Gravitational Lens Time Delays Using Polarization Monitoring
Andrew Biggs
2017-11-01
Full Text Available Gravitational lens time delays provide a means of measuring the expansion of the Universe at high redshift (and therefore in the ‘Hubble flow’ that is independent of local calibrations. It was hoped that many of the radio lenses found in the JVAS/CLASS survey would yield time delays as these were selected to have flat spectra and are dominated by multiple compact components. However, despite extensive monitoring with the Very Large Array (VLA, time delays have only been measured for three of these systems (out of 22. We have begun a programme to reanalyse the existing VLA monitoring data with the goal of producing light curves in polarized flux and polarization position angle, either to improve delay measurements or to find delays for new sources. Here, we present preliminary results on the lens system B1600+434 which demonstrate the presence of correlated and substantial polarization variability in each image.
Reduced time delay for gravitational waves with dark matter emulators
Desai, S.; Kahya, E. O.; Woodard, R. P.
2008-01-01
We discuss the implications for gravitational wave detectors of a class of modified gravity theories which dispense with the need for dark matter. These models, which are known as dark matter emulators, have the property that weak gravitational waves couple to the metric that would follow from general relativity without dark matter whereas ordinary particles couple to a combination of the metric and other fields which reproduces the result of general relativity with dark matter. We show that there is an appreciable difference in the Shapiro delays of gravitational waves and photons or neutrinos from the same source, with the gravitational waves always arriving first. We compute the expected time lags for GRB 070201, for SN 1987a and for Sco-X1. We estimate the probable error by taking account of the uncertainty in position, and by using three different dark matter profiles
The Hubble constant estimation using 18 gravitational lensing time delays
Jaelani, Anton T.; Premadi, Premana W.
2014-03-01
Gravitational lens time delay method has been used to estimate the rate of cosmological expansion, called the Hubble constant, H0, independently of the standard candle method. This gravitational lensing method requires a good knowledge of the lens mass distribution, reconstructed using the lens image properties. The observed positions of the images, and the redshifts of the lens and the images serve as strong constraints to the lens equations, which are then solved as a set of simultaneous linear equations. Here we made use of a non-parametric technique to reconstruct the lens mass distribution, which is manifested in a linear equations solver named PixeLens. Input for the calculation is chosen based on prior known parameters obtained from analyzed result of the lens case observations, including time-delay, position angles of the images and the lens, and their redshifts. In this project, 18 fairly well studied lens cases are further grouped according to a number of common properties to examine how each property affects the character of the data, and therefore affects the calculation of H0. The considered lens case properties are lens morphology, number of image, completeness of time delays, and symmetry of lens mass distribution. Analysis of simulation shows that paucity of constraints on mass distribution of a lens yields wide range value of H0, which reflects the uniqueness of each lens system. Nonetheless, gravitational lens method still yields H0 within an acceptable range of value when compared to those determined by many other methods. Grouping the cases in the above manner allowed us to assess the robustness of PixeLens and thereby use it selectively. In addition, we use glafic, a parametric mass reconstruction solver, to refine the mass distribution of one lens case, as a comparison.
COSMOLOGY FROM GRAVITATIONAL LENS TIME DELAYS AND PLANCK DATA
Suyu, S. H.; Treu, T.; Sonnenfeld, A.; Hilbert, S.; Spiniello, C.; Auger, M. W.; Collett, T.; Blandford, R. D.; Marshall, P. J.; Courbin, F.; Meylan, G.; Tewes, M.; Fassnacht, C. D.; Koopmans, L. V. E.
2014-01-01
Under the assumption of a flat ΛCDM cosmology, recent data from the Planck satellite point toward a Hubble constant that is in tension with that measured by gravitational lens time delays and by the local distance ladder. Prosaically, this difference could arise from unknown systematic uncertainties in some of the measurements. More interestingly—if systematics were ruled out—resolving the tension would require a departure from the flat ΛCDM cosmology, introducing, for example, a modest amount of spatial curvature, or a non-trivial dark energy equation of state. To begin to address these issues, we present an analysis of the gravitational lens RXJ1131–1231 that is improved in one particular regard: we examine the issue of systematic error introduced by an assumed lens model density profile. We use more flexible gravitational lens models with baryonic and dark matter components, and find that the exquisite Hubble Space Telescope image with thousands of intensity pixels in the Einstein ring and the stellar velocity dispersion of the lens contain sufficient information to constrain these more flexible models. The total uncertainty on the time-delay distance is 6.6% for a single system. We proceed to combine our improved time-delay distance measurement with the WMAP9 and Planck posteriors. In an open ΛCDM model, the data for RXJ1131–1231 in combination with Planck favor a flat universe with Ω k =0.00 −0.02 +0.01 (68% credible interval (CI)). In a flat wCDM model, the combination of RXJ1131–1231 and Planck yields w=−1.52 −0.20 +0.19 (68% CI)
Isolation of gravitational waves from displacement noise and utility of a time-delay device
Somiya, Kentaro [Max-Planck Institut fuer Gravitationsphysik, Am Muehlenberg 1, 14476 Potsdam (Germany); Goda, Keisuke [LIGO Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Chen, Yanbei [Max-Planck Institut fuer Gravitationsphysik, Am Muehlenberg 1, 14476 Potsdam (Germany); Mikhailov, Eugeniy E [Department of Physics, College of William and Mary, Williamsburg, VA 23187 (United States)
2007-05-15
Interferometers with kilometer-scale arms have been built for gravitational-wave detections on the ground; ones with much longer arms are being planned for space-based detection. One fundamental motivation for long baseline interferometry is from displacement noise. In general, the longer the arm length L, the larger the motion the gravitational-wave induces on the test masses, until L becomes comparable to the gravitational wavelength. Recently, schemes have been invented, in which displacement noise can be evaded by employing differences between the influence of test-mass motions and that of gravitational waves on light propagation. However, in these schemes, such differences only becomes significant when Lapproaches the gravitational wavelength. In this paper, we explore a use of artificial time delay in displacement-noise-free interferometers, which will shift the frequency band of the effect being significant and may improve their shot-noise-limited sensitivity at low frequencies.
Isolation of gravitational waves from displacement noise and utility of a time-delay device
Somiya, Kentaro; Goda, Keisuke; Chen, Yanbei; Mikhailov, Eugeniy E
2007-01-01
Interferometers with kilometer-scale arms have been built for gravitational-wave detections on the ground; ones with much longer arms are being planned for space-based detection. One fundamental motivation for long baseline interferometry is from displacement noise. In general, the longer the arm length L, the larger the motion the gravitational-wave induces on the test masses, until L becomes comparable to the gravitational wavelength. Recently, schemes have been invented, in which displacement noise can be evaded by employing differences between the influence of test-mass motions and that of gravitational waves on light propagation. However, in these schemes, such differences only becomes significant when Lapproaches the gravitational wavelength. In this paper, we explore a use of artificial time delay in displacement-noise-free interferometers, which will shift the frequency band of the effect being significant and may improve their shot-noise-limited sensitivity at low frequencies
General Relativistic Theory of the VLBI Time Delay in the Gravitational Field of Moving Bodies
Kopeikin, Sergei
2003-01-01
The general relativistic theory of the gravitational VLBI experiment conducted on September 8, 2002 by Fomalont and Kopeikin is explained. Equations of radio waves (light) propagating from the quasar to the observer are integrated in the time-dependent gravitational field of the solar system by making use of either retarded or advanced solutions of the Einstein field equations. This mathematical technique separates explicitly the effects associated with the propagation of gravity from those associated with light in the integral expression for the relativistic VLBI time delay of light. We prove that the relativistic correction to the Shapiro time delay, discovered by Kopeikin (ApJ, 556, L1, 2001), changes sign if one retains direction of the light propagation but replaces the retarded for the advanced solution of the Einstein equations. Hence, this correction is associated with the propagation of gravity. The VLBI observation measured its speed, and that the retarded solution is the correct one.
Time-delay interferometric ranging for space-borne gravitational-wave detectors
Tinto, Massimo; Vallisneri, Michele; Armstrong, J.W.
2005-01-01
Space-borne interferometric gravitational-wave detectors, sensitive in the low-frequency (mHz) band, will fly in the next decade. In these detectors, the spacecraft-to-spacecraft light-travel times will necessarily be unequal and time varying, and (because of aberration) will have different values on up- and down-links. In such unequal-armlength interferometers, laser-phase noise will be canceled by taking linear combinations of the laser-phase observables measured between pairs of spacecraft, appropriately time shifted by the light propagation times along the corresponding arms. This procedure, known as time-delay interferometry (TDI), requires an accurate knowledge of the light-time delays as functions of time. Here we propose a high-accuracy technique to estimate these time delays, and we study its use in the context of the Laser Interferometer Space Antenna (LISA) mission. We refer to this ranging technique, which relies on the TDI combinations themselves, as time-delay interferometric ranging (TDIR). For every TDI combination, we show that, by minimizing the rms power in that combination (averaged over integration times ∼10 4 s) with respect to the time-delay parameters, we obtain estimates of the time delays accurate enough to cancel laser noise to a level well below the secondary noises. Thus TDIR allows the implementation of TDI without the use of dedicated interspacecraft ranging systems, with a potential simplification of the LISA design. In this paper we define the TDIR procedure formally, and we characterize its expected performance via simulations with the Synthetic LISA software package
Ishak, Mustapha
2008-01-01
The contributions of the cosmological constant to the deflection angle and the time delays are derived from the integration of the gravitational potential as well as from Fermat's principle. The findings are in agreement with recent results using exact solutions to Einstein's equations and reproduce precisely the new Λ term in the bending angle and the lens equation. The consequences on time-delay expressions are explored. While it is known that Λ contributes to the gravitational time delay, it is shown here that a new Λ term appears in the geometrical time delay as well. Although these newly derived terms are perhaps small for current observations, they do not cancel out as previously claimed. Moreover, as shown before, at galaxy cluster scale, the Λ contribution can be larger than the second-order term in the Einstein deflection angle for several cluster lens systems.
Chen, Geoff C. -F; Suyu, Sherry H.; Wong, Kenneth C.; Fassnacht, Christopher D.; Chiueh, Tzihong; Halkola, Aleksi; Hu, I. Shing; Auger, Matthew W.; Koopmans, Léon V. E.; Lagattuta, David J.; McKean, John P.; Vegetti, Simona
2016-01-01
Accurate and precise measurements of the Hubble constant are critical for testing our current standard cosmological model and revealing possibly new physics. With Hubble Space Telescope (HST) imaging, each strong gravitational lens system with measured time delays can allow one to determine the
Massimo Tinto
2014-08-01
Full Text Available Equal-arm detectors of gravitational radiation allow phase measurements many orders of magnitude below the intrinsic phase stability of the laser injecting light into their arms. This is because the noise in the laser light is common to both arms, experiencing exactly the same delay, and thus cancels when it is differenced at the photo detector. In this situation, much lower level secondary noises then set the overall performance. If, however, the two arms have different lengths (as will necessarily be the case with space-borne interferometers, the laser noise experiences different delays in the two arms and will hence not directly cancel at the detector. In order to solve this problem, a technique involving heterodyne interferometry with unequal arm lengths and independent phase-difference readouts has been proposed. It relies on properly time-shifting and linearly combining independent Doppler measurements, and for this reason it has been called time-delay interferometry (TDI. This article provides an overview of the theory, mathematical foundations, and experimental aspects associated with the implementation of TDI. Although emphasis on the application of TDI to the Laser Interferometer Space Antenna (LISA mission appears throughout this article, TDI can be incorporated into the design of any future space-based mission aiming to search for gravitational waves via interferometric measurements. We have purposely left out all theoretical aspects that data analysts will need to account for when analyzing the TDI data combinations.
DETECTING GRAVITATIONAL WAVE MEMORY WITH PULSAR TIMING
Cordes, J. M.; Jenet, F. A.
2012-01-01
We compare the detectability of gravitational bursts passing through the solar system with those passing near each millisecond pulsar in an N-pulsar timing array. The sensitivity to Earth-passing bursts can exploit the correlation expected in pulse arrival times while pulsar-passing bursts, though uncorrelated between objects, provide an N-fold increase in overall time baseline that can compensate for the lower sensitivity. Bursts with memory from mergers of supermassive black holes produce step functions in apparent spin frequency that are the easiest to detect in pulsar timing. We show that the burst rate and amplitude distribution, while strongly dependent on inadequately known cosmological evolution, may favor detection in the pulsar terms rather than the Earth timing perturbations. Any contamination of timing data by red spin noise makes burst detection more difficult because both signals grow with the length of the time data span T. Furthermore, the different bursts that could appear in one or more data sets of length T ≈ 10 yr also affect the detectability of the gravitational wave stochastic background that, like spin noise, has a red power spectrum. A burst with memory is a worthwhile target in the timing of multiple pulsars in a globular cluster because it should produce a correlated signal with a time delay of less than about 10 years in some cases.
Detecting Gravitational Wave Memory with Pulsar Timing
Cordes, J. M.; Jenet, F. A.
2012-06-01
We compare the detectability of gravitational bursts passing through the solar system with those passing near each millisecond pulsar in an N-pulsar timing array. The sensitivity to Earth-passing bursts can exploit the correlation expected in pulse arrival times while pulsar-passing bursts, though uncorrelated between objects, provide an N-fold increase in overall time baseline that can compensate for the lower sensitivity. Bursts with memory from mergers of supermassive black holes produce step functions in apparent spin frequency that are the easiest to detect in pulsar timing. We show that the burst rate and amplitude distribution, while strongly dependent on inadequately known cosmological evolution, may favor detection in the pulsar terms rather than the Earth timing perturbations. Any contamination of timing data by red spin noise makes burst detection more difficult because both signals grow with the length of the time data span T. Furthermore, the different bursts that could appear in one or more data sets of length T ≈ 10 yr also affect the detectability of the gravitational wave stochastic background that, like spin noise, has a red power spectrum. A burst with memory is a worthwhile target in the timing of multiple pulsars in a globular cluster because it should produce a correlated signal with a time delay of less than about 10 years in some cases.
A new theory of space-time and gravitation
Denisov, V.I.; Logunov, A.A.
1982-01-01
Field theory of gravitation is constructed. It uses a symmetrical second rank tensor field in pseudoeuclidean space-time for describing the gravitational field. The theory is based on the condition of the presence of conservation laws for gravitational field and matter taken together and on the geometrization principle. The field theory of gravitation has the same post-newtonian parame-- ters as the general relativity theory (GRT) which implies that both theories are indistinguishable from the viewpoint of any post- newtonian experiment. The description of the effects in strong gravitational fields as well as properties of gravitational waves in the field theory of gravitation and GRT differ significantly from each other. The distinctions between two theories include also the itational red shifti curving of light trajectories and timabsence in the field theory of gravitation of the effects of grav.. delay/ in processes of propagation of gravitational waves in external fields. These distinctions made it possible to suggest a number of experiments with gravitational waves in which the predictions of the field theory of gravitation can be compared with those of the GRT. Model of the Universe in the field theory of gravitation makes it possible to describe the cosmological red shift of the frequency. Character of the evolution in this mode is determined by the delay parameter q 0 : at q 0 0 >4-3/2xα the ''expansion'' at some moment will ''change'' to contraction'' and the Universe will return to the singular state, where α=8πepsilon 0 /3M 2 (H is the Hubble constant) [ru
Time delay interferometry with moving spacecraft arrays
Tinto, Massimo; Estabrook, F.B.; Armstrong, J.W.
2004-01-01
Space-borne interferometric gravitational wave detectors, sensitive in the low-frequency (millihertz) band, will fly in the next decade. In these detectors the spacecraft-to-spacecraft light-travel-times will necessarily be unequal, time varying, and (due to aberration) have different time delays on up and down links. The reduction of data from moving interferometric laser arrays in solar orbit will in fact encounter nonsymmetric up- and down-link light time differences that are about 100 times larger than has previously been recognized. The time-delay interferometry (TDI) technique uses knowledge of these delays to cancel the otherwise dominant laser phase noise and yields a variety of data combinations sensitive to gravitational waves. Under the assumption that the (different) up- and down-link time delays are constant, we derive the TDI expressions for those combinations that rely only on four interspacecraft phase measurements. We then turn to the general problem that encompasses time dependence of the light-travel times along the laser links. By introducing a set of noncommuting time-delay operators, we show that there exists a quite general procedure for deriving generalized TDI combinations that account for the effects of time dependence of the arms. By applying our approach we are able to re-derive the 'flex-free' expression for the unequal-arm Michelson combinations X 1 , and obtain the generalized expressions for the TDI combinations called relay, beacon, monitor, and symmetric Sagnac
Fassnacht, CD; Pearson, TJ; Readhead, ACS; Browne, IWA; Koopmans, LVE; Myers, ST; Wilkinson, PN
1999-01-01
We present the results of a program to monitor the four-image gravitational lens B1608 + 656 with the VLA. The system was observed over a 7 month period from 1996 October to 1997 May. The 64 epochs of observation have an average spacing of 3.6 days. The light curves of the four images of the
Giannini, E.; Schmidt, R. W.; Wambsganss, J.
2017-01-01
Aims. We present V and R photometry of the gravitationally lensed quasars WFI 2033-4723 and HE 0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope at the ESO La Silla observatory from 2008 to 2012.Methods. Differential photometry has been carried out using...
The theory of space, time and gravitation
Fock, V
2015-01-01
The Theory of Space, Time, and Gravitation, 2nd Revised Edition focuses on Relativity Theory and Einstein's Theory of Gravitation and correction of the misinterpretation of the Einsteinian Gravitation Theory. The book first offers information on the theory of relativity and the theory of relativity in tensor form. Discussions focus on comparison of distances and lengths in moving reference frames; comparison of time differences in moving reference frames; position of a body in space at a given instant in a fixed reference frame; and proof of the linearity of the transformation linking two iner
Gravitational Waves and Time Domain Astronomy
Centrella, Joan; Nissanke, Samaya; Williams, Roy
2012-01-01
The gravitational wave window onto the universe will open in roughly five years, when Advanced LIGO and Virgo achieve the first detections of high frequency gravitational waves, most likely coming from compact binary mergers. Electromagnetic follow-up of these triggers, using radio, optical, and high energy telescopes, promises exciting opportunities in multi-messenger time domain astronomy. In the decade, space-based observations of low frequency gravitational waves from massive black hole mergers, and their electromagnetic counterparts, will open up further vistas for discovery. This two-part workshop featured brief presentations and stimulating discussions on the challenges and opportunities presented by gravitational wave astronomy. Highlights from the workshop, with the emphasis on strategies for electromagnetic follow-up, are presented in this report.
Schmelzeisen-Redeker, Günther; Schoemaker, Michael; Kirchsteiger, Harald; Freckmann, Guido; Heinemann, Lutz; del Re, Luigi
2015-01-01
Background: Continuous glucose monitoring (CGM) is a powerful tool to support the optimization of glucose control of patients with diabetes. However, CGM systems measure glucose in interstitial fluid but not in blood. Rapid changes in one compartment are not accompanied by similar changes in the other, but follow with some delay. Such time delays hamper detection of, for example, hypoglycemic events. Our aim is to discuss the causes and extent of time delays and approaches to compensate for these. Methods: CGM data were obtained in a clinical study with 37 patients with a prototype glucose sensor. The study was divided into 5 phases over 2 years. In all, 8 patients participated in 2 phases separated by 8 months. A total number of 108 CGM data sets including raw signals were used for data analysis and were processed by statistical methods to obtain estimates of the time delay. Results: Overall mean (SD) time delay of the raw signals with respect to blood glucose was 9.5 (3.7) min, median was 9 min (interquartile range 4 min). Analysis of time delays observed in the same patients separated by 8 months suggests a patient dependent delay. No significant correlation was observed between delay and anamnestic or anthropometric data. The use of a prediction algorithm reduced the delay by 4 minutes on average. Conclusions: Prediction algorithms should be used to provide real-time CGM readings more consistent with simultaneous measurements by SMBG. Patient specificity may play an important role in improving prediction quality. PMID:26243773
Takahashi, Ryuichi [Faculty of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561 (Japan)
2017-01-20
In this study we demonstrate that general relativity predicts arrival time differences between gravitational wave (GW) and electromagnetic (EM) signals caused by the wave effects in gravitational lensing. The GW signals can arrive earlier than the EM signals in some cases if the GW/EM signals have passed through a lens, even if both signals were emitted simultaneously by a source. GW wavelengths are much larger than EM wavelengths; therefore, the propagation of the GWs does not follow the laws of geometrical optics, including the Shapiro time delay, if the lens mass is less than approximately 10{sup 5} M {sub ⊙}( f /Hz){sup −1}, where f is the GW frequency. The arrival time difference can reach ∼0.1 s ( f /Hz){sup −1} if the signals have passed by a lens of mass ∼8000 M {sub ⊙}( f /Hz){sup −1} with the impact parameter smaller than the Einstein radius; therefore, it is more prominent for lower GW frequencies. For example, when a distant supermassive black hole binary (SMBHB) in a galactic center is lensed by an intervening galaxy, the time lag becomes of the order of 10 days. Future pulsar timing arrays including the Square Kilometre Array and X-ray detectors may detect several time lags by measuring the orbital phase differences between the GW/EM signals in the SMBHBs. Gravitational lensing imprints a characteristic modulation on a chirp waveform; therefore, we can deduce whether a measured arrival time lag arises from intrinsic source properties or gravitational lensing. Determination of arrival time differences would be extremely useful in multimessenger observations and tests of general relativity.
Time-delay interferometry for LISA
Tinto, Massimo; Estabrook, F.B.; Armstrong, J.W.
2002-01-01
LISA (Laser Interferometer Space Antenna) is a mission to detect and study low-frequency cosmic gravitational radiation through its influence on the phases or frequencies of laser beams exchanged between three remote spacecraft. We previously showed how, with lasers of identical frequencies on stationary spacecraft, the measurement of twelve time series of Doppler shifts could be combined to cancel exactly the phase noise of the lasers and the Doppler fluctuations due to noninertial motions of the six optical benches, while preserving gravitational wave signals. Here we generalize those results on gravitational wave detection with time-delay interferometry to the expected LISA instrument. The six lasers have different center frequencies (in the nominal LISA configuration these center frequencies may well differ by several hundred megahertz) and the distances between spacecraft pairs will change with time (these slowly varying orbital Doppler shifts are expected to be up to tens of megahertz). We develop time-delay data combinations which, as previously, preserve gravitational waves and exactly cancel the leading noise source (phase fluctuations of the six lasers); these data combinations then imply transfer functions for the remaining system noises. Using these, we plot frequency and phase power spectra for modeled system noises in the unequal Michelson combination X and the symmetric Sagnac combination ζ. Although optical bench noise can no longer be cancelled exactly, with the current LISA specifications it is suppressed to negligible levels. It is known that the presently anticipated laser center frequency differences and the orbital Doppler drifts introduce another source of phase noise, arising from the onboard oscillators required to track the photodetector fringes. For the presently planned mission, our analysis indeed demonstrates that noise from current-generation ultrastable oscillators would, if uncorrected, dominate the LISA noise budget. To meet the
Time delayed Ensemble Nudging Method
An, Zhe; Abarbanel, Henry
Optimal nudging method based on time delayed embedding theory has shows potentials on analyzing and data assimilation in previous literatures. To extend the application and promote the practical implementation, new nudging assimilation method based on the time delayed embedding space is presented and the connection with other standard assimilation methods are studied. Results shows the incorporating information from the time series of data can reduce the sufficient observation needed to preserve the quality of numerical prediction, making it a potential alternative in the field of data assimilation of large geophysical models.
Another definition for time delay
Narnhofer, H.
1980-01-01
Time delay is defined by geometrical considerations which work in classical as well as in quantum mechanics, and its connection with the S-matrix and the virial is proven for potentials with V(x vector) and x vector V(x vector) vanishing as rsup(-1-epsilon) for r -> infinity. (Author)
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Delay time. 236.563 Section 236.563 Transportation... Cab Signal Systems Rules and Instructions; Locomotives § 236.563 Delay time. Delay time of automatic... requirements of § 236.24 shall take into consideration the delay time. ...
Quantum space-time and gravitational consequences
Namsrai, K.
1986-01-01
Relativistic particle dynamics and basic physical quantities for the general theory of gravity are reconstructed from a quantum space-time point of view. An additional force caused by quantum space-time appears in the equation of particle motion, giving rise to a reformulation of the equivalence principle up to values of O(L 2 ), where L is the fundamental length. It turns out that quantum space-time leads to quantization of gravity, i.e. the metric tensor g/sub uv/ (/ZETA/) becomes operator-valued and is not commutative at different points x/sup micro/ and y/sup micro/ in usual space-time on a large scale, and its commutator depending on the ''vielbein'' field (gaugelike graviton field) is proportional to L 2 multiplied by a translationinvariant wave function propagated between points x/sup micro/ and y/sup micro/. In the given scheme, there appears to be an antigravitational effect in the motion of a particle in the gravitational force. This effect depends on the value of particle mass; when a particle is heavy its free-fall time is long compared to that for a light-weight particle. The problem of the change of time scale and the anisotropy of inertia are discussed. From experimental data from testing of the latter effect it follows that L ≤ 10 -22 cm
Effects of gravitational lensing and companion motion on the binary pulsar timing
Rafikov, Roman R.; Lai Dong
2006-01-01
The measurement of the Shapiro time delay in binary pulsar systems with highly-inclined orbit can be affected both by the motion of the pulsar's companion because of the finite time it takes a photon to cross the binary, and by the gravitational light bending if the orbit is sufficiently edge-on relative to the line of sight. Here we calculate the effect of retardation due to the companion's motion on various time delays in pulsar binaries, including the Shaipro delay, the geometric lensing delay, and the lens-induced delays associated with the pulsar rotation. Our results can be applied to systems so highly inclined that near conjunction gravitational lensing of the pulsar radiation by the companion becomes important (the recently discovered double pulsar system J0737-3039 may exemplify such a system). To the leading order, the effect of retardation is to shift all the delay curves backward in time around the orbit conjunction, without affecting the shape and amplitude of the curves. The time shift is of order the photon orbit crossing time, and ranges from a second to a few minutes for the observed binary pulsar systems. In the double pulsar system J0737-3039, the motion of the companion may also affect the interpretation of the recent correlated interstellar scintillation measurements. Finally, we show that lensing sets an upper limit on the magnitude of the frame-dragging time delay caused by the companion's spin, and makes this delay unobservable in stellar-mass binary pulsar systems
Gravitational wave detection and data analysis for pulsar timing arrays
Haasteren, Rutger van
2011-01-01
Long-term precise timing of Galactic millisecond pulsars holds great promise for measuring long-period (months-to-years) astrophysical gravitational waves. In this work we develop a Bayesian data analysis method for projects called pulsar timing arrays; projects aimed to detect these gravitational
Gravitational time dilation and length contraction in fields exterior to ...
Here, we use our new metric tensor exterior to a massiv3e oblate spheroid to study the gravitational phenomena of time dilation and length contraction. It turns out most profoundly that, the above phenomena hold good in the gravitational field exterior to an oblate spheroid. We then use the oblate spheroidal Earth to ...
Discretization of space and time: consequences of modified gravitational law
Roatta , Luca
2017-01-01
Assuming that space and time can only have discrete values, it is shown that the modified law of gravitational attraction implies that the third principle of dynamics is not fully respected and that only bodies with sufficient mass can exert gravitational attraction.
Accurate light-time correction due to a gravitating mass
Ashby, Neil [Department of Physics, University of Colorado, Boulder, CO (United States); Bertotti, Bruno, E-mail: ashby@boulder.nist.go [Dipartimento di Fisica Nucleare e Teorica, Universita di Pavia (Italy)
2010-07-21
This technical paper of mathematical physics arose as an aftermath of the 2002 Cassini experiment (Bertotti et al 2003 Nature 425 374-6), in which the PPN parameter {gamma} was measured with an accuracy {sigma}{sub {gamma}} = 2.3 x 10{sup -5} and found consistent with the prediction {gamma} = 1 of general relativity. The Orbit Determination Program (ODP) of NASA's Jet Propulsion Laboratory, which was used in the data analysis, is based on an expression (8) for the gravitational delay {Delta}t that differs from the standard formula (2); this difference is of second order in powers of m-the gravitational radius of the Sun-but in Cassini's case it was much larger than the expected order of magnitude m{sup 2}/b, where b is the distance of the closest approach of the ray. Since the ODP does not take into account any other second-order terms, it is necessary, also in view of future more accurate experiments, to revisit the whole problem, to systematically evaluate higher order corrections and to determine which terms, and why, are larger than the expected value. We note that light propagation in a static spacetime is equivalent to a problem in ordinary geometrical optics; Fermat's action functional at its minimum is just the light-time between the two end points A and B. A new and powerful formulation is thus obtained. This method is closely connected with the much more general approach of Le Poncin-Lafitte et al (2004 Class. Quantum Grav. 21 4463-83), which is based on Synge's world function. Asymptotic power series are necessary to provide a safe and automatic way of selecting which terms to keep at each order. Higher order approximations to the required quantities, in particular the delay and the deflection, are easily obtained. We also show that in a close superior conjunction, when b is much smaller than the distances of A and B from the Sun, say of order R, the second-order correction has an enhanced part of order m{sup 2}R/b{sup 2}, which
Time delays across saddles as a test of modified gravity
Magueijo, João; Mozaffari, Ali
2013-01-01
Modified gravity theories can produce strong signals in the vicinity of the saddles of the total gravitational potential. In a sub-class of these models, this translates into diverging time delays for echoes crossing the saddles. Such models arise from the possibility that gravity might be infrared divergent or confined, and if suitably designed they are very difficult to rule out. We show that Lunar Laser Ranging during an eclipse could probe the time-delay effect within metres of the saddle, thereby proving or excluding these models. Very Large Baseline Interferometry, instead, could target delays across the Jupiter–Sun saddle. Such experiments would shed light on the infrared behaviour of gravity and examine the puzzling possibility that there might be well-hidden regions of strong gravity and even singularities inside the solar system. (fast track communication)
Dynamics of Nonlinear Time-Delay Systems
Lakshmanan, Muthusamy
2010-01-01
Synchronization of chaotic systems, a patently nonlinear phenomenon, has emerged as a highly active interdisciplinary research topic at the interface of physics, biology, applied mathematics and engineering sciences. In this connection, time-delay systems described by delay differential equations have developed as particularly suitable tools for modeling specific dynamical systems. Indeed, time-delay is ubiquitous in many physical systems, for example due to finite switching speeds of amplifiers in electronic circuits, finite lengths of vehicles in traffic flows, finite signal propagation times in biological networks and circuits, and quite generally whenever memory effects are relevant. This monograph presents the basics of chaotic time-delay systems and their synchronization with an emphasis on the effects of time-delay feedback which give rise to new collective dynamics. Special attention is devoted to scalar chaotic/hyperchaotic time-delay systems, and some higher order models, occurring in different bran...
Memorized discrete systems and time-delay
Luo, Albert C J
2017-01-01
This book examines discrete dynamical systems with memory—nonlinear systems that exist extensively in biological organisms and financial and economic organizations, and time-delay systems that can be discretized into the memorized, discrete dynamical systems. It book further discusses stability and bifurcations of time-delay dynamical systems that can be investigated through memorized dynamical systems as well as bifurcations of memorized nonlinear dynamical systems, discretization methods of time-delay systems, and periodic motions to chaos in nonlinear time-delay systems. The book helps readers find analytical solutions of MDS, change traditional perturbation analysis in time-delay systems, detect motion complexity and singularity in MDS; and determine stability, bifurcation, and chaos in any time-delay system.
Pulsar timing arrays: the promise of gravitational wave detection.
Lommen, Andrea N
2015-12-01
We describe the history, methods, tools, and challenges of using pulsars to detect gravitational waves. Pulsars act as celestial clocks detecting gravitational perturbations in space-time at wavelengths of light-years. The field is poised to make its first detection of nanohertz gravitational waves in the next 10 years. Controversies remain over how far we can reduce the noise in the pulsars, how many pulsars should be in the array, what kind of source we will detect first, and how we can best accommodate our large bandwidth systems. We conclude by considering the important question of how to plan for a post-detection era, beyond the first detection of gravitational waves.
Time Delay Estimation Algoritms for Echo Cancellation
Kirill Sakhnov
2011-01-01
Full Text Available The following case study describes how to eliminate echo in a VoIP network using delay estimation algorithms. It is known that echo with long transmission delays becomes more noticeable to users. Thus, time delay estimation, as a part of echo cancellation, is an important topic during transmission of voice signals over packetswitching telecommunication systems. An echo delay problem associated with IP-based transport networks is discussed in the following text. The paper introduces the comparative study of time delay estimation algorithm, used for estimation of the true time delay between two speech signals. Experimental results of MATLab simulations that describe the performance of several methods based on cross-correlation, normalized crosscorrelation and generalized cross-correlation are also presented in the paper.
Time delays, population, and economic development
Gori, Luca; Guerrini, Luca; Sodini, Mauro
2018-05-01
This research develops an augmented Solow model with population dynamics and time delays. The model produces either a single stationary state or multiple stationary states (able to characterise different development regimes). The existence of time delays may cause persistent fluctuations in both economic and demographic variables. In addition, the work identifies in a simple way the reasons why economics affects demographics and vice versa.
Detecting stochastic backgrounds of gravitational waves with pulsar timing arrays
Siemens, Xavier
2016-03-01
For the past decade the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has been using the Green Bank Telescope and the Arecibo Observatory to monitor millisecond pulsars. NANOGrav, along with two other international collaborations, the European Pulsar Timing Array and the Parkes Pulsar Timing Array in Australia, form a consortium of consortia: the International Pulsar Timing Array (IPTA). The goal of the IPTA is to directly detect low-frequency gravitational waves which cause small changes to the times of arrival of radio pulses from millisecond pulsars. In this talk I will discuss the work of NANOGrav and the IPTA, as well as our sensitivity to stochastic backgrounds of gravitational waves. I will show that a detection of the background produced by supermassive black hole binaries is possible by the end of the decade. Supported by the NANOGrav Physics Frontiers Center.
Nanohertz gravitational wave searches with interferometric pulsar timing experiments.
Tinto, Massimo
2011-05-13
We estimate the sensitivity to nano-Hertz gravitational waves of pulsar timing experiments in which two highly stable millisecond pulsars are tracked simultaneously with two neighboring radio telescopes that are referenced to the same timekeeping subsystem (i.e., "the clock"). By taking the difference of the two time-of-arrival residual data streams we can exactly cancel the clock noise in the combined data set, thereby enhancing the sensitivity to gravitational waves. We estimate that, in the band (10(-9)-10(-8)) Hz, this "interferometric" pulsar timing technique can potentially improve the sensitivity to gravitational radiation by almost 2 orders of magnitude over that of single-telescopes. Interferometric pulsar timing experiments could be performed with neighboring pairs of antennas of the NASA's Deep Space Network and the forthcoming large arraying projects.
Limits on the speed of gravitational waves from pulsar timing
Baskaran, D.; Polnarev, A. G.; Pshirkov, M. S.; Postnov, K. A.
2008-01-01
In this work, analyzing the propagation of electromagnetic waves in the field of gravitational waves, we show the presence and significance of the so-called surfing effect for pulsar timing measurements. It is shown that, due to the transverse nature of gravitational waves, the surfing effect leads to enormous pulsar timing residuals if the speed of gravitational waves is smaller than the speed of light. This fact allows one to place significant constraints on parameter ε, which characterizes the relative deviation of the speed of gravitational waves from the speed of light. We show that the existing constraints from pulsar timing measurements already place stringent limits on ε and consequently on the mass of the graviton m g . The limits on m g -24 are 2 orders of magnitude stronger than the current constraints from Solar System tests. The current constraints also allow one to rule out massive gravitons as possible candidates for cold dark matter in the galactic halo. In the near future, the gravitational wave background from extragalactic super massive black hole binaries, along with the expected submicrosecond pulsar timing accuracy, will allow one to achieve constraints of ε < or approx. 0.4% and possibly stronger.
Space-time algebra for the generalization of gravitational field
The Maxwell–Proca-like field equations of gravitolectromagnetism are formulated using space-time algebra (STA). The gravitational wave equation with massive gravitons and gravitomagnetic monopoles has been derived in terms of this algebra. Using space-time algebra, the most generalized form of ...
Two theorems on flat space-time gravitational theories
Castagnino, M.; Chimento, L.
1980-01-01
The first theorem states that all flat space-time gravitational theories must have a Lagrangian with a first term that is an homogeneous (degree-1) function of the 4-velocity usup(i), plus a functional of nsub(ij)usup(i)usup(j). The second theorem states that all gravitational theories that satisfy the strong equivalence principle have a Lagrangian with a first term gsub(ij)(x)usup(i)usup(j) plus an irrelevant term. In both cases the theories must issue from a unique variational principle. Therefore, under this condition it is impossible to find a flat space-time theory that satisfies the strong equivalence principle. (author)
Chaos synchronization in time-delayed systems with parameter mismatches and variable delay times
Shahverdiev, E.M.; Nuriev, R.A.; Hashimov, R.H.; Shore, K.A.
2004-06-01
We investigate synchronization between two undirectionally linearly coupled chaotic nonidentical time-delayed systems and show that parameter mismatches are of crucial importance to achieve synchronization. We establish that independent of the relation between the delay time in the coupled systems and the coupling delay time, only retarded synchronization with the coupling delay time is obtained. We show that with parameter mismatch or without it neither complete nor anticipating synchronization occurs. We derive existence and stability conditions for the retarded synchronization manifold. We demonstrate our approach using examples of the Ikeda and Mackey Glass models. Also for the first time we investigate chaos synchronization in time-delayed systems with variable delay time and find both existence and sufficient stability conditions for the retarded synchronization manifold with the coupling-delay lag time. (author)
Time delay of quantum scattering processes
Martin, P.A.
1981-01-01
The author presents various aspects of the theory of the time delay of scattering processes. The author mainly studies non-relativistic two-body scattering processes, first summarizing briefly the theory of simple scattering systems. (Auth.)
Misner, Charles W; Wheeler, John Archibald
2017-01-01
First published in 1973, Gravitation is a landmark graduate-level textbook that presents Einstein’s general theory of relativity and offers a rigorous, full-year course on the physics of gravitation. Upon publication, Science called it “a pedagogic masterpiece,” and it has since become a classic, considered essential reading for every serious student and researcher in the field of relativity. This authoritative text has shaped the research of generations of physicists and astronomers, and the book continues to influence the way experts think about the subject. With an emphasis on geometric interpretation, this masterful and comprehensive book introduces the theory of relativity; describes physical applications, from stars to black holes and gravitational waves; and portrays the field’s frontiers. The book also offers a unique, alternating, two-track pathway through the subject. Material focusing on basic physical ideas is designated as Track 1 and formulates an appropriate one-semester graduate-level...
Time delay in a multichannel formalism
Haberzettl, Helmut; Workman, Ron
2007-01-01
We reexamine the time-delay formalism of Wigner, Eisenbud, and Smith, which was developed to analyze both elastic and inelastic resonances. An error in the paper of Smith has propagated through the literature. We correct this error and show how the results of Eisenbud and Smith are related. We also comment on some recent time-delay studies, based on Smith's erroneous interpretation of the Eisenbud result
The effects of orbital motion on LISA time delay interferometry
Cornish, Neil J; Hellings, Ronald W
2003-01-01
In an effort to eliminate laser phase noise in laser interferometer spaceborne gravitational wave detectors, several combinations of signals have been found that allow the laser noise to be cancelled out while gravitational wave signals remain. This process is called time delay interferometry (TDI). In the papers that defined the TDI variables, their performance was evaluated in the limit that the gravitational wave detector is fixed in space. However, the performance depends on certain symmetries in the armlengths that are available if the detector is fixed in space, but that will be broken in the actual rotating and flexing configuration produced by the LISA orbits. In this paper we investigate the performance of these TDI variables for the real LISA orbits. First, addressing the effects of rotation, we verify Daniel Shaddock's result that the Sagnac variables α (t), β (t) and γ (t) will not cancel out the laser phase noise, and we also find the same result for the symmetric Sagnac variable ζ (t). The loss of the latter variable would be particularly unfortunate since this variable also cancels out gravitational wave signal, allowing instrument noise in the detector to be isolated and measured. Fortunately, we have found a set of more complicated TDI variables, which we call Δ Sagnac variables, one of which accomplishes the same goal as ζ (t) to good accuracy. Finally, however, as we investigate the effects of the flexing of the detector arms due to non-circular orbital motion, we show that all variables, including the interferometer variables, X(t), Y(t) and Z(t), which survive the rotation-induced loss of direction symmetry, will not completely cancel laser phase noise when the armlengths are changing with time. This unavoidable problem will place a stringent requirement on laser stability of ∼5 Hz Hz -1/2
Delay time and tunneling transient phenomena
Garcia-Calderon, Gaston; Villavicencio, Jorge
2002-01-01
Analytic solutions to the time-dependent Schroedinger equation for cutoff wave initial conditions are used to investigate the time evolution of the transmitted probability density for tunneling. For a broad range of values of the potential barrier opacity α, we find that the probability density exhibits two evolving structures. One refers to the propagation of a forerunner related to a time domain resonance [Phys. Rev. A 64, 0121907 (2001)], while the other consists of a semiclassical propagating wave front. We find a regime where the forerunners are absent, corresponding to positive time delays, and show that this regime is characterized by opacities α c . The critical opacity α c is derived from the analytical expression for the delay time, which reflects a link between transient effects in tunneling and the delay time
A continuous time Cournot duopoly with delays
Gori, Luca; Guerrini, Luca; Sodini, Mauro
2015-01-01
This paper extends the classical repeated duopoly model with quantity-setting firms of Bischi et al. (1998) by assuming that production of goods is subject to some gestation lags but exchanges take place continuously in the market. The model is expressed in the form of differential equations with discrete delays. By using some recent mathematical techniques and numerical experiments, results show some dynamic phenomena that cannot be observed when delays are absent. In addition, depending on the extent of time delays and inertia, synchronisation failure can arise even in the event of homogeneous firms.
Gravitation and cosmology with York time
Roser, Philipp
Despite decades of inquiry an adequate theory of 'quantum gravity' has remained elusive, in part due to the absence of data that would guide the search and in part due to technical difficulties, prominently among them the 'problem of time'. The problem is a result of the attempt to quantise a classical theory with temporal reparameterisation and refoliation invariance such as general relativity. One way forward is therefore the breaking of this invariance via the identification of a preferred foliation of spacetime into parameterised spatial slices. In this thesis we argue that a foliation into slices of constant extrinsic curvature, parameterised by 'York time', is a viable contender. We argue that the role of York time in the initial-value problem of general relativity as well as a number of the parameter's other properties make it the most promising candidate for a physically preferred notion of time. A Hamiltonian theory describing gravity in the York-time picture may be derived from general relativity by 'Hamiltonian reduction', a procedure that eliminates certain degrees of freedom -- specifically the local scale and its rate of change -- in favour of an explicit time parameter and a functional expression for the associated Hamiltonian. In full generality this procedure is impossible to carry out since the equation that determines the Hamiltonian cannot be solved using known methods. However, it is possible to derive explicit Hamiltonian functions for cosmological scenarios (where matter and geometry is treated as spatially homogeneous). Using a perturbative expansion of the unsolvable equation enables us to derive a quantisable Hamiltonian for cosmological perturbations on such a homogeneous background. We analyse the (classical) theories derived in this manner and look at the York-time description of a number of cosmological processes. We then proceed to apply the canonical quantisation procedure to these systems and analyse the resulting quantum theories
A comparison of cosmological models using time delay lenses
Wei, Jun-Jie; Wu, Xue-Feng; Melia, Fulvio, E-mail: jjwei@pmo.ac.cn, E-mail: xfwu@pmo.ac.cn, E-mail: fmelia@email.arizona.edu [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)
2014-06-20
The use of time-delay gravitational lenses to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 12 lens systems, which have thus far been used solely for optimizing the parameters of ΛCDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between competing models. The currently available sample indicates a likelihood of ∼70%-80% that the R {sub h} = ct universe is the correct cosmology versus ∼20%-30% for the standard model. This possibly interesting result reinforces the need to greatly expand the sample of time-delay lenses, e.g., with the successful implementation of the Dark Energy Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope. In anticipation of a greatly expanded catalog of time-delay lenses identified with these surveys, we have produced synthetic samples to estimate how large they would have to be in order to rule out either model at a ∼99.7% confidence level. We find that if the real cosmology is ΛCDM, a sample of ∼150 time-delay lenses would be sufficient to rule out R {sub h} = ct at this level of accuracy, while ∼1000 time-delay lenses would be required to rule out ΛCDM if the real universe is instead R {sub h} = ct. This difference in required sample size reflects the greater number of free parameters available to fit the data with ΛCDM.
A comparison of cosmological models using time delay lenses
Wei, Jun-Jie; Wu, Xue-Feng; Melia, Fulvio
2014-01-01
The use of time-delay gravitational lenses to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 12 lens systems, which have thus far been used solely for optimizing the parameters of ΛCDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between competing models. The currently available sample indicates a likelihood of ∼70%-80% that the R h = ct universe is the correct cosmology versus ∼20%-30% for the standard model. This possibly interesting result reinforces the need to greatly expand the sample of time-delay lenses, e.g., with the successful implementation of the Dark Energy Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope. In anticipation of a greatly expanded catalog of time-delay lenses identified with these surveys, we have produced synthetic samples to estimate how large they would have to be in order to rule out either model at a ∼99.7% confidence level. We find that if the real cosmology is ΛCDM, a sample of ∼150 time-delay lenses would be sufficient to rule out R h = ct at this level of accuracy, while ∼1000 time-delay lenses would be required to rule out ΛCDM if the real universe is instead R h = ct. This difference in required sample size reflects the greater number of free parameters available to fit the data with ΛCDM.
Two-time physics with gravitational and gauge field backgrounds
Bars, Itzhak
2000-01-01
It is shown that all possible gravitational, gauge and other interactions experienced by particles in ordinary d dimensions (one time) can be described in the language of two-time physics in a spacetime with d+2 dimensions. This is obtained by generalizing the world line formulation of two-time physics by including background fields. A given two-time model, with a fixed set of background fields, can be gauged fixed from d+2 dimensions to (d-1)+1 dimensions to produce diverse one-time dynamical models, all of which are dually related to each other under the underlying gauge symmetry of the unified two-time theory. To satisfy the gauge symmetry of the two-time theory the background fields must obey certain coupled differential equations that are generally covariant and gauge invariant in the target (d+2)-dimensional spacetime. The gravitational background obeys a closed homothety condition while the gauge field obeys a differential equation that generalizes a similar equation derived by Dirac in 1936. Explicit solutions to these coupled equations show that the usual gravitational, gauge, and other interactions in d dimensions may be viewed as embedded in the higher (d+2)-dimensional space, thus displaying higher spacetime symmetries that otherwise remain hidden
Global synchronization criteria with channel time-delay for chaotic time-delay system
Sun Jitao
2004-01-01
Based on the Lyapunov stabilization theory, matrix measure, and linear matrix inequality (LMIs), this paper studies the chaos synchronization of time-delay system using the unidirectional linear error feedback coupling with time-delay. Some generic conditions of chaos synchronization with time-delay in the transmission channel is established. The chaotic Chua's circuit is used for illustration, where the coupling parameters are determined according to the criteria under which the global chaos synchronization of the time-delay coupled systems is achieved
Time-delay analyzer with continuous discretization
Bayatyan, G.L.; Darbinyan, K.T.; Mkrtchyan, K.K.; Stepanyan, S.S.
1988-01-01
A time-delay analyzer is described which when triggered by a start pulse of adjustable duration performs continuous discretization of the analyzed signal within nearly 22 ns time intervals, the recording in a memory unit with following slow read-out of the information to the computer and its processing. The time-delay analyzer consists of four CAMAC-VECTOR systems of unit width. With its help one can separate comparatively short, small-amplitude rare signals against the background of quasistationary noise processes. 4 refs.; 3 figs
The Strong Lensing Time Delay Challenge (2014)
Liao, Kai; Dobler, G.; Fassnacht, C. D.; Treu, T.; Marshall, P. J.; Rumbaugh, N.; Linder, E.; Hojjati, A.
2014-01-01
Time delays between multiple images in strong lensing systems are a powerful probe of cosmology. At the moment the application of this technique is limited by the number of lensed quasars with measured time delays. However, the number of such systems is expected to increase dramatically in the next few years. Hundred such systems are expected within this decade, while the Large Synoptic Survey Telescope (LSST) is expected to deliver of order 1000 time delays in the 2020 decade. In order to exploit this bounty of lenses we needed to make sure the time delay determination algorithms have sufficiently high precision and accuracy. As a first step to test current algorithms and identify potential areas for improvement we have started a "Time Delay Challenge" (TDC). An "evil" team has created realistic simulated light curves, to be analyzed blindly by "good" teams. The challenge is open to all interested parties. The initial challenge consists of two steps (TDC0 and TDC1). TDC0 consists of a small number of datasets to be used as a training template. The non-mandatory deadline is December 1 2013. The "good" teams that complete TDC0 will be given access to TDC1. TDC1 consists of thousands of lightcurves, a number sufficient to test precision and accuracy at the subpercent level, necessary for time-delay cosmography. The deadline for responding to TDC1 is July 1 2014. Submissions will be analyzed and compared in terms of predefined metrics to establish the goodness-of-fit, efficiency, precision and accuracy of current algorithms. This poster describes the challenge in detail and gives instructions for participation.
4-channel time delayed pulse generator
Wetzel, L.F.S.; Rossi, J.O.; Del Bosco, E.
1987-02-01
It is described the project of a 4-channel delayed pulse generator employed to trigger the plasma centrifuge experiment of the Laboratorio Associado de Plasmas. The circuit delivers pulses with amplitude of 15V, full width at half maximum of 50μs and rise time of 0.7μs. The maximum time delay is 100ms. There are two channels with a fine adjustment of 0-1ms. The system can be manually or automatically driven. (author) [pt
Quantum limit on time measurement in a gravitational field
Sinha, Supurna; Samuel, Joseph
2015-01-01
Good clocks are of importance both to fundamental physics and for applications in astronomy, metrology and global positioning systems. In a recent technological breakthrough, researchers at NIST have been able to achieve a stability of one part in 10 18 using an ytterbium clock. This naturally raises the question of whether there are fundamental limits to time keeping. In this article we point out that gravity and quantum mechanics set a fundamental limit on the fractional frequency uncertainty of clocks. This limit comes from a combination of the uncertainty relation, the gravitational redshift and the relativistic time dilation effect. For example, a single ion aluminium clock in a terrestrial gravitational field cannot achieve a fractional frequency uncertainty better than one part in 10 22 . This fundamental limit explores the interaction between gravity and quantum mechanics on a laboratory scale. (paper)
Time-delayed autosynchronous swarm control.
Biggs, James D; Bennet, Derek J; Dadzie, S Kokou
2012-01-01
In this paper a general Morse potential model of self-propelling particles is considered in the presence of a time-delayed term and a spring potential. It is shown that the emergent swarm behavior is dependent on the delay term and weights of the time-delayed function, which can be set to induce a stationary swarm, a rotating swarm with uniform translation, and a rotating swarm with a stationary center of mass. An analysis of the mean field equations shows that without a spring potential the motion of the center of mass is determined explicitly by a multivalued function. For a nonzero spring potential the swarm converges to a vortex formation about a stationary center of mass, except at discrete bifurcation points where the center of mass will periodically trace an ellipse. The analytical results defining the behavior of the center of mass are shown to correspond with the numerical swarm simulations.
Communication key using delay times in time-delayed chaos synchronization
Kim, Chil-Min; Kye, Won-Ho; Rim, Sunghwan; Lee, Soo-Young
2004-01-01
We propose an efficient key scheme, which can generate a great number of communication keys, for communication using chaos synchronization. We have attained the keys from delay times of time-delay coupled chaotic systems. We explain the scheme and the efficiency by coupling Henon and logistic maps and illustrate them by coupling Navier-Stokes and Lorenz equations as a continuous system
Moments of the Wigner delay times
Berkolaiko, Gregory; Kuipers, Jack
2010-01-01
The Wigner time delay is a measure of the time spent by a particle inside the scattering region of an open system. For chaotic systems, the statistics of the individual delay times (whose average is the Wigner time delay) are thought to be well described by random matrix theory. Here we present a semiclassical derivation showing the validity of random matrix results. In order to simplify the semiclassical treatment, we express the moments of the delay times in terms of correlation functions of scattering matrices at different energies. In the semiclassical approximation, the elements of the scattering matrix are given in terms of the classical scattering trajectories, requiring one to study correlations between sets of such trajectories. We describe the structure of correlated sets of trajectories and formulate the rules for their evaluation to the leading order in inverse channel number. This allows us to derive a polynomial equation satisfied by the generating function of the moments. Along with showing the agreement of our semiclassical results with the moments predicted by random matrix theory, we infer that the scattering matrix is unitary to all orders in the semiclassical approximation.
Maximum likelihood window for time delay estimation
Lee, Young Sup; Yoon, Dong Jin; Kim, Chi Yup
2004-01-01
Time delay estimation for the detection of leak location in underground pipelines is critically important. Because the exact leak location depends upon the precision of the time delay between sensor signals due to leak noise and the speed of elastic waves, the research on the estimation of time delay has been one of the key issues in leak lovating with the time arrival difference method. In this study, an optimal Maximum Likelihood window is considered to obtain a better estimation of the time delay. This method has been proved in experiments, which can provide much clearer and more precise peaks in cross-correlation functions of leak signals. The leak location error has been less than 1 % of the distance between sensors, for example the error was not greater than 3 m for 300 m long underground pipelines. Apart from the experiment, an intensive theoretical analysis in terms of signal processing has been described. The improved leak locating with the suggested method is due to the windowing effect in frequency domain, which offers a weighting in significant frequencies.
Fennelly, A.J.
1978-01-01
Investigations of several problems of gravitation are discussed. The question of the existence of black holes is considered. While black holes like those in Einstein's theory may not exist in other gravity theories, trapped surfaces implying such black holes certainly do. The theories include those of Brans-Dicke, Lightman-Lee, Rosen, and Yang. A similar two-tensor theory of Yilmaz is investigated and found inconsistent and nonviable. The Newman-Penrose formalism for Riemannian geometries is adapted to general gravity theories and used to implement a search for twisting solutions of the gravity theories for empty and nonempty spaces. The method can be used to find the gravitational fields for all viable gravity theories. The rotating solutions are of particular importance for strong field interpretation of the Stanford/Marshall gyroscope experiment. Inhomogeneous cosmologies are examined in Einstein's theory as generalizations of homogeneous ones by raising the dimension of the invariance groups by one more parameter. The nine Bianchi classifications are extended to Rosen's theory of gravity for homogeneous cosmological models
Information transfer via implicit encoding with delay time modulation in a time-delay system
Kye, Won-Ho, E-mail: whkye@kipo.go.kr [Korean Intellectual Property Office, Government Complex Daejeon Building 4, 189, Cheongsa-ro, Seo-gu, Daejeon 302-701 (Korea, Republic of)
2012-08-20
A new encoding scheme for information transfer with modulated delay time in a time-delay system is proposed. In the scheme, the message is implicitly encoded into the modulated delay time. The information transfer rate as a function of encoding redundancy in various noise scales is presented and it is analyzed that the implicit encoding scheme (IES) has stronger resistance against channel noise than the explicit encoding scheme (EES). In addition, its advantages in terms of secure communication and feasible applications are discussed. -- Highlights: ► We propose new encoding scheme with delay time modulation. ► The message is implicitly encoded with modulated delay time. ► The proposed scheme shows stronger resistance against channel noise.
Einstein's Symphony: A Gravitational Wave Voyage Through Space and Time
Shapiro Key, Joey; Yunes, Nico; Grimberg, Irene
2015-01-01
Einstein's Symphony: A Gravitational Wave Voyage Through Space and Time is a gravitational wave astronomy planetarium show in production by a collaboration of scientists, filmmakers, and artisits from the Center for Gravitational Wave Astonomy (CGWA) at the University of Texas at Brownsville (UTB) and Montana State University (MSU). The project builds on the success of the interdisciplinary Celebrating Einstein collaboration. The artists and scientists who created the A Shout Across Time original film and the Black (W)hole immersive art installation for Celebrating Einstein are teaming with the Museum of the Rockies Taylor Planetarium staff and students to create a new full dome Digistar planetarium show that will be freely and widely distributed to planetaria in the US and abroad. The show uses images and animations filmed and collected for A Shout Across Time and for Black (W)hole as well as new images and animations and a new soundtrack composed and produced by the MSU School of Music to use the full capability of planetarium sound systems. The planetarium show will be narrated with ideas drawn from the Celebrating Einstein danced lecture on gravitational waves that the collaboration produced. The combination of products, resources, and team members assembled for this project allows us to create an original planetarium show for a fraction of the cost of a typical show. In addition, STEM education materials for G6-12 students and teachers will be provided to complement and support the show. This project is supported by the Texas Space Grant Consortium (TSGC), Montana Space Grant Consortium (MSGC), and the American Physical Society (APS).
STEMI time delays: A clinical perspective
M.J. de Boer (Menko Jan); F. Zijlstra (Felix)
2015-01-01
textabstractSTEMI time delays have been introduced as a performance indicator or marker of quality of care. As they are only one part of a very complex medical process, one should be aware of concomitant issues that may be overlooked or even be more important with regard to clinical outcome of STEMI
Photoemission and photoionization time delays and rates
Gallmann, L.; Jordan, I.; Wörner, H. J.; Castiglioni, L.; Hengsberger, M.; Osterwalder, J.; Arrell, C. A.; Chergui, M.; Liberatore, E.; Rothlisberger, U.; Keller, U.
2017-01-01
Ionization and, in particular, ionization through the interaction with light play an important role in fundamental processes in physics, chemistry, and biology. In recent years, we have seen tremendous advances in our ability to measure the dynamics of photo-induced ionization in various systems in the gas, liquid, or solid phase. In this review, we will define the parameters used for quantifying these dynamics. We give a brief overview of some of the most important ionization processes and how to resolve the associated time delays and rates. With regard to time delays, we ask the question: how long does it take to remove an electron from an atom, molecule, or solid? With regard to rates, we ask the question: how many electrons are emitted in a given unit of time? We present state-of-the-art results on ionization and photoemission time delays and rates. Our review starts with the simplest physical systems: the attosecond dynamics of single-photon and tunnel ionization of atoms in the gas phase. We then extend the discussion to molecular gases and ionization of liquid targets. Finally, we present the measurements of ionization delays in femto- and attosecond photoemission from the solid–vacuum interface. PMID:29308414
Photoemission and photoionization time delays and rates
L. Gallmann
2017-11-01
Full Text Available Ionization and, in particular, ionization through the interaction with light play an important role in fundamental processes in physics, chemistry, and biology. In recent years, we have seen tremendous advances in our ability to measure the dynamics of photo-induced ionization in various systems in the gas, liquid, or solid phase. In this review, we will define the parameters used for quantifying these dynamics. We give a brief overview of some of the most important ionization processes and how to resolve the associated time delays and rates. With regard to time delays, we ask the question: how long does it take to remove an electron from an atom, molecule, or solid? With regard to rates, we ask the question: how many electrons are emitted in a given unit of time? We present state-of-the-art results on ionization and photoemission time delays and rates. Our review starts with the simplest physical systems: the attosecond dynamics of single-photon and tunnel ionization of atoms in the gas phase. We then extend the discussion to molecular gases and ionization of liquid targets. Finally, we present the measurements of ionization delays in femto- and attosecond photoemission from the solid–vacuum interface.
STRONG LENS TIME DELAY CHALLENGE. I. EXPERIMENTAL DESIGN
Dobler, Gregory [Kavli Institute for Theoretical Physics, University of California Santa Barbara, Santa Barbara, CA 93106 (United States); Fassnacht, Christopher D.; Rumbaugh, Nicholas [Department of Physics, University of California, 1 Shields Avenue, Davis, CA 95616 (United States); Treu, Tommaso; Liao, Kai [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Marshall, Phil [Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 20450, MS29, Stanford, CA 94309 (United States); Hojjati, Alireza [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1 (Canada); Linder, Eric, E-mail: tt@astro.ucla.edu [Lawrence Berkeley National Laboratory and University of California, Berkeley, CA 94720 (United States)
2015-02-01
The time delays between point-like images in gravitational lens systems can be used to measure cosmological parameters. The number of lenses with measured time delays is growing rapidly; the upcoming Large Synoptic Survey Telescope (LSST) will monitor ∼10{sup 3} strongly lensed quasars. In an effort to assess the present capabilities of the community, to accurately measure the time delays, and to provide input to dedicated monitoring campaigns and future LSST cosmology feasibility studies, we have invited the community to take part in a ''Time Delay Challenge'' (TDC). The challenge is organized as a set of ''ladders'', each containing a group of simulated data sets to be analyzed blindly by participating teams. Each rung on a ladder consists of a set of realistic mock observed lensed quasar light curves, with the rungs' data sets increasing in complexity and realism. The initial challenge described here has two ladders, TDC0 and TDC1. TDC0 has a small number of data sets, and is designed to be used as a practice set by the participating teams. The (non-mandatory) deadline for completion of TDC0 was the TDC1 launch date, 2013 December 1. The TDC1 deadline was 2014 July 1. Here we give an overview of the challenge, we introduce a set of metrics that will be used to quantify the goodness of fit, efficiency, precision, and accuracy of the algorithms, and we present the results of TDC0. Thirteen teams participated in TDC0 using 47 different methods. Seven of those teams qualified for TDC1, which is described in the companion paper.
Shoemaker, Ian M.; Murase, Kohta
2018-04-01
The Laser Interferometer Gravitational-Wave Observatory (LIGO) has recently discovered gravitational waves (GWs) from its first neutron star-neutron star merger at a distance of ˜40 Mpc from the Earth. The associated electromagnetic (EM) detection of the event, including the short gamma-ray burst within Δ t ˜2 s after the GW arrival, can be used to test various aspects of sources physics and GW propagation. Using GW170817 as the first GW-EM example, we show that this event provides a stringent direct test that GWs travel at the speed of light. The gravitational potential of the Milky Way provides a potential source of Shapiro time delay difference between the arrival of photons and GWs, and we demonstrate that the nearly coincident detection of the GW and EM signals can yield strong limits on anomalous gravitational time delay, through updating the previous limits taking into account details of Milky Way's gravitational potential. Finally, we also obtain an intriguing limit on the size of the prompt emission region of GRB 170817A, and discuss implications for the emission mechanism of short gamma-ray bursts.
Theory of gravitational interactions
Gasperini, Maurizio
2017-01-01
This is the second edition of a well-received book that is a modern, self-contained introduction to the theory of gravitational interactions. The new edition includes more details on gravitational waves of cosmological origin, the so-called brane world scenario, and gravitational time-delay effects. The first part of the book follows the traditional presentation of general relativity as a geometric theory of the macroscopic gravitational field, while the second, more advanced part discusses the deep analogies (and differences) between a geometric theory of gravity and the “gauge” theories of the other fundamental interactions. This fills a gap within the traditional approach to general relativity which usually leaves students puzzled about the role of gravity. The required notions of differential geometry are reduced to the minimum, allowing room for aspects of gravitational physics of current phenomenological and theoretical interest, such as the properties of gravitational waves, the gravitational inter...
Precision cosmology with time delay lenses: high resolution imaging requirements
Meng, Xiao-Lei; Liao, Kai [Department of Astronomy, Beijing Normal University, 19 Xinjiekouwai Street, Beijing, 100875 (China); Treu, Tommaso; Agnello, Adriano [Department of Physics, University of California, Broida Hall, Santa Barbara, CA 93106 (United States); Auger, Matthew W. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Marshall, Philip J., E-mail: xlmeng919@gmail.com, E-mail: tt@astro.ucla.edu, E-mail: aagnello@physics.ucsb.edu, E-mail: mauger@ast.cam.ac.uk, E-mail: liaokai@mail.bnu.edu.cn, E-mail: dr.phil.marshall@gmail.com [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305 (United States)
2015-09-01
Lens time delays are a powerful probe of cosmology, provided that the gravitational potential of the main deflector can be modeled with sufficient precision. Recent work has shown that this can be achieved by detailed modeling of the host galaxies of lensed quasars, which appear as ''Einstein Rings'' in high resolution images. The distortion of these arcs and counter-arcs, as measured over a large number of pixels, provides tight constraints on the difference between the gravitational potential between the quasar image positions, and thus on cosmology in combination with the measured time delay. We carry out a systematic exploration of the high resolution imaging required to exploit the thousands of lensed quasars that will be discovered by current and upcoming surveys with the next decade. Specifically, we simulate realistic lens systems as imaged by the Hubble Space Telescope (HST), James Webb Space Telescope (JWST), and ground based adaptive optics images taken with Keck or the Thirty Meter Telescope (TMT). We compare the performance of these pointed observations with that of images taken by the Euclid (VIS), Wide-Field Infrared Survey Telescope (WFIRST) and Large Synoptic Survey Telescope (LSST) surveys. We use as our metric the precision with which the slope γ' of the total mass density profile ρ{sub tot}∝ r{sup −γ'} for the main deflector can be measured. Ideally, we require that the statistical error on γ' be less than 0.02, such that it is subdominant to other sources of random and systematic uncertainties. We find that survey data will likely have sufficient depth and resolution to meet the target only for the brighter gravitational lens systems, comparable to those discovered by the SDSS survey. For fainter systems, that will be discovered by current and future surveys, targeted follow-up will be required. However, the exposure time required with upcoming facilitites such as JWST, the Keck Next Generation
Precision cosmology with time delay lenses: High resolution imaging requirements
Meng, Xiao -Lei [Beijing Normal Univ., Beijing (China); Univ. of California, Santa Barbara, CA (United States); Treu, Tommaso [Univ. of California, Santa Barbara, CA (United States); Univ. of California, Los Angeles, CA (United States); Agnello, Adriano [Univ. of California, Santa Barbara, CA (United States); Univ. of California, Los Angeles, CA (United States); Auger, Matthew W. [Univ. of Cambridge, Cambridge (United Kingdom); Liao, Kai [Beijing Normal Univ., Beijing (China); Univ. of California, Santa Barbara, CA (United States); Univ. of California, Los Angeles, CA (United States); Marshall, Philip J. [Stanford Univ., Stanford, CA (United States)
2015-09-28
Lens time delays are a powerful probe of cosmology, provided that the gravitational potential of the main deflector can be modeled with sufficient precision. Recent work has shown that this can be achieved by detailed modeling of the host galaxies of lensed quasars, which appear as ``Einstein Rings'' in high resolution images. The distortion of these arcs and counter-arcs, as measured over a large number of pixels, provides tight constraints on the difference between the gravitational potential between the quasar image positions, and thus on cosmology in combination with the measured time delay. We carry out a systematic exploration of the high resolution imaging required to exploit the thousands of lensed quasars that will be discovered by current and upcoming surveys with the next decade. Specifically, we simulate realistic lens systems as imaged by the Hubble Space Telescope (HST), James Webb Space Telescope (JWST), and ground based adaptive optics images taken with Keck or the Thirty Meter Telescope (TMT). We compare the performance of these pointed observations with that of images taken by the Euclid (VIS), Wide-Field Infrared Survey Telescope (WFIRST) and Large Synoptic Survey Telescope (LSST) surveys. We use as our metric the precision with which the slope γ' of the total mass density profile ρ_{tot}∝ r–γ' for the main deflector can be measured. Ideally, we require that the statistical error on γ' be less than 0.02, such that it is subdominant to other sources of random and systematic uncertainties. We find that survey data will likely have sufficient depth and resolution to meet the target only for the brighter gravitational lens systems, comparable to those discovered by the SDSS survey. For fainter systems, that will be discovered by current and future surveys, targeted follow-up will be required. Furthermore, the exposure time required with upcoming facilitites such as JWST, the Keck Next Generation Adaptive
Founding Gravitation in 4D Euclidean Space-Time Geometry
Winkler, Franz-Guenter
2010-01-01
The Euclidean interpretation of special relativity which has been suggested by the author is a formulation of special relativity in ordinary 4D Euclidean space-time geometry. The natural and geometrically intuitive generalization of this view involves variations of the speed of light (depending on location and direction) and a Euclidean principle of general covariance. In this article, a gravitation model by Jan Broekaert, which implements a view of relativity theory in the spirit of Lorentz and Poincare, is reconstructed and shown to fulfill the principles of the Euclidean approach after an appropriate reinterpretation.
Astrometric and Timing Effects of Gravitational Waves from Localized Sources
Kopeikin, Sergei M.; Schafer, Gerhard; Gwinn, Carl R.; Eubanks, T. Marshall
1998-01-01
A consistent approach for an exhaustive solution of the problem of propagation of light rays in the field of gravitational waves emitted by a localized source of gravitational radiation is developed in the first post-Minkowskian and quadrupole approximation of General Relativity. We demonstrate that the equations of light propagation in the retarded gravitational field of an arbitrary localized source emitting quadrupolar gravitational waves can be integrated exactly. The influence of the gra...
Newtonian cosmology with a time-varying constant of gravitation
McVittie, G.C.
1978-01-01
Newtonian cosmology is based on the Eulerian equations of fluid mechanics combined with Poisson's equation modified by the introduction of a time-varying G. Spherically symmetric model universes are worked out with instantaneously uniform densities. They are indeterminate unless instantaneous uniformity of the pressure is imposed. When G varies as an inverse power of the time, the models can in some cases be shown to depend on the solution of a second-order differential equation which also occurs in the Friedmann models of general relativity. In Section 3, a method for 'passing through' a singularity of this equation is proposed which entails making four arbitrary mathematical assumptions. When G varies as (time) -1 , models with initially cycloidal motion are possible, each cycle becoming longer as time progresses. Finally, gravitation becomes so weak that the model expands to infinity. Kinetic and potential energies for the whole model are derived from the basic equations; their sum is not constant. (author)
Time averaging, ageing and delay analysis of financial time series
Cherstvy, Andrey G.; Vinod, Deepak; Aghion, Erez; Chechkin, Aleksei V.; Metzler, Ralf
2017-06-01
We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black-Scholes-Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics.
Dodelson, Scott
2017-01-01
Gravitational lensing is a consequence of general relativity, where the gravitational force due to a massive object bends the paths of light originating from distant objects lying behind it. Using very little general relativity and no higher level mathematics, this text presents the basics of gravitational lensing, focusing on the equations needed to understand the phenomena. It then applies them to a diverse set of topics, including multiply imaged objects, time delays, extrasolar planets, microlensing, cluster masses, galaxy shape measurements, cosmic shear, and lensing of the cosmic microwave background. This approach allows undergraduate students and others to get quickly up to speed on the basics and the important issues. The text will be especially relevant as large surveys such as LSST and Euclid begin to dominate the astronomical landscape. Designed for a one semester course, it is accessible to anyone with two years of undergraduate physics background.
Controlling flow time delays in flexible manufacturing cells
Slomp, J.; Caprihan, R.; Bokhorst, J. A. C.
2009-01-01
Flow time delays in Flexible Manufacturing Cells (FMCs) are caused by transport and clamping/reclamping activities. This paper shows how dynamic scheduling parameters may control the flow times of jobs and the available task windows for flow time delays.
New theory of space-time and gravitation
Denisov, V.I.; Logunov, A.A.
1982-01-01
It is shown that the general theory of relativity is not satisfactory physical theory, since in it there are no laws of conservation for the matter and gravitational field taken together and it does not satisfy the principle of correspondence with Newton's theory. In the present paper, we construct a new theory of gravitation which possesses conservation laws, can describe all the existing gravitational experiments, satisfies the correspondence principle, and predicts a number of fundamental consequences
Synthetic LISA: Simulating time delay interferometry in a model LISA
Vallisneri, Michele
2005-01-01
We report on three numerical experiments on the implementation of Time-Delay Interferometry (TDI) for LISA, performed with Synthetic LISA, a C++/Python package that we developed to simulate the LISA science process at the level of scientific and technical requirements. Specifically, we study the laser-noise residuals left by first-generation TDI when the LISA armlengths have a realistic time dependence; we characterize the armlength-measurement accuracies that are needed to have effective laser-noise cancellation in both first- and second-generation TDI; and we estimate the quantization and telemetry bitdepth needed for the phase measurements. Synthetic LISA generates synthetic time series of the LISA fundamental noises, as filtered through all the TDI observables; it also provides a streamlined module to compute the TDI responses to gravitational waves according to a full model of TDI, including the motion of the LISA array and the temporal and directional dependence of the armlengths. We discuss the theoretical model that underlies the simulation, its implementation, and its use in future investigations on system-characterization and data-analysis prototyping for LISA
Time-delayed feedback control of diffusion in random walkers
Ando, Hiroyasu; Takehara, Kohta; Kobayashi, Miki U.
2017-07-01
Time delay in general leads to instability in some systems, while specific feedback with delay can control fluctuated motion in nonlinear deterministic systems to a stable state. In this paper, we consider a stochastic process, i.e., a random walk, and observe its diffusion phenomenon with time-delayed feedback. As a result, the diffusion coefficient decreases with increasing delay time. We analytically illustrate this suppression of diffusion by using stochastic delay differential equations and justify the feasibility of this suppression by applying time-delayed feedback to a molecular dynamics model.
Synchronization of delayed systems in the presence of delay time modulation
Kye, Won-Ho; Choi, Muhan; Kim, Myung-Woon; Lee, Soo-Young; Rim, Sunghwan; Kim, Chil-Min; Park, Young-Jai
2004-01-01
We investigate synchronization in the presence of delay time modulation for application to communication. We have observed that the robust synchronization is established by a common delay signal and its threshold is presented using Lyapunov exponents analysis. The influence of the delay time modulation in chaotic oscillators is also discussed
Versatile directional searches for gravitational waves with Pulsar Timing Arrays
Madison, D. R.; Zhu, X.-J.; Hobbs, G.; Coles, W.; Shannon, R. M.; Wang, J. B.; Tiburzi, C.; Manchester, R. N.; Bailes, M.; Bhat, N. D. R.; Burke-Spolaor, S.; Dai, S.; Dempsey, J.; Keith, M.; Kerr, M.; Lasky, P.; Levin, Y.; Osłowski, S.; Ravi, V.; Reardon, D.; Rosado, P.; Spiewak, R.; van Straten, W.; Toomey, L.; Wen, L.; You, X.
2016-02-01
By regularly monitoring the most stable millisecond pulsars over many years, pulsar timing arrays (PTAs) are positioned to detect and study correlations in the timing behaviour of those pulsars. Gravitational waves (GWs) from supermassive black hole binaries (SMBHBs) are an exciting potentially detectable source of such correlations. We describe a straightforward technique by which a PTA can be `phased-up' to form time series of the two polarization modes of GWs coming from a particular direction of the sky. Our technique requires no assumptions regarding the time-domain behaviour of a GW signal. This method has already been used to place stringent bounds on GWs from individual SMBHBs in circular orbits. Here, we describe the methodology and demonstrate the versatility of the technique in searches for a wide variety of GW signals including bursts with unmodelled waveforms. Using the first six years of data from the Parkes Pulsar Timing Array, we conduct an all-sky search for a detectable excess of GW power from any direction. For the lines of sight to several nearby massive galaxy clusters, we carry out a more detailed search for GW bursts with memory, which are distinct signatures of SMBHB mergers. In all cases, we find that the data are consistent with noise.
Algebraic approach to time-delay data analysis for LISA
Dhurandhar, S.V.; Nayak, K. Rajesh; Vinet, J.-Y.
2002-01-01
Cancellation of laser frequency noise in interferometers is crucial for attaining the requisite sensitivity of the triangular three-spacecraft LISA configuration. Raw laser noise is several orders of magnitude above the other noises and thus it is essential to bring it down to the level of other noises such as shot, acceleration, etc. Since it is impossible to maintain equal distances between spacecrafts, laser noise cancellation must be achieved by appropriately combining the six beams with appropriate time delays. It has been shown in several recent papers that such combinations are possible. In this paper, we present a rigorous and systematic formalism based on algebraic geometrical methods involving computational commutative algebra, which generates in principle all the data combinations canceling the laser frequency noise. The relevant data combinations form the first module of syzygies, as it is called in the literature of algebraic geometry. The module is over a polynomial ring in three variables, the three variables corresponding to the three time delays around the LISA triangle. Specifically, we list several sets of generators for the module whose linear combinations with polynomial coefficients generate the entire module. We find that this formalism can also be extended in a straightforward way to cancel Doppler shifts due to optical bench motions. The two modules are in fact isomorphic. We use our formalism to obtain the transfer functions for the six beams and for the generators. We specifically investigate monochromatic gravitational wave sources in the LISA band and carry out the maximization over linear combinations of the generators of the signal-to-noise ratios with the frequency and source direction angles as parameters
First Electromagnetic Pulse Associated with a Gravitational-wave Event: Profile, Duration, and Delay
Lin, Da-Bin; Liu, Tong; Lin, Jie; Wang, Xiang-Gao; Gu, Wei-Min; Liang, En-Wei
2018-04-01
We study the first electromagnetic (EM) pulse after the gravitational-wave (GW) chirp signal, focusing on its profile and duration. It is found that the light curve, especially the steep decay (SD) phase, can be very different by adopting different viewing angles θ view of the jet shell. For an on-axis jet with a power-law radiation spectrum, the observed flux in the SD is proportional to {t}obs}-2-β with β being the spectral index and t obs being the observer time. Here, t obs = 0 is set at the time we observe the jet being ejected from the central engine. The SD may become steep by increasing θ view. We also study the bolometric luminosity L from a jet shell with a non-power-law radiation spectrum. For an on-axis jet, L ∝ t obs ‑3 is found in the SD. However, the SD is steeper than L\\propto {t}obs}-3 for radiation from an off-axis jet. The higher value of the θ view is, the steeper SD would be. Then, we suggest that the SD phase can be used to discriminate an off-axis jet from an on-axis jet. The reason for the above behaviors is discussed. In addition, we find that the duration of first EM pulse is close to its peak time, especially for θ view ∼ 20°. This result is consistent with that found in GW 170817/GRB 170817A. Thus, the jet corresponding to the prompt emission of GRB 170817A should be ejected immediately after the merger. Our results also reveal that the duration of the first EM pulse can provide information on the time to search for GWs.
The effects of the framing of time on delay discounting.
DeHart, William Brady; Odum, Amy L
2015-01-01
We examined the effects of the framing of time on delay discounting. Delay discounting is the process by which delayed outcomes are devalued as a function of time. Time in a titrating delay discounting task is often framed in calendar units (e.g., as 1 week, 1 month, etc.). When time is framed as a specific date, delayed outcomes are discounted less compared to the calendar format. Other forms of framing time; however, have not been explored. All participants completed a titrating calendar unit delay-discounting task for money. Participants were also assigned to one of two delay discounting tasks: time as dates (e.g., June 1st, 2015) or time in units of days (e.g., 5000 days), using the same delay distribution as the calendar delay-discounting task. Time framed as dates resulted in less discounting compared to the calendar method, whereas time framed as days resulted in greater discounting compared to the calendar method. The hyperboloid model fit best compared to the hyperbola and exponential models. How time is framed may alter how participants attend to the delays as well as how the delayed outcome is valued. Altering how time is framed may serve to improve adherence to goals with delayed outcomes. © Society for the Experimental Analysis of Behavior.
LISA time-delay interferometry zero-signal solution: Geometrical properties
Tinto, Massimo; Larson, Shane L.
2004-01-01
Time-delay interferometry (TDI) is the data processing technique needed for generating interferometric combinations of data measured by the multiple Doppler readouts available onboard the three Laser Interferometer Space Antenna (LISA) spacecraft. Within the space of all possible interferometric combinations TDI can generate, we have derived a specific combination that has zero response to the gravitational wave signal, and called it the zero-signal solution (ZSS). This is a two-parameter family of linear combinations of the generators of the TDI space, and its response to a gravitational wave becomes null when these two parameters coincide with the values of the angles of the source location in the sky. Remarkably, the ZSS does not rely on any assumptions about the gravitational waveform, and in fact it works for waveforms of any kind. Our approach is analogous to the data analysis method introduced by Guersel and Tinto in the context of networks of Earth-based, wideband, interferometric gravitational wave detectors observing in coincidence a gravitational wave burst. The ZSS should be regarded as an application of the Guersel and Tinto method to the LISA data
Survey of time preference, delay discounting models
John R. Doyle
2013-03-01
Full Text Available The paper surveys over twenty models of delay discounting (also known as temporal discounting, time preference, time discounting, that psychologists and economists have put forward to explain the way people actually trade off time and money. Using little more than the basic algebra of powers and logarithms, I show how the models are derived, what assumptions they are based upon, and how different models relate to each other. Rather than concentrate only on discount functions themselves, I show how discount functions may be manipulated to isolate rate parameters for each model. This approach, consistently applied, helps focus attention on the three main components in any discounting model: subjectively perceived money; subjectively perceived time; and how these elements are combined. We group models by the number of parameters that have to be estimated, which means our exposition follows a trajectory of increasing complexity to the models. However, as the story unfolds it becomes clear that most models fall into a smaller number of families. We also show how new models may be constructed by combining elements of different models. The surveyed models are: Exponential; Hyperbolic; Arithmetic; Hyperboloid (Green and Myerson, Rachlin; Loewenstein and Prelec Generalized Hyperboloid; quasi-Hyperbolic (also known as beta-delta discounting; Benhabib et al's fixed cost; Benhabib et al's Exponential / Hyperbolic / quasi-Hyperbolic; Read's discounting fractions; Roelofsma's exponential time; Scholten and Read's discounting-by-intervals (DBI; Ebert and Prelec's constant sensitivity (CS; Bleichrodt et al.'s constant absolute decreasing impatience (CADI; Bleichrodt et al.'s constant relative decreasing impatience (CRDI; Green, Myerson, and Macaux's hyperboloid over intervals models; Killeen's additive utility; size-sensitive additive utility; Yi, Landes, and Bickel's memory trace models; McClure et al.'s two exponentials; and Scholten and Read's trade
Probing the cosmic distance duality relation using time delay lenses
Rana, Akshay; Mahajan, Shobhit; Mukherjee, Amitabha [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Jain, Deepak [Deen Dayal Upadhyaya College, University of Delhi, Sector-3, Dwarka, New Delhi 110078 (India); Holanda, R.F.L., E-mail: montirana1992@gmail.com, E-mail: djain@ddu.du.ac.in, E-mail: shobhit.mahajan@gmail.com, E-mail: amimukh@gmail.com, E-mail: holanda@uepb.edu.br [Departamento de Física, Universidade Federal de Sergipe, 49100-000, Aracaju—SE (Brazil)
2017-07-01
The construction of the cosmic distance-duality relation (CDDR) has been widely studied. However, its consistency with various new observables remains a topic of interest. We present a new way to constrain the CDDR η( z ) using different dynamic and geometric properties of strong gravitational lenses (SGL) along with SNe Ia observations. We use a sample of 102 SGL with the measurement of corresponding velocity dispersion σ{sub 0} and Einstein radius θ {sub E} . In addition, we also use a dataset of 12 two image lensing systems containing the measure of time delay Δ t between source images. Jointly these two datasets give us the angular diameter distance D {sub A} {sub ol} of the lens. Further, for luminosity distance, we use the 740 observations from JLA compilation of SNe Ia. To study the combined behavior of these datasets we use a model independent method, Gaussian Process (GP). We also check the efficiency of GP by applying it on simulated datasets, which are generated in a phenomenological way by using realistic cosmological error bars. Finally, we conclude that the combined bounds from the SGL and SNe Ia observation do not favor any deviation of CDDR and are in concordance with the standard value (η=1) within 2σ confidence region, which further strengthens the theoretical acceptance of CDDR.
Delay-dependent exponential stability of cellular neural networks with time-varying delays
Zhang Qiang; Wei Xiaopeng; Xu Jin
2005-01-01
The global exponential stability of cellular neural networks (CNNs) with time-varying delays is analyzed. Two new sufficient conditions ensuring global exponential stability for delayed CNNs are obtained. The conditions presented here are related to the size of delay. The stability results improve the earlier publications. Two examples are given to demonstrate the effectiveness of the obtained results
Space-time algebra for the generalization of gravitational field ...
the analogy in formulation between massive gravitational theory and electromagnetism has ... as the dual mass, gravitomagnetic charge (monopole) or magnetic mass [7]. ... cation in the definitions of the GEM fields in the following manner:.
Backwards time travel induced by combined magnetic and gravitational fields
Novello, M.; Svaiter, N.F.; Guimaraes, M.E.X.
1990-01-01
We analyse the behaviour of an elementary microscopic particle submitted to combined Magnetic and Gravitational Fields on Goedel's Universe. The exam is made in a local Gaussian system of coordinates. (author)
The rates and time-delay distribution of multiply imaged supernovae behind lensing clusters
Li, Xue; Hjorth, Jens; Richard, Johan
2012-11-01
Time delays of gravitationally lensed sources can be used to constrain the mass model of a deflector and determine cosmological parameters. We here present an analysis of the time-delay distribution of multiply imaged sources behind 17 strong lensing galaxy clusters with well-calibrated mass models. We find that for time delays less than 1000 days, at z = 3.0, their logarithmic probability distribution functions are well represented by P(log Δt) = 5.3 × 10-4Δttilde beta/M2502tilde beta, with tilde beta = 0.77, where M250 is the projected cluster mass inside 250 kpc (in 1014M⊙), and tilde beta is the power-law slope of the distribution. The resultant probability distribution function enables us to estimate the time-delay distribution in a lensing cluster of known mass. For a cluster with M250 = 2 × 1014M⊙, the fraction of time delays less than 1000 days is approximately 3%. Taking Abell 1689 as an example, its dark halo and brightest galaxies, with central velocity dispersions σ>=500kms-1, mainly produce large time delays, while galaxy-scale mass clumps are responsible for generating smaller time delays. We estimate the probability of observing multiple images of a supernova in the known images of Abell 1689. A two-component model of estimating the supernova rate is applied in this work. For a magnitude threshold of mAB = 26.5, the yearly rate of Type Ia (core-collapse) supernovae with time delays less than 1000 days is 0.004±0.002 (0.029±0.001). If the magnitude threshold is lowered to mAB ~ 27.0, the rate of core-collapse supernovae suitable for time delay observation is 0.044±0.015 per year.
Time-Delay System Identification Using Genetic Algorithm
Yang, Zhenyu; Seested, Glen Thane
2013-01-01
Due to the unknown dead-time coefficient, the time-delay system identification turns to be a non-convex optimization problem. This paper investigates the identification of a simple time-delay system, named First-Order-Plus-Dead-Time (FOPDT), by using the Genetic Algorithm (GA) technique. The qual......Due to the unknown dead-time coefficient, the time-delay system identification turns to be a non-convex optimization problem. This paper investigates the identification of a simple time-delay system, named First-Order-Plus-Dead-Time (FOPDT), by using the Genetic Algorithm (GA) technique...
The gravitational-wave discovery space of pulsar timing arrays
Cutler, Curt; Burke-Spolaor, Sarah; Vallisneri, Michele; Lazio, Joseph; Majid, Walid
2014-02-01
Recent years have seen a burgeoning interest in using pulsar timing arrays (PTAs) as gravitational-wave (GW) detectors. To date, that interest has focused mainly on three particularly promising source types: supermassive black hole binaries, cosmic strings, and the stochastic background from early-Universe phase transitions. In this paper, by contrast, our aim is to investigate the PTA potential for discovering unanticipated sources. We derive significant constraints on the available discovery space based solely on energetic and statistical considerations: we show that a PTA detection of GWs at frequencies above ˜10-5 Hz would either be an extraordinary coincidence or violate "cherished beliefs;" we show that for PTAs GW memory can be more detectable than direct GWs, and that, as we consider events at ever higher redshift, the memory effect increasingly dominates an event's total signal-to-noise ratio. The paper includes also a simple analysis of the effects of pulsar red noise in PTA searches, and a demonstration that the effects of periodic GWs in the ˜10-7-10-4.5 Hz band would not be degenerate with small errors in standard pulsar parameters (except in a few narrow bands).
Delay time and Hartman effect in strain engineered graphene
Chen, Xi; Deng, Zhi-Yong; Ban, Yue
2014-01-01
Tunneling times, including group delay and dwell time, are studied for massless Dirac electrons transmitting through a one-dimensional barrier in strain-engineered graphene. The Hartman effect, the independence of group delay on barrier length, is induced by the strain effect, and associated with the transmission gap and the evanescent mode. The influence of barrier height/length and strain modulus/direction on the group delay is also discussed, which provides the flexibility to control the group delay with applications in graphene-based devices. The relationship between group delay and dwell time is finally derived to clarify the nature of the Hartman effect
Lag synchronization of chaotic systems with time-delayed linear
In this paper, the lag synchronization of chaotic systems with time-delayed linear terms via impulsive control is investigated. Based on the stability theory of impulsive delayed differential equations, some sufficient conditions are obtained guaranteeing the synchronized behaviours between two delayed chaotic systems.
Saito, Ryo; Naruko, Atsushi; Hiramatsu, Takashi; Sasaki, Misao
2014-01-01
In this paper, we introduce a new approach to a treatment of the gravitational effects (redshift, time delay and lensing) on the observed cosmic microwave background (CMB) anisotropies based on the Boltzmann equation. From the Liouville's theorem in curved spacetime, the intensity of photons is conserved along a photon geodesic when non-gravitational scatterings are absent. Motivated by this fact, we derive a second-order line-of-sight formula by integrating the Boltzmann equation along a perturbed geodesic (curve) instead of a background geodesic (line). In this approach, the separation of the gravitational and intrinsic effects are manifest. This approach can be considered as a generalization of the remapping approach of CMB lensing, where all the gravitational effects can be treated on the same footing
Rahvar, Sohrab
2018-05-01
In this work, we study the interaction of the electromagnetic wave (EW) from a distant quasar with the gravitational wave (GW) sourced by the binary stars. While in the regime of geometric optics, the light bending due to this interaction is negligible, we show that the phase shifting on the wavefront of an EW can produce the diffraction pattern on the observer plane. The diffraction of the light (with the wavelength of λe) by the gravitational wave playing the role of gravitational grating (with the wavelength of λg) has the diffraction angle of Δβ ˜ λe/λg. The relative motion of the observer, the source of gravitational wave and the quasar results in a relative motion of the observer through the interference pattern on the observer plane. The consequence of this fringe crossing is the modulation in the light curve of a quasar with the period of few hours in the microwave wavelength. The optical depth for the observation of this phenomenon for a Quasar with the multiple images strongly lensed by a galaxy where the light trajectory of some of the images crosses the lensing galaxy is τ ≃ 0.2. By shifting the time-delay of the light curves of the multiple images in a strong lensed quasar and removing the intrinsic variations of a quasar, our desired signals, as a new method for detection of GWs can be detected.
Tunable delay time and Hartman effect in graphene magnetic barriers
Ban, Yue; Wang, Lin-Jun; Chen, Xi
2015-01-01
Tunable group delay and Hartman effect have been investigated for massless Dirac electrons in graphene magnetic barriers. In the presence of magnetic field, dwell time is found to be equal to net group delay plus the group delay contributing from the lateral shifts. The group delay times are discussed in both cases of normal and oblique incidence, to clarify the nature of Hartman effect. In addition, the group delay in transmission can be modulated from subluminality to superluminality by adjusting the magnetic field, which may also lead to potential applications in graphene-based microelectronics
Discrete-time BAM neural networks with variable delays
Liu, Xin-Ge; Tang, Mei-Lan; Martin, Ralph; Liu, Xin-Bi
2007-07-01
This Letter deals with the global exponential stability of discrete-time bidirectional associative memory (BAM) neural networks with variable delays. Using a Lyapunov functional, and linear matrix inequality techniques (LMI), we derive a new delay-dependent exponential stability criterion for BAM neural networks with variable delays. As this criterion has no extra constraints on the variable delay functions, it can be applied to quite general BAM neural networks with a broad range of time delay functions. It is also easy to use in practice. An example is provided to illustrate the theoretical development.
Discrete-time BAM neural networks with variable delays
Liu Xinge; Tang Meilan; Martin, Ralph; Liu Xinbi
2007-01-01
This Letter deals with the global exponential stability of discrete-time bidirectional associative memory (BAM) neural networks with variable delays. Using a Lyapunov functional, and linear matrix inequality techniques (LMI), we derive a new delay-dependent exponential stability criterion for BAM neural networks with variable delays. As this criterion has no extra constraints on the variable delay functions, it can be applied to quite general BAM neural networks with a broad range of time delay functions. It is also easy to use in practice. An example is provided to illustrate the theoretical development
Periodic flows to chaos in time-delay systems
Luo, Albert C J
2017-01-01
This book for the first time examines periodic motions to chaos in time-delay systems, which exist extensively in engineering. For a long time, the stability of time-delay systems at equilibrium has been of great interest from the Lyapunov theory-based methods, where one cannot achieve the ideal results. Thus, time-delay discretization in time-delay systems was used for the stability of these systems. In this volume, Dr. Luo presents an accurate method based on the finite Fourier series to determine periodic motions in nonlinear time-delay systems. The stability and bifurcation of periodic motions are determined by the time-delayed system of coefficients in the Fourier series and the method for nonlinear time-delay systems is equivalent to the Laplace transformation method for linear time-delay systems. Facilitates discovery of analytical solutions of nonlinear time-delay systems; Illustrates bifurcation trees of periodic motions to chaos; Helps readers identify motion complexity and singularity; Explains pro...
Time-delayed chameleon: Analysis, synchronization and FPGA implementation
Rajagopal, Karthikeyan; Jafari, Sajad; Laarem, Guessas
2017-12-01
In this paper we report a time-delayed chameleon-like chaotic system which can belong to different families of chaotic attractors depending on the choices of parameters. Such a characteristic of self-excited and hidden chaotic flows in a simple 3D system with time delay has not been reported earlier. Dynamic analysis of the proposed time-delayed systems are analysed in time-delay space and parameter space. A novel adaptive modified functional projective lag synchronization algorithm is derived for synchronizing identical time-delayed chameleon systems with uncertain parameters. The proposed time-delayed systems and the synchronization algorithm with controllers and parameter estimates are then implemented in FPGA using hardware-software co-simulation and the results are presented.
Leveraging delay discounting for health: Can time delays influence food choice?
Appelhans, Bradley M; French, Simone A; Olinger, Tamara; Bogucki, Michael; Janssen, Imke; Avery-Mamer, Elizabeth F; Powell, Lisa M
2018-03-15
Delay discounting, the tendency to choose smaller immediate rewards over larger delayed rewards, is theorized to promote consumption of immediately rewarding but unhealthy foods at the expense of long-term weight maintenance and nutritional health. An untested implication of delay discounting models of decision-making is that selectively delaying access to less healthy foods may promote selection of healthier (immediately available) alternatives, even if they may be less desirable. The current study tested this hypothesis by measuring healthy versus regular vending machine snack purchasing before and during the implementation of a 25-s time delay on the delivery of regular snacks. Purchasing was also examined under a $0.25 discount on healthy snacks, a $0.25 tax on regular snacks, and the combination of both pricing interventions with the 25-s time delay. Across 32,019 vending sales from three separate vending locations, the 25-s time delay increased healthy snack purchasing from 40.1% to 42.5%, which was comparable to the impact of a $0.25 discount (43.0%). Combining the delay and the discount had a roughly additive effect (46.0%). However, the strongest effects were seen under the $0.25 tax on regular snacks (53.7%) and the combination of the delay and the tax (50.2%). Intervention effects varied substantially between vending locations. Importantly, time delays did not harm overall vending sales or revenue, which is relevant to the real-world feasibility of this intervention. More investigation is needed to better understand how the impact of time delays on food choice varies across populations, evaluate the effects of time delays on beverage vending choices, and extend this approach to food choices in contexts other than vending machines. ClinicalTrials.gov, NCT02359916. Copyright © 2018 Elsevier Ltd. All rights reserved.
Improving Delay-Range-Dependent Stability Condition for Systems with Interval Time-Varying Delay
Wei Qian
2013-01-01
Full Text Available This paper discusses the delay-range-dependent stability for systems with interval time-varying delay. Through defining the new Lyapunov-Krasovskii functional and estimating the derivative of the LKF by introducing new vectors, using free matrices and reciprocally convex approach, the new delay-range-dependent stability conditions are obtained. Two well-known examples are given to illustrate the less conservatism of the proposed theoretical results.
Time-Delay Effects on Constitutive Gene Expression*
Feng Yan-Ling; Wang Dan; Tang Xu-Lei; Dong Jian-Min
2017-01-01
The dynamics of constitutive gene expression with delayed mRNA degradation is investigated, where the intrinsic noise caused by the small number of reactant molecules is introduced. It is found that the oscillatory behavior claimed in previous investigations does not appear in the approximation of small time delay, and the steady state distribution still follows the Poisson law. Furthermore, we introduce the extrinsic noise induced by surrounding environment to explore the effects of this noise and time delay on the Fano factor. Based on a delay Langevin equation and the corresponding Fokker–Planck equation, the distribution of mRNA copy-number is achieved analytically. The time delay and extrinsic noise play similar roles in the gene expression system, that is, they are able to result in the deviation of the Fano factor from 1 evidently. The measured Fano factor for constitutive gene expression is slightly larger than 1, which is perhaps attributed to the time-delay effect. (paper)
Turner, E.L.
1989-01-01
The author discusses how gravitational lens studies is becoming a major focus of extragalactic astronomy and cosmology. This review is organized into five parts: an overview of the observational situation, a look at the state of theoretical work on lenses, a detailed look at three recently discovered types of lensing phenomena (luminous arcs, radio rings, quasar-galaxy associations), a review of progress on two old problems in lens studies (deriving unique lens mass distribution models, measurements of differential time delays), and an attempt to look into the future of lens studies
Stability analysis of linear switching systems with time delays
Li Ping; Zhong Shouming; Cui Jinzhong
2009-01-01
The issue of stability analysis of linear switching system with discrete and distributed time delays is studied in this paper. An appropriate switching rule is applied to guarantee the stability of the whole switching system. Our results use a Riccati-type Lyapunov functional under a condition on the time delay. So, switching systems with mixed delays are developed. A numerical example is given to illustrate the effectiveness of our results.
Time delay systems theory, numerics, applications, and experiments
Ersal, Tulga; Orosz, Gábor
2017-01-01
This volume collects contributions related to selected presentations from the 12th IFAC Workshop on Time Delay Systems, Ann Arbor, June 28-30, 2015. The included papers present novel techniques and new results of delayed dynamical systems. The topical spectrum covers control theory, numerical analysis, engineering and biological applications as well as experiments and case studies. The target audience primarily comprises research experts in the field of time delay systems, but the book may also be beneficial for graduate students alike. .
Effects of the time delays in a non linear pendular Fabry-Perot
Tourrenc, P.; Deruelle, N.
1985-01-01
We study a one arm pendular Fabry-Perot interferometer with specifications corresponding to the two arms interferometers designed to detect gravitational radiation. We consider the non linearities originating from the radiation force and the effects of time delays due to the finite length of the arm. We derive the exact and the associated ''predictivised'' equations for the motion of the suspended mirror. We show that effects of time delays increase considerably the stability of the device when the optical relaxation time is of the order of the period of the pendulum, a case of relevance when light is recycled. However the thermal noise does not seem to be much modified when calculated within a simple approximation scheme
Mashhoon, B.
1982-01-01
The influence of a stochastic and isotropic background of gravitational radiation on timing measurements of pulsars is investigated, and it is shown that pulsar timing noise may be used to establish a significant upper limit of about 10 to the -10th on the total energy density of very long-wavelength stochastic gravitational waves. This places restriction on the strength of very long wavelength gravitational waves in the Friedmann model, and such a background is expected to have no significant effect on the approximately 3 K electromagnetic background radiation or on the dynamics of a cluster of galaxies.
Using Constant Time Delay to Teach Braille Word Recognition
Hooper, Jonathan; Ivy, Sarah; Hatton, Deborah
2014-01-01
Introduction: Constant time delay has been identified as an evidence-based practice to teach print sight words and picture recognition (Browder, Ahlbrim-Delzell, Spooner, Mims, & Baker, 2009). For the study presented here, we tested the effectiveness of constant time delay to teach new braille words. Methods: A single-subject multiple baseline…
Robust control of time-delay chaotic systems
Hua Changchun; Guan Xinping
2003-01-01
Robust control problem of nonlinear time-delay chaotic systems is investigated. For such uncertain systems, we propose adaptive feedback controller and novel nonlinear feedback controller. They are both independent of the time delay and can render the corresponding closed-loop systems globally uniformly ultimately bounded stable. The simulations on controlling logistic system are made and the results show the controllers are feasible
Goodwin accelerator model revisited with fixed time delays
Matsumoto, Akio; Merlone, Ugo; Szidarovszky, Ferenc
2018-05-01
Dynamics of Goodwin's accelerator business cycle model is reconsidered. The model is characterized by a nonlinear accelerator and an investment time delay. The role of the nonlinearity for the birth of persistent oscillations is fully discussed in the existing literature. On the other hand, not much of the role of the delay has yet been revealed. The purpose of this paper is to show that the delay really matters. In the original framework of Goodwin [6], it is first demonstrated that there is a threshold value of the delay: limit cycles arise for smaller values than the threshold and so do sawtooth oscillations for larger values. In the extended framework in which a consumption or saving delay, in addition to the investment delay, is introduced, three main results are demonstrated under assumption of the identical length of investment and consumption delays. The dynamics with consumption delay is basically the same as that of the single delay model. Second, in the case of saving delay, the steady state can coexist with the stable and unstable limit cycles in the stable case. Third, in the unstable case, there is an interval of delay in which the limit cycle or the sawtooth oscillation emerges depending on the choice of the constant initial function.
Delay-Dependent Exponential Stability for Discrete-Time BAM Neural Networks with Time-Varying Delays
Yonggang Chen
2008-01-01
Full Text Available This paper considers the delay-dependent exponential stability for discrete-time BAM neural networks with time-varying delays. By constructing the new Lyapunov functional, the improved delay-dependent exponential stability criterion is derived in terms of linear matrix inequality (LMI. Moreover, in order to reduce the conservativeness, some slack matrices are introduced in this paper. Two numerical examples are presented to show the effectiveness and less conservativeness of the proposed method.
Analysis of Time Delay Simulation in Networked Control System
Nyan Phyo Aung; Zaw Min Naing; Hla Myo Tun
2016-01-01
The paper presents a PD controller for the Networked Control Systems (NCS) with delay. The major challenges in this networked control system (NCS) are the delay of the data transmission throughout the communication network. The comparative performance analysis is carried out for different delays network medium. In this paper, simulation is carried out on Ac servo motor control system using CAN Bus as communication network medium. The True Time toolbox of MATLAB is used for simulation to analy...
A TWO-YEAR TIME DELAY FOR THE LENSED QUASAR SDSS J1029+2623
Fohlmeister, Janine; Wambsganss, Joachim [Astronomisches Rechen-Institut, Zentrum fuer Astronomie der Universitaet Heidelberg, Moenchhofstr. 12-14, D-69120 Heidelberg (Germany); Kochanek, Christopher S. [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States); Falco, Emilio E. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Oguri, Masamune [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Dai, Xinyu [Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks Street, Norman, OK 73019 (United States)
2013-02-20
We present 279 epochs of optical monitoring data spanning 5.4 years from 2007 January to 2012 June for the largest image separation (22.''6) gravitationally lensed quasar, SDSS J1029+2623. We find that image A leads the images B and C by {Delta} t {sub AB} = (744 {+-} 10) days (90% confidence); the uncertainty includes both statistical uncertainties and systematic differences due to the choice of models. With only a {approx}1% fractional error, the interpretation of the delay is limited primarily by cosmic variance due to fluctuations in the mean line-of-sight density. We cannot separate the fainter image C from image B, but since image C trails image B by only 2-3 days in all models, the estimate of the time delay between images A and B is little affected by combining the fluxes of images B and C. There is weak evidence for a low level of microlensing, perhaps created by the small galaxy responsible for the flux ratio anomaly in this system. Interpreting the delay depends on better constraining the shape of the gravitational potential using the lensed host galaxy, other lensed arcs, and the structure of the X-ray emission.
The space-time outside a source of gravitational radiation: the axially symmetric null fluid
Herrera, L. [Universidad Central de Venezuela, Escuela de Fisica, Facultad de Ciencias, Caracas (Venezuela, Bolivarian Republic of); Universidad de Salamanca, Instituto Universitario de Fisica Fundamental y Matematicas, Salamanca (Spain); Di Prisco, A. [Universidad Central de Venezuela, Escuela de Fisica, Facultad de Ciencias, Caracas (Venezuela, Bolivarian Republic of); Ospino, J. [Universidad de Salamanca, Departamento de Matematica Aplicada and Instituto Universitario de Fisica Fundamental y Matematicas, Salamanca (Spain)
2016-11-15
We carry out a study of the exterior of an axially and reflection symmetric source of gravitational radiation. The exterior of such a source is filled with a null fluid produced by the dissipative processes inherent to the emission of gravitational radiation, thereby representing a generalization of the Vaidya metric for axially and reflection symmetric space-times. The role of the vorticity, and its relationship with the presence of gravitational radiation is put in evidence. The spherically symmetric case (Vaidya) is, asymptotically, recovered within the context of the 1 + 3 formalism. (orig.)
Time, gravitation, and the Universe: the evolution of relativistic theories
Whitrow, G J
1974-12-31
An account is given of the historical development or the theory of relativity, particularly from Newton' s mechanics and Maxwell's electrodynamics, and with reference to the importance of the work of 19th century mathematicians such as Riemann, Klein and Neumann, leading to the work of Poincare, Minkowski, Lorentz and Einstein. The Michelson-Morley, Kennedy-Thorndike and IvesStillwell experiments are discussed, the use of the radar concept in relativity, and the discovery in 1965 of the universal black-body microwave radiation. Gravitation and cosmological problems are considered in historical review. (UK)
Managing contamination delay to improve Timing Speculation architectures
Naga Durga Prasad Avirneni
2016-08-01
Full Text Available Timing Speculation (TS is a widely known method for realizing better-than-worst-case systems. Aggressive clocking, realizable by TS, enable systems to operate beyond specified safe frequency limits to effectively exploit the data dependent circuit delay. However, the range of aggressive clocking for performance enhancement under TS is restricted by short paths. In this paper, we show that increasing the lengths of short paths of the circuit increases the effectiveness of TS, leading to performance improvement. Also, we propose an algorithm to efficiently add delay buffers to selected short paths while keeping down the area penalty. We present our algorithm results for ISCAS-85 suite and show that it is possible to increase the circuit contamination delay by up to 30% without affecting the propagation delay. We also explore the possibility of increasing short path delays further by relaxing the constraint on propagation delay and analyze the performance impact.
Passivity analysis and synthesis for uncertain time-delay systems
Magdi S. Mahmoud
2001-01-01
Full Text Available In this paper, we investigate the robust passivity analysis and synthesis problems for a class of uncertain time-delay systems. This class of systems arises in the modelling effort of studying water quality constituents in fresh stream. For the analysis problem, we derive a sufficient condition for which the uncertain time-delay system is robustly stable and strictly passive for all admissible uncertainties. The condition is given in terms of a linear matrix inequality. Both the delay-independent and delay-dependent cases are considered. For the synthesis problem, we propose an observer-based design method which guarantees that the closed-loop uncertain time-delay system is stable and strictly passive for all admissible uncertainties. Several examples are worked out to illustrate the developed theory.
Sun Jitao; Han Qinglong; Jiang Xiefu
2008-01-01
This Letter is concerned with impulsive control of a class of nonlinear time-delay systems. Some uniform stability criteria for the closed-loop time-delay system under delayed impulsive control are derived by using piecewise Lyapunov functions. Then the criteria are applied to impulsive master-slave synchronization of some secure communication systems with transmission delays and sample delays under delayed impulsive control. Two numerical examples are given to illustrate the effectiveness of the derived results
Quadratic theory and feedback controllers for linear time delay systems
Lee, E.B.
1976-01-01
Recent research on the design of controllers for systems having time delays is discussed. Results for the ''open loop'' and ''closed loop'' designs will be presented. In both cases results for minimizing a quadratic cost functional are given. The usefulness of these results is not known, but similar results for the non-delay case are being routinely applied. (author)
Search for gravitational waves associated with the August 2006 timing glitch of the Vela pulsar
Abadie, J.; Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Anderson, S. B.; Araya, M.; Aso, Y.; Ballmer, S.; Betzwieser, J.; Billingsley, G.; Black, E.; Blackburn, J. K.; Bork, R.; Brooks, A. F.; Cannon, K. C.; Cardenas, L.; Cepeda, C.; Chalermsongsak, T.; Chatterji, S.
2011-01-01
The physical mechanisms responsible for pulsar timing glitches are thought to excite quasinormal mode oscillations in their parent neutron star that couple to gravitational-wave emission. In August 2006, a timing glitch was observed in the radio emission of PSR B0833-45, the Vela pulsar. At the time of the glitch, the two colocated Hanford gravitational-wave detectors of the Laser Interferometer Gravitational-wave observatory (LIGO) were operational and taking data as part of the fifth LIGO science run (S5). We present the first direct search for the gravitational-wave emission associated with oscillations of the fundamental quadrupole mode excited by a pulsar timing glitch. No gravitational-wave detection candidate was found. We place Bayesian 90% confidence upper limits of 6.3x10 -21 to 1.4x10 -20 on the peak intrinsic strain amplitude of gravitational-wave ring-down signals, depending on which spherical harmonic mode is excited. The corresponding range of energy upper limits is 5.0x10 44 to 1.3x10 45 erg.
The International Pulsar Timing Array project: using pulsars as a gravitational wave detector
Hobbs, G; Burke-Spolaor, S; Champion, D [Australia Telescope National Facility, CSIRO, PO Box 76, Epping, NSW 1710 (Australia); Archibald, A [Department of Physics, McGill University, Montreal, PQ, H3A 2T8 (Canada); Arzoumanian, Z [CRESST/USRA, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States); Backer, D [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720-3411 (United States); Bailes, M; Bhat, N D R [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn VIC 3122 (Australia); Burgay, M [Universita di Cagliari, Dipartimento di Fisica, SP Monserrato-Sestu km 0.7, 09042 Monserrato (Canada) (Italy); Cognard, I; Desvignes, G; Ferdman, R D [Station de Radioastronomie de Nanay, Observatoire de Paris, 18330 Nancay (France); Coles, W [Electrical and Computer Engineering, University of California at San Diego, La Jolla, CA (United States); Cordes, J [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States); Demorest, P [National Radio Astronomy Observatory (NRAO), Charlottesville, VA 22903 (United States); Finn, L [Center for Gravitational Wave Physics, The Pennsylvania State University, University Park, PA 16802 (United States); Freire, P [Max-Planck-Institut fuer Radioastronomie, Auf Dem Huegel 69, 53121, Bonn (Germany); Gonzalez, M [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Hessels, J [Astronomical Institute Anton Pannekoek, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam (Netherlands); Hotan, A, E-mail: george.hobbs@csiro.a [Department of Imaging and Applied Physics, Curtin University, Bentley, WA (Australia)
2010-04-21
The International Pulsar Timing Array project combines observations of pulsars from both northern and southern hemisphere observatories with the main aim of detecting ultra-low frequency (approx 10{sup -9}-10{sup -8} Hz) gravitational waves. Here we introduce the project, review the methods used to search for gravitational waves emitted from coalescing supermassive binary black-hole systems in the centres of merging galaxies and discuss the status of the project.
Generalized Synchronization of Time-Delayed Discrete Systems
Jing Jianyi; Min Lequan
2009-01-01
This paper establishes two theorems for two time-delayed (chaotic) discrete systems to achieve time-delayed generalized synchronization (TDGS). These two theorems uncover the general forms of two TDGS systems via a prescribed transformation. As examples, we convert the Lorenz three-dimensional chaotic map to an equal time-delayed system as the driving system, and construct the TDGS driven systems according to the Theorems 1 and 2. Numerical simulations demonstrate the effectiveness of the proposed theorems. (interdisciplinary physics and related areas of science and technology)
Global chaos synchronization with channel time-delay
Jiang Guoping; Zheng Weixing; Chen Guanrong
2004-01-01
This paper addresses a practical issue in chaos synchronization where there is a time-delay in the receiver as compared with the transmitter. A new synchronization scheme and a general criterion for global chaos synchronization are proposed and developed from the approach of unidirectional linear error feedback coupling with time-delay. The chaotic Chua's circuit is used for illustration, where the coupling parameters are determined according to the criterion under which the global chaos synchronization of the time-delay coupled systems is achieved
Study of calculated and measured time dependent delayed neutron yields
Waldo, R.W.
1980-05-01
Time-dependent delayed neutron emission is of interest in reactor design, reactor dynamics, and nuclear physics studies. The delayed neutrons from neutron-induced fission of 232 U, 237 Np, 238 Pu, 241 Am, /sup 242m/Am, 245 Cm, and 249 Cf were studied for the first time. The delayed neutron emission from 232 Th, 233 U, 235 U, 238 U, 239 Pu, 241 Pu, and 242 Pu were measured as well. The data were used to develop an empirical expression for the total delayed neutron yield. The expression gives accurate results for a large variety of nuclides from 232 Th to 252 Cf. The data measuring the decay of delayed neutrons with time were used to derive another empirical expression predicting the delayed neutron emission with time. It was found that nuclides with similar mass-to-charge ratios have similar decay patterns. Thus the relative decay pattern of one nuclide can be established by any measured nuclide with a similar mass-to-charge ratio. A simple fission product yield model was developed and applied to delayed neutron precursors. It accurately predicts observed yield and decay characteristics. In conclusion, it is possible to not only estimate the total delayed neutron yield for a given nuclide but the time-dependent nature of the delayed neutrons as well. Reactors utilizing recycled fuel or burning actinides are likely to have inventories of fissioning nuclides that have not been studied until now. The delayed neutrons from these nuclides can now be incorporated so that their influence on the stability and control of reactors can be delineated. 8 figures, 39 tables
Heterogeneity of time delays determines synchronization of coupled oscillators.
Petkoski, Spase; Spiegler, Andreas; Proix, Timothée; Aram, Parham; Temprado, Jean-Jacques; Jirsa, Viktor K
2016-07-01
Network couplings of oscillatory large-scale systems, such as the brain, have a space-time structure composed of connection strengths and signal transmission delays. We provide a theoretical framework, which allows treating the spatial distribution of time delays with regard to synchronization, by decomposing it into patterns and therefore reducing the stability analysis into the tractable problem of a finite set of delay-coupled differential equations. We analyze delay-structured networks of phase oscillators and we find that, depending on the heterogeneity of the delays, the oscillators group in phase-shifted, anti-phase, steady, and non-stationary clusters, and analytically compute their stability boundaries. These results find direct application in the study of brain oscillations.
Electrically tunable photonic true-time-delay line.
Barmenkov, Yuri O; Cruz, José Luis; Díez, Antonio; Andrés, Miguel V
2010-08-16
We present a new application of the acousto-optic superlattice modulation of a fiber Bragg grating based on the dynamic phase and group delay properties of this fiber-optic component. We demonstrate a tunable photonic true-time-delay line based on the group delay change of the light reflected from the grating sidebands. The delay is electrically tuned by adjusting the voltage applied to a piezoelectric transducer that generates the acoustic wave propagating along the grating. In our experiments, a true-time delay of 400 ps is continuously adjusted (300 ps within the 3 dB amplitude range of the first sideband), using a 12 cm long uniform grating.
Delay-Dependent Guaranteed Cost Control of an Interval System with Interval Time-Varying Delay
Xiao Min
2009-01-01
Full Text Available This paper concerns the problem of the delay-dependent robust stability and guaranteed cost control for an interval system with time-varying delay. The interval system with matrix factorization is provided and leads to less conservative conclusions than solving a square root. The time-varying delay is assumed to belong to an interval and the derivative of the interval time-varying delay is not a restriction, which allows a fast time-varying delay; also its applicability is broad. Based on the Lyapunov-Ktasovskii approach, a delay-dependent criterion for the existence of a state feedback controller, which guarantees the closed-loop system stability, the upper bound of cost function, and disturbance attenuation lever for all admissible uncertainties as well as out perturbation, is proposed in terms of linear matrix inequalities (LMIs. The criterion is derived by free weighting matrices that can reduce the conservatism. The effectiveness has been verified in a number example and the compute results are presented to validate the proposed design method.
Cao Jinde
2011-01-01
Full Text Available Abstract In this paper, an integral sliding mode control approach is presented to investigate synchronization of nonidentical chaotic neural networks with discrete and distributed time-varying delays as well as leakage delay. By considering a proper sliding surface and constructing Lyapunov-Krasovskii functional, as well as employing a combination of the free-weighting matrix method, Newton-Leibniz formulation and inequality technique, a sliding mode controller is designed to achieve the asymptotical synchronization of the addressed nonidentical neural networks. Moreover, a sliding mode control law is also synthesized to guarantee the reachability of the specified sliding surface. The provided conditions are expressed in terms of linear matrix inequalities, and are dependent on the discrete and distributed time delays as well as leakage delay. A simulation example is given to verify the theoretical results.
Pyragas, V.; Pyragas, K.
2011-01-01
We propose a simple adaptive delayed feedback control algorithm for stabilization of unstable periodic orbits with unknown periods. The state dependent time delay is varied continuously towards the period of controlled orbit according to a gradient-descent method realized through three simple ordinary differential equations. We demonstrate the efficiency of the algorithm with the Roessler and Mackey-Glass chaotic systems. The stability of the controlled orbits is proven by computation of the Lyapunov exponents of linearized equations. -- Highlights: → A simple adaptive modification of the delayed feedback control algorithm is proposed. → It enables the control of unstable periodic orbits with unknown periods. → The delay time is varied continuously according to a gradient descend method. → The algorithm is embodied by three simple ordinary differential equations. → The validity of the algorithm is proven by computation of the Lyapunov exponents.
Delay-Dependent Asymptotic Stability of Cohen-Grossberg Models with Multiple Time-Varying Delays
Xiaofeng Liao
2007-01-01
Full Text Available Dynamical behavior of a class of Cohen-Grossberg models with multiple time-varying delays is studied in detail. Sufficient delay-dependent criteria to ensure local and global asymptotic stabilities of the equilibrium of this network are derived by constructing suitable Lyapunov functionals. The obtained conditions are shown to be less conservative and restrictive than those reported in the known literature. Some numerical examples are included to demonstrate our results.
A Framework for telerobotics across the time delays of space
National Aeronautics and Space Administration — The proposal will develop a novel intelligent time-delay mitigation framework to be used in bilateral space telerobotics. This framework will consist of master...
Time-delayed feedback control of coherence resonance chimeras
Zakharova, Anna; Semenova, Nadezhda; Anishchenko, Vadim; Schöll, Eckehard
2017-11-01
Using the model of a FitzHugh-Nagumo system in the excitable regime, we investigate the influence of time-delayed feedback on noise-induced chimera states in a network with nonlocal coupling, i.e., coherence resonance chimeras. It is shown that time-delayed feedback allows for the control of the range of parameter values where these chimera states occur. Moreover, for the feedback delay close to the intrinsic period of the system, we find a novel regime which we call period-two coherence resonance chimera.
Li Hongjie; Yue Dong
2010-01-01
The paper investigates the synchronization stability problem for a class of complex dynamical networks with Markovian jumping parameters and mixed time delays. The complex networks consist of m modes and the networks switch from one mode to another according to a Markovian chain with known transition probability. The mixed time delays are composed of discrete and distributed delays, the discrete time delay is assumed to be random and its probability distribution is known a priori. In terms of the probability distribution of the delays, the new type of system model with probability-distribution-dependent parameter matrices is proposed. Based on the stochastic analysis techniques and the properties of the Kronecker product, delay-dependent synchronization stability criteria in the mean square are derived in the form of linear matrix inequalities which can be readily solved by using the LMI toolbox in MATLAB, the solvability of derived conditions depends on not only the size of the delay, but also the probability of the delay-taking values in some intervals. Finally, a numerical example is given to illustrate the feasibility and effectiveness of the proposed method.
Optical resonators for true-time-delay beam steering
Gesell, Leslie H.; Evanko, Stephen M.
1996-06-01
Conventional true time delay beamforming and steering devices rely on switching between various lengths of delay line. Therefore only discrete delays are possible. Proposed is a new photonics concept for true time delay beamforming which provides a finely controlled continuum of delays with switching speeds on the order of 10's of nanoseconds or faster. The architecture uses an array of waveguide cavities with different resonate frequencies to channelize the signal. Each spectral component of the signal is phase shifted by an amount proportional to the frequency of that component and the desired time delay. These phase shifted spectral components are then summed to obtain the delayed signal. This paper provides an overview of the results of a Phase I SBIR contract where this concept has been refined and analyzed. The parameters for an operational system are determined and indication of the feasibility of this approach is given. Among the issues addressed are the requirements of the resonators and the methods necessary to implement fiber optic Bragg gratings as these resonators.
Delayed biodiversity change: no time to waste
Essl, F.; Dullinger, S.; Rabitsch, W.; Hulme, P. E.; Pyšek, Petr; Wilson, J. R. U.; Richardson, D. M.
2015-01-01
Roč. 30, č. 7 (2015), s. 375-378 ISSN 0169-5347 R&D Projects: GA ČR GB14-36079G Grant - others:AV ČR(CZ) AP1002 Program:Akademická prémie - Praemium Academiae Institutional support: RVO:67985939 Keywords : biological invasions * global change * time lags Subject RIV: EH - Ecology, Behaviour Impact factor: 16.735, year: 2015
Truncated predictor feedback for time-delay systems
Zhou, Bin
2014-01-01
This book provides a systematic approach to the design of predictor based controllers for (time-varying) linear systems with either (time-varying) input or state delays. Differently from those traditional predictor based controllers, which are infinite-dimensional static feedback laws and may cause difficulties in their practical implementation, this book develops a truncated predictor feedback (TPF) which involves only finite dimensional static state feedback. Features and topics: A novel approach referred to as truncated predictor feedback for the stabilization of (time-varying) time-delay systems in both the continuous-time setting and the discrete-time setting is built systematically Semi-global and global stabilization problems of linear time-delay systems subject to either magnitude saturation or energy constraints are solved in a systematic manner Both stabilization of a single system and consensus of a group of systems (multi-agent systems) are treated in a unified manner by applying the truncated pre...
An adaptive robust controller for time delay maglev transportation systems
Milani, Reza Hamidi; Zarabadipour, Hassan; Shahnazi, Reza
2012-12-01
For engineering systems, uncertainties and time delays are two important issues that must be considered in control design. Uncertainties are often encountered in various dynamical systems due to modeling errors, measurement noises, linearization and approximations. Time delays have always been among the most difficult problems encountered in process control. In practical applications of feedback control, time delay arises frequently and can severely degrade closed-loop system performance and in some cases, drives the system to instability. Therefore, stability analysis and controller synthesis for uncertain nonlinear time-delay systems are important both in theory and in practice and many analytical techniques have been developed using delay-dependent Lyapunov function. In the past decade the magnetic and levitation (maglev) transportation system as a new system with high functionality has been the focus of numerous studies. However, maglev transportation systems are highly nonlinear and thus designing controller for those are challenging. The main topic of this paper is to design an adaptive robust controller for maglev transportation systems with time-delay, parametric uncertainties and external disturbances. In this paper, an adaptive robust control (ARC) is designed for this purpose. It should be noted that the adaptive gain is derived from Lyapunov-Krasovskii synthesis method, therefore asymptotic stability is guaranteed.
O. M. Kwon
2012-01-01
Full Text Available The purpose of this paper is to investigate the delay-dependent stability analysis for discrete-time neural networks with interval time-varying delays. Based on Lyapunov method, improved delay-dependent criteria for the stability of the networks are derived in terms of linear matrix inequalities (LMIs by constructing a suitable Lyapunov-Krasovskii functional and utilizing reciprocally convex approach. Also, a new activation condition which has not been considered in the literature is proposed and utilized for derivation of stability criteria. Two numerical examples are given to illustrate the effectiveness of the proposed method.
Pulsar timing residuals due to individual non-evolving gravitational wave sources
Tong Ming-Lei; Zhao Cheng-Shi; Yan Bao-Rong; Yang Ting-Gao; Gao Yu-Ping
2014-01-01
The pulsar timing residuals induced by gravitational waves from non-evolving single binary sources are affected by many parameters related to the relative positions of the pulsar and the gravitational wave sources. We will analyze the various effects due to different parameters. The standard deviations of the timing residuals will be calculated with a variable parameter fixing a set of other parameters. The orbits of the binary sources will be generally assumed to be elliptical. The influences of different eccentricities on the pulsar timing residuals will also be studied in detail. We find that the effects of the related parameters are quite different, and some of them display certain regularities
Complex Time-Delay Systems Theory and Applications
Atay, Fatihcan M
2010-01-01
Time delays in dynamical systems arise as an inevitable consequence of finite speeds of information transmission. Realistic models increasingly demand the inclusion of delays in order to properly understand, analyze, design, and control real-life systems. The goal of this book is to present the state-of-the-art in research on time-delay dynamics in the framework of complex systems and networks. While the mathematical theory of delay equations is quite mature, its application to the particular problems of complex systems and complexity is a newly emerging field, and the present volume aims to play a pioneering role in this perspective. The chapters in this volume are authored by renowned experts and cover both theory and applications in a wide range of fields, with examples extending from neuroscience and biology to laser physics and vehicle traffic. Furthermore, all chapters include sufficient introductory material and extensive bibliographies, making the book a self-contained reference for both students and ...
Periodic solutions in reaction–diffusion equations with time delay
Li, Li
2015-01-01
Spatial diffusion and time delay are two main factors in biological and chemical systems. However, the combined effects of them on diffusion systems are not well studied. As a result, we investigate a nonlinear diffusion system with delay and obtain the existence of the periodic solutions using coincidence degree theory. Moreover, two numerical examples confirm our theoretical results. The obtained results can also be applied in other related fields
Relativity time-delay experiments utilizing 'Mariner' spacecraft
Esposito, P. B.; Anderson, J. D.
1974-01-01
Relativity predicts that the transit time of a signal propagated from the earth to a spacecraft and retransmitted back to earth ought to exhibit an additional, variable time delay. The present work describes some of the analytical techniques employed in experiments using Mariner spacecraft designed to test the accuracy of this prediction. Two types of data are analyzed in these relativity experiments; these include phase-coherent, two-way Doppler shift and round-trip, transit-time measurements. Results of Mariner 6 and 7 relativistic time-delay experiments are in agreement with Einstein's theory of general relativity with an uncertainty of 3%.
Visual prediction: psychophysics and neurophysiology of compensation for time delays.
Nijhawan, Romi
2008-04-01
A necessary consequence of the nature of neural transmission systems is that as change in the physical state of a time-varying event takes place, delays produce error between the instantaneous registered state and the external state. Another source of delay is the transmission of internal motor commands to muscles and the inertia of the musculoskeletal system. How does the central nervous system compensate for these pervasive delays? Although it has been argued that delay compensation occurs late in the motor planning stages, even the earliest visual processes, such as phototransduction, contribute significantly to delays. I argue that compensation is not an exclusive property of the motor system, but rather, is a pervasive feature of the central nervous system (CNS) organization. Although the motor planning system may contain a highly flexible compensation mechanism, accounting not just for delays but also variability in delays (e.g., those resulting from variations in luminance contrast, internal body temperature, muscle fatigue, etc.), visual mechanisms also contribute to compensation. Previous suggestions of this notion of "visual prediction" led to a lively debate producing re-examination of previous arguments, new analyses, and review of the experiments presented here. Understanding visual prediction will inform our theories of sensory processes and visual perception, and will impact our notion of visual awareness.
Experiments with arbitrary networks in time-multiplexed delay systems
Hart, Joseph D.; Schmadel, Don C.; Murphy, Thomas E.; Roy, Rajarshi
2017-12-01
We report a new experimental approach using an optoelectronic feedback loop to investigate the dynamics of oscillators coupled on large complex networks with arbitrary topology. Our implementation is based on a single optoelectronic feedback loop with time delays. We use the space-time interpretation of systems with time delay to create large networks of coupled maps. Others have performed similar experiments using high-pass filters to implement the coupling; this restricts the network topology to the coupling of only a few nearest neighbors. In our experiment, the time delays and coupling are implemented on a field-programmable gate array, allowing the creation of networks with arbitrary coupling topology. This system has many advantages: the network nodes are truly identical, the network is easily reconfigurable, and the network dynamics occur at high speeds. We use this system to study cluster synchronization and chimera states in both small and large networks of different topologies.
Arnaud, Nicolas; Barsuglia, Matteo; Bizouard, Marie-Anne; Canitrot, Philippe; Cavalier, Fabien; Davier, Michel; Hello, Patrice; Pradier, Thierry
2002-01-01
Detecting gravitational wave bursts (characterized by short durations and poorly modeled waveforms) requires coincidences between several interferometric detectors in order to reject nonstationary noise events. As the wave amplitude seen in a detector depends on its location with respect to the source direction and as the signal to noise ratio of these bursts is expected to be low, coincidences between antennas may not be very likely. This paper investigates this question from a statistical point of view by using a simple model of a network of detectors; it also estimates the timing precision of a detection in an interferometer, which is an important issue for the reconstruction of the source location based on time delays
Kalman filtering for time-delayed linear systems
LU Xiao; WANG Wei
2006-01-01
This paper is to study the linear minimum variance estimation for discrete- time systems. A simple approach to the problem is presented by developing re-organized innovation analysis for the systems with instantaneous and double time-delayed measurements. It is shown that the derived estimator involves solving three different standard Kalman filtering with the same dimension as the original system. The obtained results form the basis for solving some complicated problems such as H∞ fixed-lag smoothing, preview control, H∞ filtering and control with time delays.
Gravitational wave searches with pulsar timing arrays: Cancellation of clock and ephemeris noises
Tinto, Massimo
2018-04-01
We propose a data processing technique to cancel monopole and dipole noise sources (such as clock and ephemeris noises, respectively) in pulsar timing array searches for gravitational radiation. These noises are the dominant sources of correlated timing fluctuations in the lower-part (≈10-9-10-8 Hz ) of the gravitational wave band accessible by pulsar timing experiments. After deriving the expressions that reconstruct these noises from the timing data, we estimate the gravitational wave sensitivity of our proposed processing technique to single-source signals to be at least one order of magnitude higher than that achievable by directly processing the timing data from an equal-size array. Since arrays can generate pairs of clock and ephemeris-free timing combinations that are no longer affected by correlated noises, we implement with them the cross-correlation statistic to search for an isotropic stochastic gravitational wave background. We find the resulting optimal signal-to-noise ratio to be more than one order of magnitude larger than that obtainable by correlating pairs of timing data from arrays of equal size.
Robust Moving Horizon H∞ Control of Discrete Time-Delayed Systems with Interval Time-Varying Delays
F. Yıldız Tascikaraoglu
2014-01-01
Full Text Available In this study, design of a delay-dependent type moving horizon state-feedback control (MHHC is considered for a class of linear discrete-time system subject to time-varying state delays, norm-bounded uncertainties, and disturbances with bounded energies. The closed-loop robust stability and robust performance problems are considered to overcome the instability and poor disturbance rejection performance due to the existence of parametric uncertainties and time-delay appeared in the system dynamics. Utilizing a discrete-time Lyapunov-Krasovskii functional, some delay-dependent linear matrix inequality (LMI based conditions are provided. It is shown that if one can find a feasible solution set for these LMI conditions iteratively at each step of run-time, then we can construct a control law which guarantees the closed-loop asymptotic stability, maximum disturbance rejection performance, and closed-loop dissipativity in view of the actuator limitations. Two numerical examples with simulations on a nominal and uncertain discrete-time, time-delayed systems, are presented at the end, in order to demonstrate the efficiency of the proposed method.
Introduction to Focus Issue: Time-delay dynamics
Erneux, Thomas; Javaloyes, Julien; Wolfrum, Matthias; Yanchuk, Serhiy
2017-11-01
The field of dynamical systems with time delay is an active research area that connects practically all scientific disciplines including mathematics, physics, engineering, biology, neuroscience, physiology, economics, and many others. This Focus Issue brings together contributions from both experimental and theoretical groups and emphasizes a large variety of applications. In particular, lasers and optoelectronic oscillators subject to time-delayed feedbacks have been explored by several authors for their specific dynamical output, but also because they are ideal test-beds for experimental studies of delay induced phenomena. Topics include the control of cavity solitons, as light spots in spatially extended systems, new devices for chaos communication or random number generation, higher order locking phenomena between delay and laser oscillation period, and systematic bifurcation studies of mode-locked laser systems. Moreover, two original theoretical approaches are explored for the so-called Low Frequency Fluctuations, a particular chaotical regime in laser output which has attracted a lot of interest for more than 30 years. Current hot problems such as the synchronization properties of networks of delay-coupled units, novel stabilization techniques, and the large delay limit of a delay differential equation are also addressed in this special issue. In addition, analytical and numerical tools for bifurcation problems with or without noise and two reviews on concrete questions are proposed. The first review deals with the rich dynamics of simple delay climate models for El Nino Southern Oscillations, and the second review concentrates on neuromorphic photonic circuits where optical elements are used to emulate spiking neurons. Finally, two interesting biological problems are considered in this Focus Issue, namely, multi-strain epidemic models and the interaction of glucose and insulin for more effective treatment.
Generation of wideband chaos with suppressed time-delay signature by delayed self-interference.
Wang, Anbang; Yang, Yibiao; Wang, Bingjie; Zhang, Beibei; Li, Lei; Wang, Yuncai
2013-04-08
We demonstrate experimentally and numerically a method using the incoherent delayed self-interference (DSI) of chaotic light from a semiconductor laser with optical feedback to generate wideband chaotic signal. The results show that, the DSI can eliminate the domination of laser relaxation oscillation existing in the chaotic laser light and therefore flatten and widen the power spectrum. Furthermore, the DSI depresses the time-delay signature induced by external cavity modes and improves the symmetry of probability distribution by more than one magnitude. We also experimentally show that this DSI signal is beneficial to the random number generation.
Zhu Xunlin; Wang Youyi
2009-01-01
This Letter studies the exponential stability for a class of neural networks (NNs) with both discrete and distributed time-varying delays. Under weaker assumptions on the activation functions, by defining a more general type of Lyapunov functionals and developing a new convex combination technique, new less conservative and less complex stability criteria are established to guarantee the global exponential stability of the discussed NNs. The obtained conditions are dependent on both discrete and distributed delays, are expressed in terms of linear matrix inequalities (LMIs), and contain fewer decision variables. Numerical examples are given to illustrate the effectiveness and the less conservatism of the proposed conditions.
On the linearity of cross-correlation delay times
Mercerat, E. D.; Nolet, G.
2012-12-01
We investigate the question whether a P-wave delay time Δ T estimated by locating the maximum of the cross-correlation function between data d(t) and a predicted test function s(t): γ (t) = ∫ t1t_2 s(τ ) d(τ -t) \\ {d}τ, provides an estimate of the Delta T that is (quasi-)linear with the relative velocity perturbation deltaln V_P}. Such linearity is intuitive if the data d(t) is an undeformed but delayed replica of the test signal, i.e. if d(t)=s(t-Delta T). Then the maximum of gamma (t) is shifted exactly by the delay Delta T, and linearity holds even for Delta T very large. In this case, we say that the body waves are in the ray theoretical regime and their delays, because of Fermat's Principle, depend quasi-linearly on the relative velocity (or slowness) perturbations deltaln V_P in the model. However, even if we correct for dispersion induced by the instrument response and by attenuation, body waves may show frequency dependent delay times that are caused by diffraction effects around lateral heterogeneities. It is not a-priori clear that linearity holds for Delta T, as is assumed in finite-frequency theory, if the waveforms of d(t) and s(t) differ substantially because of such dispersion. To test the linearity, we generate synthetic seismograms between two boreholes, and between the boreholes and the surface, in a 3D box of 200 × 120 × 120 m. The heterogeneity is a checkerboard with cubic anomalies of size 12 × 12 × 12 m. We test two different anomaly amplitudes: ± 2% and ± 5%, and measure Delta T using a test seismogram s(t) computed for an homogeneous medium. We also predict the delays for the 5% model from those in the 2% model by multiplying with 5/2. These predictions are in error by 10-20% of the delay, which is usually acceptable for tomography when compared with actual data errors. A slight bias in the prediction indicates that the Wielandt effect - the fact that negative delays suffer less wavefront healing than positive delays - is a
Start time delays in operating room: Different perspectives
Babita Gupta
2011-01-01
Full Text Available Background: Healthcare expenditure is a serious concern, with escalating costs failing to meet the expectations of quality care. The treatment capacities are limited in a hospital setting and the operating rooms (ORs. Their optimal utilization is vital in efficient hospital management. Starting late means considerable wait time for staff, patients and waste of resources. We planned an audit to assess different perspectives of the residents in surgical specialities and anesthesia and OR staff nurses so as to know the causative factors of operative delay. This can help develop a practical model to decrease start time delays in operating room (ORs. Aims: An audit to assess different perspectives of the Operating room (OR staff with respect to the varied causative factors of operative delay in the OR. To aid in the development of a practical model to decrease start time delays in ORs and facilitate on-time starts at Jai Prakash Narayan Apex Trauma centre (JPNATC, All India Institute of Medical Sciences (AIIMS, New Delhi. Methods: We prepared a questionnaire seeking the five main reasons of delay as per their perspective. Results: The available data was analysed. Analysis of the data demonstrated the common causative factors in start time operative delays as: a lack of proper planning, deficiencies in team work, communication gap and limited availability of trained supporting staff. Conclusions: The preparation of the equipment and required material for the OR cases must be done well in advance. Utilization of newer technology enables timely booking and scheduling of cases. Improved inter-departmental coordination and compliance with preanesthetic instructions needs to be ensured. It is essential that the anesthesiologists perform their work promptly, well in time . and supervise the proceedings as the OR manager. This audit is a step forward in defining the need of effective OR planning for continuous quality improvement.
Singular perturbation methods for nonlinear dynamic systems with time delays
Hu, H.Y.; Wang, Z.H.
2009-01-01
This review article surveys the recent advances in the dynamics and control of time-delay systems, with emphasis on the singular perturbation methods, such as the method of multiple scales, the method of averaging, and two newly developed methods, the energy analysis and the pseudo-oscillator analysis. Some examples are given to demonstrate the advantages of the methods. The comparisons with other methods show that these methods lead to easier computations and higher accurate prediction on the local dynamics of time-delay systems near a Hopf bifurcation.
Extracting the relevant delays in time series modelling
Goutte, Cyril
1997-01-01
selection, and more precisely stepwise forward selection. The method is compared to other forward selection schemes, as well as to a nonparametric tests aimed at estimating the embedding dimension of time series. The final application extends these results to the efficient estimation of FIR filters on some......In this contribution, we suggest a convenient way to use generalisation error to extract the relevant delays from a time-varying process, i.e. the delays that lead to the best prediction performance. We design a generalisation-based algorithm that takes its inspiration from traditional variable...
Period doubling phenomenon in a class of time delay equations
Oliveira, C.R. de; Malta, C.P.
1985-01-01
The properties of the solution of a nonlinear time delayed differential equation (infinite dimension) as function of two parameters: the time delay tau and another parameter A (nonlinearity) are investigated. After a Hopf bifurcation period doubling may occur and is characterized by Feigenbaum's delta. A strange atractor is obtained after the period doubling cascade and the largest Lyapunov exponent is calculated indicating that the attractor has low dimension. The behaviour of this Liapunov exponent as function of tau is different from its behaviour as function of A. (Author) [pt
Time delay correlations in chaotic scattering and random matrix approach
Lehmann, N.; Savin, D.V.; Sokolov, V.V.; Sommers, H.J.
1994-01-01
We study the correlations in the time delay a model of chaotic resonance scattering based on the random matrix approach. Analytical formulae which are valid for arbitrary number of open channels and arbitrary coupling strength between resonances and channels are obtained by the supersymmetry method. The time delay correlation function, through being not a Lorentzian, is characterized, similar to that of the scattering matrix, by the gap between the cloud of complex poles of the S-matrix and the real energy axis. 28 refs.; 4 figs
Coherence resonance in an excitable system with time delay
Sethia, Gautam C.; Kurths, Juergen; Sen, Abhijit
2007-01-01
We study the noise activated dynamics of a model excitable system that consists of a subcritical Hopf oscillator with a time delayed nonlinear feedback. The coherence of the noise driven pulses of the system exhibits a novel double peaked structure as a function of the noise amplitude. The two peaks correspond to separate optimal noise levels for excitation of single spikes and multiple spikes (bursts) respectively. The relative magnitudes of these peaks are found to be a sensitive function of time delay. The physical significance of our results and its practical implications in various real life systems are discussed
Computer-games for gravitational wave science outreach: Black Hole Pong and Space Time Quest
Carbone, L; Bond, C; Brown, D; Brückner, F; Grover, K; Lodhia, D; Mingarelli, C M F; Fulda, P; Smith, R J E; Unwin, R; Vecchio, A; Wang, M; Whalley, L; Freise, A
2012-01-01
We have established a program aimed at developing computer applications and web applets to be used for educational purposes as well as gravitational wave outreach activities. These applications and applets teach gravitational wave physics and technology. The computer programs are generated in collaboration with undergraduates and summer students as part of our teaching activities, and are freely distributed on a dedicated website. As part of this program, we have developed two computer-games related to gravitational wave science: 'Black Hole Pong' and 'Space Time Quest'. In this article we present an overview of our computer related outreach activities and discuss the games and their educational aspects, and report on some positive feedback received.
Reconstruction of ensembles of coupled time-delay systems from time series.
Sysoev, I V; Prokhorov, M D; Ponomarenko, V I; Bezruchko, B P
2014-06-01
We propose a method to recover from time series the parameters of coupled time-delay systems and the architecture of couplings between them. The method is based on a reconstruction of model delay-differential equations and estimation of statistical significance of couplings. It can be applied to networks composed of nonidentical nodes with an arbitrary number of unidirectional and bidirectional couplings. We test our method on chaotic and periodic time series produced by model equations of ensembles of diffusively coupled time-delay systems in the presence of noise, and apply it to experimental time series obtained from electronic oscillators with delayed feedback coupled by resistors.
Determination of Uncalibrated Phase Delays for Real-Time PPP
Hinterberger, Fabian; Weber, Robert; Huber, Katrin; Lesjak, Roman
2014-05-01
Today PPP is a well-known technique of GNSS based positioning used for a wide range of post-processing applications. Using observations of a single GNSS receiver and applying precise orbit and clock information derived from global GNSS networks highly precise positions can be obtained. The atmospheric delays are usually mitigated by linear combination (ionosphere) and parameter estimation (troposphere). Within the last years also the demand for real-time PPP increased. In 2012, the IGS real-time working group started a pilot project to broadcast real-time precise orbits and clock correction streams. Nevertheless, real-time PPP is in its starting phase and currently only few applications make use of the technique although SSR-Messages are already implemented in RTCM3.1. The problems of still limited accuracy compared to Network-RTK as well as long convergence times might be solved by almost instantaneous integer ambiguity resolution at zero-difference level which is a major topic of current scientific investigations. Therefore a national consortium has carried out over the past 2 years the research project PPP-Serve (funded by the Austrian Research Promotion Agency - FFG), which aimed at the development of appropriate algorithms for real-time PPP with special emphasis on the ambiguity resolution of zero-difference observations. We have established a module which calculates based on GPS-reference station data-streams of a dense network (obtained from IGS via BKG) so-called wide-lane and narrow-lane satellite specific calibration phase delays. While the wide-lane phase delays are almost stable over longer periods, the estimation of narrow-lane phase delays has to be re-established every 24 hours. These phase-delays are submitted via a real-time module to the rover where they are used for point positioning via a PPP-model. This presentation deals with the process and obstacles of calculating the wide-lane and narrow-lane phase-delays (based on SD -observations between
Back-Song; Lee; Jong-Dug; Shin; Boo-Gyoun; Kim
2003-01-01
We proposed an optical true time delay (TTD) for phased array antennas (PAAs) composed of 2×2 optical MEMS switches, single-mode fiber delay lines, and a fixed wavelength laser diode. A 3-bit TTD for 10 GHz PAAs was implemented with a time delay error less than ± 0.2 ps.
Two-actor conflict with time delay: A dynamical model
Qubbaj, Murad R.; Muneepeerakul, Rachata
2012-11-01
Recent mathematical dynamical models of the conflict between two different actors, be they nations, groups, or individuals, have been developed that are capable of predicting various outcomes depending on the chosen feedback strategies, initial conditions, and the previous states of the actors. In addition to these factors, this paper examines the effect of time delayed feedback on the conflict dynamics. Our analysis shows that under certain initial and feedback conditions, a stable neutral equilibrium of conflict may destabilize for some critical values of time delay, and the two actors may evolve to new emotional states. We investigate the results by constructing critical delay surfaces for different sets of parameters and analyzing results from numerical simulations. These results provide new insights regarding conflict and conflict resolution and may help planners in adjusting and assessing their strategic decisions.
Low-complexity controllers for time-delay systems
Özbay, Hitay; Bonnet, Catherine; Mounier, Hugues
2014-01-01
This volume in the newly established series Advances in Delays and Dynamics (ADD@S) provides a collection of recent results on the design and analysis of Low Complexity Controllers for Time Delay Systems. A widely used indirect method to obtain low order controllers for time delay systems is to design a controller for the reduced order model of the plant. In the dual indirect approach, an infinite dimensional controller is designed first for the original plant model; then, the controller is approximated by keeping track of the degradation in performance and stability robustness measures. The present volume includes new techniques used at different stages of the indirect approach. It also includes new direct design methods for fixed structure and low order controllers. On the other hand, what is meant by low complexity controller is not necessarily low order controller. For example, Smith predictor or similar type of controllers include a copy of the plant internally in the controller, so they are technically ...
The International Pulsar Timing Array project: using pulsars as a gravitational wave detector
Hobbs, G.; Archibald, A.; Arzoumanian, Z.; Backer, D.; Bailes, M.; Bhat, N.D.R.; Burgay, M.; Burke-Spolaor, S.; Champion, D.; Cognard, I.; Coles, W.; Cordes, J.; Demorest, P.; Desvignes, G.; Ferdman, R.D.; Finn, L.; Freire, P.; Gonzalez, M.; Hessels, J.; Hotan, A.; Janssen, G.; Jenet, F.; Jessner, A.; Jordan, C.; Kaspi, V.; Kramer, M.; Kondratiev, V.; Lazio, J.; Lazaridis, K.; Lee, K.J.; Levin, Y.; Lommen, A.; Lorimer, D.; Lynch, R.; Lyne, A.; Manchester, R.; McLaughlin, M.; Nice, D.; Oslowski, S.; Pilia, M.; Possenti, A.; Purver, M.; Ransom, S.; Reynolds, J.; Sanidas, S.; Sarkissian, J.; Sesana, A.; Shannon, R.; Siemens, X.; Stairs, I.; Stappers, B.; Stinebring, D.; Theureau, G.; van Haasteren, R.; van Straten, W.; Verbiest, J.P.W.; Yardley, D.R.B.; You, X.P.
2010-01-01
The International Pulsar Timing Array project combines observations of pulsars from both northern and southern hemisphere observatories with the main aim of detecting ultra-low frequency (similar to 10(-9)-10(-8) Hz) gravitational waves. Here we introduce the project, review the methods used to
Losing track of time through delayed body representations.
Fritz, Thomas H; Steixner, Agnes; Boettger, Joachim; Villringer, Arno
2015-01-01
The ability to keep track of time is perceived as crucial in most human societies. However, to lose track of time may also serve an important social role, associated with recreational purpose. To this end a number of social technologies are employed, some of which may relate to a manipulation of time perception through a modulation of body representation. Here, we investigated an influence of real-time or delayed videos of own-body representations on time perception in an experimental setup with virtual mirrors. Seventy participants were asked to either stay in the installation until they thought that a defined time (90 s) had passed, or they were encouraged to stay in the installation as long as they wanted and after exiting were asked to estimate the duration of their stay. Results show that a modulation of body representation by time-delayed representations of the mirror-video displays influenced time perception. Furthermore, these time-delayed conditions were associated with a greater sense of arousal and intoxication. We suggest that feeding in references to the immediate past into working memory could be the underlying mental mechanism mediating the observed modulation of time perception. We argue that such an influence on time perception would probably not only be achieved visually, but might also work with acoustic references to the immediate past (e.g., with music).
Losing track of time through delayed body representations
Thomas Hans Fritz
2015-04-01
Full Text Available The ability to keep track of time is perceived as crucial in most human societies. However, to lose track of time may also serve an important social role, associated with recreational purpose. To this end a number of social technologies are employed, some of which may relate to a manipulation of time perception through a modulation of body representation. Here we investigated an influence of real-time or delayed videos of own-body representations on time perception in an experimental setup with virtual mirrors. Seventy participants were asked to either stay in the installation until they thought that a defined time (90 s had passed, or they were encouraged to stay in the installation as long as they wanted and after exiting were asked to estimate the duration of their stay. Results show that a modulation of body representation by time-delayed representations of the mirror-video displays influenced time perception. Furthermore, these time-delayed conditions were associated with a greater sense of arousal and intoxication. We suggest that feeding in references to the immediate past into working memory could be the underlying mental mechanism mediating the observed modulation of time perception. We argue that such an influence on time perception would probably not only be achieved visually, but might also work with acoustic references to the immediate past (e.g., with music.
On Tuning PI Controllers for Integrating Plus Time Delay Systems
David Di Ruscio
2010-10-01
Full Text Available Some analytical results concerning PI controller tuning based on integrator plus time delay models are worked out and presented. A method for obtaining PI controller parameters, Kp=alpha/(k*tau, and, Ti=beta*tau, which ensures a given prescribed maximum time delay error, dtau_max, to time delay, tau, ratio parameter delta=dau_max/tau, is presented. The corner stone in this method, is a method product parameter, c=alpha*beta. Analytical relations between the PI controller parameters, Ti, and, Kp, and the time delay error parameter, delta, is presented, and we propose the setting, beta=c/a*(delta+1, and, alpha=a/(delta+1, which gives, Ti=c/a*(delta+1*tau, and Kp=a/((delta+1*k*tau, where the parameter, a, is constant in the method product parameter, c=alpha*beta. It also turns out that the integral time, Ti, is linear in, delta, and the proportional gain, Kp, inversely proportional to, delta+1. For the original Ziegler Nichols (ZN method this parameter is approximately, c=2.38, and the presented method may e.g., be used to obtain new modified ZN parameters with increased robustness margins, also documented in the paper.
CERN. Geneva
2005-01-01
We will present a brief introduction to the physics of gravitational waves and their properties. We will review potential astrophysical sources of gravitational waves, and the physics and astrophysics that can be learned from their study. We will survey the techniques and technologies for detecting gravitational waves for the first time, including bar detectors and broadband interferometers, and give a brief status report on the international search effort, with special emphasis on the LIGO detectors and search results.
Global synchronization for time-delay of WINDMI System
Wang Junxa; Lu Dianchen; Tian Lixin
2006-01-01
Considering a time-delay in the receiver as compared with the transmitter, we addresses a practical issue in chaos synchronization of WINDMI system which is based on the Lyapunov stabilization theory and matrix measure, such that the state of the slave system at time t is asymptotically synchronizing with the master at time t - τ. The Mathematical software is used to prove the effectiveness of this method
A simple time-delayed method to control chaotic systems
Chen Maoyin; Zhou Donghua; Shang Yun
2004-01-01
Based on the adaptive iterative learning strategy, a simple time-delayed controller is proposed to stabilize unstable periodic orbits (UPOs) embedded in chaotic attractors. This controller includes two parts: one is a linear feedback part; the other is an adaptive iterative learning estimation part. Theoretical analysis and numerical simulation show the effectiveness of this controller
A time-delayed method for controlling chaotic maps
Chen Maoyin; Zhou Donghua; Shang Yun
2005-01-01
Combining the repetitive learning strategy and the optimality principle, this Letter proposes a time-delayed method to control chaotic maps. This method can effectively stabilize unstable periodic orbits within chaotic attractors in the sense of least mean square. Numerical simulations of some chaotic maps verify the effectiveness of this method
Partial synchronization in diffusively time-delay coupled oscillator networks
Steur, E.; Oguchi, T.; Leeuwen, van C.; Nijmeijer, H.
2012-01-01
We study networks of diffusively time-delay coupled oscillatory units and we show that networks with certain symmetries can exhibit a form of incomplete synchronization called partial synchronization. We present conditions for the existence and stability of partial synchronization modes in networks
Time delay between cardiac and brain activity during sleep transitions
Long, X.; Arends, J.B.A.M.; Aarts, R.M.; Haakma, R.; Fonseca, P.; Rolink, J.
2015-01-01
Human sleep consists of wake, rapid-eye-movement (REM) sleep, and non-REM (NREM) sleep that includes light and deep sleep stages. This work investigated the time delay between changes of cardiac and brain activity for sleep transitions. Here, the brain activity was quantified by
Stability Criteria for Differential Equations with Variable Time Delays
Schley, D.; Shail, R.; Gourley, S. A.
2002-01-01
Time delays are an important aspect of mathematical modelling, but often result in highly complicated equations which are difficult to treat analytically. In this paper it is shown how careful application of certain undergraduate tools such as the Method of Steps and the Principle of the Argument can yield significant results. Certain delay…
Relation between Time Perspective and Delay Discounting: A Literature Review
Teuscher, Ursina; Mitchell, Suzanne H.
2011-01-01
In this article, we examine the relation between delay discounting and future time perspective by reviewing how these concepts have been measured and quantified in order to assess their conceptual similarities. The extent to which the different measures are empirically related is reviewed by describing studies that have assessed both constructs…
Integrated optical delay lines for time-division multiplexers
Stopinski, S.T.; Malinowski, M.; Piramidowicz, R.; Kleijn, E.; Smit, M.K.; Leijtens, X.J.M.
2013-01-01
In this paper, we present a study of integrated optical delay lines (DLs) for application in optical time-division multiplexers. The investigated DLs are formed by spirally folded waveguides. The components were designed in a generic approach and fabricated in multi-project wafer runs on an
Effect of Magnetic Activity on Ionospheric Time Delay at Low ...
E) using dual frequency (1575.42 and 1227.60 MHz) GPS measurements. Data from GSV4004A GPS Iono- spheric Scintillation and TEC monitor (GISTM) have been chosen to study these effects. This paper presents the results of ionospheric time delay during quiet and disturbed days for the year 2005. Results show that.
Time Delay Measurements for the Cluster-lensed Sextuple Quasar SDSS J2222+2745
Dahle, H.; Gladders, M. D.; Sharon, K.; Bayliss, M. B.; Rigby, J. R.
2015-11-01
We report first results from an ongoing monitoring campaign to measure time delays between the six images of the quasar SDSS J2222+2745, gravitationally lensed by a galaxy cluster. The time delay between A and B, the two most highly magnified images, is measured to be {τ }{{AB}}=47.7+/- 6.0 days (95% confidence interval), consistent with previous model predictions for this lens system. The strong intrinsic variability of the quasar also allows us to derive a time delay value of {τ }{{CA}}=722+/- 24 days between image C and A, in spite of modest overlap between their light curves in the current data set. Image C, which is predicted to lead all the other lensed quasar images, has undergone a sharp, monotonic flux increase of 60%-75% during 2014. A corresponding brightening is firmly predicted to occur in images A and B during 2016. The amplitude of this rise indicates that time delays involving all six known images in this system, including those of the demagnified central images D-F, will be obtainable from further ground-based monitoring of this system during the next few years. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, and including observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnologi´a e Innovación Productiva (Argentina).
Time-dependent delayed signatures from energetic photon interrogations
Norman, Daren R.; Jones, James L.; Blackburn, Brandon W.; Haskell, Kevin J.; Johnson, James T.; Watson, Scott M.; Hunt, Alan W.; Spaulding, Randy; Harmon, Frank
2007-01-01
Pulsed photonuclear interrogation environments generated by 8-24 MeV electron linac are rich with time-dependent, material-specific, radiation signatures. Nitrogen-based explosives and nuclear materials can be detected by exploiting these signatures in different delayed-time regions. Numerical and experimental results presented in this paper show the unique time and energy dependence of these signatures. It is shown that appropriate delayed-time windows are essential to acquire material-specific signatures in pulsed photonuclear assessment environments. These developments demonstrate that pulsed, high-energy, photon-inspection environments can be exploited for time-dependent, material-specific signatures through the proper operation of specialized detectors and detection methods
Comment on ‘Time delays in molecular photoionization’
Baykusheva, Denitsa; Wörner, Hans Jakob
2017-04-01
In a recent article by Hockett et al (2016 J. Phys. B: At. Mol. Opt. Phys. 49 095602), time delays arising in the context of molecular single-photon ionization are investigated from a theoretical point of view. We argue that one of the central equations given in this article is incorrect and present a reformulation that is consistent with the established treatment of angle-dependent scattering delays (Eisenbud 1948 PhD Thesis Princeton University; Wigner 1955 Phys. Rev. 98 145-7 Smith 1960 Phys. Rev. 118 349-6 Nussenzveig 1972 Phys. Rev. D 6 1534-42).
Arbitrary digital pulse sequence generator with delay-loop timing
Hošák, Radim; Ježek, Miroslav
2018-04-01
We propose an idea of an electronic multi-channel arbitrary digital sequence generator with temporal granularity equal to two clock cycles. We implement the generator with 32 channels using a low-cost ARM microcontroller and demonstrate its capability to produce temporal delays ranging from tens of nanoseconds to hundreds of seconds, with 24 ns timing granularity and linear scaling of delay with respect to the number of delay loop iterations. The generator is optionally synchronized with an external clock source to provide 100 ps jitter and overall sequence repeatability within the whole temporal range. The generator is fully programmable and able to produce digital sequences of high complexity. The concept of the generator can be implemented using different microcontrollers and applied for controlling of various optical, atomic, and nuclear physics measurement setups.
Measurement of time delay for a prospectively gated CT simulator.
Goharian, M; Khan, R F H
2010-04-01
For the management of mobile tumors, respiratory gating is the ideal option, both during imaging and during therapy. The major advantage of respiratory gating during imaging is that it is possible to create a single artifact-free CT data-set during a selected phase of the patient's breathing cycle. The purpose of the present work is to present a simple technique to measure the time delay during acquisition of a prospectively gated CT. The time delay of a Philips Brilliance BigBore (Philips Medical Systems, Madison, WI) scanner attached to a Varian Real-Time Position Management (RPM) system (Varian Medical Systems, Palo Alto, CA) was measured. Two methods were used to measure the CT time delay: using a motion phantom and using a recorded data file from the RPM system. In the first technique, a rotating wheel phantom was altered by placing two plastic balls on its axis and rim, respectively. For a desired gate, the relative positions of the balls were measured from the acquired CT data and converted into corresponding phases. Phase difference was calculated between the measured phases and the desired phases. Using period of motion, the phase difference was converted into time delay. The Varian RPM system provides an external breathing signal; it also records transistor-transistor logic (TTL) 'X-Ray ON' status signal from the CT scanner in a text file. The TTL 'X-Ray ON' indicates the start of CT image acquisition. Thus, knowledge of the start time of CT acquisition, combined with the real-time phase and amplitude data from the external respiratory signal, provides time-stamping of all images in an axial CT scan. The TTL signal with time-stamp was used to calculate when (during the breathing cycle) a slice was recorded. Using the two approaches, the time delay between the prospective gating signal and CT simulator has been determined to be 367 +/- 40 ms. The delay requires corrections both at image acquisition and while setting gates for the treatment delivery
Measurement of time delay for a prospectively gated CT simulator
Goharian M
2010-01-01
Full Text Available For the management of mobile tumors, respiratory gating is the ideal option, both during imaging and during therapy. The major advantage of respiratory gating during imaging is that it is possible to create a single artifact-free CT data-set during a selected phase of the patient′s breathing cycle. The purpose of the present work is to present a simple technique to measure the time delay during acquisition of a prospectively gated CT. The time delay of a Philips Brilliance BigBore™ (Philips Medical Systems, Madison, WI scanner attached to a Varian Real-Time Position Management™ (RPM system (Varian Medical Systems, Palo Alto, CA was measured. Two methods were used to measure the CT time delay: using a motion phantom and using a recorded data file from the RPM system. In the first technique, a rotating wheel phantom was altered by placing two plastic balls on its axis and rim, respectively. For a desired gate, the relative positions of the balls were measured from the acquired CT data and converted into corresponding phases. Phase difference was calculated between the measured phases and the desired phases. Using period of motion, the phase difference was converted into time delay. The Varian RPM system provides an external breathing signal; it also records transistor-transistor logic (TTL ′X-Ray ON′ status signal from the CT scanner in a text file. The TTL ′X-Ray ON′ indicates the start of CT image acquisition. Thus, knowledge of the start time of CT acquisition, combined with the real-time phase and amplitude data from the external respiratory signal, provides time-stamping of all images in an axial CT scan. The TTL signal with time-stamp was used to calculate when (during the breathing cycle a slice was recorded. Using the two approaches, the time delay between the prospective gating signal and CT simulator has been determined to be 367 ± 40 ms. The delay requires corrections both at image acquisition and while setting gates for
Measurement of time delay for a prospectively gated CT simulator
Goharian, M.; Khan, R.F.H.
2010-01-01
For the management of mobile tumors, respiratory gating is the ideal option, both during imaging and during therapy. The major advantage of respiratory gating during imaging is that it is possible to create a single artifact-free CT data-set during a selected phase of the patient's breathing cycle. The purpose of the present work is to present a simple technique to measure the time delay during acquisition of a prospectively gated CT. The time delay of a Philips Brilliance BigBore (Philips Medical Systems, Madison, WI) scanner attached to a Varian Real-Time Position Management (RPM) system (Varian Medical Systems, Palo Alto, CA) was measured. Two methods were used to measure the CT time delay: using a motion phantom and using a recorded data file from the RPM system. In the first technique, a rotating wheel phantom was altered by placing two plastic balls on its axis and rim, respectively. For a desired gate, the relative positions of the balls were measured from the acquired CT data and converted into corresponding phases. Phase difference was calculated between the measured phases and the desired phases. Using period of motion, the phase difference was converted into time delay. The Varian RPM system provides an external breathing signal; it also records transistor-transistor logic (TTL) 'X-Ray ON' status signal from the CT scanner in a text file. The TTL 'X-Ray ON' indicates the start of CT image acquisition. Thus, knowledge of the start time of CT acquisition, combined with the real-time phase and amplitude data from the external respiratory signal, provides time-stamping of all images in an axial CT scan. The TTL signal with time-stamp was used to calculate when (during the breathing cycle) a slice was recorded. Using the two approaches, the time delay between the prospective gating signal and CT simulator has been determined to be 367 ± 40 ms. The delay requires corrections both at image acquisition and while setting gates for the treatment delivery
Delay-dependent asymptotic stability of a two-neuron system with different time delays
Tu Fenghua; Liao Xiaofeng; Zhang Wei
2006-01-01
In this paper, we consider a two-neuron system with time-delayed connections between neurons. Based on the construction of Lyapunov functionals, we obtain sufficient criteria to ensure local and global asymptotic stability of the equilibrium of the neural network. The obtained conditions are shown to be less conservative and restrictive than those reported in the literature. Some examples are included to illustrate our results
Tunable Optical True-Time Delay Devices Would Exploit EIT
Kulikov, Igor; DiDomenico, Leo; Lee, Hwang
2004-01-01
Tunable optical true-time delay devices that would exploit electromagnetically induced transparency (EIT) have been proposed. Relative to prior true-time delay devices (for example, devices based on ferroelectric and ferromagnetic materials) and electronically controlled phase shifters, the proposed devices would offer much greater bandwidths. In a typical envisioned application, an optical pulse would be modulated with an ultra-wideband radio-frequency (RF) signal that would convey the information that one seeks to communicate, and it would be required to couple differently delayed replicas of the RF signal to the radiating elements of a phased-array antenna. One or more of the proposed devices would be used to impose the delays and/or generate the delayed replicas of the RF-modulated optical pulse. The beam radiated or received by the antenna would be steered by use of a microprocessor-based control system that would adjust operational parameters of the devices to tune the delays to the required values. EIT is a nonlinear quantum optical interference effect that enables the propagation of light through an initially opaque medium. A suitable medium must have, among other properties, three quantum states (see Figure 1): an excited state (state 3), an upper ground state (state 2), and a lower ground state (state 1). These three states must form a closed system that exhibits no decays to other states in the presence of either or both of two laser beams: (1) a probe beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 1; and (2) a coupling beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 2. The probe beam is the one that is pulsed and modulated with an RF signal.
Ignition delay time measurements of primary reference fuel blends
Alabbad, Mohammed
2017-02-07
Ignition delay times of four different primary reference fuels (PRF), mixtures of n-heptane and iso-octane, were measured behind reflected shock waves in a high-pressure shock tube facility. The PRFs were formulated to match the RON of two high-octane gasolines (RON 95 and 91) and two prospective low-octane naphtha fuels (RON 80 and 70). Experiments were carried out over a wide range of temperatures (700–1200K), pressures (10, 20, and 40bar) and equivalence ratios (0.5 and 1). Kinetic modeling predictions from four chemical kinetic mechanisms are compared with the experimental data. Ignition delay correlations are developed to reproduce the measured ignition delay times. Brute force sensitivity analyses are carried out to identify reactions that affect ignition delay times at specific temperature, pressure and equivalence ratio. The large experimental data set provided in the current work will serve as a benchmark for the validation of chemical kinetic mechanisms of primary reference fuel blends.
Ignition delay time measurements of primary reference fuel blends
Alabbad, Mohammed; Javed, Tamour; Khaled, Fathi; Badra, Jihad; Farooq, Aamir
2017-01-01
Ignition delay times of four different primary reference fuels (PRF), mixtures of n-heptane and iso-octane, were measured behind reflected shock waves in a high-pressure shock tube facility. The PRFs were formulated to match the RON of two high-octane gasolines (RON 95 and 91) and two prospective low-octane naphtha fuels (RON 80 and 70). Experiments were carried out over a wide range of temperatures (700–1200K), pressures (10, 20, and 40bar) and equivalence ratios (0.5 and 1). Kinetic modeling predictions from four chemical kinetic mechanisms are compared with the experimental data. Ignition delay correlations are developed to reproduce the measured ignition delay times. Brute force sensitivity analyses are carried out to identify reactions that affect ignition delay times at specific temperature, pressure and equivalence ratio. The large experimental data set provided in the current work will serve as a benchmark for the validation of chemical kinetic mechanisms of primary reference fuel blends.
Optimal control for parabolic-hyperbolic system with time delay
Kowalewski, A.
1985-07-01
In this paper we consider an optimal control problem for a system described by a linear partial differential equation of the parabolic-hyperbolic type with time delay in the state. The right-hand side of this equation and the initial conditions are not continuous functions usually, but they are measurable functions belonging to L 2 or Lsup(infinity) spaces. Therefore, the solution of this equation is given by a certain Sobolev space. The time delay in the state is constant, but it can be also a function of time. The control time T is fixed in our problem. Making use of the Milutin-Dubovicki theorem, necessary and sufficient conditions of optimality with the quadratic performance functional and constrained control are derived for the Dirichlet problem. The flow chart of the algorithm which can be used in the numerical solving of certain optimization problems for distributed systems is also presented. (author)
Large Deviations for Two-Time-Scale Diffusions, with Delays
Kushner, Harold J.
2010-01-01
We consider the problem of large deviations for a two-time-scale reflected diffusion process, possibly with delays in the dynamical terms. The Dupuis-Ellis weak convergence approach is used. It is perhaps the most intuitive and simplest for the problems of concern. The results have applications to the problem of approximating optimal controls for two-time-scale systems via use of the averaged equation.
Face to phase: pitfalls in time delay estimation from coherency phase
Campfens, S.F.; van der Kooij, Herman; Schouten, Alfred Christiaan
2014-01-01
Coherency phase is often interpreted as a time delay reflecting a transmission delay between spatially separated neural populations. However, time delays estimated from corticomuscular coherency are conflicting and often shorter than expected physiologically. Recent work suggests that
Chen, S.-F.
2009-01-01
The asymptotic stability problem for discrete-time systems with time-varying delay subject to saturation nonlinearities is addressed in this paper. In terms of linear matrix inequalities (LMIs), a delay-dependent sufficient condition is derived to ensure the asymptotic stability. A numerical example is given to demonstrate the theoretical results.
Applying behavioral insights to delay school start times.
Kohl Malone, Susan; Ziporyn, Terra; Buttenheim, Alison M
2017-12-01
Healthy People 2020 established a national objective to increase the proportion of 9th-to-12th-grade students reporting sufficient sleep. A salient approach for achieving this objective is to delay middle and high school start times. Despite decades of research supporting the benefits of delayed school start times on adolescent sleep, health, and well-being, progress has been slow. Accelerating progress will require new approaches incorporating strategies that influence how school policy decisions are made. In this commentary, we introduce four strategies that influence decision-making processes and demonstrate how they can be applied to efforts aimed at changing school start time policies. Copyright © 2017 National Sleep Foundation. All rights reserved.
A new delay-independent condition for global robust stability of neural networks with time delays.
Samli, Ruya
2015-06-01
This paper studies the problem of robust stability of dynamical neural networks with discrete time delays under the assumptions that the network parameters of the neural system are uncertain and norm-bounded, and the activation functions are slope-bounded. By employing the results of Lyapunov stability theory and matrix theory, new sufficient conditions for the existence, uniqueness and global asymptotic stability of the equilibrium point for delayed neural networks are presented. The results reported in this paper can be easily tested by checking some special properties of symmetric matrices associated with the parameter uncertainties of neural networks. We also present a numerical example to show the effectiveness of the proposed theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.
Wang Shen-Quan; Feng Jian; Zhao Qing
2012-01-01
In this paper, the problem of delay-distribution-dependent stability is investigated for continuous-time recurrent neural networks (CRNNs) with stochastic delay. Different from the common assumptions on time delays, it is assumed that the probability distribution of the delay taking values in some intervals is known a priori. By making full use of the information concerning the probability distribution of the delay and by using a tighter bounding technique (the reciprocally convex combination method), less conservative asymptotic mean-square stable sufficient conditions are derived in terms of linear matrix inequalities (LMIs). Two numerical examples show that our results are better than the existing ones. (general)
Effects of computing time delay on real-time control systems
Shin, Kang G.; Cui, Xianzhong
1988-01-01
The reliability of a real-time digital control system depends not only on the reliability of the hardware and software used, but also on the speed in executing control algorithms. The latter is due to the negative effects of computing time delay on control system performance. For a given sampling interval, the effects of computing time delay are classified into the delay problem and the loss problem. Analysis of these two problems is presented as a means of evaluating real-time control systems. As an example, both the self-tuning predicted (STP) control and Proportional-Integral-Derivative (PID) control are applied to the problem of tracking robot trajectories, and their respective effects of computing time delay on control performance are comparatively evaluated. For this example, the STP (PID) controller is shown to outperform the PID (STP) controller in coping with the delay (loss) problem.
Identification of optimal inspection interval via delay-time concept
Glauco Ricardo Simões Gomes
2016-06-01
Full Text Available This paper presents an application of mathematical modeling aimed at managing maintenance based on the delay-time concept. The study scenario was the manufacturing sector of an industrial unit, which operates 24 hours a day in a continuous flow of production. The main idea was to use the concepts of this approach to determine the optimal time of preventive action by the maintenance department in order to ensure the greatest availability of equipment and facilities at appropriate maintenance costs. After a brief introduction of the subject, the article presents topics that illustrate the importance of mathematical modeling in maintenance management and the delay-time concept. It also describes the characteristics of the company where the study was conducted, as well as the data related to the production process and maintenance actions. Finally, the results obtained after applying the delay-time concept are presented and discussed, as well as the limitations of the article and the proposals for future research.
Acceleration (Deceleration Model Supporting Time Delays to Refresh Data
José Gerardo Carrillo González
2018-04-01
Full Text Available This paper proposes a mathematical model to regulate the acceleration (deceleration applied by self-driving vehicles in car-following situations. A virtual environment is designed to test the model in different circumstances: (1 the followers decelerate in time if the leader decelerates, considering a time delay of up to 5 s to refresh data (vehicles position coordinates required by the model, (2 with the intention of optimizing space, the vehicles are grouped in platoons, where 3 s of time delay (to update data is supported if the vehicles have a centre-to-centre spacing of 20 m and a time delay of 1 s is supported at a spacing of 6 m (considering a maximum speed of 20 m/s in both cases, and (3 an algorithm is presented to manage the vehicles’ priority at a traffic intersection, where the model regulates the vehicles’ acceleration (deceleration and a balance in the number of vehicles passing from each side is achieved.
Hopf Bifurcation in a Cobweb Model with Discrete Time Delays
Luca Gori
2014-01-01
Full Text Available We develop a cobweb model with discrete time delays that characterise the length of production cycle. We assume a market comprised of homogeneous producers that operate as adapters by taking the (expected profit-maximising quantity as a target to adjust production and consumers with a marginal willingness to pay captured by an isoelastic demand. The dynamics of the economy is characterised by a one-dimensional delay differential equation. In this context, we show that (1 if the elasticity of market demand is sufficiently high, the steady-state equilibrium is locally asymptotically stable and (2 if the elasticity of market demand is sufficiently low, quasiperiodic oscillations emerge when the time lag (that represents the length of production cycle is high enough.
Time Delay Systems Methods, Applications and New Trends
Vyhlídal, Tomáš; Niculescu, Silviu-Iulian; Pepe, Pierdomenico
2012-01-01
This volume is concerned with the control and dynamics of time delay systems; a research field with at least six-decade long history that has been very active especially in the past two decades. In parallel to the new challenges emerging from engineering, physics, mathematics, and economics, the volume covers several new directions including topology induced stability, large-scale interconnected systems, roles of networks in stability, and new trends in predictor-based control and consensus dynamics. The associated applications/problems are described by highly complex models, and require solving inverse problems as well as the development of new theories, mathematical tools, numerically-tractable algorithms for real-time control. The volume, which is targeted to present these developments in this rapidly evolving field, captures a careful selection of the most recent papers contributed by experts and collected under five parts: (i) Methodology: From Retarded to Neutral Continuous Delay Models, (ii) Systems, S...
Time Delay Estimation in Room Acoustic Environments: An Overview
Benesty Jacob
2006-01-01
Full Text Available Time delay estimation has been a research topic of significant practical importance in many fields (radar, sonar, seismology, geophysics, ultrasonics, hands-free communications, etc.. It is a first stage that feeds into subsequent processing blocks for identifying, localizing, and tracking radiating sources. This area has made remarkable advances in the past few decades, and is continuing to progress, with an aim to create processors that are tolerant to both noise and reverberation. This paper presents a systematic overview of the state-of-the-art of time-delay-estimation algorithms ranging from the simple cross-correlation method to the advanced blind channel identification based techniques. We discuss the pros and cons of each individual algorithm, and outline their inherent relationships. We also provide experimental results to illustrate their performance differences in room acoustic environments where reverberation and noise are commonly encountered.
EVOLVING TO TYPE Ia SUPERNOVAE WITH SHORT DELAY TIMES
Wang Bo; Chen Xuefei; Han Zhanwen; Meng Xiangcun
2009-01-01
The single-degenerate model is currently a favorable progenitor model for Type Ia supernovae (SNe Ia). Recent investigations on the white dwarf (WD) + He star channel of the single-degenerate model imply that this channel is noteworthy for producing SNe Ia. In this paper, we studied SN Ia birthrates and delay times of this channel via a detailed binary population synthesis approach. We found that the Galactic SN Ia birthrate from the WD + He star channel is ∼0.3 x 10 -3 yr -1 according to our standard model, and that this channel can explain SNe Ia with short delay times (∼4.5 x 10 7 -1.4 x 10 8 yr). Meanwhile, these WD + He star systems may be related to the young supersoft X-ray sources prior to SN Ia explosions.
Guaranteed cost control of time-delay chaotic systems
Park, Ju H.; Kwon, O.M.
2006-01-01
This article studies a guaranteed cost control problem for a class of time-delay chaotic systems. Attention is focused on the design of memory state feedback controllers such that the resulting closed-loop system is asymptotically stable and an adequate level of performance is also guaranteed. Using the Lyapunov method and LMI (linear matrix inequality) framework, two criteria for the existence of the controller are derived in terms of LMIs. A numerical example is given to illustrate the proposed method
Spectral sum rule for time delay in R2
Osborn, T.A.; Sinha, K.B.; Bolle, D.; Danneels, C.
1985-01-01
A local spectral sum rule for nonrelativistic scattering in two dimensions is derived for the potential class velement ofL 4 /sup // 3 (R 2 ). The sum rule relates the integral over all scattering energies of the trace of the time-delay operator for a finite region Σis contained inR 2 to the contributions in Σ of the pure point and singularly continuous spectra
Disequilibrium dynamics in a Keynesian model with time delays
Gori, Luca; Guerrini, Luca; Sodini, Mauro
2018-05-01
The aim of this research is to analyse a Keynesian goods market closed economy by considering a continuous-time setup with fixed delays. The work compares dynamic results based on linear and nonlinear adjustment mechanisms through which the aggregate supply (production) reacts to a disequilibrium in the goods market and consumption depends on income at a preceding date. Both analytical and geometrical (stability switching curves) techniques are used to characterise the stability properties of the stationary equilibrium.
OPTIMAL STRATEGIES FOR CONTINUOUS GRAVITATIONAL WAVE DETECTION IN PULSAR TIMING ARRAYS
Ellis, J. A.; Siemens, X.; Creighton, J. D. E.
2012-01-01
Supermassive black hole binaries (SMBHBs) are expected to emit a continuous gravitational wave signal in the pulsar timing array (PTA) frequency band (10 –9 to 10 –7 Hz). The development of data analysis techniques aimed at efficient detection and characterization of these signals is critical to the gravitational wave detection effort. In this paper, we leverage methods developed for LIGO continuous wave gravitational searches and explore the use of the F-statistic for such searches in pulsar timing data. Babak and Sesana have used this approach in the context of PTAs to show that one can resolve multiple SMBHB sources in the sky. Our work improves on several aspects of prior continuous wave search methods developed for PTA data analysis. The algorithm is implemented fully in the time domain, which naturally deals with the irregular sampling typical of PTA data and avoids spectral leakage problems associated with frequency domain methods. We take into account the fitting of the timing model and have generalized our approach to deal with both correlated and uncorrelated colored noise sources. We also develop an incoherent detection statistic that maximizes over all pulsar-dependent contributions to the likelihood. To test the effectiveness and sensitivity of our detection statistics, we perform a number of Monte Carlo simulations. We produce sensitivity curves for PTAs of various configurations and outline an implementation of a fully functional data analysis pipeline. Finally, we present a derivation of the likelihood maximized over the gravitational wave phases at the pulsar locations, which results in a vast reduction of the search parameter space.
RATES AND DELAY TIMES OF TYPE Ia SUPERNOVAE
Ruiter, Ashley J.; Belczynski, Krzysztof; Fryer, Chris
2009-01-01
We analyze the evolution of binary stars to calculate synthetic rates and delay times of the most promising Type Ia Supernovae (SNe Ia) progenitors. We present and discuss evolutionary scenarios in which a white dwarf (WD) reaches the Chandrasekhar mass and potentially explodes in a SNe Ia. We consider Double Degenerate (DDS; merger of two WDs), Single Degenerate (SDS; WD accreting from H-rich companion), and AM Canum Venaticorum (AM CVn; WD accreting from He-rich companion) scenarios. The results are presented for two different star formation histories: burst (elliptical-like galaxies) and continuous (spiral-like galaxies). It is found that delay times for the DDS in our standard model (with common envelope efficiency α CE = 1) follow a power-law distribution. For the SDS we note a wide range of delay times, while AM CVn progenitors produce a short burst of SNe Ia at early times. The DDS median delay time falls between ∼0.5 and 1 Gyr; the SDS between ∼2 and 3 Gyr; and the AM CVn between ∼0.8 and 0.6 Gyr depending on the assumed α CE . For a Milky-Way-like (MW-like) galaxy, we estimate the rates of SNe Ia arising from different progenitors as: ∼10 -4 yr -1 for the SDS and AM CVn, and ∼10 -3 yr -1 for the DDS. We point out that only the rates for two merging carbon-oxygen WDs, the only systems found in the DDS, are consistent with the observed rates for typical MW-like spirals. We also note that DDS progenitors are the dominant population in elliptical galaxies. The fact that the delay time distribution for the DDS follows a power law implies more SNe Ia (per unit mass) in young rather than in aged populations. Our results do not exclude other scenarios, but strongly indicate that the DDS is the dominant channel generating SNe Ia in spiral galaxies, at least in the framework of our adopted evolutionary models. Since it is believed that WD mergers cannot produce a thermonuclear explosion given the current understanding of accreting WDs, either the
Time domain passivity controller for 4-channel time-delay bilateral teleoperation.
Rebelo, Joao; Schiele, Andre
2015-01-01
This paper presents an extension of the time-domain passivity control approach to a four-channel bilateral controller under the effects of time delays. Time-domain passivity control has been used successfully to stabilize teleoperation systems with position-force and position-position controllers; however, the performance with such control architectures is sub-optimal both with and without time delays. This work extends the network representation of the time-domain passivity controller to the four-channel architecture, which provides perfect transparency to the user without time delay. The proposed architecture is based on modelling the controllers as dependent voltage sources and using only series passivity controllers. The obtained results are shown on a one degree-of-freedom setup and illustrate the stabilization behaviour of the proposed controller when time delay is present in the communication channel.
Lag synchronization of chaotic systems with time-delayed linear ...
delayed linear terms via impulsive control is investigated. Based on the stability theory of impulsive delayed differen- tial equations, some sufficient conditions are obtained guaranteeing the synchronized behaviours between two delayed chaotic ...
Pulsar Timing and Its Application for Navigation and Gravitational Wave Detection
Becker, Werner; Kramer, Michael; Sesana, Alberto
2018-02-01
Pulsars are natural cosmic clocks. On long timescales they rival the precision of terrestrial atomic clocks. Using a technique called pulsar timing, the exact measurement of pulse arrival times allows a number of applications, ranging from testing theories of gravity to detecting gravitational waves. Also an external reference system suitable for autonomous space navigation can be defined by pulsars, using them as natural navigation beacons, not unlike the use of GPS satellites for navigation on Earth. By comparing pulse arrival times measured on-board a spacecraft with predicted pulse arrivals at a reference location (e.g. the solar system barycenter), the spacecraft position can be determined autonomously and with high accuracy everywhere in the solar system and beyond. We describe the unique properties of pulsars that suggest that such a navigation system will certainly have its application in future astronautics. We also describe the on-going experiments to use the clock-like nature of pulsars to "construct" a galactic-sized gravitational wave detector for low-frequency (f_{GW}˜ 10^{-9} - 10^{-7} Hz) gravitational waves. We present the current status and provide an outlook for the future.
Long-time behavior for suspension bridge equations with time delay
Park, Sun-Hye
2018-04-01
In this paper, we consider suspension bridge equations with time delay of the form u_{tt}(x,t) + Δ ^2 u (x,t) + k u^+ (x,t) + a_0 u_t (x,t) + a_1 u_t (x, t- τ ) + f(u(x,t)) = g(x). Many researchers have studied well-posedness, decay rates of energy, and existence of attractors for suspension bridge equations without delay effects. But, as far as we know, there is no work about suspension equations with time delay. In addition, there are not many studies on attractors for other delayed systems. Thus we first provide well-posedness for suspension equations with time delay. And then show the existence of global attractors and the finite dimensionality of the attractors by establishing energy functionals which are related to the norm of the phase space to our problem.
Real-time pulse deinterleaving using digital delay line techniques
Lentz, L. F.; Palermo, T. J.
This paper describes an implementation of a tracking pulse sorter based on predictive gating techniques. Real-time pulse sorters or pulse train gating devices have been utilized by the ELINT signal analyst for many years. The more elementary of these devices employed a retriggerable delay interval and an acceptance gate, which were used in predictive fashion to track pulse trains whose PRIs fall within the limits of the programmed delay interval. This design utilizes the pulse hit/miss history of individual track files in a variation of a sequential observer detection algorithm. Use of a digital delay line with pulse history allows multiple pulse trains to be tracked simultaneously and independently without interference. The design also provides flexibility in lock-on and track criteria to allow maintenance of acquisition probability and false alarm rate in dense signal environments and with low SNRs. The hardware provides time interval resolution to 12.5 nsec and covers a PRI range of 50 microsec to 50 msec.
On the time delay between ultra-relativistic particles
Fleury, Pierre
2016-01-01
The time delay between the receptions of ultra-relativistic particles emitted simultaneously is a useful observable for both fundamental physics and cosmology. The expression of the delay when the particles travel through an arbitrary spacetime has been derived recently by Fanizza et al., using a particular coordinate system and self-consistent assumptions. The present article shows that this formula enjoys a simple physical interpretation: the relative velocity between two ultra-relativistic particles is constant. This result reveals an interesting kinematical property of general relativity, namely that the tidal forces experienced by ultra-relativistic particles in the direction of their motion are much smaller than those experienced orthogonally to their motion.
On the time delay between ultra-relativistic particles
Fleury, Pierre, E-mail: pierre.fleury@uct.ac.za [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa); Department of Physics, University of the Western Cape, Robert Sobukwe Road, Bellville 7535 (South Africa)
2016-09-10
The time delay between the receptions of ultra-relativistic particles emitted simultaneously is a useful observable for both fundamental physics and cosmology. The expression of the delay when the particles travel through an arbitrary spacetime has been derived recently by Fanizza et al., using a particular coordinate system and self-consistent assumptions. The present article shows that this formula enjoys a simple physical interpretation: the relative velocity between two ultra-relativistic particles is constant. This result reveals an interesting kinematical property of general relativity, namely that the tidal forces experienced by ultra-relativistic particles in the direction of their motion are much smaller than those experienced orthogonally to their motion.
Complex systems fractionality, time-delay and synchronization
Sun, Jian-Qiao
2012-01-01
"Complex Systems: Fractionality, Time-delay and Synchronization" covers the most recent developments and advances in the theory and application of complex systems in these areas. Each chapter was written by scientists highly active in the field of complex systems. The book discusses a new treatise on fractional dynamics and control, as well as the new methods for differential delay systems and control. Lastly, a theoretical framework for the complexity and synchronization of complex system is presented. The book is intended for researchers in the field of nonlinear dynamics in mathematics, physics and engineering. It can also serve as a reference book for graduate students in physics, applied mathematics and engineering. Dr. Albert C.J. Luo is a Professor at Southern Illinois University Edwardsville, USA. Dr. Jian-Qiao Sun is a Professor at the University of California, Merced, USA.
Radar time delays in the dynamic theory of gravity
Haranas I.I.
2004-01-01
Full Text Available There is a new theory gravity called the dynamic theory, which is derived from thermodynamic principles in a five dimensional space, radar signals traveling times and delays are calculated for the major planets in the solar system, and compared to those of general relativity. This is done by using the usual four dimensional spherically symmetric space-time element of classical general relativistic gravity which has now been slightly modified by a negative inverse radial exponential term due to the dynamic theory of gravity potential.
Time-delayed fronts from biased random walks
Fort, Joaquim; Pujol, Toni
2007-01-01
We generalize a previous model of time-delayed reaction-diffusion fronts (Fort and Mendez 1999 Phys. Rev. Lett. 82 867) to allow for a bias in the microscopic random walk of particles or individuals. We also present a second model which takes the time order of events (diffusion and reproduction) into account. As an example, we apply them to the human invasion front across the USA in the 19th century. The corrections relative to the previous model are substantial. Our results are relevant to physical and biological systems with anisotropic fronts, including particle diffusion in disordered lattices, population invasions, the spread of epidemics, etc
Gravitational-recoil effects on fermion propagation in space-time foam
Ellis, John R.; Nanopoulos, Dimitri V.; Volkov, G.
2000-01-01
Motivated by the possible experimental opportunities to test quantum gravity via its effects on high-energy neutrinos propagating through space-time foam, we discuss how to incorporate spin structures in our D-brane description of gravitational recoil effects in vacuo. We also point to an interesting analogous condensed-matter system. We use a suitable supersymmetrization of the Born-Infeld action for excited D-brane gravitational backgrounds to argue that energetic fermions may travel slower than the low-energy velocity of light: pulses of neutrinos at energies approaching 10^{19} eV: these would be observable only if M \\gsim 10^{27} GeV.
Hopf bifurcation of a free boundary problem modeling tumor growth with two time delays
Xu Shihe
2009-01-01
In this paper, a free boundary problem modeling tumor growth with two discrete delays is studied. The delays respectively represents the time taken for cells to undergo mitosis and the time taken for the cell to modify the rate of cell loss due to apoptosis. We show the influence of time delays on the Hopf bifurcation when one of delays as a bifurcation parameter.
Xu Chang-Jin; Li Pei-Luan; Pang Yi-Cheng
2017-01-01
This paper is concerned with fractional-order bidirectional associative memory (BAM) neural networks with time delays. Applying Laplace transform, the generalized Gronwall inequality and estimates of Mittag–Leffler functions, some sufficient conditions which ensure the finite-time stability of fractional-order bidirectional associative memory neural networks with time delays are obtained. Two examples with their simulations are given to illustrate the theoretical findings. Our results are new and complement previously known results. (paper)
Multiplicity counting from fission detector signals with time delay effects
Nagy, L.; Pázsit, I.; Pál, L.
2018-03-01
In recent work, we have developed the theory of using the first three auto- and joint central moments of the currents of up to three fission chambers to extract the singles, doubles and triples count rates of traditional multiplicity counting (Pázsit and Pál, 2016; Pázsit et al., 2016). The objective is to elaborate a method for determining the fissile mass, neutron multiplication, and (α, n) neutron emission rate of an unknown assembly of fissile material from the statistics of the fission chamber signals, analogous to the traditional multiplicity counting methods with detectors in the pulse mode. Such a method would be an alternative to He-3 detector systems, which would be free from the dead time problems that would be encountered in high counting rate applications, for example the assay of spent nuclear fuel. A significant restriction of our previous work was that all neutrons born in a source event (spontaneous fission) were assumed to be detected simultaneously, which is not fulfilled in reality. In the present work, this restriction is eliminated, by assuming an independent, identically distributed random time delay for all neutrons arising from one source event. Expressions are derived for the same auto- and joint central moments of the detector current(s) as in the previous case, expressed with the singles, doubles, and triples (S, D and T) count rates. It is shown that if the time-dispersion of neutron detections is of the same order of magnitude as the detector pulse width, as they typically are in measurements of fast neutrons, the multiplicity rates can still be extracted from the moments of the detector current, although with more involved calibration factors. The presented formulae, and hence also the performance of the proposed method, are tested by both analytical models of the time delay as well as with numerical simulations. Methods are suggested also for the modification of the method for large time delay effects (for thermalised neutrons).
Absorption dynamics and delay time in complex potentials
Villavicencio, Jorge; Romo, Roberto; Hernández-Maldonado, Alberto
2018-05-01
The dynamics of absorption is analyzed by using an exactly solvable model that deals with an analytical solution to Schrödinger’s equation for cutoff initial plane waves incident on a complex absorbing potential. A dynamical absorption coefficient which allows us to explore the dynamical loss of particles from the transient to the stationary regime is derived. We find that the absorption process is characterized by the emission of a series of damped periodic pulses in time domain, associated with damped Rabi-type oscillations with a characteristic frequency, ω = (E + ε)/ℏ, where E is the energy of the incident waves and ‑ε is energy of the quasidiscrete state of the system induced by the absorptive part of the Hamiltonian; the width γ of this resonance governs the amplitude of the pulses. The resemblance of the time-dependent absorption coefficient with a real decay process is discussed, in particular the transition from exponential to nonexponential regimes, a well-known feature of quantum decay. We have also analyzed the effect of the absorptive part of the potential on the dynamical delay time, which behaves differently from the one observed in attractive real delta potentials, exhibiting two regimes: time advance and time delay.
On the background estimation by time slides in a network of gravitational wave detectors
Was, Michal; Bizouard, Marie-Anne; Brisson, Violette; Cavalier, Fabien; Davier, Michel; Hello, Patrice; Leroy, Nicolas; Robinet, Florent; Vavoulidis, Miltiadis
2010-01-01
Time shifting the outputs of gravitational wave detectors operating in coincidence is a convenient way to estimate the background in a search for short-duration signals. However, this procedure is limited as increasing indefinitely the number of time shifts does not provide better estimates. We show that the false alarm rate estimation error saturates with the number of time shifts. In particular, for detectors with very different trigger rates, this error saturates at a large value. Explicit computations are done for two detectors, and for three detectors where the detection statistic relies on the logical 'OR' of the coincidences of the three couples in the network.
On the background estimation by time slides in a network of gravitational wave detectors
Was, Michal; Bizouard, Marie-Anne; Brisson, Violette; Cavalier, Fabien; Davier, Michel; Hello, Patrice; Leroy, Nicolas; Robinet, Florent; Vavoulidis, Miltiadis, E-mail: mwas@lal.in2p3.f [LAL, Univ. Paris-Sud, CNRS/IN2P3, Orsay (France)
2010-01-07
Time shifting the outputs of gravitational wave detectors operating in coincidence is a convenient way to estimate the background in a search for short-duration signals. However, this procedure is limited as increasing indefinitely the number of time shifts does not provide better estimates. We show that the false alarm rate estimation error saturates with the number of time shifts. In particular, for detectors with very different trigger rates, this error saturates at a large value. Explicit computations are done for two detectors, and for three detectors where the detection statistic relies on the logical 'OR' of the coincidences of the three couples in the network.
Mitryk, Shawn J; Wand, Vinzenz; Mueller, Guido, E-mail: smitryk@phys.ufl.ed, E-mail: mueller@phys.ufl.ed [Department of Physics, University of Florida, PO Box 118440, Gainesville, FL 32611-8440 (United States)
2010-04-21
Laser Interferometer Space Antenna (LISA) is a cooperative NASA/ESA mission proposed to directly measure gravitational waves (GW) in the frequency range from 30 muHz to 1 Hz with an optimal strain sensitivity of 10{sup -21}/sq root(Hz) at 3 mHz. LISA will utilize a modified Michelson interferometer to measure length changes of 40 pm/sq root(Hz) between drag-free proof masses located on three separate spacecraft (SC) separated by a distance of 5 Gm. The University of Florida has developed a hardware-in-the-loop simulator of the LISA constellation to verify the laser noise cancellation technique known as time-delay interferometry (TDI). We replicate the frequency stabilization of the laser on the local SC and the phase-locking of the lasers on the far SC. The laser photodetector beatnotes are electronically delayed, Doppler shifted and applied with a mock GW signal to simulate the laser link between the SC. The beatnotes are also measured with a LISA-like phasemeter and the data are used to extract the laser phase and residual phase-lock loop noise in post-processing through TDI. This uncovers the GW modulation signal buried under the laser noise. The results are then compared to the requirements defined by the LISA science collaboration.
YaJun Li
2015-01-01
Full Text Available The passivity problem for a class of stochastic neural networks systems (SNNs with varying delay and leakage delay has been further studied in this paper. By constructing a more effective Lyapunov functional, employing the free-weighting matrix approach, and combining with integral inequality technic and stochastic analysis theory, the delay-dependent conditions have been proposed such that SNNs are asymptotically stable with guaranteed performance. The time-varying delay is divided into several subintervals and two adjustable parameters are introduced; more information about time delay is utilised and less conservative results have been obtained. Examples are provided to illustrate the less conservatism of the proposed method and simulations are given to show the impact of leakage delay on stability of SNNs.
Londero, Louise Skovgaard; Nørgaard, Birgitte; Houlind, Kim Christian
2014-01-01
Abstract BACKGROUND: The prognosis of acute limb ischemia is severe, with amputation rates of up to 25% and in-hospital mortality of 9-15%. Delay in treatment increases the risk of major amputation and may be present at different stages, including patient delay, doctors´ delay and waiting time...... in the emergency department. It is important to identify existing problems in order to reduce time delay. The aim of this study was to collect data for patients with acute limb ischemia and to evaluate the time delay between the different events from onset of symptoms to specialist evaluation and further treatment...... (median (range)) was identified. From onset of symptoms to first contact with a doctor the time for all patients were 24 (0-1200) hours. Thirty patients needed immediate intervention. In the group of fourteen patients who had immediate operation, the median time from vascular evaluation...
Kobakhidze, Archil; Lagger, Cyril; Manning, Adrian [University of Sydney, ARC Centre of Excellence for Particle Physics at the Terascale, School of Physics, Sydney, NSW (Australia); Yue, Jason [National Taiwan Normal University, Department of Physics, Taipei (China)
2017-08-15
We investigate the properties of a stochastic gravitational wave background produced by a first-order electroweak phase transition in the regime of extreme supercooling. We study a scenario whereby the percolation temperature that signifies the completion of the transition, T{sub p}, is as low as a few MeV (nucleosynthesis temperature), while most of the true vacuum bubbles are formed much earlier at the nucleation temperature, T{sub n} ∝ 50 GeV. This implies that the gravitational wave spectrum is mainly produced by the collisions of large bubbles and characterised by a large amplitude and a peak frequency as low as f ∝ 10{sup -9}-10{sup -7} Hz. We show that such a scenario can occur in (but not limited to) a model based on a non-linear realisation of the electroweak gauge group, so that the Higgs vacuum configuration is altered by a cubic coupling. In order to carefully quantify the evolution of the phase transition of this model over such a wide temperature range we go beyond the usual fast transition approximation, taking into account the expansion of the Universe as well as the behaviour of the nucleation probability at low temperatures. Our computation shows that there exists a range of parameters for which the gravitational wave spectrum lies at the edge between the exclusion limits of current pulsar timing array experiments and the detection band of the future Square Kilometre Array observatory. (orig.)
Implementation of time-delay interferometry for LISA
Tinto, Massimo; Shaddock, Daniel A.; Sylvestre, Julien; Armstrong, J.W.
2003-01-01
We discuss the baseline optical configuration for the Laser Interferometer Space Antenna (LISA) mission, in which the lasers are not free-running, but rather one of them is used as the main frequency reference generator (the master) and the remaining five as slaves, these being phase-locked to the master (the master-slave configuration). Under the condition that the frequency fluctuations due to the optical transponders can be made negligible with respect to the secondary LISA noise sources (mainly proof-mass and shot noises), we show that the entire space of interferometric combinations LISA can generate when operated with six independent lasers (the one-way method) can also be constructed with the master-slave system design. The corresponding hardware trade-off analysis for these two optical designs is presented, which indicates that the two sets of systems needed for implementing the one-way method, and the master-slave configuration, are essentially identical. Either operational mode could therefore be implemented without major implications on the hardware configuration. We then derive the required accuracies of armlength knowledge, time synchronization of the onboard clocks, sampling times and time-shifts needed for effectively implementing time-delay interferometry for LISA. We find that an armlength accuracy of about 16 meters, a synchronization accuracy of about 50 ns, and the time jitter due to a presently existing space qualified clock will allow the suppression of the frequency fluctuations of the lasers below to the level identified by the secondary noise sources. A new procedure for sampling the data in such a way to avoid the problem of having time shifts that are not integer multiples of the sampling time is also introduced, addressing one of the concerns about the implementation of time-delay interferometry
A note on Burgers' equation with time delay: Instability via finite-time blow-up
Jordan, P.M.
2008-01-01
Burgers' equation with time delay is considered. Using the Cole-Hopf transformation, the exact solution of this nonlinear partial differential equation (PDE) is determined in the context of a (seemingly) well-posed initial-boundary value problem (IBVP) involving homogeneous Dirichlet data. The solution obtained, however, is shown to exhibit a delay-induced instability, suffering blow-up in finite-time
Complex-Vector Time-Delay Control of Power Converters
Blaabjerg, Frede; Loh, P. C.; Tang, Y.
2008-01-01
Precise controlling of current produced by power converters is an important topic that has attracted interests over the last few decades. With the recent proliferation of grid-tied converters where the control of power flow is indirectly governed by the accuracy of current tracking, motivation...... since only a small amount of memory space for storing time-delayed values and simple arithmetic computations are needed for its physical realization. In addition to that, other advantages of the scheme include its abilities to compensate for negative-sequence, load and grid harmonic components using...
Topology Identification of General Dynamical Network with Distributed Time Delays
Zhao-Yan, Wu; Xin-Chu, Fu
2009-01-01
General dynamical networks with distributed time delays are studied. The topology of the networks are viewed as unknown parameters, which need to be identified. Some auxiliary systems (also called the network estimators) are designed to achieve this goal. Both linear feedback control and adaptive strategy are applied in designing these network estimators. Based on linear matrix inequalities and the Lyapunov function method, the sufficient condition for the achievement of topology identification is obtained. This method can also better monitor the switching topology of dynamical networks. Illustrative examples are provided to show the effectiveness of this method. (general)
Real-time traffic signal optimization model based on average delay time per person
Pengpeng Jiao
2015-10-01
Full Text Available Real-time traffic signal control is very important for relieving urban traffic congestion. Many existing traffic control models were formulated using optimization approach, with the objective functions of minimizing vehicle delay time. To improve people’s trip efficiency, this article aims to minimize delay time per person. Based on the time-varying traffic flow data at intersections, the article first fits curves of accumulative arrival and departure vehicles, as well as the corresponding functions. Moreover, this article transfers vehicle delay time to personal delay time using average passenger load of cars and buses, employs such time as the objective function, and proposes a signal timing optimization model for intersections to achieve real-time signal parameters, including cycle length and green time. This research further implements a case study based on practical data collected at an intersection in Beijing, China. The average delay time per person and queue length are employed as evaluation indices to show the performances of the model. The results show that the proposed methodology is capable of improving traffic efficiency and is very effective for real-world applications.
Delay-dependent stability of neural networks of neutral type with time delay in the leakage term
Li, Xiaodi; Cao, Jinde
2010-01-01
This paper studies the global asymptotic stability of neural networks of neutral type with mixed delays. The mixed delays include constant delay in the leakage term (i.e. 'leakage delay'), time-varying delays and continuously distributed delays. Based on the topological degree theory, Lyapunov method and linear matrix inequality (LMI) approach, some sufficient conditions are derived ensuring the existence, uniqueness and global asymptotic stability of the equilibrium point, which are dependent on both the discrete and distributed time delays. These conditions are expressed in terms of LMI and can be easily checked by the MATLAB LMI toolbox. Even if there is no leakage delay, the obtained results are less restrictive than some recent works. It can be applied to neural networks of neutral type with activation functions without assuming their boundedness, monotonicity or differentiability. Moreover, the differentiability of the time-varying delay in the non-neutral term is removed. Finally, two numerical examples are given to show the effectiveness of the proposed method
Effects of time delay on stochastic resonance of the stock prices in financial system
Li, Jiang-Cheng; Li, Chun; Mei, Dong-Cheng
2014-01-01
The effect of time delay on stochastic resonance of the stock prices in finance system was investigated. The time delay is introduced into the Heston model driven by the extrinsic and intrinsic periodic information for stock price. The signal power amplification (SPA) was calculated by numerical simulation. The results indicate that an optimal critical value of delay time maximally enhances the reverse-resonance in the behaviors of SPA as a function of long-run variance of volatility or cross correlation coefficient between noises for both cases of intrinsic and extrinsic periodic information. Moreover, in both cases, being a critical value in the delay time, when the delay time takes value below the critical value, reverse-resonance increases with the delay time increasing, however, when the delay time takes value above the critical value, the reverse-resonance decrease with the delay time increasing. - Highlights: • The effects of delay time on stochastic resonance of the stock prices was investigated. • There is an optimal critical value of delay time maximally enhances the reverse-resonance • The reverse-resonance increases with the delay time increasing as the delay time takes value below the critical value • The reverse-resonance decrease with the delay time increasing as the delay time takes value above the critical value
Effects of time delay on stochastic resonance of the stock prices in financial system
Li, Jiang-Cheng [Department of Physics, Yunnan University, Kunming, 650091 (China); Li, Chun [Department of Computer Science, Puer Teachers' College, Puer 665000 (China); Mei, Dong-Cheng, E-mail: meidch@ynu.edu.cn [Department of Physics, Yunnan University, Kunming, 650091 (China)
2014-06-13
The effect of time delay on stochastic resonance of the stock prices in finance system was investigated. The time delay is introduced into the Heston model driven by the extrinsic and intrinsic periodic information for stock price. The signal power amplification (SPA) was calculated by numerical simulation. The results indicate that an optimal critical value of delay time maximally enhances the reverse-resonance in the behaviors of SPA as a function of long-run variance of volatility or cross correlation coefficient between noises for both cases of intrinsic and extrinsic periodic information. Moreover, in both cases, being a critical value in the delay time, when the delay time takes value below the critical value, reverse-resonance increases with the delay time increasing, however, when the delay time takes value above the critical value, the reverse-resonance decrease with the delay time increasing. - Highlights: • The effects of delay time on stochastic resonance of the stock prices was investigated. • There is an optimal critical value of delay time maximally enhances the reverse-resonance • The reverse-resonance increases with the delay time increasing as the delay time takes value below the critical value • The reverse-resonance decrease with the delay time increasing as the delay time takes value above the critical value.
Canonical field quantization in an external time-dependent gravitational field
Il'yn, S.B.; Tagirov, E.A.
1975-01-01
The Green functions of the quantum scalar fiels interacting with gravitation of the homogeneous isotropic closed Universe are studied. They have been determined as an expectation value of the time-ordered product of two field operators in the cyclic states of various, in general, unitary-nonequivalent representations of canonical commutation relations. The reqularity properties of these functions are shown to be the same as of the Feynman propagator obtained for arbitrary Riemannian space-time only in the representations that from a class unitary equivalence
Laryngeal sensation and pharyngeal delay time after (chemo)radiotherapy.
Maruo, Takashi; Fujimoto, Yasushi; Ozawa, Kikuko; Hiramatsu, Mariko; Suzuki, Atsushi; Nishio, Naoki; Nakashima, Tsutomu
2014-08-01
The objective of the study was to evaluate the association between changes in laryngeal sensation and initiation of swallowing reflex or swallowing function before and after (chemo)radiotherapy. A prospective study was conducted in a tertiary referral university hospital. Thirteen patients who received (chemo)radiotherapy for treatment of laryngeal or hypopharyngeal cancer were included. Laryngeal sensation was evaluated at the tip of the epiglottis before and 1, 3 months, and 1 year after (chemo)radiotherapy. Videofluoroscopy was performed at the same time. Quantitative determinations included changes in laryngeal sensation, computed analysis of pharyngeal delay time, the distance and velocity of hyoid bone movement during the phase of hyoid excursion, and pharyngeal residue rate (the proportion of the bolus that was left as residue in the pharynx at the first swallow). Laryngeal sensation significantly deteriorated 1 month after (chemo)radiotherapy, but there was a tendency to return to pretreatment levels 1 year after treatment. Neither pharyngeal delay time nor displacement of the hyoid bone changed significantly before and after (chemo)radiotherapy. In addition, there was no significant difference in the mean velocity of hyoid bone movement and the amount of stasis in the pharynx at the first swallow before and after (chemo)radiotherapy. After (chemo)radiotherapy, laryngeal sensation deteriorated. But, in this study, videofluoroscopy showed that swallowing reflex and function were maintained.
Modulator noise suppression in the LISA time-delay interferometric combinations
Tinto, Massimo; Armstrong, J W; Estabrook, Frank B
2008-01-01
Laser Interferometer Space Antenna (LISA) is a mission to detect and study low-frequency cosmic gravitational radiation through its influence on the phases of six modulated laser beams exchanged between three remote spacecraft. We previously showed how the measurements of some 18 time series of relative frequency or phase shifts could be combined (1) to cancel the phase noise of the lasers, (2) to cancel the Doppler fluctuations due to non-inertial motions of the six optical benches and (3) to remove the phase noise of the onboard reference oscillators required to track the photodetector fringes, all the while preserving signals from passing gravitational waves. Here we analyze the effect of the additional noise due to the optical modulators used for removing the phase fluctuations of the onboard reference oscillators. We use the recently measured noise spectrum of an individual modulator (Klipstein et al 2006 Proc. 6th Int. LISA Symp. (Greenbelt, MA) (AIP Conf. Proc. vol 873) ed S M Merkowitz and J C Livas pp 19-23) to quantify the contribution of modulator noise to the first and second-generation time-delay interferometric (TDI) combinations as a function of the modulation frequency. We show that modulator noise can be made smaller than the expected proof-mass acceleration and optical-path noises if the modulation frequencies are larger than ∼682 MHz in the case of the unequal-arm Michelson TDI combination X 1 , ∼ 1.08 GHz for the Sagnac TDI combination α 1 , and ∼706 MHz for the symmetrical Sagnac TDI combination ζ 1 . These modulation frequencies are substantially smaller than previously estimated and may lead to less stringent requirements on the LISA's oscillator noise calibration subsystem. The measurements in Klipstein et al were performed in a laboratory experiment for a range of modulation frequencies, but we emphasize that, for the reference oscillator noise calibration algorithm to work, the modulation frequencies must be equal to the
More, Anupreeta; Oguri, Masamune; More, Surhud [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), University of Tokyo, Chiba 277-8583 (Japan); Suyu, Sherry H. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Lee, Chien-Hsiu, E-mail: anupreeta.more@ipmu.jp [Subaru Telescope, National Astronomical Observatory of Japan, 650 North Aohoku Place, Hilo, HI 96720 (United States)
2017-02-01
We present predictions for time delays between multiple images of the gravitationally lensed supernova, iPTF16geu, which was recently discovered from the intermediate Palomar Transient Factory (iPTF). As the supernova is of Type Ia where the intrinsic luminosity is usually well known, accurately measured time delays of the multiple images could provide tight constraints on the Hubble constant. According to our lens mass models constrained by the Hubble Space Telescope F814W image, we expect the maximum relative time delay to be less than a day, which is consistent with the maximum of 100 hr reported by Goobar et al. but places a stringent upper limit. Furthermore, the fluxes of most of the supernova images depart from expected values suggesting that they are affected by microlensing. The microlensing timescales are small enough that they may pose significant problems to measure the time delays reliably. Our lensing rate calculation indicates that the occurrence of a lensed SN in iPTF is likely. However, the observed total magnification of iPTF16geu is larger than expected, given its redshift. This may be a further indication of ongoing microlensing in this system.
THE BENEFITS OF VLBI ASTROMETRY TO PULSAR TIMING ARRAY SEARCHES FOR GRAVITATIONAL RADIATION
Madison, D. R.; Chatterjee, S.; Cordes, J. M. [Department of Astronomy and Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14850 (United States)
2013-11-10
Precision astrometry is an integral component of successful pulsar timing campaigns. Astrometric parameters are commonly derived by fitting them as parameters of a timing model to a series of pulse times of arrival (TOAs). TOAs measured to microsecond precision over spans of several years can yield position measurements with sub-milliarcsecond precision. However, timing-based astrometry can become biased if a pulsar displays any red spin noise or a red signal produced by the stochastic gravitational wave background. We investigate how noise of different spectral types is absorbed by timing models, leading to significant estimation biases in the astrometric parameters. We find that commonly used techniques for fitting timing models in the presence of red noise (Cholesky whitening) prevent the absorption of noise into the timing model remarkably well if the time baseline of observations exceeds several years, but are inadequate for dealing with shorter pulsar data sets. Independent of timing, pulsar-optimized very long baseline interferometry (VLBI) is capable of providing position estimates precise to the sub-milliarcsecond levels needed for high-precision timing. In order to make VLBI astrometric parameters useful in pulsar timing models, the transformation between the International Celestial Reference Frame (ICRF) and the dynamical solar system ephemeris used for pulsar timing must be constrained to within a few microarcseconds. We compute a transformation between the ICRF and pulsar timing frames and quantitatively discuss how the transformation will improve in coming years. We find that incorporating VLBI astrometry into the timing models of pulsars for which only a couple of years of timing data exist will lead to more realistic assessments of red spin noise and could enhance the amplitude of gravitational wave signatures in post-fit timing residuals by factors of 20 or more.
Cho, Y.; Chang, C.-C.; Wang, L. V.; Zou, J.
2016-02-01
This paper reports the development of a new 16-channel parallel acoustic delay line (PADL) array for real-time photoacoustic tomography (PAT). The PADLs were directly fabricated from single-crystalline silicon substrates using deep reactive ion etching. Compared with other acoustic delay lines (e.g., optical fibers), the micromachined silicon PADLs offer higher acoustic transmission efficiency, smaller form factor, easier assembly, and mass production capability. To demonstrate its real-time photoacoustic imaging capability, the silicon PADL array was interfaced with one single-element ultrasonic transducer followed by one channel of data acquisition electronics to receive 16 channels of photoacoustic signals simultaneously. A PAT image of an optically-absorbing target embedded in an optically-scattering phantom was reconstructed, which matched well with the actual size of the imaged target. Because the silicon PADL array allows a signal-to-channel reduction ratio of 16:1, it could significantly simplify the design and construction of ultrasonic receivers for real-time PAT.
Cho, Y; Chang, C-C; Zou, J; Wang, L V
2016-01-01
This paper reports the development of a new 16-channel parallel acoustic delay line (PADL) array for real-time photoacoustic tomography (PAT). The PADLs were directly fabricated from single-crystalline silicon substrates using deep reactive ion etching. Compared with other acoustic delay lines (e.g., optical fibers), the micromachined silicon PADLs offer higher acoustic transmission efficiency, smaller form factor, easier assembly, and mass production capability. To demonstrate its real-time photoacoustic imaging capability, the silicon PADL array was interfaced with one single-element ultrasonic transducer followed by one channel of data acquisition electronics to receive 16 channels of photoacoustic signals simultaneously. A PAT image of an optically-absorbing target embedded in an optically-scattering phantom was reconstructed, which matched well with the actual size of the imaged target. Because the silicon PADL array allows a signal-to-channel reduction ratio of 16:1, it could significantly simplify the design and construction of ultrasonic receivers for real-time PAT. (paper)
On avian influenza epidemic models with time delay.
Liu, Sanhong; Ruan, Shigui; Zhang, Xinan
2015-12-01
After the outbreak of the first avian influenza A virus (H5N1) in Hong Kong in 1997, another avian influenza A virus (H7N9) crossed the species barrier in mainland China in 2013 and 2014 and caused more than 400 human cases with a death rate of nearly 40%. In this paper, we take account of the incubation periods of avian influenza A virus and construct a bird-to-human transmission model with different time delays in the avian and human populations combining the survival probability of the infective avian and human populations at the latent time. By analyzing the dynamical behavior of the model, we obtain a threshold value for the prevalence of avian influenza and investigate local and global asymptotical stability of equilibria of the system.
Bounds and enhancements for negative scattering time delays
Muga, J.G.; Egusquiza, I.L.; Damborenea, J.A.; Delgado, F.
2002-01-01
The time of passage of the transmitted wave packet in a tunneling collision of a quantum particle with a square potential barrier becomes independent of the barrier width in a range of barrier thickness. This is the Hartman effect, which has been frequently associated with 'superluminality'. A fundamental limitation on the effect is set by nonrelativistic 'causality conditions'. We demonstrate first that the causality conditions impose more restrictive bounds on the negative time delays (time advancements) when no bound states are present. These restrictive bounds are in agreement with a naive, and generally false, causality argument based on the positivity of the 'extrapolated phase time', one of the quantities proposed to characterize the duration of the barrier's traversal. Nevertheless, square wells may in fact lead to much larger advancements than square barriers. We point out that close to the thresholds of new bound states, the time advancement increases considerably, while, at the same time, the transmission probability is large, which facilitates the possible observation of the enhanced time advancement
Delay 25 an ASIC for timing adjustment in LHC
Furtado, H.; Schrader, J.H.R.; Marchioro, A.; Moreira, P.
A five channel programmable delay line ASIC was designed featuring 4 channels that allow to phase delay periodic or non-periodic digital signals and a master channel that can be used to phase delay a clock signal. The master channel serves as a calibration reference guaranteeing independence from
Liu Yuan; Du Zhihui; Chung, Shin Kee; Hooper, Shaun; Blair, David; Wen Linqing
2012-01-01
We present a graphics processing unit (GPU)-accelerated time-domain low-latency algorithm to search for gravitational waves (GWs) from coalescing binaries of compact objects based on the summed parallel infinite impulse response (SPIIR) filtering technique. The aim is to facilitate fast detection of GWs with a minimum delay to allow prompt electromagnetic follow-up observations. To maximize the GPU acceleration, we apply an efficient batched parallel computing model that significantly reduces the number of synchronizations in SPIIR and optimizes the usage of the memory and hardware resource. Our code is tested on the CUDA ‘Fermi’ architecture in a GTX 480 graphics card and its performance is compared with a single core of Intel Core i7 920 (2.67 GHz). A 58-fold speedup is achieved while giving results in close agreement with the CPU implementation. Our result indicates that it is possible to conduct a full search for GWs from compact binary coalescence in real time with only one desktop computer equipped with a Fermi GPU card for the initial LIGO detectors which in the past required more than 100 CPUs. (paper)
Relativistic theory of gravitation and new notions of space-time
Logunov, A.A.
1986-01-01
The principal insurmountable difficulties of the general theory of relativity, which make one reject GRT are briefly summarised. Relativistic theory of graviton (RTG) and its principles are presented. RTG has not these difficulties and explains the whole of the observed and experimental data, besides it predicts new notions about the evolution of the Universe and gravitational collapse. RTG is a further development of the ideas put forward by Poincare, Minkovski, Einstein and Hilbert. It delivers a blow at dogmatism, and so deeply penetrating into GRT. Indeed, much time and afforts are needed to make this dogmatism the property of history
Mathematical model of tuberculosis epidemic with recovery time delay
Iskandar, Taufiq; Chaniago, Natasya Ayuningtia; Munzir, Said; Halfiani, Vera; Ramli, Marwan
2017-12-01
Tuberculosis (TB) is a contagious disease which can cause death. The disease is caused by Mycobacterium Tuberculosis which generally affects lungs and other organs such as lymph gland, intestine, kidneys, uterus, bone, and brain. The spread of TB occurs through the bacteria-contaminated air which is inhaled into the lungs. The symptoms of the TB patients are cough, chest pain, shortness of breath, appetite lose, weight lose, fever, cold, and fatigue. World Health Organization (WHO) reported that Indonesia placed the second in term of the most TB cases after India which has 23 % cases while China is reported to have 10 % cases in global. TB has become one of the greatest death threats in global. One way to countermeasure TB disease is by administering vaccination. However, a medication is needed when one has already infected. The medication can generally take 6 months of time which consists of two phases, inpatient and outpatient. Mathematical models to analyze the spread of TB have been widely developed. One of them is the SEIR type model. In this model the population is divided into four groups, which are suspectible (S), exposed (S), infected (I), recovered (R). In fact, a TB patient needs to undergo medication with a period of time in order to recover. This article discusses a model of TB spread with considering the term of recovery (time delay). The model is developed in SIR type where the population is divided into three groups, suspectible (S), infected (I), and recovered (R). Here, the vaccine is given to the susceptible group and the time delay is considered in the group undergoing the medication.
Bondi, H.
1979-01-01
In spite of the strength of gravitational focres between celestial bodies, gravitational capture is not a simple concept. The principles of conservation of linear momentum and of conservation of angular momentum, always impose severe constraints, while conservation of energy and the vital distinction between dissipative and non-dissipative systems allows one to rule out capture in a wide variety of cases. In complex systems especially those without dissipation, long dwell time is a more significant concept than permanent capture. (author)
Real-Time Tropospheric Delay Estimation using IGS Products
Stürze, Andrea; Liu, Sha; Söhne, Wolfgang
2014-05-01
The Federal Agency for Cartography and Geodesy (BKG) routinely provides zenith tropospheric delay (ZTD) parameter for the assimilation in numerical weather models since more than 10 years. Up to now the results flowing into the EUREF Permanent Network (EPN) or E-GVAP (EUMETNET EIG GNSS water vapour programme) analysis are based on batch processing of GPS+GLONASS observations in differential network mode. For the recently started COST Action ES1206 about "Advanced Global Navigation Satellite Systems tropospheric products for monitoring severe weather events and climate" (GNSS4SWEC), however, rapid updates in the analysis of the atmospheric state for nowcasting applications require changing the processing strategy towards real-time. In the RTCM SC104 (Radio Technical Commission for Maritime Services, Special Committee 104) a format combining the advantages of Precise Point Positioning (PPP) and Real-Time Kinematic (RTK) is under development. The so-called State Space Representation approach is defining corrections, which will be transferred in real-time to the user e.g. via NTRIP (Network Transport of RTCM via Internet Protocol). Meanwhile messages for precise orbits, satellite clocks and code biases compatible to the basic PPP mode using IGS products are defined. Consequently, the IGS Real-Time Service (RTS) was launched in 2013 in order to extend the well-known precise orbit and clock products by a real-time component. Further messages e.g. with respect to ionosphere or phase biases are foreseen. Depending on the level of refinement, so different accuracies up to the RTK level shall be reachable. In co-operation of BKG and the Technical University of Darmstadt the real-time software GEMon (GREF EUREF Monitoring) is under development. GEMon is able to process GPS and GLONASS observation and RTS product data streams in PPP mode. Furthermore, several state-of-the-art troposphere models, for example based on numerical weather prediction data, are implemented. Hence, it
Finite-time stability of neutral-type neural networks with random time-varying delays
Ali, M. Syed; Saravanan, S.; Zhu, Quanxin
2017-11-01
This paper is devoted to the finite-time stability analysis of neutral-type neural networks with random time-varying delays. The randomly time-varying delays are characterised by Bernoulli stochastic variable. This result can be extended to analysis and design for neutral-type neural networks with random time-varying delays. On the basis of this paper, we constructed suitable Lyapunov-Krasovskii functional together and established a set of sufficient linear matrix inequalities approach to guarantee the finite-time stability of the system concerned. By employing the Jensen's inequality, free-weighting matrix method and Wirtinger's double integral inequality, the proposed conditions are derived and two numerical examples are addressed for the effectiveness of the developed techniques.
Time of flight and range of the motion of a projectile in a constant gravitational field
P. A. Karkantzakos
2009-01-01
Full Text Available In this paper we study the classical problem of the motion of a projectile in a constant gravitational field under the influenceof a retarding force proportional to the velocity. Specifically, we express the time of flight, the time of fall and the range ofthe motion as a function of the constant of resistance per unit mass of the projectile. We also prove that the time of fall isgreater than the time of rise with the exception of the case of zero constant of resistance where we have equality. Finally weprove a formula from which we can compute the constant of resistance per unit mass of the projectile from time of flight andrange of the motion when the acceleration due to gravity and the initial velocity of the projectile are known.
Gauge theories, time-dependence of the gravitational constant and antigravity in the early universe
Linde, A.D.
1980-01-01
It is shown that the interaction of the gravitational field with matter leads to a strong modification of the effective gravitational constant in the early universe. In certain cases this leads even to the change of sign of the gravitational constant, i.e. to antigravity in the early universe. (orig.)
Modelling biochemical networks with intrinsic time delays: a hybrid semi-parametric approach
Oliveira Rui
2010-09-01
Full Text Available Abstract Background This paper presents a method for modelling dynamical biochemical networks with intrinsic time delays. Since the fundamental mechanisms leading to such delays are many times unknown, non conventional modelling approaches become necessary. Herein, a hybrid semi-parametric identification methodology is proposed in which discrete time series are incorporated into fundamental material balance models. This integration results in hybrid delay differential equations which can be applied to identify unknown cellular dynamics. Results The proposed hybrid modelling methodology was evaluated using two case studies. The first of these deals with dynamic modelling of transcriptional factor A in mammalian cells. The protein transport from the cytosol to the nucleus introduced a delay that was accounted for by discrete time series formulation. The second case study focused on a simple network with distributed time delays that demonstrated that the discrete time delay formalism has broad applicability to both discrete and distributed delay problems. Conclusions Significantly better prediction qualities of the novel hybrid model were obtained when compared to dynamical structures without time delays, being the more distinctive the more significant the underlying system delay is. The identification of the system delays by studies of different discrete modelling delays was enabled by the proposed structure. Further, it was shown that the hybrid discrete delay methodology is not limited to discrete delay systems. The proposed method is a powerful tool to identify time delays in ill-defined biochemical networks.
Grigoryeva, Lyudmila; Henriques, Julie; Larger, Laurent; Ortega, Juan-Pablo
2014-07-01
Reservoir computing is a recently introduced machine learning paradigm that has already shown excellent performances in the processing of empirical data. We study a particular kind of reservoir computers called time-delay reservoirs that are constructed out of the sampling of the solution of a time-delay differential equation and show their good performance in the forecasting of the conditional covariances associated to multivariate discrete-time nonlinear stochastic processes of VEC-GARCH type as well as in the prediction of factual daily market realized volatilities computed with intraday quotes, using as training input daily log-return series of moderate size. We tackle some problems associated to the lack of task-universality for individually operating reservoirs and propose a solution based on the use of parallel arrays of time-delay reservoirs. Copyright © 2014 Elsevier Ltd. All rights reserved.
Time delay between cardiac and brain activity during sleep transitions
Long, Xi; Arends, Johan B.; Aarts, Ronald M.; Haakma, Reinder; Fonseca, Pedro; Rolink, Jérôme
2015-04-01
Human sleep consists of wake, rapid-eye-movement (REM) sleep, and non-REM (NREM) sleep that includes light and deep sleep stages. This work investigated the time delay between changes of cardiac and brain activity for sleep transitions. Here, the brain activity was quantified by electroencephalographic (EEG) mean frequency and the cardiac parameters included heart rate, standard deviation of heartbeat intervals, and their low- and high-frequency spectral powers. Using a cross-correlation analysis, we found that the cardiac variations during wake-sleep and NREM sleep transitions preceded the EEG changes by 1-3 min but this was not the case for REM sleep transitions. These important findings can be further used to predict the onset and ending of some sleep stages in an early manner.
Time delayed K sup + N reactions and exotic baryon resonances
Kelkar, N G; Khemchandani, K P
2003-01-01
Evidence and hints, from both the theoretical and experimental sides, of exotic baryon resonances with B = S, have been with us for the last 30 years. The poor status of the general acceptance of these Z* resonances is partly due to the prejudice against penta-quark baryons and partly due to the opinion that a proof of the existence of exotic states must be rigorous. This can refer to the quality and amount of data gathered, and also to the analytical methods applied in the study of these resonances. It then seems mandatory that all possibilities and aspects be exploited. We do that by analysing the time delay in K sup + N scattering, encountering clear signals of the exotic Z* resonances close to the pole values found in partial wave analyses.
Finite time synchronization of memristor-based Cohen-Grossberg neural networks with mixed delays
Chen, Chuan; Li, Lixiang; Peng, Haipeng; Yang, Yixian
2017-01-01
Finite time synchronization, which means synchronization can be achieved in a settling time, is desirable in some practical applications. However, most of the published results on finite time synchronization don't include delays or only include discrete delays. In view of the fact that distributed delays inevitably exist in neural networks, this paper aims to investigate the finite time synchronization of memristor-based Cohen-Grossberg neural networks (MCGNNs) with both discrete delay and di...
Xing Yin
2011-01-01
uncertain periodic switched recurrent neural networks with time-varying delays. When uncertain discrete-time recurrent neural network is a periodic system, it is expressed as switched neural network for the finite switching state. Based on the switched quadratic Lyapunov functional approach (SQLF and free-weighting matrix approach (FWM, some linear matrix inequality criteria are found to guarantee the delay-dependent asymptotical stability of these systems. Two examples illustrate the exactness of the proposed criteria.
Xiaoyu Su
2014-01-01
Full Text Available Aiming at the economy and security of the positioning system in semi-submersible platform, the paper presents a new scheme based on the mooring line switching strategy. Considering the input delay in switching process, H∞ control with time-varying input delay is designed to calculate the control forces to resist disturbing forces. In order to reduce the conservativeness, the information of the lower bound of delay is taken into account, and a Lyapunov function which contains the range of delay is constructed. Besides, the input constraint is considered to avoid breakage of mooring lines. The sufficient conditions for delay-range-dependent stabilization are derived in terms of LMI, and the controller is also obtained. The effectiveness of the proposed approach is illustrated by a realistic design example.
Frank, T.D.
2006-01-01
First-order approximations of time-dependent solutions are determined for stochastic systems perturbed by time-delayed feedback forces. To this end, the theory of delay Fokker-Planck equations is applied in combination with Bayes' theorem. Applications to a time-delayed Ornstein-Uhlenbeck process and the geometric Brownian walk of financial physics are discussed
Gravitational-Wave Tests of General Relativity with Ground-Based Detectors and Pulsar-Timing Arrays
Nicolás Yunes
2013-11-01
Full Text Available This review is focused on tests of Einstein's theory of general relativity with gravitational waves that are detectable by ground-based interferometers and pulsar-timing experiments. Einstein’s theory has been greatly constrained in the quasi-linear, quasi-stationary regime, where gravity is weak and velocities are small. Gravitational waves will allow us to probe a complimentary, yet previously unexplored regime: the non-linear and dynamical strong-field regime. Such a regime is, for example, applicable to compact binaries coalescing, where characteristic velocities can reach fifty percent the speed of light and gravitational fields are large and dynamical. This review begins with the theoretical basis and the predicted gravitational-wave observables of modified gravity theories. The review continues with a brief description of the detectors, including both gravitational-wave interferometers and pulsar-timing arrays, leading to a discussion of the data analysis formalism that is applicable for such tests. The review ends with a discussion of gravitational-wave tests for compact binary systems.
Gravitational-Wave Tests of General Relativity with Ground-Based Detectors and Pulsar-Timing Arrays.
Yunes, Nicolás; Siemens, Xavier
2013-01-01
This review is focused on tests of Einstein's theory of general relativity with gravitational waves that are detectable by ground-based interferometers and pulsar-timing experiments. Einstein's theory has been greatly constrained in the quasi-linear, quasi-stationary regime, where gravity is weak and velocities are small. Gravitational waves will allow us to probe a complimentary, yet previously unexplored regime: the non-linear and dynamical strong-field regime . Such a regime is, for example, applicable to compact binaries coalescing, where characteristic velocities can reach fifty percent the speed of light and gravitational fields are large and dynamical. This review begins with the theoretical basis and the predicted gravitational-wave observables of modified gravity theories. The review continues with a brief description of the detectors, including both gravitational-wave interferometers and pulsar-timing arrays, leading to a discussion of the data analysis formalism that is applicable for such tests. The review ends with a discussion of gravitational-wave tests for compact binary systems.
Discrete-time recurrent neural networks with time-varying delays: Exponential stability analysis
Liu, Yurong; Wang, Zidong; Serrano, Alan; Liu, Xiaohui
2007-01-01
This Letter is concerned with the analysis problem of exponential stability for a class of discrete-time recurrent neural networks (DRNNs) with time delays. The delay is of the time-varying nature, and the activation functions are assumed to be neither differentiable nor strict monotonic. Furthermore, the description of the activation functions is more general than the recently commonly used Lipschitz conditions. Under such mild conditions, we first prove the existence of the equilibrium point. Then, by employing a Lyapunov-Krasovskii functional, a unified linear matrix inequality (LMI) approach is developed to establish sufficient conditions for the DRNNs to be globally exponentially stable. It is shown that the delayed DRNNs are globally exponentially stable if a certain LMI is solvable, where the feasibility of such an LMI can be easily checked by using the numerically efficient Matlab LMI Toolbox. A simulation example is presented to show the usefulness of the derived LMI-based stability condition
Adaptive control of chaotic continuous-time systems with delay
Tian, Yu-Chu; Gao, Furong
1998-06-01
A simple delay system governed by a first-order differential-delay equation may behave chaotically, but the conditions for the system to have such behaviors have not been well recognized. In this paper, a set of rules is postulated first for the conditions for the delay system to display chaos. A model-reference adaptive control scheme is then proposed to control the chaotic system state to converge to an arbitrarily given reference trajectory with certain and uncertain system parameters. Numerical examples are given to analyze the chaotic behaviors of the delay system and to demonstrate the effectiveness of the proposed adaptive control scheme.
Finite-Time Attractivity for Diagonally Dominant Systems with Off-Diagonal Delays
T. S. Doan
2012-01-01
Full Text Available We introduce a notion of attractivity for delay equations which are defined on bounded time intervals. Our main result shows that linear delay equations are finite-time attractive, provided that the delay is only in the coupling terms between different components, and the system is diagonally dominant. We apply this result to a nonlinear Lotka-Volterra system and show that the delay is harmless and does not destroy finite-time attractivity.
The relaxation time of processes in a FitzHugh-Nagumo neural system with time delay
Gong Ailing; Zeng Chunhua; Wang Hua
2011-01-01
In this paper, we study the relaxation time (RT) of the steady-state correlation function in a FitzHugh-Nagumo neural system under the presence of multiplicative and additive white noises and time delay. The noise correlation parameter λ can produce a critical behavior in the RT as functions of the multiplicative noise intensity D, the additive noise intensity Q and the time delay τ. That is, the RT decreases as the noise intensities D and Q increase, and increases as the time delay τ increases below the critical value of λ. However, above the critical value, the RT first increases, reaches a maximum, and then decreases as D, Q and τ increase, i.e. a noise intensity D or Q and a time delay τ exist, at which the time scales of the relaxation process are at their largest. In addition, the additive noise intensity Q can also produce a critical behavior in the RT as a function of λ. The noise correlation parameter λ first increases the RT of processes, then decreases it below the critical value of Q. Above the critical value, λ increases it.
New delay-dependent absolute stability criteria for Lur'e systems with time-varying delay
Chen, Yonggang; Bi, Weiping; Li, Wenlin
2011-07-01
In this article, the absolute stability problem is investigated for Lur'e systems with time-varying delay and sector-bounded nonlinearity. By employing the delay fractioning idea, the new augmented Lyapunov functional is first constructed. Then, by introducing some slack matrices and by reserving the useful term when estimating the upper bound of the derivative of Lyapunov functional, the new delay-dependent absolute stability criteria are derived in terms of linear matrix inequalities. Several numerical examples are presented to show the effectiveness and the less conservativeness of the proposed method.
George, Daniel; Huerta, E. A.
2018-03-01
The recent Nobel-prize-winning detections of gravitational waves from merging black holes and the subsequent detection of the collision of two neutron stars in coincidence with electromagnetic observations have inaugurated a new era of multimessenger astrophysics. To enhance the scope of this emergent field of science, we pioneered the use of deep learning with convolutional neural networks, that take time-series inputs, for rapid detection and characterization of gravitational wave signals. This approach, Deep Filtering, was initially demonstrated using simulated LIGO noise. In this article, we present the extension of Deep Filtering using real data from LIGO, for both detection and parameter estimation of gravitational waves from binary black hole mergers using continuous data streams from multiple LIGO detectors. We demonstrate for the first time that machine learning can detect and estimate the true parameters of real events observed by LIGO. Our results show that Deep Filtering achieves similar sensitivities and lower errors compared to matched-filtering while being far more computationally efficient and more resilient to glitches, allowing real-time processing of weak time-series signals in non-stationary non-Gaussian noise with minimal resources, and also enables the detection of new classes of gravitational wave sources that may go unnoticed with existing detection algorithms. This unified framework for data analysis is ideally suited to enable coincident detection campaigns of gravitational waves and their multimessenger counterparts in real-time.
Delay-Dependent Guaranteed Cost H∞ Control of an Interval System with Interval Time-Varying Delay
Zhongke Shi
2009-01-01
Full Text Available This paper concerns the problem of the delay-dependent robust stability and guaranteed cost H∞ control for an interval system with time-varying delay. The interval system with matrix factorization is provided and leads to less conservative conclusions than solving a square root. The time-varying delay is assumed to belong to an interval and the derivative of the interval time-varying delay is not a restriction, which allows a fast time-varying delay; also its applicability is broad. Based on the Lyapunov-Ktasovskii approach, a delay-dependent criterion for the existence of a state feedback controller, which guarantees the closed-loop system stability, the upper bound of cost function, and disturbance attenuation lever for all admissible uncertainties as well as out perturbation, is proposed in terms of linear matrix inequalities (LMIs. The criterion is derived by free weighting matrices that can reduce the conservatism. The effectiveness has been verified in a number example and the compute results are presented to validate the proposed design method.
Effect of Time Delay on Recognition Memory for Pictures: The Modulatory Role of Emotion
Wang, Bo
2014-01-01
This study investigated the modulatory role of emotion in the effect of time delay on recognition memory for pictures. Participants viewed neutral, positive and negative pictures, and took a recognition memory test 5 minutes, 24 hours, or 1 week after learning. The findings are: 1) For neutral, positive and negative pictures, overall recognition accuracy in the 5-min delay did not significantly differ from that in the 24-h delay. For neutral and positive pictures, overall recognition accuracy in the 1-week delay was lower than in the 24-h delay; for negative pictures, overall recognition in the 24-h and 1-week delay did not significantly differ. Therefore negative emotion modulates the effect of time delay on recognition memory, maintaining retention of overall recognition accuracy only within a certain frame of time. 2) For the three types of pictures, recollection and familiarity in the 5-min delay did not significantly differ from that in the 24-h and the 1-week delay. Thus emotion does not appear to modulate the effect of time delay on recollection and familiarity. However, recollection in the 24-h delay was higher than in the 1-week delay, whereas familiarity in the 24-h delay was lower than in the 1-week delay. PMID:24971457
Siegel, Mark G
2018-06-01
There continues to be controversy over the timing of anterior cruciate ligament (ACL) surgery. Early or delayed intervention after ACL injury is a topic that has not been settled. The issue is whether ACL tears should have surgery performed in an expedient manner. Or is delay an option with no repercussions to the health of the knee? My associates in nonsurgical specialties wave the New England Journal of Medicine to support their view that surgery is not needed. I routinely espouse the literature confirming that delay of surgery may cause future damage. It is now established that a failure to intervene in a timely manner does cause additional damage. I stand vindicated and can affirm to my colleagues that I have found the answer. There is no longer any doubt or equivocation. Delay in reconstructing an unstable knee does cause damage. Copyright © 2018 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.
Minghui Yu
2017-01-01
Full Text Available The global exponential antisynchronization in mean square of memristive neural networks with stochastic perturbation and mixed time-varying delays is studied in this paper. Then, two kinds of novel delay-dependent and delay-independent adaptive controllers are designed. With the ability of adapting to environment changes, the proposed controllers can modify their behaviors to achieve the best performance. In particular, on the basis of the differential inclusions theory, inequality theory, and stochastic analysis techniques, several sufficient conditions are obtained to guarantee the exponential antisynchronization between the drive system and response system. Furthermore, two numerical simulation examples are provided to the validity of the derived criteria.
Basini, G.
2003-01-01
Asymptotic freedom, as a natural result of a theory based on a general approach, derived by a new interpretation of phenomena like the EPR paradox, the black-hole formation and the absence of primary cosmic antimatter is presented. In this approach, conservation laws are considered always and absolutely valid, leading to the possibility of topology changes, and recovering the mutual influence between fundamental forces. Moreover, a new consideration of time arrows leads to asymptotic freedom as a necessary consequence. In fact, asymptotic freedom of strong interactions seems to be a feature common also to gravitational interaction, if induced-gravity theories (t → ∞) are taken into account and a symmetric-time dynamics is recovered in the light of a general conservation principle. (authors)
Basini, G. [Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati; Capozziello, S. [E.R. Caianiello, Dipt. di Fisica, Roma (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Universita di Salerno, Boronissi, SA (Italy)
2003-09-01
Asymptotic freedom, as a natural result of a theory based on a general approach, derived by a new interpretation of phenomena like the EPR paradox, the black-hole formation and the absence of primary cosmic antimatter is presented. In this approach, conservation laws are considered always and absolutely valid, leading to the possibility of topology changes, and recovering the mutual influence between fundamental forces. Moreover, a new consideration of time arrows leads to asymptotic freedom as a necessary consequence. In fact, asymptotic freedom of strong interactions seems to be a feature common also to gravitational interaction, if induced-gravity theories (t {yields} {infinity}) are taken into account and a symmetric-time dynamics is recovered in the light of a general conservation principle. (authors)
VME-Real-Time Data Acquisition for the Ultracryogenic Gravitational Antenna of the Third Generation
Mazzitelli, G. [Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati
1996-05-01
It is described a new design of the front-end electronics for the data acquisition of NAUTILUS, the first ultra cryogenic resonant gravitational wave detector, operating in the INFN National Laboratories of Frascati. The improved sensitivity of this kind of detector poses new requirements on the data acquisition, as more speed, amplitude and timing accuracy are needed. In this work it is discussed the result obtained with a new front-end configuration based on VME standard for a data acquisition rate of 5kHz (present rate 220 Hz). Is it also described the data acquisition system for the cosmic ray telescope assembled around NAUTILUS and the timing system of both the components.
GOTHIC: Gravitational oct-tree code accelerated by hierarchical time step controlling
Miki, Yohei; Umemura, Masayuki
2017-04-01
The tree method is a widely implemented algorithm for collisionless N-body simulations in astrophysics well suited for GPU(s). Adopting hierarchical time stepping can accelerate N-body simulations; however, it is infrequently implemented and its potential remains untested in GPU implementations. We have developed a Gravitational Oct-Tree code accelerated by HIerarchical time step Controlling named GOTHIC, which adopts both the tree method and the hierarchical time step. The code adopts some adaptive optimizations by monitoring the execution time of each function on-the-fly and minimizes the time-to-solution by balancing the measured time of multiple functions. Results of performance measurements with realistic particle distribution performed on NVIDIA Tesla M2090, K20X, and GeForce GTX TITAN X, which are representative GPUs of the Fermi, Kepler, and Maxwell generation of GPUs, show that the hierarchical time step achieves a speedup by a factor of around 3-5 times compared to the shared time step. The measured elapsed time per step of GOTHIC is 0.30 s or 0.44 s on GTX TITAN X when the particle distribution represents the Andromeda galaxy or the NFW sphere, respectively, with 224 = 16,777,216 particles. The averaged performance of the code corresponds to 10-30% of the theoretical single precision peak performance of the GPU.
Park, Ju H.; Kwon, O. M.
In the letter, the global asymptotic stability of bidirectional associative memory (BAM) neural networks with delays is investigated. The delay is assumed to be time-varying and belongs to a given interval. A novel stability criterion for the stability is presented based on the Lyapunov method. The criterion is represented in terms of linear matrix inequality (LMI), which can be solved easily by various optimization algorithms. Two numerical examples are illustrated to show the effectiveness of our new result.
Steady State Analysis of Stochastic Systems with Multiple Time Delays
Xu, W.; Sun, C. Y.; Zhang, H. Q.
In this paper, attention is focused on the steady state analysis of a class of nonlinear dynamic systems with multi-delayed feedbacks driven by multiplicative correlated Gaussian white noises. The Fokker-Planck equations for delayed variables are at first derived by Novikov's theorem. Then, under small delay assumption, the approximate stationary solutions are obtained by the probability density approach. As a special case, the effects of multidelay feedbacks and the correlated additive and multiplicative Gaussian white noises on the response of a bistable system are considered. It is shown that the obtained analytical results are in good agreement with experimental results in Monte Carlo simulations.
Finite time synchronization of memristor-based Cohen-Grossberg neural networks with mixed delays
2017-01-01
Finite time synchronization, which means synchronization can be achieved in a settling time, is desirable in some practical applications. However, most of the published results on finite time synchronization don’t include delays or only include discrete delays. In view of the fact that distributed delays inevitably exist in neural networks, this paper aims to investigate the finite time synchronization of memristor-based Cohen-Grossberg neural networks (MCGNNs) with both discrete delay and distributed delay (mixed delays). By means of a simple feedback controller and novel finite time synchronization analysis methods, several new criteria are derived to ensure the finite time synchronization of MCGNNs with mixed delays. The obtained criteria are very concise and easy to verify. Numerical simulations are presented to demonstrate the effectiveness of our theoretical results. PMID:28931066
Finite time synchronization of memristor-based Cohen-Grossberg neural networks with mixed delays.
Chen, Chuan; Li, Lixiang; Peng, Haipeng; Yang, Yixian
2017-01-01
Finite time synchronization, which means synchronization can be achieved in a settling time, is desirable in some practical applications. However, most of the published results on finite time synchronization don't include delays or only include discrete delays. In view of the fact that distributed delays inevitably exist in neural networks, this paper aims to investigate the finite time synchronization of memristor-based Cohen-Grossberg neural networks (MCGNNs) with both discrete delay and distributed delay (mixed delays). By means of a simple feedback controller and novel finite time synchronization analysis methods, several new criteria are derived to ensure the finite time synchronization of MCGNNs with mixed delays. The obtained criteria are very concise and easy to verify. Numerical simulations are presented to demonstrate the effectiveness of our theoretical results.
Finite time synchronization of memristor-based Cohen-Grossberg neural networks with mixed delays.
Chuan Chen
Full Text Available Finite time synchronization, which means synchronization can be achieved in a settling time, is desirable in some practical applications. However, most of the published results on finite time synchronization don't include delays or only include discrete delays. In view of the fact that distributed delays inevitably exist in neural networks, this paper aims to investigate the finite time synchronization of memristor-based Cohen-Grossberg neural networks (MCGNNs with both discrete delay and distributed delay (mixed delays. By means of a simple feedback controller and novel finite time synchronization analysis methods, several new criteria are derived to ensure the finite time synchronization of MCGNNs with mixed delays. The obtained criteria are very concise and easy to verify. Numerical simulations are presented to demonstrate the effectiveness of our theoretical results.
Hamid Reza Karimi
2009-01-01
Full Text Available The problem of stability analysis for a class of neutral systems with mixed time-varying neutral, discrete and distributed delays and nonlinear parameter perturbations is addressed. By introducing a novel Lyapunov-Krasovskii functional and combining the descriptor model transformation, the Leibniz-Newton formula, some free-weighting matrices, and a suitable change of variables, new sufficient conditions are established for the stability of the considered system, which are neutral-delay-dependent, discrete-delay-range-dependent, and distributed-delay-dependent. The conditions are presented in terms of linear matrix inequalities (LMIs and can be efficiently solved using convex programming techniques. Two numerical examples are given to illustrate the efficiency of the proposed method.
Comment on 'Late-time tails of a self-gravitating massless scalar field revisited'
Szpak, Nikodem
2009-01-01
Bizon et al (2009 Class. Quantum Grav. 26 175006) discuss the power-law tail in the long-time evolution of a spherically symmetric self-gravitating massless scalar field in odd spatial dimensions. They derive explicit expressions for the leading-order asymptotics for solutions with small initial data by using formal series expansions. Unfortunately, this approach misses an interesting observation that the actual decay rate is a product of asymptotic cancellations occurring due to a special structure of the nonlinear terms. Here, we show that one can calculate the leading asymptotics more directly by recognizing the special structure and cancellations already on the level of the wave equation. (comments and replies)
General exact solution for homogeneous time-dependent self-gravitating perfect fluids
Gaete, P.; Hojman, R.
1988-01-01
A procedure to obtain the general exact solution of Einstein equations for a self-gravitating spherically-symmetric static perfect fluid obeying an arbitrary equation of state, is applied to time-dependent Kantowsky-Sachs line elements (with spherical, planar and hyperbolic symmetry). As in the static case, the solution is generated by an arbitrary function of the independent variable and its first derivative. To illustrate the results, the whole family of (plane-symmetric) solutions with a ''gamma-law'' equation of state is explicity obtained in terms of simple known functions. It is also shown that, while in the static plane-symmtric line elements, every metric is in one to one correspondence with a ''partner-metric'' (both originated from the same generatrix function), in this case every generatrix function univocally determines one metric. (author) [pt
Suyu, S. H.; Marshall, P. J.; Auger, M. W.; Hilbert, S.; Blandford, R. D.; Koopmans, L. V. E.; Fassnacht, C. D.; Treu, T.
2010-01-01
Strong gravitational lens systems with measured time delays between the multiple images provide a method for measuring the "time-delay distance" to the lens, and thus the Hubble constant. We present a Bayesian analysis of the strong gravitational lens system B1608+656, incorporating (1) new, deep
Generation of flat wideband chaos with suppressed time delay signature by using optical time lens.
Jiang, Ning; Wang, Chao; Xue, Chenpeng; Li, Guilan; Lin, Shuqing; Qiu, Kun
2017-06-26
We propose a flat wideband chaos generation scheme that shows excellent time delay signature suppression effect, by injecting the chaotic output of general external cavity semiconductor laser into an optical time lens module composed of a phase modulator and two dispersive units. The numerical results demonstrate that by properly setting the parameters of the driving signal of phase modulator and the accumulated dispersion of dispersive units, the relaxation oscillation in chaos can be eliminated, wideband chaos generation with an efficient bandwidth up to several tens of GHz can be achieved, and the RF spectrum of generated chaotic signal is nearly as flat as uniform distribution. Moreover, the periodicity of chaos induced by the external cavity modes can be simultaneously destructed by the optical time lens module, based on this the time delay signature can be completely suppressed.
Anticontrol of chaos in continuous-time systems via time-delay feedback.
Wang, Xiao Fan; Chen, Guanrong; Yu, Xinghuo
2000-12-01
In this paper, a systematic design approach based on time-delay feedback is developed for anticontrol of chaos in a continuous-time system. This anticontrol method can drive a finite-dimensional, continuous-time, autonomous system from nonchaotic to chaotic, and can also enhance the existing chaos of an originally chaotic system. Asymptotic analysis is used to establish an approximate relationship between a time-delay differential equation and a discrete map. Anticontrol of chaos is then accomplished based on this relationship and the differential-geometry control theory. Several examples are given to verify the effectiveness of the methodology and to illustrate the systematic design procedure. (c) 2000 American Institute of Physics.
Roatta , Luca
2017-01-01
Assuming that space and time can only have discrete values, it is shown how deformed space and time cause gravitational attraction, whose law in a discrete context is slightly different from the Newtonian, but to it exactly coincident at large distance. This difference is directly connected to the existence of black holes, which result to have the structure of a hollow sphere.
Fundamental and Subharmonic Resonances of Harmonically Oscillation with Time Delay State Feedback
A.F. EL-Bassiouny
2006-01-01
Full Text Available Time delays occur in many physical systems. In particular, when automatic control is used with structural or mechanical systems, there exists a delay between measurement of the system state and corrective action. The concept of an equivalent damping related to the delay feedback is proposed and the appropriate choice of the feedback gains and the time delay is discussed from the viewpoint of vibration control. We investigate the fundamental resonance and subharmonic resonance of order one-half of a harmonically oscillation under state feedback control with a time delay. By using the multiple scale perturbation technique, the first order approximation of the resonances are derived and the effect of time delay on the resonances is investigated. The fixed points correspond to a periodic motion for the starting system and we show the external excitation-response and frequency-response curves. We analyze the effect of time delay and the other different parameters on these oscillations.
Global dissipativity of continuous-time recurrent neural networks with time delay
Liao Xiaoxin; Wang Jun
2003-01-01
This paper addresses the global dissipativity of a general class of continuous-time recurrent neural networks. First, the concepts of global dissipation and global exponential dissipation are defined and elaborated. Next, the sets of global dissipativity and global exponentially dissipativity are characterized using the parameters of recurrent neural network models. In particular, it is shown that the Hopfield network and cellular neural networks with or without time delays are dissipative systems
Projective synchronization of time-varying delayed neural network with adaptive scaling factors
Ghosh, Dibakar; Banerjee, Santo
2013-01-01
Highlights: • Projective synchronization in coupled delayed neural chaotic systems with modulated delay time is introduced. • An adaptive rule for the scaling factors is introduced. • This scheme is highly applicable in secure communication. -- Abstract: In this work, the projective synchronization between two continuous time delayed neural systems with time varying delay is investigated. A sufficient condition for synchronization for the coupled systems with modulated delay is presented analytically with the help of the Krasovskii–Lyapunov approach. The effect of adaptive scaling factors on synchronization are also studied in details. Numerical simulations verify the effectiveness of the analytic results
Liang Jinling; Cao Jinde
2004-01-01
First, convergence of continuous-time Bidirectional Associative Memory (BAM) neural networks are studied. By using Lyapunov functionals and some analysis technique, the delay-independent sufficient conditions are obtained for the networks to converge exponentially toward the equilibrium associated with the constant input sources. Second, discrete-time analogues of the continuous-time BAM networks are formulated and studied. It is shown that the convergence characteristics of the continuous-time systems are preserved by the discrete-time analogues without any restriction imposed on the uniform discretionary step size. An illustrative example is given to demonstrate the effectiveness of the obtained results
Delay time in a single barrier for a movable quantum shutter
Hernandez, Alberto
2010-01-01
The transient solution and delay time for a δ potential scatterer with a movable quantum shutter is calculated by solving analytically the time-dependent Schroedinger equation. The delay time is analyzed as a function of the distance between the shutter and the potential barrier and also as a function of the distance between the potential barrier and the detector. In both cases, it is found that the delay time exhibits a dynamical behavior and that it tends to a saturation value Δt sat in the limit of very short distances, which represents the maximum delay produced by the potential barrier near the interaction region. The phase time τ θ , on the other hand, is not an appropriate time scale for measuring the time delay near the interaction region, except if the shutter is moved far away from the potential. The role played by the antibound state of the system on the behavior of the delay time is also discussed.
Is timing noise important in the gravitational wave detection of neutron stars?
Jones, D.I.
2004-01-01
In this paper we ask whether the phenomenon of timing noise long known in electromagnetic pulsar astronomy is likely to be important in gravitational wave (GW) observations of spinning-down neutron stars. We find that timing noise is strong enough to be of importance only in the young pulsars, which must have larger triaxialities than theory predicts for their GW emission to be detectable. However, assuming that their GW emission is detectable, we list the pulsars for which timing noise is important, either because it is strong enough that its neglect by the observer would render the source undetectable or else because it is a measurable feature of the GW signal. We also find that timing noise places a limit on the observation duration of a coherent blind GW search, and suggest that hierarchical search techniques might be able to cope with this problem. Demonstration of the presence or absence of timing noise in the GW channel would give a new probe of neutron star physics
A unified approach for impulsive lag synchronization of chaotic systems with time delay
Li Chuandong; Liao Xiaofeng; Zhang Rong
2005-01-01
In this paper, we propose a unified approach for impulsive lag-synchronization of a class of chaotic systems with time delay by employing the stability theory of impulsive delayed differential equations. Three well-known delayed chaotic systems are presented to illustrate our results. Also, the estimates of the stable regions for these systems are given, respectively
Finite-Time Stability of Large-Scale Systems with Interval Time-Varying Delay in Interconnection
T. La-inchua
2017-01-01
Full Text Available We investigate finite-time stability of a class of nonlinear large-scale systems with interval time-varying delays in interconnection. Time-delay functions are continuous but not necessarily differentiable. Based on Lyapunov stability theory and new integral bounding technique, finite-time stability of large-scale systems with interval time-varying delays in interconnection is derived. The finite-time stability criteria are delays-dependent and are given in terms of linear matrix inequalities which can be solved by various available algorithms. Numerical examples are given to illustrate effectiveness of the proposed method.
Incorporation of Time Delayed Measurements in a Discrete-time Kalman Filter
Larsen, Thomas Dall; Andersen, Nils Axel; Ravn, Ole
1998-01-01
In many practical systems there is a delay in some of the sensor devices, for instance vision measurements that may have a long processing time. How to fuse these measurements in a Kalman filter is not a trivial problem if the computational delay is critical. Depending on how much time...... using past and present estimates of the Kalman filter and calculating an optimal gain for this extrapolated measurement...... there is at hand, the designer has to make trade offs between optimality and computational burden of the filter. In this paper various methods in the literature along with a new method proposed by the authors will be presented and compared. The new method is based on “extrapolating” the measurement to present time...
Xu, Chang-Jin; Li, Pei-Luan; Pang, Yi-Cheng
2017-02-01
This paper is concerned with fractional-order bidirectional associative memory (BAM) neural networks with time delays. Applying Laplace transform, the generalized Gronwall inequality and estimates of Mittag-Leffler functions, some sufficient conditions which ensure the finite-time stability of fractional-order bidirectional associative memory neural networks with time delays are obtained. Two examples with their simulations are given to illustrate the theoretical findings. Our results are new and complement previously known results. Supported by National Natural Science Foundation of China under Grant Nos.~61673008, 11261010, 11101126, Project of High-Level Innovative Talents of Guizhou Province ([2016]5651), Natural Science and Technology Foundation of Guizhou Province (J[2015]2025 and J[2015]2026), 125 Special Major Science and Technology of Department of Education of Guizhou Province ([2012]011) and Natural Science Foundation of the Education Department of Guizhou Province (KY[2015]482)
Local Stability of AIDS Epidemic Model Through Treatment and Vertical Transmission with Time Delay
Novi W, Cascarilla; Lestari, Dwi
2016-02-01
This study aims to explain stability of the spread of AIDS through treatment and vertical transmission model. Human with HIV need a time to positively suffer AIDS. The existence of a time, human with HIV until positively suffer AIDS can be delayed for a time so that the model acquired is the model with time delay. The model form is a nonlinear differential equation with time delay, SIPTA (susceptible-infected-pre AIDS-treatment-AIDS). Based on SIPTA model analysis results the disease free equilibrium point and the endemic equilibrium point. The disease free equilibrium point with and without time delay are local asymptotically stable if the basic reproduction number is less than one. The endemic equilibrium point will be local asymptotically stable if the time delay is less than the critical value of delay, unstable if the time delay is more than the critical value of delay, and bifurcation occurs if the time delay is equal to the critical value of delay.
Stability Tests of Positive Fractional Continuous-time Linear Systems with Delays
Tadeusz Kaczorek
2013-06-01
Full Text Available Necessary and sufficient conditions for the asymptotic stability of positive fractional continuous-time linear systems with many delays are established. It is shown that: 1 the asymptotic stability of the positive fractional system is independent of their delays, 2 the checking of the asymptotic stability of the positive fractional systems with delays can be reduced to checking of the asymptotic stability of positive standard linear systems without delays.
Passivity of memristive BAM neural networks with leakage and additive time-varying delays
Wang, Weiping; Wang, Meiqi; Luo, Xiong; Li, Lixiang; Zhao, Wenbing; Liu, Linlin; Ping, Yuan
2018-02-01
This paper investigates the passivity of memristive bidirectional associate memory neural networks (MBAMNNs) with leakage and additive time-varying delays. Based on some useful inequalities and appropriate Lyapunov-Krasovskii functionals (LKFs), several delay-dependent conditions for passivity performance are obtained in linear matrix inequalities (LMIs). Moreover, the leakage delays as well as additive delays are considered separately. Finally, numerical simulations are provided to demonstrate the feasibility of the theoretical results.
Schäfer, G.; Schutz, B.
1996-01-01
Gravity is truly universal. It is the force that pulls us to the Earth, that keeps the planets and moons in their orbits, and that causes the tides on the Earth to ebb and flow. It even keeps the Sun shining. Yet on a laboratory scale gravity is extremely weak. The Coulomb force between two protons is 1039 times stronger than the gravitational force between them. Moreover, Newton's gravitational constant is the least accurately known of the fundamental constants: it has been measured to 1 par...
Langevin approach to synchronization of hyperchaotic time-delay dynamics
Budini, Adrian A [Consejo Nacional de Investigaciones CientIficas y Tecnicas, Centro Atomico Bariloche, Av. E Bustillo Km 9.5, (8400) Bariloche (Argentina); Consortium of the Americas for Interdisciplinary Science and Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States)
2008-11-07
In this paper, we characterize the synchronization phenomenon of hyperchaotic scalar nonlinear delay dynamics in a fully-developed chaos regime. Our results rely on the observation that, in that regime, the stationary statistical properties of a class of hyperchaotic attractors can be reproduced with a linear Langevin equation, defined by replacing the nonlinear delay force by a delta-correlated noise. Therefore, the synchronization phenomenon can be analytically characterized by a set of coupled Langevin equations. We apply this formalism to study anticipated synchronization dynamics subject to external noise fluctuations as well as for characterizing the effects of parameter mismatch in a hyperchaotic communication scheme. The same procedure is applied to second-order differential delay equations associated with synchronization in electro-optical devices. In all cases, the departure with respect to perfect synchronization is measured through a similarity function. Numerical simulations in discrete maps associated with the hyperchaotic dynamics support the formalism.
QUIPS: Time-dependent properties of quasi-invariant self-gravitating polytropes
Munier, A.; Feix, M.R.
1983-01-01
Quasi-invariance, a method based on group tranformations, is used to obtain time-dependent solutions for the expansion and/or contraction of a self-gravitating sphere of perfect gas with polytopic index n. Quasi-invariance transforms the equations of hydrodynamics into ''dual equations'' exhibiting extra terms such as a friction, a mass source or sink term, and a centripetal/centrifugal force. The search for stationary solutions in this ''dual space'' leads to a new class of time-dependent solutions, the QUIP (for Quasi-invariant polytrope), which generalizes Emden's static model and introduces a characteristic frequency a related to Jean's frequency. The second order differential equation describing the solution is integrated numerically. A critical point is seen always to exist for nnot =3. Solutions corresponding in the ''dual space'' to a time-dependent generalization of Eddington's standard model (n = 3) are discussed. These solutions conserve both the total mass and the energy. A transition between closed and open structures is seen to take place at a particular frequency a/sub c/. For n = 3, no critical point arises in the ''dual space'' due to the self-similar motion of the fluid. A new time-dependent mass-radius relation and a generalized Betti-Ritter relation are obtained. Conclusions about the existence of a minimum Q-factor are presented
Regenerative memory in time-delayed neuromorphic photonic resonators
Romeira, B.; Avó, R.; Figueiredo, José M. L.; Barland, S.; Javaloyes, J.
2016-01-01
We investigate a photonic regenerative memory based upon a neuromorphic oscillator with a delayed self-feedback (autaptic) connection. We disclose the existence of a unique temporal response characteristic of localized structures enabling an ideal support for bits in an optical buffer memory for storage and reshaping of data information. We link our experimental implementation, based upon a nanoscale nonlinear resonant tunneling diode driving a laser, to the paradigm of neuronal activity, the FitzHugh-Nagumo model with delayed feedback. This proof-of-concept photonic regenerative memory might constitute a building block for a new class of neuron-inspired photonic memories that can handle high bit-rate optical signals.
Exponential stability of fuzzy cellular neural networks with constant and time-varying delays
Liu Yanqing; Tang Wansheng
2004-01-01
In this Letter, the global stability of delayed fuzzy cellular neural networks (FCNN) with either constant delays or time varying delays is proposed. Firstly, we give the existence and uniqueness of the equilibrium point by using the theory of topological degree and the properties of nonsingular M-matrix and the sufficient conditions for ascertaining the global exponential stability by constructing a suitable Lyapunov functional. Secondly, the criteria for guaranteeing the global exponential stability of FCNN with time varying delays are given and the estimation of exponential convergence rate with regard to speed of vary of delays is presented by constructing a suitable Lyapunov functional
Valentine, T.E.; Mihalczo, J.T.
1996-01-01
One primary concern for design of safety systems for reactors is the time response of external detectors to changes in the core. This paper describes a way to estimate the time delay between the core power production and the external detector response using Monte Carlo calculations and suggests a technique to measure the time delay. The Monte Carlo code KENO-NR was used to determine the time delay between the core power production and the external detector response for a conceptual design of the Advanced Neutron Source (ANS) reactor. The Monte Carlo estimated time delay was determined to be about 10 ms for this conceptual design of the ANS reactor
Noise-induced coherence in bistable systems with multiple time delays
Jiang Yu; Dong, Shi-Hai; Lozada-Cassou, M.
2004-01-01
We study the correlation properties of noise-driven bistable systems with multiple time-delay feedbacks. For small noisy perturbation and feedback magnitude, we derive the autocorrelation function and the power spectrum based on the two-state model with transition rates depending on the earlier states of the system. A comparison between the single and double time delays reveals that the auto correlation functions exhibit exponential decay with small undulation for the double time delays, in contrast with the remarkable oscillatory behavior at small time lags for the single time delay
Lu, Chien-Yu
2011-01-01
This paper considers the problem of delay-dependent global robust stabilization for discrete, distributed and neutral interval time-varying delayed neural networks described by nonlinear delay differential equations of the neutral type. The parameter uncertainties are norm bounded. The activation functions are assumed to be bounded and globally Lipschitz continuous. Using a Lyapunov functional approach and linear matrix inequality (LMI) techniques, the stability criteria for the uncertain neutral neural networks with interval time-varying delays are established in the form of LMIs, which can be readily verified using the standard numerical software. An important feature of the result reported is that all the stability conditions are dependent on the upper and lower bounds of the delays. Another feature of the results lies in that it involves fewer free weighting matrix strategy, and upper bounds of the inner product between two vectors are not introduced to reduce the conservatism of the criteria. Two illustrative examples are provided to demonstrate the effectiveness and the reduced conservatism of the proposed method
Time-dependent gravitating solitons in five dimensional warped space-times
Giovannini, Massimo
2007-01-01
Time-dependent soliton solutions are explicitly derived in a five-dimensional theory endowed with one (warped) extra-dimension. Some of the obtained geometries, everywhere well defined and technically regular, smoothly interpolate between two five-dimensional anti-de Sitter space-times for fixed value of the conformal time coordinate. Time dependent solutions containing both topological and non-topological sectors are also obtained. Supplementary degrees of freedom can be also included and, in this case, the resulting multi-soliton solutions may describe time-dependent kink-antikink systems.
Firing patterns transition and desynchronization induced by time delay in neural networks
Huang, Shoufang; Zhang, Jiqian; Wang, Maosheng; Hu, Chin-Kun
2018-06-01
We used the Hindmarsh-Rose (HR) model (Hindmarsh and Rose, 1984) to study the effect of time delay on the transition of firing behaviors and desynchronization in neural networks. As time delay is increased, neural networks exhibit diversity of firing behaviors, including regular spiking or bursting and firing patterns transitions (FPTs). Meanwhile, the desynchronization of firing and unstable bursting with decreasing amplitude in neural system, are also increasingly enhanced with the increase of time delay. Furthermore, we also studied the effect of coupling strength and network randomness on these phenomena. Our results imply that time delays can induce transition and desynchronization of firing behaviors in neural networks. These findings provide new insight into the role of time delay in the firing activities of neural networks, and can help to better understand the firing phenomena in complex systems of neural networks. A possible mechanism in brain that can cause the increase of time delay is discussed.
Liu, Hongjian; Wang, Zidong; Shen, Bo; Alsaadi, Fuad E.
2016-07-01
This paper deals with the robust H∞ state estimation problem for a class of memristive recurrent neural networks with stochastic time-delays. The stochastic time-delays under consideration are governed by a Bernoulli-distributed stochastic sequence. The purpose of the addressed problem is to design the robust state estimator such that the dynamics of the estimation error is exponentially stable in the mean square, and the prescribed ? performance constraint is met. By utilizing the difference inclusion theory and choosing a proper Lyapunov-Krasovskii functional, the existence condition of the desired estimator is derived. Based on it, the explicit expression of the estimator gain is given in terms of the solution to a linear matrix inequality. Finally, a numerical example is employed to demonstrate the effectiveness and applicability of the proposed estimation approach.
Karthik Raja, U; Leelamani, A; Raja, R; Samidurai, R
2013-01-01
In this paper, the exponential stability for a class of stochastic neural networks with time-varying delays and impulsive effects is considered. By constructing suitable Lyapunov functionals and by using the linear matrix inequality optimization approach, we obtain sufficient delay-dependent criteria to ensure the exponential stability of stochastic neural networks with time-varying delays and impulses. Two numerical examples with simulation results are provided to illustrate the effectiveness of the obtained results over those already existing in the literature. (paper)
Stability of time-delay systems via Lyapunov functions
Carlos F. Alastruey
2002-01-01
Full Text Available In this paper, a Lyapunov function candidate is introduced for multivariable systems with inner delays, without assuming a priori stability for the nondelayed subsystem. By using this Lyapunov function, a controller is deduced. Such a controller utilizes an input–output description of the original system, a circumstance that facilitates practical applications of the proposed approach.
Travelling wave solutions for some time-delayed equations through factorizations
Fahmy, E.S.
2008-01-01
In this work, we use factorization method to find explicit particular travelling wave solutions for the following important nonlinear second-order partial differential equations: The generalized time-delayed Burgers-Huxley, time-delayed convective Fishers, and the generalized time-delayed Burgers-Fisher. Using the particular solutions for these equations we find the general solutions, two-parameter solution, as special cases
Synchronization of time-delayed systems with chaotic modulation and cryptography
Banerjee, Santo
2009-01-01
This paper presents a method of synchronization between two time-delayed systems where the delay times are modulated by a common chaotic signal of the driving system. The technique is well applied to two identical autonomous continuous-time-delayed systems with numerical simulations. Finally, a new method of encryption is generated for digital messages. This method is illustrated with two different encryption processes for text as well as picture messages.
Relativistic time delays in the Dirac approach to nucleon-nucleus scattering
Suzuki, T.
1993-01-01
In connection with a characteristic feature of the effective optical potential in the Dirac approach two types of time delays are considered in the relativistic eikonal approximation. One is obtained from the scattering amplitude and the other given by the wave packet motion in the interaction region. These time delays turn out to differ in sign at intermediate energies, in contrast to the agreement between corresponding nonrelativistic time delays. (orig.)
CAN LARGE TIME DELAYS OBSERVED IN LIGHT CURVES OF CORONAL LOOPS BE EXPLAINED IN IMPULSIVE HEATING?
Lionello, Roberto; Linker, Jon A.; Mikić, Zoran; Alexander, Caroline E.; Winebarger, Amy R.
2016-01-01
The light curves of solar coronal loops often peak first in channels associated with higher temperatures and then in those associated with lower temperatures. The delay times between the different narrowband EUV channels have been measured for many individual loops and recently for every pixel of an active region observation. The time delays between channels for an active region exhibit a wide range of values. The maximum time delay in each channel pair can be quite large, i.e., >5000 s. These large time delays make-up 3%–26% (depending on the channel pair) of the pixels where a trustworthy, positive time delay is measured. It has been suggested that these time delays can be explained by simple impulsive heating, i.e., a short burst of energy that heats the plasma to a high temperature, after which the plasma is allowed to cool through radiation and conduction back to its original state. In this paper, we investigate whether the largest observed time delays can be explained by this hypothesis by simulating a series of coronal loops with different heating rates, loop lengths, abundances, and geometries to determine the range of expected time delays between a set of four EUV channels. We find that impulsive heating cannot address the largest time delays observed in two of the channel pairs and that the majority of the large time delays can only be explained by long, expanding loops with photospheric abundances. Additional observations may rule out these simulations as an explanation for the long time delays. We suggest that either the time delays found in this manner may not be representative of real loop evolution, or that the impulsive heating and cooling scenario may be too simple to explain the observations, and other potential heating scenarios must be explored
Synchronization of Different Fractional Order Time-Delay Chaotic Systems Using Active Control
Jianeng Tang
2014-01-01
Full Text Available Chaos synchronization of different fractional order time-delay chaotic systems is considered. Based on the Laplace transform theory, the conditions for achieving synchronization of different fractional order time-delay chaotic systems are analyzed by use of active control technique. Then numerical simulations are provided to verify the effectiveness and feasibility of the developed method. At last, effects of the fraction order and the time delay on synchronization are further researched.
Linearized fermion-gravitation system in a (2+1)-dimensional space-time with Chern-Simons data
Mello, E.R.B. de.
1990-01-01
The fermion-graviton system at linearized level in a (2+1)-dimensional space-time with the gravitational Chern-Simons term is studied. In this approximation it is shown that this system presents anomalous rotational properties and spin, in analogy with the gauge field-matter system. (A.C.A.S.) [pt
The effect of visual-motion time delays on pilot performance in a pursuit tracking task
Miller, G. K., Jr.; Riley, D. R.
1976-01-01
A study has been made to determine the effect of visual-motion time delays on pilot performance of a simulated pursuit tracking task. Three interrelated major effects have been identified: task difficulty, motion cues, and time delays. As task difficulty, as determined by airplane handling qualities or target frequency, increases, the amount of acceptable time delay decreases. However, when relatively complete motion cues are included in the simulation, the pilot can maintain his performance for considerably longer time delays. In addition, the number of degrees of freedom of motion employed is a significant factor.
Stability analysis of fractional-order Hopfield neural networks with time delays.
Wang, Hu; Yu, Yongguang; Wen, Guoguang
2014-07-01
This paper investigates the stability for fractional-order Hopfield neural networks with time delays. Firstly, the fractional-order Hopfield neural networks with hub structure and time delays are studied. Some sufficient conditions for stability of the systems are obtained. Next, two fractional-order Hopfield neural networks with different ring structures and time delays are developed. By studying the developed neural networks, the corresponding sufficient conditions for stability of the systems are also derived. It is shown that the stability conditions are independent of time delays. Finally, numerical simulations are given to illustrate the effectiveness of the theoretical results obtained in this paper. Copyright © 2014 Elsevier Ltd. All rights reserved.
A new delay line loops shrinking time-to-digital converter in low-cost FPGA
Zhang, Jie, E-mail: zhangjie071063@163.com [State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, CAS, Wuhan, China, 430077 (China); University of Chinese Academy of Sciences, Beijing, China, 100049 (China); Zhou, Dongming [State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, CAS, Wuhan, China, 430077 (China)
2015-01-21
The article provides the design and test results of a new time-to-digital converter (TDC) based on delay line loops shrinking method and implemented in a low-cost field programmable gate array (FPGA) device. A technique that achieves high resolution with low cost and flexibility is presented. The technique is based on two delay line loops which are used to directly shrink the measured time interval in the designed TDC, and the resolution is dependent on the difference between the entire delay times of the two delay line loops. In order to realize high resolution and eliminate temperature influence, the two delay line loops consist of the same delay cells with the same number. A delay-locked loop (DLL) is used to stabilize the resolution against process variations and ambient conditions. Meanwhile, one method is used to accurately evaluate the resolution of the implemented TDC. The converter has been implemented in a general-propose FPGA device (Actel SmartFusion A2F200M3). A single shot resolution of the implemented converter is 63.3 ps and the measurement standard deviation is about 61.7 ps within the measurement range of 5 ns. - Highlights: • We provide a new FPGA-integrated time-to-digital converter based on delay line loops method which used two delay line loops to directly shrink time intervals with only rising edges. • The two delay line loops consist of the same delay cells with the same number and symmetrical structure. • The resolution is dependent on the difference between the entire delays of the two delay line loops. • We use delay-locked loop to stabilize the resolution against temperature and supply voltage.
A new delay line loops shrinking time-to-digital converter in low-cost FPGA
Zhang, Jie; Zhou, Dongming
2015-01-01
The article provides the design and test results of a new time-to-digital converter (TDC) based on delay line loops shrinking method and implemented in a low-cost field programmable gate array (FPGA) device. A technique that achieves high resolution with low cost and flexibility is presented. The technique is based on two delay line loops which are used to directly shrink the measured time interval in the designed TDC, and the resolution is dependent on the difference between the entire delay times of the two delay line loops. In order to realize high resolution and eliminate temperature influence, the two delay line loops consist of the same delay cells with the same number. A delay-locked loop (DLL) is used to stabilize the resolution against process variations and ambient conditions. Meanwhile, one method is used to accurately evaluate the resolution of the implemented TDC. The converter has been implemented in a general-propose FPGA device (Actel SmartFusion A2F200M3). A single shot resolution of the implemented converter is 63.3 ps and the measurement standard deviation is about 61.7 ps within the measurement range of 5 ns. - Highlights: • We provide a new FPGA-integrated time-to-digital converter based on delay line loops method which used two delay line loops to directly shrink time intervals with only rising edges. • The two delay line loops consist of the same delay cells with the same number and symmetrical structure. • The resolution is dependent on the difference between the entire delays of the two delay line loops. • We use delay-locked loop to stabilize the resolution against temperature and supply voltage
Li Chuandong; Liao Xiaofeng; Zhang Rong
2005-01-01
For bi-directional associative memory (BAM) neural networks (NNs) with different constant or time-varying delays, the problems of determining the exponential stability and estimating the exponential convergence rate are investigated in this paper. An approach combining the Lyapunov-Krasovskii functional with the linear matrix inequality (LMI) is taken to study the problems, which provide bounds on the interconnection matrix and the activation functions, so as to guarantee the system's exponential stability. Some criteria for the exponential stability, which give information on the delay-dependent property, are derived. The results obtained in this paper provide one more set of easily verified guidelines for determining the exponential stability of delayed BAM (DBAM) neural networks, which are less conservative and less restrictive than the ones reported so far in the literature. Some typical examples are presented to show the application of the criteria obtained in this paper
Franklin, Timothy C; Granata, Kevin P; Madigan, Michael L; Hendricks, Scott L
2008-08-01
Linear stability methods were applied to a biomechanical model of the human musculoskeletal spine to investigate effects of reflex gain and reflex delay on stability. Equations of motion represented a dynamic 18 degrees-of-freedom rigid-body model with time-delayed reflexes. Optimal muscle activation levels were identified by minimizing metabolic power with the constraints of equilibrium and stability with zero reflex time delay. Muscle activation levels and associated muscle forces were used to find the delay margin, i.e., the maximum reflex delay for which the system was stable. Results demonstrated that stiffness due to antagonistic co-contraction necessary for stability declined with increased proportional reflex gain. Reflex delay limited the maximum acceptable proportional reflex gain, i.e., long reflex delay required smaller maximum reflex gain to avoid instability. As differential reflex gain increased, there was a small increase in acceptable reflex delay. However, differential reflex gain with values near intrinsic damping caused the delay margin to approach zero. Forward-dynamic simulations of the fully nonlinear time-delayed system verified the linear results. The linear methods accurately found the delay margin below which the nonlinear system was asymptotically stable. These methods may aid future investigations in the role of reflexes in musculoskeletal stability.
Evidence for secondary gravitationally lensed images in radio quasistellar objects
Rousey, C.E.
1977-01-01
Evidence is sought for the observability of the gravitational lens effect by studying the internal radio structures of quasistellar objects. Since the majority of the radio emitting quasars were observed to be multiply structured at radio wavelengths, and since the gravitational deflection of light is essentially frequency independent, these sources are very suitable objects for the investigation of gravitational imaging. From the theoretical framework of gravitational imaging, particularly in the treatment of the gravitational lenses as ''point-mass'' deflectors, several selection criteria were imposed on a sample of 208 radio emitting quasars in order to filter out only those sources which may be exhibiting radio imaging. The employment of further selection criteria, obtained from the consideration of the observed optical fields around the quasars, resulted in a small filtered sample of 10 quasars which are good candidates for exhibiting the gravitational lens effect. In particular, two quasars, 3C 268.4 and 3C 286, are observed to have good evidence for the presence of suitable gravitational lenses. Image models were computed for the image candidates which predict the masses and distances of the gravitational deflectors as well as estimations of the ''time delays'' of the images. It is also suggested that measurements of these image time delays may enable one to place stringent limits on the value of the Hubble constant
Regenerative memory in time-delayed neuromorphic photonic resonators
Romeira, B.; Avó, R.; Figueiredo, José M. L.; Barland, S.; Javaloyes, J.
2016-01-01
We investigate a photonic regenerative memory based upon a neuromorphic oscillator with a delayed self-feedback (autaptic) connection. We disclose the existence of a unique temporal response characteristic of localized structures enabling an ideal support for bits in an optical buffer memory for storage and reshaping of data information. We link our experimental implementation, based upon a nanoscale nonlinear resonant tunneling diode driving a laser, to the paradigm of neuronal activity, the...
Liu, Hongjian; Wang, Zidong; Shen, Bo; Huang, Tingwen; Alsaadi, Fuad E
2018-06-01
This paper is concerned with the globally exponential stability problem for a class of discrete-time stochastic memristive neural networks (DSMNNs) with both leakage delays as well as probabilistic time-varying delays. For the probabilistic delays, a sequence of Bernoulli distributed random variables is utilized to determine within which intervals the time-varying delays fall at certain time instant. The sector-bounded activation function is considered in the addressed DSMNN. By taking into account the state-dependent characteristics of the network parameters and choosing an appropriate Lyapunov-Krasovskii functional, some sufficient conditions are established under which the underlying DSMNN is globally exponentially stable in the mean square. The derived conditions are made dependent on both the leakage and the probabilistic delays, and are therefore less conservative than the traditional delay-independent criteria. A simulation example is given to show the effectiveness of the proposed stability criterion. Copyright © 2018 Elsevier Ltd. All rights reserved.
General relation between the group delay and dwell time in multicomponent electron systems
Zhai, Feng; Lu, Junqiang
2016-10-01
For multicomponent electron scattering states, we derive a general relation between the Wigner group delay and the Bohmian dwell time. It is found that the definition of group delay should account for the phase of the spinor wave functions of propagating modes. The difference between the group delay and dwell time comes from both the interference delay and the decaying modes. For barrier tunneling of helical electrons on a surface of topological insulators, our calculations including the trigonal-warping term show that the decaying modes can contribute greatly to the group delay. The derived relation between the group delay and the dwell time is helpful to unify the two definitions of tunneling time in a quite general situation.
Consensus of discrete-time multi-agent systems with adversaries and time delays
Wu, Yiming; He, Xiongxiong; Liu, Shuai; Xie, Lihua
2014-05-01
This paper studies the resilient asymptotic consensus problem for discrete-time multi-agent systems in the presence of adversaries and transmission delays. The network is assumed to have ? loyal agents and ? adversarial agents, and each loyal agent in the network has no knowledge of the network topology other than an upper bound on the number of adversarial agents in its neighborhood. For the considered networked system, only locally delayed information is available for each loyal agent, and also the information flow is directed and a control protocol using only local information is designed to guarantee the realization of consensus with respect to communication graph, which satisfies a featured network robustness. Numerical examples are finally given to demonstrate the effectiveness of theoretical results.
Robust Stabilization of Discrete-Time Systems with Time-Varying Delay: An LMI Approach
Valter J. S. Leite
2008-01-01
Full Text Available Sufficient linear matrix inequality (LMI conditions to verify the robust stability and to design robust state feedback gains for the class of linear discrete-time systems with time-varying delay and polytopic uncertainties are presented. The conditions are obtained through parameter-dependent Lyapunov-Krasovskii functionals and use some extra variables, which yield less conservative LMI conditions. Both problems, robust stability analysis and robust synthesis, are formulated as convex problems where all system matrices can be affected by uncertainty. Some numerical examples are presented to illustrate the advantages of the proposed LMI conditions.
Kelley, Luke Zoltan; Blecha, Laura; Hernquist, Lars; Sesana, Alberto; Taylor, Stephen R.
2018-06-01
We calculate the properties, occurrence rates and detection prospects of individually resolvable `single sources' in the low-frequency gravitational wave (GW) spectrum. Our simulations use the population of galaxies and massive black hole binaries from the Illustris cosmological hydrodynamic simulations, coupled to comprehensive semi-analytic models of the binary merger process. Using mock pulsar timing arrays (PTA) with, for the first time, varying red-noise models, we calculate plausible detection prospects for GW single sources and the stochastic GW background (GWB). Contrary to previous results, we find that single sources are at least as detectable as the GW background. Using mock PTA, we find that these `foreground' sources (also `deterministic'/`continuous') are likely to be detected with ˜20 yr total observing baselines. Detection prospects, and indeed the overall properties of single sources, are only moderately sensitive to binary evolution parameters - namely eccentricity and environmental coupling, which can lead to differences of ˜5 yr in times to detection. Red noise has a stronger effect, roughly doubling the time to detection of the foreground between a white-noise only model (˜10-15 yr) and severe red noise (˜20-30 yr). The effect of red noise on the GWB is even stronger, suggesting that single source detections may be more robust. We find that typical signal-to-noise ratios for the foreground peak near f = 0.1 yr-1, and are much less sensitive to the continued addition of new pulsars to PTA.
Time delay and noise explaining the behaviour of the cell growth in fermentation process
Ayuobi, Tawfiqullah; Rosli, Norhayati; Bahar, Arifah; Salleh, Madihah Md
2015-01-01
This paper proposes to investigate the interplay between time delay and external noise in explaining the behaviour of the microbial growth in batch fermentation process. Time delay and noise are modelled jointly via stochastic delay differential equations (SDDEs). The typical behaviour of cell concentration in batch fermentation process under this model is investigated. Milstein scheme is applied for solving this model numerically. Simulation results illustrate the effects of time delay and external noise in explaining the lag and stationary phases, respectively for the cell growth of fermentation process
Time delay and noise explaining the behaviour of the cell growth in fermentation process
Ayuobi, Tawfiqullah; Rosli, Norhayati; Bahar, Arifah; Salleh, Madihah Md
2015-02-01
This paper proposes to investigate the interplay between time delay and external noise in explaining the behaviour of the microbial growth in batch fermentation process. Time delay and noise are modelled jointly via stochastic delay differential equations (SDDEs). The typical behaviour of cell concentration in batch fermentation process under this model is investigated. Milstein scheme is applied for solving this model numerically. Simulation results illustrate the effects of time delay and external noise in explaining the lag and stationary phases, respectively for the cell growth of fermentation process.
Time delay and noise explaining the behaviour of the cell growth in fermentation process
Ayuobi, Tawfiqullah; Rosli, Norhayati [Faculty of Industrial Sciences and Technology, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300 Gambang, Pahang (Malaysia); Bahar, Arifah [Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Salleh, Madihah Md [Department of Biotechnology Industry, Faculty of Biosciences and Bioengineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia)
2015-02-03
This paper proposes to investigate the interplay between time delay and external noise in explaining the behaviour of the microbial growth in batch fermentation process. Time delay and noise are modelled jointly via stochastic delay differential equations (SDDEs). The typical behaviour of cell concentration in batch fermentation process under this model is investigated. Milstein scheme is applied for solving this model numerically. Simulation results illustrate the effects of time delay and external noise in explaining the lag and stationary phases, respectively for the cell growth of fermentation process.
Mean Square Exponential Stability of Stochastic Switched System with Interval Time-Varying Delays
Manlika Rajchakit
2012-01-01
Full Text Available This paper is concerned with mean square exponential stability of switched stochastic system with interval time-varying delays. The time delay is any continuous function belonging to a given interval, but not necessary to be differentiable. By constructing a suitable augmented Lyapunov-Krasovskii functional combined with Leibniz-Newton’s formula, a switching rule for the mean square exponential stability of switched stochastic system with interval time-varying delays and new delay-dependent sufficient conditions for the mean square exponential stability of the switched stochastic system are first established in terms of LMIs. Numerical example is given to show the effectiveness of the obtained result.
Yu-Liang, Liu; Jie, Zhu; Xiao-Shu, Luo
2009-01-01
Based on the fluid flow time-delayed model proposed by Misra et al in internet congestion control, one modified time-delayed model is presented, where the influence of the communication delay on the router queue length is investigated in detail. The main advantage of the new model is that its stability domain is larger even without an extra controller. By linear stability analysis and numerical simulation, the effectiveness and feasibility of the novel model in internet congestion control are verified
Liu, Yu-Liang; Zhu, Jie; Luo, Xiao-Shu
2009-09-01
Based on the fluid flow time-delayed model proposed by Misra et al in internet congestion control, one modified time-delayed model is presented, where the influence of the communication delay on the router queue length is investigated in detail. The main advantage of the new model is that its stability domain is larger even without an extra controller. By linear stability analysis and numerical simulation, the effectiveness and feasibility of the novel model in internet congestion control are verified.
On the possibility of a fourth test of general relativity in earth's gravitational field
Zhang Yuan-zhong.
1981-03-01
In the paper the possibility for a fourth test of general relativity (i.e. relativistic time delay) in Earth's gravitational field is discussed. The effects of Earth's gravitational field on an interferometer and a resonant cavity are calculated by means of both two definitions of physical length. (author)
Wei, Ruoyu; Cao, Jinde; Alsaedi, Ahmed
2018-02-01
This paper investigates the finite-time synchronization and fixed-time synchronization problems of inertial memristive neural networks with time-varying delays. By utilizing the Filippov discontinuous theory and Lyapunov stability theory, several sufficient conditions are derived to ensure finite-time synchronization of inertial memristive neural networks. Then, for the purpose of making the setting time independent of initial condition, we consider the fixed-time synchronization. A novel criterion guaranteeing the fixed-time synchronization of inertial memristive neural networks is derived. Finally, three examples are provided to demonstrate the effectiveness of our main results.
New determination of the gravitational constant G with time-of-swing method
Tu Liangcheng; Li Qing; Wang Qinglan; Shao Chenggang; Yang Shanqing; Liu Linxia; Liu Qi; Luo Jun
2010-01-01
A new determination of the Newtonian gravitational constant G is presented by using a torsion pendulum with the time-of-swing method. Compared with our previous measurement with the same method, several improvements greatly reduced the uncertainties as follows: (i) two stainless steel spheres with more homogeneous density are used as the source masses instead of the cylinders used in the previous experiment, and the offset of the mass center from the geometric center is measured and found to be much smaller than that of the cylinders; (ii) a rectangular glass block is used as the main body of the pendulum, which has fewer vibration modes and hence improves the stability of the period and reduces the uncertainty of the moment of inertia; (iii) both the pendulum and source masses are placed in the same vacuum chamber to reduce the error of measuring the relative positions; (iv) changing the configurations between the ''near'' and ''far'' positions is remotely operated by using a stepper motor to lower the environmental disturbances; and (v) the anelastic effect of the torsion fiber is first measured directly by using two disk pendulums with the help of a high-Q quartz fiber. We have performed two independent G measurements, and the two G values differ by only 9 ppm. The combined value of G is (6.673 49±0.000 18)x10 -11 m 3 kg -1 s -2 with a relative uncertainty of 26 ppm.
Goldstein, Janna; Veitch, John; Sesana, Alberto; Vecchio, Alberto
2018-04-01
Super-massive black hole binaries are expected to produce a gravitational wave (GW) signal in the nano-Hertz frequency band which may be detected by pulsar timing arrays (PTAs) in the coming years. The signal is composed of both stochastic and individually resolvable components. Here we develop a generic Bayesian method for the analysis of resolvable sources based on the construction of `null-streams' which cancel the part of the signal held in common for each pulsar (the Earth-term). For an array of N pulsars there are N - 2 independent null-streams that cancel the GW signal from a particular sky location. This method is applied to the localisation of quasi-circular binaries undergoing adiabatic inspiral. We carry out a systematic investigation of the scaling of the localisation accuracy with signal strength and number of pulsars in the PTA. Additionally, we find that source sky localisation with the International PTA data release one is vastly superior than what is achieved by its constituent regional PTAs.
Zhang Min-Min; Mei Dong-Cheng; Wang Can-Jun
2011-01-01
The effects of the time delay on the upper bound of the time derivative of information entropy are investigated in a time-delayed dynamical system driven by correlated noise. Using the Markov approximation of the stochastic delay differential equations and the Schwartz inequality principle, we obtain an analytical expression for the upper bound U B (t) of the time derivative of the information entropy. The results show that there is a critical value of τ (delay time), and U B (t) presents opposite behaviours on difference sides of the critical value. For the case of the weak additive noise, τ can induce a reentrance transition. Delay time τ also causes a reversal behaviour in U B (t)-λ plot, where λ denotes the degree of the correlation between the two noises. (general)
On constraining the speed of gravitational waves following GW150914
Blas, Diego; Sawicki, Ignacy; Sibiryakov, Sergey
2016-07-31
We point out that the observed time delay between the detection of the signal at the Hanford and Livingston LIGO sites from the gravitational wave event GW150914 places an upper bound on the speed of propagation of gravitational waves, $c_{gw}\\lesssim 1.7$ in the units of speed of light. Combined with the lower bound from the absence of gravitational Cherenkov losses by cosmic rays that rules out most of subluminal velocities, this gives a model-independent double-sided constraint $1\\lesssim c_{gw}\\lesssim 1.7$. We compare this result to model-specific constraints from pulsar timing and cosmology.
Verma, Akash; Lee, Mui Yok; Wang, Chunhong; Hussein, Nurmalah B M; Selvi, Kalai; Tee, Augustine
2014-04-01
The purpose of this study was to assess the efficiency of performing pulmonary procedures in the endoscopy unit in a large teaching hospital. A prospective study from May 20 to July 19, 2013, was designed. The main outcome measures were procedure delays and their reasons, duration of procedural steps starting from patient's arrival to endoscopy unit, turnaround time, total case durations, and procedure wait time. A total of 65 procedures were observed. The most common procedure was BAL (61%) followed by TBLB (31%). Overall procedures for 35 (53.8%) of 65 patients were delayed by ≥ 30 minutes, 21/35 (60%) because of "spillover" of the gastrointestinal and surgical cases into the time block of pulmonary procedure. Time elapsed between end of pulmonary procedure and start of the next procedure was ≥ 30 minutes in 8/51 (16%) of cases. In 18/51 (35%) patients there was no next case in the room after completion of the pulmonary procedure. The average idle time of the room after the end of pulmonary procedure and start of next case or end of shift at 5:00 PM if no next case was 58 ± 53 minutes. In 17/51 (33%) patients the room's idle time was >60 minutes. A total of 52.3% of patients had the wait time >2 days and 11% had it ≥ 6 days, reason in 15/21 (71%) being unavailability of the slot. Most pulmonary procedures were delayed due to spillover of the gastrointestinal and surgical cases into the block time allocated to pulmonary procedures. The most common reason for difficulty encountered in scheduling the pulmonary procedure was slot unavailability. This caused increased procedure waiting time. The strategies to reduce procedure delays and turnaround times, along with improved scheduling methods, may have a favorable impact on the volume of procedures performed in the unit thereby optimizing the existing resources.
Travelling Solitary Wave Solutions for Generalized Time-delayed Burgers-Fisher Equation
Deng Xijun; Han Libo; Li Xi
2009-01-01
In this paper, travelling wave solutions for the generalized time-delayed Burgers-Fisher equation are studied. By using the first-integral method, which is based on the ring theory of commutative algebra, we obtain a class of travelling solitary wave solutions for the generalized time-delayed Burgers-Fisher equation. A minor error in the previous article is clarified. (general)
A New Method for Calibrating the Time Delay of a Piezoelectric Probe
Hansen, Bengt Hurup
1974-01-01
A simple method for calibrating the time delay of a piezoelectric probe of the type often used in plasma physics is described.......A simple method for calibrating the time delay of a piezoelectric probe of the type often used in plasma physics is described....
A dynamic IS-LM business cycle model with two time delays in capital accumulation equation
Zhou, Lujun; Li, Yaqiong
2009-06-01
In this paper, we analyze a augmented IS-LM business cycle model with the capital accumulation equation that two time delays are considered in investment processes according to Kalecki's idea. Applying stability switch criteria and Hopf bifurcation theory, we prove that time delays cause the equilibrium to lose or gain stability and Hopf bifurcation occurs.
The generalized correlation method for estimation of time delay in power plants
Kostic, Lj.
1981-01-01
The generalized correlation estimation is developed for determining time delay between signals received at two spatially separated sensors in the presence of uncorrelated noise in a power plant. This estimator can be realized as a pair of receiver prefilters followed by a cross correlator. The time argument at which the correlator achieves a maximum is the delay estimate. (author)
Avci, Suleyman
2013-01-01
The present study was conducted on 508 (331 female, 144 male) first grade university students in order to investigate the relations between self regulation, the future time perspectives, and the delay of gratification in the academic field. A future time perspective scale, an academic delay of gratification scale and a motivational strategies for…
Graphical Evaluation of Time-Delay Compensation Techniques for Digitally Controlled Converters
Lu, Minghui; Wang, Xiongfei; Loh, Poh Chiang
2018-01-01
A main design constraint of the digitally controlled power electronics converters is the time delay of control systems, which may lead to the reduced control loop bandwidth and even unstable dynamics. Numerous time-delay compensation methods have been developed, of which the model-free schemes...
Super-transient scaling in time-delay autonomous Boolean network motifs
D' Huys, Otti, E-mail: otti.dhuys@phy.duke.edu; Haynes, Nicholas D. [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Lohmann, Johannes [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin (Germany); Gauthier, Daniel J. [Department of Physics, Duke University, Durham, North Carolina 27708 (United States); Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)
2016-09-15
Autonomous Boolean networks are commonly used to model the dynamics of gene regulatory networks and allow for the prediction of stable dynamical attractors. However, most models do not account for time delays along the network links and noise, which are crucial features of real biological systems. Concentrating on two paradigmatic motifs, the toggle switch and the repressilator, we develop an experimental testbed that explicitly includes both inter-node time delays and noise using digital logic elements on field-programmable gate arrays. We observe transients that last millions to billions of characteristic time scales and scale exponentially with the amount of time delays between nodes, a phenomenon known as super-transient scaling. We develop a hybrid model that includes time delays along network links and allows for stochastic variation in the delays. Using this model, we explain the observed super-transient scaling of both motifs and recreate the experimentally measured transient distributions.
Electrical Activity in a Time-Delay Four-Variable Neuron Model under Electromagnetic Induction
Keming Tang
2017-11-01
Full Text Available To investigate the effect of electromagnetic induction on the electrical activity of neuron, the variable for magnetic flow is used to improve Hindmarsh–Rose neuron model. Simultaneously, due to the existence of time-delay when signals are propagated between neurons or even in one neuron, it is important to study the role of time-delay in regulating the electrical activity of the neuron. For this end, a four-variable neuron model is proposed to investigate the effects of electromagnetic induction and time-delay. Simulation results suggest that the proposed neuron model can show multiple modes of electrical activity, which is dependent on the time-delay and external forcing current. It means that suitable discharge mode can be obtained by selecting the time-delay or external forcing current, which could be helpful for further investigation of electromagnetic radiation on biological neuronal system.
Stochastic resonance in a time-delayed asymmetric bistable system with mixed periodic signal
Yong-Feng, Guo; Wei, Xu; Liang, Wang
2010-01-01
This paper studies the phenomenon of stochastic resonance in an asymmetric bistable system with time-delayed feedback and mixed periodic signal by using the theory of signal-to-noise ratio in the adiabatic limit. A general approximate Fokker–Planck equation and the expression of the signal-to-noise ratio are derived through the small time delay approximation at both fundamental harmonics and mixed harmonics. The effects of the additive noise intensity Q, multiplicative noise intensity D, static asymmetry r and delay time τ on the signal-to-noise ratio are discussed. It is found that the higher mixed harmonics and the static asymmetry r can restrain stochastic resonance, and the delay time τ can enhance stochastic resonance. Moreover, the longer the delay time τ is, the larger the additive noise intensity Q and the multiplicative noise intensity D are, when the stochastic resonance appears. (general)
New distributions of the statistical time delay of electrical breakdown in nitrogen
Markovic, V Lj; Gocic, S R; Stamenkovic, S N
2006-01-01
Two new distributions of the statistical time delay of electrical breakdown in nitrogen are reported in this paper. The Gaussian and Gauss-exponential distributions of statistical time delay have been obtained on the basis of thousands of time delay measurements on a gas tube with a plane-parallel electrode system. Distributions of the statistical time delay are theoretically founded on binomial distribution for the occurrence of initiating electrons and described by using simple analytical and numerical models. The shapes of distributions depend on the electron yields in the interelectrode space originating from residual states. It is shown that a distribution of the statistical time delay changes from exponential and Gauss-exponential to Gaussian distribution due to the influence of residual ionization
Generalized synchronization-based multiparameter estimation in modulated time-delayed systems
Ghosh, Dibakar; Bhattacharyya, Bidyut K.
2011-09-01
We propose a nonlinear active observer based generalized synchronization scheme for multiparameter estimation in time-delayed systems with periodic time delay. A sufficient condition for parameter estimation is derived using Krasovskii-Lyapunov theory. The suggested tool proves to be globally and asymptotically stable by means of Krasovskii-Lyapunov method. With this effective method, parameter identification and generalized synchronization of modulated time-delayed systems with all the system parameters unknown, can be achieved simultaneously. We restrict our study for multiple parameter estimation in modulated time-delayed systems with single state variable only. Theoretical proof and numerical simulation demonstrate the effectiveness and feasibility of the proposed technique. The block diagram of electronic circuit for multiple time delay system shows that the method is easily applicable in practical communication problems.
From dynamical systems with time-varying delay to circle maps and Koopman operators
Müller, David; Otto, Andreas; Radons, Günter
2017-06-01
In this paper, we investigate the influence of the retarded access by a time-varying delay on the dynamics of delay systems. We show that there are two universality classes of delays, which lead to fundamental differences in dynamical quantities such as the Lyapunov spectrum. Therefore, we introduce an operator theoretic framework, where the solution operator of the delay system is decomposed into the Koopman operator describing the delay access and an operator similar to the solution operator known from systems with constant delay. The Koopman operator corresponds to an iterated map, called access map, which is defined by the iteration of the delayed argument of the delay equation. The dynamics of this one-dimensional iterated map determines the universality classes of the infinite-dimensional state dynamics governed by the delay differential equation. In this way, we connect the theory of time-delay systems with the theory of circle maps and the framework of the Koopman operator. In this paper, we extend our previous work [A. Otto, D. Müller, and G. Radons, Phys. Rev. Lett. 118, 044104 (2017), 10.1103/PhysRevLett.118.044104] by elaborating the mathematical details and presenting further results also on the Lyapunov vectors.
Murphy, K. A.
1990-01-01
A parameter estimation algorithm is developed which can be used to estimate unknown time- or state-dependent delays and other parameters (e.g., initial condition) appearing within a nonlinear nonautonomous functional differential equation. The original infinite dimensional differential equation is approximated using linear splines, which are allowed to move with the variable delay. The variable delays are approximated using linear splines as well. The approximation scheme produces a system of ordinary differential equations with nice computational properties. The unknown parameters are estimated within the approximating systems by minimizing a least-squares fit-to-data criterion. Convergence theorems are proved for time-dependent delays and state-dependent delays within two classes, which say essentially that fitting the data by using approximations will, in the limit, provide a fit to the data using the original system. Numerical test examples are presented which illustrate the method for all types of delay.
Fei Chen
2013-01-01
Full Text Available This paper deals with the finite-time stabilization problem for discrete-time Markov jump nonlinear systems with time delays and norm-bounded exogenous disturbance. The nonlinearities in different jump modes are parameterized by neural networks. Subsequently, a linear difference inclusion state space representation for a class of neural networks is established. Based on this, sufficient conditions are derived in terms of linear matrix inequalities to guarantee stochastic finite-time boundedness and stochastic finite-time stabilization of the closed-loop system. A numerical example is illustrated to verify the efficiency of the proposed technique.
Hajnalka Péics
2016-08-01
Full Text Available The asymptotic behavior of solutions of the system of difference equations with continuous time and lag function between two known real functions is studied. The cases when the lag function is between two linear delay functions, between two power delay functions and between two constant delay functions are observed and illustrated by examples. The asymptotic estimates of solutions of the considered system are obtained.
A dynamic P53-MDM2 model with time delay
Mihalas, Gh.I. [Department of Biophysics and Medical Informatics, University of Medicine and Pharmacy, Piata Eftimie Murgu, nr. 3, 300041 Timisoara (Romania)]. E-mail: mihalas@medinfo.umft.ro; Neamtu, M. [Department of Forecasting, Economic Analysis, Mathematics and Statistics, West University of Timisoara, Str. Pestalozzi, nr. 14A, 300115 Timisoara (Romania)]. E-mail: mihaela.neamtu@fse.uvt.ro; Opris, D. [Department of Applied Mathematics, West University of Timisoara, Bd. V. Parvan, nr. 4, 300223 Timisoara (Romania)]. E-mail: opris@math.uvt.ro; Horhat, R.F. [Department of Biophysics and Medical Informatics, University of Medicine and Pharmacy, Piata Eftimie Murgu, nr. 3, 300041 Timisoara (Romania)]. E-mail: rhorhat@yahoo.com
2006-11-15
Specific activator and repressor transcription factors which bind to specific regulator DNA sequences, play an important role in gene activity control. Interactions between genes coding such transcription factors should explain the different stable or sometimes oscillatory gene activities characteristic for different tissues. Starting with the model P53-MDM2 described into [Mihalas GI, Simon Z, Balea G, Popa E. Possible oscillatory behaviour in P53-MDM2 interaction computer simulation. J Biol Syst 2000;8(1):21-9] and the process described into [Kohn KW, Pommier Y. Molecular interaction map of P53 and MDM2 logic elements, which control the off-on switch of P53 in response to DNA damage. Biochem Biophys Res Commun 2005;331:816-27] we enveloped a new model of this interaction. Choosing the delay as a bifurcation parameter we study the direction and stability of the bifurcating periodic solutions. Some numerical examples are finally given for justifying the theoretical results.
A dynamic P53-MDM2 model with time delay
Mihalas, Gh.I.; Neamtu, M.; Opris, D.; Horhat, R.F.
2006-01-01
Specific activator and repressor transcription factors which bind to specific regulator DNA sequences, play an important role in gene activity control. Interactions between genes coding such transcription factors should explain the different stable or sometimes oscillatory gene activities characteristic for different tissues. Starting with the model P53-MDM2 described into [Mihalas GI, Simon Z, Balea G, Popa E. Possible oscillatory behaviour in P53-MDM2 interaction computer simulation. J Biol Syst 2000;8(1):21-9] and the process described into [Kohn KW, Pommier Y. Molecular interaction map of P53 and MDM2 logic elements, which control the off-on switch of P53 in response to DNA damage. Biochem Biophys Res Commun 2005;331:816-27] we enveloped a new model of this interaction. Choosing the delay as a bifurcation parameter we study the direction and stability of the bifurcating periodic solutions. Some numerical examples are finally given for justifying the theoretical results
Stability of Nonlinear Systems with Unknown Time-varying Feedback Delay
Chunodkar, Apurva A.; Akella, Maruthi R.
2013-12-01
This paper considers the problem of stabilizing a class of nonlinear systems with unknown bounded delayed feedback wherein the time-varying delay is 1) piecewise constant 2) continuous with a bounded rate. We also consider application of these results to the stabilization of rigid-body attitude dynamics. In the first case, the time-delay in feedback is modeled specifically as a switch among an arbitrarily large set of unknown constant values with a known strict upper bound. The feedback is a linear function of the delayed states. In the case of linear systems with switched delay feedback, a new sufficiency condition for average dwell time result is presented using a complete type Lyapunov-Krasovskii (L-K) functional approach. Further, the corresponding switched system with nonlinear perturbations is proven to be exponentially stable inside a well characterized region of attraction for an appropriately chosen average dwell time. In the second case, the concept of the complete type L-K functional is extended to a class of nonlinear time-delay systems with unknown time-varying time-delay. This extension ensures stability robustness to time-delay in the control design for all values of time-delay less than the known upper bound. Model-transformation is used in order to partition the nonlinear system into a nominal linear part that is exponentially stable with a bounded perturbation. We obtain sufficient conditions which ensure exponential stability inside a region of attraction estimate. A constructive method to evaluate the sufficient conditions is presented together with comparison with the corresponding constant and piecewise constant delay. Numerical simulations are performed to illustrate the theoretical results of this paper.
Stability Analysis and H∞ Model Reduction for Switched Discrete-Time Time-Delay Systems
Zheng-Fan Liu
2014-01-01
Full Text Available This paper is concerned with the problem of exponential stability and H∞ model reduction of a class of switched discrete-time systems with state time-varying delay. Some subsystems can be unstable. Based on the average dwell time technique and Lyapunov-Krasovskii functional (LKF approach, sufficient conditions for exponential stability with H∞ performance of such systems are derived in terms of linear matrix inequalities (LMIs. For the high-order systems, sufficient conditions for the existence of reduced-order model are derived in terms of LMIs. Moreover, the error system is guaranteed to be exponentially stable and an H∞ error performance is guaranteed. Numerical examples are also given to demonstrate the effectiveness and reduced conservatism of the obtained results.
Consensus Analysis of Second-Order Multiagent Systems with General Topology and Time Delay
Bo Liu
2013-01-01
Full Text Available This paper addresses the consensus of second-order multiagent systems with general topology and time delay based on the nearest neighbor rule. By using the Laplace transform technique, it is proved that the second-order multi-agent system in the presence of time-delay can reach consensus if the network topology contains a globally reachable node and time delay is bounded. The bound of time-delay only depends on eigenvalues of the Laplacian matrix of the system. The main contribution of this paper is that the accurate state of the consensus center and the upper bound of the communication delay to make the agents reach consensus are given. Some numerical simulations are given to illustrate the theoretical results.
Attosecond time delays in the photoionization of noble gas atoms studied in TDLDA
Magrakvelidze, Maia; Chakraborty, Himadri; Madjet, Mohamed
2015-01-01
We perform time-dependent local density functional calculations of the quantum phase and time delays of valence photoionization of noble gas atoms. Results may be accessed by XUV-IR interferometric metrology. (paper)
Hydrodynamic Cucker-Smale model with normalized communication weights and time delay
Choi, Young-Pil; Haskovec, Jan
2017-01-01
with time delayed non-local alignment forces. We resort to its Lagrangian formulation and prove the existence of its global in time classical solutions. Moreover, we derive a sufficient condition for the asymptotic flocking behavior of the solutions. Finally
Time-delayed feedback technique for suppressing instabilities in time-periodic flow
Shaabani-Ardali, Léopold; Sipp, Denis; Lesshafft, Lutz
2017-11-01
A numerical method is presented that allows to compute time-periodic flow states, even in the presence of hydrodynamic instabilities. The method is based on filtering nonharmonic components by way of delayed feedback control, as introduced by Pyragas [Phys. Lett. A 170, 421 (1992), 10.1016/0375-9601(92)90745-8]. Its use in flow problems is demonstrated here for the case of a periodically forced laminar jet, subject to a subharmonic instability that gives rise to vortex pairing. The optimal choice of the filter gain, which is a free parameter in the stabilization procedure, is investigated in the context of a low-dimensional model problem, and it is shown that this model predicts well the filter performance in the high-dimensional flow system. Vortex pairing in the jet is efficiently suppressed, so that the unstable periodic flow state in response to harmonic forcing is accurately retrieved. The procedure is straightforward to implement inside any standard flow solver. Memory requirements for the delayed feedback control can be significantly reduced by means of time interpolation between checkpoints. Finally, the method is extended for the treatment of periodic problems where the frequency is not known a priori. This procedure is demonstrated for a three-dimensional cubic lid-driven cavity in supercritical conditions.
Jo, Chris H; Roh, Young Hak; Kim, Ji Eun; Shin, Sue; Yoon, Kang Sup
2013-10-01
Despite the increasing clinical use of topical platelet-rich plasma (PRP) to enhance tissue healing and regeneration, there is no properly standardized method of autologous PRP gel preparation. This study examined the effect of the centrifugation time and gravitational force (g) on the platelet recovery ratio of PRP and determined the most effective centrifugation conditions for preparing PRP. Two-step centrifugations for preparing PRP were used in 39 subjects who had consented prior to the study's start. The separating centrifugation (Step 1, used to separate whole blood into its two main components: red blood cells and plasma) was tested from 500g to 1900g at 200g increments for 5 minutes (min), and from 100g to 1300g at 200g increments for 10 minutes. After separating centrifugation, upper plasma layer was transferred to another plain tube for the condensation centrifugation and remaining lower cell layer was discarded. The condensation centrifugation (Step 2, used to condense the platelets in the separated plasma) was tested at 1000g for 15 min, 1500g for 15 min, 2000g for 5 min and 3000g for 5 min, additionally at 1000g for 10 min and 1500g for 10 min. Platelet gelation was induced by adding 10% calcium gluconate to final PRP with volume ratio of 1:10. The optimal separating centrifugation conditions were followed by 900g for 5 minutes and the condensation conditions were followed by 1500g for 15 minutes, of which recovery ratios were 92.0 ± 3.1% and 84.3 ± 10.0%, respectively.
Dynamics of Time Delay-Induced Multiple Synchronous Behaviors in Inhibitory Coupled Neurons
Gu, Huaguang; Zhao, Zhiguo
2015-01-01
The inhibitory synapse can induce synchronous behaviors different from the anti-phase synchronous behaviors, which have been reported in recent studies. In the present paper, synchronous behaviors are investigated in the motif model composed of reciprocal inhibitory coupled neurons with endogenous bursting and time delay. When coupling strength is weak, synchronous behavior appears at a single interval of time delay within a bursting period. When coupling strength is strong, multiple synchronous behaviors appear at different intervals of time delay within a bursting period. The different bursting patterns of synchronous behaviors, and time delays and coupling strengths that can induce the synchronous bursting patterns can be well interpreted by the dynamics of the endogenous bursting pattern of isolated neuron, which is acquired by the fast-slow dissection method, combined with the inhibitory coupling current. For an isolated neuron, when a negative impulsive current with suitable strength is applied at different phases of the bursting, multiple different bursting patterns can be induced. For a neuron in the motif, the inhibitory coupling current, of which the application time and strength is modulated by time delay and coupling strength, can cause single or multiple synchronous firing patterns like the negative impulsive current when time delay and coupling strength is suitable. The difference compared to the previously reported multiple synchronous behaviors that appear at time delays wider than a period of the endogenous firing is discussed. The results present novel examples of synchronous behaviors in the neuronal network with inhibitory synapses and provide a reasonable explanation. PMID:26394224
On the synchronization of neural networks containing time-varying delays and sector nonlinearity
Yan, J.-J.; Lin, J.-S.; Hung, M.-L.; Liao, T.-L.
2007-01-01
We present a systematic design procedure for synchronization of neural networks subject to time-varying delays and sector nonlinearity in the control input. Based on the drive-response concept and the Lyapunov stability theorem, a memoryless decentralized control law is proposed which guarantees exponential synchronization even when input nonlinearity is present. The supplementary requirement that the time-derivative of time-varying delays must be smaller than one is released for the proposed control scheme. A four-dimensional Hopfield neural network with time-varying delays is presented as the illustrative example to demonstrate the effectiveness of the proposed synchronization scheme
Maode Yan
2008-01-01
Full Text Available This paper considers the problem of robust discrete-time sliding-mode control (DT-SMC design for a class of uncertain linear systems with time-varying delays. By applying a descriptor model transformation and Moon's inequality for bounding cross terms, a delay-dependent sufficient condition for the existence of stable sliding surface is given in terms of linear matrix inequalities (LMIs. Based on this existence condition, the synthesized sliding mode controller can guarantee the sliding-mode reaching condition of the specified discrete-time sliding surface for all admissible uncertainties and time-varying delays. An illustrative example verifies the effectiveness of the proposed method.
Rank One Strange Attractors in Periodically Kicked Predator-Prey System with Time-Delay
Yang, Wenjie; Lin, Yiping; Dai, Yunxian; Zhao, Huitao
2016-06-01
This paper is devoted to the study of the problem of rank one strange attractor in a periodically kicked predator-prey system with time-delay. Our discussion is based on the theory of rank one maps formulated by Wang and Young. Firstly, we develop the rank one chaotic theory to delayed systems. It is shown that strange attractors occur when the delayed system undergoes a Hopf bifurcation and encounters an external periodic force. Then we use the theory to the periodically kicked predator-prey system with delay, deriving the conditions for Hopf bifurcation and rank one chaos along with the results of numerical simulations.
Using Video to Bridge the Gap Between Problem Behavior and a Delayed Time-out Procedure.
Coppage, Sara; Meindl, James N
2017-09-01
Treatment plans focused on problem behavior often include punishment contingencies to decrease problem behavior. Immediate punishers are typically more effective than delayed punishers, but immediate delivery of a punisher is not always possible. Strategies need to be developed to increase the suppressive effects of delayed punishers. This study demonstrated the effectiveness of a treatment package involving replaying a video recording of problem behavior immediately before delivering a 15 min delayed time-out. This treatment package may prove to be an accessible and inexpensive strategy when using delayed punishers.
Smart Telerobotic Surveillance System via Internet with Reduced Time Delay
Ashesh Vasalya
2012-09-01
Full Text Available This work provides an imperial solution to the problems faced by man while enduring hazardous tasks like handling and disposal of nuclear wastes, monitoring nuclear power plants, mining operations etc .which have to be aborted if expertise group running it is unavailable or on a run. This paper presents a distributed platform that allows the special group of user to control a gadget (possibly a robot through internet as a medium. An advanced version of this technology is capable of transmitting graphic images and other surrounding information as required, via internet back to the user to facilitate the effective monitoring of the existent situation using appropriate software tools. The project uses the SRV-1 Mobile Surveillance Robot which is a fully integrated system standard designed and other related technology for surveillance purposes. It is driven via web browser using JAVA based control applications with live video feeds. Specialised user group will be given separate account from where they can control and monitor the system even when they are not present at the site. End user will be connected to the gadget (robot through a central server which acts as a single channel for both sending and receiving information. But the subject of remote control over the internet has some possible anomalies namely network freezing, delay between host and recipient, congested network and many others. This system enables asynchronous object passing so that network bandwidth is used effectively and such parameters as the network condition and server states have less effect on the system. To resolve this issue, a fuzzy logic controller is used to control the robot’s motion along a predefined path with the necessary manipulation of the normal course. The robot was first modelled in Matlab Simulink and the fuzzy logic rules were optimized for the best results possible. In accordance with the fuzzy rules developed the fuzzy interference system generates the
Albers, D.J.; Hripcsak, George
2012-01-01
Highlights: ► Time-delayed mutual information for irregularly sampled time-series. ► Estimation bias for the time-delayed mutual information calculation. ► Fast, simple, PDF estimator independent, time-delayed mutual information bias estimate. ► Quantification of data-set-size limits of the time-delayed mutual calculation. - Abstract: A method to estimate the time-dependent correlation via an empirical bias estimate of the time-delayed mutual information for a time-series is proposed. In particular, the bias of the time-delayed mutual information is shown to often be equivalent to the mutual information between two distributions of points from the same system separated by infinite time. Thus intuitively, estimation of the bias is reduced to estimation of the mutual information between distributions of data points separated by large time intervals. The proposed bias estimation techniques are shown to work for Lorenz equations data and glucose time series data of three patients from the Columbia University Medical Center database.
The NANOGrav Collaboration
2016-01-01
We provide comments on the article by Shannon et al. (Sep 2015) entitled "Gravitational waves from binary supermassive black holes missing in pulsar observations". The purpose of this letter is to address several misconceptions of the public and other scientists regarding the conclusions of that work.
Robust H∞ Control of Neutral System with Time-Delay for Dynamic Positioning Ships
Dawei Zhao
2015-01-01
Full Text Available Due to the input time-delay existing in most thrust systems of the ships, the robust H∞ controller is designed for the ship dynamic positioning (DP system with time-delay. The input delay system is turned to a neutral time-delay system by a state-derivative control law. The less conservative result is derived for the neutral system with state-derivative feedback by the delay-decomposition approach and linear matrix inequality (LMI. Finally, the numerical simulations demonstrate the asymptotic stability and robustness of the controller and verify that the designed DP controller is effective in the varying environment disturbances of wind, waves, and ocean currents.
Finite-Time Stabilization and Adaptive Control of Memristor-Based Delayed Neural Networks.
Wang, Leimin; Shen, Yi; Zhang, Guodong
Finite-time stability problem has been a hot topic in control and system engineering. This paper deals with the finite-time stabilization issue of memristor-based delayed neural networks (MDNNs) via two control approaches. First, in order to realize the stabilization of MDNNs in finite time, a delayed state feedback controller is proposed. Then, a novel adaptive strategy is applied to the delayed controller, and finite-time stabilization of MDNNs can also be achieved by using the adaptive control law. Some easily verified algebraic criteria are derived to ensure the stabilization of MDNNs in finite time, and the estimation of the settling time functional is given. Moreover, several finite-time stability results as our special cases for both memristor-based neural networks (MNNs) without delays and neural networks are given. Finally, three examples are provided for the illustration of the theoretical results.Finite-time stability problem has been a hot topic in control and system engineering. This paper deals with the finite-time stabilization issue of memristor-based delayed neural networks (MDNNs) via two control approaches. First, in order to realize the stabilization of MDNNs in finite time, a delayed state feedback controller is proposed. Then, a novel adaptive strategy is applied to the delayed controller, and finite-time stabilization of MDNNs can also be achieved by using the adaptive control law. Some easily verified algebraic criteria are derived to ensure the stabilization of MDNNs in finite time, and the estimation of the settling time functional is given. Moreover, several finite-time stability results as our special cases for both memristor-based neural networks (MNNs) without delays and neural networks are given. Finally, three examples are provided for the illustration of the theoretical results.
Gain scheduling for non-linear time-delay systems using approximated model
Pham, H.T.; Lim, J.T
2012-01-01
The authors investigate a regulation problem of non-linear systems driven by an exogenous signal and time-delay in the input. In order to compensate for the input delay, they propose a reduction transformation containing the past information of the control input. Then, by utilising the Euler
Absolute stability of nonlinear systems with time delays and applications to neural networks
Xinzhi Liu
2001-01-01
Full Text Available In this paper, absolute stability of nonlinear systems with time delays is investigated. Sufficient conditions on absolute stability are derived by using the comparison principle and differential inequalities. These conditions are simple and easy to check. In addition, exponential stability conditions for some special cases of nonlinear delay systems are discussed. Applications of those results to cellular neural networks are presented.
Exponential stability of switched linear systems with time-varying delay
Satiracoo Pairote
2007-11-01
Full Text Available We use a Lyapunov-Krasovskii functional approach to establish the exponential stability of linear systems with time-varying delay. Our delay-dependent condition allows to compute simultaneously the two bounds that characterize the exponential stability rate of the solution. A simple procedure for constructing switching rule is also presented.
Global exponential stability of BAM neural networks with time-varying delays and diffusion terms
Wan Li; Zhou Qinghua
2007-01-01
The stability property of bidirectional associate memory (BAM) neural networks with time-varying delays and diffusion terms are considered. By using the method of variation parameter and inequality technique, the delay-independent sufficient conditions to guarantee the uniqueness and global exponential stability of the equilibrium solution of such networks are established
Global exponential stability of BAM neural networks with time-varying delays and diffusion terms
Wan, Li; Zhou, Qinghua
2007-11-01
The stability property of bidirectional associate memory (BAM) neural networks with time-varying delays and diffusion terms are considered. By using the method of variation parameter and inequality technique, the delay-independent sufficient conditions to guarantee the uniqueness and global exponential stability of the equilibrium solution of such networks are established.
Robust stability of bidirectional associative memory neural networks with time delays
Park, Ju H.
2006-01-01
Based on the Lyapunov Krasovskii functionals combined with linear matrix inequality approach, a novel stability criterion is proposed for asymptotic stability of bidirectional associative memory neural networks with time delays. A novel delay-dependent stability criterion is given in terms of linear matrix inequalities, which can be solved easily by various optimization algorithms.
Robust stability of bidirectional associative memory neural networks with time delays
Park, Ju H.
2006-01-01
Based on the Lyapunov-Krasovskii functionals combined with linear matrix inequality approach, a novel stability criterion is proposed for asymptotic stability of bidirectional associative memory neural networks with time delays. A novel delay-dependent stability criterion is given in terms of linear matrix inequalities, which can be solved easily by various optimization algorithms
An overview of the recent advances in delay-time-based maintenance modelling
Wang, Wenbin
2012-01-01
Industrial plant maintenance is an area which has enormous potential to be improved. It is also an area attracted significant attention from mathematical modellers because of the random phenomenon of plant failures. This paper reviews the recent advances in delay-time-based maintenance modelling, which is one of the mathematical techniques for optimising inspection planning and related problems. The delay-time is a concept that divides a plant failure process into two stages: from new until the point of an identifiable defect, and then from this point to failure. The first stage is called the normal working stage and the second stage is called the failure delay-time stage. If the distributions of the two stages can be quantified, the relationship between the number of failures and the inspection interval can be readily established. This can then be used for optimizing the inspection interval and other related decision variables. In this review, we pay particular attention to new methodological developments and industrial applications of the delay-time-based models over the last few decades. The use of the delay-time concept and modeling techniques in other areas rather than in maintenance is also reviewed. Future research directions are also highlighted. - Highlights: ► Reviewed the recent advances in delay-time-based maintenance models and applications. ► Compared the delay-time-based models with other models. ► Focused on methodologies and applications. ► Pointed out future research directions.
Gilbert, Danielle Wiggins
This study examined the effect of varying delayed polymerization times in combination with bracket manipulation on shear bond strength (SBS), degree of conversion (DC), and adhesive remnant index (ARI) score when using a resin modified glass ionomer (RMGI) adhesive. Specimens were divided into three groups of clinically relevant delay times (0.5, 2, and 4-min) to simulate the delay that frequently occurs between bracket placement and manipulation and subsequent light curing. Based on an analysis of variance (alpha=.05), the SBS was not significantly different between the three groups. While one of the goals of this study was to be the first study to quantify DC of RMGI using Raman microspectroscopy, several challenges, including weak peak signal with and without fluorescence, were encountered and as a result, DC could not be determined. A significant difference (pbracket with increasing delay time. A Spearman correlation between SBS and ARI indicated no positive association between SBS and ARI measures across delay times. The results of this study suggest that clinically relevant delay times of 0.5, 2, and 4-min do not negatively impact the SBS of a RMGI adhesive. However, with increasing delay time, the results suggest that more adhesive might remain on the bracket during debonding. With more adhesive remaining on the bracket, this could be beneficial in that less adhesive needs to be removed from enamel by grinding at the time of bracket removal when orthodontic treatment is completed.
Time delay effects on large-scale MR damper based semi-active control strategies
Cha, Y-J; Agrawal, A K; Dyke, S J
2013-01-01
This paper presents a detailed investigation on the robustness of large-scale 200 kN MR damper based semi-active control strategies in the presence of time delays in the control system. Although the effects of time delay on stability and performance degradation of an actively controlled system have been investigated extensively by many researchers, degradation in the performance of semi-active systems due to time delay has yet to be investigated. Since semi-active systems are inherently stable, instability problems due to time delay are unlikely to arise. This paper investigates the effects of time delay on the performance of a building with a large-scale MR damper, using numerical simulations of near- and far-field earthquakes. The MR damper is considered to be controlled by four different semi-active control algorithms, namely (i) clipped-optimal control (COC), (ii) decentralized output feedback polynomial control (DOFPC), (iii) Lyapunov control, and (iv) simple-passive control (SPC). It is observed that all controllers except for the COC are significantly robust with respect to time delay. On the other hand, the clipped-optimal controller should be integrated with a compensator to improve the performance in the presence of time delay. (paper)
A Fast Time-Delay Calculation Method in Through-Wall-Radar Detection Scenario
Zhang Qi
2016-01-01
Full Text Available In TWR (Through Wall Radar signal processing procedure, time delay estimation is one of the key steps in target localization and high resolution imaging. In time domain imaging procedure such as back projection imaging algorithm, round trip propagation time delay at the path of “transmitter-target-receiver” needs to be calculated for each pixel in imaging region. In typical TWR scenario, transmitter and receiver are at one side and targets at the other side of a wall. Based on two-dimensional searching algorithm or solving two variables equation of four times, traditional time delay calculation algorithms are complex and time consuming, and cannot be used to real-time imaging procedure. In this paper, a new fast time-delay (FTD algorithm is presented. Because of that incident angle at one side equals to refracting angle at the other side, an equation of lateral distance through the wall can be established. By solving this equation, the lateral distance can be obtained and total propagation time delay can be calculated subsequently. Through processing simulation data, the result shows that new algorithm can be applied effectively to real-time time-delay calculation in TWR signal processing.
ALGORITHMS AND PROGRAMS FOR STRONG GRAVITATIONAL LENSING IN KERR SPACE-TIME INCLUDING POLARIZATION
Chen, Bin; Maddumage, Prasad [Research Computing Center, Department of Scientific Computing, Florida State University, Tallahassee, FL 32306 (United States); Kantowski, Ronald; Dai, Xinyu; Baron, Eddie, E-mail: bchen3@fsu.edu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States)
2015-05-15
Active galactic nuclei (AGNs) and quasars are important astrophysical objects to understand. Recently, microlensing observations have constrained the size of the quasar X-ray emission region to be of the order of 10 gravitational radii of the central supermassive black hole. For distances within a few gravitational radii, light paths are strongly bent by the strong gravity field of the central black hole. If the central black hole has nonzero angular momentum (spin), then a photon’s polarization plane will be rotated by the gravitational Faraday effect. The observed X-ray flux and polarization will then be influenced significantly by the strong gravity field near the source. Consequently, linear gravitational lensing theory is inadequate for such extreme circumstances. We present simple algorithms computing the strong lensing effects of Kerr black holes, including the effects on polarization. Our algorithms are realized in a program “KERTAP” in two versions: MATLAB and Python. The key ingredients of KERTAP are a graphic user interface, a backward ray-tracing algorithm, a polarization propagator dealing with gravitational Faraday rotation, and algorithms computing observables such as flux magnification and polarization angles. Our algorithms can be easily realized in other programming languages such as FORTRAN, C, and C++. The MATLAB version of KERTAP is parallelized using the MATLAB Parallel Computing Toolbox and the Distributed Computing Server. The Python code was sped up using Cython and supports full implementation of MPI using the “mpi4py” package. As an example, we investigate the inclination angle dependence of the observed polarization and the strong lensing magnification of AGN X-ray emission. We conclude that it is possible to perform complex numerical-relativity related computations using interpreted languages such as MATLAB and Python.
ALGORITHMS AND PROGRAMS FOR STRONG GRAVITATIONAL LENSING IN KERR SPACE-TIME INCLUDING POLARIZATION
Chen, Bin; Maddumage, Prasad; Kantowski, Ronald; Dai, Xinyu; Baron, Eddie
2015-01-01
Active galactic nuclei (AGNs) and quasars are important astrophysical objects to understand. Recently, microlensing observations have constrained the size of the quasar X-ray emission region to be of the order of 10 gravitational radii of the central supermassive black hole. For distances within a few gravitational radii, light paths are strongly bent by the strong gravity field of the central black hole. If the central black hole has nonzero angular momentum (spin), then a photon’s polarization plane will be rotated by the gravitational Faraday effect. The observed X-ray flux and polarization will then be influenced significantly by the strong gravity field near the source. Consequently, linear gravitational lensing theory is inadequate for such extreme circumstances. We present simple algorithms computing the strong lensing effects of Kerr black holes, including the effects on polarization. Our algorithms are realized in a program “KERTAP” in two versions: MATLAB and Python. The key ingredients of KERTAP are a graphic user interface, a backward ray-tracing algorithm, a polarization propagator dealing with gravitational Faraday rotation, and algorithms computing observables such as flux magnification and polarization angles. Our algorithms can be easily realized in other programming languages such as FORTRAN, C, and C++. The MATLAB version of KERTAP is parallelized using the MATLAB Parallel Computing Toolbox and the Distributed Computing Server. The Python code was sped up using Cython and supports full implementation of MPI using the “mpi4py” package. As an example, we investigate the inclination angle dependence of the observed polarization and the strong lensing magnification of AGN X-ray emission. We conclude that it is possible to perform complex numerical-relativity related computations using interpreted languages such as MATLAB and Python
Identification of fractional-order systems with time delays using block pulse functions
Tang, Yinggan; Li, Ning; Liu, Minmin; Lu, Yao; Wang, Weiwei
2017-07-01
In this paper, a novel method based on block pulse functions is proposed to identify continuous-time fractional-order systems with time delays. First, the operational matrices of block pulse functions for fractional integral operator and time delay operator are derived. Then, these operational matrices are applied to convert the continuous-time fractional-order systems with time delays to an algebraic equation. Finally, the system's parameters along with the differentiation orders and the time delays are all simultaneously estimated through minimizing a quadric error function. The proposed method reduces the computation complexity of the identification process, and also it does not require the system's differentiation orders to be commensurate. The effectiveness of the proposed method are demonstrated by several numerical examples.
Meindl, Thomas; Coppenrath, Eva; Kahlil, Rami; Reiser, Maximilian F.; Mueller-Lisse, U.G.; Mueller-Lisse, Ulrike L.
2006-01-01
The optimal delay time after intravenous (i.v.) administration of contrast medium (CM) for opacifcation of the upper urinary tract (UUT) for multidetector computed tomography urography (MDCTU) was investigated. UUT opacification was retrospectively evaluated in 36 four-row MDCTU examinations. Single- (n=10) or dual-phase (n=26) MDCTU was performed with at least 5-min delay after i.v. CM. UUT was divided into four sections: intrarenal collecting system (IRCS), proximal, middle and distal ureter. Two independent readers rated UUT opacification: 1, none; 2, partial; 3, complete. Numbers and percentages of scores, and the 5%, 25%, 50%, 75% and 95% percentiles of delay time were calculated for each UUT section. After removing diseased segments, 344 segments were analysed. IRCS, proximal and middle ureter were completely opacified in 94% (81/86), 93% (80/86) and 77% (66/86) of cases, respectively. Median delay time was 15 min for complete opacification. The distal ureter was completely opacified in 37% (32/86) of cases and not opacified in 26% (22/86). Median delay time for complete opacification was 11 min with 25% and 75% percentiles of 10 and 16 min, respectively. At MDCTU, opacification of the IRCS, proximal and middle ureter was hardly sensitive to delay time. Delay times between 10 and 16 min were favourable in the distal ureter. (orig.)
Xiong Gang
2009-01-01
Full Text Available This paper presents theoretical results on the convergence of the distributed consensus timing synchronization (DCTS algorithm for wireless sensor networks assuming general Gaussian delay between nodes. The asymptotic expectation and mean square of the global synchronization error are computed. The results lead to the definition of a time delay balanced network in which average timing consensus between nodes can be achieved despite random delays. Several structured network architectures are studied as examples, and their associated simulation results are used to validate analytical findings.
Wigner-Smith delay times and the non-Hermitian Hamiltonian for the HOCl molecule
Barr, A.M.; Reichl, L.E.
2013-01-01
We construct the scattering matrix for a two-dimensional model of a Cl atom scattering from an OH dimer. We show that the scattering matrix can be written in terms of a non-Hermitian Hamiltonian whose complex energy eigenvalues can be used to compute Wigner-Smith delay times for the Cl-OH scattering process. We compute the delay times for a range of energies, and show that the scattering states with the longest delay times are strongly influenced by unstable periodic orbits in the classical dynamics. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Mingzhu Song
2016-01-01
Full Text Available We address the problem of globally asymptotic stability for a class of stochastic nonlinear systems with time-varying delays. By the backstepping method and Lyapunov theory, we design a linear output feedback controller recursively based on the observable linearization for a class of stochastic nonlinear systems with time-varying delays to guarantee that the closed-loop system is globally asymptotically stable in probability. In particular, we extend the deterministic nonlinear system to stochastic nonlinear systems with time-varying delays. Finally, an example and its simulations are given to illustrate the theoretical results.
Bembenutty, Héfer
2009-04-01
This study examined the associations between academic delay of gratification, self-efficacy beliefs, and time management among academically unprepared college students participating in a summer-immersion program. This study also examined whether the relation of self-efficacy with time management is mediated by academic delay of gratification. Analysis indicated that self-efficacy was directly associated with time management, as delay of gratification served to mediate this effect partially. Self-efficacy emerged as the strongest positive predictor of academic achievement.
Duan, Wei-Long
2013-01-01
The revised role of the time delay of active processes with colored noises of transmission of intracellular Ca 2+ in intracellular calcium oscillation (ICO) is investigated by means of a first-order algorithm based on stochastic simulation. The simulation results indicate that time delay induces a double critical phenomenon and a transition between the monostable and bistable states of the ICO system. In addition, as the time delay increases, for a cytosolic Ca 2+ concentration with weak colored noises there appears a calcium burst, and the Ca 2+ concentration of the calcium store shows nonmonotonic variation. (paper)
Wigner-Eisenbud-Smith photoionization time delay due to autoioinization resonances
Deshmukh, P. C.; Kumar, A.; Varma, H. R.; Banerjee, S.; Manson, Steven T.; Dolmatov, V. K.; Kheifets, A. S.
2018-03-01
An empirical ansatz for the complex photoionization amplitude and Wigner-Eisenbud-Smith time delay in the vicinity of a Fano autoionization resonance are proposed to evaluate and interpret the time delay in the resonant region. The utility of this expression is evaluated in comparison with accurate numerical calculations employing the ab initio relativistic random phase approximation and relativistic multichannel quantum defect theory. The indisputably good qualitative agreement (and semiquantitative agreement) between corresponding results of the proposed model and results produced by the ab initio theories proves the usability of the model. In addition, the phenomenology of the time delay in the vicinity of multichannel autoionizing resonances is detailed.
Relativistic effects in photoionization time delay near the Cooper minimum of noble-gas atoms
Saha, Soumyajit; Mandal, Ankur; Jose, Jobin; Varma, Hari R.; Deshmukh, P. C.; Kheifets, A. S.; Dolmatov, V. K.; Manson, S. T.
2014-11-01
Time delay of photoemission from valence n s , n p3 /2 , and n p1 /2 subshells of noble-gas atoms is theoretically scrutinized within the framework of the dipole relativistic random phase approximation. The focus is on the variation of time delay in the vicinity of the Cooper minima in photoionization of the outer subshells of neon, argon, krypton, and xenon, where the corresponding dipole matrix element changes its sign while passing through a node. It is revealed that the presence of the Cooper minimum in one photoionization channel has a strong effect on time delay in other channels. This is shown to be due to interchannel coupling.
Robustness Analysis of Hybrid Stochastic Neural Networks with Neutral Terms and Time-Varying Delays
Chunmei Wu
2015-01-01
Full Text Available We analyze the robustness of global exponential stability of hybrid stochastic neural networks subject to neutral terms and time-varying delays simultaneously. Given globally exponentially stable hybrid stochastic neural networks, we characterize the upper bounds of contraction coefficients of neutral terms and time-varying delays by using the transcendental equation. Moreover, we prove theoretically that, for any globally exponentially stable hybrid stochastic neural networks, if additive neutral terms and time-varying delays are smaller than the upper bounds arrived, then the perturbed neural networks are guaranteed to also be globally exponentially stable. Finally, a numerical simulation example is given to illustrate the presented criteria.
Operation Modes and Control Schemes for Internet-Based Teleoperation System with Time Delay
曾庆军; 宋爱国
2003-01-01
Teleoperation system plays an important role in executing task under hazard environment. As the computer networks such as the Internet are being used as the communication channel of teleoperation system, varying time delay causes the overall system unstable and reduces the performance of transparency. This paper proposed twelve operation modes with different control schemes for teleoperation on the Internet with time delay. And an optimal operation mode with control scheme was specified for teleoperation with time delay, based on the tradeoff between passivity and transparency properties. It experimentally confirmed the validity of the proposed optimal mode and control scheme by using a simple one DOF master-slave manipulator system.
Moving source localization with a single hydrophone using multipath time delays in the deep ocean.
Duan, Rui; Yang, Kunde; Ma, Yuanliang; Yang, Qiulong; Li, Hui
2014-08-01
Localizing a source of radial movement at moderate range using a single hydrophone can be achieved in the reliable acoustic path by tracking the time delays between the direct and surface-reflected arrivals (D-SR time delays). The problem is defined as a joint estimation of the depth, initial range, and speed of the source, which are the state parameters for the extended Kalman filter (EKF). The D-SR time delays extracted from the autocorrelation functions are the measurements for the EKF. Experimental results using pseudorandom signals show that accurate localization results are achieved by offline iteration of the EKF.
Longitudinal Outcomes of Start Time Delay on Sleep, Behavior, and Achievement in High School
Thacher, Pamela V.; Onyper, Serge V.
2016-01-01
Study Objectives: To establish whether sleep, health, mood, behavior, and academics improved after a 45-minute delay in high school start time, and whether changes persisted longitudinally. Methods: We collected data from school records and student self-report across a number of domains at baseline (May 2012) and at two follow-up time points (November 2012 and May 2013), at a public high school in upstate New York. Students enrolled during academic years (AY) 2011–2012 and 2012–2013 completed the Pittsburgh Sleep Quality Index; the DASS-21; the “Owl-Lark” Scale; the Daytime Sleepiness Index; and a brief self-report of health. Reports from school records regarding attendance, tardiness, disciplinary violations, and academic performance were collected for AY 2010–2011 through 2013–2014. Results: Students delayed but did not extend their sleep period; we found lasting improvements in tardiness and disciplinary violations after the start-time delay, but no changes to other variables. At the first follow-up, students reported 20 minutes longer sleep, driven by later rise times and stable bed times. At the second follow-up, students maintained later rise times but delayed bedtimes, returning total sleep to baseline levels. A delay in rise time, paralleling the delay in the start time that occurred, resulted in less tardiness and decreased disciplinary incidents, but larger improvements to sleep patterns may be necessary to affect health, attendance, sleepiness, and academic performance. Conclusions: Later start times improved tardiness and disciplinary issues at this school district. A delay in start time may be a necessary but not sufficient means to increase sleep time and may depend on preexisting individual differences. Commentary: A commentary on this article appears in this issue on page 267. Citation: Thacher PV, Onyper SV. Longitudinal outcomes of start time delay on sleep, behavior, and achievement in high school. SLEEP 2016;39(2):271–281. PMID
Incorporating time-delays in S-System model for reverse engineering genetic networks.
Chowdhury, Ahsan Raja; Chetty, Madhu; Vinh, Nguyen Xuan
2013-06-18
In any gene regulatory network (GRN), the complex interactions occurring amongst transcription factors and target genes can be either instantaneous or time-delayed. However, many existing modeling approaches currently applied for inferring GRNs are unable to represent both these interactions simultaneously. As a result, all these approaches cannot detect important interactions of the other type. S-System model, a differential equation based approach which has been increasingly applied for modeling GRNs, also suffers from this limitation. In fact, all S-System based existing modeling approaches have been designed to capture only instantaneous interactions, and are unable to infer time-delayed interactions. In this paper, we propose a novel Time-Delayed S-System (TDSS) model which uses a set of delay differential equations to represent the system dynamics. The ability to incorporate time-delay parameters in the proposed S-System model enables simultaneous modeling of both instantaneous and time-delayed interactions. Furthermore, the delay parameters are not limited to just positive integer values (corresponding to time stamps in the data), but can also take fractional values. Moreover, we also propose a new criterion for model evaluation exploiting the sparse and scale-free nature of GRNs to effectively narrow down the search space, which not only reduces the computation time significantly but also improves model accuracy. The evaluation criterion systematically adapts the max-min in-degrees and also systematically balances the effect of network accuracy and complexity during optimization. The four well-known performance measures applied to the experimental studies on synthetic networks with various time-delayed regulations clearly demonstrate that the proposed method can capture both instantaneous and delayed interactions correctly with high precision. The experiments carried out on two well-known real-life networks, namely IRMA and SOS DNA repair network in
Dynamic IQC-Based Control of Uncertain LFT Systems With Time-Varying State Delay.
Yuan, Chengzhi; Wu, Fen
2016-12-01
This paper presents a new exact-memory delay control scheme for a class of uncertain systems with time-varying state delay under the integral quadratic constraint (IQC) framework. The uncertain system is described as a linear fractional transformation model including a state-delayed linear time-invariant (LTI) system and time-varying structured uncertainties. The proposed exact-memory delay controller consists of a linear state-feedback control law and an additional term that captures the delay behavior of the plant. We first explore the delay stability and the L 2 -gain performance using dynamic IQCs incorporated with quadratic Lyapunov functions. Then, the design of exact-memory controllers that guarantee desired L 2 -gain performance is examined. The resulting delay control synthesis conditions are formulated in terms of linear matrix inequalities, which are convex on all design variables including the scaling matrices associated with the IQC multipliers. The IQC-based exact-memory control scheme provides a novel approach for delay control designs via convex optimization, and advances existing control methods in two important ways: 1) better controlled performance and 2) simplified design procedure with less computational cost. The effectiveness and advantages of the proposed approach have been demonstrated through numerical studies.
Attosecond delays in photoionization: time and quantum mechanics
Maquet, Alfred; Caillat, Jérémie; Taïeb, Richard
2014-01-01
This article addresses topics regarding time measurements performed on quantum systems. The motivation is linked to the advent of ‘attophysics’ which makes feasible to follow the motion of electrons in atoms and molecules, with time resolution at the attosecond (1 as = 10 −18 s) level, i.e. at the natural scale for electronic processes in these systems. In this context, attosecond ‘time-delays’ have been recently measured in experiments on photoionization and the question arises if such advances could cast a new light on the still active discussion on the status of the time variable in quantum mechanics. One issue still debatable is how to decide whether one can define a quantum time operator with eigenvalues associated to measurable ‘time-delays’, or time is a parameter, as it is implicit in the Newtonian classical mechanics. One objective of this paper is to investigate if the recent attophysics-based measurements could shed light on this parameter–operator conundrum. To this end, we present here the main features of the theory background, followed by an analysis of the experimental schemes that have been used to evidence attosecond ‘time-delays’ in photoionization. Our conclusion is that these results reinforce the view that time is a parameter which cannot be defined without reference to classical mechanics. (tutorial)
Recent Progress in Stability and Stabilization of Systems with Time-Delays
Magdi S. Mahmoud
2017-01-01
Full Text Available This paper overviews the research investigations pertaining to stability and stabilization of control systems with time-delays. The prime focus is the fundamental results and recent progress in theory and applications. The overview sheds light on the contemporary development on the linear matrix inequality (LMI techniques in deriving both delay-independent and delay-dependent stability results for time-delay systems. Particular emphases will be placed on issues concerned with the conservatism and the computational complexity of the results. Key technical bounding lemmas and slack variable introduction approaches will be presented. The results will be compared and connections of certain delay-dependent stability results are also discussed.
A Heterogeneous Agent Model of Asspet Price with Three Time Delays
Akio Matsumoto
2016-09-01
Full Text Available This paper considers a continuous-time heterogeneous agent model ofa ...nancial market with one risky asset, two types of agents (i.e., thefundamentalists and the chartists, and three time delays. The chartistdemand is determined through a nonlinear function of the di¤erence be-tween the current price and a weighted moving average of the delayedprices whereas the fundamentalist demand is governed by the di¤erencebetween the current price and the fundamental value. The asset price dy-namics is described by a nonlinear delay di¤erential equation. Two mainresults are analytically and numerically shown:(i the delay destabilizes the market price and generates cyclic oscillationsaround the equilibrium;(ii under multiple delays, stability loss and gain repeatedly occurs as alength of the delay increases.
Instability in time-delayed switched systems induced by fast and random switching
Guo, Yao; Lin, Wei; Chen, Yuming; Wu, Jianhong
2017-07-01
In this paper, we consider a switched system comprising finitely or infinitely many subsystems described by linear time-delayed differential equations and a rule that orchestrates the system switching randomly among these subsystems, where the switching times are also randomly chosen. We first construct a counterintuitive example where even though all the time-delayed subsystems are exponentially stable, the behaviors of the randomly switched system change from stable dynamics to unstable dynamics with a decrease of the dwell time. Then by using the theories of stochastic processes and delay differential equations, we present a general result on when this fast and random switching induced instability should occur and we extend this to the case of nonlinear time-delayed switched systems as well.
The influences of delay time on the stability of a market model with stochastic volatility
Li, Jiang-Cheng; Mei, Dong-Cheng
2013-02-01
The effects of the delay time on the stability of a market model are investigated, by using a modified Heston model with a cubic nonlinearity and cross-correlated noise sources. These results indicate that: (i) There is an optimal delay time τo which maximally enhances the stability of the stock price under strong demand elasticity of stock price, and maximally reduces the stability of the stock price under weak demand elasticity of stock price; (ii) The cross correlation coefficient of noises and the delay time play an opposite role on the stability for the case of the delay time τo. Moreover, the probability density function of the escape time of stock price returns, the probability density function of the returns and the correlation function of the returns are compared with other literatures.
Reduction of dispersive ground-roll using time delay spectrometry
Kjeldsen, Peter Møller; Larsen, Henrik C
1992-01-01
Velocity filtering seismic traces requires fulfilment of the sampling theorem in the time domain and in the space domain. Since the latter condition is seldom met in exploration seismics, a method based on τ-p transformation combined with time varying filtering is proposed for solving the problem...
Lesions Responsible for Delayed Oral Transit Time in Post-stroke Dysphagia.
Moon, Hyun Im; Yoon, Seo Yeon; Yi, Tae Im; Jeong, Yoon Jeong; Cho, Tae Hwan
2017-10-11
Some stroke patients show oral phase dysphagia, characterized by a markedly prolonged oral transit time that hinders oral feeding. The aim of this study was to clarify the clinical characteristics and lesions responsible for delayed swallowing. We reviewed 90 patients with stroke. The oral processing time plus the postfaucial aggregation time required to swallow semisolid food was assessed. The patients were divided into two groups according to oral transit time, and we analyzed the differences in characteristics such as demographic factors, lesion factors, and cognitive function. Logistic regression analyses were performed to examine the predictors of delayed oral transit time. Lesion location and volume were measured on brain magnetic resonance images. We generated statistic maps of lesions related to delayed oral phase in swallowing using voxel-based lesion symptom mapping (VLSM). The group of patients who showed delayed oral transit time had significantly low cognitive function. Also, in a regression model, delayed oral phase was predicted with low K-MMSE (Korean version of the Mini Mental Status Exam). Using VLSM, we found the lesion location to be associated with delayed oral phase after adjusting for K-MMSE score. Although these results did not reach statistical significance, they showed the lesion pattern with predominant distribution in the left frontal lobe. Delayed oral phase in post-stroke patients was not negligible clinically. Patients' cognitive impairments affect the oral transit time. When adjusting it, we found a trend that the lesion responsible for delayed oral phase was located in the left frontal lobe, though the association did not reach significance. The delay might be related to praxis function.
Sakakibara, Y.; Yamamoto, K.; Chen, D.; Tokoku, C.; Uchiyama, T.; Ohashi, M.; Kuroda, K. [Institute for Cosmic Ray Research (ICRR), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8582 (Japan); Kimura, N.; Suzuki, T.; Koike, S. [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)
2014-01-29
In interferometric cryogenic gravitational wave detectors, there are plans to cool mirrors and their suspension systems (payloads) in order to reduce thermal noise, that is, one of the fundamental noise sources. Because of the large payload masses (several hundred kg in total) and their thermal isolation, a cooling time of several months is required. Our calculation shows that a high-emissivity coating (e.g. a diamond-like carbon (DLC) coating) can reduce the cooling time effectively by enhancing radiation heat transfer. Here, we have experimentally verified the effect of the DLC coating on the reduction of the cooling time.
Attosecond time delay in the valence photoionization of C240 versus C60
Shi, Kele; Magrakvelidze, Maia; Anstine, Dylan; Chakraborty, Himadri; Madjet, Mohamed
2015-01-01
We investigate effects of electron correlations on the attosecond time delay of the photoionization from HOMO and HOMO-1 electrons in C 240 . A comparison with earlier C 60 results assesses the molecular size effect. (paper)
Li Jianlong; Zeng Lingzao
2010-01-01
We discuss in detail the effects of the multi-time-delayed feedback driven by an aperiodic signal on the output of a stochastic resonance (SR) system. The effective potential function and dynamical probability density function (PDF) are derived. To measure the performance of the SR system in the presence of a binary random signal, the bit error rate (BER) defined by the dynamical PDF is employed, as is commonly used in digital communications. We find that the delay time, strength of the feedback, and number of time-delayed terms can change the effective potential function and the effective amplitude of the signal, and then affect the BER of the SR system. The numerical simulations strongly support the theoretical results. The goal of this investigation is to explore the effects of the multi-time-delayed feedback on SR and give a guidance to nonlinear systems in the application of information processing.
Cucker-Smale model with normalized communication weights and time delay
Choi, Young-Pil; Haskovec, Jan
2017-01-01
We study a Cucker-Smale-type system with time delay in which agents interact with each other through normalized communication weights. We construct a Lyapunov functional for the system and provide sufficient conditions for asymptotic flocking, i
Multiple-parameter bifurcation analysis in a Kuramoto model with time delay and distributed shear
Niu, Ben; Zhang, Jiaming; Wei, Junjie
2018-05-01
In this paper, time delay effect and distributed shear are considered in the Kuramoto model. On the Ott-Antonsen's manifold, through analyzing the associated characteristic equation of the reduced functional differential equation, the stability boundary of the incoherent state is derived in multiple-parameter space. Moreover, very rich dynamical behavior such as stability switches inducing synchronization switches can occur in this equation. With the loss of stability, Hopf bifurcating coherent states arise, and the criticality of Hopf bifurcations is determined by applying the normal form theory and the center manifold theorem. On one hand, theoretical analysis indicates that the width of shear distribution and time delay can both eliminate the synchronization then lead the Kuramoto model to incoherence. On the other, time delay can induce several coexisting coherent states. Finally, some numerical simulations are given to support the obtained results where several bifurcation diagrams are drawn, and the effect of time delay and shear is discussed.
Saïda Bedoui
2013-01-01
Full Text Available This paper addresses the problem of simultaneous identification of linear discrete time delay multivariable systems. This problem involves both the estimation of the time delays and the dynamic parameters matrices. In fact, we suggest a new formulation of this problem allowing defining the time delay and the dynamic parameters in the same estimated vector and building the corresponding observation vector. Then, we use this formulation to propose a new method to identify the time delays and the parameters of these systems using the least square approach. Convergence conditions and statistics properties of the proposed method are also developed. Simulation results are presented to illustrate the performance of the proposed method. An application of the developed approach to compact disc player arm is also suggested in order to validate simulation results.
Positive Almost Periodic Solutions for a Time-Varying Fishing Model with Delay
Xia Li
2011-01-01
Full Text Available This paper is concerned with a time-varying fishing model with delay. By means of the continuation theorem of coincidence degree theory, we prove that it has at least one positive almost periodic solution.
Niestroj, A.; Hayano, R.S.; Ishikawa, T.; Tamura, H.; Torii, H.A.; Morita, N.; Yamazaki, T.; Sugai, I.; Nakayoshi, K.; Horvath, D.; Eades, J.; Widmann, E.
1996-01-01
An analog detection system has been developed to measure delayed antiproton annihilation time spectra for laser resonance spectroscopy of metastable antiprotonic helium atoms using the high-intensity pulsed beam of antiprotons from LEAR at CERN. (orig.)
Jones, A L; Sherwood, J C
2009-01-01
From a radiological protection point of view, the inclusion of delay times when carrying out assessments of dose from consumption of foods should be considered. A review of delay times has been carried out to update a report published in 1983, to take account of changes and modernisations in industrial food processes, together with changes in diet and popularity of different foods in the United Kingdom. The new review considered more foods and data for existing foods have been reconsidered to check whether manufacturing processes or procedures have changed the shelf-life of any products. For some foods there have been changes made to the recommended delay times because of changes in manufacture or handling of the fresh foodstuff. A discussion is also included on the appropriate use of delay times in dose assessments.
A note on chaotic synchronization of time-delay secure communication systems
Li Demin; Wang Zidong; Zhou Jie; Fang Jianan; Ni Jinjin
2008-01-01
In a real world, the signals are often transmitted through a hostile environment, and therefore the secure communication system has attracted considerable research interests. In this paper, the observer-based chaotic synchronization problem is studied for a class of time-delay secure communication systems. The system under consideration is subject to delayed state and nonlinear disturbances. The time-delay is allowed to be time-varying, and the nonlinearities are assumed to satisfy global Lipschitz conditions. The problem addressed is the design of a synchronization scheme such that, for the admissible time-delay as well as nonlinear disturbances, the response system can globally synchronize the driving system. An effective algebraic matrix inequality approach is developed to solve the chaotic synchronization problem. A numerical example is presented to show the effectiveness and efficiency of the proposed secure communication scheme
Effects of Noise and Time Delay Upon Active Control of Combustion Instabilities
Zinn, Ben
2001-01-01
To improve the performance of practical active control system (ACS) for unstable combustors, the effects of system noise and ACS time delay upon combustion instabilities and the ACS performance were studied...
Time delay induced different synchronization patterns in repulsively coupled chaotic oscillators
Yao, Chenggui; Yi, Ming; Shuai, Jianwei
2013-09-01
Time delayed coupling plays a crucial role in determining the system's dynamics. We here report that the time delay induces transition from the asynchronous state to the complete synchronization (CS) state in the repulsively coupled chaotic oscillators. In particular, by changing the coupling strength or time delay, various types of synchronous patterns, including CS, antiphase CS, antiphase synchronization (ANS), and phase synchronization, can be generated. In the transition regions between different synchronous patterns, bistable synchronous oscillators can be observed. Furthermore, we show that the time-delay-induced phase flip bifurcation is of key importance for the emergence of CS. All these findings may light on our understanding of neuronal synchronization and information processing in the brain.
H ∞ synchronization of the coronary artery system with input time-varying delay
Li Xiao-Meng; Zhao Zhan-Shan; Sun Lian-Kun; Zhang Jing
2016-01-01
This paper investigates the H ∞ synchronization of the coronary artery system with input delay and disturbance. We focus on reducing the conservatism of existing synchronization strategies. Base on the triple integral forms of the Lyapunov–Krasovskii functional (LKF), we utilize single and double integral forms of Wirtinger-based inequality to guarantee that the synchronization feedback controller has good performance against time-varying delay and external disturbance. The effectiveness of our strategy can be exhibited by simulations under the different time-varying delays and different disturbances. (paper)
Dual-anticipating, dual and dual-lag synchronization in modulated time-delayed systems
Ghosh, Dibakar; Chowdhury, A. Roy
2010-01-01
In this Letter, dual synchronization in modulated time delay system using delay feedback controller is proposed. Based on Lyapunov stability theory, we suggest a general method to achieve the dual-anticipating, dual, dual-lag synchronization of time-delayed chaotic systems and we find both its existing and sufficient stability conditions. Numerically it is shown that the dual synchronization is also possible when driving system contain two completely different systems. Effect of parameter mismatch on dual synchronization is also discussed. As an example, numerical simulations for the Mackey-Glass and Ikeda systems are conducted, which is in good agreement with the theoretical analysis.
Feng Cun-Fang; Wang Ying-Hai
2011-01-01
Projective synchronization in modulated time-delayed systems is studied by applying an active control method. Based on the Lyapunov asymptotical stability theorem, the controller and sufficient condition for projective synchronization are calculated analytically. We give a general method with which we can achieve projective synchronization in modulated time-delayed chaotic systems. This method allows us to adjust the desired scaling factor arbitrarily. The effectiveness of our method is confirmed by using the famous delay-differential equations related to optical bistable or hybrid optical bistable devices. Numerical simulations fully support the analytical approach. (general)
Discrete-time bidirectional associative memory neural networks with variable delays
Liang Jinling; Cao Jinde; Ho, Daniel W.C.
2005-01-01
Based on the linear matrix inequality (LMI), some sufficient conditions are presented in this Letter for the existence, uniqueness and global exponential stability of the equilibrium point of discrete-time bidirectional associative memory (BAM) neural networks with variable delays. Some of the stability criteria obtained in this Letter are delay-dependent, and some of them are delay-independent, they are less conservative than the ones reported so far in the literature. Furthermore, the results provide one more set of easily verified criteria for determining the exponential stability of discrete-time BAM neural networks
Discrete-time bidirectional associative memory neural networks with variable delays
Liang, variable delays [rapid communication] J.; Cao, J.; Ho, D. W. C.
2005-02-01
Based on the linear matrix inequality (LMI), some sufficient conditions are presented in this Letter for the existence, uniqueness and global exponential stability of the equilibrium point of discrete-time bidirectional associative memory (BAM) neural networks with variable delays. Some of the stability criteria obtained in this Letter are delay-dependent, and some of them are delay-independent, they are less conservative than the ones reported so far in the literature. Furthermore, the results provide one more set of easily verified criteria for determining the exponential stability of discrete-time BAM neural networks.
Completion time reduction in instantly decodable network coding through decoding delay control
Douik, Ahmed S.
2014-12-01
For several years, the completion time and the decoding delay problems in Instantly Decodable Network Coding (IDNC) were considered separately and were thought to completely act against each other. Recently, some works aimed to balance the effects of these two important IDNC metrics but none of them studied a further optimization of one by controlling the other. In this paper, we study the effect of controlling the decoding delay to reduce the completion time below its currently best known solution. We first derive the decoding-delay-dependent expressions of the users\\' and their overall completion times. Although using such expressions to find the optimal overall completion time is NP-hard, we use a heuristic that minimizes the probability of increasing the maximum of these decoding-delay-dependent completion time expressions after each transmission through a layered control of their decoding delays. Simulation results show that this new algorithm achieves both a lower mean completion time and mean decoding delay compared to the best known heuristic for completion time reduction. The gap in performance becomes significant for harsh erasure scenarios.
Completion time reduction in instantly decodable network coding through decoding delay control
Douik, Ahmed S.; Sorour, Sameh; Alouini, Mohamed-Slim; Al-Naffouri, Tareq Y.
2014-01-01
For several years, the completion time and the decoding delay problems in Instantly Decodable Network Coding (IDNC) were considered separately and were thought to completely act against each other. Recently, some works aimed to balance the effects of these two important IDNC metrics but none of them studied a further optimization of one by controlling the other. In this paper, we study the effect of controlling the decoding delay to reduce the completion time below its currently best known solution. We first derive the decoding-delay-dependent expressions of the users' and their overall completion times. Although using such expressions to find the optimal overall completion time is NP-hard, we use a heuristic that minimizes the probability of increasing the maximum of these decoding-delay-dependent completion time expressions after each transmission through a layered control of their decoding delays. Simulation results show that this new algorithm achieves both a lower mean completion time and mean decoding delay compared to the best known heuristic for completion time reduction. The gap in performance becomes significant for harsh erasure scenarios.
Determination of time delay between ventricles contraction using impedance measurements
Lewandowska, M; Poliński, A; Wtorek, J
2013-01-01
The paper presents a novel approach to assessment of ventricular dyssynchrony basing on multichannel electrical impedance measurements. Using a proper placement of electrodes, the sensitivity approach allows estimating time difference between chambers contraction from over determined nonlinear system of equations. The theoretical considerations which include Finite Element Method simulations were verified using measurements on healthy 28 year's old woman. The nonlinear least squares method was applied to obtain a time difference between heart chambers contraction. The obtained value was in a good agreement with theoretical values found in literature.
Lyapunov matrices approach to the parametric optimization of time-delay systems
Duda Józef
2015-09-01
Full Text Available In the paper a Lyapunov matrices approach to the parametric optimization problem of time-delay systems with a P-controller is presented. The value of integral quadratic performance index of quality is equal to the value of Lyapunov functional for the initial function of the time-delay system. The Lyapunov functional is determined by means of the Lyapunov matrix
Hopf bifurcation of a ratio-dependent predator-prey system with time delay
Celik, Canan
2009-01-01
In this paper, we consider a ratio dependent predator-prey system with time delay where the dynamics is logistic with the carrying capacity proportional to prey population. By considering the time delay as bifurcation parameter, we analyze the stability and the Hopf bifurcation of the system based on the normal form approach and the center manifold theory. Finally, we illustrate our theoretical results by numerical simulations.
Photonic-Enabled RF Canceller with Tunable Time-Delay Taps
2016-12-05
Photonic -Enabled RF Canceller with Tunable Time-Delay Taps Kenneth E. Kolodziej, Sivasubramaniam Yegnanarayanan, Bradley T. Perry MIT Lincoln...canceller design that uses photonics and a vector modulator architecture to provide a high number of canceller taps with tunable time-delays, which allow...microwave photonics , RF cancellation. I. INTRODUCTION In-Band Full-Duplex (IBFD) technologies are being consid- ered for 5th generation (5G) wireless
Dynamics and control of a financial system with time-delayed feedbacks
Chen, W.-C.
2008-01-01
Complex behaviors in a financial system with time-delayed feedbacks are discussed in this study via numerical modeling. The system shows complex dynamics such as periodic, quasi-periodic, and chaotic behaviors. Both period doubling and inverse period doubling routes were found in this system. This paper also shows that the attractor merging crisis is a fundamental feature of nonlinear financial systems with time-delayed feedbacks. Control of the deterministic chaos in the financial system can be realized using Pyragas feedbacks
On a new time-delayed feedback control of chaotic systems
Tian Lixin; Xu Jun; Sun Mei; Li Xiuming
2009-01-01
In this paper, using the idea of the successive dislocation feedback method, a new time-delayed feedback control method called the successive dislocation time-delayed feedback control (SDTDFC) is designed. Firstly, the idea of SDTDFC is introduced. Then some analytic sufficient conditions of the chaos control from the SDTDFC approach are derived for stabilization. Finally, some established results are further clarified via a case study of the Lorenz system with the numerical simulations.
Graffigna, Victoria
2017-01-01
The TOmographic Model of the IONospheric electron content (TOMION) software implements a simultaneous precise geodetic and ionospheric modeling, which can be used to test new approaches for real-time precise GNSS modeling (positioning, ionospheric and tropospheric delays, clock errors, among others). In this work, the software is used to estimate the Zenith Tropospheric Delay (ZTD) emulating real time and its performance is evaluated through a comparative analysis with a built-in GIPSY estima...
Global exponential stability of uncertain fuzzy BAM neural networks with time-varying delays
Syed Ali, M.; Balasubramaniam, P.
2009-01-01
In this paper, the Takagi-Sugeno (TS) fuzzy model representation is extended to the stability analysis for uncertain Bidirectional Associative Memory (BAM) neural networks with time-varying delays using linear matrix inequality (LMI) theory. A novel LMI-based stability criterion is obtained by LMI optimization algorithms to guarantee the exponential stability of uncertain BAM neural networks with time-varying delays which are represented by TS fuzzy models. Finally, the proposed stability conditions are demonstrated with numerical examples.
Song, Qiankun; Wang, Zidong
2007-01-01
In this Letter, the analysis problem for the existence and stability of periodic solutions is investigated for a class of general discrete-time recurrent neural networks with time-varying delays. For the neural networks under study, a generalized activation function is considered, and the traditional assumptions on the boundedness, monotony and differentiability of the activation functions are removed. By employing the latest free-weighting matrix method, an appropriate Lyapunov-Krasovskii functional is constructed and several sufficient conditions are established to ensure the existence, uniqueness, and globally exponential stability of the periodic solution for the addressed neural network. The conditions are dependent on both the lower bound and upper bound of the time-varying time delays. Furthermore, the conditions are expressed in terms of the linear matrix inequalities (LMIs), which can be checked numerically using the effective LMI toolbox in MATLAB. Two simulation examples are given to show the effectiveness and less conservatism of the proposed criteria
Delayed High School Starting Times. Information Capsule. Volume 0908
Blazer, Christie
2009-01-01
Educators around the nation are considering pushing high school starting times back until later in the morning, based on evidence suggesting that amount of sleep and circadian rhythms play a part in adolescents' academic performance. While research confirms that adolescents do not get enough sleep and that insufficient sleep can negatively…
Bounded Delay Timing Analysis of a Class of CSP Programs
Hulgaard, Henrik; Burns, Steven M.
1997-01-01
We describe an algebraic technique for performing timing analysis of a class of asynchronous circuits described as CSP programs (including Martin's probe operator) with the restrictions that there is no OR-causality and that guard selection is either completely free or mutually exclusive...
Time delay for resonant vibrational excitation in electron--molecule collisions
Gauyacq, J.P.
1990-01-01
An analysis of the time delay associated with vibrational excitation in electron--molecule collision is presented. It consists of a direct study of the time dependence of the process for three model systems. An electron wave packet, that is narrow in time, is sent on the target and the amplitudes in the different inelastic channels are studied as functions of time. The time delay is found to correspond to very different time effects: broadenings, shifts in time of the wave packet, but also complex distortions that cannot be represented by a time delay. The direct analysis of the scattered wave also provides new insights into the vibrational excitation process. It should be a useful tool to analyze complex collision processes
Decentralized H∞ Control of Interconnected Systems with Time-varying Delays
Amal Zouhri
2017-01-01
Full Text Available This paper focuses on the problem of delay dependent stability/stabilization of interconnected systems with time-varying delays. The approach is based on a new Lyapunov-Krasovskii functional. A decentralized delay-dependent stability analysis is performed to characterize linear matrix inequalities (LMIs based on the conditions under which every local subsystem of the linear interconnected delay system is asymptotically stable. Then we design a decentralized state-feedback stabilization scheme such that the family of closedloop feedback subsystems enjoys the delay-dependent asymptotic stability for each subsystem. The decentralized feedback gains are determined by convex optimization over LMIs. All the developed results are tested on a representative example and compared with some recent previous ones.
Balasubramaniam, P.; Kalpana, M.; Rakkiyappan, R.
2012-01-01
Fuzzy cellular neural networks (FCNNs) are special kinds of cellular neural networks (CNNs). Each cell in an FCNN contains fuzzy operating abilities. The entire network is governed by cellular computing laws. The design of FCNNs is based on fuzzy local rules. In this paper, a linear matrix inequality (LMI) approach for synchronization control of FCNNs with mixed delays is investigated. Mixed delays include discrete time-varying delays and unbounded distributed delays. A dynamic control scheme is proposed to achieve the synchronization between a drive network and a response network. By constructing the Lyapunov—Krasovskii functional which contains a triple-integral term and the free-weighting matrices method an improved delay-dependent stability criterion is derived in terms of LMIs. The controller can be easily obtained by solving the derived LMIs. A numerical example and its simulations are presented to illustrate the effectiveness of the proposed method. (interdisciplinary physics and related areas of science and technology)
CERN. Geneva HR-RFA
2006-01-01
We will present a brief introduction to the physics of gravitational waves and their properties. We will review potential astrophysical sources of gravitational waves, and the physics and astrophysics that can be learned from their study. We will survey the techniques and technologies for detecting gravitational waves for the first time, including bar detectors and broadband interferometers, and give a brief status report on the international search effort.
Longitudinal Outcomes of Start Time Delay on Sleep, Behavior, and Achievement in High School.
Thacher, Pamela V; Onyper, Serge V
2016-02-01
To establish whether sleep, health, mood, behavior, and academics improved after a 45-minute delay in high school start time, and whether changes persisted longitudinally. We collected data from school records and student self-report across a number of domains at baseline (May 2012) and at two follow-up time points (November 2012 and May 2013), at a public high school in upstate New York. Students enrolled during academic years (AY) 2011-2012 and 2012-2013 completed the Pittsburgh Sleep Quality Index; the DASS-21; the "Owl-Lark" Scale; the Daytime Sleepiness Index; and a brief self-report of health. Reports from school records regarding attendance, tardiness, disciplinary violations, and academic performance were collected for AY 2010-2011 through 2013-2014. Students delayed but did not extend their sleep period; we found lasting improvements in tardiness and disciplinary violations after the start-time delay, but no changes to other variables. At the first follow-up, students reported 20 minutes longer sleep, driven by later rise times and stable bed times. At the second follow-up, students maintained later rise times but delayed bedtimes, returning total sleep to baseline levels. A delay in rise time, paralleling the delay in the start time that occurred, resulted in less tardiness and decreased disciplinary incidents, but larger improvements to sleep patterns may be necessary to affect health, attendance, sleepiness, and academic performance. Later start times improved tardiness and disciplinary issues at this school district. A delay in start time may be a necessary but not sufficient means to increase sleep time and may depend on preexisting individual differences. A commentary on this article appears in this issue on page 267. © 2016 Associated Professional Sleep Societies, LLC.
Hopf bifurcation analysis of Chen circuit with direct time delay feedback
Hai-Peng, Ren; Wen-Chao, Li; Ding, Liu
2010-01-01
Direct time delay feedback can make non-chaotic Chen circuit chaotic. The chaotic Chen circuit with direct time delay feedback possesses rich and complex dynamical behaviours. To reach a deep and clear understanding of the dynamics of such circuits described by delay differential equations, Hopf bifurcation in the circuit is analysed using the Hopf bifurcation theory and the central manifold theorem in this paper. Bifurcation points and bifurcation directions are derived in detail, which prove to be consistent with the previous bifurcation diagram. Numerical simulations and experimental results are given to verify the theoretical analysis. Hopf bifurcation analysis can explain and predict the periodical orbit (oscillation) in Chen circuit with direct time delay feedback. Bifurcation boundaries are derived using the Hopf bifurcation analysis, which will be helpful for determining the parameters in the stabilisation of the originally chaotic circuit
Effects of stochastic time-delayed feedback on a dynamical system modeling a chemical oscillator
González Ochoa, Héctor O.; Perales, Gualberto Solís; Epstein, Irving R.; Femat, Ricardo
2018-05-01
We examine how stochastic time-delayed negative feedback affects the dynamical behavior of a model oscillatory reaction. We apply constant and stochastic time-delayed negative feedbacks to a point Field-Körös-Noyes photosensitive oscillator and compare their effects. Negative feedback is applied in the form of simulated inhibitory electromagnetic radiation with an intensity proportional to the concentration of oxidized light-sensitive catalyst in the oscillator. We first characterize the system under nondelayed inhibitory feedback; then we explore and compare the effects of constant (deterministic) versus stochastic time-delayed feedback. We find that the oscillatory amplitude, frequency, and waveform are essentially preserved when low-dispersion stochastic delayed feedback is used, whereas small but measurable changes appear when a large dispersion is applied.
Symmetry, Hopf bifurcation, and the emergence of cluster solutions in time delayed neural networks.
Wang, Zhen; Campbell, Sue Ann
2017-11-01
We consider the networks of N identical oscillators with time delayed, global circulant coupling, modeled by a system of delay differential equations with Z N symmetry. We first study the existence of Hopf bifurcations induced by the coupling time delay and then use symmetric Hopf bifurcation theory to determine how these bifurcations lead to different patterns of symmetric cluster oscillations. We apply our results to a case study: a network of FitzHugh-Nagumo neurons with diffusive coupling. For this model, we derive the asymptotic stability, global asymptotic stability, absolute instability, and stability switches of the equilibrium point in the plane of coupling time delay (τ) and excitability parameter (a). We investigate the patterns of cluster oscillations induced by the time delay and determine the direction and stability of the bifurcating periodic orbits by employing the multiple timescales method and normal form theory. We find that in the region where stability switching occurs, the dynamics of the system can be switched from the equilibrium point to any symmetric cluster oscillation, and back to equilibrium point as the time delay is increased.
Stability and oscillation of two coupled Duffing equations with time delay state feedback
El-Bassiouny, A F
2006-01-01
This paper presents an analytical study of the simultaneous principal parametric resonances of two coupled Duffing equations with time delay state feedback. The concept of an equivalent damping related to the delay feedback is proposed and the appropriate choice of the feedback gains and the time delay is discussed from the viewpoint of vibration control. The method of multiple scales is used to determine a set of ordinary differential equations governing the modulation of the amplitudes and phases of the two modes. The first order approximation of the resonances are derived and the effect of time delay on the resonances is investigated. The fixed points correspond to a periodic motion for the starting system and we show the frequency-response curves. We analyse the effect of time delay and the other different parameters on these oscillations. The stability of the fixed points is examined by using the variational method. Numerical solutions are carried out and graphical representations of the results are presented and discussed. Increasing in the time delay τ given decreasing and increasing in the regions of definition and stability respectively and the first mode has decreased magnitudes. The multivalued solutions disappear when decreasing the coefficients of cubic nonlinearities of the second mode α 3 and the detuning parameter σ 2 respectively. Both modes shift to the left for increasing linear feedback gain v 1 and the coefficient of parametric excitation f 1 respectively
Symmetry, Hopf bifurcation, and the emergence of cluster solutions in time delayed neural networks
Wang, Zhen; Campbell, Sue Ann
2017-11-01
We consider the networks of N identical oscillators with time delayed, global circulant coupling, modeled by a system of delay differential equations with ZN symmetry. We first study the existence of Hopf bifurcations induced by the coupling time delay and then use symmetric Hopf bifurcation theory to determine how these bifurcations lead to different patterns of symmetric cluster oscillations. We apply our results to a case study: a network of FitzHugh-Nagumo neurons with diffusive coupling. For this model, we derive the asymptotic stability, global asymptotic stability, absolute instability, and stability switches of the equilibrium point in the plane of coupling time delay (τ) and excitability parameter (a). We investigate the patterns of cluster oscillations induced by the time delay and determine the direction and stability of the bifurcating periodic orbits by employing the multiple timescales method and normal form theory. We find that in the region where stability switching occurs, the dynamics of the system can be switched from the equilibrium point to any symmetric cluster oscillation, and back to equilibrium point as the time delay is increased.
Measurement of time delays in gated radiotherapy for realistic respiratory motions
Chugh, Brige P.; Quirk, Sarah; Conroy, Leigh; Smith, Wendy L.
2014-01-01
Purpose: Gated radiotherapy is used to reduce internal motion margins, escalate target dose, and limit normal tissue dose; however, its temporal accuracy is limited. Beam-on and beam-off time delays can lead to treatment inefficiencies and/or geographic misses; therefore, AAPM Task Group 142 recommends verifying the temporal accuracy of gating systems. Many groups use sinusoidal phantom motion for this, under the tacit assumption that use of sinusoidal motion for determining time delays produces negligible error. The authors test this assumption by measuring gating time delays for several realistic motion shapes with increasing degrees of irregularity. Methods: Time delays were measured on a linear accelerator with a real-time position management system (Varian TrueBeam with RPM system version 1.7.5) for seven motion shapes: regular sinusoidal; regular realistic-shape; large (40%) and small (10%) variations in amplitude; large (40%) variations in period; small (10%) variations in both amplitude and period; and baseline drift (30%). Film streaks of radiation exposure were generated for each motion shape using a programmable motion phantom. Beam-on and beam-off time delays were determined from the difference between the expected and observed streak length. Results: For the system investigated, all sine, regular realistic-shape, and slightly irregular amplitude variation motions had beam-off and beam-on time delays within the AAPM recommended limit of less than 100 ms. In phase-based gating, even small variations in period resulted in some time delays greater than 100 ms. Considerable time delays over 1 s were observed with highly irregular motion. Conclusions: Sinusoidal motion shapes can be considered a reasonable approximation to the more complex and slightly irregular shapes of realistic motion. When using phase-based gating with predictive filters even small variations in period can result in time delays over 100 ms. Clinical use of these systems for patients
Measurement of time delays in gated radiotherapy for realistic respiratory motions
Chugh, Brige P.; Quirk, Sarah; Conroy, Leigh; Smith, Wendy L., E-mail: Wendy.Smith@albertahealthservices.ca [Department of Medical Physics, Tom Baker Cancer Centre, Calgary, Alberta T2N 4N2 (Canada)
2014-09-15
Purpose: Gated radiotherapy is used to reduce internal motion margins, escalate target dose, and limit normal tissue dose; however, its temporal accuracy is limited. Beam-on and beam-off time delays can lead to treatment inefficiencies and/or geographic misses; therefore, AAPM Task Group 142 recommends verifying the temporal accuracy of gating systems. Many groups use sinusoidal phantom motion for this, under the tacit assumption that use of sinusoidal motion for determining time delays produces negligible error. The authors test this assumption by measuring gating time delays for several realistic motion shapes with increasing degrees of irregularity. Methods: Time delays were measured on a linear accelerator with a real-time position management system (Varian TrueBeam with RPM system version 1.7.5) for seven motion shapes: regular sinusoidal; regular realistic-shape; large (40%) and small (10%) variations in amplitude; large (40%) variations in period; small (10%) variations in both amplitude and period; and baseline drift (30%). Film streaks of radiation exposure were generated for each motion shape using a programmable motion phantom. Beam-on and beam-off time delays were determined from the difference between the expected and observed streak length. Results: For the system investigated, all sine, regular realistic-shape, and slightly irregular amplitude variation motions had beam-off and beam-on time delays within the AAPM recommended limit of less than 100 ms. In phase-based gating, even small variations in period resulted in some time delays greater than 100 ms. Considerable time delays over 1 s were observed with highly irregular motion. Conclusions: Sinusoidal motion shapes can be considered a reasonable approximation to the more complex and slightly irregular shapes of realistic motion. When using phase-based gating with predictive filters even small variations in period can result in time delays over 100 ms. Clinical use of these systems for patients
Lars M. Göllner
2018-01-01
Full Text Available The delay of gratification (DoG in children is widely investigated with an experimental procedure originally called the “marshmallow test,” whereas the studies on self-regulation (SR in adolescents and adults usually use self-report questionnaires. Delay discounting (DD measures simplify the DoG procedure and focus on monetary rewards. The aim of this study was to investigate age differences in DoG and DD from childhood to old age using a test that is suitable for both children and adults. Furthermore, investigations were conducted on the association between DoG/DD and two future orientation constructs [future time perspective (FTP and episodic future thinking (EFT] as well as age differences in these constructs. Participants from five age groups (9–14, 18–25, 35–55, 65–80, 80+ participated in the study (N = 96. While we found no age difference for DoG, DD was the lowest [i.e., self-control (SC was the highest] in young/middle adults; however, it was the highest (i.e., SC was the lowest in children and old/oldest adults. Furthermore, we found significant age differences for DD and FTP. As predicted, there were strong correlations between DoG and FTP and between DD and FTP, but not between DoG/DD and EFT. These results indicate that age differences in SR vary across the measures used. Individuals who generally think and act in a future-oriented manner have a stronger ability to delay gratification.
Göllner, Lars M; Ballhausen, Nicola; Kliegel, Matthias; Forstmeier, Simon
2017-01-01
The delay of gratification (DoG) in children is widely investigated with an experimental procedure originally called the "marshmallow test," whereas the studies on self-regulation (SR) in adolescents and adults usually use self-report questionnaires. Delay discounting (DD) measures simplify the DoG procedure and focus on monetary rewards. The aim of this study was to investigate age differences in DoG and DD from childhood to old age using a test that is suitable for both children and adults. Furthermore, investigations were conducted on the association between DoG/DD and two future orientation constructs [future time perspective (FTP) and episodic future thinking (EFT)] as well as age differences in these constructs. Participants from five age groups (9-14, 18-25, 35-55, 65-80, 80+) participated in the study ( N = 96). While we found no age difference for DoG, DD was the lowest [i.e., self-control (SC) was the highest] in young/middle adults; however, it was the highest (i.e., SC was the lowest) in children and old/oldest adults. Furthermore, we found significant age differences for DD and FTP. As predicted, there were strong correlations between DoG and FTP and between DD and FTP, but not between DoG/DD and EFT. These results indicate that age differences in SR vary across the measures used. Individuals who generally think and act in a future-oriented manner have a stronger ability to delay gratification.
Transit time corrected arterial spin labeling technique aids to overcome delayed transit time effect
Yun, Tae Jin; Sohn, Chul-Ho; Yoo, Roh-Eul; Kang, Kyung Mi; Choi, Seung Hong; Kim, Ji-hoon; Park, Sun-Won; Hwang, Moonjung; Lebel, R.M.
2018-01-01
This study aimed to evaluate the usefulness of transit time corrected cerebral blood flow (CBF) maps based on multi-phase arterial spin labeling MR perfusion imaging (ASL-MRP). The Institutional Review Board of our hospital approved this retrospective study. Written informed consent was waived. Conventional and multi-phase ASL-MRPs and dynamic susceptibility contrast MR perfusion imaging (DSC-MRP) were acquired for 108 consecutive patients. Vascular territory-based volumes of interest were applied to CBF and time to peak (TTP) maps obtained from DSC-MRP and CBF maps obtained from conventional and multi-phase ASL-MRPs. The concordances between normalized CBF (nCBF) from DSC-MRP and nCBF from conventional and transition time corrected CBF maps from multi-phase ASL-MRP were evaluated using Bland-Altman analysis. In addition, the dependence of difference between nCBF (ΔnCBF) values obtained from DSC-MRP and conventional ASL-MRP (or multi-phase ASL-MRP) on TTP obtained from DSC-MRP was also analyzed using regression analysis. The values of nCBFs from conventional and multi-phase ASL-MRPs had lower values than nCBF based on DSC-MRP (mean differences, 0.08 and 0.07, respectively). The values of ΔnCBF were dependent on TTP values from conventional ASL-MRP technique (F = 5.5679, P = 0.0384). No dependency of ΔnCBF on TTP values from multi-phase ASL-MRP technique was revealed (F = 0.1433, P > 0.05). The use of transit time corrected CBF maps based on multi-phase ASL-MRP technique can overcome the effect of delayed transit time on perfusion maps based on conventional ASL-MRP. (orig.)
Transit time corrected arterial spin labeling technique aids to overcome delayed transit time effect
Yun, Tae Jin; Sohn, Chul-Ho; Yoo, Roh-Eul; Kang, Kyung Mi; Choi, Seung Hong; Kim, Ji-hoon [Seoul National University Medical Research Center, Institute of Radiation Medicine, Seoul (Korea, Republic of); Seoul National University Hospital, Department of Radiology, Seoul (Korea, Republic of); Park, Sun-Won [Seoul National University Medical Research Center, Institute of Radiation Medicine, Seoul (Korea, Republic of); Seoul National University Boramae Medical Center, Department of Radiology, Seoul (Korea, Republic of); Hwang, Moonjung [GE Healthcare Korea, Seoul (Korea, Republic of); Lebel, R.M. [GE Healthcare Canada, Calgary (Canada)
2018-03-15
This study aimed to evaluate the usefulness of transit time corrected cerebral blood flow (CBF) maps based on multi-phase arterial spin labeling MR perfusion imaging (ASL-MRP). The Institutional Review Board of our hospital approved this retrospective study. Written informed consent was waived. Conventional and multi-phase ASL-MRPs and dynamic susceptibility contrast MR perfusion imaging (DSC-MRP) were acquired for 108 consecutive patients. Vascular territory-based volumes of interest were applied to CBF and time to peak (TTP) maps obtained from DSC-MRP and CBF maps obtained from conventional and multi-phase ASL-MRPs. The concordances between normalized CBF (nCBF) from DSC-MRP and nCBF from conventional and transition time corrected CBF maps from multi-phase ASL-MRP were evaluated using Bland-Altman analysis. In addition, the dependence of difference between nCBF (ΔnCBF) values obtained from DSC-MRP and conventional ASL-MRP (or multi-phase ASL-MRP) on TTP obtained from DSC-MRP was also analyzed using regression analysis. The values of nCBFs from conventional and multi-phase ASL-MRPs had lower values than nCBF based on DSC-MRP (mean differences, 0.08 and 0.07, respectively). The values of ΔnCBF were dependent on TTP values from conventional ASL-MRP technique (F = 5.5679, P = 0.0384). No dependency of ΔnCBF on TTP values from multi-phase ASL-MRP technique was revealed (F = 0.1433, P > 0.05). The use of transit time corrected CBF maps based on multi-phase ASL-MRP technique can overcome the effect of delayed transit time on perfusion maps based on conventional ASL-MRP. (orig.)
Electromagnetic waves in gravitational wave spacetimes
Haney, M.; Bini, D.; Ortolan, A.; Fortini, P.
2013-01-01
We have considered the propagation of electromagnetic waves in a space-time representing an exact gravitational plane wave and calculated the induced changes on the four-potential field Aμ of a plane electromagnetic wave. By choosing a suitable photon round-trip in a Michelson interferometer, we have been able to identify the physical effects of the exact gravitational wave on the electromagnetic field, i.e. phase shift, change of the polarization vector, angular deflection and delay. These results have been exploited to study the response of an interferometric gravitational wave detector beyond the linear approximation of the general theory of relativity. A much more detailed examination of this problem can be found in our paper recently published in Classical and Quantum Gravity (28 (2011) 235007).
Construction delays causing risks on time and cost - a critical review
Chidambaram Ramanathan
2012-02-01
Full Text Available There is an increase in the number of construction projects experiencing extensive delays leading to exceeding initial time and cost budget. This paper reviews 41 studies around the world which surveyed the delay factors and classified them into Groups. The main purpose of this paper is to review literature, each of which have categorized the causes that are responsible for time delays and cost overrun in projects. The collected list has 113 causes for delays categorized in to 18 different groups. Most of the researches have analysed the responses from the Questionnaire survey. The collected data are used to rank the problem. The data are further used to investigate and analyse Important Index, Frequency Index, Severity Index, Relative Important Index, Relative Importance Weight, Weighted Average, Mean, Standard Deviation and Variance. The collective comparison has revealed that the ranking given by all the researchers is not the same. Further each and every study has different rank ratings for the different group of the delays. This review paper attempts to provide an updated compilation of the earlier studies on ranking of the delay causers, which are never similar and constant for universal projects. It is concluded that a separate study is required for identifying the factors causing delay for projects operated in Sabah, East Malaysia.
Constructing Hopf bifurcation lines for the stability of nonlinear systems with two time delays
Nguimdo, Romain Modeste
2018-03-01
Although the plethora real-life systems modeled by nonlinear systems with two independent time delays, the algebraic expressions for determining the stability of their fixed points remain the Achilles' heel. Typically, the approach for studying the stability of delay systems consists in finding the bifurcation lines separating the stable and unstable parameter regions. This work deals with the parametric construction of algebraic expressions and their use for the determination of the stability boundaries of fixed points in nonlinear systems with two independent time delays. In particular, we concentrate on the cases for which the stability of the fixed points can be ascertained from a characteristic equation corresponding to that of scalar two-delay differential equations, one-component dual-delay feedback, or nonscalar differential equations with two delays for which the characteristic equation for the stability analysis can be reduced to that of a scalar case. Then, we apply our obtained algebraic expressions to identify either the parameter regions of stable microwaves generated by dual-delay optoelectronic oscillators or the regions of amplitude death in identical coupled oscillators.
Chen, Cheng; Xu, Weijie; Guo, Tong; Chen, Kai
2017-10-01
Uncertainties in structure properties can result in different responses in hybrid simulations. Quantification of the effect of these uncertainties would enable researchers to estimate the variances of structural responses observed from experiments. This poses challenges for real-time hybrid simulation (RTHS) due to the existence of actuator delay. Polynomial chaos expansion (PCE) projects the model outputs on a basis of orthogonal stochastic polynomials to account for influences of model uncertainties. In this paper, PCE is utilized to evaluate effect of actuator delay on the maximum displacement from real-time hybrid simulation of a single degree of freedom (SDOF) structure when accounting for uncertainties in structural properties. The PCE is first applied for RTHS without delay to determine the order of PCE, the number of sample points as well as the method for coefficients calculation. The PCE is then applied to RTHS with actuator delay. The mean, variance and Sobol indices are compared and discussed to evaluate the effects of actuator delay on uncertainty quantification for RTHS. Results show that the mean and the variance of the maximum displacement increase linearly and exponentially with respect to actuator delay, respectively. Sensitivity analysis through Sobol indices also indicates the influence of the single random variable decreases while the coupling effect increases with the increase of actuator delay.
Patanarapeelert, K. [Faculty of Science, Department of Mathematics, Mahidol University, Rama VI Road, Bangkok 10400 (Thailand); Frank, T.D. [Institute for Theoretical Physics, University of Muenster, Wilhelm-Klemm-Str. 9, 48149 Muenster (Germany)]. E-mail: tdfrank@uni-muenster.de; Friedrich, R. [Institute for Theoretical Physics, University of Muenster, Wilhelm-Klemm-Str. 9, 48149 Muenster (Germany); Beek, P.J. [Faculty of Human Movement Sciences and Institute for Fundamental and Clinical Human Movement Sciences, Vrije Universiteit, Van der Boechorststraat 9, 1081 BT Amsterdam (Netherlands); Tang, I.M. [Faculty of Science, Department of Physics, Mahidol University, Rama VI Road, Bangkok 10400 (Thailand)
2006-12-18
A method is proposed to identify deterministic components of stable and unstable time-delayed systems subjected to noise sources with finite correlation times (colored noise). Both neutral and retarded delay systems are considered. For vanishing correlation times it is shown how to determine their noise amplitudes by minimizing appropriately defined Kullback measures. The method is illustrated by applying it to simulated data from stochastic time-delayed systems representing delay-induced bifurcations, postural sway and ship rolling.
Factors influencing delay time and coronary arterial density during coronary angiography with DSCT
Lijun Tang; Xiaomei Zhu; Yi Xu; Tongfu Yu; Hai Xu; Jinhua Tang; Dehang Wang; Dogra, Vikram
2011-01-01
Background: CT angiography (CTA) plays an important role in diagnosing coronary arterial disease. Delay time and density of the coronary arteries related with patient-specific factors are essential for getting an optimal CTA image. Purpose: To investigate various factors influencing delay time and coronary arterial density during coronary CTA with dual source CT. Material and Methods: One hundred and sixteen consecutive subjects who underwent cardiac DSCT with retrospective ECG-gating were included. Factors including gender, age, height, weight, transversal cardiac diameter (TCD), transversal thoracic diameter (TTD), heart rate (HR), body surface area (BSA = [weight x height/3600]1/2) and cardiothoracic ratio (CTR = TCD/TTD) were recorded, measured and calculated before administration of contrast media during coronary CT angiography. Delay time was determined as duration from the beginning of the injection to the density in the descending aorta at the level of right main pulmonary artery reaching a threshold of 100 HU. Coronary arterial density was measured at the mid portion of the right coronary artery. Regression analysis and stepwise regression analysis were used to investigate the influence of these factors on delay time and coronary arterial density. Results: Delay time decreased with an increasing HR and it was shorter in women than men. Delay time increased with an increasing TCD. Delay time could be predicted by the formula: DT = 16.651-0.110 x HR + 1.902 x gender + 0.394 x TCD (where DT is abbreviation for delay time, gender is 0 for women and 1 for men). Coronary arterial density decreased with an increasing HR and weight. Coronary arterial density could be predicted by the formula: CAD = 923.42-4.099 x HR-3.293 x weight (CAD = coronary arterial density). There was no relationship between the other factors mentioned above and delay time or coronary arterial density. Conclusion: Delay time is influenced by HR, gender and TCD. Coronary arterial density
Factors influencing delay time and coronary arterial density during coronary angiography with DSCT.
Tang, Lijun; Zhu, Xiaomei; Xu, Yi; Yu, Tongfu; Xu, Hai; Tang, Jinhua; Dogra, Vikram; Wang, Dehang
2011-02-01
CT angiography (CTA) plays an important role in diagnosing coronary arterial disease. Delay time and density of the coronary arteries related with patient-specific factors are essential for getting an optimal CTA image. To investigate various factors influencing delay time and coronary arterial density during coronary CTA with dual source CT. One hundred and sixteen consecutive subjects who underwent cardiac DSCT with retrospective ECG-gating were included. Factors including gender, age, height, weight, transversal cardiac diameter (TCD), transversal thoracic diameter (TTD), heart rate (HR), body surface area (BSA = [weight × height/3600](1/2)) and cardiothoracic ratio (CTR = TCD/TTD) were recorded, measured and calculated before administration of contrast media during coronary CT angiography. Delay time was determined as duration from the beginning of the injection to the density in the descending aorta at the level of right main pulmonary artery reaching a threshold of 100 HU. Coronary arterial density was measured at the mid portion of the right coronary artery. Regression analysis and stepwise regression analysis were used to investigate the influence of these factors on delay time and coronary arterial density. Delay time decreased with an increasing HR and it was shorter in women than men. Delay time increased with an increasing TCD. Delay time could be predicted by the formula: DT = 16.651-0.110 × HR + 1.902 × gender + 0.394 × TCD (where DT is abbreviation for delay time, gender is 0 for women and 1 for men). Coronary arterial density decreased with an increasing HR and weight. Coronary arterial density could be predicted by the formula: CAD = 923.42-4.099 × HR-3.293 × weight (CAD = coronary arterial density). There was no relationship between the other factors mentioned above and delay time or coronary arterial density. Delay time is influenced by HR, gender and TCD. Coronary arterial density also changes with HR and weight. So HR, gender, TCD and
Liu Yurong; Wang Zidong; Liu Xiaohui
2008-01-01
In this Letter, we investigate the state estimation problem for a new class of discrete-time neural networks with Markovian jumping parameters as well as mode-dependent mixed time-delays. The parameters of the discrete-time neural networks are subject to the switching from one mode to another at different times according to a Markov chain, and the mixed time-delays consist of both discrete and distributed delays that are dependent on the Markovian jumping mode. New techniques are developed to deal with the mixed time-delays in the discrete-time setting, and a novel Lyapunov-Krasovskii functional is put forward to reflect the mode-dependent time-delays. Sufficient conditions are established in terms of linear matrix inequalities (LMIs) that guarantee the existence of the state estimators. We show that both the existence conditions and the explicit expression of the desired estimator can be characterized in terms of the solution to an LMI. A numerical example is exploited to show the usefulness of the derived LMI-based conditions
Hoffmann, William F
1964-01-01
Remarks on the observational basis of general relativity ; Riemannian geometry ; gravitation as geometry ; gravitational waves ; Mach's principle and experiments on mass anisotropy ; the many faces of Mach ; the significance for the solar system of time-varying gravitation ; relativity principles and the role of coordinates in physics ; the superdense star and the critical nucleon number ; gravitation and light ; possible effects on the solar system of φ waves if they exist ; the Lyttleton-Bondi universe and charge equality ; quantization of general relativity ; Mach's principle as boundary condition for Einstein's equations.
Gravitational lensing in metric theories of gravity
Sereno, Mauro
2003-01-01
Gravitational lensing in metric theories of gravity is discussed. I introduce a generalized approximate metric element, inclusive of both post-post-Newtonian contributions and a gravitomagnetic field. Following Fermat's principle and standard hypotheses, I derive the time delay function and deflection angle caused by an isolated mass distribution. Several astrophysical systems are considered. In most of the cases, the gravitomagnetic correction offers the best perspectives for an observational detection. Actual measurements distinguish only marginally different metric theories from each other
H∞ Consensus for Multiagent Systems with Heterogeneous Time-Varying Delays
Beibei Wang
2013-01-01
Full Text Available We apply the linear matrix inequality method to consensus and H∞ consensus problems of the single integrator multiagent system with heterogeneous delays in directed networks. To overcome the difficulty caused by heterogeneous time-varying delays, we rewrite the multiagent system into a partially reduced-order system and an integral system. As a result, a particular Lyapunov function is constructed to derive sufficient conditions for consensus of multiagent systems with fixed (switched topologies. We also apply this method to the H∞ consensus of multiagent systems with disturbances and heterogeneous delays. Numerical examples are given to illustrate the theoretical results.
Global exponential stability for discrete-time neural networks with variable delays
Chen Wuhua; Lu Xiaomei; Liang Dongying
2006-01-01
This Letter provides new exponential stability criteria for discrete-time neural networks with variable delays. The main technique is to reduce exponential convergence estimation of the neural network solution to that of one component of the corresponding solution by constructing Lyapunov function based on M-matrix. By introducing the tuning parameter diagonal matrix, the delay-independent and delay-dependent exponential stability conditions have been unified in the same mathematical formula. The effectiveness of the new results are illustrated by three examples
New Results on Robust Model Predictive Control for Time-Delay Systems with Input Constraints
Qing Lu
2014-01-01
Full Text Available This paper investigates the problem of model predictive control for a class of nonlinear systems subject to state delays and input constraints. The time-varying delay is considered with both upper and lower bounds. A new model is proposed to approximate the delay. And the uncertainty is polytopic type. For the state-feedback MPC design objective, we formulate an optimization problem. Under model transformation, a new model predictive controller is designed such that the robust asymptotical stability of the closed-loop system can be guaranteed. Finally, the applicability of the presented results are demonstrated by a practical example.
Robust L2-L∞ Filtering of Time-Delay Jump Systems with Respect to the Finite-Time Interval
Shuping He
2011-01-01
Full Text Available This paper studied the problem of stochastic finite-time boundedness and disturbance attenuation for a class of linear time-delayed systems with Markov jumping parameters. Sufficient conditions are provided to solve this problem. The L2-L∞ filters are, respectively, designed for time-delayed Markov jump linear systems with/without uncertain parameters such that the resulting filtering error dynamic system is stochastically finite-time bounded and has the finite-time interval disturbance attenuation γ for all admissible uncertainties, time delays, and unknown disturbances. By using stochastic Lyapunov-Krasovskii functional approach, it is shown that the filter designing problem is in terms of the solutions of a set of coupled linear matrix inequalities. Simulation examples are included to demonstrate the potential of the proposed results.
Chifu E. N.
2009-07-01
Full Text Available Here, we present a profound and complete analytical solution to Einstein’s gravitational field equations exterior to astrophysically real or hypothetical time varying distribu- tions of mass or pressure within regions of spherical geometry. The single arbitrary function f in our proposed exterior metric tensor and constructed field equations makes our method unique, mathematically less combersome and astrophysically satisfactory. The obtained solution of Einstein’s gravitational field equations tends out to be a gen- eralization of Newton’s gravitational scalar potential exterior to the spherical mass or pressure distribution under consideration
How many segments are necessary to characterize delayed colonic transit time?
Bouchoucha, Michel; Devroede, Ghislain; Bon, Cyriaque; Raynaud, Jean-Jacques; Bejou, Bakhtiar; Benamouzig, Robert
2015-10-01
Measuring colonic transit time with radiopaque markers is simple, inexpensive, and very useful in constipated patients. Yet, the algorithm used to identify colonic segments is subjective, rather than founded on prior experimentation. The aim of the present study is to describe a rational way to determine the colonic partition in the measurement of colonic transit time. Colonic transit time was measured in seven segments: ascending colon, hepatic flexure, right and left transverse colon, splenic flexure, descending colon, and rectosigmoid in 852 patients with functional bowel and anorectal disorders. An unsupervised algorithm for modeling Gaussian mixtures served to estimate the number of subgroups from this oversegmented colonic transit time. After that, we performed a k-means clustering that separated the observations into homogenous groups of patients according to their oversegmented colonic transit time. The Gaussian mixture followed by the k-means clustering defined 4 populations of patients: "normal and fast transit" (n = 548) and three groups of patients with delayed colonic transit time "right delay" (n = 82) in which transit is delayed in the right part of the colon, "left delay" (n = 87) with transit delayed in the left part of colon and "outlet constipation" (n = 135) for patients with transit delayed in the terminal intestine. Only 3.7 % of patients were "erroneously" classified in the 4 groups recognized by clustering. This unsupervised analysis of segmental colonic transit time shows that the classical division of the colon and the rectum into three segments is sufficient to characterize delayed segmental colonic transit time.
Application of Time-Delay Absorber to Suppress Vibration of a Dynamical System to Tuned Excitation.
El-Ganaini, W A A; El-Gohary, H A
2014-08-01
In this work, we present a comprehensive investigation of the time delay absorber effects on the control of a dynamical system represented by a cantilever beam subjected to tuned excitation forces. Cantilever beam is one of the most widely used system in too many engineering applications, such as mechanical and civil engineering. The main aim of this work is to control the vibration of the beam at simultaneous internal and combined resonance condition, as it is the worst resonance case. Control is conducted via time delay absorber to suppress chaotic vibrations. Time delays often appear in many control systems in the state, in the control input, or in the measurements. Time delay commonly exists in various engineering, biological, and economical systems because of the finite speed of the information processing. It is a source of performance degradation and instability. Multiple time scale perturbation method is applied to obtain a first order approximation for the nonlinear differential equations describing the system behavior. The different resonance cases are reported and studied numerically. The stability of the steady-state solution at the selected worst resonance case is investigated applying Runge-Kutta fourth order method and frequency response equations via Matlab 7.0 and Maple11. Time delay absorber is effective, but within a specified range of time delay. It is the critical factor in selecting such absorber. Time delay absorber is better than the ordinary one as from the effectiveness point of view. The effects of the different absorber parameters on the system behavior and stability are studied numerically. A comparison with the available published work showed a close agreement with some previously published work.
A frequency-domain method for solving linear time delay systems with constant coefficients
Jin, Mengshi; Chen, Wei; Song, Hanwen; Xu, Jian
2018-03-01
In an active control system, time delay will occur due to processes such as signal acquisition and transmission, calculation, and actuation. Time delay systems are usually described by delay differential equations (DDEs). Since it is hard to obtain an analytical solution to a DDE, numerical solution is of necessity. This paper presents a frequency-domain method that uses a truncated transfer function to solve a class of DDEs. The theoretical transfer function is the sum of infinite items expressed in terms of poles and residues. The basic idea is to select the dominant poles and residues to truncate the transfer function, thus ensuring the validity of the solution while improving the efficiency of calculation. Meanwhile, the guideline of selecting these poles and residues is provided. Numerical simulations of both stable and unstable delayed systems are given to verify the proposed method, and the results are presented and analysed in detail.
Exponential stability of uncertain stochastic neural networks with mixed time-delays
Wang Zidong; Lauria, Stanislao; Fang Jian'an; Liu Xiaohui
2007-01-01
This paper is concerned with the global exponential stability analysis problem for a class of stochastic neural networks with mixed time-delays and parameter uncertainties. The mixed delays comprise discrete and distributed time-delays, the parameter uncertainties are norm-bounded, and the neural networks are subjected to stochastic disturbances described in terms of a Brownian motion. The purpose of the stability analysis problem is to derive easy-to-test criteria under which the delayed stochastic neural network is globally, robustly, exponentially stable in the mean square for all admissible parameter uncertainties. By resorting to the Lyapunov-Krasovskii stability theory and the stochastic analysis tools, sufficient stability conditions are established by using an efficient linear matrix inequality (LMI) approach. The proposed criteria can be checked readily by using recently developed numerical packages, where no tuning of parameters is required. An example is provided to demonstrate the usefulness of the proposed criteria
Memory State Feedback RMPC for Multiple Time-Delayed Uncertain Linear Systems with Input Constraints
Wei-Wei Qin
2014-01-01
Full Text Available This paper focuses on the problem of asymptotic stabilization for a class of discrete-time multiple time-delayed uncertain linear systems with input constraints. Then, based on the predictive control principle of receding horizon optimization, a delayed state dependent quadratic function is considered for incorporating MPC problem formulation. By developing a memory state feedback controller, the information of the delayed plant states can be taken into full consideration. The MPC problem is formulated to minimize the upper bound of infinite horizon cost that satisfies the sufficient conditions. Then, based on the Lyapunov-Krasovskii function, a delay-dependent sufficient condition in terms of linear matrix inequality (LMI can be derived to design a robust MPC algorithm. Finally, the digital simulation results prove availability of the proposed method.
Miller, Jonah Maxwell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-10-18
This report has slides on Gravitational Waves; Pound and Rebka: A Shocking Fact; Light is a Ruler; Gravity is the Curvature of Spacetime; Gravitational Waves Made Simple; How a Gravitational Wave Affects Stuff Here; LIGO; This Detection: Neutron Stars; What the Gravitational Wave Looks Like; The Sound of Merging Neutron Stars; Neutron Star Mergers: More than GWs; The Radioactive Cloud; The Kilonova; and finally Summary, Multimessenger Astronomy.
M. de la Sen
2010-01-01
Full Text Available This paper investigates the stability properties of a class of dynamic linear systems possessing several linear time-invariant parameterizations (or configurations which conform a linear time-varying polytopic dynamic system with a finite number of time-varying time-differentiable point delays. The parameterizations may be timevarying and with bounded discontinuities and they can be subject to mixed regular plus impulsive controls within a sequence of time instants of zero measure. The polytopic parameterization for the dynamics associated with each delay is specific, so that (q+1 polytopic parameterizations are considered for a system with q delays being also subject to delay-free dynamics. The considered general dynamic system includes, as particular cases, a wide class of switched linear systems whose individual parameterizations are timeinvariant which are governed by a switching rule. However, the dynamic system under consideration is viewed as much more general since it is time-varying with timevarying delays and the bounded discontinuous changes of active parameterizations are generated by impulsive controls in the dynamics and, at the same time, there is not a prescribed set of candidate potential parameterizations.
Robust convergence of Cohen-Grossberg neural networks with time-varying delays
Xiong Wenjun; Ma Deyi; Liang Jinling
2009-01-01
In this paper, robust convergence is studied for the Cohen-Grossberg neural networks (CGNNs) with time-varying delays. By applying the differential inequality and the Lyapunov method, some delay-independent conditions are derived ensuring the robust CGNNs to converge, globally, uniformly and exponentially, to a ball in the state space with a pre-specified convergence rate. Finally, the effectiveness of our results are verified by an illustrative example.
On global exponential stability of high-order neural networks with time-varying delays
Zhang Baoyong; Xu Shengyuan; Li Yongmin; Chu Yuming
2007-01-01
This Letter investigates the problem of stability analysis for a class of high-order neural networks with time-varying delays. The delays are bounded but not necessarily differentiable. Based on the Lyapunov stability theory together with the linear matrix inequality (LMI) approach and the use of Halanay inequality, sufficient conditions guaranteeing the global exponential stability of the equilibrium point of the considered neural networks are presented. Two numerical examples are provided to demonstrate the effectiveness of the proposed stability criteria
On global exponential stability of high-order neural networks with time-varying delays
Zhang Baoyong [School of Automation, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu (China)]. E-mail: baoyongzhang@yahoo.com.cn; Xu Shengyuan [School of Automation, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu (China)]. E-mail: syxu02@yahoo.com.cn; Li Yongmin [School of Automation, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu (China) and Department of Mathematics, Huzhou Teacher' s College, Huzhou 313000, Zhejiang (China)]. E-mail: ymlwww@163.com; Chu Yuming [Department of Mathematics, Huzhou Teacher' s College, Huzhou 313000, Zhejiang (China)
2007-06-18
This Letter investigates the problem of stability analysis for a class of high-order neural networks with time-varying delays. The delays are bounded but not necessarily differentiable. Based on the Lyapunov stability theory together with the linear matrix inequality (LMI) approach and the use of Halanay inequality, sufficient conditions guaranteeing the global exponential stability of the equilibrium point of the considered neural networks are presented. Two numerical examples are provided to demonstrate the effectiveness of the proposed stability criteria.
Liang Jinling; Cao Jinde
2003-01-01
Employing general Halanay inequality, we analyze the global exponential stability of a class of reaction-diffusion recurrent neural networks with time-varying delays. Several new sufficient conditions are obtained to ensure existence, uniqueness and global exponential stability of the equilibrium point of delayed reaction-diffusion recurrent neural networks. The results extend and improve the earlier publications. In addition, an example is given to show the effectiveness of the obtained result
Improved result on stability analysis of discrete stochastic neural networks with time delay
Wu Zhengguang; Su Hongye; Chu Jian; Zhou Wuneng
2009-01-01
This Letter investigates the problem of exponential stability for discrete stochastic time-delay neural networks. By defining a novel Lyapunov functional, an improved delay-dependent exponential stability criterion is established in terms of linear matrix inequality (LMI) approach. Meanwhile, the computational complexity of the newly established stability condition is reduced because less variables are involved. Numerical example is given to illustrate the effectiveness and the benefits of the proposed method.
Cracking chaos-based encryption systems ruled by nonlinear time delay differential equations
Udaltsov, Vladimir S.; Goedgebuer, Jean-Pierre; Larger, Laurent; Cuenot, Jean-Baptiste; Levy, Pascal; Rhodes, William T.
2003-01-01
We report that signal encoding with high-dimensional chaos produced by delayed feedback systems with a strong nonlinearity can be broken. We describe the procedure and illustrate the method with chaotic waveforms obtained from a strongly nonlinear optical system that we used previously to demonstrate signal encryption/decryption with chaos in wavelength. The method can be extended to any systems ruled by nonlinear time-delayed differential equations
Reliable Memory Feedback Design for a Class of Nonlinear Fuzzy Systems with Time-varying Delay
You-Qing Wang; Dong-Hua Zhou; Li-Heng Liu
2007-01-01
This paper is concerned with the robust reliable memory controller design for a class of fuzzy uncertain systems with time-varying delay. The system under consideration is more general than those in other existent works. The controller, which is dependent on the magnitudes and derivative of the delay, is proposed in terms of linear matrix inequality (LMI). The closed-loop system is asymptotically stable for all admissible uncertainties as well as actuator faults. A numerical example is presented for illustration.
Park, Ju H.; Lee, S.M.; Kwon, O.M.
2009-01-01
For bidirectional associate memory neural networks with time-varying delays, the problems of determining the exponential stability and estimating the exponential convergence rate are investigated by employing the Lyapunov functional method and linear matrix inequality (LMI) technique. A novel criterion for the stability, which give information on the delay-dependent property, is derived. A numerical example is given to demonstrate the effectiveness of the obtained results.