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Sample records for attosecond time delays

  1. Time delays for attosecond streaking in photoionization of neon

    CERN Document Server

    Feist, Johannes; Nagele, Stefan; Pazourek, Renate; Burgdörfer, Joachim; Guan, Xiaoxu; Bartschat, Klaus; Schneider, Barry I

    2014-01-01

    We revisit the time-resolved photoemission in neon atoms as probed by attosecond streaking. We calculate streaking time shifts for the emission of 2p and 2s electrons and compare the relative delay as measured in a recent experiment by Schultze et al. [Science 328, 1658 (2010)]. The B-spline R-matrix method is employed to calculate accurate Eisenbud-Wigner-Smith time delays from multi- electron dipole transition matrix elements for photoionization. The additional laser field-induced time shifts in the exit channel are obtained from separate, time-dependent simulations of a full streaking process by solving the time-dependent Schr\\"odinger equation on the single-active-electron level. The resulting accurate total relative streaking time shifts between 2s and 2p emission lie well below the experimental data. We identify the presence of unresolved shake-up satellites in the experiment as a potential source of error in the determination of streaking time shifts.

  2. Spectral enhancement of single attosecond pulses by time-delayed control field

    CERN Document Server

    Chu, Wei-Chun

    2012-01-01

    An optical coherent control scheme has been proposed where an extreme ultraviolet single attosecond pulse (SAP) propagates through a dense helium gas dressed by a time-delayed femtosecond laser pulse. The laser pulse couples the 2s2p(^1P) and 2s^2(^1S) autoionizing states when the SAP excites the 2s2p state. After going through the gas, the spectral and temporal profiles of the SAP are strongly distorted. A narrowed but enhanced spike in the spectrum shows up for specific intensities and time delays of the laser, which exemplifies the control of a broadband photon wave packet by an ultrashort dressing field for the first time. We analyze the photon and electron dynamics and conclude on the dressing condition that maximizes this enhancement. The result demonstrates new possibilities of attosecond optical control.

  3. Time-resolved photoemission using attosecond streaking

    Science.gov (United States)

    Nagele, S.; Pazourek, R.; Wais, M.; Wachter, G.; Burgdörfer, J.

    2014-04-01

    We theoretically study time-resolved photoemission in atoms as probed by attosecond streaking. We review recent advances in the study of the photoelectric efect in the time domain and show that the experimentally accessible time shifts can be decomposed into distinct contributions that stem from the feld-free photoionization process itself and from probe-field induced corrections. We perform accurate quantum-mechanical as well as classical simulations of attosecond streaking for efective one-electron systems and determine all relevant contributions to the time delay with attosecond precision. In particular, we investigate the properties and limitations of attosecond streaking for the transition from short-ranged potentials (photodetachment) to long-ranged Coulomb potentials (photoionization). As an example for a more complex system, we study time-resolved photoionization for endohedral fullerenes A@C60 and discuss how streaking time shifts are modifed due to the interaction of the C60 cage with the probing infrared streaking field.

  4. Doubly-excited state effects on two-photon double ionization of helium by time-delayed, oppositely circularly-polarized attosecond pulses

    Science.gov (United States)

    Ngoko Djiokap, J. M.; Starace, Anthony F.

    2017-12-01

    We study two-photon double ionization (TPDI) of helium by a pair of time-delayed (non-overlapping), oppositely circularly-polarized attosecond pulses whose carrier frequencies are resonant with 1P o doubly-excited states. All of our TPDI results are obtained by numerical solution of the two-electron time-dependent Schrödinger equation for the six-dimensional case of circularly-polarized attosecond pulses, and they are analyzed using perturbation theory (PT). As compared with the corresponding nonresonant TPDI process, we find that the doubly-excited states change the character of vortex patterns in the two-electron momentum distributions for the case of back-to-back detection of the two ionized electrons in the polarization plane. The doubly-excited states also completely change the structure of fixed-energy, two-electron angular distributions. Moreover, both the fixed-energy and energy-integrated angular distributions, as well as the two-electron energy distributions, exhibit a periodicity with time delay τ between the two attosecond pulses of about 69 as, i.e. the beat period between the (2s2p){}1{{{P}}}o doubly-excited state and the He ground state. Using PT we derive an expression for an angle-integrated energy distribution that is sensitive to the slower beat period ∼1.2 fs between different doubly-excited states as well as to the long timescale ∼17 fs of autoionization lifetimes. However, with our current computer codes we are only able to study numerically the time-dependent phenomena occurring on an attosecond time scale.

  5. Probing single-photon ionization on the attosecond time scale

    CERN Document Server

    Klünder, K; Gisselbrecht, M; Fordell, T; Swoboda, M; Guénot, D; Johnsson, P; Caillat, J; Mauritsson, J; Maquet, A; Taïeb, R; L'Huillier, A

    2010-01-01

    We study photoionization of argon atoms excited by attosecond pulses using an interferometric measurement technique. We measure the difference in time delays between electrons emitted from the $3s^2$ and from the $3p^6$ shell, at different excitation energies ranging from 32 to 42 eV. The determination of single photoemission time delays requires to take into account the measurement process, involving the interaction with a probing infrared field. This contribution can be estimated using an universal formula and is found to account for a substantial fraction of the measured delay.

  6. Attosecond delay of xenon $4d$ photoionization at the giant resonance and Cooper minimum

    CERN Document Server

    Magrakvelidze, Maia; Chakraborty, Himadri S

    2016-01-01

    A Kohn-Sham time-dependent local-density-functional scheme is utilized to predict attosecond time delays of xenon 4d photoionization that involves the 4d giant dipole resonance and Cooper minimum. The fundamental effect of electron correlations to uniquely determine the delay at both regions is demonstrated. In particular, for the giant dipole resonance, the delay underpins strong collective effect, emulating the recent prediction at C60 giant plasmon resonance [T. Barillot et al, Phys. Rev. A 91, 033413 (2015)]. For the Cooper minimum, a qualitative similarity with a photorecombination experiment near argon 3p minimum [S. B. Schoun et al, Phys. Rev. Lett. 112, 153001 (2014)] is found. The result should encourage attosecond measurements of Xe 4d photoemission.

  7. Attosecond delays in laser-assisted photodetachment from closed-shell negative ions

    Science.gov (United States)

    Lindroth, Eva; Dahlström, Jan Marcus

    2017-07-01

    We study laser-assisted photodetachment time delays by attosecond pulse trains from the closed-shell negative ions F- and Cl-. We investigate the separability of the delay into two contributions: (i) the Wigner-like delay associated with one-photon ionization by the attosecond pulse train and (ii) the delay associated with the exchange of an additional laser photon in the presence of the potential of the remaining target. Based on the asymptotic form of the wave packet, the latter term is expected to be negligible because the ion is neutralized, leading to a vanishing laser-ion interaction with increasing electron-atom separation. While this asymptotic behavior is verified at high photoelectron energies, we also quantify sharp deviations at low photoelectron energies. Further, these low-energy delays are clearly different for the two studied anions, indicating a breakdown of the universality of laser-ion-induced delays. The fact that the short-range potential can induce a delay of as much as 50 as can have implications for the interpretation of delay measurements also in other systems that lack long-range potential.

  8. Attosecond relative delay among xenon 5p, 5s, and 4d photoionization

    Science.gov (United States)

    Magrakvelidze, Maia; Madjet, Mohamed; Chakraborty, Himadri

    2017-04-01

    Attosecond Wigner-Smith (WS) time delays of the photoemissions of Xe valence 5p, 5s, and core 4d electrons are investigated in details using the time-dependent local density approximation (TDLDA). Electron correlations determine the energy-dependent structures in ionization phases of the dipole channels and in the resulting WS delays at various shape resonances, induced by the collective motion of 4d electrons, and at various Cooper minima. We find that our calculation closely agrees with the streaking measurement for the delay of 4d relative to 5s, and predicts accelerated emission of 5p with respect to 4d as was experimentally observed at similar photon energies for Xe atoms adsorbed on the tungsten surface. This work was supported by the U.S. National Science Foundation.

  9. Attosecond Timing in Optical-to-Electrical Conversion

    CERN Document Server

    Baynes, Fred N; Fortier, Tara; Zhou, Qiugui; Beling, Andreas; Campbell, Joe C; Diddames, Scott A

    2014-01-01

    The most frequency-stable sources of electromagnetic radiation are produced optically, and optical frequency combs provide the means for high fidelity frequency transfer across hundreds of terahertz and into the microwave domain. A critical step in this photonic-based synthesis of microwave signals is the optical-to-electrical conversion process. Here we show that attosecond (as) timing stability can be preserved across the opto-electronic interface of a photodiode, despite an intrinsic temporal response that is more than six orders of magnitude slower. The excess timing noise in the photodetection of a periodic train of ultrashort optical pulses behaves as flicker noise (1/f) with amplitude of 4 as/Sqrt(Hz) at 1 Hz offset. The corresponding fractional frequency fluctuations are 1.4x10-17 at 1 second and 5.5x10-20 at 1000 seconds. These results demonstrate that direct photodetection, as part of frequency-comb-based microwave synthesis, can support the timing performance of the best optical frequency standards...

  10. Photoemission and photoionization time delays and rates

    Directory of Open Access Journals (Sweden)

    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.

  11. Mapping the Dissociative Ionization Dynamics of Molecular Nitrogen with Attosecond Time Resolution

    Directory of Open Access Journals (Sweden)

    A. Trabattoni

    2015-12-01

    Full Text Available Studying the interaction of molecular nitrogen with extreme ultraviolet (XUV radiation is of prime importance to understand radiation-induced processes occurring in Earth’s upper atmosphere. In particular, photoinduced dissociation dynamics involving excited states of N_{2}^{+} leads to N and N^{+} atomic species that are relevant in atmospheric photochemical processes. However, tracking the relaxation dynamics of highly excited states of N_{2}^{+} is difficult to achieve, and its theoretical modeling is notoriously complex. Here, we report on an experimental and theoretical investigation of the dissociation dynamics of N_{2}^{+} induced by isolated attosecond XUV pulses in combination with few-optical-cycle near-infrared/visible (NIR/VIS pulses. The momentum distribution of the produced N^{+} fragments is measured as a function of pump-probe delay with subfemtosecond resolution using a velocity map imaging spectrometer. The time-dependent measurements reveal the presence of NIR/VIS-induced transitions between N_{2}^{+} states together with an interference pattern that carries the signature of the potential energy curves activated by the XUV pulse. We show that the subfemtosecond characterization of the interference pattern is essential for a semiquantitative determination of the repulsive part of these curves.

  12. EDITORIAL: Focus on Attosecond Physics

    Science.gov (United States)

    Bandrauk, André D.; Krausz, Ferenc; Starace, Anthony F.

    2008-02-01

    Chelkowski and A D Bandrauk Broadband generation in a Raman crystal driven by a pair of time-delayed linearly chirped pulses Miaochan Zhi and Alexei V Sokolov Ultrafast nanoplasmonics under coherent control Mark I Stockman Attosecond pulse carrier-envelope phase effects on ionized electron momentum and energy distributions: roles of frequency, intensity and an additional IR pulse Liang-You Peng, Evgeny A Pronin and Anthony F Starace Angular encoding in attosecond recollision Markus Kitzler, Xinhua Xie, Stefan Roither, Armin Scrinzi and Andrius Baltuska Polarization-resolved pump-probe spectroscopy with high harmonics Y Mairesse, S Haessler, B Fabre, J Higuet, W Boutu, P Breger, E Constant, D Descamps, E Mével, S Petit and P Salières Macroscopic effects in attosecond pulse generation T Ruchon, C P Hauri, K Varjú, E Mansten, M Swoboda, R López-Martens and A L'Huillier Monitoring long-term evolution of molecular vibrational wave packet using high-order harmonic generation M Yu Emelin, M Yu Ryabikin and A M Sergeev Intense single attosecond pulses from surface harmonics using the polarization gating technique S G Rykovanov, M Geissler, J Meyer-ter-Vehn and G D Tsakiris Imaging of carrier-envelope phase effects in above-threshold ionization with intense few-cycle laser fields M F Kling, J Rauschenberger, A J Verhoef, E Hasović, T Uphues, D B Milošević, H G Muller and M J J Vrakking Self-compression of optical laser pulses by filamentation A Mysyrowicz, A Couairon and U Keller Towards efficient generation of attosecond pulses from overdense plasma targets N M Naumova, C P Hauri, J A Nees, I V Sokolov, R Lopez-Martens and G A Mourou Quantum-path control in high-order harmonic generation at high photon energies Xiaoshi Zhang, Amy L Lytle, Oren Cohen, Margaret M Murnane and Henry C Kapteyn Time-resolved mapping of correlated electron emission from helium atom in an intense laser pulse C Ruiz and A Becker Pump and probe ultrafast electron dynamics in LiH: a computational study

  13. Characterization and Application of Isolated Attosecond Pulses

    Science.gov (United States)

    Wei, Hui

    Isolated attosecond pulse (IAP) is a tool of probing electronic dynamics occurring in atoms, molecules, clusters and solids, since the time scale of electronic motion is on the order of attoseconds. The generation, characterization and applications of IAPs has become one of the fast frontiers of laser experiments. This dissertation focuses on several aspects of attosecond physics. First, we study the driving wavelength scaling of the yield of high-order harmonic generation (HHG) by applying the quantum orbit theory. The unfavorable scaling law especially for the short quantum orbit is of great importance to attoseond pulse generation toward hundreds of eVs or keV photon energy region by mid-infrared (mid-IR) lasers. Second, we investigate the accuracy of the current frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG-CRAB) and phase retrieval by omega oscillation filtering (PROOF) methods for IAP characterization by simulating the experimental data by theoretical calculation. This calibration is critical but has not been carefully carried out before. We also present an improved method, namely the swPROOF which is more universal and robust than the original PROOF method. Third, we investigate the controversial topic of photoionization time delay. We find the limitation of the FROG-CRAB method which has been used to extract the photoionization time delay between the 2s and 2p channels in neon. The time delay retrieval is sensitive to the attochirp of the XUV pulse, which may lead to discrepancies between experiment and theory. A new fitting method is proposed in order to overcome the limitations of FROG-CRAB. Finally, IAPs are used to probe the dynamic of electron correlation in helium atom by means of attosecond transient absorption spectroscopy. The agreement between the measurement and our analytical model verifies the observation of time-dependent build up of the 2s2p Fano resonance.

  14. Statistical approach to tunneling time in attosecond experiments

    Science.gov (United States)

    Demir, Durmuş; Güner, Tuğrul

    2017-11-01

    Tunneling, transport of particles through classically forbidden regions, is a pure quantum phenomenon. It governs numerous phenomena ranging from single-molecule electronics to donor-acceptor transition reactions. The main problem is the absence of a universal method to compute tunneling time. This problem has been attacked in various ways in the literature. Here, in the present work, we show that a statistical approach to the problem, motivated by the imaginary nature of time in the forbidden regions, lead to a novel tunneling time formula which is real and subluminal (in contrast to various known time definitions implying superluminal tunneling). In addition to this, we show explicitly that the entropic time formula is in good agreement with the tunneling time measurements in laser-driven He ionization. Moreover, it sets an accurate range for long-range electron transfer reactions. The entropic time formula is general enough to extend to the photon and phonon tunneling phenomena.

  15. Angle-resolved time delay in photoemission of neon

    CERN Document Server

    Wätzel, J; Pavlyukh, Y; Berakdar, J

    2013-01-01

    We investigate theoretically the relative time delay of photoelectrons originating from the different subshells (2s and 2p) of neon. This quantity was measured via attosecond streaking and studied theoretically by Schultze et al. [Science 328, 1658 (2010)]. A substantial discrepancy was found between the measured and the calculated values of the relative time delay. Several theoretical studies has been put forward to resolve this issue, e.g. by including correlation effects. In the present paper we explore the directional dependence of the photoelectron emission and the consequences for the inferred time delay. Our quantum mechanical calculations for an electron subject to laser fields and an effective single particle potential show that the time delay is indeed strongly angular dependent. Compared to strict forward emission we find that accounting for emission within a cone of 45 deg aperture, leads to a substantially increase of the relative time delay.

  16. Attosecond photoionization dynamics in neon

    Science.gov (United States)

    Omiste, Juan J.; Madsen, Lars Bojer

    2018-01-01

    We study the role of electron-electron correlation in the ground state of Ne, as well as in photoionization dynamics induced by an attosecond XUV pulse. For a selection of central photon energies around 100 eV, we find that while the mean-field time-dependent Hartree-Fock method provides qualitatively correct results for the total ionization yield, the photoionization cross section, the photoelectron momentum distribution, as well as for the time delay in photoionization, electron-electron correlation is important for a quantitative description of these quantities.

  17. Theory of attosecond absorption spectroscopy in krypton

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Lindroth, Eva; Madsen, Lars Bojer

    2012-01-01

    A theory for time-domain attosecond pump–attosecond probe photoabsorption spectroscopy is formulated and related to the atomic response. The theory is illustrated through a study of attosecond absorption spectroscopy in krypton. The atomic parameters entering the formulation such as energies...

  18. Attosecond photoelectron spectroscopy of electron transport in solids

    Energy Technology Data Exchange (ETDEWEB)

    Magerl, Elisabeth

    2011-03-31

    Time-resolved photoelectron spectroscopy of condensed matter systems in the attosecond regime promises new insights into excitation mechanisms and transient dynamics of electrons in solids. This timescale became accessible directly only recently with the development of the attosecond streak camera and of laser systems providing few-cycle, phase-controlled laser pulses in the near-infrared, which are used to generate isolated, sub-femtosecond extreme-ultraviolet pulses with a well-defined timing with respect to the near-infrared pulse. Employing these pulses, the attosecond streak camera offers time resolutions as short as a few 10 attoseconds. In the framework of this thesis, a new, versatile experimental apparatus combining attosecond pulse generation in gases with state of the art surface science techniques is designed, constructed, and commissioned. Employing this novel infrastructure and the technique of the attosecond transient recorder, we investigate transport phenomena occurring after photoexcitation of electrons in tungsten and rhenium single crystals and show that attosecond streaking is a unique method for resolving extremely fast electronic phenomena in solids. It is demonstrated that electrons originating from different energy levels, i.e. from the conduction band and the 4f core level, are emitted from the crystal surface at different times. The origin of this time delay, which is below 150 attoseconds for all studied systems, is investigated by a systematic variation of several experimental parameters, in particular the photon energy of the employed attosecond pulses. These experimental studies are complemented by theoretical studies of the group velocity of highly-excited electrons based on ab initio calculations. While the streaking technique applied on single crystals can provide only information about the relative time delay between two types of photoelectrons, the absolute transport time remains inaccessible. We introduce a scheme of a reference

  19. Flexible attosecond beamline for high harmonic spectroscopy and XUV/near-IR pump probe experiments requiring long acquisition times

    Science.gov (United States)

    Weber, S. J.; Manschwetus, B.; Billon, M.; Böttcher, M.; Bougeard, M.; Breger, P.; Géléoc, M.; Gruson, V.; Huetz, A.; Lin, N.; Picard, Y. J.; Ruchon, T.; Salières, P.; Carré, B.

    2015-03-01

    We describe the versatile features of the attosecond beamline recently installed at CEA-Saclay on the PLFA kHz laser. It combines a fine and very complete set of diagnostics enabling high harmonic spectroscopy (HHS) through the advanced characterization of the amplitude, phase, and polarization of the harmonic emission. It also allows a variety of photo-ionization experiments using magnetic bottle and COLTRIMS (COLd Target Recoil Ion Momentum Microscopy) electron spectrometers that may be used simultaneously, thanks to a two-foci configuration. Using both passive and active stabilization, special care was paid to the long term stability of the system to allow, using both experimental approaches, time resolved studies with attosecond precision, typically over several hours of acquisition times. As an illustration, applications to multi-orbital HHS and electron-ion coincidence time resolved spectroscopy are presented.

  20. Time-Delay Interferometry

    Directory of Open Access Journals (Sweden)

    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.

  1. Angular anisotropy of time delay in XUV/IR photoionization of H$_2^+$

    CERN Document Server

    Serov, Vladislav V

    2016-01-01

    We develop a novel technique for modeling of atomic and molecular ionization in superposition of XUV and IR fields with characteristics typical for attosecond streaking and RABBITT experiments. The method is based on solving the time-dependent Schr\\"odinger equation in the coordinate frame expanding along with the photoelectron wave packet. The efficiency of the method is demonstrated by calculating angular anisotropy of photoemission time delay of the H$_2^+$ ion in a field configuration of recent RABBITT experiments.

  2. Attosecond VUV Coherent Control of Molecular Dynamics

    CERN Document Server

    Ranitovic, P; Riviere, P; Palacios, A; Tong, X M; Toshima, N; Gonzalez-Castrillo, A; Martin, L; Martin, F; Murnane, M M; Kapteyn, H C

    2014-01-01

    High harmonic light sources make it possible to access attosecond time-scales, thus opening up the prospect of manipulating electronic wave packets for steering molecular dynamics. However, two decades after the birth of attosecond physics, the concept of attosecond chemistry has not yet been realized. This is because excitation and manipulation of molecular orbitals requires precisely controlled attosecond waveforms in the deep ultraviolet, which have not yet been synthesized. Here, we present a novel approach using attosecond vacuum ultraviolet pulse-trains to coherently excite and control the outcome of a simple chemical reaction in a deuterium molecule in a non-Born Oppenheimer regime. By controlling the interfering pathways of electron wave packets in the excited neutral and singly-ionized molecule, we unambiguously show that we can switch the excited electronic state on attosecond timescales, coherently guide the nuclear wave packets to dictate the way a neutral molecule vibrates, and steer and manipula...

  3. Wigner time delay and spin-orbit activated confinement resonances

    Science.gov (United States)

    Keating, D. A.; Deshmukh, P. C.; Manson, S. T.

    2017-09-01

    A study of the photoionization of spin-orbit split subshells of high-Z atoms confined in C60 has been performed using the relativistic-random-phase approximation. Specifically, Hg@C60 5p, Rn@C60 6p and Ra@C60 5d were investigated and the near-threshold confinement resonances in the j = l - 1/2 channels were found to engender structures in the j = l + 1/2 cross sections via correlation in the form of interchannel coupling. These structures are termed spin-orbit induced confinement resonances and they are found to profoundly influence the Wigner time delay spectrum resulting in time delays of tens or hundreds of attoseconds along with dramatic swings in time delay over small energy intervals. Pronounced relativistic effects in time delay are also found. These structures, including their manifestation in time delay spectra, are expected to be general phenomena in the photoionization of spin-orbit doublets in confined high-Z atoms.

  4. Attosecond correlation dynamics

    Science.gov (United States)

    Ossiander, M.; Siegrist, F.; Shirvanyan, V.; Pazourek, R.; Sommer, A.; Latka, T.; Guggenmos, A.; Nagele, S.; Feist, J.; Burgdörfer, J.; Kienberger, R.; Schultze, M.

    2017-03-01

    Photoemission of an electron is commonly treated as a one-particle phenomenon. With attosecond streaking spectroscopy we observe the breakdown of this single active-electron approximation by recording up to six attoseconds retardation of the dislodged photoelectron due to electronic correlations. We recorded the photon-energy-dependent emission timing of electrons, released from the helium ground state by an extreme-ultraviolet photon, either leaving the ion in its ground state or exciting it into a shake-up state. We identify an optical field-driven d.c. Stark shift of charge-asymmetric ionic states formed after the entangled photoemission as a key contribution to the observed correlation time shift. These findings enable a complete wavepacket reconstruction and are universal for all polarized initial and final states. Sub-attosecond agreement with quantum mechanical ab initio modelling allows us to determine the absolute zero of time in the photoelectric effect to a precision better than 1/25th of the atomic unit of time.

  5. Time Delay of CGM Sensors

    Science.gov (United States)

    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

  6. Attosecond beamline with actively stabilized and spatially separated beam paths.

    Science.gov (United States)

    Huppert, M; Jordan, I; Wörner, H J

    2015-12-01

    We describe a versatile and compact beamline for attosecond spectroscopy. The setup consists of a high-order harmonic source followed by a delay line that spatially separates and then recombines the extreme-ultraviolet (XUV) and residual infrared (IR) pulses. The beamline introduces a controlled and actively stabilized delay between the XUV and IR pulses on the attosecond time scale. A new active-stabilization scheme combining a helium-neon-laser and a white-light interferometer minimizes fluctuations and allows to control delays accurately (26 as rms during 1.5 h) over long time scales. The high-order-harmonic-generation region is imaged via optical systems, independently for XUV and IR, into an interaction volume to perform pump-probe experiments. As a consequence of the spatial separation, the pulses can be independently manipulated in intensity, polarization, and frequency content. The beamline can be combined with a variety of detectors for measuring attosecond dynamics in gases, liquids, and solids.

  7. Time Delay in Molecular Photoionization

    CERN Document Server

    Hockett, P; Villeneuve, D M; Corkum, P B

    2015-01-01

    Time-delays in the photoionization of molecules are investigated. As compared to atomic ionization, the time-delays expected from molecular ionization present a much richer phenomenon, with a strong spatial dependence due to the anisotropic nature of the molecular scattering potential. We investigate this from a scattering theory perspective, and make use of molecular photoionization calculations to examine this effect in representative homonuclear and hetronuclear diatomic molecules, nitrogen and carbon monoxide. We present energy and angle-resolved maps of the Wigner delay time for single-photon valence ionization, and discuss the possibilities for experimental measurements.

  8. Attosecond physics at the nanoscale

    CERN Document Server

    Ciappina, M F; Landsman, A S; Okell, W; Zherebtsov, S; Förg, B; Schötz, J; Seiffert, J L; Fennel, T; Shaaran, T; Zimmermann, T; Chacón, A; Guichard, R; Zaïr, A; Tisch, J W G; Marangos, J P; Witting, T; Braun, A; Maier, S A; Roso, L; Krüger, M; Hommelhoff, P; Kling, M F; Krausz, F; Lewenstein, M

    2016-01-01

    Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds, which is comparable with the optical field. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this article we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spati...

  9. Attosecond photoionization dynamics in neon

    DEFF Research Database (Denmark)

    Omiste, Juan J.; Madsen, Lars Bojer

    2018-01-01

    We study the role of electron-electron correlation in the ground-state of Ne, as well as in photoionization dynamics induced by an attosecond XUV pulse. For a selection of central photon energies around 100 eV, we find that while the mean-field time-dependent Hartree-Fock method provides qualitat...

  10. Circularly polarized attosecond pulse generation and applications to ultrafast magnetism

    Science.gov (United States)

    Bandrauk, André D.; Guo, Jing; Yuan, Kai-Jun

    2017-12-01

    Attosecond science is a growing new field of research and potential applications which relies on the development of attosecond light sources. Achievements in the generation and application of attosecond pulses enable to investigate electron dynamics in the nonlinear nonperturbative regime of laser-matter interactions on the electron’s natural time scale, the attosecond. In this review, we describe the generation of circularly polarized attosecond pulses and their applications to induce attosecond magnetic fields, new tools for ultrafast magnetism. Simulations are performed on aligned one-electron molecular ions by using nonperturbative nonlinear solutions of the time-dependent Schrödinger equation. We discuss how bichromatic circularly polarized laser pulses with co-rotating or counter-rotating components induce electron-parent ion recollisions, thus producing circularly polarized high-order harmonic generation, the source of circularly polarized attosecond pulses. Ultrafast quantum electron currents created by the generated attosecond pulses give rise to attosecond magnetic field pulses. The results provide a guiding principle for producing circularly polarized attosecond pulses and ultrafast magnetic fields in complex molecular systems for future research in ultrafast magneto-optics.

  11. Design and test of a broadband split-and-delay unit for attosecond XUV-XUV pump-probe experiments

    Science.gov (United States)

    Campi, F.; Coudert-Alteirac, H.; Miranda, M.; Rading, L.; Manschwetus, B.; Rudawski, P.; L'Huillier, A.; Johnsson, P.

    2016-02-01

    We present the design of a split-and-delay unit for the production of two delayed replicas of an incident extreme ultraviolet (XUV) pulse. The device features a single grazing incidence reflection in combination with attenuation of remaining infrared light co-propagating with the XUV beam, offering a high throughput without the need of introducing additional optics that would further decrease the XUV flux. To achieve the required spatial and temporal stabilities, the device is controlled by two PID-controllers monitoring the delay and the beam pointing using an optical reference laser beam, making collimation of the beam by additional optics unnecessary. Finally, we demonstrate the stability of the split-and-delay unit by performing all-reflective autocorrelation measurements on broadband few-cycle laser pulses.

  12. 49 CFR 236.563 - Delay time.

    Science.gov (United States)

    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. ...

  13. Probing electronic binding potentials with attosecond photoelectron wavepackets

    Science.gov (United States)

    Kiesewetter, D.; Jones, R. R.; Camper, A.; Schoun, S. B.; Agostini, P.; Dimauro, L. F.

    2018-01-01

    The central goal of attosecond science is to visualize, understand and ultimately control electron dynamics in matter over the fastest relevant timescales. To date, numerous schemes have demonstrated exquisite temporal resolution, on the order of ten attoseconds, in measurements of the response of photo-excited electrons to time-delayed probes. However, attributing this response to specific dynamical mechanisms is difficult, requiring guidance from advanced calculations. Here we show that energy transfer between an oscillating field and low-energy attosecond photoelectron wavepackets directly provides coarse-grained information on the effective binding potential from which the electrons are liberated. We employ a dense extreme ultraviolet (XUV) harmonic comb to photoionize He, Ne and Ar atoms and record the electron spectra as a function of the phase of a mid-infrared dressing field. The amplitude and phase of the resulting interference modulations in the electron spectra reveal the average momentum and change in momentum of the electron wavepackets during the first quarter-period of the dressing field after their creation, reflecting the corresponding coarse characteristics of the binding potential.

  14. Decoherence in attosecond photoionization.

    Science.gov (United States)

    Pabst, Stefan; Greenman, Loren; Ho, Phay J; Mazziotti, David A; Santra, Robin

    2011-02-04

    The creation of superpositions of hole states via single-photon ionization using attosecond extreme-ultraviolet pulses is studied with the time-dependent configuration-interaction singles (TDCIS) method. Specifically, the degree of coherence between hole states in atomic xenon is investigated. We find that interchannel coupling not only affects the hole populations, but it also enhances the entanglement between the photoelectron and the remaining ion, thereby reducing the coherence within the ion. As a consequence, even if the spectral bandwidth of the ionizing pulse exceeds the energy splittings among the hole states involved, perfectly coherent hole wave packets cannot be formed. For sufficiently large spectral bandwidth, the coherence can only be increased by increasing the mean photon energy.

  15. PRECISION TIME-DELAY GENERATOR

    Science.gov (United States)

    Carr, B.J.; Peckham, V.D.

    1959-06-16

    A precision time-delay generator circuit with low jitter is described. The first thyratron has a series resonant circuit and a diode which is connected to the second thyratron. The first thyratron is triggered at the begin-ning of a time delay and a capacitor is discharged through the first thyratron and the diode, thereby, triggering the second thyratron. (T.R.H.) l6l9O The instrument described can measure pressures between sea level and 300,000 ft. The pressure- sensing transducer of the instrument is a small cylindrical tube with a thin foil of titanium-tritium fastened around the inside of the tube. Output is a digital signal which can be used for storage or telemetering more conveniently than an analog signal. (W.D.M.) l6l9l An experimental study was made on rolling contacts in the temperature range of 550 to 1000 deg F. Variables such as material composition, hardness, and operating conditions were investigated in a rolling test stand. Ball bearing tests were run to determine the effect of design parameters, bearing materials, lubricants, and operating conditions. (auth)

  16. Synchronizing time delay systems using variable delay in coupling

    Energy Technology Data Exchange (ETDEWEB)

    Ambika, G., E-mail: g.ambika@iiserpune.ac.in [Indian Institute of Science Education and Research, Pune 411 021 (India); Amritkar, R.E., E-mail: amritkar@prl.res.in [Physical Research Laboratory, Ahmedabad 380 009 (India)

    2011-11-15

    Highlights: > Delay and anticipation in coupling function varies with system dynamics. > Delay or anticipation of the synchronized state is independent of system delay. > Stability analysis developed is quite general. > We demonstrate enhanced security in communication. > Generalized synchronization possible over a wide range of parameter mismatch. - Abstract: We present a mechanism for synchronizing time delay systems using one way coupling with a variable delay in coupling that is reset at finite intervals. We present the analysis of the error dynamics that helps to isolate regions of stability of the synchronized state in the parameter space of interest for single and multiple delays. We supplement this by numerical simulations in a standard time delay system like Mackey Glass system. This method has the advantage that it can be adjusted to be delay or anticipatory in synchronization with a time which is independent of the system delay. We demonstrate the use of this method in communication using the bi channel scheme. We show that since the synchronizing channel carries information from transmitter only at intervals of reset time, it is not susceptible to an easy reconstruction.

  17. How to understand the tunneling in attosecond experiment?. Bohr-Einstein photon box Gedanken experiment, tunneling time and the wave particle duality

    Science.gov (United States)

    Kullie, Ossama

    2018-02-01

    The measurement of the tunneling time (T-time) in today's attosecond and strong field (low-frequency) experiments, despite its controversial discussion, offers a fruitful opportunity to understand time measurement and the time in quantum mechanics. In addition, as we will see in this work, a related controversial issue is the particulate nature of the radiation. The T-time in attosecond experiment and its different aspects and models, is discussed in this work, especially in relation to my model of real T-time (Kullie, 2015), where a good agreement with the experiment and an intriguing similarity to the Bohr-Einstein photon box Gedanken experiment was found. The tunneling process itself is still not well understood, but I am arguing that a scattering mechanism (by the laser wave packet) offers a possibility to understand the tunneling process in the tunneling region. This is related to the question about the corpuscular nature of light which is widely discussed in modern quantum optics experiments.

  18. Attosecond physics at the nanoscale.

    Science.gov (United States)

    Ciappina, M F; Pérez-Hernández, J A; Landsman, A S; Okell, W A; Zherebtsov, S; Förg, B; Schötz, J; Seiffert, L; Fennel, T; Shaaran, T; Zimmermann, T; Chacón, A; Guichard, R; Zaïr, A; Tisch, J W G; Marangos, J P; Witting, T; Braun, A; Maier, S A; Roso, L; Krüger, M; Hommelhoff, P; Kling, M F; Krausz, F; Lewenstein, M

    2017-05-01

    Recently two emerging areas of research, attosecond and nanoscale physics, have started to come together. Attosecond physics deals with phenomena occurring when ultrashort laser pulses, with duration on the femto- and sub-femtosecond time scales, interact with atoms, molecules or solids. The laser-induced electron dynamics occurs natively on a timescale down to a few hundred or even tens of attoseconds (1 attosecond  =  1 as  =  10 -18 s), which is comparable with the optical field. For comparison, the revolution of an electron on a 1s orbital of a hydrogen atom is  ∼152 as. On the other hand, the second branch involves the manipulation and engineering of mesoscopic systems, such as solids, metals and dielectrics, with nanometric precision. Although nano-engineering is a vast and well-established research field on its own, the merger with intense laser physics is relatively recent. In this report on progress we present a comprehensive experimental and theoretical overview of physics that takes place when short and intense laser pulses interact with nanosystems, such as metallic and dielectric nanostructures. In particular we elucidate how the spatially inhomogeneous laser induced fields at a nanometer scale modify the laser-driven electron dynamics. Consequently, this has important impact on pivotal processes such as above-threshold ionization and high-order harmonic generation. The deep understanding of the coupled dynamics between these spatially inhomogeneous fields and matter configures a promising way to new avenues of research and applications. Thanks to the maturity that attosecond physics has reached, together with the tremendous advance in material engineering and manipulation techniques, the age of atto-nanophysics has begun, but it is in the initial stage. We present thus some of the open questions, challenges and prospects for experimental confirmation of theoretical predictions, as well as experiments aimed at characterizing the

  19. Attosecond control of orbital parity mix interferences and the relative phase of even and odd harmonics in an attosecond pulse train.

    Science.gov (United States)

    Laurent, G; Cao, W; Li, H; Wang, Z; Ben-Itzhak, I; Cocke, C L

    2012-08-24

    We experimentally demonstrate that atomic orbital parity mix interferences can be temporally controlled on an attosecond time scale. Electron wave packets are formed by ionizing argon gas with a comb of odd and even high-order harmonics, in the presence of a weak infrared field. Consequently, a mix of energy-degenerate even and odd parity states is fed in the continuum by one- and two-photon transitions. These interfere, leading to an asymmetric electron emission along the polarization vector. The direction of the emission can be controlled by varying the time delay between the comb and infrared field pulses. We show that such asymmetric emission provides information on the relative phase of consecutive odd and even order harmonics in the attosecond pulse train.

  20. Telepresence, time delay, and adaptation

    Science.gov (United States)

    Held, Richard; Durlach, Nathaniel

    1989-01-01

    Displays are now being used extensively throughout the society. More and more time is spent watching television, movies, computer screens, etc. Furthermore, in an increasing number of cases, the observer interacts with the display and plays the role of operator as well as observer. To a large extent, the normal behavior in the normal environment can also be thought of in these same terms. Taking liberties with Shakespeare, it might be said, all the world's a display and all the individuals in it are operators in and on the display. Within this general context of interactive display systems, a discussion is began with a conceptual overview of a particular class of such systems, namely, teleoperator systems. The notion is considered of telepresence and the factors that limit telepresence, including decorrelation between the: (1) motor output of the teleoperator as sensed directly via the kinesthetic/tactual system, and (2) the motor output of the teleoperator as sensed indirectly via feedback from the slave robot, i.e., via a visual display of the motor actions of the slave robot. Finally, the deleterious effect of time delay (a particular decorrelation) on sensory-motor adaptation (an important phenomenon related to telepresence) is examined.

  1. Quantum Chemistry on the time axis: electron correlations and rearrangements on femtosecond and attosecond scales

    CERN Document Server

    Nicolaides, Cleanthes A

    2015-01-01

    Recent developments toward the production and laboratory use of pulses of high intensity, and/or of very high frequency, and/or of ultrashort duration, make possible experiments which can produce time-resolved data on ultrafast transformations involving motions of electrons. The formulation, quantitative understanding and prediction of related new phenomena entail the possibility of computing and applying solutions of the many-electron time-dependent Schroedinger equation, for arbitrary electronic structures, including the dominant effects of Rydberg series, of multiply excited states and of the multi-channel continuous spectrum. To this purpose, we have proposed and applied to many prototypical cases the state-specific expansion approach (SSEA). (Mercouris, Komninos and Nicolaides, Adv. Quantum Chem. 60, 333 (2010)). The paper explains briefly the SSEA, and outlines four of its applications to recently formulated problems concerning time-resolved electronic processes, where electron correlations are crucial....

  2. Attosecond nonlinear optics using gigawatt-scale isolated attosecond pulses

    Science.gov (United States)

    Takahashi, Eiji J.; Lan, Pengfei; Mücke, Oliver D.; Nabekawa, Yasuo; Midorikawa, Katsumi

    2013-10-01

    High-energy isolated attosecond pulses required for the most intriguing nonlinear attosecond experiments as well as for attosecond-pump/attosecond-probe spectroscopy are still lacking at present. Here we propose and demonstrate a robust generation method of intense isolated attosecond pulses, which enable us to perform a nonlinear attosecond optics experiment. By combining a two-colour field synthesis and an energy-scaling method of high-order harmonic generation, the maximum pulse energy of the isolated attosecond pulse reaches as high as 1.3 μJ. The generated pulse with a duration of 500 as, as characterized by a nonlinear autocorrelation measurement, is the shortest and highest-energy pulse ever with the ability to induce nonlinear phenomena. The peak power of our tabletop light source reaches 2.6 GW, which even surpasses that of an extreme-ultraviolet free-electron laser.

  3. Attosecond nonlinear optics using gigawatt-scale isolated attosecond pulses.

    Science.gov (United States)

    Takahashi, Eiji J; Lan, Pengfei; Mücke, Oliver D; Nabekawa, Yasuo; Midorikawa, Katsumi

    2013-01-01

    High-energy isolated attosecond pulses required for the most intriguing nonlinear attosecond experiments as well as for attosecond-pump/attosecond-probe spectroscopy are still lacking at present. Here we propose and demonstrate a robust generation method of intense isolated attosecond pulses, which enable us to perform a nonlinear attosecond optics experiment. By combining a two-colour field synthesis and an energy-scaling method of high-order harmonic generation, the maximum pulse energy of the isolated attosecond pulse reaches as high as 1.3 μJ. The generated pulse with a duration of 500 as, as characterized by a nonlinear autocorrelation measurement, is the shortest and highest-energy pulse ever with the ability to induce nonlinear phenomena. The peak power of our tabletop light source reaches 2.6 GW, which even surpasses that of an extreme-ultraviolet free-electron laser.

  4. Memorized discrete systems and time-delay

    CERN Document Server

    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.

  5. Dynamics of Nonlinear Time-Delay Systems

    CERN Document Server

    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...

  6. Attosecond Electron Correlation Dynamics in Double Ionization of Benzene Probed with Two-Electron Angular Streaking

    Science.gov (United States)

    Winney, Alexander H.; Lee, Suk Kyoung; Lin, Yun Fei; Liao, Qing; Adhikari, Pradip; Basnayake, Gihan; Schlegel, H. Bernhard; Li, Wen

    2017-09-01

    With a novel three-dimensional electron-electron coincidence imaging technique and two-electron angular streaking method, we show that the emission time delay between two electrons can be measured from tens of attoseconds to more than 1 fs. Surprisingly, in benzene, the double ionization rate decays as the time delay between the first and second electron emission increases during the first 500 as. This is further supported by the decay of the Coulomb repulsion in the direction perpendicular to the laser polarization. This result reveals that laser-induced electron correlation plays a major role in strong field double ionization of benzene driven by a nearly circularly polarized field.

  7. Fractional high-harmonic combs by attosecond-precision split-spectrum pulse control

    Directory of Open Access Journals (Sweden)

    Laux Martin

    2013-03-01

    Full Text Available Few-cycle laser fields enable pulse-shaping control of high-order harmonic generation by time delaying variable broadband spectral sections. We report the experimental generation of fractional (noninteger high-harmonic combs by the controlled interference of two attosecond pulse trains. Additionally the energy of the high harmonics is strongly tuned with the relative time delay. We quantify the tuning to directly result from the controlled variation of the instantaneous laser frequency at the shaped driver pulse intensity maximum.

  8. Time Delay Estimation Algoritms for Echo Cancellation

    Directory of Open Access Journals (Sweden)

    Boris Simak

    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.

  9. Attosecond pump-probe electron interferometry

    CERN Document Server

    Mauritsson, J; Swoboda, M; Klunder, K; L'Huillier, A; Schafer, K J; Ghafur, O; Kelkensberg, F; Siu, W; Johnsson, P; Vrakking, M J J; Znakovskaya, I; Uphues, T; Zherebtsov, S; Kling, M F; Lepine, F; Benedetti, E; Ferrari, F; Sansone, G; Nisoli, M

    2010-01-01

    Attosecond science has as its goal the measurement and ultimately the control of electron dynamics on its natural time scale, the atomic unit of time, which is 24 attoseconds. The short pulses required to reach this time scale imply large bandwidths, leading to the excitation not of a single state but of a broad and coherent superposition of states, i.e., a wave packet. In this paper we present a novel interferometric method that uses a free wave packet as a reference to measure a bound wave packet. The resulting interferogram contains both quantum beats as well as multi-path interference and provides precise and state-specific time-resolved amplitude and phase information about the bound electron wave packet. We demonstrate our method experimentally by measuring a bound attosecond wave packet in helium, prepared using an isolated 350 attosecond pulse with a central energy in the vicinity of the ionization threshold. In addition we show that our approach can also be applied to bound wave packets irrespective ...

  10. Imaging attosecond electron wavepackets around the ionization threshold

    Energy Technology Data Exchange (ETDEWEB)

    Swoboda, Marko; Remetter, Thomas; Mauritsson, Johan; L' Huillier, Anne [Dept. of Physics, Lund University (Sweden); Schafer, Kenneth J. [Louisiana State Univ., Baton Rouge, Louisiana (United States); Kelkensberg, Freek; Siu, Wing-Kiu; Johnsson, Per; Vrakking, Marc J.J. [AMOLF Institute, Amsterdam (Netherlands); Kling, Matthias F.; Znakovskaya, Irina; Uphues, Thorsten; Zherebtsov, Sergey [MPI fuer Quantenoptik, Garching (Germany); Lepine, Franck [Univ. Lyon 1, CNRS, LASIM, UMR, Villeurbanne (France); Benedetti, Enrico; Ferrari, Federico; Sansone, Giuseppe; Nisoli, Mauro [CUSBO, ULTRAS-INFM, Politecnico, Milano (Italy)

    2008-07-01

    We image the momentum distributions of attosecond electron wavepackets generated from the ionization of Helium by attosecond XUV pulses. Using an infrared probing field, the evolution of these wavepackets can be captured in time and space. Tuning the central frequency of the pulses allows us to initiate a number of processes that originate from the interplay of partially bound and continuum wavepackets or returning electrons and the atomic potential. Using this attosecond pump-probe scheme, we can track electron dynamics around the ionization barrier, performing interferometric measurements of different ionization pathways.

  11. Attosecond control of dissociative ionization of O{sub 2} molecules

    Energy Technology Data Exchange (ETDEWEB)

    Siu, W.; Kelkensberg, F.; Gademann, G. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Rouzee, A.; Vrakking, M. J. J. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Max-Born-Institut, Max-Born Strasse 2A, D-12489 Berlin (Germany); Johnsson, P. [FOM Institute AMOLF, Science Park 104, NL-1098 XG Amsterdam (Netherlands); Department of Physics, Lund University, Post Office Box 118, SE-221 00 Lund (Sweden); Dowek, D. [Laboratoire des Collisions Atomiques et Moleculaires (UMR Universite Paris-Sud et CNRS, 8625), Batiment 351, Universite Paris-Sud, F-91405 Orsay Cedex (France); Lucchini, M.; Calegari, F. [Department of Physics, Politecnico di Milano, Istituto di Fotonica e Nanotecnologie CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); De Giovannini, U.; Rubio, A. [Nano-bio Spectroscopy Group, ETSF Scientific Development Centre, Universidad del Pais Vasco, Avenida Tolosa 72, E-20018 San Sebastian (Spain); Lucchese, R. R. [Department of Chemistry, Texas A and M University, Post Office Box 30012, College Station, Texas 77842-3012 (United States); Kono, H. [Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan); Lepine, F. [Universite Lyon 1/CNRS/LASIM, UMR 5579, 43 Boulevard Du 11 Novembre 1918, F-69622 Villeurbane (France)

    2011-12-15

    We demonstrate that dissociative ionization of O{sub 2} can be controlled by the relative delay between an attosecond pulse train (APT) and a copropagating infrared (IR) field. Our experiments reveal a dependence of both the branching ratios between a range of electronic states and the fragment angular distributions on the extreme ultraviolet (XUV) to IR time delay. The observations go beyond adiabatic propagation of dissociative wave packets on IR-induced quasistatic potential energy curves and are understood in terms of an IR-induced coupling between electronic states in the molecular ion.

  12. Observation of molecular dipole excitations by attosecond self-streaking

    CERN Document Server

    Wachter, Georg; Sato, Shunsuke A; Pazourek, Renate; Wais, Michael; Lemell, Christoph; Tong, Xiao-Min; Yabana, Kazuhiro; Burgdörfer, Joachim

    2015-01-01

    We propose a protocol to probe the ultrafast evolution and dephasing of coherent electronic excitation in molecules in the time domain by the intrinsic streaking field generated by the molecule itself. Coherent electronic motion in the endohedral fullerene \\Necsixty~is initiated by a moderately intense femtosecond UV-VIS pulse leading to coherent oscillations of the molecular dipole moment that persist after the end of the laser pulse. The resulting time-dependent molecular near-field is probed through the momentum modulation of photoemission from the central neon atom by a time-delayed attosecond XUV pulse. Our ab-initio time-dependent density functional theory and classical trajectory simulations predict that this self-streaking signal accurately traces the molecular dipole oscillations in real time. We discuss the underlying processes and give an analytical model that captures the essence of our ab-initio simulations.

  13. Attosecond control of optical waveforms

    Energy Technology Data Exchange (ETDEWEB)

    Fuji, Takao [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Rauschenberger, Jens [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Gohle, Christoph [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Apolonski, Alexander [Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Am Coulombwall 1, D-85748 Garching (Germany); Institute of Automation and Electrometry, Russian Academy of Science, 630090 Novosibirsk, Russia (Russian Federation); Udem, Thomas [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Yakovlev, Vladislav S [Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Am Coulombwall 1, D-85748 Garching (Germany); Tempea, Gabriel [Femtolasers Produktions GmbH, Fernkorngasse 10, A-1100 Vienna (Austria); Haensch, Theodor W [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Krausz, Ferenc [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Department fuer Physik, Ludwig-Maximilians-Universitaet Muenchen, Am Coulombwall 1, D-85748 Garching (Germany); Institut fuer Photonik, Technische Universitaet Wien, Gusshausstrasse 27/387, A-1040 Vienna (Austria)

    2005-05-01

    A new, monolithic scheme for stabilizing the phase between the carrier wave and the envelope (CE phase) in a train of few-cycle laser pulses is demonstrated. Self-phase modulation and second-harmonic generation or difference-frequency generation in a single periodically poled lithium niobate crystal, that transmits the main laser beam, allows for the CE-phase locking directly in the usable output. The monolithic scheme obviates the need for splitting off a fraction of the laser output for CE-phase control, coupling into microstructured fibre, as well as separation and recombination of spectral components. As a result, the CE-phase error integrated over the spectral range of 0.2 mHz-35 MHz is as small as 0.016 x 2{pi} rad. This implies that the phase of the field oscillations ({lambda} {approx} 830 nm) with respect to the pulse peak is locked to within 44 attoseconds, resulting in optical waveform control with subhundred attosecond fidelity for the first time.

  14. Monolithic Time Delay Integrated APD Arrays Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The overall goal of the proposed program by Epitaxial Technologies is to develop monolithic time delay integrated avalanche photodiode (APD) arrays with sensitivity...

  15. Photoelectron spectrometer for attosecond spectroscopy of liquids and gases

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, I.; Huppert, M.; Wörner, H. J., E-mail: hwoerner@ethz.ch [Laboratory of Physical Chemistry, ETH Zurich, Vladimir-Prelog-Weg 2, 8093 Zurich (Switzerland); Brown, M. A. [Laboratory for Surface Science and Technology, Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich (Switzerland); Bokhoven, J. A. van [Institute for Chemical and Bioengineering, ETH Zurich, Vladimir-Prelog-Weg 1, 8093 Zurich (Switzerland); Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute, 5232 Villigen (Switzerland)

    2015-12-15

    A new apparatus for attosecond time-resolved photoelectron spectroscopy of liquids and gases is described. It combines a liquid microjet source with a magnetic-bottle photoelectron spectrometer and an actively stabilized attosecond beamline. The photoelectron spectrometer permits venting and pumping of the interaction chamber without affecting the low pressure in the flight tube. This pressure separation has been realized through a sliding skimmer plate, which effectively seals the flight tube in its closed position and functions as a differential pumping stage in its open position. A high-harmonic photon spectrometer, attached to the photoelectron spectrometer, exit port is used to acquire photon spectra for calibration purposes. Attosecond pulse trains have been used to record photoelectron spectra of noble gases, water in the gas and liquid states as well as solvated species. RABBIT scans demonstrate the attosecond resolution of this setup.

  16. Attosecond Control of Photoabsorption Through Manipulating the Electron-Electron Correlation

    Science.gov (United States)

    Hu, S. X.

    2014-05-01

    This talk reports on studies of photoabsorption control by manipulating the electron -electron correlation in a double-ionization process with an attosecond extreme ultraviolet (EUV) pulse. Electron correlation plays an essential role in a wide range of fundamentally important many-body phenomena in modern physics and chemistry. An example is the importance of electron-electron correlation in multiple ionization of multielectron atoms and molecules exposed to intense laser pulses. Manipulating the dynamic electron correlation in such photoinduced processes is a crucial step toward the coherent control of chemical reactions and photobiological processes. We will show for the first time, from full-dimensional ab initio calculations of double ionization of helium in intense laser pulses (λ = 780 nm), that the electron-electron interactions can be instantaneously tuned using a time-delayed attosecond EUV pulse. Consequently, the probability of producing energetic electrons from excessive photoabsorption can be enhanced by an order of magnitude through the attosecond control of electron-electron correlation. This work was partially supported by the Department of Energy National Nuclear Security Administration under Award No. DE-NA0001944, the University of Rochester, and the New York State Energy Research and Development Authority. Computations have been conducted utilizing the ``Kraken'' Supercomputer at NICS.

  17. dependent time-delay: Stability and stabilizability

    Directory of Open Access Journals (Sweden)

    E. K. Boukas

    2002-01-01

    Full Text Available This paper considers stochastic stability and stochastic stabilizability of linear discrete-time systems with Markovian jumps and mode-dependent time-delays. Linear matrix inequality (LMI techniques are used to obtain sufficient conditions for the stochastic stability and stochastic stabilizability of this class of systems. A control design algorithm is also provided. A numerical example is given to demonstrate the effectiveness of the obtained theoretical results.

  18. Microlensing makes lensed quasar time delays significantly time variable

    Science.gov (United States)

    Tie, S. S.; Kochanek, C. S.

    2018-01-01

    The time delays of gravitationally lensed quasars are generally believed to be unique numbers whose measurement is limited only by the quality of the light curves and the models for the contaminating contribution of gravitational microlensing to the light curves. This belief is incorrect - gravitational microlensing also produces changes in the actual time delays on the ∼day(s) light-crossing time-scale of the emission region. This is due to a combination of the inclination of the disc relative to the line of sight and the differential magnification of the temperature fluctuations producing the variability. We demonstrate this both mathematically and with direct calculations using microlensing magnification patterns. Measuring these delay fluctuations can provide a physical scale for microlensing observations, removing the need for priors on either the microlens masses or the component velocities. That time delays in lensed quasars are themselves time variable likely explains why repeated delay measurements of individual lensed quasars appear to vary by more than their estimated uncertainties. This effect is also a new important systematic problem for attempts to use time delays in lensed quasars for cosmology or to detect substructures (satellites) in lens galaxies.

  19. Attosecond chirp-encoded dynamics of light nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Haessler, S; Boutu, W; Weber, S; Breger, P; Monchicourt, P; Carre, B; Salieres, P [CEA Saclay, IRAMIS, Service des Photons, Atomes et Molecules, 91191 Gif-sur-Yvette (France); Stankiewicz, M [Institute of Physics, Jagiellonian University, ul. Reymonta 4, 30-059 Krakow (Poland); Frasinski, L J [The Blackett Laboratory, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Caillat, J; Taieb, R; Maquet, A [UMPC Universite Paris 06, CNRS, UMR 7614, LCPMR, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France)], E-mail: pascal.salieres@cea.fr

    2009-07-14

    We study the spectral phase of high-order harmonic emission as an observable for probing ultrafast nuclear dynamics after the ionization of a molecule. Using a strong-field approximation theory that includes nuclear dynamics, we relate the harmonic phase to the phase of the overlap integral of the nuclear wavefunctions of the initial neutral molecule and the molecular ion after an attosecond probe delay. We determine experimentally the group delay of the high harmonic emission from D{sub 2} and H{sub 2} molecules, which allows us to verify the relation between harmonic frequency and the attosecond delay. The small difference in the harmonic phase between H{sub 2} and D{sub 2} calculated theoretically is consistent with our experimental results.

  20. Nano-plasmonic near field phase matching of attosecond pulses.

    Science.gov (United States)

    Shaaran, Tahir; Nicolas, Rana; Iwan, Bianca; Kovacev, Milutin; Merdji, Hamed

    2017-07-25

    Nano-structures excited by light can enhance locally the electric field when tuned to plasmonic resonances. This phenomenon can be used to boost non-linear processes such as harmonic generation in crystals or in gases, Raman excitation, and four wave mixing. Here we present a theoretical investigation of the near-field phase matching of attosecond pulses emitted by high-order harmonic generation (HHG) of an atom immersed in a multi-cycle femtosecond infrared laser field and a spatially inhomogeneous plasmonic field. We demonstrate that the spatial inhomogeneity factor of the plasmonic field strongly affects the electron trajectory and recombination time which can be used to control the attosecond emission. For further insight into the plasmonic field effect, we monitor the phase of each quantum path as a function of the inhomogeneity strength. Moreover, we investigate the attosecond emission as a function of near-field phase matching effects. This is achieved by calculating the coherent field superposition of attosecond pulses emitted from various intensities or field inhomogeneities. Finally, far-field and near-field phase matching effects are combined to modulate the harmonic spectral phase towards the emission of a single attosecond pulse.

  1. Optimal Control with Time Delays via the Penalty Method

    Directory of Open Access Journals (Sweden)

    Mohammed Benharrat

    2014-01-01

    Full Text Available We prove necessary optimality conditions of Euler-Lagrange type for a problem of the calculus of variations with time delays, where the delay in the unknown function is different from the delay in its derivative. Then, a more general optimal control problem with time delays is considered. Main result gives a convergence theorem, allowing us to obtain a solution to the delayed optimal control problem by considering a sequence of delayed problems of the calculus of variations.

  2. Time averaging, ageing and delay analysis of financial time series

    Science.gov (United States)

    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.

  3. Delay in atomic photoionization

    CERN Document Server

    Kheifets, A S

    2010-01-01

    We analyze the time delay between emission of photoelectrons from the outer valence $ns$ and $np$ sub-shells in noble gas atoms following absorption of an attosecond XUV pulse. By solving the time dependent Schr\\"odinger equation and carefully examining the time evolution of the photoelectron wave packet, we establish the apparent "time zero" when the photoelectron leaves the atom. Various processes such as elastic scattering of the photoelectron on the parent ion and many-electron correlation affect the quantum phase of the dipole transition matrix element, the energy dependence of which defines the emission timing. This qualitatively explains the time delay between photoemission from the $2s$ and $2p$ sub-shells of Ne as determined experimentally by attosecond streaking [{\\em Science} {\\bf 328}, 1658 (2010)]. However, with our extensive numerical modeling, we were only able to account for less than a half of the measured time delay of $21\\pm5$~as. We argue that the XUV pulse alone cannot produce such a larg...

  4. Electron Interference in Molecular Circular Polarization Attosecond XUV Photoionization

    Directory of Open Access Journals (Sweden)

    Kai-Jun Yuan

    2015-01-01

    Full Text Available Two-center electron interference in molecular attosecond photoionization processes is investigated from numerical solutions of time-dependent Schrödinger equations. Both symmetric H\\(_2^+\\ and nonsymmetric HHe\\(^{2+}\\ one electron diatomic systems are ionized by intense attosecond circularly polarized XUV laser pulses. Photoionization of these molecular ions shows signature of interference with double peaks (minima in molecular attosecond photoelectron energy spectra (MAPES at critical angles \\(\\vartheta_c\\ between the molecular \\(\\textbf{R}\\ axis and the photoelectron momentum \\(\\textbf{p}\\. The interferences are shown to be a function of the symmetry of electronic states and the interference patterns are sensitive to the molecular orientation and pulse polarization. Such sensitivity offers possibility for imaging of molecular structure and orbitals.

  5. Controlling flow time delays in flexible manufacturing cells

    NARCIS (Netherlands)

    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.

  6. An Attosecond Transient Absorption Spectroscopy Setup with a Water Window Attosecond source

    Science.gov (United States)

    Chew, Andrew; Yin, Yanchun; Li, Jie; Ren, Xiaoming; Wang, Yang; Wu, Yi; Chang, Zenghu

    2017-04-01

    Attosecond transient absorption, or time-resolved pump-probe spectroscopy, are excellent tools that can be used to investigate fast electron dynamics for a given atomic or molecular system. Recent push for high energy long wavelength few cycle laser sources has resulted in the production of x-ray spectra that would allow the probing of electron dynamics at the carbon k-edge in molecules such as CH4 and CO2. The motion of charges can be caused by photo-dissociation and charge migration. We present here the first results from our experimental setup where we produce a broadband attosecond pulse with spectra that stretches into the water window. National Science Foundation (1068604), Army Research Oce (W911NF-14-1-0383), Air Force Oce of Scientic Research (FA9550-15-1-0037, FA9550-16-1-0013) and the DARPA PULSE program by a Grant from AMRDEC (W31P4Q1310017).

  7. Probing attosecond pulse structures by XUV-induced hole dynamics

    CERN Document Server

    You, Jhih-An; Dahlström, Jan Marcus

    2015-01-01

    We investigate a two-photon ionization process in neon by an isolated attosecond pump pulse and two coherent extreme ultraviolet probe fields. The probe fields, tuned to the 2s-2p transition in the residual ion, allow for coherent control of the photoelectron via indirect interactions with the hole. We show that the photoelectron-ion coincidence signal contains an interference pattern that can be used to reconstruct the temporal structure of attosecond pump pulses. Our results are supported by simulations based on time-dependent configuration-interaction singles and lowest-order perturbation theory within second quantization.

  8. Photoionization of water molecules by a train of attosecond pulses assisted by a near-infrared laser: delay and polarization control

    Science.gov (United States)

    Martini, Lara; Boll, Diego I. R.; Fojón, Omar A.

    2017-08-01

    Basic reactions involving water molecules are essential to understand the interaction between radiation and the biological tissue because living cells are composed mostly by water. Therefore, the knowledge of ionization of the latter is crucial in many domains of Biology and Physics. So, we study theoretically the photoionization of water molecules by extreme ultraviolet attopulse trains assisted by lasers in the near-infrared range. We use a separable Coulomb-Volkov model in which the temporal evolution of the system can be divided into three stages allowing spatial and temporal separation for the Coulomb and Volkov final state wavefunctions. First, we analyze photoelectron angular distributions for different delays between the attopulse train and the assistant laser field. We compare our results for water and Ne atoms as they belong to the same isoelectronic series. Moreover, we contrast our calculations with previous theoretical and experimental work for Ar atoms due to the similarities of the orbitals involved in the reaction. Second, we study the effect of varying the relative orientations of the attopulse and laser field polarizations and we compare our predictions with other theories and experiments. We expect these studies contribute to the improvement of polarization experiments and the development of the attopulse trains and assistant laser fields technologies. Finally, we hope our work promote progress on the control of the chemical reactivity of water molecules since this could be useful in different fields such as radiobiology and medical physics.

  9. Delay-range-dependent chaos synchronization approach under varying time-lags and delayed nonlinear coupling.

    Science.gov (United States)

    Zaheer, Muhammad Hamad; Rehan, Muhammad; Mustafa, Ghulam; Ashraf, Muhammad

    2014-11-01

    This paper proposes a novel state feedback delay-range-dependent control approach for chaos synchronization in coupled nonlinear time-delay systems. The coupling between two systems is esteemed to be nonlinear subject to time-lags. Time-varying nature of both the intrinsic and the coupling delays is incorporated to broad scope of the present study for a better-quality synchronization controller synthesis. Lyapunov-Krasovskii (LK) functional is employed to derive delay-range-dependent conditions that can be solved by means of the conventional linear matrix inequality (LMI)-tools. The resultant control approach for chaos synchronization of the master-slave time-delay systems considers non-zero lower bound of the intrinsic as well as the coupling time-delays. Further, the delay-dependent synchronization condition has been established as a special case of the proposed LK functional treatment. Furthermore, a delay-range-dependent condition, independent of the delay-rate, has been provided to address the situation when upper bound of the delay-derivative is unknown. A robust state feedback control methodology is formulated for synchronization of the time-delay chaotic networks against the L2 norm bounded perturbations by minimizing the L2 gain from the disturbance to the synchronization error. Numerical simulation results are provided for the time-delay chaotic networks to show effectiveness of the proposed delay-range-dependent chaos synchronization methodologies. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

  10. Sub-100 attosecond timing jitter from low-noise passively mode-locked solid-state laser at telecom wavelength.

    Science.gov (United States)

    Portuondo-Campa, E; Paschotta, R; Lecomte, S

    2013-08-01

    We report on the ultralow timing jitter of the 100 MHz pulse trains generated by two identical passively mode-locked diode-pumped solid-state lasers (DPSSLs) emitting at 1556 nm. Ultralow timing jitter of 83 as (integrated from 10 kHz to 50 MHz) for one laser has been measured with a balanced optical cross-correlator as timing discriminator. Extremely low intensity noise has been measured as well. Several measurement techniques have been used and show similar jitter results. Different possible noise sources have been theoretically investigated and compared to the measured jitter power spectral density. It is found that although the measured integrated jitter is quite low, it is still significantly above the quantum limit in the considered frequency span. Therefore, there is a substantial potential for technical improvements that could make passively mode-locked DPSSL outperform fiber lasers as source of microwaves with low phase noise.

  11. Attosecond light sources in the water window

    Science.gov (United States)

    Ren, Xiaoming; Li, Jie; Yin, Yanchun; Zhao, Kun; Chew, Andrew; Wang, Yang; Hu, Shuyuan; Cheng, Yan; Cunningham, Eric; Wu, Yi; Chini, Michael; Chang, Zenghu

    2018-02-01

    As a compact and burgeoning alternative to synchrotron radiation and free-electron lasers, high harmonic generation (HHG) has proven its superiority in static and time-resolved extreme ultraviolet spectroscopy for the past two decades and has recently gained many interests and successes in generating soft x-ray emissions covering the biologically important water window spectral region. Unlike synchrotron and free-electron sources, which suffer from relatively long pulse width or large time jitter, soft x-ray sources from HHG could offer attosecond time resolution and be synchronized with their driving field to investigate time-resolved near edge absorption spectroscopy, which could reveal rich structural and dynamical information of the interrogated samples. In this paper, we review recent progresses on generating and characterizing attosecond light sources in the water window region. We show our development of an energetic, two-cycle, carrier-envelope phase stable laser source at 1.7 μm and our achievement in producing a 53 as soft x-ray pulse covering the carbon K-edge in the water window. Such source paves the ways for the next generation x-ray spectroscopy with unprecedented temporal resolution.

  12. Noether Theorem for Nonholonomic Systems with Time Delay

    Directory of Open Access Journals (Sweden)

    Shi-Xin Jin

    2015-01-01

    Full Text Available The paper focuses on studying the Noether theorem for nonholonomic systems with time delay. Firstly, the differential equations of motion for nonholonomic systems with time delay are established, which is based on the Hamilton principle with time delay and the Lagrange multiplier rules. Secondly, based upon the generalized quasi-symmetric transformations for nonconservative systems with time delay, the Noether theorem for corresponding holonomic systems is given. Finally, we obtain the Noether theorem for the nonholonomic nonconservative systems with time delay. At the end of the paper, an example is given to illustrate the application of the results.

  13. Cosmological Constraints from Gravitational Lens Time Delays

    Science.gov (United States)

    Coe, Dan; Moustakas, Leonidas A.

    2009-11-01

    Future large ensembles of time delay (TD) lenses have the potential to provide interesting cosmological constraints complementary to those of other methods. In a flat universe with constant w including a Planck prior, The Large Synoptic Survey Telescope TD measurements for ~4000 lenses should constrain the local Hubble constant h to ~0.007 (~1%), Ω de to ~0.005, and w to ~0.026 (all 1σ precisions). Similar constraints could be obtained by a dedicated gravitational lens observatory (OMEGA) which would obtain precise TD and mass model measurements for ~100 well-studied lenses. We compare these constraints (as well as those for a more general cosmology) to the "optimistic Stage IV" constraints expected from weak lensing, supernovae, baryon acoustic oscillations, and cluster counts, as calculated by the Dark Energy Task Force. TDs yield a modest constraint on a time-varying w(z), with the best constraint on w(z) at the "pivot redshift" of z ≈ 0.31. Our Fisher matrix calculation is provided to allow TD constraints to be easily compared to and combined with constraints from other experiments. We also show how cosmological constraining power varies as a function of numbers of lenses, lens model uncertainty, TD precision, redshift precision, and the ratio of four-image to two-image lenses.

  14. Attomicroscopy: from femtosecond to attosecond electron microscopy

    Science.gov (United States)

    Hassan, Mohammed Th

    2018-02-01

    In the last decade, the development of ultrafast electron diffraction (UED) and microscopy (UEM) have enabled the imaging of atomic motion in real time and space. These pivotal table-top tools opened the door for a vast range of applications in different areas of science spanning chemistry, physics, materials science, and biology. We first discuss the basic principles and recent advancements, including some of the important applications, of both UED and UEM. Then, we discuss the recent advances in the field that have enhanced the spatial and temporal resolutions, where the latter, is however, still limited to a few hundreds of femtoseconds, preventing the imaging of ultrafast dynamics of matter lasting few tens of femtoseconds. Then, we present our new optical gating approach for generating an isolated 30 fs electron pulse with sufficient intensity to attain a temporal resolution on the same time scale. This achievement allows, for the first time, imaging the electron dynamics of matter. Finally, we demonstrate the feasibility of the optical gating approach to generate an isolated attosecond electron pulse, utilizing our recently demonstrated optical attosecond laser pulse, which paves the way for establishing the field of ‘Attomicroscopy’, ultimately enabling us to image the electron motion in action.

  15. Single 100-terawatt attosecond X-ray light pulse generation

    CERN Document Server

    Xu, X R; Zhang, Y X; Lu, H Y; Zhang, H; Dromey, B; Zhu, S P; Zhou, C T; Zepf, M; He, X T

    2016-01-01

    The birth of attosecond light sources is expected to inspire a breakthrough in ultrafast optics, which may extend human real-time measurement and control techniques into atomic-scale electronic dynamics. For applications, it is essential to obtain a single attosecond pulse of high intensity, large photon energy and short duration. Here we show that single 100-terawatt attosecond X-ray light pulse with intensity ${1\\times10^{21}}\\textrm{W}/\\textrm{cm}^{{ 2}}$ and duration ${7.9} \\textrm{as}$ can be produced by intense laser irradiation on a capacitor-nanofoil target composed of two separate nanofoils. In the interaction, a strong electrostatic potential develops between two nanofoils, which drags electrons out of the second foil and piles them up in vacuum, forming an ultradense relativistic electron nanobunch. This nanobunch exists in only half a laser cycle and smears out in others, resulting in coherent synchrotron emission of a single pulse. Such an unprecedentedly giant attosecond X-ray pulse may bring us...

  16. Dynamic Programming based Time-Delay Estimation (TDE) Technique for Analysis of Time-varying Time-delay

    CERN Document Server

    Gupta, Deepak K; Fonck, Raymond R

    2008-01-01

    A new time-delay estimation (TDE) technique based on dynamic programming is developed, to measures the time-varying time-delay between two signals. Dynamic programming based TDE technique provides a frequency response 5 to 10 times higher than previously known TDE techniques, namely those based on time-lag cross-correlation or wavelet analysis. Effects of frequency spectrum, signal-to-noise ratio and amplitude of time-delay on response (represented as transfer function) of TDE technique is studied using simulated data signals. Transfer function for the technique decreases with increase in noise in signal; however it is independent of signal spectrum shape. Dynamic programming based TDE technique is applied to the Beam-Emission-Spectroscopy (BES) diagnostic data to measure poloidal velocity fluctuations, which led to the observation of theoretically predicted zonal flows in high-temperature tokamak plasmas.

  17. Periodic flows to chaos in time-delay systems

    CERN Document Server

    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...

  18. Time-delayed chameleon: Analysis, synchronization and FPGA implementation

    Science.gov (United States)

    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.

  19. Order and chaos in quantum irregular scattering Wigner's time delay

    CERN Document Server

    Eckhardt, B

    1993-01-01

    Abstract: Recent developments in the semiclassical analysis of chaotic systems are reviewed and illustrated for Wigner's time delay in elastic scattering of a point particle from three disks in the plane. The convergence of the cycle expanded periodic orbit expression for Wigners time delay is demonstrated. Different regimes in form factor (the Fourier transform of the two point correlation function) of the semiclassical time delay are identified and their relation to Berry's semiclassical theory of the spectral rigidity are discussed.

  20. Time Delay Evolution of Five Active Galactic Nuclei

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Astrophysics and Astronomy; Volume 36; Issue 4. Time Delay Evolution of Five ... Here we investigate light curves of the continuum and emission lines of five type 1 active galactic nuclei (AGN) from our monitoring campaign, to test time-evolution of their time delays. Using both modeled and ...

  1. Improving Delay-Range-Dependent Stability Condition for Systems with Interval Time-Varying Delay

    Directory of Open Access Journals (Sweden)

    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.

  2. Single attosecond pulse production with an ellipticity-modulated driving IR pulse

    Energy Technology Data Exchange (ETDEWEB)

    Strelkov, V [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Zair, A [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Tcherbakoff, O [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Lopez-Martens, R [Department of Physics, Lund Institute of Technology, PO Box 118, S-22100, Lund (Sweden); Cormier, E [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Mevel, E [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France); Constant, E [CELIA, Universite Bordeaux 1, 351 Cours de la liberation, 33405 Talence (France)

    2005-05-28

    We theoretically study attosecond pulse production via high-harmonic generation using a driving laser pulse with a time-dependent ellipticity. The theoretical approach produces results that agree with our experimental data obtained using 35 fs driving laser pulses and is further used to study the generation of single attosecond pulses with shorter laser pulses. We find an equation for the duration of the temporal window created by the time-varying driving laser polarization in which high-harmonic emission can occur. We formulate the necessary requirements concerning the driving laser field in order to confine the high-harmonic emission in the form of a single attosecond pulse. Indeed, we show that using incident 12 fs laser pulses single attosecond pulses can be produced for certain carrier-envelope phase (CEP) values of the driving pulse. For 6 fs incident laser pulses, single attosecond pulses are produced for all values of the CEP (the intensity of the attosecond pulse still depends on the actual value of the CEP). If implemented with state-of-the-art 5 fs laser pulses, this technique can even lead to the production of sub-100 as pulses. (letter to the editor)

  3. Time delay systems theory, numerics, applications, and experiments

    CERN Document Server

    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. .

  4. Attosecond streaking of shake-up and Auger electrons in xenon

    Directory of Open Access Journals (Sweden)

    Drescher M.

    2013-03-01

    Full Text Available We present first results of simultaneous attosecond streaking measurements of shake-up electrons and Auger electrons emitted from xenon. We extract relative photo-emission delays for electrons emitted from the 4d, 5s and 5p subshell, as well as for the 5p−25d correlation satellite (shake-up electrons.

  5. Lag synchronization of chaotic systems with time-delayed linear ...

    Indian Academy of Sciences (India)

    ... delayed chaotic systems. Numerical simulations on time-delayed Lorenz and hyperchaotic Chen systems are also carried out to show the effectiveness of the proposed scheme. Note that under the scheme the chaotic system is controlled only at discrete time instants, and so it reduces the control cost in real applications.

  6. Using Constant Time Delay to Teach Braille Word Recognition

    Science.gov (United States)

    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…

  7. Delay-Dependent Exponential Stability for Discrete-Time BAM Neural Networks with Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    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.

  8. Photonic Circuits with Time Delays and Quantum Feedback.

    Science.gov (United States)

    Pichler, Hannes; Zoller, Peter

    2016-03-04

    We study the dynamics of photonic quantum circuits consisting of nodes coupled by quantum channels. We are interested in the regime where the time delay in communication between the nodes is significant. This includes the problem of quantum feedback, where a quantum signal is fed back on a system with a time delay. We develop a matrix product state approach to solve the quantum stochastic Schrödinger equation with time delays, which accounts in an efficient way for the entanglement of nodes with the stream of emitted photons in the waveguide, and thus the non-Markovian character of the dynamics. We illustrate this approach with two paradigmatic quantum optical examples: two coherently driven distant atoms coupled to a photonic waveguide with a time delay, and a driven atom coupled to its own output field with a time delay as an instance of a quantum feedback problem.

  9. Tunable optical delay line for optical time-division multiplexer

    Science.gov (United States)

    Yu, Zhihua; Zhang, Qi; Wang, Hong; Zhang, Jingjing; Selviah, David R.

    2017-07-01

    A novel three-stage all-pass filter (APF) is proposed as a tunable optical delay line to construct an optical time division multiplexer (OTDM), with which, we can get ultrahigh bit rates with several low-speed channels. The proposed design mitigates the deleterious effects of group delay dispersion and provides wide bandwidth with small ripples and continuously tunable long delays achieved with small variations in the effective refraction index, making it suitable for high-speed optical networks on chip.

  10. Can strong-field ionization prepare attosecond dynamics?

    CERN Document Server

    Pabst, Stefan

    2015-01-01

    Strong-field ionization (SFI) has been shown to prepare wave packets with few-femtosecond periods. Here, we explore whether this technique can be extended to the attosecond time scale. We introduce an intuitive model for predicting the bandwidth of ionic states that can be coherently prepared by SFI. This bandwidth is given by the Fourier-transformed sub-cycle SFI rate and decreases considerably with increasing central wavelength of the ionizing pulse. Many-body calculations based on time-dependent configuration-interaction singles (TDCIS) quantitatively support this result and reveal an additional decrease of the bandwidth as a consequence of channel interactions and non-adiabatic dynamics. Our results further predict that multi-cycle femtosecond pulses can coherently prepare attosecond wave packets with higher selectivity and versatility compared to single-cycle pulses.

  11. Attosecond physics at the nanoscale

    Czech Academy of Sciences Publication Activity Database

    Ciappina, Marcelo F.; Perez-Hernandez, J.A.; Landsman, A.S.; Okell, W.A.; Zherebtsov, S.; Foerg, B.; Schoetz, J.; Seiffert, L.; Fennel, T.; Shaaran, T.; Zimmermann, T.; Chacon, A.; Guichard, R.; Zair, A.; Tisch, J.W.G.; Marangos, J.P.; Witting, T.; Braun, A.; Maier, S. A.; Roso, L.; Krueger, M.; Hommelhoff, P.; Kling, M.F.; Krausz, F.; Lewenstein, M.

    2017-01-01

    Roč. 80, č. 5 (2017), 1-50, č. článku 054401. ISSN 0034-4885 R&D Projects: GA MŠk EF15_008/0000162; GA MŠk LQ1606 Grant - others:ELI Beamlines(XE) CZ.02.1.01/0.0/0.0/15_008/0000162 Institutional support: RVO:68378271 Keywords : attosecond physics * plasmonic fields * strong field physics Subject RIV: BH - Optics, Masers, Lasers Impact factor: 14.311, year: 2016

  12. Managing contamination delay to improve Timing Speculation architectures

    Directory of Open Access Journals (Sweden)

    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.

  13. Extracting the relevant delays in time series modelling

    DEFF Research Database (Denmark)

    Goutte, Cyril

    1997-01-01

    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...

  14. The estimation and compensation of processes with time delays

    OpenAIRE

    O'Dwyer, Aidan

    1996-01-01

    The estimation and compensation of processes with time delays have been of interest to academics and practitioners for several decades. A full review of the literature for both model parameter and time delay estimation is presented. Gradient methods of parameter estimation, in open loop, in the time and frequency domains are subsequently considered in detail. Firstly, an algorithm is developed, using an appropriate gradient algorithm, for the estimation of all the parameters of an appropriate...

  15. Synchronization of nonidentical chaotic neural networks with leakage delay and mixed time-varying delays

    Directory of Open Access Journals (Sweden)

    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.

  16. Relation Between Time Perspective and Delay Discounting: A Literature Review

    National Research Council Canada - National Science Library

    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...

  17. Time Delay for Aerial Ammonia Concentration Measurements in Livestock Buildings

    OpenAIRE

    Rom; Zhang

    2010-01-01

    Correct measurements of ammonia concentration in air still present considerable challenges. The high water solubility and polarity can cause it to adsorb on surfaces in the entire sampling system, including sampling lines, filters, valves, pumps and instruments, causing substantial measuring errors and time delays. To estimate time delay characteristics of a Photo Acoustic Multi Gas Monitor 1312 and a Multi Point Sampler continuous measurement of aerial ammonia concentrations at different lev...

  18. Extreme events in time-delayed nonlinear optics.

    Science.gov (United States)

    Dal Bosco, Andreas Karsaklian; Wolfersberger, Delphine; Sciamanna, Marc

    2013-03-01

    We report experimentally on extreme events in the pulsating dynamics of an optical time-delayed system, i.e., a diode laser subject to a phase-conjugate feedback. We study the effect of the feedback strength on extreme events' properties. We show a transition to non-Gaussian statistics of the pulse intensity and an increased number of extreme events as the mirror reflectivity increases. The extreme event pulse is anticipated and followed by smaller pulses with time-delay periodicity.

  19. Solar oscillation time delay measurement assisted celestial navigation method

    Science.gov (United States)

    Ning, Xiaolin; Gui, Mingzhen; Zhang, Jie; Fang, Jiancheng; Liu, Gang

    2017-05-01

    Solar oscillation, which causes the sunlight intensity and spectrum frequency change, has been studied in great detail, both observationally and theoretically. In this paper, owing to the existence of solar oscillation, the time delay between the sunlight coming from the Sun directly and the sunlight reflected by the other celestial body such as the satellite of planet or asteroid can be obtained with two optical power meters. Because the solar oscillation time delay is determined by the relative positions of the spacecraft, reflective celestial body and the Sun, it can be adopted as the navigation measurement to estimate the spacecraft's position. The navigation accuracy of single solar oscillation time delay navigation system depends on the time delay measurement accuracy, and is influenced by the distance between spacecraft and reflective celestial body. In this paper, we combine it with the star angle measurement and propose a solar oscillation time delay measurement assisted celestial navigation method for deep space exploration. Since the measurement model of time delay is an implicit function, the Implicit Unscented Kalman Filter (IUKF) is applied. Simulations demonstrate the effectiveness and superiority of this method.

  20. Truncated predictor feedback for time-delay systems

    CERN Document Server

    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...

  1. Time-Delay System Identification Using Genetic Algorithm

    DEFF Research Database (Denmark)

    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 quality and performance of the GA-based identification are compared with those based on extended Least-Mean-Square (LMS) methods, subject to the consideration of different types of time-delay systems, excitation signals, Signal-to-Noise Ratios, and different evaluation criteria. The obtained results...... exhibit that the GA technique has a very promising capability in handling this type of non-convex system identification problem....

  2. Complex Time-Delay Systems Theory and Applications

    CERN Document Server

    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 ...

  3. Logarithmic based optical delay for time-resolved data collection.

    Science.gov (United States)

    Cole, Richard L; Barisas, B George; Levinger, Nancy E

    2010-09-01

    A method has been established that generates values spaced according to a mathematical function, specifically the logarithm function that can be applied to a stepper motor. Here, it is applied to yield logarithmically spaced time delay points for subnanosecond interferometric time-resolved experiments using a stepper motor controlled translation stage. Application of this method is discussed in terms of three input parameters: the optical delay stage time resolution, dt; the time of maximum delay, d(stop); and the desired number of data points, N. The method improves the efficiency of interferometric time-resolved data collection while providing data collection effective to determine decay parameters. In principle, this technique could be generalized to any mathematical function.

  4. Visual prediction: psychophysics and neurophysiology of compensation for time delays.

    Science.gov (United States)

    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.

  5. Calibrating a spatially encoded time delay for transient absorption spectroscopy

    Science.gov (United States)

    Wilson, Kelly S.; Wong, Cathy Y.

    2017-08-01

    A novel spectroscopy termed single shot transient absorption (SSTA) is presented that can collect a transient absorption spectrum in 6 ms by using laser pulses with tilted wavefronts to spatially encode the delay between pump and probe pulse arrival times at the sample. The transient absorption technique determines the change in sample transmission that results from sample photoexcitation, and tracks this change as a function of the time delay between the arrival of the pump pulse and the probe pulse. Typically, these time delays are generated using a retroreflecting mirror mounted on a motorized translation stage, with a measurement collected at each translation stage position. Because these measurements must be performed in series, data collection requires a significant amount of time. This limits transient absorption to the measurement of systems that are static for the duration of the experiment. SSTA overcomes this restriction by employing pump and probe pulses which are each focused into a line and tilted with respect to each other to spatially encode time delays within the sample. Here, we describe the SSTA technique and instrumentation, demonstrate the principle of this spectroscopy, and present a method for calibrating the spatially encoded time delay by autocorrelation. This instrument will broaden the scop

  6. Modified active disturbance rejection control for time-delay systems.

    Science.gov (United States)

    Zhao, Shen; Gao, Zhiqiang

    2014-07-01

    Industrial processes are typically nonlinear, time-varying and uncertain, to which active disturbance rejection control (ADRC) has been shown to be an effective solution. The control design becomes even more challenging in the presence of time delay. In this paper, a novel modification of ADRC is proposed so that good disturbance rejection is achieved while maintaining system stability. The proposed design is shown to be more effective than the standard ADRC design for time-delay systems and is also a unified solution for stable, critical stable and unstable systems with time delay. Simulation and test results show the effectiveness and practicality of the proposed design. Linear matrix inequality (LMI) based stability analysis is provided as well. © 2013 ISA Published by ISA All rights reserved.

  7. Time-Delay Estimation in Dispersed Spectrum Cognitive Radio Systems

    Directory of Open Access Journals (Sweden)

    Celebi Hasari

    2010-01-01

    Full Text Available Time-delay estimation is studied for cognitive radio systems, which facilitate opportunistic use of spectral resources. A two-step approach is proposed to obtain accurate time-delay estimates of signals that occupy multiple dispersed bands simultaneously, with significantly lower computational complexity than the optimal maximum likelihood (ML estimator. In the first step of the proposed approach, an ML estimator is used for each band of the signal in order to estimate the unknown parameters of the signal occupying that band. Then, in the second step, the estimates from the first step are combined in various ways in order to obtain the final time-delay estimate. The combining techniques that are used in the second step are called optimal combining, signal-to-noise ratio (SNR combining, selection combining, and equal combining. It is shown that the performance of the optimal combining technique gets very close to the Cramer-Rao lower bound at high SNRs. These combining techniques provide various mechanisms for diversity combining for time-delay estimation and extend the concept of diversity in communications systems to the time-delay estimation problem in cognitive radio systems. Simulation results are presented to evaluate the performance of the proposed estimators and to verify the theoretical analysis.

  8. Obtaining two attosecond pulses pulses for x-ray stimulated Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zholents, Alexander; Penn, G.

    2009-06-23

    Attosecond x-ray pulses are an indispensable tool for the study of electronic and structural changes in molecules undergoing chemical reactions. They have a wide bandwidth comparable to the energy bands of valence electronic states and, therefore, are well suited for making and probing multiple valence electronic excitations using core electron transitions. Here we propose a method of creating a sequence of two attosecond soft x-ray pulses in a free electron laser by optical manipulation of electrons located in two different sections of the electron bunch. The energy of each x-ray pulse can be of the order of 100 nJ and the pulse width of the order of 250 attoseconds. The carrier frequency of each x-ray pulse can be independently tuned to a resonant core electron transition of a specific atom of the molecule. The time interval between the two attosecond pulses is tunable from a few femtoseconds to a hundred femtoseconds with better than 100 attoseconds precision.

  9. Robust Moving Horizon H∞ Control of Discrete Time-Delayed Systems with Interval Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    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.

  10. Introduction to Focus Issue: Time-delay dynamics

    Science.gov (United States)

    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.

  11. Distinguishing attosecond electron-electron scattering and screening in transition metals

    Science.gov (United States)

    Chen, Cong; Tao, Zhensheng; Carr, Adra; Matyba, Piotr; Szilvási, Tibor; Emmerich, Sebastian; Piecuch, Martin; Keller, Mark; Zusin, Dmitriy; Eich, Steffen; Rollinger, Markus; You, Wenjing; Mathias, Stefan; Thumm, Uwe; Mavrikakis, Manos; Aeschlimann, Martin; Oppeneer, Peter M.; Kapteyn, Henry; Murnane, Margaret

    2017-07-01

    Electron-electron interactions are the fastest processes in materials, occurring on femtosecond to attosecond timescales, depending on the electronic band structure of the material and the excitation energy. Such interactions can play a dominant role in light-induced processes such as nano-enhanced plasmonics and catalysis, light harvesting, or phase transitions. However, to date it has not been possible to experimentally distinguish fundamental electron interactions such as scattering and screening. Here, we use sequences of attosecond pulses to directly measure electron-electron interactions in different bands of different materials with both simple and complex Fermi surfaces. By extracting the time delays associated with photoemission we show that the lifetime of photoelectrons from the d band of Cu are longer by ˜100 as compared with those from the same band of Ni. We attribute this to the enhanced electron-electron scattering in the unfilled d band of Ni. Using theoretical modeling, we can extract the contributions of electron-electron scattering and screening in different bands of different materials with both simple and complex Fermi surfaces. Our results also show that screening influences high-energy photoelectrons (≈20 eV) significantly less than low-energy photoelectrons. As a result, high-energy photoelectrons can serve as a direct probe of spin-dependent electron-electron scattering by neglecting screening. This can then be applied to quantifying the contribution of electron interactions and screening to low-energy excitations near the Fermi level. The information derived here provides valuable and unique information for a host of quantum materials.

  12. Absolute Stability of Discrete-Time Systems with Delay

    Directory of Open Access Journals (Sweden)

    Medina Rigoberto

    2008-01-01

    Full Text Available We investigate the stability of nonlinear nonautonomous discrete-time systems with delaying arguments, whose linear part has slowly varying coefficients, and the nonlinear part has linear majorants. Based on the "freezing" technique to discrete-time systems, we derive explicit conditions for the absolute stability of the zero solution of such systems.

  13. Start time delays in operating room: Different perspectives

    Directory of Open Access Journals (Sweden)

    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.

  14. Start time delays in operating room: Different perspectives.

    Science.gov (United States)

    Gupta, Babita; Agrawal, Pramendra; D'souza, Nita; Soni, Kapil Dev

    2011-07-01

    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). 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. We prepared a questionnaire seeking the five main reasons of delay as per their perspective. 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. 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.

  15. Delay time calculation for dual-wavelength quantum cascade lasers

    Energy Technology Data Exchange (ETDEWEB)

    Hamadou, A., E-mail: abd-hamado@yahoo.fr [Département des Sciences et Techniques, Faculté des Sciences et de la Technologie, Université de Bordj Bou Arreridj 34000 (Algeria); Laboratoire d’étude des surfaces et interfaces des matériaux solides (LESIMS), Sétif 19000 (Algeria); Lamari, S. [Laboratoire d’étude des surfaces et interfaces des matériaux solides (LESIMS), Sétif 19000 (Algeria); Département de Physique, Faculté des Sciences, Université Sétif 1, 19000 (Algeria); Thobel, J.-L. [Institut d' Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR 8520, Université Lille1, Avenue Poincaré, BP 60069, 59652 Villeneuve d' Ascq Cédex (France)

    2013-11-28

    In this paper, we calculate the turn-on delay (t{sub th}) and buildup (Δt) times of a midinfrared quantum cascade laser operating simultaneously on two laser lines having a common upper level. The approach is based on the four-level rate equations model describing the variation of the electron number in the states and the photon number present within the cavity. We obtain simple analytical formulae for the turn-on delay and buildup times that determine the delay times and numerically apply our results to both the single and bimode states of a quantum cascade laser, in addition the effects of current injection on t{sub th} and Δt are explored.

  16. New Delay-Dependent Exponential Stability Criteria for Neural Networks with Mixed Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Wu Wen

    2015-01-01

    Full Text Available This study is concerned with the problem of new delay-dependent exponential stability criteria for neural networks (NNs with mixed time-varying delays via introducing a novel integral inequality approach. Specifically, first, by taking fully the relationship between the terms in the Leibniz-Newton formula into account, several improved delay-dependent exponential stability criteria are obtained in terms of linear matrix inequalities (LMIs. Second, together with some effective mathematical techniques and a convex optimization approach, less conservative conditions are derived by constructing an appropriate Lyapunov-Krasovskii functional (LKF. Third, the proposed methods include the least numbers of decision variables while keeping the validity of the obtained results. Finally, three numerical examples with simulations are presented to illustrate the validity and advantages of the theoretical results.

  17. Attosecond evolution of energy- and angle-resolved photoemission spectra in two-color (XUV + IR) ionization of rare gases

    Science.gov (United States)

    Picard, Y. J.; Manschwetus, B.; Géléoc, M.; Böttcher, M.; Casagrande, E. M. Staicu; Lin, N.; Ruchon, T.; Carré, B.; Hergott, J.-F.; Lepetit, F.; Taïeb, R.; Maquet, A.; Huetz, A.

    2014-03-01

    We have analyzed the angular distributions of the photoelectrons emitted upon photoionization of rare gases by a comb of harmonics in the extreme ultraviolet range, in the presence of a "dressing" infrared (IR) field with controlled delay τ, stabilized down to about ±60 as. The measurements have been performed with the help of the coincidence momentum imaging technique. We evidence marked differences in the measured angular distributions of the photoelectrons, depending on the number of IR photons exchanged. Joined to a theoretical interpretation, these observations bring new insights into the dynamics of this class of two-color photoionization processes that are a key step towards studying photoionization in the time domain, with attosecond time resolution.

  18. Losing track of time through delayed body representations

    Directory of Open Access Journals (Sweden)

    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.

  19. A matter of time: internal delays in binaural processing.

    Science.gov (United States)

    Joris, Philip; Yin, Tom C T

    2007-02-01

    As an animal navigates its surroundings, the sounds reaching its two ears change in waveform similarity (interaural correlation) and in time of arrival (interaural time difference, ITD). Humans are exquisitely sensitive to these binaural cues, and it is generally agreed that this sensitivity involves coincidence detectors and internal delays that compensate for external acoustic delays (ITDs). Recent data show an unexpected relationship between the tuning of a neuron to frequency and to ITD, leading to several proposals for sources of internal delay and the neural coding of interaural temporal cues. We review the alternatives, and argue that an understanding of binaural mechanisms requires consideration of sensitivity not only to ITDs, but also to interaural correlation.

  20. Bilateral Teleoperation in Cartesian Space with Time-Varying Delay

    Directory of Open Access Journals (Sweden)

    Zhang Chen

    2012-10-01

    Full Text Available The bilateral control of a teleoperator in Cartesian space with time-varying delay is studied in this paper. Compared with the traditional joint-space teleoperation mode, bilateral control in Cartesian space has advantages when dealing with the kinematically dissimilar (KDS teleoperation systems. A Cartesian space-based PD-like bilateral controller with dissipation factors is designed. Considering the fact that attitude errors derived by rotation matrix cannot be directly used for PD control, a quaternion-based approach is adopted to calculate the attitude errors in Cartesian space. In order to overcome the instability brought about by communication delay, local damping components are employed at both ends of the teleoperator system. The variation of time delay may generate extra energy and influence the stability of the system, thus dissipation factors are introduced into the controller. The stability of the proposed bilateral controller is proved and the simulations show the effectiveness of the approach.

  1. Low-complexity controllers for time-delay systems

    CERN Document Server

    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 ...

  2. On Tuning PI Controllers for Integrating Plus Time Delay Systems

    Directory of Open Access Journals (Sweden)

    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.

  3. Attosecond science in atomic, molecular, and condensed matter physics.

    Science.gov (United States)

    Leone, Stephen R; Neumark, Daniel M

    2016-12-16

    Attosecond science represents a new frontier in atomic, molecular, and condensed matter physics, enabling one to probe the exceedingly fast dynamics associated with purely electronic dynamics in a wide range of systems. This paper presents a brief discussion of the technology required to generate attosecond light pulses and gives representative examples of attosecond science carried out in several laboratories. Attosecond transient absorption, a very powerful method in attosecond science, is then reviewed and several examples of gas phase and condensed phase experiments that have been carried out in the Leone/Neumark laboratories are described.

  4. Time-delayed chameleon: Analysis, synchronization and FPGA ...

    Indian Academy of Sciences (India)

    A novel adaptive modified functional projective lag synchronization algorithm is derived for synchronizing identical time-delayed chameleon systems with uncertain ... Centre for Nonlinear Dynamics, Department of Electrical and Communication Engineering, The PNG University of Technology, Lae, Papua New Guinea ...

  5. Stability Criteria for Differential Equations with Variable Time Delays

    Science.gov (United States)

    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…

  6. Introduction to time-delay systems analysis and control

    CERN Document Server

    Fridman, Emilia

    2014-01-01

    The beginning of the 21st century can be characterized as the ”time-delay boom” leading to numerous important results. The purpose of this book is two-fold, to familiarize the non-expert reader with time-delay systems and to provide a systematic treatment of modern ideas and techniques for experts. This book is based on the course ”Introduction to time-delay systems” for graduate students in Engineering and Applied Mathematics that the author taught in Tel Aviv University in 2011-2012 and 2012-2013 academic years. The sufficient background to follow most of the material are the undergraduate courses in mathematics and an introduction to control. The book leads the reader from some basic classical results on time-delay systems to recent developments on Lyapunov-based analysis and design with applications to the hot topics of sampled-data and network-based control. The objective is to provide useful tools that will allow the reader not only to apply the existing methods, but also to develop new ones. It...

  7. A time-delayed method for controlling chaotic maps

    Energy Technology Data Exchange (ETDEWEB)

    Chen Maoyin [Department of Automation, Tsinghua University, Beijing 100084 (China)]. E-mail: maoyinchen@163.com; Zhou Donghua [Department of Automation, Tsinghua University, Beijing 100084 (China); Shang Yun [College of Mathematics and Information Science, Shaanxi Normal University, Xi' an 710062 (China)

    2005-12-19

    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.

  8. Measurement of time delay for a prospectively gated CT simulator

    Science.gov (United States)

    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

  9. Measurement of time delay for a prospectively gated CT simulator

    Directory of Open Access Journals (Sweden)

    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

  10. The generalized Burgers equation with and without a time delay

    Directory of Open Access Journals (Sweden)

    Nejib Smaoui

    2004-01-01

    Full Text Available We consider the generalized Burgers equation with and without a time delay when the boundary conditions are periodic with period 2π. For the generalized Burgers equation without a time delay, that is, ut=vuxx−uux+u+h(x, 00, u(0,t=u(2π,t, u(x,0=u0(x, a Lyapunov function method is used to show boundedness and uniqueness of a steady state solution and global stability of the equation. As for the generalized time-delayed Burgers equation, that is, ut(x,t=vuxx(x,t−u(x,t−τux(x,t+u(x,t, 00, u(0,t=u(2π,t, t>0, u(x,s=u0(x,s, 0delays. Using a pseudospectral method, we present some numerical results illustrating and reinforcing the analytical results.

  11. Ignition delay time measurements of primary reference fuel blends

    KAUST Repository

    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.

  12. Generation of bright isolated attosecond soft X-ray pulses driven by multicycle midinfrared lasers.

    Science.gov (United States)

    Chen, Ming-Chang; Mancuso, Christopher; Hernández-García, Carlos; Dollar, Franklin; Galloway, Ben; Popmintchev, Dimitar; Huang, Pei-Chi; Walker, Barry; Plaja, Luis; Jaroń-Becker, Agnieszka A; Becker, Andreas; Murnane, Margaret M; Kapteyn, Henry C; Popmintchev, Tenio

    2014-06-10

    High harmonic generation driven by femtosecond lasers makes it possible to capture the fastest dynamics in molecules and materials. However, to date the shortest subfemtosecond (attosecond, 10(-18) s) pulses have been produced only in the extreme UV region of the spectrum below 100 eV, which limits the range of materials and molecular systems that can be explored. Here we experimentally demonstrate a remarkable convergence of physics: when midinfrared lasers are used to drive high harmonic generation, the conditions for optimal bright, soft X-ray generation naturally coincide with the generation of isolated attosecond pulses. The temporal window over which phase matching occurs shrinks rapidly with increasing driving laser wavelength, to the extent that bright isolated attosecond pulses are the norm for 2-µm driving lasers. Harnessing this realization, we experimentally demonstrate the generation of isolated soft X-ray attosecond pulses at photon energies up to 180 eV for the first time, to our knowledge, with a transform limit of 35 attoseconds (as), and a predicted linear chirp of 300 as. Most surprisingly, advanced theory shows that in contrast with as pulse generation in the extreme UV, long-duration, 10-cycle, driving laser pulses are required to generate isolated soft X-ray bursts efficiently, to mitigate group velocity walk-off between the laser and the X-ray fields that otherwise limit the conversion efficiency. Our work demonstrates a clear and straightforward approach for robustly generating bright isolated attosecond pulses of electromagnetic radiation throughout the soft X-ray region of the spectrum.

  13. Macroscopic effects in attosecond pulse generation

    Energy Technology Data Exchange (ETDEWEB)

    Ruchon, T; Varju, K; Mansten, E; Swoboda, M; L' Huillier, A [Department of Physics, Lund University, PO Box 118, SE-221 00 Lund (Sweden); Hauri, C P; Lopez-Martens, R [Laboratoire d' Optique Appliquee, Ecole Nationale Superieure des Techniques Avancees (ENSTA)-Ecole Polytechnique CNRS UMR 7639, 91761 Palaiseau (France)], E-mail: anne.lhuillier@fysik.lth.se

    2008-02-15

    We examine how the generation and propagation of high-order harmonics in a partly ionized gas medium affect their strength and synchronization. The temporal properties of the resulting attosecond pulses generated in long gas targets can be significantly influenced by macroscopic effects, in particular by the intensity in the medium and the degree of ionization which control the dispersion. Under some conditions, the use of gas targets longer than the absorption length can lead to the generation of compressed attosecond pulses. We show these macroscopic effects experimentally, using a 6 mm-long argon-filled gas cell as the generating medium.

  14. Benchmarking Attosecond Physics with Atomic Hydrogen

    Science.gov (United States)

    2015-05-25

    Final 3. DATES COVERED (From - To) 12 Mar 12 – 11 Mar 15 4. TITLE AND SUBTITLE Benchmarking attosecond physics with atomic hydrogen 5a...AND SUBTITLE Benchmarking attosecond physics with atomic hydrogen 5a. CONTRACT NUMBER FA2386-12-1-4025 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER...THIS PAGE unclassified Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 Final Report for AOARD Grant FA2386-12-1-4025 “ Benchmarking

  15. Bounded Delay Timing Analysis of a Class of CSP Programs

    DEFF Research Database (Denmark)

    Hulgaard, Henrik; Burns, Steven M.

    1997-01-01

    . Such a description is transformed into a safe Petri net with interval time delays specified on the places of the net. The timing analysis we perform determines the extreme separation in time between two communication actions of the CSP program for all possible timed executions of the system. We formally define......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...

  16. Face to phase: pitfalls in time delay estimation from coherency phase

    NARCIS (Netherlands)

    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

  17. A new delay-independent condition for global robust stability of neural networks with time delays.

    Science.gov (United States)

    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.

  18. Erasure of Time Delay Signatures in the Output of an Optoelectronic Feedback Laser with Modulated Delays and Chaos Synchronization

    OpenAIRE

    Shahverdiev, E. M.; Shore, K. A.

    2009-01-01

    By studying the autocorrelation function of the optoelectronic feedback semiconductor laser output we establish that the signatures of time delays can be erased in systems incorporating modulated feedback time delays. This property is of importance for the suitability of such laser systems for secure chaos-based communication systems. We also make the first report on chaos synchronization in both unidirectionally and bidirectionally coupled multiple time delay chaotic semiconductor lasers wit...

  19. Applications of stability criteria to time delay systems

    Directory of Open Access Journals (Sweden)

    D. Popescu

    2004-08-01

    Full Text Available Stability and stabilization of time delay systems (even of the linear ones is again in the mainstream of the research. A most recent example is the stability analysis of feedback control loops containing a first order controlled object with pure delay and a standard PID controller, thus generating a system with a second degree quasi-polynomial as characteristic equation. Since the classical memoir of Čebotarev and Meiman (1949 up to the more recent monographs by Stepan (1989 and Górecki et al (1989 several approaches to this problem have been given, aiming to find the most complete Routh-Hurwitz type conditions for this case. In fact the main problem is here a missing case in the original memoir of Čebotarev and Meiman and its significance within the framework of the most recent analysis of Górecki et al. The present paper aims to a fairly complete analysis of the problem combined with some hints for the nonlinear case (Aizerman problem. State feedback stabilization based on Artstein reduction of a system with input delay to a system without delay is also considered.

  20. Delayed Timing of Eating: Impact on Weight and Metabolism.

    Science.gov (United States)

    Allison, Kelly C; Goel, Namni; Ahima, Rexford S

    2014-03-01

    Animal studies of delayed eating have provided useful information regarding the potential relationship between nighttime eating and increased weight and metabolic dysregulation, which occur in the absence of increased locomotion or increased caloric intake. We first review recent studies detailing these relationships and possible mechanisms in rodents. We then examine human data showing that sleep restriction leads to increased energy intake and weight gain, followed by a review of the human phenotype of delayed eating, night eating syndrome, and its relation to weight and metabolism. Finally, we examine human experimental studies of delayed eating and discuss preliminary data that show slight weight gain, dysfunction in energy expenditure, and abnormalities in the circadian rhythms of appetitive, stress, and sleep hormones. Well-controlled, longer-term experimental studies in humans are warranted to test the effect of delayed eating without sleep restriction to clarify whether limiting or eliminating nighttime eating could lead to weight loss and significantly improve related disorders, such as diabetes and heart disease, over time.

  1. Lagrange time delay estimation for scanning electron microscope image magnification.

    Science.gov (United States)

    Sim, K-S; Thong, L W; Ting, H Y; Tso, C P

    2010-02-01

    Interpolation techniques that are used for image magnification to obtain more useful details of the surface such as morphology and mechanical contrast usually rely on the signal information distributed around edges and areas of sharp changes and these signal information can also be used to predict missing details from the sample image. However, many of these interpolation methods tend to smooth or blur out image details around the edges. In the present study, a Lagrange time delay estimation interpolator method is proposed and this method only requires a small filter order and has no noticeable estimation bias. Comparing results with the original scanning electron microscope magnification and results of various other interpolation methods, the Lagrange time delay estimation interpolator is found to be more efficient, more robust and easier to execute.

  2. Nonlinear optical generation of time-delayed entanglement

    Energy Technology Data Exchange (ETDEWEB)

    McRae, Terry G; Bowen, Warwick P, E-mail: wbowen@physics.uq.edu.au [Centre for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, St Lucia, Brisbane, QLD 4072 (Australia)

    2011-05-14

    A model is presented of nth order nonlinear processes in whispering gallery mode resonators, with scattering coherently coupling degenerate counter propagating modes. It is shown that such systems generate strong squeezing and time-delayed entanglement. The model can be generally applied to any pair of nonlinear coherently coupled cavities and is of particular relevance to whispering gallery mode resonators. A feature of the entanglement is that, by tuning the coherent coupling rate the peak entanglement can be tuned to occur away from the carrier frequency. This has technological significance allowing low frequency noise sources around the carrier frequency to be avoided. All-optical time-delayed entanglement has many applications, such as an all-optical quantum memory.

  3. Control of unstable processes with time delays via ADRC.

    Science.gov (United States)

    Fu, Caifen; Tan, Wen

    2017-11-01

    Active disturbance rejection control (ADRC) treats the external disturbance and internal uncertainties as a general disturbance, and uses an extended state observer (ESO) to estimate it in real-time and feeds it back in the control loop, thus can achieve good disturbance rejection performance. However, ADRC is not quite suitable for unstable delayed processes due to its inherent structure. In this paper, a two-degree-of-freedom (2DOF) control structure is proposed for unstable time- delayed systems. Set-point tracking and disturbance rejection are separated in this structure and ADRC is solely responsible for disturbance rejection. A method to tune the ADRC parameters using all the information of the system is proposed, and robustness and performance of the proposed method are analyzed. Simulation examples show that 2DOF-ADRC can achieve good tracking and disturbance rejection performance. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  4. Hopf Bifurcation in a Cobweb Model with Discrete Time Delays

    Directory of Open Access Journals (Sweden)

    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.

  5. Discussion on 'State feedback control with time delay'

    Science.gov (United States)

    Araújo, José M.

    2018-01-01

    This note is a short discussion on the paper 'State feedback control with time delay', in which an a posteriori analysis on the primary closed-loop eigenvalues is proposed to ensure that the chosen location is accurately achieved by state feedback. The goal is twofold. First, a qualitative evaluation of closed-loop stability can be carried out by using classical control techniques, as systems margins or Nyquist plot, without the necessity of evaluating the primary closed-loop eigenvalues; and second, the well-known Padé approximants for time delay in frequency domain is shown to be as accurate as that the truncation of the Taylor exponential expansion proposed in that work.

  6. Time Delay Estimation in Room Acoustic Environments: An Overview

    Directory of Open Access Journals (Sweden)

    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.

  7. Ignition Delay Times of Kerosene(Jet-A)/Air Mixtures

    CERN Document Server

    Zhukov, V P; Starikovskii, A Yu

    2012-01-01

    Ignition of Jet-A/air mixtures was studied behind reflected shock waves. Heating of shock tube at temperature of 150 C was used to prepare a homogeneous fuel mixture. Ignition delay times were measured from OH emission at 309 nm and from absorption of He-Ne laser radiation at 3.3922 micrometers. The conditions behind shock waves were calculated by one-dimensional shock wave theory from initial conditions T1, P1, mixture composition and incident shock wave velocity. The ignition delay times were obtained at two fixed pressures 10, 20 atm for lean, stoichiometric and rich mixtures (ER=0.5, 1, 2) at an overall temperature range of 1040-1380 K.

  8. Anesthesia residents’ training and start time delays in operating room

    OpenAIRE

    Zahed Husaain Khan; Seydeh Shohreh Alavi; Shahriar Arbabi; Jalil Makarem

    2014-01-01

    Background: Education is the main mission of teaching hospitals, but the residents’ learning in acquiring new techniques does interfere in the overall treatment process of patients. Studies pertaining to the effect of anesthesia residents’ training in operating room on treatment procedures have reported conflicting results. Therefore, this study was performed to investigate the effects of anesthesia residents’ training on start time operative delays. Methods: This cohort study was done in ...

  9. Time delay for aerial ammonia concentration measurements in livestock buildings.

    Science.gov (United States)

    Rom, Hans Benny; Zhang, Guo-Qiang

    2010-01-01

    Correct measurements of ammonia concentration in air still present considerable challenges. The high water solubility and polarity can cause it to adsorb on surfaces in the entire sampling system, including sampling lines, filters, valves, pumps and instruments, causing substantial measuring errors and time delays. To estimate time delay characteristics of a Photo Acoustic Multi Gas Monitor 1312 and a Multi Point Sampler continuous measurement of aerial ammonia concentrations at different levels was performed. In order to obtain reproducible data, a wind tunnel was used to generate selected concentrations inside and a background concentration representing the air inlet of the tunnel. Four different concentration levels (0.8 ppm, 6.2 ppm, 9.7 ppm and 13.7 ppm) were used in the experiments, with an additional outdoor concentration level as background. The results indicated a substantial time delay when switching between the measuring positions with high and low concentration and vice versa. These properties may course serious errors for estimation of e.g. gas emissions whenever more than one measuring channel is applied. To reduce the measurement errors, some suggestions regarding design of the measurement setup and measuring strategies were presented.

  10. Time Delay for Aerial Ammonia Concentration Measurements in Livestock Buildings

    Directory of Open Access Journals (Sweden)

    Hans Benny Rom

    2010-05-01

    Full Text Available Correct measurements of ammonia concentration in air still present considerable challenges. The high water solubility and polarity can cause it to adsorb on surfaces in the entire sampling system, including sampling lines, filters, valves, pumps and instruments, causing substantial measuring errors and time delays. To estimate time delay characteristics of a Photo Acoustic Multi Gas Monitor 1312 and a Multi Point Sampler continuous measurement of aerial ammonia concentrations at different levels was performed. In order to obtain reproducible data, a wind tunnel was used to generate selected concentrations inside and a background concentration representing the air inlet of the tunnel. Four different concentration levels (0.8 ppm, 6.2 ppm, 9.7 ppm and 13.7 ppm were used in the experiments, with an additional outdoor concentration level as background. The results indicated a substantial time delay when switching between the measuring positions with high and low concentration and vice versa. These properties may course serious errors for estimation of e.g. gas emissions whenever more than one measuring channel is applied. To reduce the measurement errors, some suggestions regarding design of the measurement setup and measuring strategies were presented.

  11. Time domain passivity controller for 4-channel time-delay bilateral teleoperation.

    Science.gov (United States)

    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.

  12. Extended time-delay autosynchronization for the buck converter

    CERN Document Server

    Batlle, C; Olivar, G

    1996-01-01

    Time-delay autosynchronization (TDAS) can be used to stabilize unstable periodic orbits in dynamical systems. The technique involves continuous feedback of signals delayed by the orbit's period. One variant, ETDAS, uses information further in the past. In both cases, the feedback signal vanishes on the target periodic orbit and hence the stabilized periodic orbit is one of the original dynamical system. Furthermore, this control method only requires the knowledge of the period of the unstable orbit. The amount of feedback gain needed to achieve stabilization varies with the bifurcation parameter(s) of the system, resulting in a domain of control. In this paper we compute the domain of control of the unstable periodic orbits of the \\textit{buck} converter. We obtain a closed analytical expression for the curve $g:S^1 \\rightarrow\\C$ whose index determines the stability, and this index is then numerically computed. We run several simulations of the controlled system and discuss the results.

  13. On the time delay between ultra-relativistic particles

    Directory of Open Access Journals (Sweden)

    Pierre Fleury

    2016-09-01

    Full Text Available 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.

  14. Transmission ultrasonography. [time delay spectrometry for soft tissue transmission imaging

    Science.gov (United States)

    Heyser, R. C.; Le Croissette, D. H.

    1973-01-01

    Review of the results of the application of an advanced signal-processing technique, called time delay spectrometry, in obtaining soft tissue transmission images by transmission ultrasonography, both in vivo and in vitro. The presented results include amplitude ultrasound pictures and phase ultrasound pictures obtained by this technique. While amplitude ultrasonographs of tissue are closely analogous to X-ray pictures in that differential absorption is imaged, phase ultrasonographs represent an entirely new source of information based on differential time of propagation. Thus, a new source of information is made available for detailed analysis.

  15. Multiplicity counting from fission detector signals with time delay effects

    Science.gov (United States)

    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).

  16. Predictive active disturbance rejection control for processes with time delay.

    Science.gov (United States)

    Zheng, Qinling; Gao, Zhiqiang

    2014-07-01

    Active disturbance rejection control (ADRC) has been shown to be an effective tool in dealing with real world problems of dynamic uncertainties, disturbances, nonlinearities, etc. This paper addresses its existing limitations with plants that have a large transport delay. In particular, to overcome the delay, the extended state observer (ESO) in ADRC is modified to form a predictive ADRC, leading to significant improvements in the transient response and stability characteristics, as shown in extensive simulation studies and hardware-in-the-loop tests, as well as in the frequency response analysis. In this research, it is assumed that the amount of delay is approximately known, as is the approximated model of the plant. Even with such uncharacteristic assumptions for ADRC, the proposed method still exhibits significant improvements in both performance and robustness over the existing methods such as the dead-time compensator based on disturbance observer and the Filtered Smith Predictor, in the context of some well-known problems of chemical reactor and boiler control problems. © 2013 Published by ISA on behalf of ISA.

  17. Incorporation of Time Delayed Measurements in a Discrete-time Kalman Filter

    DEFF Research Database (Denmark)

    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 there is a......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...

  18. Isolated atto-second pulse generated by spatial shaping of femtosecond laser beam

    Energy Technology Data Exchange (ETDEWEB)

    Strelkov, V.; Mevel, E.; Constant, E. [Univ Bordeaux 1, CELIA, F-33405 Talence (France); Strelkov, V. [Russian Acad Sci, Inst Gen Phys, Moscow 119991 (Russian Federation)

    2009-08-15

    We study numerically the time-dependent HHG phase-matching in the laser beam having a flat-top radial intensity profile. A flat-top profile is the key to produce similar ionization degree at the axis and at the periphery and thus to achieve simultaneous phase-matched generation. Such a profile can be obtained experimentally by using two concentric phase plates that introduce a specific phase shift between the central and the outer part of a focused Gaussian beam. We find realistic laser field parameters and medium density that allow obtaining (after spectral filtering) single atto-second pulse using 10 fs driving laser pulse. Our technique provides isolated atto-second pulse emission almost insensitive on the CEP of the laser pulse. Moreover, the technique is effective both for the mid-plateau and the cut-off spectral range. In particular, the XUV from Ar target in the cut-off spectral range (compatible with the Zr filter) provides isolated atto-second pulse with 185 as duration at a central energy of 92 eV. Using achievable multi mJ 10 fs laser pulses this technique could provide atto-second pulses approaching the {mu}J energy range. (authors)

  19. Compensation of high order harmonic long quantum-path attosecond chirp

    Science.gov (United States)

    Guichard, R.; Caillat, J.; Lévêque, C.; Risoud, F.; Maquet, A.; Taïeb, R.; Zaïr, A.

    2017-12-01

    We propose a method to compensate for the extreme ultra violet (XUV) attosecond chirp associated with the long quantum-path in the high harmonic generation process. Our method employs an isolated attosecond pulse (IAP) issued from the short trajectory contribution in a primary target to assist the infrared driving field to produce high harmonics from the long trajectory in a secondary target. In our simulations based on the resolution of the time-dependent Schrödinger equation, the resulting high harmornics present a clear phase compensation of the long quantum-path contribution, near to Fourier transform limited attosecond XUV pulse. Employing time–frequency analysis of the high harmonic dipole, we found that the compensation is not a simple far-field photonic interference between the IAP and the long-path harmonic emission, but a coherent phase transfer from the weak IAP to the long quantum-path electronic wavepacket. Our approach opens the route to utilizing the long quantum-path for the production and applications of attosecond pulses.

  20. Improving time-delay cosmography with spatially resolved kinematics

    Science.gov (United States)

    Shajib, Anowar J.; Treu, Tommaso; Agnello, Adriano

    2018-01-01

    Strongly gravitational lensed quasars can be used to measure the so-called time-delay distance DΔt, and thus the Hubble constant H0 and other cosmological parameters. Stellar kinematics of the deflector galaxy play an essential role in this measurement by: (i) helping break the mass-sheet degeneracy; (ii) determining in principle the angular diameter distance Dd to the deflector and thus further improving the cosmological constraints. In this paper we simulate observations of lensed quasars with integral field spectrographs and show that spatially resolved kinematics of the deflector enables further progress by helping break the mass-anisotropy degeneracy. Furthermore, we use our simulations to obtain realistic error estimates with current/upcoming instruments like OSIRIS on Keck and NIRSPEC on the James Webb Space Telescope for both distances (typically ∼6 per cent on DΔt and ∼10 per cent on Dd). We use the error estimates to compute cosmological forecasts for the sample of nine lenses that currently have well-measured time delays and deep Hubble Space Telescope images and for a sample of 40 lenses that is projected to be available in a few years through follow-up of candidates found in ongoing wide field surveys. We find that H0 can be measured with 2 per cent (1 per cent) precision from nine (40) lenses in a flat Λcold dark matter cosmology. We study several other cosmological models beyond the flat Λcold dark matter model and find that time-delay lenses with spatially resolved kinematics can greatly improve the precision of the cosmological parameters measured by cosmic microwave background data.

  1. Digital decoupling controller design for multiple time-delay continuous-time transfer function matrices

    Science.gov (United States)

    Xie, L. B.; Wu, C. Y.; Shieh, L. S.; Tsai, J. S. H.

    2015-03-01

    This paper presents an extended adjoint decoupling method to conduct the digital decoupling controller design for the continuous-time transfer function matrices with multiple (integer/fractional) time delays in both the denominator and the numerator matrix. First, based on the sampled unit-step response data of the afore-mentioned multiple time-delay system, the conventional balanced model-reduction method is utilised to construct an approximated discrete-time model of the original (known/unknown) multiple time-delay continuous-time transfer function matrix. Then, a digital decoupling controller is designed by utilising the extended adjoint decoupling method together with the conventional discrete-time root-locus method. An illustrative example is given to demonstrate the effectiveness of the proposed method.

  2. Analysis and Design of Adaptive Synchronization of a Complex Dynamical Network with Time-Delayed Nodes and Coupling Delays

    Directory of Open Access Journals (Sweden)

    Yu Miao

    2017-01-01

    Full Text Available This paper is devoted to the study of synchronization problems in uncertain dynamical networks with time-delayed nodes and coupling delays. First, a complex dynamical network model with time-delayed nodes and coupling delays is given. Second, for a complex dynamical network with known or unknown but bounded nonlinear couplings, an adaptive controller is designed, which can ensure that the state of a dynamical network asymptotically synchronizes at the individual node state locally or globally in an arbitrary specified network. Then, the Lyapunov-Krasovskii stability theory is employed to estimate the network coupling parameters. The main results provide sufficient conditions for synchronization under local or global circumstances, respectively. Finally, two typical examples are given, using the M-G system as the nodes of the ring dynamical network and second-order nodes in the dynamical network with time-varying communication delays and switching communication topologies, which illustrate the effectiveness of the proposed controller design methods.

  3. The radio-gamma time delay of the Crab pulsar.

    Science.gov (United States)

    Masnou, J. L.; Agrinier, B.; Barouch, E.; Comte, R.; Costa, E.; Christy, J. C.; Cusumano, G.; Gerardi, G.; Lemoine, D.; Mandrou, P.; Massaro, E.; Matt, G.; Mineo, T.; Niel, M.; Olive, J. F.; Parlier, B.; Sacco, B.; Salvati, M.; Scarsi, L.

    1994-10-01

    Gamma-ray observations of the pulsar of the Crab nebula, PSR0531+21, have been performed in the low energy range (0.15-4.0 MeV) with FIGARO II, a large area balloon borne NaI(Tl) detector, during two flights performed on 1986 July 11 and 1990 July 9. A Kernel estimator built from the phases of the individual gamma-ray arrival times has allowed an accurate derivation of the radio-gamma time delay from those short duration gamma-ray observations. The gamma-ray pulse is found ahead of the radio pulse by 600+/-145μs and 375+/-148μs for the 1986 and 1990 observations respectively. Both radio-gamma delays could be attributed to variability of the interstellar dispersion since dispersion measures are available from radio measurements respectively two months before the 1986 flight and six days after the 1990 flight. An alternative explanation, particularly from the 1990 observation, could be that maximum gamma-ray and radio emissions originate from spatially different regions of the magnetosphere, distant by about 100 km.

  4. Measurement and Control of Attosecond Pulses

    Science.gov (United States)

    2016-04-25

    the re-collision electron wave packet and therefore on the attosecond pulse that it produces. This modification deflects the beam and the deflection ...TYPE. State the type of report, such as final, technical, interim, memorandum, master’s thesis , progress, quarterly, research, special, group study...illustrated in Figure 1. A weak beam is incident on the nonlinear medium at a slight angle to the fundamental. It imposes a phased modification on

  5. Stabilizing unstable steady states using extended time-delay autosynchronization.

    Science.gov (United States)

    Chang, Austin; Bienfang, Joshua C.; Hall, G. Martin; Gardner, Jeff R.; Gauthier, Daniel J.

    1998-12-01

    We describe a method for stabilizing unstable steady states in nonlinear dynamical systems using a form of extended time-delay autosynchronization. Specifically, stabilization is achieved by applying a feedback signal generated by high-pass-filtering in real time the dynamical state of the system to an accessible system parameter or variables. Our technique is easy to implement, does not require knowledge of the unstable steady state coordinates in phase space, automatically tracks changes in the system parameters, and is more robust to broadband noise than previous schemes. We demonstrate the controller's efficacy by stabilizing unstable steady states in an electronic circuit exhibiting low-dimensional temporal chaos. The simplicity and robustness of the scheme suggests that it is ideally suited for stabilizing unstable steady states in ultra-high-speed systems. (c) 1998 American Institute of Physics.

  6. Delay 25 an ASIC for timing adjustment in LHC

    NARCIS (Netherlands)

    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

  7. Mathematical model of tuberculosis epidemic with recovery time delay

    Science.gov (United States)

    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.

  8. Real-Time Tropospheric Delay Estimation using IGS Products

    Science.gov (United States)

    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

  9. Generation of isolated attosecond pulses with double optical gating and electronic dynamics in molecules studied via attosecond pump-probe experiment

    Science.gov (United States)

    Mashiko, Hiroki

    2010-03-01

    Single isolated attosecond pulses are useful tools for studying electron dynamics. Previously, such as pulses can be generated by few cycle 5 fs driving lasers. It is still a technical challenge to reproduce daily such pulses. In order to allow longer driving laser pulses, two optical gating methods of polarization gating and two-color gating are combined. This approach is dubbed double optical gating. Due to less depletion of the ground state population by the leading edge of the field, this technique can produce isolated 250 as pulses using up to ˜25 fs driving laser pulses. Also, the supercontinuous spectra (28-620 eV) can in principle support a 16 as pulse duration, obtained from 8 fs driving lasers. Because of the relaxation on the driving laser requirements, more laboratories can enter the isolated attosecond pulse science field. Pump-probe experiments with such isolated attosecond pulses and IR pulses can provide quantitative information on electronic dynamics. In recent work, the photoelectron spectra of sulfur hexafluoride (SF6) clearly indicates the precise shape of the IR driving pulse (1.5 eV), verifying that isolated ˜400 as pulses (93 eV) are achieved and these pulses produce an instantaneous inner valence ionization in the molecule. The pump-probe spectra of cation fragments resulting from double and triple ionization show 6-7 fs rise times (SF4^2+, SF3^2+, SF2^2+ and S^2+) or decay times (SF^+ and S^+) times governed by the overlap of the IR and XUV pulses. A suppression or enhancement of certain fragmentation channels is tentatively interpreted as resulting from the IR laser exciting the initial cations to higher states that exhibit different decay channels. This type of pump-probe experiment with isolated attosecond pulses is powerful for the study of electronic dynamics as well as resulting nuclear fragmentation measurements.

  10. Modelling biochemical networks with intrinsic time delays: a hybrid semi-parametric approach

    Directory of Open Access Journals (Sweden)

    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.

  11. Stochastic nonlinear time series forecasting using time-delay reservoir computers: performance and universality.

    Science.gov (United States)

    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.

  12. A high-resolution time interpolator based on a delay locked loop and an RC delay line

    CERN Document Server

    Mota, M

    1999-01-01

    An architecture for a time interpolation circuit with an rms error of ~25 ps has been developed in a 0.7- mu m CMOS technology. It is based on a delay locked loop (DLL) driven by a 160-MHz reference clock and a passive RC delay line controlled by an autocalibration circuit. Start-up calibration of the RC delay line is performed using code density tests (CDT). The very small temperature/voltage dependence of R and C parameters and the self calibrating DLL results in a low- power, high-resolution time interpolation circuit in a standard digital CMOS technology. (11 refs).

  13. Complex-Vector Time-Delay Control of Power Converters

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Loh, P. C.; Tang, Y.

    2008-01-01

    to develop dynamically fast and accurate current controllers is even more intensive with more features expected to be embedded within a single control module. Believing in its continual importance, this paper contributes by proposing a complex-vector time-delay control scheme that can achieve high tracking......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...... a set of load-matching control characteristics that are less sensitive to external noise interferences. These added features, complementing the basic requirement of fast and accurate fundamental positive-sequence tracking, render the proposed scheme as an attractive alternative for high-end converter...

  14. Time delay between cardiac and brain activity during sleep transitions

    Science.gov (United States)

    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.

  15. Control by time delayed feedback near a Hopf bifurcation point

    Directory of Open Access Journals (Sweden)

    Sjoerd Verduyn Lunel

    2017-12-01

    Full Text Available In this paper we study the stabilization of rotating waves using time delayed feedback control. It is our aim to put some recent results in a broader context by discussing two different methods to determine the stability of the target periodic orbit in the controlled system: 1 by directly studying the Floquet multipliers and 2 by use of the Hopf bifurcation theorem. We also propose an extension of the Pyragas control scheme for which the controlled system becomes a functional differential equation of neutral type. Using the observation that we are able to determine the direction of bifurcation by a relatively simple calculation of the root tendency, we find stability conditions for the periodic orbit as a solution of the neutral type equation.

  16. Dithered Time Delays and Chaos Synchronization in Lasers with Multiple Feedbacks

    OpenAIRE

    Shahverdiev, E. M.; Shore, K. A.

    2009-01-01

    By studying laser systems with multiple time delays, we demonstrate that the signatures of time delays in the autocorrelation coefficient and the mutual information of the laser output can be erased for systems with variable time delays. This property makes such laser systems highly suitable for secure chaos-based communication systems. We also present the first report on chaos synchronization in both unidirectionally and bidirectionally coupled variable multiple time delay laser diodes with ...

  17. Delay-Dependent Stability Criteria of Uncertain Periodic Switched Recurrent Neural Networks with Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    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.

  18. Helicity-Selective Enhancement and Polarization Control of Attosecond High Harmonic Waveforms Driven by Bichromatic Circularly Polarized Laser Fields

    Science.gov (United States)

    Dorney, Kevin M.; Ellis, Jennifer L.; Hernández-García, Carlos; Hickstein, Daniel D.; Mancuso, Christopher A.; Brooks, Nathan; Fan, Tingting; Fan, Guangyu; Zusin, Dmitriy; Gentry, Christian; Grychtol, Patrik; Kapteyn, Henry C.; Murnane, Margaret M.

    2017-08-01

    High harmonics driven by two-color counterrotating circularly polarized laser fields are a unique source of bright, circularly polarized, extreme ultraviolet, and soft x-ray beams, where the individual harmonics themselves are completely circularly polarized. Here, we demonstrate the ability to preferentially select either the right or left circularly polarized harmonics simply by adjusting the relative intensity ratio of the bichromatic circularly polarized driving laser field. In the frequency domain, this significantly enhances the harmonic orders that rotate in the same direction as the higher-intensity driving laser. In the time domain, this helicity-dependent enhancement corresponds to control over the polarization of the resulting attosecond waveforms. This helicity control enables the generation of circularly polarized high harmonics with a user-defined polarization of the underlying attosecond bursts. In the future, this technique should allow for the production of bright highly elliptical harmonic supercontinua as well as the generation of isolated elliptically polarized attosecond pulses.

  19. Time-delay control of ionic polymer metal composite actuator

    Science.gov (United States)

    Lee, Joon Hwan; Kim, Byung Jo; Kim, Jin Seong; Song, Dae Seok; Lee, Min Gyu; Jho, Jae Young; Kim, Dong Min; Rhee, Kyehan; Lee, Soo Jin

    2015-04-01

    This paper presents the control of an ionic polymer metal composite (IPMC) strip, which is an electro-active polymer actuator. IPMC can produce mechanical bending motion in response to an electrical excitation. Although IPMC has many beneficial properties, such as low power consumption, large deformation, and bi-directional actuation, it is very challenging to control because of its time-varying and nonlinear properties. Time-delay control (TDC) was applied to an IPMC strip in order to obtain a robust and precise tracking performance. The TDC scheme has shown good tracking performance with exceptional robustness in many other applications, in addition to having a simple and efficient structure and design process. A first-order filter was applied to the control input to reduce the sensor noise. An anti-windup scheme was also used because of its inherent integral effect. The simulation and experimental results of an IPMC strip controlled by TDC showed good performance in the steady state and transient responses. Furthermore, the control output responses tracked the desired model even when the IPMC parameters varied in repetitive experiments. In addition, it was shown through Nyquist analysis that the stability of the IPMC strip controlled by TDC is always maintained with the time-varying parameters. These results demonstrate that the TDC law applied to a time-varying and nonlinear IPMC provides robustness in performance and stability, while yielding precise transient and steady state tracking performance.

  20. Improved Stability Analysis for Neural Networks with Time-Varying Delay

    Directory of Open Access Journals (Sweden)

    Yongming Li

    2012-01-01

    Full Text Available This paper concerned the problem of delay-dependent asymptotic stability for neural networks with time-varying delay. A new class of Lyapunov functional dividing the interval delay is constructed to derive some new delay-dependent stability criteria. The obtained criteria are less conservative because free-weighting matrices method, a convex optimization approach, and a mixed dividing delay interval approach are considered. Finally, numerical examples are given to illustrate the effectiveness of the proposed method.

  1. Multiscale dynamics of C60 from attosecond to statistical physics

    Science.gov (United States)

    Lépine, F.

    2015-06-01

    C60 is a fascinating object that has become remarkably useful for experimentalists and theoreticians to study photo-induced processes in large many-particle systems. In this review article, we discuss how the knowledge accumulated over the past 30 years on this molecule provides a large panel of mechanisms that occur from the intrinsic time scale of electronic motion that is attosecond, to long ‘macroscopic’ time scale (second). This illustrates the multiscale aspect of dynamics in photo-excited systems, which connects coherent quantum processes to classical and statistical mechanisms. This also shines light onto future experiments and theoretical work required to complete the global picture of light-induced mechanisms in fullerenes.

  2. A Time Delay Estimation Method Based on Wavelet Transform and Speech Envelope for Distributed Microphone Arrays

    Directory of Open Access Journals (Sweden)

    YIN, F.

    2013-08-01

    Full Text Available A time delay estimation method based on wavelet transform and speech envelope is proposed for distributed microphone arrays. This method first extracts the speech envelopes of the signals processed with multi-level discrete wavelet transform, and then makes use of the speech envelopes to estimate a coarse time delay. Finally it searches for the accurate time delay near the coarse time delay by the cross-correlation function calculated in time domain. The simulation results illustrate that the proposed method can accurately estimate the time delay between two distributed microphone array signals.

  3. Patient delay is the main cause of treatment delay in acute limb ischemia: an investigation of pre- and in-hospital time delay

    DEFF Research Database (Denmark)

    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...... phases between the time of occurrence of symptoms and completion of treatment was recorded prospectively. All patients who underwent intervention had a 30 days follow-up with regard to major amputation of the leg and survival. RESULTS: A total of 42 patients (21 men and 21 women) age 73 (20-95) years...... to revascularization was 324.5 (122-873) minutes and in the group of eight patients that went through an imaging procedure before an operation the median delay was 822 (494-1185) minutes from specialist assessment to revascularization. The median time for revascularization among four patients, who were treated...

  4. Finite-Time Attractivity for Diagonally Dominant Systems with Off-Diagonal Delays

    Directory of Open Access Journals (Sweden)

    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.

  5. The relaxation time of processes in a FitzHugh-Nagumo neural system with time delay

    Energy Technology Data Exchange (ETDEWEB)

    Gong Ailing; Zeng Chunhua [Faculty of Science, Kunming University of Science and Technology, Kunming 650093 (China); Wang Hua, E-mail: zchh2009@126.com [Province Engineering Research Center of Industrial Energy Conservation and New Technology, Kunming University of Science and Technology, Kunming, Yunnan 650093 (China)

    2011-08-01

    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 {lambda} 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 {tau}. That is, the RT decreases as the noise intensities D and Q increase, and increases as the time delay {tau} increases below the critical value of {lambda}. However, above the critical value, the RT first increases, reaches a maximum, and then decreases as D, Q and {tau} increase, i.e. a noise intensity D or Q and a time delay {tau} 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 {lambda}. The noise correlation parameter {lambda} first increases the RT of processes, then decreases it below the critical value of Q. Above the critical value, {lambda} increases it.

  6. Precision cosmology with time delay lenses: High resolution imaging requirements

    Energy Technology Data Exchange (ETDEWEB)

    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 ρtot∝ 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

  7. Effect of time delay on recognition memory for pictures: the modulatory role of emotion.

    Directory of Open Access Journals (Sweden)

    Bo Wang

    Full Text Available 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.

  8. Effect of Time Delay on Recognition Memory for Pictures: The Modulatory Role of Emotion

    Science.gov (United States)

    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

  9. Effect of time delay on recognition memory for pictures: the modulatory role of emotion.

    Science.gov (United States)

    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.

  10. Wideband RF beamforming: architectures, time-delays and cmos implementations

    NARCIS (Netherlands)

    Garakoui, S.K.

    2015-01-01

    A phased array antenna is a kind of antenna which is electronically reconfigurable to realize different antenna beam patterns. Delay blocks are an essential part of phased array antenna systems. Their delay-range, noise, nonlinearity, bandwidth, size, cost and power consumption have a dominant

  11. Effect of Magnetic Activity on Ionospheric Time Delay at Low ...

    Indian Academy of Sciences (India)

    The ionospheric refraction remains a major error source in Global Positioning ... spheric error. This error is negative for carrier phase pseudoranges and positive for the code pseudoranges (Komjathy 1997). The ionospheric delay is ... cause significant changes in the ionospheric morphology, producing large delays of.

  12. On the stability of the telegraph equation with time delay

    Science.gov (United States)

    Ashyralyev, Allaberen; Agirseven, Deniz; Turk, Koray

    2016-08-01

    In this study, the initial value problem for telegraph equations with delay in a Hilbert space is considered. Theorem on stability estimates for the solution of this problem is established. As a test problem, one-dimensional delay telegraph equation with Dirichlet boundary conditions is considered. Numerical solutions of this problem are obtained by first and second order of accuracy difference schemes.

  13. Exponential Antisynchronization Control of Stochastic Memristive Neural Networks with Mixed Time-Varying Delays Based on Novel Delay-Dependent or Delay-Independent Adaptive Controller

    Directory of Open Access Journals (Sweden)

    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.

  14. Time-delayed subsidies: interspecies population effects in salmon.

    Directory of Open Access Journals (Sweden)

    Michelle C Nelson

    Full Text Available Cross-boundary nutrient inputs can enhance and sustain populations of organisms in nutrient-poor recipient ecosystems. For example, Pacific salmon (Oncorhynchus spp. can deliver large amounts of marine-derived nutrients to freshwater ecosystems through their eggs, excretion, or carcasses. This has led to the question of whether nutrients from one generation of salmon can benefit juvenile salmon from subsequent generations. In a study of 12 streams on the central coast of British Columbia, we found that the abundance of juvenile coho salmon was most closely correlated with the abundance of adult pink salmon from previous years. There was a secondary role for adult chum salmon and watershed size, followed by other physical characteristics of streams. Most of the coho sampled emerged in the spring, and had little to no direct contact with spawning salmon nutrients at the time of sampling in the summer and fall. A combination of techniques suggest that subsidies from spawning salmon can have a strong, positive, time-delayed influence on the productivity of salmon-bearing streams through indirect effects from previous spawning events. This is the first study on the impacts of nutrients from naturally-occurring spawning salmon on juvenile population abundance of other salmon species.

  15. Relationship of Reaction Time to Perception of a Stimulus and Volitionally Delayed Response.

    Science.gov (United States)

    Meador, Kimford J; Boyd, Alan; Loring, David W

    2017-06-01

    Initiation of response in a simple reaction time (RT) task may precede conscious perception of the stimulus. Since volitionally delayed responses may require conscious perception of the stimulus before response initiation, it has been hypothesized that volitionally delayed responses will markedly delay RT. We conducted two experiments with separate groups of healthy volunteers (n=16; n=13) who performed computerized simple and choice RT tasks. In the standard condition, we instructed the participants to respond to a visual stimulus by pushing a button as quickly as possible. In the second condition, we instructed the participants to respond after a slight volitional delay. The second experiment had an additional volitional delay condition in which we asked participants to delay their responses by an estimated 50% above their usual standard response. We found marked delays and increased variability when participants volitionally delayed their responses, averaging 322 ms for standard and 861 ms for delayed simple RTs (267% increase), and 650 ms for standard and 1018 ms for delayed choice RTs (157% increase). Effects did not differ across age, sex, or handedness. However, a minority of participants did not meaningfully delay their RT during the volitional delay conditions. On average, participants had marked delays when they tried to delay their responses slightly, but a subset of participants exhibited essentially no delay despite trying to delay. We suggest some potential mechanisms that future investigations might delineate.

  16. Fixed-Time Synchronization for Hybrid Coupled Dynamical Networks with Multilinks and Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Baolin Qiu

    2017-01-01

    Full Text Available This paper concerns the problem of fixed/finite-time synchronization of hybrid coupled dynamical networks. The considered dynamical networks with multilinks contain only one transmittal time-varying delay for each subnetwork, which makes us get hold of more interesting and practical points. Two kinds of delay-dependent feedback controllers with multilinks as well as appropriate Lyapunov functions are defined to achieve the goal of fixed-time synchronization and finite-time synchronization for the networks. Some novel and effective criteria of hybrid coupled networks are derived based on fixed-time and finite-time stability analysis. Finally, two numerical simulation examples are given to show the effectiveness of the results proposed in our paper.

  17. Exponential stabilisation for time-varying delay system with actuator faults: an average dwell time method

    Science.gov (United States)

    Wang, Limin; Shao, Cheng

    2010-04-01

    The issue of exponential stabilisation for a class of special time-varying delay switched systems resulting from actuator faults is considered in this article. The time-varying delay is assumed to belong to an interval and can be a slow or fast time-varying function. A hybrid state feedback strategy is redesigned to guarantee the system stable since the original controller is unavailable for some actuators failures. A class of switching laws incorporating the average dwell time method is proposed so that the special switched system with interval time-varying delay is exponentially stable. New delay-range-dependent stabilisation conditions using state feedback controllers are formulated in terms of linear matrix inequalities (LMIs) by choosing appropriate Lyapunov-Krasovskii functional without neglecting some useful knowledge on system states. Parameterised characterisations of the controllers are given in terms of the feasibility solutions to the LMIs. Two numeral examples are given to demonstrate the applicability and the effectiveness of the proposed method.

  18. Distribution of residence times in bistable noisy systems with time-delayed feedback

    OpenAIRE

    Curtin, D.

    2004-01-01

    We analyze theoretically and experimentally the residence time distribution of bistable systems in the presence of noise and time-delayed feedback. We explain various nonexponential features of the residence time distribution using a two-state model and obtain a quantitative agreement with an experiment based on a Schmitt trigger. The limitations of the two-state model are also analyzed theoretically and experimentally using a semiconductor laser with optoelectronic feedback.

  19. Optical circular deflector with attosecond resolution for ultrashort electron beam

    Directory of Open Access Journals (Sweden)

    Zhen Zhang

    2017-05-01

    Full Text Available A novel method using high-power laser as a circular deflector is proposed for the measurement of femtosecond (fs and sub-fs electron beam. In the scheme, the electron beam interacts with a laser pulse operating in a radially polarized doughnut mode (TEM_{01^{*}} in a helical undulator, generating angular kicks along the beam in two directions at the same time. The phase difference between the two angular kicks makes the beam form a ring after a propagation section with appropriate phase advance, which can reveal the current profile of the electron beam. Detailed theoretical analysis of the method and numerical results with reasonable parameters are both presented. It is shown that the temporal resolution can reach up to ∼100 attosecond, which is a significant improvement for the diagnostics of ultrashort electron beam.

  20. Attosecond interference in strong-field nonsequential double ionization

    Science.gov (United States)

    Liao, Qing; Li, Ye; Qin, Meiyan; Lu, Peixiang

    2017-12-01

    Kinetic-energy spectra of a single electron from strong-field nonsequential double ionization are investigated in a high-intensity regime with a quantum mechanical model. We find interference fringes with large energy spacings, which increases with the electron kinetic energy. These interference fringes originate from the electronic wave packets born in the recollision by the returning electronic wave packets from the "short" and the "long" quantum paths. Since the recollision happens in a fraction of a near-infrared (NIR) optical cycle, i.e., in an attosecond time interval, the resulting interference fringes exhibit energy spacings much larger than the NIR photon energy. The comparison of the quantum mechanical results with a classical collision model suggests a near-equal energy sharing between two electrons during the recollision process at very high intensities, in contrast to the extremely unequal energy sharing at low intensities.

  1. Detection of time delays and directional interactions based on time series from complex dynamical systems

    Science.gov (United States)

    Ma, Huanfei; Leng, Siyang; Tao, Chenyang; Ying, Xiong; Kurths, Jürgen; Lai, Ying-Cheng; Lin, Wei

    2017-07-01

    Data-based and model-free accurate identification of intrinsic time delays and directional interactions is an extremely challenging problem in complex dynamical systems and their networks reconstruction. A model-free method with new scores is proposed to be generally capable of detecting single, multiple, and distributed time delays. The method is applicable not only to mutually interacting dynamical variables but also to self-interacting variables in a time-delayed feedback loop. Validation of the method is carried out using physical, biological, and ecological models and real data sets. Especially, applying the method to air pollution data and hospital admission records of cardiovascular diseases in Hong Kong reveals the major air pollutants as a cause of the diseases and, more importantly, it uncovers a hidden time delay (about 30-40 days) in the causal influence that previous studies failed to detect. The proposed method is expected to be universally applicable to ascertaining and quantifying subtle interactions (e.g., causation) in complex systems arising from a broad range of disciplines.

  2. Chirped-pulse programming of optical coherent transient true-time delays.

    Science.gov (United States)

    Merkel, K D; Babbitt, W R

    1998-04-01

    Programming an optical coherent transient true-time delay device with two frequency-chirped pulses provides a novel means of performing broadband (> >GHz) true-time delay with a wide dynamic range of delays with fine temporal resolution. We have demonstrated true-time delays exceeding 2micros with sub-100-ps resolution. Chirped-pulse programming has the advantages over the previously proposed brief pulse programming [Opt. Lett. 21 1102 (1996)] of reduced instantaneous power requirements and the ability to control the true-time delay by frequency shifting the programming pulses.

  3. Study on the Business Cycle Model with Fractional-Order Time Delay under Random Excitation

    Directory of Open Access Journals (Sweden)

    Zifei Lin

    2017-07-01

    Full Text Available Time delay of economic policy and memory property in a real economy system is omnipresent and inevitable. In this paper, a business cycle model with fractional-order time delay which describes the delay and memory property of economic control is investigated. Stochastic averaging method is applied to obtain the approximate analytical solution. Numerical simulations are done to verify the method. The effects of the fractional order, time delay, economic control and random excitation on the amplitude of the economy system are investigated. The results show that time delay, fractional order and intensity of random excitation can all magnify the amplitude and increase the volatility of the economy system.

  4. Loss of time-delay signature in chaotic semiconductor ring lasers.

    Science.gov (United States)

    Nguimdo, Romain Modeste; Verschaffelt, Guy; Danckaert, Jan; Van der Sande, Guy

    2012-07-01

    We investigate the possibility of concealing the time-delay signatures in semiconductor ring lasers (SRLs) with external feedback. Through the autocorrelation and delayed mutual information, we report different scenarios leading to simultaneous time-delay concealment both in the intensity and the phase dynamics of such systems. In particular, the fact that such delay signatures can be eliminated in a SRL subject to short feedback constitutes a step toward the possibility of implementing secure communication schemes and random number generators on chip.

  5. Steady State Analysis of Stochastic Systems with Multiple Time Delays

    Science.gov (United States)

    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.

  6. Finite time synchronization of memristor-based Cohen-Grossberg neural networks with mixed delays.

    Science.gov (United States)

    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.

  7. Finite time synchronization of memristor-based Cohen-Grossberg neural networks with mixed delays.

    Directory of Open Access Journals (Sweden)

    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.

  8. Time-delay polynomial networks and rates of approximation

    Directory of Open Access Journals (Sweden)

    Irwin W. Sandberg

    1998-01-01

    Full Text Available We consider a large family of finite memory causal time-invariant maps G from an input set S to a set of ℝ-valued functions, with the members of both sets of functions defined on the nonnegative integers, and we give an upper bound on the error in approximating a G using a two-stage structure consisting of a tapped delay line and a static polynomial network N . This upper bound depends on the degree of the multivariable polynomial that characterizes N. Also given is a lower bound on the worst-case error in approximating a G using polynomials of a fixed maximum degree. These upper and lower bounds differ only by a multiplicative constant. We also give a corresponding result for the approximation of not-necessarily-causal input–output maps with inputs and outputs that may depend on more than one variable. This result is of interest, for example, in connection with image processing.

  9. Probing the cosmic distance duality relation using time delay lenses

    Science.gov (United States)

    Rana, Akshay; Jain, Deepak; Mahajan, Shobhit; Mukherjee, Amitabha; Holanda, R. F. L.

    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 σ0 and Einstein radius θE. 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 DAol 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.

  10. New Delay-Dependent Stability Criteria for Uncertain Neutral Systems with Mixed Time-Varying Delays and Nonlinear Perturbations

    Directory of Open Access Journals (Sweden)

    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.

  11. Delay-dependent asymptotic stability for neural networks with time-varying delays

    Directory of Open Access Journals (Sweden)

    Xiaofeng Liao

    2006-01-01

    ensure local and global asymptotic stability of the equilibrium of the neural network. Our results are applied to a two-neuron system with delayed connections between neurons, and some novel asymptotic stability criteria are also derived. 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.

  12. Attosecond Optics and Technology: Progress to Date and Future Prospects [Invited

    Science.gov (United States)

    2016-06-01

    shown to depend on Rabi frequencies with intermediate excited states [116]. Circularly polarized attosecond pulses are theoretically proposed to inves... lattice of 6 pm. The results clearly separate the electronic and nuclear time scales through the experiment. 5. FUTURE PERSPECTIVES The rapid progress in...step-like features in the electronic response, (c) conduction band shift, and (d) slower lattice response. From [119]. Reprinted with permission from

  13. Macroscopic generation of attosecond-pulse trains in strongly ionized media

    Science.gov (United States)

    Tosa, V.; Kim, K. T.; Nam, C. H.

    2009-04-01

    The characteristics of attosecond-pulse trains (APT) obtained from high-order harmonics are investigated by using a nonadiabatic three-dimensional model. A time-dependent phase matching approach is used in order to analyze the macroscopic formation of the APT. Under high ionization conditions, the process of APT formation is found to be the result of an interlace among the driving laser field, single atom response, phase matching effects in the near field and burst interference in the far field.

  14. Bezier Curves Based Numerical Solutions of Delay Systems with Inverse Time

    Directory of Open Access Journals (Sweden)

    F. Ghomanjani

    2014-01-01

    Full Text Available This paper applied, for the first time, the Bernstein’s approximation on delay differential equations and delay systems with inverse delay that models these problems. The direct algorithm is given for solving this problem. The delay function and inverse time function are expanded by the Bézier curves. The Bézier curves are chosen as piecewise polynomials of degree n, and the Bézier curves are determined on any subinterval by n+1 control points. The approximated solution of delay systems containing inverse time is derived. To validate accuracy of the present algorithm, some examples are solved.

  15. Attosecond dynamics of light-induced resonant hole transfer in high-order-harmonic generation

    Science.gov (United States)

    You, Jhih-An; Dahlström, Jan Marcus; Rohringer, Nina

    2017-02-01

    We present a study of high-order-harmonic generation (HHG) assisted by extreme ultraviolet (XUV) attosecond pulses, which can lead to the excitation of inner-shell electrons and the generation of a second HHG plateau. With the treatment of a one-dimensional model of krypton, based on time-dependent configuration interaction singles (TDCIS) of an effective two-electron system, we show that the XUV-assisted HHG spectrum reveals the duration of the semiclassical electron trajectories. The results are interpreted by the strong-field approximation (SFA) and the importance of the hole transfer during the tunneling process is emphasized. Finally, coherent population transfer between the inner and outer holes with attosecond pulse trains is discussed.

  16. Spectral shaping of attosecond pulses using two-colour laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Mansten, E; Dahlstroem, J M; Johnsson, P; Swoboda, M; L' Huillier, A; Mauritsson, J [Department of Physics, Lund University, P O Box 118, SE-221 00 Lund (Sweden)], E-mail: erik.mansten@fysik.lth.se, E-mail: johan.mauritsson@fysik.lth.se

    2008-08-15

    We use a strong two-colour laser field composed of the fundamental (800 nm) and the second harmonic (400 nm) of an infrared (IR) laser field to generate attosecond pulses with controlled spectral and temporal properties. With a second-harmonic intensity equal to 15% of the IR intensity the second-harmonic field is strong enough to significantly alter and control the electron trajectories in the generation process. This enables us to tune the central photon energy of the attosecond pulses by changing the phase difference between the IR and the second-harmonic fields. In the time domain the radiation is emitted as a sequence of pulses separated by a full IR cycle. We also perform calculations showing that the effect of even stronger second-harmonic fields leads to an extended tunable range under conditions that are experimentally feasible.

  17. Finite-Time Stability for Fractional-Order Bidirectional Associative Memory Neural Networks with Time Delays

    Science.gov (United States)

    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)

  18. Generation and Characterization of Attosecond Pulses

    Energy Technology Data Exchange (ETDEWEB)

    Ian A. Walmsley; Robert W. Boyd

    2006-04-24

    The research undertaken in this project has been directed toward the area of attoscience, in particular the problem of attosecond metrology. That is, the accurate determination of the electric field of attosecond XUV radiation. This outstanding problem has been identified as a critical technology for further development of the field, and our research adds to the area by providing the first method for characterization using the harmonic radiation itself as a tool. The technical effectiveness of this approach is very high, since it is vastly easier to detect XUV radiation directly than via the spectrum of photoelectrons liberated from atoms by it. This means that the experimental data rate can be much higher in principle using all-optical detection that electron detection, which will greatly aid the utility of harmonic XUV sources in attoscience applications. There are as yet no direct public benefits from this area of scientific research, though access to material structural dynamics on unprecedented brief timescales are expected to yield significant benefits for the future.

  19. Local Stability of AIDS Epidemic Model Through Treatment and Vertical Transmission with Time Delay

    Science.gov (United States)

    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.

  20. Stability Tests of Positive Fractional Continuous-time Linear Systems with Delays

    Directory of Open Access Journals (Sweden)

    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.

  1. Spatial Patterns of a Predator-Prey System of Leslie Type with Time Delay.

    Directory of Open Access Journals (Sweden)

    Caiyun Wang

    Full Text Available Time delay due to maturation time, capturing time or other reasons widely exists in biological systems. In this paper, a predator-prey system of Leslie type with diffusion and time delay is studied based on mathematical analysis and numerical simulations. Conditions for both delay induced and diffusion induced Turing instability are obtained by using bifurcation theory. Furthermore, a series of numerical simulations are performed to illustrate the spatial patterns, which reveal the information of density changes of both prey and predator populations. The obtained results show that the interaction between diffusion and time delay may give rise to rich dynamics in ecosystems.

  2. Stability and Time Delay Tolerance Analysis Approach for Networked Control Systems

    Directory of Open Access Journals (Sweden)

    Ashraf F. Khalil

    2015-01-01

    Full Text Available Networked control system is a research area where the theory is behind practice. Closing the feedback loop through shared network induces time delay and some of the data could be lost. So the network induced time delay and data loss are inevitable in networked control Systems. The time delay may degrade the performance of control systems or even worse lead to system instability. Once the structure of a networked control system is confirmed, it is essential to identify the maximum time delay allowed for maintaining the system stability which, in turn, is also associated with the process of controller design. Some studies reported methods for estimating the maximum time delay allowed for maintaining system stability; however, most of the reported methods are normally overcomplicated for practical applications. A method based on the finite difference approximation is proposed in this paper for estimating the maximum time delay tolerance, which has a simple structure and is easy to apply.

  3. Connecting Lab-Based Attosecond Science with FEL research

    CERN Multimedia

    CERN. Geneva

    2011-01-01

    In the last few years laboratory-scale femtosecond laser-based research using XUV light has developed dramatically following the successful development of attosecond laser pulses by means of high-harmonic generation. Using attosecond laser pulses, studies of electron dynamics on the natural timescale that electronic processes occur in atoms, molecules and solids can be contemplated, providing unprecedented insight into the fundamental role that electrons play in photo-induced processes. In my talk I will briefly review the present status of the attosecond science research field in terms of present and foreseen capabilities, and discuss a few recent applications, including a first example of the use of attosecond laser pulses in molecular science. In addition, I will discuss very recent results of experiments where photoionization of dynamically aligned molecules is investigated using a high-harmonics XUV source. Photoionization of aligned molecules becomes all the more interesting if the experiment is perfo...

  4. The Delay Hypothesis: The Manifestation of Media Effects over Time

    Science.gov (United States)

    Jensen, Jakob D.; Bernat, Jennifer K.; Wilson, Kari M.; Goonewardene, Julie

    2011-01-01

    A between-participants experiment (N = 147) tested for the presence of a delayed effect following exposure to an episode of a legal drama that contained false information. Participants were more likely to endorse false beliefs if they were queried two weeks after watching the program rather than immediately following exposure. The relationship…

  5. Stability of time-delay systems via Lyapunov functions

    Directory of Open Access Journals (Sweden)

    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.

  6. Tuning PD and PID Controllers for Double Integrating Plus Time Delay Systems

    OpenAIRE

    Ruscio, David Luigi Di; Dalen, Christer

    2017-01-01

    An existing method for tuning a PI controller for an integrating plus time delay plant are extended to be used for the design of a PD controller for a double integrating plus time delay plant. The PD controller is extended with integral action and an ideal PID controller is suggested in order to achieve optimality of the closed loop responses. Furthermore, some analytical results concerning the proposed PD and PID controller algorithm regarding the relative time-delay margin are worked out an...

  7. Synchronization of Different Fractional Order Time-Delay Chaotic Systems Using Active Control

    OpenAIRE

    Jianeng Tang

    2014-01-01

    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.

  8. Synchronization of Different Fractional Order Time-Delay Chaotic Systems Using Active Control

    Directory of Open Access Journals (Sweden)

    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.

  9. Compact optically-fed microwave true-time delay using liquid crystal photonic bandgap fiber device

    DEFF Research Database (Denmark)

    Wei, Lei; Xue, Weiqi; Chen, Yaohui

    2009-01-01

    Electrically tunable liquid crystal photonic bandgap fiber device based optically-fed microwave true-time delay is demonstrated. A maximum ~60° phase shift and an averaged ~7.2ps true time delay are obtained over the modulation frequency range 1GHz-19GHz.......Electrically tunable liquid crystal photonic bandgap fiber device based optically-fed microwave true-time delay is demonstrated. A maximum ~60° phase shift and an averaged ~7.2ps true time delay are obtained over the modulation frequency range 1GHz-19GHz....

  10. Stability analysis of fractional-order Hopfield neural networks with time delays.

    Science.gov (United States)

    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.

  11. A new delay line loops shrinking time-to-digital converter in low-cost FPGA

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. H∞ Control of Four-Wheel-Independent-Drive Electric Vehicles with Random Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Gang Qin

    2015-01-01

    Full Text Available The random time-varying delays would reduce control performance and even deteriorate the EV system. To deal with random time-varying delays and achieve a real-time steady-state response, considering randomness of delay and a rapid response, an H∞-based delay-tolerant linear quadratic regulator (LQR control method based on Taylor series expansion is proposed in this paper. The results of cosimulations with Simulink and CarSim demonstrate the effectiveness of the proposed controller through the control performance of yaw rate, sideslip angle, and the running track. Moreover, the results of comparison with the other controller illustrate the strength of explicitly.

  13. Attosecond spectroscopy of autoionizing states

    OpenAIRE

    Jiménez Galán, Álvaro

    2015-01-01

    Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química. Fecha de lectura: 15-12-2015 In this PhD Thesis we report a theoretical time-resolved study of the effects of electron correlation in the single photoionization spectrum of atomic systems, with particular focus on multi-photon transitions occurring in the presence of autoionizing states. For this task, we take two complementary approaches. On the one hand, we solve ...

  14. Delay decomposition at a single server queue with constant service time and multiple inputs. [Waiting time on computer network

    Science.gov (United States)

    Ziegler, C.; Schilling, D. L.

    1977-01-01

    Two networks consisting of single server queues, each with a constant service time, are considered. The external inputs to each network are assumed to follow some general probability distribution. Several interesting equivalencies that exist between the two networks considered are derived. This leads to the introduction of an important concept in delay decomposition. It is shown that the waiting time experienced by a customer can be decomposed into two basic components called self delay and interference delay.

  15. Delay decomposition at a single server queue with constant service time and multiple inputs

    Science.gov (United States)

    Ziegler, C.; Schilling, D. L.

    1978-01-01

    Two network consisting of single server queues, each with a constant service time, are considered. The external inputs to each network are assumed to follow some general probability distribution. Several interesting equivalencies that exist between the two networks considered are derived. This leads to the introduction of an important concept in delay decomposition. It is shown that the waiting time experienced by a customer can be decomposed into two basic components called self-delay and interference delay.

  16. Modifications of the optimal velocity traffic model to include delay due to driver reaction time

    Science.gov (United States)

    Davis, L. C.

    2003-03-01

    Straightforward inclusion of a delay time due to driver reaction time in the optimal velocity (OV) model reveals an unphysical sensitivity to driver reaction times. For delay times of nearly 1 s, which are typical for most drivers, oscillations in vehicle velocity induced by encountering a slower vehicle grow until limited by non-linear effects. Simulations demonstrate that unrealistically small delay times are needed for lengthy platoons of vehicles to avoid collisions. This is a serious limitation of the OV model. Other models, such as the inertial car-following model, allow somewhat larger delay times, but also show unphysical effects. Modifications of the OV model to overcome this deficiency are demonstrated. In addition, unphysical short-period oscillations of vehicle velocity are eliminated by introducing partial car-following into the model. Traffic jams are caused primarily by the delay due to driver reaction time in the modified OV model.

  17. Finite-time and fixed-time synchronization analysis of inertial memristive neural networks with time-varying delays.

    Science.gov (United States)

    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.

  18. Analysis of a HBV Model with Diffusion and Time Delay

    Directory of Open Access Journals (Sweden)

    Noé Chan Chí

    2012-01-01

    Full Text Available This paper discussed a hepatitis B virus infection with delay, spatial diffusion, and standard incidence function. The local stability of equilibrium is obtained via characteristic equations. By using comparison arguments, it is proved that if the basic reproduction number is less than unity, the infection-free equilibrium is globally asymptotically stable. If the basic reproductive number is greater than unity, by means of an iteration technique, sufficiently conditions are obtained for the global asymptotic stability of the infected steady state. Numerical simulations are carried out to illustrate our findings.

  19. Effect of Magnetic Activity on Ionospheric Time Delay at Low Latitude

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Astrophysics and Astronomy; Volume 29; Issue 1-2 ... The purpose of this work is to investigate the effect of magnetic activity on ionospheric time delay at low latitude Station Bhopal (geom. lat. ... We also study the ionospheric time delay during magnetic storm conditions for the same period.

  20. Delay of Gratification and Time Concept in Reflective and Impulsive Children.

    Science.gov (United States)

    Goldman, Amy P.; Everett, Frances

    1985-01-01

    Investigated time conceptualizations and delay of gratification capacities of 64 6- to 10-year-olds identified as impulsive or reflective according to performance on Kagan's Matching Familiar Figures Test. They were administered a maintenance of delay of gratification task, a time concept questionnaire, and several measures of temporal perspective…

  1. Relations between Self Regulation, Future Time Perspective and the Delay of Gratification in University Students

    Science.gov (United States)

    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…

  2. Fokker-Planck equations for globally coupled many body systems with time delays

    NARCIS (Netherlands)

    Frank, T.D.; Beek, P.J.

    2005-01-01

    A Fokker-Planck description for globally coupled many-body systems with time delays was developed by integrating previously derived Fokker-Planck equations for many-body systems and for time-delayed systems. By means of the Fokker-Planck description developed, we examined the dependence of the

  3. High-throughput beamline for attosecond pulses based on toroidal mirrors with microfocusing capabilities.

    Science.gov (United States)

    Frassetto, F; Trabattoni, A; Anumula, S; Sansone, G; Calegari, F; Nisoli, M; Poletto, L

    2014-10-01

    We have developed a novel attosecond beamline designed for attosecond-pump/attosecond probe experiments. Microfocusing of the Extreme-ultraviolet (XUV) radiation is obtained by using a coma-compensated optical configuration based on the use of three toroidal mirrors controlled by a genetic algorithm. Trains of attosecond pulses are generated with a measured peak intensity of about 3 × 10(11) W/cm(2).

  4. Synchronization in a neural network of phase oscillators with time delayed coupling

    Science.gov (United States)

    Luzyanina, T. B.

    1994-08-01

    We investigate a neural network model designed as a system of the central oscillator and peripheral oscillators interacting with a time delay τ in a phase-locking loop. The delay corresponds to the finite velocity of signal propagation along nerve fibers. We study the synchronization under various values of τ. It is shown that under some conditions for a finite delay time there exist a multitude of synchronization frequencies in contrast to the case without delay where one has at most one solution. The criteria for the existence of multiple solutions and their stability are found. The asymptotic behavior under increasing connection strengths is analyzed.

  5. Dynamical Performances of a Vibration Absorber for Continuous Structure considering Time-Delay Coupling

    Directory of Open Access Journals (Sweden)

    Xiuting Sun

    2016-01-01

    Full Text Available The nonlinear effect incurred by time delay in vibration control is investigated in this study via a vibration absorber coupled with a continuous beam structure. The stability of the vibration absorber coupled structure system with time-delay coupling is firstly studied, which provides a general guideline for the potential time delay to be introduced to the system. Then it is shown that there is a specific region for the time delay which can bring bifurcation modes to the dynamic response of the coupling system, and the vibration energy at low frequencies can be transferred or absorbed due to the bifurcation mode and the vibration in the corresponding frequency range is thus suppressed. The nonlinear mechanism of this vibration suppression incurred by the coupling time delay is discussed in detail, which provides a novel and alternative approach to the analysis, design, and control of vibration absorbers in engineering practice.

  6. Time-delay effects on dynamics of a two-actor conflict model

    Science.gov (United States)

    Rojas-Pacheco, A.; Obregón-Quintana, B.; Liebovitch, L. S.; Guzmán-Vargas, L.

    2013-02-01

    We present a study of time-delay effects on a two-actor conflict model based on nonlinear differential equations. The state of each actor depends on its own state in isolation, its previous state, its inertia to change, the positive or negative feedback and a time delay in the state of the other actor. We use both theoretical and numerical approaches to characterize the evolution of the system for several values of time delays. We find that, under particular conditions, a time delay leads to the appearance of oscillations in the states of the actors. Besides, phase portraits for the trajectories are presented to illustrate the evolution of the system for different time delays. Finally, we discuss our results in the context of social conflict models.

  7. Generalized synchronization-based multiparameter estimation in modulated time-delayed systems

    Science.gov (United States)

    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.

  8. Dissipativity and stability analysis of fractional-order complex-valued neural networks with time delay.

    Science.gov (United States)

    Velmurugan, G; Rakkiyappan, R; Vembarasan, V; Cao, Jinde; Alsaedi, Ahmed

    2017-02-01

    As we know, the notion of dissipativity is an important dynamical property of neural networks. Thus, the analysis of dissipativity of neural networks with time delay is becoming more and more important in the research field. In this paper, the authors establish a class of fractional-order complex-valued neural networks (FCVNNs) with time delay, and intensively study the problem of dissipativity, as well as global asymptotic stability of the considered FCVNNs with time delay. Based on the fractional Halanay inequality and suitable Lyapunov functions, some new sufficient conditions are obtained that guarantee the dissipativity of FCVNNs with time delay. Moreover, some sufficient conditions are derived in order to ensure the global asymptotic stability of the addressed FCVNNs with time delay. Finally, two numerical simulations are posed to ensure that the attention of our main results are valuable. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Electrical Activity in a Time-Delay Four-Variable Neuron Model under Electromagnetic Induction

    Directory of Open Access Journals (Sweden)

    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.

  10. From dynamical systems with time-varying delay to circle maps and Koopman operators

    Science.gov (United States)

    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.

  11. Neural Network Based Finite-Time Stabilization for Discrete-Time Markov Jump Nonlinear Systems with Time Delays

    Directory of Open Access Journals (Sweden)

    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.

  12. Stochastic modeling of biochemical systems with multistep reactions using state-dependent time delay

    Science.gov (United States)

    Wu, Qianqian; Tian, Tianhai

    2016-08-01

    To deal with the growing scale of molecular systems, sophisticated modelling techniques have been designed in recent years to reduce the complexity of mathematical models. Among them, a widely used approach is delayed reaction for simplifying multistep reactions. However, recent research results suggest that a delayed reaction with constant time delay is unable to describe multistep reactions accurately. To address this issue, we propose a novel approach using state-dependent time delay to approximate multistep reactions. We first use stochastic simulations to calculate time delay arising from multistep reactions exactly. Then we design algorithms to calculate time delay based on system dynamics precisely. To demonstrate the power of proposed method, two processes of mRNA degradation are used to investigate the function of time delay in determining system dynamics. In addition, a multistep pathway of metabolic synthesis is used to explore the potential of the proposed method to simplify multistep reactions with nonlinear reaction rates. Simulation results suggest that the state-dependent time delay is a promising and accurate approach to reduce model complexity and decrease the number of unknown parameters in the models.

  13. Angular momentum-induced delays in solid-state photoemission enhanced by intra-atomic interactions.

    Science.gov (United States)

    Siek, Fabian; Neb, Sergej; Bartz, Peter; Hensen, Matthias; Strüber, Christian; Fiechter, Sebastian; Torrent-Sucarrat, Miquel; Silkin, Vyacheslav M; Krasovskii, Eugene E; Kabachnik, Nikolay M; Fritzsche, Stephan; Muiño, Ricardo Díez; Echenique, Pedro M; Kazansky, Andrey K; Müller, Norbert; Pfeiffer, Walter; Heinzmann, Ulrich

    2017-09-22

    Attosecond time-resolved photoemission spectroscopy reveals that photoemission from solids is not yet fully understood. The relative emission delays between four photoemission channels measured for the van der Waals crystal tungsten diselenide (WSe 2 ) can only be explained by accounting for both propagation and intra-atomic delays. The intra-atomic delay depends on the angular momentum of the initial localized state and is determined by intra-atomic interactions. For the studied case of WSe 2 , the photoemission events are time ordered with rising initial-state angular momentum. Including intra-atomic electron-electron interaction and angular momentum of the initial localized state yields excellent agreement between theory and experiment. This has required a revision of existing models for solid-state photoemission, and thus, attosecond time-resolved photoemission from solids provides important benchmarks for improved future photoemission models. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  14. A dynamic P53-MDM2 model with time delay

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Stability Analysis and H∞ Model Reduction for Switched Discrete-Time Time-Delay Systems

    Directory of Open Access Journals (Sweden)

    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.

  16. Novel interrogation technique for Tilted Fiber Bragg Gratings sensors based on single wavelength time delay measurements

    Science.gov (United States)

    Pisco, M.; Ricciardi, A.; Campopiano, S.; Caucheteur, C.; Mégret, P.; Cutolo, A.; Cusano, A.

    2009-10-01

    A novel interrogation scheme for Tilted Fiber Bragg Gratings (TFBGs) sensors is here proposed based on single wavelength time delay measurements. To this aim, the group delay of a weakly tilted TFBG has been characterized by direct time domain measurement. The experimental characterization shows the capability of TFBGs to enable superluminal and subluminal propagation of an optical pulse in optical fibers. The sharp group delay features of the TFBGs are exploited for refractometric applications to detect the SRI variations by single wavelength time delay measurements. The obtained preliminary results demonstrate the possibility to detect SRI changes by means of single wavelength time delay measurements with a sensitivity enhanced in the range 1.33-1.40 with respect to previously reported interrogation techniques.

  17. Insensitivity of synchronization to network structure in chaotic pendulum systems with time-delay coupling

    Science.gov (United States)

    Yao, Chenggui; Zhan, Meng; Shuai, Jianwei; Ma, Jun; Kurths, Jürgen

    2017-12-01

    It has been generally believed that both time delay and network structure could play a crucial role in determining collective dynamical behaviors in complex systems. In this work, we study the influence of coupling strength, time delay, and network topology on synchronization behavior in delay-coupled networks of chaotic pendulums. Interestingly, we find that the threshold value of the coupling strength for complete synchronization in such networks strongly depends on the time delay in the coupling, but appears to be insensitive to the network structure. This lack of sensitivity was numerically tested in several typical regular networks, such as different locally and globally coupled ones as well as in several complex networks, such as small-world and scale-free networks. Furthermore, we find that the emergence of a synchronous periodic state induced by time delay is of key importance for the complete synchronization.

  18. Stability of adaptive cruise control systems taking account of vehicle response time and delay

    Energy Technology Data Exchange (ETDEWEB)

    Davis, L.C., E-mail: ldavis7@mailaps.org [10244 Normandy Dr., Plymouth, MI 48170 (United States)

    2012-08-20

    The region of string stability of a platoon of adaptive cruise control vehicles, taking into account the delay and response of the vehicle powertrain, is found. An upper bound on the explicit delay time as a function the first-order powertrain response time constant is determined. The system is characterized by a headway time constant, a sensitivity parameter, relative (to the vehicle immediately in front) velocity control, and delayed-velocity feedback or acceleration feedback. -- Highlights: ► I find the region of stability for a realistic adaptive cruise control system. ► Vehicle response time and explicit delay are included in the analysis. ► Delayed-feedback enlarges the parameter space that gives string stability.

  19. Attosecond pre-determination of reaction dynamics in polyatomic molecules

    Science.gov (United States)

    Kitzler, Markus

    2014-05-01

    An important aim of Ultrafast Laser Science and Attosecond Physics is the measurement of valence electron dynamics in molecules during complex restructuring and fragmentation reactions. Such reactions may be triggered by the removal of electrons, e.g., by ionization with intense, ultrashort laser pulses. Depending on the valence-shell from which the electrons are removed, the molecular ion might be put into a binding state or a certain dissociative state. With control over the ionization process it might thus be possible to gain control over the subsequent restructuring and fragmentation processes on a purely electronic level. Detailed insight into the process of electron removal can be obtained from interferometric measurements using two bound state wavepackets released at different times within a sub-cycle of a laser field. I will present results of experiments that exploit this kind of electron wavepacket interferometry with sub-10 attosecond resolution for tracing the evolution of the phase of the bound state of an atom or molecule during the removal of an electron. I will furthermore present two conceptually similar schemes that allow pre-determining the outcome of molecular restructuring and fragmentation processes in polyatomic molecules on sub-femtosecond time-scales by gaining control over the process of electron removal. The first method involves recollision double ionization in intense few-cycle laser fields with a known carrier-envelope phase (CEP). Tuning of the CEP allows controlling the removal of inner-valence electrons and the controlled population of dissociative excited states. Using this method I will show experimental CEP-control over various fragmentation reactions of a series of polyatomic molecules. The second control scheme uses the strong preponderance of ionization from specific molecular orbitals to the alignment of the molecular axis with respect to the laser polarization direction for determining which valence level the electrons are

  20. Apparatus and Method for Compensating for Process, Voltage, and Temperature Variation of the Time Delay of a Digital Delay Line

    Science.gov (United States)

    Seefeldt, James (Inventor); Feng, Xiaoxin (Inventor); Roper, Weston (Inventor)

    2013-01-01

    A process, voltage, and temperature (PVT) compensation circuit and a method of continuously generating a delay measure are provided. The compensation circuit includes two delay lines, each delay line providing a delay output. The two delay lines may each include a number of delay elements, which in turn may include one or more current-starved inverters. The number of delay lines may differ between the two delay lines. The delay outputs are provided to a combining circuit that determines an offset pulse based on the two delay outputs and then averages the voltage of the offset pulse to determine a delay measure. The delay measure may be one or more currents or voltages indicating an amount of PVT compensation to apply to input or output signals of an application circuit, such as a memory-bus driver, dynamic random access memory (DRAM), a synchronous DRAM, a processor or other clocked circuit.

  1. Time-delayed feedback technique for suppressing instabilities in time-periodic flow

    Science.gov (United States)

    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.

  2. Using Video to Bridge the Gap Between Problem Behavior and a Delayed Time-out Procedure.

    Science.gov (United States)

    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.

  3. Prehospital delay and time to reperfusion therapy in ST elevation myocardial infarction.

    Science.gov (United States)

    George, Linsha; Ramamoorthy, Lakshmi; Satheesh, Santhosh; Saya, Rama Prakasha; Subrahmanyam, D K S

    2017-01-01

    Despite efforts aimed at reducing the prehospital delay and treatment delay, a considerable proportion of patients with ST elevation myocardial infarction (STEMI) present late and receive the reperfusion therapy after unacceptably long time periods. This study aimed at finding out the patients' decision delay, prehospital delay, door-to-electrocardiography (ECG), door-to-needle, and door-to-primary percutaneous coronary intervention (PCI) times and their determinants among STEMI patients. A cross-sectional study conducted among 96 patients with STEMI admitted in a tertiary care center in South India. The data were collected using interview of the patients and review of records. The distribution of the data was assessed using Kolmogorov-Smirnov test, and the comparisons of the patients' decision delay, prehospital delay, and time to start reperfusion therapy with the different variables were done using Mann-Whitney U-test or Kruskal-Wallis test based on the number of groups. The mean (standard deviation) and median (range) age of the participants were 55 (11) years and 57 (51) years, respectively. The median patients' decision delay, prehospital delay, door-to-ECG, door-to-needle, and door-to-primary PCI times were 75, 290, 12, 75, 110 min, respectively. Significant factors associated (P Prehospital delay was significantly associated (P prehospital delay time among the South Indian population is still unacceptably high. Public education, improving the systems of prehospital care, and measures to improve the patient flow and management in the emergency department are essentially required. The time taken to take ECG and to initiate reperfusion therapy in this study points to scope for improvement to meet the American Heart Association recommended timings.

  4. Smart Telerobotic Surveillance System via Internet with Reduced Time Delay

    Directory of Open Access Journals (Sweden)

    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

  5. Asset Price Dynamics in a Chartist-Fundamentalist Model with Time Delays: A Bifurcation Analysis

    Directory of Open Access Journals (Sweden)

    Loretti I. Dobrescu

    2016-01-01

    Full Text Available This paper studies the dynamic behavior of asset prices using a chartist-fundamentalist model with two speculative markets. To this effect, we employ a differential system with delays à la Dibeh (2007 to describe the price dynamics and we assume that the two markets are coupled via diffusive coupling terms. We study two different time delay cases, namely, when both markets experience the same time delay and when the time delay is different across markets. First, we theoretically determine that the equilibrium exists and investigate its stability. Second, we establish the general conditions for the existence of local Hopf bifurcations and analyze their direction and stability. The common conclusion from both the delay scenarios we consider is that coupled speculative markets with heterogeneous agents in each, but with different price dynamics, can be synchronized through diffusive coupling. Finally, we provide some numerical illustrations to confirm our theoretical findings.

  6. Robust H∞ Control of Neutral System with Time-Delay for Dynamic Positioning Ships

    Directory of Open Access Journals (Sweden)

    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.

  7. Finite-Time Stabilization and Adaptive Control of Memristor-Based Delayed Neural Networks.

    Science.gov (United States)

    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.

  8. A systematic molecular circuit design method for gene networks under biochemical time delays and molecular noises

    Directory of Open Access Journals (Sweden)

    Chang Yu-Te

    2008-11-01

    Full Text Available Abstract Background Gene networks in nanoscale are of nonlinear stochastic process. Time delays are common and substantial in these biochemical processes due to gene transcription, translation, posttranslation protein modification and diffusion. Molecular noises in gene networks come from intrinsic fluctuations, transmitted noise from upstream genes, and the global noise affecting all genes. Knowledge of molecular noise filtering and biochemical process delay compensation in gene networks is crucial to understand the signal processing in gene networks and the design of noise-tolerant and delay-robust gene circuits for synthetic biology. Results A nonlinear stochastic dynamic model with multiple time delays is proposed for describing a gene network under process delays, intrinsic molecular fluctuations, and extrinsic molecular noises. Then, the stochastic biochemical processing scheme of gene regulatory networks for attenuating these molecular noises and compensating process delays is investigated from the nonlinear signal processing perspective. In order to improve the robust stability for delay toleration and noise filtering, a robust gene circuit for nonlinear stochastic time-delay gene networks is engineered based on the nonlinear robust H∞ stochastic filtering scheme. Further, in order to avoid solving these complicated noise-tolerant and delay-robust design problems, based on Takagi-Sugeno (T-S fuzzy time-delay model and linear matrix inequalities (LMIs technique, a systematic gene circuit design method is proposed to simplify the design procedure. Conclusion The proposed gene circuit design method has much potential for application to systems biology, synthetic biology and drug design when a gene regulatory network has to be designed for improving its robust stability and filtering ability of disease-perturbed gene network or when a synthetic gene network needs to perform robustly under process delays and molecular noises.

  9. Using Time-Delay to Improve Social Play Skills with Peers for Children with Autism

    Science.gov (United States)

    Liber, Daniella B.; Frea, William D.; Symon, Jennifer B. G.

    2008-01-01

    Interventions that teach social communication and play skills are crucial for the development of children with autism. The time delay procedure is effective in teaching language acquisition, social use of language, discrete behaviors, and chained activities to individuals with autism and developmental delays. In this study, three boys with autism,…

  10. Absolute stability of nonlinear systems with time delays and applications to neural networks

    Directory of Open Access Journals (Sweden)

    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.

  11. Impacts of Wake Effect and Time Delay on the Dynamic Analysis of Wind Farms Models

    Science.gov (United States)

    El-Fouly, Tarek H. M.; El-Saadany, Ehab F.; Salama, Magdy M. A.

    2008-01-01

    This article investigates the impacts of proper modeling of the wake effects and wind speed delays, between different wind turbines' rows, on the dynamic performance accuracy of the wind farms models. Three different modeling scenarios were compared to highlight the impacts of wake effects and wind speed time-delay models. In the first scenario,…

  12. Inherent Association Between Academic Delay of Gratification, Future Time Perspective, and Self-Regulated Learning

    Science.gov (United States)

    Bembenutty, Hefer; Karabenick, Stuart A.

    2004-01-01

    We review the association between delay of gratification and future time perspective (FTP), which can be incorporated within the theoretical perspective of self-regulation of learning. We propose that delay of gratification in academic contexts, along with facilitative beliefs about the future, increase the likelihood of completing academic tasks.…

  13. Nonlinear transition dynamics in a time-delayed vibration isolator under combined harmonic and stochastic excitations

    Science.gov (United States)

    Yang, Tao; Cao, Qingjie

    2017-04-01

    Based on the quasi-zero stiffness vibration isolation (QZS-VI) system, nonlinear transition dynamics have been investigated coupled with both time-delayed displacement and velocity feedbacks. Using a delayed nonlinear Langevin approach, we discuss a new mechanism for the transition of a vibration isolator in which the energy originates from harmonic and noise excitations. For this stochastic process, the effective displacement potential, stationary probability density function and the escape ratio are obtained. We investigate a variety of noise-induced behaviors affecting the transitions between system equilibria states. The results indicate that the phenomena of transition, resonant activation and delay-enhanced stability may emerge in the QZS-VI system. Moreover, we also show that the time delay, delay feedback intensities, and harmonic excitation play significant roles in the resonant activation and delay-enhanced stability phenomena. Finally, a quantitative measure for amplitude response has been carried out to evaluate the isolation performance of the controlled QZS-VI system. The results show that with properly designed feedback parameters, time delay and displacement feedback intensity can play the role of a damping force. This research provides instructive ideas on the application of the time-delayed control in practical engineering.

  14. Effects of delayed polymerization time and bracket manipulation on orthodontic resin modified glass ionomer adhesive

    Science.gov (United States)

    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.

  15. A Fast Time-Delay Calculation Method in Through-Wall-Radar Detection Scenario

    Directory of Open Access Journals (Sweden)

    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.

  16. Attosecond polarization control in atomic RABBITT-like experiments assisted by a circularly polarized laser

    Science.gov (United States)

    Boll, D. I. R.; Fojón, O. A.

    2017-12-01

    We study theoretically the single ionization of noble gas atoms by the combined action of an attosecond pulse train with linear polarization and an assistant laser field with circular polarization. We employ a non-perturbative model that under certain approximations gives closed-form expressions for the angular distributions of photoelectrons. Interestingly, our model allow us to interpret these angular distributions as two-centre interferences where the orientation and the modulus of the separation vector between the virtual emitters is governed by the assistant laser field. Additionally, we show that such a configuration of light fields is similar to the polarization control technique, where both the attosecond pulse train and the assistant laser field have linear polarizations whose relative orientation may be controlled. Moreover, in order to compare our results with the available experimental data, we obtain analytical expressions for the cross sections integrated over the photoelectron emission angles. By means of these expressions, we define the ‘magic time’ as the delay for which the total cross sections for atomic targets exhibit the same functional form as the one of the monochromatic photoionization of diatomic molecular targets.

  17. A time-delay neural network for solving time-dependent shortest path problem.

    Science.gov (United States)

    Huang, Wei; Yan, Chunwang; Wang, Jinsong; Wang, Wei

    2017-06-01

    This paper concerns the time-dependent shortest path problem, which is difficult to come up with global optimal solution by means of classical shortest path approaches such as Dijkstra, and pulse-coupled neural network (PCNN). In this study, we propose a time-delay neural network (TDNN) framework that comes with the globally optimal solution when solving the time-dependent shortest path problem. The underlying idea of TDNN comes from the following mechanism: the shortest path depends on the earliest auto-wave (from start node) that arrives at the destination node. In the design of TDNN, each node on a network is considered as a neuron, which comes in the form of two units: time-window unit and auto-wave unit. Time-window unit is used to generate auto-wave in each time window, while auto-wave unit is exploited here to update the state of auto-wave. Whether or not an auto-wave leaves a node (neuron) depends on the state of auto-wave. The evaluation of the performance of the proposed approach was carried out based on online public Cordeau instances and New York Road instances. The proposed TDNN was also compared with the quality of classical approaches such as Dijkstra and PCNN. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. MDCT urography: retrospective determination of optimal delay time after intravenous contrast administration.

    Science.gov (United States)

    Meindl, Thomas; Coppenrath, Eva; Kahlil, Rami; Müller-Lisse, Ulrike L; Reiser, Maximilian F; Müller-Lisse, Ullrich G

    2006-08-01

    The optimal delay time after intravenous (i.v.) administration of contrast medium (CM) for opacification 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.

  19. MDCT urography: retrospective determination of optimal delay time after intravenous contrast administration

    Energy Technology Data Exchange (ETDEWEB)

    Meindl, Thomas; Coppenrath, Eva; Kahlil, Rami; Reiser, Maximilian F.; Mueller-Lisse, U.G. [University Munich, Institute for Clinical Radiology, Munich (Germany); Mueller-Lisse, Ulrike L. [University Munich, Department of Urology, Munich (Germany)

    2006-08-15

    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.)

  20. Academic delay of gratification, self-efficacy, and time management among academically unprepared college students.

    Science.gov (United States)

    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.

  1. Synchronisation of fractional-order time delayed chaotic systems with ring connection

    Science.gov (United States)

    He, S.; Sun, K.; Wang, H.

    2016-02-01

    In this paper, synchronisation of fractional-order time delayed chaotic systems in ring networks is investigated. Based on Lyapunov stability theory, a new generic synchronisation criterion for N-coupled chaotic systems with time delay is proposed. The synchronisation scheme is applied to N-coupled fractional-order time delayed simplified Lorenz systems, and the Adomian decomposition method (ADM) is developed for solving these chaotic systems. Performance analysis of the synchronisation network is carried out. Numerical experiments demonstrate that synchronisation realises in both state variables and intermediate variables, which verifies the effectiveness of the proposed method.

  2. Dynamics of Uncertain Discrete-Time Neural Network with Delay and Impulses

    Directory of Open Access Journals (Sweden)

    Xuehui Mei

    2015-01-01

    Full Text Available The stability of discrete-time impulsive delay neural networks with and without uncertainty is investigated. First, by using Razumikhin-type theorem, a new less conservative condition for the exponential stability of discrete-time neural network with delay and impulse is proposed. Moreover, some new sufficient conditions are derived to guarantee the stability of uncertain discrete-time neural network with delay and impulse by using Lyapunov function and linear matrix inequality (LMI. Finally, several examples with numerical simulation are presented to demonstrate the effectiveness of the obtained results.

  3. Tuning PD and PID Controllers for Double Integrating Plus Time Delay Systems

    Directory of Open Access Journals (Sweden)

    David Di Ruscio

    2017-04-01

    Full Text Available An existing method for tuning a PI controller for an integrating plus time delay plant are extended to be used for the design of a PD controller for a double integrating plus time delay plant. The PD controller is extended with integral action and an ideal PID controller is suggested in order to achieve optimality of the closed loop responses. Furthermore, some analytical results concerning the proposed PD and PID controller algorithm regarding the relative time-delay margin are worked out and presented. The algorithm and an existing method are successfully compared against each other on some examples, e.g. the planar movement control of a mariner vessel.

  4. Globally Asymptotic Stability of Stochastic Nonlinear Systems with Time-Varying Delays via Output Feedback Control

    Directory of Open Access Journals (Sweden)

    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.

  5. Modeling and Bifurcation Research of a Worm Propagation Dynamical System with Time Delay

    OpenAIRE

    Yao, Yu; Zhang, Zhao; Xiang, Wenlong; Yang, Wei; Gao, Fuxiang

    2014-01-01

    Both vaccination and quarantine strategy are adopted to control the Internet worm propagation. By considering the interaction infection between computers and external removable devices, a worm propagation dynamical system with time delay under quarantine strategy is constructed based on anomaly intrusion detection system (IDS). By regarding the time delay caused by time window of anomaly IDS as the bifurcation parameter, local asymptotic stability at the positive equilibrium and local Hopf bi...

  6. Longitudinal Outcomes of Start Time Delay on Sleep, Behavior, and Achievement in High School

    Science.gov (United States)

    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

  7. Dynamic IQC-Based Control of Uncertain LFT Systems With Time-Varying State Delay.

    Science.gov (United States)

    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 L2 -gain performance using dynamic IQCs incorporated with quadratic Lyapunov functions. Then, the design of exact-memory controllers that guarantee desired L2 -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.

  8. Dynamical analysis in a bioeconomic phytoplankton zooplankton system with double time delays and environmental stochasticity

    Science.gov (United States)

    Liu, Chao; Wang, Luping; Zhang, Qingling; Yan, Yun

    2017-09-01

    This paper presents a double delayed bioeconomic phytoplankton zooplankton system with commercial harvesting on zooplankton and environmental stochasticity. Maturation delay for toxin producing phytoplankton and gestation delay for zooplankton are considered. Environmental stochasticity is incorporated into the proposed system in form of Gaussian white noises. Some sufficient conditions are derived to show that the proposed system has a unique global positive solution. In absence of double time delays, stochastic stability and existence of stochastic Hopf bifurcation are studied based on invariant measure theory and singular boundary theory of diffusion process for the proposed system. In presence of double time delays, asymptotic behaviors of the interior equilibrium are discussed by constructing some appropriate Lyapunov functions.

  9. A Heterogeneous Agent Model of Asspet Price with Three Time Delays

    Directory of Open Access Journals (Sweden)

    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.

  10. Global properties of vector-host disease models with time delays.

    Science.gov (United States)

    Cai, Li-Ming; Li, Xue-Zhi; Fang, Bin; Ruan, Shigui

    2017-05-01

    Since there exist extrinsic and intrinsic incubation periods of pathogens in the feedback interactions between the vectors and hosts, it is necessary to consider the incubation delays in vector-host disease transmission dynamics. In this paper, we propose vector-host disease models with two time delays, one describing the incubation period in the vector population and another representing the incubation period in the host population. Both distributed and discrete delays are used. By constructing suitable Liapunov functions, we obtain sufficient conditions for the global stability of the endemic equilibria of these models. The analytic results reveal that the global dynamics of such vector-host disease models with time delays are completely determined by the basic reproduction number. Some specific cases with discrete delay are studied and the corresponding results are improved.

  11. The influences of delay time on the stability of a market model with stochastic volatility

    Science.gov (United States)

    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.

  12. Instability in time-delayed switched systems induced by fast and random switching

    Science.gov (United States)

    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.

  13. Impact of delaying school start time on adolescent sleep, mood, and behavior.

    Science.gov (United States)

    Owens, Judith A; Belon, Katherine; Moss, Patricia

    2010-07-01

    To examine the impact of a 30-minute delay in school start time on adolescents' sleep, mood, and behavior. Participants completed the online retrospective Sleep Habits Survey before and after a change in school start time. An independent high school in Rhode Island. Students (n = 201) in grades 9 through 12. Intervention Institution of a delay in school start time from 8 to 8:30 am. Sleep patterns and behavior, daytime sleepiness, mood, data from the Health Center, and absences/tardies. After the start time delay, mean school night sleep duration increased by 45 minutes, and average bedtime advanced by 18 minutes (95% confidence interval, 7-29 minutes [t(423) = 3.36; P class attendance also improved. A modest delay in school start time was associated with significant improvements in measures of adolescent alertness, mood, and health. The results of this study support the potential benefits of adjusting school schedules to adolescents' sleep needs, circadian rhythm, and developmental stage.

  14. Phase transition time delays in irradiated superheated superconducting granules

    CERN Document Server

    Abplanalp, M; Czapek, G; Diggelmann, U; Furlan, M; Gabutti, A; Janos, S; Moser, U; Pozzi, R; Pretzl, Klaus P; Schmiemann, K; Perret-Gallix, D; Van den Brandt, B; Konter, J A; Mango, S

    1994-01-01

    The time difference between a particle interaction in a Superheated Superconducting Granule (SSG) and the resulting phase transition signal has been explored. Detectors containing Zn and Sn SSG were irradiated with neutrons and protons to study the heating mechanism taking place in nuclear recoil and ionizing events. Scattered neutrons have been detected by a scintillator hodoscope behind the SSG with a recoil energy measurement resolution of 10\\% and an interaction time resolution of 1ns. The fast transition of the metastable granules allowed to determine the elapsed time between an energy deposition and the phase transition signal. In the case of Sn granules, the results show that the time distributions are narrow and independent of the deposited energy in nuclear recoil and ionizing events. In Zn, however, the time distributions are much broader and depend on the energy deposition in the granule.

  15. Mean square stability of uncertain stochastic BAM neural networks with interval time-varying delays.

    Science.gov (United States)

    Wu, Haixia; Liao, Xiaofeng; Feng, Wei; Guo, Songtao

    2012-10-01

    The robust asymptotic stability analysis for uncertain BAM neural networks with both interval time-varying delays and stochastic disturbances is considered. By using the stochastic analysis approach, employing some free-weighting matrices and introducing an appropriate type of Lyapunov functional which takes into account the ranges for delays, some new stability criteria are established to guarantee the delayed BAM neural networks to be robustly asymptotically stable in the mean square. Unlike the most existing mean square stability conditions for BAM neural networks, the supplementary requirements that the time derivatives of time-varying delays must be smaller than 1 are released and the lower bounds of time varying delays are not restricted to be 0. Furthermore, in the proposed scheme, the stability conditions are delay-range-dependent and rate-dependent/independent. As a result, the new criteria are applicable to both fast and slow time-varying delays. Three numerical examples are given to illustrate the effectiveness of the proposed criteria.

  16. Attosecond experiments on plasmonic nanostructures principles and experiments

    CERN Document Server

    Schötz, Johannes

    2016-01-01

    Johannes Schötz presents the first measurements of optical electro-magnetic near-fields around nanostructures with subcycle-resolution. The ability to measure and understand light-matter interactions on the nanoscale is an important component for the development of light-wave-electronics, the control and steering of electron dynamics with the frequency of light, which promises a speed-up by several orders of magnitude compared to conventional electronics. The experiments presented here on metallic nanotips, widely used in experiments and applications, do not only demonstrate the feasibility of attosecond streaking as a unique tool for fundamental studies of ultrafast nanophotonics but also represent a first important step towards this goal. Contents Electron Scattering in Solids Attosecond Streaking from Metal Nanotips Target Groups Lecturers and students of physics, especially in the area of nanophotonics and attosecond physics About the Author Johannes Schötz received his Master's degree in physics and cu...

  17. Effects of Noise and Time Delay Upon Active Control of Combustion Instabilities

    National Research Council Canada - National Science Library

    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...

  18. Delay Activity in Rodent Frontal Cortex During a Simple Reaction Time Task

    National Research Council Canada - National Science Library

    Nandakumar S. Narayanan; Mark Laubach

    2009-01-01

    ...—dorsomedial prefrontal cortex (dmPFC) and motor cortex—during a simple reaction time task. Principal component analysis was used to identify major patterns of delay-related activity in frontal cortex...

  19. Integrated High-Speed Digital Optical True-Time-Delay Modules for Synthetic Aperture Radars Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Crystal Research, Inc. proposes an integrated high-speed digital optical true-time-delay module for advanced synthetic aperture radars. The unique feature of this...

  20. Nonlinear Dynamical Analysis on Four Semi-Active Dynamic Vibration Absorbers with Time Delay

    Directory of Open Access Journals (Sweden)

    Yongjun Shen

    2013-01-01

    Full Text Available In this paper four semi-active dynamic vibration absorbers (DVAs are analytically studied, where the time delay induced by measurement and execution in control procedure is included in the system. The first-order approximate analytical solutions of the four semi-active DVAs are established by the averaging method, based on the illustrated phase difference of the motion parameters. The comparisons between the analytical and the numerical solutions are carried out, which verify the correctness and satisfactory precision of the approximate analytical solutions. Then the effects of the time delay on the dynamical responses are analyzed, and it is found that the stability conditions for the steady-state responses of the primary systems are all periodic functions of time delay, with the same period as the excitation one. At last the effects of time delay on control performance are discussed.

  1. Spiking Neurons Learning Phase Delays: How Mammals May Develop Auditory Time-Difference Sensitivity

    Science.gov (United States)

    Leibold, Christian; van Hemmen, J. Leo

    2005-04-01

    Time differences between the two ears are an important cue for animals to azimuthally locate a sound source. The first binaural brainstem nucleus, in mammals the medial superior olive, is generally believed to perform the necessary computations. Its cells are sensitive to variations of interaural time differences of about 10 μs. The classical explanation of such a neuronal time-difference tuning is based on the physical concept of delay lines. Recent data, however, are inconsistent with a temporal delay and rather favor a phase delay. By means of a biophysical model we show how spike-timing-dependent synaptic learning explains precise interplay of excitation and inhibition and, hence, accounts for a physical realization of a phase delay.

  2. Time Delay: A Technique to Increase Language Use and Facilitate Generalization in Retarded Children.

    Science.gov (United States)

    Halle, James W.; And Others

    1979-01-01

    Institutional breakfast serving procedures were manipulated with regard to time delay to assess the effects of such changes on language use (requests for food) in six severely retarded children (ages 11 to 15 years). (Author/DLS)

  3. Secure Communication Based on Hyperchaotic Chen System with Time-Delay

    Science.gov (United States)

    Ren, Hai-Peng; Bai, Chao; Huang, Zhan-Zhan; Grebogi, Celso

    An experimental secure communication method based on the Chen system with time-delay is being proposed in this paper. The Chen system with time-delay is an infinite-dimensional system having more than one positive Lyapunov exponent. The message to be transmitted is encrypted using an hyperchaotic signal generated by the Chen system with time-delay and multishift cipher function. This encryption makes difficult for an eavesdropper to reconstruct the attractor by using time-delay embedding techniques, return map reconstruction, or spectral analysis, consequently, improving the security. Simulations and experiments on TI TMS320C6713 Digital Signal Processor (DSP) show improved resilience against attack and the feasibility of the proposed scheme.

  4. Graphical Evaluation of Time-Delay Compensation Techniques for Digitally Controlled Converters

    DEFF Research Database (Denmark)

    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...... are independent to model accuracy whereas the model-based alternatives are sensitive to system modeling. This paper first presents a graphical illustration of four model-free delay compensation techniques, where their principles and performances are intuitively elaborated and compared by means of the impulse area....... Simulations and experimental test results validate the effectiveness of the graphical comparisons and the proposed approach....

  5. On Couple-Group Consensus of Multiagent Networks with Communication and Input Time Delays

    Directory of Open Access Journals (Sweden)

    Liang-hao Ji

    2016-01-01

    Full Text Available This paper investigated the couple-group consensus problems of the multiagent networks with the influence of communication and input time delays. Based on the frequency-domain theory, some algebraic criteria are addressed analytically. From the results, it is found that the input time delays and the coupling strengths between agents of the systems play a crucial role in reaching group consensus. The convergence of the system is independent of the communication delays, but it will affect the convergence rate of the system. Finally, several simulated examples are provided to verify the validity and correctness of our theoretical results.

  6. Global Exponential Stability Criteria for Bidirectional Associative Memory Neural Networks with Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    J. Thipcha

    2013-01-01

    Full Text Available The global exponential stability for bidirectional associative memory neural networks with time-varying delays is studied. In our study, the lower and upper bounds of the activation functions are allowed to be either positive, negative, or zero. By constructing new and improved Lyapunov-Krasovskii functional and introducing free-weighting matrices, a new and improved delay-dependent exponential stability for BAM neural networks with time-varying delays is derived in the form of linear matrix inequality (LMI. Numerical examples are given to demonstrate that the derived condition is less conservative than some existing results given in the literature.

  7. Completion time reduction in instantly decodable network coding through decoding delay control

    KAUST Repository

    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.

  8. Harmonic and attosecond pulse enhancement in the presence of noise

    Science.gov (United States)

    Feng, Li-Qiang; Chu, Tian-Shu

    2012-12-01

    In this paper, we theoretically investigate the effect of noise on the photoionization, the generation of the high-order harmonic and the attosecond pulse irradiated from a model He+ ion. It shows that by properly adding noise fields, such as Gaussian white noise, random light or colored noise, both the ionization probabilities (IPs) and the harmonic yields can be enhanced by several orders of magnitude. Further, by tuning the noise intensity, a stochastic resonance-like curve is observed, showing the existence of an optimal noise in the ionization enhancement process. Finally, by superposing a properly selected harmonic, an intense attosecond pulse with a duration of 67 as is directly generated.

  9. Reduction of dispersive ground-roll using time delay spectrometry

    DEFF Research Database (Denmark)

    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...... of reducing dispersive ground-roll in a seismic trace. Although it is possible to mask out ground-roll in the τ-p domain, mapping of the τ-p domain back into the original x-t domain involves numerical difficulties because the used inverse discrete Radon transform is ill-posed. To circumvent this problem...

  10. Integrated Backstepping Design of Missile Guidance andControl with Time delay Adaptive Scheme

    Science.gov (United States)

    2016-03-30

    Guidance and Control with Time-delay Adaptive Scheme Seong-Min Hong 1 , Min-Guk Seo 1 , Chang-Hun Lee 2 and Min-Jea Tahk 1 1 Department...engagement kinematics are merged. Control input for the overall system is derived by backstepping approach. The stability of control logic is proved...estimated by using a time-delay adaptive control law. The performance of designed controller is investigated by numerical simulation. Keywords

  11. Adaptive Synchronization of Fractional Neural Networks with Unknown Parameters and Time Delays

    Directory of Open Access Journals (Sweden)

    Weiyuan Ma

    2014-12-01

    Full Text Available In this paper, the parameters identification and synchronization problem of fractional-order neural networks with time delays are investigated. Based on some analytical techniques and an adaptive control method, a simple adaptive synchronization controller and parameter update laws are designed to synchronize two uncertain complex networks with time delays. Besides, the system parameters in the uncertain network can be identified in the process of synchronization. To demonstrate the validity of the proposed method, several illustrative examples are presented.

  12. Numerical test for hyperbolicity in chaotic systems with multiple time delays

    Science.gov (United States)

    Kuptsov, Pavel V.; Kuznetsov, Sergey P.

    2018-03-01

    We develop an extension of the fast method of angles for hyperbolicity verification in chaotic systems with an arbitrary number of time-delay feedback loops. The adopted method is based on the theory of covariant Lyapunov vectors and provides an efficient algorithm applicable for systems with high-dimensional phase space. Three particular examples of time-delay systems are analyzed and in all cases the expected hyperbolicity is confirmed.

  13. Preamble-aided time delay estimation in frequency selective channels for wireless OFDM systems

    Directory of Open Access Journals (Sweden)

    Qun Yu

    2014-08-01

    Full Text Available In this Letter, an improved method for estimating the time delay in preamble-aided orthogonal frequency division multiplexing systems is presented. It uses a conventional preamble structure and combines cross-correlation techniques to achieve estimations of time delay and the number of multipaths without any additional overhead. Computer simulations results show that the proposed method is of near-ideal property in frequency-selected channels.

  14. Delay Analysis of AVB traffic in Time-Sensitive Networks (TSN)

    OpenAIRE

    Maxim, Dorin; Song, Ye-Qiong

    2017-01-01

    International audience; Future autonomous vehicles and ADAS (Advanced Driver Assistance Systems) need real-time audio and video transmission together with control data traac (CDT). Audio/video stream delay analysis has been largely investigated in AVB (Audio Video Bridging) context, but not yet with the presence of the CDT in the new TSN context. In this paper we present a local delay analysis of AVB frames under hierarchical scheduling of credit-based shaping and time-aware shaping on TSN sw...

  15. Lyapunov matrices approach to the parametric optimization of time-delay systems

    Directory of Open Access Journals (Sweden)

    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

  16. Delayed High School Starting Times. Information Capsule. Volume 0908

    Science.gov (United States)

    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…

  17. Decentralized H∞ Control of Interconnected Systems with Time-varying Delays

    Directory of Open Access Journals (Sweden)

    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.

  18. Subjective Preference of Cellists for the Delay Time of a Single Reflection in a Performance

    Science.gov (United States)

    SATO, S.; ANDO, Y.; OTA, S.

    2000-04-01

    To provide knowledge useful in designing the stage enclosure in a concert hall, Nakayama reported the subjective preference of alto-recorder players for sound fields with a single reflection [Acustica54, 217-221 (1984)]. The present study evaluates the subjective preferences, with regard to ease of performance, of five cello soloists for the delay time of a single reflection. The scale values of preference for the delay time of a single reflection were obtained using a paired comparison method, and the results were compared with those for the alto-recorder players and listeners. The scale values of preference for both individuals and for global cellists with regard to the delay time of reflection can be expressed by a single approximate formula, normalizing the delay time by the most-preferred delay time observed for different music motifs. A notable finding is that the most-preferred delay time of a single reflection for each cellist can be calculated from the amplitude of the reflection and the minimum value of the effective duration (τe)minof the running autocorrelation function of the music motifs played by each cellist.

  19. Effects of time delay on the stochastic resonance in small-world neuronal networks.

    Science.gov (United States)

    Yu, Haitao; Wang, Jiang; Du, Jiwei; Deng, Bin; Wei, Xile; Liu, Chen

    2013-03-01

    The effects of time delay on stochastic resonance in small-world neuronal networks are investigated. Without delay, an intermediate intensity of additive noise is able to optimize the temporal response of the neural system to the subthreshold periodic signal imposed on all neurons constituting the network. The time delay in the coupling process can either enhance or destroy stochastic resonance of neuronal activity in the small-world network. In particular, appropriately tuned delays can induce multiple stochastic resonances, which appear intermittently at integer multiples of the oscillation period of weak external forcing. It is found that the delay-induced multiple stochastic resonances are most efficient when the forcing frequency is close to the global-resonance frequency of each individual neuron. Furthermore, the impact of time delay on stochastic resonance is largely independent of the small-world topology, except for resonance peaks. Considering that information transmission delays are inevitable in intra- and inter-neuronal communication, the presented results could have important implications for the weak signal detection and information propagation in neural systems.

  20. Longitudinal Outcomes of Start Time Delay on Sleep, Behavior, and Achievement in High School.

    Science.gov (United States)

    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.

  1. Modeling and Output Feedback Control of Networked Control Systems with Both Time Delays; and Packet Dropouts

    Directory of Open Access Journals (Sweden)

    Li Qiu

    2013-01-01

    Full Text Available This paper is concerned with the problem of modeling and output feedback controller design for a class of discrete-time networked control systems (NCSs with time delays and packet dropouts. A Markovian jumping method is proposed to deal with random time delays and packet dropouts. Different from the previous studies on the issue, the characteristics of networked communication delays and packet dropouts can be truly reflected by the unified model; namely, both sensor-to-controller (S-C and controller-to-actuator (C-A time delays, and packet dropouts are modeled and their history behavior is described by multiple Markov chains. The resulting closed-loop system is described by a new Markovian jump linear system (MJLS with Markov delays model. Based on Lyapunov stability theory and linear matrix inequality (LMI method, sufficient conditions of the stochastic stability and output feedback controller design method for NCSs with random time delays and packet dropouts are presented. A numerical example is given to illustrate the effectiveness of the proposed method.

  2. Symmetry, Hopf bifurcation, and the emergence of cluster solutions in time delayed neural networks

    Science.gov (United States)

    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.

  3. Does it Pay to Delay? Flesh Flies Show Adaptive Plasticity in Reproductive Timing

    Science.gov (United States)

    Kristal, Ross; Netter, Fleta; Hatle, John D.; Hahn, Daniel A.

    2013-01-01

    Life-history plasticity is widespread among organisms. However, an important question is whether this plasticity is adaptive, enhancing the organism’s fitness. Most models for plasticity in life-history timing predict that once they have reached the minimal nutritional threshold animals under poor conditions will accelerate timing to development or reproduction. Adaptive delays in reproductive timing are not common, especially in short-lived species. Examples of adaptive reproductive delays exist in mammalian populations experiencing strong interspecific (e.g. predation) and intraspecific (e.g. infanticide) competition. But are there other environmental factors that may trigger an adaptive delay in reproductive timing? We show that the short-lived flesh fly Sarcophaga crassipalpis will delay reproductive timing under nutrient poor conditions, even though it has already met the minimal nutritional threshold for reproduction. We test if this delay strategy is consistent with an adaptive response allowing the scavenger time to locate more resources by providing additional protein pulses (early, mid and late) throughout the reproductive delay period. Flies receiving additional protein produced more eggs and larger eggs, demonstrating a benefit of the delay. In addition, by tracking the allocation of carbon from the pulses using stable isotopes, we show that flies receiving earlier pulses incorporated more carbon into eggs and somatic tissue than those provided a later pulse. These results indicate that the reproductive delay in S. crassipalpis is consistent with adaptive post-threshold plasticity, a nutritionally-linked reproductive strategy that has not been previously reported in an invertebrate species. PMID:20953961

  4. Construction delays causing risks on time and cost - a critical review

    Directory of Open Access Journals (Sweden)

    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.

  5. Analysis of actuator delay and its effect on uncertainty quantification for real-time hybrid simulation

    Science.gov (United States)

    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.

  6. True-time delay by slow light in a semiconductor waveguide with alternating amplifying and absorbing sections

    DEFF Research Database (Denmark)

    Öhman, Filip; Mørk, Jesper

    2006-01-01

    Modeling of slow light in a semiconductor waveguide with alternating gain and absorption sections demonstrate an increase in time delay by concatenating segments. A true-time delay is predicted over a large bandwidth at high frequency.......Modeling of slow light in a semiconductor waveguide with alternating gain and absorption sections demonstrate an increase in time delay by concatenating segments. A true-time delay is predicted over a large bandwidth at high frequency....

  7. Robust L2-L∞ Filtering of Time-Delay Jump Systems with Respect to the Finite-Time Interval

    Directory of Open Access Journals (Sweden)

    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.

  8. Economy with the time delay of information flow—The stock market case

    Science.gov (United States)

    Miśkiewicz, Janusz

    2012-02-01

    Any decision process requires information about the past and present state of the system, but in an economy acquiring data and processing it is an expensive and time-consuming task. Therefore, the state of the system is often measured over some legal interval, analysed after the end of well defined time periods and the results announced much later before any strategic decision is envisaged. The various time delay roles have to be crucially examined. Here, a model of stock market coupled with an economy is investigated to emphasise the role of the time delay span on the information flow. It is shown that the larger the time delay the more important the collective behaviour of agents since one observes time oscillations in the absolute log-return autocorrelations.

  9. Pattern Formation in a Predator-Prey Model with Both Cross Diffusion and Time Delay

    Directory of Open Access Journals (Sweden)

    Boli Xie

    2014-01-01

    Full Text Available A predator-prey model with both cross diffusion and time delay is considered. We give the conditions for emerging Turing instability in detail. Furthermore, we illustrate the spatial patterns via numerical simulations, which show that the model dynamics exhibits a delay and diffusion controlled formation growth not only of spots and stripe-like patterns, but also of the two coexist. The obtained results show that this system has rich dynamics; these patterns show that it is useful for the diffusive predation model with a delay effect to reveal the spatial dynamics in the real model.

  10. H∞ Consensus for Multiagent Systems with Heterogeneous Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    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.

  11. Finite-time resilient decentralized control for interconnected impulsive switched systems with neutral delay.

    Science.gov (United States)

    Ren, Hangli; Zong, Guangdeng; Hou, Linlin; Yang, Yi

    2017-03-01

    This paper is concerned with the problem of finite-time control for a class of interconnected impulsive switched systems with neutral delay in which the time-varying delay appears in both the state and the state derivative. The concepts of finite-time boundedness and finite-time stability are respectively extended to interconnected impulsive switched systems with neutral delay for the first time. By applying the average dwell time method, sufficient conditions are first derived to cope with the problem of finite-time boundedness and finite-time stability for interconnected impulsive switched systems with neutral delay. In addition, the purpose of finite-time resilient decentralized control is to construct a resilient decentralized state-feedback controller such that the closed-loop system is finite-time bounded and finite-time stable. All the conditions are formulated in terms of linear matrix inequalities to ensure finite-time boundedness and finite-time stability of the given system. Finally, an example is presented to illustrate the effectiveness of the proposed approach. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

  12. Memory State Feedback RMPC for Multiple Time-Delayed Uncertain Linear Systems with Input Constraints

    Directory of Open Access Journals (Sweden)

    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.

  13. Stability analysis of switched stochastic neural networks with time-varying delays.

    Science.gov (United States)

    Wu, Xiaotai; Tang, Yang; Zhang, Wenbing

    2014-03-01

    This paper is concerned with the global exponential stability of switched stochastic neural networks with time-varying delays. Firstly, the stability of switched stochastic delayed neural networks with stable subsystems is investigated by utilizing the mathematical induction method, the piecewise Lyapunov function and the average dwell time approach. Secondly, by utilizing the extended comparison principle from impulsive systems, the stability of stochastic switched delayed neural networks with both stable and unstable subsystems is analyzed and several easy to verify conditions are derived to ensure the exponential mean square stability of switched delayed neural networks with stochastic disturbances. The effectiveness of the proposed results is illustrated by two simulation examples. Copyright © 2013 Elsevier Ltd. All rights reserved.

  14. Partial state estimation for linear systems with output and input time delays.

    Science.gov (United States)

    Ha, Q P; That, Nguyen D; Nam, Phan T; Trinh, H

    2014-03-01

    This paper deals with the problem of partial state observer design for linear systems that are subject to time delays in the measured output as well as the control input. By choosing a set of appropriate augmented Lyapunov-Krasovskii functionals with a triple-integral term and using the information of both the delayed output and input, a novel approach to design a minimal-order observer is proposed to guarantee that the observer error is ε-convergent with an exponential rate. Existence conditions of such an observer are derived in terms of matrix inequalities for the cases with time delays in both the output and input and with output delay only. Constructive design algorithms are introduced. Numerical examples are provided to illustrate the design procedure, practicality and effectiveness of the proposed observer. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

  15. Superluminal and negative delay times in isotropic-anisotropic one-dimensional photonic crystal

    Science.gov (United States)

    Ouchani, N.; El Moussaouy, A.; Aynaou, H.; El Hassouani, Y.; El Boudouti, E. H.; Djafari-Rouhani, B.

    2017-11-01

    In this work, we investigate the possibility of superluminal and negative delay times for electromagnetic wave propagation in a linear and passive periodic structure consisting of alternating isotropic and anisotropic media. This phenomenon is due to the birefringence of the anisotropic layers of the structure. By adjusting the orientations of these layers, the delay times of transmitted waves can be controlled from subluminality to superluminality and vice versa. Numerical results indicate that the apparent superluminal propagation of light occurs inside the photonic band-gaps when the principal axes of the anisotropic layers are parallel or perpendicular to the fixed axes. For other orientations of these layers, tunneling and superluminal regimes appear inside the photonic bandgaps and in the allowed bands for frequencies close to the transmission minima. The effect of the number of unit cells of the photonic crystal structure on the propagation of light with superluminal and negative delay times is also investigated. We show that the structure exhibits the Hartman effect in which the tunneling delay time of the electromagnetic wave through the photonic band-gap of the structure converges asymptotically to a finite value with increasing the number of layers. The Green's function approach has been used to derive the transmission and reflection coefficients, the density of states, and the delay times of electromagnetic waves propagating through the structure. The control of the magnitude and the sign of the delay time of light propagation represent a key point in slow and fast light technologies. The proposed structure in this study represents a new system for controlling the delay times of wave propagation without a need of active or non-linear media as well as lossy or asymmetric periodic structures.

  16. First-order, worldwide, ionospheric, time-delay algorithm. Air force surveys in geophysics

    Energy Technology Data Exchange (ETDEWEB)

    Klobuchar, J.A.

    1975-09-25

    A first-order model algorithm designed to reduce ionospheric time-delay errors by approximately 50% rms on a world-wide basis for single frequency users of the Global Positioning Systen/NAVSTAR is described. The algorithm was designed for greatest accuracy during times of day when ionospheric time-delay errors are expected to be largest. The algorithm is available in several options, from one which requires only a monthly mean solar-flux value to one which requires 9 daily or monthly update coefficients. Several approximations also are made in the geometry calculations to reduce further operational user computer storage and running time requirements. (auth)

  17. Influence of time delay on fractional-order PI-controlled system for a second-order oscillatory plant model with time delay

    Directory of Open Access Journals (Sweden)

    Sadalla Talar

    2017-12-01

    Full Text Available The paper aims at presenting the influence of an open-loop time delay on the stability and tracking performance of a second-order open-loop system and continuoustime fractional-order PI controller. The tuning method of this controller is based on Hermite- Biehler and Pontryagin theorems, and the tracking performance is evaluated on the basis of two integral performance indices, namely IAE and ISE. The paper extends the results and methodology presented in previous work of the authors to analysis of the influence of time delay on the closed-loop system taking its destabilizing properties into account, as well as concerning possible application of the presented results and used models.

  18. Generating ultrarelativistic attosecond electron bunches with laser wakefield accelerators

    NARCIS (Netherlands)

    Luttikhof, M.J.H.; Khachatryan, A.G.; van Goor, F.A.; Boller, Klaus J.

    2010-01-01

    Femtosecond electron bunches with ultrarelativistic energies were recently generated by laser wakefield accelerators. Here we predict that laser wakefield acceleration can generate even attosecond bunches, due to a strong chirp of the betatron frequency. We show how the bunch duration scales with

  19. Next Generation Driver for Attosecond and Laser-plasma Physics.

    Science.gov (United States)

    Rivas, D E; Borot, A; Cardenas, D E; Marcus, G; Gu, X; Herrmann, D; Xu, J; Tan, J; Kormin, D; Ma, G; Dallari, W; Tsakiris, G D; Földes, I B; Chou, S-W; Weidman, M; Bergues, B; Wittmann, T; Schröder, H; Tzallas, P; Charalambidis, D; Razskazovskaya, O; Pervak, V; Krausz, F; Veisz, L

    2017-07-12

    The observation and manipulation of electron dynamics in matter call for attosecond light pulses, routinely available from high-order harmonic generation driven by few-femtosecond lasers. However, the energy limitation of these lasers supports only weak sources and correspondingly linear attosecond studies. Here we report on an optical parametric synthesizer designed for nonlinear attosecond optics and relativistic laser-plasma physics. This synthesizer uniquely combines ultra-relativistic focused intensities of about 1020 W/cm2 with a pulse duration of sub-two carrier-wave cycles. The coherent combination of two sequentially amplified and complementary spectral ranges yields sub-5-fs pulses with multi-TW peak power. The application of this source allows the generation of a broad spectral continuum at 100-eV photon energy in gases as well as high-order harmonics in relativistic plasmas. Unprecedented spatio-temporal confinement of light now permits the investigation of electric-field-driven electron phenomena in the relativistic regime and ultimately the rise of next-generation intense isolated attosecond sources.

  20. Secondary-electron cascade in attosecond photoelectron spectroscopy from metals

    DEFF Research Database (Denmark)

    Baggesen, Jan Conrad; Madsen, Lars Bojer

    2009-01-01

    Attosecond spectroscopy is currently restricted to photon energies around 100 eV. We show that under these conditions, electron-electron scatterings, as the photoelectrons leave the metal, give rise to a tail of secondary electrons with lower energies and hence a significant background. We develop...

  1. Effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks.

    Science.gov (United States)

    Sun, Xiaojuan; Perc, Matjaž; Kurths, Jürgen

    2017-05-01

    In this paper, we study effects of partial time delays on phase synchronization in Watts-Strogatz small-world neuronal networks. Our focus is on the impact of two parameters, namely the time delay τ and the probability of partial time delay pdelay, whereby the latter determines the probability with which a connection between two neurons is delayed. Our research reveals that partial time delays significantly affect phase synchronization in this system. In particular, partial time delays can either enhance or decrease phase synchronization and induce synchronization transitions with changes in the mean firing rate of neurons, as well as induce switching between synchronized neurons with period-1 firing to synchronized neurons with period-2 firing. Moreover, in comparison to a neuronal network where all connections are delayed, we show that small partial time delay probabilities have especially different influences on phase synchronization of neuronal networks.

  2. Modeling and Bifurcation Research of a Worm Propagation Dynamical System with Time Delay

    Directory of Open Access Journals (Sweden)

    Yu Yao

    2014-01-01

    Full Text Available Both vaccination and quarantine strategy are adopted to control the Internet worm propagation. By considering the interaction infection between computers and external removable devices, a worm propagation dynamical system with time delay under quarantine strategy is constructed based on anomaly intrusion detection system (IDS. By regarding the time delay caused by time window of anomaly IDS as the bifurcation parameter, local asymptotic stability at the positive equilibrium and local Hopf bifurcation are discussed. Through theoretical analysis, a threshold τ0 is derived. When time delay is less than τ0, the worm propagation is stable and easy to predict; otherwise, Hopf bifurcation occurs so that the system is out of control and the containment strategy does not work effectively. Numerical analysis and discrete-time simulation experiments are given to illustrate the correctness of theoretical analysis.

  3. Generation of Attosecond Light Pulses from Gas and Solid State Media

    Directory of Open Access Journals (Sweden)

    Stefanos Chatziathanasiou

    2017-03-01

    Full Text Available Real-time observation of ultrafast dynamics in the microcosm is a fundamental approach for understanding the internal evolution of physical, chemical and biological systems. Tools for tracing such dynamics are flashes of light with duration comparable to or shorter than the characteristic evolution times of the system under investigation. While femtosecond (fs pulses are successfully used to investigate vibrational dynamics in molecular systems, real time observation of electron motion in all states of matter requires temporal resolution in the attosecond (1 attosecond (asec = 10−18 s time scale. During the last decades, continuous efforts in ultra-short pulse engineering led to the development of table-top sources which can produce asec pulses. These pulses have been synthesized by using broadband coherent radiation in the extreme ultraviolet (XUV spectral region generated by the interaction of matter with intense fs pulses. Here, we will review asec pulses generated by the interaction of gas phase media and solid surfaces with intense fs IR laser fields. After a brief overview of the fundamental process underlying the XUV emission form these media, we will review the current technology, specifications and the ongoing developments of such asec sources.

  4. Stochastic resonance in a tumor-immune system subject to bounded noises and time delay

    Science.gov (United States)

    Guo, Wei; Mei, Dong-Cheng

    2014-12-01

    Immunotherapy is one of the most recent approaches in cancer therapy. A mathematical model of tumor-immune interaction, subject to a periodic immunotherapy treatment (imitated by a periodic signal), correlative and bounded stochastic fluctuations and time delays, is investigated by numerical simulations for its signal power amplification (SPA). Within the tailored parameter regime, the synchronous response of tumor growth to the immunotherapy, stochastic resonance (SR), versus both the noises and delays is obtained. The details are as follows (i) the peak values of SPA versus the noise intensity (A) in the proliferation term of tumor cells decrease as the frequency of periodic signal increases, i.e. an increase of the frequency restrains the SR; (ii) an increase of the amplitude of periodic signal restrains the SR versus A, but boosts up the SR versus the noise intensity B in the immune term; (iii) there is an optimum cross-correlated degree between the two bounded noises, at which the system exhibits the strongest SR versus the delay time τα(the reaction time of tumor cell population to their surrounding environment constraints); (iv) upon increasing the delay time τα, double SR versus the delay time τβ (the time taken by both the tumor antigen identification and tumor-stimulated proliferation of effectors) emerges. These results may be helpful for an immunotherapy treatment for the sufferer.

  5. Using GeneReg to construct time delay gene regulatory networks

    Directory of Open Access Journals (Sweden)

    Qian Ziliang

    2010-05-01

    Full Text Available Abstract Background Understanding gene expression and regulation is essential for understanding biological mechanisms. Because gene expression profiling has been widely used in basic biological research, especially in transcription regulation studies, we have developed GeneReg, an easy-to-use R package, to construct gene regulatory networks from time course gene expression profiling data; More importantly, this package can provide information about time delays between expression change in a regulator and that of its target genes. Findings The R package GeneReg is based on time delay linear regression, which can generate a model of the expression levels of regulators at a given time point against the expression levels of their target genes at a later time point. There are two parameters in the model, time delay and regulation coefficient. Time delay is the time lag during which expression change of the regulator is transmitted to change in target gene expression. Regulation coefficient expresses the regulation effect: a positive regulation coefficient indicates activation and negative indicates repression. GeneReg was implemented on a real Saccharomyces cerevisiae cell cycle dataset; more than thirty percent of the modeled regulations, based entirely on gene expression files, were found to be consistent with previous discoveries from known databases. Conclusions GeneReg is an easy-to-use, simple, fast R package for gene regulatory network construction from short time course gene expression data. It may be applied to study time-related biological processes such as cell cycle, cell differentiation, or causal inference.

  6. When should we recommend use of dual time-point and delayed time-point imaging techniques in FDG PET?

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Gang [Philadelphia VA Medical Center, Department of Radiology, Philadelphia, PA (United States); Hospital of the University of Pennsylvania, Department of Radiology, Philadelphia, PA (United States); Torigian, Drew A.; Alavi, Abass [Hospital of the University of Pennsylvania, Department of Radiology, Philadelphia, PA (United States); Zhuang, Hongming [Children' s Hospital of Philadelphia, Department of Radiology, Philadelphia, PA (United States)

    2013-05-15

    FDG PET and PET/CT are now widely used in oncological imaging for tumor characterization, staging, restaging, and response evaluation. However, numerous benign etiologies may cause increased FDG uptake indistinguishable from that of malignancy. Multiple studies have shown that dual time-point imaging (DTPI) of FDG PET may be helpful in differentiating malignancy from benign processes. However, exceptions exist, and some studies have demonstrated significant overlap of FDG uptake patterns between benign and malignant lesions on delayed time-point images. In this review, we summarize our experience and opinions on the value of DTPI and delayed time-point imaging in oncology, with a review of the relevant literature. We believe that the major value of DTPI and delayed time-point imaging is the increased sensitivity due to continued clearance of background activity and continued FDG accumulation in malignant lesions, if the same diagnostic criteria (as in the initial standard single time-point imaging) are used. The specificity of DTPI and delayed time-point imaging depends on multiple factors, including the prevalence of malignancies, the patient population, and the cut-off values (either SUV or retention index) used to define a malignancy. Thus, DTPI and delayed time-point imaging would be more useful if performed for evaluation of lesions in regions with significant background activity clearance over time (such as the liver, the spleen, the mediastinum), and if used in the evaluation of the extent of tumor involvement rather than in the characterization of the nature of any specific lesion. Acute infectious and non-infectious inflammatory lesions remain as the major culprit for diminished diagnostic performance of these approaches (especially in tuberculosis-endemic regions). Tumor heterogeneity may also contribute to inconsistent performance of DTPI. The authors believe that selective use of DTPI and delayed time-point imaging will improve diagnostic accuracy and

  7. Time delay estimation in a reverberant environment by low rate sampling of impulsive acoustic sources

    KAUST Repository

    Omer, Muhammad

    2012-07-01

    This paper presents a new method of time delay estimation (TDE) using low sample rates of an impulsive acoustic source in a room environment. The proposed method finds the time delay from the room impulse response (RIR) which makes it robust against room reverberations. The RIR is considered a sparse phenomenon and a recently proposed sparse signal reconstruction technique called orthogonal clustering (OC) is utilized for its estimation from the low rate sampled received signal. The arrival time of the direct path signal at a pair of microphones is identified from the estimated RIR and their difference yields the desired time delay. Low sampling rates reduce the hardware and computational complexity and decrease the communication between the microphones and the centralized location. The performance of the proposed technique is demonstrated by numerical simulations and experimental results. © 2012 IEEE.

  8. Cucker-Smale model with normalized communication weights and time delay

    KAUST Repository

    Choi, Young-Pil

    2017-03-06

    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.e., convergence to a common velocity vector. We also carry out a rigorous limit passage to the mean-field limit of the particle system as the number of particles tends to infinity. For the resulting Vlasov-type equation we prove the existence, stability and large-time behavior of measure-valued solutions. This is, to our best knowledge, the first such result for a Vlasov-type equation with time delay. We also present numerical simulations of the discrete system with few particles that provide further insights into the flocking and oscillatory behaviors of the particle velocities depending on the size of the time delay.

  9. Ignition delay times of Gasoline Distillation Cuts measured with Ignition Quality Tester

    KAUST Repository

    Naser, Nimal

    2017-04-21

    Tailoring fuel properties to maximize the efficiency of internal combustion engines is a way towards achieving cleaner combustion systems. In this work, the ignition properties of various gasoline fuel distillation cuts are analyzed to better understand fuel properties of the full boiling range fuel. An advanced distillation column (ADC) provides a more realistic representation of volatility characteristics, which can be modeled using equilibrium thermodynamic methods. The temperature reported is that of the liquid, as opposed to the vapor temperature in conventional ASTM D86 distillation standard. Various FACE (fuels for advanced combustion engines) gasolines were distilled and various cuts were obtained. The separated fractions were then tested in an ignition quality tester (IQT) to see the effect of chemical composition of different fractions on their ignition delay time. Fuels with lower aromatic content showed decreasing ignition delay time with increasing boiling point (i.e., molecular weight). However, fuels with higher aromatic content showed an initial decrease in ignition delay time with increasing boiling point, followed by drastic increase in ignition delay time due to fractions containing aromatics. This study also provides an understanding on contribution of different fractions to the ignition delay time of the fuel, which provides insights into fuel stratification utilized in gasoline compression ignition (GCI) engines to tailor heat release rates.

  10. A CS Recovery Algorithm for Model and Time Delay Identification of MISO-FIR Systems

    Directory of Open Access Journals (Sweden)

    Yanjun Liu

    2015-09-01

    Full Text Available This paper considers identifying the multiple input single output finite impulse response (MISO-FIR systems with unknown time delays and orders. Generally, parameters, orders and time delays of an MISO system are separately identified from different algorithms. In this paper, we aim to perform the model identification and time delay estimation simultaneously from a limited number of observations. For an MISO-FIR system with many inputs and unknown input time delays, the corresponding identification model contains a large number of parameters, requiring a great number of observations for identification and leading to a heavy computational burden. Inspired by the compressed sensing (CS recovery theory, a threshold orthogonal matching pursuit algorithm (TH-OMP is presented to simultaneously identify the parameters, the orders and the time delays of the MISO-FIR systems. The proposed algorithm requires only a small number of sampled data compared to the conventional identification methods, such as the least squares method. The effectiveness of the proposed algorithm is verified by simulation results.

  11. Dual-time-point Imaging and Delayed-time-point Fluorodeoxyglucose-PET/Computed Tomography Imaging in Various Clinical Settings

    DEFF Research Database (Denmark)

    Houshmand, Sina; Salavati, Ali; Antonsen Segtnan, Eivind

    2016-01-01

    The techniques of dual-time-point imaging (DTPI) and delayed-time-point imaging, which are mostly being used for distinction between inflammatory and malignant diseases, has increased the specificity of fluorodeoxyglucose (FDG)-PET for diagnosis and prognosis of certain diseases. A gradually...... increasing trend of FDG uptake over time has been shown in malignant cells, and a decreasing or constant trend has been shown in inflammatory/infectious processes. Tumor heterogeneity can be assessed by using early and delayed imaging because differences between primary versus metastatic sites become more...

  12. Hydrodynamic Cucker-Smale model with normalized communication weights and time delay

    KAUST Repository

    Choi, Young-Pil

    2017-07-17

    We study a hydrodynamic Cucker-Smale-type model with time delay in communication and information processing, in which agents interact with each other through normalized communication weights. The model consists of a pressureless Euler system 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, we show the presence of a critical phenomenon for the Eulerian system posed in the spatially one-dimensional setting.

  13. Statistics of time delay and scattering correlation functions in chaotic systems. I. Random matrix theory

    Science.gov (United States)

    Novaes, Marcel

    2015-06-01

    We consider the statistics of time delay in a chaotic cavity having M open channels, in the absence of time-reversal invariance. In the random matrix theory approach, we compute the average value of polynomial functions of the time delay matrix Q = - iħS†dS/dE, where S is the scattering matrix. Our results do not assume M to be large. In a companion paper, we develop a semiclassical approximation to S-matrix correlation functions, from which the statistics of Q can also be derived. Together, these papers contribute to establishing the conjectured equivalence between the random matrix and the semiclassical approaches.

  14. Statistics of time delay and scattering correlation functions in chaotic systems. I. Random matrix theory

    Energy Technology Data Exchange (ETDEWEB)

    Novaes, Marcel [Instituto de Física, Universidade Federal de Uberlândia, Ave. João Naves de Ávila, 2121, Uberlândia, MG 38408-100 (Brazil)

    2015-06-15

    We consider the statistics of time delay in a chaotic cavity having M open channels, in the absence of time-reversal invariance. In the random matrix theory approach, we compute the average value of polynomial functions of the time delay matrix Q = − iħS{sup †}dS/dE, where S is the scattering matrix. Our results do not assume M to be large. In a companion paper, we develop a semiclassical approximation to S-matrix correlation functions, from which the statistics of Q can also be derived. Together, these papers contribute to establishing the conjectured equivalence between the random matrix and the semiclassical approaches.

  15. Delay time for fine particle ignition within gas with fluctuating temperature

    Science.gov (United States)

    Derevich, I. V.; Galdina, D. D.

    2017-03-01

    The Pontryagin equation was applied to calculating the average time for the random process escaping the assign interval: this gives the average delay time for waiting of particle ignition moment in a turbulent flow of gas. A direct numerical simulation method was developed for gas temperature fluctuations with assigned autocorrelation function and particle temperature fluctuations due to exothermal chemical reaction. The method was based on numerical solution of a system of stochastic differential equations. Results of direct simulation were validated through comparing with the analytical solution available for particles without exothermal reaction. Analytical calculations and results of direct numerical simulation for the delay time of particle ignition are in agreement.

  16. A Distributed Algorithm for Economic Dispatch Over Time-Varying Directed Networks With Delays

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Tao; Lu, Jie; Wu, Di; Wu, Junfeng; Shi, Guodong; Meng, Ziyang; Johansson, Karl Henrik

    2017-06-01

    In power system operation, economic dispatch problem (EDP) is designed to minimize the total generation cost while meeting the demand and satisfying generator capacity limits. This paper proposes an algorithm based on the gradient-push method to solve the EDP in a distributed manner over communication networks potentially with time-varying topologies and communication delays. It has been shown that the proposed method is guaranteed to solve the EDP if the time-varying directed communication network is uniformly jointly strongly connected. Moreover, the proposed algorithm is also able to handle arbitrarily large but bounded time delays on communication links. Numerical simulations are used to illustrate and validate the proposed algorithm.

  17. Event-Triggered Faults Tolerant Control for Stochastic Systems with Time Delays

    Directory of Open Access Journals (Sweden)

    Ling Huang

    2016-01-01

    Full Text Available This paper is concerned with the state-feedback controller design for stochastic networked control systems (NCSs with random actuator failures and transmission delays. Firstly, an event-triggered scheme is introduced to optimize the performance of the stochastic NCSs. Secondly, stochastic NCSs under event-triggered scheme are modeled as stochastic time-delay systems. Thirdly, some less conservative delay-dependent stability criteria in terms of linear matrix inequalities for the codesign of both the controller gain and the trigger parameters are obtained by using delay-decomposition technique and convex combination approach. Finally, a numerical example is provided to show the less sampled data transmission and less conservatism of the proposed theory.

  18. Two-dimensional dissipative rogue waves due to time-delayed feedback in cavity nonlinear optics.

    Science.gov (United States)

    Tlidi, Mustapha; Panajotov, Krassimir

    2017-01-01

    We demonstrate a way to generate two-dimensional rogue waves in two types of broad area nonlinear optical systems subject to time-delayed feedback: in the generic Lugiato-Lefever model and in the model of a broad-area surface-emitting laser with saturable absorber. The delayed feedback is found to induce a spontaneous formation of rogue waves. In the absence of delayed feedback, spatial pulses are stationary. The rogue waves are exited and controlled by the delay feedback. We characterize their formation by computing the probability distribution of the pulse height. The long-tailed statistical contribution, which is often considered as a signature of the presence of rogue waves, appears for sufficiently strong feedback. The generality of our analysis suggests that the feedback induced instability leading to the spontaneous formation of two-dimensional rogue waves is a universal phenomenon.

  19. Impact of time delay on the dynamics of SEIR epidemic model using cellular automata

    Science.gov (United States)

    Sharma, Natasha; Gupta, Arvind Kumar

    2017-04-01

    The delay of an infectious disease is significant when aiming to predict its strength and spreading patterns. In this paper the SEIR ​(susceptible-exposed-infected-recovered) epidemic spread with time delay is analyzed through a two-dimensional cellular automata model. The time delay corresponding to the infectious span, predominantly, includes death during the latency period in due course of infection. The advancement of whole system is described by SEIR transition function complemented with crucial factors like inhomogeneous population distribution, birth and disease independent mortality. Moreover, to reflect more realistic population dynamics some stochastic parameters like population movement and connections at local level are also considered. The existence and stability of disease free equilibrium is investigated. Two prime behavioral patterns of disease dynamics is found depending on delay. The critical value of delay, beyond which there are notable variations in spread patterns, is computed. The influence of important parameters affecting the disease dynamics on basic reproduction number is also examined. The results obtained show that delay plays an affirmative role to control disease progression in an infected host.

  20. CORRECTING FOR INTERSTELLAR SCATTERING DELAY IN HIGH-PRECISION PULSAR TIMING: SIMULATION RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Palliyaguru, Nipuni; McLaughlin, Maura [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Stinebring, Daniel [Department of Physics and Astronomy, Oberlin College, 110 North Professor Street, Oberlin, OH 44074 (United States); Demorest, Paul [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Jones, Glenn, E-mail: npalliya@mix.wvu.edu, E-mail: maura.mclaughlin@mail.wvu.edu, E-mail: dan.stinebring@oberlin.edu, E-mail: pdemores@nrao.edu, E-mail: glenn.caltech@gmail.com [Department of Physics, Columbia University, New York, NY 10027 (United States)

    2015-12-20

    Light travel time changes due to gravitational waves (GWs) may be detected within the next decade through precision timing of millisecond pulsars. Removal of frequency-dependent interstellar medium (ISM) delays due to dispersion and scattering is a key issue in the detection process. Current timing algorithms routinely correct pulse times of arrival (TOAs) for time-variable delays due to cold plasma dispersion. However, none of the major pulsar timing groups correct for delays due to scattering from multi-path propagation in the ISM. Scattering introduces a frequency-dependent phase change in the signal that results in pulse broadening and arrival time delays. Any method to correct the TOA for interstellar propagation effects must be based on multi-frequency measurements that can effectively separate dispersion and scattering delay terms from frequency-independent perturbations such as those due to a GW. Cyclic spectroscopy, first described in an astronomical context by Demorest (2011), is a potentially powerful tool to assist in this multi-frequency decomposition. As a step toward a more comprehensive ISM propagation delay correction, we demonstrate through a simulation that we can accurately recover impulse response functions (IRFs), such as those that would be introduced by multi-path scattering, with a realistic signal-to-noise ratio (S/N). We demonstrate that timing precision is improved when scatter-corrected TOAs are used, under the assumptions of a high S/N and highly scattered signal. We also show that the effect of pulse-to-pulse “jitter” is not a serious problem for IRF reconstruction, at least for jitter levels comparable to those observed in several bright pulsars.

  1. Analysis of the effects of time delay in clock recovery circuits based on Phase-locked loops

    DEFF Research Database (Denmark)

    Zibar, Darko; Oxenløwe, Leif Katsuo; Clausen, Anders

    2004-01-01

    Influence of time delay in a balanced optical phase-locked loops (OPLL) with a proportional integrator (Pl) filter is investigated using a delayed differential equation (DDE) is investigated. The limitations, which a time delay imposes on the Pl filter bandwidth, at increasing values of loop gain...

  2. Time Delay for the Initiation of an Emergency Shutdown at the Peruvian Nuclear Reactor RP-10

    Energy Technology Data Exchange (ETDEWEB)

    Ramon, A.; Ovalle, E.; Canaza, D.; Salazar, A.; Zapata, A.; Felix, J.; Arrieta, R.; Vela, M. [Instituto Peruano de Energia Nuclear, Av. Canada 1470, San Borja, Lima (Peru)

    2008-07-01

    In this paper we show the measurement of the time delay for the initiation of an emergency shutdown state at the RP-10 Reactor. This time delay is the one corresponding to the delay between the detection of a signal of any fixed limit and the start of a protective action to get the reactor in a safety state. The experimental method used is based on monitoring two signals in an oscilloscope, one signal is the elected initiate event and the other is the de-energizing of electromagnets of the security bars. The time delay for each safety and control rods, was measured for seven energizing current values in a range of 36 - 52 mA. The results showed that the minimum value is (84 {+-} 1.26) ms and the maximum is (108 {+-} 1.60) ms. In all cases it is noted that, the delay time is less than the limit values prefixed down in the reactor safety report. (authors)

  3. On the Global Asymptotic Stability of Switched Linear Time-Varying Systems with Constant Point Delays

    Directory of Open Access Journals (Sweden)

    M. de la Sen

    2008-01-01

    Full Text Available This paper investigates the asymptotic stability of switched linear time-varying systems with constant point delays under not very stringent conditions on the matrix functions of parameters. Such conditions are their boundedness, the existence of bounded time derivatives almost everywhere, and small amplitudes of the appearing Dirac impulses where such derivatives do not exist. It is also assumed that the system matrix for zero delay is stable with some prescribed stability abscissa for all time in order to obtain sufficiency-type conditions of asymptotic stability dependent on the delay sizes. Alternatively, it is assumed that the auxiliary system matrix defined for all the delayed system matrices being zero is stable with prescribed stability abscissa for all time to obtain results for global asymptotic stability independent of the delays. A particular subset of the switching instants is the so-called set of reset instants where switching leads to the parameterization to reset to a value within a prescribed set.

  4. Ignition delay time correlation of fuel blends based on Livengood-Wu description

    KAUST Repository

    Khaled, Fathi

    2017-08-17

    In this work, a universal methodology for ignition delay time (IDT) correlation of multicomponent fuel mixtures is reported. The method is applicable over wide ranges of temperatures, pressures, and equivalence ratios. n-Heptane, iso-octane, toluene, ethanol and their blends are investigated in this study because of their relevance to gasoline surrogate formulation. The proposed methodology combines benefits from the Livengood-Wu integral, the cool flame characteristics and the Arrhenius behavior of the high-temperature ignition delay time to suggest a simple and comprehensive formulation for correlating the ignition delay times of pure components and blends. The IDTs of fuel blends usually have complex dependences on temperature, pressure, equivalence ratio and composition of the blend. The Livengood-Wu integral is applied here to relate the NTC region and the cool flame phenomenon. The integral is further extended to obtain a relation between the IDTs of fuel blends and pure components. Ignition delay times calculated using the proposed methodology are in excellent agreement with those simulated using a detailed chemical kinetic model for n-heptane, iso-octane, toluene, ethanol and blends of these components. Finally, very good agreement is also observed for combustion phasing in homogeneous charge compression ignition (HCCI) predictions between simulations performed with detailed chemistry and calculations using the developed ignition delay correlation.

  5. Existence and Stability of Traveling Waves for Degenerate Reaction-Diffusion Equation with Time Delay

    Science.gov (United States)

    Huang, Rui; Jin, Chunhua; Mei, Ming; Yin, Jingxue

    2018-01-01

    This paper deals with the existence and stability of traveling wave solutions for a degenerate reaction-diffusion equation with time delay. The degeneracy of spatial diffusion together with the effect of time delay causes us the essential difficulty for the existence of the traveling waves and their stabilities. In order to treat this case, we first show the existence of smooth- and sharp-type traveling wave solutions in the case of c≥c^* for the degenerate reaction-diffusion equation without delay, where c^*>0 is the critical wave speed of smooth traveling waves. Then, as a small perturbation, we obtain the existence of the smooth non-critical traveling waves for the degenerate diffusion equation with small time delay τ >0 . Furthermore, we prove the global existence and uniqueness of C^{α ,β } -solution to the time-delayed degenerate reaction-diffusion equation via compactness analysis. Finally, by the weighted energy method, we prove that the smooth non-critical traveling wave is globally stable in the weighted L^1 -space. The exponential convergence rate is also derived.

  6. Symmetric bifurcation analysis of synchronous states of time-delayed coupled Phase-Locked Loop oscillators

    Science.gov (United States)

    Ferruzzo Correa, Diego Paolo; Wulff, Claudia; Piqueira, José Roberto Castilho

    2015-05-01

    In recent years there has been an increasing interest in studying time-delayed coupled networks of oscillators since these occur in many real life applications. In many cases symmetry patterns can emerge in these networks, as a consequence a part of the system might repeat itself, and properties of this subsystem are representative of the dynamics on the whole phase space. In this paper an analysis of the second order N-node time-delay fully connected network is presented which is based on previous work: synchronous states in time-delay coupled periodic oscillators: a stability criterion. Correa and Piqueira (2013), for a 2-node network. This study is carried out using symmetry groups. We show the existence of multiple eigenvalues forced by symmetry, as well as the existence of Hopf bifurcations. Three different models are used to analyze the network dynamics, namely, the full-phase, the phase, and the phase-difference model. We determine a finite set of frequencies ω , that might correspond to Hopf bifurcations in each case for critical values of the delay. The Sn map is used to actually find Hopf bifurcations along with numerical calculations using the Lambert W function. Numerical simulations are used in order to confirm the analytical results. Although we restrict attention to second order nodes, the results could be extended to higher order networks provided the time-delay in the connections between nodes remains equal.

  7. A longitudinal study on time perspectives: relations with academic delay of gratification and learning environment

    NARCIS (Netherlands)

    Peetsma, T.; Schuitema, J.; van der Veen, I.

    2012-01-01

    After they start secondary school (at age 12 in the Netherlands), students' time perspectives on school and professional career and self-regulated learning decrease, while their perspectives on leisure increase. We aimed to investigate relations in the developments in time perspectives and delay of

  8. Vartiational Optimal-Control Problems with Delayed Arguments on Time Scales

    Directory of Open Access Journals (Sweden)

    Abdeljawad (Maraaba Thabet

    2009-01-01

    Full Text Available This paper deals with variational optimal-control problems on time scales in the presence of delay in the state variables. The problem is considered on a time scale unifying the discrete, the continuous, and the quantum cases. Two examples in the discrete and quantum cases are analyzed to illustrate our results.

  9. Stability of Delayed Hopfield Neural Networks with Variable-Time Impulses

    Directory of Open Access Journals (Sweden)

    Yangjun Pei

    2014-01-01

    Full Text Available In this paper the globally exponential stability criteria of delayed Hopfield neural networks with variable-time impulses are established. The proposed criteria can also be applied in Hopfield neural networks with fixed-time impulses. A numerical example is presented to illustrate the effectiveness of our theoretical results.

  10. Design of the Congestion Control for TCP/AQM Network with Time-Delay

    Directory of Open Access Journals (Sweden)

    Dazhong Wang

    2014-01-01

    Full Text Available The purpose of this paper is to design congestion controller for TCP/AQM (transmission control protocol/active queue management networks using model following control; the equilibrium of a class of TCP/AQM networks with time-delay is investigated, and the effect of communication time-delay on the stability is addressed. The features of this design method are bounded property of the internal states of the control system being given and the utility of this control. Such design exhibits important attributes including fast convergence with high accuracy to a desired queue length. Simulation results show that the time-delay nonlinear behavior of the system can be controlled by this method.

  11. Regression model for tuning the PID controller with fractional order time delay system

    Directory of Open Access Journals (Sweden)

    S.P. Agnihotri

    2014-12-01

    Full Text Available In this paper a regression model based for tuning proportional integral derivative (PID controller with fractional order time delay system is proposed. The novelty of this paper is that tuning parameters of the fractional order time delay system are optimally predicted using the regression model. In the proposed method, the output parameters of the fractional order system are used to derive the regression function. Here, the regression model depends on the weights of the exponential function. By using the iterative algorithm, the best weight of the regression model is evaluated. Using the regression technique, fractional order time delay systems are tuned and the stability parameters of the system are maintained. The effectiveness and feasibility of the proposed technique is demonstrated through the MATLAB/Simulink platform, as well as testing and comparison using the classical PID controller, Ziegler–Nichols tuning method, Wang tuning method and curve fitting technique base tuning method.

  12. Time delay control of power converters: Mixed frame and stationary-frame variants

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Loh, P.C.; Tang, Y.

    2008-01-01

    In this paper, a mixed-frame and a stationary-frame time delay current controller are proposed for high precision reference tracking and disturbance rejection of power converters. In particular, the controllers use a proportional-resonant regulator in the stationary frame for regulating...... the positive and negative-sequence fundamental currents, which are known to directly influence the flow of active and reactive power in most energy conversion systems. Moreover, for the tracking or compensation of harmonics, the controllers include a time delay control path in either the synchronous...... or stationary frame, whose inherent feedback and feedforward structure can be proven to resemble a bank of resonant filters in either reference frames. Unlike other existing controllers, the proposed time delay controllers function by introducing multiple resonant peaks at only those harmonic frequencies...

  13. Extended Lock Range Zero-Crossing Digital Phase-Locked Loop with Time Delay

    Directory of Open Access Journals (Sweden)

    Nasir Qassim

    2005-01-01

    Full Text Available The input frequency limit of the conventional zero-crossing digital phase-locked loop (ZCDPLL is due to the operating time of the digital circuitry inside the feedback loop. A solution that has been previously suggested is the introduction of a time delay in the feedback path of the loop to allow the digital circuits to complete their sample processing before the next sample is received. However, this added delay will limit the stable operation range and hence lock range of the loop. The objective of this work is to extend the lock range of ZCDPLL with time delay by using a chaos control. The tendency of the loop to diverge is measured and fed back as a form of linear stabilization. The lock range extension has been confirmed through the use of a bifurcation diagram, and Lyapunov exponent.

  14. Leader-Following Consensus of Multi-agent in Switching Networks with Time-Delay

    OpenAIRE

    Hui Yu; Gaoyang Liu; Yi Zhang

    2013-01-01

    This paper is devoted to the study of multi-agent consensus with a time-varying reference state in directed networks with both switching topology and constant time delay. Stability analysis is performed based on a proposed Lyapunov–Krasovskii function. Sufficient conditions based on linear matrix inequalities (LMIs) are given to guarantee multi-agent consensus on a time-vary reference state under arbitrary switching of the network topology even if the network communication is affected by time...

  15. Stochastic resonance enhancement of small-world neural networks by hybrid synapses and time delay

    Science.gov (United States)

    Yu, Haitao; Guo, Xinmeng; Wang, Jiang

    2017-01-01

    The synergistic effect of hybrid electrical-chemical synapses and information transmission delay on the stochastic response behavior in small-world neuronal networks is investigated. Numerical results show that, the stochastic response behavior can be regulated by moderate noise intensity to track the rhythm of subthreshold pacemaker, indicating the occurrence of stochastic resonance (SR) in the considered neural system. Inheriting the characteristics of two types of synapses-electrical and chemical ones, neural networks with hybrid electrical-chemical synapses are of great improvement in neuron communication. Particularly, chemical synapses are conducive to increase the network detectability by lowering the resonance noise intensity, while the information is better transmitted through the networks via electrical coupling. Moreover, time delay is able to enhance or destroy the periodic stochastic response behavior intermittently. In the time-delayed small-world neuronal networks, the introduction of electrical synapses can significantly improve the signal detection capability by widening the range of optimal noise intensity for the subthreshold signal, and the efficiency of SR is largely amplified in the case of pure chemical couplings. In addition, the stochastic response behavior is also profoundly influenced by the network topology. Increasing the rewiring probability in pure chemically coupled networks can always enhance the effect of SR, which is slightly influenced by information transmission delay. On the other hand, the capacity of information communication is robust to the network topology within the time-delayed neuronal systems including electrical couplings.

  16. Mathematical model describing the thyroids-pituitary axis with distributed time delays in hormone transportation

    Science.gov (United States)

    Neamţu, Mihaela; Stoian, Dana; Navolan, Dan Bogdan

    2014-12-01

    In the present paper we provide a mathematical model that describe the hypothalamus-pituitary-thyroid axis in autoimmune (Hashimoto's) thyroiditis. Since there is a spatial separation between thyroid and pituitary gland in the body, time is needed for transportation of thyrotropin and thyroxine between the glands. Thus, the distributed time delays are considered as both weak and Dirac kernels. The delayed model is analyzed regarding the stability and bifurcation behavior. The last part contains some numerical simulations to illustrate the effectiveness of our results and conclusions.

  17. Systematic identification and robust control design for uncertain time delay processes

    DEFF Research Database (Denmark)

    Huusom, Jakob Kjøbsted; Poulsen, Niels Kjølstad; Jørgensen, Sten Bay

    2011-01-01

    A systematic procedure is proposed to handle the standard process control problem. The considered standard problem involves infrequent step disturbances to processes with large delays and measurement noise. The process is modeled as an ARX model and extended with a suitable noise model in order...... to reject unmeasured step disturbances and unavoidable model errors. This controller is illustrated to perform well for both set point tracking and a disturbance rejection for a SISO process example of a furnace which has a time delay which is significantly longer than the dominating time constant....

  18. Adaptive Constrained Control for Uncertain Nonlinear Time-Delay System with Application to Unmanned Helicopter

    Directory of Open Access Journals (Sweden)

    Rong Li

    2018-01-01

    Full Text Available This paper investigates a class of nonlinear time-delayed systems with output prescribed performance constraint. The neural network and DOB (disturbance observer are designed to tackle the uncertainties and external disturbance, and prescribed performance function is constructed for the output prescribed performance constrained problem. Then the robust controller is designed by using adaptive backstepping method, and the stability analysis is considered by using Lyapunov-Krasovskii. Furthermore, the proposed method is employed into the unmanned helicopter system with time-delay aerodynamic uncertainty. Finally, the simulation results illustrate that the proposed robust prescribed performance control system achieved a good control performance.

  19. Hybrid Projective Synchronization of Fractional-Order Chaotic Systems with Time Delay

    Directory of Open Access Journals (Sweden)

    Li-xin Yang

    2013-01-01

    Full Text Available The hybrid projective synchronization for fractional-order chaotic systems with time delay is investigated in this paper. On the basis of stability analysis of fractional-order systems and pole placement technique, a novel and general approach is proposed. The hybrid projective synchronization of fractional-order chaotic and hyperchaotic systems with time delay is achieved via designing an appropriate controller. Corresponding numerical results are presented to demonstrate the effectiveness of the proposed synchronization scheme. Furthermore, the influence of the fractional order on the synchronization process is discussed. The result reveals that the fractional order has a significant effect on the synchronization speed.

  20. SYNCHRONIZATION IN NETWORKS OF COUPLED HARMONIC OSCILLATORS WITH STOCHASTIC PERTURBATION AND TIME DELAYS

    Directory of Open Access Journals (Sweden)

    Yilun Shang

    2012-07-01

    Full Text Available In this paper, we investigate the leader-follower synchronization ofcoupled second-order linear harmonic oscillators with the presence ofrandom noises and time delays. The interaction topology is modeledby a weighted directed graph and the weights are perturbed by whitenoise. On the basis of stability theory of stochastic differential delayequations, algebraic graph theory and matrix theory, we show that thecoupled harmonic oscillators can be synchronized almost surely withrandom perturbation and time delays. Numerical examples are presentedto illustrate our theoretical results.

  1. Stochastic multiresonance for a fractional linear oscillator with time-delayed kernel and quadratic noise

    Science.gov (United States)

    Guo, Feng; Wang, Xue-Yuan; Zhu, Cheng-Yin; Cheng, Xiao-Feng; Zhang, Zheng-Yu; Huang, Xu-Hui

    2017-12-01

    The stochastic resonance for a fractional oscillator with time-delayed kernel and quadratic trichotomous noise is investigated. Applying linear system theory and Laplace transform, the system output amplitude (SPA) for the fractional oscillator is obtained. It is found that the SPA is a periodical function of the kernel delayed-time. Stochastic multiplicative phenomenon appears on the SPA versus the driving frequency, versus the noise amplitude, and versus the fractional exponent. The non-monotonous dependence of the SPA on the system parameters is also discussed.

  2. Analytic Root Locus and Lambert W Function in Control of a Process with Time Delay

    Science.gov (United States)

    Cogan, Brian; de Paor, Annraoi M.

    2011-11-01

    Recently, the Lambert W function has arisen in the analysis of many systems including a restricted class of time-delay systems. An alternative approach to this analysis, based on the well-established root locus method, is shown here to contain the Lambert W function as a special case. As a purely illustrative example of the equivalence between the Lambert W function and analytic root locus a system comprising a Proportional controller with a time-delay process is analysed. Controller designs based on rightmost eigenvalue location and the dominant eigenvalue method are described.

  3. The Application of Time-Delay Dependent H∞ Control Model in Manufacturing Decision Optimization

    Directory of Open Access Journals (Sweden)

    Haifeng Guo

    2015-01-01

    Full Text Available This paper uses a time-delay dependent H∞ control model to analyze the effect of manufacturing decisions on the process of transmission from resources to capability. We establish a theoretical framework of manufacturing management process based on three terms: resource, manufacturing decision, and capability. Then we build a time-delay H∞ robust control model to analyze the robustness of manufacturing management. With the state feedback controller between manufacturing resources and decision, we find that there is an optimal decision to adjust the process of transmission from resources to capability under uncertain environment. Finally, we provide an example to prove the robustness of this model.

  4. ANOMALY NETWORK INTRUSION DETECTION SYSTEM BASED ON DISTRIBUTED TIME-DELAY NEURAL NETWORK (DTDNN

    Directory of Open Access Journals (Sweden)

    LAHEEB MOHAMMAD IBRAHIM

    2010-12-01

    Full Text Available In this research, a hierarchical off-line anomaly network intrusion detection system based on Distributed Time-Delay Artificial Neural Network is introduced. This research aims to solve a hierarchical multi class problem in which the type of attack (DoS, U2R, R2L and Probe attack detected by dynamic neural network. The results indicate that dynamic neural nets (Distributed Time-Delay Artificial Neural Network can achieve a high detection rate, where the overall accuracy classification rate average is equal to 97.24%.

  5. Basins of attraction of the bistable region of time-delayed cutting dynamics

    Science.gov (United States)

    Yan, Yao; Xu, Jian; Wiercigroch, Marian

    2017-09-01

    This paper investigates the effects of bistability in a nonsmooth time-delayed dynamical system, which is often manifested in science and engineering. Previous studies on cutting dynamics have demonstrated persistent coexistence of chatter and chatter-free responses in a bistable region located in the linearly stable zone. As there is no widely accepted definition of basins of attraction for time-delayed systems, bistable regions are coined as unsafe zones (UZs). Hence, we have attempted to define the basins of attraction and stability basins for a typical delayed system to get insight into the bistability in systems with time delays. Special attention was paid to the influences of delayed initial conditions, starting points, and states at time zero on the long-term dynamics of time-delayed systems. By using this concept, it has been confirmed that the chatter is prone to occur when the waviness frequency in the workpiece surface coincides with the effective natural frequency of the cutting process. Further investigations unveil a thin "boundary layer" inside the UZ in the immediate vicinity of the stability boundary, in which we observe an extremely fast growth of the chatter basin stability. The results reveal that the system is more stable when the initial cutting depth is smaller. The physics of the tool deflection at the instant of the tool-workpiece engagement is used to evaluate the cutting safety, and the safe level could be zero when the geometry of tool engagement is unfavorable. Finally, the basins of attraction are used to quench the chatter by a single strike, where the resultant "islands" offer an opportunity to suppress the chatter even when the cutting is very close to the stability boundary.

  6. A Comparison of Floating Car vs. Loop Detector Estimated Freeway Travel Time Delay

    Directory of Open Access Journals (Sweden)

    Zhongren Wang, Ph.D. P.E. T.E.

    2012-06-01

    Full Text Available Floating car- and loop detector-based methods are two different types of methods frequently used to collect travel time delay information across a freeway network. Sometimes, it is necessary to use them jointly to achieve the necessary freeway network coverage, due to the high labor costs for the floating car-based method and the indispensability of sufficient network instrumentation for the loop detector-based method. For example, both floating car- and loop detector-based methods were once used in the Highway Congestion Monitoring Program in the California Department of Transportation. It is therefore necessary to evaluate whether these two types of methods estimate similarly in terms of total travel time delay. To this end, corresponding delay information estimated using both types of methods from 37 freeway segments in the Greater Sacramento Area were collected and compared. It was found that these two types of methods do not estimate similarly in terms of total segment travel time delay. The mean absolute relative difference (MARD can be as high as 78%, especially when delay is defined using a lower reference speed, such as 56 km/h. However, in terms of total segment travel time, the loop detector and the modified floating car method estimated similarly. The MARD is 19%. It was also found that the estimation from the different methods did correlate fairly well, which provides a means of conversion when different methods are used to monitor the total delay across a freeway network. As a spin-off, it was also found that a 1.5 km spacing of loop detectors is sufficient to achieve the 19% MARD as compared with the modified floating car method in terms of total travel time estimation.

  7. Development of a Marx-coupled trigger generator with high voltages and low time delay

    Science.gov (United States)

    Hu, Yixiang; Zeng, Jiangtao; Sun, Fengju; Cong, Peitian; Su, Zhaofeng; Yang, Shi; Zhang, Xinjun; Qiu, Ai'ci

    2016-10-01

    Coupled by the Marx of the "JianGuang-I" facility, a high voltage, low time-delay trigger generator was developed. Working principles of this trigger generator and its key issues were described in detail. Structures of this generator were also carefully designed and optimized. Based on the "JianGuang-I" Marx generator, a test stand was established. And a series of experiment tests were carried out to the study performance of this trigger generator. Experiment results show that the output voltage of this trigger generator can be continuously adjusted from 58 kV to 384 kV. The time delay (from the beginning of the Marx-discharging pulse to the time that the output pulse of the trigger generator arises) of this trigger pulse is about 200 ns and its peak time (0%˜100%) is less than 50 ns. Experiment results also indicate that the time-delay jitter of trigger voltages decreases rapidly with the increase in the peak voltage of trigger pulses. When the trigger voltage is higher than 250 kV, the time-delay jitters (the standard deviation) are less than 7.7 ns.

  8. Estimating characteristic phase and delay from broadband interaural time difference tuning curves.

    Science.gov (United States)

    Lehmann, Jessica; Tellers, Philipp; Wagner, Hermann; Führ, Hartmut

    2015-02-01

    Characteristic delay and characteristic phase are shape parameters of interaural time difference tuning curves. The standard procedure for the estimation of these parameters is based on the measurement of delay curves measured for tonal stimuli with varying frequencies. Common to all procedures is the detection of a linear behavior of the phase spectrum. Hence a reliable estimate can only be expected if sufficiently many relevant frequencies are tested. Thus, the estimation precision depends on the given bandwidth. Based on a linear model, we develop and implement methods for the estimation of characteristic phase and delay from a single broadband tuning curve. We present two different estimation algorithms, one based on a Fourier-analytic interpretation of characteristic delay and phase, and the other based on mean square error minimization. Estimation precision and robustness of the algorithms are tested on artificially generated data with predetermined characteristic delay and phase values, and on sample data from electrophysiological measurements in birds and in mammals. Increasing the signal-to-noise ratio or the bandwidth increases the estimation accuracy of the algorithms. Frequency band location and strong rectification also affect the estimation accuracy. For realistic bandwidths and signal-to-noise ratios, the minimization algorithm reliably and robustly estimates characteristic delay and phase and is superior to the Fourier-analytic method. Bandwidth-dependent significance thresholds allow to assess whether the estimated characteristic delay and phase values are meaningful shape parameters of a measured tuning curve. These thresholds also indicate the sampling rates needed to obtain reliable estimates from interaural time difference tuning curves.

  9. Application of fuzzy adaptive control to a MIMO nonlinear time-delay pump-valve system.

    Science.gov (United States)

    Lai, Zhounian; Wu, Peng; Wu, Dazhuan

    2015-07-01

    In this paper, a control strategy to balance the reliability against efficiency is introduced to overcome the common off-design operation problem in pump-valve systems. The pump-valve system is a nonlinear multi-input-multi-output (MIMO) system with time delays which cannot be accurately measured but can be approximately modeled using Bernoulli Principle. A fuzzy adaptive controller is applied to approximate system parameters and achieve the control of delay-free model since the system model is inaccurate and the direct feedback linearization method cannot be applied. An extended Smith predictor is introduced to compensate time delays of the system using the inaccurate system model. The experiment is carried out to verify the effectiveness of the control strategy whose results show that the control performance is well achieved. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

  10. Time-delayed transition of normal-to-abnormal glow in pin-to-water discharge

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, S.-Y.; Byeon, Y.-S.; Yoo, S.; Hong, E. J.; Kim, S. B.; Yoo, S. J.; Ryu, S., E-mail: smryu@nfri.re.kr [Plasma Technology Research Center of National Fusion Research Institute, 37, Dongjangsan-ro, Gunsan-si, Jeollabuk-do, Gunsan 54004 (Korea, Republic of)

    2016-08-15

    Time-delayed transition of normal-to-abnormal glow was investigated in discharge between spoke-like pins and ultrapure water by applying AC-driven power at a frequency of 14.3 kHz at atmospheric pressure. The normal-to-abnormal transition can be recognized from the slope changes of current density, gas temperature, electrode temperature, and OH density. The slope changes took place in tens of minutes rather than just after discharge, in other words, the transition was delayed. The time-delay of the transition was caused by the interaction between the plasma and water. The plasma affected water properties, and then the water affected plasma properties.

  11. Decoding Delay Controlled Completion Time Reduction in Instantly Decodable Network Coding

    KAUST Repository

    Douik, Ahmed

    2016-06-27

    For several years, the completion time and the decoding delay problems in Instantly Decodable Network Coding (IDNC) were considered separately and were thought to act completely 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. This paper investigates the effect of controlling the decoding delay to reduce the completion time below its currently best-known solution in both perfect and imperfect feedback with persistent erasure channels. To solve the problem, the decodingdelay- dependent expressions of the users’ and overall completion times are derived in the complete feedback scenario. Although using such expressions to find the optimal overall completion time is NP-hard, the paper proposes two novel heuristics 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. Afterward, the paper extends the study to the imperfect feedback scenario in which uncertainties at the sender affects its ability to anticipate accurately the decoding delay increase at each user. The paper formulates the problem in such environment and derives the expression of the minimum increase in the completion time. Simulation results show the performance of the proposed solutions and suggest that both heuristics achieves a lower mean completion time as compared to the best-known heuristics for the completion time reduction in perfect and imperfect feedback. The gap in performance becomes more significant as the erasure of the channel increases.

  12. Continuous neural identifier for uncertain nonlinear systems with time delays in the input signal.

    Science.gov (United States)

    Alfaro-Ponce, M; Argüelles, A; Chairez, I

    2014-12-01

    Time-delay systems have been successfully used to represent the complexity of some dynamic systems. Time-delay is often used for modeling many real systems. Among others, biological and chemical plants have been described using time-delay terms with better results than those models that have not consider them. However, getting those models represented a challenge and sometimes the results were not so satisfactory. Non-parametric modeling offered an alternative to obtain suitable and usable models. Continuous neural networks (CNN) have been considered as a real alternative to provide models over uncertain non-parametric systems. This article introduces the design of a specific class of non-parametric model for uncertain time-delay system based on CNN considering the so-called delayed learning laws analysis. The convergence analysis as well as the learning laws were produced by means of a Lyapunov-Krasovskii functional. Three examples were developed to demonstrate the effectiveness of the modeling process forced by the identifier proposed in this study. The first example was a simple nonlinear model used as benchmark example. The second example regarded the human immunodeficiency virus dynamic behavior is used to show the performance of the suggested non-parametric identifier based on CNN for no fictitious neither academic models. Finally, a third example describing the evolution of hepatitis B virus served to test the identifier presented in this study and was also useful to provide evidence of its superior performance against a non-delayed identifier based on CNN. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Delay-time distribution in the scattering of time-narrow wave packets (II)—quantum graphs

    Science.gov (United States)

    Smilansky, Uzy; Schanz, Holger

    2018-02-01

    We apply the framework developed in the preceding paper in this series (Smilansky 2017 J. Phys. A: Math. Theor. 50 215301) to compute the time-delay distribution in the scattering of ultra short radio frequency pulses on complex networks of transmission lines which are modeled by metric (quantum) graphs. We consider wave packets which are centered at high wave number and comprise many energy levels. In the limit of pulses of very short duration we compute upper and lower bounds to the actual time-delay distribution of the radiation emerging from the network using a simplified problem where time is replaced by the discrete count of vertex-scattering events. The classical limit of the time-delay distribution is also discussed and we show that for finite networks it decays exponentially, with a decay constant which depends on the graph connectivity and the distribution of its edge lengths. We illustrate and apply our theory to a simple model graph where an algebraic decay of the quantum time-delay distribution is established.

  14. Estimation of time delay and wavelength shift for highly nonlinear multilayer waveguide by using time transformation approach

    Science.gov (United States)

    Chatterjee, Roshmi; Basu, Mousumi

    2018-02-01

    The well known time transformation method is used here to derive the temporal and spectral electric field distribution at the output end of a multilayer waveguide which consists of different layers of Kerr nonlinear media. A highly nonlinear CS 3-68 glass is considered as one of the materials of the waveguide which mainly comprises of different chalcogenide glass layers. The results indicate that there is sufficient time delay as well as frequency shift between the input and output pulses which is associated with the phenomenon of adiabatic wavelength conversion (AWC). Depending on different arrangements of materials, the time delay and frequency shift can be changed. As a result an input pulse in visible green region can be blue-shifted or red-shifted according to the choices of refractive index of the non-dispersive Kerr nonlinear media. The results show that under certain conditions the input pulse is broadened or compressed for different combinations of materials. This process of AWC also includes the variation of temporal and spectral phase, time delay, temporal peak power etc. For different input pulse shapes the change in time delay is also presented. The study may be useful to find applications of AWC in optical resonators or optical signal processing to be applicable to different photonic devices.

  15. Effect of delayed polymerization time and bracket manipulation on orthodontic bracket bonding

    Science.gov (United States)

    Ponikvar, Michael J.

    This study examined the effect of bracket manipulation in combination with delayed polymerization times on orthodontic bracket shear bond strength and degree of resin composite conversion. Orthodontics brackets were bonded to extracted third molars in a simulated oral environment after a set period of delayed polymerization time and bracket manipulation. After curing the bracket adhesive, each bracket underwent shear bond strength testing followed by micro-Raman spectroscopy analysis to measure the degree of conversion of the resin composite. Results demonstrated the shear bond strength and the degree of conversion of ceramic brackets did not vary over time. However, with stainless steel brackets there was a significant effect (p ≤ 0.05) of delay time on shear bond strength between the 0.5 min and 10 min bracket groups. In addition, stainless steel brackets showed significant differences related to degree of conversion over time between the 0.5 min and 5 min groups, in addition to the 0.5 min and 10 min groups. This investigation suggests that delaying bracket adhesive polymerization up to a period of 10 min then adjusting the orthodontic bracket may increase both shear bond strength and degree of conversion of stainless steel brackets while having no effect on ceramic brackets.

  16. Delayed School Start Times and Adolescent Sleep: A Systematic Review of the Experimental Evidence

    OpenAIRE

    Minges, Karl E.; Redeker, Nancy S.

    2015-01-01

    Many schools have instituted later morning start times to improve sleep, academic, and other outcomes in response to the mismatch between youth circadian rhythms and early morning start times. However, there has been no systematic synthesis of the evidence on the effects of this practice. To examine the impact of delayed school start time on students’ sleep, health, and academic outcomes, electronic databases were systematically searched and data were extracted using the Preferred Reporting I...

  17. TimeDelay-ARACNE: Reverse engineering of gene networks from time-course data by an information theoretic approach

    Directory of Open Access Journals (Sweden)

    Morganella Sandro

    2010-03-01

    Full Text Available Abstract Background One of main aims of Molecular Biology is the gain of knowledge about how molecular components interact each other and to understand gene function regulations. Using microarray technology, it is possible to extract measurements of thousands of genes into a single analysis step having a picture of the cell gene expression. Several methods have been developed to infer gene networks from steady-state data, much less literature is produced about time-course data, so the development of algorithms to infer gene networks from time-series measurements is a current challenge into bioinformatics research area. In order to detect dependencies between genes at different time delays, we propose an approach to infer gene regulatory networks from time-series measurements starting from a well known algorithm based on information theory. Results In this paper we show how the ARACNE (Algorithm for the Reconstruction of Accurate Cellular Networks algorithm can be used for gene regulatory network inference in the case of time-course expression profiles. The resulting method is called TimeDelay-ARACNE. It just tries to extract dependencies between two genes at different time delays, providing a measure of these dependencies in terms of mutual information. The basic idea of the proposed algorithm is to detect time-delayed dependencies between the expression profiles by assuming as underlying probabilistic model a stationary Markov Random Field. Less informative dependencies are filtered out using an auto calculated threshold, retaining most reliable connections. TimeDelay-ARACNE can infer small local networks of time regulated gene-gene interactions detecting their versus and also discovering cyclic interactions also when only a medium-small number of measurements are available. We test the algorithm both on synthetic networks and on microarray expression profiles. Microarray measurements concern S. cerevisiae cell cycle, E. coli SOS pathways and a

  18. TimeDelay-ARACNE: Reverse engineering of gene networks from time-course data by an information theoretic approach.

    Science.gov (United States)

    Zoppoli, Pietro; Morganella, Sandro; Ceccarelli, Michele

    2010-03-25

    One of main aims of Molecular Biology is the gain of knowledge about how molecular components interact each other and to understand gene function regulations. Using microarray technology, it is possible to extract measurements of thousands of genes into a single analysis step having a picture of the cell gene expression. Several methods have been developed to infer gene networks from steady-state data, much less literature is produced about time-course data, so the development of algorithms to infer gene networks from time-series measurements is a current challenge into bioinformatics research area. In order to detect dependencies between genes at different time delays, we propose an approach to infer gene regulatory networks from time-series measurements starting from a well known algorithm based on information theory. In this paper we show how the ARACNE (Algorithm for the Reconstruction of Accurate Cellular Networks) algorithm can be used for gene regulatory network inference in the case of time-course expression profiles. The resulting method is called TimeDelay-ARACNE. It just tries to extract dependencies between two genes at different time delays, providing a measure of these dependencies in terms of mutual information. The basic idea of the proposed algorithm is to detect time-delayed dependencies between the expression profiles by assuming as underlying probabilistic model a stationary Markov Random Field. Less informative dependencies are filtered out using an auto calculated threshold, retaining most reliable connections. TimeDelay-ARACNE can infer small local networks of time regulated gene-gene interactions detecting their versus and also discovering cyclic interactions also when only a medium-small number of measurements are available. We test the algorithm both on synthetic networks and on microarray expression profiles. Microarray measurements concern S. cerevisiae cell cycle, E. coli SOS pathways and a recently developed network for in vivo

  19. Time delay and duration of ionospheric total electron content responses to geomagnetic disturbances

    Directory of Open Access Journals (Sweden)

    J. Liu

    2010-03-01

    Full Text Available Although positive and negative signatures of ionospheric storms have been reported many times, global characteristics such as the time of occurrence, time delay and duration as well as their relations to the intensity of the ionospheric storms have not received enough attention. The 10 years of global ionosphere maps (GIMs of total electron content (TEC retrieved at Jet Propulsion Laboratory (JPL were used to conduct a statistical study of the time delay of the ionospheric responses to geomagnetic disturbances. Our results show that the time delays between geomagnetic disturbances and TEC responses depend on season, magnetic local time and magnetic latitude. In the summer hemisphere at mid- and high latitudes, the negative storm effects can propagate to the low latitudes at post-midnight to the morning sector with a time delay of 4–7 h. As the earth rotates to the sunlight, negative phase retreats to higher latitudes and starts to extend to the lower latitude toward midnight sector. In the winter hemisphere during the daytime and after sunset at mid- and low latitudes, the negative phase appearance time is delayed from 1–10 h depending on the local time, latitude and storm intensity compared to the same area in the summer hemisphere. The quick response of positive phase can be observed at the auroral area in the night-side of the winter hemisphere. At the low latitudes during the dawn-noon sector, the ionospheric negative phase responses quickly with time delays of 5–7 h in both equinoctial and solsticial months. Our results also manifest that there is a positive correlation between the intensity of geomagnetic disturbances and the time duration of both the positive phase and negative phase. The durations of both negative phase and positive phase have clear latitudinal, seasonal and magnetic local time (MLT dependence. In the winter hemisphere, long durations for the positive phase are 8–11 h and 12–14 h during the daytime at middle

  20. Time delay and duration of ionospheric total electron content responses to geomagnetic disturbances

    Directory of Open Access Journals (Sweden)

    J. Liu

    2010-03-01

    Full Text Available Although positive and negative signatures of ionospheric storms have been reported many times, global characteristics such as the time of occurrence, time delay and duration as well as their relations to the intensity of the ionospheric storms have not received enough attention. The 10 years of global ionosphere maps (GIMs of total electron content (TEC retrieved at Jet Propulsion Laboratory (JPL were used to conduct a statistical study of the time delay of the ionospheric responses to geomagnetic disturbances. Our results show that the time delays between geomagnetic disturbances and TEC responses depend on season, magnetic local time and magnetic latitude. In the summer hemisphere at mid- and high latitudes, the negative storm effects can propagate to the low latitudes at post-midnight to the morning sector with a time delay of 4–7 h. As the earth rotates to the sunlight, negative phase retreats to higher latitudes and starts to extend to the lower latitude toward midnight sector. In the winter hemisphere during the daytime and after sunset at mid- and low latitudes, the negative phase appearance time is delayed from 1–10 h depending on the local time, latitude and storm intensity compared to the same area in the summer hemisphere. The quick response of positive phase can be observed at the auroral area in the night-side of the winter hemisphere. At the low latitudes during the dawn-noon sector, the ionospheric negative phase responses quickly with time delays of 5–7 h in both equinoctial and solsticial months.

    Our results also manifest that there is a positive correlation between the intensity of geomagnetic disturbances and the time duration of both the positive phase and negative phase. The durations of both negative phase and positive phase have clear latitudinal, seasonal and magnetic local time (MLT dependence. In the winter hemisphere, long durations for the positive phase are 8–11 h and 12–14 h during the daytime at

  1. Systematic identification and robust control design for uncertain time delay processes

    DEFF Research Database (Denmark)

    Huusom, Jakob Kjøbsted; Poulsen, Niels Kjølstad; Jørgensen, Sten Bay

    be effectively rejected. We proposed a model predictive control implementation with a dead-band on the penalty of the tracking error as a mean to achieve good closed loop performance on time delay system. We have in simulation tested our controller on a SISO system of an industrial furnace and a MIMO system...

  2. Time Delay Estimation in Two-Phase Flow Investigation Using the γ-Ray Attenuation Technique

    Directory of Open Access Journals (Sweden)

    Robert Hanus

    2014-01-01

    Full Text Available Time delay estimation is an important research question having many applications in a range of technologies. Measurement of a two-phase flow in a pipeline or an open channel using radioisotopes is an example of such application. For instance, the determination of velocity of dispersed phase in that case is based on estimation of the time delay between two stochastic signals provided by scintillation probes. The proper analysis of such signals, usually in presence of noise, requires the use of advanced statistical signal processing. In this paper, the simulation studies of time delay estimation were carried out with the use of the following differential methods: average magnitude difference function, and average square difference function and proposed combined methods comprising the above-mentioned differential and cross-correlation functions are presented. Attached simulations have been carried out for models of stochastic signals corresponding to the signals obtained in gamma-ray absorption measurements of gas-liquid flow in a horizontal pipeline. The standard uncertainties of time delay estimations have been determined for each of the methods. Improved metrological properties have been stated in the combined methods in comparison with the classical cross-correlation procedure.

  3. Slow light in a semiconductor waveguide for true-time delay applications in microwave photonics

    DEFF Research Database (Denmark)

    Öhman, Filip; Yvind, Kresten; Mørk, Jesper

    2007-01-01

    We have investigated the slowand fast light properties of a semiconductor waveguide device employing concatenated gain and absorber sections. This letter presents the experimental results as well as theoretical modeling. A large phase shift of 110 and a true-time delay of more than 150 ps...

  4. The hyperbolic step potential: Anti-bound states, SUSY partners and Wigner time delays

    Energy Technology Data Exchange (ETDEWEB)

    Gadella, M. [Departamento de Física Teórica, Atómica y Óptica and IMUVA, Universidad de Valladolid, E-47011 Valladolid (Spain); Kuru, Ş. [Department of Physics, Faculty of Science, Ankara University, 06100 Ankara (Turkey); Negro, J., E-mail: jnegro@fta.uva.es [Departamento de Física Teórica, Atómica y Óptica and IMUVA, Universidad de Valladolid, E-47011 Valladolid (Spain)

    2017-04-15

    We study the scattering produced by a one dimensional hyperbolic step potential, which is exactly solvable and shows an unusual interest because of its asymmetric character. The analytic continuation of the scattering matrix in the momentum representation has a branch cut and an infinite number of simple poles on the negative imaginary axis which are related with the so called anti-bound states. This model does not show resonances. Using the wave functions of the anti-bound states, we obtain supersymmetric (SUSY) partners which are the series of Rosen–Morse II potentials. We have computed the Wigner reflection and transmission time delays for the hyperbolic step and such SUSY partners. Our results show that the more bound states a partner Hamiltonian has the smaller is the time delay. We also have evaluated time delays for the hyperbolic step potential in the classical case and have obtained striking similitudes with the quantum case. - Highlights: • The scattering matrix of hyperbolic step potential is studied. • The scattering matrix has a branch cut and an infinite number of poles. • The poles are associated to anti-bound states. • Susy partners using antibound states are computed. • Wigner time delays for the hyperbolic step and partner potentials are compared.

  5. Detecting Probable Cheating during Online Assessments Based on Time Delay and Head Pose

    Science.gov (United States)

    Chuang, Chia Yuan; Craig, Scotty D.; Femiani, John

    2017-01-01

    This study investigated the ability of test takers' behaviors during online assessments to detect probable cheating incidents. Specifically, this study focused on the role of time delay and head pose for detection of cheating incidences in a lab-based online testing session. The analysis of a test taker's behavior indicated that not only time…

  6. The time delay of patients presenting with symptoms of TB at TC ...

    African Journals Online (AJOL)

    Tuberculosis (TB) is a major health problem in South Africa. The early detection and treatment of TB cases are essential. The impression of senior staff working at the TC Newman Community Health Centre (TCN), Paarl was that there often is an unnecessary time delay between the presentation of TB symptoms and the ...

  7. Computation of stabilizing PI and PID controllers for processes with time delay.

    Science.gov (United States)

    Tan, Nusret

    2005-04-01

    In this paper, a new method for the computation of all stabilizing PI controllers for processes with time delay is given. The proposed method is based on plotting the stability boundary locus in the (kp, ki) plane and then computing the stabilizing values of the parameters of a PI controller for a given time delay system. The technique presented does not need to use Pade approximation and does not require sweeping over the parameters and also does not use linear programming to solve a set of inequalities. Thus it offers several important advantages over existing results obtained in this direction. Beyond stabilization, the method is used to compute stabilizing PI controllers which achieve user specified gain and phase margins. The proposed method is also used to design PID controllers for control systems with time delay. The limiting values of a PID controller which stabilize a given system with time delay are obtained in the (kp, ki) plane, (kp, kd) plane, and (ki, kd) plane. Examples are given to show the benefits of the method presented.

  8. Travelling Waves of an n-Species Food Chain Model with Spatial Diffusion and Time Delays

    OpenAIRE

    Fei Hu; Yuyin Xu; Z. Wang; Wei Ding

    2014-01-01

    We investigate an n-species food chain model with spatial diffusion and time delays. By using Schauder’s fixed point theorem, we obtain the result about the existence of the travelling wave solutions of the food chain model with reaction term satisfying the partial quasimonotonicity conditions.

  9. Travelling Waves of an n-Species Food Chain Model with Spatial Diffusion and Time Delays

    Directory of Open Access Journals (Sweden)

    Fei Hu

    2014-01-01

    Full Text Available We investigate an n-species food chain model with spatial diffusion and time delays. By using Schauder’s fixed point theorem, we obtain the result about the existence of the travelling wave solutions of the food chain model with reaction term satisfying the partial quasimonotonicity conditions.

  10. A real time QRS detection using delay-coordinate mapping for the microcontroller implementation.

    Science.gov (United States)

    Lee, Jeong-Whan; Kim, Kyeong-Seop; Lee, Bongsoo; Lee, Byungchae; Lee, Myoung-Ho

    2002-01-01

    In this article, we propose a new algorithm using the characteristics of reconstructed phase portraits by delay-coordinate mapping utilizing lag rotundity for a real-time detection of QRS complexes in ECG signals. In reconstructing phase portrait the mapping parameters, time delay, and mapping dimension play important roles in shaping of portraits drawn in a new dimensional space. Experimentally, the optimal mapping time delay for detection of QRS complexes turned out to be 20 ms. To explore the meaning of this time delay and the proper mapping dimension, we applied a fill factor, mutual information, and autocorrelation function algorithm that were generally used to analyze the chaotic characteristics of sampled signals. From these results, we could find the fact that the performance of our proposed algorithms relied mainly on the geometrical property such as an area of the reconstructed phase portrait. For the real application, we applied our algorithm for designing a small cardiac event recorder. This system was to record patients' ECG and R-R intervals for 1 h to investigate HRV characteristics of the patients who had vasovagal syncope symptom and for the evaluation, we implemented our algorithm in C language and applied to MIT/BIH arrhythmia database of 48 subjects. Our proposed algorithm achieved a 99.58% detection rate of QRS complexes.

  11. Implementation of High Time Delay Accuracy of Ultrasonic Phased Array Based on Interpolation CIC Filter

    Directory of Open Access Journals (Sweden)

    Peilu Liu

    2017-10-01

    Full Text Available In order to improve the accuracy of ultrasonic phased array focusing time delay, analyzing the original interpolation Cascade-Integrator-Comb (CIC filter, an 8× interpolation CIC filter parallel algorithm was proposed, so that interpolation and multichannel decomposition can simultaneously process. Moreover, we summarized the general formula of arbitrary multiple interpolation CIC filter parallel algorithm and established an ultrasonic phased array focusing time delay system based on 8× interpolation CIC filter parallel algorithm. Improving the algorithmic structure, 12.5% of addition and 29.2% of multiplication was reduced, meanwhile the speed of computation is still very fast. Considering the existing problems of the CIC filter, we compensated the CIC filter; the compensated CIC filter’s pass band is flatter, the transition band becomes steep, and the stop band attenuation increases. Finally, we verified the feasibility of this algorithm on Field Programming Gate Array (FPGA. In the case of system clock is 125 MHz, after 8× interpolation filtering and decomposition, time delay accuracy of the defect echo becomes 1 ns. Simulation and experimental results both show that the algorithm we proposed has strong feasibility. Because of the fast calculation, small computational amount and high resolution, this algorithm is especially suitable for applications with high time delay accuracy and fast detection.

  12. Generation of time delays: simplified models of intracellular signaling in cerebellar Purkinje cells

    NARCIS (Netherlands)

    Steuber, V.; Willshaw, D.; van Ooyen, A.

    2006-01-01

    In many neuronal systems, information is encoded in temporal spike patterns. The recognition and storage of temporal patterns requires the generation and modulation of time delays between inputs and outputs. In cerebellar Purkinje cells, stimulation of metabotropic glutamate receptors (mGluRs)

  13. Time delays prior to movement alter the drawing kinematics of elderly adults

    NARCIS (Netherlands)

    Romero, D.H.; Gemmert, A.W.A. van; Adler, C.H.; Bekkering, H.; Stelmach, G.E.

    2003-01-01

    Position sense has been found to decay as a function of the time delay the limb remains in a static position prior to movement onset. Position sense has also been found to deteriorate as a function of aging, with increased reliance on vision by the elderly. This study investigated whether the

  14. Time delays prior to movement alter the drawing kinematics of elderly adults

    NARCIS (Netherlands)

    Romero, DH; Van Gemmert, AWA; Adler, CH; Bekkering, H; Stelmach, GE

    Position sense has been found to decay as a function of the time delay the limb remains in a static position prior to movement onset. Position sense has also been found to deteriorate as a function of aging, with increased reliance on vision by the elderly. This study investigated whether the

  15. Multiagent System-Based Distributed Coordinated Control for Radial DC Microgrid Considering Transmission Time Delays

    DEFF Research Database (Denmark)

    Dou, Chun-Xia; Yue, Dong; Guerrero, Josep M.

    2017-01-01

    This paper focuses on a multi-agent based distributed coordinated control for radial DC microgrid considering trans-mission time delays. Firstly, a two-level multi-agent system is constructed, where local control is formulated based on local states and executed by means of the first-level agent...

  16. The WS transform for the Kuramoto model with distributed amplitudes, phase lag and time delay

    Science.gov (United States)

    Lohe, M. A.

    2017-12-01

    We apply the Watanabe–Strogatz (WS) transform to a generalized Kuramoto model with distributed parameters describing the amplitude of oscillation, phase lag, and time delay at each node of the system. The model has global coupling and identical frequencies, but allows for repulsive interactions at arbitrary nodes leading to conformist-contrarian phenomena together with variable amplitude and time-delay effects. We show how to determine the initial values of the WS system for any initial conditions for the Kuramoto system, and investigate the asymptotic behaviour of the WS variables. For the case of zero time delay the possible asymptotic configurations are determined by the sign of a single parameter μ which measures whether or not the attractive nodes dominate the repulsive nodes. If μ>0 the system completely synchronizes from general initial conditions, whereas if μ<0 one of two types of phase-locked synchronization occurs, depending on the initial values, while for μ=0 periodic solutions can occur. For the case of arbitrary non-uniform time delays we derive a stability condition for completely synchronized solutions.

  17. Using a Constant Time Delay Procedure to Teach Foundational Swimming Skills to Children with Autism

    Science.gov (United States)

    Rogers, Laura; Hemmeter, Mary Louise; Wolery, Mark

    2010-01-01

    The purpose of this study was to evaluate the effectiveness of using a constant time delay procedure to teach foundational swimming skills to three children with autism. The skills included flutter kick, front-crawl arm strokes, and head turns to the side. A multiple-probe design across behaviors and replicated across participants was used.…

  18. Statistical inference for discrete-time samples from affine stochastic delay differential equations

    DEFF Research Database (Denmark)

    Küchler, Uwe; Sørensen, Michael

    2013-01-01

    Statistical inference for discrete time observations of an affine stochastic delay differential equation is considered. The main focus is on maximum pseudo-likelihood estimators, which are easy to calculate in practice. A more general class of prediction-based estimating functions is investigated...

  19. The Impact of a Time Delay on the Depleted Proportion of the Viral ...

    African Journals Online (AJOL)

    Journal of the Nigerian Association of Mathematical Physics ... activity, the inclusion of a time delay which mimics the African culture of diverse health inhibiting belief system is a new numerical simulation perspective of solving the mathematical problem and the health policy dimension of HIV/AIDS intervention strategy.

  20. Small-Signal Analysis of the Microgrid Secondary Control Considering a Communication Time Delay

    DEFF Research Database (Denmark)

    Coelho, Ernane Antônio Alves; Wu, Dan; Guerrero, Josep M.

    2016-01-01

    , and an external power controller based on frequency and voltage droops. The frequency restoration function is implemented at the secondary control level, which executes a consensus algorithm that consists of a load-frequency control and a single time delay communication network. The consensus network consists...

  1. Microcontroller based system for electrical breakdown time delay measurement in gas-filled devices.

    Science.gov (United States)

    Pejović, Milić M; Denić, Dragan B; Pejović, Momčilo M; Nešić, Nikola T; Vasović, Nikola

    2010-10-01

    This paper presents realization of a digital embedded system for measuring electrical breakdown time delay. The proposed system consists of three major parts: dc voltage supply, analog subsystem, and a digital subsystem. Any dc power source with the range from 100 to 1000 V can be used in this application. The analog subsystem should provide fast and accurate voltage switching on the testing device as well as transform the signals that represent the voltage pulse on the device and the device breakdown into the form suitable for detection by a digital subsystem. The insulated gate bipolar transistor IRG4PH40KD driven by TC429 MOSFET driver is used for high voltage switching on the device. The aim of a digital subsystem is to detect the signals from the analog subsystem and to measure the elapsed time between their occurrences. Moreover, the digital subsystem controls various parameters that influence time delay and provides fast data storage for a large number of measured data. For this propose, we used the PIC18F4550 microcontroller with a full-speed compatible universal serial bus (USB) engine. Operation of this system is verified on different commercial and custom made gas devices with different structure and breakdown mechanisms. The electrical breakdown time delay measurements have been carried out as a function of several parameters, which dominantly influence electrical breakdown time delay. The obtained results have been verified using statistical methods, and they show good agreement with the theory. The proposed system shows good repeatability, sensitivity, and stability for measuring the electrical breakdown time delay.

  2. Improved exponential convergence result for generalized neural networks including interval time-varying delayed signals.

    Science.gov (United States)

    Rajchakit, G; Saravanakumar, R; Ahn, Choon Ki; Karimi, Hamid Reza

    2017-02-01

    This article examines the exponential stability analysis problem of generalized neural networks (GNNs) including interval time-varying delayed states. A new improved exponential stability criterion is presented by establishing a proper Lyapunov-Krasovskii functional (LKF) and employing new analysis theory. The improved reciprocally convex combination (RCC) and weighted integral inequality (WII) techniques are utilized to obtain new sufficient conditions to ascertain the exponential stability result of such delayed GNNs. The superiority of the obtained results is clearly demonstrated by numerical examples. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Energy harvesting of nonlinear damping system under time delayed feedback gain

    Directory of Open Access Journals (Sweden)

    Bichri A.

    2016-01-01

    Full Text Available This paper presents the application of delayed feedback velocity for optimizing the harvested power in cubic nonlinear damper system. We consider a harvester consisting of a nonlinear single degree of freedom system (spring-masse-damper subjected to a base excitation near the primary resonance. Analytical investigation using the multiple scales method is performed to obtain approximation of the amplitude response. This amplitude can be used to extract the average power. Results show that for appropriate values of the feedback gain, energy harvesting is more efficient at resonance compared to the cubic nonlinear damper system without time delay.

  4. Analysis on Passivity for Uncertain Neural Networks with Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    O. M. Kwon

    2014-01-01

    Full Text Available The problem of passivity analysis for neural networks with time-varying delays and parameter uncertainties is considered. By the consideration of newly constructed Lyapunov-Krasovskii functionals, improved sufficient conditions to guarantee the passivity of the concerned networks are proposed with the framework of linear matrix inequalities (LMIs, which can be solved easily by various efficient convex optimization algorithms. The enhancement of the feasible region of the proposed criteria is shown via two numerical examples by the comparison of maximum allowable delay bounds.

  5. Quasipolynomial Approach to Simultaneous Robust Control of Time-Delay Systems

    Directory of Open Access Journals (Sweden)

    Nikolaj Semenič

    2014-01-01

    Full Text Available A control law for retarded time-delay systems is considered, concerning infinite closed-loop spectrum assignment. An algebraic method for spectrum assignment is presented with a unique optimization algorithm for minimization of spectral abscissa and effective shaping of the chains of infinitely many closed-loop poles. Uncertainty of plant delays of a certain structure is considered in a sense of a robust simultaneous stabilization. Robust performance is achieved using mixed sensitivity design, which is incorporated into the addressed control law.

  6. Multi-scale approach for simulating time-delay biochemical reaction systems.

    Science.gov (United States)

    Niu, Yuanling; Burrage, Kevin; Zhang, Chengjian

    2015-02-01

    This study presents a multi-scale approach for simulating time-delay biochemical reaction systems when there are wide ranges of molecular numbers. The authors construct a new efficient approach based on partitioning into slow and fast subsets in conjunction with predictor-corrector methods. This multi-scale approach is shown to be much more efficient than existing methods such as the delay stochastic simulation algorithm and the modified next reaction method. Numerical testing on several important problems in systems biology confirms the accuracy and computational efficiency of this approach.

  7. Robust H∞ Filtering for Uncertain Neutral Stochastic Systems with Markovian Jumping Parameters and Time Delay

    Directory of Open Access Journals (Sweden)

    Yajun Li

    2015-01-01

    Full Text Available This paper deals with the robust H∞ filter design problem for a class of uncertain neutral stochastic systems with Markovian jumping parameters and time delay. Based on the Lyapunov-Krasovskii theory and generalized Finsler Lemma, a delay-dependent stability condition is proposed to ensure not only that the filter error system is robustly stochastically stable but also that a prescribed H∞ performance level is satisfied for all admissible uncertainties. All obtained results are expressed in terms of linear matrix inequalities which can be easily solved by MATLAB LMI toolbox. Numerical examples are given to show that the results obtained are both less conservative and less complicated in computation.

  8. Robust Exponential Stability Criteria of LPD Systems with Mixed Time-Varying Delays and Nonlinear Perturbations

    Directory of Open Access Journals (Sweden)

    Kanit Mukdasai

    2012-01-01

    Full Text Available This paper investigates the problem of robust exponential stability for linear parameter-dependent (LPD systems with discrete and distributed time-varying delays and nonlinear perturbations. Parameter dependent Lyapunov-Krasovskii functional, Leibniz-Newton formula, and linear matrix inequality are proposed to analyze the stability. On the basis of the estimation and by utilizing free-weighting matrices, new delay-dependent exponential stability criteria are established in terms of linear matrix inequalities (LMIs. Numerical examples are given to demonstrate the effectiveness and less conservativeness of the proposed methods.

  9. Global Exponential Stability of Delayed Cohen-Grossberg BAM Neural Networks with Impulses on Time Scales

    Directory of Open Access Journals (Sweden)

    Fei Yu

    2009-01-01

    Full Text Available Based on the theory of calculus on time scales, the homeomorphism theory, Lyapunov functional method, and some analysis techniques, sufficient conditions are obtained for the existence, uniqueness, and global exponential stability of the equilibrium point of Cohen-Grossberg bidirectional associative memory (BAM neural networks with distributed delays and impulses on time scales. This is the first time applying the time-scale calculus theory to unify the discrete-time and continuous-time Cohen-Grossberg BAM neural network with impulses under the same framework.

  10. Using the focal phase to control attosecond processes

    Science.gov (United States)

    Hoff, Dominik; Krüger, Michael; Maisenbacher, Lothar; Paulus, Gerhard G.; Hommelhoff, Peter; Sayler, A. M.

    2017-12-01

    The spatial evolution of the electric field of focused broadband light is crucial for many emerging attosecond technologies. Here the effects of the input beam parameters on the evolution of few-cycle laser pulses in the focus are discussed. Specifically, we detail how the frequency-dependent input beam geometry, chirp and chromatic aberration can affect the spatial dependence of the carrier-envelope phase (CEP), central frequency and pulse duration in the focus. These effects are confirmed by a direct, three-dimensional measurement of the CEP-evolution in the focus of a typical few-cycle pulse laser using electron rescattering at metal nanotips in combination with a CEP-metre. Moreover, we demonstrate a simple measurement technique to estimate the focal CEP evolution by input-beam parameters. These parameters can be used in novel ways in order to control attosecond dynamics and tailor highly nonlinear light–matter interactions.

  11. Modulation of attosecond beating in resonant two-photon ionization

    CERN Document Server

    Galán, Álvaro J; Martín, Fernando

    2014-01-01

    We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.

  12. Simplified stochastic models with time delay for studying the degradation process of mRNA molecules.

    Science.gov (United States)

    Tian, Tianhai

    2014-01-01

    Message RNA (mRNA) is the template for protein synthesis. It carries information from DNA in the nucleus to the ribosome sites of protein synthesis in the cell. The turnover process of mRNA is a chemical event with multiple small step reactions and the degradation of mRNA molecules is an important step in gene expression. A number of mathematical models have been proposed to study the dynamics of mRNA turnover, ranging from a one-step first order reaction model to the linear multi-component models. Although the linear multi-component models provide detailed dynamics of mRNA degradation, the simple first-order reaction model has been widely used in mathematical modelling of genetic regulatory networks. To illustrate the difference between these models, we first considered a stochastic model based on the multi-component model. Then a simpler stochastic model was proposed to approximate the linear multi-component model. We also discussed the delayed one-step reaction models with different types of time delay, including the constant delay, exponentially distributed delay and Erlang distributed delay. The comparison study suggested that the one-step reaction models failed to realise the dynamics of mRNA turnover accurately. Therefore, more sophisticated one-step reaction models are needed to study the dynamics of mRNA degradation.

  13. Time-delayed beam splitting with energy separation of x-ray channels

    Energy Technology Data Exchange (ETDEWEB)

    Stetsko, Yuri P.; Shvyd' ko, Yuri V.; Brian Stephenson, G. [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2013-10-21

    We introduce a time-delayed beam splitting method based on the energy separation of x-ray photon beams. It is implemented and theoretically substantiated on an example of an x-ray optical scheme similar to that of the classical Michelson interferometer. The splitter/mixer uses Bragg-case diffraction from a thin diamond crystal. Another two diamond crystals are used as back-reflectors. Because of energy separation and a minimal number (three) of optical elements, the split-delay line has high efficiency and is simple to operate. Due to the high transparency of diamond crystal, the split-delay line can be used in a beam sharing mode at x-ray free-electron laser facilities.

  14. Tunable microwave-photonic filter using frequency-to-time mapping-based delay lines.

    Science.gov (United States)

    Mokhtari, Arash; Jamshidi, Kambiz; Preußler, Stefan; Zadok, Avi; Schneider, Thomas

    2013-09-09

    A new implementation of microwave-photonic filters (MPFs) based on tunable optical delay lines is proposed and demonstrated. The variable delay is based on mapping of the spectral components of an incoming waveform onto the time domain, the application of linearly-varying temporal phase offsets, and an inverse mapping back to the frequency domain. The linear phase correction is equivalent to a frequency offset, and realized though suppressed-carrier single-sideband modulation by a radio-frequency sine wave. The variable delay element, controlled by the selected frequency, is used in one arm of a two-tap MPF. In a proof-of-concept experiment, the free spectral range (FSR) of the MPF was varied by over a factor of four: between 1.2 GHz and 5.3 GHz.

  15. Passivity analysis of memristor-based impulsive inertial neural networks with time-varying delays.

    Science.gov (United States)

    Wan, Peng; Jian, Jigui

    2018-02-15

    This paper focuses on delay-dependent passivity analysis for a class of memristive impulsive inertial neural networks with time-varying delays. By choosing proper variable transformation, the memristive inertial neural networks can be rewritten as first-order differential equations. The memristive model presented here is regarded as a switching system rather than employing the theory of differential inclusion and set-value map. Based on matrix inequality and Lyapunov-Krasovskii functional method, several delay-dependent passivity conditions are obtained to ascertain the passivity of the addressed networks. In addition, the results obtained here contain those on the passivity for the addressed networks without impulse effects as special cases and can also be generalized to other neural networks with more complex pulse interference. Finally, one numerical example is presented to show the validity of the obtained results. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

  16. Robust H∞ control of uncertain systems with two additive time-varying delays

    Science.gov (United States)

    Syed, Ali M.; Saravanakumar, R.

    2015-09-01

    This paper is concerned with the problem of delay-dependent robust H∞ control for a class of uncertain systems with two additive time-varying delays. A new suitable Lyapunov-Krasovskii functional (LKF) with triple integral terms is constructed and a tighter upper bound of the derivative of the LKF is derived. By applying a convex optimization technique, new delay-dependent robust H∞ stability criteria are derived in terms of linear matrix inequalities (LMI). Based on the stability criteria, a state feedback controller is designed such that the closed-loop system is asymptotically stable. Finally, numerical examples are given to illustrate the effectiveness of the proposed method. Comparison results show that our results are less conservative than the existing methods. Project supported by the Fund from the Department of Science and Technology of India (Grant No. SR/FTP/MS-039/2011).

  17. Stability and Stabilization of Networked Control System with Forward and Backward Random Time Delays

    Directory of Open Access Journals (Sweden)

    Ye-Guo Sun

    2012-01-01

    Full Text Available This paper deals with the problem of stabilization for a class of networked control systems (NCSs with random time delay via the state feedback control. Both sensor-to-controller and controller-to-actuator delays are modeled as Markov processes, and the resulting closed-loop system is modeled as a Markovian jump linear system (MJLS. Based on Lyapunov stability theorem combined with Razumikhin-based technique, a new delay-dependent stochastic stability criterion in terms of bilinear matrix inequalities (BMIs for the system is derived. A state feedback controller that makes the closed-loop system stochastically stable is designed, which can be solved by the proposed algorithm. Simulations are included to demonstrate the theoretical result.

  18. Lens Model and Time Delay Predictions for the Sextuply Lensed Quasar SDSS J2222+2745*

    Science.gov (United States)

    Sharon, Keren; Bayliss, Matthew B.; Dahle, Hakon; Florian, Michael K.; Gladders, Michael D.; Johnson, Traci L.; Paterno-Mahler, Rachel; Rigby, Jane R.; Whitaker, Katherine E.; Wuyts, Eva

    2017-01-01

    SDSS J2222+2745 is a galaxy cluster at z = 0.49, strongly lensing a quasar at z = 2.805 into six widely separated images. In recent Hubble Space Telescope imaging of the field, we identify additional multiply lensed galaxies and confirm the sixth quasar image that was identified by Dahle et al. We used the Gemini-North telescope to measure a spectroscopic redshift of z = 4.56 of one of the lensed galaxies. These data are used to refine the lens model of SDSS J2222+2745, compute the time delay and magnifications of the lensed quasar images, and reconstruct the source image of the quasar host and a lensed galaxy at z = 2.3. This galaxy also appears in absorption in our Gemini spectra of the lensed quasar, at a projected distance of 34 kpc. Our model is in agreement with the recent time delay measurements of Dahle et al., who found T(sub AB) = 47.7 +/- 6.0 days and T(sub AC) = 722 +/- 24 days. We use the observed time delays to further constrain the model, and find that the model-predicted time delays of the three faint images of the quasar are T(sub AD) = 502+/- 68 days, T( sub AE) = 611 +/- 75 days, and T(sub AF) = 415 +/- 72 days. We have initiated a follow-up campaign to measure these time delays with Gemini North. Finally, we present initial results from an X-ray monitoring program with Swift, indicating the presence of hard X-ray emission from the lensed quasar, as well as extended X-ray emission from the cluster itself, which is consistent with the lensing mass measurement and the cluster velocity dispersion.

  19. Nonlinear stabilization for a class of time delay systems via inverse optimality approach.

    Science.gov (United States)

    Ordaz, Patricio; Santos-Sánchez, Omar-Jacobo; Rodríguez-Guerrero, Liliam; González-Facundo, Alberto

    2017-03-01

    This paper is devoted to obtain a stabilizing optimal nonlinear controller based on the well known Control Lyapunov-Krasovskii Functional (CLKF) approach, aimed to solve the inverse optimality problem for a class of nonlinear time delay systems. To determine sufficient conditions for the Bellman's equation solution of the system under consideration, the CLKF and the inverse optimality approach are considered in this paper. In comparison with previous results, this scheme allows us to obtain less conservative controllers, implying energy saving (in terms of average power consumption for a specific thermo-electrical process). Sufficient delay-independent criteria in terms of CLKF is obtained such that the closed-loop nonlinear time-delay system is guaranteed to be local Asymptotically Stable. To illustrate the effectiveness of the theoretical results, a comparative study with an industrial PID controller tuned by the Ziegler-Nichols methodology (Z-N) and a Robust-PID tuned by using the D-partition method is presented by online experimental tests for an atmospheric drying process with time delay in its dynamics. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  20. Enhanced robust finite-time passivity for Markovian jumping discrete-time BAM neural networks with leakage delay.

    Science.gov (United States)

    Sowmiya, C; Raja, R; Cao, Jinde; Rajchakit, G; Alsaedi, Ahmed

    2017-01-01

    This paper is concerned with the problem of enhanced results on robust finite-time passivity for uncertain discrete-time Markovian jumping BAM delayed neural networks with leakage delay. By implementing a proper Lyapunov-Krasovskii functional candidate, the reciprocally convex combination method together with linear matrix inequality technique, several sufficient conditions are derived for varying the passivity of discrete-time BAM neural networks. An important feature presented in our paper is that we utilize the reciprocally convex combination lemma in the main section and the relevance of that lemma arises from the derivation of stability by using Jensen's inequality. Further, the zero inequalities help to propose the sufficient conditions for finite-time boundedness and passivity for uncertainties. Finally, the enhancement of the feasible region of the proposed criteria is shown via numerical examples with simulation to illustrate the applicability and usefulness of the proposed method.

  1. Power-Level Control for MHTGRs with Time-Delay in Helium Temperature Measurement

    Science.gov (United States)

    Dong, Zhe

    2014-06-01

    The modular high temperature gas-cooled reactor (MHTGR), which has the inherent safety feature, high thermal efficiency and satisfactory economic feasibility, can be applied for electricity and process heat production. Power-level control is an important technique for providing both the stable operation and load-following performance. Since the coolant temperature sensors of an MHTGR are usually installed near the primary side of the corresponding steam generator, there must be time-delay effect in the feedback loop of the coolant temperatures. Moreover, the measurement signal transducing may also induce time-delay effect. Therefore, it is meaningful to give the power-level control design method by considering this time-delay effect. In this paper, a simple output-feedback power-level control is proposed for the MHTGRs by using the delayed measurement signal of average reactor coolant temperature. In the aspect of theoretical analysis, a sufficient condition, under which it is well guaranteed that this newly-built power-level control is a globally asymptotic stabilizer, is firstly given. In the aspect of verification, numerical simulation results not only verify the feasibility of the theoretical results but also show the relationship between the performance and values of parameters of this novel power-level controller. The meaning of this work lies in two aspects. The first one is deeply revealing the relationship between the closed-loop stability and values of the controller parameters. The second one is giving the approach of designing a simple and effective power-level control strategy to suppress the negative influence induced by the time-delay in the feedback loop of the coolant temperatures.

  2. An Analysis of Cost Overruns and Time Delays of INDOT Projects

    OpenAIRE

    Bordat, Claire; McCullouch, Bob G.; Labi, Samuel; Sinha, Kumares C.

    2004-01-01

    A commonality among state Departments of Transportation is the inability to complete projects on time and within budget. This project assessed the extent of the problem of cost overruns, time delays, and change orders associated with Indiana Department of Transportation (INDOT) construction projects, identified the reasons for such problems, and finally developed a set of recommendations aimed at their future reduction. For comparison purposes, data from other states were collected and studie...

  3. Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction

    OpenAIRE

    Zapartas, E.; de, Mink SE; Izzard, Robert George; Yoon, S-C; Badenes, C.; Götberg, Y; de Koter A.; Neijssel, CJ; Renzo, M; Schootemeijer, A.; Shrotriya, TS

    2017-01-01

    Most massive stars, the progenitors of core-collapse supernovae, are in close binary systems and may interact with their companion through mass transfer or merging. We undertake a population synthesis study to compute the delay-time distribution of core-collapse supernovae, that is, the supernova rate versus time following a starburst, taking into account binary interactions. We test the systematic robustness of our results by running various simulations to account for the uncertainties in ou...

  4. Investigation of the delay time distribution of high power microwave surface flashover

    Science.gov (United States)

    Foster, J.; Krompholz, H.; Neuber, A.

    2011-01-01

    Characterizing and modeling the statistics associated with the initiation of gas breakdown has proven to be difficult due to a variety of rather unexplored phenomena involved. Experimental conditions for high power microwave window breakdown for pressures on the order of 100 to several 100 torr are complex: there are little to no naturally occurring free electrons in the breakdown region. The initial electron generation rate, from an external source, for example, is time dependent and so is the charge carrier amplification in the increasing radio frequency (RF) field amplitude with a rise time of 50 ns, which can be on the same order as the breakdown delay time. The probability of reaching a critical electron density within a given time period is composed of the statistical waiting time for the appearance of initiating electrons in the high-field region and the build-up of an avalanche with an inherent statistical distribution of the electron number. High power microwave breakdown and its delay time is of critical importance, since it limits the transmission through necessary windows, especially for high power, high altitude, low pressure applications. The delay time distribution of pulsed high power microwave surface flashover has been examined for nitrogen and argon as test gases for pressures ranging from 60 to 400 torr, with and without external UV illumination. A model has been developed for predicting the discharge delay time for these conditions. The results provide indications that field induced electron generation, other than standard field emission, plays a dominant role, which might be valid for other gas discharge types as well.

  5. Infinite dwell time and group delay in resonant electron tunneling through double complex potential barrier

    Science.gov (United States)

    Opacak, Nikola; Milanović, Vitomir; Radovanović, Jelena

    2017-12-01

    Tunneling times in complex potentials are investigated. Analytical expressions for dwell time, self-interference time and group delay are obtained for the case of complex double delta potentials. It is shown that we can always find a set of parameters of the potential so that the tunneling times achieve very large values and even approach infinity for the case of resonance. The phenomenon of infinite tunneling times occurs for only one particular positive value of the imaginary part of the potential, if all other parameters are given.

  6. Finite-Time Bounded Synchronization of the Growing Complex Network with Nondelayed and Delayed Coupling

    Directory of Open Access Journals (Sweden)

    Yuhua Xu

    2017-01-01

    Full Text Available The objective of this paper is to discuss finite-time bounded synchronization for a class of the growing complex network with nondelayed and delayed coupling. In order to realize finite-time synchronization of complex networks, a new finite-time stable theory is proposed; effective criteria are developed to realize synchronization of the growing complex dynamical network in finite time. Moreover, the error of two growing networks is bounded simultaneously in the process of finite-time synchronization. Finally, some numerical examples are provided to verify the theoretical results established in this paper.

  7. Causes of delay in door-to-balloon time in south-east Asian patients undergoing primary percutaneous coronary intervention.

    Directory of Open Access Journals (Sweden)

    Wen Jun Sim

    Full Text Available To evaluate causes and impact of delay in the door-to-balloon (D2B time for patients undergoing primary percutaneous coronary intervention (PPCI.From January 2009 to December 2012, 1268 patients (86% male, mean age of 58 ± 12 years presented to our hospital for ST-elevation myocardial infarction (STEMI and underwent PPCI. They were divided into two groups: Non-delay defined as D2B time ≤ 90 mins and delay group defined as D2B time > 90 mins. Data were collected retrospectively on baseline clinical characteristics, mode of presentation, angiographic findings, therapeutic modality and inhospital outcome.202 patients had delay in D2B time. There were more female patients in the delay group. They were older and tend to self-present to hospital. They were less likely to be smokers and have a higher prevalence of prior MI. The incidence of posterior MI was higher in the delay group. They also had a higher incidence of triple vessel disease. The 3 most common reasons for D2B delay was delay in the emergency department (39%, atypical clinical presentation (37.6% and unstable medical condition requiring stabilisation/computed tomographic imaging (26.7%. The inhospital mortality was numerically higher in the delay group (7.4% versus 4.8%, p = 0.12.Delay in D2B occurred in 16% of our patients undergoing PPCI. Several key factors for delay were identified and warrant further intervention.

  8. Causes of delay in door-to-balloon time in south-east Asian patients undergoing primary percutaneous coronary intervention.

    Science.gov (United States)

    Sim, Wen Jun; Ang, An Shing; Tan, Mae Chyi; Xiang, Wen Wei; Foo, David; Loh, Kwok Kong; Jafary, Fahim Haider; Watson, Timothy James; Ong, Paul Jau Lueng; Ho, Hee Hwa

    2017-01-01

    To evaluate causes and impact of delay in the door-to-balloon (D2B) time for patients undergoing primary percutaneous coronary intervention (PPCI). From January 2009 to December 2012, 1268 patients (86% male, mean age of 58 ± 12 years) presented to our hospital for ST-elevation myocardial infarction (STEMI) and underwent PPCI. They were divided into two groups: Non-delay defined as D2B time ≤ 90 mins and delay group defined as D2B time > 90 mins. Data were collected retrospectively on baseline clinical characteristics, mode of presentation, angiographic findings, therapeutic modality and inhospital outcome. 202 patients had delay in D2B time. There were more female patients in the delay group. They were older and tend to self-present to hospital. They were less likely to be smokers and have a higher prevalence of prior MI. The incidence of posterior MI was higher in the delay group. They also had a higher incidence of triple vessel disease. The 3 most common reasons for D2B delay was delay in the emergency department (39%), atypical clinical presentation (37.6%) and unstable medical condition requiring stabilisation/computed tomographic imaging (26.7%). The inhospital mortality was numerically higher in the delay group (7.4% versus 4.8%, p = 0.12). Delay in D2B occurred in 16% of our patients undergoing PPCI. Several key factors for delay were identified and warrant further intervention.

  9. Delayed school start times and adolescent sleep: A systematic review of the experimental evidence.

    Science.gov (United States)

    Minges, Karl E; Redeker, Nancy S

    2016-08-01

    Many schools have instituted later morning start times to improve sleep, academic, and other outcomes in response to the mismatch between youth circadian rhythms and early morning start times. However, there has been no systematic synthesis of the evidence on the effects of this practice. To examine the impact of delayed school start time on students' sleep, health, and academic outcomes, electronic databases were systematically searched and data were extracted using the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Six studies satisfied selection criteria and used pre-post, no control (n = 3), randomized controlled trial (n = 2), and quasi-experimental (n = 1) designs. School start times were delayed 25-60 min, and correspondingly, total sleep time increased from 25 to 77 min per weeknight. Some studies revealed reduced daytime sleepiness, depression, caffeine use, tardiness to class, and trouble staying awake. Overall, the evidence supports recent non-experimental study findings and calls for policy that advocates for delayed school start time to improve sleep. This presents a potential long-term solution to chronic sleep restriction during adolescence. However, there is a need for rigorous randomized study designs and reporting of consistent outcomes, including objective sleep measures and consistent measures of health and academic performance. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Chaos and Hopf bifurcation control in a fractional-order memristor-based chaotic system with time delay

    Science.gov (United States)

    Ding, Dawei; Qian, Xin; Hu, Wei; Wang, Nian; Liang, Dong

    2017-11-01

    In this paper, a time-delayed feedback controller is proposed in order to control chaos and Hopf bifurcation in a fractional-order memristor-based chaotic system with time delay. The associated characteristic equation is established by regarding the time delay as a bifurcation parameter. A set of conditions which ensure the existence of the Hopf bifurcation are gained by analyzing the corresponding characteristic equation. Then, we discuss the influence of feedback gain on the critical value of fractional order and time delay in the controlled system. Theoretical analysis shows that the controller is effective in delaying the Hopf bifurcation critical value via decreasing the feedback gain. Finally, some numerical simulations are presented to prove the validity of our theoretical analysis and confirm that the time-delayed feedback controller is valid in controlling chaos and Hopf bifurcation in the fractional-order memristor-based system.

  11. COMPARISON OF PI CONTROLLER PERFORMANCE FOR FIRST ORDER SYSTEMS WITH TIME DELAY

    Directory of Open Access Journals (Sweden)

    RAMAKOTESWARA RAO ALLA

    2017-04-01

    Full Text Available Delays appear often in all real world engineering systems. Delay systems have the property that the rate of variation in the system state depends on the previous states also. They are frequently a source of instability and poor system performance. In order to get the required performance from the delay system controller design plays a vital role. Because of the robust nature, easy structure Proportional Integral Derivative (PID controllers are extensively used in many industrial loops. Parameter tuning of the PID controller is an essential task. Numerous industrial processes, whose transfer function is of first order, can be easily controlled with PI controllers. This paper presents the comparative analysis of an approach based on Lambert W function for PI controller design for first order systems with time delay among Smith predictor (SP and ZeiglerNichols (ZN methods of design. Performance of the considered methods in terms of various performance specifications through simulation results has been illustrated. Results demonstrate that the Lambert W function based PI tuning results in adequate performance compared to other methods with respect to parameters settling time, overshoot, errors, etc.

  12. Robust Exponential Stability for Uncertain Discrete-Time Switched Systems with Interval Time-Varying Delay through a Switching Signal

    Directory of Open Access Journals (Sweden)

    Jenq-Der Chen

    2014-12-01

    Full Text Available This paper deals with the switching signal design to robust exponential stability for uncertain discrete-time switched systems with interval time-varying delay. The lower and upper bounds of the time-varying delay are assumed to be known. By construction of a new Lyapunov-Krasovskii functional and employing linear matrix inequality, some novel sufficient conditions are proposed to guarantee the global exponential stability for such system with parametric perturbations by using a switching signal. In addition, some nonnegative inequalities are used to provide additional degrees of freedom and reduce the conservativeness of systems. Finally, some numerical examples are given to illustrate performance of the proposed design methods.

  13. An optimal PID controller via LQR for standard second order plus time delay systems.

    Science.gov (United States)

    Srivastava, Saurabh; Misra, Anuraag; Thakur, S K; Pandit, V S

    2016-01-01

    An improved tuning methodology of PID controller for standard second order plus time delay systems (SOPTD) is developed using the approach of Linear Quadratic Regulator (LQR) and pole placement technique to obtain the desired performance measures. The pole placement method together with LQR is ingeniously used for SOPTD systems where the time delay part is handled in the controller output equation instead of characteristic equation. The effectiveness of the proposed methodology has been demonstrated via simulation of stable open loop oscillatory, over damped, critical damped and unstable open loop systems. Results show improved closed loop time response over the existing LQR based PI/PID tuning methods with less control effort. The effect of non-dominant pole on the stability and robustness of the controller has also been discussed. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

  14. Global exponential stability and dissipativity of generalized neural networks with time-varying delay signals.

    Science.gov (United States)

    Manivannan, R; Samidurai, R; Cao, Jinde; Alsaedi, Ahmed; Alsaadi, Fuad E

    2017-03-01

    This paper investigates the problems of exponential stability and dissipativity of generalized neural networks (GNNs) with time-varying delay signals. By constructing a novel Lyapunov-Krasovskii functionals (LKFs) with triple integral terms that contain more advantages of the state vectors of the neural networks, and the upper bound on the time-varying delay signals are formulated. We employ a new integral inequality technique (IIT), free-matrix-based (FMB) integral inequality approach, and Wirtinger double integral inequality (WDII) technique together with the reciprocally convex combination (RCC) approach to bound the time derivative of the LKFs. An improved exponential stability and strictly (Q,S,R)-γ-dissipative conditions of the addressed systems are represented by the linear matrix inequalities (LMIs). Finally, four interesting numerical examples are developed to verify the usefulness of the proposed method with a practical application to a biological network. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Robust Stability of Fractional Order Time-Delay Control Systems: A Graphical Approach

    Directory of Open Access Journals (Sweden)

    Radek Matušů

    2015-01-01

    Full Text Available The paper deals with a graphical approach to investigation of robust stability for a feedback control loop with an uncertain fractional order time-delay plant and integer order or fractional order controller. Robust stability analysis is based on plotting the value sets for a suitable range of frequencies and subsequent verification of the zero exclusion condition fulfillment. The computational examples present the typical shapes of the value sets of a family of closed-loop characteristic quasipolynomials for a fractional order plant with uncertain gain, time constant, or time-delay term, respectively, and also for combined cases. Moreover, the practically oriented example focused on robust stability analysis of main irrigation canal pool controlled by either classical integer order PID or fractional order PI controller is included as well.

  16. Observer-based approximate optimal tracking control for time-delay systems with external disturbances

    Science.gov (United States)

    Su, Hao; Tang, Gong-You

    2016-09-01

    This paper proposes a successive approximation design approach of observer-based optimal tracking controllers for time-delay systems with external disturbances. To solve a two-point boundary value problem with time-delay and time-advance terms and obtain the optimal tracking control law, two sequences of vector differential equations are constructed first. Second, the convergence of the sequences of the vector differential equations is proved to guarantee the existence and uniqueness of the control law. Third, a design algorithm of the optimal tracking control law is presented and the physically realisable problem is addressed by designing a disturbance state observer and a reference input state observer. An example of an industrial electric heater is given to demonstrate the efficiency of the proposed approach.

  17. Reliable filtering with strict dissipativity for T-S fuzzy time-delay systems.

    Science.gov (United States)

    Su, Xiaojie; Shi, Peng; Wu, Ligang; Basin, Michael V

    2014-12-01

    In this paper, the problem of reliable filter design with strict dissipativity has been investigated for a class of discrete-time T-S fuzzy time-delay systems. Our attention is focused on the design of a reliable filter to ensure a strictly dissipative performance for the filtering error system. Based on the reciprocally convex approach, firstly, a sufficient condition of reliable dissipativity analysis is proposed for T-S fuzzy systems with time-varying delays and sensor failures. Then, a reliable filter with strict dissipativity is designed by solving a convex optimization problem, which can be efficiently solved by standard numerical algorithms. Finally, numerical examples are provided to illustrate the effectiveness of the developed techniques.

  18. Internet based gripper teleoperation with random time delay by using haptic feedback and SEMG

    Science.gov (United States)

    Xu, Xiaonong; Song, Aiguo; Zhang, Huatao; Ji, Peng

    2016-10-01

    Random time delay may cause instability in the internet based teleoperation system. Transparency and intuitiveness are also very important for operator to control the system to accurately perform the desired action, especially for the gripper teleoperation system. This paper presents a new grip force control method of gripper teleoperation system with haptic feedback. The system employs the SEMG signal as the control parameter in order to enhance the intuitive control experience for operator. In order to eliminate the impacts on the system stability caused by random time delay, a non-time based teleoperation method is applied to the control process. Besides, neural network and designed fuzzy logic controller is also utilized to improve this control method. The effectiveness of the proposed method is demonstrated by experiment results.

  19. Tuning of IMC based PID controllers for integrating systems with time delay.

    Science.gov (United States)

    Kumar, D B Santosh; Padma Sree, R

    2016-07-01

    Design of Proportional Integral and Derivative (PID) controllers based on IMC principles for various types of integrating systems with time delay is proposed. PID parameters are given in terms of process model parameters and a tuning parameter. The tuning parameter is IMC filter time constant. In the present work, the IMC filter (Q) is chosen in such a manner that the order of the denominator of IMC controller is one less than the order of the numerator. The IMC filter time constant (λ) is tuned in such a way that a good compromise is made between performance and robustness for both servo and regulatory problems. To improve servo response of the controller a set point filter is designed such that the closed loop response is similar to that of first order plus time delay system. The proposed controller design method is applied to various transfer function models and to the non-linear model equations of jacketed CSTR to demonstrate its applicability and effectiveness. The performance of the proposed controller is compared with the recently reported methods in terms of IAE and ITAE. The smooth functioning of the controller is determined in terms of total variation and compared with recently reported methods. Simulation studies are carried out on various integrating systems with time delay to show the effectiveness and superiority of the proposed controllers. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

  20. The dynamics of the HIV infection: a time-delay differential equation approach

    CERN Document Server

    Bacelar, Flora S; Santos, Rita M Zorzenon dos

    2010-01-01

    In this work we introduce a differential equation model with time-delay that describes the three-stage dynamics and the two time scales observed in HIV infection. Assuming that the virus has high mutation and rapid reproduction rates that stress the immune system throughout the successive activation of new responses to new undetectable strains, the delay term describes the time interval necessary to mount new specific immune responses. This single term increases the number of possible solutions and changes the phase space dynamics if compared to the model without time delay. We observe very slow transits near the unstable fixed point, corresponding to a healthy state, and long time decay to the stable fixed point that corresponds to the infected state. In contrast to the results obtained for models using regular ODE, which only allow for partial descriptions of the course of the infection, our model describes the entire course of infection observed in infected patients: the primary infection, the latency peri...

  1. Simulation of hard X-ray time delays in solar flares

    Directory of Open Access Journals (Sweden)

    Yuri E. Charikov

    2015-06-01

    The spectra were derived from HXR integral over the active region. They were interpreted on the basis of a model of kinetics of accelerated electrons propagating in the flaring loop with the given plasma concentration distribution and magnetic field configuration. The kinetics in question is governed by the processes of Coulomb scattering, reflecting in the converging magnetic field, and with the return current factored in. Solving the time-dependent relativistic Fokker–Planck equation for the given initial conditions allowed to find the time-dependent electron distribution function along the loop. The brightness distribution of the bremsstrahlung of HXR derived from the electron distribution functions was calculated for different quantum energies along the flaring loop and used to plot the time-delays spectra. The calculated data showed that decreasing time-delay spectra were tractable assuming regions of electrons acceleration and injection were separated. The distinction between time-delays spectra from the looptop and footpoints was established. Hence the measurements with high resolving power may produce comprehensive data on the processes of electron transport and acceleration during solar flares.

  2. Photonic-assisted time-interleaved ADC based on optical delay line

    Science.gov (United States)

    Xu, Chen; Zheng, Shilie; Chen, Xinyi; Chi, Hao; Jin, Xiaofeng; Zhang, Xianmin

    2016-01-01

    An approach to implement photonic-assisted time-interleaved analog-to-digital conversion and its calibration method are presented. The analog modulated optical signal is divided into M channels, suffering different time delay induced by optical delay lines which provide great flexibility in producing time intervals and is then sampled by electronic analog-to-digital converters (ADCs). The channel mismatches resulting in performance degradation are estimated by a modified sine wave fitting method. The time mismatch and other mismatches are corrected by fine optical delay adjustment and digital processing, respectively. A four-channel photonic-assisted time-interleaved analog-to-digital converter (TIADC) system operating at 40 GSa s-1 was demonstrated experimentally. The photonic-assisted TIADC system was tested with a 6.31 GHz sine wave signal, exhibiting 40.3 dB signal-to-noise and distortion ratio (SINAD) and 57.6 dBc spurious-free dynamic range (SFDR). It is shown that the SINAD is dominated by the signal-to-noise ratio (SNR) of the analog optical link and the SFDR of the proposed system is limited by the linearity of the link.

  3. Force-linearization closure for non-Markovian Langevin systems with time delay

    Science.gov (United States)

    Loos, Sarah A. M.; Klapp, Sabine H. L.

    2017-07-01

    This paper is concerned with the Fokker-Planck (FP) description of classical stochastic systems with discrete time delay. The non-Markovian character of the corresponding Langevin dynamics naturally leads to a coupled infinite hierarchy of FP equations for the various n -time joint distribution functions. Here, we present an approach to close the hierarchy at the one-time level based on a linearization of the deterministic forces in all members of the hierarchy starting from the second one. This leads to a closed equation for the one-time probability density in the steady state. Considering two generic nonlinear systems, a colloidal particle in a sinusoidal or bistable potential supplemented by a linear delay force, we demonstrate that our approach yields a very accurate representation of the density as compared to quasiexact numerical results from direct solution of the Langevin equation. Moreover, the results are significantly improved against those from a small-delay approximation and a perturbation-theoretical approach. We also discuss the possibility of accessing transport-related quantities, such as escape times, based on an additional Kramers approximation. Our approach applies to a wide class of models with nonlinear deterministic forces.

  4. A position- and time-sensitive photon-counting detector with delay- line read-out

    Science.gov (United States)

    Jagutzki, Ottmar; Dangendorf, Volker; Lauck, Ronald; Czasch, Achim; Milnes, James

    2007-05-01

    We have developed image intensifier tubes with delay-anode read-out for time- and position-sensitive photon counting. The timing precision is better than 1 ns with 1000x1000 pixels position resolution and up to one megacounts/s processing rate. Large format detectors of 40 and 75 mm active diameter with internal helical-wire delay-line anodes have been produced and specified. A different type of 40 and 25 mm tubes with semi-conducting screen for image charge read-out allow for an economic and robust tube design and for placing the read-out anodes outside the sealed housing. Two types of external delay-line anodes, i.e. pick-up electrodes for the image charge, have been tested. We present tests of the detector and anode performance. Due to the low background this technique is well suited for applications with very low light intensity and especially if a precise time tagging for each photon is required. As an example we present the application of scintillator read-out in time-of-flight (TOF) neutron radiography. Further applications so far are Fluorescence Life-time Microscopy (FLIM) and Astronomy.

  5. The giant acoustic atom - a single quantum system with a deterministic time delay

    Science.gov (United States)

    Guo, Lingzhen; Grimsmo, Arne; Frisk Kockum, Anton; Pletyukhov, Mikhail; Johansson, Göran

    2017-04-01

    We investigate the quantum dynamics of a single transmon qubit coupled to surface acoustic waves (SAWs) via two distant connection points. Since the acoustic speed is five orders of magnitude slower than the speed of light, the travelling time between the two connection points needs to be taken into account. Therefore, we treat the transmon qubit as a giant atom with a deterministic time delay. We find that the spontaneous emission of the system, formed by the giant atom and the SAWs between its connection points, initially follows a polynomial decay law instead of an exponential one, as would be the case for a small atom. We obtain exact analytical results for the scattering properties of the giant atom up to two-phonon processes by using a diagrammatic approach. The time delay gives rise to novel features in the reflection, transmission, power spectra, and second-order correlation functions of the system. Furthermore, we find the short-time dynamics of the giant atom for arbitrary drive strength by a numerically exact method for open quantum systems with a finite-time-delay feedback loop. L. G. acknowledges financial support from Carl-Zeiss Stiftung (0563-2.8/508/2).

  6. Discovery of time-delayed gene regulatory networks based on temporal gene expression profiling

    Directory of Open Access Journals (Sweden)

    Guo Zheng

    2006-01-01

    Full Text Available Abstract Background It is one of the ultimate goals for modern biological research to fully elucidate the intricate interplays and the regulations of the molecular determinants that propel and characterize the progression of versatile life phenomena, to name a few, cell cycling, developmental biology, aging, and the progressive and recurrent pathogenesis of complex diseases. The vast amount of large-scale and genome-wide time-resolved data is becoming increasing available, which provides the golden opportunity to unravel the challenging reverse-engineering problem of time-delayed gene regulatory networks. Results In particular, this methodological paper aims to reconstruct regulatory networks from temporal gene expression data by using delayed correlations between genes, i.e., pairwise overlaps of expression levels shifted in time relative each other. We have thus developed a novel model-free computational toolbox termed TdGRN (Time-delayed Gene Regulatory Network to address the underlying regulations of genes that can span any unit(s of time intervals. This bioinformatics toolbox has provided a unified approach to uncovering time trends of gene regulations through decision analysis of the newly designed time-delayed gene expression matrix. We have applied the proposed method to yeast cell cycling and human HeLa cell cycling and have discovered most of the underlying time-delayed regulations that are supported by multiple lines of experimental evidence and that are remarkably consistent with the current knowledge on phase characteristics for the cell cyclings. Conclusion We established a usable and powerful model-free approach to dissecting high-order dynamic trends of gene-gene interactions. We have carefully validated the proposed algorithm by applying it to two publicly available cell cycling datasets. In addition to uncovering the time trends of gene regulations for cell cycling, this unified approach can also be used to study the complex

  7. Producing High Intense Attosecond Pulse Train by Interaction of Three-Color Pulse and Overdense Plasma

    Science.gov (United States)

    Salehi, M.; Mirzanejad, S.

    2017-05-01

    Amplifying the attosecond pulse by the chirp pulse amplification method is impossible. Furthermore, the intensity of attosecond pulse is low in the interaction of laser pulse and underdense plasma. This motivates us to propose using a multi-color pulse to produce the high intense attosecond pulse. In the present study, the relativistic interaction of a three-color linearly-polarized laser-pulse with highly overdense plasma is studied. We show that the combination of {{ω }}1, {{ω }}2 and {{ω }}3 frequencies decreases the instance full width at half maximum reflected attosecond pulse train from the overdense plasma surface. Moreover, we show that the three-color pulse increases the intensity of generated harmonics, which is explained by the relativistic oscillating mirror model. The obtained results demonstrate that if the three-color laser pulse interacts with overdense plasma, it will enhance two orders of magnitude of intensity of ultra short attosecond pulses in comparison with monochromatic pulse.

  8. Emergent bimodality and switch induced by time delays and noises in a synthetic gene circuit

    Science.gov (United States)

    Zhang, Chun; Du, Liping; Xie, Qingshuang; Wang, Tonghuan; Zeng, Chunhua; Nie, Linru; Duan, Weilong; Jia, Zhenglin; Wang, Canjun

    2017-10-01

    Based on the kinetic model for obtaining emergent bistability proposed by Tan et al. (2009), the effects of the fluctuations of protein synthesis rate and maximum dilution rate, the cross-correlation between two noises, and the time delay and the strength of the feedback loop in the synthetic gene circuit have been investigated through theoretical analysis and numerical simulation. Our results show that: (i) the fluctuations of protein synthesis rate and maximum dilution rate enhance the emergent bimodality of the probability distribution phenomenon, while the cross-correlation between two noises(λ), the time delay(τ) and the strength of the feedback loop(K) cause it to disappear; and (ii) the mean first passage time(MFPT) as functions of the noise strengths exhibits a maximum, this maximum is called noise-delayed switching (NDS) of the high concentration state. The NDS phenomenon shows that the noise can modify the stability of a metastable system in a counterintuitive way, the system remains in the metastable state for a longer time compared to the deterministic case. And the τ and the K enhances the stability of the ON state. The physical mechanisms for the switch between the ON and OFF states can be explained from the point of view of the effective potential.

  9. Dynamical Analysis of the Hindmarsh-Rose Neuron With Time Delays.

    Science.gov (United States)

    Lakshmanan, S; Lim, C P; Nahavandi, S; Prakash, M; Balasubramaniam, P

    2017-08-01

    This brief is mainly concerned with a series of dynamical analyses of the Hindmarsh-Rose (HR) neuron with state-dependent time delays. The dynamical analyses focus on stability, Hopf bifurcation, as well as chaos and chaos control. Through the stability and bifurcation analysis, we determine that increasing the external current causes the excitable HR neuron to exhibit periodic or chaotic bursting/spiking behaviors and emit subcritical Hopf bifurcation. Furthermore, by choosing a fixed external current and varying the time delay, the stability of the HR neuron is affected. We analyze the chaotic behaviors of the HR neuron under a fixed external current through time series, bifurcation diagram, Lyapunov exponents, and Lyapunov dimension. We also analyze the synchronization of the chaotic time-delayed HR neuron through nonlinear control. Based on an appropriate Lyapunov-Krasovskii functional with triple integral terms, a nonlinear feedback control scheme is designed to achieve synchronization between the uncontrolled and controlled models. The proposed synchronization criteria are derived in terms of linear matrix inequalities to achieve the global asymptotical stability of the considered error model under the designed control scheme. Finally, numerical simulations pertaining to stability, Hopf bifurcation, periodic, chaotic, and synchronized models are provided to demonstrate the effectiveness of the derived theoretical results.

  10. Advances in high-order harmonic generation sources for time-resolved investigations

    Energy Technology Data Exchange (ETDEWEB)

    Reduzzi, Maurizio [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Carpeggiani, Paolo [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Kühn, Sergei [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Calegari, Francesca [Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Nisoli, Mauro; Stagira, Salvatore [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Vozzi, Caterina [Institute of Photonics and Nanotechnologies, CNR-IFN, Piazza Leonardo da Vinci 32, 20133 Milano (Italy); Dombi, Peter [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Wigner Research Center for Physics, 1121 Budapest (Hungary); Kahaly, Subhendu [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Tzallas, Paris; Charalambidis, Dimitris [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Foundation for Research and Technology – Hellas, Institute of Electronic Structure and Lasers, P.O. Box 1527, GR-711 10 Heraklion, Crete (Greece); Varju, Katalin [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); Department of Optics and Quantum Electronics, University of Szeged, Dóm tér 9, 6720 Szeged (Hungary); Osvay, Karoly [ELI-ALPS, ELI-Hu Kft., Dugonics ter 13, H-6720 Szeged (Hungary); and others

    2015-10-15

    We review the main research directions ongoing in the development of extreme ultraviolet sources based on high-harmonic generation for the synthesization and application of trains and isolated attosecond pulses to time-resolved spectroscopy. A few experimental and theoretical works will be discussed in connection to well-established attosecond techniques. In this context, we present the unique possibilities offered for time-resolved investigations on the attosecond timescale by the new Extreme Light Infrastructure Attosecond Light Pulse Source, which is currently under construction.

  11. About Robust Stability of Dynamic Systems with Time Delays through Fixed Point Theory

    Directory of Open Access Journals (Sweden)

    2009-02-01

    Full Text Available This paper investigates the global asymptotic stability independent of the sizes of the delays of linear time-varying systems with internal point delays which possess a limiting equation via fixed point theory. The error equation between the solutions of the limiting equation and that of the current one is considered as a perturbation equation in the fixed- point and stability analyses. The existence of a unique fixed point which is later proved to be an asymptotically stable equilibrium point is investigated. The stability conditions are basically concerned with the matrix measure of the delay-free matrix of dynamics to be negative and to have a modulus larger than the contribution of the error dynamics with respect to the limiting one. Alternative conditions are obtained concerned with the matrix dynamics for zero delay to be negative and to have a modulus larger than an appropriate contributions of the error dynamics of the current dynamics with respect to the limiting one. Since global stability is guaranteed under some deviation of the current solution related to the limiting one, which is considered as nominal, the stability is robust against such errors for certain tolerance margins.

  12. Exponential Stability of the Monotubular Heat Exchanger Equation with Time Delay in Boundary Observation

    Directory of Open Access Journals (Sweden)

    Xue-Lian Jin

    2017-01-01

    Full Text Available The exponential stability of the monotubular heat exchanger equation with boundary observation possessing a time delay and inner control was investigated. Firstly, the close-loop system was translated into an abstract Cauchy problem in the suitable state space. A uniformly bounded C0-semigroup generated by the close-loop system, which implies that the unique solution of the system exists, was shown. Secondly, the spectrum configuration of the closed-loop system was analyzed and the eventual differentiability and the eventual compactness of the semigroup were shown by the resolvent estimates on some resolvent sets. This implies that the spectrum-determined growth assumption holds. Finally, a sufficient condition, which is related to the physical parameters in the system and is independent of the time delay, of the exponential stability of the closed-loop system was given.

  13. Robustness analysis of uncertain dynamical neural networks with multiple time delays.

    Science.gov (United States)

    Senan, Sibel

    2015-10-01

    This paper studies the problem of global robust asymptotic stability of the equilibrium point for the class of dynamical neural networks with multiple time delays with respect to the class of slope-bounded activation functions and in the presence of the uncertainties of system parameters of the considered neural network model. By using an appropriate Lyapunov functional and exploiting the properties of the homeomorphism mapping theorem, we derive a new sufficient condition for the existence, uniqueness and global robust asymptotic stability of the equilibrium point for the class of neural networks with multiple time delays. The obtained stability condition basically relies on testing some relationships imposed on the interconnection matrices of the neural system, which can be easily verified by using some certain properties of matrices. An instructive numerical example is also given to illustrate the applicability of our result and show the advantages of this new condition over the previously reported corresponding results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Path Tracking Control of Automatic Parking Cloud Model considering the Influence of Time Delay

    Directory of Open Access Journals (Sweden)

    Yiding Hua

    2017-01-01

    Full Text Available This paper establishes the kinematic model of the automatic parking system and analyzes the kinematic constraints of the vehicle. Furthermore, it solves the problem where the traditional automatic parking system model fails to take into account the time delay. Firstly, based on simulating calculation, the influence of time delay on the dynamic trajectory of a vehicle in the automatic parking system is analyzed under the transverse distance Dlateral between different target spaces. Secondly, on the basis of cloud model, this paper utilizes the tracking control of an intelligent path closer to human intelligent behavior to further study the Cloud Generator-based parking path tracking control method and construct a vehicle path tracking control model. Moreover, tracking and steering control effects of the model are verified through simulation analysis. Finally, the effectiveness and timeliness of automatic parking controller in the aspect of path tracking are tested through a real vehicle experiment.

  15. Sliding-Mode Synchronization Control for Uncertain Fractional-Order Chaotic Systems with Time Delay

    Directory of Open Access Journals (Sweden)

    Haorui Liu

    2015-06-01

    Full Text Available Specifically setting a time delay fractional financial system as the study object, this paper proposes a single controller method to eliminate the impact of model uncertainty and external disturbances on the system. The proposed method is based on the stability theory of Lyapunov sliding-mode adaptive control and fractional-order linear systems. The controller can fit the system state within the sliding-mode surface so as to realize synchronization of fractional-order chaotic systems. Analysis results demonstrate that the proposed single integral, sliding-mode control method can control the time delay fractional power system to realize chaotic synchronization, with strong robustness to external disturbance. The controller is simple in structure. The proposed method was also validated by numerical simulation.

  16. The effect of laser wavelength on the delay time of laser triggered vacuum switch

    Science.gov (United States)

    Xin, Yinan; He, Zhenghao; Liu, Yuchen

    2017-11-01

    The study on the influence of laser wavelength on the initial plasma properties of laser-triggered vacuum switch (LTVS) is not only beneficial to understanding the trigger mechanism but also to optimizing its design for miniaturization and generalization. In this paper, the one-dimensional heat conduction model of the target was developed and then the effect of laser wavelength on the depth of laser ablation and the quantity of initial plasma were investigated experimentally and theoretically with the laser absorption rate. The theoretical analysis was in good agreement with experimental measurement of the delay time of the LTVS. It is clear that the shorter the wavelength, the shorter the delay time will be after the LTVS is triggered.

  17. Signal Subspace Smoothing Technique for Time Delay Estimation Using MUSIC Algorithm.

    Science.gov (United States)

    Sun, Meng; Wang, Yide; Le Bastard, Cédric; Pan, Jingjing; Ding, Yuehua

    2017-12-10

    In civil engineering, Time Delay Estimation (TDE) is one of the most important tasks for the media structure and quality evaluation. In this paper, the MUSIC algorithm is applied to estimate the time delay. In practice, the backscattered echoes are highly correlated (even coherent). In order to apply the MUSIC algorithm, an adaptation of signal subspace smoothing is proposed to decorrelate the correlation between echoes. Unlike the conventional sub-band averaging techniques, we propose to directly use the signal subspace, which can take full advantage of the signal subspace and reduce the influence of noise. Moreover, the proposed method is adapted to deal with any radar pulse shape. The proposed method is tested on both numerical and experimental data. Both results show the effectiveness of the proposed method.

  18. Discontinuous attractor dimension at the synchronization transition of time-delayed chaotic systems.

    Science.gov (United States)

    Zeeb, Steffen; Dahms, Thomas; Flunkert, Valentin; Schöll, Eckehard; Kanter, Ido; Kinzel, Wolfgang

    2013-04-01

    The attractor dimension at the transition to complete synchronization in a network of chaotic units with time-delayed couplings is investigated. In particular, we determine the Kaplan-Yorke dimension from the spectrum of Lyapunov exponents for iterated maps and for two coupled semiconductor lasers. We argue that the Kaplan-Yorke dimension must be discontinuous at the transition and compare it to the correlation dimension. For a system of Bernoulli maps, we indeed find a jump in the correlation dimension. The magnitude of the discontinuity in the Kaplan-Yorke dimension is calculated for networks of Bernoulli units as a function of the network size. Furthermore, the scaling of the Kaplan-Yorke dimension as well as of the Kolmogorov entropy with system size and time delay is investigated.

  19. Quantification of time delay between damages caused by windstorms and by Ips typographus

    Directory of Open Access Journals (Sweden)

    Modlinger Roman

    2015-12-01

    Full Text Available Damages by wind and by European spruce bark beetle (I. typographus L. were compared on the basis of the reports about the occurrence of harmful forest agents for the period 1964−1991 across former regional state forest directorates. In the given period, the quantity of salvage logging (70 million m3 was more than five times that of sanitation felling (13 million m3. Damage intensity increased over the decades. Using a cross-correlation function between the time series, an increase in the abundance of I. typographus due to windfall was demonstrated with a delay of 1–3 years. Wind damage was also shown to arise as a result of disturbed stand stability after sanitation felling with a stochastic delay of 1−5 years. Thus, disturbance of static stability of forest stands may be considered as one of the main harmful consequences of bark beetle outbreaks for the near future. Consequences for forest management are discussed.

  20. Robust Adaptive Time Delay Estimation for Speaker Localization in Noisy and Reverberant Acoustic Environments

    Directory of Open Access Journals (Sweden)

    Simon Doclo

    2003-10-01

    Full Text Available Two adaptive algorithms are presented for robust time delay estimation (TDE in acoustic environments with a large amount of background noise and reverberation. Recently, an adaptive eigenvalue decomposition (EVD algorithm has been developed for TDE in highly reverberant acoustic environments. In this paper, we extend the adaptive EVD algorithm to noisy and reverberant acoustic environments, by deriving an adaptive stochastic gradient algorithm for the generalized eigenvalue decomposition (GEVD or by prewhitening the noisy microphone signals. We have performed simulations using a localized and a diffuse noise source for several SNRs, showing that the time delays can be estimated more accurately using the adaptive GEVD algorithm than using the adaptive EVD algorithm. In addition, we have analyzed the sensitivity of the adaptive GEVD algorithm with respect to the accuracy of the noise correlation matrix estimate, showing that its performance may be quite sensitive, especially for low SNR scenarios.

  1. Linear parameter-varying and time-delay systems analysis, observation, filtering & control

    CERN Document Server

    Briat, Corentin

    2015-01-01

    This book provides an introduction to the analysis and control of Linear Parameter-Varying Systems and Time-Delay Systems and their interactions. The purpose is to give the readers some fundamental theoretical background on these topics and to give more insights on the possible applications of these theories. This self-contained monograph is written in an accessible way for readers ranging from undergraduate/PhD students to engineers and researchers willing to know more about the fields of time-delay systems, parameter-varying systems, robust analysis, robust control, gain-scheduling techniques in the LPV fashion and LMI based approaches. The only prerequisites are basic knowledge in linear algebra, ordinary differential equations and (linear) dynamical systems. Most of the results are proved unless the proof is too complex or not necessary for a good understanding of the results. In the latter cases, suitable references are systematically provided. The first part pertains on the representation, analysis and ...

  2. Model Predictive Load Frequency Control of two-area Interconnected Time Delay Power System with TCSC

    Science.gov (United States)

    Deng, Yan; Liu, Wenze

    2017-05-01

    In order to reduce the influence of non-linear constraint and time delay on load frequency control of interconnected power system, this paper, based on Model Predictive Control (MPC), designed a load frequency control scheme for two-area interconnected power system with TCSC device. First, considering the Generation Rate Constraint (GRC) and time delay, this paper builds the dynamics model of two-area interconnected power system with Thyristor Controlled Series Compensation device (TCSC). Then the whole system is decomposed into two subsystems. And each subsystem has its own local area MPC controller. Second, collaborative control is implemented by integrating the control information (measurement value, predictive value, etc.) of subsystems’ MPC controllers into the local control goal. In the end, under consideration of physical constraints, the Matlab simulation is conducted. The calculation results showed that the MPC strategy has better dynamic performance and robustness compared to the traditional PI control.

  3. Smart-Grid Backbone Network Real-Time Delay Reduction via Integer Programming.

    Science.gov (United States)

    Pagadrai, Sasikanth; Yilmaz, Muhittin; Valluri, Pratyush

    2016-08-01

    This research investigates an optimal delay-based virtual topology design using integer linear programming (ILP), which is applied to the current backbone networks such as smart-grid real-time communication systems. A network traffic matrix is applied and the corresponding virtual topology problem is solved using the ILP formulations that include a network delay-dependent objective function and lightpath routing, wavelength assignment, wavelength continuity, flow routing, and traffic loss constraints. The proposed optimization approach provides an efficient deterministic integration of intelligent sensing and decision making, and network learning features for superior smart grid operations by adaptively responding the time-varying network traffic data as well as operational constraints to maintain optimal virtual topologies. A representative optical backbone network has been utilized to demonstrate the proposed optimization framework whose simulation results indicate that superior smart-grid network performance can be achieved using commercial networks and integer programming.

  4. Adaptive control for time-delay teleoperation systems with uncertain dynamics

    Science.gov (United States)

    Liu, Shan; Zhang, Xia; Zheng, Wenfeng; Yang, Bo

    2017-08-01

    In most teleoperation systems, the dynamics are uncertain and the communications exhibit time delays. In order to confront these problems, this paper reports a position error-based bilateral adaptive controller, in which the unknown operator dynamical parameters and environmental dynamical parameters are included in the unknown vector of the system to be evaluated, adaptive estimate laws are compensated by estimate errors and dissipation by time delays are compensated. By using Lyapunov-Krasovskii stability theorem, it is proved that both position errors and velocities of the teleoperation system asymptotically convergent to zero. Simulations are performed to compare the performance of the proposed controller with the traditional adaptive controller and to demonstrate the efficiency of the developed teleoperation control system.

  5. Does a deformation of special relativity imply energy dependent photon time delays?

    Science.gov (United States)

    Carmona, J. M.; Cortés, J. L.; Relancio, J. J.

    2018-01-01

    Theoretical arguments in favor of energy dependent photon time delays from a modification of special relativity (SR) have met with recent gamma ray observations that put severe constraints on the scale of such deviations. We review the case of the generality of this theoretical prediction in the case of a deformation of SR and find that, at least in the simple model based on the analysis of photon worldlines which is commonly considered, there are many scenarios compatible with a relativity principle which do not contain a photon time delay. This will be the situation for any modified dispersion relation which reduces to E=\\vert p\\vert for photons, independently of the quantum structure of spacetime. This fact opens up the possibility of a phenomenologically consistent relativistic generalization of SR with a new mass scale many orders of magnitude below the Planck mass.

  6. Attosecond Interference Induced by Coulomb-Field-Driven Transverse Backward-Scattering Electron Wave-Packets

    CERN Document Server

    Song, Xiaohong; Lin, Cheng; Sheng, Zhihao; Yu, Xianhuan; Yang, Weifeng; Hu, Shilin; Chen, Jing; Xu, SongPo; Chen, YongJu; Quan, Wei; Liu, XiaoJun

    2016-01-01

    A novel and universal interference structure is found in the photoelectron momentum distribution of atoms in intense infrared laser field. Theoretical analysis shows that this structure can be attributed to a new form of Coulomb-field-driven backward-scattering of photoelectrons in the direction perpendicular to the laser field, in contrast to the conventional rescattering along the laser polarization direction. This transverse backward-scattering process is closely related to a family of photoelectrons initially ionized within a time interval of less than 200 attosecond around the crest of the laser electric field. Those electrons, acquiring near-zero return energy in the laser field, will be pulled back solely by the ionic Coulomb field and backscattered in the transverse direction. Moreover, this rescattering process mainly occurs at the first or the second return times, giving rise to different phases of the photoelectrons. The interference between these photoelectrons leads to unique curved interference ...

  7. Robust fixed-time synchronization of delayed Cohen-Grossberg neural networks.

    Science.gov (United States)

    Wan, Ying; Cao, Jinde; Wen, Guanghui; Yu, Wenwu

    2016-01-01

    The fixed-time master-slave synchronization of Cohen-Grossberg neural networks with parameter uncertainties and time-varying delays is investigated. Compared with finite-time synchronization where the convergence time relies on the initial synchronization errors, the settling time of fixed-time synchronization can be adjusted to desired values regardless of initial conditions. Novel synchronization control strategy for the slave neural network is proposed. By utilizing the Filippov discontinuous theory and Lyapunov stability theory, some sufficient schemes are provided for selecting the control parameters to ensure synchronization with required convergence time and in the presence of parameter uncertainties. Corresponding criteria for tuning control inputs are also derived for the finite-time synchronization. Finally, two numerical examples are given to illustrate the validity of the theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Existence of Solutions of a Partial Integrodifferential Equation with Thermostat and Time Delay

    Directory of Open Access Journals (Sweden)

    Carlo Bianca

    2014-01-01

    Full Text Available This paper deals with the mathematical analysis of a retarded partial integrodifferential equation that belongs to the class of thermostatted kinetic equations with time delay. Specifically, the paper is devoted to the proof of the existence and uniqueness of mild solutions of the related Cauchy problem. The main result is obtained by employing integration along the characteristic curves and successive approximations sequence arguments. Applications and perspective are also discussed within the paper.

  9. A mathematical theory of stochastic microlensing. I. Random time delay functions and lensing maps

    Science.gov (United States)

    Petters, A. O.; Rider, B.; Teguia, A. M.

    2009-07-01

    Stochastic microlensing is a central tool in probing dark matter on galactic scales. From first principles, we initiate the development of a mathematical theory of stochastic microlensing. Beginning with the random time delay function and associated lensing map, we determine exact expressions for the mean and variance of these transformations. In addition, we derive the probability density function (pdf) of a random point-mass potential, which form the constituent of a stochastic microlens potential. We characterize the exact pdf of a normalized random time delay function at the origin, showing that it is a shifted gamma distribution, which also holds at leading order in the limit of a large number of point masses if the normalized time delay function was at a general point of the lens plane. For the large number of point-mass limit, we also prove that the asymptotic pdf of the random lensing map under a specified scaling converges to a bivariate normal distribution. We show analytically that the pdf of the random scaled lensing map at leading order depends on the magnitude of the scaled bending angle due purely to point masses as well as demonstrate explicitly how this radial symmetry is broken at the next order. Interestingly, we found at leading order a formula linking the expectation and variance of the normalized random time delay function to the first Betti number of its domain. We also determine an asymptotic pdf for the random bending angle vector and find an integral expression for the probability of a lens plane point being near a fixed point. Lastly, we show explicitly how the results are affected by location in the lens plane. The results of this paper are relevant to the theory of random fields and provide a platform for further generalizations as well as analytical limits for checking astrophysical studies of stochastic microlensing.

  10. STRONGLY LENSED JETS, TIME DELAYS, AND THE VALUE OF H {sub 0}

    Energy Technology Data Exchange (ETDEWEB)

    Barnacka, Anna; Geller, Margaret J.; Benbow, Wystan [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-20, Cambridge, MA 02138 (United States); Dell' Antonio, Ian P., E-mail: abarnacka@cfa.harvard.edu [Department of Physics, Brown University, Box 1843, Providence, RI 02912 (United States)

    2015-01-20

    In principle, the most straightforward method of estimating the Hubble constant relies on time delays between mirage images of strongly lensed sources. It is a puzzle, then, that the values of H {sub 0} obtained with this method span a range from ∼50-100 km s{sup –1}Mpc{sup –1}. Quasars monitored to measure these time delays are multi-component objects. The variability may arise from different components of the quasar or may even originate from a jet. Misidentifying a variable-emitting region in a jet with emission from the core region may introduce an error in the Hubble constant derived from a time delay. Here, we investigate the complex structure of the sources as the underlying physical explanation of the wide spread in values of the Hubble constant based on gravitational lensing. Our Monte Carlo simulations demonstrate that the derived value of the Hubble constant is very sensitive to the offset between the center of the emission and the center of the variable emitting region. Therefore, we propose using the value of H {sub 0} known from other techniques to spatially resolve the origin of the variable emission once the time delay is measured. We particularly advocate this method for gamma-ray astronomy, where the angular resolution of detectors reaches approximately 0.°1; lensed blazars offer the only route for identify the origin of gamma-ray flares. Large future samples of gravitationally lensed sources identified with Euclid, SKA, and LSST will enable a statistical determination of H {sub 0}.

  11. A numerical solution for a class of time fractional diffusion equations with delay

    Directory of Open Access Journals (Sweden)

    Pimenov Vladimir G.

    2017-09-01

    Full Text Available This paper describes a numerical scheme for a class of fractional diffusion equations with fixed time delay. The study focuses on the uniqueness, convergence and stability of the resulting numerical solution by means of the discrete energy method. The derivation of a linearized difference scheme with convergence order O(τ2−α+ h4 in L∞-norm is the main purpose of this study. Numerical experiments are carried out to support the obtained theoretical results.

  12. Photonic-Enabled RF Canceller with Tunable Time-Delay Taps

    Science.gov (United States)

    2016-12-05

    reducing this SI in the analog domain, before the receiver’s low- noise amplifier (LNA), sat- uration can be avoided and spurious signals minimized in order...communications C-band, 191.50 to 196.25 THz, and had +10 dBm of output power . Our initial design utilized 20 such lasers, which resulted in 20 RF canceller...Photonic-Enabled RF Canceller with Tunable Time-Delay Taps Kenneth E. Kolodziej, Sivasubramaniam Yegnanarayanan, Bradley T. Perry MIT Lincoln

  13. Adaptive Neural Control for a Class of Outputs Time-Delay Nonlinear Systems

    Directory of Open Access Journals (Sweden)

    Ruliang Wang

    2012-01-01

    Full Text Available This paper considers an adaptive neural control for a class of outputs time-delay nonlinear systems with perturbed or no. Based on RBF neural networks, the radius basis function (RBF neural networks is employed to estimate the unknown continuous functions. The proposed control guarantees that all closed-loop signals remain bounded. The simulation results demonstrate the effectiveness of the proposed control scheme.

  14. Adaptive Asymptotical Synchronization for Stochastic Complex Networks with Time-Delay and Markovian Switching

    Directory of Open Access Journals (Sweden)

    Xueling Jiang

    2014-01-01

    Full Text Available The problem of adaptive asymptotical synchronization is discussed for the stochastic complex dynamical networks with time-delay and Markovian switching. By applying the stochastic analysis approach and the M-matrix method for stochastic complex networks, several sufficient conditions to ensure adaptive asymptotical synchronization for stochastic complex networks are derived. Through the adaptive feedback control techniques, some suitable parameters update laws are obtained. Simulation result is provided to substantiate the effectiveness and characteristics of the proposed approach.

  15. Travel Times, Congestion Levels, and Delays at Intersections Calculated on the Basis of Floating Car Data

    DEFF Research Database (Denmark)

    Lahrmann, Harry; Torp, Kristian

    2010-01-01

    traffic only a few meters away from the measuring spots. The situation is totally the opposite when it comes to log data from GPS receivers in cars. Here detailed information about individual cars in the entire road network is obtained. However, the GPS data is only available from a small subset...... of the cars. This paper presents a method to determine travel time, congestion levels and delays using GPS data from moving vehicles – the so-called floating car data....

  16. Stabilization of a Wireless Networked Control System with Packet Loss and Time Delay: An ADS Approach

    Directory of Open Access Journals (Sweden)

    Jing Wang

    2012-01-01

    Full Text Available The stabilization problem of a wireless networked control system is considered in this paper. Both time delay and packet loss exist simultaneously in the wireless network. The system is modeled as an asynchronous dynamic system (ADS with unstable subsystems. A sufficient condition for the system to be stable is presented. A numerical example is given to demonstrate the effectiveness of the proposed approach.

  17. Observer Design for a Time Delay System via the Razumikhin Approach

    Czech Academy of Sciences Publication Activity Database

    Rehák, Branislav

    2017-01-01

    Roč. 19, č. 6 (2017), s. 2226-2231 ISSN 1561-8625 R&D Projects: GA ČR GA13-02149S Institutional support: RVO:67985556 Keywords : observer * time-delay system * input-to-state stability * quantization Subject RIV: BC - Control Systems Theory Impact factor: 1.421, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/asjc.1507/full

  18. Pulse Compression of Phase-matched High Harmonic Pulses from a Time-Delay Compensated Monochromator

    Directory of Open Access Journals (Sweden)

    Ito Motohiko

    2013-03-01

    Full Text Available Pulse compression of single 32.6-eV high harmonic pulses from a time-delay compensated monochromator was demonstrated down to 11±3 fs by compensating the pulse front tilt. The photon flux was intensified up to 5.7×109 photons/s on target by implementing high harmonic generation under a phase matching condition in a hollow fiber used for increasing the interaction length.

  19. Time Delay Measurements for the Cluster-lensed Sextuple Quasar SDSS J2222+2745

    Science.gov (United States)

    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).

  20. Leader-Following Consensus in Networks of Agents with Nonuniform Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Zhao-Jun Tang

    2012-01-01

    Full Text Available This paper is concerned with a leader-following consensus problem for networks of agents with fixed and switching topologies as well as nonuniform time-varying communication delays. By employing Lyapunov-Razumikhin function, a necessary and sufficient condition is derived in the case of fixed topology, and a sufficient condition is obtained in the case when the interconnection topology is switched and satisfies certain condition. Simulation results are provided to illustrate the theoretical results.