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Nonlinear dynamics

C Riek, P Sulzer, M Seeger, A S Moskalenko, G Burkard, D V Seletskiy, A Leitenstorfer
Squeezed states of electromagnetic radiation have quantum fluctuations below those of the vacuum field. They offer a unique resource for quantum information systems and precision metrology, including gravitational wave detectors, which require unprecedented sensitivity. Since the first experiments on this non-classical form of light, quantum analysis has been based on homodyning techniques and photon correlation measurements. These methods currently function in the visible to near-infrared and microwave spectral ranges...
January 18, 2017: Nature
Nawel Jmail, Martine Gavaret, F Bartolomei, Christian-G Bénar
Interictal epileptiform discharges, or 'interictal spikes', are the hallmark of epilepsy. Still, there is growing evidence that oscillatory activity-whether in the gamma band (30-120 Hz) or at higher frequencies is another important marker of hyperexcitable tissues. A major difficulty arises from the fact that interictal spikes and oscillations overlap in the frequency domain. This hampers the correct delineation of the cortex producing pathological oscillations by simple filtering. Here, we propose a nonlinear technique for fitting the spike waveform in order to remove it, resulting in a 'despiked' signal...
January 18, 2017: Physiological Measurement
Aidan T Brown, Wilson C K Poon, Christian Holm, Joost de Graaf
Polar solvents like water support the bulk dissociation of themselves and their solutes into ions, and the re-association of these ions into neutral molecules in a dynamic equilibrium, e.g., H2O2 ⇌ H(+) + HO2(-). Using continuum theory, we study the influence of these association-dissociation reactions on the self-propulsion of colloids driven by surface chemical reactions (chemical swimmers). We find that association-dissociation reactions should have a strong influence on swimmers' behaviour, and therefore should be included in future modelling...
January 18, 2017: Soft Matter
Arash Samadi, Timothy P Lillicrap, Douglas B Tweed
Recent work in computer science has shown the power of deep learning driven by the backpropagation algorithm in networks of artificial neurons. But real neurons in the brain are different from most of these artificial ones in at least three crucial ways: they emit spikes rather than graded outputs, their inputs and outputs are related dynamically rather than by piecewise-smooth functions, and they have no known way to coordinate arrays of synapses in separate forward and feedback pathways so that they change simultaneously and identically, as they do in backpropagation...
January 17, 2017: Neural Computation
Kian Jalaleddini, Chuanxin Niu, Suraj Chakravarthi Raja, Won Joon Sohn, Gerald Loeb, Terence Sanger, Francisco Valero-Cuevas
OBJECTIVE: We studied the fundamentals of muscle afferentation by building a neuro-mechano-morphic system actuating a cadaveric finger. This system is a faithful implementation of the stretch reflex circuitry. It allowed the systematic exploration of the effects of different fusimotor drives to the muscle spindle on the closed-loop stretch reflex response. APPROACH: As in Part I of this work, sensory neurons conveyed proprioceptive information from muscle spindles (with static and dynamic fusimotor drive) to populations of ��-motor neurons (with recruitment and rate coding properties)...
January 17, 2017: Journal of Neural Engineering
Aurelien Crut, Paolo Maioli, Fabrice Vallee, Natalia Del Fatti
Single-particle optical investigations have greatly improved our understanding of the fundamental properties of nano-objects, avoiding the spurious inhomogeneous effects that affect ensemble experiments. Correlation with high-resolution imaging techniques providing morphological information (e.g., electron microscopy) allows a quantitative interpretation of the optical measurements by means of analytical models and numerical simulations. In this topical review, we first briefly recall the principles underlying some of the most commonly used single-particle optical techniques: near-field, dark-field, spatial modulation and photothermal microscopies/spectroscopies...
January 17, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Xiangyang Zhou, Beilei Zhao, Wei Liu, Haixiao Yue, Ruixia Yu, Yulong Zhao
A compound scheme is proposed to compensate the effect of nonlinear friction disturbance on the control precision of a three-axis inertially stabilized platform (ISP) for aerial remote sensing applications. The scheme consists of friction parameters identification and adaptive compensation. A LuGre model-based ISP friction model is first developed. Then, a comprehensive experimental scheme is proposed to obtain the static friction parameters. Further, the dynamic parameters are identified by experiments and dynamic optimization...
January 13, 2017: ISA Transactions
Ramón Ramírez-Villalobos, Luis T Aguilar, Luis N Coria
In this paper, a sensorless speed tracking control is proposed for a surface-mount permanent magnet synchronous motor by using a nonlinear H∞-controller via stator currents measurements for feedback. An output feedback nonlinear H∞-controller was designed such that the undisturbed system is uniformly asymptotically stable around the desired speed reference, while also the effects of external vanishing and non-vanishing disturbances, noise, and input backlash were attenuated locally. The rotor position was calculated from the causal dynamic output feedback compensator and from the desired speed reference...
January 13, 2017: ISA Transactions
Asaf Dahan, Assaf Levanon, Mordechai Katz, Haim Suchowski
We introduce a generalization of the adiabatic frequency conversion method for an efficient conversion of ultrashort pulses in the full nonlinear regime. Our analysis takes into account dispersion as well as two-photon processes and Kerr effect, allowing complete analysis of any three waves with arbitrary phase mismatched design and any nonlinear optical process. We use this analysis to design an efficient and robust second harmonic generation, the most widely used nonlinear process for both fundamental and applied research...
January 16, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Wei Wang, Shaocheng Tong
This paper studies the adaptive fuzzy bounded control problem for leader-follower multiagent systems, where each follower is modeled by the uncertain nonlinear strict-feedback system. Combining the fuzzy approximation with the dynamic surface control, an adaptive fuzzy control scheme is developed to guarantee the output consensus of all agents under directed communication topologies. Different from the existing results, the bounds of the control inputs are known as a priori, and they can be determined by the feedback control gains...
January 10, 2017: IEEE Transactions on Cybernetics
Yuanheng Zhu, Dongbin Zhao, Xiong Yang, Qichao Zhang
Sum of squares (SOS) polynomials have provided a computationally tractable way to deal with inequality constraints appearing in many control problems. It can also act as an approximator in the framework of adaptive dynamic programming. In this paper, an approximate solution to the H∞ optimal control of polynomial nonlinear systems is proposed. Under a given attenuation coefficient, the Hamilton-Jacobi-Isaacs equation is relaxed to an optimization problem with a set of inequalities. After applying the policy iteration technique and constraining inequalities to SOS, the optimization problem is divided into a sequence of feasible semidefinite programming problems...
January 10, 2017: IEEE Transactions on Cybernetics
Shaocheng Tong, Yongming Li
This paper investigates a robust adaptive fuzzy control stabilization problem for a class of uncertain nonlinear systems with arbitrary switching signals that use an observer-based output feedback scheme. The considered switched nonlinear systems possess the unstructured uncertainties, unmodeled dynamics, and without requiring the states being available for measurement. A state observer which is independent of switching signals is designed to solve the problem of unmeasured states. Fuzzy logic systems are used to identify unknown lumped nonlinear functions so that the problem of unstructured uncertainties can be solved...
February 2017: IEEE Transactions on Cybernetics
Shinjiro Miyawaki, Eric A Hoffman, Ching-Long Lin
Advances in quantitative computed tomography (CT) has provided methods to assess the detailed structure of the pulmonary airways and parenchyma, providing the means of applying computational fluid dynamics-based modeling to better understand subject-specific differences in structure-to-function relationships. Most of the previous numerical studies, seeking to predict patterns of inhaled particle deposition, have considered airway geometry and regional ventilation derived from static images. Because geometric alterations of the airway and parenchyma associated with regional ventilation may greatly affect particle transport, we have sought to investigate the effect of rigid vs...
October 2016: Journal of Aerosol Science
Chao Li, Min Wang, Jun-Fang Wu
Fano resonance is widely used to realize high-contrast nonreciprocal transmission. However, resonance-enhanced all-optical diodes (AOD) are bandwidth-limited, and their transmission rates are normally low, which restricts realistic application. In this Letter, we analytically and numerically demonstrate that this limitation can be overcome once multistability of cascaded nonlinear cavities is appropriately excited. By precisely molding the transiting of the signal light between multistable states, a high-contrast-ratio, high-unidirectional-transmission-rate, and reversal-controllable AOD is achieved with a bandwidth over 2...
January 15, 2017: Optics Letters
Meng Liu, Ai-Ping Luo, Zhi-Chao Luo, Wen-Cheng Xu
Ultrafast fiber laser, as a dissipative nonlinear optical system, plays an important role in investigating various nonlinear phenomena and soliton dynamics. Vector features of solitons, including polarization locked and polarization rotation vector solitons (PRVSs), are interesting nonlinear dynamics in ultrafast fiber lasers. Herein, we experimentally reveal the trapping characteristics of PRVSs for the first time, to the best of our best knowledge. We show that, for the conventional soliton trapping in the ultrafast fiber laser, the soliton central wavelengths of the two polarization components are constant at the laser output port...
January 15, 2017: Optics Letters
Pamela M Cole, Jason J Bendezú, Nilam Ram, Sy-Miin Chow
Self-regulation can be conceptualized in terms of dynamic tension between highly probable reactions (prepotent responses) and use of strategies that can modulate those reactions (executive processes). This study investigated the value of a dynamical systems approach to the study of early childhood self-regulation. Specifically, ordinary differential equations (ODEs) were used to model the interactive influences of 115 36-month-olds' executive processes (strategy use) and prepotent responses to waiting to open a gift (desire for the gift and frustration about waiting to open it)...
January 12, 2017: Emotion
Diana Ruiz Bueno, Luis Montano
OBJECTIVE: Neuromusculoskeletal models involve many subject-specific physiological parameters that need to be adjusted to adequately represent muscle properties. Traditionally, neuromusculoskeletal models have been calibrated with a forward-inverse dynamic optimization which is time-consuming and unfeasible for rehabilitation therapy. Non self-calibration algorithms have been applied to these models. To the best of our knowledge, the algorithm proposed in this work is the first on-line calibration algorithm for muscle models that allows a generic model to be adjusted to different subjects in a few steps...
January 12, 2017: Journal of Neural Engineering
Sophie J Rhodes, Charlotte Sarfas, Gwenan M Knight, Andrew White, Ansar A Pathan, Helen McShane, Thomas G Evans, Helen Fletcher, Sally Sharpe, Richard G White
INTRODUCTION: Macaques play a central role in human tuberculosis(TB) vaccine development. Immune and challenge responses differ across macaque and human subpopulations. We determined which macaque subpopulations best predicted immune responses in different human subpopulations, using novel immunostimulation/immunodynamic modelling methods in a proof of concept study. METHODS: Data on IFN-γ secreting CD4+ T cells over time after recent BCG vaccination were available for 55 humans and 81 macaques...
January 11, 2017: Clinical and Vaccine Immunology: CVI
James M Kunert, Joshua L Proctor, Steven L Brunton, J Nathan Kutz
Using a computational model of the Caenorhabditis elegans connectome dynamics, we show that proprioceptive feedback is necessary for sustained dynamic responses to external input. This is consistent with the lack of biophysical evidence for a central pattern generator, and recent experimental evidence that proprioception drives locomotion. The low-dimensional functional response of the Caenorhabditis elegans network of neurons to proprioception-like feedback is optimized by input of specific spatial wavelengths which correspond to the spatial scale of real body shape dynamics...
January 2017: PLoS Computational Biology
Denis Peruzzo, Marco Castellaro, Gianluigi Pillonetto, Alessandra Bertoldo
PURPOSE: To present the stable spline (SS) deconvolution method for the quantification of the cerebral blood flow (CBF) from dynamic susceptibility contrast MRI. METHODS: The SS method was compared with both the block-circulant singular value decomposition (oSVD) and nonlinear stochastic regularization (NSR) methods. oSVD is one of the most popular deconvolution methods in dynamic susceptibility contrast MRI (DSC-MRI). NSR is an alternative approach that we proposed previously...
January 9, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
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