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1

Pulsatory Patterns in Active Fluids

NASA Astrophysics Data System (ADS)

We show that pulsatory patterns arise in thin active films in which two chemical species regulate active stress. The regulating species diffuse within the film and are advected by self-generated flows resulting from active stress gradients. Spontaneous pulsatory patterns emerge when the following conditions are met: (i) the fast-diffusing species up-regulates and the slow-diffusing species down-regulates active stress, or (ii) the active stress up-regulator turns over faster compared to the active stress down-regulator. Our study, motivated by pulsatory patterns in the actomyosin cortex in cells and tissues, provides a simple generic mechanism for oscillatory patterns in active fluids.

Kumar, K. Vijay; Bois, Justin S.; Jülicher, Frank; Grill, Stephan W.

2014-05-01

2

Quasi-Periodic Hopf Bifurcation.

National Technical Information Service (NTIS)

In the paper, the authors study quasi-periodic Hopf bifurcations for the model problem of a quasi-periodically forced oscillator, where the frequencies remain fixed. For this purpose, they first consider Stoker's problem for small damping.

B. L. J. Braaksma H. W. Broer

1985-01-01

3

Talbot effect of quasi-periodic grating.

Theoretic and experimental studies of the Talbot effect of quasi-periodic gratings are performed in this paper. The diffractions of periodic and quasi-periodic square aperture arrays in Fresnel fields are analyzed according to the scalar diffraction theory. The expressions of the diffraction intensities of two types of quasi-periodic gratings are deduced. Talbot images of the quasi-periodic gratings are predicted to appear at multiple certain distances. The quasi-periodic square aperture arrays are produced with the aid of a liquid crystal light modulator, and the self-images of the quasi-periodic gratings are measured successfully in the experiment. This study indicates that even a structure in short-range disorder may take on the self-imaging effect in a Fresnel field. PMID:23872752

Zhang, Chong; Zhang, Wei; Li, Furui; Wang, Junhong; Teng, Shuyun

2013-07-20

4

Toward a Quasi-Periodic Bifurcation Theory,

National Technical Information Service (NTIS)

The subject of the paper concerns families of dynamical systems having invariant tori with parallel and, more specifically, quasi-periodic motion. In particular, questions are posed of stability (persistence) and, more importantly, bifurcation. The settin...

B. L. J. Braaksma H. W. Broer G. B. Huitema

1988-01-01

5

Quasi Periodicity in Local Bifurcation Theory.

National Technical Information Service (NTIS)

The paper presents an overview of some results obtained recently in the local theory of bifurcations of dynamical systems, which are concerned with quasi periodic flow. With this 'local theory' we here mean the qualitative (topological) behavior of parame...

H. W. Broer

1982-01-01

6

Quasi-periodic solutions of a quasi-periodically forced nonlinear beam equation

NASA Astrophysics Data System (ADS)

In this paper, one quasi-periodically forced nonlinear beam equation utt+uxxxx+?u+?g(?t,x)u3=0,?>0,x?[0,?] with hinged boundary conditions is considered. Here ? is a small positive parameter, g( ?t, x) is real analytic in all variables and quasi-periodic in t with a frequency vector ? = ( ?1, ?2, … , ?m). It is proved that the above equation admits small-amplitude quasi-periodic solutions.

Wang, Yi

2012-06-01

7

Quasi-periodically forced nonlinear Helmholtz oscillators

In this paper we study a model that describes the dynamics of the tidal elevation within an almost-enclosed short basin that is connected to a tidal sea by a narrow strait. This model has the form of a forced nonlinear Helmholtz oscillator. The forcing is prescribed by the tide at sea and has a quasi-periodic character of a special nature,

Arjen Doelman; A. Femius Koenderink; Leo R. M. Maasc

8

Quasi-periodic quantum dot arrays produced by electrochemical synthesis.

National Technical Information Service (NTIS)

We discuss a ''gentle'' electrochemical technique for fabricating quasi-periodic quantum dot arrays. The technique exploits a self-organizing phenomenon to produce quasi-periodic arrangement of dots and provides excellent control over dot size and interdo...

S. Bandyopadhyay A. E. Miller D. F. Yue G. Banerjee R. E. Ricker

1994-01-01

9

Quasi-periodic oscillations in superfluid magnetars

NASA Astrophysics Data System (ADS)

We study the time evolution of axisymmetric oscillations of superfluid magnetars with a poloidal magnetic field and an elastic crust, working in Newtonian gravity. Extending earlier models, we study the effects of composition gradients and entrainment on the magneto-elastic wave spectrum and on the potential identification of the observed quasi-periodic oscillations (QPOs). We use two-fluid polytropic equations of state to construct our stellar models, which mimic realistic composition gradient configurations. The basic features of the axial axisymmetric spectrum of normal fluid stars are reproduced by our results and in addition we find several magneto-elastic waves with a mixed character. In the core, these oscillations mimic the shear mode pattern of the crust as a result of the strong dynamical coupling between these two regions. Incorporating the most recent entrainment configurations in our models, we find that they have a double effect on the spectrum: the magnetic oscillations of the core have a frequency enhancement, while the mixed magneto-elastic waves originating in the crust are moved towards the frequencies of the single-fluid case. The distribution of lower frequency magneto-elastic oscillations for our models is qualitatively similar to the observed magnetar QPOs with ? < 155 Hz.

Passamonti, A.; Lander, S. K.

2014-02-01

10

NASA Astrophysics Data System (ADS)

In this paper, we prove that any analytic quasi-periodic cocycle close to constant is the Poincaré map of an analytic quasi-periodic linear system close to constant, which bridges both methods and results in quasi-periodic linear systems and cocycles. We also show that the almost reducibility of an analytic quasi-periodic linear system is equivalent to the almost reducibility of its corresponding Poincaré cocycle. By the local embedding theorem and the equivalence, we transfer the recent local almost reducibility results of quasi-periodic linear systems (Hou and You, in Invent Math 190:209-260, 2012) to quasi-periodic cocycles, and the global reducibility results of quasi-periodic cocycles (Avila, in Almost reducibility and absolute continuity, 2010; Avila et al., in Geom Funct Anal 21:1001-1019, 2011) to quasi-periodic linear systems. Finally, we give a positive answer to a question of Avila et al. (Geom Funct Anal 21:1001-1019, 2011) and use it to study point spectrum of long-range quasi-periodic operator with Liouvillean frequency. The embedding also holds for some nonlinear systems.

You, Jiangong; Zhou, Qi

2013-11-01

11

Characteristics of quasi-periodic scintillations observed at low latitude

NASA Astrophysics Data System (ADS)

Quasi-periodic scintillations are characterized as primary deep fadeout in field strength, associated with regular ringing patterns before and after it. In this paper, observations of quasi-periodic scintillations using geostationary satellite (FLEETSAT) transmissions operating at frequency 250 MHz at low-latitude ground station, Varanasi (geomagnetic latitude 14°55'N, longitude 153°59'E), are reported. The results indicate that the quasi-periodic scintillations are most likely produced by plasma blobs/bubbles present in the E and F regions of the ionosphere which are helpful in identifying the generation mechanism of the associated irregularities. The various characteristic features of the different types of quasi-periodic scintillations observed at low latitude are discussed for the first time in detail based on a highly comprehensive analysis of longer data sets using autocorrelation, power spectrum, and scintillation index analysis. The computed horizontal scale size of the quasi-periodic scintillations producing irregularity varies from 100 to 1300 m which shows that the irregularities are of intermediate-scale sizes. The spectral index obtained from the slopes of power spectrum varies from -2 to -8. All of these observed results are important for identifying the generation mechanism of ionospheric irregularities associated with quasi-periodic scintillations. The observed fading patterns, especially the modulation of the diffraction patterns (fading envelopes), can be explained by considering an obstacle called radio lens in the ionosphere elongated in one direction. For the first time, we have successfully simulated the amplitude versus time plots of almost all types of quasi-periodic scintillation patches and found that our modeled and observed characteristics of quasi-periodic scintillation patches compare well with each other.

Patel, Kalpana; Singh, Ashutosh K.; Singh, A. K.; Singh, R. P.

2009-12-01

12

Quasi-periodic solutions of forced isochronous oscillators at resonance

NASA Astrophysics Data System (ADS)

We deal with the existence of quasi-periodic solutions of forced isochronous oscillators with a repulsive singularity, the nonlinearity is a bounded perturbation. Using a variant of Moser's twist theorem of invariant curves, due to Ortega [R. Ortega, Boundedness in a piecewise linear oscillator and a variant of the small twist theorem, Proc. London Math. Soc. 79 (1999) 381-413], we show that there are many quasi-periodic solutions and the boundedness of all solutions.

Liu, Bin

13

The Ten-Rotation Quasi-periodicity in Sunspot Areas

NASA Astrophysics Data System (ADS)

Sunspot-area fluctuations over an epoch of 12 solar cycles (12 - 23) are investigated in detail using wavelets. Getko ( Universal Heliophysical Processes, IAU Symp. 257, 169, 2009) found three significant quasi-periodicities at 10, 17, and 23 solar rotations, but two longer periods could be treated as subharmonics of the ten-rotation quasi-periodicity. Therefore we focused the analysis on the occurrence of this quasi-periodicity during the low- and high-activity periods of each solar cycle. Because of the N - S asymmetry, each solar hemisphere was considered separately. The skewness of each fluctuation-probability distribution suggests that the positive and negative fluctuations could be examined separately. To avoid the problem that occurs when a few strong fluctuations create a wavelet peak, we applied fluctuation transformations for which the amplitudes at the high- and the low-activity periods are almost the same. The wavelet analyses show that the ten-rotation quasi-periodicity is mainly detected during the high-activity periods, but it also exists during a few low-activity periods. The division of each solar hemisphere into 30?-wide longitude bins and the wavelet calculations for the areas of sunspot clusters belonging to these 30? bins enable one to detect longitude zones in which the ten-rotation quasi-periodicity exists. These zones are present during the whole high-activity periods and dominate the integrated spectra.

Getko, R.

2014-06-01

14

Pressure-driven reconnection and quasi periodical oscillations in plasmas

NASA Astrophysics Data System (ADS)

This paper presents a model for an ohmically heated plasma in which a feedback exists between thermal conduction and transport, on one side, and the magneto-hydro-dynamical stability of the system, on the other side. In presence of a reconnection threshold for the magnetic field, a variety of periodical or quasi periodical oscillations for the physical quantities describing the system are evidenced. The model is employed to interpret the observed quasi periodical oscillations of electron temperature and perturbed magnetic field around the so called "Single Helical" state in the reversed field pinch, but its relevance for other periodical phenomena observed in magnetic confinement systems, especially in tokamaks, is suggested.

Paccagnella, R.

2014-03-01

15

A result on quasi-periodic solutions of a nonlinear beam equation with a quasi-periodic forcing term

NASA Astrophysics Data System (ADS)

In this paper, a quasi-periodically forced nonlinear beam equation {u_{tt}+u_{xxxx}+? u+\\varepsilon?(t)h(u)=0} with hinged boundary conditions is considered, where ? > 0, {\\varepsilon} is a small positive parameter, {?} is a real analytic quasi-periodic function in t with a frequency vector ? = ( ? 1, ? 2 . . . , ? m ), and the nonlinearity h is a real analytic odd function of the form {h(u)=?_1u+?_{2bar{r}+1}u^{2bar{r}+1}+sum_{k? bar{r}+1}?_{2k+1}u^{2k+1},?_1,?_{2bar{r}+1} neq0, bar{r} in {mathbb {N}}.} The above equation admits a quasi-periodic solution.

Wang, Yi; Si, Jianguo

2012-02-01

16

Scattering Theory for Jacobi Operators with Quasi-Periodic Background

NASA Astrophysics Data System (ADS)

We develop direct and inverse scattering theory for Jacobi operators which are short range perturbations of quasi-periodic finite-gap operators. We show existence of transformation operators, investigate their properties, derive the corresponding Gel'fand-Levitan-Marchenko equation, and find minimal scattering data which determine the perturbed operator uniquely.

Egorova, Iryna; Michor, Johanna; Teschl, Gerald

2006-06-01

17

Construction of Quasi-Periodic Breathersvia KAM Technique

NASA Astrophysics Data System (ADS)

By developing a KAM theorem which involves an infinitely multiple normal frequency, it is shown that there are plenty of breathers, quasi-periodic in time and super-exponentially localized in space, for the networks of weakly coupled oscillators. This answers an open problem by Aubry [A2] in case the linearized system has no continuous spectrum.

Yuan, Xiaoping

18

TT Ari and its Quasi-Periodic Oscillations

NASA Astrophysics Data System (ADS)

Quasi-periodic oscillation (QPO) of TT Ari are transient, short-lived phenomena. They appear and disappear and their periods and amplitudes vary on a time scale as short as 1 hour. Consequently the periodograms covering longer intervals of time are generally meaningless.

Smak, J.

2014-06-01

19

Normal linear stability of quasi-periodic tori

NASA Astrophysics Data System (ADS)

We consider families of dynamical systems having invariant tori that carry quasi-periodic motions. Our interest is the persistence of such tori under small, nearly-integrable perturbations. This persistence problem is studied in the dissipative, the Hamiltonian and the reversible setting, as part of a more general KAM theory for classes of structure preserving dynamical systems. This concerns the parametrized KAM theory as initiated by Moser [J.K. Moser, On the theory of quasiperiodic motions, SIAM Rev. 8 (2) (1966)145-172; J.K. Moser, Convergent series expansions for quasi-periodic motions, Math. Ann. 169 (1967) 136-176] and further developed in [G.B. Huitema, Unfoldings of quasi-periodic tori, PhD thesis, University of Groningen, 1988; H.W. Broer, G.B. Huitema, F. Takens, Unfoldings of quasi-periodic tori, Mem. Amer. Math. Soc. 83 (421) (1990) 1-82; H.W. Broer, G.B. Huitema, Unfoldings of quasi-periodic tori in reversible systems, J. Dynam. Differential Equations 7 (1) (1995) 191-212]. The corresponding nondegeneracy condition involves certain (trans-)versality conditions on the normal linear, leading, part at the invariant tori. We show that as a consequence, a Cantor family of Diophantine tori with positive Hausdorff measure is persistent under nearly-integrable perturbations. This result extends the above references since presently the case of multiple Floquet exponents is included. Our leading example is the normal 1 :-1 resonance, which occurs a lot in applications, both Hamiltonian and reversible. As an illustration of this we briefly describe the Lagrange top coupled to an oscillator.

Broer, H. W.; Hoo, J.; Naudot, V.

20

Quasi-periodic quantum dot arrays produced by electrochemical synthesis

We discuss a ``gentle`` electrochemical technique for fabricating quasi-periodic quantum dot arrays. The technique exploits a self-organizing phenomenon to produce quasi-periodic arrangement of dots and provides excellent control over dot size and interdot spacing. Unlike conventional nanolithography, it does not cause radiation damage to the structures during exposure to pattern delineating beams (e-beam, ion-beam or x-ray). Moreover, it does not require harsh processing steps like reactive ion etching, offers a minimum feature size of {approximately}40 {angstrom}, allows the fabrication of structures on nonplanar surfaces (e.g. spherical or cylindrical substrates), is amenable to mass production (millions of wafers can be processed simultaneously) and is potentially orders of magnitude cheaper than conventional nanofabrication. In this paper, we describe our initial results and show the promise of this technique for low-cost and high-yield nanosynthesis.

Bandyopadhyay, S.; Miller, A.E.; Yue, D.F.; Banerjee, G. [Univ. of Notre Dame, Notre Dame, IN (United States). Dept. of Electrical Engineering; Ricker, R.E.; Jones, S. [National Inst. of Standards and Technology, Gaithersburg, MD (United States). Materials Science and Engineering Laboratory; Eastman, J.A. [Argonne National Lab., IL (United States); Baugher, E.; Chandrasekhar, M. [Univ. of Missouri-Columbia, Columbia, MS (United States). Dept. of Physics and Astronomy

1994-06-01

21

Anderson Localization for Time Quasi Periodic Random Sch\\\\\\

We prove that at large disorder, with large probability and for a set of\\u000aDiophantine frequencies of large measure, Anderson localization in $\\\\Bbb Z^d$\\u000ais {\\\\it stable} under localized time-quasi-periodic perturbations by proving\\u000athat the associated quasi-energy operator has pure point spectrum. The main\\u000atools are the Fr\\\\\\

Jean Bourgain; Wei-Min Wang

2002-01-01

22

Quasi-periodic orbits about the translunar libration point

Analytical solutions for quasi-periodic orbits about the translunar libration point are obtained by using the method of Lindstedt-Poincaré and computerized algebraic manipulations. The solutions include the effects of nonlinearities, lunar orbital eccentricity, and the Sun's gravitational field. For a small-amplitude orbit, the orbital path as viewed from the Earth traces out a Lissajous figure. This is due to a small

Robert W. Farquhar; Ahmed A. Kamel

1973-01-01

23

Quasi-periodic vertical structures of dusty plasma crystals

A semi-analytical model is proposed for understanding the quasi-periodic vertical structures in a plasma crystal, which are shown to be sustained by the combined effects of an ion flow, gravity and horizontal bonds of the dust particles. These structures are the manifestations of large-amplitude standing wake fields that lead to strong vertical bonds for the formation of an oriented hexagonal

Tzihong Chiueh; D. Ming-Ting Kuo

1999-01-01

24

Quasi-periodic modulations of the Jovian magnetotail

Measurements with the Energetic Particles Detector (EPD) on Galileo orbit C9 in the Jovian magnetotail revealed the existence of distinct quasi-periodic variations of energetic ion intensities which are superimposed on the well-known 10-hour modulations due to the planetary rotation. The intensity variations are associated with changes of the particle energy spectra and the plasma flow pattern. They are clearly of

J. Woch; N. Krupp; A. Lagg; B. Wilken; S. Livi; D. J. Williams

1998-01-01

25

Explicit quasi-periodic solutions of the Vakhnenko equation

NASA Astrophysics Data System (ADS)

The trigonal curve associated with the Vakhnenko equation is introduced by using the Lax matrix for the nth stationary positive flow. Based on the theory of the trigonal curve and the properties of the three kinds of Abel differentials, the Riemann theta function representation for the Baker-Akhiezer function is derived, from which the straightening out of flows in the Jacobian variety is exactly given through the Abel maps. We finally arrive at quasi-periodic solutions of the Vakhnenko equation.

Zhai, Yunyun; Geng, Xianguo; He, Guoliang

2014-05-01

26

QUASI-PERIODIC OSCILLATIONS IN LASCO CORONAL MASS EJECTION SPEEDS

Quasi-periodic oscillations in the speed profile of coronal mass ejections (CMEs) in the radial distance range 2-30 solar radii are studied. We considered the height-time data of the 307 CMEs recorded by the Large Angle and Spectrometric Coronagraph (LASCO) during 2005 January-March. In order to study the speed-distance profile of the CMEs, we have used only 116 events for which there are at least 10 height-time measurements made in the LASCO field of view. The instantaneous CME speed is estimated using a pair of height-time data points, providing the speed-distance profile. We found quasi-periodic patterns in at least 15 speed-distance profiles, where the speed amplitudes are larger than the speed errors. For these events we have determined the speed amplitude and period of oscillations. The periods of quasi-periodic oscillations are found in the range 48-240 minutes, tending to increase with height. The oscillations have similar properties as those reported by Krall et al., who interpreted them in terms of the flux-rope model. The nature of forces responsible for the motion of CMEs and their oscillations are discussed.

Shanmugaraju, A. [Department of Physics, Arul Anandar College, Karumathur-625 514 (India); Moon, Y.-J. [School of Space Research, Kyung Hee University, Yongin 446-701 (Korea, Republic of); Cho, K.-S.; Bong, S. C. [Korea Astronomy and Space Science Institute (KASI), Whaamdong, Yuseong-gu, Daejeon, 305-348 (Korea, Republic of); Gopalswamy, N.; Akiyama, S.; Yashiro, S. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Umapathy, S. [School of Physics, Madurai Kamaraj University, Madurai (India); Vrsnak, B., E-mail: shanmugaraju_a@yahoo.co, E-mail: moonyj@khu.ac.k [Hvar Observatory, Faculty of Geodesy, Zagreb (Croatia)

2010-01-01

27

Overall ultimate yield strength of a quasi-periodic masonry

NASA Astrophysics Data System (ADS)

The purpose of this Note is the determination of the in-plane homogenized strength domain of a "quasi-periodic" masonry under the assumption of infinitely resistant blocks connected by cohesionless Mohr-Coulomb interfaces. This masonry is obtained by introducing a random perturbation on the horizontal width of the blocks of a periodic running bond masonry. It is found that in some non-trivial cases the strength domain coincides exactly with that of the initial periodic masonry. To cite this article: K. Sab, C. R. Mecanique 337 (2009).

Sab, Karam

2009-08-01

28

The quasi-periodicity of the minority game revisited

NASA Astrophysics Data System (ADS)

We analyze two well-known related aspects regarding the sequence of minority sides from the Minority Game (MG) in its symmetric phase: period-two dynamics and quasi-periodic behavior. We also study the sequence of minority sides in a general way within a graph-theoretical framework. In order to analyze the outcome dynamics of the MG, it is useful to define the MG, namely an MG with a new choosing rule of the strategy to play, which takes into account both prior preferences and game information. In this way, each time an agent is undecided because two of her best strategies predict different choices while being equally successful so far, she selects her a priori favorite strategy to play, instead of performing a random tie-break as in the MG. This new choosing rule leaves the generic behavior of the model unaffected and simplifies the game analysis. Furthermore, interesting properties arise which are only partially present in the MG, like the quasi-periodic behavior of the sequence of minority sides, which turns out to be periodic for the MG.

Acosta, Gabriel; Caridi, Inés; Guala, Sebastián; Marenco, Javier

2013-10-01

29

Quasi-periodic Solutions of the Kaup-Kupershmidt Hierarchy

NASA Astrophysics Data System (ADS)

Based on solving the Lenard recursion equations and the zero-curvature equation, we derive the Kaup-Kupershmidt hierarchy associated with a 3×3 matrix spectral problem. Resorting to the characteristic polynomial of the Lax matrix for the Kaup-Kupershmidt hierarchy, we introduce a trigonal curve {K}_{m-1} and present the corresponding Baker-Akhiezer function and meromorphic function on it. The Abel map is introduced to straighten out the Kaup-Kupershmidt flows. With the aid of the properties of the Baker-Akhiezer function and the meromorphic function and their asymptotic expansions, we arrive at their explicit Riemann theta function representations. The Riemann-Jacobi inversion problem is achieved by comparing the asymptotic expansion of the Baker-Akhiezer function and its Riemann theta function representation, from which quasi-periodic solutions of the entire Kaup-Kupershmidt hierarchy are obtained in terms of the Riemann theta functions.

Geng, Xianguo; Wu, Lihua; He, Guoliang

2013-08-01

30

Quasi-periodic orbits about the translunar libration point.

NASA Technical Reports Server (NTRS)

Analytical solutions for quasi-periodic orbits about the translunar libration point are obtained by using the method of Lindstedt-Poincare and computerized algebraic manipulations. The solutions include the effects of nonlinearities, lunar orbital eccentricity, and the sun's gravitational field. For a small-amplitude orbit, the orbital path as viewed from the earth traces out a Lissajous figure. This is due to a small difference in the fundamental frequencies of the in-plane and out-of-plane oscillations. However, when the amplitude of the in-plane oscillation is greater than 32,379 km, there is a corresponding value of the out-of-plane amplitude that will produce a path where the fundamental frequencies are equal. This synchronized trajectory describes a 'halo orbit' of the moon.

Farquhar, R. W.; Kamel, A. A.

1972-01-01

31

Quasi-periodic orbits about the translunar libration point.

NASA Technical Reports Server (NTRS)

Analytical solutions for quasi-periodic orbits about the translunar libration point are obtained by using the method of Lindstedt-Poincare and computerized algebraic manipulations. The solutions include the effects of nonlinearities, lunar orbital eccentricity, and the sun's gravitational field. For a small-amplitude orbit, the orbital path as viewed from the earth traces out a Lissajous figure. This is due to a small difference in the fundamental frequencies of the in-plane and out-of-plane oscillations. However, when the amplitude of the in-plane oscillation is greater than 32,379 km, there is a corresponding value of the out-of-plane amplitude that will produce a path where the fundamental frequencies are equal. This synchronized trajectory describes a 'halo orbit' of the moon.

Farquhar, R. W.; Kamel, A. A.

1973-01-01

32

Search for Quasi-Periodic Oscillations in Quasars and AGNS

NASA Astrophysics Data System (ADS)

Quasars and Active galaxies such OJ287 RX J0437.4-4711 exhibit variabilities in a wide range of time-scales and in almost all the wavelengths. We show that some of these variabilities are periodic and have similarities with the Quasi-periodic oscillations of their micro-quasar counterparts such as GRS1915+105 Cyg. X1 GRO J1655-40 etc. Only difference is that the periodicity scales with the mass of the central engine. We explain these QPOs in terms of the oscillation of standing shocks around the central black holes. Our work conclusively proves that the physical phenomena around stellar mass and supermassive black holes are similar.

Nandi, Anuj; Chakrabarti, Sandip K.

33

Quasi-periodic oscillations in GX 17 + 2

NASA Technical Reports Server (NTRS)

X-ray observations of GX 17 + 2 were made in March and April, 1988 with the Large Area Counter of the Ginga satellite. The source was observed in the flaring, normal, and horizontal branches. Quasi-periodic oscillations (QPOs) were oberved in all three of these branches. The relationship between QPO behavior and the X-ray spectral properties of GX 17 + 2 is examined. Continuous variation of QPO behavior is observed as GX 17 + 2 moves from the normal to flaring branch, indicating that the normal-branch QPO and the flaring-branch QPO are probably one physical phenomenon. This QPO behavior is similar to that observed in Sco X-1. Also, it is found that GX 17 + 2 is an example of the Z-type sources defined by Hasinger et al. (1989).

Penninx, W.; Lewin, W. H. G.; Mitsuda, K.; Van Der Klis, M.; Van Paradijs, J.

1990-01-01

34

Aperiodic and Quasi-Periodic Variability in Scorpius X-1

NASA Astrophysics Data System (ADS)

Low mass X-ray binary star systems (LMXBs) are among the brightest and most well-studied objects in the X-ray sky-indeed, the first extrasolar X-ray source discovered, Sco X-1, is an LMXB. But despite the wealth of available data, LMXBs remain enigmatic, in large part due to the fact that they show little or no coherent periodicity. LMXBs show aperiodic and quasi-periodic variability, for which the underlying mechanisms are poorly understood. Much information remains locked in archival data. Here we address this issue by re-analyzing archival EXOSAT data of Sco X-1 using modern time-series techniques, including multi-tapering, wavelet transforms and scalegrams, and nonlinear dynamical modelling, which are not yet commonly used in the analysis of astronomical data, with the goal of characterizing Sco X-1's variability and developing a formalism to take us from timing data to mathematical models to astrophysical models. The power spectra of Sco X-1 show several components: (i) very low frequency noise (VLFN), a colored noise component seen below ~0.25 Hz, (ii) high frequency noise (HFN), a colored noise component seen above ~30-40 Hz, and (iii) quasi-periodic oscillations (QPOs), localized excesses of Fourier power. The VLFN contains ~1.3% [1/over2]-peak-to-peak pulsed power on the average, can be described by a power law with an index of ~1.4, and is correlated with the 'flickeriness' of the source. QPOs contain ~4.6% [1/over2]-peak-to-peak pulsed power, have centroid frequencies of 6.7 Hz or 15 Hz, and are associated with extended 'quiescent' states and with brief gaps in 'flaring' states. HFN is difficult to characterize (though others have had success describing it as a damped power law), and is not strongly associated with any other source feature. It contains ~2.1% [1/over2]-peak-to-peak pulsed power. Several models have been proposed to explain the VLFN, QPOs, and HFN in Sco X-1, but none are completely satisfactory. Most models seek to explain only QPOs. Here we investigate the dripping handrail model (DHR), a nonlinear dynamical model. The DHR is a deterministic, spatially extended, diffusive model which shows a complex variety of behaviors including QPOs and transient chaos. It can reproduce the entire observed power spectra of Sco X-1, from 0.5 mHz to 128 Hz, including VLFN, QPOs, and HFN.

Parker, Neil Ivan

35

Quasi-periodic fluctuations in default mode network electrophysiology.

The study of human brain electrophysiology has extended beyond traditional frequency ranges identified by the classical EEG rhythms, encompassing both higher and lower frequencies. Changes in high-gamma-band (>70 Hz) power have been identified as markers of local cortical activity. Fluctuations at infra-slow (<0.1 Hz) frequencies have been associated with functionally significant cortical networks elucidated using fMRI studies. In this study, we examined infra-slow changes in band-limited power across a range of frequencies (1-120 Hz) in the default mode network (DMN). Measuring the coherence in band-limited power fluctuations between spatially separated electrodes makes it possible to detect small, spatially extended, and temporally coherent fluctuating components in the presence of much larger incoherent fluctuations. We show that the default network is characterized by significant high-gamma-band (65-110 Hz) coherence at infra-slow (<0.1 Hz) frequencies. This coherence occurs over a narrow frequency range, centered at 0.015 Hz, commensurate with the frequency of BOLD signal fluctuations seen by fMRI, suggesting that quasi-periodic, infra-slow changes in local cortical activity form the neurophysiological basis for this network. PMID:21832202

Ko, Andrew L; Darvas, Felix; Poliakov, Andrew; Ojemann, Jeffrey; Sorensen, Larry B

2011-08-10

36

Quasi-periodic vertical structures of dusty plasma crystals

NASA Astrophysics Data System (ADS)

A semi-analytical model is proposed for understanding the quasi-periodic vertical structures in a plasma crystal, which are shown to be sustained by the combined effects of an ion flow, gravity and horizontal bonds of the dust particles. These structures are the manifestations of large-amplitude standing wake fields that lead to strong vertical bonds for the formation of an oriented hexagonal lattice. The orientational symmetry breaking is caused by a gravity-induced thick sheath, which can preferentially accelerate a supersonic ion flow in the vertical direction. The electron and streaming ion densities and the electric potential are found to be all in phase in the plasma crystal, whereas the dust density is 180 degrees out of phase. With each dust layer playing a similar role as the plasma wall, the Bohm sheath criterion is also found to be satisfied. Crystal melting may also be qualitatively described by the present model when the horizontal bonds of the dust particles are sufficiently weakened.

Chiueh, Tzihong; Ming-Ting Kuo, D.

1999-04-01

37

NASA Astrophysics Data System (ADS)

A microwave quasi-periodic pulsation with zigzag pattern (Z-QPP) in a solar flare on 2005-01-15 is observed by the Chinese Solar Broadband Spectrometer in Huairou (SBRS/Huairou) at 1.10-1.34 GHz. The zigzag pulsation occurred just in the early rising phase of the flare with weakly right-handed circular polarization. Its period is only several decades millisecond. Particularly, before and after the pulsation, there are many spectral fine structures, such as zebra patterns, fibers, and millisecond spikes. The microwave Z-QPP can provide some kinematic information of the source region in the early rising phase of the flare, and the source width changes from ~1000 km to 3300 km, even if we have no imaging observations. The abundant spectral fine structures possibly reflect the dynamic features of non-thermal particles.

Tan, Baolin

2013-07-01

38

Omnidirectional reflection from Fibonacci quasi-periodic one-dimensional photonic crystal

NASA Astrophysics Data System (ADS)

It is shown that omnidirectional reflection (ODR) is possible from quasi-periodic isotropic dielectric stacks following a Fibonacci sequence (FS). The transition from truly periodic to fully quasi-periodic structure is investigated by building periodic structures having unit cells made of FS of order j. The number of periods required to achieve ODR decreases as j increases until only a single period is required at which the structure is fully quasi-periodic. As compared to the periodic case, for the quasi-periodic structure the spectral range is wider, the thickness of the single layers is smaller and the tolerance on the layer thicknesses is smaller.

Lusk, D.; Abdulhalim, I.; Placido, F.

2001-11-01

39

Are Flare Quasi-periodic Pulsations Signatures of Intermittent Reconnection?

NASA Astrophysics Data System (ADS)

Flare quasi-periodic pulsations (QPPs) have been observed over a vast energy spectrum, from radio to hard x-rays. The periodicities of these fine structures range from tens of milliseconds to tens of seconds and suggest highly structured but intermittent energy release. In some cases, the sources of microwaves and thermal hard x-rays are situated near the apex of the flare loop arcades and are not stationary. Although it is unclear whether all the observed varieties of QPPs can be explained via a single, unified process, our recent high-resolution simulations of a breakout eruptive flare (Karpen et al. 2012) indicate that spatially and temporally localized reconnection is a plausible candidate for these bursts of radiation. With our null-tracking capabilities, we follow the creation and evolution of X- and O-type nulls in the flare current sheet and characterize their periodicity. QPPs located at the apex of the flare arcade may result from the interaction of downward-moving islands in the sheet with the arcade below. Each island is composed of highly twisted magnetic field lines that comprise a single reconnected flux tube. Upon arrival at the top of the flare loops, secondary reconnection events between the island and the arcade produce discrete energy release events that could be related to observed QPPs in that region. Different regimes of current-sheet reconnection (slow/fast), island sizes, rates of island coalescence, and rates of reconnection between islands and arcades may all help to explain the variety of energy and time scales exhibited by the flare QPPs.Abstract (2,250 Maximum Characters): Flare quasi-periodic pulsations (QPPs) have been observed over a vast energy spectrum, from radio to hard x-rays. The periodicities of these fine structures range from tens of milliseconds to tens of seconds and suggest highly structured but intermittent energy release. In some cases, the sources of microwaves and thermal hard x-rays are situated near the apex of the flare loop arcades and are not stationary. Although it is unclear whether all the observed varieties of QPPs can be explained via a single, unified process, our recent high-resolution simulations of a breakout eruptive flare (Karpen et al. 2012) indicate that spatially and temporally localized reconnection is a plausible candidate for these bursts of radiation. With our null-tracking capabilities, we follow the creation and evolution of X- and O-type nulls in the flare current sheet and characterize their periodicity. QPPs located at the apex of the flare arcade may result from the interaction of downward-moving islands in the sheet with the arcade below. Each island is composed of highly twisted magnetic field lines that comprise a single reconnected flux tube. Upon arrival at the top of the flare loops, secondary reconnection events between the island and the arcade produce discrete energy release events that could be related to observed QPPs in that region. Different regimes of current-sheet reconnection (slow/fast), island sizes, rates of island coalescence, and rates of reconnection between islands and arcades may all help to explain the variety of energy and time scales exhibited by the flare QPPs.

Guidoni, Silvina; Karpen, J. T.; DeVore, C. R.

2013-07-01

40

Quasi-Periodicities, Magnetic Clusters and Solar Activity

NASA Astrophysics Data System (ADS)

To investigate quasi-periodicities, 12 hour averages of the radial component of the interplanetary magnetic field and the solar wind speed, covering ~ 42 (1963-2005) years were analyzed. A Lomb periodogram for data up to 1998 showed a dominant period of 27.03 days as fpund in earlier results. Including cycle 23, a dominant period of 27.06 days was identified. Analysis of the solar cycles independently showed a dominant period of 27.03 days in solar cycle 20, but not in the other cycles. To investigate the degree of persistency of a particular signal, the technique of complex demodulation was applied since it permits the determination of continuous changes in time of the amplitude and frequency of the signal relative to the test signal. It was found that a period of ~27.6 days gave an overall flat phase function in time, while other periods < ~0.5 day shorter and longer, with comparable but lesser amplitude, come and go. To investigate the solar sources of these periods, the method of principal component analysis (PCA) was applied to ~ 27 years (1976-2003) of synoptic maps obtained with the NSO Kitt Peak Vaccum Telescope. Before the analysis, the original synoptic maps were shifted relative to the previous maps using the period under investigation. Using PCA the Empirical Orthogonal Functions (EOFs) and Pricipal Components (PCs) were found for the set of synoptic maps rescaled to the rotation rate 27.03 days in 1999-2003. The patterns characterized by EOFs 1 and 2 are mostly axisymmetric and PCs 1 and 2 show solar cycle variability. EOF3 shows only one well-localized pattern in the Southern Hemisphere which is markedly non-axisymmetric and PC3 has peaks at times when fast CMEs occur.

Cadavid, A. C.; Lawrence, J. K.; Sandor, C.; Ruzmaikin, A.

2006-12-01

41

Quasi-periodic emissions observed by Cluster and DEMETER spacecraft

NASA Astrophysics Data System (ADS)

Quasi-periodic (QP) emissions are electromagnetic emissions in the frequency range of about 0.5-4 kHz that are characterized by a periodic modulation of wave intensity. Typical periods of this modulation are on the order of minutes. Although there are many observations of these events by ground-based instruments, satellite observations are still rather sparse. Nevertheless, these are of great importance, as they allow us to analyze wave properties in situ, close to the probable generation region, and, moreover, they are not affected by the wave propagation in the Earth-ionosphere waveguide. We present a survey of QP events observed by the WBD instruments on board the four Cluster spacecraft during their perigee passes at radial distances of about 4 RE. Moreover, a conjugate observation of a QP event by Cluster spacecraft and by the low-altitude DEMETER spacecraft has been identified. Simultaneous observations of the same event by several different spacecraft enable us to distinguish between spatial and temporal variations of the phenomenon. It is shown that during a QP event, the same modulation is observed at the same time at very different locations of the inner magnetosphere. The results of a detailed wave analysis based on multi-component measurements by the STAFF-SA instruments indicate that the emissions propagate unducted, with oblique wave normal angles at larger geomagnetic latitudes. Finally, ULF magnetic field data are inspected for the presence of magnetic field fluctuations with a period corresponding to the period of modulation and a possible generation mechanism of the events is discussed.

Nemec, F.; Santolik, O.; Parrot, M.; Hayosh, M.; Pickett, J. S.; Cornilleau-Wehrlin, N.

2012-12-01

42

Quasi-periodic solutions and periodic bursters in quasiperiodically driven oscillators

In this paper, we propose a perturbation method to determine an approximation and conditions of existence of quasi-periodic (QP) solutions and bursting dynamics in a quasi-periodically driven system. The QP forcing consists of two periodic excitations, one with a very slow frequency and the other with a frequency of the same order of the proper frequency of the oscillator. A

Faouzi Lakrad; Mohamed Belhaq

2009-01-01

43

Omnidirectional reflection from Fibonacci quasi-periodic one-dimensional photonic crystal

It is shown that omnidirectional reflection (ODR) is possible from quasi-periodic isotropic dielectric stacks following a Fibonacci sequence (FS). The transition from truly periodic to fully quasi-periodic structure is investigated by building periodic structures having unit cells made of FS of order j. The number of periods required to achieve ODR decreases as j increases until only a single period

D. Lusk; I. Abdulhalim; F. Placido

2001-01-01

44

Observation and modeling of quasi-periodic scintillations observed at low latitude

NASA Astrophysics Data System (ADS)

Quasi-periodic scintillations are characterized as primary deep fade-out infield strength, associated with regular ringing patterns before and after it. In this paper, observations of quasi-periodic scintillation using geostationary satellite (FLEETSAT) transmissions operating at frequency 250 MHz at low latitude ground station, Varanasi (geomag. lat 14° 55' N, long. 154°E) are reported. The results indicate that the quasi-periodic scintillations are most likely produced by plasma blobs/bubbles present in the E and F-region of the ionosphere. The various characteristics features of the quasi periodic scintillations are discussed after the autocorrelation, power spectrum and scintillation index analysis. The computed horizontal scale size of the quasi periodic scintillation producing irregularity varies from 100 m to 1300 m which shows that the irregularities are of intermediate-scale sizes. The spectral index obtained from the slopes of power spectrum varies from -2 to -8. The observed fading patterns, especially the modulation of the diffraction pattern (fading envelope) can be explained by considering an obstacle called radio lens in the ionosphere elongated in one direction. We have simulated successfully the amplitude versus time plot of quasi periodic scintillation patches and found that our theoretical and experimental results of quasi periodic scintillation patches compares well with each other and also with the earlier published works.

Patel, Kalpana; Singh, A. K.; Singh, R. P.

2010-02-01

45

Construction of quasi-periodic solutions of delay differential equations via KAM techniques

NASA Astrophysics Data System (ADS)

This work focuses on the existence of quasi-periodic solutions for linear autonomous delay differential equation under quasi-periodic time-dependent perturbation near an elliptic-hyperbolic equilibrium point. Using the time-1 map of the solution operator, Newton iteration scheme, space splitting and KAM techniques, it is shown that under appropriate hypothesis, there exist quasi-periodic solutions with the same frequencies as the perturbation for most parameters. We show that if the delay differential equation is analytic, we obtain analytic parameterizations of the solutions.

Li, Xuemei; de la Llave, Rafael

46

Quasi-periodic Oscillations in XMM-Newton Timing data of Blazars

NASA Astrophysics Data System (ADS)

In the present talk, I will report our findings of Quasi-periodic Oscillations in XMM-Newton light curves of Blazars. I will also discuss the possible radio-loud active galactic nuclei models which can explain our findings.

Gupta, Alok Chandra

2012-07-01

47

The "Approximate 150 Day Quasi-Periodicity" in Interplanetary and Solar Phenomena During Cycle 23

NASA Technical Reports Server (NTRS)

A"quasi-periodicity" of approx. 150 days in various solar and interplanetary phenomena has been reported in earlier solar cycles. We suggest that variations in the occurrence of solar energetic particle events, inter-planetary coronal mass ejections, and geomagnetic storm sudden commenceents during solar cycle 23 show evidence of this quasi-periodicity, which is also present in the sunspot number, in particular in the northern solar hemisphere. It is not, however, prominent in the interplanetary magnetic field strength.

Richardson, I. G.; Cane, H. V.

2004-01-01

48

Manipulation of quadratic cascading processes in a locally quasi-periodic ?(²) medium.

We theoretically and numerically investigate the quadratic cascading effect of third-harmonic (TH) generation in a locally quasi-periodic nonlinear photonic structure. We study the effect of structure parameters on the acceptance bandwidth and conversion efficiency of the cascading process. We demonstrate that the conversion efficiency of the cascading process can be enhanced by using a longer locally quasi-periodic nonlinear photonic crystal, without adversely affecting the acceptance bandwidth of the emitted radiation. PMID:24664046

Wang, Wenjie; Sheng, Yan; Liu, Shaoding; Niu, Xiaoying; Krolikowski, Wieslaw

2014-03-24

49

The general solution is obtained for a Schrodinger equation with a tile-dependent magnetic field as well as a quasi-periodic potential in two dimensions (2D). The behaviour of the noninteracting electrons (quasi-Bloch electrons) in this quasi-periodic system may be treated as the projection of the behaviour of the Bloch pseudo-electrons in D dimensions. The physical quasi-periodicity of the 2D quasi-periodic system

J. Q. You

1988-01-01

50

Dipolar mode localization and spectral gaps in quasi-periodic arrays of ferromagnetic nanoparticles

NASA Astrophysics Data System (ADS)

In this paper we study the spectral, localization, and dispersion properties of the ferromagnetic dipolar modes around a stable, saturated, and spatially uniform equilibrium in quasi-periodically modulated arrays of ferromagnetic nanoparticles based on the Fibonacci sequence. The Fibonacci sequence is the chief example of deterministic quasi-periodic order. The problem is reduced to the study of a linear-generalized eigenvalue equation for a suitable Hermitian operator connected to the micromagnetic effective field, which accounts for the magnetostatic, anisotropy, and Zeeman interactions. The coupling with a weak applied magnetic field, varying sinusoidally in time, is dealt with and the role of the losses is highlighted. By calculating the resonance frequencies and eigenmodes of the Fibonacci arrays we demonstrate the presence of large spectral gaps and strongly localized modes and we evaluate the pseudodispersion diagrams. The magnetization oscillation modes in quasi-periodic arrays of magnetic nanoparticles show, at microwave frequencies, behaviors that are very similar to those shown, at optical frequencies, by plasmon modes in quasi-periodic arrays of metal nanoparticles. The presence of band gaps and strongly localized states in magnetic nanoparticle arrays based on quasi-periodic order may have an impact in the design and fabrication of new microwave nanodevices and magnetic nanosensors.

Forestiere, Carlo; Miano, Giovanni; Serpico, Claudio; D'Aquino, Massimiliano; Dal Negro, Luca

2009-06-01

51

Quasi-periodic breathers in Hamiltonian networks of long-range coupling

NASA Astrophysics Data System (ADS)

This work is concerned with Hamiltonian networks of weakly and long-range coupled oscillators with either variable or constant on-site frequencies. We derive an infinite dimensional KAM-like theorem by which we establish that, given any N-sites of the lattice, there is a positive measure set of small amplitude, quasi-periodic breathers (solutions of the Hamiltonian network that are quasi-periodic in time and exponentially localized in space) having N-frequencies which are only slightly deformed from the on-site frequencies.

Geng, Jiansheng; Viveros, Jorge; Yi, Yingfei

2008-11-01

52

Acoustic lens: A thin plate with quasi-periodic array of holes

NASA Astrophysics Data System (ADS)

A thin steel plate with quasi-periodic array of holes is fabricated, which is demonstrated to be able to function as an acoustic lens. With either a plane wave or a point source in object space, hotspots with the smallest size up to one-fifth wavelength are observed in the post-evanescent field regime in image space. Imaging of a point source with good resolution at different positions is also exhibited. The singular field distributions originate from the interference of the diffractive beams specific to quasi-periodic structures, which generates distinct and plentiful diffractive patterns.

Ye, Yangtao; Ke, Manzhu; Li, Chunhui; Wang, Tian; Qiu, Chunyin; Liu, Zhengyou

2014-05-01

53

Asymptotic solutions for a damped non-linear quasi-periodic Mathieu equation

Quasi-periodic (QP) solutions of a weakly damped non-linear QP Mathieu equation are investigated near a double primary parametric resonance. A double multiple scales method is applied to reduce the original QP oscillator to an autonomous system performing two successive reduction. The problem for approximating QP solutions of the original system is then transformed to the study of stationary regimes of

Mohamed Belhaq; Kamar Guennoun; Mohamed Houssni

2002-01-01

54

Scaling of torus-doubling terminal points in a quasi-periodically forced map

NASA Astrophysics Data System (ADS)

The torus-doubling bifurcations of a quasi-periodically forced two-dimensional map are investigated numerically. The scaling law on the terminal points of the torus-doubling bifurcation sequences is obtained by a simple method, based on hyper-stable period point and phase sensitivity exponent analyses.

Fu, Wu-Jiu; He, Dai-Hai; Shi, Peng-Liang; Kang, Wei; Hu, Gang

2002-01-01

55

Quasi-periodic oscillations and chaos in a gas-discharge active mode-locked laser

It is shown that the quasi-periodic oscillations and chaos that appear on the destruction of active mode locking in an He-Ne laser operated at 1150 nm are connected with the high supermodes. Consideration is given to the different stationary pulse profiles that may be identified with these supermodes. A difference is found to exist between positive and negative tuning of

L. A. Melnikov; E. M. Rabinovich; V. V. Tuchin

1988-01-01

56

We formulate and justify rigorously a numerically efficient criterion for the computation of the analyticity breakdown of quasi-periodic solutions in symplectic maps (any dimension) and 1D statistical mechanics models. Depending on the physical interpretation of the model, the analyticity breakdown may correspond to the onset of mobility of dislocations, or of spin waves (in the 1D models) and to the

Renato Calleja; Rafael de la Llave

2010-01-01

57

Dripping handrails and the quasi-periodic oscillations of the AM Herculis objects

NASA Technical Reports Server (NTRS)

AM Her objects exhibit periodic, quasi-periodic, and aperiodic variability on timescales ranging from seconds to years. Here, we investigate a process for the production of aperiodic and quasi-periodic accretion rate fluctuations. We consider the nonlinear dynamical model known as the dripping handrail (DHR). The DHR, basically a model for certain types of spatially extended systems and loosely based on water condensing on and dripping off a handrail, has recently been used as a model for the quasi-periodic oscillations (QPO) and very low frequency noise of the low-mass X-ray binary Sco X-1. Here, we show that (1) the DHR is a robust QPO generation process in that it leads to QPO production under a wide range of conditions and assumptions; (2) the phenomenology of the DHR is consistent with the observed aperiodic and quasi-periodic varibility of the AM Her QPO source VV Pup over timescales ranging from 16 ms to 20 s; and (3) a single DHR model can produce both broadband QPOs and features with quality Q greater than 20 as observed in several AM Her QPO sources.

Steiman-Cameron, Thomas Y.; Young, Karl; Scargle, Jeffrey D.; Crutchfield, James P.; Imamura, James N.; Wolff, Michael T.; Wood, Kent S.

1994-01-01

58

GENERAL: Quasi-Periodic Waves and Asymptotic Property for Boiti-Leon-Manna-Pempinelli Equation

NASA Astrophysics Data System (ADS)

In this paper, multi-periodic (quasi-periodic) wave solutions are constructed for the Boiti-Leon-Manna-Pempinelli (BLMP) equation by using Hirota bilinear method and Riemann theta function. At the same time, we analyze in details asymptotic properties of the multi-periodic wave solutions and give their asymptotic relations between the periodic wave solutions and the soliton solutions.

Luo, Lin

2010-08-01

59

We prove that the 1-d quantum harmonic oscillator is stable under spatially localized, time quasi-periodic perturbations on a set of Diophantine\\u000a frequencies of positive measure. This proves a conjecture raised by Enss-Veselic in their 1983 paper [EV] in the general quasi-periodic\\u000a setting. The motivation of the present paper also comes from construction of quasi-periodic solutions for the corresponding\\u000a nonlinear equation.

W.-M. Wang

2008-01-01

60

Towards modeling quasi-periodic oscillations of microquasars with oscillating slender tori

NASA Astrophysics Data System (ADS)

Context. One of the often discussed models for high-frequency quasi-periodic oscillations of X-ray binaries is the oscillating torus model, which considers oscillation modes of slender accretion tori. Aims: Here, we aim at developing this model by considering the observable signature of an optically thick slender accretion torus subject to simple periodic deformations. Methods: We compute light curves and power spectra of a slender accretion torus subject to simple periodic deformations: vertical or radial translation, rotation, expansion, and shear. Results: We show that different types of deformations lead to very different Fourier power spectra and therefore could be observationally distinguished. Conclusions: This work is a first step in a longer term study of the observable characteristics of the oscillating torus model. It gives promising perspectives on the possibility of constraining this model by studying the observed power spectra of quasi-periodic oscillations.

Mazur, G. P.; Vincent, F. H.; Johansson, M.; Šramková, E.; Török, G.; Bakala, P.; Abramowicz, M. A.

2013-06-01

61

NASA Astrophysics Data System (ADS)

The tunneling lifetimes of quasi-resonant states for electrons in various kinds of generalized Fibonacci and generalized Thue-Morse GaAs-AlxGa1-xAs superlattices have been evaluated numerically under variable dc bias conditions. All the quasi-periodic systems have been framed using the generalized block model. The variation of the lifetime at different quasi-resonant levels with respect to the external dc field undergoes a remarkable change due to the effect of quasi-periodicity. The occurrence of a minimum value of the average lifetime and its dependence on quasi-periodicity have been analyzed. It is shown that the low-order quasi-periodicity in the case of the generalized Fibonacci superlattice and the high-order quasi-periodicity for the generalized Thue-Morse superlattice hold promise for potential device applications. The impact of an increase in the number of barriers on the tunneling lifetime has also been studied exhaustively.

Panchadhyayee, P.; Biswas, R.; Sinha, C.; Mahapatra, P. K.

2008-11-01

62

Quasi-periodic solutions of the spatial lunar three-body problem

NASA Astrophysics Data System (ADS)

In this paper, we consider the spatial lunar three-body problem in which one body is far away from the other two. By applying a well-adapted version of KAM theorem to Lidov-Ziglin's global study of the quadrupolar approximation of the spatial lunar three-body problem, we establish the existence of several families of quasi-periodic orbits in the spatial lunar three-body problem.

Zhao, Lei

2014-05-01

63

Rayleigh-Taylor Gravity Waves and Quasi-periodic Oscillation Phenomena in X-Ray Binaries

Accretion onto compact objects in X-ray binaries (black hole, neutron star [NS], white dwarf) is characterized by nonuniform flow density profiles. Such an effect of heterogeneity in the presence of gravitational forces and pressure gradients causes Rayleigh-Taylor gravity waves. They should be seen as quasi-periodic wave oscillations (QPOs) of the accretion flow in the transition (boundary) layer between the Keplerian

Lev Titarchuk

2003-01-01

64

Periodic and quasi-periodic solutions for multi-instabilities involved in brake squeal

This paper is devoted to the computation of nonlinear dynamic steady-state solutions of autonomous systems subjected to multi-instabilities and proposes a new nonlinear method for predicting periodic and quasi-periodic solutions intended for application to the disc brake squeal phenomenon. Firstly, finite element models of a pad and a disc are reduced to include only their contact nodes by using a

N. Coudeyras; S. Nacivet; J.-J. Sinou

2009-01-01

65

The transmission properties of Fibonacci quasi-periodic one-dimensional photonic crystals (1DPCs) containing superconducting material are theoretically investigated based on the transfer matrix method. It is shown that the 1DPCs can possess a same photonic band gap property as the periodic structure superconducting PC. The results of transmittance spectra show that the cutoff frequency can be manipulated through the thicknesses of the

Ji-jiang Wu; Jin-xia Gao

66

By studying the deformed Fibonacci quasi-periodic structure, a broad omnidirectional reflection band covering all telecommunication bands is obtained. Deformation was introduced by applying a power law, so that the coordinates y of the deformed object were determined through the coordinates x of the non-deformed structure in accordance with the following rule: y = x1+k. Here k is the coefficient defining

K. Ben Abdelaziz; J. Zaghdoudi; M. Kanzari; B. Rezig

2005-01-01

67

The transmission properties of Fibonacci quasi-periodic one-dimensional photonic crystals (1DPCs) containing indefinite metamaterials are theoretically studied. It is found that 1DPCs can possess an omnidirectional zero average index (zero-n?) gap which exists in all Fibonacci sequences. In contrast to Bragg gaps, such zero-n? gap is less sensitive to the incidence angle, the scale length and the polarizations of electromagnetic waves.

Liwei Zhang; Kai Fang; Guiqiang Du; Haitao Jiang; Junfang Zhao

2011-01-01

68

Scattering theory for Jacobi operators with a steplike quasi-periodic background

NASA Astrophysics Data System (ADS)

We develop direct and inverse scattering theory for Jacobi operators with a steplike quasi-periodic finite-gap background in the same isospectral class. We derive the corresponding Gel'fand-Levitan-Marchenko equation and find minimal scattering data which determine the perturbed operator uniquely. In addition, we show how the transmission coefficients can be reconstructed from the eigenvalues and one of the reflection coefficients.

Egorova, Iryna; Michor, Johanna; Teschl, Gerald

2007-06-01

69

Phase-rectified signal averaging detects quasi-periodicities in non-stationary data

We present an efficient technique for the study of quasi-periodic oscillations in noisy, non-stationary signals, which allows the assessment of system dynamics despite phase resetting and noise. It is based on the definition of anchor points in the signal (in the simplest case increases or decreases of the signal) which are used to align (i.e., phase-rectify) the oscillatory fluctuations followed

Axel Bauer; Jan W. Kantelhardt; Armin Bunde; Petra Barthel; Raphael Schneider; Marek Malik; Georg Schmidt

2006-01-01

70

Quasi-periodic hard X-ray oscillations before impulsive phase of solar flares

NASA Astrophysics Data System (ADS)

Using observations from the YOHKOH Hard X-ray Telescope and Compton Gamma Ray Ob-servatory spectrometer we have found small-amplitude quasi-periodic hard X-ray oscillations before impulsive phase (OBIP) of solar flares. We have been investigating properties of the oscillations and transition from the OBIP to impulsive phase. Our results support the model of electron acceleration in oscillating magnetic traps (Jakimiec and Tomczak 2010, Solar Physics, 261, 233).

Tomczak, Michal; Jakimiec, Jerzy

71

Exact quasi-periodic solutions of the Konno–Oono equations

NASA Astrophysics Data System (ADS)

On the basis of the Lax matrix and elliptic variables, the Konno–Oono equations are decomposed into solvable ordinary differential equations. The Konno–Oono flows are straightened with the aid of the theory of algebraic curves and the Abel–Jacobi coordinates. The asymptotic properties of the meromorphic function at infinite points and its algebro-geometric characteristics are studied, from which exact quasi-periodic solutions of the Konno–Oono equations are obtained.

Guan, Liang; Geng, Xianguo; Li, Zhu

2014-07-01

72

Quasi-periodical components in the radial distributions of cosmologically remote objects

NASA Astrophysics Data System (ADS)

A statistical analysis of radial (line-of-sight) 1D-distributions of brightest cluster galaxies (BCGs) within the redshift interval 0.044 ? z ? 0.78 and Mg II absorption-line systems (0.37 ? z ? 2.28) is carried out. Power spectra and two-point radial correlation functions are calculated. It is found that both radial distributions of spectroscopic redshifts of 52 683 BCGs and 32 840 Mg II absorption systems incorporate similar quasi-periodical components relatively to the comoving distance. Significance of the components exceeds 4?-level and admits an increase ( ? 5?) for some broad subsamples. For the ? cold dark matter cosmological model the periodicities correspond to spatial comoving scales (98 ± 3) and (101 ± 2) h-1 Mpc, respectively. These quasi-periods turn out to be close to the characteristic scale (101 ± 6) h-1 Mpc of the quasi-periodical component obtained earlier for the radial distribution of luminous red galaxies (LRGs). On the other hand, the scales are close to the spatial scale corresponding to the baryon acoustic oscillations (BAOs) revealed by many authors at the last decade. Fourier transform phases obtained for the BCGs and LRGs are found to be close, while the phases calculated for the Mg II absorption systems and LRGs are opposite. Discussions of the results in a context of the BAO and large-scale structure characteristic scales are outlined.

Ryabinkov, A. I.; Kaminker, A. D.

2014-05-01

73

Quasi-periodic flares in Jupiter's auroraÂ : new results

NASA Astrophysics Data System (ADS)

Two recent Hubble Space Telescope observation campaigns have been dedicated to the Jovian Far-UV aurora (GO 12883 - PI: D. Grodent and GO 13035 - PI: S. Badman). Both of them made use of the Time-Tag mode of the Space Telescope Imaging Spectrograph (STIS), a high time resolution mode which allows to observe temporal variations on timescales of tens of seconds. In the present study, we focus on sudden and spectacular bursts of auroral emissions taking place in the active region located poleward of the main emissions and called "flares". A previous study, based on only two image sequences acquired with rather unfavorable viewing angles, showed that these flares could reappear quasi-periodically on time scales of 2-3 minutes. Phenomena with similar timescales have been identified by in-situ spacecraft in relativistic electron and radio data as well as in reconnection signatures, for example. But the physical mechanism behind these ubiquitous signatures remains to be unveiled. Here we make use of the most recent and much larger data set to study in further details the occurrence rate, the period, the location, the extent and the motion of these quasi-periodic flares and to compare their behavior in both hemispheres. Quantifying these parameters allows us to narrow down the possibilities among likely explanations and provide a tentative scenario for these short timescale quasi-periodic features.

Bonfond, Bertrand; Grodent, Denis; Badman, Sarah; Gérard, Jean-Claude; Radioti, Aikaterini; Gustin, Jacques; Kimura, Tomoki

2014-05-01

74

The 8 second optical quasi-periodic oscillations in GX 339 - 4

NASA Technical Reports Server (NTRS)

Submillisecond optical photometry of the black hole candidate GX 339 - 4 was obtained on August 1, 1989, (UT) using the 1.5 m telescope of the Cerro Tololo Inter-American Observatory. Eight second quasi-periodic oscillations of width 0.02-0.04 Hz and root mean square amplitude 4-6 percent are found. The visual magnitude of GX 339 - 4 at the beginning of the observation was m(v) = 17.7. Motch et al. (1985) have previously reported 7 s optical quasi-periodic oscillations when GX 339 - 4 was also m(v) = 17.7 and in an X-ray off-state. No X-ray observations were made during the present optical observations and so the X-ray state of GX 339 - 4 cannot be ascertained. In addition, Motch et al. have also reported 20 s optical quasi-periodic oscillations with 30-40 percent full amplitude but when GX 339 - 4 was much brighter, m(v) = 15.4, and in a hard X-ray state.

Imamura, James N.; Kristian, Jerome; Middleditch, John; Steiman-Cameron, Thomas Y.

1990-01-01

75

NASA Astrophysics Data System (ADS)

By combining two Fibonacci quasi-periodic structures and a periodic structure to form a heterostructure, a broad omnidirectional reflection band is obtained. From the numerical results performed by the transfer matrix method, it is found that the reflection bands of the two Fibonacci quasi-periodic sub-structures and the periodic sub-structure can be compensated for each other. This method is expected to be useful in constructing a one-dimensional quasi-periodic photonic crystal structure with a broad omnidirectional reflection band.

Dong, Jian-Wen; Han, Peng; Wang, He-Zhou

2003-11-01

76

NASA Astrophysics Data System (ADS)

By studying the deformed Fibonacci quasi-periodic structure, a broad omnidirectional reflection band covering all telecommunication bands is obtained. Deformation was introduced by applying a power law, so that the coordinates y of the deformed object were determined through the coordinates x of the non-deformed structure in accordance with the following rule: y = x1+k. Here k is the coefficient defining the deformation degree. From the numerical results performed by the transfer matrix method, it is found that the reflection band of the deformed 15th generation Fibonacci sequence structure covered all optical telecommunication bands.

Ben Abdelaziz, K.; Zaghdoudi, J.; Kanzari, M.; Rezig, B.

2005-10-01

77

NASA Astrophysics Data System (ADS)

The transmission properties of Fibonacci quasi-periodic one-dimensional photonic crystals (1DPCs) containing indefinite metamaterials are theoretically studied. It is found that 1DPCs can possess an omnidirectional zero average index (zero- n?) gap which exists in all Fibonacci sequences. In contrast to Bragg gaps, such zero- n? gap is less sensitive to the incidence angle, the scale length and the polarizations of electromagnetic waves. When an impurity is introduced, a defect mode appears inside the zero- n? gap with a very weak dependence on the incidence angle and scaling.

Zhang, Liwei; Fang, Kai; Du, Guiqiang; Jiang, Haitao; Zhao, Junfang

2011-02-01

78

Resonance in Forced Oscillations of an Accretion Disk and Kilohertz Quasi-periodic Oscillations

NASA Astrophysics Data System (ADS)

We have performed numerical simulations of a radially perturbed ``accretion'' torus around a black hole or neutron star and find that the torus performs radial and vertical motions at the appropriate epicyclic frequencies. We find clear evidence that vertical motions are excited in a nonlinear resonance when the applied perturbation is periodic in time. The strongest resonant response occurs when the frequency difference of the two oscillations is equal to one-half the forcing frequency, precisely as recently observed in the accreting pulsar SAX J1808.4-3658, where the observed kilohertz quasi-periodic oscillation peak separation is half the spin frequency of 401 Hz.

Lee, William H.; Abramowicz, Marek A.; Klu?niak, W?odek

2004-03-01

79

Combined In-situ and Ground-based Observations of Quasi-periodic Radar Echoes

NASA Astrophysics Data System (ADS)

A series of combined rocket/radar investigation of the electrodynamics and neutral- plasma coupling associated with sporadic-E layers and quasi-periodic backscatter radar echoes has been carried out from launch sites at both Puerto Rico and the Wallops Flight Facility, Virginia (USA) between 1998-2001. The instrumented rock- ets consisted of main and sub-payloads and were launched while strong quasi- periodic VHF echoes were observed simultaneously with the Univ. of Illinois 50 MHz backscatter radar. The rocket apogee was purposely limited so that the payloads would dwell in the sporadic-E region (90-115 km). The main payload included vector DC and AC electric field detectors, a DC magnetometer, an ion mass spectrometer, an ioniza- tion gauge, and spaced-electric field receivers to measure the wavelength and phase velocity of the unstable plasma waves. The sub-payload was instrumented to measure DC and wave electric fields and plasma density. In one case, a separate rocket was launched a few minutes later which released luminous TMA trails to measure the neu- tral wind, its velocity shear, and embedded neutral structures. In this experiment, the payloads successfully pierced a well-defined, 2-3 km thick metallic sporadic-E layer of approximately 10**5 e/cc near 103 km altitude. In-situ DC electric field measure- ments revealed ~5mV/m ambient meridional fields above and below the layer with 1-2 mV/m amplitude, large scale structures superimposed. The wavelengths of these structures were approximately 2-4 km and may be related to the seat of the quasi- periodic echoes. Intense (~5 mV/m), higher frequency (shorter scale) broadband waves were also observed in-situ, both above and below the layer, consistent with the VHF backscatter observations during the time of the launch. Neither the large scale nor short scale plasma waves appeared to be distinctly organized by the sporadic-E den- sity layer. The TMA release showed large amplitude (~ 100 m/s) meridional winds near 102-105 km, with the most intense shears directly below these altitudes, where the short scale electric field fluctuations were most intense. We summarize the ob- servations from the different experiments and discuss them in the context of current theories regarding quasi-periodic echoes.

Pfaff, R.; Kudeki, E.; Larsen, M.; Clemmons, J.; Earle, G.

80

Quasi-periodic behavior of ion acoustic solitary waves in electron-ion quantum plasma

The ion acoustic solitary waves are investigated in an unmagnetized electron-ion quantum plasmas. The one dimensional quantum hydrodynamic model is used to study small as well as arbitrary amplitude ion acoustic waves in quantum plasmas. It is shown that ion temperature plays a critical role in the dynamics of quantum electron ion plasma, especially for arbitrary amplitude nonlinear waves. In the small amplitude region Korteweg-de Vries equation describes the solitonic nature of the waves. However, for arbitrary amplitude waves, in the fully nonlinear regime, the system exhibits possible existence of quasi-periodic behavior for small values of ion temperature.

Sahu, Biswajit [Department of Mathematics, West Bengal State University Barasat, Kolkata-700126 (India); Poria, Swarup [Department of Applied Mathematics, University of Calcutta Kolkata-700009 (India); Narayan Ghosh, Uday [Department of Mathematics, Siksha Bhavana, Visva Bharati University Santiniketan (India); Roychoudhury, Rajkumar [Physics and Applied Mathematics Unit, Indian Statistical Institute Kolkata-700108 (India)

2012-05-15

81

On quasi-periodic motions around the collinear libration points in the real Earth–Moon system

Due to various perturbations, the collinear libration points of the real Earth–Moon system are not equilibrium points anymore.\\u000a Under the assumption that the Moon’s motion is quasi-periodic, special quasi-periodic orbits called dynamical substitutes\\u000a exist. These dynamical substitutes replace the geometrical collinear libration points as time-varying equilibrium points.\\u000a In the paper, the dynamical substitutes of the three collinear libration points in

X. Y. Hou; L. Liu

2011-01-01

82

By combining two Fibonacci quasi-periodic structures and a periodic structure to form a heterostructure, a broad omnidirectional reflection band is obtained. From the numerical results performed by the transfer matrix method, it is found that the reflection bands of the two Fibonacci quasi-periodic sub-structures and the periodic sub-structure can be compensated for each other. This method is expected to be

Jian-Wen Dong; Peng Han; He-Zhou Wang

2003-01-01

83

An analysis is given of the dynamic of a one-degree-of-freedom oscillator with quadratic and cubic nonlinearities subjected to parametric and external excitations having incommensurate frequencies. A new method is given for constructing an asymptotic expansion of the quasi-periodic solutions. The generalized averaging method is first applied to reduce the original quasi-periodically driven system to a periodically driven one. This method

M. Belhaq; M. Houssni

1999-01-01

84

GENERATION OF QUASI-PERIODIC WAVES AND FLOWS IN THE SOLAR ATMOSPHERE BY OSCILLATORY RECONNECTION

We investigate the long-term evolution of an initially buoyant magnetic flux tube emerging into a gravitationally stratified coronal hole environment and report on the resulting oscillations and outflows. We perform 2.5-dimensional nonlinear numerical simulations, generalizing the models of McLaughlin et al. and Murray et al. We find that the physical mechanism of oscillatory reconnection naturally generates quasi-periodic vertical outflows, with a transverse/swaying aspect. The vertical outflows consist of both a periodic aspect and evidence of a positively directed flow. The speed of the vertical outflow (20-60 km s{sup -1}) is comparable to those reported in the observational literature. We also perform a parametric study varying the magnetic strength of the buoyant flux tube and find a range of associated periodicities: 1.75-3.5 minutes. Thus, the mechanism of oscillatory reconnection may provide a physical explanation to some of the high-speed, quasi-periodic, transverse outflows/jets recently reported by a multitude of authors and instruments.

McLaughlin, J. A.; Verth, G. [School of Computing, Engineering and Information Sciences, Northumbria University, Newcastle Upon Tyne, NE1 8ST (United Kingdom); Fedun, V.; Erdelyi, R., E-mail: james.a.mclaughlin@northumbria.ac.uk, E-mail: gary.verth@northumbria.ac.uk, E-mail: v.fedun@sheffield.ac.uk, E-mail: robertus@sheffield.ac.uk [Solar Physics and Space Plasma Research Centre (SP2RC), School of Mathematics and Statistics, University of Sheffield, Hounsfield Road, Hicks Building, Sheffield, S3 7RH (United Kingdom)

2012-04-10

85

Low altitude quasi-periodic radar echoes observed by the Gadanki VHF radar

NASA Astrophysics Data System (ADS)

We report here on the low altitude quasi-periodic (LQP) radar echoes from low latitude sporadic E layer (Es) observed by the Gadanki (13.5°N, 79.2°E geomagnetic latitude 6.3°N) VHF radar. The LQP echoes occurred both during daytime and nighttime and are confined to a slowly descending layer with a thickness of about 2-4 km in the height range of 90-100 km. The periods are found to range from tens of seconds to less than about 3 minutes. The Doppler velocities vary over a range of -20 to +20 m/s during daytime and 0 to 10 m/s during nighttime and are known to be sensitive to the layer height, being dominated by the effect of zonal electric field above and meridional neutral wind below a height of ~97 km for the type 2 irregularities [Krishna Murthy et al., 1998]. The spectral widths are found to be of the order of 50 to 75 m/s during daytime and 30 to 60 m/s during nighttime. The LQP echoes reported here are similar to that observed recently over midlatitudes [Rao et al., 2000; Urbina et al., 2000], but distinctly different from the widely reported quasi-periodic (QP) echoes occurring at higher altitudes (>100 km). The observations are discussed briefly in terms of the potential source mechanisms.

Pan, C. J.; Rao, P. B.

2002-06-01

86

The statistical study of quasi-periodic oscillations of the radio emission in solar quiet regions

NASA Astrophysics Data System (ADS)

In this study we discuss variations of the radio emission from the Quiet Sun Areas (QSA) at centimeter wavelength (1.76 cm). Data were obtained from Nobeyama Radioheliograph (NoRH). Oscillations of selected areas were studied carefully from data taken over one week. We try to find quasi-periodic solar oscillations from the QSA. We used the traditional Fast Fourier Transform (FFT), Global Wavelet Spectrum (GWS) and Wavelet (Morlet) for studying signals in the frequency/time-frequency domain. We used the Fisher randomization test to verify the significance of the observed signal. Instrumental and sky noises were studied using a cross-correlation analysis. Additionally, a single pixel analysis were done. Wide ranges of solar oscillation periods were found from the Quiet Sun Area (QSA): 3-15, 35-70, and 90 minutes. Some physical explanations are suggested for these oscillations. However, it is not possible to give a conclusive statement about the origin of the long quasi-periodic (>60 min) oscillations from the QSA.

Kallunki, J.; Riehokainen, A.

2012-01-01

87

NASA Astrophysics Data System (ADS)

We study numerically the "analyticity breakdown" transition in 1-dimensional quasi-periodic media. This transition corresponds physically to the transition between pinned down and sliding ground states. Mathematically, it corresponds to the solutions of a functional equation losing their analyticity properties. We implemented some recent numerical algorithms that are efficient and backed up by rigorous results so that we can compute with confidence even close to the breakdown. We have uncovered several phenomena that we believe deserve a theoretical explanation: (A) The transition happens in a smooth surface. (B) There are scaling relations near breakdown. (C) The scaling near breakdown is very anisotropic. Derivatives in different directions blow up at different rates. Similar phenomena seem to happen in other KAM problems.

Blass, Timothy; de la Llave, Rafael

2013-03-01

88

QUASI-PERIODIC FORMALDEHYDE MASER FLARES IN THE MASSIVE PROTOSTELLAR OBJECT IRAS 18566+0408

We report results of an extensive observational campaign of the 6 cm formaldehyde maser in the young massive stellar object IRAS 18566+0408 (G37.55+0.20) conducted from 2002 to 2009. Using the Arecibo Telescope, the Very Large Array, and the Green Bank Telescope, we discovered quasi-periodic formaldehyde flares (P {approx} 237 days). Based on Arecibo observations, we also discovered correlated variability between formaldehyde (H{sub 2}CO) and methanol (CH{sub 3}OH) masers. The H{sub 2}CO and CH{sub 3}OH masers are not spatially coincident, as demonstrated by different line velocities and high angular resolution MERLIN observations. The flares could be caused by variations in the infrared radiation field, possibly modulated by periodic accretion onto a young binary system.

Araya, E. D. [Physics Department, Western Illinois University, 1 University Circle, Macomb, IL 61455 (United States); Hofner, P.; Goss, W. M. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Kurtz, S. [Centro de RadioastronomIa y Astrofisica, Universidad Nacional Autonoma de Mexico, Apdo. Postal 3-72, 58089 Morelia, Michoacan (Mexico); Richards, A. M. S. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Linz, H. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Olmi, L. [University of Puerto Rico at Rio Piedras, Physics Department, P.O. Box 23343, San Juan, PR 00931 (Puerto Rico); Sewilo, M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2010-07-10

89

Growth of Sobolev Norms in Linear Schrödinger Equations with Quasi-Periodic Potential

NASA Astrophysics Data System (ADS)

In this paper, we consider the following problem. Let iut+?u+V(x,t)u= 0 be a linear Schrödinger equation ( periodic boundary conditions) where V is a real, bounded, real analytic potential which is periodic in x and quasi periodic in t with diophantine frequency vector ?. Denote S(t) the corresponding flow map. Thus S(t) preserves the L2-norm and our aim is to study its behaviour on Hs(TD), s> 0. Our main result is the growth in time is at most logarithmic; thus if ??Hs, then

Bourgain, J.

90

NASA Astrophysics Data System (ADS)

Based on a multi-dimensional Riemann theta function, the Hirota bilinear method is extended to explicitly construct multi-periodic (quasi-periodic) wave solutions for the asymmetrical Nizhnik-Novikov-Veselov equation. Among these periodic waves, two-periodic waves are a direct generalization of well-known cnoidal waves; their surface pattern is two dimensional. The main physical result is the description of the behavior of nonlinear waves in shallow water. A limiting procedure is presented to analyze asymptotic properties of the two-periodic waves in details. Relations between the periodic wave solutions and the well-known soliton solutions are established. It is rigorously shown that the periodic wave solutions tend to the soliton solutions under a 'small amplitude' limit.

Fan, Engui

2009-03-01

91

Quasi-periodic Wiggles of Microwave Zebra Structures in a Solar Flare

NASA Astrophysics Data System (ADS)

Quasi-periodic wiggles of microwave zebra pattern (ZP) structures with periods ranging from about 0.5 s to 1.5 s are found in an X-class solar flare on 2006 December 13 at the 2.6-3.8 GHz with the Chinese Solar Broadband Radio Spectrometer (SBRS/Huairou). Periodogram and correlation analysis show that the wiggles have two to three significant periodicities and are almost in phase between stripes at different frequencies. The Alfvén speed estimated from the ZP structures is about 700 km s-1. We find the spatial size of the wave-guiding plasma structure to be about 1 Mm with a detected period of about 1 s. This suggests that the ZP wiggles can be associated with the fast magnetoacoustic oscillations in the flaring active region. The lack of a significant phase shift between wiggles of different stripes suggests that the ZP wiggles are caused by a standing sausage oscillation.

Yu, Sijie; Nakariakov, V. M.; Selzer, L. A.; Tan, Baolin; Yan, Yihua

2013-11-01

92

Quasi-periodic oscillations in the Z source GX 5-1

NASA Technical Reports Server (NTRS)

A detailed study has been conducted of the time variability in the Z source GX 5-1 using Ginga, which observed the source in the horizontal and normal branches (HB, NB). Intensity-dependent HF, quasi-periodic oscillations (QPO) were observed in the HB, in which the source flux varied by a factor of 1.9. The QPO frequency in this portion of the HB ranges from about 13 to 17 Hz; this is lower than previously observed in any Z source. The HF and LF QPO were simultaneously observed in the NB. The strength of both forms of QPO and the strength of the LF noise increase rapidly with increasing photon energy.

Lewin, Walter H. G.; Lubin, Lori M.; Tan, Jianmin; Van Der Klis, Michiel; Van Paradijs, Jan; Penninx, Wim; Dotani, Tadayasu; Mitsuda, Kazuhisa

1992-01-01

93

Periodic and quasi-periodic solutions for multi-instabilities involved in brake squeal

NASA Astrophysics Data System (ADS)

This paper is devoted to the computation of nonlinear dynamic steady-state solutions of autonomous systems subjected to multi-instabilities and proposes a new nonlinear method for predicting periodic and quasi-periodic solutions intended for application to the disc brake squeal phenomenon. Firstly, finite element models of a pad and a disc are reduced to include only their contact nodes by using a Craig and Bampton strategy. Secondly, a complex eigenvalue analysis is performed showing two unstable modes for a wide range of friction coefficients, after which a Generalized Constrained Harmonic Balance Method (GCHBM) is presented. This method can compute nonlinear periodic or pseudo-periodic responses depending on the number of unstable frequencies. The numerical results are in good agreement with those of time marching methods.

Coudeyras, N.; Nacivet, S.; Sinou, J.-J.

2009-12-01

94

Ginga observations of quasi-periodic oscillations in type II bursts from the Rapid Burster

NASA Technical Reports Server (NTRS)

During Ginga observations of the 'Rapid Burster' in August 1988, strong quasi-periodic oscillations (QPOs) were detected in its X-ray intensity. The QPOs had centroid frequencies of 5 and 2 Hz during type II X-ray bursts which lasted for 10 and 30 s, respectively. The presence of the QPOs is correlated with the time scale-invariant burst profile. They are very strong during the initial peak in the burst, absent in the second peak, and strong again at the onset of the third peak. From an analysis of the X-ray spectrum as observed during the maxima and minima of the oscillations, it is found that the oscillations can be described by changes of the temperature of a blackbody emitter of constant apparent area.

Dotani, T.; Mitsuda, K.; Inoue, H.; Tanaka, Y.; Kawai, N.

1990-01-01

95

Singular Density of States Measure for Subshift and Quasi-Periodic Schrödinger Operators

NASA Astrophysics Data System (ADS)

Simon's subshift conjecture states that for every aperiodic minimal subshift of Verblunsky coefficients, the common essential support of the associated measures has zero Lebesgue measure. We disprove this conjecture in this paper, both in the form stated and in the analogous formulation of it for discrete Schrödinger operators. In addition we prove a weak version of the conjecture in the Schrödinger setting. Namely, under some additional assumptions on the subshift, we show that the density of states measure, a natural measure associated with the operator family and whose topological support is equal to the spectrum, is singular. We also consider one-frequency quasi-periodic Schrödinger operators with continuous sampling functions and show that generically, the density of states measure is singular as well.

Avila, Artur; Damanik, David; Zhang, Zhenghe

2014-03-01

96

Time lags in the quasi-periodic oscillations of the rapid burster (MXB 1730-335)

Time lags in the 0.4-5-Hz quasi-periodic oscillations (QPOs) of the rapid burster are investigated using two Exosat observations. Different QPO modes were noted during long type 2 bursts and in the persistent emission. The 1-5 keV X-ray signal lagged behind the 5-21-keV signal by 7.6 + or - 2.1 ms in the persistent emission QPO with frequencies of greater than 3.6 Hz. The fractional strength of the QPO was found to increase with photon energy during the persistent emission interval. The results provide evidence for a soft lag in QPOs which is suggested to be due to spectral softening during each QPO cycle. 16 references.

Stella, L.; Haberl, F.; Parmar, A.N.; Van Der Klis, M.; Lewin, W.H.G.

1988-04-01

97

Synchronizations of Quasi-period and Hyperchaos in Injected Two-section Semiconductor Lasers

NASA Astrophysics Data System (ADS)

A novel hyperchaos synchronization system is presented. Hyperchaos synchronization in injection two-section semiconductor lasers was achieved for its application in secure communication. We found also a route from single-period to hyperchaos after passing quasi-period and chaos with increasing frequency detuning while the receiver synchronized with the transmitter in these dynamical regions. All optical private data communication encoded by a rate of 0.16 Gbit/s on/off phase shift key and a rate of 0.16 Gbit/s amplitude modulation and photoelectric private data communication encoded by a rate of 0.2 Gbit/s on/off current shift key and a current modulation of 0.12 GHz frequency, respectively, are simulated via this hyperchaos synchronization system. Decoding has been numerically demonstrated to achieve successfully.

Yan, Sen-lin

2013-03-01

98

NASA Astrophysics Data System (ADS)

The transmission properties of one-dimensional quasi-periodic Fibonacci photonic crystal containing negative permittivity/permeability material are investigated by use of the transfer matrix method. We find that perfect transmission peaks exist at a series of dimensionless wavelength points in the transmission spectra, and the discrete localized modes appear inside the photonic band gap in the case of normal incidence. In the case of oblique incidence, the detailed numerical calculations show that the transmission peaks and angles strongly depend on the polarization of incident waves and the periodicity of the photonic crystals. In addition, we notice that the one-dimensional quasi-periodic photonic crystal can exhibit omni-directional reflection in a certain frequency region for all incident angles and polarizations. We also investigate the possibility of realizing the omni-directional reflection by means of the simple one-dimensional quasi-periodic Fibonacci photonic crystal.

Tao, Bo; Li, Fu-Li; Yu, Feng

99

Optimizing light absorption in a thin-film p-i-n solar cell using a quasi-periodic grating

NASA Astrophysics Data System (ADS)

A p-i-n solar cell is best suited for strong absorbers with poor collection capabilities. However, the absorption naturally decreases at photon energies close to the electronic bandgap of the semiconductor. We hypothesized that a quasi-periodic surface textures in the role of diffraction gratings at the back contact can efficiently scatter light increasing the optical path length inside the absorber layer. The effect of quasi-periodic corrugated backing metallic contact of various types was studied theoretically. To help optimizing the design of the quasi periodic grating the corresponding canonical problem was considered. The absorption of light was calculated using the rigorous coupled-wave approach. The n- and i-layers consist of isotropic nonhomogeneous multilayered semiconductor.

Atalla, Mahmoud R. M.

2014-03-01

100

GB6 J1058+5628: A NEW QUASI-PERIODIC BL LAC OBJECT FROM THE ASIAGO PLATE ARCHIVE

We present the historic photographic light curves of three little known blazars (two BL Lac objects and one FSRQ), GB6 J1058+5628, GB6 J1148+5254, and GB6 J1209+4119, spanning a time interval of about 50 years, mostly built using the Asiago plate archive. All objects show evident long-term variability, over which short-term variations are superposed. One source, GB6 J1058+5628, showed a marked quasi-periodic variability of 1 mag on timescale of about 6.3 years, making it one of the few BL Lac objects with a quasi-periodic behavior.

Nesci, R., E-mail: roberto.nesci@uniroma1.i [Physics Department, University of Roma La Sapienza, Piazzale A. Moro 2, I-00185 Roma (Italy)

2010-06-15

101

A Model for Backscattering from Quasi Periodic Corn Canopies at L-Band

NASA Technical Reports Server (NTRS)

In this study, a model for backscattering at L-band from a corn canopy is proposed. The canopy consists of a quasi-periodic distribution of stalks and a random distribution of leaves. The Distorted Born Approximation (DBA) is employed to calculate the single scattered return from the corn field. The new feature of the method is that the coherence of the stalks in the row direction is incorporated in the model in a systematic fashion. Since the wavelength is on the order of the distance between corn stalks in a row, grating lobe behavior is observed at certain azimuth angles of incidence. The results are compared with experimental values measured in Huntsville, Alabama in 1998. The mean field and the effective dielectric constant of the canopy are obtained by using the Foldy approximation. The stalks are placed in the effective medium in a two dimensional lattice to simulate the row structure of a corn field. In order to mimic a real corn field, a quasi-periodic stalk distribution is assumed where the stalks are given small random perturbations about their lattice locations. Corn leaves are also embedded in the effective medium and the backscattered field from the stalks and the leaves is computed. The backscattering coefficient is calculated and averaged over successive stalk position perturbations. It is assumed that soil erosion has smoothed the soil sufficiently so that it can be assumed flat. Corn field backscatter data was collected from cornfields during the Huntsville 98 experimental campaign held at Alabama A&M University Research Station, Huntsville, Alabama in 1998 using the NASA/GW truck mounted radar. Extensive ground truth data was collected. This included soil moisture measurements and corn plant architectural data to be used in the model. In particular, the distances between the stalks in a single row have been measured. The L-band radar backscatter data was collected for both H and V polarizations and for look angles of 15o and 45o over a two week period under varying soil moisture conditions. These measured backscattering values will be compared with the model backscattering values and a discussion of the results will be presented.

Lang, R.; Utku, C.; Zhao, Q.; O'Neill, P.

2010-01-01

102

Combined in-situ and ground-based observations of quasi-periodic radar echoes

NASA Astrophysics Data System (ADS)

A series of combined rocket/radar investigation of the electrodynamics and neutralplasma coupling associated with sporadic-E layers and quasi-periodic backscatter radar echoes has been carried out from launch sites at both Puerto Rico and the Wallops Flight Facility, Virginia (USA) between 1998-2001. The instrumented rockets consisted of main and sub-payloads and were launched while strong quasiperiodic VHF echoes were observed simultaneously with the Univ. of Illinois 50 MHz backscatter radar. The rocket apogee was purposely limited so that the payloads would dwell in the sporadic-E region (90-115 km). The main payload included vector DC and AC electric field detectors, a DC magnetometer, an ion mass spectrometer, an ionization gauge, and spaced-electric field receivers to measure the wavelength and phase velocity of the unstable plasma waves. The sub-payload was instrumented to measure DC and wave electric fields and plasma density. In one case, a separate rocket was launched a few minutes later which released luminous TMA trails to measure the neutral wind, its velocity shear, and embedded neutral structures. In this experiment, the payloads successfully pierced a well-defined, 2-3 km thick metallic sporadic-E layer of approximately 10**5 e/cc near 103 km altitude. In-situ DC electric field measurements revealed ~5mV/m ambient meridional fields above and below the layer with 1-2 mV/m amplitude, large scale structures superimposed. The wavelengths of these structures were approximately 2-4 km and may be related to the seat of the quasiperiodic echoes. Intense (~5 mV/m), higher frequency (shorter scale) broadband waves were also observed in-situ, both above and below the layer, consistent with the VHF backscatter observations during the time of the launch. Neither the large scale nor short scale plasma waves appeared to be distinctly organized by the sporadic-E density layer. The TMA release showed large amplitude (~ 100 m/s) meridional winds near 102-105 km, with the most intense shears directly below these altitudes, where the short scale electric field fluctuations were most intense. We summarize the observations from the different experiments and discuss them in the context of current theories regarding quasi-periodic echoes.

Pfaff, R.; Kudeki, E.; Larsen, M.; Clemmons, J.; Earle, G.

103

A parsec-scale 'superjet' and quasi-periodic structure in the HH 34 outflow?

NASA Astrophysics Data System (ADS)

We report the detection of a new Herbig-Haro (HH) object, HH 173, near the young stellar object HH 34* in the L1641 molecular cloud in Orion. The new object appears to be part of a remarkable bipolar chain that includes known HH objects in this region and extends symmetrically about HH 34* for 1.5 pc. The chain terminates in the north at the position of HH 33 and includes HH 40, HH 85, HH 126, and HH 34N. Toward the south, the chain ends at the position of HH 88 and includes HH 87, HH 86, HH 173, HH 34X, HH 34, and the HH 34 jet. All HH objects in the chain that have recognizable bow shock morphologies point to a driving source in the HH 34* cloud core. We propose that this chain delineates a 3 pc long bipolar outflow from HH 34* with blueshifted gas in the south and redshifted gas in the north. The quasi-periodic spacing of the HH objects may be a consequence of episodic mass-loss events from HH 34* occurring roughly every 900/V300 yr (for a flow velocity V300 measured in units of 300 km/sec). The dynamic age of the most distant HH object from HH 34* is approximately 5000 yr. The S-shaped symmetry of the HH objects about the central source may result from jet precession with a period of approximately 104 yr.

Bally, John; Devine, David

1994-06-01

104

Submillimeter Quasi-periodic Oscillations in Magnetically Choked Accretion Flow Models of SgrA*

NASA Astrophysics Data System (ADS)

High-frequency quasi-periodic oscillations (QPOs) appear in general-relativistic magnetohydrodynamic simulations of magnetically choked accretion flows around rapidly rotating black holes (BHs). We perform polarized radiative transfer calculations with the ASTRORAY code to explore the manifestations of these QPOs for SgrA*. We construct a simulation-based model of a radiatively inefficient accretion flow and find model parameters by fitting the mean polarized source spectrum. The simulated QPOs have a total submillimeter flux amplitude up to 5% and a linearly polarized flux amplitude up to 2%. The oscillations reach high levels of significance 10?-30? and high-quality factors Q ? 5. The oscillation period T ? 100 M ? 35 minutes corresponds to the rotation period of the BH magnetosphere that produces a trailing spiral in resolved disk images. The total flux signal is significant over noise for all tested frequencies 87 GHz, 230 GHz, and 857 GHz and inclination angles 10°, 37°, and 80°. The non-detection in the 230 GHz SubMillimeter Array light curve is consistent with a low signal level and a low sampling rate. The presence of submillimeter QPOs in SgrA* will be better tested with the Atacama Large Millimeter Array.

Shcherbakov, Roman V.; McKinney, Jonathan C.

2013-09-01

105

Search for Persistent Quasi-Periodicities in the Solar and Interplanetary Magnetic Fields

NASA Astrophysics Data System (ADS)

Previous analysis of the radial component of the interplanetary magnetic field from 1962 - 1998 has revealed a dominant frequency of 27.03 days to 0.02 day accuracy (Neugebauer, et al., 2000). We have repeated and extended this analysis with OMNI data from 1963 - 2007 obtained from the Coordinated Heliospheric Observations (COHO) database. Over this longer data string we find that the 27.03 day Lomb-Scargle periodogram peak is reduced while two side peaks near 26.8 days and 27.6 days become almost as strong. In the interval 1999-2007 there are two dominant periods near 26.5 days and 27.2 days. As a solar counterpart to the above analysis we have searched for persistent rotation periods near 27 days of global patterns of photospheric magnetic fields derived from Wilcox Solar Observatory synoptic Carrington rotation maps. Techniques applied include, principal components analysis, independent component analysis, singular spectrum analysis, wavelet spectral analysis, and complex demodulation. We find a variety of quasi- periodicities between 26 and 29 days that remain coherent for 1 - 2 years. In the southern solar hemisphere the strongest periodicity is at 28.2 days, while in the northern hemisphere it is around 26.5 days. Neugebauer, M., Smith, Smith, E.J., Ruzmaikin, A., Feynman, J., Vaughan, A.H. 2000, J. Geophys. Res., 106, A5, 8363.

Lawrence, J. K.; Cadavid, A. C.; Ruzmaikin, A.

2007-12-01

106

High-frequency quasi-periodic oscillations in black hole binaries

NASA Astrophysics Data System (ADS)

We present the results of the analysis of a large data base of X-ray observations of 22 galactic black hole transients with the Rossi X-Ray Timing Explorer throughout its operative life for a total exposure time of ˜12 ms. We excluded persistent systems and the peculiar source GRS 1915+105, as well as the most recently discovered sources. The semi-automatic homogeneous analysis was aimed at the detection of high-frequency (100-1000 Hz) quasi-periodic oscillations (QPO), of which several cases were previously reported in the literature. After taking into account the number of independent trials, we obtained 11 detections from two sources only: XTE J1550-564 and GRO J1655-40. For the former, the detected frequencies are clustered around 180 and 280 Hz, as previously found. For the latter, the previously reported dichotomy 300-450 Hz is found to be less sharp. We discuss our results in comparison with kHz QPO in neutron-star X-ray binaries and the prospects for future timing X-ray missions.

Belloni, T. M.; Sanna, A.; Méndez, M.

2012-11-01

107

The X-ray binary analogy to the first AGN quasi-periodic oscillation

NASA Astrophysics Data System (ADS)

The narrow line Seyfert 1 galaxy REJ 1034+396 is so far unique amongst active galaxies (AGN) in showing a quasi-periodic oscillation (QPO) in its variability power spectrum. There are multiple types of QPO seen in black hole binary (BHB) systems, so we need to identify which BHB QPO corresponds to the one seen in the AGN. A key hint is the `hot disc dominated' energy spectrum of REJ 1034+396 which is sufficiently unusual that it suggests a mildly super-Eddington flow, also favoured by the most recent mass estimates for the AGN. This suggests the 67 Hz QPO seen occasionally in the mildly super-Eddington BHB GRS 1915+105 as the most likely counterpart, assuming mass scaling of the QPO frequency. This is supported by the fact that these data from GRS 1915+105 have an energy spectrum which is also dominated by a `hot disc' component. Here we show that the underlying broad band power spectral shape and normalization are also similar, providing further consistency checks for this identification. Thus the AGN QPO adds to the growing evidence for a simple mass scaling of the accretion flow properties between stellar and supermassive black holes.

Middleton, Matthew; Done, Chris

2010-03-01

108

Correlation between spectral state and quasi-periodic oscillation parameters in GX 5-1

In a series of seven Exosat observations, the bimodal spectral behavior and the quasi-periodic oscillation (QPO)/red noise properties of GX 5-1 show a strict correlation. In one of the two spectral states (characterized by a 'horizontal branch' in the hardness-intensity diagram), strong 20-40 Hz QPO and red noise below about 60 Hz were always present. In the other ('normal branch'), no QPO between 6 and 60 Hz or red noise above 1 Hz were detected, but there was an indication for weak QPO near 5 Hz. In both states 'very low frequency noise' (VLFN) is detected below 0.1 Hz which has a power-law shape and and which extends down to the lowest observed frequencies (0.0001 Hz). The VLFN is probably not directly related to the QPO. The results are compared to those on Sco X-1 and Cyg X-2 and it is concluded that, although all three sources show bimodal spectral and QPO/red noise behavior, there is a qualitative difference between GX 5-1 and Cyg X-2 on one hand and Sco X-1 on the other. 25 references.

Van der klis, M.; Jansen, F.; Van paradijs, J.; Lewin, W.H.G.; Sztajno, M.

1987-02-01

109

Discovery of Millihertz ULTRAVIOLET Quasi-periodic Oscillations in Hercules X-1

NASA Astrophysics Data System (ADS)

Observations of the ultraviolet continuum of the X-ray binary system Her X-1/HZ Herculis with the Space Telescope Imaging Spectrograph on the Hubble Space Telescope (HST) show quasi-periodic oscillations (QPOs) at frequencies of 8+/-2 and 43+/-2 mHz, with rms amplitudes of 2% and 4% of the steady flux. Observations with the Keck Telescope confirm the presence of the higher frequency QPO in the optical continuum, with a rms amplitude of 1.6%+/-0.2%. The QPOs are most prominent in the HST data near ?=0.5 (where ?=0 is the middle of the X-ray eclipse), suggesting that they arise not in the accretion disk but on the X-ray-heated face of the companion star. We discuss scenarios in which the companion star reprocesses oscillations in the disk which are caused by either Keplerian rotation or a beat frequency between the neutron star spin and Keplerian rotation at some radius in the accretion disk.

Boroson, Bram; O'Brien, Kieran; Horne, Keith; Kallman, Timothy; Still, Martin; Boyd, Patricia T.; Quaintrell, Hannah; Vrtilek, Saeqa Dil

2000-12-01

110

Kilo-Second Quasi-Periodic Oscillations in the Cataclysmic Variable DW Cancri

NASA Astrophysics Data System (ADS)

Our photometric monitoring revealed that DWCnc, which was originally classified as a dwarf nova (V=15 - 17.5) remained at a bright state of Rc=14.68 +/- 0.07 for 61days. In conjunction with optical spectra lacking a strong He II emission line, we propose that the object is not a dwarf nova, but a non-magnetic nova-like variable. Throughout our monitoring, the object showed strong quasi-periodic oscillations (QPOs) with amplitudes reaching about 0.3mag. Our period analysis yielded a power spectrum with two peaks of QPOs, whose center periods are 37.5 +/- 0.1 and 73.4 +/- 0.4 min and, furthermore, with a significant power in frequencies lower than the QPOs. DWCnc is a unique cataclysmic variable in which kilo-second QPOs were continuously detected for 61days. We propose two possible interpretations of DWCnc: (i) A permanent superhumper below the period minimum of hydrogen-rich cataclysmic variab les. (ii) A nova-like variable having an orbital period over 3hours. In this case, the QPOs may be caused by trapped disk oscillations.

Uemura, Makoto; Kato, Taichi; Ishioka, Ryoko; Novak, Rudolf; Pietz, Jochen

2002-04-01

111

Conjugate observations of quasi-periodic emissions by Cluster and DEMETER spacecraft

NASA Astrophysics Data System (ADS)