system

    Science.gov (United States)

    Harne, R. L.; Sun, A.; Wang, K. W.

    2016-02-01

    Trees exploit intriguing mechanisms such as multimodal frequency distributions and nonlinearities to distribute and dampen the aerodynamically-induced vibration energies to which they are subjected. In dynamical systems, these mechanisms are comparable to internal resonance phenomena. In recent years, researchers have harnessed strong nonlinearities, including internal resonance, to induce energetic dynamics that enhance performance of vibration energy harvesting systems. For trees, the internal resonance-like dynamics are evidently useful to dampen swaying motions in spite of the high variation associated with excitation and structural parameters. Yet for dynamic systems, studies show narrow operating regimes which exhibit internal resonance-based behaviors; this additionally suggests that the energetic dynamics may be susceptible to deactivation if stochastic inputs corrupt ideal excitation properties. To address these issues and to investigate whether the underlying motivation of exploiting internal resonance-induced saturation dynamics is truly justified, this research evaluates the opportunities enabled by exploiting nonlinear, multimodal motions in an L-shaped energy harvester platform. The system dynamics are probed analytically, numerically, and experimentally for comprehensive insights on the versatility of internal resonance-based behaviors for energy harvesting. It is found that although activating the high amplitude nonlinear dynamics to enhance power generation is robust to significant additive noise in the harmonic excitations, parameter sensitivities may pose practical challenges in application. Discussion is provided on means to address such concerns and on future strategies that may favorably exploit nonlinearity and multimodal dynamics for robust energy harvesting performance.

  15. Nonlinear Dynamics of Ultra-Cold Gas: Collapse of Bose Gas With Attractive Interaction

    OpenAIRE

    Flambaum, V. V.; Kuznetsov, E.

    2012-01-01

    Solutions for the Nonlinear Schrodinger equation for collapsing Bose gas with attraction. This is a copy of the paper published in 1992 in Proceedings of NATO Advanced Research workshop on Singularities in Fluids, Plasmas and Optics (Heraklion, Greece) edited by R.E. Caflisch and G.C. Papanicolaou (Kluwer Academic).

  16. Cross-polarized wave generation by effective cubic nonlinear optical interaction.

    Science.gov (United States)

    Petrov, G I; Albert, O; Etchepare, J; Saltiel, S M

    2001-03-15

    A new cubic nonlinear optical effect in which a linearly polarized wave propagating in a single quadratic medium is converted into a wave that is cross polarized to the input wave is observed in BBO crystal. The effect is explained by cascading of two different second-order processes: second-harmonic generation and difference frequency mixing. PMID:18040322

  17. Interactive analysis of geodata based intelligence

    Science.gov (United States)

    Wagner, Boris; Eck, Ralf; Unmüessig, Gabriel; Peinsipp-Byma, Elisabeth

    2016-05-01

    When a spatiotemporal events happens, multi-source intelligence data is gathered to understand the problem, and strategies for solving the problem are investigated. The difficulties arising from handling spatial and temporal intelligence data represent the main problem. The map might be the bridge to visualize the data and to get the most understand model for all stakeholders. For the analysis of geodata based intelligence data, a software was developed as a working environment that combines geodata with optimized ergonomics. The interaction with the common operational picture (COP) is so essentially facilitated. The composition of the COP is based on geodata services, which are normalized by international standards of the Open Geospatial Consortium (OGC). The basic geodata are combined with intelligence data from images (IMINT) and humans (HUMINT), stored in a NATO Coalition Shared Data Server (CSD). These intelligence data can be combined with further information sources, i.e., live sensors. As a result a COP is generated and an interaction suitable for the specific workspace is added. This allows the users to work interactively with the COP, i.e., searching with an on board CSD client for suitable intelligence data and integrate them into the COP. Furthermore, users can enrich the scenario with findings out of the data of interactive live sensors and add data from other sources. This allows intelligence services to contribute effectively to the process by what military and disaster management are organized.

  18. Implementation of neural network based non-linear predictive

    DEFF Research Database (Denmark)

    Sørensen, Paul Haase; Nørgård, Peter Magnus; Ravn, Ole; Poulsen, Niels Kjølstad

    -linear systems. GPC is model-based and in this paper we propose the use of a neural network for the modeling of the system. Based on the neural network model a controller with extended control horizon is developed and the implementation issues are discussed, with particular emphasis on an efficient Quasi......-Newton optimization algorithm. The performance is demonstrated on a pneumatic servo system....

  19. Nonlinear Hamiltonian modelling of magnetic shape memory alloy based actuators.

    OpenAIRE

    Gauthier, Jean-Yves; Hubert, Arnaud; Abadie, Joël; Chaillet, Nicolas; Lexcellent, Christian

    2008-01-01

    This paper proposes an application of the Lagrangian formalism and its Hamiltonian extension to design, model and control a mechatronic system using Magnetic Shape Memory Alloys. In this aim, an original dynamical modelling of a Magnetic Shape Memory Alloy based actuator is presented. Energy-based techniques are used to obtain a coherent modelling of the magnetical, mechanical and thermodynamic phenomena. The Lagrangian formalism, well suited in such a case, is introduced and used to take int...

  20. Non-linear finite element analysis for prediction of seismic response of buildings considering soil-structure interaction

    Directory of Open Access Journals (Sweden)

    E. Çelebi

    2012-11-01

    Full Text Available The objective of this paper focuses primarily on the numerical approach based on two-dimensional (2-D finite element method for analysis of the seismic response of infinite soil-structure interaction (SSI system. This study is performed by a series of different scenarios that involved comprehensive parametric analyses including the effects of realistic material properties of the underlying soil on the structural response quantities. Viscous artificial boundaries, simulating the process of wave transmission along the truncated interface of the semi-infinite space, are adopted in the non-linear finite element formulation in the time domain along with Newmark's integration. The slenderness ratio of the superstructure and the local soil conditions as well as the characteristics of input excitations are important parameters for the numerical simulation in this research. The mechanical behavior of the underlying soil medium considered in this prediction model is simulated by an undrained elasto-plastic Mohr-Coulomb model under plane-strain conditions. To emphasize the important findings of this type of problems to civil engineers, systematic calculations with different controlling parameters are accomplished to evaluate directly the structural response of the vibrating soil-structure system. When the underlying soil becomes stiffer, the frequency content of the seismic motion has a major role in altering the seismic response. The sudden increase of the dynamic response is more pronounced for resonance case, when the frequency content of the seismic ground motion is close to that of the SSI system. The SSI effects under different seismic inputs are different for all considered soil conditions and structural types.

  1. Fuzzy rule base design using tabu search algorithm for nonlinear system modeling.

    Science.gov (United States)

    Bagis, Aytekin

    2008-01-01

    This paper presents an approach to fuzzy rule base design using tabu search algorithm (TSA) for nonlinear system modeling. TSA is used to evolve the structure and the parameter of fuzzy rule base. The use of the TSA, in conjunction with a systematic neighbourhood structure for the determination of fuzzy rule base parameters, leads to a significant improvement in the performance of the model. To demonstrate the effectiveness of the presented method, several numerical examples given in the literature are examined. The results obtained by means of the identified fuzzy rule bases are compared with those belonging to other modeling approaches in the literature. The simulation results indicate that the method based on the use of a TSA performs an important and very effective modeling procedure in fuzzy rule base design in the modeling of the nonlinear or complex systems. PMID:17945233

  2. Interactive Knowledge Acquisition in Case Based Reasoning

    OpenAIRE

    Cordier, Amélie; Fuchs, Béatrice; Lieber, Jean; Mille, Alain

    2007-01-01

    International audience In Case Based Reasoning (CBR), knowledge acquisition plays an important role as it allows to progressively improve the system's competencies. One of the approaches of knowledge acquisition consists in performing it while the system is used to solve a problem. An advantage of this strategy is that it is not to constraining for the expert: the system exploits its interactions to acquire pieces of knowledge it needs to solve the current problem and takes the opportunity...

  3. Image-Based Visual Servoing for Robotic Systems: A Nonlinear Lyapunov-Based Control Approach

    International Nuclear Information System (INIS)

    There is significant motivation to provide robotic systems with improved autonomy as a means to significantly accelerate deactivation and decommissioning (DandD) operations while also reducing the associated costs, removing human operators from hazardous environments, and reducing the required burden and skill of human operators. To achieve improved autonomy, this project focused on the basic science challenges leading to the development of visual servo controllers. The challenge in developing these controllers is that a camera provides 2-dimensional image information about the 3-dimensional Euclidean-space through a perspective (range dependent) projection that can be corrupted by uncertainty in the camera calibration matrix and by disturbances such as nonlinear radial distortion. Disturbances in this relationship (i.e., corruption in the sensor information) propagate erroneous information to the feedback controller of the robot, leading to potentially unpredictable task execution. This research project focused on the development of a visual servo control methodology that targets compensating for disturbances in the camera model (i.e., camera calibration and the recovery of range information) as a means to achieve predictable response by the robotic system operating in unstructured environments. The fundamental idea is to use nonlinear Lyapunov-based techniques along with photogrammetry methods to overcome the complex control issues and alleviate many of the restrictive assumptions that impact current robotic applications. The outcome of this control methodology is a plug-and-play visual servoing control module that can be utilized in conjunction with current technology such as feature recognition and extraction to enable robotic systems with the capabilities of increased accuracy, autonomy, and robustness, with a larger field of view (and hence a larger workspace). The developed methodology has been reported in numerous peer-reviewed publications and the

  4. GA-based tuning of nonlinear observers for sensorless control of IPMSMs

    OpenAIRE

    Bhangu, B S; Bingham, Chris

    2004-01-01

    The paper considers two observer-based rotor position estimation schemes for sensorless control of interior permanent magnet synchronous machines (IPMSMs). Emphasis is given to techniques based on feedback linearisation followed by Luenberger observer design, and direct design of nonlinear observers. Genetic algorithms (GAs) based on the principles of evolution, natural selection and genetic mutation are employed to address difficulties in selecting correction gains for the observers, since n...

  5. Effects on the Floor Response Spectra by the Nonlinear Behavior of a Seismic Base Isolation System

    International Nuclear Information System (INIS)

    An evaluation of safety being carried out for various risk factors of prevents for nuclear power plant accident. In general, an evaluation of the structural integrity was performed about seismic risk. In recent years, an assessment of integrity of internal equipment being carried out for earthquake loads owing to the possibility of severe accidents caused by the destruction of internal equipment or a blackout. Floor response spectra of the structure should be sought for evaluating of the integrity of internal equipment. The floor response spectra depends on the characteristics of seismic base isolation system such as the natural frequency, damping ratio, and height of the floor of the structure. An evaluation of the structural integrity using the equivalent stiffness of the seismic base isolation system was satisfactory. In this study, the effect of the non-linearity of isolated system in the floor response spectrum of the structure is analyzed. In this study, the floor response spectrum of the seismic base isolation system by the non-linear effect of the rubber isolator was analyzed. As a result, the influence of the non-linear isolated system was increased in hi-frequency domain. In addition, each floor exhibited a more different of responses compared with the equivalent linear model of the isolated structure. The non-linearity of the isolation system of the structure was considered, because of a more reliable assessment of integrity of equipment at each floor of seismic base the isolation system

  6. Nonlinear Dynamic Behaviors of Rotated Blades with Small Breathing Cracks Based on Vibration Power Flow Analysis

    Directory of Open Access Journals (Sweden)

    Hailong Xu

    2016-01-01

    Full Text Available Rotated blades are key mechanical components in turbomachinery and high cycle fatigues often induce blade cracks. Accurate detection of small cracks in rotated blades is very significant for safety, reliability, and availability. In nature, a breathing crack model is fit for a small crack in a rotated blade rather than other models. However, traditional vibration displacements-based methods are less sensitive to nonlinear characteristics due to small breathing cracks. In order to solve this problem, vibration power flow analysis (VPFA is proposed to analyze nonlinear dynamic behaviors of rotated blades with small breathing cracks in this paper. Firstly, local flexibility due to a crack is derived and then time-varying dynamic model of the rotated blade with a small breathing crack is built. Based on it, the corresponding vibration power flow model is presented. Finally, VPFA-based numerical simulations are done to validate nonlinear behaviors of the cracked blade. The results demonstrate that nonlinear behaviors of a crack can be enhanced by power flow analysis and VPFA is more sensitive to a small breathing crack than displacements-based vibration analysis. Bifurcations will occur due to breathing cracks and subharmonic resonance factors can be defined to identify breathing cracks. Thus the proposed method can provide a promising way for detecting and predicting small breathing cracks in rotated blades.

  7. Scene matching based on non-linear pre-processing on reference image and sensed image

    Institute of Scientific and Technical Information of China (English)

    Zhong Sheng; Zhang Tianxu; Sang Nong

    2005-01-01

    To solve the heterogeneous image scene matching problem, a non-linear pre-processing method for the original images before intensity-based correlation is proposed. The result shows that the proper matching probability is raised greatly. Especially for the low S/N image pairs, the effect is more remarkable.

  8. A new approach of binary addition and subtraction by non-linear material based switching technique

    Indian Academy of Sciences (India)

    Archan Kumar Das; Partha Partima Das; Sourangshu Mukhopadhyay

    2005-02-01

    Here, we refer a new proposal of binary addition as well as subtraction in all-optical domain by exploitation of proper non-linear material-based switching technique. In this communication, the authors extend this technique for both adder and subtractor accommodating the spatial input encoding system.

  9. A finite element-based perturbation method for nonlinear free vibration analysis of composite cylindrical shells

    NARCIS (Netherlands)

    Rahman, T.; Jansen, E.L.; Tiso, P.

    2011-01-01

    In this paper, a finite element-based approach for nonlinear vibration analysis of shell structures is presented. The approach makes use of a perturbation method that gives an approximation for the amplitude-frequency relation of the structure. The method is formulated using a functional notation an

  10. Cascaded Optical Buffer Based on Nonlinear Polarization Rotation in Semiconductor Optical Amplifiers

    Institute of Scientific and Technical Information of China (English)

    CHENG Mu; WU Chong-Qing; LIU Hua

    2008-01-01

    A cascaded buffer based on nonlinear polarization rotation in semiconductor optical amplifiers is proposed, which is suitable for fast reconfiguration of buffering time at picoseconds. With the proposed buffer, sixty different buffer times are demonstrated at 2.5 Gb/s.

  11. Sensitivity of acoustic nonlinearity parameter to the microstructural changes in cement-based materials

    Science.gov (United States)

    Kim, Gun; Kim, Jin-Yeon; Kurtis, Kimberly E.; Jacobs, Laurence J.

    2015-03-01

    This research experimentally investigates the sensitivity of the acoustic nonlinearity parameter to microcracks in cement-based materials. Based on the second harmonic generation (SHG) technique, an experimental setup using non-contact, air-coupled detection is used to receive the consistent Rayleigh surface waves. To induce variations in the extent of microscale cracking in two types of specimens (concrete and mortar), shrinkage reducing admixture (SRA), is used in one set, while a companion specimen is prepared without SRA. A 50 kHz wedge transducer and a 100 kHz air-coupled transducer are implemented for the generation and detection of nonlinear Rayleigh waves. It is shown that the air-coupled detection method provides more repeatable fundamental and second harmonic amplitudes of the propagating Rayleigh waves. The obtained amplitudes are then used to calculate the relative nonlinearity parameter βre, the ratio of the second harmonic amplitude to the square of the fundamental amplitude. The experimental results clearly demonstrate that the nonlinearity parameter (βre) is highly sensitive to the microstructural changes in cement-based materials than the Rayleigh phase velocity and attenuation and that SRA has great potential to avoid shrinkage cracking in cement-based materials.

  12. Nonlinear Model-Based Fault Detection for a Hydraulic Actuator

    NARCIS (Netherlands)

    Van Eykeren, L.; Chu, Q.P.

    2011-01-01

    This paper presents a model-based fault detection algorithm for a specific fault scenario of the ADDSAFE project. The fault considered is the disconnection of a control surface from its hydraulic actuator. Detecting this type of fault as fast as possible helps to operate an aircraft more cost effect

  13. Nonlinear stimulated Brillouin scattering based photonic signal processors

    Energy Technology Data Exchange (ETDEWEB)

    Minasian, Robert A. [School of Electrical and Information Engineering, Institute of Photonics and Optical Science, University of Sydney, NSW, Sydney, 2006 (Australia)

    2014-10-06

    Recent new methods in photonic signal processing based on stimulated Brillouin scattering, that enable the realization of photonic mixers with high conversion efficiency, ultra-wide continuously tunable high-resolution microwave photonic filters and programmable switchable microwave photonic tunable filters, are presented. These processors provide new capabilities for the realisation of high-performance and high-resolution signal processing.

  14. Nonlinear stimulated Brillouin scattering based photonic signal processors

    International Nuclear Information System (INIS)

    Recent new methods in photonic signal processing based on stimulated Brillouin scattering, that enable the realization of photonic mixers with high conversion efficiency, ultra-wide continuously tunable high-resolution microwave photonic filters and programmable switchable microwave photonic tunable filters, are presented. These processors provide new capabilities for the realisation of high-performance and high-resolution signal processing

  15. New nonlinear optical effect: self-reflection phenomenon due to exciton-biexciton-light interaction in semiconductors

    Science.gov (United States)

    Khadzhi, P. I.; Lyakhomskaya, K. D.; Nadkin, L. Y.; Markov, D. A.

    2002-05-01

    The characteristic peculiarities of the self-reflection of a strong electromagnetic wave in a system of coherent excitons and biexcitons due to the exciton-photon interaction and optical exciton-biexciton conversion in semiconductors were investigated as one of the manifestations of nonlinear optical Stark-effect. It was found that a monotonously decreasing standing wave with an exponential decreasing spatial tail is formed in the semiconductor. Under the action of the field of a strong pulse, an optically homogeneous medium is converted, into the medium with distributed feedback. The appearance of the spatially separated narrow pears of the reflective index, extinction and reflection coefficients is predicted.

  16. Application of the non-linear harmonic method to study the rotor-stator interaction in Francis-99 test case

    Science.gov (United States)

    Buron, J. D.; Houde, S.; Lestriez, R.; Deschênes, C.

    2015-01-01

    Steady state and non-linear harmonic (NLH) flow simulations were performed within the framework of the Francis-99 project in order to assess the capacity of the NLH method to capture the main pressure fluctuations associated with the rotor-stator interactions between the distributor and the runner of the turbine. This paper focusses on the methodology developed to obtain harmonic solutions and presents preliminary results from the simulations using the flow solver NUMECA FineTURBO on intermediate grid level meshes. Comparisons of the first simulations to experimental data reveal good agreement concerning the predicted pressure amplitudes notably at high load operating condition.

  17. Numerical simulation of the interaction between a nonlinear elastic structure and compressible flow by the discontinuous Galerkin method

    Czech Academy of Sciences Publication Activity Database

    Kosík, Adam; Feistauer, M.; Hadrava, Martin; Horáček, Jaromír

    2015-01-01

    Roč. 267, September (2015), s. 382-396. ISSN 0096-3003 R&D Projects: GA ČR(CZ) GAP101/11/0207 Institutional support: RVO:61388998 Keywords : discontinuous Galerkin method * nonlinear elasticity * compressible viscous flow * fluid–structure interaction Subject RIV: BI - Acoustics Impact factor: 1.551, year: 2014 http://www.sciencedirect.com/science/article/pii/S0096300315002453/pdfft?md5=02d46bc730e3a7fb8a5008aaab1da786&pid=1-s2.0-S0096300315002453-main.pdf

  18. Study of giant resonances in stable and unstable nuclei in relativistic RPA with non-linear interactions

    International Nuclear Information System (INIS)

    The nuclear isoscalar and isovector giant resonances in stable and unstable nuclei are studied in the framework of the relativistic random phase approximation. The classical meson propagators with non-linear self-interactions are constructed in momentum space from the second variation of the action. The relativistic models with the parameter sets, TM1 and NL-SH, which provide good account of static ground state properties, can also well describe the collective states of nuclei, such as giant resonances. The isovector giant dipole resonances in the unstable Ar-isotope chain are investigated. (author)

  19. ARTICLES: Nonlinear interaction of infrared waves on a VO2 surface at a semiconductor-metal phase transition

    Science.gov (United States)

    Berger, N. K.; Zhukov, E. A.; Novokhatskiĭ, V. V.

    1984-04-01

    The use of a semiconductor-metal phase transition for wavefront reversal of laser radiation was proposed. An investigation was made of nonlinear reflection of CO2 laser radiation at a phase transition in VO2. A three-wave interaction on a VO2 surface was achieved using low-power cw and pulsed CO2 lasers. In the first case, the intensity reflection coefficient was 0.5% for a reference wave intensity of 0.9 W/cm2 and in the second case, it was 42% for a threshold reference wave energy density of 0.6-0.8 mJ/cm2.

  20. A framework for simulating ultrasound imaging based on first order nonlinear pressure–velocity relations

    DEFF Research Database (Denmark)

    Du, Yigang; Fan, Rui; Li, Yong;

    2016-01-01

    An ultrasound imaging framework modeled with the first order nonlinear pressure–velocity relations (NPVR) based simulation and implemented by a half-time staggered solution and pseudospectral method is presented in this paper. The framework is capable of simulating linear and nonlinear ultrasound...... ultrasound image can be obtained by beamforming the simulated channel data. Various results simulated by different algorithms are illustrated for comparisons. The root mean square (RMS) errors for each compared pulses are calculated. The linear propagation is validated by an angular spectrum approach (ASA...

  1. Likelihood-based inference for cointegration with nonlinear error-correction

    DEFF Research Database (Denmark)

    Kristensen, Dennis; Rahbek, Anders Christian

    2010-01-01

    We consider a class of nonlinear vector error correction models where the transfer function (or loadings) of the stationary relationships is nonlinear. This includes in particular the smooth transition models. A general representation theorem is given which establishes the dynamic properties of the...... linear trend in general. Gaussian likelihood-based estimators are considered for the long-run cointegration parameters, and the short-run parameters. Asymptotic theory is provided for these and it is discussed to what extend asymptotic normality and mixed normality can be found. A simulation study...

  2. UNDERSTANDING THE APPLICABILITY OF LINEAR & NON-LINEAR MODELS USING A CASE-BASED STUDY

    OpenAIRE

    Gaurav Singh Thakur; Anubhav Gupta; Ankur Bhardwaj; Biju R Mohan

    2014-01-01

    This paper uses a case based study – “product sales estimation” on real-time data to help us understand the applicability of linear and non-linear models in machine learning and data mining. A systematic approach has been used here to address the given problem statement of sales estimation for a particular set of products in multiple categories by applying both linear and non-linear machine learning techniques on a data set of selected features from the original data set. Feature ...

  3. Nonlinear Control of Wind Turbines with Hydrostatic Transmission Based on Takagi-Sugeno Model

    International Nuclear Information System (INIS)

    A nonlinear model-based control concept for wind turbines with hydrostatic transmission is proposed. The complete mathematical model of a wind turbine drive train with variable displacement pump and variable displacement motor is presented. The controller design takes into consideration the nonlinearity of the aerodynamic maps and hydrostatic drive train by an convex combination of state space controller with measurable generator speed and hydraulic motor displacement as scheduling parameters. The objectives are the set point control of generator speed and tracking control of the rotor speed to reach the maximum power according to the power curve in the partial-load region

  4. Nonlinear Control of Wind Turbines with Hydrostatic Transmission Based on Takagi-Sugeno Model

    Science.gov (United States)

    Schulte, Horst; Georg, Soren

    2014-06-01

    A nonlinear model-based control concept for wind turbines with hydrostatic transmission is proposed. The complete mathematical model of a wind turbine drive train with variable displacement pump and variable displacement motor is presented. The controller design takes into consideration the nonlinearity of the aerodynamic maps and hydrostatic drive train by an convex combination of state space controller with measurable generator speed and hydraulic motor displacement as scheduling parameters. The objectives are the set point control of generator speed and tracking control of the rotor speed to reach the maximum power according to the power curve in the partial-load region.

  5. Precipitate Contribution to the Acoustic Nonlinearity in Nickel-Based Superalloy

    Institute of Scientific and Technical Information of China (English)

    Chung-Seok KIM; Cliff J.LISSENDEN

    2009-01-01

    The influence of γ' precipitate on the acoustic nonlinearity is investigated for a nickel-based superalloy,which is subjected to creep deformation.During creep deformation,the cuboidal γ' precipitate is preferentially coarsened in a direction perpendicular to the applied stress axis.The length and shape factor of the γ' precipitate increase with creep time.The increase of relative acoustic nonlinearity with increasing fraction of creep life is discussed in relation to the rafting of γ' precipitate,which is closely related to the scattering and distortion of the acoustic wave.

  6. Vehicle position estimation using GPS/CAN data based on nonlinear programming

    Czech Academy of Sciences Publication Activity Database

    Pavelková, Lenka

    Cambridge: IASTED, 2011 - (Whidborne, J.; Willis, P.), s. 208-215 ISBN 978-0-88986-889-2. [13th IASTED International Conference on Intelligent Systems and Control. Cambridge (GB), 11.07.2011-13.07.2011] R&D Projects: GA MŠk(CZ) 1M0572; GA ČR GA102/08/0567 Institutional research plan: CEZ:AV0Z10750506 Keywords : nonlinear state-space model * state filtering * incomplete data * bounded noise * vehicle position estimation Subject RIV: BC - Control Systems Theory http://library.utia.cas.cz/separaty/2011/AS/pavelkova-vehicle position estimation using gps -can data based on nonlinear programming.pdf

  7. Nonlinear dynamic analysis of a structure with a friction-based seismic base isolation system

    NARCIS (Netherlands)

    Suy, H.M.R.; Fey, R.H.B.; Galanti, F.M.B.; Nijmeijer, H.

    2007-01-01

    Many dynamical systems are subject to some form of non-smooth or discontinuous nonlinearity. One eminent example of such a nonlinearity is friction. This is caused by the fact that friction always opposes the direction of movement, thus changing sign when the sliding velocity changes sign. In this p

  8. A new nonlinear turbulence model based on Partially-Averaged Navier-Stokes Equations

    International Nuclear Information System (INIS)

    Partially-averaged Navier-Stokes (PANS) Model was recognized as a Reynolds-averaged Navier-Stokes (RANS) to direct numerical simulation (DNS) bridging method. PANS model was purported for any filter width-from RANS to DNS. PANS method also shared some similarities with the currently popular URANS (unsteady RANS) method. In this paper, a new PANS model was proposed, which was based on RNG k-ε turbulence model. The Standard and RNG k-ε turbulence model were both isotropic models, as well as PANS models. The sheer stress in those PANS models was solved by linear equation. The linear hypothesis was not accurate in the simulation of complex flow, such as stall phenomenon. The sheer stress here was solved by nonlinear method proposed by Ehrhard. Then, the nonlinear PANS model was set up. The pressure coefficient of the suction side of the NACA0015 hydrofoil was predicted. The result of pressure coefficient agrees well with experimental result, which proves that the nonlinear PANS model can capture the high pressure gradient flow. A low specific centrifugal pump was used to verify the capacity of the nonlinear PANS model. The comparison between the simulation results of the centrifugal pump and Particle Image Velocimetry (PIV) results proves that the nonlinear PANS model can be used in the prediction of complex flow field

  9. A Fully Associative, Non-Linear Kinematic, Unified Viscoplastic Model for Titanium Based Matrices

    Science.gov (United States)

    Arnold, S. M.; Saleeb, A. F.; Castelli, M. G.

    1994-01-01

    Specific forms for both the Gibb's and complementary dissipation potentials are chosen such that a complete (i.e., fully associative) potential based multiaxial unified viscoplastic model is obtained. This model possesses one tensorial internal state variable that is associated with dislocation substructure, with an evolutionary law that has nonlinear kinematic hardening and both thermal and strain induced recovery mechanisms. A unique aspect of the present model is the inclusion of non-linear hardening through the use of a compliance operator, derived from the Gibb's potential, in the evolution law for the back stress. This non-linear tensorial operator is significant in that it allows both the flow and evolutionary laws to be fully associative (and therefore easily integrated) and greatly influences the multiaxial response under non-proportional loading paths. In addition to this nonlinear compliance operator, a new consistent, potential preserving, internal strain unloading criterion has been introduced to prevent abnormalities in the predicted stress-strain curves, which are present with nonlinear hardening formulations, during unloading and reversed loading of the external variables. Specification of an experimental program for the complete determination of the material functions and parameters for characterizing a metallic matrix, e.g., TIMETAL 21S, is given. The experiments utilized are tensile, creep, and step creep tests. Finally, a comparison of this model and a commonly used Bodner-Partom model is made on the basis of predictive accuracy and numerical efficiency.

  10. Characteristics of the Main Journal Bearings of an Engine Based on Non-linear Dynamics

    Institute of Scientific and Technical Information of China (English)

    NI Guangjian; ZHANG Junhong; CHENG Xiaoming

    2009-01-01

    Many simple nonlinear main journal bearing models have been studied theoretically, but the connection to existing engineering system has not been equally investigated. The consideration of the characteristics of engine main journal bearings may provide a prediction of the bearing load and lubrication. Due to the strong non-linear features in bearing lubrication procedure, it is difficult to predict those characteristics. A non-linear dynamic model is described for analyzing the characteristics of engine main journal bearings. Components such as crankshaft, main journals and con rods are found by applying the finite element method. Non-linear spring/dampers are introduced to imitate the constraint and supporting functions provided by the main bearing and oil film. The engine gas pressure is imposed as excitation on the model via the engine piston, con rod, etc. The bearing reaction force is calculated over one engine cycle, and meanwhile, the oil film thickness and pressure distribution are obtained based on Reynolds differential equation. It can be found that the maximum bearing reaction force always occurs when the maximum cylinder pressure arises in the cylinder adjacent to that bearing. The simulated minimum oil film thickness, which is 3 μm, demonstrates the reliability of the main journal bearings. This non-linear dynamic analysis may save computing efforts of engine main bearing design and also is of good precision and close connection to actual engine main journal bearing conditions.

  11. A chaotic communication system of improved performance based on the Derivative-free nonlinear Kalman filter

    Science.gov (United States)

    Rigatos, Gerasimos

    2016-07-01

    The Derivative-free nonlinear Kalman Filter is used for developing a communication system that is based on a chaotic modulator such as the Duffing system. In the transmitter's side, the source of information undergoes modulation (encryption) in which a chaotic signal generated by the Duffing system is the carrier. The modulated signal is transmitted through a communication channel and at the receiver's side demodulation takes place, after exploiting the estimation provided about the state vector of the chaotic oscillator by the Derivative-free nonlinear Kalman Filter. Evaluation tests confirm that the proposed filtering method has improved performance over the Extended Kalman Filter and reduces significantly the rate of transmission errors. Moreover, it is shown that the proposed Derivative-free nonlinear Kalman Filter can work within a dual Kalman Filtering scheme, for performing simultaneously transmitter-receiver synchronisation and estimation of unknown coefficients of the communication channel.

  12. Observer-based Adaptive Iterative Learning Control for Nonlinear Systems with Time-varying Delays

    Institute of Scientific and Technical Information of China (English)

    Wei-Sheng Chen; Rui-Hong Li; Jing Li

    2010-01-01

    An observer-based adaptive iterative learning control (AILC) scheme is developed for a class of nonlinear systems with unknown time-varying parameters and unknown time-varying delays. The linear matrix inequality (LMI) method is employed to design the nonlinear observer. The designed controller contains a proportional-integral-derivative (PID) feedback term in time domain. The learning law of unknown constant parameter is differential-difference-type, and the learning law of unknown time-varying parameter is difference-type. It is assumed that the unknown delay-dependent uncertainty is nonlinearly parameterized. By constructing a Lyapunov-Krasovskii-like composite energy function (CEF), we prove the boundedness of all closed-loop signals and the convergence of tracking error. A simulation example is provided to illustrate the effectiveness of the control algorithm proposed in this paper.

  13. NONLINEAR FILTER METHOD OF GPS DYNAMIC POSITIONING BASED ON BANCROFT ALGORITHM

    Institute of Scientific and Technical Information of China (English)

    ZHANGQin; TAOBen-zao; ZHAOChao-ying; WANGLi

    2005-01-01

    Because of the ignored items after linearization, the extended Kalman filter (EKF) becomes a form of suboptimal gradient descent algorithm. The emanative tendency exists in GPS solution when the filter equations are ill-posed. The deviation in the estimation cannot be avoided. Furthermore, the true solution may be lost in pseudorange positioning because the linearized pseudorange equations are partial solutions. To solve the above problems in GPS dynamic positioning by using EKF, a closed-form Kalman filter method called the two-stage algorithm is presented for the nonlinear algebraic solution of GPS dynamic positioning based on the global nonlinear least squares closed algorithm--Bancroft numerical algorithm of American. The method separates the spatial parts from temporal parts during processing the GPS filter problems, and solves the nonlinear GPS dynamic positioning, thus getting stable and reliable dynamic positioning solutions.

  14. On the Nonlinear Behavior of the Piezoelectric Coupling on Vibration-Based Energy Harvesters

    Directory of Open Access Journals (Sweden)

    Luciana L. Silva

    2015-01-01

    Full Text Available Vibration-based energy harvesting with piezoelectric elements has an increasing importance nowadays being related to numerous potential applications. A wide range of nonlinear effects is observed in energy harvesting devices and the analysis of the power generated suggests that they have considerable influence on the results. Linear constitutive models for piezoelectric materials can provide inconsistencies on the prediction of the power output of the energy harvester, mainly close to resonant conditions. This paper investigates the effect of the nonlinear behavior of the piezoelectric coupling. A one-degree of freedom mechanical system is coupled to an electrical circuit by a piezoelectric element and different coupling models are investigated. Experimental tests available in the literature are employed as a reference establishing the best matches of the models. Subsequently, numerical simulations are carried out showing different responses of the system indicating that nonlinear piezoelectric couplings can strongly modify the system dynamics.

  15. Nonlinear adaptive control systems design of BTT missile based on fully tuned RBF neural networks

    Science.gov (United States)

    Hu, Yunan; Jin, Yuqiang; Li, Jing

    2003-09-01

    Based on fully tuned RBF neural networks and backstepping control techniques, a novel nonlinear adaptive control scheme is proposed for missile control systems with a general set of uncertainties. The effect of the uncertainties is synthesized one term in the design procedure. Then RBF neural networks are used to eliminate its effect. The nonlinear adaptive controller is designed using backstepping control techniques. The control problem is resolved while the control coefficient matrix is unknown. The adaptive tuning rules for updating all of the parameters of the fully tuned RBF neural networks are firstly derived by the Lyapunov stability theorem. Finally, nonlinear 6-DOF numerical simulation results for a BTT missile model are presented to demonstrate the effectiveness of the proposed method.

  16. Nonlinear consensus protocols for multi-agent systems based on centre manifold reduction

    Institute of Scientific and Technical Information of China (English)

    Li Yu-Mei; Guan Xin-Ping

    2009-01-01

    Nonlinear consensus protocols for dynamic directed networks of multi-agent systems with fixed and switching topologies are investigated separately in this paper. Based on the centre manifold reduction technique,nonlinear consensus protocols are presented.We prove that a group of agents can reach a β-consensus,the value of which is the group decision value varying from the minimum and the maximum values of the initial states of the agents.Moreover,we derive the conditions to guarantee that all the agents reach a β-consensus on a desired group decision value.Finally,a simulation study concerning the vertical alignment manoeuvere of a team of unmanned air vehicles is performed.Simulation results show that the nonlinear consensus protocols proposed are more effective than the linear protocols for the formation control of the agents and they are an improvement over existing protocols.

  17. Correlation dimension based nonlinear analysis of network traffics with different application protocols

    Institute of Scientific and Technical Information of China (English)

    Wang Jun-Song; Yuan Jing; Li Qiang; Yuan Rui-Xi

    2011-01-01

    This paper uses a correlation dimension based nonlinear analysis approach to analyse the dynamics of network traffics with three different application protocols-HTTP, FTP and SMTP. First, the phase space is reconstructed and the embedding parameters are obtained by the mutual information method. Secondly, the correlation dimensions of three different traffics are calculated and the results of analysis have demonstrated that the dynamics of the three different application protocol traffics is different from each other in nature, i.e. HTTP and FTP traffics are chaotic,furthermore, the former is more complex than the later; on the other hand, SMTP traffic is stochastic. It is shown that correlation dimension approach is an efficient method to understand and to characterize the nonlinear dynamics of HTTP, FTP and SMTP protocol network traffics. This analysis provided insight into and a more accurate understanding of nonlinear dynamics of internet traffics which have a complex mixture of chaotic and stochastic components.

  18. On Observer-Based Control of Nonlinear Systems

    OpenAIRE

    Robertsson, Anders

    1999-01-01

    Filtering and reconstruction of signals play a fundamental role in modern signal processing, telecommunications, and control theory and are used in numerous applications. The feedback principle is an important concept in control theory. Many different control strategies are based on the assumption that all internal states of the control object are available for feedback. In most cases, however, only a few of the states or some functions of the states can be measured. This circumstance ...

  19. A Nonlinear dynamical model for studying DNA damage-induced p53-Mdm2 interaction

    International Nuclear Information System (INIS)

    Exploring the nonlinear dynamics of the negative feedback loop composed of p53 and Mdm2 proteins, the authors propose a signal-response model to study the dynamical mechanism of the different oscillatory behaviors for the activities of p53 and Mdm2 proteins both in individual and population of cells. It is shown that the sustained and damped oscillatory dynamics could be described in a unified way when the dynamics of damage-derived signal is properly introduced. (authors)

  20. Improved Quark Mass Density-Dependent Model with Non-Linear Scalar Interaction

    Institute of Scientific and Technical Information of China (English)

    WU Chen; QIAN Wei-Liang; SU Ru-Keng

    2005-01-01

    @@ We present an improved quark mass density-dependent model which includes the quark and non-linear scalar field coupling. The wavefunction of quark is given. The rms charge radius, the magnetic moment, and the ratio between the axial-vector and the vectorβ-decay coupling constants of the nucleon are calculated. We find that the results given the present model are in agreement with experiments.

  1. Time-Spectral Visualization of Fundamental Ultrafast Nonlinear-Optical Interactions in Photonic Fibers

    OpenAIRE

    Efimov, Anatoly

    2010-01-01

    Thorough understanding of fundamental nonlinear processes occurring as optical signals propagate along a waveguide require obtaining as much experimental information as possible. It was recognized a long time ago (Treacy, 1971) that spectrogram representation of optical pulses, that is 2D plots of signal amplitude in time and frequency showing relative temporal positions of different frequency components comprising the pulse, is, in fact, the most intuitive and rich way to describe the pulse....

  2. Interaction dynamics and nontopological soliton stability in the essentially nonlinear model of a complex scalar field

    International Nuclear Information System (INIS)

    Stability and interaction dynamics of ''charged'' solitons in the framework of the relativistically invariant Klein-Gordon equation with the self-action of the ''current-current'' form are studied in numerical experiments. The particle-like solution stability region is found. The computations reveal a rich spectrum of interactions versus the particle-like soliton charge signs and velocities: weak inelastic interaction, inelastic interaction and production of an additional soliton

  3. Quantum Entanglement Concentration Based on Nonlinear Optics for Quantum Communications

    Directory of Open Access Journals (Sweden)

    Yu-Bo Sheng

    2013-05-01

    Full Text Available Entanglement concentration is of most importance in long distance quantum communication and quantum computation. It is to distill maximally entangled states from pure partially entangled states based on the local operation and classical communication. In this review, we will mainly describe two kinds of entanglement concentration protocols. One is to concentrate the partially entangled Bell-state, and the other is to concentrate the partially entangled W state. Some protocols are feasible in current experimental conditions and suitable for the optical, electric and quantum-dot and optical microcavity systems.

  4. Distributed model-based nonlinear sensor fault diagnosis in wireless sensor networks

    Science.gov (United States)

    Lo, Chun; Lynch, Jerome P.; Liu, Mingyan

    2016-01-01

    Wireless sensors operating in harsh environments have the potential to be error-prone. This paper presents a distributive model-based diagnosis algorithm that identifies nonlinear sensor faults. The diagnosis algorithm has advantages over existing fault diagnosis methods such as centralized model-based and distributive model-free methods. An algorithm is presented for detecting common non-linearity faults without using reference sensors. The study introduces a model-based fault diagnosis framework that is implemented within a pair of wireless sensors. The detection of sensor nonlinearities is shown to be equivalent to solving the largest empty rectangle (LER) problem, given a set of features extracted from an analysis of sensor outputs. A low-complexity algorithm that gives an approximate solution to the LER problem is proposed for embedment in resource constrained wireless sensors. By solving the LER problem, sensors corrupted by non-linearity faults can be isolated and identified. Extensive analysis evaluates the performance of the proposed algorithm through simulation.

  5. Nonlinear Statistical Process Monitoring Based on Control Charts with Memory Effect and Kernel Independent Component Analysis

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A novel nonlinear combination process monitoring method was proposed based on techniques with memory effect (multivariate exponentially weighted moving average (MEWMA)) and kernel independent component analysis (KICA). The method was developed for dealing with nonlinear issues and detecting small or moderate drifts in one or more process variables with autocorrelation. MEWMA charts use additional information from the past history of the process for keeping the memory effect of the process behavior trend. KICA is a recently developed statistical technique for revealing hidden, nonlinear statistically independent factors that underlie sets of measurements and it is a two-phase algorithm: whitened kernel principal component analysis (KPCA) plus independent component analysis (ICA). The application to the fluid catalytic cracking unit (FCCU) simulated process indicates that the proposed combined method based on MEWMA and KICA can effectively capture the nonlinear relationship and detect small drifts in process variables. Its performance significantly outperforms monitoring method based on ICA, MEWMA-ICA and KICA, especially for long-term performance deterioration.

  6. Nonlinear scoring functions for similarity-based ligand docking and binding affinity prediction.

    Science.gov (United States)

    Brylinski, Michal

    2013-11-25

    A common strategy for virtual screening considers a systematic docking of a large library of organic compounds into the target sites in protein receptors with promising leads selected based on favorable intermolecular interactions. Despite a continuous progress in the modeling of protein-ligand interactions for pharmaceutical design, important challenges still remain, thus the development of novel techniques is required. In this communication, we describe eSimDock, a new approach to ligand docking and binding affinity prediction. eSimDock employs nonlinear machine learning-based scoring functions to improve the accuracy of ligand ranking and similarity-based binding pose prediction, and to increase the tolerance to structural imperfections in the target structures. In large-scale benchmarking using the Astex/CCDC data set, we show that 53.9% (67.9%) of the predicted ligand poses have RMSD of <2 Å (<3 Å). Moreover, using binding sites predicted by recently developed eFindSite, eSimDock models ligand binding poses with an RMSD of 4 Å for 50.0-39.7% of the complexes at the protein homology level limited to 80-40%. Simulations against non-native receptor structures, whose mean backbone rearrangements vary from 0.5 to 5.0 Å Cα-RMSD, show that the ratio of docking accuracy and the estimated upper bound is at a constant level of ∼0.65. Pearson correlation coefficient between experimental and predicted by eSimDock Ki values for a large data set of the crystal structures of protein-ligand complexes from BindingDB is 0.58, which decreases only to 0.46 when target structures distorted to 3.0 Å Cα-RMSD are used. Finally, two case studies demonstrate that eSimDock can be customized to specific applications as well. These encouraging results show that the performance of eSimDock is largely unaffected by the deformations of ligand binding regions, thus it represents a practical strategy for across-proteome virtual screening using protein models. eSimDock is freely

  7. Nonlinear and multi-wave effects in fast-scale laser-plasma interactions

    Science.gov (United States)

    Lindberg, Ryan Roger

    A new model of kinetic effects in Langmuir wave dynamics is developed. A nonlinear distribution function is constructed that accounts for particle separatrix crossing and self-consistent electrostatic evolution, assuming that the Langmuir wave changes slowly with respect to the particle bounce frequency in the wave. Using simple physical arguments, the distribution function is shown to be nearly invariant in the canonical action, such that slow evolution results in an overall translation of the distribution in action. Requirements of self-consistency with the electrostatic potential yield the key properties of the nonlinear distribution function, including a frequency shift of the wave and the incoherent energy associated with developing the final, phase-mixed state. These Bernstein-Greene-Kruskal (BGK) type waves naturally arise in weakly driven, thermal plasmas, and extend earlier work on nonlinear plasma waves by Morales and O'Neil and by Dewar. The bulk properties of these BGK-type waves are used to develop a fluid model describing nonlinear, kinetic Langmuir waves in a driven plasma that is shown to agree closely with electrostatic particle simulations over a wide range of temperatures (0.1 ≤ klambdaD ≤ 0.4). This model is then applied to the fundamental problem of including kinetic effects in Raman backscatter. To obtain the coupled mode equations relevant to Raman backscatter in a plasma, we average the Vlasov-Maxwell system over the fine spatio-temporal scales of the laser phase. The resulting set of envelope equations coupling the two counter-propagating lasers with the plasma wave is then analyzed in two limits: that of an initial, linear Langmuir wave, and that of the time-asymptotic state in which the particles become phase-mixed in the wave. In the former limit, the standard natural frequency and Landau damping is obtained, while the latter case leads to a vanishing damping and a nonlinear frequency shift of the wave, in agreement with recent

  8. Regular and chaotic distribution of Bose-Einstein condensed atoms with a space-dependent nonlinear interaction

    International Nuclear Information System (INIS)

    This paper studies the regular and chaotic spatial distribution of Bose-Einstein condensed atoms with a space-dependent nonlinear interaction. There exists a steady atomic current in the system due to the space-dependent phase of condensate. For the system with a positive chemical potential and repulsive interatomic interaction, we construct the general solution of the 1st-order equation, whose boundedness conditions contain the famous Mel'nikov chaotic criterion. When the system doesn't satisfy the perturbation conditions, numerical simulations reveal that increasing the atomic current can destroy the spatial symmetry of the distributional structure of condensed atoms, whether the condensed atoms in a chaotic or regular distribution. (authors)

  9. Dynamical behaviours of the nonlinear atom-field interaction in the presence of classical gravity: f-deformation approach

    International Nuclear Information System (INIS)

    In this paper, we investigate the effects of a classical gravitational field on the dynamical behaviour of the nonlinear atom-field interaction within the framework of the f-deformed Jaynes-Cummings model. For this purpose, we first introduce a set of new atomic operators obeying an f-deformed su(2) algebraic structure to derive an effective Hamiltonian for the system under consideration. Then by solving the Schroedinger equation in the interaction picture and considering certain initial quantum states for the atomic and radiation subsystems, we analyse the influence of gravity on the temporal evolution of the atomic population inversion, atomic dipole squeezing, atomic momentum diffusion, photon counting statistics and deformed quadrature squeezing of the radiation field.

  10. Parameters Estimation and Stability Analysis of Nonlinear Fractional-Order Economic System Based on Empirical Data

    OpenAIRE

    Lei He; Xiong Wang

    2014-01-01

    This paper is devoted to propose a novel method for studying the macroeconomic system with fractional derivative, which can depict the memory property of actual data of economic variables. First of all, we construct a constrained optimal problem to evaluate the coefficients of nonlinear fractional financial system based on empirical data and design the corresponding genetic algorithm. Then, based on the stability criteria of fractional dynamical systems, the methodology of stability analysis ...

  11. Frequency domain analysis and design of nonlinear systems based on Volterra series expansion a parametric characteristic approach

    CERN Document Server

    Jing, Xingjian

    2015-01-01

    This book is a systematic summary of some new advances in the area of nonlinear analysis and design in the frequency domain, focusing on the application oriented theory and methods based on the GFRF concept, which is mainly done by the author in the past 8 years. The main results are formulated uniformly with a parametric characteristic approach, which provides a convenient and novel insight into nonlinear influence on system output response in terms of characteristic parameters and thus facilitate nonlinear analysis and design in the frequency domain.  The book starts with a brief introduction to the background of nonlinear analysis in the frequency domain, followed by recursive algorithms for computation of GFRFs for different parametric models, and nonlinear output frequency properties. Thereafter the parametric characteristic analysis method is introduced, which leads to the new understanding and formulation of the GFRFs, and nonlinear characteristic output spectrum (nCOS) and the nCOS based analysis a...

  12. A new interpretation of large amplitude earthquake acceleration from non-linear local soil-structure interaction

    Energy Technology Data Exchange (ETDEWEB)

    Kojima, Kotaro [Department of Architecture and Architectural Engineering, Kyoto University, Kyoto 615-8540 (Japan); Kamagata, Shuichi [Nuclear Power Department, Kajima Corporation, Tokyo 107-8348 (Japan); Takewaki, Izuru, E-mail: takewaki@archi.kyoto-u.ac.jp [Department of Architecture and Architectural Engineering, Kyoto University, Kyoto 615-8540 (Japan)

    2014-07-01

    Highlights: • A new interpretation of large earthquake accelerations is provided. • Non-linear interaction between an embedded building and its surrounding soil is a key. • A bi-linear restoring-force characteristic with a gap-slip process is used for analysis. • Ricker wavelet and a continuous sweep sinusoidal wave are adopted as input. • The amplification is induced by a higher mode due to the change of a support condition. - Abstract: A new interpretation of large amplitude earthquake accelerations recorded at the Kashiwazaki-Kariwa nuclear power station during the Niigata-ken Chuetsu-oki earthquake in 2007 is provided from the viewpoint of non-linear local interaction between an embedded building and its surrounding soil. An occurrence mechanism is investigated by the dynamic response analysis in which a bi-linear restoring-force characteristic with a gap-slip process is used. The Ricker wavelet and the continuous sweep sinusoidal wave are adopted as an input. The amplification is explained to be induced by an additional higher mode due to the change of a support condition, such as a gap between an embedded building and its surrounding soil.

  13. A new interpretation of large amplitude earthquake acceleration from non-linear local soil-structure interaction

    International Nuclear Information System (INIS)

    Highlights: • A new interpretation of large earthquake accelerations is provided. • Non-linear interaction between an embedded building and its surrounding soil is a key. • A bi-linear restoring-force characteristic with a gap-slip process is used for analysis. • Ricker wavelet and a continuous sweep sinusoidal wave are adopted as input. • The amplification is induced by a higher mode due to the change of a support condition. - Abstract: A new interpretation of large amplitude earthquake accelerations recorded at the Kashiwazaki-Kariwa nuclear power station during the Niigata-ken Chuetsu-oki earthquake in 2007 is provided from the viewpoint of non-linear local interaction between an embedded building and its surrounding soil. An occurrence mechanism is investigated by the dynamic response analysis in which a bi-linear restoring-force characteristic with a gap-slip process is used. The Ricker wavelet and the continuous sweep sinusoidal wave are adopted as an input. The amplification is explained to be induced by an additional higher mode due to the change of a support condition, such as a gap between an embedded building and its surrounding soil

  14. Energy analysis of stability of twin shallow tunnels based on nonlinear failure criterion

    Institute of Scientific and Technical Information of China (English)

    张佳华; 许敬叔; 张标

    2014-01-01

    Based on nonlinear Mohr−Coulomb failure criterion, the analytical solutions of stability number and supporting force on twin shallow tunnels were derived using upper bound theorem of limit analysis. The optimized solutions were obtained by the technique of sequential quadratic programming. When nonlinear coefficient equals 1 and internal friction angle equals 0, the nonlinear Mohr−Coulomb failure criterion degenerates into linear failure criterion. The calculated results of stability number in this work were compared with previous results, and the agreement verifies the effectiveness of the present method. Under the condition of nonlinear Mohr−Coulomb failure criterion, the results show that the supporting force on twin shallow tunnels obviously increases when the nonlinear coefficient, burial depth, ground load or pore water pressure coefficients increase. When the clear distance is 0.5 to 1.0 times the diameter of tunnel, the supporting force of twin shallow tunnels reaches its maximum value, which means that the tunnels are the easiest to collapse. While the clear distance increases to 3.5 times the diameter of tunnel, the calculation for twin shallow tunnels can be carried out by the method for independent single shallow tunnel. Therefore, 3.5 times the diameter of tunnel serves as a critical value to determine whether twin shallow tunnels influence each other. In designing twin shallow tunnels, appropriate clear distance value must be selected according to its change rules and actual topographic conditions, meanwhile, the influences of nonlinear failure criterion of soil materials and pore water must be completely considered. During the excavation process, supporting system should be intensified at the positions of larger burial depth or ground load to avoid collapses.

  15. Flatly broadened supercontinuum generation in nonlinear fibers using a mode locked bismuth oxide based erbium doped fiber laser

    International Nuclear Information System (INIS)

    Supercontinuum generation with considerable flatness and low fluctuation is investigated in nonlinear fibers by amplification of pulsed seed signal of a stable mode locked bismuth oxide based erbium doped fiber laser. Spectral expansion from 980 to 1750 nm is obtained by 340 fs pulses at 1560 nm amplified up to 177 kW in a dispersion flattened highly non-linear fiber. A comparison is made for different types of nonlinear fibers and evaluation of spectral bandwidth at high powers is probed

  16. Analytical and numerical modelling of thermoviscous shocks in their interactions in nonlinear fluids including dissipation

    DEFF Research Database (Denmark)

    Rasmussen, Anders Rønne; Sørensen, Mads Peter; Gaididei, Yuri Borisovich; Christiansen, Peter Leth

    A wave equation, that governs finite amplitude acoustic disturbances in a thermoviscous Newtonian fluid, and includes nonlinear terms up to second order, is proposed. The equation preserves the Hamiltonian structure of the fundamental fluid dynamical equations in the non dissipative limit. An exact...... thermoviscous shock solution is derived. This solution is, in an overall sense, equivalent to the Taylor shock solution of the Burgers equation. However, in contrast to the Burgers equation, the model equation considered here is capable to describe waves propagating in opposite directions. Studies of head on...

  17. Nonlinear vortex-phonon interactions in a Bose–Einstein condensate

    Science.gov (United States)

    Mendonça, J. T.; Haas, F.; Gammal, A.

    2016-07-01

    We consider the nonlinear coupling between an exact vortex solution in a Bose–Einstein condensate and a spectrum of elementary excitations in the medium. These excitations, or Bogoliubov–de Gennes modes, are indeed a special kind of phonons. We treat the spectrum of elementary excitations in the medium as a gas of quantum particles, sometimes also called bogolons. An exact kinetic equation for the bogolon gas is derived, and an approximate form of this equation, valid in the quasi-classical limit, is also obtained. We study the energy transfer between the vortex and the bogolon gas, and establish conditions for vortex instability and damping.

  18. A Projected Non-linear Conjugate Gradient Method for Interactive Inverse Kinematics

    DEFF Research Database (Denmark)

    Engell-Nørregård, Morten; Erleben, Kenny

    2009-01-01

    Inverse kinematics is the problem of posing an articulated figure to obtain a wanted goal, without regarding inertia and forces. Joint limits are modeled as bounds on individual degrees of freedom, leading to a box-constrained optimization problem. We present A projected Non-linear Conjugate...... Gradient optimization method suitable for box-constrained optimization problems for inverse kinematics. We show application on inverse kinematics positioning of a human figure. Performance is measured and compared to a traditional Jacobian Transpose method. Visual quality of the developed method is...

  19. Nonlinear Interaction of Intense Attosecond XUV Pulses with Atoms and Molecules

    Science.gov (United States)

    Midorikawa, K.; Shimizu, T.; Nabekawa, Y.

    We have observed nonlinear optical processes such as two-photon double ionization and above threshold ionization of rare gases in the xuv region with intense high-order harmonics. Using two-photon double ionization in He, the pulse width of the 27th (42 eV) harmonic was measured by an autocorrelation technique, and found it to be 8 ns. A train of attosecond pulses was also characterized directly by the energy-resolved autocorrelation of the above threshold ionized electrons.

  20. Effects of Interaction Between Gravitation and Nonlinear Electrodynamics On Scalar Field Evolution

    Institute of Scientific and Technical Information of China (English)

    CHEN Ju-Hua; WANG Yong-Jiu

    2011-01-01

    In this paper we investigate the scalar field evolution in the dyadosphere spacetime by using the third-order WKB approximation.We find that the coupling term between the gravitation and the nonlinear electrodynamics makes the scalar field decay more quickly and it also makes the scalar field oscillate more slowly.On the other words, this coupling term takes effect on the scalar field evolution as a damping factor.At the same time these effects become more obvious for the scalar field with higher angle quantum number.

  1. Non-linear interaction of a blasting electron beam with a surface plasma wave

    International Nuclear Information System (INIS)

    Numerical methods are applied to solve the problem on nonlinear dynamics of a surface wave excited by an electron beam which blows round cylindrical or plane surfaces of a plasma. The mechanism of instability saturation consists in the particle beam capture by the wave field. The time behaviour and the maximum value of the wave amplitude, the fraction of the beam energy transferred to the field are determined in dependence on the beam and plasma thicknesses. It is shown that owing to the phase mixing of captured particles caused by strong space inhomogeneity of the wave field, the wave amplitude can reach monotonously the maximum steady-state value

  2. Bi-population Based on Evolutionary Algorithm for Solving Nonlinear Constrained Programming

    Directory of Open Access Journals (Sweden)

    ZOU Guo-cheng

    2009-06-01

    Full Text Available It is difficult to handle constrained conditions in solving nonlinear constrained programming. In this paper a bi-population based on evolutionary algorithm for solving nonlinear constrained programming is proposed. The algorithm is different from other algorithms in that one difines the voilation based on constrained conditions to measure the individuals, and defines the optimal value based on objective value to measure quality of individuals in population. Firstly, we consider the standard constrained optimization problem and state different methods to handle constraints, then present a different method. For degree of violation, we difine two populations:feasible and infeasible population. Finally, we present the detailed steps of bi-population evolutionary algorithm. The feasibility and effectiveness are verified by comparing other existed algorithms with the same five benchmark functions.

  3. Interactive early warning technique based on SVDD

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    After reviewing current researches on early warning,it is found that"bad" data of some systems is not easy to obtain,which makes methods proposed by these researches unsuitable for monitored systems.An interactive early warning technique based on SVDD(support vector data description)is proposed to adopt"good" data as samples to overcome the difficulty in obtaining the"bad"data.The process consists of two parts:(1)A hypersphere is fitted on"good"data using SVDD.If the data object are outside the hypersphere,it would be taken as"suspicious";(2)A group of experts would decide whether the suspicious data is"bad"or"good",early warning messages would be issued according to the decisions.And the detailed process of implementation is proposed.At last,an experiment based on data of a macroeconomic system is conducted to verify the proposed technique.

  4. Global existence and nonexistence for the viscoelastic wave equation with nonlinear boundary damping-source interaction

    KAUST Repository

    Said-Houari, Belkacem

    2012-09-01

    The goal of this work is to study a model of the viscoelastic wave equation with nonlinear boundary/interior sources and a nonlinear interior damping. First, applying the Faedo-Galerkin approximations combined with the compactness method to obtain existence of regular global solutions to an auxiliary problem with globally Lipschitz source terms and with initial data in the potential well. It is important to emphasize that it is not possible to consider density arguments to pass from regular to weak solutions if one considers regular solutions of our problem where the source terms are locally Lipschitz functions. To overcome this difficulty, we use an approximation method involving truncated sources and adapting the ideas in [13] to show that the existence of weak solutions can still be obtained for our problem. Second, we show that under some restrictions on the initial data and if the interior source dominates the interior damping term, then the solution ceases to exist and blows up in finite time provided that the initial data are large enough.

  5. Laboratory Studies of Nonlinear Alfvén Interactions and Decay Instabilities

    Science.gov (United States)

    Dorfman, S.; Carter, T.; Vincena, S.; Pribyl, P.; Rossi, G.; Sydora, R.; Lin, Y.

    2015-11-01

    Alfvén waves, a fundamental mode of magnetized plasmas, are ubiquitous in lab and space. The non-linear behavior of these modes is thought to play a key role in important problems such as the heating of the solar corona, solar wind turbulence, and Alfvén eigenmodes in tokamaks. In particular, theoretical predictions show that these Alfvén waves may be unstable to various decay instabilities, even at low amplitudes (δB / B heart of the Parametric Decay Instability. More recently, efforts have focused on the non-linear decay of a KAW into daughter modes with frequencies and wave numbers that suggest co-propagating KAWs. The observed process is parametric, with the frequency of the daughter modes varying as a function of pump amplitude. Efforts are underway to fully characterize this set of experiments and compare with decay instabilities predicted by theory and simulations. Supported by DOE, NSF, and DOE FES and NASA Eddy Postdoctoral Fellowships.

  6. Nonlinear interaction of intense hypergeometric Gaussian subfamily laser beams in plasma

    Science.gov (United States)

    Sobhani, H.; Vaziri (Khamedi), M.; Rooholamininejad, H.; Bahrampour, A. R.

    2016-07-01

    Propagation of Hypergeometric-Gaussian laser beam in a nonlinear plasma medium is investigated by considering the Source Dependent Expansion method. A subfamily of Hypergeometric-Gaussian beams with a non-negative, even and integer radial index, can be expressed as the linear superposition of finite number of Laguerre-Gaussian functions. Propagation of Hypergeometric-Gaussian beams in a nonlinear plasma medium depends on the value of radial index. The bright rings' number of these beams is changed during the propagation in plasma medium. The effect of beam vortex charge number l and initial (input) beam intensity on the self-focusing of Hypergeometric-Gaussian beams is explored. Also, by choosing the suitable initial conditions, Hypergeometric-Gaussian subfamily beams can be converted to one or more mode components that a typical of mode conversion may be occurred. The self-focusing of these winding beams can be used to control the focusing force and improve the electron bunch quality in laser plasma accelerators.

  7. Arbitrary-ratio power splitter based on nonlinear multimode interference coupler

    Energy Technology Data Exchange (ETDEWEB)

    Tajaldini, Mehdi [School of Physics, Universiti Sains Malaysia, 11800 Pulau Pinang (Malaysia); Young Researchers and Elite Club, Baft Branch, Islamic Azad University, Baft (Iran, Islamic Republic of); Jafri, Mohd Zubir Mat [School of Physics, Universiti Sains Malaysia, 11800 Pulau Pinang (Malaysia)

    2015-04-24

    We propose an ultra-compact multimode interference (MMI) power splitter based on nonlinear effects from simulations using nonlinear modal propagation analysis (NMPA) cooperation with finite difference Method (FDM) to access free choice of splitting ratio. Conventional multimode interference power splitter could only obtain a few discrete ratios. The power splitting ratio may be adjusted continuously while the input set power is varying by a tunable laser. In fact, using an ultra- compact MMI with a simple structure that is launched by a tunable nonlinear input fulfills the problem of arbitrary-ratio in integrated photonics circuits. Silicon on insulator (SOI) is used as the offered material due to the high contrast refractive index and Centro symmetric properties. The high-resolution images at the end of the multimode waveguide in the simulated power splitter have a high power balance, whereas access to a free choice of splitting ratio is not possible under the linear regime in the proposed length range except changes in the dimension for any ratio. The compact dimensions and ideal performance of the device are established according to optimized parameters. The proposed regime can be extended to the design of M×N arbitrary power splitters ratio for programmable logic devices in all optical digital signal processing. The results of this study indicate that nonlinear modal propagation analysis solves the miniaturization problem for all-optical devices based on MMI couplers to achieve multiple functions in a compact planar integrated circuit and also overcomes the limitations of previously proposed methods for nonlinear MMI.

  8. The nonlinear interaction of Tollmien-Schlichting waves and Taylor-Goertler vortices in curved channel flows

    Science.gov (United States)

    Hall, P.; Smith, F. T.

    1988-06-01

    The development of Tollmien-Schlichting waves (TSWs) and Taylor-Goertler vortices (TGVs) in fully developed viscous curved-channel flows is investigated analytically, with a focus on their nonlinear interactions. Two types of interactions are identified, depending on the amplitude of the initial disturbances. In the low-amplitude type, two TSWs and one TGV interact, and the scaled amplitudes go to infinity on a finite time scale; in the higher-amplitude type, which can also occur in a straight channel, the same singularity occurs if the angle between the TSW wavefront and the TGV is greater than 41.6 deg, but the breakdown is exponential and takes an infinite time if the angle is smaller. The implications of these findings for external flow problems such as the design of laminar-flow wings are indicated. It is concluded that longitudinal vortices like those observed in the initial stages of the transition to turbulence can be produced unless the present interaction mechanism is destroyed by boundary-layer growth.

  9. Large and Ultrafast Third-Order Nonlinear Optical Properties of Ge-S Based Chalcogenide Glasses

    Institute of Scientific and Technical Information of China (English)

    CHU Sai-Sai; WANG Shu-Feng; TAO Hai-Zheng; WANG Zhen-Wei; YANG Hong; LIN Chang-Gui; GONG Qi-Huang; ZHAO Xiu-Jian

    2007-01-01

    We report ultrafast third-order nonlinear optical (NLO) properties of several chalcogenide glasses GeSx (x = 1.8,2.0, 2.5) measured by femtosecond time-resolved optical Kerr gate technique at 820nm. The third-order nonlinear susceptibility of GeS1.8 glass is determined to be as large as 1.41 × 10-12 esu, which is the maximum value of the third order nonlinear susceptibility X(3) for the three compositions investigated. The symmetric Gauss profiles of optical Kerr signals reveal the nature of ultrafast nonlinear response of these samples, which are originated from the ultrafast polarization of the electron clouds. By detailed microstructural analysis of these glasses based on the chain-crossing model (CCM) and the random-covalent-network model (RCNM), it can be concluded that X(3) value of GeSx glasses can be enhanced greatly by S-S covalent bonds or S3Ge-GeS3 ethane-like units.

  10. Acousto-ultrasonics-based fatigue damage characterization: Linear versus nonlinear signal features

    Science.gov (United States)

    Su, Zhongqing; Zhou, Chao; Hong, Ming; Cheng, Li; Wang, Qiang; Qing, Xinlin

    2014-03-01

    Engineering structures are prone to fatigue damage over service lifespan, entailing early detection and continuous monitoring of the fatigue damage from its initiation through growth. A hybrid approach for characterizing fatigue damage was developed, using two genres of damage indices constructed based on the linear and the nonlinear features of acousto-ultrasonic waves. The feasibility, precision and practicability of using linear and nonlinear signal features, for quantitatively evaluating multiple barely visible fatigue cracks in a metallic structure, was compared. Miniaturized piezoelectric elements were networked to actively generate and acquire acousto-ultrasonic waves. The active sensing, in conjunction with a diagnostic imaging algorithm, enabled quantitative evaluation of fatigue damage and facilitated embeddable health monitoring. Results unveiled that the nonlinear features of acousto-ultrasonic waves outperform their linear counterparts in terms of the detectability. Despite the deficiency in perceiving small-scale damage and the possibility of conveying false alarms, linear features show advantages in noise tolerance and therefore superior practicability. The comparison has consequently motivated an amalgamation of linear and nonlinear features of acousto-ultrasonic waves, targeting the prediction of multi-scale damage ranging from microscopic fatigue cracks to macroscopic gross damage.

  11. Cubical Mass-Spring Model design based on a tensile deformation test and nonlinear material model.

    Science.gov (United States)

    San-Vicente, Gaizka; Aguinaga, Iker; Tomás Celigüeta, Juan

    2012-02-01

    Mass-Spring Models (MSMs) are used to simulate the mechanical behavior of deformable bodies such as soft tissues in medical applications. Although they are fast to compute, they lack accuracy and their design remains still a great challenge. The major difficulties in building realistic MSMs lie on the spring stiffness estimation and the topology identification. In this work, the mechanical behavior of MSMs under tensile loads is analyzed before studying the spring stiffness estimation. In particular, the performed qualitative and quantitative analysis of the behavior of cubical MSMs shows that they have a nonlinear response similar to hyperelastic material models. According to this behavior, a new method for spring stiffness estimation valid for linear and nonlinear material models is proposed. This method adjusts the stress-strain and compressibility curves to a given reference behavior. The accuracy of the MSMs designed with this method is tested taking as reference some soft-tissue simulations based on nonlinear Finite Element Method (FEM). The obtained results show that MSMs can be designed to realistically model the behavior of hyperelastic materials such as soft tissues and can become an interesting alternative to other approaches such as nonlinear FEM. PMID:22156291

  12. Investigation of mental fatigue through EEG signal processing based on nonlinear analysis: Symbolic dynamics

    International Nuclear Information System (INIS)

    Highlights: Mental fatigue indices’ variation discussed during simple long-term attentive task. Symbolic dynamics of reaction time and EEG signal determine mental state variation. Nonlinear quantifiers such as entropy can display chaotic behaviors of the brain. Frontal and central lobes of the brain are effective in attention investigations. Mental fatigue causes a reduction in the complexity of the brain’s activity. Abstract: To investigate nonlinear analysis of attention physiological indices this study used a simple repetitive attentive task in four consecutive trials that resulted in mental fatigue. Traditional performance indices, such as reaction time, error responses, and EEG signals, were simultaneously recorded to evaluate differences between the trials. Performance indices analysis demonstrated that a selected task leads to mental fatigue. In addition, the study aimed to find a method to determine mental fatigue based on nonlinear analysis of EEG signals. Symbolic dynamics was selected as a qualitative method used to extract some quantitative qualifiers such as entropy. This method was executed on the reaction time of responses, and EEG signals to distinguish mental states. The results revealed that nonlinear analysis of reaction time, and EEG signals of the frontal and central lobes of the brain could differentiate between attention, and occurrence of mental fatigue in trials. In addition, the trend of entropy variation displayed a reduction in the complexity of mental activity as fatigue occurred.

  13. A Comparison of PDE-based Non-Linear Anisotropic Diffusion Techniques for Image Denoising

    Energy Technology Data Exchange (ETDEWEB)

    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.

  14. Effect of nonlinearity of spin interaction with electromagnetic resonance field on characteristics of polarized nuclear target

    International Nuclear Information System (INIS)

    Interaction of incident nuclear particle beam with J = 1/2 (neutrons) spin and (J = 1/2) protons with the target substance is considered. It is shown that neutron polarization at the target exit and neutron transparency (G) of the target depend significantly on incident wave amplitude level and physical parameter values which characterize the target, such as target temperature, resonator mirror reflection factor, number of spins interacting with the field, etc. Under interaction of neutrons with a target resonator which features a high mirror reflection factor and low losses for absorption which is not related to magnetic dipole absorption, a bistable response of neutron polarization and G manifests itself. 1 ref

  15. A non-linear camera calibration with modified teaching-learning-based optimization algorithm

    Science.gov (United States)

    Zhang, Buyang; Yang, Hua; Yang, Shuo

    2015-12-01

    In this paper, we put forward a novel approach based on hierarchical teaching-and-learning-based optimization (HTLBO) algorithm for nonlinear camera calibration. This algorithm simulates the teaching-learning ability of teachers and learners of a classroom. Different from traditional calibration approach, the proposed technique can find the nearoptimal solution without the need of accurate initial parameters estimation (with only very loose parameter bounds). With the introduction of cascade of teaching, the convergence speed is rapid and the global search ability is improved. Results from our study demonstrate the excellent performance of the proposed technique in terms of convergence, accuracy, and robustness. The HTLBO can also be used to solve many other complex non-linear calibration optimization problems for its good portability.

  16. Finite time control for MIMO nonlinear system based on higher-order sliding mode.

    Science.gov (United States)

    Liu, Xiangjie; Han, Yaozhen

    2014-11-01

    Considering a class of MIMO uncertain nonlinear system, a novel finite time stable control algorithm is proposed based on higher-order sliding mode concept. The higher-order sliding mode control problem of MIMO nonlinear system is firstly transformed into finite time stability problem of multivariable system. Then continuous control law, which can guarantee finite time stabilization of nominal integral chain system, is employed. The second-order sliding mode is used to overcome the system uncertainties. High frequency chattering phenomenon of sliding mode is greatly weakened, and the arbitrarily fast convergence is reached. The finite time stability is proved based on the quadratic form Lyapunov function. Examples concerning the triple integral chain system with uncertainty and the hovercraft trajectory tracking are simulated respectively to verify the effectiveness and the robustness of the proposed algorithm. PMID:25277626

  17. Series-based approximate approach of optimal tracking control for nonlinear systems with time-delay

    Institute of Scientific and Technical Information of China (English)

    Gongyou Tang; Mingqu Fan

    2008-01-01

    The optimal output tracking control (OTC) problem for nonlinear systems with time-delay is considered.Using a series-based approx-imate approach,the original OTC problem is transformed into iteration solving linear two-point boundary value problems without time-delay.The OTC law obtained consists of analytical linear feedback and feedforward terms and a nonlinear compensation term with an infinite series of the adjoint vectors.By truncating a finite sum of the adjoint vector series,an approximate optimal tracking control law is obtained.A reduced-order reference input observer is constructed to make the feedforward term physically realizable.Simulation exam-pies are used to test the validity of the series-based approximate approach.

  18. Neural-network-observer-based optimal control for unknown nonlinear systems using adaptive dynamic programming

    Science.gov (United States)

    Liu, Derong; Huang, Yuzhu; Wang, Ding; Wei, Qinglai

    2013-09-01

    In this paper, an observer-based optimal control scheme is developed for unknown nonlinear systems using adaptive dynamic programming (ADP) algorithm. First, a neural-network (NN) observer is designed to estimate system states. Then, based on the observed states, a neuro-controller is constructed via ADP method to obtain the optimal control. In this design, two NN structures are used: a three-layer NN is used to construct the observer which can be applied to systems with higher degrees of nonlinearity and without a priori knowledge of system dynamics, and a critic NN is employed to approximate the value function. The optimal control law is computed using the critic NN and the observer NN. Uniform ultimate boundedness of the closed-loop system is guaranteed. The actor, critic, and observer structures are all implemented in real-time, continuously and simultaneously. Finally, simulation results are presented to demonstrate the effectiveness of the proposed control scheme.

  19. Neural network approximation of nonlinearity in laser nano-metrology system based on TLMI

    Energy Technology Data Exchange (ETDEWEB)

    Olyaee, Saeed; Hamedi, Samaneh, E-mail: s_olyaee@srttu.edu [Nano-photonics and Optoelectronics Research Laboratory (NORLab), Faculty of Electrical and Computer Engineering, Shahid Rajaee Teacher Training University (SRTTU), Lavizan, 16788, Tehran (Iran, Islamic Republic of)

    2011-02-01

    In this paper, an approach based on neural network (NN) for nonlinearity modeling in a nano-metrology system using three-longitudinal-mode laser heterodyne interferometer (TLMI) for length and displacement measurements is presented. We model nonlinearity errors that arise from elliptically and non-orthogonally polarized laser beams, rotational error in the alignment of laser head with respect to the polarizing beam splitter, rotational error in the alignment of the mixing polarizer, and unequal transmission coefficients in the polarizing beam splitter. Here we use a neural network algorithm based on the multi-layer perceptron (MLP) network. The simulation results show that multi-layer feed forward perceptron network is successfully applicable to real noisy interferometer signals.

  20. Neural network approximation of nonlinearity in laser nano-metrology system based on TLMI

    International Nuclear Information System (INIS)

    In this paper, an approach based on neural network (NN) for nonlinearity modeling in a nano-metrology system using three-longitudinal-mode laser heterodyne interferometer (TLMI) for length and displacement measurements is presented. We model nonlinearity errors that arise from elliptically and non-orthogonally polarized laser beams, rotational error in the alignment of laser head with respect to the polarizing beam splitter, rotational error in the alignment of the mixing polarizer, and unequal transmission coefficients in the polarizing beam splitter. Here we use a neural network algorithm based on the multi-layer perceptron (MLP) network. The simulation results show that multi-layer feed forward perceptron network is successfully applicable to real noisy interferometer signals.