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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
Ben Niu, Yanjun Liu, Guangdeng Zong, Zhaoyu Han, Jun Fu
In this paper, a new adaptive approximation-based tracking controller design approach is developed for a class of uncertain nonlinear switched lower-triangular systems with an output constraint using neural networks (NNs). By introducing a novel barrier Lyapunov function (BLF), the constrained switched system is first transformed into a new system without any constraint, which means the control objectives of the both systems are equivalent. Then command filter technique is applied to solve the so-called "explosion of complexity" problem in traditional backstepping procedure, and radial basis function NNs are directly employed to model the unknown nonlinear functions...
January 16, 2017: IEEE Transactions on Cybernetics
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
Hamed Rezaee, Farzaneh Abdollahi
The leaderless consensus problem over a class of high-order nonlinear multiagent systems (MASs) is studied. A robust protocol is proposed which guarantees achieving consensus in the network in the presences of uncertainties in agents models. Achieving consensus in the case of stochastic links failure is studied as well. Based on the concept super-martingales, it is shown that if the probability of the network connectivity is not zero, under some conditions, achieving almost sure consensus in the network can be guaranteed...
December 6, 2016: IEEE Transactions on Cybernetics
Wei Liu, Jie Huang
This paper studies the cooperative global robust output regulation problem for a class of heterogeneous second-order nonlinear uncertain multiagent systems with jointly connected switching networks. The main contributions consist of the following three aspects. First, we generalize the result of the adaptive distributed observer from undirected jointly connected switching networks to directed jointly connected switching networks. Second, by performing a new coordinate and input transformation, we convert our problem into the cooperative global robust stabilization problem of a more complex augmented system via the distributed internal model principle...
January 11, 2017: IEEE Transactions on Neural Networks and Learning Systems
Jae-Seok Choi, Munchurl Kim
Super-resolution (SR) has become more vital, because of its capability to generate high-quality ultra-high definition (UHD) high-resolution (HR) images from low-resolution (LR) input images. Conventional SR methods entail high computational complexity, which makes them difficult to be implemented for up-scaling of full-high-definition (FHD) input images into UHD-resolution images. Nevertheless, our previous super-interpolation (SI) method showed a good compromise between PSNR performances and computational complexity...
January 10, 2017: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
Craig Abbey, Yang Zhu, Sara Bahramian, Michael Insana
Despite a great deal of work characterizing the statistical properties of radio-frequency backscattered ultrasound signals, less is known about the statistical properties of demodulated intensity signals. Analysis of intensity is made more difficult by a strong nonlinearity that arises in the process of demodulation. This limits our ability to characterize the spatial resolution and noise properties of B-mode ultrasound images. In this work, we generalize earlier results on two-point intensity covariance using a multivariate systems approach...
January 16, 2017: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
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
Nahid Elyasi, Kimia Karimi Taheri, Keivan Narooei, Ali Karimi Taheri
In this research, the nonlinear elastic behavior of human extensor apparatus was investigated. To this goal, firstly the best material parameters of hyperelastic strain energy density functions consisting of the Mooney-Rivlin, Ogden, invariants, and general exponential models were derived for the simple tension experimental data. Due to the significance of stress response in other deformation modes of nonlinear models, the calculated parameters were used to study the pure shear and balance biaxial tension behavior of the extensor apparatus...
January 16, 2017: Biomechanics and Modeling in Mechanobiology
Fei-Fei Mao, Chun-Li Hu, Xiang Xu, Dong Yan, Bing-Ping Yang, Jiang-Gao Mao
The first metal iodate fluoride, Bi(IO3 )F2 , with a strong second harmonic generation (SHG) effect has been prepared. Bi(IO3 )F2 crystallizes in the polar space group C2 and features a three-dimensional [BiF2 ](+) cationic framework with IO3 groups capping the inner walls of the one-dimensional tunnels. This [BiF2 ](+) cationic framework acts as a template for the assembly of the polar IO3 units in a favorable superposed fashion, which leads to the polar structure of the material. Bi(IO3 )F2 displays a rather wide transmittance window (0...
January 16, 2017: Angewandte Chemie
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
Mohammed Salman Shazeeb, Christopher H Sotak
NMR relaxation agents have long been employed as contrast agents in MRI. In many cases, the contrast agent is confined to either (i) the vascular and/or extracellular compartment (EC), as is the case with gadolinium(III)-based agents, or (ii) the intracellular compartment (IC), as is the case with manganese(II) ions. The compartmentalization of contrast agents often results in tissue-water (1)H relaxation profiles that are well modeled as biexponential. It has long been recognized that water exchange between compartments modifies the biexponential relaxation parameters (amplitudes and rate constants) from those that would be found in the absence of exchange...
January 6, 2017: Journal of Magnetic Resonance
L E Moraes, S A Burgos, E J DePeters, R Zhang, J G Fadel
The objective of the study was to quantify the rate of urea hydrolysis in dairy cattle manure under different initial urea concentration, temperature, and pH conditions. In particular, by varying all 3 factors simultaneously, the interactions between them could also be determined. Fresh feces and artificial urine solutions were combined into a slurry to characterize the rate of urea hydrolysis under 2 temperatures (15°C and 35°C), 3 urea concentrations in urine solutions (500, 1,000, and 1,500 mg of urea-N/dL), and 3 pH levels (6, 7, and 8)...
January 11, 2017: Journal of Dairy Science
Sandra Vieira, Walter H L Pinaya, Andrea Mechelli
Deep learning (DL) is a family of machine learning methods that has gained considerable attention in the scientific community, breaking benchmark records in areas such as speech and visual recognition. DL differs from conventional machine learning methods by virtue of its ability to learn the optimal representation from the raw data through consecutive nonlinear transformations, achieving increasingly higher levels of abstraction and complexity. Given its ability to detect abstract and complex patterns, DL has been applied in neuroimaging studies of psychiatric and neurological disorders, which are characterised by subtle and diffuse alterations...
January 10, 2017: Neuroscience and Biobehavioral Reviews
Javier Tarrío-Saavedra, Cécilia Galindo González, Salvador Naya, Jorge López-Beceiro, Alain Ponton
This study investigated a methodology based on image processing and statistics to characterize and model the deformation upon controlled and uniform magnetic field and the relaxation under zero field of droplets observed in aqueous solutions of sodium alginate incorporating magnetic maghemite nanoparticles stabilized by adsorption of citrate ions. The changes of droplet geometry were statistically analyzed using a new approach based on the data obtained from optical microscopy, image processing, nonlinear regression, evolutionary optimization, analysis of variance and resampling...
2017: PloS One
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
B Hafizi, J R Peñano, J P Palastro, R P Fischer, G DiComo
A high-power laser beam propagating through a dielectric in the presence of fluctuations is subject to diffraction, dissipation, and optical Kerr nonlinearity. A method of moments was applied to a stochastic, nonlinear enveloped wave equation to analyze the evolution of the long-term spot radius. For propagation in atmospheric turbulence described by a Kolmogorov-von Kármán spectral density, the analysis was benchmarked against field experiments in the low-power limit and compared with simulation results in the high-power regime...
January 15, 2017: Optics Letters
A Bendahmane, J Fatome, C Finot, G Millot, B Kibler
We investigate the coherent or incoherent seeding of dissipative modulation instability (MI) in a nonlinear fiber ring cavity. By varying wavelength and degree of coherence of the seed signal across the MI gain band, we observe a strong sensitivity of the resulting MI sidebands in terms of bandwidth and amplification. Both spectral and temporal characterizations are performed to reveal intensity coherence properties (over a single round-trip) of the generated temporal patterns. Experimental observations are well confirmed by numerical simulations...
January 15, 2017: Optics Letters
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