Analysis of Conductor Impedances Accounting for Skin Effect and Nonlinear Permeability
Perkins, M P; Ong, M M; Brown, C G; Speer, R D
2011-07-20
It is often necessary to protect sensitive electrical equipment from pulsed electric and magnetic fields. To accomplish this electromagnetic shielding structures similar to Faraday Cages are often implemented. If the equipment is inside a facility that has been reinforced with rebar, the rebar can be used as part of a lighting protection system. Unfortunately, such shields are not perfect and allow electromagnetic fields to be created inside due to discontinuities in the structure, penetrations, and finite conductivity of the shield. In order to perform an analysis of such a structure it is important to first determine the effect of the finite impedance of the conductors used in the shield. In this paper we will discuss the impedances of different cylindrical conductors in the time domain. For a time varying pulse the currents created in the conductor will have different spectral components, which will affect the current density due to skin effects. Many construction materials use iron and different types of steels that have a nonlinear permeability. The nonlinear material can have an effect on the impedance of the conductor depending on the B-H curve. Although closed form solutions exist for the impedances of cylindrical conductors made of linear materials, computational techniques are needed for nonlinear materials. Simulations of such impedances are often technically challenging due to the need for a computational mesh to be able to resolve the skin depths for the different spectral components in the pulse. The results of such simulations in the time domain will be shown and used to determine the impedances of cylindrical conductors for lightning current pulses that have low frequency content.
Optimal geometry of nonlinear silicon slot waveguides accounting for the effect of waveguide losses.
Ong, Jun Rong; Chen, Valerian H
2015-12-28
The optimal geometry of silicon-organic hybrid slot waveguides is investigated in the context of the efficiency of four-wave mixing (FWM), a χ(3) nonlinear optical process. We study the effect of slot and waveguide widths, as well as waveguide asymmetry on the two-photon absorption (TPA) figure of merit and the roughness scattering loss. The optimal waveguide core width is shown to be 220nm (symmetric) with a slot width of 120nm, at a fixed waveguide height of 220nm. We also show that state-of-the-art slot waveguides can outperform rib waveguides, especially at high powers, due to the high TPA figure-of-merit.
Accounting For Nonlinearity In A Microwave Radiometer
NASA Technical Reports Server (NTRS)
Stelzried, Charles T.
1991-01-01
Simple mathematical technique found to account adequately for nonlinear component of response of microwave radiometer. Five prescribed temperatures measured to obtain quadratic calibration curve. Temperature assumed to vary quadratically with reading. Concept not limited to radiometric application; applicable to other measuring systems in which relationships between quantities to be determined and readings of instruments differ slightly from linearity.
Poggiolini, P; Bosco, G; Carena, A; Curri, V; Forghieri, F
2010-05-24
Coherent-detection (CoD) permits to fully exploit the four-dimensional (4D) signal space consisting of the in-phase and quadrature components of the two fiber polarizations. A well-known and successful format exploiting such 4D space is Polarization-multiplexed QPSK (PM-QPSK). Recently, new signal constellations specifically designed and optimized in 4D space have been proposed, among which polarization-switched QPSK (PS-QPSK), consisting of a 8-point constellation at the vertices of a 4D polychoron called hexadecachoron. We call it HEXA because of its geometrical features and to avoid acronym mix-up with PM-QPSK, as well as with other similar acronyms. In this paper we investigate the performance of HEXA in direct comparison with PM-QPSK, addressing non-linear propagation over realistic links made up of 20 spans of either standard single mode fiber (SSMF) or non-zero dispersion-shifted fiber (NZDSF). We show that HEXA not only confirms its theoretical sensitivity advantage over PM-QPSK in back-to-back, but also shows a greater resilience to non-linear effects, allowing for substantially increased span loss margins. As a consequence, HEXA appears as an interesting option for dual-format transceivers capable to switch on-the-fly between PM-QPSK and HEXA when channel propagation degrades. It also appears as a possible direct competitor of PM-QPSK, especially over NZDSF fiber and uncompensated links.
NASA Astrophysics Data System (ADS)
Sharma, Arvind; Nagar, A. K.
2016-05-01
The origin of optical bistability and hysterectic reflectivity on account of nonlinearity at optically induced Gallium silica interface has been investigated. Assuming the wave to be incident from the gallium nano particle layer side at gallium silica interface. The coupling between incident and reflected waves has shown nonlinear effects on Snell's law and Fresnel law. Effect of these nonlinear processes optical bistability and hysterectic reflectivity theoretically has been investigated. Theoretical results obtained are consistent with the available experimental results.
Identification of nonlinear boundary effects using nonlinear normal modes
NASA Astrophysics Data System (ADS)
Ahmadian, Hamid; Zamani, Arash
2009-08-01
Local nonlinear effects due to micro-slip/slap introduced in boundaries of structures have dominant influence on their lower modal model. This paper studies these effects by experimentally observing the behavior of a clamped-free beam structure with local nonlinearities due to micro-slip at the clamped end. The structure is excited near one of its resonance frequencies and recorded responses are employed to identify the nonlinear effects at the boundary. The nonlinear response of structure is defined using an amplitude-dependent nonlinear normal mode identified from measured responses. A new method for reconstructing nonlinear normal mode is represented in this paper by relating the nonlinear normal mode to the clamped end displacement-dependent stiffness parameters using an eigensensitivity analysis. Solution of obtained equations results equivalent stiffness models at different vibration amplitudes and the corresponding nonlinear normal mode is identified. The approach results nonlinear modes with efficient capabilities in predicting dynamical behavior of the structure at different loading conditions. To evaluate the efficiency of the identified model, the structure is excited at higher excitation load levels than those employed in identification procedures and the observed responses are compared with the predictions of the model at the corresponding input force levels. The predictions are in good agreement with the observed behavior indicating success of identification procedure in capturing the physical merits involve in the boundary local nonlinearities.
Prediction of nonlinear soil effects
Hartzell, S.; Bonilla, L.F.; Williams, R.A.
2004-01-01
Mathematical models of soil nonlinearity in common use and recently developed nonlinear codes compared to investigate the range of their predictions. We consider equivalent linear formulations with and without frequency-dependent moduli and damping ratios and nonlinear formulations for total and effective stress. Average velocity profiles to 150 m depth with midrange National Earthquake Hazards Reduction Program site classifications (B, BC, C, D, and E) in the top 30 m are used to compare the response of a wide range of site conditions from rock to soft soil. Nonlinear soil models are compared using the amplification spectrum, calculated as the ratio of surface ground motion to the input motion at the base of the velocity profile. Peak input motions from 0.1g to 0.9g are considered. For site class B, no significant differences exist between the models considered in this article. For site classes BC and C, differences are small at low input motions (0.1g to 0.2g), but become significant at higher input levels. For site classes D and E the overdamping of frequencies above about 4 Hz by the equivalent linear solution with frequency-independent parameters is apparent for the entire range of input motions considered. The equivalent linear formulation with frequency-dependent moduli and damping ratios under damps relative to the nonlinear models considered for site class C with larger input motions and most input levels for site classes D and E. At larger input motions the underdamping for site classes D and E is not as severe as the overdamping with the frequency-independent formulation, but there are still significant differences in the time domain. A nonlinear formulation is recommended for site classes D and E and for site classes BC and C with input motions greater than a few tenths of the acceleration of gravity. The type of nonlinear formulation to use is driven by considerations of the importance of water content and the availability of laboratory soils data. Our
Loizou, Philipos C.; Ma, Jianfen
2011-01-01
The conventional articulation index (AI) measure cannot be applied in situations where non-linear operations are involved and additive noise is present. This is because the definitions of the target and masker signals become vague following non-linear processing, as both the target and masker signals are affected. The aim of the present work is to modify the basic form of the AI measure to account for non-linear processing. This was done using a new definition of the output or effective SNR obtained following non-linear processing. The proposed output SNR definition for a specific band was designed to handle cases where the non-linear processing affects predominantly the target signal rather than the masker signal. The proposed measure also takes into consideration the fact that the input SNR in a specific band cannot be improved following any form of non-linear processing. Overall, the proposed measure quantifies the proportion of input band SNR preserved or transmitted in each band after non-linear processing. High correlation (r = 0.9) was obtained with the proposed measure when evaluated with intelligibility scores obtained by normal-hearing listeners in 72 noisy conditions involving noise-suppressed speech corrupted in four different real-world maskers. PMID:21877811
NASA Astrophysics Data System (ADS)
Vavulin, D. N.; Sukhorukov, A. A.
2016-08-01
We present an analytical description of the process of spontaneous four-wave mixing in a cubic nonlinear fiber with linear losses. We consider the generation of photon pairs in the fiber when in the input of fiber is fed the pumping wave and single signal photon. The focus of attention is on three cases: when the signal photon propagates in the fiber without generating of biphotons; when the photon pair is generated; and when the photon is lost in the fiber. We also consider the cascade processes, but do not give them an analytical description because of their smallness. Description of the biphotons generation process we provide using the Schrodinger-type equation, and take into account the losses in the fiber through the introduction of the virtual beam splitters. We demonstrate the effectiveness of the generation of photon pairs through parametric processes.
Higher-order nonlinear effects in a Josephson parametric amplifier
NASA Astrophysics Data System (ADS)
Kochetov, Bogdan A.; Fedorov, Arkady
2015-12-01
Nonlinearity of the current-phase relationship of a Josephson junction is the key resource for a Josephson parametric amplifier (JPA) as well as for a Josephson traveling-wave parametric amplifier, the only devices in which the quantum limit for added noise has so far been approached at microwave frequencies. A standard approach to describe JPA takes into account only the lowest order (cubic) nonlinearity resulting in a Duffing-like oscillator equation of motion or in a Kerr-type nonlinearity term in the Hamiltonian. In this paper we derive the quantum expression for the gain of JPA including all orders of the Josephson junction nonlinearity in the linear response regime. We then analyze gain saturation effect for stronger signals within a semiclassical approach. Our results reveal nonlinear effects of higher orders and their implications for operation of a JPA.
An enhanced nonlinear damping approach accounting for system constraints in active mass dampers
NASA Astrophysics Data System (ADS)
Venanzi, Ilaria; Ierimonti, Laura; Ubertini, Filippo
2015-11-01
Active mass dampers are a viable solution for mitigating wind-induced vibrations in high-rise buildings and improve occupants' comfort. Such devices suffer particularly when they reach force saturation of the actuators and maximum extension of their stroke, which may occur in case of severe loading conditions (e.g. wind gust and earthquake). Exceeding actuators' physical limits can impair the control performance of the system or even lead to devices damage, with consequent need for repair or substitution of part of the control system. Controllers for active mass dampers should account for their technological limits. Prior work of the authors was devoted to stroke issues and led to the definition of a nonlinear damping approach, very easy to implement in practice. It consisted of a modified skyhook algorithm complemented with a nonlinear braking force to reverse the direction of the mass before reaching the stroke limit. This paper presents an enhanced version of this approach, also accounting for force saturation of the actuator and keeping the simplicity of implementation. This is achieved by modulating the control force by a nonlinear smooth function depending on the ratio between actuator's force and saturation limit. Results of a numerical investigation show that the proposed approach provides similar results to the method of the State Dependent Riccati Equation, a well-established technique for designing optimal controllers for constrained systems, yet very difficult to apply in practice.
GENERAL RELATIVISTIC EFFECTS ON NONLINEAR POWER SPECTRA
Jeong, Donghui; Gong, Jinn-Ouk; Noh, Hyerim; Hwang, Jai-chan E-mail: jgong@lorentz.leidenuniv.nl E-mail: jchan@knu.ac.kr
2011-01-20
The nonlinear nature of Einstein's equation introduces genuine relativistic higher order corrections to the usual Newtonian fluid equations describing the evolution of cosmological perturbations. We study the effect of such novel nonlinearities on the next-to-leading order matter and velocity power spectra for the case of a pressureless, irrotational fluid in a flat Friedmann background. We find that pure general relativistic corrections are negligibly small over all scales. Our result guarantees that, in the current paradigm of standard cosmology, one can safely use Newtonian cosmology even in nonlinear regimes.
NASA Astrophysics Data System (ADS)
Mengistu, Demmelash H.; May, Sylvio
2008-09-01
The nonlinear Poisson-Boltzmann model is used to derive analytical expressions for the free energies of both mixed anionic-zwitterionic and mixed cationic-zwitterionic lipid membranes as function of the mole fraction of charged lipids. Accounting explicitly for the electrostatic properties of the zwitterionic lipid species affects the free energy of anionic and cationic membranes in a qualitatively different way: That of an anionic membrane changes monotonously as a function of the mole fraction of charged lipids, whereas it passes through a pronounced minimum for a cationic membrane.
Solovchuk, Maxim; Sheu, Tony W H; Thiriet, Marc
2013-11-01
This study investigates the influence of blood flow on temperature distribution during high-intensity focused ultrasound (HIFU) ablation of liver tumors. A three-dimensional acoustic-thermal-hydrodynamic coupling model is developed to compute the temperature field in the hepatic cancerous region. The model is based on the nonlinear Westervelt equation, bioheat equations for the perfused tissue and blood flow domains. The nonlinear Navier-Stokes equations are employed to describe the flow in large blood vessels. The effect of acoustic streaming is also taken into account in the present HIFU simulation study. A simulation of the Westervelt equation requires a prohibitively large amount of computer resources. Therefore a sixth-order accurate acoustic scheme in three-point stencil was developed for effectively solving the nonlinear wave equation. Results show that focused ultrasound beam with the peak intensity 2470 W/cm(2) can induce acoustic streaming velocities up to 75 cm/s in the vessel with a diameter of 3 mm. The predicted temperature difference for the cases considered with and without acoustic streaming effect is 13.5 °C or 81% on the blood vessel wall for the vein. Tumor necrosis was studied in a region close to major vessels. The theoretical feasibility to safely necrotize the tumors close to major hepatic arteries and veins was shown. PMID:24180802
Rotational Doppler effect in nonlinear optics
NASA Astrophysics Data System (ADS)
Li, Guixin; Zentgraf, Thomas; Zhang, Shuang
2016-08-01
The translational Doppler effect of electromagnetic and sound waves has been successfully applied in measurements of the speed and direction of vehicles, astronomical objects and blood flow in human bodies, and for the Global Positioning System. The Doppler effect plays a key role for some important quantum phenomena such as the broadened emission spectra of atoms and has benefited cooling and trapping of atoms with laser light. Despite numerous successful applications of the translational Doppler effect, it fails to measure the rotation frequency of a spinning object when the probing wave propagates along its rotation axis. This constraint was circumvented by deploying the angular momentum of electromagnetic waves--the so-called rotational Doppler effect. Here, we report on the demonstration of rotational Doppler shift in nonlinear optics. The Doppler frequency shift is determined for the second harmonic generation of a circularly polarized beam passing through a spinning nonlinear optical crystal with three-fold rotational symmetry. We find that the second harmonic generation signal with circular polarization opposite to that of the fundamental beam experiences a Doppler shift of three times the rotation frequency of the optical crystal. This demonstration is of fundamental significance in nonlinear optics, as it provides us with insight into the interaction of light with moving media in the nonlinear optical regime.
The Effects of Accountability on Higher Education
ERIC Educational Resources Information Center
Rezende, Marcelo
2010-01-01
This paper analyzes the effects of a higher education accountability system in Brazil. For each discipline, colleges were assigned a grade that depended on the scores of their students on the ENC, an annual mandatory exam. These grades were then disclosed to the public and colleges were rewarded or penalized based on them. I find that the ENC had…
Nonlinear buffer layers relevant for reduced nonlinear effects in HTS microwave devices
NASA Astrophysics Data System (ADS)
Seron, D.
2008-02-01
Microwave devices made of a High-Temperature Superconductor (HTS) exhibit a nonlinear response as the microwave power increases. The HTS nonlinearities generate a nonlinear inductance Ld(irf) and a nonlinear resistance Rd(irf) in a device. Ld(irf) and Rd(irf) are responsible for an increase of the device loss, a small frequency dispersion as well as the generation of spurious signals like Intermodulation Distortion (IMD). Nevertheless, the HTS nonlinearities in a microwave device can be reduced using a nonlinear dielectric like a ParaElectric Material (PEM). This assumption has recently been demonstrated theoretically. In a microwave device made of a HTS and a PEM, the nonlinear contribution to the capacitance Cd(vrf) from the PEM acts oppositely to the nonlinear contribution to Ld(irf). This may cancel the effect of the HTS inductive nonlinearities. The PEM also produces a nonlinear conductance Gd(vrf) in a device. All these nonlinear terms contribute to the IMD output power and the nonlinear quality factor (Q0) of a resonant passive microwave device. In this paper, the dependence of the different nonlinear contributions on frequency and applied dc bias voltage (Vdc) is investigated. The relevance to employ PEM in order to reduce the nonlinearities in HTS microwave devices is discussed.
Spatial nonlinear absorption of Alfven waves by dissipative plasma taking account bremsstrahlung
NASA Astrophysics Data System (ADS)
Taiurskii, A. A.; Gavrikov, M. B.
2016-10-01
We study numerically the nonlinear absorption of a plane Alfven wave falling on the stationary boundary of dissipative plasma. This absorption is caused by such factors as the magnetic viscosity, hydrodynamic viscosity, and thermal conductivity of electrons and ions, bremsstrahlung and energy exchange between plasma components. The relevance of this investigation is due to some works, published in 2011, with regard to the heating mechanism of the solar corona and solar wind generation as a result of the absorption of plasma Alfven waves generated in the lower significantly colder layers of the Sun. Numerical analysis shows that the absorption of Alfven waves occurs at wavelengths of the order of skin depth, in which case the classical MHD equations are inapplicable. Therefore, our research is based on equations of two-fluid magnetohydrodynamics that take into account the inertia of the electrons. The implicit difference scheme proposed here for calculating plane-parallel flows of two-fluid plasma reveals a number of important patterns of absorption and thus allows us to study the dependence of the absorption on the Alfven wave frequency and the electron thermal conductivity and viscosity, as well as to evaluate the depth and the velocity of plasma heating during the penetration of Alfven waves interacting with dissipative plasma.
Nonlinear Talbot effect of rogue waves.
Zhang, Yiqi; Belić, Milivoj R; Zheng, Huaibin; Chen, Haixia; Li, Changbiao; Song, Jianping; Zhang, Yanpeng
2014-03-01
Akhmediev and Kuznetsov-Ma breathers are rogue wave solutions of the nonlinear Schrödinger equation (NLSE). Talbot effect (TE) is an image recurrence phenomenon in the diffraction of light waves. We report the nonlinear TE of rogue waves in a cubic medium. It is different from the linear TE, in that the wave propagates in a NL medium and is an eigenmode of NLSE. Periodic rogue waves impinging on a NL medium exhibit recurrent behavior, but only at the TE length and at the half-TE length with a π-phase shift; the fractional TE is absent. The NL TE is the result of the NL interference of the lobes of rogue wave breathers. This interaction is related to the transverse period and intensity of breathers, in that the bigger the period and the higher the intensity, the shorter the TE length.
Nonlinear friction effects on precise motion control of a manipulator
NASA Astrophysics Data System (ADS)
Warshaw, G. D.; Jnifene, A.; Necsulescu, D.
1991-05-01
The need for accurate robot manipulators generated in the last few years an active interest in the effects of nonlinear friction on position and force control of a robot arm. Linear viscous friction has been easily included in robot dynamics models while the inclusion of nonlinear discontinuous friction, and in particular stiction end Coulomb friction resulted in more complex computational requirement for robot dynamic simulation and compensation. A detailed analysis, based on simulations, is performed in order to identify the problem posed by stiction end Coulomb friction on controlling low speed motion in the vicinity of a target point for a robot servomotor and a jointed two-degree of freedom robot arm. The effect of the limited bandwidth of the actuators on filtering the discontinuous friction torque in the closed loop control scheme is investigated. The local effects, around the low speed motion in the vicinity of a moving target for a two-degree of freedom arm is also analyzed. It was shown that the discontinuous nature of the nonlinear stiction end Coulomb friction around zero velocity motion leads to positioning accuracy problems in robot motion control. The apparent erratic behavior at low velocity motion is caused by the discontinuous friction torques which can also excite higher frequency vibration modes which are not usually taken into account in the controller design.
Nonlinear effects in a model of a thermoacoustic refrigerator driven by a loudspeaker
NASA Astrophysics Data System (ADS)
Fan, Li; Chen, Zhe; Zhu, Jun-jie; Ding, Jin; Xia, Jie; Zhang, Shu-yi; Zhang, Hui; Ge, Huan
2015-03-01
It is known that acoustic nonlinear effects in thermoacoustic refrigerators are unfavorable to the performance because they transfer the acoustic energy of the fundamental wave to harmonic waves, while only the former is useful for refrigeration. To study the nonlinear effects in loudspeaker-drive thermoacoustic refrigerators, we measure the acoustic performance in a coupling system composed of a resonant pipe driven by an electrodynamic loudspeaker via an inverse horn. It is found that the nonlinear effects increase both the acoustic pressure of fundamental wave in the resonant pipe and the electroacoustic transfer efficiency of the system. Then, a theoretical model is established to study the nonlinear effects in the coupling system, in which the nonlinearities arising from the loudspeaker, inverse horn, and resonant pipe are taken into account, and the simulated results are used to explain the experimental phenomena.
NASA Technical Reports Server (NTRS)
Starnes, James H., Jr.; Rose, Cheryl A.; Rankin, Charles C.
1996-01-01
The results of an analytical study of the nonlinear response of stiffened fuselage shells with long cracks are presented. The shells are modeled with a hierarchical modeling strategy and analyzed with a nonlinear shell analysis code that maintains the shell in a nonlinear equilibrium state while the crack is grown. The analysis accurately accounts for global and local structural response phenomena. Results are presented for various combinations of internal pressure and mechanical loads, and the effects of crack orientation on the shell response are described. The effects of combined loading conditions and the effects of varying structural parameters on the stress-intensity factors associated with a crack are presented.
An Energy Approach to a Micromechanics Model Accounting for Nonlinear Interface Debonding.
Tan, H.; Huang, Y.; Geubelle, P. H.; Liu, C.; Breitenfeld, M. S.
2005-01-01
We developed a micromechanics model to study the effect of nonlinear interface debonding on the constitutive behavior of composite materials. While implementing this micromechanics model into a large simulation code on solid rockets, we are challenged by problems such as tension/shear coupling and the nonuniform distribution of displacement jump at the particle/matrix interfaces. We therefore propose an energy approach to solve these problems. This energy approach calculates the potential energy of the representative volume element, including the contribution from the interface debonding. By minimizing the potential energy with respect to the variation of the interface displacement jump, the traction balanced interface debonding can be found and the macroscopic constitutive relations established. This energy approach has the ability to treat different load conditions in a unified way, and the interface cohesive law can be in any arbitrary forms. In this paper, the energy approach is verified to give the same constitutive behaviors as reported before.
NASA Astrophysics Data System (ADS)
Peng, Guanghan; Lu, Weizhen; He, Hongdi; Gu, Zhenghua
2016-11-01
We, in this study, construct a new car-following model by accounting for the effect of the optimal velocity changes with memory in terms of the full velocity difference (FVD) model. The stability condition and mKdV equation concerning the optimal velocity changes with memory are derived through both linear stability and nonlinear analyses, respectively. Then, the space concerned can be divided into three regions classified as the stable, the metastable and the unstable ones. Moreover, it is shown that the effect of the optimal velocity changes with memory could enhance the stability of traffic flow. Furthermore, the numerical results verify that not only the sensitivity parameter of the optimal velocity changes with memory of driver but also the memory step could effectively stabilize the traffic flow. In addition, the stability of traffic flow is strengthened by increasing the memory step-size of optimal velocity changes and the intensity of drivers' memory with such changes. Most importantly, the effect of the optimal velocity changes with memory may avoid the disadvantage of historical information, which decreases the stability of traffic flow on road.
Graphene-clad tapered fiber: effective nonlinearity and propagation losses.
Gorbach, A V; Marini, A; Skryabin, D V
2013-12-15
We derive a pulse propagation equation for a graphene-clad optical fiber, treating the optical response of the graphene and nonlinearity of the dielectric fiber core as perturbations in asymptotic expansion of Maxwell equations. We analyze the effective nonlinear and attenuation coefficients due to the graphene layer. Based on the recent experimental measurements of the nonlinear graphene conductivity, we predict considerable enhancement of the effective nonlinearity for subwavelength fiber core diameters. PMID:24322228
Magnetoresistance in organic spintronic devices: the role of nonlinear effects
NASA Astrophysics Data System (ADS)
Shumilin, A. V.; Kabanov, V. V.; Dediu, V. A.
2015-02-01
We derive kinetic equations describing injection and transport of spin-polarized carriers in organic semiconductors with hopping conductivity via an impurity level. The model predicts a strongly voltage dependent magnetoresistance, defined as resistance variation between devices with parallel and antiparallel electrode magnetizations (spin-valve effect). The voltage dependence of the magnetoresistance splits into three distinct regimes. The first regime matches well-known inorganic spintronic regimes, corresponding to barrier-controlled spin injection or the well-known conductivity mismatch case. The second regime at intermediate voltages corresponds to strongly suppressed magnetoresistance. The third regime develops at higher voltages and accounts for a novel paradigm. It is promoted by the strong nonlinearity in the charge transport whose strength is characterized by the dimensionless parameter eU/kBT. This nonlinearity, depending on device conditions, can lead to both significant enhancement or to exponential suppression of the spin-valve effect in organic devices. We believe that these predictions are valid beyond the case of organic semiconductors and should be considered for any material characterized by strongly nonlinear charge transport.
Sustainability science: accounting for nonlinear dynamics in policy and social-ecological systems
Resilience is an emergent property of complex systems. Understanding resilience is critical for sustainability science, as linked social-ecological systems and the policy process that governs them are characterized by non-linear dynamics. Non-linear dynamics in these systems mean...
Nonlinear analysis of bonded joints with thermal effects
NASA Technical Reports Server (NTRS)
Humphreys, E. A.; Herakovich, C. T.
1977-01-01
Nonlinear results are presented for adhesive bonded joints. It is shown that adhesive nonlinearities are only significant in the predicted adhesive shear stresses. Adherend nonlinearities and temperature dependent properties are shown to have little effect upon the adhesive stress predictions under mechanical and thermal loadings.
ERIC Educational Resources Information Center
Mullen, David J., Ed.
This monograph, prepared to assist Georgia elementary principals to better understand accountability and its implications for educational improvement, sets forth many of the theoretical and philosophical bases from which accountability is being considered. Leon M. Lessinger begins this 5-paper presentation by describing the need for accountability…
ERIC Educational Resources Information Center
Lashway, Larry
1999-01-01
This issue reviews publications that provide a starting point for principals looking for a way through the accountability maze. Each publication views accountability differently, but collectively these readings argue that even in an era of state-mandated assessment, principals can pursue proactive strategies that serve students' needs. James A.…
ERIC Educational Resources Information Center
The Newsletter of the Comprehensive Center-Region VI, 1999
1999-01-01
Controversy surrounding the accountability movement is related to how the movement began in response to dissatisfaction with public schools. Opponents see it as one-sided, somewhat mean-spirited, and a threat to the professional status of teachers. Supporters argue that all other spheres of the workplace have accountability systems and that the…
Nonvolatile Memory Based on Nonlinear Magnetoelectric Effects
NASA Astrophysics Data System (ADS)
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.
Functional methods and effective potentials for non-linear composites
NASA Astrophysics Data System (ADS)
Pellegrini, Yves-Patrick; Barthélémy, Marc; Perrin, Gilles
2000-03-01
A formulation of variational principles in terms of functional integrals is proposed for any type of local plastic potentials. The minimization problem is reduced to the computation of a path integral. This integral can be used as a starting point for different approximations. As a first application, it is shown how to compute to second order the weak-disorder perturbative expansion of the effective potentials in random composite. The three-dimensional results of Suquet and Ponte-Castañeda (Suquet, P., Ponte-Castañeda, P., 1993. Small-contrast perturbation expansions for the effective properties of nonlinear composites. C. R. Acad. Sci. (Paris) Ser. II 317, 1515-1522) for the plastic dissipation potential with uniform applied tractions are retrieved and extended to any space dimension, taking correlations into account. In addition, the viscoplastic potential is also computed for uniform strain rates.
Responding Effectively to Test-Based Accountability
ERIC Educational Resources Information Center
Hamilton, Laura; Stecher, Brian
2004-01-01
The No Child Left Behind (NCLB) Act of 2001 has focused the attention of educators, policy makers, and the public on accountability for performance in public education. Yet many of those who will be responsible for improving school performance lack guidance on how to proceed in the brave new world of NCLB accountability. For the most part, state…
Kinetic effects on Alfven wave nonlinearity. II - The modified nonlinear wave equation
NASA Technical Reports Server (NTRS)
Spangler, Steven R.
1990-01-01
A previously developed Vlasov theory is used here to study the role of resonant particle and other kinetic effects on Alfven wave nonlinearity. A hybrid fluid-Vlasov equation approach is used to obtain a modified version of the derivative nonlinear Schroedinger equation. The differences between a scalar model for the plasma pressure and a tensor model are discussed. The susceptibilty of the modified nonlinear wave equation to modulational instability is studied. The modulational instability normally associated with the derivative nonlinear Schroedinger equation will, under most circumstances, be restricted to left circularly polarized waves. The nonlocal term in the modified nonlinear wave equation engenders a new modulational instability that is independent of beta and the sense of circular polarization. This new instability may explain the occurrence of wave packet steepening for all values of the plasma beta in the vicinity of the earth's bow shock.
Nonlinear dynamical effects on reaction rates in thermally fluctuating environments.
Kawai, Shinnosuke; Komatsuzaki, Tamiki
2010-07-21
A framework to calculate the rate constants of condensed phase chemical reactions of manybody systems is presented without relying on the concept of transition state. The theory is based on a framework we developed recently adopting a multidimensional underdamped Langevin equation in the region of a rank-one saddle. The theory provides a reaction coordinate expressed as an analytical nonlinear functional of the position coordinates and velocities of the system (solute), the friction constants, and the random force of the environment (solvent). Up to moderately high temperature, the sign of the reaction coordinate can determine the final destination of the reaction in a thermally fluctuating media, irrespective of what values the other (nonreactive) coordinates may take. In this paper, it is shown that the reaction probability is analytically derived as the probability of the reaction coordinate being positive, and that the integration with the Boltzmann distribution of the initial conditions leads to the exact reaction rate constant when the local equilibrium holds and the quantum effect is negligible. Because of analytical nature of the theory taking into account all nonlinear effects and their combination with fluctuation and dissipation, the theory naturally provides us with the firm mathematical foundation of the origin of the reactivity of the reaction in a fluctuating media.
Nonlinear dynamical effects on reaction rates in thermally fluctuating environments.
Kawai, Shinnosuke; Komatsuzaki, Tamiki
2010-07-21
A framework to calculate the rate constants of condensed phase chemical reactions of manybody systems is presented without relying on the concept of transition state. The theory is based on a framework we developed recently adopting a multidimensional underdamped Langevin equation in the region of a rank-one saddle. The theory provides a reaction coordinate expressed as an analytical nonlinear functional of the position coordinates and velocities of the system (solute), the friction constants, and the random force of the environment (solvent). Up to moderately high temperature, the sign of the reaction coordinate can determine the final destination of the reaction in a thermally fluctuating media, irrespective of what values the other (nonreactive) coordinates may take. In this paper, it is shown that the reaction probability is analytically derived as the probability of the reaction coordinate being positive, and that the integration with the Boltzmann distribution of the initial conditions leads to the exact reaction rate constant when the local equilibrium holds and the quantum effect is negligible. Because of analytical nature of the theory taking into account all nonlinear effects and their combination with fluctuation and dissipation, the theory naturally provides us with the firm mathematical foundation of the origin of the reactivity of the reaction in a fluctuating media. PMID:20544104
Rapid assessment of nonlinear optical propagation effects in dielectrics
NASA Astrophysics Data System (ADS)
Hoyo, J. Del; de La Cruz, A. Ruiz; Grace, E.; Ferrer, A.; Siegel, J.; Pasquazi, A.; Assanto, G.; Solis, J.
2015-01-01
Ultrafast laser processing applications need fast approaches to assess the nonlinear propagation of the laser beam in order to predict the optimal range of processing parameters in a wide variety of cases. We develop here a method based on the simple monitoring of the nonlinear beam shaping against numerical prediction. The numerical code solves the nonlinear Schrödinger equation with nonlinear absorption under simplified conditions by employing a state-of-the art computationally efficient approach. By comparing with experimental results we can rapidly estimate the nonlinear refractive index and nonlinear absorption coefficients of the material. The validity of this approach has been tested in a variety of experiments where nonlinearities play a key role, like spatial soliton shaping or fs-laser waveguide writing. The approach provides excellent results for propagated power densities for which free carrier generation effects can be neglected. Above such a threshold, the peculiarities of the nonlinear propagation of elliptical beams enable acquiring an instantaneous picture of the deposition of energy inside the material realistic enough to estimate the effective nonlinear refractive index and nonlinear absorption coefficients that can be used for predicting the spatial distribution of energy deposition inside the material and controlling the beam in the writing process.
Rapid assessment of nonlinear optical propagation effects in dielectrics.
del Hoyo, J; de la Cruz, A Ruiz; Grace, E; Ferrer, A; Siegel, J; Pasquazi, A; Assanto, G; Solis, J
2015-01-07
Ultrafast laser processing applications need fast approaches to assess the nonlinear propagation of the laser beam in order to predict the optimal range of processing parameters in a wide variety of cases. We develop here a method based on the simple monitoring of the nonlinear beam shaping against numerical prediction. The numerical code solves the nonlinear Schrödinger equation with nonlinear absorption under simplified conditions by employing a state-of-the art computationally efficient approach. By comparing with experimental results we can rapidly estimate the nonlinear refractive index and nonlinear absorption coefficients of the material. The validity of this approach has been tested in a variety of experiments where nonlinearities play a key role, like spatial soliton shaping or fs-laser waveguide writing. The approach provides excellent results for propagated power densities for which free carrier generation effects can be neglected. Above such a threshold, the peculiarities of the nonlinear propagation of elliptical beams enable acquiring an instantaneous picture of the deposition of energy inside the material realistic enough to estimate the effective nonlinear refractive index and nonlinear absorption coefficients that can be used for predicting the spatial distribution of energy deposition inside the material and controlling the beam in the writing process.
Rapid assessment of nonlinear optical propagation effects in dielectrics.
del Hoyo, J; de la Cruz, A Ruiz; Grace, E; Ferrer, A; Siegel, J; Pasquazi, A; Assanto, G; Solis, J
2015-01-01
Ultrafast laser processing applications need fast approaches to assess the nonlinear propagation of the laser beam in order to predict the optimal range of processing parameters in a wide variety of cases. We develop here a method based on the simple monitoring of the nonlinear beam shaping against numerical prediction. The numerical code solves the nonlinear Schrödinger equation with nonlinear absorption under simplified conditions by employing a state-of-the art computationally efficient approach. By comparing with experimental results we can rapidly estimate the nonlinear refractive index and nonlinear absorption coefficients of the material. The validity of this approach has been tested in a variety of experiments where nonlinearities play a key role, like spatial soliton shaping or fs-laser waveguide writing. The approach provides excellent results for propagated power densities for which free carrier generation effects can be neglected. Above such a threshold, the peculiarities of the nonlinear propagation of elliptical beams enable acquiring an instantaneous picture of the deposition of energy inside the material realistic enough to estimate the effective nonlinear refractive index and nonlinear absorption coefficients that can be used for predicting the spatial distribution of energy deposition inside the material and controlling the beam in the writing process. PMID:25564243
Global non-linear effect of temperature on economic production.
Burke, Marshall; Hsiang, Solomon M; Miguel, Edward
2015-11-12
Growing evidence demonstrates that climatic conditions can have a profound impact on the functioning of modern human societies, but effects on economic activity appear inconsistent. Fundamental productive elements of modern economies, such as workers and crops, exhibit highly non-linear responses to local temperature even in wealthy countries. In contrast, aggregate macroeconomic productivity of entire wealthy countries is reported not to respond to temperature, while poor countries respond only linearly. Resolving this conflict between micro and macro observations is critical to understanding the role of wealth in coupled human-natural systems and to anticipating the global impact of climate change. Here we unify these seemingly contradictory results by accounting for non-linearity at the macro scale. We show that overall economic productivity is non-linear in temperature for all countries, with productivity peaking at an annual average temperature of 13 °C and declining strongly at higher temperatures. The relationship is globally generalizable, unchanged since 1960, and apparent for agricultural and non-agricultural activity in both rich and poor countries. These results provide the first evidence that economic activity in all regions is coupled to the global climate and establish a new empirical foundation for modelling economic loss in response to climate change, with important implications. If future adaptation mimics past adaptation, unmitigated warming is expected to reshape the global economy by reducing average global incomes roughly 23% by 2100 and widening global income inequality, relative to scenarios without climate change. In contrast to prior estimates, expected global losses are approximately linear in global mean temperature, with median losses many times larger than leading models indicate.
Global non-linear effect of temperature on economic production
NASA Astrophysics Data System (ADS)
Burke, Marshall; Hsiang, Solomon M.; Miguel, Edward
2015-11-01
Growing evidence demonstrates that climatic conditions can have a profound impact on the functioning of modern human societies, but effects on economic activity appear inconsistent. Fundamental productive elements of modern economies, such as workers and crops, exhibit highly non-linear responses to local temperature even in wealthy countries. In contrast, aggregate macroeconomic productivity of entire wealthy countries is reported not to respond to temperature, while poor countries respond only linearly. Resolving this conflict between micro and macro observations is critical to understanding the role of wealth in coupled human-natural systems and to anticipating the global impact of climate change. Here we unify these seemingly contradictory results by accounting for non-linearity at the macro scale. We show that overall economic productivity is non-linear in temperature for all countries, with productivity peaking at an annual average temperature of 13 °C and declining strongly at higher temperatures. The relationship is globally generalizable, unchanged since 1960, and apparent for agricultural and non-agricultural activity in both rich and poor countries. These results provide the first evidence that economic activity in all regions is coupled to the global climate and establish a new empirical foundation for modelling economic loss in response to climate change, with important implications. If future adaptation mimics past adaptation, unmitigated warming is expected to reshape the global economy by reducing average global incomes roughly 23% by 2100 and widening global income inequality, relative to scenarios without climate change. In contrast to prior estimates, expected global losses are approximately linear in global mean temperature, with median losses many times larger than leading models indicate.
Global non-linear effect of temperature on economic production.
Burke, Marshall; Hsiang, Solomon M; Miguel, Edward
2015-11-12
Growing evidence demonstrates that climatic conditions can have a profound impact on the functioning of modern human societies, but effects on economic activity appear inconsistent. Fundamental productive elements of modern economies, such as workers and crops, exhibit highly non-linear responses to local temperature even in wealthy countries. In contrast, aggregate macroeconomic productivity of entire wealthy countries is reported not to respond to temperature, while poor countries respond only linearly. Resolving this conflict between micro and macro observations is critical to understanding the role of wealth in coupled human-natural systems and to anticipating the global impact of climate change. Here we unify these seemingly contradictory results by accounting for non-linearity at the macro scale. We show that overall economic productivity is non-linear in temperature for all countries, with productivity peaking at an annual average temperature of 13 °C and declining strongly at higher temperatures. The relationship is globally generalizable, unchanged since 1960, and apparent for agricultural and non-agricultural activity in both rich and poor countries. These results provide the first evidence that economic activity in all regions is coupled to the global climate and establish a new empirical foundation for modelling economic loss in response to climate change, with important implications. If future adaptation mimics past adaptation, unmitigated warming is expected to reshape the global economy by reducing average global incomes roughly 23% by 2100 and widening global income inequality, relative to scenarios without climate change. In contrast to prior estimates, expected global losses are approximately linear in global mean temperature, with median losses many times larger than leading models indicate. PMID:26503051
Designing More Effective Accountability Report Cards
ERIC Educational Resources Information Center
Sabbah, Faris M.
2011-01-01
The purpose of this study was to identify and design standards and procedures for creating easily interpreted accountability reports cards, consistent with the requirements spelled out in the No Child Left Behind Act of 2001 (NCLB). The use of public report cards was first raised during the debate that took place immediately prior to the passage…
NASA Astrophysics Data System (ADS)
Song, Pengchao
Recent studies of the occurrence of post-flutter limit cycle oscillations (LCO) of the F-16 have provided good support to the long-standing hypothesis that this phenomenon involves a nonlinear structural damping. A potential mechanism for the appearance of nonlinearity in the damping are the nonlinear geometric effects that arise when the deformations become large enough to exceed the linear regime. In this light, the focus of this investigation is first on extending nonlinear reduced order modeling (ROM) methods to include viscoelasticity which is introduced here through a linear Kelvin-Voigt model in the undeformed configuration. Proceeding with a Galerkin approach, the ROM governing equations of motion are obtained and are found to be of a generalized van der Pol-Duffing form with parameters depending on the structure and the chosen basis functions. An identification approach of the nonlinear damping parameters is next proposed which is applicable to structures modeled within commercial finite element software. The effects of this nonlinear damping mechanism on the post-flutter response is next analyzed on the Goland wing through time-marching of the aeroelastic equations comprising a rational fraction approximation of the linear aerodynamic forces. It is indeed found that the nonlinearity in the damping can stabilize the unstable aerodynamics and lead to finite amplitude limit cycle oscillations even when the stiffness related nonlinear geometric effects are neglected. The incorporation of these latter effects in the model is found to further decrease the amplitude of LCO even though the dominant bending motions do not seem to stiffen as the level of displacements is increased in static analyses.
An alternative approach to characterize nonlinear site effects
Zhang, R.R.; Hartzell, S.; Liang, J.; Hu, Y.
2005-01-01
This paper examines the rationale of a method of nonstationary processing and analysis, referred to as the Hilbert-Huang transform (HHT), for its application to a recording-based approach in quantifying influences of soil nonlinearity in site response. In particular, this paper first summarizes symptoms of soil nonlinearity shown in earthquake recordings, reviews the Fourier-based approach to characterizing nonlinearity, and offers justifications for the HHT in addressing nonlinearity issues. This study then uses the HHT method to analyze synthetic data and recordings from the 1964 Niigata and 2001 Nisqually earthquakes. In doing so, the HHT-based site response is defined as the ratio of marginal Hilbert amplitude spectra, alternative to the Fourier-based response that is the ratio of Fourier amplitude spectra. With the Fourier-based approach in studies of site response as a reference, this study shows that the alternative HHT-based approach is effective in characterizing soil nonlinearity and nonlinear site response.
Nonlinear effective pressure law for permeability
NASA Astrophysics Data System (ADS)
Li, M.; Xiao, W.-L.; Bernabé, Y.; Zhao, J.-Z.
2014-01-01
The permeability k of porous rocks is known to vary with confining pressure pc and pore fluid pressure pf. But it is, in principle, possible to replace the two-variable function k(pf, pc) by a function k(peff) of a single variable, peff(pf, pc), called the effective pressure. Our goal in this paper is to establish an experimental method for determining a possibly nonlinear, effective pressure law (EPL) for permeability, i.e., find the function κs(pf, pc) such that the effective pressure is given by peff = pc - κs(pf, pc) pf. We applied this method to a set of 26 sandstone cores from various hydrocarbon reservoirs in China. We found that κs greatly varied, from sample to sample, in magnitude and range, sometimes even reaching theoretically prohibited values (i.e., greater than 1 or lower than porosity). One interesting feature of κs(pf, pc) is that it could be approximately described in all rocks but one as a decreasing function κs(pc - pf) of Terzaghi's differential pressure. We also investigated the dependence of permeability on peff for each of our samples. Three models from the literature, i.e., exponential (E), power law (P), and the Walsh model (W), were tested. The (W) model was more likely to fit the experimental data of cores with a high pressure dependence of permeability whereas (E) occurred more frequently in low-pressure-sensitive rocks. Finally, we made various types of two- and three-dimensional microstructural observations that generally supported the trend mentioned above.
A Novel Effective Approach for Solving Fractional Nonlinear PDEs
Aminikhah, Hossein; Malekzadeh, Nasrin; Rezazadeh, Hadi
2014-01-01
The present work introduces an effective modification of homotopy perturbation method for the solution of nonlinear time-fractional biological population model and a system of three nonlinear time-fractional partial differential equations. In this approach, the solution is considered a series expansion that converges to the nonlinear problem. The new approximate analytical procedure depends only on two iteratives. The analytical approximations to the solution are reliable and confirm the ability of the new homotopy perturbation method as an easy device for computing the solution of nonlinear equations. PMID:27419212
Effects of nonlinear propagation in ultrasound contrast agent imaging.
Tang, Meng-Xing; Kamiyama, Naohisa; Eckersley, Robert J
2010-03-01
This paper investigates two types of nonlinear propagation and their effects on image intensity and contrast-to-tissue ratio (CTR) in contrast ultrasound images. Previous studies have shown that nonlinear propagation can occur when ultrasound travels through tissue and microbubble clouds, making tissue farther down the acoustic path appear brighter in pulse inversion (PI) images, thus reducing CTR. In this study, the effect of nonlinear propagation through tissue or microbubbles on PI image intensity and CTR are compared at low mechanical index. A combination of simulation and experiment with SonoVue microbubbles were performed using a microbubble dynamics model, a laboratory ultrasound system and a clinical prototype scanner. The results show that, close to the bubble resonance frequency, nonlinear propagation through a bubble cloud of a few centimeter thickness with a modest concentration (1:10000 dilution of SonoVue microbubbles) is much more significant than through tissue-mimicking material. Consequently, CTR in regions distal to the imaging probe is greatly reduced for nonlinear propagation through the bubble cloud, with as much as a 12-dB reduction compared with nonlinear propagation through tissue-mimicking material. Both types of nonlinear propagation cause only a small change in bubble PI signals at the bubble resonance frequency. When the driving frequency increases beyond bubble resonance, nonlinear propagation through bubbles is greatly reduced in absolute values. However because of a greater reduction in nonlinear scattering from bubbles at higher frequencies, the corresponding CTR is much lower than that at bubble resonance frequency.
Artemyev, A. V. Vasiliev, A. A.; Mourenas, D.; Krasnoselskikh, V. V.
2014-10-15
In this paper, we consider high-energy electron scattering and nonlinear trapping by oblique whistler waves via the Landau resonance. We use recent spacecraft observations in the radiation belts to construct the whistler wave model. The main purpose of the paper is to provide an estimate of the critical wave amplitude for which the nonlinear wave-particle resonant interaction becomes more important than particle scattering. To this aim, we derive an analytical expression describing the particle scattering by large amplitude whistler waves and compare the corresponding effect with the nonlinear particle acceleration due to trapping. The latter is much more rare but the corresponding change of energy is substantially larger than energy jumps due to scattering. We show that for reasonable wave amplitudes ∼10–100 mV/m of strong whistlers, the nonlinear effects are more important than the linear and nonlinear scattering for electrons with energies ∼10–50 keV. We test the dependencies of the critical wave amplitude on system parameters (background plasma density, wave frequency, etc.). We discuss the role of obtained results for the theoretical description of the nonlinear wave amplification in radiation belts.
A Nonlinear Mixed Effects Model for Latent Variables
ERIC Educational Resources Information Center
Harring, Jeffrey R.
2009-01-01
The nonlinear mixed effects model for continuous repeated measures data has become an increasingly popular and versatile tool for investigating nonlinear longitudinal change in observed variables. In practice, for each individual subject, multiple measurements are obtained on a single response variable over time or condition. This structure can be…
Xiong, Caiqiao; Zhou, Xiaoyu; Zhang, Ning; Zhan, Lingpeng; Chen, Yongtai; Nie, Zongxiu
2016-02-01
The nonlinear harmonics within the ion motion are the fingerprint of the nonlinear fields. They are exclusively introduced by these nonlinear fields and are responsible to some specific nonlinear effects such as nonlinear resonance effect. In this article, the ion motion in the quadrupole field with a weak superimposed octopole component, described by the nonlinear Mathieu equation (NME), was studied by using the analytical harmonic balance (HB) method. Good accuracy of the HB method, which was comparable with that of the numerical fourth-order Runge-Kutta (4th RK), was achieved in the entire first stability region, except for the points at the stability boundary (i.e., β = 1) and at the nonlinear resonance condition (i.e., β = 0.5). Using the HB method, the nonlinear 3β harmonic series introduced by the octopole component and the resultant nonlinear resonance effect were characterized. At nonlinear resonance, obvious resonant peaks were observed in the nonlinear 3β series of ion motion, but were not found in the natural harmonics. In addition, both resonant excitation and absorption peaks could be observed, simultaneously. These are two unique features of the nonlinear resonance, distinguishing it from the normal resonance. Finally, an approximation equation was given to describe the corresponding working parameter, q nr , at nonlinear resonance. This equation can help avoid the sensitivity degradation due to the operation of ion traps at the nonlinear resonance condition. PMID:26497312
The Effects of Different Teaching Approaches in Introductory Financial Accounting
ERIC Educational Resources Information Center
Chiang, Bea; Nouri, Hossein; Samanta, Subarna
2014-01-01
The purpose of the research is to examine the effect of the two different teaching approaches in the first accounting course on student performance in a subsequent finance course. The study compares 128 accounting and finance students who took introductory financial accounting by either a user approach or a traditional preparer approach to examine…
Topological nature of nonlinear optical effects in solids
Morimoto, Takahiro; Nagaosa, Naoto
2016-01-01
There are a variety of nonlinear optical effects including higher harmonic generations, photovoltaic effects, and nonlinear Kerr rotations. They are realized by strong light irradiation to materials that results in nonlinear polarizations in the electric field. These are of great importance in studying the physics of excited states of the system as well as for applications to optical devices and solar cells. Nonlinear properties of materials are usually described by nonlinear susceptibilities, which have complex expressions including many matrix elements and energy denominators. On the other hand, a nonequilibrium steady state under an electric field periodic in time has a concise description in terms of the Floquet bands of electrons dressed by photons. We show theoretically, using the Floquet formalism, that various nonlinear optical effects, such as the shift current in noncentrosymmetric materials, photovoltaic Hall response, and photo-induced change of order parameters under the continuous irradiation of monochromatic light, can be described in a unified fashion by topological quantities involving the Berry connection and Berry curvature. We found that vector fields defined with the Berry connections in the space of momentum and/or parameters govern the nonlinear responses. This topological view offers a route to designing nonlinear optical materials. PMID:27386523
Topological nature of nonlinear optical effects in solids.
Morimoto, Takahiro; Nagaosa, Naoto
2016-05-01
There are a variety of nonlinear optical effects including higher harmonic generations, photovoltaic effects, and nonlinear Kerr rotations. They are realized by strong light irradiation to materials that results in nonlinear polarizations in the electric field. These are of great importance in studying the physics of excited states of the system as well as for applications to optical devices and solar cells. Nonlinear properties of materials are usually described by nonlinear susceptibilities, which have complex expressions including many matrix elements and energy denominators. On the other hand, a nonequilibrium steady state under an electric field periodic in time has a concise description in terms of the Floquet bands of electrons dressed by photons. We show theoretically, using the Floquet formalism, that various nonlinear optical effects, such as the shift current in noncentrosymmetric materials, photovoltaic Hall response, and photo-induced change of order parameters under the continuous irradiation of monochromatic light, can be described in a unified fashion by topological quantities involving the Berry connection and Berry curvature. We found that vector fields defined with the Berry connections in the space of momentum and/or parameters govern the nonlinear responses. This topological view offers a route to designing nonlinear optical materials. PMID:27386523
Enhancement of the Sagnac effect due to nonlinearly induced nonreciprocity
NASA Astrophysics Data System (ADS)
Kaplan, A. E.; Meystre, P.
1981-12-01
A novel method is proposed for enhancing the Sagnac effect through the use of a nonlinear ring interferometer. The proposed method takes advantage of the nonlinearly induced nonreciprocity of counterpropagating waves caused by the formation of an index grating in the nonlinear medium. The enhancement of the Sagnac effect could find applications in cases where high sensitivity is required, e.g. in optical tests of general relativity. The measurement of the enhancement factor also provides a novel spectroscopic method for analyzing nonlocal interactions (nonreciprocal Sagnac spectroscopy).
Effective mass Schrödinger equation and nonlinear algebras
NASA Astrophysics Data System (ADS)
Roy, B.; Roy, P.
2005-06-01
Using supersymmetry we obtain solutions of Schrödinger equation with a position dependent effective mass exhibiting a harmonic oscillator like spectrum. We also discuss the underlying nonlinear algebraic symmetry of the problem.
Nonlinear chorus wave effects on energetic electrons reexamined
NASA Astrophysics Data System (ADS)
Zheng, Q.; Fok, M. H.; Zheng, Y.; Lui, A.
2012-12-01
Electron energy transport due to nonlinear plasma wave particle interactions are carried out by wave and particles resonating with each other. Many nonlinear wave studies conducted in the past have only considered the main resonance between wave and electrons. However, we have found through test particle simulations that although independent, separate contributions from higher order resonances can be small, but they can have a rather significant impact on the main-order contribution hence the total nonlinear wave effects. Contribution from different orders can interfere with each other hence the overall nonlinear wave effect is significantly different from that of just the major resonance. Therefore in the nonlinear wave particle interaction regime, contribution from different resonant orders is inseparable and contributions from higher order wave-particle resonances should be all included. For the same token, banded plasma waves should be used in nonlinear wave studies instead of assumed monochromatic waves. By including all the essential factors mentioned above, the overall electron transport due to the nonlinear plasma wave effects take the form of diffusion-like rather than advection, which was reported in many previous studies. It is also found that chorus wave induced electron transport is one important mechanism for the formation of electron butterfly pitch angle distribution.
Effect of Nozzle Nonlinearities upon Nonlinear Stability of Liquid Propellant Rocket Motors
NASA Technical Reports Server (NTRS)
Padmanabhan, M. S.; Powell, E. A.; Zinn, B. T.
1975-01-01
A three dimensional, nonlinear nozzle admittance relation is developed by solving the wave equation describing finite amplitude oscillatory flow inside the subsonic portion of a choked, slowly convergent axisymmetric nozzle. This nonlinear nozzle admittance relation is then used as a boundary condition in the analysis of nonlinear combustion instability in a cylindrical liquid rocket combustor. In both nozzle and chamber analyses solutions are obtained using the Galerkin method with a series expansion consisting of the first tangential, second tangential, and first radial modes. Using Crocco's time lag model to describe the distributed unsteady combustion process, combustion instability calculations are presented for different values of the following parameters: (1) time lag, (2) interaction index, (3) steady-state Mach number at the nozzle entrance, and (4) chamber length-to-diameter ratio. In each case, limit cycle pressure amplitudes and waveforms are shown for both linear and nonlinear nozzle admittance conditions. These results show that when the amplitudes of the second tangential and first radial modes are considerably smaller than the amplitude of the first tangential mode the inclusion of nozzle nonlinearities has no significant effect on the limiting amplitude and pressure waveforms.
NASA Astrophysics Data System (ADS)
Liang, Peixin; Chai, Feng; Bi, Yunlong; Pei, Yulong; Cheng, Shukang
2016-11-01
Based on subdomain model, this paper presents an analytical method for predicting the no-load magnetic field distribution, back-EMF and torque in general spoke-type motors with magnetic bridges. Taking into account the saturation and nonlinearity of magnetic material, the magnetic bridges are equivalent to fan-shaped saturation regions. For getting standard boundary conditions, a lumped parameter magnetic circuit model and iterative method are employed to calculate the permeability. The final field domain is divided into five types of simple subdomains. Based on the method of separation of variables, the analytical expression of each subdomain is derived. The analytical results of the magnetic field distribution, Back-EMF and torque are verified by finite element method, which confirms the validity of the proposed model for facilitating the motor design and optimization.
The Negative Testing Effect and Multifactor Account
ERIC Educational Resources Information Center
Peterson, Daniel J.; Mulligan, Neil W.
2013-01-01
Across 3 experiments, we investigated the factors that dictate when taking a test improves subsequent memory performance (the "testing effect"). In Experiment 1, participants retrieving a set of targets during a retrieval practice phase ultimately recalled fewer of those targets compared with a group of participants who studied the…
Non-linear effects in bunch compressor of TARLA
NASA Astrophysics Data System (ADS)
Yildiz, Hüseyin; Aksoy, Avni; Arikan, Pervin
2016-03-01
Transport of a beam through an accelerator beamline is affected by high order and non-linear effects such as space charge, coherent synchrotron radiation, wakefield, etc. These effects damage form of the beam, and they lead particle loss, emittance growth, bunch length variation, beam halo formation, etc. One of the known non-linear effects on low energy machine is space charge effect. In this study we focus on space charge effect for Turkish Accelerator and Radiation Laboratory in Ankara (TARLA) machine which is designed to drive InfraRed Free Electron Laser covering the range of 3-250 µm. Moreover, we discuss second order effects on bunch compressor of TARLA.
Non-Linear Effects in Knowledge Production
NASA Astrophysics Data System (ADS)
Purica, Ionut
2007-04-01
The generation of technological knowledge is paramount to our present development; the production of technological knowledge is governed by the same Cobb Douglas type model, with the means of research and the intelligence level replacing capital, respectively labor. We are exploring the basic behavior of present days' economies that are producing technological knowledge, along with the `usual' industrial production and determine a basic behavior that turns out to be a `Henon attractor'. Measures are introduced for the gain of technological knowledge and for the information of technological sequences that are based respectively on the underlying multi-valued modal logic of the technological research and on nonlinear thermodynamic considerations.
Nonlinear Geometric Effects in Mechanical Bistable Morphing Structures
NASA Astrophysics Data System (ADS)
Chen, Zi; Guo, Qiaohang; Majidi, Carmel; Chen, Wenzhe; Srolovitz, David J.; Haataja, Mikko P.
2012-09-01
Bistable structures associated with nonlinear deformation behavior, exemplified by the Venus flytrap and slap bracelet, can switch between different functional shapes upon actuation. Despite numerous efforts in modeling such large deformation behavior of shells, the roles of mechanical and nonlinear geometric effects on bistability remain elusive. We demonstrate, through both theoretical analysis and tabletop experiments, that two dimensionless parameters control bistability. Our work classifies the conditions for bistability, and extends the large deformation theory of plates and shells.
NASA Astrophysics Data System (ADS)
ElNady, Khaled; Goda, Ibrahim; Ganghoffer, Jean-François
2016-09-01
The asymptotic homogenization technique is presently developed in the framework of geometrical nonlinearities to derive the large strains effective elastic response of network materials viewed as repetitive beam networks. This works extends the small strains homogenization method developed with special emphasis on textile structures in Goda et al. (J Mech Phys Solids 61(12):2537-2565, 2013). A systematic methodology is established, allowing the prediction of the overall mechanical properties of these structures in the nonlinear regime, reflecting the influence of the geometrical and mechanical micro-parameters of the network structure on the overall response of the chosen equivalent continuum. Internal scale effects of the initially discrete structure are captured by the consideration of a micropolar effective continuum model. Applications to the large strain response of 3D hexagonal lattices and dry textiles exemplify the powerfulness of the proposed method. The effective mechanical responses obtained for different loadings are validated by FE simulations performed over a representative unit cell.
Effects of Accountancy Internship on Subsequent Academic Performance.
ERIC Educational Resources Information Center
Kwong, K. S.; Lui, Gladie
1991-01-01
Explores the effects of accounting internships upon subsequent academic achievement. Reports that grade point averages and degree examination results of 10 Chinese University of Hong Kong students who had been interns were compared to scores of 236 accounting majors who had not. Concludes that internships increased student knowledge and…
Kinetic equations for a density matrix describing nonlinear effects in spectral line wings
Parkhomenko, A. I. Shalagin, A. M.
2011-11-15
Kinetic quantum equations are derived for a density matrix with collision integrals describing nonlinear effects in spectra line wings. These equations take into account the earlier established inequality of the spectral densities of Einstein coefficients for absorption and stimulated radiation emission by a two-level quantum system in the far wing of a spectral line in the case of frequent collisions. The relationship of the absorption and stimulated emission probabilities with the characteristics of radiation and an elementary scattering event is found.
NASA Technical Reports Server (NTRS)
Cantrell, John H.; Yost, William T.
1990-01-01
The effects of material structure on the nonlinearity parameters are reviewed. Problems discussed include definition of nonlinearity parameters, square-law nonlinearity and collinear beam-mixing, structure dependence of the nonlinearity parameters, negative nonlinearity parameters, and implications for materials characterization.
Space charge induced nonlinear effects in quadrupole ion traps.
Guo, Dan; Wang, Yuzhuo; Xiong, Xingchuang; Zhang, Hua; Zhang, Xiaohua; Yuan, Tao; Fang, Xiang; Xu, Wei
2014-03-01
A theoretical method was proposed in this work to study space charge effects in quadrupole ion traps, including ion trapping, ion motion frequency shift, and nonlinear effects on ion trajectories. The spatial distributions of ion clouds within quadrupole ion traps were first modeled for both 3D and linear ion traps. It is found that the electric field generated by space charge can be expressed as a summation of even-order fields, such as quadrupole field, octopole field, etc. Ion trajectories were then solved using the harmonic balance method. Similar to high-order field effects, space charge will result in an "ocean wave" shape nonlinear resonance curve for an ion under a dipolar excitation. However, the nonlinear resonance curve will be totally shifted to lower frequencies and bend towards ion secular frequency as ion motion amplitude increases, which is just the opposite effect of any even-order field. Based on theoretical derivations, methods to reduce space charge effects were proposed.
Nonlinear effects associated with kinetic Alfvén wave
NASA Astrophysics Data System (ADS)
Gaur, Nidhi; Sharma, R. P.
2015-04-01
The nonlinear phenomena are of striking importance in understanding the particle acceleration, heating, and turbulence in the interplanetary space. Kinetic Alfvén wave (KAW) is one of the strong candidates responsible for accelerating the solar wind and powering the solar wind turbulence. Therefore, the nonlinear properties of KAW are attracting a good attention. In the present work, we have investigated the nonlinear effects associated with KAW in the solar wind plasma at around 1 A.U. The ponderomotive force of (relatively high frequency, high power) pump KAW may be used to excite the low-frequency KAW (LKAW). For this purpose, we have derived the dynamical equations to analyze the nonlinear dynamics of relatively high frequency pump KAW in the presence of LKAW perturbation. The numerical solution has been carried out for the coupled system of equations by using the pseudospectral method for space integration and finite difference method along with the predictor corrector scheme for the evolution in time. The coupled system of nonlinear dynamical equations has been analyzed to study the nonlinear effects associated with pump KAW and the resulting turbulent spectra at 1 A.U.
NASA Astrophysics Data System (ADS)
Lee, Chieh-Han; Yu, Hwa-Lung; Chien, Lung-Chang
2014-05-01
Dengue fever has been identified as one of the most widespread vector-borne diseases in tropical and sub-tropical. In the last decade, dengue is an emerging infectious disease epidemic in Taiwan especially in the southern area where have annually high incidences. For the purpose of disease prevention and control, an early warning system is urgently needed. Previous studies have showed significant relationships between climate variables, in particular, rainfall and temperature, and the temporal epidemic patterns of dengue cases. However, the transmission of the dengue fever is a complex interactive process that mostly understated the composite space-time effects of dengue fever. This study proposes developing a one-week ahead warning system of dengue fever epidemics in the southern Taiwan that considered nonlinear associations between weekly dengue cases and meteorological factors across space and time. The early warning system based on an integration of distributed lag nonlinear model (DLNM) and stochastic Bayesian Maximum Entropy (BME) analysis. The study identified the most significant meteorological measures including weekly minimum temperature and maximum 24-hour rainfall with continuous 15-week lagged time to dengue cases variation under condition of uncertainty. Subsequently, the combination of nonlinear lagged effects of climate variables and space-time dependence function is implemented via a Bayesian framework to predict dengue fever occurrences in the southern Taiwan during 2012. The result shows the early warning system is useful for providing potential outbreak spatio-temporal prediction of dengue fever distribution. In conclusion, the proposed approach can provide a practical disease control tool for environmental regulators seeking more effective strategies for dengue fever prevention.
Self-similar rogue waves and nonlinear tunneling effects in inhomogeneous nonlinear fiber optics
NASA Astrophysics Data System (ADS)
Wang, Lei; Zhu, Yu-Jie; Jiang, Dong-Yang
2016-04-01
Analytical first- and second-order rogue wave solutions of the inhomogeneous modified nonlinear Schrödinger equation are presented by using similarity transformation. Then, by the proper choices of the inhomogeneous coefficients and free parameters, the controllable behaviors of the optical rogue waves are graphically discussed in the nonlinear fiber optics context. It is found that the width of the rogue wave can be tuned by adjusting the parameter ? and the locations of the rogue waves are linearly controlled by the parameter ?. The intensities of the rogue waves are influenced by the inhomogeneous linear gain/loss coefficient ? and parameter ?. The dispersion management function ? has effects on the periods and trajectories of the rogue waves and can induce maintenance (or annihilation) along ? direction. Interestingly, the composite rogue waves are revealed, the location of which is manipulated through changing the dispersion management function ?. Additionally, the nonlinear tunneling of those rogue waves is investigated as they propagate through a dispersion barrier (or well) and nonlinear barrier (or well).
Chen, Fei; Hu, Yi
2013-05-01
In this study, two methods are proposed to modify the normalized covariance metric (NCM) measure to reduce the effects of gain-induced nonlinear distortions introduced by most noise-suppression algorithms. Considering that the gain-induced distortions behave differently dependent on the signal-to-noise ratio between the noise-reduced speech and the noise, the first approach introduces a penalty factor involving this ratio in the modified NCM measure. The second approach deemphasizes segments marked with amplification distortions that contribute less to intelligibility via adaptive thresholding. Significantly higher correlations with intelligibility scores were obtained from the modified NCM measures compared with the original NCM measures.
Surface effect on the nonlinear forced vibration of cantilevered nanobeams
NASA Astrophysics Data System (ADS)
Dai, H. L.; Zhao, D. M.; Zou, J. J.; Wang, L.
2016-06-01
The nonlinear forced vibration behavior of a cantilevered nanobeam is investigated in this paper, essentially considering the effect due to the surface elastic layer. The governing equation of motion for the nano-cantilever is derived, with consideration of the geometrical nonlinearity and the effects of additional flexural rigidity and residual stress of the surface layer. Then, the nonlinear partial differential equation (PDE) is discretized into a set of nonlinear ordinary differential equations (ODEs) by means of the Galerkin's technique. It is observed that surface effects on the natural frequency of the nanobeam is of significance, especially for the case when the aspect ratio of the nanobeam is large. The nonlinear resonant dynamics of the nanobeam system is evaluated by varying the excitation frequency around the fundamental resonance, showing that the nanobeam would display hardening-type behavior and hence the frequency-response curves bend to the right in the presence of positive residual surface stress. However, with the negative residual surface stress, this hardening-type behavior can be shifted to a softening-type one which becomes even more evident with increase of the aspect ratio parameter. It is also demonstrated that the combined effects of the residual stress and aspect ratio on the maximum amplitude of the nanobeam may be pronounced.
Joint nonlinearity effects in the design of a flexible truss structure control system
NASA Technical Reports Server (NTRS)
Mercadal, Mathieu
1986-01-01
Nonlinear effects are introduced in the dynamics of large space truss structures by the connecting joints which are designed with rather important tolerances to facilitate the assembly of the structures in space. The purpose was to develop means to investigate the nonlinear dynamics of the structures, particularly the limit cycles that might occur when active control is applied to the structures. An analytical method was sought and derived to predict the occurrence of limit cycles and to determine their stability. This method is mainly based on the quasi-linearization of every joint using describing functions. This approach was proven successful when simple dynamical systems were tested. Its applicability to larger systems depends on the amount of computations it requires, and estimates of the computational task tend to indicate that the number of individual sources of nonlinearity should be limited. Alternate analytical approaches, which do not account for every single nonlinearity, or the simulation of a simplified model of the dynamical system should, therefore, be investigated to determine a more effective way to predict limit cycles in large dynamical systems with an important number of distributed nonlinearities.
Solvent effects on the nonlinear optical responses of anil derivatives
NASA Astrophysics Data System (ADS)
Plaquet, Aurélie; Bogdan, Elena; Antonov, Liudmil; Rodriguez, Vincent; Ducasse, Laurent; Champagne, Benoıît; Castet, Frédéric
2015-01-01
This contribution addresses the solvent effects on the second-order nonlinear optical responses of three representative anil derivatives, and in particular on their variations upon switching between the enol-imine and keto-amine forms. The impact of solute-solvent interactions is investigated by means of ab initio and DFT calculations in which solvent effects are included through the polarizable continuum model. In addition, for one of the compounds, Hyper-Rayleigh Scattering experiments and ab initio calculations are combined to highlight the impact of the solvent-induced equilibrium displacement. These studies show that the global solvent effect on the nonlinear optical responses originates from both the displacement of the tautomeric equilibrium and from the modification of the second-order nonlinear optical response of the individual tautomeric forms.
Coriolis effects on nonlinear oscillations of rotating cylinders and rings
NASA Technical Reports Server (NTRS)
Padovan, J.
1976-01-01
The effects which moderately large deflections have on the frequency spectrum of rotating rings and cylinders are considered. To develop the requisite solution, a variationally constrained version of the Lindstedt-Poincare procedure is employed. Based on the solution developed, in addition to considering the effects of displacement induced nonlinearity, the role of Coriolis forces is also given special consideration.
Competition between the tensor light shift and nonlinear Zeeman effect
Chalupczak, W.; Wojciechowski, A.; Pustelny, S.; Gawlik, W.
2010-08-15
Many precision measurements (e.g., in spectroscopy, atomic clocks, quantum-information processing, etc.) suffer from systematic errors introduced by the light shift. In our experimental configuration, however, the tensor light shift plays a positive role enabling the observation of spectral features otherwise masked by the cancellation of the transition amplitudes and creating resonances at a frequency unperturbed either by laser power or beam inhomogeneity. These phenomena occur thanks to the special relation between the nonlinear Zeeman and light shift effects. The interplay between these two perturbations is systematically studied and the cancellation of the nonlinear Zeeman effect by the tensor light shift is demonstrated.
Low-intensity nonlinear spectral effects in compton scattering.
Hartemann, Frederic V; Albert, Félicie; Siders, Craig W; Barty, C P J
2010-09-24
Nonlinear effects are known to occur in Compton scattering light sources, when the laser normalized potential A approaches unity. In this Letter, it is shown that nonlinear spectral features can appear at arbitrarily low values of A, if the fractional bandwidth of the laser pulse Δϕ⁻¹ is sufficiently small to satisfy A²Δϕ≃1. A three-dimensional analysis, based on a local plane wave, slow-varying envelope approximation, enables the study of these effects for realistic interactions between an electron beam and a laser pulse, and their influence on high-precision Compton scattering light sources.
Low-Intensity Nonlinear Spectral Effects in Compton Scattering
NASA Astrophysics Data System (ADS)
Hartemann, Frederic V.; Albert, Félicie; Siders, Craig W.; Barty, C. P. J.
2010-09-01
Nonlinear effects are known to occur in Compton scattering light sources, when the laser normalized potential A approaches unity. In this Letter, it is shown that nonlinear spectral features can appear at arbitrarily low values of A, if the fractional bandwidth of the laser pulse Δϕ-1 is sufficiently small to satisfy A2Δϕ≃1. A three-dimensional analysis, based on a local plane wave, slow-varying envelope approximation, enables the study of these effects for realistic interactions between an electron beam and a laser pulse, and their influence on high-precision Compton scattering light sources.
Low-intensity nonlinear spectral effects in compton scattering.
Hartemann, Frederic V; Albert, Félicie; Siders, Craig W; Barty, C P J
2010-09-24
Nonlinear effects are known to occur in Compton scattering light sources, when the laser normalized potential A approaches unity. In this Letter, it is shown that nonlinear spectral features can appear at arbitrarily low values of A, if the fractional bandwidth of the laser pulse Δϕ⁻¹ is sufficiently small to satisfy A²Δϕ≃1. A three-dimensional analysis, based on a local plane wave, slow-varying envelope approximation, enables the study of these effects for realistic interactions between an electron beam and a laser pulse, and their influence on high-precision Compton scattering light sources. PMID:21230757
NASA Astrophysics Data System (ADS)
Niculescu, Ecaterina C.; Eseanu, Nicoleta; Radu, Adrian
2013-05-01
An investigation of the laser radiation effects on the nonlinear optical rectification in an AlGaAs inverse parabolic quantum well with asymmetrical barriers is performed within the effective mass approximation, taking into account the dielectric mismatch between the semiconductor and the surrounding medium. Using the accurate dressing effect for the confinement potential and electrostatic self-energy due to the image-charges, we prove that: (i) a spatially dependent effective mass in the laser-dressing parameter definition is required for precise calculations of the energy levels; (ii) the dielectric confinement provides a potential mechanism for controlling electronic states and optical properties of quantum wells. In addition, the laser dependence of the energy where the optical rectification reaches its maximum can be adjusted by external electric fields. The joint action of the intense high-frequency laser and static electric fields may provide tuning of the nonlinear properties in this type of dielectrically modulated heterostructures.
Collisional effects on nonlinear ion drag force for small grains
Hutchinson, I. H.; Haakonsen, C. B.
2013-08-15
The ion drag force arising from plasma flow past an embedded spherical grain is calculated self-consistently and non-linearly using particle in cell codes, accounting for ion-neutral collisions. Using ion velocity distribution appropriate for ion drift driven by a force field gives wake potential and force greatly different from a shifted Maxwellian distribution, regardless of collisionality. The low-collisionality forces are shown to be consistent with estimates based upon cross-sections for scattering in a Yukawa (shielded) grain field, but only if non-linear shielding length is used. Finite collisionality initially enhances the drag force, but only by up to a factor of 2. Larger collisionality eventually reduces the drag force. In the collisional regime, the drift distribution gives larger drag than the shift distribution even at velocities where their collisionless drags are equal. Comprehensive practical analytic formulas for force that fit the calculations are provided.
Effect of Forcing Function on Nonlinear Acoustic Standing Waves
NASA Technical Reports Server (NTRS)
Finkheiner, Joshua R.; Li, Xiao-Fan; Raman, Ganesh; Daniels, Chris; Steinetz, Bruce
2003-01-01
Nonlinear acoustic standing waves of high amplitude have been demonstrated by utilizing the effects of resonator shape to prevent the pressure waves from entering saturation. Experimentally, nonlinear acoustic standing waves have been generated by shaking an entire resonating cavity. While this promotes more efficient energy transfer than a piston-driven resonator, it also introduces complicated structural dynamics into the system. Experiments have shown that these dynamics result in resonator forcing functions comprised of a sum of several Fourier modes. However, previous numerical studies of the acoustics generated within the resonator assumed simple sinusoidal waves as the driving force. Using a previously developed numerical code, this paper demonstrates the effects of using a forcing function constructed with a series of harmonic sinusoidal waves on resonating cavities. From these results, a method will be demonstrated which allows the direct numerical analysis of experimentally generated nonlinear acoustic waves in resonators driven by harmonic forcing functions.
The Effects of Pre-College Accounting on the College Accounting Student.
ERIC Educational Resources Information Center
Schroeder, Nicholas
1985-01-01
Through a research project, the author found that the attitudes of college accounting students toward high school accounting as the starting point for an accounting education and also the introductory financial accounting grades of college students are often closely associated with extensive accounting coursework completed prior to college. (CT)
Modified Rindler acceleration as a nonlinear electromagnetic effect
NASA Astrophysics Data System (ADS)
Halilsoy, M.; Gurtug, O.; Mazharimousavi, S. H.
2015-08-01
The model proposed originally by Mannheim and Kazanas for fitting the shapes of galactic rotation curves has recently been considered by Grumiller to describe gravity of a central object at large distances. Herein we employ the same geometry within the context of nonlinear electrodynamics (NED). Pure electrical NED model is shown to generate the novel Rindler acceleration term in the metric which explains anomalous behaviors of test particles/satellites. Remarkably a pure magnetic model of NED yields flat rotation curves that may account for the missing dark matter. Weak and strong energy conditions are satisfied in such models of NED.
Effects of nonlinear dispersion relations on non-Gaussianities
Ashoorioon, Amjad; Danielsson, Ulf; Chialva, Diego E-mail: diego.chialva@umons.ac.be
2011-06-01
We investigate the effect of non-linear dispersion relations on the bispectrum. In particular, we study the case were the modified relations do not violate the WKB condition at early times, focusing on a particular example which is exactly solvable: the Jacobson-Corley dispersion relation with quartic correction with positive coefficient to the squared linear relation. We find that the corrections to the standard result for the bispectrum are suppressed by a factor H{sup 2}/p{sub c}{sup 2} where p{sub c} is the scale where the modification to the dispersion relation becomes relevant. The modification is mildly configuration-dependent and equilateral configurations are more suppressed with respect to the local ones, by a factor of one percent. There is no configuration leading to enhancements. We then analyze the results in the framework of particle creation using the approximate gluing method of Brandenberger and Martin, which relates more directly to the modeling of the trans-Planckian physics via modifications of the vacuum at a certain cutoff scale. We show that the gluing method overestimates the leading order correction to the spectrum and bispectrum by one and two orders, respectively, in H/p{sub c}. We discuss the various approximation and conclude that for dispersion relations not violating WKB at early times the particle creation is small and does not lead to enhanced contributions to the bispectrum. We also show that in many cases enhancements do not occur when modeling the trans-Planckian physics via modifications of the vacuum at a certain cutoff scale. Most notably they are only of order O(1) when the Bogolyubov coefficients accounting for particle creation are determined by the Wronskian condition and the minimization of the uncertainty between the field and its conjugate momentum.
Nonlinear theory of intense laser-plasma interactions modified by vacuum polarization effects
Chen, Wenbo; Bu, Zhigang; Li, Hehe; Luo, Yuee; Ji, Peiyong
2013-07-15
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.
Effective volumes of hard homonuclear nonlinear triatomic molecules
NASA Astrophysics Data System (ADS)
Maeso, M. J.; Solana, J. R.
Expressions to determine effective molecular volumes for nonlinear hard homonuclear triatomic molecules are derived. They are used, in combination with an equation of state previously proposed for hard-body molecular fluids, to reproduce accurately the existing simulation data for this kind of fluid, covering a wide range of bond angles.
Nonlinear effects in the dynamics of clouds of bubbles.
Kumar, S; Brennen, C E
1991-02-01
This paper presents a spectral analysis of the response of a fluid containing bubbles to the motions of a wall oscillating normal to itself. First, a Fourier analysis of the Rayleigh-Plesset equation is used to obtain an approximate solution for the nonlinear effects in the oscillation of a single bubble in an infinite fluid. This is used in the approximate solution of the oscillating wall problem, and the resulting expressions are evaluated numerically in order to examine the nonlinear effects. Harmonic generation results from the nonlinearity. It is observed that the bubble natural frequency remains the dominant natural frequency in the volume oscillations of the bubbles near the wall. On the other hand, the pressure perturbations near the wall are dominated by the first and second harmonics present at twice the natural frequency while the pressure perturbation at the natural frequency of the bubble is inhibited. The response at the forcing frequency and its harmonics is explored along with the variation with amplitude of wall oscillation, void fraction, and viscous and surface tension effects. Splitting and cancellation of frequencies of maximum and minimum response due to enhanced nonlinear effects are also observed.
Imaging the Anisotropic Nonlinear Meissner Effect in Unconventional Superconductors
NASA Astrophysics Data System (ADS)
Anlage, Steven; Zhuravel, A. P.; Ghamsari, B. G.; Kurter, C.; Abrahams, J.; Remillard, S.; Jung, P.; Lukashenko, A. V.; Ustinov, Alexey
2013-03-01
We have directly imaged the anisotropic nonlinear Meissner effect in an unconventional superconductor through the nonlinear electrodynamic response of both (bulk) gap nodes and (surface) Andreev bound states. A superconducting thin film is patterned into a compact self-resonant spiral structure, excited near resonance in the radio-frequency range, and scanned with a focused laser beam perturbation. At low temperatures, direction-dependent nonlinearities in the reactive and resistive properties of the resonator create photoresponse that maps out the directions of nodes, or of bound states associated with these nodes, on the Fermi surface of the superconductor. The method is demonstrated on the nodal superconductor YBa_2Cu_3O_7- ∖delta and the results are consistent with theoretical predictions for the bulk and surface contributions. This was supported by the US DOE DESC 0004950, the ONR AppEl Center, Task D10 (N000140911190), and CNAM.
NASA Astrophysics Data System (ADS)
Nguyen, Quan Minh
2011-12-01
We investigate the propagation of solitons of the perturbed nonlinear Schrodinger equation (NLSE) via asymptotic perturbation techniques and numerical simulations. The dissertation consists of several inter-related projects [22, 98, 103, 108, 109] that are focused on the effects of nonlinear processes and randomness on dynamics of pulses of light in optical waveguides. We particularly consider two of the most important nonlinear processes affecting pulse dynamics in multichannel optical waveguides: weak cubic loss and delayed Raman response. In the presence of weak cubic loss [98], we obtain the analytic expressions for the amplitude and frequency shifts in a single two-soliton collision and show that the impact of a fast three-soliton collision is given by the sum of the two-soliton interactions. Furthermore, we show that amplitude dynamics in an N-channel waveguide system is described by a Lotka-Volterra model for N competing species. We find the conditions on the time slot width and the soliton's equilibrium amplitude value under which the transmission is stable. The predictions of the reduced Lotka-Volterra model are confirmed by numerical solution of a coupled-NLSE model, which takes into account intra-pulse and inter-pulse effects due to cubic nonlinearity and cubic loss. These results uncover an interesting analogy between the dynamics of energy exchange in pulse collisions and population dynamics in Lotka-Volterra models. In the presence of delayed Raman response [103,108,109], we show that the dynamics of pulse amplitudes in an N-channel transmission system in differential phase shift keying (DPSK) scheme is described by an N-dimensional predator-prey model. We find the equilibrium states with non-zero amplitudes and prove their stability by obtaining the Lyapunov function. We then show that stable transmission can be achieved by a proper choice of the frequency profile of linear amplifier gain. We also investigate the impact of Raman self- and collsion
Effect of dynamical friction on nonlinear energetic particle modes
Lilley, M. K.; Breizman, B. N.; Sharapov, S. E.
2010-09-15
A fully nonlinear model is developed for the bump-on-tail instability including the effects of dynamical friction (drag) and velocity space diffusion on the energetic particles driving the wave. The results show that drag provides a destabilizing effect on the nonlinear evolution of waves. Specifically, in the early nonlinear phase of the instability, the drag facilitates the explosive scenario of the wave evolution, leading to the creation of phase space holes and clumps that move away from the original eigenfrequency. Later in time, the electric field associated with a hole is found to be enhanced by the drag, whereas for a clump it is reduced. This leads to an asymmetry of the frequency evolution between holes and clumps. The combined effect of drag and diffusion produces a diverse range of nonlinear behaviors including hooked frequency chirping, undulating, and steady state regimes. An analytical model is presented, which explains the aforementioned diversity. A continuous production of hole-clump pairs in the absence of collisions is also observed.
The effective transverse response of fiber reinforced composites with nonlinear interfaces
NASA Astrophysics Data System (ADS)
Dong, Zhifa
In this dissertation detailed analyses of two previously unsolved problems in the mechanics of composite media are presented. Both related problems involve the prediction of the effective response of a class of nonlinear two-phase composite consisting of linear elastic inclusions randomly embedded in a linear elastic matrix and separated from it by interfaces characterized by general nonlinear cohesive zones of vanishing thickness. The first problem is to predict the response of such a composite consisting of a dilute distribution of inclusions. The second, more difficult problem concerns the prediction of composite response when the inclusions are distributed at finite concentration. Throughout this work the direct method of composite materials theory is employed, which consists of writing exact relations that mediate between local nonlinear inclusion fields and global nonlinear aggregate response. For the dilute estimate local fields are obtained from a representative inclusion problem consisting of a solitary inclusion separated from a remotely stressed (or strained) unbounded matrix by a nonlinear cohesive zone. To account for aspects of inclusion-inclusion interaction at finite concentration the Mori-Tanaka mean field model is employed to predict local inclusion fields. A proof that self-consistency is preserved for this model when interfaces are allowed to separate nonlinearly is also presented. Both the dilute and mean field problems give rise to effective constitutive relations that fall within the conceptual framework of continuum damage mechanics, i.e., stress-strain relations containing internal "damage" variables which themselves are governed by "damage" evolution relations. In this work however the damage variables have geometrical meaning on the microscale. They are expansion coefficients arising in an eigenfunction representation of displacement jump at a representative inclusion-matrix interface. Also, in this work damage evolution equations are not
New non-linear photovoltaic effect in uniform bipolar semiconductor
Volovichev, I.
2014-11-21
A linear theory of the new non-linear photovoltaic effect in the closed circuit consisting of a non-uniformly illuminated uniform bipolar semiconductor with neutral impurities is developed. The non-uniform photo-excitation of impurities results in the position-dependant current carrier mobility that breaks the semiconductor homogeneity and induces the photo-electromotive force (emf). As both the electron (or hole) mobility gradient and the current carrier generation rate depend on the light intensity, the photo-emf and the short-circuit current prove to be non-linear functions of the incident light intensity at an arbitrarily low illumination. The influence of the sample size on the photovoltaic effect magnitude is studied. Physical relations and distinctions between the considered effect and the Dember and bulk photovoltaic effects are also discussed.
Nonlinear and Non-ideal Effects on FRC Stability
E.V. Belova; R.C. Davidson; H. Ji; M. Yamada
2002-10-21
New computational results are presented which advance the understanding of the stability properties of the Field-Reversed Configuration (FRC). We present results of hybrid and two-fluid (Hall-MHD) simulations of prolate FRCs in strongly kinetic and small-gyroradius, MHD-like regimes. The n = 1 tilt instability mechanism and stabilizing factors are investigated in detail including nonlinear and resonant particle effects, particle losses along the open field lines, and Hall stabilization. It is shown that the Hall effect determines the mode rotation and change in the linear mode structure in the kinetic regime; however, the reduction in the growth rate is mostly due to the finite Larmor radius effects. Resonant particle effects are important in the large gyroradius regime regardless of the separatrix shape, and even in cases when a large fraction of the particle orbits are stochastic. Particle loss along the open field lines has a destabilizing effect on the tilt mode and contributes to the ion spin up in toroidal direction. The nonlinear evolution of unstable modes in both kinetic and small-gyroradius FRCs is shown to be considerably slower than that in MHD simulations. Our simulation results demonstrate that a combination of kinetic and nonlinear effects is a key for understanding the experimentally observed FRC stability properties.
NASA Astrophysics Data System (ADS)
Peeters, L. J. M.; Podger, G. M.; Smith, T.; Pickett, T.; Bark, R. H.; Cuddy, S. M.
2014-09-01
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 Plischke et al. (2013), is applied to an eWater Source river management model. This sensitivity analysis methodology is extended to not only account for main effects but also for interaction effects. The combination of sensitivity indices and scatter plots enables the identification of major linear effects as well as subtle minor and nonlinear effects. The case study is an idealized river management model representing typical conditions of the southern Murray-Darling Basin in Australia for which the sensitivity of a variety of model outcomes to variations in the driving forces, inflow to the system, rainfall and potential evapotranspiration, is examined. The model outcomes are most sensitive to the inflow to the system, but the sensitivity analysis identified minor effects of potential evapotranspiration and nonlinear interaction effects between inflow and potential evapotranspiration.
Nonlinear effects on composite laminate thermal expansion
NASA Technical Reports Server (NTRS)
Hashin, Z.; Rosen, B. W.; Pipes, R. B.
1979-01-01
Analyses of Graphite/Polyimide laminates shown that the thermomechanical strains cannot be separated into mechanical strain and free thermal expansion strain. Elastic properties and thermal expansion coefficients of unidirectional Graphite/Polyimide specimens were measured as a function of temperature to provide inputs for the analysis. The + or - 45 degrees symmetric Graphite/Polyimide laminates were tested to obtain free thermal expansion coefficients and thermal expansion coefficients under various uniaxial loads. The experimental results demonstrated the effects predicted by the analysis, namely dependence of thermal expansion coefficients on load, and anisotropy of thermal expansion under load. The significance of time dependence on thermal expansion was demonstrated by comparison of measured laminate free expansion coefficients with and without 15 day delay at intermediate temperature.
The Performing School: The Effects of Market & Accountability Policies
ERIC Educational Resources Information Center
Falabella, Alejandra
2014-01-01
Market and accountability educational reforms have proliferated around the globe, along with high expectations of solving countries' school quality deficits and inequities. In this paper I develop an analytical framework from a critical sociology angle for analyzing the effects of these policies within schools. First I discuss conceptually…
Contrast effects in spontaneous evaluations: a psychophysical account.
Klauer, Karl Christoph; Teige-Mocigemba, Sarah; Spruyt, Adriaan
2009-02-01
In the affective-priming paradigm, target stimuli are preceded by evaluatively polarized prime stimuli and then are to be classified as either good or bad as fast as possible. The typical and robust finding is assimilation: Primes facilitate the processing of evaluatively consistent targets relative to evaluatively inconsistent targets. Nevertheless, contrast effects have repeatedly been observed. The authors propose a new psychophysical account of normal (assimilative) and reversed (contrastive) priming effects and test new predictions derived from it in 5 studies: In Studies 1 and 2, the authors' account is shown to provide a better explanation of contrastive effects in a priming paradigm with two primes than the traditional attentional account does. Furthermore, as predicted by the new account, contrast effects emerge at an intermediate stimulus-onset asynchrony (SOA, Study 3) and even with short SOAs when target onset takes participants by surprise (Study 4). Finally, the use of extremely valenced primes triggers corrective efforts (Study 5) as predicted. Implications for priming measures of evaluative associations are discussed. PMID:19159132
Dynamic nonlinear thermal optical effects in coupled ring resonators
NASA Astrophysics Data System (ADS)
Huang, Chenguang; Fan, Jiahua; Zhu, Lin
2012-09-01
We investigate the dynamic nonlinear thermal optical effects in a photonic system of two coupled ring resonators. A bus waveguide is used to couple light in and out of one of the coupled resonators. Based on the coupling from the bus to the resonator, the coupling between the resonators and the intrinsic loss of each individual resonator, the system transmission spectrum can be classified by three different categories: coupled-resonator-induced absorption, coupled-resonator-induced transparency and over coupled resonance splitting. Dynamic thermal optical effects due to linear absorption have been analyzed for each category as a function of the input power. The heat power in each resonator determines the thermal dynamics in this coupled resonator system. Multiple "shark fins" and power competition between resonators can be foreseen. Also, the nonlinear absorption induced thermal effects have been discussed.
An interference account of the missing-VP effect
Häussler, Jana; Bader, Markus
2015-01-01
Sentences with doubly center-embedded relative clauses in which a verb phrase (VP) is missing are sometimes perceived as grammatical, thus giving rise to an illusion of grammaticality. In this paper, we provide a new account of why missing-VP sentences, which are both complex and ungrammatical, lead to an illusion of grammaticality, the so-called missing-VP effect. We propose that the missing-VP effect in particular, and processing difficulties with multiply center-embedded clauses more generally, are best understood as resulting from interference during cue-based retrieval. When processing a sentence with double center-embedding, a retrieval error due to interference can cause the verb of an embedded clause to be erroneously attached into a higher clause. This can lead to an illusion of grammaticality in the case of missing-VP sentences and to processing complexity in the case of complete sentences with double center-embedding. Evidence for an interference account of the missing-VP effect comes from experiments that have investigated the missing-VP effect in German using a speeded grammaticality judgments procedure. We review this evidence and then present two new experiments that show that the missing-VP effect can be found in German also with less restricting procedures. One experiment was a questionnaire study which required grammaticality judgments from participants without imposing any time constraints. The second experiment used a self-paced reading procedure and did not require any judgments. Both experiments confirm the prior findings of missing-VP effects in German and also show that the missing-VP effect is subject to a primacy effect as known from the memory literature. Based on this evidence, we argue that an account of missing-VP effects in terms of interference during cue-based retrieval is superior to accounts in terms of limited memory resources or in terms of experience with embedded structures. PMID:26136698
An interference account of the missing-VP effect.
Häussler, Jana; Bader, Markus
2015-01-01
Sentences with doubly center-embedded relative clauses in which a verb phrase (VP) is missing are sometimes perceived as grammatical, thus giving rise to an illusion of grammaticality. In this paper, we provide a new account of why missing-VP sentences, which are both complex and ungrammatical, lead to an illusion of grammaticality, the so-called missing-VP effect. We propose that the missing-VP effect in particular, and processing difficulties with multiply center-embedded clauses more generally, are best understood as resulting from interference during cue-based retrieval. When processing a sentence with double center-embedding, a retrieval error due to interference can cause the verb of an embedded clause to be erroneously attached into a higher clause. This can lead to an illusion of grammaticality in the case of missing-VP sentences and to processing complexity in the case of complete sentences with double center-embedding. Evidence for an interference account of the missing-VP effect comes from experiments that have investigated the missing-VP effect in German using a speeded grammaticality judgments procedure. We review this evidence and then present two new experiments that show that the missing-VP effect can be found in German also with less restricting procedures. One experiment was a questionnaire study which required grammaticality judgments from participants without imposing any time constraints. The second experiment used a self-paced reading procedure and did not require any judgments. Both experiments confirm the prior findings of missing-VP effects in German and also show that the missing-VP effect is subject to a primacy effect as known from the memory literature. Based on this evidence, we argue that an account of missing-VP effects in terms of interference during cue-based retrieval is superior to accounts in terms of limited memory resources or in terms of experience with embedded structures.
Candidate mechanisms accounting for effects of physical activity on breast carcinogenesis.
Thompson, Henry J; Jiang, Weiqin; Zhu, Zongjian
2009-09-01
Evidence is strong that a reduction in risk for breast cancer is associated with moderate to vigorous physical activity (PA); however, there is limited understanding of the role of type, intensity, duration, and frequency of PA and their mechanisms in accounting for this health benefit. The objective of this review is to stimulate investigations of candidate mechanisms that may account for the effects of the intensity and duration of aerobic PA on breast cancer risk and tumor burden. Three hypotheses are considered: 1) the mTOR network hypothesis: PA inhibits carcinogenesis by suppressing the activation of the mTOR signaling network in mammary carcinomas; 2) the hormesis hypothesis: the carcinogenic response to PA is nonlinear and accounted for by a physiological cellular stress response; and 3) the metabolic reprogramming hypothesis: PA limits the amount of glucose and glutamine available to mammary carcinomas thereby inducing apoptosis because tumor-associated metabolic programming is reversed. To link these hypotheses to systemic effects of PA, it is recommended that consideration be given to determining: 1) what contracting muscle releases into circulation or removes from circulation that would directly modulate the carcinogenic process in epithelial cells; 2) whether the effects of muscle contraction on epithelial cell carcinogenesis are exerted in an endocrine, paracrine, autocrine, or intracrine manner; and 3) if the effects of muscle contraction on malignant cells differ from effects on normal or premalignant cells that do not manifest the hallmarks of malignancy. PMID:19588523
Spatial nonlinearities: Cascading effects in the earth system
Peters, Debra P.C.; Pielke, R.A.; Bestelmeyer, B.T.; Allen, Craig D.; Munson-McGee, S.; Havstad, K. M.
2006-01-01
Nonlinear interactions and feedbacks associated with thresholds through time and across space are common features of biological, physical and materials systems. These spatial nonlinearities generate surprising behavior where dynamics at one scale cannot be easily predicted based on information obtained at finer or broader scales. These cascading effects often result in severe consequences for the environment and human welfare (i.e., catastrophes) that are expected to be particularly important under conditions of changes in climate and land use. In this chapter, we illustrate the usefulness of a general conceptual and mathematical framework for understanding and forecasting spatially nonlinear responses to global change. This framework includes cross-scale interactions, threshold behavior and feedback mechanisms. We focus on spatial nonlinearities produced by fine-scale processes that cascade through time and across space to influence broad spatial extents. Here we describe the spread of catastrophic events in the context of our cross-disciplinary framework using examples from biology (wildfires, desertification, infectious diseases) and engineering (structural failures) and discuss the consequences of applying these ideas to forecasting future dynamics under a changing global environment.
Dissipative effects in nonlinear Klein-Gordon dynamics
NASA Astrophysics Data System (ADS)
Plastino, A. R.; Tsallis, C.
2016-03-01
We consider dissipation in a recently proposed nonlinear Klein-Gordon dynamics that admits exact time-dependent solutions of the power-law form e_qi(kx-wt) , involving the q-exponential function naturally arising within the nonextensive thermostatistics (e_qz \\equiv [1+(1-q)z]1/(1-q) , with e_1^z=ez ). These basic solutions behave like free particles, complying, for all values of q, with the de Broglie-Einstein relations p=\\hbar k , E=\\hbar ω and satisfying a dispersion law corresponding to the relativistic energy-momentum relation E2 = c^2p2 + m^2c4 . The dissipative effects explored here are described by an evolution equation that can be regarded as a nonlinear generalization of the celebrated telegraph equation, unifying within one single theoretical framework the nonlinear Klein-Gordon equation, a nonlinear Schrödinger equation, and the power-law diffusion (porous-media) equation. The associated dynamics exhibits physically appealing traveling solutions of the q-plane wave form with a complex frequency ω and a q-Gaussian square modulus profile.
NASA Astrophysics Data System (ADS)
Tereshchenko, S. A.; Savelyev, M. S.; Podgaetsky, V. M.; Gerasimenko, A. Yu.; Selishchev, S. V.
2016-09-01
A threshold model is described which permits one to determine the properties of limiters for high-powered laser light. It takes into account the threshold characteristics of the nonlinear optical interaction between the laser beam and the limiter working material. The traditional non-threshold model is a particular case of the threshold model when the limiting threshold is zero. The nonlinear characteristics of carbon nanotubes in liquid and solid media are obtained from experimental Z-scan data. Specifically, the nonlinear threshold effect was observed for aqueous dispersions of nanotubes, but not for nanotubes in solid polymethylmethacrylate. The threshold model fits the experimental Z-scan data better than the non-threshold model. Output characteristics were obtained that integrally describe the nonlinear properties of the optical limiters.
New approximation for the effective energy of nonlinear conducting composites
NASA Astrophysics Data System (ADS)
Gibiansky, Leonid; Torquato, Salvatore
1998-07-01
Approximations for the effective energy and, thus, effective conductivity of nonlinear, isotropic conducting dispersions are developed. This is accomplished by using the Ponte Castaneda variational principles [Philos. Trans. R. Soc. London Ser. A 340, 1321 (1992)] and the Torquato approximation [J. Appl. Phys. 58, 3790 (1985)] of the effective conductivity of corresponding linear composites. The results are obtained for dispersions with superconducting or insulating inclusions, and, more generally, for phases with a power-law energy. It is shown that the new approximations lie within the best available rigorous upper and lower bounds on the effective energy.
Nonlinear dynamics of long-wave Marangoni convection in a binary mixture with the Soret effect
NASA Astrophysics Data System (ADS)
Morozov, M.; Oron, A.; Nepomnyashchy, A. A.
2013-05-01
We investigate the nonlinear dynamics of long-wave Marangoni convection in a 2D binary-liquid layer heated from below. Free surface deformations and the Soret effect are taken into account. We employ the set of evolution equations derived in earlier work in the case of small Galileo and Lewis numbers and solve it numerically with periodic boundary conditions. We validate our numerical solution by comparison between the results obtained via two different numerical methods, as well as by comparison with the prior analytical results. We study the transitions between the nonlinear regimes emerging at finite supercriticality values and find a rich variety of patterns. In a sufficiently large computational domain, we observe multistability of waves chaotic in time and spatially replicated periodic and quasiperiodic solutions. For sufficiently high values of the Marangoni number, we also observe a breakdown of model equations.
Effect of reflexology on EEG--a nonlinear approach.
Kannathal, N; Paul, Joseph K; Lim, C M; Chua, K P
2004-01-01
Reflexology is a 4000-year-old art of healing practiced in ancient India, China and Egypt. In the beginning of the 20th century, it spread to the Western world. Reflexologic clinics and massage centers can be found all around the world. In spite of the widespread popularity, to the best of our knowledge, no serious research work has been done in this area, although much scientific research work has been carried out in other Eastern techniques like meditation and yoga. This is why a humble attempt is done in this work to quantitatively assess the effect of reflexological stimulation from a systems point of view. In this work, nonlinear techniques have been used to assess the complexity of EEG with and without reflexological stimulation. We prefer the nonlinear approach, as we believe that the effects are taking place in a subtle way, since there is no direct correlation between reflexological points and modern neuroanatomy.
Effect of reflexology on EEG--a nonlinear approach.
Kannathal, N; Paul, Joseph K; Lim, C M; Chua, K P
2004-01-01
Reflexology is a 4000-year-old art of healing practiced in ancient India, China and Egypt. In the beginning of the 20th century, it spread to the Western world. Reflexologic clinics and massage centers can be found all around the world. In spite of the widespread popularity, to the best of our knowledge, no serious research work has been done in this area, although much scientific research work has been carried out in other Eastern techniques like meditation and yoga. This is why a humble attempt is done in this work to quantitatively assess the effect of reflexological stimulation from a systems point of view. In this work, nonlinear techniques have been used to assess the complexity of EEG with and without reflexological stimulation. We prefer the nonlinear approach, as we believe that the effects are taking place in a subtle way, since there is no direct correlation between reflexological points and modern neuroanatomy. PMID:15481653
Multiple carbon accounting to support just and effective climate policies
NASA Astrophysics Data System (ADS)
Steininger, Karl W.; Lininger, Christian; Meyer, Lukas H.; Muñoz, Pablo; Schinko, Thomas
2016-01-01
Negotiating reductions in greenhouse gas emission involves the allocation of emissions and of emission reductions to specific agents, and notably, within the current UN framework, to associated countries. As production takes place in supply chains, increasingly extending over several countries, there are various options available in which emissions originating from one and the same activity may be attributed to different agents along the supply chain and thus to different countries. In this way, several distinct types of national carbon accounts can be constructed. We argue that these accounts will typically differ in the information they provide to individual countries on the effects their actions have on global emissions; and they may also, to varying degrees, prove useful in supporting the pursuit of an effective and just climate policy. None of the accounting systems, however, prove 'best' in achieving these aims under real-world circumstances; we thus suggest compiling reliable data to aid in the consistent calculation of multiple carbon accounts on a global level.
NASA Technical Reports Server (NTRS)
Lee, Ho-Jun; Saravanos, Dimitris A.
1997-01-01
Previously developed analytical formulations for piezoelectric composite plates are extended to account for the nonlinear effects of temperature on material properties. The temperature dependence of the composite and piezoelectric properties are represented at the material level through the thermopiezoelectric constitutive equations. In addition to capturing thermal effects from temperature dependent material properties, this formulation also accounts for thermal effects arising from: (1) coefficient of thermal expansion mismatch between the various composite and piezoelectric plies and (2) pyroelectric effects on the piezoelectric material. The constitutive equations are incorporated into a layerwise laminate theory to provide a unified representation of the coupled mechanical, electrical, and thermal behavior of smart structures. Corresponding finite element equations are derived and implemented for a bilinear plate element with the inherent capability to model both the active and sensory response of piezoelectric composite laminates. Numerical studies are conducted on a simply supported composite plate with attached piezoceramic patches under thermal gradients to investigate the nonlinear effects of material property temperature dependence on the displacements, sensory voltages, active voltages required to minimize thermal deflections, and the resultant stress states.
Connected cruise control: modelling, delay effects, and nonlinear behaviour
NASA Astrophysics Data System (ADS)
Orosz, Gábor
2016-08-01
Connected vehicle systems (CVS) are considered in this paper where vehicles exchange information using wireless vehicle-to-vehicle (V2V) communication. The concept of connected cruise control (CCC) is established that allows control design at the level of individual vehicles while exploiting V2V connectivity. Due to its high level of modularity the proposed design can be applied to large heterogeneous traffic systems. The dynamics of a simple CVS is analysed in detail while taking into account nonlinearities in the vehicle dynamics as well as in the controller. Time delays that arise due to intermittencies and packet drops in the communication channels are also incorporated. The results are summarised using stability charts which allow one to select control gains to maintain stability and ensure disturbance attenuation when the delay is below a critical value.
Effects on non-linearities on aircraft poststall motion
Rohacs, J.; Thomasson, P.; Mosehilde, E.
1994-12-31
The poststall maneuverability controlled by thrust vectoring has become one of the important aspects of new fighter development projects. In simplified case, the motion of aircraft can be described by 6DOF nonlinear system. The lecture deals with the longitudinal motion of poststall maneuverable aircraft. The investigation made about the effects of non-linearities in aerodynamic coefficients having considerable non-linearities and hysteresisis an the poststall motions. There were used some different models of aerodynamic coefficients. The results of investigation have shown that the poststall domain of vectored aircraft can be divided into five different pHs in field of thrust - pitch vector angle, and the chaotic motions of aircraft can be found at the different frequencies of thrust deflection. There were defined an unstable right domain with an unstable oscillation and a field of overpulling at poststall motion. The certain frequency chaotic attractors were got at frequencies of Oxitation between the 0.15 and 0.65 rad/sec. The pitching moment derivatives had the big influence on the chaotic motions, while the lift coefficient derivatives bad the reasonable effects, only.
Effect of nonlinear instability on gravity-wave momentum transport
NASA Technical Reports Server (NTRS)
Dunkerton, Timothy J.
1987-01-01
This paper investigates the nonlinear instability of internal gravity waves and the effects of their nonlinear interaction on momentum flux, using simple theoretical and numerical models. From the result of an analysis of parametric instability of a two-dimensional internal gravity wave as discussed by Yeh and Liu (1981) and Klostermeyer (1982), a group trajectory length scale for a gravity wave packet was determined, expressed in terms of the dominant vertical wavelenght and the degree of convective saturation. It is shown that this analysis justifies the Eikonal saturation method for relatively transient packets, that are well below the saturation amplitude, propagating in a slowly varying mean flow. Conversely, linear theory fails for persistent disturbances and trasient wave packets near convective saturation.
Doppler effect of nonlinear waves and superspirals in oscillatory media.
Brusch, Lutz; Torcini, Alessandro; Bär, Markus
2003-09-01
Nonlinear waves emitted from a moving source are studied. A meandering spiral in a reaction-diffusion medium provides an example in which waves originate from a source exhibiting a back-and-forth movement in a radial direction. The periodic motion of the source induces a Doppler effect that causes a modulation in wavelength and amplitude of the waves ("superspiral"). Using direct simulations as well as numerical nonlinear analysis within the complex Ginzburg-Landau equation, we show that waves subject to a convective Eckhaus instability can exhibit monotonic growth or decay as well as saturation of these modulations depending on the perturbation frequency. Our findings elucidate recent experimental observations concerning superspirals and their decay to spatiotemporal chaos.
ERIC Educational Resources Information Center
Theuri, Peter; Weickgenannt, Andrea
2008-01-01
This study examines the impact of recent ethical scandals on business students' perceptions of the accounting profession and related regulatory reforms, and whether such perceptions may be differentiated by maturity. Student maturity is distinguished by age, class standing, and number of accounting classes taken so far. The study results are based…
Nonlinear viscoelastic characterization of polycarbonate
NASA Technical Reports Server (NTRS)
Caplan, E. S.; Brinson, H. F.
1982-01-01
Uniaxial tensile creep and recovery data from polycarbonate at six temperatures and six stress levels are analyzed for nonlinear viscoelastic constitutive modeling. A theory to account for combined effects of two or more accelerating factors is presented.
Attenuation, dispersion and nonlinearity effects in graphene-based waveguides.
Lima, Almir Wirth; Mota, João Cesar Moura; Sombra, Antonio Sergio Bezerra
2015-01-01
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.
Motion analysis of a motorcycle taking into account the rider's effects
NASA Astrophysics Data System (ADS)
Zhu, Shaopeng; Murakami, Shintaroh; Nishimura, Hidekazu
2012-08-01
In this paper, to analyse the rider's effects on the motion of a motorcycle, we model a rider-motorcycle system by taking into account the leaning motion of the rider's upper torso and his/her arm connection with the handlebars. The nonlinearity of the tyre force is introduced by utilising hyperbolic tangent functions to approximate a Magic Formula tyre model. On the basis of a derived nonlinear state-space model, we analyse the effects of not only the rider's arms but also his/her postures during steady turning by simulations. The rider's postures including lean-with, lean-in and lean-out are realised by adding the lean torque to the rider's upper torso. The motorcycle motion and the rider's effects are analysed in the case where the friction coefficient of the road surface changes severely during steady turning. In addition, a linearised state-space model is derived during steady turning, and a stability analysis of the rider-motorcycle system is performed.
Effects of Plasma Shaping on Nonlinear Gyrokinetic Turbulence
E. A. Belli; Hammett, G. W.; Dorland, W.
2008-08-01
The effects of flux surface shape on the gyrokinetic stability and transport of tokamak plasmas are studied using the GS2 code [M. Kotschenreuther, G. Rewoldt, and W.M. Tang, Comput. Phys. Commun. 88, 128 (1995); W. Dorland, F. Jenko, M. Kotschenreuther, and B.N. Rogers, Phys. Rev. Lett. 85, 5579 (2000)]. Studies of the scaling of nonlinear turbulence with shaping parameters are performed using analytic equilibria based on interpolations of representative shapes of the Joint European Torus (JET) [P.H. Rebut and B.E. Keen, Fusion Technol. 11, 13 (1987)]. High shaping is found to be a stabilizing influence on both the linear ion-temperature-gradient (ITG) instability and the nonlinear ITG turbulence. For the parameter regime studied here, a scaling of the heat flux with elongation of χ ~ κ^{-1.5} or κ^{-2.0}, depending on the triangularity, is observed at fixed average temperature gradient. While this is not as strong as empirical elongation scalings, it is also found that high shaping results in a larger Dimits upshift of the nonlinear critical temperature gradient due to an enhancement of the Rosenbluth-Hinton residual zonal flows.
Effects of nonlinear reservoir compaction on casing behavior
Chia, Y.P.; Bradley, D.A.
1988-08-01
Depletion of overpressured, undercompacted reservoirs can cause large reservoir pressure drops and sediment compaction, which may result in casing deformation and well failure. To predict soil and casing deformation during depletion, a finite-element model was developed. Nonlinear elastic and plastic behavior of the soils and slippage along the wellbore boundary are major advancements in this study. This axisymmetric model is composed of casing wall, cement column, slippage interface, and sediments from 11,400 to 13,200 ft (3475 to 4025 m) in depth with a radius of 3,400 ft (1035 m). This study features a process of concurrent fluid flow, nonlinear elastic and plastic soil deformation, slippage from the wellbore boundary, and casing deformation. The modeling results show that the decline in near-wellbore reservoir pressure during depletion causes vertical compaction in both the sand reservoirs and the confining shale formations. Slippage next to the wellbore decreases the axial shear load placed on the casing by the sediments. Nonlinear elastic and plastic soils show a greater tendency for casing deformation with depletion than do linear elastic soils. Axial strains in the casing above the yield strain eventually developed as near-wellbore reservoir pressure was allowed to decline to a minimum. Because this effect is quantified, the production rate may be held to a safe maximum so that the operating limits of the casing are not exceeded. Criteria are given to improve both completion design and production rate specification.
Associative Accounts of Recovery-from-Extinction Effects
McConnell, Bridget L.; Miller, Ralph R.
2014-01-01
Recovery-from-extinction effects (e.g., spontaneous recovery, renewal, reinstatement, and facilitated reacquisition) have become the focus of much research in recent years. However, despite a great deal of empirical data, there are few theoretical explanations for these effects. This paucity poses a severe limitation on our understanding of these behavioral effects, impedes advances in uncovering neural mechanisms of response recovery, and reduces our potential to prevent relapse after exposure therapy. Towards correcting this oversight, this review takes prominent models of associative learning that have been used in the past and continue to be used today to explain Pavlovian conditioning and extinction, and assesses how each model can be applied to account for recovery-from-extinction effects. The models include the Rescorla-Wagner (1972) model, Mackintosh's (1975) attentional model, Pearce and Hall's (1980) attentional model, Wagner's (1981) SOP model, Pearce's (1987) configural model, McLaren and Mackintosh's (2002) elemental model, and Stout and Miller's (2007) SOCR (comparator hypothesis) model. Each model is assessed for how well it explains or does not explain the various recovery-from-extinction phenomena. We offer some suggestions for how the models might be modified to account for these effects in those instances in which they initially fail. PMID:24707062
Gries, J M; Verotta, D
2000-08-01
In a frequently performed pharmacokinetics study, different subjects are given different doses of a drug. After each dose is given, drug concentrations are observed according to the same sampling design. The goal of the experiment is to obtain a representation for the pharmacokinetics of the drug, and to determine if drug concentrations observed at different times after a dose are linear in respect to dose. The goal of this paper is to obtain a representation for concentration as a function of time and dose, which (a) makes no assumptions on the underlying pharmacokinetics of the drug; (b) takes into account the repeated measure structure of the data; and (c) detects nonlinearities in respect to dose. To address (a) we use a multivariate adaptive regression splines representation (MARS), which we recast into a linear mixed-effects model, addressing (b). To detect nonlinearity we describe a general algorithm that obtains nested (mixed-effect) MARS representations. In the pharmacokinetics application, the algorithm obtains representations containing time, and time and dose, respectively, with the property that the bases functions of the first representation are a subset of the second. Standard statistical model selection criteria are used to select representations linear or nonlinear in respect to dose. The method can be applied to a variety of pharmacokinetics (and pharmacodynamic) preclinical and phase I-III trials. Examples of applications of the methodology to real and simulated data are reported.
Clinical Trials: Spline Modeling is Wonderful for Nonlinear Effects.
Cleophas, Ton J
2016-01-01
Traditionally, nonlinear relationships like the smooth shapes of airplanes, boats, and motor cars were constructed from scale models using stretched thin wooden strips, otherwise called splines. In the past decades, mechanical spline methods have been replaced with their mathematical counterparts. The objective of the study was to study whether spline modeling can adequately assess the relationships between exposure and outcome variables in a clinical trial and also to study whether it can detect patterns in a trial that are relevant but go unobserved with simpler regression models. A clinical trial assessing the effect of quantity of care on quality of care was used as an example. Spline curves consistent of 4 or 5 cubic functions were applied. SPSS statistical software was used for analysis. The spline curves of our data outperformed the traditional curves because (1) unlike the traditional curves, they did not miss the top quality of care given in either subgroup, (2) unlike the traditional curves, they, rightly, did not produce sinusoidal patterns, and (3) unlike the traditional curves, they provided a virtually 100% match of the original values. We conclude that (1) spline modeling can adequately assess the relationships between exposure and outcome variables in a clinical trial; (2) spline modeling can detect patterns in a trial that are relevant but may go unobserved with simpler regression models; (3) in clinical research, spline modeling has great potential given the presence of many nonlinear effects in this field of research and given its sophisticated mathematical refinement to fit any nonlinear effect in the mostly accurate way; and (4) spline modeling should enable to improve making predictions from clinical research for the benefit of health decisions and health care. We hope that this brief introduction to spline modeling will stimulate clinical investigators to start using this wonderful method.
Nonlinear and edge effects in a thermoacoustic refrigerator
NASA Astrophysics Data System (ADS)
Blanc-Benon, Philippe; Marx, David
2006-05-01
In the present work, the full compressible Navier-Stokes equations are solved numerically, and the flow and heat transfer around a 2-D stack plate immerged in an acoustic standing wave are computed. Distortion of the waveform temperature are found and are explained using the results of a former nonlinear analysis. The temperature difference between the ends of the plate is investigated and compared to linear theory. The effects of the acoustic Mach number and geometrical parameters on refrigerator performance are investigated.Results reported here may explain a part of the difference between theoretical predictions and experimental results.
Supersonic flow past oscillating airfoils including nonlinear thickness effects
NASA Technical Reports Server (NTRS)
Van Dyke, Milton D
1954-01-01
A solution to second order in thickness is derived for harmonically oscillating two-dimensional airfoils in supersonic flow. For slow oscillations of an arbitrary profile, the result is found as a series including the third power of frequency. For arbitrary frequencies, the method of solution for any specific profile is indicated, and the explicit solution derived for a single wedge. Nonlinear thickness effects are found generally to reduce the torsional damping, and so enlarge the range of Mach numbers within which torsional instability is possible.
Engine control techniques to account for fuel effects
Kumar, Shankar; Frazier, Timothy R.; Stanton, Donald W.; Xu, Yi; Bunting, Bruce G.; Wolf, Leslie R.
2014-08-26
A technique for engine control to account for fuel effects including providing an internal combustion engine and a controller to regulate operation thereof, the engine being operable to combust a fuel to produce an exhaust gas; establishing a plurality of fuel property inputs; establishing a plurality of engine performance inputs; generating engine control information as a function of the fuel property inputs and the engine performance inputs; and accessing the engine control information with the controller to regulate at least one engine operating parameter.
Revisiting heritability accounting for shared environmental effects and maternal inheritance.
Liu, Chunyu; Dupuis, Josée; Larson, Martin G; Cupples, L Adrienne; Ordovas, Jose M; Vasan, Ramachandran S; Meigs, James B; Jacques, Paul F; Levy, Daniel
2015-02-01
Heritability measures the proportion of phenotypic variation attributable to genetic factors. In addition to a shared nuclear genetic component, a number of additional variance components, such as spousal correlation, sibship, household and maternal effects, may have strong contributions to inter-individual phenotype variation. In humans, the confounding effects of these components on heritability have not been studied thoroughly. We sought to obtain unbiased heritability estimates for complex traits in the presence of multiple variance components and also to estimate the contributions of these variance components to complex traits. We compared regression and variance component methods to estimate heritability in simulations when additional variance components existed. We then revisited heritability for several traits in Framingham Heart Study (FHS) participants. Using simulations, we found that failure to account for or misclassification of necessary variance components yielded biased heritability estimates. The direction and magnitude of the bias varied depending on a variance structure and an estimation method. Using the best fitted models to account for necessary variance components, we found that heritability estimates for most FHS traits were overestimated, ranging from 4 to 47 %, when we compared models that considered necessary variance components to models that only considered familial relationships. Spousal correlation explained 14-36 % of phenotypic variation in several anthropometric and lifestyle traits. Maternal and sibling effects also contributed to phenotypic variation, ranging from 3 to 5 % and 4 to 7 %, respectively, in several anthropometric and metabolic traits. Our findings may explain, in part, the missing heritability for some traits.
Prerequisite Change and Its Effect on Intermediate Accounting Performance
ERIC Educational Resources Information Center
Huang, Jiunn; O'Shaughnessy, John; Wagner, Robin
2005-01-01
As of Fall 1996, San Francisco State University changed its introductory financial accounting course to focus on a "user's" perspective, de-emphasizing the accounting cycle. Anticipating that these changes could impair subsequent performance, the Department of Accounting instituted a new prerequisite for intermediate accounting: Students would…
A strategic account of the cue-depreciation effect.
Thapar, A; Greene, R L
1995-12-01
A word fragment is less likely to be completed if it is presented incrementally (R______P, R____R _ P, R_I__R_P, R_I__R O P) than if it is presented all at once (e.g., R_I__R O P). This phenomenon is known as the cue-depreciation effect. The present study examined the role of strategies in this phenomenon. The magnitude of the cue-depreciation effect was increased when subjects were asked to adopt a passive generation approach to word fragment completion. The current study investigated an extension of Bruner and Potter's (1964) early hypothesis-generation account of the cue-depreciation effect. Findings demonstrated the influence of completion strategies for a general theory of fragment completion.
Eliminating Nonlinear Acoustical Effects From Thermoacoustic Refrigeration Systems
NASA Astrophysics Data System (ADS)
Garrett, Steven L.; Smith, Robert W. M.; Poese, Matthew E.
2006-05-01
Nonlinear acoustical effects dissipate energy that degrades thermoacoustic refrigerator performance. The largest of these effects occur in acoustic resonators and include shock formation; turbulence and boundary layer disruption; and entry/exit (minor) losses induced by changes in resonator cross-sectional area. Effects such as these also make the creation of accurate performance models more complicated. Suppression of shock formation by intentional introduction of resonator anharmonicity has been common practice for the past two decades. Recent attempts to increase cooling power density by increasing pressure amplitudes has required reduction of turbulence and minor loss by using an new acousto-mechanical resonator topology. The hybrid resonator still stores potential energy in the compressibility of the gaseous working fluid, but stores kinetic energy in the moving (solid) mass of the motor and piston. This talk will first present nonlinear acoustical loss measurements obtained in a "conventional" double-Helmholtz resonator geometry (TRITON) that dissipated four kilowatts of acoustic power. We will then describe the performance of the new "bellows bounce" resonator configuration and "vibromechanical multiplier" used in the first successful implementation of this approach that created an ice cream freezer produced at Penn State for Ben & Jerry's.
Nonlinear dynamics induced anomalous Hall effect in topological insulators
Wang, Guanglei; Xu, Hongya; Lai, Ying-Cheng
2016-01-01
We uncover an alternative mechanism for anomalous Hall effect. In particular, we investigate the magnetisation dynamics of an insulating ferromagnet (FM) deposited on the surface of a three-dimensional topological insulator (TI), subject to an external voltage. The spin-polarised current on the TI surface induces a spin-transfer torque on the magnetisation of the top FM while its dynamics can change the transmission probability of the surface electrons through the exchange coupling and hence the current. We find a host of nonlinear dynamical behaviors including multistability, chaos, and phase synchronisation. Strikingly, a dynamics mediated Hall-like current can arise, which exhibits a nontrivial dependence on the channel conductance. We develop a physical understanding of the mechanism that leads to the anomalous Hall effect. The nonlinear dynamical origin of the effect stipulates that a rich variety of final states exist, implying that the associated Hall current can be controlled to yield desirable behaviors. The phenomenon can find applications in Dirac-material based spintronics. PMID:26819223
Nonlinear cosmological consistency relations and effective matter stresses
Ballesteros, Guillermo; Hollenstein, Lukas; Jain, Rajeev Kumar; Kunz, Martin E-mail: lukas.hollenstein@unige.ch E-mail: martin.kunz@unige.ch
2012-05-01
We propose a fully nonlinear framework to construct consistency relations for testing generic cosmological scenarios using the evolution of large scale structure. It is based on the covariant approach in combination with a frame that is purely given by the metric, the normal frame. As an example, we apply this framework to the ΛCDM model, by extending the usual first order conditions on the metric potentials to second order, where the two potentials start to differ from each other. We argue that working in the normal frame is not only a practical choice but also helps with the physical interpretation of nonlinear dynamics. In this frame, effective pressures and anisotropic stresses appear at second order in perturbation theory, even for ''pressureless'' dust. We quantify their effect and compare them, for illustration, to the pressure of a generic clustering dark energy fluid and the anisotropic stress in the DGP model. Besides, we also discuss the effect of a mismatch of the potentials on the determination of galaxy bias.
High beta effects and nonlinear evolution of the TAE instability
NASA Astrophysics Data System (ADS)
Spong, D. A.
The toroidal Alfven eigenmode has recently been observed experimentally on DIII-D and TFTR when neutral beams are injected near the Alfven velocity. This instability is also of concern for future high beta D-T devices where fusion by-product alpha populations will generally be super-Alfvenic. We have developed a gyrofluid model (with Landau closure) of the TAE mode which can include most of the relevant damping mechanisms (continuum damping, ion and electron damping, ion FLR and collisional trapped electron damping) as well as reproducing analytically predicted undamped growth rates relatively accurately. An important consideration in predicting future unstable TAE regimes is the effect of finite beta in the background plasma. Due to the Shafranov shift and distortion of the flux surfaces, the location of the stable TAE root and the continuum will shift with increasing beta. The net effect of this is to generally enhance continuum damping and stabilize the TAF instability. Also, as the pressure gradient drive from the background becomes increasingly important, coupling between TAE and background driven modes can alter the TAE mode. A further application of our gyrofluid model which will be discussed is the nonlinear evolution of the TAE instability. Gyrofluid models offer a convenient reduced description which is more amenable to computational nonlinear modeling than full kinetic particle models. Our results demonstrate the rise and crash phases of TAE activity similar to experimental observations. The saturation is caused by generation of m=0 n=0 components through nonlinear beatings of the n greater than 1 modes; these cause modifications to the original equilibrium profiles in such a direction as to decrease the instability drive. This is the gyrofluid analog of direct particle losses. The peak magnetic fluctuation level increases with increasing energetic species beta, resulting in non-resonant stochastization of magnetic field lines.
Effects of Analog-to-Digital Converter Nonlinearities on Radar Range-Doppler Maps
Doerry, Armin Walter; Dubbert, Dale F.; Tise, Bertice L.
2014-07-01
Radar operation, particularly Ground Moving Target Indicator (GMTI) radar modes, are very sensitive to anomalous effects of system nonlinearities. These throw off harmonic spurs that are sometimes detected as false alarms. One significant source of nonlinear behavior is the Analog to Digital Converter (ADC). One measure of its undesired nonlinearity is its Integral Nonlinearity (INL) specification. We examine in this report the relationship of INL to GMTI performance.
Linear and nonlinear effects in detonation wave structure formation
NASA Astrophysics Data System (ADS)
Borisov, S. P.; Kudryavtsev, A. N.
2016-06-01
The role of linear and nonlinear effects in the process of formation of detonation wave structure is investigated using linear stability analysis and direct numerical simulation. A simple model with a one-step irreversible chemical reaction is considered. For linear stability computations, both the local iterative shooting procedure and the global Chebyshev pseudospectral method are employed. Numerical simulations of 1D pulsating instability are performed using a shock fitting approach based on a 5th order upwind-biased compact-difference discretization and a shock acceleration equation deduced from the Rankine-Hugoniot conditions. A shock capturing WENO scheme of the 5th order is used to simulate propagation of detonation wave in a plane channel. It is shown that the linear analysis predicts correctly the mode dominating on early stages of flow evolution and the size of detonation cells which emerge during these stages. Later, however, when a developed self-reproducing cellular structure forms, the cell size is approximately doubled due to nonlinear effects.
Adler's zero and effective Lagrangians for nonlinearly realized symmetry
NASA Astrophysics Data System (ADS)
Low, Ian
2015-05-01
Long ago Coleman, Callan, Wess and Zumino (CCWZ) constructed the general effective Lagrangian for nonlinearly realized symmetry by finding all possible nonlinear representations of the broken group G which become linear when restricted to the unbroken group H . However, in the case of a single Nambu-Goldstone boson (NGB), which corresponds to a broken U (1 ) , the effective Lagrangian can also be obtained by imposing a constant shift symmetry. In this work we generalize the shift symmetry approach to multiple NGBs and show that, when they furnish a linear representation of H that can be embedded in a symmetric coset, it is possible to derive the CCWZ Lagrangian by imposing (1) "the Adler's zero condition," which requires scattering amplitudes to vanish when emitting a single soft NGB and (2) closure of shift symmetry with the linearly realized symmetry. Knowledge of the broken group G is not required at all. Using only generators of H , the NGB covariant derivative and the associated gauge field can be computed to all orders in the NGB decay constant f .
Criteria for Determination of Material Control and Accountability System Effectiveness
John Wright
2008-03-01
The Nevada Test Site (NTS) is a test bed for implementation of the Safeguards First Principles Initiative (SFPI), a risk-based approach to Material Control & Accountability (MC&A) requirements. The Comprehensive Assessment of Safeguards Strategies (COMPASS) model is used to determine the effectiveness of MC&A systems under SFPI. Under this model, MC&A is divided into nine primary elements. Each element is divided into sub-elements. Then each sub-element is assigned two values, effectiveness and contribution, that are used to calculate the rating. Effectiveness is a measure of subelement implementation and how well it meets requirements. Contribution is a relative measure of the importance, and functions as a weighting factor. The COMPASS model provides the methodology for calculation of sub-element and element ratings, but not the actual criteria. Each site must develop its own criteria. For the rating to be meaningful, the effectiveness criteria must be objective and based on explicit, measurable criteria. Contribution (weights) must reflect the importance within the MC&A program. This paper details the NTS approach to system effectiveness and contribution values, and will cover the following: the basis for the ratings, an explanation of the contribution “weights,” and the objective, performance based effectiveness criteria. Finally, the evaluation process will be described.
Li, Bing-Xuan; Wei, Yong; Huang, Cheng-Hui; Zhuang, Feng-Jiang; Zhang, Ge; Guo, Guo-Cong
2014-01-01
In the present paper the authors report a research on testing the nonlinear optical performance of optical materials in visible and infrared band. Based on the second order nonlinear optic principle and the photoelectric signal detection technology, the authors have proposed a new testing scheme in which a infrared OPO laser and a method for separating the beams arising from frequency matching and the light produced by other optical effects were used. The OPO laser is adopted as light source to avoid the error of measurement caused by absorption because the double frequency signal of the material is in the transmittance band Our research work includes testing system composition, operational principle and experimental method. The experimental results of KTP, KDP, AGS tested by this method were presented. In the experiment several new infrared non-linear materials were found. This method possesses the merits of good stability and reliability, high sensitivity, simple operation and good reproducibility, which can effectively make qualitative and semi-quantitative test for optical material's nonlinear optical properties from visible to infrared. This work provides an important test -method for the research on second order nonlinear optical materials in visible, infrared and ultraviolet bands.
Effective phonocardiogram segmentation using time statistics and nonlinear prediction
NASA Astrophysics Data System (ADS)
Sridharan, Rajeswari; Janet, J.
2010-02-01
In the fields of image processing, signal processing and recognition, image Segmentation is an efficient method for segmenting the phonocardiograph signals (PCG) is offered. Primarily, inter-beat segmentation is approved and carried out by means of DII lead of the ECG recording for identifying the happenings of the very first heart sound (S1). Then, the intra-beat segmentation is attained by the use of recurrence time statistics (RTS), and that is very sensitive to variations of the renovated attractor in a state space derived from nonlinear dynamic analysis. Apart from this if the segmentation with RTS is unsuccessful, a special segmentation is proposed using threshold that is extracted from the high frequency rate decomposition and the feature extraction of the disorder is classified based on the murmur sounds. In the Inter-beat segmentation process the accuracy was 100% of the over all PCG recording. Taking into account a different level of PCG beats were strongly concerned by different types of cardiac murmurs and intra-beat segmentation are give up for an accurate result.
A Bayesian nonlinear mixed-effects disease progression model
Kim, Seongho; Jang, Hyejeong; Wu, Dongfeng; Abrams, Judith
2016-01-01
A nonlinear mixed-effects approach is developed for disease progression models that incorporate variation in age in a Bayesian framework. We further generalize the probability model for sensitivity to depend on age at diagnosis, time spent in the preclinical state and sojourn time. The developed models are then applied to the Johns Hopkins Lung Project data and the Health Insurance Plan for Greater New York data using Bayesian Markov chain Monte Carlo and are compared with the estimation method that does not consider random-effects from age. Using the developed models, we obtain not only age-specific individual-level distributions, but also population-level distributions of sensitivity, sojourn time and transition probability. PMID:26798562
Attenuation, dispersion and nonlinearity effects in graphene-based waveguides
Mota, João Cesar Moura; Sombra, Antonio Sergio Bezerra
2015-01-01
Summary 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. PMID:26171299
A neurocomputational account of the face configural effect.
Xu, Xiaokun; Biederman, Irving; Shah, Manan P
2014-01-01
A striking phenomenon in face perception is the configural effect in which a difference in a single part appears more distinct in the context of a face than it does by itself. The face context would be expected to increase search complexity, rendering discrimination more--not less--difficult. Remarkably, there has never been a biologically plausible explanation of this fundamental signature of face recognition.We show that the configural effect can be simply derived from a model composed of overlapping receptive fields (RFs) characteristic of early cortical simple-cell tuning but also present in face-selective areas. Because of the overlap in RFs, the difference in a single part is not only represented in the RFs centered on it but also propagated to larger RFs centered on distant parts of the face. Dissimilarity values computed from the model between pairs of faces and pairs of face parts closely matched the recognition accuracy of human observers who had learned a set of faces composed of composite parts and were tested on wholes (Which is Larry?) and parts (Which is Larry’s nose?). When stimuli were high versus low passed the contributions of different spatial frequency (SF) bands to the configural effect were largely comparable. Therefore, it was the larger RFs rather than the low SFs that accounted for most of the configural effect. The representation explains why, relative to objects, face recognition is so adversely affected by inversion and contrast reversal and why distinctions between similar faces are ineffable. PMID:25009359
Huang, Hong-Zhong; Yuan, Rong
2014-01-01
Many structures are subjected to variable amplitude loading in engineering practice. The foundation of fatigue life prediction under variable amplitude loading is how to deal with the fatigue damage accumulation. A nonlinear fatigue damage accumulation model to consider the effects of load sequences was proposed in earlier literature, but the model cannot consider the load interaction effects, and sometimes it makes a major error. A modified nonlinear damage accumulation model is proposed in this paper to account for the load interaction effects. Experimental data of two metallic materials are used to validate the proposed model. The agreement between the model prediction and experimental data is observed, and the predictions by proposed model are more possibly in accordance with experimental data than that by primary model and Miner's rule. Comparison between the predicted cumulative damage by the proposed model and an existing model shows that the proposed model predictions can meet the accuracy requirement of the engineering project and it can be used to predict the fatigue life of welded aluminum alloy joint of Electric Multiple Units (EMU); meanwhile, the accuracy of approximation can be obtained from the proposed model though more simple computing process and less material parameters calling for extensive testing than the existing model. PMID:24574866
The chaotic effects in a nonlinear QCD evolution equation
NASA Astrophysics Data System (ADS)
Zhu, Wei; Shen, Zhenqi; Ruan, Jianhong
2016-10-01
The corrections of gluon fusion to the DGLAP and BFKL equations are discussed in a united partonic framework. The resulting nonlinear evolution equations are the well-known GLR-MQ-ZRS equation and a new evolution equation. Using the available saturation models as input, we find that the new evolution equation has the chaos solution with positive Lyapunov exponents in the perturbative range. We predict a new kind of shadowing caused by chaos, which blocks the QCD evolution in a critical small x range. The blocking effect in the evolution equation may explain the Abelian gluon assumption and even influence our expectations to the projected Large Hadron Electron Collider (LHeC), Very Large Hadron Collider (VLHC) and the upgrade (CppC) in a circular e+e- collider (SppC).
Nonlinear effects in the correlation of tracks and covariance propagation
NASA Astrophysics Data System (ADS)
Sabol, C.; Hill, K.; Alfriend, K.; Sukut, T.
2013-03-01
Even though there are methods for the nonlinear propagation of the covariance the propagation of the covariance in current operational programs is based on the state transition matrix of the 1st variational equations, thus it is a linear propagation. If the measurement errors are zero mean Gaussian, the orbit errors, statistically represented by the covariance, are Gaussian. When the orbit errors become too large they are no longer Gaussian and not represented by the covariance. One use of the covariance is the association of uncorrelated tracks (UCTs). A UCT is an object tracked by a space surveillance system that does not correlate to another object in the space object data base. For an object to be entered into the data base three or more tracks must be correlated. Associating UCTs is a major challenge for a space surveillance system since every object entered into the space object catalog begins as a UCT. It has been proved that if the orbit errors are Gaussian, the error ellipsoid represented by the covariance is the optimum association volume. When the time between tracks becomes large, hours or even days, the orbit errors can become large and are no longer Gaussian, and this has a negative effect on the association of UCTs. This paper further investigates the nonlinear effects on the accuracy of the covariance for use in correlation. The use of the best coordinate system and the unscented Kalman Filter (UKF) for providing a more accurate covariance are investigated along with assessing how these approaches would result in the ability to correlate tracks that are further separated in time.
Dispersion and nonlinear effects in OFDM-RoF system
NASA Astrophysics Data System (ADS)
Alhasson, Bader H.; Bloul, Albe M.; Matin, M.
2010-08-01
The radio-over-fiber (RoF) network has been a proven technology to be the best candidate for the wireless-access technology, and the orthogonal frequency division multiplexing (OFDM) technique has been established as the core technology in the physical layer of next generation wireless communication system, as a result OFDM-RoF has drawn attentions worldwide and raised many new research topics recently. At the present time, the trend of information industry is towards mobile, wireless, digital and broadband. The next generation network (NGN) has motivated researchers to study higher-speed wider-band multimedia communication to transmit (voice, data, and all sorts of media such as video) at a higher speed. The NGN would offer services that would necessitate broadband networks with bandwidth higher than 2Mbit/s per radio channel. Many new services emerged, such as Internet Protocol TV (IPTV), High Definition TV (HDTV), mobile multimedia and video stream media. Both speed and capacity have been the key objectives in transmission. In the meantime, the demand for transmission bandwidth increased at a very quick pace. The coming of 4G and 5G era will provide faster data transmission and higher bit rate and bandwidth. Taking advantages of both optical communication and wireless communication, OFDM Radio over Fiber (OFDM-RoF) system is characterized by its high speed, large capacity and high spectral efficiency. However, up to the present there are some problems to be solved, such as dispersion and nonlinearity effects. In this paper we will study the dispersion and nonlinearity effects and their elimination in OFDM-radio-over-fiber system.
NASA Astrophysics Data System (ADS)
Hüter, Claas; Friák, Martin; Weikamp, Marc; Neugebauer, Jörg; Goldenfeld, Nigel; Svendsen, Bob; Spatschek, Robert
2016-06-01
We investigate nonlinear elastic deformations in the phase field crystal model and derived amplitude equation formulations. Two sources of nonlinearity are found, one of them is based on geometric nonlinearity expressed through a finite strain tensor. This strain tensor is based on the inverse right Cauchy-Green deformation tensor and correctly describes the strain dependence of the stiffness for anisotropic and isotropic behavior. In isotropic one- and two-dimensional situations, the elastic energy can be expressed equivalently through the left deformation tensor. The predicted isotropic low-temperature nonlinear elastic effects are directly related to the Birch-Murnaghan equation of state with bulk modulus derivative K'=4 for bcc. A two-dimensional generalization suggests K2D '=5 . These predictions are in agreement with ab initio results for large strain bulk deformations of various bcc elements and graphene. Physical nonlinearity arises if the strain dependence of the density wave amplitudes is taken into account and leads to elastic weakening. For anisotropic deformation, the magnitudes of the amplitudes depend on their relative orientation to the applied strain.
Bohr effect of hemoglobins: Accounting for differences in magnitude.
Okonjo, Kehinde O
2015-09-01
The basis of the difference in the Bohr effect of various hemoglobins has remained enigmatic for decades. Fourteen amino acid residues, identical in pairs and located at specific 'Bohr group positions' in human hemoglobin, are implicated in the Bohr effect. All 14 are present in mouse, 11 in dog, eight in pigeon and 13 in guinea pig hemoglobin. The Bohr data for human and mouse hemoglobin are identical: the 14 Bohr groups appear at identical positions in both molecules. The dog data are different from the human because three Bohr group positions are occupied by non-ionizable groups in dog hemoglobin; the pigeon data are vastly different from the human because six Bohr group positions are occupied by non-ionizable groups in pigeon hemoglobin. The guinea pig data are quite complex. Quantitative analyses showed that only the pigeon data could be fitted with the Wyman equation for the Bohr effect. We demonstrate that, apart from guinea pig hemoglobin, the difference between the Bohr effect of each of the other hemoglobins and of pigeon hemoglobin can be accounted for quantitatively on the basis of the occupation of some of their Bohr group positions by non-ionizable groups in pigeon hemoglobin. We attribute the anomalous guinea pig result to a new salt-bridge formed in its R2 quaternary structure between the terminal NH3(+) group of one β-chain and the COO(-) terminal group of the partner β-chain in the same molecule. The pKas of this NH3(+) group are 6.33 in the R2 and 4.59 in the T state.
Effects of Inertial and Geometric Nonlinearities in the Simulation of Flexible Aircraft Dynamics
NASA Astrophysics Data System (ADS)
Bun Tse, Bosco Chun
This thesis examines the relative importance of the inertial and geometric nonlinearities in modelling the dynamics of a flexible aircraft. Inertial nonlinearities are derived by employing an exact definition of the velocity distribution and lead to coupling between the rigid body and elastic motions. The geometric nonlinearities are obtained by applying nonlinear theory of elasticity to the deformations. Peters' finite state unsteady aerodynamic model is used to evaluate the aerodynamic forces. Three approximate models obtained by excluding certain combinations of nonlinear terms are compared with that of the complete dynamics equations to obtain an indication of which terms are required for an accurate representation of the flexible aircraft behavior. A generic business jet model is used for the analysis. The results indicate that the nonlinear terms have a significant effect for more flexible aircraft, especially the geometric nonlinearities which leads to increased damping in the dynamics.
Nuclear Material Control and Accountability System Effectiveness Tool (MSET)
Powell, Danny H; Elwood Jr, Robert H; Roche, Charles T; Campbell, Billy J; Hammond, Glenn A; Meppen, Bruce W; Brown, Richard F
2011-01-01
A nuclear material control and accountability (MC&A) system effectiveness tool (MSET) has been developed in the United States for use in evaluating material protection, control, and accountability (MPC&A) systems in nuclear facilities. The project was commissioned by the National Nuclear Security Administration's Office of International Material Protection and Cooperation. MSET was developed by personnel with experience spanning more than six decades in both the U.S. and international nuclear programs and with experience in probabilistic risk assessment (PRA) in the nuclear power industry. MSET offers significant potential benefits for improving nuclear safeguards and security in any nation with a nuclear program. MSET provides a design basis for developing an MC&A system at a nuclear facility that functions to protect against insider theft or diversion of nuclear materials. MSET analyzes the system and identifies several risk importance factors that show where sustainability is essential for optimal performance and where performance degradation has the greatest impact on total system risk. MSET contains five major components: (1) A functional model that shows how to design, build, implement, and operate a robust nuclear MC&A system (2) A fault tree of the operating MC&A system that adapts PRA methodology to analyze system effectiveness and give a relative risk of failure assessment of the system (3) A questionnaire used to document the facility's current MPC&A system (provides data to evaluate the quality of the system and the level of performance of each basic task performed throughout the material balance area [MBA]) (4) A formal process of applying expert judgment to convert the facility questionnaire data into numeric values representing the performance level of each basic event for use in the fault tree risk assessment calculations (5) PRA software that performs the fault tree risk assessment calculations and produces risk importance factor reports on the
Integrating Effective Writing Skills in the Accounting Curriculum.
ERIC Educational Resources Information Center
May, Gordon S.; Arevalo, Claire
1983-01-01
The J. M. Tull School of Accounting at the University of Georgia has developed a program that integrates the teaching of writing skills with the regular accounting courses. Students in a three-course sequence write a total of eight papers--technical, memos, or reports--in assignments that resemble writing tasks encountered by professional…
Nonlinear optical effects in colloidal carbon nanohorns—a new optical limiting material
NASA Astrophysics Data System (ADS)
Dengler, Stefanie; Muller, Olivier; Hege, Cordula; Eberle, Bernd
2016-09-01
Many carbon based nanomaterials exhibit nonlinear optical response over a large wavelength range when irradiated with intense laser light what makes them promising candidates for optical limiting purposes. Besides nonlinear absorption some of these well studied nanostructures like carbon nanotubes or carbon black owe their prominent limiting efficiency particularly to induced nonlinear scattering. In this paper, our investigations on carbon nanohorns are presented—a new and very promising nonlinear optical material. It offers excellent properties like a low optical limiting threshold and a high nonlinear attenuation when tested with nanosecond laser pulses at wavelengths of 532 nm or 1064 nm. At moderate irradiation levels near the nonlinear threshold our measurements performed on colloidal carbon nanohorns reveal broadband nonlinear absorption as the dominant optical limiting effect. Towards higher irradiation levels significant nonlinear scattering takes place as a secondary process. In contrast to 532 nm, at 1064 nm nonlinear scattering is less strong even at high irradiation levels and the nonlinear response is dominated by nonlinear absorption.
Gonçalves, M A D; Bello, N M; Dritz, S S; Tokach, M D; DeRouchey, J M; Woodworth, J C; Goodband, R D
2016-05-01
Advanced methods for dose-response assessments are used to estimate the minimum concentrations of a nutrient that maximizes a given outcome of interest, thereby determining nutritional requirements for optimal performance. Contrary to standard modeling assumptions, experimental data often present a design structure that includes correlations between observations (i.e., blocking, nesting, etc.) as well as heterogeneity of error variances; either can mislead inference if disregarded. Our objective is to demonstrate practical implementation of linear and nonlinear mixed models for dose-response relationships accounting for correlated data structure and heterogeneous error variances. To illustrate, we modeled data from a randomized complete block design study to evaluate the standardized ileal digestible (SID) Trp:Lys ratio dose-response on G:F of nursery pigs. A base linear mixed model was fitted to explore the functional form of G:F relative to Trp:Lys ratios and assess model assumptions. Next, we fitted 3 competing dose-response mixed models to G:F, namely a quadratic polynomial (QP) model, a broken-line linear (BLL) ascending model, and a broken-line quadratic (BLQ) ascending model, all of which included heteroskedastic specifications, as dictated by the base model. The GLIMMIX procedure of SAS (version 9.4) was used to fit the base and QP models and the NLMIXED procedure was used to fit the BLL and BLQ models. We further illustrated the use of a grid search of initial parameter values to facilitate convergence and parameter estimation in nonlinear mixed models. Fit between competing dose-response models was compared using a maximum likelihood-based Bayesian information criterion (BIC). The QP, BLL, and BLQ models fitted on G:F of nursery pigs yielded BIC values of 353.7, 343.4, and 345.2, respectively, thus indicating a better fit of the BLL model. The BLL breakpoint estimate of the SID Trp:Lys ratio was 16.5% (95% confidence interval [16.1, 17.0]). Problems with
Nanoscale nonlinear radio frequency properties of bulk Nb: Origins of extrinsic nonlinear effects
NASA Astrophysics Data System (ADS)
Tai, Tamin; Ghamsari, B. G.; Bieler, T.; Anlage, Steven M.
2015-10-01
The performance of niobium-based superconducting radio frequency (SRF) particle-accelerator cavities can be sensitive to localized defects that give rise to quenches at high accelerating gradients. In order to identify these material defects on bulk Nb surfaces at their operating frequency and temperature, a wide-bandwidth microwave microscope with localized and strong RF magnetic fields is developed by integrating a magnetic write head into the near-field microwave microscope to enable mapping of the local electrodynamic response in the multi-GHz frequency regime at cryogenic temperatures. This magnetic writer demonstrates a localized and strong RF magnetic field on bulk Nb surface with Bsurface>102 mT and submicron resolution. By measuring the nonlinear response of the superconductor, nonlinearity coming from the nanoscale weak-link Josephson junctions due to the contaminated surface in the cavity-fabrication process is demonstrated.
NASA Technical Reports Server (NTRS)
Subrahmanyam, K. B.; Kaza, K. R. V.; Brown, G. V.; Lawrence, C.
1986-01-01
The coupled bending-bending-torsional equations of dynamic motion of rotating, linearly pretwisted blades are derived including large precone, second degree geometric nonlinearities and Coriolis effects. The equations are solved by the Galerkin method and a linear perturbation technique. Accuracy of the present method is verified by comparisons of predicted frequencies and steady state deflections with those from MSC/NASTRAN and from experiments. Parametric results are generated to establish where inclusion of only the second degree geometric nonlinearities is adequate. The nonlinear terms causing torsional divergence in thin blades are identified. The effects of Coriolis terms and several other structurally nonlinear terms are studied, and their relative importance is examined.
NASA Technical Reports Server (NTRS)
Subrahmanyam, K. B.; Kaza, K. R. V.; Brown, G. V.; Lawrence, C.
1987-01-01
The coupled bending-bending-torsional equations of dynamic motion of rotating, linearly pretwisted blades are derived including large precone, second degree geometric nonlinearities and Coriolis effects. The equations are solved by the Galerkin method and a linear perturbation technique. Accuracy of the present method is verified by conparisons of predicted frequencies and steady state deflections with those from MSC/NASTRAN and from experiments. Parametric results are generated to establish where inclusion of only the second degree geometric nonlinearities is adequate. The nonlinear terms causing torsional divergence in thin blades are identified. The effects of Coriolis terms and several other structurally nonlinear terms are studied, and their relative importance is examined.
Hyperspectral Unmixing in Presence of Endmember Variability, Nonlinearity, or Mismodeling Effects.
Halimi, Abderrahim; Honeine, Paul; Bioucas-Dias, Jose M
2016-10-01
This paper presents three hyperspectral mixture models jointly with Bayesian algorithms for supervised hyperspectral unmixing. Based on the residual component analysis model, the proposed general formulation assumes the linear model to be corrupted by an additive term whose expression can be adapted to account for nonlinearities (NLs), endmember variability (EV), or mismodeling effects (MEs). The NL effect is introduced by considering a polynomial expression that is related to bilinear models. The proposed new formulation of EV accounts for shape and scale endmember changes while enforcing a smooth spectral/spatial variation. The ME formulation considers the effect of outliers and copes with some types of EV and NL. The known constraints on the parameter of each observation model are modeled via suitable priors. The posterior distribution associated with each Bayesian model is optimized using a coordinate descent algorithm, which allows the computation of the maximum a posteriori estimator of the unknown model parameters. The proposed mixture and Bayesian models and their estimation algorithms are validated on both synthetic and real images showing competitive results regarding the quality of the inferences and the computational complexity, when compared with the state-of-the-art algorithms. PMID:27416597
Hyperspectral Unmixing in Presence of Endmember Variability, Nonlinearity, or Mismodeling Effects.
Halimi, Abderrahim; Honeine, Paul; Bioucas-Dias, Jose M
2016-10-01
This paper presents three hyperspectral mixture models jointly with Bayesian algorithms for supervised hyperspectral unmixing. Based on the residual component analysis model, the proposed general formulation assumes the linear model to be corrupted by an additive term whose expression can be adapted to account for nonlinearities (NLs), endmember variability (EV), or mismodeling effects (MEs). The NL effect is introduced by considering a polynomial expression that is related to bilinear models. The proposed new formulation of EV accounts for shape and scale endmember changes while enforcing a smooth spectral/spatial variation. The ME formulation considers the effect of outliers and copes with some types of EV and NL. The known constraints on the parameter of each observation model are modeled via suitable priors. The posterior distribution associated with each Bayesian model is optimized using a coordinate descent algorithm, which allows the computation of the maximum a posteriori estimator of the unknown model parameters. The proposed mixture and Bayesian models and their estimation algorithms are validated on both synthetic and real images showing competitive results regarding the quality of the inferences and the computational complexity, when compared with the state-of-the-art algorithms.
Accounting for Basin Effects Will Improve Seismic Risk Assessments
NASA Astrophysics Data System (ADS)
Magistrale, Harold
2010-05-01
determine the basin amplification factor as a function of depth to Vs=1.5 km/s (a measure of basin depth), and find period-dependent amplifications of ~1.5 to 8 relative to a 1D hard rock reference structure. Recent simulations (Rotan et al., 2009) of a M7 earthquake on the Wasatch fault zone in the Salt Lake basin model show a similar strong effect of basin structure on strong ground motions. These results indicate that the strong influences of basin structures on earthquake ground motions must be accounted for to achieve rational seismic hazard and risk assessments.
Explanation of the inverse Doppler effect observed in nonlinear transmission lines.
Kozyrev, Alexander B; van der Weide, Daniel W
2005-05-27
The theory of the inverse Doppler effect recently observed in magnetic nonlinear transmission lines is developed. We explain the crucial role of the backward spatial harmonic in the occurrence of an inverse Doppler effect and draw analogies of the magnetic nonlinear transmission line to the backward wave oscillator.
Li, Qian; Matula, Thomas J; Tu, Juan; Guo, Xiasheng; Zhang, Dong
2013-02-21
It has been accepted that the dynamic responses of ultrasound contrast agent (UCA) microbubbles will be significantly affected by the encapsulating shell properties (e.g., shell elasticity and viscosity). In this work, a new model is proposed to describe the complicated rheological behaviors in an encapsulating shell of UCA microbubbles by applying the nonlinear 'Cross law' to the shell viscous term in the Marmottant model. The proposed new model was verified by fitting the dynamic responses of UCAs measured with either a high-speed optical imaging system or a light scattering system. The comparison results between the measured radius-time curves and the numerical simulations demonstrate that the 'compression-only' behavior of UCAs can be successfully simulated with the new model. Then, the shell elastic and viscous coefficients of SonoVue microbubbles were evaluated based on the new model simulations, and compared to the results obtained from some existing UCA models. The results confirm the capability of the current model for reducing the dependence of bubble shell parameters on the initial bubble radius, which indicates that the current model might be more comprehensive to describe the complex rheological nature (e.g., 'shear-thinning' and 'strain-softening') in encapsulating shells of UCA microbubbles by taking into account the nonlinear changes of both shell elasticity and shell viscosity. PMID:23339902
Strong Glacial Cooling In The Middle Tropical Troposphere Due To Non-linear Effects
NASA Astrophysics Data System (ADS)
Lorenz, S. J.; Lohmann, G.
Numerical experiments with an atmospheric general circulation model for glacial and interglacial climates have been performed. Our model experiments reveal that slightly cooler tropical sea surface temperatures (SST) relative to the ones previously recon- structed by the CLIMAP project (1981) are sufficient to exhibit a strong glacial cool- ing reconstructed by tropical snow lines. The increased cooling in our experiments can be attributed to two non-linear effects: Firstly, there is an increased environmental lapse rate in the free atmosphere. Slightly cooler glacial SSTs provide for less abso- lute moisture content and the Clausius-Clapeyron equation of moisture is accountable for an increased lapse rate. In our LGM simulation we find an additional two degrees cooling in the tropical middle troposphere. Secondly, the surface air temperature near tropical glaciers is further cooled by a longer duration of snow cover. Our model result provides a consistent view of the last glacial maximum climate with much colder tem- peratures than today in the tropical mountains in concordance with moderate lowering of tropical SSTs. We propose that these non-linearities in the climate system are also important when detecting global warming from tropical snow lines.
NASA Astrophysics Data System (ADS)
Liao, Ying-Po; Safak, Ilgar; Kaihatu, James M.; Sheremet, Alex
2015-11-01
The sensitivity of wave-mud interaction on directionality and nonlinearity is investigated. A phase-resolving nonlinear wave model which accounts for directional wave propagation and mud damping is used to simulate wave propagation over a muddy shelf. Field data from an experiment conducted at the central chenier plain coast, western Louisiana, USA are used to validate the model. Recently, verification of a one-dimensional wave model with the field data showed that this model was able to replicate the evolution of wave spectra over muddy bottoms. In this study, unidirectional wave spectra were also run through the parabolic model, but with various initial angles. Linear wave model runs were also performed in order to gauge the effect of nonlinear evolution on the results. Significant wave height and total energy contained in three different spectral bands from the model are compared to the data over the shelf, and correlation metrics calculated. While the model generally performs well no matter the initial angle, at no point does a zero initial angle compare best to the data, indicating that a unidirectional model may be missing some of the dynamical features of wave propagation over a muddy shelf. Furthermore, despite similar correlation scores between linear and nonlinear model comparisons of bulk statistics, it is seen the linear model does not replicate some aspects of the spectral evolution (such as low-frequency generation and amplification) shown in the data and captured by the nonlinear model. Despite the relatively short propagation distance, the effects of both directionality and nonlinearity play a noticeable role in wave evolution over a muddy seabed.
Accounting for Recoil Effects in Geochronometers: A New Model Approach
NASA Astrophysics Data System (ADS)
Lee, V. E.; Huber, C.
2012-12-01
dated grain is a major control on the magnitude of recoil loss, the first feature is the ability to calculate recoil effects on isotopic compositions for realistic, complex grain shapes and surface roughnesses. This is useful because natural grains may have irregular shapes that do not conform to simple geometric descriptions. Perhaps more importantly, the surface area over which recoiled nuclides are lost can be significantly underestimated when grain surface roughness is not accounted for, since the recoil distances can be of similar characteristic lengthscales to surface roughness features. The second key feature is the ability to incorporate dynamical geologic processes affecting grain surfaces in natural settings, such as dissolution and crystallization. We describe the model and its main components, and point out implications for the geologically-relevant chronometers mentioned above.
Energy localization in nonlinear fiber arrays: Collapse-effect compressor
Aceves, A.B.; Luther, G.G.; De Angelis, C.; Turitsyn, S.K.
1995-07-03
We analyze a collapse mechanism of energy localization in nonlinear fiber arrays. The nonlinear fiber array is suggested as a device to amplify and compress optical pulses. Pulse propagation in one-dimensional fiber arrays has features of collapse (self-focusing) dynamics. Collapse-type compression leads to the localization of all energy initially dispersed in array into a few fibers. Numerical simulations demonstrate the robustness of the suggested compression mechanism.
Stochastic nonlinear mixed effects: a metformin case study.
Matzuka, Brett; Chittenden, Jason; Monteleone, Jonathan; Tran, Hien
2016-02-01
In nonlinear mixed effect (NLME) modeling, the intra-individual variability is a collection of errors due to assay sensitivity, dosing, sampling, as well as model misspecification. Utilizing stochastic differential equations (SDE) within the NLME framework allows the decoupling of the measurement errors from the model misspecification. This leads the SDE approach to be a novel tool for model refinement. Using Metformin clinical pharmacokinetic (PK) data, the process of model development through the use of SDEs in population PK modeling was done to study the dynamics of absorption rate. A base model was constructed and then refined by using the system noise terms of the SDEs to track model parameters and model misspecification. This provides the unique advantage of making no underlying assumptions about the structural model for the absorption process while quantifying insufficiencies in the current model. This article focuses on implementing the extended Kalman filter and unscented Kalman filter in an NLME framework for parameter estimation and model development, comparing the methodologies, and illustrating their challenges and utility. The Kalman filter algorithms were successfully implemented in NLME models using MATLAB with run time differences between the ODE and SDE methods comparable to the differences found by Kakhi for their stochastic deconvolution.
Nonlinear fluctuation effects in dynamics of freely suspended films
NASA Astrophysics Data System (ADS)
Kats, E. I.; Lebedev, V. V.
2015-03-01
Long-scale dynamic fluctuation phenomena in freely suspended films is analyzed. We consider isotropic films that, say, can be pulled from bulk smectic-A liquid crystals. The key feature of such objects is possibility of bending deformations of the film. The bending (also known as flexular) mode turns out to be anomalously weakly attenuated. In the harmonic approximation there is no viscous-like damping of the bending mode, proportional to q2 (q is the wave vector of the mode), since it is forbidden by the rotational symmetry. Therefore, the bending mode is strongly affected by nonlinear dynamic fluctuation effects. We calculate the dominant fluctuation contributions to the damping of the bending mode due to its coupling to the inplane viscous mode, which restores the viscous-like q2 damping of the bending mode. Our calculations are performed in the framework of the perturbation theory where the coupling of the modes is assumed to be small, then the bending mode damping is relatively weak. We discuss our results in the context of existing experiments and numeric simulations of the freely suspended films and propose possible experimental observations of our predictions.
An effective analytic approach for solving nonlinear fractional partial differential equations
NASA Astrophysics Data System (ADS)
Ma, Junchi; Zhang, Xiaolong; Liang, Songxin
2016-08-01
Nonlinear fractional differential equations are widely used for modelling problems in applied mathematics. A new analytic approach with two parameters c1 and c2 is first proposed for solving nonlinear fractional partial differential equations. These parameters are used to improve the accuracy of the resulting series approximations. It turns out that much more accurate series approximations are obtained by choosing proper values of c1 and c2. To demonstrate the applicability and effectiveness of the new method, two typical fractional partial differential equations, the nonlinear gas dynamics equation and the nonlinear KdV-Burgers equation, are solved.
NASA Astrophysics Data System (ADS)
Pazand, Kamran; Nobari, A. S.
2016-10-01
In this paper, inverse-eigen sensitivity identification technique is used to investigate the effect of damage on the effective damping of a viscoelastic adhesive, in both linear and nonlinear regions of adhesive behavior. The modal parameters derived from the measured linear and nonlinear Frequency Response Functions (FRF) of the bonded structure are used in identification process. Experimental FRFs are employed to identify linear and nonlinear bending and shear modes which are then used for identifying of damping coefficient at different frequencies. The nonlinear FRFs are measured using the Optimum Equivalent Linear System (OELS) concept. The results indicate that the damping of the adhesive decreases with frequency. Also, debonding damage has a decreasing effect on damping of adhesive, both in linear and nonlinear regions, and with increasing the damage percentage the reduction becomes more significant. Results also show that the linear and nonlinear effective damping are different and hence depend on both amplitude of response and the mode shapes involved.
14 CFR Section 18 - Objective Classification-Cumulative Effect of Changes in Accounting Principles
Code of Federal Regulations, 2010 CFR
2010-01-01
... of Changes in Accounting Principles Section 18 Section 18 Aeronautics and Space OFFICE OF THE... Objective Classification—Cumulative Effect of Changes in Accounting Principles 98Cumulative Effect of Changes in Accounting Principles. Record here the difference between the amount of retained earnings...
Estimation of the Nonlinear Random Coefficient Model when Some Random Effects Are Separable
ERIC Educational Resources Information Center
du Toit, Stephen H. C.; Cudeck, Robert
2009-01-01
A method is presented for marginal maximum likelihood estimation of the nonlinear random coefficient model when the response function has some linear parameters. This is done by writing the marginal distribution of the repeated measures as a conditional distribution of the response given the nonlinear random effects. The resulting distribution…
Materialism Moderates the Effect of Accounting for Time on Prosocial Behaviors.
Li, Jibo; Chen, Yingying; Huang, Xiting
2015-01-01
Accounting for time is defined as putting a price on time. Researchers have demonstrated that accounting for time reduces the time individuals spend on others; however, its association with monetary donations has not been examined. We hypothesized that accounting for time will activate a utility mindset that would affect one's allocation of time and money. In Study 1, the mediating effect of utility mindsets on the relationship between accounting for time and prosocial behavior was examined. In Study 2, we examined the effect of accounting for time on time spent helping and donating money, and the moderating role of material values on the relationship between accounting for time and prosocial behavior. Results showed that accounting for time activated a mindset of utility maximization that, in turn, reduced participants' prosocial behavior; moreover, materialism moderated the effect of accounting for time on prosocial behavior.
Daulatabadkar, Pragya Ghosh, S.
2015-07-31
An investigation is carried out in III-V compound semiconductor when a strong transverse magnetic field is applied. By considering the heating effect of carriers, an analytical investigation is made for n-InSb in which the nonlinearity arises due to dependence of effective mass on electronic temperature. At optical frequencies the temperature dependence part of momentum transfer collision frequency is assumed to be negligibly small. The linear and nonlinear parts of optical parameters are evaluated through the first and third order susceptibility of InSb sample. The analysis reveals that the nonlinear part of refractive index increases with intensity which leads to self-focusing of the beam. Thus by adjusting the doping concentration pump frequency and intensity, one may achieve desired nonlinearity in the crystal. Hence n - InSb sample establishes its potentials as candidate material for fabrication of cubic nonlinear devices.
Almaraz, Pablo; Green, Andy J; Aguilera, Eduardo; Rendón, Miguel A; Bustamante, Javier
2012-09-01
1. Understanding the impact of environmental variability on migrating species requires the estimation of sequential abiotic effects in different geographic areas across the life cycle. For instance, waterfowl (ducks, geese and swans) usually breed widely dispersed throughout their breeding range and gather in large numbers in their wintering headquarters, but there is a lack of knowledge on the effects of the sequential environmental conditions experienced by migrating birds on the long-term community dynamics at their wintering sites. 2. Here, we analyse multidecadal time-series data of 10 waterfowl species wintering in the Guadalquivir Marshes (SW Spain), the single most important wintering site for waterfowl breeding in Europe. We use a multivariate state-space approach to estimate the effects of biotic interactions, local environmental forcing during winter and large-scale climate during breeding and migration on wintering multispecies abundance fluctuations, while accounting for partial observability (observation error and missing data) in both population and environmental data. 3. The joint effect of local weather and large-scale climate explained 31·6% of variance at the community level, while the variability explained by interspecific interactions was negligible (<5%). In general, abiotic conditions during winter prevailed over conditions experienced during breeding and migration. Across species, a pervasive and coherent nonlinear signal of environmental variability on population dynamics suggests weaker forcing at extreme values of abiotic variables. 4. Modelling missing observations through data augmentation increased the estimated magnitude of environmental forcing by an average 30·1% and reduced the impact of stochasticity by 39·3% when accounting for observation error. Interestingly however, the impact of environmental forcing on community dynamics was underestimated by an average 15·3% and environmental stochasticity overestimated by 14·1% when
Dynamical Casimir effect in microwave cavities containing nonlinear crystals
NASA Astrophysics Data System (ADS)
Dodonov, V. V.
2015-06-01
I consider a possibility of parametric amplification of the microwave vacuum field in a reentrant cavity enclosing a nonlinear crystal whose refractive index is modulated by periodic high-intensity short laser pulses. The main result is that the total number of created ‘Casimir quanta’ depends neither on the laser beam shape, nor on the duration or power of individual pulses, but it depends on the total energy of all the pulses, provided the duration of each pulse is much shorter than the period of field oscillations in the selected resonant mode. The scheme can be feasible if reliable materials with high nonlinear coefficients can be found.
Spectral investigation of nonlinear local field effects in Ag nanoparticles
Sato, Rodrigo Takeda, Yoshihiko; Ohnuma, Masato; Oyoshi, Keiji
2015-03-21
The capability of Ag nanoparticles to modulate their optical resonance condition, by optical nonlinearity, without an external feedback system was experimentally demonstrated. These optical nonlinearities were studied in the vicinity of the localized surface plasmon resonance (LSPR), using femtosecond pump-and-probe spectroscopy with a white-light continuum probe. Transient transmission changes ΔT/T exhibited strong photon energy and particle size dependence and showed a complex and non-monotonic change with increasing pump light intensity. Peak position and change of sign redshift with increasing pump light intensity demonstrate the modulation of the LSPR. These features are discussed in terms of the intrinsic feedback via local field enhancement.
NASA Astrophysics Data System (ADS)
Deng, Jiechun; Xu, Haiming; Zhang, Leying
2016-05-01
Anthropogenic aerosols and urban land cover change induce opposite thermal effects on the atmosphere near surface as well as in the troposphere. One can think of these anthropogenic effects as composed of two parts: the individual effect due to an individual anthropogenic forcing and the nonlinear effects resulting from the coexistence of two forcing factors. In this study, we explored the role of such nonlinear effects in affecting East Asian climate, as well as individual forcing effects, using the Community Atmosphere Model version 5.1 coupled with the Community Land Model version 4. Atmospheric responses were simulated by including anthropogenic aerosol emission only, urban cover only, or the combination of the two, over eastern China. Results showed that nonlinear responses were different from any effects by an individual forcing or the linear combination of individual responses. The nonlinear interaction could generate cold horizontal temperature advection to cool the troposphere, which induced anomalous subsidence along the Yangtze River Valley (YRV). This anomalous vertical motion, together with a weakened low-level southwesterly, favored below-normal (above-normal) rainfall over the YRV (southern China), shifting the spring rain belt southward. The resultant diabatic cooling, in turn, amplified the anomalous descent and further decreased tropospheric temperature over the YRV, forming a positive feedback loop to maintain the nonlinear effects. Consequently, the nonlinear effects acted to reduce the climate anomalies from a simple linear combination of two individual effects and played an important role in regional responses to one anthropogenic forcing when the other is prescribed.
Nonlinear effective-medium theory of disordered spring networks.
Sheinman, M; Broedersz, C P; MacKintosh, F C
2012-02-01
Disordered soft materials, such as fibrous networks in biological contexts, exhibit a nonlinear elastic response. We study such nonlinear behavior with a minimal model for networks on lattice geometries with simple Hookian elements with disordered spring constant. By developing a mean-field approach to calculate the differential elastic bulk modulus for the macroscopic network response of such networks under large isotropic deformations, we provide insight into the origins of the strain stiffening and softening behavior of these systems. We find that the nonlinear mechanics depends only weakly on the lattice geometry and is governed by the average network connectivity. In particular, the nonlinear response is controlled by the isostatic connectivity, which depends strongly on the applied strain. Our predictions for the strain dependence of the isostatic point as well as the strain-dependent differential bulk modulus agree well with numerical results in both two and three dimensions. In addition, by using a mapping between the disordered network and a regular network with random forces, we calculate the nonaffine fluctuations of the deformation field and compare them to the numerical results. Finally, we discuss the limitations and implications of the developed theory.
Nonlinear effective-medium theory of disordered spring networks.
Sheinman, M; Broedersz, C P; MacKintosh, F C
2012-02-01
Disordered soft materials, such as fibrous networks in biological contexts, exhibit a nonlinear elastic response. We study such nonlinear behavior with a minimal model for networks on lattice geometries with simple Hookian elements with disordered spring constant. By developing a mean-field approach to calculate the differential elastic bulk modulus for the macroscopic network response of such networks under large isotropic deformations, we provide insight into the origins of the strain stiffening and softening behavior of these systems. We find that the nonlinear mechanics depends only weakly on the lattice geometry and is governed by the average network connectivity. In particular, the nonlinear response is controlled by the isostatic connectivity, which depends strongly on the applied strain. Our predictions for the strain dependence of the isostatic point as well as the strain-dependent differential bulk modulus agree well with numerical results in both two and three dimensions. In addition, by using a mapping between the disordered network and a regular network with random forces, we calculate the nonaffine fluctuations of the deformation field and compare them to the numerical results. Finally, we discuss the limitations and implications of the developed theory. PMID:22463230
ERIC Educational Resources Information Center
Hosal-Akman, Nazli; Simga-Mugan, Can
2010-01-01
This study explores the effect of teaching methods on the academic performance of students in accounting courses. The study was carried out over two semesters at a well-known university in Turkey in principles of financial accounting and managerial accounting courses. Students enrolled in the courses were assigned to treatment and control groups.…
A Pilot Study Examining the Effects of Time Constraints on Student Performance in Accounting Classes
ERIC Educational Resources Information Center
Morris, David E., Sr.; Scott, John
2015-01-01
The purpose of this study was to examine the effects, if any, of time constraints on the success of accounting students completing exams. This study examined how time allowed to take exams affected the grades on examinations in three different accounting classes. Two were sophomore classes and one was a senior accounting class. This limited pilot…
Effect of transverse shears on complex nonlinear vibrations of elastic beams
NASA Astrophysics Data System (ADS)
Krysko, V. A.; Zhigalov, M. V.; Saltykova, O. A.; Krysko, A. V.
2011-09-01
Models of geometrically nonlinear Euler-Bernoulli, Timoshenko, and Sheremet'ev-Pelekh beams under alternating transverse loading were constructed using the variational principle and the hypothesis method. The obtained differential equation systems were analyzed based on nonlinear dynamics and the qualitative theory of differential equations with using the finite difference method with the approximation O(h2) and the Bubnov-Galerkin finite element method. It is shown that for a relative thickness λ ⩽ 50, accounting for the rotation and bending of the beam normal leads to a significant change in the beam vibration modes.
The effect of accountable care organizations on oncology practice.
Shulman, Lawrence N
2014-01-01
Cancer care accounts for a significant portion of the rise in health care costs, and therefore, as national efforts escalate to control cost, cancer care will be a focus of concern. Cost increases in cancer care are related to many factors, including increasing cancer incidence in an aging population, the introduction of new high-cost therapeutics, and the high cost of end-of-life care. Accountable care organizations (ACOs) have been one of the major efforts directed at controlling health care costs. How cancer care will fit into the rubric of ACOs is not entirely clear but will certainly evolve over the coming years. The oncology profession has the opportunity to play a role in this evolution or could leave the evolution to others driving the process, such as the Centers for Medicare and Medicaid Services (CMS), private payers, and ACOs. Ideally all parties will work together to provide a construct for high-value, high-quality care for patients with cancer while contributing to cost control in overall health care. PMID:24857141
Brandt, Holger; Umbach, Nora; Kelava, Augustin
2015-01-01
The application of mixture models to flexibly estimate linear and nonlinear effects in the SEM framework has received increasing attention (e.g., Jedidi et al., 1997b; Bauer, 2005; Muthén and Asparouhov, 2009; Wall et al., 2012; Kelava and Brandt, 2014; Muthén and Asparouhov, 2014). The advantage of mixture models is that unobserved subgroups with class-specific relationships can be extracted (direct application), or that the mixtures can be used as a statistical tool to approximate nonnormal (latent) distributions (indirect application). Here, we provide a general standardization procedure for linear and nonlinear interaction and quadratic effects in mixture models. The procedure can also be applied to multiple group models or to single class models with nonlinear effects like LMS (Klein and Moosbrugger, 2000). We show that it is necessary to take nonnormality of the data into account for a correct standardization. We present an empirical example from education science applying the proposed procedure. PMID:26648886
Surface-enhanced nonlinear optical effects and detection of adsorbed molecular monolayers
Shen, Y.R.; Chen, C.K.; Heinz, T.F.; Ricard, D.
1981-01-01
The observation of a number of surface-enhanced nonlinear optical effects is discussed. The feasibility of using second-harmonic generation to detect the adsorption of molecular monolayers on a metal surface in an electrolytic solution is shown.
An enhanced temperature index model for debris-covered glaciers accounting for thickness effect
NASA Astrophysics Data System (ADS)
Carenzo, M.; Pellicciotti, F.; Mabillard, J.; Reid, T.; Brock, B. W.
2016-08-01
Debris-covered glaciers are increasingly studied because it is assumed that debris cover extent and thickness could increase in a warming climate, with more regular rockfalls from the surrounding slopes and more englacial melt-out material. Debris energy-balance models have been developed to account for the melt rate enhancement/reduction due to a thin/thick debris layer, respectively. However, such models require a large amount of input data that are not often available, especially in remote mountain areas such as the Himalaya, and can be difficult to extrapolate. Due to their lower data requirements, empirical models have been used extensively in clean glacier melt modelling. For debris-covered glaciers, however, they generally simplify the debris effect by using a single melt-reduction factor which does not account for the influence of varying debris thickness on melt and prescribe a constant reduction for the entire melt across a glacier. In this paper, we present a new temperature-index model that accounts for debris thickness in the computation of melt rates at the debris-ice interface. The model empirical parameters are optimized at the point scale for varying debris thicknesses against melt rates simulated by a physically-based debris energy balance model. The latter is validated against ablation stake readings and surface temperature measurements. Each parameter is then related to a plausible set of debris thickness values to provide a general and transferable parameterization. We develop the model on Miage Glacier, Italy, and then test its transferability on Haut Glacier d'Arolla, Switzerland. The performance of the new debris temperature-index (DETI) model in simulating the glacier melt rate at the point scale is comparable to the one of the physically based approach, and the definition of model parameters as a function of debris thickness allows the simulation of the nonlinear relationship of melt rate to debris thickness, summarised by the
Nonlinear optical properties and optical power limiting effect of Giemsa dye
NASA Astrophysics Data System (ADS)
Al-Saidi, Imad Al-Deen Hussein A.; Abdulkareem, Saif Al-Deen
2016-08-01
The nonlinear optical properties of Giemsa dye in chloroform solution for different concentrations and dye mixed with poly(methylmethacrylate) (PMMA) as a dye-doped polymer film were investigated using continuous wave (CW) low power solid-state laser (SSL) operating at wavelength of 532 nm as an excitation source. Using the single beam z-scan technique, the nonlinear refractive index (n2), the nonlinear absorption coefficient (β), and the third-order nonlinear optical susceptibility (χ(3)) of Giemsa dye were measured. The measurements reveal that both n2 and β are dependent on the dye concentration. The obtained results indicate that the Giemsa dye exhibits positive nonlinear saturable absorption (SA) and negative refraction nonlinearity, manifestation of self-defocusing effect. Optical power limiting characteristics of the Giemsa dye at different concentrations in solution and polymer film were studied. The observed large third-order optical nonlinearity of Giemsa dye confirms that Giemsa dye is a promising nonlinear material for the optical power limiting and photonic devices applications.
The effect of problem perturbations on nonlinear dynamical systems and their reduced order models
Serban, R; Homescu, C; Petzold, L
2005-03-03
Reduced order models are used extensively in many areas of science and engineering for simulation, design, and control. Reduction techniques for nonlinear dynamical systems produce models that depend strongly on the nominal set of parameters for which the reduction is carried out. In this paper we address the following two questions: 'What is the effect of perturbations in the problem parameters on the output functional of a nonlinear dynamical system?' and 'To what extent does the reduced order model capture this effect?'
Effect of motor dynamics on nonlinear feedback robot arm control
NASA Technical Reports Server (NTRS)
Tarn, Tzyh-Jong; Li, Zuofeng; Bejczy, Antal K.; Yun, Xiaoping
1991-01-01
A nonlinear feedback robot controller that incorporates the robot manipulator dynamics and the robot joint motor dynamics is proposed. The manipulator dynamics and the motor dynamics are coupled to obtain a third-order-dynamic model, and differential geometric control theory is applied to produce a linearized and decoupled robot controller. The derived robot controller operates in the robot task space, thus eliminating the need for decomposition of motion commands into robot joint space commands. Computer simulations are performed to verify the feasibility of the proposed robot controller. The controller is further experimentally evaluated on the PUMA 560 robot arm. The experiments show that the proposed controller produces good trajectory tracking performances and is robust in the presence of model inaccuracies. Compared with a nonlinear feedback robot controller based on the manipulator dynamics only, the proposed robot controller yields conspicuously improved performance.
Effect of nonlinear electromechanical interaction upon wind power generator behavior
NASA Astrophysics Data System (ADS)
Selyutskiy, Yury D.; Klimina, Liubov A.
2014-12-01
A mathematical model is developed for describing a small horizontal axis wind turbine with electric generator, such that the electromechanical interaction is non-linear in current. Dependence of steady regimes of the system upon parameters of the model is studied. In particular, it is shown that increase of wind speed causes qualitative restructuring of the set of steady regimes, which leads to considerable change in behavior of the wind power generator. The proposed model is verified against data obtained in experiments.
Liu, Chang; Dodin, Ilya Y.
2015-08-15
The nonlinear frequency shift is derived in a transparent asymptotic form for intense Langmuir waves in general collisionless plasma. The formula describes both fluid and kinetic effects simultaneously. The fluid nonlinearity is expressed, for the first time, through the plasma dielectric function, and the kinetic nonlinearity accounts for both smooth distributions and trapped-particle beams. Various known limiting scalings are reproduced as special cases. The calculation avoids differential equations and can be extended straightforwardly to other nonlinear plasma waves.
Nonlinear effects in propagation of long-range surface plasmon polaritons in gold strip waveguides
NASA Astrophysics Data System (ADS)
Lysenko, Oleg; Bache, Morten; Malureanu, Radu; Lavrinenko, Andrei
2016-04-01
This paper is devoted to experimental and theoretical studies of nonlinear propagation of a long-range surface plasmon polariton (LRSPP) in gold strip waveguides. The plasmonic waveguides are fabricated in house, and contain a gold layer, tantalum pentoxide adhesion layers, and silicon dioxide cladding. The optical characterization was performed using a high power picosecond laser at 1064 nm. The experiments reveal two nonlinear optical effects: nonlinear power transmission and spectral broadening of the LRSPP mode in the waveguides. Both nonlinear optical effects depend on the gold layer thickness. The theoretical model of these effects is based on the third-order susceptibility of the constituent materials. The linear and nonlinear parameters of the LRSPP mode are obtained, and the nonlinear Schrödinger equation is solved. The dispersion length is much larger than the waveguides length, and the chromatic dispersion does not affect the propagation of the plasmonic mode. We find that the third-order susceptibility of the gold layer has a dominant contribution to the effective third-order susceptibility of the LRSPP mode. The real part of the effective third-order susceptibility leads to the observed spectral broadening through the self-phase modulation effect, and its imaginary part determines the nonlinear absorption parameter and leads to the observed nonlinear power transmission. The experimental values of the third-order susceptibility of the gold layers are obtained. They indicate an effective enhancement of the third-order susceptibility for the gold layers, comparing to the bulk gold values. This enhancement is explained in terms of the change of the electrons motion.
The relative importance of relative nonlinearity and the storage effect in the lottery model.
Yuan, Chi; Chesson, Peter
2015-11-01
Although it is likely that many coexistence mechanisms contribute to maintenance of species diversity, most approaches to understanding species coexistence proceed as if only one mechanism would be present. In studies of species coexistence in a temporally fluctuating environment, the storage effect, believed to be the most important coexistence mechanism, has been the focus. Although a different coexistence mechanism--relative nonlinearity--is also predicted to arise frequently with environmental variation, its effect has been overshadowed by the storage effect. The relatively nonlinear growth rates on which the mechanism depends arise simply from differences in life history traits. Many kinds of temporal variation can then interact with these nonlinearity differences to create the relative nonlinearity coexistence mechanism. Much is unknown about when this mechanism is important and its total neglect is not justified. Here, we use the lottery model to provide a much needed quantitative assessment of the relative and combined effects of relative nonlinearity and the storage effect. Our analysis takes advantage of recently developed techniques for quantifying coexistence mechanisms when multiple mechanisms operate in concert. We find that relative nonlinearity is able to contribute substantially to species coexistence in the lottery model when two conditions are satisfied: (1) species must differ greatly in their adult death rates, (2) sensitivity of recruitment to environmental variation must be greater for species with larger adult death rates. In addition, relative nonlinearity has a critical role in compensating for a weakened storage effect when there is high correlation between species in their responses to the varying environment. In some circumstances relative nonlinearity is stronger than the storage effect or is even the sole mechanism of coexistence. PMID:26307205
Nonlinear Effects in Single-Pass ICRF Heating
NASA Technical Reports Server (NTRS)
Arefiev, A. V.; Breizman, B. N.
1999-01-01
The Variable Specific Impulse Magnetoplasma Rocket (VASIMR) concept employs Ion Cyclotron Resonant Frequency (ICRF) heating as the main power deposition mechanism. Since the ions accelerate to the full energy in a single pass through the cyclotron resonance, their response to the RF-field will be essentially nonlinear - hence the motivation to amend the commonly used linear approach to the problem. In a collisionless plasma, the energy gain of an accelerated ion is limited by the time the particle spends at the resonance. This time is affected by: (1) incident flow velocity, (2) longitudinal grad B force, (3) ambipolar electric field, and (4) ponderomotive force of the RF-field. Our analysis shows that the grad B force is the dominant factor at low to moderate levels of RF-power. We present nonlinear scaling for the energy gain and the absorption efficiency with RF-power and plasma parameters. We also demonstrate that the nonlinear regime exhibits a steep decrease in the plasma density at the resonance.
Manifestation of the Kondo effect in nonlinear optical absorption
NASA Astrophysics Data System (ADS)
Shahbazyan, T. V.; Perakis, I. E.; Raikh, M. E.
2000-03-01
We study the nonlinear optical absorption due to transitions from a deep impurity to states above a Fermi sea. Previous calculations(See, e.g., S. Mukamel, Principles of Nonlinear Optical Spectroscopy), (Oxford University Press, 1995). of \\chi^(3) included contributions from virtual processes involving doubly occupied impurity state. This indicates the necessity of incorporating the Hubbard repulsion of electrons at the impurity in calculation of nonlinear optical properties. Detailed calculations are performed for pump-probe spectrum. We demonstrate that Hubbard-repulsion-induced suppression of two-electron states leads to the divergency in \\chi^(3) near the absorption threshold. The origin of this divergency lies in the Kondo-physics;(See, e.g., A. C. Hewson, The Kondo Problem to Heavy Fermions), (Cambridge University Press, 1993). a monochromatic optical field induces the coupling between the impurity and conduction band states that is similar to the hybridization terms in the Anderson model.^3 Remarkably, for light-induced Kondo-absorption, the Kondo temperature can be tuned by the intensity and frequency of the pump field.
NASA Astrophysics Data System (ADS)
Kim, Pyeongeun; Young-Gonzales, Amanda R.; Richert, Ranko
2016-08-01
We have re-measured the third harmonic non-linear dielectric response of supercooled glycerol using zero-bias sinusoidal electric fields, with the aim of comparing the resulting susceptibilities with a phenomenological model of non-linear dielectric responses. In the absence of known chemical effects in this liquid, the present model accounts for three sources of non-linear behavior: dielectric saturation, field induced entropy reduction, and energy absorption from the time dependent field. Using parameters obtained from static high field results, the present model reproduces the characteristic features observed in the third harmonic susceptibility spectra: a low frequency plateau originating from dielectric saturation and a peak positioned below the loss peak frequency whose amplitude increases with decreasing temperature. Semi-quantitative agreement is achieved between experiment and the present model, which does not involve spatial scales or dynamical correlations explicitly. By calculating the three contributions separately, the model reveals that the entropy effect is the main source of the "hump" feature of this third harmonic response.
Nonlinear effects in spin relaxation of cavity polaritons
Solnyshkov, D. D.; Shelykh, I. A. Glazov, M. M.; Malpuech, G.; Amand, T.; Renucci, P.; Marie, X.; Kavokin, A. V.
2007-09-15
We present the general kinetic formalism for the description of spin and energy relaxation of the cavity polaritons in the framework of the Born-Markov approximation. All essential mechanisms of polariton redistribution in reciprocal space together with the final state bosonic stimulation are taken into account from our point of view. The developed theory is applied to describe our experimental results on the polarization dynamics obtained in the polariton parametric amplifier geometry (pumping at the so-called magic angle). Under circular pumping, we show that the spin relaxation time is strongly dependent on the detuning between the exciton and cavity mode energies mainly because of the influence of the detuning on the coupling strength between the photon-like part of the exciton-polariton lower dispersion branch and the reservoir of uncoupled exciton states. In the negative detuning case we find a very long spin relaxation time of about 300 ps. In the case of excitation by a linearly polarized light, we have experimentally confirmed that the anisotropy of the polariton-polariton interaction is responsible for the build-up of the cross-linear polarization of the signal. In the spontaneous regime the polarization degree of the signal is -8% but it can reach -65% in the stimulated regime. The long-living linear polarization observed at zero detuning indicates that the reservoir is formed by excitons localized at the anisotropic islands oriented along the crystallographic axes. Finally, under elliptical pumping, we have directly measured in the time domain and modeled the effect of self-induced Larmor precession, i.e., the rotation of the linear polarization of a state about an effective magnetic field proportional to the projection of the total spin of exciton-polaritons in the cavity on its growth axis.
NASA Astrophysics Data System (ADS)
Korman, Murray S.; Sabatier, James M.; Pauls, Kathleen E.; Genis, Sean A.
2006-05-01
When airborne sound at two primary tones, f I, f II (closely spaced near a resonance) excites the soil surface over a buried landmine, soil wave motion interacts with the landmine generating a scattered surface profile which can be measured over the "target." Profiles at the primaries f I, f II, and nonlinearly generated combination frequencies f I-(f II-f I) and f II+(f II-f I) , 2f I-(f II-f I), f I+f II and 2f II+(f II-f I) (among others) have been measured for a VS 2.2 plastic, inert, anti-tank landmine, buried at 3.6 cm in sifted loess soil and in a gravel road bed. [M.S. Korman and J.M. Sabatier, J. Acoust. Soc. Am. 116, 3354-3369 (2004)]. It is observed that the "on target" to "off target" contrast ratio for the sum frequency component can be ~20 dB higher than for either primary. The vibration interaction between the top-plate interface of a buried plastic landmine and the soil above it appears to exhibit many characteristics of the mesoscopic/nanoscale nonlinear effects that are observed in geomaterials like sandstone. Near resonance, the bending (softening) of a family of increasing amplitude tuning curves, involving the vibration over the landmine, exhibits a linear relationship between the peak particle velocity and corresponding frequency. Tuning curve experiments are performed both on and off the mine in an effort to understand the nonlinearities in each case.
Dagne, Getachew; Huang, Yangxin
2012-01-01
Censored data are characteristics of many bioassays in HIV/AIDS studies where assays may not be sensitive enough to determine gradations in viral load determination among those below a detectable threshold. Not accounting for such left-censoring appropriately can lead to biased parameter estimates in most data analysis. To properly adjust for left-censoring, this paper presents an extension of the Tobit model for fitting nonlinear dynamic mixed-effects models with skew distributions. Such extensions allow one to specify the conditional distributions for viral load response to account for left-censoring, skewness and heaviness in the tails of the distributions of the response variable. A Bayesian modeling approach via Markov Chain Monte Carlo (MCMC) algorithm is used to estimate model parameters. The proposed methods are illustrated using real data from an HIV/AIDS study. PMID:22992288
A Response-Discrimination Account of the Simon Effect
ERIC Educational Resources Information Center
Ansorge, Ulrich; Wuhr, Peter
2004-01-01
Simon effects might partly reflect stimulus-triggered response activation. According to the response-discrimination hypothesis, however, stimulus-triggered response activation shows up in Simon effects only when stimulus locations match the top-down selected spatial codes used to discriminate between alternative responses. Five experiments support…
Returns to Education: Accounting for Enrolment and Completion Effects
ERIC Educational Resources Information Center
Hérault, Nicolas; Zakirova, Rezida
2015-01-01
This paper contributes to the literature by separately analysing the course enrolment and completion effects of vocational education and training (VET) as well as higher education. Moreover, we investigate the persistence of these wage effects over time while controlling for two potential selection biases. We take advantage of the Longitudinal…
Nonlinear effects in collision cascades and high energy shock waves during ta-C:H growth
Piazza, F.; Resto, O.; Morell, G.
2007-07-01
The surface topography of hydrogenated tetrahedral amorphous carbon (ta-C:H) is critical for various applications such as microelectromechanical devices, magnetic and optical storage devices, and medical implants. The surface topography of ta-C:H films deposited by distributed electron cyclotron resonance plasma from C{sub 2}H{sub 2} gas precursor was investigated. The effects of pressure, together with ion flux and energy, are studied by atomic force microscopy in relation to the structural evolution of the films. The results are compared with the predictions of the Edward-Wilkinson model [Proc. R. Soc. London, Ser. A 44, 1039 (1966)] recently proposed to account for ta-C:H growth and with previous interpretations based on hypersonic shock waves. The random hillocks observed on the smooth surfaces of ta-C:H films deposited at high pressure are thought to result from the interference of high energy shock waves triggered by C{sub 4}H{sub x}{sup +} ions that produce overlapping collision cascades and induce nonlinear effects.
NASA Technical Reports Server (NTRS)
Subrahmanyam, K. B.; Kaza, K. R. V.
1985-01-01
The effects of pretwist, precone, setting angle, Coriolis forces and second degree geometric nonlinearities on the natural frequencies, steady state deflections and mode shapes of rotating, torsionally rigid, cantilevered beams were studied. The governing coupled equations of flap lag extensional motion are derived including the effects of large precone and retaining geometric nonlinearities up to second degree. The Galerkin method, with nonrotating normal modes, is used for the solution of both steady state nonlinear equations and linear perturbation equations. Parametric indicating the individual and collective effects of pretwist, precone, Coriolis forces and second degree geometric nonlinearities on the steady state deflection, natural frequencies and mode shapes of rotating blades are presented. It is indicated that the second degree geometric nonlinear terms, which vanish for zero precone, can produce frequency changes of engineering significance. Further confirmation of the validity of including those generated by MSC NASTRAN. It is indicated that the linear and nonlinear Coriolis effects must be included in analyzing thick blades. The Coriolis effects are significant on the first flatwise and the first edgewise modes.
Noise-induced transitions and resonant effects in nonlinear systems
NASA Astrophysics Data System (ADS)
Zaikin, Alexei
2003-02-01
Our every-day experience is connected with different acoustical noise or music. Usually noise plays the role of nuisance in any communication and destroys any order in a system. Similar optical effects are known: strong snowing or raining decreases quality of a vision. In contrast to these situations noisy stimuli can also play a positive constructive role, e.g. a driver can be more concentrated in a presence of quiet music. Transmission processes in neural systems are of especial interest from this point of view: excitation or information will be transmitted only in the case if a signal overcomes a threshold. Dr. Alexei Zaikin from the Potsdam University studies noise-induced phenomena in nonlinear systems from a theoretical point of view. Especially he is interested in the processes, in which noise influences the behaviour of a system twice: if the intensity of noise is over a threshold, it induces some regular structure that will be synchronized with the behaviour of neighbour elements. To obtain such a system with a threshold one needs one more noise source. Dr. Zaikin has analyzed further examples of such doubly stochastic effects and developed a concept of these new phenomena. These theoretical findings are important, because such processes can play a crucial role in neurophysics, technical communication devices and living sciences. Unsere alltägliche Erfahrung ist mit verschiedenen akustischen Einfluessen wie Lärm, aber auch Musik verbunden. Jeder weiss, wie Lärm stören kann und Kommunikation behindert oder gar unterbindet. Ähnliche optische Effekte sind bekannt: starkes Schneetreiben oder Regengüsse verschlechtern die Sicht und lassen uns Umrisse nur noch schemenhaft erkennen. Jedoch koennen ähnliche Stimuli auch sehr positive Auswirkungen haben: Autofahrer fahren bei leiser Musik konzentrierter -- die Behauptung von Schulkindern, nur bei dröhnenden Bässen die Mathehausaufgaben richtig rechnen zu können, ist allerdings nicht wissenschaftlich
Vacuum Rabi splitting effect in nanomechanical QED system with nonlinear resonator
NASA Astrophysics Data System (ADS)
Zhao, MingYue; Gao, YiBo
2016-08-01
Considering the intrinsic nonlinearity in a nanomechanical resonator coupled to a charge qubit, vacuum Rabi splitting effect is studied in a nanomechanical QED (qubit-resonator) system. A driven nonlinear Jaynes-Cummings model describes the dynamics of this qubit-resonator system. Using quantum regression theorem and master equation approach, we have calculated the two-time correlation spectrum analytically. In the weak driving limit, these analytical results clarify the influence of the driving strength and nonlinearity parameter on the correlation spectrum. Also, numerical calculations confirm these analytical results.
Nonlinear and stochastic effects in ENSO variability: From observations to intermediate models
NASA Astrophysics Data System (ADS)
Chekroun, Mickael David; Kondrashov, Dmitri; Neelin, David; Ghil, Michael
2010-05-01
The El-Nino/Southern-Oscillation (ENSO) phenomenon dominates interannual climate signals in and around the Tropical Pacific and affects the atmospheric circulation and air-sea interaction over many parts of the globe. Observational campaigns over the last decades have helped infer the most relevant processes, time scales and spatial patterns. A hierarchy of models has been developed to understand these processes and their interaction. These models have been, by-and-large, either deterministic and nonlinear or stochastic and linear, and have been applied to the prediction of future variability as well. The purpose of our work is to combine these two complementary points of view, and thus account for (i) the most robust and relevant aspects of the observations; (ii) the advances in understanding the nonlinear, deterministic interactions between the largest and most energetic scales; and (iii) the impact of small-scale ("noise") and remote ("external") processes. The main thrust of our approach is based on the concepts and tools of the theory of random dynamical systems (RDS). So far, two of the co-authors (MC & MG), in collaboration with E. Simonnet, have successfully applied RDS theory to, and described in detail the random attractors of several idealized climate models, such as the Lorenz (JAS, 1963) model of convection and the ENSO model of Timmermann and Jin (GRL, 2002). In the present work, we are extending these results to more detailed and realistic models, on the way to their eventual application to IPCC-class general circulation models (GCMs). Specifically, we address here two classes of such intermediate models. The first class is that of nonlinear inverse models derived by empirical mode reduction (EMR), as developed by two of the co-authors (MG and DK), in collaboration with S. Kravtsov, A. W. Robertson and others. In particular, we are studying the random attractor of the ENSO model derived in 2005 from sea surface temperature data over the past century
Meander migration modeling accounting for the effect of riparian vegetation
NASA Astrophysics Data System (ADS)
Eke, E.; Parker, G.
2010-12-01
A numerical model is proposed to study the development of meandering rivers so as to reproduce patterns of both migration and spatial/temporal width variation pattern observed in nature. The model comprises of: a) a depth-averaged channel hydrodynamic/morphodynamic model developed using a two-parameter perturbation expansion technique that considers perturbations induced by curvature and spatial channel width variation and b) a bank migration model which separately considers bank erosional and depositional processes. Unlike most previous meandering river models where channel migration is characterized only in terms of bank erosion, channel dynamics are here defined at channel banks which are allowed to migrate independently via deposition/erosion based on the local flow field and bank characteristics. A bank erodes (deposits) if the near bank Shields stress computed from the flow field is greater (less) than a specified threshold. This threshold Shields number is equivalent to the formative Shields stress characterizing bankfull flow. Excessive bank erosion is controlled by means of natural armoring provided by cohesive/rooted slump blocks produced when a stream erodes into the lower non-cohesive part of a composite bank. Bank deposition is largely due to sediment trapping by vegetation; resultant channel narrowing is related to both a natural rate of vegetal encroachment and flow characteristics. This new model allows the channel freedom to vary in width both spatially and in time as it migrates, so accounting for the bi-directional coupling between vegetation and flow dynamics and reproducing more realistic planform geometries. Preliminary results based on the model are presented.
Engineering chromatic dispersion and effective nonlinearity in a dual-slot waveguide.
Liu, Yan; Yan, Jing; Han, Genquan
2014-09-20
In this paper, we propose a new dual slot based on rib-like structure, which exhibits a flat and near-zero dispersion over a 198 nm wide wavelength range. Chromatic dispersion of dual-slot silicon (Si) waveguide is mainly determined by waveguide dispersion due to the manipulating mode effective area rather than by the material dispersion. Moreover, the nonlinear coefficient and effective mode area of the waveguide are also explored in detail. A nonlinear coefficient of 1460/m/W at 1550 nm is achieved, which is 10 times larger than that of the Si rib waveguide. By changing different waveguide variables, both the dispersion and nonlinear coefficient can be tailored, thus enabling the potential for a highly nonlinear waveguide with uniform dispersion over a wide wavelength range, which could benefit the performance of broadband optical signal systems.
NASA Technical Reports Server (NTRS)
Denier, James P.; Hall, Philip
1992-01-01
The development of fully nonlinear Goertler vortices in high Reynolds number flow in a symmetrically constricted channel is investigated. Attention is restricted to the case of 'strongly' constricted channels considered by Smith and Daniels (1981) for which the scaled constriction height is asymptotically large. Such flows are known to develop a Goldstein singularity and subsequently become separated at some downstream station past the point of maximum channel constriction. It is shown that these flows can support fully nonlinear Goertler vortices, of the form elucidated by Hall and Lakin (1988), for constrictions which have an appreciable region of local concave curvature upstream of the position at which separation occurs. The effect on the onset of separation due to the nonlinear Goertler modes is discussed. A brief discussion of other possible nonlinear states which may also have a dramatic effect in delaying (or promoting) separation is given.
NASA Astrophysics Data System (ADS)
Denier, James P.; Hall, Philip
1992-07-01
The development of fully nonlinear Goertler vortices in high Reynolds number flow in a symmetrically constricted channel is investigated. Attention is restricted to the case of 'strongly' constricted channels considered by Smith and Daniels (1981) for which the scaled constriction height is asymptotically large. Such flows are known to develop a Goldstein singularity and subsequently become separated at some downstream station past the point of maximum channel constriction. It is shown that these flows can support fully nonlinear Goertler vortices, of the form elucidated by Hall and Lakin (1988), for constrictions which have an appreciable region of local concave curvature upstream of the position at which separation occurs. The effect on the onset of separation due to the nonlinear Goertler modes is discussed. A brief discussion of other possible nonlinear states which may also have a dramatic effect in delaying (or promoting) separation is given.
Redesign of the mixed-mode bending delamination test to reduce nonlinear effects
NASA Technical Reports Server (NTRS)
Reeder, James R.; Crews, John H., Jr.
1992-01-01
The mixed-mode bending (MMB) test uses a lever to apply simultaneously mode I and mode II loading to a split-beam specimen. An iterative analysis that accounts for the geometric nonlinearity of the MMB test was developed. The analysis accurately predicted the measured load-displacement response and the strain energy release rate, G, of an MMB test specimen made of AS4/PEEK. The errors in G when calculated using linear theory were found to be as large as 30 percent in some cases. Because it would be inconvenient to use a nonlinear analysis to analyze MMB data, the MMB apparatus was redesigned to minimize the nonlinearity. With the improved apparatus, loads are applied just above the midplane of the test specimen through a roller attached to the lever. This apparatus was demonstrated by measuring the mixed-mode delamination fracture toughhess of the test specimen. The nonlinearity errors associated with testing this tough composite material were less than +/- 3 percent. The data from the improved MMB apparatus analyzed with a linear analysis were similar to those found with the original apparatus and the nonlinear analysis.
Strong electronic correlation effects in coherent multidimensional nonlinear optical spectroscopy.
Karadimitriou, M E; Kavousanaki, E G; Dani, K M; Fromer, N A; Perakis, I E
2011-05-12
We discuss a many-body theory of the coherent ultrafast nonlinear optical response of systems with a strongly correlated electronic ground state that responds unadiabatically to photoexcitation. We introduce a truncation of quantum kinetic density matrix equations of motion that does not rely on an expansion in terms of the interactions and thus applies to strongly correlated systems. For this we expand in terms of the optical field, separate out contributions to the time-evolved many-body state due to correlated and uncorrelated multiple optical transitions, and use "Hubbard operator" density matrices to describe the exact dynamics of the individual contributions within a subspace of strongly coupled states, including "pure dephasing". Our purpose is to develop a quantum mechanical tool capable of exploring how, by coherently photoexciting selected modes, one can trigger nonlinear dynamics of strongly coupled degrees of freedom. Such dynamics could lead to photoinduced phase transitions. We apply our theory to the nonlinear response of a two-dimensional electron gas (2DEG) in a magnetic field. We coherently photoexcite the two lowest Landau level (LL) excitations using three time-delayed optical pulses. We identify some striking temporal and spectral features due to dynamical coupling of the two LLs facilitated by inter-Landau-level magnetoplasmon and magnetoroton excitations and compare to three-pulse four-wave-mixing (FWM) experiments. We show that these features depend sensitively on the dynamics of four-particle correlations between an electron-hole pair and a magnetoplasmon/magnetoroton, reminiscent of exciton-exciton correlations in undoped semiconductors. Our results shed light into unexplored coherent dynamics and relaxation of the quantum Hall system (QHS) and can provide new insight into non-equilibrium co-operative phenomena in strongly correlated systems.
Shear flow effects on the nonlinear evolution of thermal instabilities
Leboeuf, J.; Charlton, L.A.; Carreras, B.A. )
1993-08-01
In the weak radiation drive regime, the coupling between the thermal instability driven by impurity radiation and the self-consistent flow profile modification leads to a simple dynamical system that can be approximated by the Volterra--Lotka equations. In this system the shear flow acts as a predator and the temperature fluctuations act as prey. The solutions are oscillatory, and their behavior resembles that of edge-localized modes (ELM's). The solutions of the simplified model are compared with the three-dimensional and two-dimensional nonlinear numerical results for this instability.
Strong Surface Contribution to the Nonlinear Meissner Effect in d-Wave Superconductors
NASA Astrophysics Data System (ADS)
Zare, A.; Dahm, T.; Schopohl, N.
2010-06-01
We demonstrate that in a d-wave superconductor the bulk nonlinear Meissner effect is dominated by a surface effect due to Andreev bound states at low temperatures. The contribution of this surface effect to the nonlinear response coefficient follows a 1/T3 law with the opposite sign compared to the bulk 1/T behavior. The crossover from bulk dominated behavior to surface dominated behavior occurs at a temperature of T/Tc˜1/κ. We present an approximate analytical calculation, which supports our numerical calculations and provides a qualitative understanding of the effect. The effect can be probed by intermodulation distortion experiments.
Strong surface contribution to the nonlinear Meissner effect in d-wave superconductors.
Zare, A; Dahm, T; Schopohl, N
2010-06-11
We demonstrate that in a d-wave superconductor the bulk nonlinear Meissner effect is dominated by a surface effect due to Andreev bound states at low temperatures. The contribution of this surface effect to the nonlinear response coefficient follows a 1/T3 law with the opposite sign compared to the bulk 1/T behavior. The crossover from bulk dominated behavior to surface dominated behavior occurs at a temperature of T/Tc∼1/square root(κ). We present an approximate analytical calculation, which supports our numerical calculations and provides a qualitative understanding of the effect. The effect can be probed by intermodulation distortion experiments. PMID:20867262
Nonlinear Bubble Dynamics And The Effects On Propagation Through Near-Surface Bubble Layers
NASA Astrophysics Data System (ADS)
Leighton, Timothy G.
2004-11-01
Nonlinear bubble dynamics are often viewed as the unfortunate consequence of having to use high acoustic pressure amplitudes when the void fraction in the near-surface oceanic bubble layer is great enough to cause severe attenuation (e.g. >50 dB/m). This is seen as unfortunate since existing models for acoustic propagation in bubbly liquids are based on linear bubble dynamics. However, the development of nonlinear models does more than just allow quantification of the errors associated with the use of linear models. It also offers the possibility of propagation modeling and acoustic inversions which appropriately incorporate the bubble nonlinearity. Furthermore, it allows exploration and quantification of possible nonlinear effects which may be exploited. As a result, high acoustic pressure amplitudes may be desirable even in low void fractions, because they offer opportunities to gain information about the bubble cloud from the nonlinearities, and options to exploit the nonlinearities to enhance communication and sonar in bubbly waters. This paper presents a method for calculating the nonlinear acoustic cross-sections, scatter, attenuations and sound speeds from bubble clouds which may be inhomogeneous. The method allows prediction of the time dependency of these quantities, both because the cloud may vary and because the incident acoustic pulse may have finite and arbitrary time history. The method can be readily adapted for bubbles in other environments (e.g. clouds of interacting bubbles, sediments, structures, in vivo, reverberant conditions etc.). The possible exploitation of bubble acoustics by marine mammals, and for sonar enhancement, is explored.
Facilitative Orthographic Neighborhood Effects: The SERIOL Model Account
ERIC Educational Resources Information Center
Whitney, Carol; Lavidor, Michal
2005-01-01
A large orthographic neighborhood (N) facilitates lexical decision for central and left visual field/right hemisphere (LVF/RH) presentation, but not for right visual field/left hemisphere (RVF/LH) presentation. Based on the SERIOL model of letter-position encoding, this asymmetric N effect is explained by differential activation patterns at the…
Non-Gaussian microwave background fluctuations from nonlinear gravitational effects
NASA Technical Reports Server (NTRS)
Salopek, D. S.; Kunstatter, G. (Editor)
1991-01-01
Whether the statistics of primordial fluctuations for structure formation are Gaussian or otherwise may be determined if the Cosmic Background Explorer (COBE) Satellite makes a detection of the cosmic microwave-background temperature anisotropy delta T(sub CMB)/T(sub CMB). Non-Gaussian fluctuations may be generated in the chaotic inflationary model if two scalar fields interact nonlinearly with gravity. Theoretical contour maps are calculated for the resulting Sachs-Wolfe temperature fluctuations at large angular scales (greater than 3 degrees). In the long-wavelength approximation, one can confidently determine the nonlinear evolution of quantum noise with gravity during the inflationary epoch because: (1) different spatial points are no longer in causal contact; and (2) quantum gravity corrections are typically small-- it is sufficient to model the system using classical random fields. If the potential for two scalar fields V(phi sub 1, phi sub 2) possesses a sharp feature, then non-Gaussian fluctuations may arise. An explicit model is given where cold spots in delta T(sub CMB)/T(sub CMB) maps are suppressed as compared to the Gaussian case. The fluctuations are essentially scale-invariant.
Nonlinear effects of stretch on the flame front propagation
Halter, F.; Tahtouh, T.; Mounaim-Rousselle, C.
2010-10-15
In all experimental configurations, the flames are affected by stretch (curvature and/or strain rate). To obtain the unstretched flame speed, independent of the experimental configuration, the measured flame speed needs to be corrected. Usually, a linear relationship linking the flame speed to stretch is used. However, this linear relation is the result of several assumptions, which may be incorrected. The present study aims at evaluating the error in the laminar burning speed evaluation induced by using the traditional linear methodology. Experiments were performed in a closed vessel at atmospheric pressure for two different mixtures: methane/air and iso-octane/air. The initial temperatures were respectively 300 K and 400 K for methane and iso-octane. Both methodologies (linear and nonlinear) are applied and results in terms of laminar speed and burned gas Markstein length are compared. Methane and iso-octane were chosen because they present opposite evolutions in their Markstein length when the equivalence ratio is increased. The error induced by the linear methodology is evaluated, taking the nonlinear methodology as the reference. It is observed that the use of the linear methodology starts to induce substantial errors after an equivalence ratio of 1.1 for methane/air mixtures and before an equivalence ratio of 1 for iso-octane/air mixtures. One solution to increase the accuracy of the linear methodology for these critical cases consists in reducing the number of points used in the linear methodology by increasing the initial flame radius used. (author)
Primarily nonlinear effects observed in a driven asymmetrical vibrating wire
NASA Astrophysics Data System (ADS)
Hanson, Roger J.; Macomber, H. Kent; Morrison, Andrew C.; Boucher, Matthew A.
2005-01-01
The purpose of the work reported here is to further experimentally explore the wide variety of behaviors exhibited by driven vibrating wires, primarily in the nonlinear regime. When the wire is driven near a resonant frequency, it is found that most such behaviors are significantly affected by the splitting of the resonant frequency and by the existence of a ``characteristic'' axis associated with each split frequency. It is shown that frequency splitting decreases with increasing wire tension and can be altered by twisting. Two methods are described for determining the orientation of characteristic axes. Evidence is provided, with a possible explanation, that each axis has the same orientation everywhere along the wire. Frequency response data exhibiting nonlinear generation of transverse motion perpendicular to the driving direction, hysteresis, linear generation of perpendicular motion (sometimes tubular), and generation of motion at harmonics of the driving frequency are exhibited and discussed. Also reported under seemingly unchanging conditions are abrupt large changes in the harmonic content of the motion that sometimes involve large subharmonics and harmonics thereof. Slow transitions from one stable state of vibration to another and quasiperiodic motions are also exhibited. Possible musical significance is discussed. .
Bilgel, Murat; Prince, Jerry L; Wong, Dean F; Resnick, Susan M; Jedynak, Bruno M
2016-07-01
It is important to characterize the temporal trajectories of disease-related biomarkers in order to monitor progression and identify potential points of intervention. These are especially important for neurodegenerative diseases, as therapeutic intervention is most likely to be effective in the preclinical disease stages prior to significant neuronal damage. Neuroimaging allows for the measurement of structural, functional, and metabolic integrity of the brain at the level of voxels, whose volumes are on the order of mm(3). These voxelwise measurements provide a rich collection of disease indicators. Longitudinal neuroimaging studies enable the analysis of changes in these voxelwise measures. However, commonly used longitudinal analysis approaches, such as linear mixed effects models, do not account for the fact that individuals enter a study at various disease stages and progress at different rates, and generally consider each voxelwise measure independently. We propose a multivariate nonlinear mixed effects model for estimating the trajectories of voxelwise neuroimaging biomarkers from longitudinal data that accounts for such differences across individuals. The method involves the prediction of a progression score for each visit based on a collective analysis of voxelwise biomarker data within an expectation-maximization framework that efficiently handles large amounts of measurements and variable number of visits per individual, and accounts for spatial correlations among voxels. This score allows individuals with similar progressions to be aligned and analyzed together, which enables the construction of a trajectory of brain changes as a function of an underlying progression or disease stage. We apply our method to studying cortical β-amyloid deposition, a hallmark of preclinical Alzheimer's disease, as measured using positron emission tomography. Results on 104 individuals with a total of 300 visits suggest that precuneus is the earliest cortical region to
Multiphase continuum model to describe dynamic loading effects in nonlinear porous media
Swift, R.P.; Burton, D.E.; Bryan, J.B.; Glenn, H.D.
1985-03-01
A multiphase constitutive model that couples nonlinear deformation to porous flow has been developed for numerical analyses of dynamic behavior of geological media. The model has been incorporated into the explicit finite-difference code TENSOR and applied to examine the phenomenology associated with contained explosions and nuclear surface cratering in a coral geology. For contained explosions in nearly saturated media, the model predicts a region of liquefaction to exist adjacent to the cavity. This region is markedly enhanced for the case of total saturation and the associated pore pressure buildup indicate that the stability of the residual stress field may be threatened. Based on plausible assumptions about the geology and the constitutive relations of coral, we have shown that the multiphase constitutive model can relate subsidence to calculational parameters such as peak effective stress. Most of the observed volume of the Koa crater at the Pacific Proving Grounds can be accounted for by late time consolidation of the damaged coral. 21 refs., 10 figs.
Testing the item-order account of design effects using the production effect.
Jonker, Tanya R; Levene, Merrick; Macleod, Colin M
2014-03-01
A number of memory phenomena evident in recall in within-subject, mixed-lists designs are reduced or eliminated in between-subject, pure-list designs. The item-order account (McDaniel & Bugg, 2008) proposes that differential retention of order information might underlie this pattern. According to this account, order information may be encoded when a common form of processing is used alone in a list (e.g., reading), but not when an unusual form of processing is used (e.g., generation) or when a common form and an unusual form are mixed within a list. The production effect--better memory for words said aloud than for words read silently--shows this same design-contingent pattern. In 2 experiments, we investigated whether differential order retention might underlie the production effect. Consistent with the item-order account, we found that retention of order information was better in pure silent lists than in either pure aloud lists or mixed lists, as measured using an order reconstruction test. Moreover, in Experiment 2, order was better preserved in free recall of pure silent lists than of either pure aloud or mixed lists. Thus, production joins the set of tasks identified by McDaniel and Bugg (2008), and our findings suggest a role for order processing in explaining the production effect.
NASA Astrophysics Data System (ADS)
Kang, Dong-Keun; Yang, Hyun-Ik; Kim, Chang-Wan
2015-11-01
A mass sensor using a nano-resonator has high detection sensitivity, and mass sensitivity is higher with smaller resonators. Therefore, carbon nanotubes (CNTs) are the ultimate materials for these applications and have been actively studied. In particular, CNT-based nanomechanical devices may experience high temperatures that lead to thermal expansion and residual stress in devices, which affects the device reliability. In this letter, to demonstrate the influence of the temperature change (i.e., thermal effect) on the mass detection sensitivity of CNT-based mass sensor, dynamic analysis is carried out for a CNT resonator with thermal effects in both linear and nonlinear oscillation regimes. Based on the continuum mechanics model, the analytical solution method with an assumed deflection eigenmode is applied to solve the nonlinear differential equation which involves the von Karman nonlinear strain-displacement relation and the additional axial force associated with thermal effects. A thermal effect on the fundamental resonance behavior and resonance frequency shift due to adsorbed mas, i.e., mass detection sensitivity, is examined in high-temperature environment. Results indicate a valid improvement of fundamental resonance frequency by using nonlinear oscillation in a thermal environment. In both linear and nonlinear oscillation regimes, the mass detection sensitivity becomes worse due to the increasing of temperature in a high-temperature environment. The thermal effect on the detection sensitivity is less effective in the nonlinear oscillation regime. It is concluded that a temperature change of a mass sensor with a CNT-based resonator can be utilized to enhance the detection sensitivity depending on the CNT length, linear/nonlinear oscillation behaviors, and the thermal environment.
Non-linear effects of soda taxes on consumption and weight outcomes.
Fletcher, Jason M; Frisvold, David E; Tefft, Nathan
2015-05-01
The potential health impacts of imposing large taxes on soda to improve population health have been of interest for over a decade. As estimates of the effects of existing soda taxes with low rates suggest little health improvements, recent proposals suggest that large taxes may be effective in reducing weight because of non-linear consumption responses or threshold effects. This paper tests this hypothesis in two ways. First, we estimate non-linear effects of taxes using the range of current rates. Second, we leverage the sudden, relatively large soda tax increase in two states during the early 1990s combined with new synthetic control methods useful for comparative case studies. Our findings suggest virtually no evidence of non-linear or threshold effects. PMID:24615758
Non-linear effects of soda taxes on consumption and weight outcomes.
Fletcher, Jason M; Frisvold, David E; Tefft, Nathan
2015-05-01
The potential health impacts of imposing large taxes on soda to improve population health have been of interest for over a decade. As estimates of the effects of existing soda taxes with low rates suggest little health improvements, recent proposals suggest that large taxes may be effective in reducing weight because of non-linear consumption responses or threshold effects. This paper tests this hypothesis in two ways. First, we estimate non-linear effects of taxes using the range of current rates. Second, we leverage the sudden, relatively large soda tax increase in two states during the early 1990s combined with new synthetic control methods useful for comparative case studies. Our findings suggest virtually no evidence of non-linear or threshold effects.
Effect of nonlinear chirped Gaussian laser pulse on plasma wake field generation
Afhami, Saeedeh; Eslami, Esmaeil
2014-08-15
An ultrashort laser pulse propagating in plasma can excite a nonlinear plasma wake field which can accelerate charged particles up to GeV energies within a compact space compared to the conventional accelerator devices. In this paper, the effect of different kinds of nonlinear chirped Gaussian laser pulse on wake field generation is investigated. The numerical analysis of our results depicts that the excitation of plasma wave with large and highly amplitude can be accomplished by nonlinear chirped pulses. The maximum amplitude of excited wake in nonlinear chirped pulse is approximately three times more than that of linear chirped pulse. In order to achieve high wake field generation, chirp parameters and functions should be set to optimal values.
NASA Astrophysics Data System (ADS)
Henari, F. Z.; Al-Saie, A.
2006-12-01
We report the observation of self-action phenomena, such as self-focusing, self-defocusing, self-phase modulation and beam fanning in Roselle-Hibiscus Sabdariffa solutions. This material is found to be a new type of natural nonlinear media, and the nonlinear reflective index coefficient has been determined using a Z-scan technique and by measuring the critical power for the self-trapping effect. Z-scan measurements show that this material has a large negative nonlinear refractive index, n 2 = 1 × 10-4 esu. A comparison between the experimental n 2 values and the calculated thermal value for n 2 suggests that the major contribution to nonlinear response is of thermal origin.
NASA Astrophysics Data System (ADS)
Zhang, Jianfeng; Xuan, Fu-Zhen; Xiang, Yanxun; Zhao, Peng
2016-05-01
The effect of plastic deformations on the nonlinear ultrasonic response in austenite stainless steel was investigated under the tensile, asymmetric cyclic, and symmetric cyclic loadings. Nonlinear ultrasonic wave measurement was performed on the interrupted specimens. Results show that cyclic and monotonic plastic deformations lead to the significantly different acoustic nonlinear response. The increase of dislocation density and martensite transformation causes the increase of acoustic nonlinearity. By contrast, the well-developed cell structures decrease the acoustic nonlinear response. Under the asymmetric cyclic loading condition, the lightly decrease of acoustic nonlinearity is caused by the development of cell structures, while the slight increase of acoustic nonlinearity should be attributed to the increase of martensite transformation. Comparatively, the severe increase of acoustic nonlinearity during the first stage under symmetric cyclic loading is ascribed to the fast generation of dislocation structures and martensite transformation.
Nanoscale nonlinear effects in Erbium-implanted Yttrium Orthosilicate
NASA Astrophysics Data System (ADS)
Kukharchyk, Nadezhda; Shvarkov, Stepan; Probst, Sebastian; Xia, Kangwei; Becker, Hans-Werner; Pal, Shovon; Markmann, Sergej; Kolesov, Roman; Siyushev, Petr; Wrachtrup, Jörg; Ludwig, Arne; Ustinov, Alexey V.; Wieck, Andreas D.; Bushev, Pavel
2016-09-01
Doping of substrates at desired locations is a key technology for spin-based quantum memory devices. Focused ion beam implantation is well-suited for this task due to its high spacial resolution. In this work, we investigate ion-beam implanted erbium ensembles in Yttrium Orthosilicate crystals by means of confocal photoluminescence spectroscopy. The sample temperature and the post-implantation annealing step strongly reverberate in the properties of the implanted ions. We find that hot implantation leads to a higher activation rate of the ions. At high enough fluences, the relation between the fluence and final concentration of ions becomes non-linear. Two models are developed explaining the observed behaviour.
Nonlinear effects in gases in the Couette problem
Chernyak, V. G. Polikarpov, A. Ph.
2010-01-15
The nonlinear processes of heat and mass transfer in a rarefied gas confined between two infinite parallel plates maintained at different temperatures and moving at a relative velocity are considered. The profiles of the gas macroscopic flow velocity, density, temperature, heat fluxes, and shear stress were calculated on the basis of kinetic equations by the discrete velocity method in a wide range of Knudsen numbers at different values of temperature difference between the plates and plate velocities. It was shown that under certain conditions, the direction of gas flow near the 'hot' plate can change to the opposite. It was discovered that the longitudinal and normal components of heat flux at a certain temperature difference between the plates change their orientation to the opposite in transition and nearly free molecular regimes.
Nonlinear effects of dark energy clustering beyond the acoustic scales
Anselmi, Stefano; Sefusatti, Emiliano E-mail: dlopez_n@ictp.it
2014-07-01
We extend the resummation method of Anselmi and Pietroni (2012) to compute the total density power spectrum in models of quintessence characterized by a vanishing speed of sound. For standard ΛCDM cosmologies, this resummation scheme allows predictions with an accuracy at the few percent level beyond the range of scales where acoustic oscillations are present, therefore comparable to other, common numerical tools. In addition, our theoretical approach indicates an approximate but valuable and simple relation between the power spectra for standard quintessence models and models where scalar field perturbations appear at all scales. This, in turn, provides an educated guess for the prediction of nonlinear growth in models with generic speed of sound, particularly valuable since no numerical results are yet available.
Nonlinear and linear bottom interaction effects in shallow water
NASA Technical Reports Server (NTRS)
Shemdin, O.; Hsiao, S. V.; Hasselmann, K.; Herterich, K.
1978-01-01
The paper examines wave-energy dissipation rates in shallow water calculated from measured wave spectra at different distances from the shore. Different linear and nonlinear transfer and dissipation mechanisms are discussed. The various data sets are interpreted in terms of prevailing mechanisms at the respective sites. The incorporation of different processes in a predictive shallow-water model is outlined. The analysis suggests that bottom motion is primarily responsible for wave-energy dissipation in the Delta Region of the Gulf of Mexico, that friction is mainly responsible for wave-energy dissipation in Marineland, Panama City and Melkbosstrand, and that percolation is probably the dominant mechanism in the JONSWAP area of the North Sea.
The neural correlates of placebo effects: a disruption account.
Lieberman, Matthew D; Jarcho, Johanna M; Berman, Steve; Naliboff, Bruce D; Suyenobu, Brandall Y; Mandelkern, Mark; Mayer, Emeran A
2004-05-01
The neurocognitive pathways by which placebo effects operate are poorly understood. Positron emission tomography (PET) imaging was used to assess the brain response of patients with chronic abdominal pain (irritable bowel syndrome; IBS) to induced intestinal discomfort both before and after a 3-week placebo regimen. A daily symptom diary was used to measure symptom improvement. Increases in right ventrolateral prefrontal cortex (RVLPFC) activity from pre- to post-placebo predicted self-reported symptom improvement, and this relationship was mediated by changes in dorsal anterior cingulate (dACC), typically associated with pain unpleasantness. These results are consistent with disruption theory [Lieberman, M.D., 2003. Reflective and reflexive judgment processes: a social cognitive neuroscience approach. In: Forgas, J.P., Williams, K.R., von Hippel, W. (Eds.), Social Judgments: Explicit and Implicit Processes. Cambridge Univ. Press, New York, pp. 44-67], which proposes that activation of prefrontal regions associated with thinking about negative affect can diminish dACC and amygdala reactivity to negative affect stimuli. This is the first study to identify a neural pathway from a region of the brain associated with placebos and affective thought to a region closely linked to the placebo-related outcome of diminished pain unpleasantness.
Third Order Nonlinear Optical Effects in Some Polybenzidines
NASA Astrophysics Data System (ADS)
Cheng, Chi Fai
Third order nonlinear optical properties of organic compounds with pi electron delocalization are currently receiving much attention in view of potential applications in switching and optical information processing. Polymers of Benzidine were synthesized by hydrogen peroxide reaction catalyzed by horseradish peroxidase enzyme. The polymerization reaction was carried out at room temperature in a monophasic organic solvent with a small amount of water at pH 7.5. The technique of Degenerate Four Wave Mixing with picosecond and nanosecond pulses was employed to measure the third order susceptibility chi^{(3) } of polybenzidine. The observed values for chi^{(3)} are of order 10^{-9} to 10 ^{-8} esu. In order to understand the origin of these high values of chi^ {(3)}, we measured the real and imaginary components of chi^{(3)} . Investigation of total energy transmission as a function of incident intensity and fluence at 532 nm for picosecond and nanosecond laser pulses using a frequency doubled Nd:YAG laser indicates reverse saturable absorption. The experiments are carried out for the sample in solution in Dimethyl Sulfoxide and Methanol (DMSO:MeOH) 4:1 ratio. As we observe the nanosecond and picosecond curves to be superimposed for intensity dependence and not for fluence, we conclude that the third order nonlinearity is predominantly due to two photon absorption. Values for Im chi ^{(3)} determined by our experiments are of order 10^{-9} to 10^{-8} esu. We measure the real part of chi^{(3)} by optical Kerr gate technique. The value is about one order lower compared to the imaginary component. In view of the reverse saturable absorption characteristics observed for the samples, the material is a good candidate for applications in optical power limiting.
A pattern-based method for bounding the effective response of a nonlinear composite
NASA Astrophysics Data System (ADS)
Peigney, Michaël
2005-04-01
This paper deals with the prediction of the effective properties of nonlinear composites. Rather than bounding the effective energy, this work aims at bounding directly the effective stress-strain response, by extending a method originally introduced by Milton and Serkov (J. Mech. Phys. Solids 48 (2000) 1295) and recently refined by Talbot and Willis (Proc. Roy. Soc. 460 (2004) 2705). In this paper, bounding the effective response is achieved by introducing a linear comparison composite with the same micro-geometry as the given nonlinear composite, as Ponte Castañeda (J. Mech. Phys. Solids 39 (1991) 45) did for the energy. It is found that any lower bound for the energy of the linear comparison composite generates a corresponding bound for the stress-strain response of the nonlinear composite. A selection of examples is presented to illustrate the method and compare the bounds obtained with existing results.
Effect of plate permeability on nonlinear stability of the asymptotic suction boundary layer
NASA Astrophysics Data System (ADS)
Wedin, Hâkan; Cherubini, Stefania; Bottaro, Alessandro
2015-07-01
The nonlinear stability of the asymptotic suction boundary layer is studied numerically, searching for finite-amplitude solutions that bifurcate from the laminar flow state. By changing the boundary conditions for disturbances at the plate from the classical no-slip condition to more physically sound ones, the stability characteristics of the flow may change radically, both for the linearized as well as the nonlinear problem. The wall boundary condition takes into account the permeability K ̂ of the plate; for very low permeability, it is acceptable to impose the classical boundary condition (K ̂=0 ). This leads to a Reynolds number of approximately Rec=54 400 for the onset of linearly unstable waves, and close to Reg=3200 for the emergence of nonlinear solutions [F. A. Milinazzo and P. G. Saffman, J. Fluid Mech. 160, 281 (1985), 10.1017/S0022112085003482; J. H. M. Fransson, Ph.D. thesis, Royal Institute of Technology, KTH, Sweden, 2003]. However, for larger values of the plate's permeability, the lower limit for the existence of linear and nonlinear solutions shifts to significantly lower Reynolds numbers. For the largest permeability studied here, the limit values of the Reynolds numbers reduce down to Rec=796 and Reg=294 . For all cases studied, the solutions bifurcate subcritically toward lower Re, and this leads to the conjecture that they may be involved in the very first stages of a transition scenario similar to the classical route of the Blasius boundary layer initiated by Tollmien-Schlichting (TS) waves. The stability of these nonlinear solutions is also investigated, showing a low-frequency main unstable mode whose growth rate decreases with increasing permeability and with the Reynolds number, following a power law Re-ρ, where the value of ρ depends on the permeability coefficient K ̂. The nonlinear dynamics of the flow in the vicinity of the computed finite-amplitude solutions is finally investigated by direct numerical simulations, providing a
Kerr Nonlinearity via Cascaded Optical Rectification and the Linear Electro-optic Effect
NASA Astrophysics Data System (ADS)
Bosshard, Ch.; Spreiter, R.; Zgonik, M.; Günter, P.
1995-04-01
We show both theoretically and experimentally that the combined processes of optical rectification and the linear electro-optic effect lead to an effective nonlinear refractive index n2 in noncentrosymmetric materials. This cascaded second-order nonlinear optical effect arises in addition to the well-known contribution due to second-harmonic generation and difference-frequency mixing and is of comparable magnitude. However, it has the advantage of a broad acceptance angle because no precise phase matching is needed. Experimental results in KNbO3 crystals are presented.
"Catalyst Data": Perverse Systemic Effects of Audit and Accountability in Australian Schooling
ERIC Educational Resources Information Center
Lingard, Bob; Sellar, Sam
2013-01-01
This paper examines the perverse effects of the new accountability regime central to the Labor government's national reform agenda in schooling. The focus is on National Assessment Program -- Literacy and Numeracy (NAPLAN) results that now act as "catalyst data" and are pivotal to school and system accountability. We offer a case…
ERIC Educational Resources Information Center
Rich, Anne J.; Dereshiwsky, Mary I.
2011-01-01
This paper presents the results of a study assessing the comparative effectiveness of teaching an undergraduate intermediate accounting course in the online classroom format. Students in a large state university were offered an opportunity to complete the first course in intermediate accounting either online or on-campus. Students were required to…
Cramming: The Effects of School Accountability on College-Bound Students. Working Paper 7
ERIC Educational Resources Information Center
Donovan, Colleen; Figlio, David; Rush, Mark
2007-01-01
This paper presents the first evidence of the effects of school accountability systems on the long-term human capital development of high-performing, college-bound students. The results are mixed. On the one hand, the evidence is consistent that school accountability sanction threats are associated with changes in student study habits. Students…
ERIC Educational Resources Information Center
Cheng, K. W. Kevin
2009-01-01
This study mainly explored the effect of applying web-based collaborative learning instruction to the accounting curriculum on student's problem-solving attitudes in Technical Education. The research findings and proposed suggestions would serve as a reference for the development of accounting-related curricula and teaching strategies. To achieve…
Effect of nonlinear soil-structure interaction on seismic response of low-rise SMRF buildings
NASA Astrophysics Data System (ADS)
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.
The role of nonlinear effects in the propagation of noise from high-power jet aircraft.
Gee, Kent L; Sparrow, Victor W; James, Michael M; Downing, J Micah; Hobbs, Christopher M; Gabrielson, Thomas B; Atchley, Anthony A
2008-06-01
To address the question of the role of nonlinear effects in the propagation of noise radiated by high-power jet aircraft, extensive measurements were made of the F-22A Raptor during static engine run-ups. Data were acquired at low-, intermediate-, and high-thrust engine settings with microphones located 23-305 m from the aircraft along several angles. Comparisons between the results of a generalized-Burgers-equation-based nonlinear propagation model and the measurements yield favorable agreement, whereas application of a linear propagation model results in spectral predictions that are much too low at high frequencies. The results and analysis show that significant nonlinear propagation effects occur for even intermediate-thrust engine conditions and at angles well away from the peak radiation angle. This suggests that these effects are likely to be common in the propagation of noise radiated by high-power aircraft.
Nonlinear dynamics of the tearing mode with two-fluid and curvature effects in tokamaks
Meshcheriakov, Dmytro; Maget, Patrick; Garbet, Xavier; Lütjens, Hinrich; Beyer, Peter
2014-01-15
Curvature and diamagnetic effects are both known to have an influence on tearing mode dynamics. In this paper, we investigate the impact of these effects on the nonlinear stability and saturation of a (2, 1) island using non-linear two-fluid MHD simulations and we apply our results to Tore Supra experiments, where its behavior is not well understood from the single fluid MHD model. Simulations show that a metastable state induced by diamagnetic effect exists for this mode and that it also produces a reduction of the saturated island size, in presence of toroidal curvature. The mode is found to be nonlinearly destabilized by a seed island and it saturates at a macroscopic level causing a significant confinement degradation. The interpretation of dual states, with either no island on q = 2 or a large one, observed on discharges with high non inductive current source on Tore Supra, is revisited.
Nonlinear mode interactions and frequency-jump effects in a doubly tuned oscillator configuration
NASA Astrophysics Data System (ADS)
Grun, J.; Lashinsky, H.
1980-05-01
Frequency-jump effects associated with nonlinear mode competition are investigated in an oscillator configuration consisting of a passive linear resonance system coupled to an active nonlinear resonance system. These effects give rise to a hysteresis pattern whose height and width can be related to system parameters such as the resonance frequencies, dissipation, coupling coefficient, etc. It is noted that these effects offer a novel means of determining these parameters in cases in which conventional techniques may not be desirable or as advantageous. The analysis provides an qualitative explanation of empirical observations in a recent nuclear magnetic resonance experiment (Timsit and Daniels, 1976). The results also apply to other nonlinear resonance systems such as lasers, microwave generators, and electronic oscillators.
Nonlinear effects in propagation of radiation of X-ray free-electron lasers
NASA Astrophysics Data System (ADS)
Nosik, V. L.
2016-05-01
Nonlinear effects accompanying the propagation of high-intensity beams of X-ray free-electron lasers are considered. It is shown that the X-ray wave field in the crystal significantly changes due to the formation of "hollow" atomic shells as a result of the photoelectric effect.
An Investigation of the Effect of Nonlinearity of Regression on the ANCOVA F Test.
ERIC Educational Resources Information Center
Harwell, Michael
The effect of a nonlinear regression term on the behavior of the standard analysis of covariance (ANCOVA) F test was investigated for balanced and randomized designs through a Monte Carlo study. The results indicate that the use of the standard analysis of covariance model when a quadratic term is present has little effect on Type I error rates…
Cross-polarized wave generation by effective cubic nonlinear optical interaction.
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.
Pu, Hao; Liu, Yanmin; Jiang, Haijun; Hu, Cheng
2015-08-01
In this paper, the globally exponential synchronization of delayed fuzzy cellular neural networks with nonlinear impulsive effects are concerned. By utilizing inequality techniques and Lyapunov functional method, some sufficient conditions on the exponential synchronization are obtained based on [Formula: see text]-norm. Finally, a simulation example is given to illustrate the effectiveness of the theoretical results.
NASA Astrophysics Data System (ADS)
Germanis, S.; Katsidis, C.; Tsintzos, S.; Stavrinidis, A.; Konstantinidis, G.; Florini, N.; Kioseoglou, J.; Dimitrakopulos, G. P.; Kehagias, Th.; Hatzopoulos, Z.; Pelekanos, N. T.
2016-07-01
We report enhanced Stark tuning of single exciton lines in self-assembled (211 )B InAs quantum dots (QDs) as a consequence of pronounced piezoelectric effects in polar orientations, making this QD system particularly sensitive to relatively "small" applied external fields. The Stark shifts in the first hundreds of kilovolts per centimeter of applied external field are at least 2.5 times larger, compared to those observed in nonpiezoelectric (100) InAs QDs of similar size. To account quantitatively for the observed transition energies and Stark shifts, we utilize a graded In-composition potential profile, as deduced from local strain analysis performed on high-resolution transmission microscopy images of the QDs. Our results provide a direct demonstration of the importance of nonlinear piezoelectric effects in zincblende semiconductors.
Xu, Hao; Sun, Yujun; Wang, Xinjie; Fu, Yao; Dong, Yunfei; Li, Ying
2014-01-01
An individual-tree diameter growth model was developed for Cunninghamia lanceolata in Fujian province, southeast China. Data were obtained from 72 plantation-grown China-fir trees in 24 single-species plots. Ordinary non-linear least squares regression was used to choose the best base model from among 5 theoretical growth equations; selection criteria were the smallest absolute mean residual and root mean square error and the largest adjusted coefficient of determination. To account for autocorrelation in the repeated-measures data, we developed one-level and nested two-level nonlinear mixed-effects (NLME) models, constructed on the selected base model; the NLME models incorporated random effects of the tree and plot. The best random-effects combinations for the NLME models were identified by Akaike's information criterion, Bayesian information criterion and -2 logarithm likelihood. Heteroscedasticity was reduced with two residual variance functions, a power function and an exponential function. The autocorrelation was addressed with three residual autocorrelation structures: a first-order autoregressive structure [AR(1)], a combination of first-order autoregressive and moving average structures [ARMA(1,1)] and a compound symmetry structure (CS). The one-level (tree) NLME model performed best. Independent validation data were used to test the performance of the models and to demonstrate the advantage of calibrating the NLME models.
NASA Technical Reports Server (NTRS)
Goldberg, Robert K.; Carney, Kelly S.
2004-01-01
An analysis method based on a deformation (as opposed to damage) approach has been developed to model the strain rate dependent, nonlinear deformation of woven ceramic matrix composites, such as the Reinforced Carbon Carbon (RCC) material used on the leading edges of the Space Shuttle. In the developed model, the differences in the tension and compression deformation behaviors have also been accounted for. State variable viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the effective stress and effective inelastic strain definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear response is independent of the stiffness in the normal directions. The developed equations have been implemented into LS-DYNA through the use of user defined subroutines (UMATs). Several sample qualitative calculations have been conducted, which demonstrate the ability of the model to qualitatively capture the features of the deformation response present in woven ceramic matrix composites.
Effects of ADC Nonlinearity on the Spurious Dynamic Range Performance of Compressed Sensing
Tian, Pengwu; Yu, Hongyi
2014-01-01
Analog-to-information converter (AIC) plays an important role in the compressed sensing system; it has the potential to significantly extend the capabilities of conventional analog-to-digital converter. This paper evaluates the impact of AIC nonlinearity on the dynamic performance in practical compressed sensing system, which included the nonlinearity introduced by quantization as well as the circuit non-ideality. It presents intuitive yet quantitative insights into the harmonics of quantization output of AIC, and the effect of other AIC nonlinearity on the spurious dynamic range (SFDR) performance is also analyzed. The analysis and simulation results demonstrated that, compared with conventional ADC-based system, the measurement process decorrelates the input signal and the quantization error and alleviate the effect of other decorrelates of AIC, which results in a dramatic increase in spurious free dynamic range (SFDR). PMID:24895645
Nonlinear soil parameter effects on dynamic embedment of offshore pipeline on soft clay
NASA Astrophysics Data System (ADS)
Yu, Su Young; Choi, Han Suk; Lee, Seung Keon; Park, Kyu-Sik; Kim, Do Kyun
2015-06-01
In this paper, the effects of nonlinear soft clay on dynamic embedment of offshore pipeline were investigated. Seabed embedment by pipe-soil interactions has impacts on the structural boundary conditions for various subsea structures such as pipeline, riser, pile, and many other systems. A number of studies have been performed to estimate real soil behavior, but their estimation of seabed embedment has not been fully identified and there are still many uncertainties. In this regards, comparison of embedment between field survey and existing empirical models has been performed to identify uncertainties and investigate the effect of nonlinear soil parameter on dynamic embedment. From the comparison, it is found that the dynamic embedment with installation effects based on nonlinear soil model have an influence on seabed embedment. Therefore, the pipe embedment under dynamic condition by nonlinear parameters of soil models was investigated by Dynamic Embedment Factor (DEF) concept, which is defined as the ratio of the dynamic and static embedment of pipeline, in order to overcome the gap between field embedment and currently used empirical and numerical formula. Although DEF through various researches is suggested, its range is too wide and it does not consider dynamic laying effect. It is difficult to find critical parameters that are affecting to the embedment result. Therefore, the study on dynamic embedment factor by soft clay parameters of nonlinear soil model was conducted and the sensitivity analyses about parameters of nonlinear soil model were performed as well. The tendency on dynamic embedment factor was found by conducting numerical analyses using OrcaFlex software. It is found that DEF was influenced by shear strength gradient than other factors. The obtained results will be useful to understand the pipe embedment on soft clay seabed for applying offshore pipeline designs such as on-bottom stability and free span analyses.
NASA Astrophysics Data System (ADS)
Hu, Tao; Ma, Li
2010-09-01
An internal wave observation experiment was performed near the south of Hai-Nan Island in the South China Sea in July 2004. Three vertical thermistor arrays were moored to estimate internal wave propagation direction and velocity. A nonlinear internal wave packet was observed in this experiment. It appeared at flood tide time of wee hours. Computation indicated that the nonlinear internal wave packet's velocity was 0.54 m/s and its propagation direction was northwest. From its propagation direction, we estimated that the nonlinear internal wave packet was generated near Xi-Sha Islands. The dnoidal model of KdV(Korteweg-deVries) equation was used to simulate the waveform of thid nonlinear internal wave. Measured data shows the crest interval of nonlinear internal waves was shorter when they propagated. In the last section of this paper we simulate a nonlinear internal wave packet's effect on sound propagation and analyzed mode coupling led by the nonlinear internal wave packet.
Fu, Liyong; Zhang, Huiru; Lu, Jun; Zang, Hao; Lou, Minghua; Wang, Guangxing
2015-01-01
In this study, an individual tree crown ratio (CR) model was developed with a data set from a total of 3134 Mongolian oak (Quercus mongolica) trees within 112 sample plots allocated in Wangqing Forest Bureau of northeast China. Because of high correlation among the observations taken from the same sampling plots, the random effects at levels of both blocks defined as stands that have different site conditions and plots were taken into account to develop a nested two-level nonlinear mixed-effect model. Various stand and tree characteristics were assessed to explore their contributions to improvement of model prediction. Diameter at breast height, plot dominant tree height and plot dominant tree diameter were found to be significant predictors. Exponential model with plot dominant tree height as a predictor had a stronger ability to account for the heteroskedasticity. When random effects were modeled at block level alone, the correlations among the residuals remained significant. These correlations were successfully reduced when random effects were modeled at both block and plot levels. The random effects from the interaction of blocks and sample plots on tree CR were substantially large. The model that took into account both the block effect and the interaction of blocks and sample plots had higher prediction accuracy than the one with the block effect and population average considered alone. Introducing stand density into the model through dummy variables could further improve its prediction. This implied that the developed method for developing tree CR models of Mongolian oak is promising and can be applied to similar studies for other tree species. PMID:26241912
But, D. B.; Drexler, C.; Ganichev, S. D.; Sakhno, M. V.; Sizov, F. F.; Dyakonova, N.; Drachenko, O.; Gutin, A.; Knap, W.
2014-04-28
Terahertz power dependence of the photoresponse of field effect transistors, operating at frequencies from 0.1 to 3 THz for incident radiation power density up to 100 kW/cm{sup 2} was studied for Si metal–oxide–semiconductor field-effect transistors and InGaAs high electron mobility transistors. The photoresponse increased linearly with increasing radiation intensity up to the kW/cm{sup 2} range. Nonlinearity followed by saturation of the photoresponse was observed for all investigated field effect transistors for intensities above several kW/cm{sup 2}. The observed photoresponse nonlinearity is explained by nonlinearity and saturation of the transistor channel current. A theoretical model of terahertz field effect transistor photoresponse at high intensity was developed. The model explains quantitative experimental data both in linear and nonlinear regions. Our results show that dynamic range of field effect transistors is very high and can extend over more than six orders of magnitudes of power densities (from ∼0.5 mW/cm{sup 2} to ∼5 kW/cm{sup 2})
NASA Astrophysics Data System (ADS)
Camporeale, E.; Pezzi, O.; Valentini, F.
2015-12-01
The longstanding problem of collisions in plasmas is a very fascinating and huge topic in plasma physics. The 'natural' operator that describes the Coulombian interactions between charged particles is the Landau (LAN) integral operator. The LAN operator is a nonlinear, integro-differential and Fokker-Planck type operator which satisfies the H theorem for the entropy growth. Due to its nonlinear nature and multi-dimensionality, any approach to the solution of the Landau integral is almost prohibitive. Therefore collisions are usually modeled by simplified collisional operators. Here collisional effects are modeled by i) the one-dimensional Lenard-Bernstein (LB) operator and ii) the three-dimensional Dougherty (DG) operator. In the first case i), by focusing on a 1D-1V phase space, we study recurrence effects in a weakly collisional plasma, being collisions modeled by the LB operator. By decomposing the linear Vlasov-Poisson system in the Fourier-Hermite space, the recurrence problem is investigated in the linear regime of the damping of a Langmuir wave and of the onset of the bump-on-tail instability. The analysis is then confirmed and extended to the nonlinear regime through a Eulerian collisional Vlasov-Poisson code. Despite being routinely used, an artificial collisionality is not in general a viable way of preventing recurrence in numerical simulations. Moreover, recursive phenomena affect both the linear exponential growth and the nonlinear saturation of a linear instability by producing a fake growth in the electric field, thus showing that, although the filamentation is usually associated with low amplitude fluctuations contexts, it can occur also in nonlinear phenomena. On the other hand ii), the effects of electron-electron collisions on the propagation of nonlinear electrostatic waves are shown by means of Eulerian simulations in a 1D-3V (one dimension in physical space, three dimensions in velocity space) phase space. The nonlinear regime of the symmetric
Kuramoto, Lisa; Cragg, Jacquelyn; Nandhagopal, Ramachandiran; Mak, Edwin; Sossi, Vesna; de la Fuente-Fernández, Raul; Stoessl, A. Jon; Schulzer, Michael
2013-01-01
Background To date, statistical methods that take into account fully the non-linear, longitudinal and multivariate aspects of clinical data have not been applied to the study of progression in Parkinson’s disease (PD). In this paper, we demonstrate the usefulness of such methodology for studying the temporal and spatial aspects of the progression of PD. Extending this methodology further, we also explore the presymptomatic course of this disease. Methods Longitudinal Positron Emission Tomography (PET) measurements were collected on 78 PD patients, from 4 subregions on each side of the brain, using 3 different radiotracers. Non-linear, multivariate, longitudinal random effects modelling was applied to analyze and interpret these data. Results The data showed a non-linear decline in PET measurements, which we modelled successfully by an exponential function depending on two patient-related covariates duration since symptom onset and age at symptom onset. We found that the degree of damage was significantly greater in the posterior putamen than in the anterior putamen throughout the disease. We also found that over the course of the illness, the difference between the less affected and more affected sides of the brain decreased in the anterior putamen. Younger patients had significantly poorer measurements than older patients at the time of symptom onset suggesting more effective compensatory mechanisms delaying the onset of symptoms. Cautious extrapolation showed that disease onset had occurred some 8 to 17 years prior to symptom onset. Conclusions Our model provides important biological insights into the pathogenesis of PD, as well as its preclinical aspects. Our methodology can be applied widely to study many other chronic progressive diseases. PMID:24204641
Predicting the phonon spectra of coupled nonlinear chains using effective phonon theory
NASA Astrophysics Data System (ADS)
Su, Ruixia; Yuan, Zongqiang; Wang, Jun; Zheng, Zhigang
2016-06-01
In general one-dimensional nonlinear lattices, extensive studies have discovered the existence of renormalized phonons due to nonlinear interactions and found these renormalized phonons, as the energy carriers, are responsible for heat transport. Within the framework of renormalized phonons, a generic form of renormalized phonon spectrum has been derived and effective phonon theory (EPT) has been developed to explain the heat transport in general 1D nonlinear lattices. Our attention is dedicated to generalizing the EPT for two-layer nonlinear lattices and deriving the analytic expression of phonon spectra. By calculating the phonon spectra of different coupled models with EPT, it is found that the phonon dispersion relation is in good agreement with the result obtained from the spectral energy density method. It is demonstrated that the EPT of a coupled system can predict the phonon spectra of two-layer nonlinear lattices well. Thus, this finding may shed light on the prediction of heat conduction behavior in a coupled system, qualitatively, and provide a useful guide for designing thermal devices.
NASA Astrophysics Data System (ADS)
Jackson, E. J.; Coussios, C.-C.; Cleveland, R. O.
2014-06-01
Thermal ablation by high intensity focused ultrasound (HIFU) has a great potential for the non-invasive treatment of solid tumours. Due to the high pressure amplitudes involved, nonlinear acoustic effects must be understood and the relevant medium property is the parameter of nonlinearity B/A. Here, B/A was measured in ex vivo bovine liver, over a heating/cooling cycle replicating temperatures reached during HIFU ablation, adapting a finite amplitude insertion technique, which also allowed for measurement of sound-speed and attenuation. The method measures the nonlinear progression of a plane wave through liver and B/A was chosen so that numerical simulations matched the measured waveforms. To create plane-wave conditions, sinusoidal bursts were transmitted by a 100 mm diameter 1.125 MHz unfocused transducer and measured using a 15 mm diameter 2.25 MHz broadband transducer in the near field. Attenuation and sound-speed were calculated using a reflected pulse from the smaller transducer using the larger transducer as the reflecting interface. Results showed that attenuation initially decreased with heating then increased after denaturation, the sound-speed initially increased with temperature and then decreased, and B/A showed an increase with temperature but no significant post-heating change. The B/A data disagree with other reports that show a significant change and we suggest that any nonlinear enhancement in the received ultrasound signal post-treatment is likely due to acoustic cavitation rather than changes in tissue nonlinearity.
Effects of a nonlinear damping force in synchrotrons with electron cooling
Caussyn, D.D.; Ball, M.; Budnick, J.; East, G.; Ellison, M.; Hamilton, B.; Hedblom, K.; Kang, X.; Lee, S.Y.; Li, D.; Liu, J.Y.; Ng, K.Y.; Riabko, A.; Wang, L.; Wang, Y. ||
1995-05-01
The longitudinal dynamics of a stored proton beam bunch, under the influence of a nonlinear damping force produced by electron cooling, was studied experimentally. The effect of the nonlinear damping force was explored by varying the relative velocity between the cooling electrons and the stored protons. Maintained longitudinal oscillations developed, which grew rapidly once a critical threshold in the relative velocity was exceeded. The bifurcation of a fixed point into a limit cycle is also known as a Hopf bifurcation. Comparisons of experimental data with numerical simulations and analytical calculations are made. Implications for cooled beam acceleration will be discussed.
Nonlinear effects in the energy loss of a slow dipole in a free-electron gas
Alducin, M.; Juaristi, J.I.
2002-11-01
We analyze beyond linear-response theory the energy loss of a slow dipole moving inside a free-electron gas. The energy loss is obtained from a nonlinear treatment of the scattering of electrons at the dipole-induced potential. This potential and the total electronic density are calculated with density-functional theory. We focus on the interference effects, i.e., the difference between the energy loss of a dipole and that of the isolated charges forming it. Comparison of our results to those obtained in linear-response theory shows that a nonlinear treatment of the screening is required to accurately describe the energy loss of slow dipoles.
Nonlinear Waves in Reaction Diffusion Systems: The Effect of Transport Memory
HURD,ALAN J.; KENKRE,V.M.; MANNE,K.K.
1999-11-04
Motivated by the problem of determining stress distributions in granular materials, we study the effect of finite transport correlation times on the propagation of nonlinear wavefronts in reaction diffusion systems. We obtain new results such as the possibility of spatial oscillations in the wavefront shape for certain values of the system parameters and high enough wavefront speeds. We also generalize earlier known results concerning the minimum wavefront speed and shape-speed relationships stemming from the finiteness of the correlation times. Analytic investigations are made possible by a piece-wise linear representation of the nonlinearity.
The nature of enhanced linear and nonlinear optical effects in fullerene solutions
Sheka, E. F. Razbirin, B. S. Starukhin, A. N.; Nelson, D. K.; Degunov, M. Yu.; Lyubovskaya, R. N.; Troshin, P. A.
2009-05-15
The 'blue' emission from fullerene C{sub 60} and its derivatives in frozen toluene solution is discovered and analyzed in the framework of the electromagnetic theory of enhanced optical effects. It is shown that the emission, combining enhanced spectra of Raman scattering and one-photon luminescence, is due to clustering of fullerene molecules in solution. Photoexcitation of charge-transfer excitons in clusters provides the polarization required for the enhancement. A direct relationship is established between the observed phenomenon and nonlinear optical properties of the medium. Empirical and computational tests are proposed to select matrices with various nonlinear optical properties.
Remembered study mode: support for the distinctiveness account of the production effect.
Ozubko, Jason D; Major, Jennifer; MacLeod, Colin M
2014-01-01
The production effect is the finding that words spoken aloud at study are subsequently remembered better than are words read silently at study. According to the distinctiveness account, aloud words are remembered better because the act of speaking those words aloud is encoded and later recovery of this information can be used to infer that those words were studied. An alternative account (the strength-based account) is that memory strength is simply greater for words read aloud. To discriminate these two accounts, we investigated study mode judgements (i.e., "aloud"/"silent"/"new" ratings): The strength-based account predicts that "aloud" responses should positively correlate with memory strength, whereas the distinctiveness account predicts that accuracy of study mode judgements will be independent of memory strength. Across three experiments, where the strength of some silent words was increased by repetition, study mode was discriminable regardless of strength-even when the strength of aloud and repeated silent items was equivalent. Consistent with the distinctiveness account, we conclude that memory for "aloudness" is independent of memory strength and a likely candidate to explain the production effect.
Effect of quantum correction on nonlinear thermal wave of electrons driven by laser heating
NASA Astrophysics Data System (ADS)
Nafari, F.; Ghoranneviss, M.
2016-08-01
In thermal interaction of laser pulse with a deuterium-tritium (DT) plane, the thermal waves of electrons are generated instantly. Since the thermal conductivity of electron is a nonlinear function of temperature, a nonlinear heat conduction equation is used to investigate the propagation of waves in solid DT. This paper presents a self-similar analytic solution for the nonlinear heat conduction equation in a planar geometry. The thickness of the target material is finite in numerical computation, and it is assumed that the laser energy is deposited at a finite initial thickness at the initial time which results in a finite temperature for electrons at initial time. Since the required temperature range for solid DT ignition is higher than the critical temperature which equals 35.9 eV, the effects of quantum correction in thermal conductivity should be considered. This letter investigates the effects of quantum correction on characteristic features of nonlinear thermal wave, including temperature, penetration depth, velocity, heat flux, and heating and cooling domains. Although this effect increases electron temperature and thermal flux, penetration depth and propagation velocity are smaller. This effect is also applied to re-evaluate the side-on laser ignition of uncompressed DT.
CONSEQUENCES OF NON-LINEAR DENSITY EFFECTS ON BUOYANCY AND PLUME BEHAVIOR
Aquatic plumes, as turbulent streams, grow by entraining ambient water. Buoyant plumes rise and dense ones sink, but, non-linear kinetic effects can reverse the buoyant force in mid-phenomenon. The class of nascent-density plumes begin as buoyant, upwardly accelerating plumes tha...
ERIC Educational Resources Information Center
Kelava, Augustin; Werner, Christina S.; Schermelleh-Engel, Karin; Moosbrugger, Helfried; Zapf, Dieter; Ma, Yue; Cham, Heining; Aiken, Leona S.; West, Stephen G.
2011-01-01
Interaction and quadratic effects in latent variable models have to date only rarely been tested in practice. Traditional product indicator approaches need to create product indicators (e.g., x[superscript 2] [subscript 1], x[subscript 1]x[subscript 4]) to serve as indicators of each nonlinear latent construct. These approaches require the use of…
Introduction to the Treatment of Non-Linear Effects Using a Gravitational Pendulum
ERIC Educational Resources Information Center
Weltner, Klaus; Esperidiao, Antonio Sergio C.; Miranda, Paulo
2004-01-01
We show that the treatment of pendulum movement, other than the linear approximation,may be an instructive experimentally based introduction to the physics of non-linear effects. Firstly the natural frequency of a gravitational pendulum is measured as function of its amplitude. Secondly forced oscillations of a gravitational pendulum are…
Effects of focusing on third-order nonlinear processes in isotropic media. [laser beam interactions
NASA Technical Reports Server (NTRS)
Bjorklund, G. C.
1975-01-01
Third-order nonlinear processes in isotropic media have been successfully used for tripling the efficiency of high-power laser radiation for the production of tunable and fixed-frequency coherent vacuum UV radiation and for up-conversion of IR radiation. The effects of focusing on two processes of this type are studied theoretically and experimentally.
The nonlinear effect of two-color light on bacterial viability
NASA Astrophysics Data System (ADS)
Lukyanovich, P. A.; Zon, B. A.; Grabovich, M. Yu; Shchelukhina, E. V.; Danilova, I. I.; Orlova, M. V.; Sapeltseva, I. O.; Sinugina, D. I.
2016-01-01
A bacterial (Escherichia coli) viability nonlinear effect is found experimentally after continuous irradiation by composite red and blue light. The dependence of bacterial viability on irradiance at equal specific doses is interpreted as possible two-photon absorption causing DNA damage that is similar to damage from the absorption of UV quanta.
Effects of heat exchange and nonlinearity on acoustic streaming in a vibrating cylindrical cavity.
Gubaidullin, Amir A; Yakovenko, Anna V
2015-06-01
Acoustic streaming in a gas filled cylindrical cavity subjected to the vibration effect is investigated numerically. Both thermally insulated walls and constant temperature walls are considered. The range of vibration frequencies from low frequencies, at which the process can be described by an approximate analytical solution, to high frequencies giving rise to strong nonlinear effects is studied. Frequencies lower than the resonant one are chosen, and nonlinearity is achieved due to the large amplitude. The problem is solved in an axisymmetric statement. The dependence of acoustic streaming in narrow channels at vibration frequencies lower than the resonant one on the type of thermal boundary conditions is shown. The streaming vortices' directions of rotation in the case of constant temperature walls are found to be opposite to those in the case of thermally insulated walls. Different nonlinear effects, which increase with the frequency of vibration, are obtained. Nonlinear effects manifesting as the nonuniformity of average temperature, pressure, and density are in turn found to be influencing the streaming velocity and streaming structure.
Nonlinear effects in an acoustic metamaterial with simultaneous negative modulus and density
NASA Astrophysics Data System (ADS)
Li, Yifeng; Lan, Jun; Li, Baoshun; Liu, Xiaozhou; Zhang, Jiashu
2016-10-01
Nonlinear effects in an acoustic metamaterial with simultaneous negative modulus and density based on Helmholtz resonators and membranes periodically distributed along a pipe are studied theoretically. Analyses of the transmission coefficient and dispersion relation of the composite system are realized using the acoustic transmission line method and Bloch theory, respectively. Due to the nonlinearities of the Helmholtz resonators and membranes, the acoustic wave propagation properties vary with the different incident acoustic intensities, and the frequency band gaps of the transmission coefficient are amplitude dependent. The nonlinearities shift the double negative pass band into the adjacent modulus negative forbidden band and transform the metamaterial from an acoustic insulator into an acoustic conductor, leading to some new potential acoustic applications.
NASA Technical Reports Server (NTRS)
Rizzi, Stephen A.; Przekop, Adam
2004-01-01
The goal of this investigation is to further develop nonlinear modal numerical simulation methods for prediction of geometrically nonlinear response due to combined thermal-acoustic loadings. As with any such method, the accuracy of the solution is dictated by the selection of the modal basis, through which the nonlinear modal stiffness is determined. In this study, a suite of available bases are considered including (i) bending modes only; (ii) coupled bending and companion modes; (iii) uncoupled bending and companion modes; and (iv) bending and membrane modes. Comparison of these solutions with numerical simulation in physical degrees-of-freedom indicates that inclusion of any membrane mode variants (ii - iv) in the basis affects the bending displacement and stress response predictions. The most significant effect is on the membrane displacement, where it is shown that only the type (iv) basis accurately predicts its behavior. Results are presented for beam and plate structures in the thermally pre-buckled regime.
Nonlinear effects of inertial Alfvén wave in low beta plasmas
Rinawa, M. L. Gaur, Nidhi Sharma, R. P.
2015-02-15
This paper is devoted to the study of the nonlinear interaction and propagation of high frequency pump inertial Alfvén wave (IAW) with comparatively low frequency IAW with emphasis on nonlinear effects and applications within space plasma and astrophysics for low β-plasma (β≪m{sub e}/m{sub i}). We have developed a set of dimensionless equations in the presence of ponderomotive nonlinearity due to high frequency pump IAW in the dynamics of comparatively low frequency IAW. Stability analysis and numerical simulation have been carried out for the coupled system comprising of pump IAW and low frequency IAW to study the localization and turbulent spectra, applicable to auroral region. The result reveals that localized structures become more complex and intense in nature at the quasi steady state. From the obtained result, we found that the present model may be useful to study the turbulent fluctuations in accordance with the observations of FAST/THEMIS spacecraft.
Third order nonlinear optical effects in a new chalcone derivative embedded in a polymer host
NASA Astrophysics Data System (ADS)
Shetty, T. Chandra Shekhara; Raghavendra, S.; Dharmaprakaskh, S. M.
2015-06-01
A new organic nonlinear optical (NLO) material from the chalcone family: (2E)-1-(3,4-dichlorophenyl)-3-[4-(methylsulfanyl)phenyl]prop-2-en-1-one (DPMS) is crystallised in DMF solution. The functional groups in DPMS are identified by FTIR spectra. The thermal stability is studied using TGA/DTA. The polymethylmethacrylate (PMMA) film doped with DPMS was prepared. Direct and indirect band gap energy of DPMS doped PMMA is determined using U. V. Visible spectra. The nonlinear absorption coefficient and optical power limiting of the film was studied using Z-scan technique. The film exhibits a self focussing effect at a wavelength of 532nm. The results of optical limiting studies, shows that the film possesses reverse saturable absorption due to excited state absorption. The nonlinear optical properties of DPMS have been retained in the presence of a polymer material.
Interpretation of nonlinear effects on the dynamic response of a TLP
Palk, I.; Mekha, B.B.; Powers, E.J.; Roesset, J.M.
1995-12-31
To determine the nature and importance of various nonlinear effects on the dynamic response of a TLP, a number of parametric studies have been conducted determining the dynamic response of a simplified model to wave and current action. The results of these analyses were then used to compute linear, quadratic and cubic transfer functions, based on Volterra series, to assess the type of nonlinearity which controls the response over the different frequency ranges. The nonlinearities result in the existence of response amplitudes and energy at frequencies which are outside of the range of the excitation frequencies but which correspond to the natural frequencies of the TLP in surge, heave and pitch. They are of different order (quadratic or cubic) over the different frequency ranges (below or above the wave frequency range).
Aidun, J.B.; Addessio, F.L.
1995-11-01
The theoretical basis of the homogenization technique developed by Aboudi is presented and assessed. Given the constitutive relations of the constituents, this technique provides an equivalent, homogeneous, constitutive model of unidirectional, continuous-fiber-reinforced composites. The expressions that comprise the first-order version of the technique are given special attention as this treatment has considerable practical value. Nonlinear elasticity effects are added to it. This extension increases the accuracy of numerical simulations of high strain-rate loadings. It is particularly important for any dynamic loading in which shock waves might be produced, including crash safety, armor, and munitions applications. Examples illustrate that elastic nonlinearity can make substantial contributions at strains of only a few per cent. These contributions are greatest during post-yield inelastic deformation. The micromechanics-based homogenization technique is shown to facilitate use of an efficient approximate treatment of elastic nonlinearity in composites with isotropic matrix materials.
The Effect of Crack Orientation on the Nonlinear Interaction of a P-wave with an S-wave
TenCate, J. A.; Malcolm, A. E.; Feng, X.; Fehler, M. C.
2016-06-06
Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presencemore » and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal.« less
The effect of crack orientation on the nonlinear interaction of a P wave with an S wave
NASA Astrophysics Data System (ADS)
TenCate, J. A.; Malcolm, A. E.; Feng, X.; Fehler, M. C.
2016-06-01
Cracks, joints, fluids, and other pore-scale structures have long been hypothesized to be the cause of the large elastic nonlinearity observed in rocks. It is difficult to definitively say which pore-scale features are most important, however, because of the difficulty in isolating the source of the nonlinear interaction. In this work, we focus on the influence of cracks on the recorded nonlinear signal and in particular on how the orientation of microcracks changes the strength of the nonlinear interaction. We do this by studying the effect of orientation on the measurements in a rock with anisotropy correlated with the presence and alignment of microcracks. We measure the nonlinear response via the traveltime delay induced in a low-amplitude P wave probe by a high-amplitude S wave pump. We find evidence that crack orientation has a significant effect on the nonlinear signal.
NASA Astrophysics Data System (ADS)
Vasoya, Manish; Unni, Aparna Beena; Leblond, Jean-Baptiste; Lazarus, Veronique; Ponson, Laurent
2016-04-01
Crack pinning by heterogeneities is a central toughening mechanism in the failure of brittle materials. So far, most analytical explorations of the crack front deformation arising from spatial variations of fracture properties have been restricted to weak toughness contrasts using first order approximation and to defects of small dimensions with respect to the sample size. In this work, we investigate the non-linear effects arising from larger toughness contrasts by extending the approximation to the second order, while taking into account the finite sample thickness. Our calculations predict the evolution of a planar crack lying on the mid-plane of a plate as a function of material parameters and loading conditions, especially in the case of a single infinitely elongated obstacle. Peeling experiments are presented which validate the approach and evidence that the second order term broadens its range of validity in terms of toughness contrast values. The work highlights the non-linear response of the crack front to strong defects and the central role played by the thickness of the specimen on the pinning process.
Effects of time ordering in quantum nonlinear optics
NASA Astrophysics Data System (ADS)
Quesada, Nicolás; Sipe, J. E.
2014-12-01
We study time-ordering corrections to the description of spontaneous parametric down-conversion (SPDC), four-wave mixing (SFWM), and frequency conversion using the Magnus expansion. Analytic approximations to the evolution operator that are unitary are obtained. They are Gaussian preserving, and allow us to understand order-by-order the effects of time ordering. We show that the corrections due to time ordering vanish exactly if the phase-matching function is sufficiently broad. The calculation of the effects of time ordering on the joint spectral amplitude of the photons generated in SPDC and SFWM are reduced to quadrature.
Consequences of Unmodeled Nonlinear Effects in Multilevel Models
ERIC Educational Resources Information Center
Bauer, Daniel J.; Cai, Li
2009-01-01
Applications of multilevel models have increased markedly during the past decade. In incorporating lower-level predictors into multilevel models, a key interest is often whether or not a given predictor requires a random slope, that is, whether the effect of the predictor varies over upper-level units. If the variance of a random slope…
Effect of background plasma nonlinearities on dissipation processes in plasmas
NASA Astrophysics Data System (ADS)
Nekrasov, F. M.; Elfimov, A. G.; de Azevedo, C. A.; de Assis, A. S.
1999-01-01
The Coulomb collision effect on the bounce-resonance dissipation is considered for toroidal magnetized plasmas. The solution of the Vlasov equation with a simplified Fokker-Planck collision operator is presented. The parallel components of the dielectric tensor are obtained. A collisionless limit of wave dissipation is found.
EFFECTS OF THE NEUTRINO MASS SPLITTING ON THE NONLINEAR MATTER POWER SPECTRUM
Wagner, Christian; Verde, Licia; Jimenez, Raul
2012-06-20
We have performed cosmological N-body simulations which include the effect of the masses of the individual neutrino species. The simulations were aimed at studying the effect of different neutrino hierarchies on the matter power spectrum. Compared to the linear theory predictions, we find that nonlinearities enhance the effect of hierarchy on the matter power spectrum at mildly nonlinear scales. The maximum difference between the different hierarchies is about 0.5% for a sum of neutrino masses of 0.1 eV. Albeit this is a small effect, it is potentially measurable from upcoming surveys. In combination with neutrinoless double-{beta} decay experiments, this opens up the possibility of using the sky to determine if neutrinos are Majorana or Dirac fermions.
NASA Astrophysics Data System (ADS)
Selvendran, S.; Sivanantharaja, A.; Arivazhagan, S.; Kannan, M.
2016-09-01
We propose an index profiled, highly nonlinear ultraflattened dispersion fibre (HN-UFF) with appreciable values of fibre parameters such as dispersion, dispersion slope, effective area, nonlinearity, bending loss and splice loss. The designed fibre has normal zero flattened dispersion over S, C, L, U bands and extends up to 1.9857 μm. The maximum dispersion variation observed for this fibre is as low as 1.61 ps km-1 nm-1 over the 500-nm optical fibre transmission spectrum. This fibre also has two zero dispersion wavelengths at 1.487 and 1.9857 μm and the respective dispersion slopes are 0.02476 and 0.0068 ps nm-2 km-1. The fibre has a very low ITU-T cutoff wavelength of 1.2613 μm and a virtuous nonlinear coefficient of 9.43 W-1 km-1. The wide spectrum of zero flattened dispersion and a good nonlinear coefficient make the designed fibre very promising for different nonlinear optical signal processing applications.
Kim, JeongYeon
2014-01-01
This study reviews new pension accounting with K-IFRS and provides empirical changes in liability for retirement allowances with adoption of K-IFRS. It will help to understand the effect of pension accounting on individual firm's financial report and the importance of public announcement of actuarial assumptions. Firms that adopted K-IFRS had various changes in retirement liability compared to the previous financial report not based on K-IFRS. Their actuarial assumptions for pension accounting should be announced, but only few of them were published. Data analysis shows that the small differences of the actuarial assumption may result in a big change of retirement related liability. Firms within IT industry also have similar behaviors, which means that additional financial regulations for pension accounting are recommended. PMID:25013868
2014-01-01
This study reviews new pension accounting with K-IFRS and provides empirical changes in liability for retirement allowances with adoption of K-IFRS. It will help to understand the effect of pension accounting on individual firm's financial report and the importance of public announcement of actuarial assumptions. Firms that adopted K-IFRS had various changes in retirement liability compared to the previous financial report not based on K-IFRS. Their actuarial assumptions for pension accounting should be announced, but only few of them were published. Data analysis shows that the small differences of the actuarial assumption may result in a big change of retirement related liability. Firms within IT industry also have similar behaviors, which means that additional financial regulations for pension accounting are recommended. PMID:25013868
Kim, JeongYeon
2014-01-01
This study reviews new pension accounting with K-IFRS and provides empirical changes in liability for retirement allowances with adoption of K-IFRS. It will help to understand the effect of pension accounting on individual firm's financial report and the importance of public announcement of actuarial assumptions. Firms that adopted K-IFRS had various changes in retirement liability compared to the previous financial report not based on K-IFRS. Their actuarial assumptions for pension accounting should be announced, but only few of them were published. Data analysis shows that the small differences of the actuarial assumption may result in a big change of retirement related liability. Firms within IT industry also have similar behaviors, which means that additional financial regulations for pension accounting are recommended.
Lee, Miriam Chang Yi; Chow, Jia Yi; Komar, John; Tan, Clara Wee Keat; Button, Chris
2014-01-01
Learning a sports skill is a complex process in which practitioners are challenged to cater for individual differences. The main purpose of this study was to explore the effectiveness of a Nonlinear Pedagogy approach for learning a sports skill. Twenty-four 10-year-old females participated in a 4-week intervention involving either a Nonlinear Pedagogy (i.e.,manipulation of task constraints including equipment and rules) or a Linear Pedagogy (i.e., prescriptive, repetitive drills) approach to learn a tennis forehand stroke. Performance accuracy scores, movement criterion scores and kinematic data were measured during pre-intervention, post-intervention and retention tests. While both groups showed improvements in performance accuracy scores over time, the Nonlinear Pedagogy group displayed a greater number of movement clusters at post-test indicating the presence of degeneracy (i.e., many ways to achieve the same outcome). The results suggest that degeneracy is effective for learning a sports skill facilitated by a Nonlinear Pedagogy approach. These findings challenge the common misconception that there must be only one ideal movement solution for a task and thus have implications for coaches and educators when designing instructions for skill acquisition. PMID:25140822
Comparing Smoothing Techniques for Fitting the Nonlinear Effect of Covariate in Cox Models
Roshani, Daem; Ghaderi, Ebrahim
2016-01-01
Background and Objective: Cox model is a popular model in survival analysis, which assumes linearity of the covariate on the log hazard function, While continuous covariates can affect the hazard through more complicated nonlinear functional forms and therefore, Cox models with continuous covariates are prone to misspecification due to not fitting the correct functional form for continuous covariates. In this study, a smooth nonlinear covariate effect would be approximated by different spline functions. Material and Methods: We applied three flexible nonparametric smoothing techniques for nonlinear covariate effect in the Cox models: penalized splines, restricted cubic splines and natural splines. Akaike information criterion (AIC) and degrees of freedom were used to smoothing parameter selection in penalized splines model. The ability of nonparametric methods was evaluated to recover the true functional form of linear, quadratic and nonlinear functions, using different simulated sample sizes. Data analysis was carried out using R 2.11.0 software and significant levels were considered 0.05. Results: Based on AIC, the penalized spline method had consistently lower mean square error compared to others to selection of smoothed parameter. The same result was obtained with real data. Conclusion: Penalized spline smoothing method, with AIC to smoothing parameter selection, was more accurate in evaluate of relation between covariate and log hazard function than other methods. PMID:27041809
The hysteresis-free negative capacitance field effect transistors using non-linear poly capacitance
NASA Astrophysics Data System (ADS)
Fan, S.-T.; Yan, J.-Y.; Lai, D.-C.; Liu, C. W.
2016-08-01
A gate structure design for negative capacitance field effect transistors (NCFETs) is proposed. The hysteresis loop in current-voltage performances is eliminated by the nonlinear C-V dependence of polysilicon in the gate dielectrics. Design considerations and optimizations to achieve the low SS and hysteresis-free transfer were elaborated. The effects of gate-to-source/drain overlap, channel length scaling, interface trap states and temperature impact on SS are also investigated.
NASA Astrophysics Data System (ADS)
Drozd-Rzoska, Aleksandra; Rzoska, Sylwester J.; Rzoska, Agata Angelika
2016-06-01
The nonlinear dielectric effect describes changes of dielectric permittivity induced by the strong electric field. This report shows the evidence for the critical-like pretransitional behavior for the liquid-solid transition in the supercooled nitrobenzene. Hallmarks of such behavior extend even above the melting temperature. A method for the analysis of pretransitional effects, avoiding the biasing impact of the noncritical background contribution, is proposed.
Nonlinear vibrations of viscoelastic rectangular plates
NASA Astrophysics Data System (ADS)
Amabili, Marco
2016-02-01
Nonlinear vibrations of viscoelastic thin rectangular plates subjected to normal harmonic excitation in the spectral neighborhood of the lowest resonances are investigated. The von Kármán nonlinear strain-displacement relationships are used and geometric imperfections are taken into account. The material is modeled as a Kelvin-Voigt viscoelastic solid by retaining all the nonlinear terms. The discretized nonlinear equations of motion are studied by using the arclength continuation and collocation method. Numerical results are obtained for the fundamental mode of a simply supported square plate with immovable edges by using models with 16 and 22 degrees of freedom and investigating solution convergence. Comparison to viscous damping and the effect of neglecting nonlinear viscoelastic damping terms are shown. The change of the frequency-response with the retardation time parameter is also investigated as well as the effect of geometric imperfections.
Surface mediated nonlinear optic effects in liquid crystals
NASA Astrophysics Data System (ADS)
Merlin, Jessica M.
Liquid crystals have become a significant part of technology, mainly through their use in the display industry. This is due in part to the fact that the optical properties of liquid crystals are easily manipulated electronically. It has been recognized that the optical properties liquid crystals may also be controlled using light. Because of this, there are other various applications being explored for liquid crystals in photorefraction, optical limiting and switching, and in spatial light modulators. Although, the photorefractive effect was reported in liquid crystals over 10 years ago, there is still controversy over the exact mechanism for the reorientation of the liquid crystal director. This difficulty may be due in part to the fact that it is difficult to characterize the effect using photorefractive measurements and figures of merit. The optical and electronic control of liquid crystals will be studied here using a Friedericksz transition measurement in a twist cell geometry. This type of apparatus was chosen because it leads to a more direct demonstration of the surface effect. Namely, by studying changes in the Friedericksz transition threshold in a twist cell, a more direct observation of changes in the internal field may be observed. First a brief introduction to liquid crystals and their role in technology will be presented. This will be followed by a more rigorous discussion of the physics of liquid crystals and a review of the important literature. The experimental apparatus and the materials and cell geometry used will be described followed by the results of those measurements. Finally, the results will be considered in terms of a model involving interfacial charge and discussed in the context of previous work.
NASA Technical Reports Server (NTRS)
Goldberg, Robert K.; Carney, Kelly S.
2004-01-01
An analysis method based on a deformation (as opposed to damage) approach has been developed to model the strain rate dependent, nonlinear deformation of woven ceramic matrix composites with a plain weave fiber architecture. In the developed model, the differences in the tension and compression response have also been considered. State variable based viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the effective stress and effective inelastic strain definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear stiffness is independent of the stiffness in the normal directions. The developed equations have been implemented into a commercially available transient dynamic finite element code, LS-DYNA, through the use of user defined subroutines (UMATs). The tensile, compressive, and shear deformation of a representative plain weave woven ceramic matrix composite are computed and compared to experimental results. The computed values correlate well to the experimental data, demonstrating the ability of the model to accurately compute the deformation response of woven ceramic matrix composites.
Diffraction Interference Induced Superfocusing in Nonlinear Talbot Effect
Liu, Dongmei; Zhang, Yong; Wen, Jianming; Chen, Zhenhua; Wei, Dunzhao; Hu, Xiaopeng; Zhao, Gang; Zhu, S. N.; Xiao, Min
2014-01-01
We report a simple, novel subdiffraction method, i.e. diffraction interference induced superfocusing in second-harmonic (SH) Talbot effect, to achieve focusing size of less than λSH/4 (or λpump/8) without involving evanescent waves or subwavelength apertures. By tailoring point spread functions with Fresnel diffraction interference, we observe periodic SH subdiffracted spots over a hundred of micrometers away from the sample. Our demonstration is the first experimental realization of the Toraldo di Francia's proposal pioneered 62 years ago for superresolution imaging. PMID:25138077
Nonlinear Plasma Effects in Natural and Artificial Aurora
Mishin, E. V.
2011-01-04
This report describes common features of natural ('Enhanced') aurora and 'artificial aurora'(AA) created by electron beams injected from sounding rockets. These features cannot be explained solely by col-lisional degradation of energetic electrons, thereby pointing to collisionless plasma effects. The fundamental role in electron beam-ionosphere interactions belongs to Langmuir turbulence. Its development in the (weakly-ionized) ionosphere is significantly affected by electron-neutral collisions, so that the heating and acceleration of plasma electrons proceed more efficiently than in collisionless plasmas. As a result, a narrow layer of enhanced auroral glow/ionization is formed above the standard collisional peak.
Nonlinear simulations of particle source effects on edge localized mode
Huang, J.; Tang, C. J.; Chen, S. Y.; Wang, Z. H.
2015-12-15
The effects of particle source (PS) with different intensities and located positions on Edge Localized Mode (ELM) are systematically studied with BOUT++ code. The results show the ELM size strongly decreases with increasing the PS intensity once the PS is located in the middle or bottom of the pedestal. The effects of PS on ELM depend on the located position of PS. When it is located at the top of the pedestal, peeling-ballooning (P-B) modes can extract more free energy from the pressure gradient and grow up to be a large filament at the initial crash phase and the broadening of mode spectrum can be suppressed by PS, which leads to more energy loss. When it is located in the middle or bottom of the pedestal, the extraction of free energy by P-B modes can be suppressed, and a small filament is generated. During the turbulence transport phase, the broader mode spectrum suppresses the turbulence transport when PS is located in the middle, while the zonal flow plays an important role in damping the turbulence transport when PS is located at the bottom.
Study of statis and dynamic stress effects in nonlinear solids
NASA Technical Reports Server (NTRS)
Namkung, M.
1985-01-01
As the basic physical principles behind the low-field magnetoacoustic interactions have been unfolded, a new step in the present research had to be taken. First, the stress measurements began in samples obtained in real railroad wheel and rail materials. Second, the effect of texture, which is the prime obstacle of conventional NDE techniques, has been investigated. The first stage shows experimental results on these subjects again confirmed that the present technique is most suited for nondestructive stress characterization in steel components. The stress effects on the magnetoacoustic interaction obtained in a sample made from railroad rail which were very similar to those obtained previously in 1045 steel. These results being somewhat different from the results with low (1020) and high (1095) carbon steels, there seemed to be certain range of medium carbon steels having the same characteristics. Also, as expected from the model, the stress information obtained by this technique has been confirmed to be least affected by the presence of texture.
Nonlinear effects of food aggregation on interference competition in mallards
van Rooij, Erica P.; Nolet, Bart A.
2010-01-01
Previous studies of interference competition have shown an asymmetric effect on intake rate of foragers on clumped resources, with only subordinate individuals suffering. However, the food distributions in these studies were uniform or highly clumped, whereas in many field situations, food aggregation is intermediate. Here we investigated whether food distribution (i.e., uniform, slightly clumped, and highly clumped) affects the behavioral response of mallards foraging alone or competing with another. Although the amount of food was the same in all distributions, the mallards reached higher intake rates, visited fewer patches, and showed longer average feeding times in the highly clumped distribution. Competing mallards had lower intake rates on the slightly clumped than on the uniform or highly clumped food distributions. Subordinates generally visited more patches and had shorter feeding times per patch, but their intake rates were not significantly lower than those of dominants. Therefore, we propose that subordinates do not necessarily suffer from interference competition in terms of intake rate, but do suffer higher search costs. In addition, although dominants had significantly higher average feeding times on the best quality patches of the highly clumped food distribution, such an effect was not found in the slightly clumped distribution. These findings indicate that in environments where food is aggregated to a lesser extent, monopolization is not the best strategy for dominants. Our results suggest that interference experiments should use food distributions that resemble the natural situation animals are faced with in the field. PMID:20976292
NASA Astrophysics Data System (ADS)
Zhang, Juanjuan; Wen, Jianbiao; Gao, Yuanwen
2016-06-01
In previous works, most of them employ a linear constitutive model to describe magnetocapacitance (MC) effect in magnetoelectric (ME) composites, which lead to deficiency in their theoretical results. In view of this, based on a nonlinear magnetostrictive constitutive relation and a linear piezoelectric constitutive relation, we establish a nonlinear model for MC effect in PZT-ring/Terfenol-D-strip ME composites. The numerical results in this paper coincide better with experimental data than that of a linear model, thus, it's essential to utilize a nonlinear constitutive model for predicting MC effect in ME composites. Then the influences of external magnetic fields, pre-stresses, frequencies, and geometric sizes on the MC effect are discussed, respectively. The results show that the external magnetic field is responsible for the resonance frequency shift. And the resonance frequency is sensitive to the ratio of outer and inner radius of the PZT ring. Moreover, some other piezoelectric materials are employed in this model and the corresponding MC effects are calculated, and we find that different type of piezoelectric materials affect the MC effect obviously. The proposed model is more accurate for multifunction devices designing.
Giessner, Steffen R; van Knippenberg, Daan; van Ginkel, Wendy; Sleebos, Ed
2013-07-01
We examined the interactive effects of leader group prototypicality, accountability, and team identification on team-oriented behavior of leaders, thus extending the social identity perspective on leadership to the study of leader behavior. An experimental study (N = 152) supported our hypothesis that leader accountability relates more strongly to team-oriented behavior for group nonprototypical leaders than for group prototypical leaders. A multisource field study with leaders (N = 64) and their followers (N = 209) indicated that this interactive effect is more pronounced for leaders who identify more strongly with their team. We discuss how these findings further develop the social identity analysis of leadership.
Nonlinearity Effects of Lateral Density Diffusion Coefficient on Gain-Guided VCSEL Performance
NASA Technical Reports Server (NTRS)
Li, Jian-Zhong; Cheung, Samson H.; Ning, C. Z.; Biegel, Bryan (Technical Monitor)
2001-01-01
Electron and hole diffusions in the plane of semiconductor quantum wells play an important part in the static and dynamic operations of semiconductor lasers. In this paper, we apply a hydrodynamic model developed from the semiconductor Bloch equations to numerically study the effects of nonlinearity in the diffusion coefficient on single mode operation and direct modulation of a gain-guided InGaAs/GaAs multiple quantum well laser, operating not too far from threshold. We found that a small diffusion coefficient is advantageous for lowering the threshold current and increasing the modulation bandwidth. Most importantly, the effects of nonlinearity in the coefficient can be approximately reproduced by replacing the coefficient with an effective constant diffusion coefficient, which corresponds roughly to the half height density of the density distribution.
Optical authentication based on moiré effect of nonlinear gratings in phase space
NASA Astrophysics Data System (ADS)
Liao, Meihua; He, Wenqi; Wu, Jiachen; Lu, Dajiang; Liu, Xiaoli; Peng, Xiang
2015-12-01
An optical authentication scheme based on the moiré effect of nonlinear gratings in phase space is proposed. According to the phase function relationship of the moiré effect in phase space, an arbitrary authentication image can be encoded into two nonlinear gratings which serve as the authentication lock (AL) and the authentication key (AK). The AL is stored in the authentication system while the AK is assigned to the authorized user. The authentication procedure can be performed using an optoelectronic approach, while the design process is accomplished by a digital approach. Furthermore, this optical authentication scheme can be extended for multiple users with different security levels. The proposed scheme can not only verify the legality of a user identity, but can also discriminate and control the security levels of legal users. Theoretical analysis and simulation experiments are provided to verify the feasibility and effectiveness of the proposed scheme.
Beam-shape effects in nonlinear Compton and Thomson scattering
Heinzl, T.; Seipt, D.; Kaempfer, B.
2010-02-15
We discuss intensity effects in collisions between beams of optical photons from a high-power laser and relativistic electrons. Our main focus is on the modifications of the emission spectra due to realistic finite-beam geometries. By carefully analyzing the classical limit we precisely quantify the distinction between strong-field QED Compton scattering and classical Thomson scattering. A purely classical, but fully covariant, calculation of the bremsstrahlung emitted by an electron in a plane-wave laser field yields radiation into harmonics, as expected. This result is generalized to pulses of finite duration and explains the appearance of line broadening and harmonic substructure as an interference phenomenon. The ensuing numerical treatment confirms that strong focusing of the laser leads to a broad continuum while higher harmonics become visible only at moderate focusing, and hence lower intensity. We present a scaling law for the backscattered photon spectral density which facilitates averaging over electron beam phase space. Finally, we propose a set of realistic parameters such that the observation of intensity-induced spectral red shift, higher harmonics, and their substructure becomes feasible.
Fluctuating temperatures and ectotherm growth: distinguishing non-linear and time-dependent effects.
Kingsolver, Joel G; Higgins, Jessica K; Augustine, Kate E
2015-07-01
Most terrestrial ectotherms experience diurnal and seasonal variation in temperature. Because thermal performance curves are non-linear, mean performance can differ in fluctuating and constant thermal environments. However, time-dependent effects--effects of the order and duration of exposure to temperature--can also influence mean performance. We quantified the non-linear and time-dependent effects of diurnally fluctuating temperatures for larval growth rates in the tobacco hornworm, Manduca sexta L., with four main results. First, the shape of the thermal performance curve for growth rate depended on the duration of exposure: for example, optimal temperature and thermal breadth were greater for growth rates measured over short (24 h during the last instar) compared with long (the entire period of larval growth) time periods. Second, larvae reared in diurnally fluctuating temperatures had significantly higher optimal temperatures and maximal growth rates than larvae reared in constant temperatures. Third, for larvae maintained at three mean temperatures (20, 25 and 30°C) and three diurnal temperature ranges (±0, ±5 and ±10°C), diurnal fluctuations had opposite effects on mean growth rates at low versus high mean temperature. Fourth, both short- and long-term thermal performance curves yielded poor predictions of the non-linear effects of fluctuating temperature on mean growth rates (compared with our experimental results) at higher mean temperatures. Our results suggest caution in using constant temperature studies to model the consequences of variable thermal environments. PMID:25987738
On the effective behavior of nonlinear inelastic composites: II. A second-order procedure
NASA Astrophysics Data System (ADS)
Lahellec, Noël; Suquet, Pierre
2007-09-01
A new method for determining the overall behavior of composite materials comprising nonlinear viscoelastic and elasto-viscoplastic constituents is presented. Part I of this work showed that upon use of an implicit time-discretization scheme, the evolution equations describing the constitutive behavior of the phases can be reduced to the minimization of an incremental energy function. This minimization problem is rigorously equivalent to a nonlinear thermoelastic problem with a transformation strain which is a nonuniform field (not even uniform within the phases). In part I of this paper the nonlinearity was handled using a variational (or secant) technique. In this second part of the study, a proper modification of the second-order procedure of Ponte Castañeda is proposed and leads to replacing, at each time-step, the actual nonlinear viscoelastic composite by a linear viscoelastic one. The linearized problem is even further simplified by using an "effective internal variable" in each individual phase. The resulting predictions are in good agreement with exact results and improve on the predictions of the secant model proposed in part I of this paper.
ERIC Educational Resources Information Center
Yang, Ji Seung
2012-01-01
Nonlinear multilevel latent variable modeling has been suggested as an alternative to traditional hierarchical linear modeling to more properly handle measurement error and sampling error issues in contextual effects modeling. However, a nonlinear multilevel latent variable model requires significant computational effort because the estimation…
Testing the Item-Order Account of Design Effects Using the Production Effect
ERIC Educational Resources Information Center
Jonker, Tanya R.; Levene, Merrick; MacLeod, Colin M.
2014-01-01
A number of memory phenomena evident in recall in within-subject, mixed-lists designs are reduced or eliminated in between-subject, pure-list designs. The item-order account (McDaniel & Bugg, 2008) proposes that differential retention of order information might underlie this pattern. According to this account, order information may be encoded…
Nonlinear growing neutrino cosmology
NASA Astrophysics Data System (ADS)
Ayaita, Youness; Baldi, Marco; Führer, Florian; Puchwein, Ewald; Wetterich, Christof
2016-03-01
The energy scale of dark energy, ˜2 ×10-3 eV , is a long way off compared to all known fundamental scales—except for the neutrino masses. If dark energy is dynamical and couples to neutrinos, this is no longer a coincidence. The time at which dark energy starts to behave as an effective cosmological constant can be linked to the time at which the cosmic neutrinos become nonrelativistic. This naturally places the onset of the Universe's accelerated expansion in recent cosmic history, addressing the why-now problem of dark energy. We show that these mechanisms indeed work in the growing neutrino quintessence model—even if the fully nonlinear structure formation and backreaction are taken into account, which were previously suspected of spoiling the cosmological evolution. The attractive force between neutrinos arising from their coupling to dark energy grows as large as 106 times the gravitational strength. This induces very rapid dynamics of neutrino fluctuations which are nonlinear at redshift z ≈2 . Nevertheless, a nonlinear stabilization phenomenon ensures only mildly nonlinear oscillating neutrino overdensities with a large-scale gravitational potential substantially smaller than that of cold dark matter perturbations. Depending on model parameters, the signals of large-scale neutrino lumps may render the cosmic neutrino background observable.
NASA Astrophysics Data System (ADS)
Zhang, Xiaozhong; Luo, Zhaochu
Size limitation of silicon FET hinders the further scaling down of silicon based CPU. To solve this problem, spin based magnetic logic devices were proposed but almost all of them could not be realized experimentally except for NOT logic operation. A magnetic field controlled reconfigurable semiconductor logic using InSb was reported. However, InSb is very expensive and not compatible with the silicon technology. Based on our Si based magnetoresistance (MR) device, we developed a Si based reconfigurable magnetic logic device, which could do all four Boolean logic operations including AND, OR, NOR and NAND. By coupling nonlinear transport effect of semiconductor and anomalous Hall effect of magnetic material, we propose a PMA material based MR device with a remarkable non local MR of >20000 % at ~1 mT. Based on this MR device, we further developed a PMA material based magnetic logic device which could do all four Boolean logic operations. This makes it possible that magnetic material does both memory and logic. This may result in a memory-logic integrated system leading to a non von Neumann computer
Nonlinear kinetic effects in inductively coupled plasmas via particle-in-cell simulations
NASA Astrophysics Data System (ADS)
Froese, Aaron; Smolyakov, Andrei; Sydorenko, Dmytro
2007-11-01
Kinetic effects in inductively coupled plasmas due to thermal motion of particles modified by self-consistent magnetic fields are studied using a particle-in-cell code. In the low pressure, low frequency regime, electron mean free paths are large relative to device size and the trajectories are strongly curved by the induced rf magnetic field. Analytic linear theories are unable to recover effects accumulated along each nonlinear path. Therefore, the simulated ICP is made progressively more complex to find the source of observed plasma behaviours. With only thermal motion modifying the wave-particle interaction, nonlocal behaviour becomes dominant at low frequencies, causing an anomalous skin effect with increased skin depth and power absorption and decreased ponderomotive force. However, when influenced by magnetic fields, the nonlocal effects are suppressed at large wave amplitudes due to nonlinear trapping. A mechanism is proposed for this low frequency restoration of local behaviour. Finally, a low rate of electron-neutral collisions is found to counteract the nonlinear behaviour, and hence reinforces nonlocal behaviour.
Optical nonlinearity of liquid nanosuspensions: Kerr versus exponential model
NASA Astrophysics Data System (ADS)
Wright, E. M.; Lee, W. M.; Dholakia, K.; El-Ganainy, R.; Christodoulides, D. N.
2009-08-01
We report our experimental and theoretical progress towards elucidating the nonlinear optical response of nanosuspensions. To date, we have devised a fiber-optic variant of the Z-scan method to accurately measure the nonlinearity of liquid nanosuspensions. Furthermore, we shall show that the optical nonlinearity may be properly accounted theoretically by including both the virial coefficients for the soft-condensed matter system in addition to the exponential term, which does not account for particleparticle interactions, yielding an effective or renormalized Kerr effect in many cases.
Investigation of nonlinear effects in the instabilities and noise radiation of supersonic jets
NASA Astrophysics Data System (ADS)
Janjua, S. I.; McLaughlin, D. K.
1985-01-01
The nonlinear interactions of fluctuating components which produce noise in supersonic jet flows were studied experimentally. Attention was given to spectral components interactions and the spectral effects of increasing Re. A jet exhausted in perfectly expanded conditions was monitored by microphones in the maximum noise emission direction. Trials were run at Mach 1.4 and 2.1 and the Re was varied from 5000-20,000 and 9000-25,000, respectively. Hot-wire data were gathered to examine the mode-mode interactions and a point glow discharge was used to excite the jets. The noise was found to exhibit discrete frequency components and a single tone instability at Re below 10,000. Mode interactions were found to weaken after the instabilities reached a crescendo and then decayed, leading to a nonlinear spectral broadening effect.
Wu, Heng-Qing; Sun, Shi-Ling; Zhong, Rong-Lin; Xu, Hong-Liang; Su, Zhong-Min
2012-11-01
In the present work, Li@porphyrins and their derivatives were designed in order to explore the effect of dehydrogenation/hydrogenation on linear and nonlinear optical properties. Their stable structures were obtained by the M06-2X method. Moreover, the M06-2X method showed that dehydrogenation/hydrogenation has greatly influences polarizabilities (α₀ values) and hyperpolarizabilities (β(tot) and γ(tot) values): α₀ values ranged from 331 to 389 au, β(tot) values from 0 to 2465 au, and γ(tot) values from -21.2 × 10⁴ to 21.4 × 10⁴ au. This new knowledge of the effect of dehydrogenation/hydrogenation on nonlinear optical properties may prove beneficial to the design and development of high-performance porphyrin materials. PMID:22722697
Gang, Noa; Persinger, Michael A
2011-12-01
There have been multiple claims that exposing water to a static magnetic field affects its properties which influence living systems. To test this hypothesis, planarian subsequent to dissection were maintained in spring water that had been previously exposed for only one day to one of three (16, 160, or 1,600 G) intensity static magnetic fields or to a reference condition. Although there was no significant difference in regeneration rates over the subsequent seven-day period, there was a statistically significant nonlinear effect for planarian mobility and diffusion rates. Both mobility rates and diffusion velocity of a liquid within the water that had been exposed to the 16 G field was about twice that for water exposed to the other intensities. These results imply that nonlinear biophysical effects may emerge under specific conditions of intensity ranges for particular volumes of water.
NASA Technical Reports Server (NTRS)
Li, Xiao-Fan; Finkbeiner, Joshua; Raman, Ganesh; Daniels, Christopher; Steinetz, Bruce M.
2003-01-01
Optimizing resonator shapes for maximizing the ratio of maximum to minimum gas pressure at an end of the resonator is investigated numerically. It is well known that the resonant frequencies and the nonlinear standing waveform in an acoustical resonator strongly depend on the resonator geometry. A quasi-Newton type scheme was used to find optimized axisymmetric resonator shapes achieving the maximum pressure compression ratio with an acceleration of constant amplitude. The acoustical field was solved using a one-dimensional model, and the resonance frequency shift and hysteresis effects were obtained through an automation scheme based on continuation method. Results are presented for optimizing three types of geometry: a cone, a horn-cone and a half cosine- shape. For each type, different optimized shapes were found when starting with different initial guesses. Further, the one-dimensional model was modified to study the effect of an axisymmetric central blockage on the nonlinear standing wave.
The effect of process delay on dynamical behaviors in a self-feedback nonlinear oscillator
NASA Astrophysics Data System (ADS)
Yao, Chenggui; Ma, Jun; Li, Chuan; He, Zhiwei
2016-10-01
The delayed feedback loops play a crucial role in the stability of dynamical systems. The effect of process delay in feedback is studied numerically and theoretically in the delayed feedback nonlinear systems including the neural model, periodic system and chaotic oscillator. The process delay is of key importance in determining the evolution of systems, and the rich dynamical phenomena are observed. By introducing a process delay, we find that it can induce bursting electric activities in the neural model. We demonstrate that this novel regime of amplitude death also exists in the parameter space of feedback strength and process delay for the periodic system and chaotic oscillator. Our results extend the effect of process delay in the paper of Zou et al.(2013) where the process delay can eliminate the amplitude death of the coupled nonlinear systems.
Quantum plasmonics: nonlinear effects in the field enhancement of a plasmonic nanoparticle dimer.
Marinica, D C; Kazansky, A K; Nordlander, P; Aizpurua, J; Borisov, A G
2012-03-14
A fully quantum mechanical investigation using time-dependent density functional theory reveals that the field enhancement in a coupled nanoparticle dimer can be strongly affected by nonlinear effects. We show that both classical as well as linear quantum mechanical descriptions of the system fail even for moderate incident light intensities. An interparticle current resulting from the strong field photoemission tends to neutralize the plasmon-induced surface charge densities on the opposite sides of the nanoparticle junction. Thus, the coupling between the two nanoparticles and the field enhancement is reduced as compared to linear theory. A substantial nonlinear effect is revealed already at incident powers of 10(9) W/cm(2) for interparticle separation distances as large as 1 nm and down to the touching limit.
NASA Technical Reports Server (NTRS)
Li, Xiaofan; Finkbeiner, Joshua; Raman, Ganesh; Daniels, Christopher; Steinetz, Bruce M.
2003-01-01
Optimizing resonator shapes for maximizing the ratio of maximum to minimum gas pressure at an end of the resonator is investigated numerically. It is well known that the resonant frequencies and the nonlinear standing waveform in an acoustical resonator strongly depend on the resonator geometry. A quasi-Newton type scheme was used to find optimized axisymmetric resonator shapes achieving the maximum pressure compression ratio with an acceleration of constant amplitude. The acoustical field was solved using a one-dimensional model, and the resonance frequency shift and hysteresis effects were obtained through an automation scheme based on continuation method. Results are presented for optimizing three types of geometry: a cone, a horn-cone and a half cosine-shape. For each type, different optimized shapes were found when starting with different initial guesses. Further, the one-dimensional model was modified to study the effect of an axisymmetric central blockage on the nonlinear standing wave.
NASA Astrophysics Data System (ADS)
Li, Nianbei; Li, Baowen
2012-12-01
Heat transport in low-dimensional systems has attracted enormous attention from both theoretical and experimental aspects due to its significance to the perception of fundamental energy transport theory and its potential applications in the emerging field of phononics: manipulating heat flow with electronic anologs. We consider the heat conduction of one-dimensional nonlinear lattice models. The energy carriers responsible for the heat transport have been identified as the renormalized phonons. Within the framework of renormalized phonons, a phenomenological theory, effective phonon theory, has been developed to explain the heat transport in general one-dimensional nonlinear lattices. With the help of numerical simulations, it has been verified that this effective phonon theory is able to predict the scaling exponents of temperature-dependent thermal conductivities quantitatively and consistently.
Linear and nonlinear effect of sheared plasma flow on resistive tearing modes
Hu, Qiming Hu, Xiwei; Yu, Q.
2014-12-15
The effect of sheared plasma flow on the m/n = 2/1 tearing mode is studied numerically (m and n are the poloidal and toroidal mode numbers). It is found that in the linear phase the plasma flow with a weak or moderate shear plays a stabilizing effect on tearing mode. However, the mode is driven to be more unstable by sufficiently strong sheared flow when approaching the shear Alfvén resonance (AR). In the nonlinear phase, a moderate (strong) sheared flow leads to a smaller (larger) saturated island width. The stabilization of tearing modes by moderate shear plasma flow is enhanced for a larger plasma viscosity and a lower Alfvén velocity. It is also found that in the nonlinear phase AR accelerates the plasma rotation around the 2/1 rational surface but decelerates it at the AR location, and the radial location satisfying AR spreads inwards towards the magnetic axis.
ERIC Educational Resources Information Center
McGuire, Luke; Rutland, Adam; Nesdale, Drew
2015-01-01
The present study examined the interactive effects of school norms, peer norms, and accountability on children's intergroup attitudes. Participants (n = 229) aged 5-11 years, in a between-subjects design, were randomly assigned to a peer group with an inclusion or exclusion norm, learned their school either had an inclusion norm or not, and were…
ERIC Educational Resources Information Center
Opfer, V. Darleen; Henry, Gary T.; Mashburn, Andrew J.
2008-01-01
High stakes accountability (HSA) reforms were enacted in state after state and federally through the No Child Left Behind law, based on the belief that incentives that have consequences attached are effective ways to motivate educators to improve student performance. Our focus for this article is on school district level responses to HSA reforms…
Federal Register 2010, 2011, 2012, 2013, 2014
2011-04-14
... AGENCY Implications of Climate Change for Bioassessment Programs and Approaches To Account for Effects... external peer review workshop to review the external review draft report titled, ``Implications of Climate... by climate change. The study (1) Investigates the potential to identify biological response...
ERIC Educational Resources Information Center
Trevors, Gregory J.; Muis, Krista R.; Pekrun, Reinhard; Sinatra, Gale M.; Winne, Philip H.
2016-01-01
Recent research has shown that for some topics, messages to refute and revise misconceptions may backfire. The current research offers one possible account for this backfire effect (i.e., the ironic strengthening of belief in erroneous information after an attempted refutation) from an educational psychology perspective and examines whether…
A Retrieved Context Account of Spacing and Repetition Effects in Free Recall
ERIC Educational Resources Information Center
Siegel, Lynn L.; Kahana, Michael J.
2014-01-01
Repeating an item in a list benefits recall performance, and this benefit increases when the repetitions are spaced apart (Madigan, 1969; Melton, 1970). Retrieved context theory incorporates 2 mechanisms that account for these effects: contextual variability and study-phase retrieval. Specifically, if an item presented at position "i" is…
Lee, Hwa-Young; Yang, Bong-Ming; Kang, Minah
2016-01-01
Background Despite continued global efforts, HIV/AIDS outcomes in developing countries have not made much progress. Poor governance in recipient countries is often seen as one of the reasons for ineffectiveness of aid efforts to achieve stated objectives and desired outcomes. Objective This study examines the impact of two important dimensions of governance – control of corruption and democratic accountability – on the effectiveness of HIV/AIDS official development assistance. Design An empirical analysis using dynamic panel Generalized Method of Moments estimation was conducted on 2001–2010 datasets. Results Control of corruption and democratic accountability revealed an independent effect and interaction with the amount of HIV/AIDS aid on incidence of HIV/AIDS, respectively, while none of the two governance variables had a significant effect on HIV/AIDS prevalence. Specifically, in countries with accountability level below −2.269, aid has a detrimental effect on incidence of HIV/AIDS. Conclusion The study findings suggest that aid programs need to be preceded or at least accompanied by serious efforts to improve governance in recipient countries and that democratic accountability ought to receive more critical attention. PMID:27189199
Effects of Individual Development Accounts (IDAs) on Household Wealth and Saving Taste
ERIC Educational Resources Information Center
Huang, Jin
2010-01-01
This study examines effects of individual development accounts (IDAs) on household wealth of low-income participants. Methods: This study uses longitudinal survey data from the American Dream Demonstration (ADD) involving experimental design (treatment group = 537, control group = 566). Results: Results from quantile regression analysis indicate…
ERIC Educational Resources Information Center
Lee, Moosung; Walker, Allan; Chui, Yuk Ling
2012-01-01
Purpose: The purpose of this paper is to examine the effects of different dimensions of instructional leadership on student learning in Hong Kong secondary schools, whose broader institutional contexts are critically characterized by high accountability policy environments. Design/methodology/approach: This study utilizes standardized test scores…
Outputs as Educator Effectiveness in the United States: Shifting towards Political Accountability
ERIC Educational Resources Information Center
Piro, Jody S.; Mullen, Laurie
2013-01-01
The definition of educator effectiveness is being redefined by econometric modeling to evidence student achievement on standardized tests. While the reasons that econometric frameworks are in vogue are many, it is clear that the strength of such models lie in the quantifiable evidence of student learning. Current accountability models frame…
ERIC Educational Resources Information Center
Vicknair, David; Wright, Jeffrey
2015-01-01
Evidence of confusion in intermediate accounting textbooks regarding the annual percentage rate (APR) and annual effective rate (AER) is presented. The APR and AER are briefly discussed in the context of a note payable and correct formulas for computing each is provided. Representative examples of the types of confusion that we found is presented…
Jackson, E J; Coussios, C-C; Cleveland, R O
2014-06-21
Thermal ablation by high intensity focused ultrasound (HIFU) has a great potential for the non-invasive treatment of solid tumours. Due to the high pressure amplitudes involved, nonlinear acoustic effects must be understood and the relevant medium property is the parameter of nonlinearity B/A. Here, B/A was measured in ex vivo bovine liver, over a heating/cooling cycle replicating temperatures reached during HIFU ablation, adapting a finite amplitude insertion technique, which also allowed for measurement of sound-speed and attenuation. The method measures the nonlinear progression of a plane wave through liver and B/A was chosen so that numerical simulations matched the measured waveforms. To create plane-wave conditions, sinusoidal bursts were transmitted by a 100 mm diameter 1.125 MHz unfocused transducer and measured using a 15 mm diameter 2.25 MHz broadband transducer in the near field. Attenuation and sound-speed were calculated using a reflected pulse from the smaller transducer using the larger transducer as the reflecting interface. Results showed that attenuation initially decreased with heating then increased after denaturation, the sound-speed initially increased with temperature and then decreased, and B/A showed an increase with temperature but no significant post-heating change. The B/A data disagree with other reports that show a significant change and we suggest that any nonlinear enhancement in the received ultrasound signal post-treatment is likely due to acoustic cavitation rather than changes in tissue nonlinearity.
NASA Astrophysics Data System (ADS)
Sarkhosh, L.; Mansour, N.
2015-06-01
In nanoparticle colloidal systems, the thermal nonlinearity is affected by the thermal parameters of the surrounding solution. Having a low temperature gradient rate solution may be a key factor in producing high thermal nonlinear properties in colloids. In this manuscript, the effect of the thermal conductivity of the surrounding liquid environment on the thermal nonlinear refraction of gold nanoparticles (AuNPs) synthesized by laser ablation of a gold target in different solutions is investigated. Gold nanoparticles colloids have been fabricated by the nanosecond pulsed laser ablation of a pure gold plate in different liquid environments with a thermal conductivity range of 0.14-0.60 W mK-1 including cyclohexanone, castor oil, dimethyl sulfoxide, ethylene glycol, glycerin and water. The AuNPs colloids exhibit a UV-Vis absorption spectrum with a surface plasmon absorption peak at about 540 ± 20 nm. The thermal nonlinear optical responses of the gold colloids are measured using the Z-scan technique under low power CW laser irradiation at 532 nm near the surface plasmon peak of the nanoparticles. Our results show that the nonlinear refractive index of the nanoparticle colloids is considerably affected by the thermal conductivity of liquid medium. The largest nonlinear refractive index of -3.1 × 10-7 cm2 W-1 is obtained for AuNP in cyclohexanone with the lowest thermal conductivity of 0.14 W mK-1 whereas the lowest one of -0.1 × 10-7 cm2 W-1 is obtained for AuNP in water with the highest thermal conductivity of 0.60 W mK-1. This study shows that the nonlinear refractive index value of colloids can be controlled by the thermal conductivity of the used liquid’s environment. This allows us to design low threshold optical limiters by choosing a solution with low thermal conductivity for colloidal nanoparticles.
NASA Astrophysics Data System (ADS)
Shafiei, Navvab; Kazemi, Mohammad; Ghadiri, Majid
2016-08-01
This study is concerned with the small-scale effect on the nonlinear flapwise bending vibration of rotating cantilever and propped cantilever nanobeams. Euler-Bernoulli beam theory is used to model the nanobeam with nonlinearity. Nonlinear strain-displacement relations are employed to account for geometric nonlinearity of the system. The axial forces are modeled as the true spatial and thermal variations due to the rotation. Hamilton's principle is used to derive the nonlinear governing equation and nonlocal nonlinear boundary conditions based on Eringen's nonlocal elasticity theory. Finally, the differential quadrature method is used in conjunction with the direct iterative method to derive the nonlinear vibration frequencies of the nanobeam. The effects of the angular velocity, nonlocal small-scale parameter, temperature change and nonlinear amplitude on nonlinear vibration of the rotary nanobeam are discussed. The results of this work can be used in nanosensors, nanomotors, nanoturbines and NEMS applications.
NASA Astrophysics Data System (ADS)
Carrara, P.; De Lorenzis, L.; Bentz, D. P.
2016-08-01
The diffusion of chloride ions in hardened cement paste (HCP) under steady-state conditions and accounting for the highly heterogeneous nature of the material is investigated. The three-dimensional HCP microstructures are obtained through segmentation of x-ray images of real samples as well as from simulations using the cement hydration model CEMHYD3D. Moreover, the physical and chemical interactions between chloride ions and HCP phases (binding), along with their effects on the diffusive process, are explicitly taken into account. The homogenized diffusivity of the HCP is then derived through a least square homogenization technique. Comparisons between numerical results and experimental data from the literature are presented.
Nonlinear hybrid simulation of internal kink with beam ion effects in DIII-D
Shen, Wei; Sheng, Zheng-Mao; Fu, G. Y.; Tobias, Benjamin; Zeeland, Michael Van; Wang, Feng
2015-04-15
In DIII-D sawteething plasmas, long-lived (1,1) kink modes are often observed between sawtooth crashes. The saturated kink modes have two distinct frequencies. The mode with higher frequency transits to a fishbone-like mode with sufficient on-axis neutral beam power. In this work, hybrid simulations with the global kinetic-magnetohydrodynamic (MHD) hybrid code M3D-K have been carried out to investigate the linear stability and nonlinear dynamics of the n = 1 mode with effects of energetic beam ions for a typical DIII-D discharge where both saturated kink mode and fishbone were observed. Linear simulation results show that the n = 1 internal kink mode is unstable in MHD limit. However, with kinetic effects of beam ions, a fishbone-like mode is excited with mode frequency about a few kHz depending on beam pressure profile. The mode frequency is higher at higher beam power and/or narrower radial profile consistent with the experimental observation. Nonlinear simulations have been performed to investigate mode saturation as well as energetic particle transport. The nonlinear MHD simulations show that the unstable kink mode becomes a saturated kink mode after a sawtooth crash. With beam ion effects, the fishbone-like mode can also transit to a saturated kink mode with a small but finite mode frequency. These results are consistent with the experimental observation of saturated kink mode between sawtooth crashes.
Q-switched laser in an SMS cavity for inhibiting nonlinear effects.
Zhou, Jiaqi; Lu, Yi; He, Bing; Gu, Xijia
2015-07-01
In the design of high-power Q-switched fiber lasers, nonlinear effects often become barriers that prevent the scale up of pulse energy and peak power. New designs and components that could inhibit or suppress nonlinear effects are in high demand, particularly in all-fiber configurations. In this paper, we demonstrated a Q-switched Yb-doped fiber laser in a single-mode multimode single-mode (SMS) structure to inhibit fiber nonlinear effects. The laser-generated Q-switched pulses with a peak power close to 1 kW (pulse width and energy of 100 ns and 92 μJ, respectively). The output spectrum of this laser was compared with that of a Q-switched Yb-doped fiber laser built in a conventional configuration with similar output peak power. The results showed, for the first time to our knowledge, that the SMS Q-switched laser completely inhibited the stimulated Raman scattering and significantly reduced self-phase modulation. PMID:26193155
A nonlinear generalized continuum approach for electro-elasticity including scale effects
NASA Astrophysics Data System (ADS)
Skatulla, S.; Arockiarajan, A.; Sansour, C.
2009-01-01
Materials characterized by an electro-mechanically coupled behaviour fall into the category of so-called smart materials. In particular, electro-active polymers (EAP) recently attracted much interest, because, upon electrical loading, EAP exhibit a large amount of deformation while sustaining large forces. This property can be utilized for actuators in electro-mechanical systems, artificial muscles and so forth. When it comes to smaller structures, it is a well-known fact that the mechanical response deviates from the prediction of classical mechanics theory. These scale effects are due to the fact that the size of the microscopic material constituents of such structures cannot be considered to be negligible small anymore compared to the structure's overall dimensions. In this context so-called generalized continuum formulations have been proven to account for the micro-structural influence to the macroscopic material response. Here, we want to adopt a strain gradient approach based on a generalized continuum framework [Sansour, C., 1998. A unified concept of elastic-viscoplastic Cosserat and micromorphic continua. J. Phys. IV Proc. 8, 341-348; Sansour, C., Skatulla, S., 2007. A higher gradient formulation and meshfree-based computation for elastic rock. Geomech. Geoeng. 2, 3-15] and extend it to also encompass the electro-mechanically coupled behaviour of EAP. The approach introduces new strain and stress measures which lead to the formulation of a corresponding generalized variational principle. The theory is completed by Dirichlet boundary conditions for the displacement field and its derivatives normal to the boundary as well as the electric potential. The basic idea behind this generalized continuum theory is the consideration of a micro- and a macro-space which together span the generalized space. As all quantities are defined in this generalized space, also the constitutive law, which is in this work conventional electro-mechanically coupled nonlinear
Schmidt, James R
2016-09-01
Performance is impaired when a distracting stimulus is incongruent with the target stimulus (e.g., "green" printed in red). This congruency effect is decreased when the proportion of incongruent trials is increased, termed the proportion congruent effect. This effect is typically interpreted in terms of the adaptation of attention in response to conflict. In contrast, the contingency account argues that the effect is driven by the learning of predictive relationships between words and responses. In a recent report, Abrahamse, Duthoo, Notebaert, and Risko (2013) demonstrated larger changes in the magnitude of the proportion congruent effect when switching from a mostly congruent list to a mostly incongruent list, relative to the reverse order. They argued that this asymmetric list shifting effect fits only with the conflict adaptation perspective. However, the current paper presents reanalyses of this data and an adaptation of the Parallel Episodic Processing model that together demonstrate how the contingency account can explain these findings equally well when considering the generally accepted notion that performance improves with practice. The contingency account may still be the most parsimonious view. (PsycINFO Database Record
A computational account of the production effect: Still playing twenty questions with nature.
Jamieson, Randall K; Mewhort, D J K; Hockley, William E
2016-06-01
People remember words that they read aloud better than words that they read silently, a result known as the production effect. The standing explanation for the production effect is that producing a word renders it distinctive in memory and, thus, memorable at test. By 1 key account, distinctiveness is defined in terms of sensory feedback. We formalize the sensory-feedback account using MINERVA 2, a standard model of memory. The model accommodates the basic result in recognition as well as the fact that the mixed-list production effect is larger than its pure-list counterpart, that the production effect is robust to forgetting, and that the production and generation effects have additive influences on performance. A final simulation addresses the strength-based account and suggests that it will be more difficult to distinguish a strength-based versus distinctiveness-based explanation than is typically thought. We conclude that the production effect is consistent with existing theory and discuss our analysis in relation to Alan Newell's (1973) classic criticism of psychology and call for an analysis of psychological principles instead of laboratory phenomena. (PsycINFO Database Record
Schmidt, James R
2016-09-01
Performance is impaired when a distracting stimulus is incongruent with the target stimulus (e.g., "green" printed in red). This congruency effect is decreased when the proportion of incongruent trials is increased, termed the proportion congruent effect. This effect is typically interpreted in terms of the adaptation of attention in response to conflict. In contrast, the contingency account argues that the effect is driven by the learning of predictive relationships between words and responses. In a recent report, Abrahamse, Duthoo, Notebaert, and Risko (2013) demonstrated larger changes in the magnitude of the proportion congruent effect when switching from a mostly congruent list to a mostly incongruent list, relative to the reverse order. They argued that this asymmetric list shifting effect fits only with the conflict adaptation perspective. However, the current paper presents reanalyses of this data and an adaptation of the Parallel Episodic Processing model that together demonstrate how the contingency account can explain these findings equally well when considering the generally accepted notion that performance improves with practice. The contingency account may still be the most parsimonious view. (PsycINFO Database Record PMID:27585071
Time-Ordering Effects in the Generation of Entangled Photons Using Nonlinear Optical Processes
NASA Astrophysics Data System (ADS)
Quesada, Nicolás; Sipe, J. E.
2015-03-01
We study the effects of time ordering in photon generation processes such as spontaneous parametric down-conversion (SPDC) and four wave mixing (SFWM). The results presented here are used to construct an intuitive picture that allows us to predict when time-ordering effects significantly modify the joint spectral amplitude (JSA) of the photons generated in SPDC and SFWM. These effects become important only when the photons being generated lie with the pump beam that travels through the nonlinear material for a significant amount of time. Thus sources of spectrally separable photons are ideal candidates for the observation of modifications of the JSA due to time ordering.
Dendritic crystal growth for weak undercooling. II. Surface energy effects on nonlinear evolution
NASA Astrophysics Data System (ADS)
Kunka, M. D.; Foster, M. R.; Tanveer, S.
1999-01-01
We extend the previous work of Kunka, Foster, and Tanveer [Phys. Rev. E 56, 3068 (1997)] by incorporating small but nonzero surface energy effects in the nonlinear dynamics of a conformal mapping function z(ζ,t) that maps the upper-half ζ plane into the exterior of a dendrite. In this paper, we specifically examine surface energy effects on the singularities of z(ζ,t) in the lower-half ζ plane, as they move toward the real axis from below. Until the time when any of the singularities of the corresponding zero-surface-energy solution or a surface-energy-generated daughter singularity cluster comes very close to the real axis, the leading-order outer solution is the zero-surface-energy solution in a strip of the lower-half complex that includes the real axis (i.e., the interface). There is an inner region around each singularity of the zero-surface-energy solution where surface energy plays a dominant role. However, the scalings in such an inner region, and hence the equation itself, must be modified when such singularities are very close to the real axis. The relative ordering of anisotropy, surface energy, and singularity strength strongly influences the form of the inner equations and hence their solutions. A singularity with initial strength weaker than some critical value is dissipated over a fast time scale by surface energy effects, leaving no trace of the initial singularity. This cutoff in singularity strength limits the size and growth rate of the interfacial disturbances that singularities generate. Also, the variation of time scale over which surface energy acts, due to differing singularity strengths in an ensemble, is shown to account for a \\|y\\|1/2 coarsening rate for some intermediate range of distances, \\|y\\|, from the dendrite tip. As in the case of the isotropic Hele-Shaw problem [S. Tanveer, Philos. Trans. R. Soc. London, Ser. A 343, 155 (1993)], we find here too that each initial zero of zζ gives birth to a ``daughter'' singularity
Kohagen, Miriam; Mason, Philip E; Jungwirth, Pavel
2016-03-01
Modeled ions, described by nonpolarizable force fields, can suffer from unphysical ion pairing and clustering in aqueous solutions well below their solubility limit. The electronic continuum correction takes electronic polarization effects of the solvent into account in an effective way by scaling the charges on the ions, resulting in a much better description of the ionic behavior. Here, we present parameters for the sodium ion consistent with this effective polarizability approach and in agreement with experimental data from neutron scattering, which could be used for simulations of complex aqueous systems where polarization effects are important.
NASA Astrophysics Data System (ADS)
Panyam Mohan Ram, Meghashyam
In the last few years, advances in micro-fabrication technologies have lead to the development of low-power electronic devices spanning critical fields related to sensing, data transmission, and medical implants. Unfortunately, effective utilization of these devices is currently hindered by their reliance on batteries. In many of these applications, batteries may not be a viable choice as they have a fixed storage capacity and need to be constantly replaced or recharged. In light of such challenges, several novel concepts for micro-power generation have been recently introduced to harness, otherwise, wasted ambient energy from the environment and maintain these low-power devices. Vibratory energy harvesting is one such concept which has received significant attention in recent years. While linear vibratory energy harvesters have been well studied in the literature and their performance metrics have been established, recent research has focused on deliberate introduction of stiffness nonlinearities into the design of these devices. It has been shown that, nonlinear energy harvesters have a wider steady-state frequency bandwidth as compared to their linear counterparts, leading to the premise that they can used to improve performance, and decrease sensitivity to variations in the design and excitation parameters. This dissertation aims to investigate this premise by developing an analytical framework to study the influence of stiffness nonlinearities on the performance and effective bandwidth of nonlinear vibratory energy harvesters. To achieve this goal, the dissertation is divided into three parts. The first part investigates the performance of bi-stable energy harvesters possessing a symmetric quartic potential energy function under harmonic excitations and carries out a detailed analysis to define their effective frequency bandwidth. The second part investigates the relative performance of mono- and bi-stable energy harvesters under optimal electric loading
NASA Astrophysics Data System (ADS)
Liu, Yanping; Zhang, Feng; Wei, Jianzhou
2016-12-01
By constructing a population model of multi-species competition, a community with nonlinear interaction relationship is investigated, in which the species' response delay and environmental fluctuation effects (i.e., seasonal fluctuation of resource supplies and species' reproductive activities) on population are considered. Firstly, the conditions about competitive coexistence (i.e., persistence of all species) and competitive exclusion (i.e., only partial of species, but not all, keep persistence) of the community are established, and the underlying ecological mechanism of these results are analyzed. Secondly, by some illustrative examples, the interactive effects of nonlinear competition, species' response delay and environmental fluctuation on the structure of community are explored. It is demonstrated that small response delay and slight deviation of nonlinear competition indexes from 1 have little impact on the coexistence of community, but acute changes have distinct negative influence on community coexistence. This reveals to us that parameter perturbations of natural communities should keep in an appropriate range, which is of great significance in conservation and restoration biology.
NASA Astrophysics Data System (ADS)
Bhattacharyya, S.; De, Simanta
2016-09-01
The impact of the solid polarization of a charged dielectric particle in gel electrophoresis is studied without imposing a weak-field or a thin Debye length assumption. The electric polarization of a dielectric particle due to an external electric field creates a non-uniform surface charge density, which in turn creates a non-uniform Debye layer at the solid-gel interface. The solid polarization of the particle, the polarization of the double layer, and the electro-osmosis of mobile ions within the hydrogel medium create a nonlinear effect on the electrophoresis. We have incorporated those nonlinear effects by considering the electrokinetics governed by the Stokes-Brinkman-Nernst-Planck-Poisson equations. We have computed the governing nonlinear coupled set of equations numerically by adopting a finite volume based iterative algorithm. Our numerical method is tested for accuracy by comparing with several existing results on free-solution electrophoresis as well as results based on the Debye-Hückel approximation. Our computed result shows that the electrophoretic velocity decreases with the rise of the particle dielectric permittivity constant and attains a saturation limit at large values of permittivity. A significant impact of the solid polarization is found in gel electrophoresis compared to the free-solution electrophoresis.
Shape-dependent effects of dielectrically nonlinear inclusions in heterogeneous media
NASA Astrophysics Data System (ADS)
Giordano, Stefano; Rocchia, Walter
2005-11-01
In this work the electrical response of a mixture composed of dielectrically nonlinear ellipsoids dispersed in a linear matrix is modeled. The inclusions may be randomly oriented. The aim is both to set up a methodology apt to deal with this kind of system and to use it to study the effect of marked nonsphericity of inclusions on the global behavior of a mixture. The results are quite interesting from both these points of view. The method here developed extends the Maxwell-Garnett theory [A Treatise on Electricity and Magnetism (Clarendon, Oxford, 1881)], which deals with dielectrically linear inclusions, and it allows, inter alia, to obtain a closed-form expression for the hypersusceptibility ratio of the mixture to the dispersed inclusions. These latter can range from cylinders to spheres, already present in the literature, to "penny-shaped" particles. The theoretical framework is based on the assumption that the dispersion is very dilute. We were able to show that in a specific case, when oblate particles such as elliptic lamellae are dispersed in a matrix having dielectric constant lower than the linear term of inclusion permittivity, a remarkable nonlinear effect occurs. This theory finds application in fields such as nonlinear optics and, more broadly, in many branches of material science.
Experimental study of strong nonlinear-optics effects in liquid crystals
NASA Astrophysics Data System (ADS)
Darbin, S. D.; Arakelyan, S. M.; Cheung, M. M.; Shen, Y. R.
1984-07-01
Nonlinear optical effects that arise in nematic liquid crystals as a result of a change in the index of refraction induced by a laser field are considered. Since the resultant nonlinearity is extremely high, the approximation of perturbation theory cannot be used in calculations. However, the change in refractive index results mainly in phase advance as waves propagate through a thin film of liquid crystal, while the change of intensity is significant. Moreover, if there is no change in polarization of the pumping field, calculations are relatively simple. An investigation is made of the propagation of a cross sectionally bounded laser beam through a homeotropically oriented liquid crystal, giving rise to spatial phase modulation of emission. When the intensity of the laser beam exceeds a certain value, a system of aberation rings is observed in the output radiation. Effects of dynamic self-diffraction accompanying degenerate four-wave mixing when a change in refractive index is induced in a homeotropic liquid crystal film, and optical bistability in a nonlinear Fabry-Perot optical cavity, as well as generation of a self-oscillatory state in such a resonator are discussed.
Electrorheological Source of Nonlinear Dielectric Effects in Molecular Glass-Forming Liquids.
Samanta, Subarna; Richert, Ranko
2016-08-11
We have measured the dielectric relaxation spectra of eight glass-forming liquids in the presence of electric direct current (dc)-bias fields ranging from 100 to 500 kV/cm. For every sample, we observe two distinct field-induced effects: a reduction in the relaxation amplitude and an increase in the primary structural relaxation time that is associated with viscous flow. Whereas amplitude change is typical of the well-known dielectric saturation, the field-induced increase in viscosity is a source of nonlinear behavior that has been recognized only recently. We find that this electrorheological behavior occurs in all polar liquids of this study, and its magnitude is correlated with the field-induced change in thermodynamic entropy. It constitutes a significant source of nonlinear dielectric behavior, which occurs for both dc and alternating current fields. PMID:27404019
Non-linear effects in the support motion of an elastically mounted slider crank mechanism
NASA Astrophysics Data System (ADS)
Davidson, I.
1983-01-01
A study is made of an in-line slider crank mechanism in which the sliding mass is elastically supported. The ratio of crank length to connecting rod length is not assumed small and relatively large displacements of the support are allowed. Ordinary and parametric non-linear terms are thus retained in the equations of motion. It is shown that the presence of parametric terms gives rise to additional conditions for resonance in the support motion. Approximate solutions are obtained for the fundamental and half subharmonic steady state responses and the effect of the non-linear and parametric terms examined. The stability of the steady state responses is considered and it is shown that instability is associated with a negative slope of the amplitude frequency characteristic.
NASA Astrophysics Data System (ADS)
Liu, Haiwen; Lei, Jiuhuai; Jiang, Hao; Guan, Xuehui; Ji, Laiyun; Ma, Zhewang
2015-10-01
Artificial structures with negative permittivity or permeability have attracted significant attention in the science community because they provide a pathway for obtaining exotic electromagnetic properties not found in natural materials. At the moment, the great challenge of these artificial structures in microwave frequency exhibits a relatively large loss. It is well-known that superconducting thin films have extremely low surface resistance. Hence, it is a good candidate to resolve this constraint. Besides, the reported artificial structures with negative permittivity or permeability are mainly focusing on linear regime of wave propagation. However, any future effort in creating tunable structures would require knowledge of nonlinear properties. In this work, a tunable superconducting filter with composite right/left-hand transmission property is proposed and fabricated. Its nonlinear effects on temperature and power are studied by theoretical analysis and experiments.
Liu, Haiwen; Lei, Jiuhuai; Jiang, Hao; Guan, Xuehui; Ji, Laiyun; Ma, Zhewang
2015-01-01
Artificial structures with negative permittivity or permeability have attracted significant attention in the science community because they provide a pathway for obtaining exotic electromagnetic properties not found in natural materials. At the moment, the great challenge of these artificial structures in microwave frequency exhibits a relatively large loss. It is well-known that superconducting thin films have extremely low surface resistance. Hence, it is a good candidate to resolve this constraint. Besides, the reported artificial structures with negative permittivity or permeability are mainly focusing on linear regime of wave propagation. However, any future effort in creating tunable structures would require knowledge of nonlinear properties. In this work, a tunable superconducting filter with composite right/left-hand transmission property is proposed and fabricated. Its nonlinear effects on temperature and power are studied by theoretical analysis and experiments. PMID:26442447
NASA Astrophysics Data System (ADS)
Sajan, D.; Devi, T. Uma; Safakath, K.; Philip, Reji; Němec, Ivan; Karabacak, M.
2013-05-01
FT-IR, FT-Raman and UV-Vis spectra of the nonlinear optical molecule ninhydrin have been recorded and analyzed. The equilibrium geometry, bonding features, and harmonic vibrational wavenumbers have been investigated with the help of B3LYP density functional theory method. A detailed interpretation of the vibrational spectra is carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Solvent effects have been calculated using time-dependent density functional theory in combination with the polarized continuum model. Natural bond orbital analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule. Employing the open-aperture z-scan technique, nonlinear optical absorption of the sample has been studied in the ultrafast and short-pulse excitation regimes, using 100 fs and 5 ns laser pulses respectively. It is found that ninhydrin exhibits optical limiting for both excitations, indicating potential photonic applications.
NASA Astrophysics Data System (ADS)
Sabatini, R.; Bailly, C.; Marsden, O.; Gainville, O.
2016-09-01
The long-range atmospheric propagation of explosion-like waves of frequency in the infrasound range is investigated using nonlinear ray theory. Simulations are performed for sources of increasing amplitude on rays up to the lower thermosphere and for distances of hundreds of kilometres. A study of the attenuation of the waveforms observed at ground level induced by both the classical mechanisms and the vibrational relaxation of the molecules comprising the atmospheric gas is carried out. The relative importance of classical absorption and vibrational relaxation along the typical atmospheric propagation trajectories is assessed. Nonlinear effects are highlighted as well and particular emphasis is placed on their strong interaction with absorption phenomena. A detailed description of the propagation model and of the numerical algorithm used in the present work is first reported. Results are then discussed and the importance of the different mechanisms is clarified.
Enhancement of optical pulse extinction-ratio using the nonlinear Kerr effect for phase-OTDR.
Baker, Chams; Vanus, Benoit; Wuilpart, Marc; Chen, Liang; Bao, Xiaoyi
2016-08-22
We present a novel approach for the generation of high extinction-ratio square pulses based on self-phase modulation of sinusoidally modulated optical signals (SMOS). A SMOS in a nonlinear medium experiences self-phase modulation induced by the nonlinear Kerr effect leading to the generation of distinct sidebands. A small variation in the peak power of the SMOS leads to a large variation in the power of the sidebands. Impressing a square pulse on the SMOS and filtering a sideband component results in a higher extinction-ratio square pulse. The advantage of high extinction-ratio pulses is demonstrated by a reduced background noise level in the Rayleigh backscattering traces of a phase-OTDR vibration measurement system. PMID:27557220
Gate tunable nonlinear rectification effects in three-terminal graphene nanojunctions
NASA Astrophysics Data System (ADS)
Zhu, R. J.; Huang, Y. Q.; Kang, N.; Xu, H. Q.
2014-04-01
We report on a study of the room-temperature nonlinear charge transport properties of three-terminal junction devices made from graphene. We demonstrate that the graphene three terminal junction devices show a rectification characteristic, namely, when voltages VL = V and VR = -V are applied to the left and the right terminal in a push-pull configuration, the voltage output from the central terminal VC is finite and is scaled approximately with V2. The rectification coefficient can be effectively tuned by a gate voltage and shows a transport carrier polarity dependence. We further show that the nonlinear charge transport characteristics can be used to probe the electronic structure of graphene nanostructures and to study the thermoelectrical power of graphene. These results show that the graphene three-terminal junction devices could be used as novel building blocks for nanoelectronics and as novel devices for the study of the material properties of graphene on the nanoscale.
Nonlinear Faraday effect in CdS semiconductor in an ultrahigh magnetic field
Druzhinin, V.V.; Tatsenko, O.M.; Bykov, A.I.
1994-08-01
A significant nonlinearity in the angle of rotation polarization plane was observed in CdS at wavelengths of 494 in the presence of high magnetic fields (0.5-5 MG). The onset significant nonlinearity also depended on sample temperature. An absorption study with probe wavelength of {approximately} 494 nm revealed an increase in optical transmission associated with a splitting of the conduction band. Dispersion, field and temperature curves indicate a low conduction electron mass m{sub e} = 0.3 m{sub o}. A numerical calculation and interpretation of the observed effects was carried out using band theory. The optical and magnetooptical properties of semiconducting crystals of CdS were studied, reviews of which are presented in [1,2]. This article describes joint American-Russian experiments to study the optical and magnetooptical properties of CdS in ultrahigh fields to {approximately} 7 MG.
NASA Astrophysics Data System (ADS)
Wu, Sheldon; Hartemann, Frederic; Siders, Craig; Barty, Christopher
2009-11-01
A study of thermally induced vacuum polarization stemming from the Euler-Heisenberg radiation correction to Maxwell equations is conducted. While nonlinear effects associated with interactions of electromagnetic pulse with a background photon gas had been previously calculated, we examine the possibility of nonlinear corrective terms to the blackbody radiation spectrum. Suitable conditions can be found in both astrophysical and laboratory environments. Inertial confined, ignited thermonuclear plasmas will produce intense blackbody radiation at temperatures in excess of 20 keV. In this theoretical investigation, our analysis shows that in an ideal incoherent blackbody the radiation spectrum is unaffected in the regime studied. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Effect of joint damping and joint nonlinearity on the dynamics of space structures
NASA Technical Reports Server (NTRS)
Bowden, Mary; Dugundji, John
1988-01-01
Analyses of the effect of linear joint characteristics on the vibrations of a free-free, three-joint beam model show that increasing joint damping increases resonant frequencies and increases modal damping but only to the point where the joint gets 'locked up' by damping. This behavior is different from that predicted by modeling joint damping as proportional damping. Nonlinear analyses of the three-joint model with cubic springs at the joints show all the classical single DOF nonlinear response behavior at each resonance of the multiple DOF system: nondoubling of response for a doubling of forcing amplitude, multiple solutions, jump behavior, and resonant frequency shifts. These properties can be concisely quantified by characteristic backbone curves, which show the locus of resonant peaks for increasing forcing amplitude.
Accounting for Behavior in Treatment Effects: New Applications for Blind Trials.
Chassang, Sylvain; Snowberg, Erik; Seymour, Ben; Bowles, Cayley
2015-01-01
The double-blind randomized controlled trial (DBRCT) is the gold standard of medical research. We show that DBRCTs fail to fully account for the efficacy of treatment if there are interactions between treatment and behavior, for example, if a treatment is more effective when patients change their exercise or diet. Since behavioral or placebo effects depend on patients' beliefs that they are receiving treatment, clinical trials with a single probability of treatment are poorly suited to estimate the additional treatment benefit that arises from such interactions. Here, we propose methods to identify interaction effects, and use those methods in a meta-analysis of data from blinded anti-depressant trials in which participant-level data was available. Out of six eligible studies, which included three for the selective serotonin re-uptake inhibitor paroxetine, and three for the tricyclic imipramine, three studies had a high (>65%) probability of treatment. We found strong evidence that treatment probability affected the behavior of trial participants, specifically the decision to drop out of a trial. In the case of paroxetine, but not imipramine, there was an interaction between treatment and behavioral changes that enhanced the effectiveness of the drug. These data show that standard blind trials can fail to account for the full value added when there are interactions between a treatment and behavior. We therefore suggest that a new trial design, two-by-two blind trials, will better account for treatment efficacy when interaction effects may be important. PMID:26062024
Accounting for Behavior in Treatment Effects: New Applications for Blind Trials
Chassang, Sylvain; Snowberg, Erik; Seymour, Ben; Bowles, Cayley
2015-01-01
The double-blind randomized controlled trial (DBRCT) is the gold standard of medical research. We show that DBRCTs fail to fully account for the efficacy of treatment if there are interactions between treatment and behavior, for example, if a treatment is more effective when patients change their exercise or diet. Since behavioral or placebo effects depend on patients’ beliefs that they are receiving treatment, clinical trials with a single probability of treatment are poorly suited to estimate the additional treatment benefit that arises from such interactions. Here, we propose methods to identify interaction effects, and use those methods in a meta-analysis of data from blinded anti-depressant trials in which participant-level data was available. Out of six eligible studies, which included three for the selective serotonin re-uptake inhibitor paroxetine, and three for the tricyclic imipramine, three studies had a high (>65%) probability of treatment. We found strong evidence that treatment probability affected the behavior of trial participants, specifically the decision to drop out of a trial. In the case of paroxetine, but not imipramine, there was an interaction between treatment and behavioral changes that enhanced the effectiveness of the drug. These data show that standard blind trials can fail to account for the full value added when there are interactions between a treatment and behavior. We therefore suggest that a new trial design, two-by-two blind trials, will better account for treatment efficacy when interaction effects may be important. PMID:26062024
Accounting for Behavior in Treatment Effects: New Applications for Blind Trials.
Chassang, Sylvain; Snowberg, Erik; Seymour, Ben; Bowles, Cayley
2015-01-01
The double-blind randomized controlled trial (DBRCT) is the gold standard of medical research. We show that DBRCTs fail to fully account for the efficacy of treatment if there are interactions between treatment and behavior, for example, if a treatment is more effective when patients change their exercise or diet. Since behavioral or placebo effects depend on patients' beliefs that they are receiving treatment, clinical trials with a single probability of treatment are poorly suited to estimate the additional treatment benefit that arises from such interactions. Here, we propose methods to identify interaction effects, and use those methods in a meta-analysis of data from blinded anti-depressant trials in which participant-level data was available. Out of six eligible studies, which included three for the selective serotonin re-uptake inhibitor paroxetine, and three for the tricyclic imipramine, three studies had a high (>65%) probability of treatment. We found strong evidence that treatment probability affected the behavior of trial participants, specifically the decision to drop out of a trial. In the case of paroxetine, but not imipramine, there was an interaction between treatment and behavioral changes that enhanced the effectiveness of the drug. These data show that standard blind trials can fail to account for the full value added when there are interactions between a treatment and behavior. We therefore suggest that a new trial design, two-by-two blind trials, will better account for treatment efficacy when interaction effects may be important.
NASA Astrophysics Data System (ADS)
Mustafa, M.; Khan, Junaid Ahmad
2015-07-01
Present work deals with the magneto-hydro-dynamic flow and heat transfer of Casson nanofluid over a non-linearly stretching sheet. Non-linear temperature distribution across the sheet is considered. More physically acceptable model of passively controlled wall nanoparticle volume fraction is accounted. The arising mathematical problem is governed by interesting parameters which include Casson fluid parameter, magnetic field parameter, power-law index, Brownian motion parameter, thermophoresis parameter, Prandtl number and Schmidt number. Numerical solutions are computed through fourth-fifth-order-Runge-Kutta integration approach combined with the shooting technique. Both temperature and nanoparticle volume fraction are increasing functions of Casson fluid parameter.
NASA Technical Reports Server (NTRS)
Rizzi, Stephen A.; Przekop, Adam
2005-01-01
An investigation of the effect of basis selection on geometric nonlinear response prediction using a reduced-order nonlinear modal simulation is presented. The accuracy is dictated by the selection of the basis used to determine the nonlinear modal stiffness. This study considers a suite of available bases including bending modes only, bending and membrane modes, coupled bending and companion modes, and uncoupled bending and companion modes. The nonlinear modal simulation presented is broadly applicable and is demonstrated for nonlinear quasi-static and random acoustic response of flat beam and plate structures with isotropic material properties. Reduced-order analysis predictions are compared with those made using a numerical simulation in physical degrees-of-freedom to quantify the error associated with the selected modal bases. Bending and membrane responses are separately presented to help differentiate the bases.
NASA Astrophysics Data System (ADS)
Shen, Chunyun; Yang, Mo; Zhang, Yuwen; Li, Zheng
2016-09-01
Natural convection in a cylinder with an internally slotted annulus was solved by SIMPLE algorithm, and the effects of different slotted structures on nonlinear characteristics of natural convection were investigated. The results show that the equivalent thermal conductivity Keq increases with Rayleigh number, and reaches the maximum in the vertical orientation. Nonlinear results were obtained by simulating the fluid flow at different conditions. With increasing Rayleigh number, heat transfer is intensified and the state of heat transfer changes from the steady to unsteady. We investigated different slotted structures effects on natural convection, and analyze the corresponding nonlinear characteristics.
Preheating ablation effects on the Rayleigh-Taylor instability in the weakly nonlinear regime
Wang, L. F.; Ye, W. H.; He, X. T.; Sheng, Z. M.; Don, Wai-Sun; Li, Y. J.
2010-12-15
The two-dimensional Rayleigh-Taylor instability (RTI) with and without thermal conduction is investigated by numerical simulation in the weakly nonlinear regime. A preheat model {kappa}(T)={kappa}{sub SH}[1+f(T)] is introduced for the thermal conduction [W. H. Ye, W. Y. Zhang, and X. T. He, Phys. Rev. E 65, 057401 (2002)], where {kappa}{sub SH} is the Spitzer-Haerm electron thermal conductivity coefficient and f(T) models the preheating tongue effect in the cold plasma ahead of the ablation front. The preheating ablation effects on the RTI are studied by comparing the RTI with and without thermal conduction with identical density profile relevant to inertial confinement fusion experiments. It is found that the ablation effects strongly influence the mode coupling process, especially with short perturbation wavelength. Overall, the ablation effects stabilize the RTI. First, the linear growth rate is reduced, especially for short perturbation wavelengths and a cutoff wavelength is observed in simulations. Second, the second harmonic generation is reduced for short perturbation wavelengths. Third, the third-order negative feedback to the fundamental mode is strengthened, which plays a stabilization role. Finally, on the contrary, the ablation effects increase the generation of the third harmonic when the perturbation wavelengths are long. Our simulation results indicate that, in the weakly nonlinear regime, the ablation effects are weakened as the perturbation wavelength is increased. Numerical results obtained are in general agreement with the recent weakly nonlinear theories as proposed in [J. Sanz, J. Ramirez, R. Ramis et al., Phys. Rev. Lett. 89, 195002 (2002); J. Garnier, P.-A. Raviart, C. Cherfils-Clerouin et al., Phys. Rev. Lett. 90, 185003 (2003)].
Brillouin/Raman compensation of the Kerr-effect-induced bias in a nonlinear ring laser gyroscope.
Luo, Zhang; Yuan, Xiaodong; Zhu, Zhihong; Liu, Ken; Ye, Weimin; Zeng, Chun; Ji, Jiarong
2013-04-01
In this Letter, the beat frequency at rest of a ring laser gyroscope with nonlinear effects is discussed in detail. Even without an additional intensity-stabilizing system, the random nullshift bias induced by the Kerr effect is compensated by the phase shift associated with the stimulated Brillouin/Raman scattering. And the nonlinear stimulated scattering also serves as the gain mechanism of the gyroscope. And thus the influence of the fluctuation of the injected pump intensity on the beat frequency is eliminated.
A recency-based account of the primacy effect in free recall.
Tan, L; Ward, G
2000-11-01
Seven experiments investigated the role of rehearsal in free recall to determine whether accounts of recency effects based on the ratio rule could be extended to provide an account of primacy effects based on the number, distribution, and recency of the rehearsals of the study items. Primacy items were rehearsed more often and further toward the end of the list than middle items, particularly with a slow presentation rate (Experiment 1) and with high-frequency words (Experiment 2). Recency, but not primacy, was reduced by a filled delay (Experiment 3), although significant recency survived a filled retention interval when a fixed-rehearsal strategy was used (Experiment 4). Experimenter-presented schedules of rehearsals resulted in similar serial position curves to those observed with participant-generated rehearsals (Experiment 5) and were used to confirm the main findings in Experiments 6 and 7.
Survival analysis approach to account for non-exponential decay rate effects in lifetime experiments
NASA Astrophysics Data System (ADS)
Coakley, K. J.; Dewey, M. S.; Huber, M. G.; Huffer, C. R.; Huffman, P. R.; Marley, D. E.; Mumm, H. P.; O`Shaughnessy, C. M.; Schelhammer, K. W.; Thompson, A. K.; Yue, A. T.
2016-03-01
In experiments that measure the lifetime of trapped particles, in addition to loss mechanisms with exponential survival probability functions, particles can be lost by mechanisms with non-exponential survival probability functions. Failure to account for such loss mechanisms produces systematic measurement error and associated systematic uncertainties in these measurements. In this work, we develop a general competing risks survival analysis method to account for the joint effect of loss mechanisms with either exponential or non-exponential survival probability functions, and a method to quantify the size of systematic effects and associated uncertainties for lifetime estimates. As a case study, we apply our survival analysis formalism and method to the Ultra Cold Neutron lifetime experiment at NIST. In this experiment, neutrons can escape a magnetic trap before they decay due to a wall loss mechanism with an associated non-exponential survival probability function.
Accounting for strong localized heterogeneities and local transport effect in core calculations
Ruggieri, J.M.; Doriath, J.Y.; Finck, P.J.; Boyer, R.
1996-09-01
Two methods based on the variational nodal transport method have been developed to account for localized heterogeneities and local transport effects in full core calculations. A local mesh refinement technique relies on using the projected partial ingoing surface currents produced during coarse-mesh iterations as boundary conditions for fine-mesh calculations embedded within the coarse-mesh calculations. The outgoing fine-mesh partial currents are averaged to serve in the coarse-mesh iterations. Then, a mixed transport-diffusion method using two levels of angular approximations for the surface partial currents depending on the node considered has been implemented to account for local transport effects in full core diffusion calculations. These methods have been tested for a model of the Superphenix complementary shutdown rods.
Fitness Effects of Network Non-Linearity Induced by Gene Expression Noise
NASA Astrophysics Data System (ADS)
Ray, Christian; Cooper, Tim; Balazsi, Gabor
2012-02-01
In the non-equilibrium dynamics of growing microbial cells, metabolic enzymes can create non-linearities in metabolite concentration because of non-linear degradation (utilization): an enzyme can saturate in the process of metabolite utilization. Increasing metabolite production past the saturation point then results in an ultrasensitive metabolite response. If the production rate of a metabolite depends on a second enzyme or other protein-mediated process, uncorrelated gene expression noise can thus cause transient metabolite concentration bursts. Such bursts are physiologically unnecessary and may represent a source of selection against the ultrasensitive switch, especially if the fluctuating metabolic intermediate is toxic. Selection may therefore favor correlated gene expression fluctuations for enzymes in the same pathway, such as by same-operon membership in bacteria. Using a modified experimental lac operon system, we are undertaking a combined theoretical-experimental approach to demonstrate that (i) the lac operon has an implicit ultrasensitive switch that we predict is avoided by gene expression correlations induced by same-operon membership; (ii) bacterial growth rates are sensitive to crossing the ultrasensitive threshold. Our results suggest that correlations in intrinsic gene expression noise are exploited by evolution to ameliorate the detrimental effects of nonlinearities in metabolite concentrations.
Jiménez-Sánchez, Arturo; Isunza-Manrique, Itzel; Ramos-Ortiz, Gabriel; Rodríguez-Romero, Jesús; Farfán, Norberto; Santillan, Rosa
2016-06-30
Design parameters derived from structure-property relationships play a very important role in the development of efficient molecular-based functional materials with optical properties. Here, we report on the linear and nonlinear optical properties of a fluorene-derived dipolar system (DS) and its octupolar analogue (OS), in which donor and acceptor groups are connected by a phenylacetylene linkage, as a strategy to increase the number of delocalized electrons in the π-conjugated system. The optical nonlinear response was analyzed in detail by experimental and theoretical methods, showing that, in the octupolar system OS, the dipolar effects induced a strong two-photon absorption process whose magnitude is as large as 2210 GM at infrared wavelengths. Solvatochromism studies were implemented to obtain further insight on the charge transfer process. We found that the triple bond plays a fundamental role in the linear and nonlinear optical responses. The strong solvatochromism behavior in DS and OS was analyzed by using four empirical solvent scales, namely Lippert-Mataga, Kamlet-Taft, Catalán, and the recently proposed scale of Laurence et al., finding consistent results of strong solvent polarizability and viscosity dependence. Finally, the role of the acceptor groups was further studied by synthesizing the analogous compound 2DS, having no acceptor group.
Pitch glide effect induced by a nonlinear string-barrier interaction
NASA Astrophysics Data System (ADS)
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.
Jiménez-Sánchez, Arturo; Isunza-Manrique, Itzel; Ramos-Ortiz, Gabriel; Rodríguez-Romero, Jesús; Farfán, Norberto; Santillan, Rosa
2016-06-30
Design parameters derived from structure-property relationships play a very important role in the development of efficient molecular-based functional materials with optical properties. Here, we report on the linear and nonlinear optical properties of a fluorene-derived dipolar system (DS) and its octupolar analogue (OS), in which donor and acceptor groups are connected by a phenylacetylene linkage, as a strategy to increase the number of delocalized electrons in the π-conjugated system. The optical nonlinear response was analyzed in detail by experimental and theoretical methods, showing that, in the octupolar system OS, the dipolar effects induced a strong two-photon absorption process whose magnitude is as large as 2210 GM at infrared wavelengths. Solvatochromism studies were implemented to obtain further insight on the charge transfer process. We found that the triple bond plays a fundamental role in the linear and nonlinear optical responses. The strong solvatochromism behavior in DS and OS was analyzed by using four empirical solvent scales, namely Lippert-Mataga, Kamlet-Taft, Catalán, and the recently proposed scale of Laurence et al., finding consistent results of strong solvent polarizability and viscosity dependence. Finally, the role of the acceptor groups was further studied by synthesizing the analogous compound 2DS, having no acceptor group. PMID:27281172
NASA Astrophysics Data System (ADS)
Masson, R.; Bornert, M.; Suquet, P.; Zaoui, A.
2000-06-01
Variational approaches for nonlinear elasticity show that Hill's incremental formulation for the prediction of the overall behaviour of heterogeneous materials yields estimates which are too stiff and may even violate rigorous bounds. This paper aims at proposing an alternative 'affine' formulation, based on a linear thermoelastic comparison medium, which could yield softer estimates. It is first described for nonlinear elasticity and specified by making use of Hashin-Shtrikman estimates for the linear comparison composite; the associated affine self-consistent predictions are satisfactorily compared with incremental and tangent ones for power-law creeping polycrystals. Comparison is then made with the second-order procedure (Ponte Castañeda, P., 1996. Exact second-order estimates for the effective mechanical properties of nonlinear composite materials. J. Mech. Phys. Solids, 44 (6), 827-862) and some limitations of the affine method are pointed out; explicit comparisons between different procedures are performed for isotropic, two-phase materials. Finally, the affine formulation is extended to history-dependent behaviours; application to the self-consistent modelling of the elastoplastic behaviour of polycrystals shows that it offers an improved alternative to Hill's incremental formulation.
Yu, Kyung-Hun; Suk, Min-Hwa; Kang, Shin-Woo; Shin, Yun-A
2014-01-01
The purpose of this study was to investigate the effect of combined linear and nonlinear periodic training on physical fitness and competition times in finswimmers. The linear resistance training model (6 days/week) and nonlinear underwater training (4 days/week) were applied to 12 finswimmers (age, 16.08± 1.44 yr; career, 3.78± 1.90 yr) for 12 weeks. Body composition measures included weight, body mass index (BMI), percent fat, and fat-free mass. Physical fitness measures included trunk flexion forward, trunk extension backward, sargent jump, 1-repetition-maximum (1 RM) squat, 1 RM dead lift, knee extension, knee flexion, trunk extension, trunk flexion, and competition times. Body composition and physical fitness were improved after the 12-week periodic training program. Weight, BMI, and percent fat were significantly decreased, and trunk flexion forward, trunk extension backward, sargent jump, 1 RM squat, 1 RM dead lift, and knee extension (right) were significantly increased. The 50- and 100-m times significantly decreased in all 12 athletes. After 12 weeks of training, all finswimmers who participated in this study improved their times in a public competition. These data indicate that combined linear and nonlinear periodic training enhanced the physical fitness and competition times in finswimmers. PMID:25426469
Effect of gas velocity on the weakly nonlinear instability of a planar viscous sheet
Yang, Li-Jun Chen, Pi-Min; Wang, Chen
2014-07-15
A weakly nonlinear spatial instability of a two-dimensional planar viscous sheet for sinuous disturbances in a co-flowing inviscid gas stream is investigated theoretically, with an emphasis on the effect of the surrounding gas velocity. The solutions of the second-order interface disturbances are derived and the wave deformation has been computed. The results indicate that the second-order surface disturbance of the fundamental sinuous mode is varicose, which causes the thinning and the subsequent breakup of the liquid sheet. The nonlinear behaviors of the planar sheet are quite sensitive to variations in gas-to-liquid velocity ratio. The deviation of the velocity ratio from the value of unity leads to a larger growth rate, a larger second-order initial amplitude, and a shorter breakup length, and therefore enhances the instability. The growth rates predicted by the present nonlinear analysis according to the shortest breakup length are generally smaller than the linear predictions and can better conform to the experimental measures of Barreras et al. [“Linear instability analysis of the viscous longitudinal perturbation on an air-blasted liquid sheets,” Atomization Sprays 11, 139 (2001)]. Furthermore, the wave deformations of the most unstable disturbances are presented. The nonlinear instability of the planar sheet for a fixed velocity difference is performed. An equal increase of the gas and liquid velocity reduces the spatial growth rate and increases the breakup length, but generally has no influences on the second-order initial amplitude and the wavelength of the disturbance.
Nonlinear delta(f) Simulations of Collective Effects in Intense Charged Particle Beams
Hong Qin
2003-01-21
A nonlinear delta(f) particle simulation method based on the Vlasov-Maxwell equations has been recently developed to study collective processes in high-intensity beams, where space-charge and magnetic self-field effects play a critical role in determining the nonlinear beam dynamics. Implemented in the Beam Equilibrium, Stability and Transport (BEST) code [H. Qin, R.C. Davidson, and W.W. Lee, Physical Review -- Special Topics on Accelerator and Beams 3 (2000) 084401; 3 (2000) 109901.], the nonlinear delta(f) method provides a low-noise and self-consistent tool for simulating collective interactions and nonlinear dynamics of high-intensity beams in modern and next-generation accelerators and storage rings, such as the Spallation Neutron Source and heavy ion fusion drivers. A wide range of linear eigenmodes of high-intensity charged-particle beams can be systematically studied using the BEST code. Simulation results for the electron-proton two-stream instability in the Proton Storage Ring experiment [R. Macek, et al., in Proc. of the Particle Accelerator Conference, Chicago, 2001 (IEEE, Piscataway, NJ, 2001), Vol. 1, p. 688.] at the Los Alamos National Laboratory agree well with experimental observations. Large-scale parallel simulations have also been carried out for the ion-electron two-stream instability in the very-high-intensity heavy ion beams envisioned for heavy ion fusion applications. In both cases, the simulation results indicate that the dominant two-stream instability has a dipole-mode (hose-like) structure and can be stabilized by a modest axial momentum spread of the beam particles.
NASA Astrophysics Data System (ADS)
Ayten, B.; Westerhof, E.; the ASDEX Upgrade Team
2014-07-01
Due to the smallness of the volumes associated with the flux surfaces around the O-point of a magnetic island, the electron cyclotron power density applied inside the island for the stabilization of neoclassical tearing modes (NTMs) can exceed the threshold for non-linear effects as derived previously by Harvey et al (1989 Phys. Rev. Lett. 62 426). We study the non-linear electron cyclotron current drive (ECCD) efficiency through bounce-averaged, quasi-linear Fokker-Planck calculations in the magnetic geometry as created by the islands. The calculations are performed for the parameters of a typical NTM stabilization experiment on ASDEX Upgrade. A particular feature of these experiments is that the rays of the EC wave beam propagate tangential to the flux surfaces in the power deposition region. The calculations show significant non-linear effects on the ECCD efficiency, when the ECCD power is increased from its experimental value of 1 MW to a larger value of 4 MW. The nonlinear effects are largest in the case of locked islands or when the magnetic island rotation period is longer than the collisional time scale. The non-linear effects result in an overall reduction of the current drive efficiency for this case with absorption of the EC power on the low-field side of the electron cyclotron resonance layer. As a consequence of the non-linear effects, also the stabilizing effect of the ECCD on the island is reduced from linear expectations.
Origin of the effective mobility in non-linear active micro-rheology
NASA Astrophysics Data System (ADS)
Santamaría-Holek, I.; Pérez-Madrid, A.
2016-10-01
The distinction between the damping coefficient and the effective non-linear mobility of driven particles in active micro-rheology of supercooled liquids is explained in terms of individual and collective dynamics. The effective mobility arises as a collective effect which gives insight into the energy landscape of the system. On the other hand, the damping coefficient is a constant that modulates the effect of external forces over the thermal energy which particles have at their disposition to perform Brownian motion. For long times, these thermal fluctuations become characterized in terms of an effective temperature that is a consequence of the dynamic coupling between kinetic and configurational degrees of freedom induced by the presence of the strong external force. The interplay between collective mobility and effective temperature allows to formulate a generalized Stokes-Einstein relation that may be used to determine the collective diffusion coefficient. The explicit relations we deduce reproduce simulation data remarkably well.
Semi-Empirical Characterization of Ground Motions Including Source, Path and Nonlinear Site Effects
NASA Astrophysics Data System (ADS)
Seyhan, Emel
The objective of this thesis is to improve the physical understanding of earthquake ground motion characteristics related to source, path and nonlinear site effects and our ability to model those effects with engineering models. Site database work was performed within the context of the NGA-West 2 project. Starting with the site database from original (2008) NGA project (last edited in 2006), we provided site classifications for 2538 new sites and re-classifications of previous sites. The principal site parameter is the time-averaged shear wave velocity in the upper 30 m (Vs30 ), which is characterized using measurements where available, and proxy-based relationships otherwise. We improved the documentation and consistency of site descriptors used as proxies for the estimation of Vs30, developed evidence-based protocols for Vs30 estimation from available proxies, and augmented estimates of various basin depth parameters. Site factors typically have a small-strain site amplification that captures impedance and resonance effects coupled with nonlinear components. Site factors in current NEHRP Provisions are empirically-derived at relatively small ground motion levels and feature simulation-based nonlinearity. We show that current NEHRP site factors have discrepancies with respect to the site terms in the original NGA GMPEs both in the linear site amplification (especially for Classes B, C, D, and E) and the degree of nonlinearity (Classes C and D). We analyzed the NGA-West 2 dataset and simulation-based models for site amplification to develop a new model. The model has linear and nonlinear additive components. The linear component is fully empirical, being derived from worldwide ground motion data (regional effects were examined but found to not be sufficiently important to be included in the model). The model features linear Vs30-scaling in a log-log sense below a corner velocity (Vc), and no Vs30-scaling for velocities faster than Vc. The nonlinear component is
DC magnetic field sensing based on the nonlinear magnetoelectric effect in magnetic heterostructures
NASA Astrophysics Data System (ADS)
Burdin, Dmitrii; Chashin, Dmitrii; Ekonomov, Nikolai; Fetisov, Leonid; Fetisov, Yuri; Shamonin, Mikhail
2016-09-01
Recently, highly sensitive magnetic field sensors using the magnetoelectric effect in composite ferromagnetic-piezoelectric layered structures have been demonstrated. However, most of the proposed concepts are not useful for measuring dc magnetic fields, because the conductivity of piezoelectric layers results in a strong decline of the sensor’s sensitivity at low frequencies. In this paper, a novel functional principle of magnetoelectric sensors for dc magnetic field measurements is described. The sensor employs the nonlinear effect of voltage harmonic generation in a composite magnetoelectric structure under the simultaneous influence of a strong imposed ac magnetic field and a weak dc magnetic field to be measured. This physical effect arises due to the nonlinear dependence of the magnetostriction in the ferromagnetic layer on the magnetic field. A sensor prototype comprising of a piezoelectric fibre transducer sandwiched between two layers of the amorphous ferromagnetic Metglas® alloy was fabricated. The specifications regarding the magnetic field range, frequency characteristics, and noise level were studied experimentally. The prototype showed the responsivity of 2.5 V mT-1 and permitted the measurement of dc magnetic fields in the range of ~10 nT to about 0.4 mT. Although sensor operation is based on the nonlinear effect, the sensor response can be made linear with respect to the measured magnetic field in a broad dynamic range extending over 5 orders of magnitude. The underlying physics is explained through a simplified theory for the proposed sensor. The functionality, differences and advantages of the magnetoelectric sensor compare well with fluxgate magnetometers. The ways to enhance the sensor performance are considered.
DC magnetic field sensing based on the nonlinear magnetoelectric effect in magnetic heterostructures
NASA Astrophysics Data System (ADS)
Burdin, Dmitrii; Chashin, Dmitrii; Ekonomov, Nikolai; Fetisov, Leonid; Fetisov, Yuri; Shamonin, Mikhail
2016-09-01
Recently, highly sensitive magnetic field sensors using the magnetoelectric effect in composite ferromagnetic-piezoelectric layered structures have been demonstrated. However, most of the proposed concepts are not useful for measuring dc magnetic fields, because the conductivity of piezoelectric layers results in a strong decline of the sensor’s sensitivity at low frequencies. In this paper, a novel functional principle of magnetoelectric sensors for dc magnetic field measurements is described. The sensor employs the nonlinear effect of voltage harmonic generation in a composite magnetoelectric structure under the simultaneous influence of a strong imposed ac magnetic field and a weak dc magnetic field to be measured. This physical effect arises due to the nonlinear dependence of the magnetostriction in the ferromagnetic layer on the magnetic field. A sensor prototype comprising of a piezoelectric fibre transducer sandwiched between two layers of the amorphous ferromagnetic Metglas® alloy was fabricated. The specifications regarding the magnetic field range, frequency characteristics, and noise level were studied experimentally. The prototype showed the responsivity of 2.5 V mT‑1 and permitted the measurement of dc magnetic fields in the range of ~10 nT to about 0.4 mT. Although sensor operation is based on the nonlinear effect, the sensor response can be made linear with respect to the measured magnetic field in a broad dynamic range extending over 5 orders of magnitude. The underlying physics is explained through a simplified theory for the proposed sensor. The functionality, differences and advantages of the magnetoelectric sensor compare well with fluxgate magnetometers. The ways to enhance the sensor performance are considered.
NASA Astrophysics Data System (ADS)
Bagarello, F.; Haven, E.
2016-02-01
We discuss a non linear extension of a model of alliances in politics, recently proposed by one of us. The model is constructed in terms of operators, describing the interest of three parties to form, or not, some political alliance with the other parties. The time evolution of what we call the decision functions is deduced by introducing a suitable Hamiltonian, which describes the main effects of the interactions of the parties amongst themselves and with their environments, which are generated by their electors and by people who still have no clear idea for which party to vote (or even if to vote). The Hamiltonian contains some non-linear effects, which takes into account the role of a party in the decision process of the other two parties. Moreover, we show how the same Hamiltonian can also be used to construct a formal structure which can describe the dynamics of buying and selling financial assets (without however implying a specific price setting mechanism).
NASA Astrophysics Data System (ADS)
Han, Liyuan; Yin, Dewu; Xu, Qin; Yang, Xinyu; Gao, Xiaoli; Lu, Xue; Liu, Haitao
2016-11-01
We fabricated a highly transmitted Ag–In2O3/glass nanocomposite material through a sol–gel method plus a controlled gas. Microstructural analysis revealed that the Ag and In elements in the Ag–In2O3 nanostructure exist in two forms: crystalline Ag nanoparticles and non-crystalline In2O3. And the crystalline Ag nanoparticles show the small size, uniform distribution and good dispersion in the glass host, thus triggering the surface plasmon resonance (SPR) effect and the quantum confinement effect. Remarkably, the Ag–In2O3/glass nanocomposite material exhibits the high transmittance greater than 70% in almost the whole visible spectral range. Open-aperture Z-scan technique further showed a typical two-photon absorption effect in the Ag–In2O3/glass nanocomposite material, where the nonlinear absorption coefficient was determined to be ~1.1 × 10‑9 cm W‑1, and interestingly, the normalized transmittance decreased with increasing input fluence. The present results blaze a new path to develop the metal/glass nanocomposite materials with high transmittance, significant nonlinear absorption effects and potential optical limiting behavior. In addition, the mechanism on the nonlinear absorption effects were also discussed in this paper, such as the SPR effect, the quantum confinement effect, the thermal effects, the nonlinear scattering effect and the resonant nonlinear effect.
Density gradient effects in weakly nonlinear ablative Rayleigh-Taylor instability
Wang, L. F.; Ye, W. H.; He, X. T.
2012-01-15
In this research, density gradient effects (i.e., finite thickness of ablation front effects) in ablative Rayleigh-Taylor instability (ARTI), in the presence of preheating within the weakly nonlinear regime, are investigated numerically. We analyze the weak, medium, and strong ablation surfaces which have different isodensity contours, respectively, to study the influences of finite thickness of ablation front on the weakly nonlinear behaviors of ARTI. Linear growth rates, generation coefficients of the second and the third harmonics, and coefficients of the third-order feedback to the fundamental mode are obtained. It is found that the linear growth rate which has a remarkable maximum, is reduced, especially when the perturbation wavelength {lambda} is short and a cut-off perturbation wavelength {lambda}{sub c} appears when the perturbation wavelength {lambda} is sufficiently short, where no higher harmonics exists when {lambda}<{lambda}{sub c}. The phenomenon of third-order positive feedback to the fundamental mode near the {lambda}{sub c}[J. Sanz et al., Phys. Rev. Lett. 89, 195002 (2002); J. Garnier et al., Phys. Rev. Lett. 90, 185003 (2003); J. Garnier and L. Masse, Phys. Plasmas 12, 062707 (2005)] is confirmed in numerical simulations, and the physical mechanism of the third-order positive feedback is qualitatively discussed. Moreover, it is found that generations and growths of the second and the third harmonics are stabilized (suppressed and reduced) by the ablation effect. Meanwhile, the third-order negative feedback to the fundamental mode is also reduced by the ablation effect, and hence, the linear saturation amplitude (typically {approx}0.2{lambda} in our simulations) is increased significantly and therefore exceeds the classical prediction 0.1{lambda}, especially for the strong ablation surface with a small perturbation wavelength. Overall, the ablation effect stabilizes the ARTI in the weakly nonlinear regime. Numerical results obtained are in
De la Cruz, Rolando; Meza, Cristian; Arribas-Gil, Ana; Carroll, Raymond J.
2016-01-01
Joint models for a wide class of response variables and longitudinal measurements consist on a mixed-effects model to fit longitudinal trajectories whose random effects enter as covariates in a generalized linear model for the primary response. They provide a useful way to assess association between these two kinds of data, which in clinical studies are often collected jointly on a series of individuals and may help understanding, for instance, the mechanisms of recovery of a certain disease or the efficacy of a given therapy. When a nonlinear mixed-effects model is used to fit the longitudinal trajectories, the existing estimation strategies based on likelihood approximations have been shown to exhibit some computational efficiency problems (De la Cruz et al., 2011). In this article we consider a Bayesian estimation procedure for the joint model with a nonlinear mixed-effects model for the longitudinal data and a generalized linear model for the primary response. The proposed prior structure allows for the implementation of an MCMC sampler. Moreover, we consider that the errors in the longitudinal model may be correlated. We apply our method to the analysis of hormone levels measured at the early stages of pregnancy that can be used to predict normal versus abnormal pregnancy outcomes. We also conduct a simulation study to assess the importance of modelling correlated errors and quantify the consequences of model misspecification. PMID:27274601
NASA Astrophysics Data System (ADS)
Sun, Young; Shang, Dashan; Chai, Yisheng; Cao, Zexian; Lu, Jun
2015-09-01
From the viewpoint of electric circuit theory, the three fundamental two-terminal passive circuit elements, resistor R , capacitor C, and inductor L, are defined in terms of a relationship between two of the four basic circuit variables, charge q, current i, voltage v, and magnetic flux φ. From a symmetry concern, there should be a fourth fundamental element defined from the relationship between charge q and magnetic flux φ. Here we present both theoretical analysis and experimental evidences to demonstrate that a two-terminal passive device employing the magnetoelectric (ME) effects can exhibit a direct relationship between charge q and magnetic flux φ, and thus is able to act as the fourth fundamental circuit element. The ME effects refer to the induction of electric polarization by a magnetic field or magnetization by an electric field, and have attracted enormous interests due to their promise in many applications. However, no one has linked the ME effects with fundamental circuit theory. Both the linear and nonlinear-memory devices, termed transtor and memtranstor, respectively, have been experimentally realized using multiferroic materials showing strong ME effects. Based on our work, a full map of fundamental two-terminal circuit elements is constructed, which consists of four linear and four nonlinear-memory elements. This full map provides an invaluable guide to developing novel circuit functionalities in the future.
Effects of breathing patterns and light exercise on linear and nonlinear heart rate variability.
Weippert, Matthias; Behrens, Kristin; Rieger, Annika; Kumar, Mohit; Behrens, Martin
2015-08-01
Despite their use in cardiac risk stratification, the physiological meaning of nonlinear heart rate variability (HRV) measures is not well understood. The aim of this study was to elucidate effects of breathing frequency, tidal volume, and light exercise on nonlinear HRV and to determine associations with traditional HRV indices. R-R intervals, blood pressure, minute ventilation, breathing frequency, and respiratory gas concentrations were measured in 24 healthy male volunteers during 7 conditions: voluntary breathing at rest, and metronome guided breathing (0.1, 0.2 and 0.4 Hz) during rest, and cycling, respectively. The effect of physical load was significant for heart rate (HR; p < 0.001) and traditional HRV indices SDNN, RMSSD, lnLFP, and lnHFP (p < 0.01 for all). It approached significance for sample entropy (SampEn) and correlation dimension (D2) (p < 0.1 for both), while HRV detrended fluctuation analysis (DFA) measures DFAα1 and DFAα2 were not affected by load condition. Breathing did not affect HR but affected all traditional HRV measures. D2 was not affected by breathing; DFAα1 was moderately affected by breathing; and DFAα2, approximate entropy (ApEn), and SampEn were strongly affected by breathing. DFAα1 was strongly increased, whereas DFAα2, ApEn, and SampEn were decreased by slow breathing. No interaction effect of load and breathing pattern was evident. Correlations to traditional HRV indices were modest (r from -0.14 to -0.67, p < 0.05 to <0.01). In conclusion, while light exercise does not significantly affect short-time HRV nonlinear indices, respiratory activity has to be considered as a potential contributor at rest and during light dynamic exercise.
Effects of breathing patterns and light exercise on linear and nonlinear heart rate variability.
Weippert, Matthias; Behrens, Kristin; Rieger, Annika; Kumar, Mohit; Behrens, Martin
2015-08-01
Despite their use in cardiac risk stratification, the physiological meaning of nonlinear heart rate variability (HRV) measures is not well understood. The aim of this study was to elucidate effects of breathing frequency, tidal volume, and light exercise on nonlinear HRV and to determine associations with traditional HRV indices. R-R intervals, blood pressure, minute ventilation, breathing frequency, and respiratory gas concentrations were measured in 24 healthy male volunteers during 7 conditions: voluntary breathing at rest, and metronome guided breathing (0.1, 0.2 and 0.4 Hz) during rest, and cycling, respectively. The effect of physical load was significant for heart rate (HR; p < 0.001) and traditional HRV indices SDNN, RMSSD, lnLFP, and lnHFP (p < 0.01 for all). It approached significance for sample entropy (SampEn) and correlation dimension (D2) (p < 0.1 for both), while HRV detrended fluctuation analysis (DFA) measures DFAα1 and DFAα2 were not affected by load condition. Breathing did not affect HR but affected all traditional HRV measures. D2 was not affected by breathing; DFAα1 was moderately affected by breathing; and DFAα2, approximate entropy (ApEn), and SampEn were strongly affected by breathing. DFAα1 was strongly increased, whereas DFAα2, ApEn, and SampEn were decreased by slow breathing. No interaction effect of load and breathing pattern was evident. Correlations to traditional HRV indices were modest (r from -0.14 to -0.67, p < 0.05 to <0.01). In conclusion, while light exercise does not significantly affect short-time HRV nonlinear indices, respiratory activity has to be considered as a potential contributor at rest and during light dynamic exercise. PMID:26187271
NASA Astrophysics Data System (ADS)
Nagaraja, K. K.; Pramodini, S.; Poornesh, P.; Nagaraja, H. S.
2013-02-01
We report on the studies of the effects of annealing on the structural and third-order nonlinear optical properties of ZnO thin films deposited on quartz substrates by the RF magnetron sputtering technique. The films were annealed in the temperature range 400-1000 °C. The third-order nonlinear optical studies were carried out using the z-scan technique under continuous wave (cw) He-Ne laser irradiation at 633 nm wavelength. The effects of annealing on the structural properties were examined using x-ray diffraction and atomic force microscopy (AFM). The (0 0 2) preferred orientation increased with increase in annealing temperature up to 800 °C. The crystalline phases of SiO2 were observed at higher annealing temperatures. The appearance of an extraneous phase was confirmed by AFM images and optical transmittance spectra. The samples exhibited nonlinear absorption and nonlinear refraction under the experimental conditions. The negative sign of the nonlinear refractive index n2 indicated that the films exhibit self-defocusing property due to thermal nonlinearity. The nonlinear refractive index n2, the nonlinear absorption coefficient βeff and the third-order optical susceptibility χ(3) were found to be of the highest orders. The estimated value of third-order optical susceptibility χ(3) was of the order of 10-3 esu. Multiple diffraction rings were observed when the samples were exposed to the laser beam. The appearance of rings was due to the refractive index change and thermal lensing. With increase in laser intensity, the variations of the self-diffraction ring patterns were studied experimentally. The films also exhibited strong optical limiting properties under cw laser excitation, and reverse saturable absorption was the dominant process leading to the observed nonlinear behaviour.
Control of a Bose-Einstein condensate by dissipation: Nonlinear Zeno effect
Shchesnovich, V. S.; Konotop, V. V.
2010-05-15
We show that controlled dissipation can be used as a tool for exploring fundamental phenomena and managing mesoscopic systems of cold atoms and Bose-Einstein condensates. Even the simplest boson-Josephson junction, that is, a Bose-Einstein condensate in a double-well trap, subjected to removal of atoms from one of the two potential minima allows one to observe such phenomena as the suppression of losses and the nonlinear Zeno effect. In such a system the controlled dissipation can be used to create desired macroscopic states and implement controlled switching among different quantum regimes.
Transmutation of skyrmions to half-solitons driven by the nonlinear optical spin Hall effect.
Flayac, H; Solnyshkov, D D; Shelykh, I A; Malpuech, G
2013-01-01
We show that the spin domains, generated in the linear optical spin Hall effect by the analog of spin-orbit interaction for exciton polaritons, are associated with the formation of a Skyrmion lattice. In the nonlinear regime, the spin anisotropy of the polariton-polariton interactions results in a spatial compression of the domains and in a transmutation of the Skyrmions into oblique half-solitons. This phase transition is associated with both the focusing of the spin currents and the emergence of a strongly anisotropic emission pattern.
NASA Astrophysics Data System (ADS)
Gapochka, M. G.; Denisov, M. M.; Denisova, I. P.; Kalenova, N. V.; Korolev, A. F.
2015-11-01
The paper is devoted to mathematical modeling of the nonlinear vacuum electrodynamics effect: the action of the strong magnetic field of a pulsar on the propagation of electromagnetic waves. It is shown that, due to the birefringence of the vacuum, for one normal wave, it takes more time to travel from a pulsar to a detector installed on astrophysical satellites than for the other normal wave. The delay of the pulse carried by the second normal wave relative to pulse carried by the first normal wave from the common point of origin to the satellite is calculated.
The effect of Coulomb interactions on nonlinear thermovoltage and thermocurrent in quantum dots
Zimbovskaya, Natalya A.
2015-06-28
In the present work, we theoretically study the nonlinear regime of charge transport through a quantum dot coupled to the source and drain reservoirs. The investigation is carried out using a nonequilibrium Green’s function formalism beyond the Hartree-Fock approximation. Employed approximations for the relevant Green’s functions allow to trace a transition from Coulomb blockade regime to Kondo regime in the thermoelectric transport. Effects arising when electrons move in response to thermal gradient applied across the system are discussed, including experimentally observed thermovoltage zeros.
FEA study of non-linear effect of coupling media to Sonic infrared imaging
NASA Astrophysics Data System (ADS)
Song, Yuyang; Han, Xiaoyan
2015-03-01
Sonic Infrared (IR) imaging technique is a promising NDE technology to find cracks through thermography analysis of vibration-induced crack heating. In Sonic IR, coupling materials are usually engaged between an ultrasound transducer and a sample. It was discovered by the authors that coupling materials actually has strong nonlinear effect to the vibration and the temperature increase in cracks in the target. In this paper, we will present our research results using a 3-D finite element analysis. The predicted results are used for validation of the experimental results as well. The site to site comparison between experiment and FEA analysis is laid out in this paper.
NASA Astrophysics Data System (ADS)
Wang, Jun; Lim, Teik C.; Li, Mingfeng
2007-11-01
A generalized nonlinear time-varying (NLTV) dynamic model of a hypoid gear pair with backlash nonlinearity is formulated which is also applicable to spur, helical, spiral bevel and worm gears. Firstly, the fundamental harmonic form of time-varying mesh parameters is used to study the effects of mesh parameter variations on the dynamic response, and the interactions between them and backlash nonlinearity. The analysis also examines the effects of mean load and mesh damping. Secondly, based on a three-dimensional quasi-static tooth contact analysis, a new significantly more exact time-varying mesh model is proposed, which describes the true mesh characteristics of hypoid gear pairs. The enhanced time-varying mesh model is applied to perform further dynamic analysis. Computational results reveal numerous interesting nonlinear characteristics, such as jump discontinuities, sub-harmonic and chaotic behaviors, especially for lightly loaded and lightly damped cases.
THE EFFECT OF NONLINEAR LANDAU DAMPING ON ULTRARELATIVISTIC BEAM PLASMA INSTABILITIES
Chang, Philip; Lamberts, Astrid; Broderick, Avery E.; Shalaby, Mohamad; Pfrommer, Christoph; Puchwein, Ewald
2014-12-20
Very high energy gamma-rays from extragalactic sources produce pairs from the extragalactic background light, yielding an electron-positron pair beam. This pair beam is unstable to various plasma instabilities, especially the ''oblique'' instability, which can be the dominant cooling mechanism for the beam. However, recently, it has been claimed that nonlinear Landau damping renders it physically irrelevant by reducing the effective damping rate to a low level. Here we show with numerical calculations that the effective damping rate is 8 × 10{sup –4} the growth rate of the linear instability, which is sufficient for the ''oblique'' instability to be the dominant cooling mechanism of these pair beams. In particular, we show that previous estimates of this rate ignored the exponential cutoff in the scattering amplitude at large wave numbers and assumed that the damping of scattered waves entirely depends on collisions, ignoring collisionless processes. We find that the total wave energy eventually grows to approximate equipartition with the beam by increasingly depositing energy into long-wavelength modes. As we have not included the effect of nonlinear wave-wave interactions on these long-wavelength modes, this scenario represents the ''worst case'' scenario for the oblique instability. As it continues to drain energy from the beam at a faster rate than other processes, we conclude that the ''oblique'' instability is sufficiently strong to make it the physically dominant cooling mechanism for high-energy pair beams in the intergalactic medium.
ERIC Educational Resources Information Center
de Wolf, Inge F.; Janssens, Frans J. G.
2007-01-01
This paper presents an overview of studies into effects and side effects of control mechanisms in education. We focus on effects and side effects of inspection visits and public performance indicators. A first conclusion is that the studies do not provide us with a clear answer to the question of whether inspections have positive causal effects on…
A recency-based account of the list length effect in free recall.
Ward, Geoff
2002-09-01
Free recall was examined using the overt rehearsal methodology with lists of 10, 20, and 30 words. The standard list length effects were obtained: As list length increased, there was an increase in the number and a decrease in the proportion of words that were recalled. There were significant primacy and recency effects with all list lengths. However, when the data were replotted in terms of when the words were last rehearsed, recall was characterized by extended recency effects, and the data from the different list lengths were superimposed upon one another. These findings support a recency-based account of episodic memory. The list length effect reflects the facts that unrehearsed words are less recent with longer lists, and that with longer lists, a reduced proportion of primacy and middle items may be rehearsed to later positions.
Naimi, Ashley I.; Richardson, David B.; Cole, Stephen R.
2013-01-01
In a recent issue of the Journal, Kirkeleit et al. (Am J Epidemiol. 2013;177(11):1218–1224) provided empirical evidence for the potential of the healthy worker effect in a large cohort of Norwegian workers across a range of occupations. In this commentary, we provide some historical context, define the healthy worker effect by using causal diagrams, and use simulated data to illustrate how structural nested models can be used to estimate exposure effects while accounting for the healthy worker survivor effect in 4 simple steps. We provide technical details and annotated SAS software (SAS Institute, Inc., Cary, North Carolina) code corresponding to the example analysis in the Web Appendices, available at http://aje.oxfordjournals.org/. PMID:24077092
Veronese, Mattia; Gunn, Roger N; Zamuner, Stefano; Bertoldo, Alessandra
2013-02-01
Quantitative PET studies with arterial blood sampling usually require the correction of the measured total plasma activity for the presence of metabolites. In particular, if labelled metabolites are found in the plasma in significant amounts their presence has to be accounted for, because it is the concentration of the parent tracer which is required for data quantification. This is achieved by fitting a Parent Plasma fraction (PPf) model to discrete metabolite measurements. The commonly used method is based on an individual approach, i.e. for each subject the PPf model parameters are estimated from its own metabolite samples, which are, in general, sparse and noisy. This fact can compromise the quality of the reconstructed arterial input functions, and, consequently, affect the quantification of tissue kinetic parameters. In this study, we proposed a Non-Linear Mixed Effect Modelling (NLMEM) approach to describe metabolite kinetics. Since NLMEM has been developed to provide robust parameter estimates in the case of sparse and/or noisy data, it has the potential to be a reliable method for plasma metabolite correction. Three different PET datasets were considered: [11C]-(+)-PHNO (54 scans), [11C]-PIB (22 scans) and [11C]-DASB (30 scans). For each tracer both simulated and measured data were considered and NLMEM performance was compared with that provided by individual analysis. Results showed that NLMEM provided improved estimates of the plasma parent input function over the individual approach when the metabolite data were sparse or contained outliers.
NASA Astrophysics Data System (ADS)
Olmez, O.; Ozbulut, M.; Yildiz, M.; Goren, O.
2016-06-01
The present study investigates the vortical and nonlinear effects in the roll motion of a 2-D body with square cross-sections by using Smoothed Particle Hydrodynamics (SPH). A 2-D rigid body with square cross-section is taken into account for the benchmark study and subjected to the oscillatory roll motion with a given angular frequency. The governing equations are continuity equation and Euler's equation with artificial viscosity term. Weakly Compressible SPH (WCSPH) scheme is employed for the discretization of the governing equations. Velocities of the fluid particles are updated by means of XSPH+Artificial Particle Displacement (VXSPH+APD) algorithm. In this method only the free surface fluid particles are subjected to VXSPH algorithm while the APD algorithm is employed for the fully populated flow regions. The hybrid usage of numerical treatment keeps free surface particles together by creating an artificial surface tension on the free surface. VXSPH+APD is a proven numerical treatment to provide the most accurate results for this type of free surface flows (Ozbulut et al. 2014). The results of the present study are compared with those of the experimental studies as well as with those of the numerical methods obtained from the current literature.
Thorvaldsson, Valgeir; Skoog, Ingmar; Hofer, Scott M; Börjesson-Hanson, Anne; Ostling, Svante; Sacuiu, Simona; Johansson, Boo
2012-06-01
Midlife hypertension is associated with increased risk of cognitive impairment in later life. The association between blood pressure (BP) in older ages and cognition is less clear. In this study we provide estimates of between-person and within-person associations of BP and cognition in a population-based sample (N = 382) followed from age 70 across 12 occasions over 30 years. Between-person associations refer to how individual differences in BP relates to individual differences in cognition. Within-person associations refer to how individual and time specific changes in BP relate to variation in cognition. Hierarchical linear models were fitted to data from three cognitive measurements (verbal ability, spatial ability, and perceptual speed) while accounting for demographic and health-related covariates. We found consistent nonlinear between-person associations between diastolic BP (DBP) and cognition, such that both low (<75 mmHg) and high (>95 mmHg) pressure were associated with poorer cognition. Within-person decreases in systolic BP (SBP) and DBP were associated with decreases in perceptual speed. Notably, between-person and within-person estimates did not reveal similar associations, suggesting the need to separate the two effects in the analysis of associations between BP and cognition in old age.
Simulating the effect of non-linear mode coupling in cosmological parameter estimation
NASA Astrophysics Data System (ADS)
Kiessling, A.; Taylor, A. N.; Heavens, A. F.
2011-09-01
Fisher Information Matrix methods are commonly used in cosmology to estimate the accuracy that cosmological parameters can be measured with a given experiment and to optimize the design of experiments. However, the standard approach usually assumes both data and parameter estimates are Gaussian-distributed. Further, for survey forecasts and optimization it is usually assumed that the power-spectrum covariance matrix is diagonal in Fourier space. However, in the low-redshift Universe, non-linear mode coupling will tend to correlate small-scale power, moving information from lower to higher order moments of the field. This movement of information will change the predictions of cosmological parameter accuracy. In this paper we quantify this loss of information by comparing naïve Gaussian Fisher matrix forecasts with a maximum likelihood parameter estimation analysis of a suite of mock weak lensing catalogues derived from N-body simulations, based on the SUNGLASS pipeline, for a 2D and tomographic shear analysis of a Euclid-like survey. In both cases, we find that the 68 per cent confidence area of the Ωm-σ8 plane increases by a factor of 5. However, the marginal errors increase by just 20-40 per cent. We propose a new method to model the effects of non-linear shear-power mode coupling in the Fisher matrix by approximating the shear-power distribution as a multivariate Gaussian with a covariance matrix derived from the mock weak lensing survey. We find that this approximation can reproduce the 68 per cent confidence regions of the full maximum likelihood analysis in the Ωm-σ8 plane to high accuracy for both 2D and tomographic weak lensing surveys. Finally, we perform a multiparameter analysis of Ωm, σ8, h, ns, w0 and wa to compare the Gaussian and non-linear mode-coupled Fisher matrix contours. The 6D volume of the 1σ error contours for the non-linear Fisher analysis is a factor of 3 larger than for the Gaussian case, and the shape of the 68 per cent confidence
Lima, Mauricio; Ernest, S K Morgan; Brown, James H; Belgrano, Andrea; Stenseth, Nils C
2008-09-01
Using long-term data on two kangaroo rats in the Chihuahuan Desert of North America, we fitted logistic models including the exogenous effects of seasonal rainfall patterns. Our aim was to test the effects of intraspecific interactions and seasonal rainfall in explaining and predicting the numerical fluctuations of these two kangaroo rats. We found that logistic models fit both data sets quite well; Dipodomys merriami showed lower maximum per capita growth rates than Dipodomys ordii, and in both cases logistic models were nonlinear. Summer rainfall appears to be the most important exogenous effect for both rodent populations; models including this variable were able to predict independent data better than models including winter rainfall. D. merriami was also negatively affected by another kangaroo rat (Dipodomys spectabilis), consistent with previous experimental evidence. We hypothesized that summer rainfall influences the carrying capacity of the environment by affecting seed availability and the intensity of intraspecific competition.
Effects of nonlinear sound propagation on the characteristic timbres of brass instruments.
Myers, Arnold; Pyle, Robert W; Gilbert, Joël; Campbell, D Murray; Chick, John P; Logie, Shona
2012-01-01
The capacity of a brass instrument to generate sounds with strong high-frequency components is dependent on the extent to which its bore profile supports nonlinear sound propagation. At high dynamic levels some instruments are readily sounded in a "cuivré" (brassy) manner: this phenomenon is due to the nonlinear propagation of sound in ducts of the proportions typical of labrosones (lip-reed aerophones). The effect is also evident at lower dynamic levels and contributes to the overall tonal character of the various kinds of brass instrument. This paper defines a brassiness potential parameter derived from the bore geometries of brass instruments. The correlation of the brassiness potential parameter with spectral enrichment as measured by the spectral centroid of the radiated sound is examined in playing tests using musicians, experiments using sine-wave excitation of instruments, and simulations using a computational tool. The complementary effects of absolute bore size on spectral enrichment are investigated using sine-wave excitation of cylindrical tubes and of instruments, establishing the existence of a trade-off between bore size and brassiness potential. The utility of the brassiness potential parameter in characterizing labrosones is established, and the graphical presentation of results in a 2D space defined by bore size and brassiness potential demonstrated. PMID:22280689
Nonlinear effect of elastic vortexlike motion on the dynamic stress state of solids.
Shilko, Evgeny V; Grinyaev, Yurii V; Popov, Mikhail V; Popov, Valentin L; Psakhie, Sergey G
2016-05-01
We present a theoretical analysis of the dynamic stress-strain state of regions in a solid body that are involved in a collective elastic vortexlike motion. It is shown that the initiation of elastic vortexlike motion in the material is accompanied by the appearance of dilatancy and equivalent strain, the magnitudes of which are proportional to the square of the ratio of linear velocity on the periphery of the elastic vortex to the velocity of longitudinal elastic waves (P wave). Under conditions of dynamic loading the described dynamic effects are able to initiate inelastic deformation or destruction of the material at loading speeds of a few percent of the P-wave speed. The obtained analytical estimates suggest that dynamic nonlinear strains can make a significant contribution in a number of widely studied nonlinear dynamic phenomena in solids. Among them are the effect of acoustic (dynamic) dilatancy in solids and granular media, which leads to the generation of longitudinal elastic waves by transverse waves [V. Tournat et al., Phys. Rev. Lett. 92, 085502 (2004)10.1103/PhysRevLett.92.085502] and the formation of an array of intense "hot spots" (reminiscent of shear-induced hydrodynamic instabilities in fluids) in adiabatic shear bands [P. R. Guduru et al., Phys. Rev. E 64, 036128 (2001)10.1103/PhysRevE.64.036128]. PMID:27300971
Non-Linear Oscillation in Ionic Current Due to Size Effect in Glass Nanopipette
NASA Astrophysics Data System (ADS)
Takami, Tomohide; Deng, Xiao Long; Son, Jong Wan; Kang, Eun Ji; Kawai, Tomoji; Park, Bae Ho
2012-11-01
We studied the size effect of the ionic current in glass pipette, and found an interesting 2.7 mHz oscillation at 50 nm. In this study, we would like to discuss the mechanism of the non-linear oscillation. Cation-rich layer with its Debye length λ exists in nanopipette, and its conductivity σd is lower than that in the central bulk layer σb in this study. The pressure difference ΔP = ΔcRT where Δc is the difference in concentrations between in and out of the pipette. Then, the ionic current I can be estimated by using Hagen-Poiseuille equation; I =π/8 η ΔcRT/l {σdr4 + (σb -σd) (λ - r) 2 (r2 + 2 rλ -λ2) } . (r : inner radius, l: pipette length, η: viscosity) The last term indicates the non-linear oscillation. Moreover, we roughly estimated λ = 2.08 ×(2r) 1 / 2. Then, the bulk layer appears appropriately when 2 r 50 nm, which causes the effective ionic current oscillation. This work was supported by KOSEF NRL Program grant funded by the Korea Government MEST (Grant No. 2010-0024525 and R0A-2008-000-20052-0), and WCU Program through the KOSEF funded by the MEST (Grant No. R31-2008-000-10057-0).
NASA Technical Reports Server (NTRS)
Callegari, A. J.
1979-01-01
A nonlinear theory for sound propagation in variable area ducts carrying a nearly sonic flow is presented. Linear acoustic theory is shown to be singular and the detailed nature of the singularity is used to develop the correct nonlinear theory. The theory is based on a quasi-one dimensional model. It is derived by the method of matched asymptotic expansions. In a nearly chocked flow, the theory indicates the following processes to be acting: a transonic trapping of upstream propagating sound causing an intensification of this sound in the throat region of the duct; generation of superharmonics and an acoustic streaming effect; development of shocks in the acoustic quantities near the throat. Several specific problems are solved analytically and numerical parameter studies are carried out. Results indicate that appreciable acoustic power is shifted to higher harmonics as shocked conditions are approached. The effect of the throat Mach number on the attenuation of upstream propagating sound excited by a fixed source is also determined.
Nonlinear effect of elastic vortexlike motion on the dynamic stress state of solids.
Shilko, Evgeny V; Grinyaev, Yurii V; Popov, Mikhail V; Popov, Valentin L; Psakhie, Sergey G
2016-05-01
We present a theoretical analysis of the dynamic stress-strain state of regions in a solid body that are involved in a collective elastic vortexlike motion. It is shown that the initiation of elastic vortexlike motion in the material is accompanied by the appearance of dilatancy and equivalent strain, the magnitudes of which are proportional to the square of the ratio of linear velocity on the periphery of the elastic vortex to the velocity of longitudinal elastic waves (P wave). Under conditions of dynamic loading the described dynamic effects are able to initiate inelastic deformation or destruction of the material at loading speeds of a few percent of the P-wave speed. The obtained analytical estimates suggest that dynamic nonlinear strains can make a significant contribution in a number of widely studied nonlinear dynamic phenomena in solids. Among them are the effect of acoustic (dynamic) dilatancy in solids and granular media, which leads to the generation of longitudinal elastic waves by transverse waves [V. Tournat et al., Phys. Rev. Lett. 92, 085502 (2004)10.1103/PhysRevLett.92.085502] and the formation of an array of intense "hot spots" (reminiscent of shear-induced hydrodynamic instabilities in fluids) in adiabatic shear bands [P. R. Guduru et al., Phys. Rev. E 64, 036128 (2001)10.1103/PhysRevE.64.036128].
Raman-free nonlinear optical effects in high pressure gas-filled hollow core PCF.
Azhar, M; Wong, G K L; Chang, W; Joly, N Y; Russell, P St J
2013-02-25
The effective Kerr nonlinearity of hollow-core kagomé-style photonic crystal fiber (PCF) filled with argon gas increases to ~15% of that of bulk silica glass when the pressure is increased from 1 to 150 bar, while the zero dispersion wavelength shifts from 300 to 900 nm. The group velocity dispersion of the system is uniquely pressure-tunable over a wide range while avoiding Raman scattering-absent in noble gases-and having an extremely high optical damage threshold. As a result, detailed and well-controlled studies of nonlinear effects can be performed, in both normal and anomalous dispersion regimes, using only a fixed-frequency pump laser. For example, the absence of Raman scattering permits clean observation, at high powers, of the interaction between a modulational instability side-band and a soliton-created dispersive wave. Excellent agreement is obtained between numerical simulations and experimental results. The system has great potential for the realization of reconfigurable supercontinuum sources, wavelength convertors and short-pulse laser systems.
Devi, Anita; De, Arijit K
2016-09-19
The use of low-power high-repetition-rate ultrafast pulsed excitation in stable optical trapping of dielectric nanoparticles has been demonstrated in the recent past; the high peak power of each pulse leads to instantaneous trapping of a nanoparticle with fast inertial response and the high repetition-rate ensures repetitive trapping by successive pulses However, with such high peak power pulsed excitation under a tight focusing condition, nonlinear optical effects on trapping efficiency also become significant and cannot be ignored. Thus, in addition to the above mentioned repetitive instantaneous trapping, trapping efficiency under pulsed excitation is also influenced by the optical Kerr effect, which we theoretically investigate here. Using dipole approximation we show that with an increase in laser power the radial component of the trapping potential becomes progressively more stable but the axial component is dramatically modulated due to increased Kerr nonlinearity. We justify that the relevant parameter to quantify the trapping efficiency is not the absolute depth of the highly asymmetric axial trapping potential but the height of the potential barrier along the beam propagation direction. We also discuss the optimal excitation parameters leading to the most stable dipole trap. Our results show excellent agreement with previous experiments.
Devi, Anita; De, Arijit K
2016-09-19
The use of low-power high-repetition-rate ultrafast pulsed excitation in stable optical trapping of dielectric nanoparticles has been demonstrated in the recent past; the high peak power of each pulse leads to instantaneous trapping of a nanoparticle with fast inertial response and the high repetition-rate ensures repetitive trapping by successive pulses However, with such high peak power pulsed excitation under a tight focusing condition, nonlinear optical effects on trapping efficiency also become significant and cannot be ignored. Thus, in addition to the above mentioned repetitive instantaneous trapping, trapping efficiency under pulsed excitation is also influenced by the optical Kerr effect, which we theoretically investigate here. Using dipole approximation we show that with an increase in laser power the radial component of the trapping potential becomes progressively more stable but the axial component is dramatically modulated due to increased Kerr nonlinearity. We justify that the relevant parameter to quantify the trapping efficiency is not the absolute depth of the highly asymmetric axial trapping potential but the height of the potential barrier along the beam propagation direction. We also discuss the optimal excitation parameters leading to the most stable dipole trap. Our results show excellent agreement with previous experiments. PMID:27661888
Nonlinear effect of elastic vortexlike motion on the dynamic stress state of solids
NASA Astrophysics Data System (ADS)
Shilko, Evgeny V.; Grinyaev, Yurii V.; Popov, Mikhail V.; Popov, Valentin L.; Psakhie, Sergey G.
2016-05-01
We present a theoretical analysis of the dynamic stress-strain state of regions in a solid body that are involved in a collective elastic vortexlike motion. It is shown that the initiation of elastic vortexlike motion in the material is accompanied by the appearance of dilatancy and equivalent strain, the magnitudes of which are proportional to the square of the ratio of linear velocity on the periphery of the elastic vortex to the velocity of longitudinal elastic waves (P wave). Under conditions of dynamic loading the described dynamic effects are able to initiate inelastic deformation or destruction of the material at loading speeds of a few percent of the P -wave speed. The obtained analytical estimates suggest that dynamic nonlinear strains can make a significant contribution in a number of widely studied nonlinear dynamic phenomena in solids. Among them are the effect of acoustic (dynamic) dilatancy in solids and granular media, which leads to the generation of longitudinal elastic waves by transverse waves [V. Tournat et al., Phys. Rev. Lett. 92, 085502 (2004), 10.1103/PhysRevLett.92.085502] and the formation of an array of intense "hot spots" (reminiscent of shear-induced hydrodynamic instabilities in fluids) in adiabatic shear bands [P. R. Guduru et al., Phys. Rev. E 64, 036128 (2001), 10.1103/PhysRevE.64.036128].
Effects of nonlinear sound propagation on the characteristic timbres of brass instruments.
Myers, Arnold; Pyle, Robert W; Gilbert, Joël; Campbell, D Murray; Chick, John P; Logie, Shona
2012-01-01
The capacity of a brass instrument to generate sounds with strong high-frequency components is dependent on the extent to which its bore profile supports nonlinear sound propagation. At high dynamic levels some instruments are readily sounded in a "cuivré" (brassy) manner: this phenomenon is due to the nonlinear propagation of sound in ducts of the proportions typical of labrosones (lip-reed aerophones). The effect is also evident at lower dynamic levels and contributes to the overall tonal character of the various kinds of brass instrument. This paper defines a brassiness potential parameter derived from the bore geometries of brass instruments. The correlation of the brassiness potential parameter with spectral enrichment as measured by the spectral centroid of the radiated sound is examined in playing tests using musicians, experiments using sine-wave excitation of instruments, and simulations using a computational tool. The complementary effects of absolute bore size on spectral enrichment are investigated using sine-wave excitation of cylindrical tubes and of instruments, establishing the existence of a trade-off between bore size and brassiness potential. The utility of the brassiness potential parameter in characterizing labrosones is established, and the graphical presentation of results in a 2D space defined by bore size and brassiness potential demonstrated.
NASA Astrophysics Data System (ADS)
Wei, Nijun; Coffey, William T.; Déjardin, Pirre-Michel; Kalmykov, Yuri P.
External dc bias field effects on the nonlinear dielectric relaxation and dynamic Kerr effect of a system of permanent dipoles in a uniaxial mean field potential are studied via the rotational Brownian motion model. Postulated in terms of the infinite hierarchy of differential-recurrence equations for the statistical moments (the expectation value of the Legendre polynomials), the dielectric and Kerr effect ac stationary responses may be evaluated for arbitrary dc bias field strength via perturbation theory in the ac field. We have given two complementary approaches for treating the nonlinear effects. The first is based on perturbation theory allowing one to calculate the nonlinear ac stationary responses using powerful matrix methods. The second approach based on the accurate two-mode approximation [D.A. Garanin, Phys. Rev. E. 54, 3250 (1996)] effectively generalizes the existing results for dipolar systems in superimposed ac and dc fields to a mean field potential. The results apply both to nonlinear dielectric relaxation and dynamic Kerr effect of nematics and to magnetic birefringence relaxation of ferrofluids. Furthermore, the given methods of the solution of infinite hierarchies of multi-term recurrence relations are quite general and can be applied to analogous nonlinear response problems.
The Effect of Moral Intensity on Ethical Decision Making in Accounting
ERIC Educational Resources Information Center
Yang, Hui-Ling; Wu, Wei-Pang
2009-01-01
The purpose of this study was to examine the dimensionality of a moral intensity construct in four ethical accounting scenarios and how the dimensions directly affect the specific processes of moral decision making of accounting students. A survey was conducted with 233 accounting students enrolled in the school of accounting in a university of…
Diependaele, Kevin; Lemhöfer, Kristin; Brysbaert, Marc
2013-01-01
We investigate the origin of differences in the word frequency effect between native speakers and second-language speakers. In a large-scale analysis of English word identification times we find that group-level differences are fully accounted for by the individual language proficiency scores. Furthermore, exactly the same quantitative relation between word frequency and proficiency is found for monolinguals and three different bilingual populations (Dutch-English, French-English, and German-English). We conclude that the larger frequency effects for second-language processing than for native-language processing can be explained by within-language characteristics and thus need not be the consequence of "being bilingual" (i.e., a qualitative difference). More specifically, we argue that language proficiency increases lexical entrenchment, which leads to a reduced frequency effect, irrespective of bilingualism, language dominance, and language similarity.
Riès, Stephanie K; Fraser, Douglas; McMahon, Katie L; de Zubicaray, Greig I
2015-10-01
The "distractor-frequency effect" refers to the finding that high-frequency (HF) distractor words slow picture naming less than low-frequency distractors in the picture-word interference paradigm. Rival input and output accounts of this effect have been proposed. The former attributes the effect to attentional selection mechanisms operating during distractor recognition, whereas the latter attributes it to monitoring/decision mechanisms operating on distractor and target responses in an articulatory buffer. Using high-density (128-channel) EEG, we tested hypotheses from these rival accounts. In addition to conducting stimulus- and response-locked whole-brain corrected analyses, we investigated the correct-related negativity, an ERP observed on correct trials at fronto-central electrodes proposed to reflect the involvement of domain general monitoring. The whole-brain ERP analysis revealed a significant effect of distractor frequency at inferior right frontal and temporal sites between 100 and 300-msec post-stimulus onset, during which lexical access is thought to occur. Response-locked, region of interest (ROI) analyses of fronto-central electrodes revealed a correct-related negativity starting 121 msec before and peaking 125 msec after vocal onset on the grand averages. Slope analysis of this component revealed a significant difference between HF and low-frequency distractor words, with the former associated with a steeper slope on the time window spanning from 100 msec before to 100 msec after vocal onset. The finding of ERP effects in time windows and components corresponding to both lexical processing and monitoring suggests the distractor frequency effect is most likely associated with more than one physiological mechanism.
Huang, Cheng-Hsuan; Cheng, Wen-Li; He, Yan-Ying; Lee, Eric
2010-08-12
Electrophoresis of a soft particle along the centerline of a cylindrical pore is investigated theoretically in this study. The soft particle consists of an inner hard sphere covered by a concentric porous layer with fixed charge uniformly distributed in it. The polarization effect, the deformation of ion clouds surrounding the particle due to convection flow, is taken into account properly by adopting the full nonlinear Poisson-Boltzmann equation. The study reveals that recent investigation in the literature without consideration of the polarization effect could severely overestimate the particle mobility up to nearly two times if the fixed charge in the porous layer is high. The boundary effect in terms of the reduction of particle mobility is very significant when the double layer is thick and diminishes as it gets very thin. The effect of the highly charged cylindrical wall is analyzed, in particular, among other factors of electrokinetic interest. The presence of the cylindrical wall retards the particle motion in general, as compared with an isolated particle. With the generation of an electroosmotic flow, however, the charged wall can either enhance the particle motion or deter it, depending on the surface potential on the wall and the double-layer thickness. The thinner the double layer, the more significant the influence of the osmotic flow on the particle motion in general. The direction of particle motion may even change twice as the reciprocal of the double-layer thickness increases when both the wall and the particle are highly charged. This is due to the competition between the electric driving force of the charged particle and the hydrodynamic retarding force from the background electroosmotic flow. This has direct impact in practical applications of nanofluidics when a weak electric field is applied. Conducting operations near these critical double-layer thicknesses should be avoided in practice.
El Nady, K; Ganghoffer, J F
2016-05-01
The asymptotic homogenization technique is involved to derive the effective elastic response of biological membranes viewed as repetitive beam networks. Thereby, a systematic methodology is established, allowing the prediction of the overall mechanical properties of biological membranes in the nonlinear regime, reflecting the influence of the geometrical and mechanical micro-parameters of the network structure on the overall response of the equivalent continuum. Biomembranes networks are classified based on nodal connectivity, so that we analyze in this work 3, 4 and 6-connectivity networks, which are representative of most biological networks. The individual filaments of the network are described as undulated beams prone to entropic elasticity, with tensile moduli determined from their persistence length. The effective micropolar continuum evaluated as a continuum substitute of the biological network has a kinematics reflecting the discrete network deformation modes, involving a nodal displacement and a microrotation. The statics involves the classical Cauchy stress and internal moments encapsulated into couple stresses, which develop internal work in duality to microcurvatures reflecting local network undulations. The relative ratio of the characteristic bending length of the effective micropolar continuum to the unit cell size determines the relevant choice of the equivalent medium. In most cases, the Cauchy continuum is sufficient to model biomembranes. The peptidoglycan network may exhibit a re-entrant hexagonal configuration due to thermal or pressure fluctuations, for which micropolar effects become important. The homogenized responses are in good agreement with FE simulations performed over the whole network. The predictive nature of the employed homogenization technique allows the identification of a strain energy density of a hyperelastic model, for the purpose of performing structural calculations of the shape evolutions of biomembranes.
El Nady, K; Ganghoffer, J F
2016-05-01
The asymptotic homogenization technique is involved to derive the effective elastic response of biological membranes viewed as repetitive beam networks. Thereby, a systematic methodology is established, allowing the prediction of the overall mechanical properties of biological membranes in the nonlinear regime, reflecting the influence of the geometrical and mechanical micro-parameters of the network structure on the overall response of the equivalent continuum. Biomembranes networks are classified based on nodal connectivity, so that we analyze in this work 3, 4 and 6-connectivity networks, which are representative of most biological networks. The individual filaments of the network are described as undulated beams prone to entropic elasticity, with tensile moduli determined from their persistence length. The effective micropolar continuum evaluated as a continuum substitute of the biological network has a kinematics reflecting the discrete network deformation modes, involving a nodal displacement and a microrotation. The statics involves the classical Cauchy stress and internal moments encapsulated into couple stresses, which develop internal work in duality to microcurvatures reflecting local network undulations. The relative ratio of the characteristic bending length of the effective micropolar continuum to the unit cell size determines the relevant choice of the equivalent medium. In most cases, the Cauchy continuum is sufficient to model biomembranes. The peptidoglycan network may exhibit a re-entrant hexagonal configuration due to thermal or pressure fluctuations, for which micropolar effects become important. The homogenized responses are in good agreement with FE simulations performed over the whole network. The predictive nature of the employed homogenization technique allows the identification of a strain energy density of a hyperelastic model, for the purpose of performing structural calculations of the shape evolutions of biomembranes. PMID:26541071
Holmgren, Milena; Gómez-Aparicio, Lorena; Quero, José Luis; Valladares, Fernando
2012-06-01
The combined effects of shade and drought on plant performance and the implications for species interactions are highly debated in plant ecology. Empirical evidence for positive and negative effects of shade on the performance of plants under dry conditions supports two contrasting theoretical models about the role of shade under dry conditions: the trade-off and the facilitation hypotheses. We performed a meta-analysis of field and greenhouse studies evaluating the effects of drought at two or more irradiance levels on nine response variables describing plant physiological condition, growth, and survival. We explored differences in plant response across plant functional types, ecosystem types and methodological approaches. The data were best fit using quadratic models indicating a humped-back shape response to drought along an irradiance gradient for survival, whole plant biomass, maximum photosynthetic capacity, stomatal conductance and maximal photochemical efficiency. Drought effects were ameliorated at intermediate irradiance, becoming more severe at higher or lower light levels. This general pattern was maintained when controlling for potential variations in the strength of the drought treatment among light levels. Our quantitative meta-analysis indicates that dense shade ameliorates drought especially among drought-intolerant and shade-tolerant species. Wet tropical species showed larger negative effects of drought with increasing irradiance than semiarid and cold temperate species. Non-linear responses to irradiance were stronger under field conditions than under controlled greenhouse conditions. Non-linear responses to drought along the irradiance gradient reconciliate opposing views in plant ecology, indicating that facilitation is more likely within certain range of environmental conditions, fading under deep shade, especially for drought-tolerant species. PMID:22083284
Liu, W. H.; He, X. T.; Yu, C. P.
2012-07-15
When an incident shock collides with a corrugated interface separating two fluids of different densities, the interface is prone to Richtmyer-Meshkov instability (RMI). Based on the formal perturbation expansion method as well as the potential flow theory, we present a simple method to investigate the cylindrical effects in weakly nonlinear RMI with the transmitted and reflected cylindrical shocks by considering the nonlinear corrections up to fourth order. The cylindrical results associated with the material interface show that the interface expression consists of two parts: the result in the planar system and that from the cylindrical effects. In the limit of the cylindrical radius tending to infinity, the cylindrical results can be reduced to those in the planar system. Our explicit results show that the cylindrical effects exert an inward velocity on the whole perturbed interface, regardless of bubbles or spikes of the interface. On the one hand, outgoing bubbles are constrained and ingoing spikes are accelerated for different Atwood numbers (A) and mode numbers k'. On the other hand, for ingoing bubbles, when |A|k'{sup 3/2} Less-Than-Or-Equivalent-To 1, bubbles are considerably accelerated especially at the small |A| and k'; otherwise, bubbles are decelerated. For outgoing spikes, when |A|k' Greater-Than-Or-Equivalent-To 1, spikes are dramatically accelerated especially at large |A| and k'; otherwise, spikes are decelerated. Furthermore, the cylindrical effects have a significant influence on the amplitudes of the ingoing spike and bubble for large k'. Thus, it should be included in applications where the cylindrical effects play a role, such as inertial confinement fusion ignition target design.
Santiago, Julio; Lakens, Daniël
2015-03-01
Conceptual congruency effects have been interpreted as evidence for the idea that the representations of abstract conceptual dimensions (e.g., power, affective valence, time, number, importance) rest on more concrete dimensions (e.g., space, brightness, weight). However, an alternative theoretical explanation based on the notion of polarity correspondence has recently received empirical support in the domains of valence and morality, which are related to vertical space (e.g., good things are up). In the present study we provide empirical arguments against the applicability of the polarity correspondence account to congruency effects in two conceptual domains related to lateral space: number and time. Following earlier research, we varied the polarity of the response dimension (left-right) by manipulating keyboard eccentricity. In a first experiment we successfully replicated the congruency effect between vertical and lateral space and its interaction with response eccentricity. We then examined whether this modulation of a concrete-concrete congruency effect can be extended to two types of concrete-abstract effects, those between left-right space and number (in both parity and magnitude judgment tasks), and temporal reference. In all three tasks response eccentricity failed to modulate the congruency effects. We conclude that polarity correspondence does not provide an adequate explanation of conceptual congruency effects in the domains of number and time.
ACCOUNTING FOR CALIBRATION UNCERTAINTIES IN X-RAY ANALYSIS: EFFECTIVE AREAS IN SPECTRAL FITTING
Lee, Hyunsook; Kashyap, Vinay L.; Drake, Jeremy J.; Ratzlaff, Pete; Siemiginowska, Aneta E-mail: vkashyap@cfa.harvard.edu E-mail: rpete@head.cfa.harvard.edu
2011-04-20
While considerable advance has been made to account for statistical uncertainties in astronomical analyses, systematic instrumental uncertainties have been generally ignored. This can be crucial to a proper interpretation of analysis results because instrumental calibration uncertainty is a form of systematic uncertainty. Ignoring it can underestimate error bars and introduce bias into the fitted values of model parameters. Accounting for such uncertainties currently requires extensive case-specific simulations if using existing analysis packages. Here, we present general statistical methods that incorporate calibration uncertainties into spectral analysis of high-energy data. We first present a method based on multiple imputation that can be applied with any fitting method, but is necessarily approximate. We then describe a more exact Bayesian approach that works in conjunction with a Markov chain Monte Carlo based fitting. We explore methods for improving computational efficiency, and in particular detail a method of summarizing calibration uncertainties with a principal component analysis of samples of plausible calibration files. This method is implemented using recently codified Chandra effective area uncertainties for low-resolution spectral analysis and is verified using both simulated and actual Chandra data. Our procedure for incorporating effective area uncertainty is easily generalized to other types of calibration uncertainties.
A repetition-suppression account of between-trial effects in a modified Stroop paradigm.
Juvina, Ion; Taatgen, Niels A
2009-05-01
Theories that postulate cognitive inhibition are very common in psychology and cognitive neuroscience [e.g., Hasher, L., Lustig, C., & Zacks, R. T. (2007). Inhibitory mechanisms and the control of attention. In A. Conway, C. Jarrold, M. Kane, A. Miyake, A. Towse, & J. Towse (Eds.), Variation in working memory (pp. 227-249). New York, NY: Oxford, University Press], although they have recently been severely criticized [e.g., MacLeod, C. M., Dodd, M. D., Sheard, E. D., Wilson, D. E., & Bibi, U. (2003). In opposition to inhibition. In H. Ross (Ed.), The psychology of learning and motivation (Vol. 43, pp. 163-214). Elsevier Science]. This paper poses and attempts to answer the question whether a research program with cognitive inhibition as its main theoretical assumption is still worth pursuing. We present a set of empirical data from a modified Stroop paradigm that replicates previously reported findings. These findings refer to between-trial effects previously described in the literature on Stroop, negative priming, and inhibition-of-return. Existing theoretical accounts fail to explain all these effects in an integrated way. A repetition-suppression mechanism is proposed in order to account for these data. This mechanism is instantiated as a computational cognitive model. The theoretical implications of this model are discussed.
Nonlinear optical effects of ultrahigh-Q silicon photonic nanocavities immersed in superfluid helium
Sun, Xiankai; Zhang, Xufeng; Schuck, Carsten; Tang, Hong X.
2013-01-01
Photonic nanocavities are a key component in many applications because of their capability of trapping and storing photons and enhancing interactions of light with various functional materials and structures. The maximal number of photons that can be stored in silicon photonic cavities is limited by the free-carrier and thermo-optic effects at room temperature. To reduce such effects, we performed the first experimental study of optical nonlinearities in ultrahigh-Q silicon disk nanocavities at cryogenic temperatures in a superfluid helium environment. At elevated input power, the cavity transmission spectra exhibit distinct blue-shifted bistability behavior when temperature crosses the liquid helium lambda point. At even lower temperatures, the spectra restore to symmetric Lorentzian shapes. Under this condition, we obtain a large intracavity photon number of about 40,000, which is limited ultimately by the local helium phase transition. These new discoveries are explained by theoretical calculations and numerical simulations. PMID:23486445
Possibilities of Verifying Dynamical Casimir Effect with Nonlinear Materials in Microwave Cavities
NASA Astrophysics Data System (ADS)
Dodonov, Viktor
2015-03-01
I evaluate the number of ``Casimir quanta'' that could be created in high-quality electromagnetic cavities containing materials with big third-order nonlinear optical coefficients, due to the parametric amplification of the microwave vacuum field, if the effective refractive index of the material is modulated by periodic high-intensity short laser pulses. The main result is that the expected total number of created microwave photons depends neither on the laser beam shape, nor on the duration or power of individual pulses, but it is determined by the total energy of all pulses, provided the duration of each pulse is much shorter than the period of field oscillations in the selected resonant mode. The experiment can be feasible in small cavities with high resonance frequencies. Possible spurious effects will be discussed, too.
Takagi, Y
1994-09-20
An optical pulse-width measurement in the ultraviolet spectral region has been performed in a simple manner by introducing into the second-order autocorrelator a nonlinear response of the optical detector based on the two-photon photoelectric effect. The pulse widths of the third, fourth, and fifth harmonics of a mode-locked Nd:YAG laser were measured by the use of a photomultiplier with a cesium iodide photocathode with a minimum required pulse energy of 10 nJ and a power density of 10 kW/cm(2). The effect of transient interband optical excitation with different photon energies on the intensity correlation profile was also studied for the case of a copper iodide photocathode, and the result provides a background-free intensity correlation in a part of the ultraviolet spectral region.
Thermodynamic Self-Limiting Growth of Heteroepitaxial Islands Induced by Nonlinear Elastic Effect.
Hu, Hao; Niu, Xiaobin; Liu, Feng
2016-06-01
We investigate nonlinear elastic effect (NLEF) on the growth of heteroepitaxial islands, a topic of both scientific and technological significance for their applications as quantum dots. We show that the NLEF induces a thermodynamic self-limiting growth mechanism that hinders the strain relaxation of coherent island beyond a maximum size, which is in contrast to indefinite strain relaxation with increasing island size in the linear elastic regime. This self-limiting growth effect shows a strong dependence on the island facet angle, which applies also to islands inside pits patterned in a substrate surface with an additional dependence on the pit inclination angle. Consequently, primary islands nucleate and grow first in the pits and then secondary islands nucleate at the rim around the pits after the primary islands reach the self-limited maximum size. Our theory sheds new lights on understanding the heteroepitaxial island growth and explains a number of past and recent experimental observations. PMID:27203611
Nonlinear magneto-optical effects in all-garnet magnetophotonic crystals
NASA Astrophysics Data System (ADS)
Murzina, T. V.; Razdolski, I. E.; Aktsipetrov, O. A.; Grishin, A. M.; Khartsev, S. I.
2009-04-01
Nonlinear magneto-optical properties of all-garnet magnetophotonic crystals composed of alternating layers of ferromagnetic Bi 3Fe 5O 12 (BIG) and Sm 3Ga 5O 12 quarter-wavelength layers with a half-wavelength BIG microcavity mode are presented. The samples are grown by rf-magnetron sputtering on non-magnetic GGG substrate. Many-fold enhancement of the magnetization-induced effects in second-harmonic generation (SHG) as compared with linear magneto-optical effects are observed: the SHG magnetic contrast up to 50% and magnetization-induced rotation of the polarization plane of about 90° are measured at the resonance microcavity wavelengh of λ=779 nm.
Evaluation of fractional photothermolysis effect in a mouse model using nonlinear optical microscopy
NASA Astrophysics Data System (ADS)
Guo, Han Wen; Tseng, Te-Yu; Dong, Chen-Yuan; Tsai, Tsung-Hua
2014-07-01
Fractional photothermolysis (FP) induces discrete columns of photothermal damage in skin dermis, thereby promoting collagen regeneration. This technique has been widely used for treating wrinkles, sun damage, and scar. In this study, we evaluate the potential of multiphoton microscopy as a noninvasive imaging modality for the monitoring of skin rejuvenation following FP treatment. The dorsal skin of a nude mouse underwent FP treatment in order to induce microthermal zones (MTZs). We evaluated the effect of FP on skin remodeling at 7 and 14 days after treatment. Corresponding histology was performed for comparison. After 14 days of FP treatment at 10 mJ, the second harmonic generation signal recovered faster than the skin treated with 30 mJ, indicating a more rapid regeneration of dermal collagen at 10 mJ. Our results indicate that nonlinear optical microscopy is effective in detecting the damaged areas of MTZ and monitoring collagen regeneration following FP treatment.
Examination of time-variable input effects in a nonlinear analogue magnetosphere model
NASA Technical Reports Server (NTRS)
Baker, D. N.; Klimas, A. J.; Roberts, D. A.
1991-01-01
The plasma physical analog model (an extension of the damped, harmonic-oscillator dripping faucet model) is employed to consider explicitly the effect of time-varying the inputs. This work is equivalent to considering the effects of northward and southward turnings of the interplanetary magnetic field for various periods of time. It is found that relatively extended episodes (not less than 2 hours) of turned-on input with shorter (about 1 hour) periods of turned-off input lead to model behavior much like the continuously driven case. Going to short input intervals with longer periods of zero input leads to highly irregular and dramatically fluctuating episodes of magnetotail unloading. These results give an insight into the diversity of apparent magnetospheric responses during relatively isolated substorm conditions. This work shows the absolutely critical interdependence (in a nonlinear dynamical system) of input phasing and internal magnetospheric response cycles.
Effective Lagrangian in nonlinear electrodynamics and its properties of causality and unitarity
Shabad, Anatoly E.; Usov, Vladimir V.
2011-05-15
In nonlinear electrodynamics, by implementing the causality principle as the requirement that the group velocity of elementary excitations over a background field should not exceed the speed of light in the vacuum c=1, and the unitarity principle as the requirement that the residue of the propagator should be nonnegative, we establish the positive convexity of the effective Lagrangian on the class of constant fields, also the positivity of all characteristic dielectric and magnetic permittivity constants that are derivatives of the effective Lagrangian with respect to the field invariants. Violation of the general principles by the one-loop approximation in QED at exponentially large magnetic field is analyzed, resulting in complex energy ghosts that signal the instability of the magnetized vacuum. Superluminal excitations (tachyons) appear, too, but for the magnetic field exceeding its instability threshold. Also other popular Lagrangians are tested to establish that the ones leading to spontaneous vacuum magnetization possess wrong convexity.
Nonlinear absorption of SWNT film and its effects to the operation state of pulsed fiber laser.
Li, Xiaohui; Wang, Yonggang; Wang, Yishan; Zhao, Wei; Yu, Xuechao; Sun, Zhipei; Cheng, Xueping; Yu, Xia; Zhang, Ying; Wang, Qi Jie
2014-07-14
We study a single-wall carbon nanotube (SWNT) Polyvinyl alcohol (PVA) composite as a saturable absorber (SA) for pulse generation in Yb-doped fiber lasers. The saturable absorption and optical limiting (OL) characteristics of the SWNT device are investigated. By combing these two nonlinear effects, we find out for the first time, to the best of our knowledge, that mode-locking can be obtained in the dissipative soliton regime at low pumping followed by Q-switching at high pumping, which is quite different from conventional pulse dynamic evolutions. The Q-switched state operating at higher pump powers is due to the OL effect. The inverted operating fiber laser can be applied in various potential applications such as versatile material processing, optical communication and radar system etc.
NASA Technical Reports Server (NTRS)
Giles, Gary L.; Tatum, Kenneth E.; Foss, Willard E., Jr.
1989-01-01
During conceptual design studies of advanced aircraft, the usual practice is to use linear theory to calculate the aerodynamic characteristics of candidate rigid (nonflexible) geometric external shapes. Recent developments and improvements in computational methods, especially computational fluid dynamics (CFD), provide significantly improved capability to generate detailed analysis data for the use of all disciplines involved in the evaluation of a proposed aircraft design. A multidisciplinary application of such analysis methods to calculate the effects of nonlinear aerodynamics and static aeroelasticity on the mission performance of a fighter aircraft concept is described. The aircraft configuration selected for study was defined in a previous study using linear aerodynamics and rigid geometry. The results from the previous study are used as a basis of comparison for the data generated herein. Aerodynamic characteristics are calculated using two different nonlinear theories, potential flow and rotational (Euler) flow. The aerodynamic calculations are performed in an iterative procedure with an equivalent plate structural analysis method to obtain lift and drag data for a flexible (nonrigid) aircraft. These static aeroelastic data are then used in calculating the combat and mission performance characteristics of the aircraft.
Toward a broadband astro-comb: effects of nonlinear spectral broadening in optical fibers.
Chang, Guoqing; Li, Chih-Hao; Phillips, David F; Walsworth, Ronald L; Kärtner, Franz X
2010-06-01
We propose and analyze a new approach to generate a broadband astro-comb by spectral broadening of a narrowband astro-comb inside a highly nonlinear optical fiber. Numerical modeling shows that cascaded four-wave-mixing dramatically degrades the input comb's side-mode suppression and causes side-mode amplitude asymmetry. These two detrimental effects can systematically shift the center-of-gravity of astro-comb spectral lines as measured by an astrophysical spectrograph with resolution approximately 100,000; and thus lead to wavelength calibration inaccuracy and instability. Our simulations indicate that this performance penalty, as a result of nonlinear spectral broadening, can be compensated by using a filtering cavity configured for double-pass. As an explicit example, we present a design based on an Yb-fiber source comb (with 1 GHz repetition rate) that is filtered by double-passing through a low finesse cavity (finesse = 208), and subsequent spectrally broadened in a 2-cm, SF6-glass photonic crystal fiber. Spanning more than 300 nm with 16 GHz line spacing, the resulting astro-comb is predicted to provide 1 cm/s (approximately 10 kHz) radial velocity calibration accuracy for an astrophysical spectrograph. Such extreme performance will be necessary for the search for and characterization of Earth-like extra-solar planets, and in direct measurements of the change of the rate of cosmological expansion.
Bari, Vlasta; Marchi, Andrea; De Maria, Beatrice; Rossato, Gianluca; Nollo, Giandomenico; Faes, Luca; Porta, Alberto
2016-05-13
Cardiovascular and cerebrovascular regulatory systems are vital control mechanisms responsible for guaranteeing homeostasis and are affected by respiration. This work proposes the investigation of cardiovascular and cerebrovascular control systems and the nonlinear influences of respiration on both regulations through joint symbolic analysis (JSA), conditioned or unconditioned on respiration. Interactions between cardiovascular and cerebrovascular regulatory systems were evaluated as well by performing correlation analysis between JSA indexes describing the two control systems. Heart period, systolic and mean arterial pressure, mean cerebral blood flow velocity and respiration were acquired on a beat-to-beat basis in 13 subjects experiencing recurrent syncope episodes (SYNC) and 13 healthy individuals (non-SYNC) in supine resting condition and during head-up tilt test at 60° (TILT). Results showed that JSA distinguished conditions and groups, whereas time domain parameters detected only the effect of TILT. Respiration affected cardiovascular and cerebrovascular regulatory systems in a nonlinear way and was able to modulate the interactions between the two control systems with different outcome in non-SYNC and SYNC groups, thus suggesting that the analysis of the impact of respiration on cardiovascular and cerebrovascular regulatory systems might improve our understanding of the mechanisms underpinning the development of postural-related syncope.
Toward a broadband astro-comb: effects of nonlinear spectral broadening in optical fibers.
Chang, Guoqing; Li, Chih-Hao; Phillips, David F; Walsworth, Ronald L; Kärtner, Franz X
2010-06-01
We propose and analyze a new approach to generate a broadband astro-comb by spectral broadening of a narrowband astro-comb inside a highly nonlinear optical fiber. Numerical modeling shows that cascaded four-wave-mixing dramatically degrades the input comb's side-mode suppression and causes side-mode amplitude asymmetry. These two detrimental effects can systematically shift the center-of-gravity of astro-comb spectral lines as measured by an astrophysical spectrograph with resolution approximately 100,000; and thus lead to wavelength calibration inaccuracy and instability. Our simulations indicate that this performance penalty, as a result of nonlinear spectral broadening, can be compensated by using a filtering cavity configured for double-pass. As an explicit example, we present a design based on an Yb-fiber source comb (with 1 GHz repetition rate) that is filtered by double-passing through a low finesse cavity (finesse = 208), and subsequent spectrally broadened in a 2-cm, SF6-glass photonic crystal fiber. Spanning more than 300 nm with 16 GHz line spacing, the resulting astro-comb is predicted to provide 1 cm/s (approximately 10 kHz) radial velocity calibration accuracy for an astrophysical spectrograph. Such extreme performance will be necessary for the search for and characterization of Earth-like extra-solar planets, and in direct measurements of the change of the rate of cosmological expansion. PMID:20588402
NASA Astrophysics Data System (ADS)
Bari, Vlasta; Marchi, Andrea; De Maria, Beatrice; Rossato, Gianluca; Nollo, Giandomenico; Faes, Luca; Porta, Alberto
2016-05-01
Cardiovascular and cerebrovascular regulatory systems are vital control mechanisms responsible for guaranteeing homeostasis and are affected by respiration. This work proposes the investigation of cardiovascular and cerebrovascular control systems and the nonlinear influences of respiration on both regulations through joint symbolic analysis (JSA), conditioned or unconditioned on respiration. Interactions between cardiovascular and cerebrovascular regulatory systems were evaluated as well by performing correlation analysis between JSA indexes describing the two control systems. Heart period, systolic and mean arterial pressure, mean cerebral blood flow velocity and respiration were acquired on a beat-to-beat basis in 13 subjects experiencing recurrent syncope episodes (SYNC) and 13 healthy individuals (non-SYNC) in supine resting condition and during head-up tilt test at 60° (TILT). Results showed that JSA distinguished conditions and groups, whereas time domain parameters detected only the effect of TILT. Respiration affected cardiovascular and cerebrovascular regulatory systems in a nonlinear way and was able to modulate the interactions between the two control systems with different outcome in non-SYNC and SYNC groups, thus suggesting that the analysis of the impact of respiration on cardiovascular and cerebrovascular regulatory systems might improve our understanding of the mechanisms underpinning the development of postural-related syncope.
Effect of nonlinearity in hybrid kinetic Monte Carlo-continuum models.
Balter, Ariel; Lin, Guang; Tartakovsky, Alexandre M
2012-01-01
Recently there has been interest in developing efficient ways to model heterogeneous surface reactions with hybrid computational models that couple a kinetic Monte Carlo (KMC) model for a surface to a finite-difference model for bulk diffusion in a continuous domain. We consider two representative problems that validate a hybrid method and show that this method captures the combined effects of nonlinearity and stochasticity. We first validate a simple deposition-dissolution model with a linear rate showing that the KMC-continuum hybrid agrees with both a fully deterministic model and its analytical solution. We then study a deposition-dissolution model including competitive adsorption, which leads to a nonlinear rate, and show that in this case the KMC-continuum hybrid and fully deterministic simulations do not agree. However, we are able to identify the difference as a natural result of the stochasticity coming from the KMC surface process. Because KMC captures inherent fluctuations, we consider it to be more realistic than a purely deterministic model. Therefore, we consider the KMC-continuum hybrid to be more representative of a real system.
NASA Astrophysics Data System (ADS)
Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.
2015-02-01
Cuprous oxide nano clusters, micro cubes and micro particles were successfully synthesized by reducing copper (II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction studies revealed the formation of pure single phase cubic. Raman spectrum shows the inevitable presence of CuO on the surface of the Cu2O powders which may have an impact on the stability of the phase. Transmission electron microscopy (TEM) data revealed that the morphology evolves from nanoclusters to micro cubes and micro particles by increasing the concentration of NaOH. Linear optical measurements show that the absorption peak maximum shifts towards red with changing morphology from nano clusters to micro cubes and micro particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm, 6 ns laser pulses. Samples exhibited saturable as well as reverse saturable absorption. The results show that the transition from SA to RSA is ascribed to excited-state absorption (ESA) induced by two-photon absorption (TPA) process. Due to confinement effects (enhanced band gap) we observed enhanced nonlinear absorption coefficient (βeff) in the case of nano-clusters compared to their micro-cubes and micro-particles.
Beam-beam interaction and pacman effects in the SSC with random nonlinear multipoles
Goderre, G.P.; Mahale, N.K.; Ohnuma, S.
1989-05-25
In order to find the combined effects of beam-beam interaction (head-on and long-range) and random nonlinear multipoles in dipole magnets, transverse tunes and smears have been calculated as a function of oscillation amplitudes. Two types of particles, ''regular'' and ''pacman,'' have been investigated using a modified version of the tracking code TEAPOT. Regular particles experience beam-beam interactions in all four interaction regions (IR's), both head-on and long-range, while pacman particles interact with bunches of the other beam in one medium-beta and one low-beta IR's only. The model for the beam-beam interaction is of weak-strong type and the strong beam is assumed to have a round Gaussian charge distribution. Furthermore, it is assumed that the vertical closed orbit deviation arising from the finite crossing angle of 70 ..mu..rad is perfectly compensated for regular particles. The same compensation applied to pacman particles creates a closed orbit distortion. Linear tunes are adjusted for regular particles to the design values but there are no nonlinear corrections except for chromaticity correcting sextupoles in two families. Results obtained in this study do not show any reduction of dynamic or linear apertures for pacman particles when the oscillation amplitude is less than /approximately/10sigma. However, smears often exhibit a strong dependence on tunes, casting some doubts on the validity of defining the linear aperture from the smear alone. 10 refs., 16 figs., 3 tabs.
Accelerating oscillatory fronts in a nonlinear sonic vacuum with strong nonlocal effects.
Gendelman, O V; Zolotarevskiy, V; Savin, A V; Bergman, L A; Vakakis, A F
2016-03-01
We describe and explore accelerating oscillatory fronts in sonic vacua with nonlocal interactions. As an example, a chain of particles oscillating in the plane and coupled by linear springs, with fixed ends, is considered. When one end of this system is harmonically excited in the transverse direction, one observes accelerated propagation of the excitation front, accompanied by an almost monochromatic oscillatory tail. Position of the front obeys the scaling law l(t) ∼ t(4/3). The frequency of the oscillatory tail remains constant, and the wavelength scales as λ ∼ t(1/3). These scaling laws result from the nonlocal effects; we derive them analytically (including the scaling coefficients) from a continuum approximation. Moreover, a certain threshold excitation amplitude is required in order to initiate the front propagation. The initiation threshold is evaluated on the basis of a simplified discrete model, further reduced to a completely integrable nonlinear system. Given their simplicity, nonlinear sonic vacua of the type considered herein should be common in periodic lattices. PMID:27078353
Paolo Delsanto, Pier; Hirsekorn, Sigrun
2004-04-01
Recent experiments on rocks and other materials, such as soil, cement, concrete and damaged elastic materials, have led to the discovery of nonlinear (NL) hysteretic effects in their elastic behaviour. These observations suggest the existence of a NL mesoscopic elasticity universality class, to which all the aforementioned materials belong. The purpose of the present contribution is to search for the basic mathematical roots for nonclassical nonlinearity, in order to explain its universality, classify it and correlate it with the underlying meso- or microscopic interaction mechanisms. In our discussions we explicitly consider two quite different kinds of specimens: a two-bonded-elements structure and a thin multigrained bar. It is remarkable that, although the former includes only one interface and the latter very many interstices, the same "interaction box" formalism can be applied to both. Another important result of the proposed formalism is that the spectral contents of an arbitrary system for any input amplitude may be predicted, under certain assumptions, from the result of a single experiment at a higher amplitude.
Surface and Atmospheric Parameter Retrieval From AVIRIS Data: The Importance of Non-Linear Effects
NASA Technical Reports Server (NTRS)
Green Robert O.; Moreno, Jose F.
1996-01-01
AVIRIS data represent a new and important approach for the retrieval of atmospheric and surface parameters from optical remote sensing data. Not only as a test for future space systems, but also as an operational airborne remote sensing system, the development of algorithms to retrieve information from AVIRIS data is an important step to these new approaches and capabilities. Many things have been learned since AVIRIS became operational, and the successive technical improvements in the hardware and the more sophisticated calibration techniques employed have increased the quality of the data to the point of almost meeting optimum user requirements. However, the potential capabilities of imaging spectrometry over the standard multispectral techniques have still not been fully demonstrated. Reasons for this are the technical difficulties in handling the data, the critical aspect of calibration for advanced retrieval methods, and the lack of proper models with which to invert the measured AVIRIS radiances in all the spectral channels. To achieve the potential of imaging spectrometry, these issues must be addressed. In this paper, an algorithm to retrieve information about both atmospheric and surface parameters from AVIRIS data, by using model inversion techniques, is described. Emphasis is put on the derivation of the model itself as well as proper inversion techniques, robust to noise in the data and an inadequate ability of the model to describe natural variability in the data. The problem of non-linear effects is addressed, as it has been demonstrated to be a major source of error in the numerical values retrieved by more simple, linear-based approaches. Non-linear effects are especially critical for the retrieval of surface parameters where both scattering and absorption effects are coupled, as well as in the cases of significant multiple-scattering contributions. However, sophisticated modeling approaches can handle such non-linear effects, which are especially
NASA Astrophysics Data System (ADS)
Li, Bo; Liu, Richeng; Jiang, Yujing
2016-07-01
Fluid flow tests were conducted on two crossed fracture models for which the geometries of fracture segments and intersections were measured by utilizing a visualization technique using a CCD (charged coupled device) camera. Numerical simulations by solving the Navier-Stokes equations were performed to characterize the fluid flow at fracture intersections. The roles of hydraulic gradient, surface roughness, intersecting angle, and scale effect in the nonlinear fluid flow behavior through single fracture intersections were investigated. The simulation results of flow rate agreed well with the experimental results for both models. The experimental and simulation results showed that with the increment of the hydraulic gradient, the ratio of the flow rate to the hydraulic gradient, Q/J, decreases and the relative difference of Q/J between the calculation results employing the Navier-Stokes equations and the cubic law, δ, increases. When taking into account the fracture surface roughness quantified by Z2 ranging 0-0.42 for J = 1, the value of δ would increase by 0-10.3%. The influences of the intersecting angle on the normalized flow rate that represents the ratio of the flow rate in a segment to the total flow rate, Ra, and the ratio of the hydraulic aperture to the mechanical aperture, e/E, are negligible when J < 10-3, whereas their values change significantly when J > 10-2. Based on the regression analysis on simulation results, a mathematical expression was proposed to quantify e/E, involving variables of J and Rr, where Rr is the radius of truncating circles centered at an intersection. For E/Rr > 10-2, e/E varies significantly and the scale of model has large impacts on the nonlinear flow behavior through intersections, while for E/Rr < 10-3, the scale effect is negligibly small. Finally, a necessary condition to apply the cubic law to fluid flow through fracture intersections is suggested as J < 10-3, E/Rr < 10-3, and Z2 = 0.
NASA Astrophysics Data System (ADS)
Jayakrishnan, K.; Joseph, Antony; Bhattathiripad, Jayakrishnan; Ramesan, M. T.; Chandrasekharan, K.; Siji Narendran, N. K.
2016-04-01
We report our results on the identification of large order enhancement in nonlinear optical coefficients of polymerized indole and its comparative study with reference to its monomer counterpart. Indole monomer shows virtually little third order effects whereas its polymerized version exhibits phenomenal increase in its third order nonlinear optical parameters such as nonlinear refractive index and nonlinear absorption. Open aperture Z-scan trace of polyindole done with Q-switched Nd:YAG laser source (532 nm, 7 ns), shows β value as high as 89 cm/GW at a beam energy of 0.83 GW/cm2. Closed aperture Z-scan done at identical energies reveals nonlinear refractive index of the order of -3.55 × 10-17 m2/W. Band gap measurement of polyindole was done with UV-Vis absorption spectra and compared with that of Indole. FTIR spectra of the monomer and polymerized versions were recorded and relevant bond formations were confirmed from the characteristic peaks. Photo luminescent spectra were investigated to know the emission features of both molecules. Beam energy (I0) versus nonlinear absorption coefficient (β) plot indicates reverse saturable type of absorption behaviour in polyindole molecules. Degenerate Four Wave Mixing (DFWM) plot of polyindole reveals quite a cubic dependence between probe and phase conjugate signal and the resulting χ(3) is comparable with Z-scan results. Optical limiting efficiency of polyindole is comparable with certain derivatives of porphyrins, phthalocyanines and graphene oxides.
Accounting for the tongue-and-groove effect using a robust direct aperture optimization approach
Salari, Ehsan; Men Chunhua; Romeijn, H. Edwin
2011-03-15
Purpose: Traditionally, the tongue-and-groove effect due to the multileaf collimator architecture in intensity-modulated radiation therapy (IMRT) has typically been deferred to the leaf sequencing stage. The authors propose a new direct aperture optimization method for IMRT treatment planning that explicitly incorporates dose calculation inaccuracies due to the tongue-and-groove effect into the treatment plan optimization stage. Methods: The authors avoid having to accurately estimate the dosimetric effects of the tongue-and-groove architecture by using lower and upper bounds on the dose distribution delivered to the patient. They then develop a model that yields a treatment plan that is robust with respect to the corresponding dose calculation inaccuracies. Results: Tests on a set of ten clinical head-and-neck cancer cases demonstrate the effectiveness of the new method in developing robust treatment plans with tight dose distributions in targets and critical structures. This is contrasted with the very loose bounds on the dose distribution that are obtained by solving a traditional treatment plan optimization model that ignores tongue-and-groove effects in the treatment planning stage. Conclusions: A robust direct aperture optimization approach is proposed to account for the dosimetric inaccuracies caused by the tongue-and-groove effect. The experiments validate the ability of the proposed approach in designing robust treatment plans regardless of the exact consequences of the tongue-and-groove architecture.
Nonlinear kinetic modeling of stimulated Raman scattering
NASA Astrophysics Data System (ADS)
Benisti, Didier
2011-10-01
Despite its importance for many applications, such as or Raman amplification or inertial confinement fusion, deriving a nonlinear estimate of Raman reflectivity in a plasma has remained quite a challenge for decades. This is mainly due to the nonlinear modification of the electron distribution function induced by the plasma wave (EPW), which, in turn, modifies the propagation of this wave. In this paper is derived an envelope equation for the EPW valid in 3D and which accounts for the nonlinear change of its collisionless (Landau-like) damping rate, group velocity, coupling to the electromagnetic drive, frequency and wave number. Our theoretical predictions for each of these terms are carefully compared against results from Vlasov simulations of stimulated Raman scattering (SRS), as well as with other theories. Moreover, our envelope model shows to be as accurate as a Vlasov code in predicting Raman threshold in 1D. Making comparisons with experimental results nevertheless requires including transverse dimensions and letting Raman start from noise. To this end, we performed a completely new derivation of the electrostatic fluctuations in a plasma, which accounts nonlinear effects. Moreover, based on our Multi-D simulations of Raman scattering with our envelope code BRAMA, we discuss the effect on SRS of wave front bowing, transverse detrapping and of a completely new defocussing effect due to the local change in the direction of the EPW group velocity induced by the nonlinear decrease of Landau damping.
NASA Astrophysics Data System (ADS)
Santer, B. D.; Wigley, T. M. L.; Doutriaux, C.; Boyle, J. S.; Hansen, J. E.; Jones, P. D.; Meehl, G. A.; Roeckner, E.; Sengupta, S.; Taylor, K. E.
2001-11-01
Several previous studies have attempted to remove the effects of explosive volcanic eruptions and El Niño-Southern Oscillation (ENSO) variability from time series of globally averaged surface and tropospheric temperatures. Such work has largely ignored the nonzero correlation between volcanic signals and ENSO. Here we account for this collinearity using an iterative procedure. We remove estimated volcano and ENSO signals from the observed global mean temperature data, and then calculate trends over 1979-1999 in the residuals. Residual trends are sensitive to the choice of index used for removing ENSO effects and to uncertainties in key volcanic parameters. Despite these sensitivities, residual surface and lower tropospheric (2LT) trends are almost always larger than trends in the raw observational data. After removal of volcano and ENSO effects, the differential warming between the surface and lower troposphere is generally reduced. These results suggest that the net effect of volcanoes and ENSO over 1979-1999 was to reduce globally averaged surface and tropospheric temperatures and cool the troposphere by more than the surface. ENSO and incomplete volcanic forcing effects can hamper reliable assessment of the true correspondence between modeled and observed trends. In the second part of our study, we remove these effects from model data and compare simulated and observed residual trends. Residual temperature trends are not significantly different at the surface. In the lower troposphere the statistical significance of trend differences depends on the experiment considered, the choice of ENSO index, and the volcanic signal decay time. The simulated difference between surface and tropospheric warming rates is significantly smaller than observed in 51 out of 54 cases considered. We also examine multiple realizations of model experiments with relatively complete estimates of natural and anthropogenic forcing. ENSO and volcanic effects are not removed from these
ERIC Educational Resources Information Center
Fast, Ellen Forte
This guide was developed to serve as a resource for the staffs of state education agencies and local education agencies who are responsible for producing state, district, or school report cards of the type required under many state or district accountability systems as well as under the No Child Left Behind Act (NCLB). The guide is not intended to…
NASA Astrophysics Data System (ADS)
Singh, Karamdeep; Kaur, Gurmeet; Singh, Maninder Lal
2016-07-01
A multifunctional combinational logic module capable of performing several signal manipulation tasks all-optically, such as half-addition/subtraction, single-bit comparison, and 2-to-4 decoding simultaneously is proposed. Several logic functions (A+B¯, A.B, A¯.B, A.B¯, A⊕B, and A⊙B) between two input signals A and B are implemented by harnessing a number of nonlinear effects, such as cross-phase modulation (XPM), cross-gain modulation (XGM), and four-wave mixing (FWM) inside only two highly nonlinear fibers (HNLF) arranged in a parallel structure. The NOR gate (A+B¯) is realized by the means of XPM effect in the first HNLF, whereas, A‾.B, A.B¯, and A.B logics have relied on utilization of XGM and FWM processes, respectively, in parametric medium made up of the second HNLF of parallel arrangement. The remaining A⊕B and A⊙B logics required for successful implementation of the proposed simultaneous scheme are attained by temporally combining previously achieved (A‾.B and A.B‾) and (A.B and A+B‾) logics. Quality-factor ≥7.4 and extinction ratio ≥12.30 dB have been achieved at repetition rates of 100 Gbps for all logic functions (A+B‾, A.B, A¯.B, A.B¯, A⊕B, and A⊙B), suggesting successful simultaneous implementation.
Grinstein-Weiss, Michal; Sherraden, Michael; Gale, William G; Rohe, William M; Schreiner, Mark; Key, Clinton; Oliphant, Jane E
2015-01-01
We examine the 10-year follow-up effects on retirement saving of an individual development account (IDA) program using data from a randomized experiment that ran from 1998 to 2003 in Tulsa, Oklahoma. The IDA program included financial education, encouragement to save, and matching funds for several qualified uses of the saving, including contributions to retirement accounts. The results indicate that as of 2009, 6 years after the program ended, the IDA program had no impact on the propensity to hold a retirement account, the account balance, or the sufficiency of retirement balances to meet retirement expenses.
ERIC Educational Resources Information Center
Hochwarter, Wayne A.; Ferris, Gerald R.; Gavin, Mark B.; Perrewe, Pamela L.; Hall, Angela T.; Frink, Dwight D.
2007-01-01
This study examined the effects of felt accountability, political skill, and job tension on job performance ratings. Specifically, we hypothesized that felt accountability would lead to higher (lower) job performance ratings when coupled with high (low) levels of political skill, and that these relationships would be mediated by job tension. Data…
NASA Astrophysics Data System (ADS)
Karpov, S. V.; Kodirov, M. K.; Ryasnyansky, A. I.; Slabko, V. V.
2001-10-01
The relation between the degree of aggregation of silver hydrosols and their nonlinear refractive index n2 is studied experimentally. It is found that the sign of n2 at a wavelength of 1.064 μm changes with increasing the aggregation degree, which corresponds to the replacing of self-focusing by self-defocusing. The observed effects are explained based on the analysis of a change in nonlinear dispersion of the medium, taking into account the interaction between phases and the photochromic effects, which are typical for colloidal structures with fractal geometry. It is shown that the change in the sign of the nonlinear refractive index of hydrosols upon irradiation by laser pulses of duration of less than 10-7 s is caused by the perturbation of resonances of silver and water and by the competition between Kerr nonlinear polarisations involving these resonances.
Tessier, Adrien; Bertrand, Julie; Chenel, Marylore; Comets, Emmanuelle
2015-05-01
Genetic data is now collected in many clinical trials, especially in population pharmacokinetic studies. There is no consensus on methods to test the association between pharmacokinetics and genetic covariates. We performed a simulation study inspired by real clinical trials, using the pharmacokinetics (PK) of a compound under development having a nonlinear bioavailability along with genotypes for 176 single nucleotide polymorphisms (SNPs). Scenarios included 78 subjects extensively sampled (16 observations per subject) to simulate a phase I study, or 384 subjects with the same rich design. Under the alternative hypothesis (H1), six SNPs were drawn randomly to affect the log-clearance under an additive linear model. For each scenario, 200 PK data sets were simulated under the null hypothesis (no gene effect) and H1. We compared 16 combinations of four association tests, a stepwise procedure and three penalised regressions (ridge regression, Lasso, HyperLasso), applied to four pharmacokinetic phenotypes, two observed concentrations, area under the curve estimated by noncompartmental analysis and model-based clearance. The different combinations were compared in terms of true and false positives and probability to detect the genetic effects. In presence of nonlinearity and/or variability in bioavailability, model-based phenotype allowed a higher probability to detect the SNPs than other phenotypes. In a realistic setting with a limited number of subjects, all methods showed a low ability to detect genetic effects. Ridge regression had the best probability to detect SNPs, but also a higher number of false positives. No association test showed a much higher power than the others. PMID:25693489
Theory of the nonlinear Rashba-Edelstein effect: The clean electron gas limit
NASA Astrophysics Data System (ADS)
Vignale, Giovanni; Tokatly, I. V.
2016-01-01
It is well known that a current driven through a two-dimensional electron gas with Rashba spin-orbit coupling induces a spin polarization in the perpendicular direction (Edelstein effect). This phenomenon has been extensively studied in the linear response regime, i.e., when the average drift velocity of the electrons is a small fraction of the Fermi velocity. Here we investigate the phenomenon in the nonlinear regime, meaning that the average drift velocity is comparable to or exceeds the Fermi velocity. This regime is realized when the electric field is very large or when electron-impurity scattering is very weak. We consider the limiting case of a two-dimensional noninteracting electron gas with no impurities. In this case, the quantum kinetic equation for the density matrix is exactly and analytically solvable, reducing to a problem of spin dynamics for "unpaired" electrons near the Fermi surface. The crucial parameter is γ =e E Ls/EF , where E is the electric field, e is the absolute value of the electron charge, EF is the Fermi energy, and Ls=ℏ /(2 m α ) is the spin-precession length in the Rashba spin-orbit field with coupling strength α . If γ ≪1 , the evolution of the spin is adiabatic, resulting in a spin polarization that grows monotonically in time and eventually saturates at the maximum value n (α /vF) , where n is the electron density and vF is the Fermi velocity. If γ ≫1 the evolution of the spin becomes strongly nonadiabatic and the spin polarization is progressively reduced and eventually suppressed for γ →∞ . We also predict an inverse nonlinear Edelstein effect, in which an electric current is driven by a magnetic field that grows linearly in time. The "conductivities" for the direct and the inverse effects satisfy generalized Onsager reciprocity relations, which reduce to the standard ones in the linear response regime.
NASA Astrophysics Data System (ADS)
Thankappan, Aparna; Thomas, Sheenu; Nampoori, V. P. N.
2013-10-01
We report on the solvent effect on the third order optical nonlinearity of betanin natural dye extracted from red beet root and their third order nonlinear optical (NLO) properties have been studied using a Q-switched Nd:YAG laser at 532 nm. The third order nonlinearity of these samples are dominated by nonlinear absorption, which leads to strong optical limiting and their strength is influenced by the solvent used, suggesting that betanin natural dyes are promising candidate for the development of photonic nonlinear optic devices.
NASA Technical Reports Server (NTRS)
Wheeler, A. A.; Mcfadden, G. B.; Coriell, S. R.; Hurle, D. T. J.
1990-01-01
The effect of a constant electric current on the crystal-melt interface morphology during directional solidification at constant velocity of a binary alloy is considered. A linear temperature field is assumed, and thermoelectric effects and Joule heating are neglected; electromigration and differing electrical conductivities of crystal and melt are taken into account. A two-dimensional weakly nonlinear analysis is carried out to third order in the interface amplitude, resulting in a cubic amplitude equation that describes whether the bifurcation from the planar state is supercritical or subcritical. For wavelengths corresponding to the most dangerous mode of linear theory, the demarcation between supercritical and subcritical behavior is calculated as a function of processing conditions and material parameters. The bifurcation behavior is a sensitive function of the magnitude and direction of the electric current and of the electrical conductivity ratio.
Keeping management effects separate from environmental effects in terrestrial carbon accounting.
Houghton, Richard A
2013-09-01
This study proposes that carbon fluxes identified as being from land use and land-cover change (LULCC) include only that component of a flux that can be attributed to LULCC, exclusive of the effects of environmental change (CO2 , climate, N, etc.). This proposal seems too obvious to need saying, but published estimates of the LULCC flux are widely variable for reasons that have more to do with modeling environmental effects than with LULCC.
NASA Astrophysics Data System (ADS)
Sateesh, V. L.; Upadhyay, C. S.; Venkatesan, C.
2010-07-01
Polarization-electric-field (P-E) interaction results in rendering the stress tensor non-symmetric and in a nonlinear force term in the equilibrium equation. In this paper, an attempt is made to study these (P-E) nonlinear effects on the static response of laminated composite plates with piezo actuators. Further, this paper also focuses on finding the most effective piezo lay-up and ply orientation which gives the maximum deflections. Four different piezo lay-up configurations and three ply orientations are considered. It has been observed from the study that width-wise strips show more transverse bending and twisting. However, full length piezo layers show maximum longitudinal bending. The results of nonlinear analysis show a more considerable softening trend in deformations than that of the linear analysis in the case of longitudinal bending and twisting. In the case of transverse bending this nonlinear effect shows a hardening trend. Further, it has been observed that the influence of P-E nonlinearity depends on the stiffness of the core material, the geometric arrangement of piezo patches, the boundary conditions and the actuation voltage.
Nonlinear Theory of Entrainment in EEG Under Photo-Stimulation by Periodic Rectangular Pulse
NASA Astrophysics Data System (ADS)
Konno, H.; Chatani, H.; Sakata, A.; Tobimatsu, S.
2007-07-01
Nonlinear theory of entrainment is presented based on a generalized Kubo oscillator (GKO) wherein effect of frequency modulation and that of photo-stimulation with periodic rectangular pulse are accounted. It is shown that the GKO model gives qualitative properties of nonlinear responses under the photo-stimulation in human brain.
NASA Technical Reports Server (NTRS)
Jongen, T.; Machiels, L.; Gatski, T. B.
1997-01-01
Three types of turbulence models which account for rotational effects in noninertial frames of reference are evaluated for the case of incompressible, fully developed rotating turbulent channel flow. The different types of models are a Coriolis-modified eddy-viscosity model, a realizable algebraic stress model, and an algebraic stress model which accounts for dissipation rate anisotropies. A direct numerical simulation of a rotating channel flow is used for the turbulent model validation. This simulation differs from previous studies in that significantly higher rotation numbers are investigated. Flows at these higher rotation numbers are characterized by a relaminarization on the cyclonic or suction side of the channel, and a linear velocity profile on the anticyclonic or pressure side of the channel. The predictive performance of the three types of models are examined in detail, and formulation deficiencies are identified which cause poor predictive performance for some of the models. Criteria are identified which allow for accurate prediction of such flows by algebraic stress models and their corresponding Reynolds stress formulations.
Mano, Shuhei; Suto, Yumiko
2014-11-01
The dicentric chromosome assay (DCA) is one of the most sensitive and reliable methods of inferring doses of radiation exposure in patients. In DCA, one calibration curve is prepared in advance by in vitro irradiation to blood samples from one or sometimes multiple healthy donors in considering possible inter-individual variability. Although the standard method has been demonstrated to be quite accurate for actual dose estimates, it cannot account for random effects, which come from such as the blood donor used to prepare the calibration curve, the radiation-exposed patient, and the examiners. To date, it is unknown how these random effects impact on the standard method of dose estimation. We propose a novel Bayesian hierarchical method that incorporates random effects into the dose estimation. To demonstrate dose estimation by the proposed method and to assess the impact of inter-individual variability in samples from multiple donors on the estimation, peripheral blood samples from 13 occupationally non-exposed, non-smoking, healthy individuals were collected and irradiated with gamma rays. The results clearly showed significant inter-individual variability and the standard method using a sample from a single donor gave anti-conservative confidence interval of the irradiated dose. In contrast, the Bayesian credible interval for irradiated dose calculated by the proposed method using samples from multiple donors properly covered the actual doses. Although the classical confidence interval of calibration curve with accounting inter-individual variability in samples from multiple donors was roughly coincident with the Bayesian credible interval, the proposed method has better reasoning and potential for extensions.
Teachers' perceptions of value and effects of outdoor education during an age of accountability
NASA Astrophysics Data System (ADS)
Schmitt, Thomas R.
The purpose of this study was to gain an understanding of teachers' perceptions of the value and effects of a residential Outdoor Education experience during an age of accountability, which was defined as the era which commenced with the passage of the No Child Left Behind Act of 2001. Focus group interviews were conducted with four groups of teachers who participated in a residential Outdoor Education experience with their students during the 2004-2005 school year. The major findings of this study were: (1) Teachers perceive value in the OE experience because of the multi-faceted effects upon their students and classes; (2) Teachers perceived the OE experience positively affected their students' learning through providing hands-on and authentic experiences, development of thinking skills, and enhancing the school's curriculum; (3) Teachers perceived the OE experience positively affected their students' social and emotional development as evidenced by an increase in self esteem, independence, maturity, personal responsibility, and an expanded worldview; (4) Teachers perceived the OE experience positively affected their students' sense of community as evidenced by an increase in team building and cohesiveness, more productive staff-student relationships, the emergence of different "star" students, and greater inclusion of special needs students; (5) Teachers perceived students' appreciation of the environment increased; and (6) Teachers did not perceive any imminent changes to their school's Outdoor Education programming due to the accountability provisions of No Child Left behind (2001). This study's findings suggested implications for school administrators, which were that they should: articulate desired effects to stakeholders; communicate connections to learning standards; and expand the OE experience to foster greater environmental issue focus.
Dumont, Cyrielle; Chenel, Marylore; Mentré, France
2014-01-01
Nonlinear mixed-effect models are used increasingly during drug development. For design, an alternative to simulations is based on the Fisher information matrix. Its expression was derived using a first-order approach, was then extended to include covariance and implemented into the R function PFIM. The impact of covariance on standard errors, amount of information, and optimal designs was studied. It was also shown how standard errors can be predicted analytically within the framework of rich individual data without the model. The results were illustrated by applying this extension to the design of a pharmacokinetic study of a drug in pediatric development.
The Effect of International Financial Reporting Standards Convergence on U. S. Accounting Curriculum
ERIC Educational Resources Information Center
Bates, Homer L.; Waldrup, Bobby E.; Shea, Vincent
2011-01-01
Major changes are coming to U.S. financial accounting and accounting education as U. S. generally accepted accounting principles (GAAP) and international financial reporting standards (IFRS) converge within the next few years. In 2008, the U.S. Securities and Exchange Commission (SEC) published a proposed "road map" for the potential…
The Effects of Accountability System Design on Teachers' Use of Test Score Data
ERIC Educational Resources Information Center
Jennings, Jennifer L.
2012-01-01
Background/Context: Many studies have concluded that educational accountability policies increase data use, but we know little about how to design accountability systems to encourage productive versus distortive uses of test score data. Purpose: I propose that five features of accountability systems affect how test score data are used and examine…
Model of optical nonlinearity of air in the mid-IR wavelength range
Geints, Yu E; Zemlyanov, A A
2014-09-30
A model of optical nonlinearity of air (atmospheric nitrogen and oxygen) is developed. This model can be used to calculate numerically the propagation of radiation with a wavelength close to 10 μm. It takes into account the electronic Kerr effect, higher order nonlinearities, ionisation of a gas medium by electron impact, and pulse group-velocity dispersion. The applicability limits of the Drude approximation for calculating the impact-ionisation rate are also considered. (nonlinear optical phenomena)
Effect of thickness on nonlinear absorption properties of graphite oxide thin films
NASA Astrophysics Data System (ADS)
Sreeja, V. G.; Cheruvalathu, Ajina; Reshmi, R.; Anila, E. I.; Thomas, Sheenu; Jayaraj, M. K.
2016-10-01
We report the thickness dependent structural, linear and nonlinear optical properties of graphite oxide (GO) thin films synthesized by spin coating method. We observed that the structural, linear and nonlinear optical properties can be tuned by the film thickness in GO. The nonlinear absorption studies by open aperture z scan technique exhibited a saturable absorption. The nonlinear absorption coefficient and saturation intensity varies with film thickness which is attributed to increased localized defect states in the energy band gap. Our results emphasize relatively large thickness dependent optical nonlinearity of GO thin films and its potential for optical pulse generation, exploring the way to GO based nonlinear applications in Q switched mode locking laser systems. All the coated GO films were characterized by X-Ray diffraction method (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, UV-Vis absorption spectroscopy (UV-Vis), Photoluminescence (PL) and Scanning electron microscope (SEM) measurements.
NASA Astrophysics Data System (ADS)
Kulkarni, Manas; Kolmakov, German
2015-03-01
Given recent remarkable experimental success on capturing hydrodynamic features of exciton-polariton condensates in optical microcavities and their potential implications for quantum and optical computing and information technologies, we present an effective chiral description for such systems. This description captures the fingerprints of hydrodynamics, namely, nonlinearity, dispersion and dissipation in the exciton-polariton system. The resulting chiral equation for the condensate perturbation wave dynamics is found to be of Burgers-type thereby providing a more transparent understanding of the complicated underlying coupled exciton-photon dynamics. By using analytical calculations and numerical simulations, we describe the phenomenon of polariton shock waves, solitons and defects in such systems. Our mapping is expected to have broad implications for other polariton and photon systems including dipolar exciton and magnon condensates. This mapping can further help one in engineering a delicate balance between the pump and damping to produce stable optical signals propagating in polariton circuits.
Nonlinear effects in optical pumping of a cold and slow atomic beam
NASA Astrophysics Data System (ADS)
Porfido, N.; Bezuglov, N. N.; Bruvelis, M.; Shayeganrad, G.; Birindelli, S.; Tantussi, F.; Guerri, I.; Viteau, M.; Fioretti, A.; Ciampini, D.; Allegrini, M.; Comparat, D.; Arimondo, E.; Ekers, A.; Fuso, F.
2015-10-01
By photoionizing hyperfine (HF) levels of the Cs state 6 2P3 /2 in a slow and cold atom beam, we find how their population depends on the excitation laser power. The long time (around 180 μ s ) spent by the slow atoms inside the resonant laser beam is large enough to enable exploration of a unique atom-light interaction regime heavily affected by time-dependent optical pumping. We demonstrate that, under such conditions, the onset of nonlinear effects in the population dynamics and optical pumping occurs at excitation laser intensities much smaller than the conventional respective saturation values. The evolution of population within the HF structure is calculated by numerical integration of the multilevel optical Bloch equations. The agreement between numerical results and experiment outcomes is excellent. All main features in the experimental findings are explained by the occurrence of "dark" and "bright" resonances leading to power-dependent branching coefficients.
Harring, Jeffrey R; Blozis, Shelley A
2014-06-01
Nonlinear mixed-effects (NLME) models remain popular among practitioners for analyzing continuous repeated measures data taken on each of a number of individuals when interest centers on characterizing individual-specific change. Within this framework, variation and correlation among the repeated measurements may be partitioned into interindividual variation and intraindividual variation components. The covariance structure of the residuals are, in many applications, consigned to be independent with homogeneous variances, [Formula: see text], not because it is believed that intraindividual variation adheres to this structure, but because many software programs that estimate parameters of such models are not well-equipped to handle other, possibly more realistic, patterns. In this article, we describe how the programmatic environment within SAS may be utilized to model residual structures for serial correlation and variance heterogeneity. An empirical example is used to illustrate the capabilities of the module.
Effects of finite-precision arithmetic on interior-point methods for nonlinear programming.
Wright, S. J.; Mathematics and Computer Science
2001-10-23
We show that the effects of finite-precision arithmetic in forming and solving the linear system that arises at each iteration of primal-dual interior-point algorithms for nonlinear programming are benign, provided that the iterates satisfy centrality and feasibility conditions of the type usually associated with path-following methods. When we replace the standard assumption that the active constraint gradients are independent by the weaker Mangasarian--Fromovitz constraint qualification, rapid convergence usually is attainable, even when cancellation and roundoff errors occur during the calculations. In deriving our main results, we prove a key technical result about the size of the exact primal-dual step. This result can be used to modify existing analysis of primal-dual interior-point methods for convex programming, making it possible to extend the superlinear local convergence results to the nonconvex case.
Aoki, Yasunori; Nordgren, Rikard; Hooker, Andrew C
2016-03-01
As the importance of pharmacometric analysis increases, more and more complex mathematical models are introduced and computational error resulting from computational instability starts to become a bottleneck in the analysis. We propose a preconditioning method for non-linear mixed effects models used in pharmacometric analyses to stabilise the computation of the variance-covariance matrix. Roughly speaking, the method reparameterises the model with a linear combination of the original model parameters so that the Hessian matrix of the likelihood of the reparameterised model becomes close to an identity matrix. This approach will reduce the influence of computational error, for example rounding error, to the final computational result. We present numerical experiments demonstrating that the stabilisation of the computation using the proposed method can recover failed variance-covariance matrix computations, and reveal non-identifiability of the model parameters.
Non-linear electro-optical effects in the study of the helical smectic liquid crystals
NASA Astrophysics Data System (ADS)
Nowicka, K.; Kuczyński, W.
2016-04-01
Measurements of the non-linear electro-optical effects for the well-known prototype liquid crystal material (MHPOBC) are presented. The method to identify liquid crystalline phases and to determine temperatures of phase transitions based on the analysis of the second harmonic component of electro-optical response spectra is used. Applying that method, the values of the frequency (?) at which the second harmonic electro-optic response (EOR) possesses an extremum are determined for each smectic phase. We suggest that this characteristic frequency correspond to the phase-type mode processes. Furthermore, we show that the usually neglected results on heating can be useful in discussions of dynamical behaviour of second harmonic EOR in case of smectic phases.
Multiple Reflection Effects in Nonlinear Mixture Model for Hyperspectral Image Analysis
NASA Astrophysics Data System (ADS)
Liu, C. Y.; Ren, H.
2016-06-01
Hyperspectral spectrometers can record electromagnetic energy with hundreds or thousands of spectral channels. With such high spectral resolution, the spectral information has better capability for material identification. Because of the spatial resolution, one pixel in hyperspectral images usually covers several meters, and it may contain more than one material. Therefore, the mixture model must be considered. Linear mixture model (LMM) has been widely used for remote sensing target classifications, because of its simplicity and yields reasonable results for smooth surfaces. For rough surfaces, the physical interactions of the light scattered between multiple materials in the scene must be considered. Recently, Generalized Bilinear Model (GBM) is proposed and it includes the double reflection between different materials into a nonlinear model, but it ignores the interactions within the same material. In this study, we propose a modified version of GBM to further consider this effect in our model, called Modified Generalized Bilinear Model (MGBM).
Non-linear plasma effects on laser-induced terahertz emission from the atmosphere
NASA Astrophysics Data System (ADS)
Shin, J.-H.; Zhidkov, A.; Jin, Z.; Hosokai, T.; Kodama, R.
2012-02-01
Power, spectral characteristics, and angle distribution of terahertz (THz) radiation from air irradiated by a single (ω) or coupled (ω, 2ω) femtosecond laser pulses are analyzed for higher intensities, for which non-linear plasma effects on the pulse propagation become essential, by means of multidimensional particle-in-cell simulations exploiting the self-consistent plasma kinetics. THz radiation is shown to be a result of beat waves generated at ionization front with fundamental and second harmonic waves. At lower intensities, the THz power growth is far faster than the linear; at pulse intensities over I > 1015 W/cm2, the power increases slower than the linear. Along with the forward emission, strong power in around 30o angles occurs at high intensities. Ionization of air results in poor focusing of laser pulses and, therefore, lower efficiency of THz emission.
Nonlinear effects related to circularly polarized dispersive Alfvén waves
NASA Astrophysics Data System (ADS)
Sharma, Swati; Gaur, Nidhi; Sharma, R. P.
2016-09-01
In situ measurements of solar wind have strongly implicated its turbulent behavior. The observed power spectra report a breakpoint around length scales of the order of ion scales. As one of the responsible mechanisms for the observed steepening in power spectrum, our approach includes a right circularly polarized dispersive Alfvén wave (DAW) with finite frequency correction which, when subjected to transverse collapse/filamentation instability, may possibly result in steepening of spectrum and progressive transfer of energy from larger scales to smaller scales. We have studied the nonlinear effects associated with coupling of DAW with kinetic Alfvén wave in solar wind at 1 A.U. The formation of localized structures provides a clue about the emergence of turbulence. Numerical simulation is performed to study localization and power spectral density of the field and density fluctuations. The results show steeper spectrum indicating transfer of large scale turbulent energy down to small scales.
Tribeche, Mouloud; Boumezoued, Ghania
2008-05-15
The effect of nonthermal electrons with excess of fast energetic electrons on large amplitude electrostatic solitary waves is investigated in a charge varying dusty plasma. The correct nonthermal electron charging is investigated based on the orbit-motion-limited approach. It is found that the nonlinear localized potential structure shrinks when the electrons deviate from isothermality. The dust particles are locally expelled and pushed out the region of the soliton localization as the electrons evolve far away from their thermodynamic equilibrium. Under certain conditions, the dust charge fluctuation may provide an alternate physical mechanism causing anomalous dissipation, the strength of which becomes important and may prevail over that of dispersion as the value of the electron nonthermal parameter {alpha} increases.
Effective integration of ultra-elliptic solutions of the focusing nonlinear Schrödinger equation
NASA Astrophysics Data System (ADS)
Wright, O. C.
2016-05-01
An effective integration method based on the classical solution of the Jacobi inversion problem, using Kleinian ultra-elliptic functions and Riemann theta functions, is presented for the quasi-periodic two-phase solutions of the focusing cubic nonlinear Schrödinger equation. Each two-phase solution with real quasi-periods forms a two-real-dimensional torus, modulo a circle of complex-phase factors, expressed as a ratio of theta functions associated with the Riemann surface of the invariant spectral curve. The initial conditions of the Dirichlet eigenvalues satisfy reality conditions which are explicitly parametrized by two physically-meaningful real variables: the squared modulus and a scalar multiple of the wavenumber. Simple new formulas for the maximum modulus and the minimum modulus are obtained in terms of the imaginary parts of the branch points of the Riemann surface.
Memory and nonlinear transport effects in charging-discharging of a supercapacitor
NASA Astrophysics Data System (ADS)
Uchaikin, V. V.; Ambrozevich, A. S.; Sibatov, R. T.; Ambrozevich, S. A.; Morozova, E. V.
2016-02-01
We report on the results of analysis of the kinetics of charge-discharge current of Panasonic supercapacitors in a wide range of time from 10-1 to 104 s. The non-Debye behavior of relaxation observed earlier by us and other authors is confirmed experimentally, and the influence of the supercapacitor charging regime on this process for various previous histories (values of applied voltage, charging time, and load resistance) is analyzed. The results are compared with available experimental data for paper-oil and electrolytic capacitors and with the results of calculations in the linear response model. It is found that in contrast to conventional capacitors, the response of the supercapacitor under investigation to variations of the charging regime does not match the linear response model. The relation of this nonlinearity to processes in the double electric layer, the morphology of the porous electrode, and the effect of charge reversal in pores is considered.
Analyticity in Time and Smoothing Effect of Solutions to Nonlinear Schrödinger Equations
NASA Astrophysics Data System (ADS)
Hayashi, Nakao; Kato, Keiichi
In this paper we consider analyticity in time and smoothing effect of solutions to nonlinear Schrödinger equations
Jarvis, Gavin E; Barbosa, Roseli; Thompson, Andrew J
2016-03-01
Citral, eucalyptol, and linalool are widely used as flavorings, fragrances, and cosmetics. Here, we examined their effects on electrophysiological and binding properties of human 5-HT3 receptors expressed in Xenopus oocytes and human embryonic kidney 293 cells, respectively. Data were analyzed using nonlinear mixed-effects modeling to account for random variance in the peak current response between oocytes. The oils caused an insurmountable inhibition of 5-HT-evoked currents (citral IC50 = 120 µM; eucalyptol = 258 µM; linalool = 141 µM) and did not compete with fluorescently labeled granisetron, suggesting a noncompetitive mechanism of action. Inhibition was not use-dependent but required a 30-second preapplication. Compound washout caused a slow (∼180 seconds) but complete recovery. Coapplication of the oils with bilobalide or diltiazem indicated they did not bind at the same locations as these channel blockers. Homology modeling and ligand docking predicted binding to a transmembrane cavity at the interface of adjacent subunits. Liquid chromatography coupled to mass spectrometry showed that an essential oil extracted from Lippia alba contained 75.9% citral. This inhibited expressed 5-HT3 receptors (IC50 = 45 µg ml(-1)) and smooth muscle contractions in rat trachea (IC50 = 200 µg ml(-1)) and guinea pig ileum (IC50 = 20 µg ml(-1)), providing a possible mechanistic explanation for why this oil has been used to treat gastrointestinal and respiratory ailments. These results demonstrate that citral, eucalyptol, and linalool inhibit 5-HT3 receptors, and their binding to a conserved cavity suggests a valuable target for novel allosteric modulators. PMID:26669427
Jarvis, Gavin E; Barbosa, Roseli; Thompson, Andrew J
2016-03-01
Citral, eucalyptol, and linalool are widely used as flavorings, fragrances, and cosmetics. Here, we examined their effects on electrophysiological and binding properties of human 5-HT3 receptors expressed in Xenopus oocytes and human embryonic kidney 293 cells, respectively. Data were analyzed using nonlinear mixed-effects modeling to account for random variance in the peak current response between oocytes. The oils caused an insurmountable inhibition of 5-HT-evoked currents (citral IC50 = 120 µM; eucalyptol = 258 µM; linalool = 141 µM) and did not compete with fluorescently labeled granisetron, suggesting a noncompetitive mechanism of action. Inhibition was not use-dependent but required a 30-second preapplication. Compound washout caused a slow (∼180 seconds) but complete recovery. Coapplication of the oils with bilobalide or diltiazem indicated they did not bind at the same locations as these channel blockers. Homology modeling and ligand docking predicted binding to a transmembrane cavity at the interface of adjacent subunits. Liquid chromatography coupled to mass spectrometry showed that an essential oil extracted from Lippia alba contained 75.9% citral. This inhibited expressed 5-HT3 receptors (IC50 = 45 µg ml(-1)) and smooth muscle contractions in rat trachea (IC50 = 200 µg ml(-1)) and guinea pig ileum (IC50 = 20 µg ml(-1)), providing a possible mechanistic explanation for why this oil has been used to treat gastrointestinal and respiratory ailments. These results demonstrate that citral, eucalyptol, and linalool inhibit 5-HT3 receptors, and their binding to a conserved cavity suggests a valuable target for novel allosteric modulators.
Nonlinear optical effects on the surface of acridine yellow-doped lead-tin fluorophosphate glass
NASA Technical Reports Server (NTRS)
He, K. X.; Bryant, William; Venkateswarlu, Putcha
1991-01-01
The second- and third-order nonlinear optical properties of acridine yellow-doped lead-tin fluorophosphate (LTF) glass have been directly studied by measurement of surface enhanced second harmonic generation and third harmonic generation. The three photon excitation fluorescence is also observed. Based on these results, the large nonlinearities of the acridine LTF system which is a new nonlinear optical material are experimentally demonstrated.
Radiative Effect of Saharan Mineral Dust on the Nonlinear Dynamics of African Easterly Waves
NASA Astrophysics Data System (ADS)
Grogan, D.; Nathan, T. R.; Chen, S. H.
2014-12-01
The radiative effects of Saharan mineral dust aerosols on the nonlinear dynamics of African easterly waves (AEWs) are examined using the Weather Research and Forecasting Dust (WRFD) model. The WRFD model is governed by the Advanced Research WRF dynamical core, and continuity equations for twelve dust particle sizes that represent the spectrum of mineral dust aerosols observed in the atmosphere. To incorporate dust radiative effects in the model, aerosol optical properties (i.e. optical depth, single scattering albedo, and asymmetric parameters) for all dust sizes are inputted into the shortwave and longwave radiation schemes. By choosing zonal-mean distributions of zonal wind and temperature that are consistent with summer over Northwest Africa, idealized dry simulations explore the nonlinear behavior of AEWs in the presence of dust. The initial zonal-mean dust fields are represented as simple distributions that vary in structure and concentration, which are consistent with observed dust events over Africa. Specific AEW features investigated in the simulations include the evolution of wave energy, Eliassen-Palm fluxes, and spatial structures. Among the questions to be addressed are the following: How does the concentration and spatial distribution of the dust field affect the strength and timing of AEW amplitude saturation? What impact will the dust induced wave fluxes have on the horizontal or vertical shear of the zonal-mean AEJ? Does the interaction between the AEJ, AEW and dust affect the timing and location of the AEW trough, and thus the formation of critical latitudes? Answers to these questions will aid in the understanding and forecasting of AEWs, and their possible subsequent development into tropical storms.
Ramler, D; Mitteroecker, P; Shama, L N S; Wegner, K M; Ahnelt, H
2014-03-01
Theoretical models predict that nonlinear environmental effects on the phenotype also affect developmental canalization, which in turn can influence the tempo and course of organismal evolution. Here, we used an oceanic population of threespine stickleback (Gasterosteus aculeatus) to investigate temperature-induced phenotypic plasticity of body size and shape using a paternal half-sibling, split-clutch experimental design and rearing offspring under three different temperature regimes (13, 17 and 21 °C). Body size and shape of 466 stickleback individuals were assessed by a set of 53 landmarks and analysed using geometric morphometric methods. At approximately 100 days, individuals differed significantly in both size and shape across the temperature groups. However, the temperature-induced differences between 13 and 17 °C (mainly comprising relative head and eye size) deviated considerably from those between 17 and 21 °C (involving the relative size of the ectocoracoid, the operculum and the ventral process of the pelvic girdle). Body size was largest at 17 °C. For both size and shape, phenotypic variance was significantly smaller at 17 °C than at 13 and 21 °C, indicating that development is most stable at the intermediate temperature matching the conditions encountered in the wild. Higher additive genetic variance at 13 and 21 °C indicates that the plastic response to temperature had a heritable basis. Understanding nonlinear effects of temperature on development and the underlying genetics are important for modelling evolution and for predicting outcomes of global warming, which can lead not only to shifts in average morphology but also to destabilization of development.
The Effect of Surface Topography on the Nonlinear Dynamics of Rossby Waves
NASA Technical Reports Server (NTRS)
Abarzhi, S. I.; Desjardins, O.; Pitsch, H.
2003-01-01
Boussinesq convection in rotating systems attracts a sustained attention of the fluid dynamics community, because it has intricate non-linear dynamics (Cross & Hohenberg 1993) and plays an important role in geophysical and astrophysical applications, such as the motion of the liquid outer core of Earth, the Red Spot in Jupiter, the giant cells in the Sun etc. (Alridge et al. 1990). A fundamental distinction between the real geo- and astrophysical problems and the idealized laboratory studies is that natural systems are inhomogeneous (Alridge et al. 1990). Heterogeneities modulate the flow and influence significantly the dynamics of convective patterns (Alridge et al. 1990; Hide 1971). The effect of modulations on pattern formation and transition to turbulence in Boussinesq convection is far from being completely understood (Cross & Hohenberg 1993; Aranson & Kramer 2002). It is generally accepted that in the liquid outer core of the Earth the transport of the angular momentum and internal heat occurs via thermal Rossby waves (Zhang et al. 2001; Kuang & Bloxham 1999). These waves been visualized in laboratory experiments in rotating liquid-filled spheres and concentric spherical shells (Zhang et al. 2001; Kuang & Bloxham 1999). The basic dynamical features of Rossby waves have been reproduced in a cylindrical annulus, a system much simpler than the spherical ones (Busse & Or 1986; Or & Busse 1987). For convection in a cylindrical annulus, the fluid motion is two-dimensional, and gravity is replaced by a centrifugal force, (Busse & Or 1986; Or & Busse 1987). Hide (1971) has suggested that the momentum and heat transport in the core might be influenced significantly by so-called bumps, which are heterogeneities on the mantle-core boundary. To model the effect of surface topography on the transport of momentum and energy in the liquid outer core of the Earth, Bell & Soward (1996), Herrmann & Busse (1998) and Westerburg & Busse (2001) have studied the nonlinear dynamics