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...... in the emergency department. It is important to identify existing problems in order to reduce time delay. The aim of this study was to collect data for patients with acute limb ischemia and to evaluate the time delay between the different events from onset of symptoms to specialist evaluation and further treatment...... with focus on pre-hospital and in-hospital time delays. METHODS: We conducted a prospective cross-sectional cohort study including all patients suspected with acute limb ischemia who were admitted to the emergency department of a community hospital in a six months period. Temporal delay in the different...
Treu, Tommaso; Marshall, Philip J.
2016-01-01
Gravitational time delays, observed in strong lens systems where the variable background source is multiply-imaged by a massive galaxy in the foreground, provide direct measurements of cosmological distance that are very complementary to other cosmographic probes. The success of the technique depends on the availability and size of a suitable sample of lensed quasars or supernovae, precise measurements of the time delays, accurate modeling of the gravitational potential of the main deflector,...
Treu, Tommaso
2016-01-01
Gravitational time delays, observed in strong lens systems where the variable background source is multiply-imaged by a massive galaxy in the foreground, provide direct measurements of cosmological distance that are very complementary to other cosmographic probes. The success of the technique depends on the availability and size of a suitable sample of lensed quasars or supernovae, precise measurements of the time delays, accurate modeling of the gravitational potential of the main deflector, and our ability to characterize the distribution of mass along the line of sight to the source. We review the progress made during the last 15 years, during which the first competitive cosmological inferences with time delays were made, and look ahead to the potential of significantly larger lens samples in the near future.
Treu, Tommaso; Marshall, Philip J.
2016-07-01
Gravitational time delays, observed in strong lens systems where the variable background source is multiply imaged by a massive galaxy in the foreground, provide direct measurements of cosmological distance that are very complementary to other cosmographic probes. The success of the technique depends on the availability and size of a suitable sample of lensed quasars or supernovae, precise measurements of the time delays, accurate modeling of the gravitational potential of the main deflector, and our ability to characterize the distribution of mass along the line of sight to the source. We review the progress made during the last 15 years, during which the first competitive cosmological inferences with time delays were made, and look ahead to the potential of significantly larger lens samples in the near future.
Theoretical Delay Time Distributions
Nelemans, Gijs; Bours, Madelon
2012-01-01
We briefly discuss the method of population synthesis to calculate theoretical delay time distributions of type Ia supernova progenitors. We also compare the results of the different research groups and conclude that although one of the main differences in the results for single degenerate progenitors is the retention efficiency with which accreted hydrogen is added to the white dwarf core, this cannot explain all the differences.
Theoretical Delay Time Distributions
Nelemans, Gijs; Toonen, Silvia; Bours, Madelon
2013-01-01
We briefly discuss the method of population synthesis to calculate theoretical delay time distributions of Type Ia supernova progenitors. We also compare the results of different research groups and conclude that, although one of the main differences in the results for single degenerate progenitors is the retention efficiency with which accreted hydrogen is added to the white dwarf core, this alone cannot explain all the differences.
Geometric Time Delay Interferometry
Vallisneri, Michele
2005-01-01
The space-based gravitational-wave observatory LISA, a NASA-ESA mission to be launched after 2012, will achieve its optimal sensitivity using Time Delay Interferometry (TDI), a LISA-specific technique needed to cancel the otherwise overwhelming laser noise in the inter-spacecraft phase measurements. The TDI observables of the Michelson and Sagnac types have been interpreted physically as the virtual measurements of a synthesized interferometer. In this paper, I present Geometric TDI, a new an...
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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.
Huang, Qiang; Ma, Qing-feng; Feng, Juan; Cheng, Wei-yang; Jia, Jian-ping; Song, Hai-qing; Chang, Hong; Wu, Jian
2015-01-01
In-hospital delay reduces the benefit of intravenous thrombolysis (IVT) in acute ischemic stroke (AIS), while factors affecting in-hospital delay are less well known in Chinese. We are aiming at determining the specific factors associated with in-hospital delay through a hospital based cohort. In-hospital delay was defined as door-to-needle time (DTN) ≥60 min (standard delay criteria) or ≥75% percentile of all DTNs (severe delay criteria). Demographic data, time intervals [onset-to-door time (OTD), DTN, door-to-examination time (DTE), door-to-imaging time (DTI), door-to-laboratory time (DTL) and final-test-to-needle time (FTN, the time interval between the time obtaining the result of the last screening test and the needle time)], medical history and additional variables were calculated using Mann-Whitney U or Pearson Chi-Square tests for group comparison, and multivariate linear regression analysis was performed to identify independent variables of in-hospital delay. A total of 202 IVT cases were enrolled. The median age was 61 years and 25.2% were female. The cutoff points for the upper quartile of DTN (severe delay criteria) was 135 min.When compared with the reference group without in-hospital delay, older age, shorter OTD and less referral were found in the standard delay group and male sex, presence with transient ischemic attacks or rapidly improving symptom, and with multi-model CT imaging were more frequent in the severe delay group. In the multivariate linear regression analysis, FTN (PDTL (P = 0.002) were significantly associated with standard delay; while DTE (P = 0.005), DTI (P = 0.033), DTL (P<0.001), and FTN (P<0.001) were positively associated with severe delay. There was not a significant change in the trend of DTNs during the study period (P = 0.054). In-hospital delay was due to multifactors in China, in which time delays of decision-making process and laboratory tests contributed the most. Efforts aiming at reducing the delay should be
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Qiang Huang
Full Text Available In-hospital delay reduces the benefit of intravenous thrombolysis (IVT in acute ischemic stroke (AIS, while factors affecting in-hospital delay are less well known in Chinese. We are aiming at determining the specific factors associated with in-hospital delay through a hospital based cohort. In-hospital delay was defined as door-to-needle time (DTN ≥60 min (standard delay criteria or ≥75% percentile of all DTNs (severe delay criteria. Demographic data, time intervals [onset-to-door time (OTD, DTN, door-to-examination time (DTE, door-to-imaging time (DTI, door-to-laboratory time (DTL and final-test-to-needle time (FTN, the time interval between the time obtaining the result of the last screening test and the needle time], medical history and additional variables were calculated using Mann-Whitney U or Pearson Chi-Square tests for group comparison, and multivariate linear regression analysis was performed to identify independent variables of in-hospital delay. A total of 202 IVT cases were enrolled. The median age was 61 years and 25.2% were female. The cutoff points for the upper quartile of DTN (severe delay criteria was 135 min.When compared with the reference group without in-hospital delay, older age, shorter OTD and less referral were found in the standard delay group and male sex, presence with transient ischemic attacks or rapidly improving symptom, and with multi-model CT imaging were more frequent in the severe delay group. In the multivariate linear regression analysis, FTN (P<0.001 and DTL (P = 0.002 were significantly associated with standard delay; while DTE (P = 0.005, DTI (P = 0.033, DTL (P<0.001, and FTN (P<0.001 were positively associated with severe delay. There was not a significant change in the trend of DTNs during the study period (P = 0.054. In-hospital delay was due to multifactors in China, in which time delays of decision-making process and laboratory tests contributed the most. Efforts aiming at reducing the delay
On the Gravitomagnetic Time Delay
Ciufolini, I.; Kopeikin, S.; Mashhoon, B.; Ricci, F
2002-01-01
We study the gravitational time delay in ray propagation due to rotating masses in the linear approximation of general relativity. Simple expressions are given for the gravitomagnetic time delay that occurs when rays of radiation cross a slowly rotating shell and propagate in the field of a distant rotating source. Moreover, we calculate the local gravitational time delay in the Goedel universe. The observational consequences of these results in the case of weak gravitational lensing are disc...
Dhurandhar Sanjeev V.; Tinto Massimo
2005-01-01
Equal-arm interferometric 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 overall performance. If, however, the two arms have different lengths (...
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
Institute of Scientific and Technical Information of China (English)
洪峰
2002-01-01
In this paper, existing damping theories are briefly reviewed. On the basis of the existing damping theories, a new kind of damping theory, i.e., the time-delay damping theory, is developed. In the time-delay damping theory, the damping force is considered to be directly proportional to the increment of displacement. The response analysis of an SDOF time-delay damping system is carried out, and the methods for obtaining the solution for a time-delay damping system in the time domain as well as the frequency domain are given. The comparison between results from different damping theories shows that the time-delay damping theory is both reasonable and convenient.
Imitation dynamics with time delay.
Wang, Shi-Chang; Yu, Jie-Ru; Kurokawa, Shun; Tao, Yi
2017-05-07
Based on the classic imitation dynamics (Hofbauer and Sigmund, 1998, Evolutionary Games and Population Dynamics, Cambridge University Press), the imitation dynamics with time delay is investigated, where the probability that an individual will imitate its opponent's own strategy is assumed to depend on the comparison between the past expected payoff of this individual's own strategy and the past expected payoff of its opponent's own strategy, i.e. there is a time delay effect. For the two-phenotype model, we show that if the system has an interior equilibrium and this interior equilibrium is stable when there is no time delay, then there must be a critical value of time delay such that the system tends to a stable periodic solution when the time delay is larger than the critical value. On the other hand, for three-phenotype (rock-scissors-paper) model, the numerical analysis shows that for the stable periodic solution induced by the time delay, the amplitude and the period will increase with the increase of the time delay. These results should help to understand the evolution of behavior based on the imitation dynamics with time delay. Copyright © 2017 Elsevier Ltd. All rights reserved.
Time Delay in Molecular Photoionization
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.
Leibniz Dynamics with Time Delay
Albu, I. D.; Opris, D.
2005-01-01
In this paper we show that several dynamical systems with time delay can be described as vector fields associated to smooth functions via a bracket of Leibniz structure. Some examples illustrate the theoretical considerations.
Time Delay in Molecular Photoionization
Hockett, P.; Frumker, E.; 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, nitroge...
Delay-independent stabilization for teleoperation with time varying delay
Fujita, Hiroyuki; Namerikawa, Toru
2009-01-01
This paper deals with the stability for nonlinear teleoperation with time varying communication delays. The proposed method is passivity-based controllers with time varying gains which depend on the rate of change of time varying delay. In our proposed method, stability condition is independent of the magnitude of the communication delay and the damping of the system. The delay-independent stability is shown via Lyapunov stability methods. Several experimental results show the effectiveness o...
Time delay and distance measurement
Abshire, James B. (Inventor); Sun, Xiaoli (Inventor)
2011-01-01
A method for measuring time delay and distance may include providing an electromagnetic radiation carrier frequency and modulating one or more of amplitude, phase, frequency, polarization, and pointing angle of the carrier frequency with a return to zero (RZ) pseudo random noise (PN) code. The RZ PN code may have a constant bit period and a pulse duration that is less than the bit period. A receiver may detect the electromagnetic radiation and calculate the scattering profile versus time (or range) by computing a cross correlation function between the recorded received signal and a three-state RZ PN code kernel in the receiver. The method also may be used for pulse delay time (i.e., PPM) communications.
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....
Time-domain nature of group delay
Institute of Scientific and Technical Information of China (English)
王建武; 冯正和
2015-01-01
The characteristic of group delay is analyzed based on an electronic circuit, and its time-domain nature is studied with time-domain simulation and experiment. The time-domain simulations and experimental results show that group delay is the delay of the energy center of the amplitude-modulated pulse, rather than the propagation delay of the electromagnetic field. As group velocity originates from the definition of group delay and group delay is different from the propagation delay, the superluminality or negativity of group velocity does not mean the superluminal or negative propagation of the electromagnetic field.
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.
Xun, Yi-Wen; Yang, Jin-Gang; Song, Li; Sun, Yi-Hong; Lu, Chang-Lin; Yang, Yue-Jin; Hu, Da-Yi
2010-04-05
Evidence indicates that early reperfusion therapy in patients with ST-elevation myocardial infarction (STEMI) reduces complications. This study was undertaken to compare the in-hospital delay to primary percutaneous coronary intervention (PPCI) for patients with STEMI between specialized hospitals and non-specialized hospitals in Beijing, China. Two specialized hospitals and fifteen non-specialized hospitals capable of performing PPCI were selected to participate in this study. A total of 308 patients, within 12 hours of the onset of symptoms and undergoing PPCI between November 1, 2005 and December 31, 2006 were enrolled. Data were collected by structured interview and review of medical records. The median in-hospital delay was 98 (interquartile range 105 to 180) minutes, and 16.9% of the patients were treated within 90 minutes. Total in-hospital delay and ECG-to-treatment decision-making time were longer in the non-specialized hospitals than in the cardiac specialized hospitals (147 minutes vs. 120 minutes, P hospitals were independently associated with an increased risk of being in the upper median of in-hospital delays. There were substantial in-hospital delays between arrival at the hospital and the administration of PPCI for patients with STEMI in Beijing. Patients admitted to the cardiac specialized hospitals had a shorter in-hospital delay than those to the non-specialized hospitals because of a shorter time of ECG-to-treatment decision-making.
Generalization of the Right Acute Stroke Prevention Strategies in Reducing in-Hospital Delays.
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Qiang Huang
Full Text Available The aim of this study was to reduce the door-to-needle (DTN time of intravenous thrombolysis (IVT in acute ischemic stroke (AIS through a comprehensive, hospital-based implementation strategy. The intervention involved a systemic literature review, identifying barriers to rapid IVT treatment at our hospital, setting target DTN time intervals, and building an evolving model for IVT candidate selection. The rate of non-in-hospital delay (DTN time ≤ 60 min was set as the primary endpoint. A total of 348 IVT cases were enrolled in the study (202 and 146 in the pre- and post-intervention group, respectively. The median age was 61 years in both groups; 25.2% and 26.7% of patients in the pre- and post-intervention groups, respectively, were female. The post-intervention group had higher rates of dyslipidemia and minor stroke [defined as National Institutes of Health Stroke Scale (NIHSS ≤ 3]; less frequent atrial fibrillation; higher numbers of current smokers, heavy drinkers, referrals, and multi-model head imaging cases; and lower NIHSS scores and blood sugar level (all P 0.05. These findings indicate that it is possible to achieve a DTN time ≤ 60 min for up to 60% of hospitals in the current Chinese system, and that this logistical change can yield a notable improvement in the outcome of IVT patients.
Dynamics of Nonlinear Time-Delay Systems
Lakshmanan, Muthusamy
2010-01-01
Synchronization of chaotic systems, a patently nonlinear phenomenon, has emerged as a highly active interdisciplinary research topic at the interface of physics, biology, applied mathematics and engineering sciences. In this connection, time-delay systems described by delay differential equations have developed as particularly suitable tools for modeling specific dynamical systems. Indeed, time-delay is ubiquitous in many physical systems, for example due to finite switching speeds of amplifiers in electronic circuits, finite lengths of vehicles in traffic flows, finite signal propagation times in biological networks and circuits, and quite generally whenever memory effects are relevant. This monograph presents the basics of chaotic time-delay systems and their synchronization with an emphasis on the effects of time-delay feedback which give rise to new collective dynamics. Special attention is devoted to scalar chaotic/hyperchaotic time-delay systems, and some higher order models, occurring in different bran...
Memorized discrete systems and time-delay
Luo, Albert C J
2017-01-01
This book examines discrete dynamical systems with memory—nonlinear systems that exist extensively in biological organisms and financial and economic organizations, and time-delay systems that can be discretized into the memorized, discrete dynamical systems. It book further discusses stability and bifurcations of time-delay dynamical systems that can be investigated through memorized dynamical systems as well as bifurcations of memorized nonlinear dynamical systems, discretization methods of time-delay systems, and periodic motions to chaos in nonlinear time-delay systems. The book helps readers find analytical solutions of MDS, change traditional perturbation analysis in time-delay systems, detect motion complexity and singularity in MDS; and determine stability, bifurcation, and chaos in any time-delay system.
Estimation of time delay by coherence analysis
Govindan, R B; Kopper, F; Claussen, J C; Deuschl, G
2004-01-01
Using coherence analysis (which is an extensively used method to study the correlations in frequency domain, between two simultaneously measured signals) we estimate the time delay between two signals. This method is suitable for time delay estimation of narrow band coherence signals for which the conventional methods cannot be reliably applied. We show by analysing coupled R\\"ossler attractors with a known delay, that the method yields satisfactory results. Then, we apply this method to human pathologic tremor. The delay between simultaneously measured traces of Electroencephalogram (EEG) and Electromyogram (EMG) data of subjects with essential hand tremor is calculated. We find that there is a delay of 11-27 milli-seconds ($ms$) between the tremor correlated parts (cortex) of the brain (EEG) and the trembling hand (EMG) which is in agreement with the experimentally observed delay value of 15 $ms$ for the cortico-muscular conduction time. By surrogate analysis we calculate error-bars of the estimated delay.
Time-delay and fractional derivatives
Tenreiro Machado JA
2011-01-01
This paper proposes the calculation of fractional algorithms based on time-delay systems. The study starts by analyzing the memory properties of fractional operators and their relation with time delay. Based on the Fourier analysis an approximation of fractional derivatives through time-delayed samples is developed. Furthermore, the parameters of the proposed approximation are estimated by means of genetic algorithms. The results demonstrate the feasibility of the new perspective.
Angle-resolved time delay in photoemission
Wätzel, Jonas; Pavlyukh, Yaroslav; Berakdar, Jamal
2014-01-01
We investigate theoretically the relative time delay of photoelectrons originating from different atomic subshells of noble gases. This quantity was measured via attosecond streaking and studied theoretically by Schultze et al. [Science 328, 1658 (2010)] for neon. A substantial discrepancy was found between the measured and the calculated values of the relative time delay. Several theoretical studies were put forward to resolve this issue, e.g., by including correlation effects. In the present paper we explore a further aspect, namely the directional dependence of time delay. In contrast to neon, for argon target a strong angular dependence of time delay is found near a Cooper minimum.
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Levy Adrian R
2008-09-01
Full Text Available Abstract Background Many health care systems now use priority wait lists for scheduling elective coronary artery bypass grafting (CABG surgery, but there have not yet been any direct estimates of reductions in in-hospital mortality rate afforded by ensuring that the operation is performed within recommended time periods. Methods We used a population-based registry to identify patients with established coronary artery disease who underwent isolated CABG in British Columbia, Canada. We studied whether postoperative survival during hospital admission for CABG differed significantly among patients who waited for surgery longer than the recommended time, 6 weeks for patients needing semi-urgent surgery and 12 weeks for those needing non-urgent surgery. Results Among 7316 patients who underwent CABG, 97 died during the same hospital admission, for a province-wide death rate at discharge of 1.3%. The observed proportion of patients who died during the same admission was 1.0% (27 deaths among 2675 patients for patients treated within the recommended time and 1.5% (70 among 4641 for whom CABG was delayed. After adjustment for age, sex, anatomy, comorbidity, calendar period, hospital, and mode of admission, patients with early CABG were only 2/3 as likely as those for whom CABG was delayed to experience in-hospital death (odds ratio 0.61; 95% confidence interval [CI] 0.39 to 0.96. There was a linear trend of 5% increase in the odds of in-hospital death for every additional month of delay before surgery, adjusted OR = 1.05 (95% CI 1.00 to 1.11. Conclusion We found a significant survival benefit from performing surgical revascularization within the time deemed acceptable to consultant surgeons for patients requiring the treatment on a semi-urgent or non-urgent basis.
Time Delay Estimation Algoritms for Echo Cancellation
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Kirill Sakhnov
2011-01-01
Full Text Available The following case study describes how to eliminate echo in a VoIP network using delay estimation algorithms. It is known that echo with long transmission delays becomes more noticeable to users. Thus, time delay estimation, as a part of echo cancellation, is an important topic during transmission of voice signals over packetswitching telecommunication systems. An echo delay problem associated with IP-based transport networks is discussed in the following text. The paper introduces the comparative study of time delay estimation algorithm, used for estimation of the true time delay between two speech signals. Experimental results of MATLab simulations that describe the performance of several methods based on cross-correlation, normalized crosscorrelation and generalized cross-correlation are also presented in the paper.
Delay Independent Criterion for Multiple Time-delay Systems
Chang, C. J.; Liu, K. F. R.; Yeh, K.; Chen, C. W.; Chung, P. Y.
Based on the fuzzy Lyapunov method, this work addresses the stability conditions for nonlinear systems with multiple time delays to ensure the stability of building structure control systems. The delay independent conditions are derived via the traditional Lyapunov and fuzzy Lyapunov methods for multiple time-delay systems as approximated by the Tagagi-Sugeno (T-S) fuzzy model. The fuzzy Lyapunov function is defined as a fuzzy blending of quadratic Lyapunov functions. A parallel distributed compensation (PDC) scheme is utilized to construct a global fuzzy logic control (FLC) by blending all linear local state feedback controllers in the controller design procedure. Furthermore, the H infinity performance and robustness of the design for modeling errors also need to be considered in the stability conditions.
Estimating Time Delays With Antenna Array
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This paper discusses the problem of estimating the time delays of multipath signals in wireless communications. The new multipath channel model is presented. And based on this new channel model, we generalize the classical MUSIC algorithm to estimate the time delays of multipath signals. Simulation examples are included to illustrate the algorithm performance.
Photonic Quantum Circuits with Time Delays
Pichler, Hannes
2015-01-01
We study the dynamics of photonic quantum circuits consisting of nodes coupled by quantum channels. We are interested in the regime where 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 Schr\\"odinger 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.
Institute of Scientific and Technical Information of China (English)
XUN Yi-wen; YANG Jin-gang; SONG Li; SUN Yi-hong; LU Chang-lin; YANG Yue-jin; HU Da-yi
2010-01-01
Background Evidence indicates that early reperfusion therapy in patients with ST-elevation myocardial infarction (STEMI) reduces complications. This study was undertaken to compare the in-hospital delay to primary percutaneous coronary intervention (PPCI) for patients with STEMI between specialized hospitals and non-specialized hospitals in Beijing, China. Methods Two specialized hospitals and fifteen non-specialized hospitals capable of performing PPCI were selected to participate in this study. A total of 308 patients, within 12 hours of the onset of symptoms and undergoing PPCI between November 1, 2005 and December 31, 2006 were enrolled. Data were collected by structured interview and review of medical records.Results The median in-hospital delay was 98 (interquartile range 105 to 180) minutes, and 16.9% of the patients were treated within 90 minutes. Total in-hospital delay and ECG-to-treatment decision-making time were longer in the non-specialized hospitals than in the cardiac specialized hospitals (147 minutes vs. 120 minutes, P<0.001; 55 minutes vs. 45 minutes, P=0.035). After controlling the confounding factors, the non-specialized hospitals were independently associated with an increased risk of being in the upper median of in-hospital delays.Conclusions There were substantial in-hospital delays between arrival at the hospital and the administration of PPCI for patients with STEMI in Beijing. Patients admitted to the cardiac specialized hospitals had a shorter in-hospital delay than those to the non-specialized hospitals because of a shorter time of ECG-to-treatment decision-making.
Reconstruction of time-delay systems from chaotic time series.
Bezruchko, B P; Karavaev, A S; Ponomarenko, V I; Prokhorov, M D
2001-11-01
We propose a method that allows one to estimate the parameters of model scalar time-delay differential equations from time series. The method is based on a statistical analysis of time intervals between extrema in the time series. We verify our method by using it for the reconstruction of time-delay differential equations from their chaotic solutions and for modeling experimental systems with delay-induced dynamics from their chaotic time series.
Dimensional reduction of nonlinear time delay systems
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M. S. Fofana
2005-01-01
infinite-dimensional problem without the assumption of small time delay. This dimensional reduction is illustrated in this paper with the delay versions of the Duffing and van der Pol equations. For both nonlinear delay equations, transcendental characteristic equations of linearized stability are examined through Hopf bifurcation. The infinite-dimensional nonlinear solutions of the delay equations are decomposed into stable and centre subspaces, whose respective dimensions are determined by the linearized stability of the transcendental equations. Linear semigroups, infinitesimal generators, and their adjoint forms with bilinear pairings are the additional candidates for the infinite-dimensional reduction.
Comment on "Time delays in molecular photoionization"
Baykusheva, D
2016-01-01
In a recent article by P. Hockett \\textit{et al.}, time delays arising in the context of molecular single-photon ionization are investigated from a theoretical point of view. We argue that one of the central equations derived in the paper is incorrect and present a reformulation that is consistent with the established treatment of angle-dependent scattering delays.
Delayed biodiversity change: no time to waste.
Essl, Franz; Dullinger, Stefan; Rabitsch, Wolfgang; Hulme, Philip E; Pyšek, Petr; Wilson, John R U; Richardson, David M
2015-07-01
Delayed biodiversity responses to environmental forcing mean that rates of contemporary biodiversity changes are underestimated, yet these delays are rarely addressed in conservation policies. Here, we identify mechanisms that lead to such time lags, discuss shifting human perceptions, and propose how these phenomena should be addressed in biodiversity management and science.
Synchronisation of time-delay systems
Bünner, M J; Bünner, Martin J.; Just, Wolfram
1998-01-01
We present the linear-stability analysis of synchronised states in coupled time-delay systems. There exists a synchronisation threshold, for which we derive upper bounds, which does not depend on the delay time. We prove that at least for scalar time-delay systems synchronisation is achieved by transmitting a single scalar signal, even if the synchronised solution is given by a high-dimensional chaotic state with a large number of positive Lyapunov-exponents. The analytical results are compared with numerical simulations of two coupled Mackey-Glass equations.
Monolithic Time Delay Integrated APD Arrays Project
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...
Phase synchronization in time-delay systems.
Senthilkumar, D V; Lakshmanan, M; Kurths, J
2006-09-01
Though the notion of phase synchronization has been well studied in chaotic dynamical systems without delay, it has not been realized yet in chaotic time-delay systems exhibiting non-phase-coherent hyperchaotic attractors. In this paper we report identification of phase synchronization in coupled time-delay systems exhibiting hyperchaotic attractor. We show that there is a transition from nonsynchronized behavior to phase and then to generalized synchronization as a function of coupling strength. These transitions are characterized by recurrence quantification analysis, by phase differences based on a transformation of the attractors, and also by the changes in the Lyapunov exponents. We have found these transitions in coupled piecewise linear and in Mackey-Glass time-delay systems.
Almström, Markus; Svensson, Jan F; Patkova, Barbora; Svenningsson, Anna; Wester, Tomas
2017-03-01
To investigate the correlation between in-hospital surgical delay before appendectomy for suspected appendicitis and the finding of perforated appendicitis in children. All children undergoing acute appendectomy for suspected acute appendicitis at Karolinska University Hospital, Stockholm, Sweden from 2006 to 2013 were reviewed for the exposure of surgical delay. Primary endpoint was the histopathologic finding of perforated appendicitis. The main explanatory variable was in-hospital surgical delay, using surgery within 12 hours as reference. Secondary endpoints were postoperative wound infection, intra-abdominal abscess, reoperation, length of hospital stay, and readmission. To adjust for selection bias, a logistic regression model was created to estimate odds ratios for the main outcome measures. Missing data were replaced using multiple imputation. The study comprised 2756 children operated for acute appendicitis. Six hundred sixty-one (24.0%) had a histopathologic diagnosis of perforated appendicitis. In the multivariate logistic regression analysis, increased time to surgery was not associated with increased risk of histopathologic perforation. There was no association between the timing of surgery and postoperative wound infection, intra-abdominal abscess, reoperation, or readmission. In-hospital delay of acute appendectomy in children was not associated with an increased rate of histopathologic perforation. Timing of surgery was not an independent risk factor for postoperative complications. The results were not dependent on the magnitude of the surgical delay. The findings are analogous with previous findings in adults and may aid the utilization of available hospital- and operative resources.
Time delay measurement in the frequency domain
Energy Technology Data Exchange (ETDEWEB)
Durbin, Stephen M., E-mail: durbin@purdue.edu; Liu, Shih-Chieh [Purdue University, West Lafayette, IN 47907 (United States); Dufresne, Eric M.; Li, Yuelin; Wen, Haidan [Argonne National Laboratory, Argonne, IL 60439 (United States)
2015-08-06
A simple frequency domain technique for determining the time delay between laser pump and X-ray probe pulses achieves 1 ps resolution even for ∼100 ps synchrotron pulses, permitting improved pump–probe characterization of ultrafast processes. Pump–probe studies at synchrotrons using X-ray and laser pulses require accurate determination of the time delay between pulses. This becomes especially important when observing ultrafast responses with lifetimes approaching or even less than the X-ray pulse duration (∼100 ps). The standard approach of inspecting the time response of a detector sensitive to both types of pulses can have limitations due to dissimilar pulse profiles and other experimental factors. Here, a simple alternative is presented, where the frequency response of the detector is monitored versus time delay. Measurements readily demonstrate a time resolution of ∼1 ps. Improved precision is possible by simply extending the data acquisition time.
Delay differential analysis of time series.
Lainscsek, Claudia; Sejnowski, Terrence J
2015-03-01
Nonlinear dynamical system analysis based on embedding theory has been used for modeling and prediction, but it also has applications to signal detection and classification of time series. An embedding creates a multidimensional geometrical object from a single time series. Traditionally either delay or derivative embeddings have been used. The delay embedding is composed of delayed versions of the signal, and the derivative embedding is composed of successive derivatives of the signal. The delay embedding has been extended to nonuniform embeddings to take multiple timescales into account. Both embeddings provide information on the underlying dynamical system without having direct access to all the system variables. Delay differential analysis is based on functional embeddings, a combination of the derivative embedding with nonuniform delay embeddings. Small delay differential equation (DDE) models that best represent relevant dynamic features of time series data are selected from a pool of candidate models for detection or classification. We show that the properties of DDEs support spectral analysis in the time domain where nonlinear correlation functions are used to detect frequencies, frequency and phase couplings, and bispectra. These can be efficiently computed with short time windows and are robust to noise. For frequency analysis, this framework is a multivariate extension of discrete Fourier transform (DFT), and for higher-order spectra, it is a linear and multivariate alternative to multidimensional fast Fourier transform of multidimensional correlations. This method can be applied to short or sparse time series and can be extended to cross-trial and cross-channel spectra if multiple short data segments of the same experiment are available. Together, this time-domain toolbox provides higher temporal resolution, increased frequency and phase coupling information, and it allows an easy and straightforward implementation of higher-order spectra across time
Delay Differential Analysis of Time Series
Lainscsek, Claudia; Sejnowski, Terrence J.
2015-01-01
Nonlinear dynamical system analysis based on embedding theory has been used for modeling and prediction, but it also has applications to signal detection and classification of time series. An embedding creates a multidimensional geometrical object from a single time series. Traditionally either delay or derivative embeddings have been used. The delay embedding is composed of delayed versions of the signal, and the derivative embedding is composed of successive derivatives of the signal. The delay embedding has been extended to nonuniform embeddings to take multiple timescales into account. Both embeddings provide information on the underlying dynamical system without having direct access to all the system variables. Delay differential analysis is based on functional embeddings, a combination of the derivative embedding with nonuniform delay embeddings. Small delay differential equation (DDE) models that best represent relevant dynamic features of time series data are selected from a pool of candidate models for detection or classification. We show that the properties of DDEs support spectral analysis in the time domain where nonlinear correlation functions are used to detect frequencies, frequency and phase couplings, and bispectra. These can be efficiently computed with short time windows and are robust to noise. For frequency analysis, this framework is a multivariate extension of discrete Fourier transform (DFT), and for higher-order spectra, it is a linear and multivariate alternative to multidimensional fast Fourier transform of multidimensional correlations. This method can be applied to short or sparse time series and can be extended to cross-trial and cross-channel spectra if multiple short data segments of the same experiment are available. Together, this time-domain toolbox provides higher temporal resolution, increased frequency and phase coupling information, and it allows an easy and straightforward implementation of higher-order spectra across time
Yamazaki, Tatsuya; Hagiwara, Tomomichi
2014-08-01
A new stability analysis method of time-delay systems (TDSs) called the monodromy operator approach has been studied under the assumption that a TDS is represented as a time-delay feedback system consisting of a finite-dimensional linear time-invariant (LTI) system and a pure delay. For applying this approach to TDSs described by delay-differential equations (DDEs), the problem of converting DDEs into representation as time-delay feedback systems has been studied. With regard to such a problem, it was shown that, under discontinuous initial functions, it is natural to define the solutions of DDEs in two different ways, and the above conversion problem was solved for each of these two definitions. More precisely, the solution of a DDE was represented as either the state of the finite-dimensional part of a time-delay feedback system or a part of the output of another time-delay feedback system, depending on which definition of the DDE solution one is talking about. Motivated by the importance in establishing a thorough relationship between time-delay feedback systems and DDEs, this paper discusses the opposite problem of converting time-delay feedback systems into representation as DDEs, including the discussions about the conversion of the initial conditions. We show that the state of (the finite-dimensional part of) a time-delay feedback system can be represented as the solution of a DDE in the sense of one of the two definitions, while its 'essential' output can be represented as that of another DDE in the sense of the other type of definition. Rigorously speaking, however, it is also shown that the latter representation is possible regardless of the initial conditions, while some initial condition could prevent the conversion into the former representation. This study hence establishes that the representation of TDSs as time-delay feedback systems possesses higher ability than that with DDEs, as description methods for LTI TDSs with commensurate delays.
Pradhan, Prabhakar; Sahay, Peeyush; Almabadi, Huda M.
2016-01-01
Considering the complex reflection amplitude R=|R|exp(i{\\theta}) of a light wave, real delay time {\\tau}_r (i.e., sojourn or Wigner delay time), which is the energy derivative of the real phase ({\\tau}_r =d{\\theta}/cdk), and complex delay time {\\tau}_i , which is the energy derivative of the reflection coefficient ({\\tau}_i=d{\\theta}_i/cdk, |R|=r^1/2=exp(-{\\theta}_i)), have the same statistical form and a mirror image with a shift in time in weak disorder and short length regime. Real delay t...
Wigner photoemission time delay from endohedral anions
Kumar, Ashish; Varma, Hari R.; Deshmukh, Pranawa C.; Manson, Steven T.; Dolmatov, Valeriy K.; Kheifets, Anatoli
2016-10-01
Characteristic features of Wigner photoemission time delay from endohedral anions A@C60q along with their dependence on the anion charge q are unraveled. Specifically, significant enhancement of the time delay in the innermost dipole photoionization channels near threshold is found, owing to the presence of the Coulomb confined resonances (CRs). Moreover, it is shown that interchannel coupling of the inner-shell Coulomb CRs with outer-shell photoionization channels results in resonantly enhanced time delay in the release of the outer-shell photoelectron well above, several hundreds eV, the outer-shell thresholds. It is also demonstrated that, and explained why, photoionization cross sections of the innermost subshells as well as outer subshells (near the inner-subshell threshold) depends only very weakly on the anion charge q , but the dependence of the corresponding time delays on q can be significant. Furthermore, Coulomb CRs are found to emerge in the innermost quadrupole photoionization channels as well, thereby causing considerable time delay in the quadrupole photoemission. These findings are illustrated in calculations of the photoionization of inner and outer subshells of the endohedral anions Ne@C60-1 and Ne@C60-5 that were chosen as case studies.
Time Delay for the Dirac Equation
Naumkin, Ivan; Weder, Ricardo
2016-10-01
We consider time delay for the Dirac equation. A new method to calculate the asymptotics of the expectation values of the operator {intlimits0 ^{∞}e^{iH0t}ζ(\\vert x\\vert /R) e^{-iH0t}dt}, as {R → ∞}, is presented. Here, H 0 is the free Dirac operator and {ζ(t)} is such that {ζ(t) = 1} for {0 ≤ t ≤ 1} and {ζ(t) = 0} for {t > 1}. This approach allows us to obtain the time delay operator {δ {T}(f)} for initial states f in {{H} 2^{3/2+ɛ}({R}3;{C}4)}, {ɛ > 0}, the Sobolev space of order {3/2+ɛ} and weight 2. The relation between the time delay operator {δ{T}(f)} and the Eisenbud-Wigner time delay operator is given. In addition, the relation between the averaged time delay and the spectral shift function is presented.
BOLD delay times using group delay in sickle cell disease
Coloigner, Julie; Vu, Chau; Bush, Adam; Borzage, Matt; Rajagopalan, Vidya; Lepore, Natasha; Wood, John
2016-03-01
Sickle cell disease (SCD) is an inherited blood disorder that effects red blood cells, which can lead to vasoocclusion, ischemia and infarct. This disease often results in neurological damage and strokes, leading to morbidity and mortality. Functional Magnetic Resonance Imaging (fMRI) is a non-invasive technique for measuring and mapping the brain activity. Blood Oxygenation Level-Dependent (BOLD) signals contain also information about the neurovascular coupling, vascular reactivity, oxygenation and blood propagation. Temporal relationship between BOLD fluctuations in different parts of the brain provides also a mean to investigate the blood delay information. We used the induced desaturation as a label to profile transit times through different brain areas, reflecting oxygen utilization of tissue. In this study, we aimed to compare blood flow propagation delay times between these patients and healthy subjects in areas vascularized by anterior, middle and posterior cerebral arteries. In a group comparison analysis with control subjects, BOLD changes in these areas were found to be almost simultaneous and shorter in the SCD patients, because of their increased brain blood flow. Secondly, the analysis of a patient with a stenosis on the anterior cerebral artery indicated that signal of the area vascularized by this artery lagged the MCA signal. These findings suggest that sickle cell disease causes blood propagation modifications, and that these changes could be used as a biomarker of vascular damage.
Time Delay Interferometry with Moving Spacecraft Arrays
Tinto, M; Armstrong, J W; Tinto, Massimo; Estabrook, Frank B.; Armstrong, adn J.W.
2004-01-01
Space-borne interferometric gravitational wave detectors, sensitive in the low-frequency (millihertz) band, will fly in the next decade. In these detectors the spacecraft-to-spacecraft light-travel-times will necessarily be unequal, time-varying, and (due to aberration) have different time delays on up- and down-links. Reduction of data from moving interferometric laser arrays in solar orbit will in fact encounter non-symmetric up- and downlink light time differences that are about 100 times larger than has previously been recognized. The time-delay interferometry (TDI) technique uses knowledge of these delays to cancel the otherwise dominant laser phase noise and yields a variety of data combinations sensitive to gravitational waves. Under the assumption that the (different) up- and downlink time delays are constant, we derive the TDI expressions for those combinations that rely only on four inter-spacecraft phase measurements. We then turn to the general problem that encompasses time-dependence of the light...
The Strong Lensing Time Delay Challenge (2014)
Liao, Kai; Dobler, G.; Fassnacht, C. D.; Treu, T.; Marshall, P. J.; Rumbaugh, N.; Linder, E.; Hojjati, A.
2014-01-01
Time delays between multiple images in strong lensing systems are a powerful probe of cosmology. At the moment the application of this technique is limited by the number of lensed quasars with measured time delays. However, the number of such systems is expected to increase dramatically in the next few years. Hundred such systems are expected within this decade, while the Large Synoptic Survey Telescope (LSST) is expected to deliver of order 1000 time delays in the 2020 decade. In order to exploit this bounty of lenses we needed to make sure the time delay determination algorithms have sufficiently high precision and accuracy. As a first step to test current algorithms and identify potential areas for improvement we have started a "Time Delay Challenge" (TDC). An "evil" team has created realistic simulated light curves, to be analyzed blindly by "good" teams. The challenge is open to all interested parties. The initial challenge consists of two steps (TDC0 and TDC1). TDC0 consists of a small number of datasets to be used as a training template. The non-mandatory deadline is December 1 2013. The "good" teams that complete TDC0 will be given access to TDC1. TDC1 consists of thousands of lightcurves, a number sufficient to test precision and accuracy at the subpercent level, necessary for time-delay cosmography. The deadline for responding to TDC1 is July 1 2014. Submissions will be analyzed and compared in terms of predefined metrics to establish the goodness-of-fit, efficiency, precision and accuracy of current algorithms. This poster describes the challenge in detail and gives instructions for participation.
Time-delayed autosynchronous swarm control.
Biggs, James D; Bennet, Derek J; Dadzie, S Kokou
2012-01-01
In this paper a general Morse potential model of self-propelling particles is considered in the presence of a time-delayed term and a spring potential. It is shown that the emergent swarm behavior is dependent on the delay term and weights of the time-delayed function, which can be set to induce a stationary swarm, a rotating swarm with uniform translation, and a rotating swarm with a stationary center of mass. An analysis of the mean field equations shows that without a spring potential the motion of the center of mass is determined explicitly by a multivalued function. For a nonzero spring potential the swarm converges to a vortex formation about a stationary center of mass, except at discrete bifurcation points where the center of mass will periodically trace an ellipse. The analytical results defining the behavior of the center of mass are shown to correspond with the numerical swarm simulations.
Information transfer via implicit encoding with delay time modulation in a time-delay system
Energy Technology Data Exchange (ETDEWEB)
Kye, Won-Ho, E-mail: whkye@kipo.go.kr [Korean Intellectual Property Office, Government Complex Daejeon Building 4, 189, Cheongsa-ro, Seo-gu, Daejeon 302-701 (Korea, Republic of)
2012-08-20
A new encoding scheme for information transfer with modulated delay time in a time-delay system is proposed. In the scheme, the message is implicitly encoded into the modulated delay time. The information transfer rate as a function of encoding redundancy in various noise scales is presented and it is analyzed that the implicit encoding scheme (IES) has stronger resistance against channel noise than the explicit encoding scheme (EES). In addition, its advantages in terms of secure communication and feasible applications are discussed. -- Highlights: ► We propose new encoding scheme with delay time modulation. ► The message is implicitly encoded with modulated delay time. ► The proposed scheme shows stronger resistance against channel noise.
Time delay measurement in the frequency domain
Durbin, Stephen M.; Liu, Shih-Chieh; Dufresne, Eric M.; Li, Yuelin; Wen, Haidan
2015-01-01
Pump–probe studies at synchrotrons using X-ray and laser pulses require accurate determination of the time delay between pulses. This becomes especially important when observing ultrafast responses with lifetimes approaching or even less than the X-ray pulse duration (∼100 ps). The standard approach of inspecting the time response of a detector sensitive to both types of pulses can have limitations due to dissimilar pulse profiles and other experimental factors. Here, a simple alternative is presented, where the frequency response of the detector is monitored versus time delay. Measurements readily demonstrate a time resolution of ∼1 ps. Improved precision is possible by simply extending the data acquisition time. PMID:26289282
On the time delay between ultrarelativistic particles
Fleury, Pierre
2016-01-01
The time delay between the receptions of ultrarelativistic particles emitted simultaneously is an observable for both fundamental physics and cosmology. The expression of the delay when the particles travel through an arbitrary spacetime has been derived recently in arXiv:1512.08489, using a particular coordinate system and self-consistent assumptions. In this article I show that this formula enjoys a simple physical interpretation: the relative velocity between two ultrarelativistic particles is constant. This result reveals an interesting kinematical property of general relativity, namely that the tidal forces experienced by ultrarelativistic particles in the direction of their motion are much smaller than those experienced orthogonally to their motion.
Time-delayed electromagnetic radiation reaction
Faci, Sofiane
2016-01-01
The Lorentz-Abraham-Dirac (LAD) equation has proved valuable in describing the motion of radiating electric charges but suffers from runaway, pre-acceleration and other ambiguities. The usual scheme is problematic because of locality, which leads to self-interaction with the propagating radiation (i.e. real photons). Instead, the present heuristic model relies on an infinitesimal time delay between the action of external forces and the inertial reaction by the charge. This yields a new and pathology-free equation of motion whereas the radiated energy-momentum is expressed as an infinite series that generalises Larmor's formula and leads to testable predictions using current and near future ultra-intense lasers. The time-delay hypothesis is to be put in parallel with recently observed delays of order $10^{-18}$s (attosecond) in photoemission by atoms and small molecules. Such behaviour is extended here to elementary charges which are supposed to exhibit delays given by the time taken by light to cross the char...
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.
Model Epidemi Sirs Dengan Time Delay
Sinuhaji, Ferdinand
2016-01-01
The epidemic is an outbreak of an infectious disease situation in the population at a place that exceeds the normal approximation in a short period. When the disease is always contained in any place as well as with the causes, it is called endemic. This study discusses decrease SIRS epidemic models with time delay through a mathematical model based on the model of SIRS epidemic (Susceptible, Infective, Recovered, Susceptible). SIRS models used in this study with the assumption ...
Cosmic Neutrino Time Delay Relative to Photons
Institute of Scientific and Technical Information of China (English)
LUO Xin-Lian; PENG Qiu-He; ZHANG Ling-Di; BAI Hua; CHOU Chih-Kang
2004-01-01
By solving the Friedmann-Robertson-Walker (FRW) geodesic equations for a free test particle with finite mass,we extend the widely used time-of-flight delay expression, which is just valid locally in the neighbourhood of our Galaxy, to the cosmic distance scale. If neutrino masses are known, this may provide a potential method to determine a large scale geometry of the Universe.
Dark energy with gravitational lens time delays
Treu, T; Cyr-Racine, F -Y; Fassnacht, C D; Keeton, C R; Linder, E V; Moustakas, L A; Bradac, M; Buckley-Geer, E; Collett, T; Courbin, F; Dobler, G; Finley, D A; Hjorth, J; Kochanek, C S; Komatsu, E; Koopmans, L V E; Meylan, G; Natarajan, P; Oguri, M; Suyu, S H; Tewes, M; Wong, K C; Zabludoff, A I; Zaritsky, D; Anguita, T; Brunner, R J; Cabanac, R; Falco, E E; Fritz, A; Seidel, G; Howell, D A; Giocoli, C; Jackson, N; Lopez, S; Metcalf, R B; Motta, V; Verdugo, T
2013-01-01
Strong lensing gravitational time delays are a powerful and cost effective probe of dark energy. Recent studies have shown that a single lens can provide a distance measurement with 6-7 % accuracy (including random and systematic uncertainties), provided sufficient data are available to determine the time delay and reconstruct the gravitational potential of the deflector. Gravitational-time delays are a low redshift (z~0-2) probe and thus allow one to break degeneracies in the interpretation of data from higher-redshift probes like the cosmic microwave background in terms of the dark energy equation of state. Current studies are limited by the size of the sample of known lensed quasars, but this situation is about to change. Even in this decade, wide field imaging surveys are likely to discover thousands of lensed quasars, enabling the targeted study of ~100 of these systems and resulting in substantial gains in the dark energy figure of merit. In the next decade, a further order of magnitude improvement will...
Delay-Dependent Observers for Uncertain Nonlinear Time-Delay Systems
Directory of Open Access Journals (Sweden)
Dongmei Yan
2013-05-01
Full Text Available This paper is concerned with the observer design problem for a class of discrete-time uncertain nonlinear systems with time-varying delay. The nonlinearities are assumed to satisfy global Lipschitz conditions which appear in both the state and measurement equations. The uncertainties are assumed to be time-varying but norm-bounded. Two Luenberger-like observers are proposed. One is delay observer and the other is delay-free observer. The delay observer which has an internal time delay is applicable when the time delay is known. The delay-free observer which does not use delayed information is especially applicable when the time delay is not known explicitly. Delay-dependent conditions for the existences of these two observers are derived based on Lyapunpv functional approach. Based on these conditions, the observer gains are obtained using the cone complementarity linearization algorithm. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.
H∞ State Feedback Delay-dependent Control for Discrete Systems with Multi-time-delay
Institute of Scientific and Technical Information of China (English)
Bai-Da Qu
2005-01-01
In this paper,H∞ state feedback control with delay information for discrete systems with multi-time-delay is discussed. Making use of linear matrix inequality (LMI) approach, a time-delay-dependent criterion for a discrete system with multi-time-delay to satisfy H∞ performance indices is induced, and then a strategy for H∞ state feedback control with delay values for plant with multi-time-delay is obtained. By solving corresponding LMI, a delay-dependent state feedback controller satisfying H∞ performance indices is designed. Finally, a simulation example demonstrates the validity of the proposed approach.
Synchronization of time-delay chaotic systems on small-world networks with delayed coupling
Institute of Scientific and Technical Information of China (English)
Qi Wei; Wang Ying-Hai
2009-01-01
By using the well-known Ikeda model as the node dynamics,this paper studies synchronization of time-delay systems on small-world networks where the connections between units involve time delays.It shows that,in contrast with the undelayed case,networks with delays can actually synchronize more easily.Specifically,for randomly distributed delays,time-delayed mutual coupling suppresses the chaotic behaviour by stabilizing a fixed point that is unstable for the uncoupled dynamical system.
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.
What Do Gravitational Lens Time Delays Measure?
Kochanek, C S
2002-01-01
Gravitational lens time delays depend on the Hubble constant, the observed image positions, and the surface mass density of the lens in the annulus between the images. Simple time delay lenses like PG1115+080, SBS1520+530, B1600+434, PKS1830-211 and HE2149-2745 have H0 = A(1-)+B(e-1) where the two coefficients A ~ 90km/s Mpc and B ~ 10km/s Mpc depend on the measured delays and the observed image positions, is the mean surface density in the annulus between the images, and there is a small correction from the logarithmic slope e ~ 2 of the surface density profile, k ~ R^(1-e), in the annulus. These 5 systems are very homogeneous, since for fixed H0=100h km/s Mpc they must have the same surface density, =1.11-1.22 h +/- 0.04, with an upper bound of 0.07 on any dispersion in beyond those due to the measurement errors. If the lenses have their expected dark halos, ~ 0.5 and H0=51+/-5 km/s Mpc, while if they have constant mass-to-light ratios, ~ 0.1-0.2 and H0=73+/-8 km/s Mpc. More complicated lenses with mult...
Absolute Stability for Lurie Control System with Unbound Time Delays
Institute of Scientific and Technical Information of China (English)
王天成; 王耀才; 洪留荣
2004-01-01
Time delay existes widely in various real engineering systems and can result in unsatisfactory performance or even an instability of control systems. Therefore, to investigate the stability for time delay systems is of vitul importance in control theory and its applications. Many researchers have studied the stability criteria of systems with constant delay or bound varying time delay, but few of them studied large time delay or unbound time delay. Large time delay existes commonly in various engineering applications. In this paper, the absolute stability of Lurie type direct control systems and indirect control systems with several time delays are discussed. Based on Lyapunov theory, the new delay dependent absolute stability criteria are derived. In our theorem, time delays can be unbound functions, which shows that the results are less conservative than that of existed criteria.
Delay Time Analysis of Reconfigurable Firewall Unit
Directory of Open Access Journals (Sweden)
Tomoaki Sato
2012-10-01
Full Text Available A firewall function is indispensable for mobile devices and it demands low-power operations. To realize this demand, the authors have developed a firewall unit with a reconfigurable device. The firewall unit needs a large amount of register for the timing adjustment of packets. Using the registers is the cause of power consumption. In this paper, to solve the problem of power consumption, the firewall unit has developed by using wave-pipelining technique and detailed delay time for the technique is analyzed.
Delay time for a single resonance
Energy Technology Data Exchange (ETDEWEB)
Moshinsky, M.; Monsivais, G. [Instituto de Fisica, UNAM, Apartado Postal 20-364, 01000 Mexico, DF (Mexico)
1997-05-01
Delay time is usually discussed in terms of a wavepacket going through a potential barrier and its time of reappearance on the other side of it, as compared with the corresponding problem in free motion. Wigner stressed though that an interaction should be described by an R matrix and a particular case would be that of a single resonance. Long ago a dynamical model was developed for this case in which the interaction takes place at a point through boundary conditions. It is used here to discuss the passage to x>0 of a plane wave initially constrained to the interval -{infinity}
Time averaging, ageing and delay analysis of financial time series
Cherstvy, Andrey G.; Vinod, Deepak; Aghion, Erez; Chechkin, Aleksei V.; Metzler, Ralf
2017-06-01
We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black-Scholes-Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics.
Ailing Qi; Xuewei Ju; Qing Zhang; Zengqiang Chen
2016-01-01
This paper is concerned with the structural controllability analysis for discrete-time linear control systems with time-delay. By adding virtual delay nodes, the linear systems with time-delay are transformed into corresponding linear systems without time-delay, and the structural controllability of them is equivalent. That is to say, the time-delay does not affect or change the controllability of the systems. Several examples are also presented to illustrate the theoretical results.
Delay and Its Time-Derivative Dependent Bounded Real Lemma for Linear Time-Delay Systems
Institute of Scientific and Technical Information of China (English)
JIANGXiefu; XUWenli
2004-01-01
Based on an appropriate Lyapunov-Krasovskii functional, this paper deals with the problem of the bounded real lemma for linear continuous-time systems with state delay. The system under consideration involves state time-varying time-delay. A sufficient condition for the system to possess a H∞-norm that is less than a prescribed level, is presented in a Linear matrix inequality(LMI) form which is dependent on both the size of timedelay and the size of its time-derivative. Due to that fewercross terms should be bounded, our result is less conservative. Finally, an example is presented to demonstrate the effectiveness of our result.
Time Delay of Microdialysis in vitro
Huang, Shao-Hong; Zhang, Jian; Li, Yun; Rong, Jian; Wu, Zhong-Kai
2013-01-01
Background: Microdialysis is a specific and local sampling method to collect free molecules from the extracellular fluid, however, there are no reports on time delay issues of microdialysis applications. Aims: This study was to check the time gap between the start of target molecule changes in detected fluid and corresponding stable concentration formation in the sampled dialysate. Materials and Methods: A designated microdialysis system for free calcium ion was set up in vitro and perfused with saline. The dialysate was diluted synchronously, and collected in a vial every 10 min. The free calcium concentration [Ca++] of the sample was measured by an atomic absorption spectrophotometer. A signal-switching method was introduced to mimic the target molecule [Ca++] changes in the detected fluid, standard calcium solution and saline. Results: There was a notable lag in dialysates [Ca++] for both uprising and down going course in spite of instant switching between the detected fluids. The recovery time (RT) of the microdialysis system was extrapolated to be 20 min for [Ca++] detection. Conclusions: With 10 min sampling interval, [Ca++] time delay of the microdialysis system existed, and could not be estimated precisely beforehand. The signal-switching method was applicable for RT calibration in vitro with a dedicated microdialysis system. PMID:23641379
Time delay of microdialysis in vitro
Directory of Open Access Journals (Sweden)
Shao-Hong Huang
2013-01-01
Full Text Available Background : Microdialysis is a specific and local sampling method to collect free molecules from the extracellular fluid, however, there are no reports on time delay issues of microdialysis applications. Aims : This study was to check the time gap between the start of target molecule changes in detected fluid and corresponding stable concentration formation in the sampled dialysate. Materials and Methods : A designated microdialysis system for free calcium ion was set up in vitro and perfused with saline. The dialysate was diluted synchronously, and collected in a vial every 10 min. The free calcium concentration [Ca++] of the sample was measured by an atomic absorption spectrophotometer. A signal-switching method was introduced to mimic the target molecule [Ca++] changes in the detected fluid, standard calcium solution and saline. Results : There was a notable lag in dialysates [Ca++] for both uprising and down going course in spite of instant switching between the detected fluids. The recovery time (RT of the microdialysis system was extrapolated to be 20 min for [Ca++] detection. Conclusions : With 10 min sampling interval, [Ca++] time delay of the microdialysis system existed, and could not be estimated precisely beforehand. The signal-switching method was applicable for RT calibration in vitro with a dedicated microdialysis system.
Angular dependence of Wigner time delay: Relativistic Effects
Mandal, A.; Deshmukh, P. C.; Manson, S. T.; Kkeifets, A. S.
2016-05-01
Laser assisted photoionization time delay mainly consists of two parts: Wigner time delay, and time delay in continuum-continuum transition. Wigner time delay results from the energy derivative of the phase of the photoionization amplitude (matrix element). In general, the photoionization time delay is not the same in all directions relative to the incident photon polarization, although when a single transition dominates the amplitude, the resultant time delay is essentially isotropic. The relativistic-random-phase approximation is employed to determine the Wigner time delay in photoionization from the outer np subshells of the noble gas atoms, Ne through Xe. The time delay is found to significantly depend on angle, as well as energy. The angular dependence of the time delay is found to be quite sensitive to atomic dynamics and relativistic effects, and exhibit strong energy and angular variation in the neighborhood of Cooper minima. Work supported by DOE, Office of Chemical Sciences and DST (India).
Controlling flow time delays in flexible manufacturing cells
Slomp, J.; Caprihan, R.; Bokhorst, J. A. C.
2009-01-01
Flow time delays in Flexible Manufacturing Cells (FMCs) are caused by transport and clamping/reclamping activities. This paper shows how dynamic scheduling parameters may control the flow times of jobs and the available task windows for flow time delays.
Diagonal loading least squares time delay estimation
Institute of Scientific and Technical Information of China (English)
LI Xuan; YAN Shefeng; MA Xiaochuan
2012-01-01
Least squares （LS） time delay estimation is a classical and effective method. However, the performance is degraded severely in the scenario of low ratio of signal-noise （SNR） due to the instability of matrix inversing. In order to solve the problem, diagonal loading least squares （DL-LS） is proposed by adding a positive definite matrix to the inverse matrix. Furthermore, the shortcoming of fixed diagonal loading is analyzed from the point of regularization that when the tolerance of low SNR is increased, veracity is decreased. This problem is resolved by reloading. The primary estimation＇s reciprocal is introduced as diagonal loading and it leads to small diagonal loading at the time of arrival and larger loading at other time. Simulation and pool experiment prove the algorithm has better performance.
Time-delay feedback control in a delayed dynamical chaos system and its applications
Institute of Scientific and Technical Information of China (English)
Ye Zhi-Yong; Yang Guang; Deng Cun-Bing
2011-01-01
The feedback control of a delayed dynamical system, which also includes various chaotic systems with time delays, is investigated. On the basis of stability analysis of a nonautonomons system with delays, some simple yet less conservative criteria are obtained for feedback control in a delayed dynamical system. Finally, the theoretical result is applied to a typical class of chaotic Lorenz system and Chua circuit with delays. Numerical simulations are also given to verify the theoretical results.
Distributed Time Delay Goodwin's Models of the Business Cycle
Antonova, A. O.; Reznik, S. N.; Todorov, M. D.
2011-11-01
We consider continuously distributed time delay Goodwin's model of the business cycle. We show that the delay induced sawtooth oscillations, similar to those detected by R. H. Strotz, J. C. McAnulty, J. B. Naines, Econometrica, 21, 390-411 (1953) for Goodwin's model with fixed investment time lag, exist only for very narrow delay distribution when the variance of the delay distribution much less than the average delay.
Effect of shift working on reaction time in hospital employees.
Namita; Ranjan, Din Prakash; Shenvi, Dhangauri N
2010-01-01
Visual and Auditory reaction time (VRT, ART) were studied in 286 hospital employees during day duty and night duty in the age group of 20 to 60 years to find out the effect of shift working on reaction time in hospital employees. Subjects were presented with two visual stimuli i.e. red and green light and two auditory stimuli, i.e., high pitch and low pitch sound stimuli. The significance of difference of VRT and ART during day duty and night duty was studied with the use of standard error of difference between two means. The statistical difference was determined by 'z' test. VRT during day duty (231.60 +/- 30.93) were less than VRT during night duty (234.98 +/- 32.27) and ART during day duty (224.69 +/- 46.95) were also less than ART during night duty (228.74 +/- 47.01). Our results indicate that reaction time is more during night duty as compared to day duty but the difference is not significant. It may be because of hospital employees get adapted to reduced sleep after working continuously in the shift system.
Variable-delay feedback control of unstable steady states in retarded time-delayed systems
Gjurchinovski, Aleksandar; 10.1103/PhysRevE.81.016209
2010-01-01
We study the stability of unstable steady states in scalar retarded time-delayed systems subjected to a variable-delay feedback control. The important aspect of such a control problem is that time-delayed systems are already infinite-dimensional before the delayed feedback control is turned on. When the frequency of the modulation is large compared to the system's dynamics, the analytic approach consists of relating the stability properties of the resulting variable-delay system with those of an analogous distributed delay system. Otherwise, the stability domains are obtained by a numerical integration of the linearized variable-delay system. The analysis shows that the control domains are significantly larger than those in the usual time-delayed feedback control, and that the complexity of the domain structure depends on the form and the frequency of the delay modulation.
Delay-dependent state feedback robust stabilization for uncertain singular time-delay systems
Institute of Scientific and Technical Information of China (English)
Gao Huanli; Xu Bugong
2008-01-01
The problem of robust stabilization for uncertain singular time-delay systems is studied.First,a new delay-dependent asymptotic stability criteria for normal singular time-delay systems is given,which is less conservative.Using this result,the problem of state feedback robust stabilization for uncertain singular time-delay systems is discussed.Finally,two examples are given to illustrate the effectiveness of the results.
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.
Relativistic calculations of angular dependent photoemission time delay
Kheifets, A S; Deshmukh, P C; Dolmatov, V K; Manson, S T
2016-01-01
Angular dependence of photoemission time delay for the valence $np_{3/2}$ and $np_{1/2}$ subshells of Ar, Kr and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold.
14 CFR 417.221 - Time delay analysis.
2010-01-01
... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Time delay analysis. 417.221 Section 417... OF TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.221 Time delay analysis. (a) General. A flight safety analysis must include a time delay analysis that establishes the mean...
Relativistic calculations of angle-dependent photoemission time delay
Kheifets, Anatoli; Mandal, Ankur; Deshmukh, Pranawa C.; Dolmatov, Valeriy K.; Keating, David A.; Manson, Steven T.
2016-07-01
Angular dependence of photoemission time delay for the valence n p3 /2 and n p1 /2 subshells of Ar, Kr, and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold.
Delay-dependent stability analysis for discrete-time systems with time varying state delay
Directory of Open Access Journals (Sweden)
Stojanović Sreten B.
2011-01-01
Full Text Available The stability of discrete systems with time-varying delay is considered. Some sufficient delaydependent stability conditions are derived using an appropriate model transformation of the original system. The criteria are presented in the form of LMI, which are dependent on the minimum and maximum delay bounds. It is shown that the stability criteria are approximately the same conservative as the existing ones, but have much simpler mathematical form. The numerical example is presented to illustrate the applicability of the developed results.
Mixed delay-independent/delay-dependent stability of uncertain linear time-delayed systems
Institute of Scientific and Technical Information of China (English)
LI Wenlin; DONG Rui
2004-01-01
@@ Consider uncertain linear time delay systems described by the following state equation: x(t)=[A0+Δ A0(t)]x(t)+∑ri=1[Ai+ΔAi(t)]x(t-τi).(1) x(t)=(t)t∈[-,0];=maxri=1{τi}(2) where Δ A0(*) and Δ Ai(*)(i=1,…,r) are real matrix functions.Δ Ai(t)=LiFi(t)Ei,ΔA0(t)=L0F0(t)E0, where Li,Ei are known real constant matrices and Fi(t) are unknown real time-varying matrices with Lebesgue measurable elements satisfying ‖Fi(t)‖I,t(i=0,1,…,r). In this note, we develop the methods of robust stability which is dependent on the size of some delays but independent on the size of the others and is based on the solution of linear matrix inequalities.
The effects of the framing of time on delay discounting.
DeHart, William Brady; Odum, Amy L
2015-01-01
We examined the effects of the framing of time on delay discounting. Delay discounting is the process by which delayed outcomes are devalued as a function of time. Time in a titrating delay discounting task is often framed in calendar units (e.g., as 1 week, 1 month, etc.). When time is framed as a specific date, delayed outcomes are discounted less compared to the calendar format. Other forms of framing time; however, have not been explored. All participants completed a titrating calendar unit delay-discounting task for money. Participants were also assigned to one of two delay discounting tasks: time as dates (e.g., June 1st, 2015) or time in units of days (e.g., 5000 days), using the same delay distribution as the calendar delay-discounting task. Time framed as dates resulted in less discounting compared to the calendar method, whereas time framed as days resulted in greater discounting compared to the calendar method. The hyperboloid model fit best compared to the hyperbola and exponential models. How time is framed may alter how participants attend to the delays as well as how the delayed outcome is valued. Altering how time is framed may serve to improve adherence to goals with delayed outcomes.
Zhong-Da Tian; Shu-Jiang Li; Yan-Hong Wang; Hong-Xia Yu
2015-01-01
The random time delay in a networked control system can usually deteriorate the control performance and stability of the networked control system. In order to solve this problem, this paper puts forward a networked control system random time-delay compensation method based on time-delay prediction and improved implicit generalized predictive control (GPC). The least squares support vector machine is used to predict the future time delay of network. The parameters of the least squares support...
Estimation of time delays from unresolved photometry
Hirv, A; Liimets, T; Liivam"agi, L J; Pelt, J; Liimets, Tiina
2006-01-01
Long-time monitoring of gravitational lens systems is often done using telescopes and recording equipment with a modest resolution. Still, it would be interesting to get as much information as possible from the measured lightcurves. From high resolution images we know that the recorded quasar images are often blends and that the corresponding time series are not pure shifted replicas of the source variability. In this paper we will develop an algorithm to unscramble this kind of blended data. The proposed method is based on a simple idea. We use one of the photometric curves, which is supposedly a simple shifted replica of the source curve, to build different artificial combined curves. Then we compare these artificial curves with the blended curves. Proper solutions for a full set of time delays are then obtained by varying free input parameters and estimating statistical distances between the artificial and blended curves. We performed a check of feasibility and applicability of the new algorithm. For numer...
Phase and Complete Synchronizations in Time-Delay Systems
Senthilkumar, D. V.; Manju Shrii, M.; Kurths, J.
2013-01-01
Synchronization is a fundamental nonlinear phenomenon that has been intensively investigated during a couple of decades. Recently, synchronization of time-delay systems with or without delay coupling and even synchronization of low-dimensional dynamical systems described by ordinary differential equations and maps with delay coupling have become an active area of research in view of its potential applications. In this article, we provide an overview of our recent results on phase synchronization in time-delay systems, which usually exhibits hyperchaotic attractors with complex topological properties, noise-enhanced phase and noise-induced complete synchronizations in time-delay systems. Further, we demonstrate the phenomena of delay-enhanced and delay-induced stable synchronous chaos in a delay coupled network of time continuous dynamical system using the framework of master stability formalism (MSF) for the first time.
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.
Recovery of delay time from time series based on the nearest neighbor method
Energy Technology Data Exchange (ETDEWEB)
Prokhorov, M.D., E-mail: mdprokhorov@yandex.ru [Saratov Branch of Kotel' nikov Institute of Radio Engineering and Electronics of Russian Academy of Sciences, Zelyonaya Street, 38, Saratov 410019 (Russian Federation); Ponomarenko, V.I. [Saratov Branch of Kotel' nikov Institute of Radio Engineering and Electronics of Russian Academy of Sciences, Zelyonaya Street, 38, Saratov 410019 (Russian Federation); Department of Nano- and Biomedical Technologies, Saratov State University, Astrakhanskaya Street, 83, Saratov 410012 (Russian Federation); Khorev, V.S. [Department of Nano- and Biomedical Technologies, Saratov State University, Astrakhanskaya Street, 83, Saratov 410012 (Russian Federation)
2013-12-09
We propose a method for the recovery of delay time from time series of time-delay systems. The method is based on the nearest neighbor analysis. The method allows one to reconstruct delays in various classes of time-delay systems including systems of high order, systems with several coexisting delays, and nonscalar time-delay systems. It can be applied to time series heavily corrupted by additive and dynamical noise.
Recovery of delay time from time series based on the nearest neighbor method
Prokhorov, M. D.; Ponomarenko, V. I.; Khorev, V. S.
2013-12-01
We propose a method for the recovery of delay time from time series of time-delay systems. The method is based on the nearest neighbor analysis. The method allows one to reconstruct delays in various classes of time-delay systems including systems of high order, systems with several coexisting delays, and nonscalar time-delay systems. It can be applied to time series heavily corrupted by additive and dynamical noise.
Survey of time preference, delay discounting models
Directory of Open Access Journals (Sweden)
John R. Doyle
2013-03-01
Full Text Available The paper surveys over twenty models of delay discounting (also known as temporal discounting, time preference, time discounting, that psychologists and economists have put forward to explain the way people actually trade off time and money. Using little more than the basic algebra of powers and logarithms, I show how the models are derived, what assumptions they are based upon, and how different models relate to each other. Rather than concentrate only on discount functions themselves, I show how discount functions may be manipulated to isolate rate parameters for each model. This approach, consistently applied, helps focus attention on the three main components in any discounting model: subjectively perceived money; subjectively perceived time; and how these elements are combined. We group models by the number of parameters that have to be estimated, which means our exposition follows a trajectory of increasing complexity to the models. However, as the story unfolds it becomes clear that most models fall into a smaller number of families. We also show how new models may be constructed by combining elements of different models. The surveyed models are: Exponential; Hyperbolic; Arithmetic; Hyperboloid (Green and Myerson, Rachlin; Loewenstein and Prelec Generalized Hyperboloid; quasi-Hyperbolic (also known as beta-delta discounting; Benhabib et al's fixed cost; Benhabib et al's Exponential / Hyperbolic / quasi-Hyperbolic; Read's discounting fractions; Roelofsma's exponential time; Scholten and Read's discounting-by-intervals (DBI; Ebert and Prelec's constant sensitivity (CS; Bleichrodt et al.'s constant absolute decreasing impatience (CADI; Bleichrodt et al.'s constant relative decreasing impatience (CRDI; Green, Myerson, and Macaux's hyperboloid over intervals models; Killeen's additive utility; size-sensitive additive utility; Yi, Landes, and Bickel's memory trace models; McClure et al.'s two exponentials; and Scholten and Read's trade
Energy Technology Data Exchange (ETDEWEB)
Kwon, O.M., E-mail: madwind@chungbuk.ac.k [School of Electrical Engineering, Chungbuk National University, Cheongju (Korea, Republic of); Lee, S.M., E-mail: moony@daegu.ac.k [School of Electronics Engineering, Daegu University, Kyongsan (Korea, Republic of); Park, Ju H., E-mail: jessie@ynu.ac.k [Department of Electrical Engineering, Yeungnam University, Kyongsan (Korea, Republic of)
2010-02-22
This Letter investigates the problem of delay-dependent exponential stability analysis for uncertain stochastic neural networks with time-varying delay. Based on the Lyapunov stability theory, improved delay-dependent exponential stability criteria for the networks are established in terms of linear matrix inequalities (LMIs).
Influence of Dark Energy on Gravitational Time Delay
Institute of Scientific and Technical Information of China (English)
CHEN Ju-Hua; WANG Yong-Jiu
2008-01-01
We investigate the gravitational time delay of light in the Schwarzschild black hole space-time surrounded by quintessence.With the analysis and numerical methods,we find that the gravitational time delay of light in the Schwarzschild black hole space-time surrounded by quintessence incrcases when the normalization factor c incrcases,and that the gravitational time delay also decrcases when the quintessential state parameter ωq incrcases.
Time to implement delayed cord clamping.
McAdams, Ryan M
2014-03-01
Immediate umbilical cord clamping after delivery is routine in the United States despite little evidence to support this practice. Numerous trials in both term and preterm neonates have demonstrated the safety and benefit of delayed cord clamping. In premature neonates, delayed cord clamping has been shown to stabilize transitional circulation, lessening needs for inotropic medications and reducing blood transfusions, necrotizing enterocolitis, and intraventricular hemorrhage. In term neonates, delayed cord clamping has been associated with decreased iron-deficient anemia and increased iron stores with potential valuable effects that extend beyond the newborn period, including improvements in long-term neurodevelopment. The failure to more broadly implement delayed cord clamping in neonates ignores published benefits of increased placental blood transfusion at birth and may represent an unnecessary harm for vulnerable neonates.
Delay time and Hartman effect in strain engineered graphene
Energy Technology Data Exchange (ETDEWEB)
Chen, Xi, E-mail: xchen@shu.edu.cn; Deng, Zhi-Yong [Department of Physics, Shanghai University, 200444 Shanghai (China); Ban, Yue, E-mail: yban@shu.edu.cn [Department of Electronic Information Materials, Shanghai University, 200444 Shanghai (China)
2014-05-07
Tunneling times, including group delay and dwell time, are studied for massless Dirac electrons transmitting through a one-dimensional barrier in strain-engineered graphene. The Hartman effect, the independence of group delay on barrier length, is induced by the strain effect, and associated with the transmission gap and the evanescent mode. The influence of barrier height/length and strain modulus/direction on the group delay is also discussed, which provides the flexibility to control the group delay with applications in graphene-based devices. The relationship between group delay and dwell time is finally derived to clarify the nature of the Hartman effect.
Time Delay Tracking for Multiuser Synchronization in CDMA Networks
Directory of Open Access Journals (Sweden)
Zahid Ali
2013-09-01
Full Text Available Multipath propagation, multiple access interference and non-line of sight propagation, etc. have impeded the accuracy in mobile data measurements. Multiuser receivers in asynchronous Code Division Multiple Access (CDMA systems require the knowledge of several parameters such as timing delay between users. In this paper, the problem of time delay estimation for CDMA systems is examined by proposing an approach based on blind nonlinear least mean squares (LMS based early-late delay tracker. A system model is developed and a delay tracking algorithm is presented. The simulation results of the proposed delay tracker are compared with the classical delay-locked loop (DLL approach in a multipath scenario and these show that the proposed delay tracker provides very good performance in challenging cases of closely spaced multipath delays.
Interval estimation for uncertain systems with time-varying delays
Efimov, Denis; Perruquetti, Wilfrid; Richard, Jean-Pierre
2013-10-01
The estimation problem for uncertain time-delay systems is addressed. A design method of reduced-order interval observers is proposed. The observer estimates the set of admissible values (the interval) for the state at each instant of time. The cases of known fixed delays and uncertain time-varying delays are analysed. The proposed approach can be applied to linear delay systems and nonlinear time-delay systems in the output canonical form. It involves the properties of quasi-monotone/Metzler/cooperative systems. In this framework, it is shown that if under a suitable coordinate transformation the delay-free subsystem is cooperative, then the delayed estimation error dynamics inherits this property. The conditions to find the observer gains are formulated in the form of LMI. The framework efficiency is demonstrated on examples of nonlinear systems.
Isochronal synchronization of time delay and delay-coupled chaotic systems
Energy Technology Data Exchange (ETDEWEB)
Grzybowski, J M V; Yoneyama, T [Instituto Tecnologico de Aeronautica, ITA, Praca Marechal Eduardo Gomes, 50, Vila das Acacias, Sao Jose dos Campos, SP, Brazil, CEP 12.228-900 (Brazil); Macau, E E N, E-mail: zzmariovic@yahoo.com.br, E-mail: elbert@lac.inpe.br, E-mail: takashi@ita.br [Instituto Nacional de Pesquisas Espaciais, INPE, PO Box 515, Sao Jose dos Campos, SP, Brazil, CEP 12.227-010 (Brazil)
2011-04-29
This paper studies the problem of isochronal synchronization of time-delay chaotic systems featuring also coupling delay. Based on the Lyapunov-Krasovskii stability theory, sufficient conditions are derived for the stability of isochronal synchronization between a pair of identical chaotic systems. Such criteria permit the proper design of stable proportional linear feedback controller, more specifically, the design of adequate proportional feedback gain matrices. The proposed criteria are suited to systems with (i) intrinsic delay, (ii) coupling delay or (iii) both. Numerical simulations of the synchronization of delay-coupled systems are presented as examples of the application of the criteria.
Delay dependent stability criteria for recurrent neural networks with time varying delays
Institute of Scientific and Technical Information of China (English)
Zhanshan WANG; Huaguang ZHANG
2009-01-01
This paper aims to present some delay-dependent global asymptotic stability criteria for recurrent neural networks with time varying delays.The obtained results have no restriction on the magnitude of derivative of time varying delay,and can be easily checked due to the form of linear matrix inequality.By comparison with some previous results,the obtained results are less conservative.A numerical example is utilized to demonstrate the effectiveness of the obtained results.
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...
Controller Design for a Teleoperation System with Time Delay
Institute of Scientific and Technical Information of China (English)
SHE Jun; JIAO Shou-jiang; LUO Xiao-yuan; GUAN Xin-ping
2005-01-01
A robust controller design method is presented to guarantee the stability and zero tracking error for teleoperation system with time delay. Through choosing appropriate master and slave parameters, extended state equation about master and master-slave error is achieved, which can be analyzed by using time delay knowledge. Thus delay-independent and delay-dependent criteria are derived in terms of the Lyapunov stability theorem, control parameters are obtained by the feasible of linear matrix inequalities. Experimental results show the validity of these approaches and the performance of master and slave manipulators with delay variations is analyzed.
Tunable delay time and Hartman effect in graphene magnetic barriers
Energy Technology Data Exchange (ETDEWEB)
Ban, Yue; Wang, Lin-Jun [School of Materials Science and Engineering, Shanghai University, Shanghai 200444 (China); Chen, Xi, E-mail: xchen@shu.edu.cn [Department of Physics, Shanghai University, Shanghai 200444 (China)
2015-04-28
Tunable group delay and Hartman effect have been investigated for massless Dirac electrons in graphene magnetic barriers. In the presence of magnetic field, dwell time is found to be equal to net group delay plus the group delay contributing from the lateral shifts. The group delay times are discussed in both cases of normal and oblique incidence, to clarify the nature of Hartman effect. In addition, the group delay in transmission can be modulated from subluminality to superluminality by adjusting the magnetic field, which may also lead to potential applications in graphene-based microelectronics.
Periodic flows to chaos in time-delay systems
Luo, Albert C J
2017-01-01
This book for the first time examines periodic motions to chaos in time-delay systems, which exist extensively in engineering. For a long time, the stability of time-delay systems at equilibrium has been of great interest from the Lyapunov theory-based methods, where one cannot achieve the ideal results. Thus, time-delay discretization in time-delay systems was used for the stability of these systems. In this volume, Dr. Luo presents an accurate method based on the finite Fourier series to determine periodic motions in nonlinear time-delay systems. The stability and bifurcation of periodic motions are determined by the time-delayed system of coefficients in the Fourier series and the method for nonlinear time-delay systems is equivalent to the Laplace transformation method for linear time-delay systems. Facilitates discovery of analytical solutions of nonlinear time-delay systems; Illustrates bifurcation trees of periodic motions to chaos; Helps readers identify motion complexity and singularity; Explains pro...
A novel online adaptive time delay identification technique
Bayrak, Alper; Tatlicioglu, Enver
2016-05-01
Time delay is a phenomenon which is common in signal processing, communication, control applications, etc. The special feature of time delay that makes it attractive is that it is a commonly faced problem in many systems. A literature search on time-delay identification highlights the fact that most studies focused on numerical solutions. In this study, a novel online adaptive time-delay identification technique is proposed. This technique is based on an adaptive update law through a minimum-maximum strategy which is firstly applied to time-delay identification. In the design of the adaptive identification law, Lyapunov-based stability analysis techniques are utilised. Several numerical simulations were conducted with Matlab/Simulink to evaluate the performance of the proposed technique. It is numerically demonstrated that the proposed technique works efficiently in identifying both constant and disturbed time delays, and is also robust to measurement noise.
Time-Delay Estimation using the Characteristic Roots of Delay Differential Equations
Directory of Open Access Journals (Sweden)
Sun Yi
2012-01-01
Full Text Available Problem statement: For ordinary dynamic systems (i.e., non-delayed, various methods such as linear least-squares, gradient-weighted least-squares, Kalman filtering and other robust techniques have been widely used in signal processing, robotics, civil engineering. On the other hand, time-delay estimation of systems with unknown time-delay is still a challenging problem due to difficulty in formulation caused. Approach: The presented method makes use of the Lambert W function and analytical solutions of scalar first-order Delay Differential Equations (DDEs. The Lambert W function has been known to be useful in solving delay differential equations. From the solutions in terms of the Lambert W function, the dominant characteristic roots can be obtained and used to estimate time-delays. The function is already embedded in various software packages (e.g., MATLAB and thus, the presented method can be readily used for time-delay systems. Results: The presented method and the provided examples show ease of formulation and accuracy of time-delay estimation. Conclusion: Estimation of time-delays can be conducted in an analytical way. The presented method will be extended to general systems of DDEs and application to physical systems.
Solving Nonlinear Time Delay Control Systems by Fourier series
Directory of Open Access Journals (Sweden)
Mohammad Hadi Farahi
2014-06-01
Full Text Available In this paper we present a method to find the solution of time-delay optimal control systems using Fourier series. The method is based upon expanding various time functions in the system as their truncated Fourier series. Operational matrices of integration and delay are presented and are utilized to reduce the solution of time-delay control systems to the solution of algebraic equations. Illustrative examples are included to demonstrate the validity and applicability of the technique.
Generalized Synchronization of Time-Delayed Discrete Systems
Institute of Scientific and Technical Information of China (English)
JING Jian-Yi; MIN Le-Quan
2009-01-01
This paper establishes two theorems for two time-delayed (chaotic) discrete systems to achieve time-delayed generalized synchronization (TDGS). These two theorems uncover the general forms of two TDGS systems via a prescribed transformation. As examples, we convert the Lorenz three-dimensional chaotic map to an equal time-delayed system as the driving system, and construct the TDGS driven systems according to the Theorems 1 and 2. Numerical simulations demonstrate the effectiveness of the proposed theorems.
Stability of neutral equations with constant time delays
Barker, L. K.; Whitesides, J. L.
1976-01-01
A method was developed for determining the stability of a scalar neutral equation with constant coefficients and constant time delays. A neutral equation is basically a differential equation in which the highest derivative appears both with and without a time delay. Time delays may appear also in the lower derivatives or the independent variable itself. The method is easily implemented, and an illustrative example is presented.
Consensus networks with time-delays over finite fields
Li, Xiuxian; Su, Housheng; Chen, Michael Z. Q.
2016-05-01
In this paper, we investigate the consensus problem in networks with time-delays over finite fields. The delays are categorised into three cases: single constant delay, multiple constant delays, and time-varying bounded delays. For all cases, some sufficient and necessary conditions for consensus are derived. Furthermore, assuming that the communication graph is strongly connected, some of the obtained necessary conditions reveal that the conditions for consensus with time-delays over finite fields depend not only on the diagonal entries but also on the off-diagonal entries, something that is intrinsically distinct from the case over real numbers (where having at least one nonzero diagonal entry is a sufficient and necessary condition to guarantee consensus). In addition, it is shown that delayed networks cannot achieve consensus when the interaction graph is a tree if the corresponding delay-free networks cannot reach consensus, which is consistent with the result over real numbers. As for average consensus, we show that it can never be achieved for delayed networks over finite fields, although it indeed can be reached under several conditions for delay-free networks over finite fields. Finally, networks with time-varying delays are discussed and one sufficient condition for consensus is presented by graph-theoretic method.
Delayed Hopf bifurcation in time-delayed slow-fast systems
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
This paper presents an investigation on the phenomenon of delayed bifurcation in time-delayed slow-fast differential systems.Here the two delayed’s have different meanings.The delayed bifurcation means that the bifurcation does not happen immediately at the bifurcation point as the bifurcation parameter passes through some bifurcation point,but at some other point which is above the bifurcation point by an obvious distance.In a time-delayed system,the evolution of the system depends not only on the present state but also on past states.In this paper,the time-delayed slow-fast system is firstly simplified to a slow-fast system without time delay by means of the center manifold reduction,and then the so-called entry-exit function is defined to characterize the delayed bifurcation on the basis of Neishtadt’s theory.It shows that delayed Hopf bifurcation exists in time-delayed slow-fast systems,and the theoretical prediction on the exit-point is in good agreement with the numerical calculation,as illustrated in the two illustrative examples.
Controllability of Linear Discrete-Time Systems with Both Delayed States and Delayed Inputs
Directory of Open Access Journals (Sweden)
Hong Shi
2013-01-01
Full Text Available The controllability issues for discrete-time linear systems with delay in state and control are addressed. By introducing a new concept, the controllability realization index (CRI, the characteristic of controllability is revealed. An easily testable necessary and sufficient condition for the controllability of discrete-time linear systems with state and control delay is established.
Impulsive control of nonlinear systems with time-varying delays
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Yu Yong-Bin; Bao Jing-Fu; Zhang Hong-Bin; Zhong Qi-Shui; Liao Xiao-Feng; Yu Jue-Sang
2008-01-01
A whole impulsive control scheme of nonlinear systems with time-varying delays, which is an extension for impulsive control of nonlinear systems without time delay, is presented in this paper. Utilizing the Lyapunov functions and the impulsive-type comparison principles, we establish a series of different conditions under which impulsively controlled nonlinear systems with time-varying delays are asymptotically stable. Then we estimate upper bounds of impulse interval and time-varying delays for asymptotically stable control. Finally a numerical example is given to illustrate the effectiveness of the method.
Projective Synchronization in Time-Delayed Chaotic Systems
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FENG Cun-Fang; ZHANG Yan; WANG Ying-Hai
2006-01-01
For the first time, we report on projective synchronization between two time delay chaotic systems with single time delays. It overcomes some limitations of the previous wort, where projective synchronization has been investigated only in finite-dimensional chaotic systems, so we can achieve projective synchronization in infinite-dimensional chaotic systems. We give a general method with which we can achieve projective synchronization in time-delayed chaotic systems. The method is illustrated using the famous delay-differential equations related to optical bistability. Numerical simulations fully support the analytical approach.
Simultaneous quadratic performance stabilization for linear time-delay systems
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Chen Yuepeng; Zhou Zude; Liu Huanbin; Zhang Qingling
2006-01-01
A newly designed approach of simultaneous stabilization is given for linear discrete time-delay systems. The problem of stabilization for a collection of systems is discussed initially. Adequate condition are obtained in terms of linear matrix inequalities (LMIs) which are independent of time delays such that the resultant collection of discrete time-delay systems are stable with an upper bound of the quadratic performance index. Subsequently, controllers are designed such that the resultant closed-loop discrete time-delay systems are simultaneously stabilized with the upper bound of the quadratic performance index. Finally,a numerical example is given to illustrate the design method.
Stability interval for time-varying delay systems
Ariba, Yassine; Gouaisbaut, F.; Johansson, Karl Henrik
2010-01-01
We investigate the stability analysis of linear time-delay systems. The time-delay is assumed to be a time-varying continuous function belonging to an interval (possibly excluding zero) with a bound on its derivative. To this end, we propose to use the quadratic separation framework to assess the intervals on the delay that preserves the stability. Nevertheless, to take the time-varying nature of the delay into account, the quadratic separation principle has to be extended to cope with the ge...
Dynamical behaviour of Liu system with time delayed feedback
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Qian Qin; Wang Lin; Ni Qiao
2008-01-01
This paper investigates the dynamical behaviour of the Liu system with time delayed feedback.Two typical situations are considered and the effect of time-delay parameter on the dynamics of the system is discussed.It is shown that the Liu system with time delayed feedback may exhibit interesting and extremely rich dynamical behaviour.The evolution of the dynamics is shown to be complex with varying time-delay parameter.Moreover,the strange attractor like 'wormhole' is detected via numerical simulations.
Controlling a time-delay system using multiple delay feedback control
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Qi Wei; Zhang Yan; Wang Ying-Hai
2007-01-01
In this paper multiple delay feedback control (MDFC) with different and independent delay times is shown to be an efficient method for stabilizing fixed points in finite-dimensional dynamical systems. Whether MDFC can be applied to infinite-dimensional systems has been an open question. In this paper we find that for infinite-dimensional systems modelled by delay differential equations, MDFC works well for stabilizing (unstable) steady states in long-, moderate-and short-time delay regions, in particular for the hyperchaotic case.
Delay-dependent criteria for the robust stability of systems with time-varying delay
Institute of Scientific and Technical Information of China (English)
Min WU; Yong HE; Jinhua SHE
2003-01-01
The problem of delay-dependent robust stability for systems with titne-varying delay has been considered. By using the S-procedure and the Park' s inequality in the recent issue, a delay-dependent robust stability criterion which is less conservative than the previous results has been derived for time-delay systems with time-varying structured uncertainties. The same idea has also been easily extended to the systems with nonlinear perturbations. Numerical examples illustrated the effectiveness and the improvement of the proposed approach.
Delay-dependent H-infinity control for continuous time-delay systems via state feedback
Institute of Scientific and Technical Information of China (English)
Xinchun JIA; Yibo GAO; Jingmei ZHANG; Nanning ZHENG
2007-01-01
The delay-dependent H-infinity analysis and H-infinity control problems for continuous time-delay systems are studied. By introducing an equality with some free weighting matrices, an improved criterion of delay-dependent stability with H-infinity performance for such systems is presented, and a criterion of existence and some design methods of delay-dependent H-infinity controller for such systems are proposed in term of a set of matrix inequalities, which is solved efficiently by an iterative algorithm. Further, the corresponding results for the delay-dependent robust H-infinity analysis and robust H-infinity control problems for continuous time-delay uncertain systems are given. Finally, two numerical examples are given to illustrate the efficiency of the proposed method by comparing with the other existing results.
Interconnected delay and state observer for nonlinear systems with time-varying input delay
Léchappé, V; Moulay, Emmanuel; Plestan, F; Glumineau, A.
2016-01-01
International audience; This work presents a general framework to estimate both state and delay thanks to two interconnected observers. This scheme can be applied to a large class of nonlinear systems with time-varying input delay. In order to illustrate this approach, a new delay observer based on an optimization technique is proposed. Theoretical results are illustrated and compared with existing works in simulation.
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.
Effects of time delays on bifurcation and chaos in a non-autonomous system with multiple time delays
Energy Technology Data Exchange (ETDEWEB)
Sun Zhongkui [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China)]. E-mail: sunzk205@mail.nwpu.edu.cn; Xu Wei [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China)]. E-mail: weixu@nwpu.edu.cn; Yang Xiaoli [Department of Applied Mathematics, Northwestern Polytechnical University, Xi' an 710072 (China); College of Mathematics and Information Science, Shaanxi Normal University, Xi' an 710062 (China); Fang Tong [Department of Applied Mechanics, Northwestern Polytechnical University, Xi' an 710072 (China)
2007-01-15
Time delays are often sources of complex behavior in dynamic systems. Yet its complexity needs to be further explored, particularly when multiple time delays are present. As a purpose to gain insight into such complexity under multiple time delays, we investigate the mechanism for the action of multiple time delays on a particular non-autonomous system in this paper. The original mathematical model under consideration is a Duffing oscillator with harmonic excitation. A delayed system is obtained by adding delayed feedbacks to the original system. Two time delays are involved in such system, one of which in the displacement feedback and the other in the velocity feedback. The time delays are taken as adjustable parameters to study their effects on the dynamics of the system. Firstly, the stability of the trivial equilibrium of the linearized system is discussed and the condition under which the equilibrium loses its stability is obtained. This leads to a critical stability boundary where Hopf bifurcation or double Hopf bifurcation may occur. Then, the chaotic behavior of such system is investigated in detail. Particular emphasis is laid on the effect of delay difference between two time delays on the chaotic properties. A Melnikov's analysis is employed to obtain the necessary condition for onset of chaos resulting from homoclinic bifurcation. And numerical analyses via the bifurcation diagram and the top Lyapunov exponent are carried out to show the actual time delay effect. Both the results obtained by the two analyses show that the delay difference between two time delays plays a very important role in inducing or suppressing chaos, so that it can be taken as a simple but efficient 'switch' to control the motion of a system: either from order to chaos or from chaos to order.
Subspace-based identification of discrete time-delay system
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Qiang LIU; Jia-chen MA
2016-01-01
We investigate the identification problems of a class of linear stochastic time-delay systems with unknown delayed states in this study. A time-delay system is expressed as a delay differential equation with a single delay in the state vector. We first derive an equivalent linear time-invariant (LTI) system for the time-delay system using a state augmentation technique. Then a conventional subspace identification method is used to estimate augmented system matrices and Kalman state sequences up to a similarity transformation. To obtain a state-space model for the time-delay system, an alternate convex search (ACS) algorithm is presented to find a similarity transformation that takes the identified augmented system back to a form so that the time-delay system can be recovered. Finally, we reconstruct the Kalman state sequences based on the similarity transformation. The time-delay system matrices under the same state-space basis can be recovered from the Kalman state sequences and input-output data by solving two least squares problems. Numerical examples are to show the effectiveness of the proposed method.
Robust Stability Criterion for Uncertain Neural Networks with Time Delays
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LIN Zhi-wei; ZHANG Ning; YANG Hong-jiu
2010-01-01
The robust stability of uncertain neural network with time-varying delay was investigated. The norm-bounded un-certainties are included in the system matrices. The constraint on time-varying delays is removed, which means that a fast time-varying delay is admissible. Some new delay-dependent stability criteria were presented by using Lyapunov-Krasovskii functional and linear matrix inequalities (LMIs) approaches. Finally, a numerical example was given to illustrate the effec-tiveness and innovation nature of the developed techniques.
Time delay systems theory, numerics, applications, and experiments
Ersal, Tulga; Orosz, Gábor
2017-01-01
This volume collects contributions related to selected presentations from the 12th IFAC Workshop on Time Delay Systems, Ann Arbor, June 28-30, 2015. The included papers present novel techniques and new results of delayed dynamical systems. The topical spectrum covers control theory, numerical analysis, engineering and biological applications as well as experiments and case studies. The target audience primarily comprises research experts in the field of time delay systems, but the book may also be beneficial for graduate students alike. .
Epidemic spreading with time delay in complex networks
Xu, X J; Wang, X M; Wang, Y H
2006-01-01
We present a modified \\emph{susceptible-infected-susceptible} (SIS) model on complex networks, small-world and scale-free, to study epidemic spreading with the effect of time delay which is introduced to the infected phase. Considering the topology of the network, both uniform and degree-dependent delays are studied during the contagion process. We find that the existence of time delay will enhance both outbreaks and prevalence of infectious diseases in the network.
Bifurcations and Chaos in Time Delayed Piecewise Linear Dynamical Systems
Senthilkumar, D. V.; Lakshmanan, M.
2004-01-01
We reinvestigate the dynamical behavior of a first order scalar nonlinear delay differential equation with piecewise linearity and identify several interesting features in the nature of bifurcations and chaos associated with it as a function of the delay time and external forcing parameters. In particular, we point out that the fixed point solution exhibits a stability island in the two parameter space of time delay and strength of nonlinearity. Significant role played by transients in attain...
In-hospital outcomes and delayed neurologic sequelae of seizure-related endosulfan poisoning.
Moon, J M; Chun, B J; Lee, S D
2017-07-29
This study investigated the predictive factors for progression from seizure-related endosulfan poisoning to status epilepticus (SE) and refractory SE (RSE). This study also investigated delayed neurologic sequelae in seizure-related endosulfan poisoning. This retrospective, observational case series consisted of 73 patients who developed at least one seizure after endosulfan ingestion. The progression rates from seizure-related endosulfan poisoning to SE and from SE-related endosulfan poisoning to RSE were 78.1% and 54.4%, respectively. The SE and RSE fatality rates were 19.2% and 41.9%, respectively. No patients reported the development of delayed neurological sequelae at least six months after discharge. Glasgow coma scale (GCS) score were identified as an independent factor for progression from seizure-related endosulfan poisoning to SE and from SE-related endosulfan poisoning to RSE. Lorazepam administration was independently associated with preventing progression from SE-related endosulfan poisoning to RSE. Seizure-related endosulfan poisoning had higher progression rates to SE and RSE and higher fatality rates than other drug-induced seizures. However, delayed neurologic sequelae after discharge were not demonstrated. Due to the high progression rates from seizure-related endosulfan poisoning to SE and RSE and the absence of an established treatment for SE-related endosulfan poisoning, physicians should aggressively treat patients who experience a seizure after endosulfan poisoning and who present with decreased GCS score. Lorazepam should be considered a first-line anti-epileptic drug for controlling seizures in patients with endosulfan poisoning. Copyright © 2017 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.
Recovery of the Time-Evolution Equation of Time-Delay Systems from Time Series
Bünner, M J; Kittel, A; Parisi, J; Meyer, Th.
1997-01-01
We present a method for time series analysis of both, scalar and nonscalar time-delay systems. If the dynamics of the system investigated is governed by a time-delay induced instability, the method allows to determine the delay time. In a second step, the time-delay differential equation can be recovered from the time series. The method is a generalization of our recently proposed method suitable for time series analysis of {\\it scalar} time-delay systems. The dynamics is not required to be settled on its attractor, which also makes transient motion accessible to the analysis. If the motion actually takes place on a chaotic attractor, the applicability of the method does not depend on the dimensionality of the chaotic attractor - one main advantage over all time series analysis methods known until now. For demonstration, we analyze time series, which are obtained with the help of the numerical integration of a two-dimensional time-delay differential equation. After having determined the delay time, we recover...
Institute of Scientific and Technical Information of China (English)
Huaicheng YAN; Xinhan HUANG; Min WANG
2006-01-01
This paper deals with the problem of delay-dependent stability and stabilization for networked control systems(NCSs)with multiple time-delays. In view of multi-input and multi-output(MIMO) NCSs with many independent sensors and actuators, a continuous time model with distributed time-delays is proposed. Utilizing the Lyapunov stability theory combined with linear matrix inequalities(LMIs) techniques, some new delay-dependent stability criteria for NCSs in terms of generalized Lyapunov matrix equation and LMIs are derived. Stabilizing controller via state feedback is formulated by solving a set of LMIs. Compared with the reported methods, the proposed methods give a less conservative delay bound and more general results. Numerical example and simulation show that the methods are less conservative and more effective.
Time-Delay Systems Lyapunov Functionals and Matrices
Kharitonov, Vladimir L
2013-01-01
Stability is one of the most studied issues in the theory of time-delay systems, but the corresponding chapters of published volumes on time-delay systems do not include a comprehensive study of a counterpart of classical Lyapunov theory for linear delay free systems. The principal goal of the book is to fill this gap, and to provide readers with a systematic and exhaustive treatment of the basic concepts of the Lyapunov-Krasovskii approach to the stability analysis of linear time-delay systems. The book is organized into two parts. The first part is dedicated to the case of retarded type time-delay systems; it consists of four chapters, which respectively deal with results concerning the existence and uniqueness of the solutions of an initial value problem, the class of linear systems with one delay, the case of systems with several delays, and the case of systems with distributed delays. The second part of the book studies the case of neutral type time-delay systems, containing three chapters that e...
Using Constant Time Delay to Teach Braille Word Recognition
Hooper, Jonathan; Ivy, Sarah; Hatton, Deborah
2014-01-01
Introduction: Constant time delay has been identified as an evidence-based practice to teach print sight words and picture recognition (Browder, Ahlbrim-Delzell, Spooner, Mims, & Baker, 2009). For the study presented here, we tested the effectiveness of constant time delay to teach new braille words. Methods: A single-subject multiple baseline…
STUDY ON AN SIS EPIDEMIC MODEL WITH TIME VARIANT DELAY
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无
2002-01-01
In this paper,we study an SIS epidemic model with a time variant delay.By means of Liapunov functional,some sufficient conditions of global stability to endemic equilibrium and disease free equilibrium have been obtained.The influence of time delay on the stability of equilibria is displayed.
STUDY ON AN SIS EPIDEMIC MODEL WITH TIME VARIANT DELAY
Institute of Scientific and Technical Information of China (English)
YUAN Sanling; MA Zhien
2002-01-01
In this paper, we study an SIS epidemic model with a time variant delay.By means of Liapunov functional, some sufficient conditions of global stability to endemic equilibrium and disease free equilibrium have been obtained. The influence of time delay on the stability of equilibria is displayed.
Time-Delay Systems with Band-Limited Feedback
2005-08-01
used as generators of chaos in applications such as communication, chaos control , and ranging. As an example, such devices are studied as a signal...tions [Lukin, 1997; Myneni, 2001]. Furthermore, time delayed feedback is used in the chaos control scheme known as time-delay autosynchronization
Adaptive synchronization of neural networks with time-varying delay and distributed delay
Wang, Kai; Teng, Zhidong; Jiang, Haijun
2008-01-01
In this paper, the adaptive synchronization of neural networks with time-varying delay and distributed delay is discussed. Based on the LaSalle invariant principle of functional differential equations and the adaptive feedback control technique, some sufficient conditions for adaptive synchronization of such a system are obtained. Finally, a numerical example is given to show the effectiveness of the proposed synchronization method.
Delay-Dependent Exponential Stability Criterion for BAM Neural Networks with Time-Varying Delays
Institute of Scientific and Technical Information of China (English)
Wei-Wei Su; Yi-Ming Chen
2008-01-01
By employing the Lyapunov stability theory and linear matrix inequality (LMI) technique, delay dependent stability criterion is derived to ensure the exponential stability of bi-directional associative memory (BAM) neural networks with time-varying delays. The proposed condition can be checked easily by LMI control toolbox in Matlab. A numerical example is given to demonstrate the effectiveness of our results.
Directory of Open Access Journals (Sweden)
Chun-Hung Chen
2007-11-01
Full Text Available The biggest hurdle for early hospital presentation is the narrow therapeutic window after stroke. The aims of our study were to investigate the time lags and the factors causing pre-hospital and emergency department (ED delay during acute ischemic stroke attack. Between June 2004 and October 2005, we prospectively studied 129 acute ischemic stroke patients who presented to the ED of the study hospital within 4 hours after symptom onset. Chi-square testing for trend, uni-variate and multiple logistic regression analyses was performed to evaluate the factors influencing delays in the ED presentation of acute ischemic stroke patients. The median time from symptom onset to ED arrival was 71 (mean ± SD, 82.7 ± 57.7 minutes. The median times from ED arrival to neurologic consultation, computed tomography scan, electrocardiogram, and laboratory data completion were 10 (11.3±9.9 minutes, 17 (9.6±11.3 minutes, 14 (23.3±55 minutes, and 39 (44.4±24.5 minutes, respectively. Univariate and multiple logistic regression models revealed that age < 65 years, illiteracy and awakening with symptoms were the most significant factors related to a delay in ED presentation. This study indicates that 2 hours of pre-hospital delay is the cutoff point for thrombolytic therapy. Organization of a stroke team and standardized stroke pathways may help to shorten in-hospital time consumption. Educational efforts should not only focus on the public, but also on the training of ED physicians and other medical personnel.
Analysis of Absolute Stability for Time-delay Teleoperation Systems
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Qi-Wen Deng; Qing Wei; Ze-Xiang Li
2007-01-01
In this paper, a new bilateral control algorithm based on absolute stability theory is put forward, which aims at the time-delay teleoperation system with force feedback from the slave directly. In the new control algorithm, the delay-dependent stability,instead of delay-independent stability, is taken as the aim of control design. It improves the transparency of the system at the price of unnecessary stability. With this algorithm, the time-delay teleoperation systems have good transparency and stability. A simulation system is established to verify the effect of this algorithm.
Institute of Scientific and Technical Information of China (English)
Xianming ZHANG; Min WU; Jinhua SHE; Dongsheng HAN
2006-01-01
This paper examines the delay-dependent H-infinity control problem for discrete-time linear systems with time-varying state delays and norm-bounded uncertainties. A new inequality for the finite sum of quadratic terms is first established. Then, some new delay-dependent criteria are derived by employing the new inequality to guarantee the robust stability of a closed-loop system with a prescribed H-infinity norm bound for all admissible uncertainties and bounded time-vary delays. A numerical example demonstrates that the proposed method is an improvement over existing ones.
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.
Time-delay identification for vibration systems with multiple feedback
Sun, Yi-Qiang; Jin, Meng-Shi; Song, Han-Wen; Xu, Jian
2016-12-01
An approach for time-delay identification is proposed in multiple-degree-of-freedom (MDOF) linear systems with multiple feedback. The applicability of the approach is discussed in detail. Based on the characteristics of frequency domain in feedback controlled system with multiple time-delays, this paper proposes a time-delay identification approach, which is based on the pseudo impedance function of reference point. Treating feedback time-delays as the "frequencies" of the oscillation curve, the time-delays can be obtained from the "frequencies" of the curve. Numerical simulation is conducted to validate the proposed approach. The application scope of the approach is discussed with regard to different forms of feedback.
Time-delay identification for vibration systems with multiple feedback
Institute of Scientific and Technical Information of China (English)
Yi-Qiang Sun; Meng-Shi Jin; Han-Wen Song; Jian Xu
2016-01-01
An approach for time-delay identification is pro-posed in multiple-degree-of-freedom (MDOF) linear sys-tems with multiple feedback. The applicability of the approach is discussed in detail. Based on the characteris-tics of frequency domain in feedback controlled system with multiple time-delays, this paper proposes a time-delay iden-tification approach, which is based on the pseudo impedance function of reference point. Treating feedback time-delays as the“frequencies”of the oscillation curve, the time-delays can be obtained from the“frequencies”of the curve. Numerical simulation is conducted to validate the proposed approach. The application scope of the approach is discussed with regard to different forms of feedback.
Variable-time-delay optical coherent transient signal processing.
Merkel, K D; Babbitt, W R; Anderson, K E; Wagner, K H
1999-10-15
A technique is proposed and experimentally demonstrated that achieves simultaneous optical pattern waveform storage and programmable time delay for continuous real-time signal processing by use of optical coherent transient technology. We achieve variable-time-delay and broadband signal processing by frequency shifting of two chirped programming pulses, the chirp rate of one being twice that of the other, without using brief reference pulses and without changing the timing of the programming sequence. We demonstrate the technique experimentally in Tm(3+): YAG at 5 K for 40-MHz chirps by performing temporal signal convolution with true-time delays that vary over a 250-ns range.
Stability Analysis of Uncertain Discrete Time-Delay Control Systems
Institute of Scientific and Technical Information of China (English)
Long Xuming; Duan Ping
2006-01-01
Based on Lyapunov stability theory, a less conservative sufficient conditions for the stabilities of uncertain discrete delay-independent and delay-dependent control systems are obtained by using the linear matrix inequality (LMI) approach. Judgement of the stability of time-delay systems is transformed to judgement of the feasible solution of an LMI, and hence is solved by use of MATLAB. Numerical simulations verify the validity of the proposed method.
Indian Academy of Sciences (India)
Arturo C Martí; Marcelo Ponce; Cristina Masoller
2008-06-01
We review our recent work on the synchronization of a network of delay-coupled maps, focusing on the interplay of the network topology and the delay times that take into account the finite velocity of propagation of interactions. We assume that the elements of the network are identical ( logistic maps in the regime where the individual maps, without coupling, evolve in a chaotic orbit) and that the coupling strengths are uniform throughout the network. We show that if the delay times are su±ciently heterogeneous, for adequate coupling strength the network synchronizes in a spatially homogeneous steady state, which is unstable for the individual maps without coupling. This synchronization behavior is referred to as `suppression of chaos by random delays' and is in contrast with the synchronization when all the interaction delay times are homogeneous, because with homogeneous delays the network synchronizes in a state where the elements display in-phase time-periodic or chaotic oscillations. We analyze the influence of the network topology considering four different types of networks: two regular (a ring-type and a ring-type with a central node) and two random (free-scale Barabasi-Albert and small-world Newman-Watts). We find that when the delay times are sufficiently heterogeneous the synchronization behavior is largely independent of the network topology but depends on the network's connectivity, i.e., on the average number of neighbors per node.
An SIRS Epidemic Model Incorporating Media Coverage with Time Delay
Lin, Yiping; Dai, Yunxian
2014-01-01
An SIRS epidemic model incorporating media coverage with time delay is proposed. The positivity and boundedness are studied firstly. The locally asymptotical stability of the disease-free equilibrium and endemic equilibrium is studied in succession. And then, the conditions on which periodic orbits bifurcate are given. Furthermore, we show that the local Hopf bifurcation implies the global Hopf bifurcation after the second critical value of the delay. The obtained results show that the time delay in media coverage can not affect the stability of the disease-free equilibrium when the basic reproduction number R0 1, the stability of the endemic equilibrium will be affected by the time delay; there will be a family of periodic orbits bifurcating from the endemic equilibrium when the time delay increases through a critical value. Finally, some examples for numerical simulations are also included. PMID:24723967
Next Generation Strong Lensing Time Delay Estimation with Gaussian Processes
Hojjati, Alireza
2014-01-01
Strong gravitational lensing forms multiple, time delayed images of cosmological sources, with the "focal length" of the lens serving as a cosmological distance probe. Robust estimation of the time delay distance can tightly constrain the Hubble constant as well as the matter density and dark energy. Current and next generation surveys will find hundreds to thousands of lensed systems but accurate time delay estimation from noisy, gappy lightcurves is potentially a limiting systematic. Using a large sample of blinded lightcurves from the Strong Lens Time Delay Challenge we develop and demonstrate a Gaussian Process crosscorrelation technique that delivers an average bias within 0.1% depending on the sampling, necessary for subpercent Hubble constant determination. The fits are accurate (80% of them within 1 day) for delays from 5-100 days and robust against cadence variations shorter than 6 days. We study the effects of survey characteristics such as cadence, season, and campaign length, and derive requiremen...
Lin, Aijing; Liu, Kang K L; Bartsch, Ronny P; Ivanov, Plamen Ch
2016-05-13
Within the framework of 'Network Physiology', we ask a fundamental question of how modulations in cardiac dynamics emerge from networked brain-heart interactions. We propose a generalized time-delay approach to identify and quantify dynamical interactions between physiologically relevant brain rhythms and the heart rate. We perform empirical analysis of synchronized continuous EEG and ECG recordings from 34 healthy subjects during night-time sleep. For each pair of brain rhythm and heart interaction, we construct a delay-correlation landscape (DCL) that characterizes how individual brain rhythms are coupled to the heart rate, and how modulations in brain and cardiac dynamics are coordinated in time. We uncover characteristic time delays and an ensemble of specific profiles for the probability distribution of time delays that underly brain-heart interactions. These profiles are consistently observed in all subjects, indicating a universal pattern. Tracking the evolution of DCL across different sleep stages, we find that the ensemble of time-delay profiles changes from one physiologic state to another, indicating a strong association with physiologic state and function. The reported observations provide new insights on neurophysiological regulation of cardiac dynamics, with potential for broad clinical applications. The presented approach allows one to simultaneously capture key elements of dynamic interactions, including characteristic time delays and their time evolution, and can be applied to a range of coupled dynamical systems.
Lin, Aijing; Liu, Kang K. L.; Bartsch, Ronny P.; Ivanov, Plamen Ch.
2016-05-01
Within the framework of `Network Physiology', we ask a fundamental question of how modulations in cardiac dynamics emerge from networked brain-heart interactions. We propose a generalized time-delay approach to identify and quantify dynamical interactions between physiologically relevant brain rhythms and the heart rate. We perform empirical analysis of synchronized continuous EEG and ECG recordings from 34 healthy subjects during night-time sleep. For each pair of brain rhythm and heart interaction, we construct a delay-correlation landscape (DCL) that characterizes how individual brain rhythms are coupled to the heart rate, and how modulations in brain and cardiac dynamics are coordinated in time. We uncover characteristic time delays and an ensemble of specific profiles for the probability distribution of time delays that underly brain-heart interactions. These profiles are consistently observed in all subjects, indicating a universal pattern. Tracking the evolution of DCL across different sleep stages, we find that the ensemble of time-delay profiles changes from one physiologic state to another, indicating a strong association with physiologic state and function. The reported observations provide new insights on neurophysiological regulation of cardiac dynamics, with potential for broad clinical applications. The presented approach allows one to simultaneously capture key elements of dynamic interactions, including characteristic time delays and their time evolution, and can be applied to a range of coupled dynamical systems.
Robust delay-dependent feedforward control of neutral time-delay systems via dynamic IQCs
Ucun, L.; Küçükdemiral, I. B.
2014-05-01
This paper studies the design problem of delay-dependent ? based robust and optimal feedforward controller design for a class of time-delay control systems having state, control and neutral type delays which are subject to norm-bounded uncertainties and ? type measurable or observable disturbance signals. Two independent loops which include state-feedback and dynamic feedforward controller form the basis of the proposed control scheme in this study. State-feedback controller is generally used in stabilisation of the nominal delay-free system, whereas the feedforward controller is used for improving disturbance attenuation performance of the overall system. In order to obtain less conservative results, the delay and parametric uncertainty effects are treated in operator view point and represented by frequency-dependent (dynamic) integral quadratic constraints (IQCs). Moreover, sufficient delay-dependent criterion is developed in terms of linear matrix inequalities (LMIs) such that the time-delay system having parametric uncertainties is guaranteed to be asymptotically stable with minimum achievable disturbance attenuation level. Plenty of numerical examples are provided at the end, in order to illustrate the efficiency of the proposed technique. The achieved results on minimum achievable disturbance attenuation level and maximum allowable delay bounds are exhibited to be less conservative in comparison to those of controllers having only feedback loop.
Adaptive control for a class of discrete-time time-delay systems with regard to delay parameter
Institute of Scientific and Technical Information of China (English)
Chai Lin; Cheng Ming; Fei Shumin; Zhai Junyong
2009-01-01
The memory state feedback control problem for a class of discrete-time systems with input delay and unknown state delay is addressed based on LMIs and Lyapunov-Krasovskii functional method. Under the action of our designed adaptive control law, the unknown time-delay parameter is included in memory state feedback controller. Using LMI technique, delay-dependent sufficient conditions for the existence of the feedback controller are obtained. Finally, the effectiveness of the proposed design method is demonstrated by a numerical example.
Global Asymplotic Stability of Neural Networks with Time Delay
Institute of Scientific and Technical Information of China (English)
肖晓丹; 张洁
2008-01-01
The global asymptotic stability problem of Cellular neural networks with delay is investigated.A new stability condition is presented based on Lyapunov-Krasovskii method,which is dependent On the size of delay.The result is given in the form of LMI.and the admitted upper bound of the delay can be obtained easily.The time delay dependent and independent results can be obtained,which include some results in the former literature.Finally,a numerical example is siven to illustrate the effectiveness of the main results.
Passivity analysis and synthesis for uncertain time-delay systems
Directory of Open Access Journals (Sweden)
Magdi S. Mahmoud
2001-01-01
Full Text Available In this paper, we investigate the robust passivity analysis and synthesis problems for a class of uncertain time-delay systems. This class of systems arises in the modelling effort of studying water quality constituents in fresh stream. For the analysis problem, we derive a sufficient condition for which the uncertain time-delay system is robustly stable and strictly passive for all admissible uncertainties. The condition is given in terms of a linear matrix inequality. Both the delay-independent and delay-dependent cases are considered. For the synthesis problem, we propose an observer-based design method which guarantees that the closed-loop uncertain time-delay system is stable and strictly passive for all admissible uncertainties. Several examples are worked out to illustrate the developed theory.
Energy Technology Data Exchange (ETDEWEB)
Sun Jitao [Department of Mathematics, Tongji University, Shanghai 200092 (China); Centre for Intelligent and Networked Systems, Central Queensland University, Rockhampton Qld 4702 (Australia); Han Qinglong [Centre for Intelligent and Networked Systems, Central Queensland University, Rockhampton Qld 4702 (Australia); School of Computing Sciences, Central Queensland University, Rockhampton Qld 4702 (Australia)], E-mail: q.han@cqu.edu.au; Jiang Xiefu [Centre for Intelligent and Networked Systems, Central Queensland University, Rockhampton Qld 4702 (Australia); School of Automation, Hangzhou Dianzi University, Hangzhou 310018, Zhejiang (China)
2008-10-13
This Letter is concerned with impulsive control of a class of nonlinear time-delay systems. Some uniform stability criteria for the closed-loop time-delay system under delayed impulsive control are derived by using piecewise Lyapunov functions. Then the criteria are applied to impulsive master-slave synchronization of some secure communication systems with transmission delays and sample delays under delayed impulsive control. Two numerical examples are given to illustrate the effectiveness of the derived results.
Regenerative memory in time-delayed neuromorphic photonic systems
Romeira, B; Figueiredo, José M L; Barland, S; Javaloyes, J
2015-01-01
We investigate a regenerative memory based upon a time-delayed neuromorphic photonic oscillator and discuss the link with temporal localized structures. Our experimental implementation is based upon a optoelectronic system composed of a nanoscale nonlinear resonant tunneling diode coupled to a laser that we link to the paradigm of neuronal activity, the FitzHugh-Nagumo model with delayed feedback.
Institute of Scientific and Technical Information of China (English)
Huaicheng YAN; Xinhan HUANG; Min WANG
2007-01-01
In this paper, delay-dependent robust stability for a class of uncertain networked control systems (NCSs)with multiple state time-delays is investigated. Modeling of multi-input and multi-output (MIMO) NCSs with networkinduced delays and uncertainties through new methods are proposed. Some new stability criteria in terms of LMIs are derived by using Lyapunov stability theory combined with linear matrix inequalities (LMIs) techniques. We analyze the delay-dependent asymptotic stability and obtain maximum allowable delay bound (MADB) for the NCSs with the proposed methods. Compared with the reported results, the proposed results obtain a much less conservative MADB which are more general. Numerical example and simulation is used to illustrate the effectiveness of the proposed methods.
Reconstruction of time-delay systems using small impulsive disturbances.
Prokhorov, M D; Ponomarenko, V I
2009-12-01
We propose a method for the reconstruction of time-delayed feedback systems from time series. The method is based on the analysis of the system response to a weak external disturbance having the form of rectangular pulses. To apply the method one must have access to the state variable of the system in order to perturb it and the time series of the driving signal and the system response having at least about one hundred points on the time interval equal to the delay time. The method is intended to recover delays in low-order time-delay systems performing periodic oscillations, but can also be applied to systems in chaotic regimes in the presence of high level of noise. We verify the method by applying it to both numerical and experimental data.
Stability domains of the delay and PID coefficients for general time-delay systems
Almodaresi, Elham; Bozorg, Mohammad; Taghirad, Hamid D.
2016-04-01
Time delays are encountered in many physical systems, and they usually threaten the stability and performance of closed-loop systems. The problem of determining all stabilising proportional-integral-derivative (PID) controllers for systems with perturbed delays is less investigated in the literature. In this study, the Rekasius substitution is employed to transform the system parameters to a new space. Then, the singular frequency (SF) method is revised for the Rekasius transformed system. A novel technique is presented to compute the ranges of time delay for which stable PID controller exists. This stability range cannot be readily computed from the previous methods. Finally, it is shown that similar to the original SF method, finite numbers of singular frequencies are sufficient to compute the stable regions in the space of time delay and controller coefficients.
Institute of Scientific and Technical Information of China (English)
2008-01-01
Based on an appropriate Lyapunov function,this paper analyzes the design of a delay-dependent robust H∞ state feedback control,with a focus on a class of non linear uncertainty linear time-delay systems with input delay using linear matrix inequalities.Under the condition that the nonlinear uncertain functions are gain bounded,a sufficient condition dependent on the delays of the state and input is presented for the existence of H∞ controller.The proposed controller not only stabilized closed-loop uncertain systems but also guaranteed a prescribed H∞ norm bound of closed-loop transfer matrix from the disturbance to controlled output.By solving a linear matrix inequation,we can obtain the robust H∞ controller.An example is given to show the effectiveness of the proposed method.
On the eigenvalue spectrum for time-delayed Floquet problems
Just, Wolfram
2000-08-01
A linear homogeneous scalar differential-difference equation with harmonic time dependence is investigated. The associated eigenvalue problem is solved in terms of a continued fraction expansion for the characteristic equation. The dependence of the largest eigenvalue on the system parameters, being relevant for stability of periodic states in delay systems, is discussed in detail. The competition between the two timescales, the delay and the external period cause intricate structures. The result suggests features to improve control of chaos by time-delayed feedback schemes with time-dependent control amplitudes.
Performance analysis of adaptive turbo coded modulation with time delay
Institute of Scientific and Technical Information of China (English)
伍守豪; 宋文涛; 罗汉文
2004-01-01
The method of data fitting is applied to obtain the BER expression for turbo coded modulation, and a fitting mathematical model is proposed, which resolves the problem that there is no exact BER expression for turbo coded modulation in performance analysis. With the time delay consideration, the performance of BER of adaptive turbo coded modulation is analyzed and simulated. The results show that adaptive turbo coded modulation is very sensitive to time delay. In order to meet the target BER requirement, the total time delay should be less than 0. 001/fD.
Projective Synchronization Between Two Nonidentical Variable Time Delayed Systems
Institute of Scientific and Technical Information of China (English)
FENG Cun-Fang; WANG Ying-Hai
2012-01-01
In this paper, we propose a method for the projective synchronization between two different chaotic systems with variable time delays. Using active control approach, the suitable controller is constructed to make the states of two different diverse time delayed systems asymptotically synchronize up to the desired scaling factor. Based on the Lyapunov stability theory, the sufficient condition for the projective synchronization is calculated theoretically. Numerical simulations of the projective synchronization between Maekey-Glass system and Ikeda system with variable time delays are shown to validate the effectiveness of the proposed algorithm.
Output regulation problem for discrete-time linear time-delay systems by output feedback control
Institute of Scientific and Technical Information of China (English)
Yamin YAN; Jie HUANG
2016-01-01
In this paper, we study the output regulation problem of discrete linear time-delay systems by output feedback control. We have established some results parallel to those for the output regulation problem of continuous linear time-delay systems.
Chaos synchronization by resonance of multiple delay times
Martin, Manuel Jimenez; D'Huys, Otti; Lauerbach, Laura; Korutcheva, Elka; Kinzel, Wolfgang
2016-02-01
Chaos synchronization may arise in networks of nonlinear units with delayed couplings. We study complete and sublattice synchronization generated by resonance of two large time delays with a specific ratio. As it is known for single-delay networks, the number of synchronized sublattices is determined by the greatest common divisor (GCD) of the network loop lengths. We demonstrate analytically the GCD condition in networks of iterated Bernoulli maps with multiple delay times and complement our analytic results by numerical phase diagrams, providing parameter regions showing complete and sublattice synchronization by resonance for Tent and Bernoulli maps. We compare networks with the same GCD with single and multiple delays, and we investigate the sensitivity of the correlation to a detuning between the delays in a network of coupled Stuart-Landau oscillators. Moreover, the GCD condition also allows detection of time-delay resonances, leading to high correlations in nonsynchronizable networks. Specifically, GCD-induced resonances are observed both in a chaotic asymmetric network and in doubly connected rings of delay-coupled noisy linear oscillators.
Uniformed model of networked control systems with long time delay
Institute of Scientific and Technical Information of China (English)
Zhu Qixin; Liu Hongli; Hu Shousong
2008-01-01
Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems (NCS). The defining feature of an NCS is that information is exchanged using a network among control system components. Two new concepts including long time delay and short time delay are proposed.The sensor is almost always clock driven. The controller or the actuator is either clock driven or event driven. Four possible driving modes of networked control systems are presented. The open loop mathematic models of networked control systems with long time delay are developed when the system is driven by anyone of the four different modes.The uniformed modeling method of networked control systems with long time delay is proposed. The simulation results are given in the end.
Negative time delay of light by a gravitational concave lens
Nakajima, Koki; Asada, Hideki
2014-01-01
Gravitational lens models, some of which might act as if a concave lens, have been recently investigated by using a static and spherically symmetric modified spacetime metric that depends on the inverse distance to the $n$-th power [Kitamura, Nakajima and Asada, PRD 87, 027501 (2013)]. We reexamine the time delay of light in a gravitational concave lens as well as a gravitational convex one. The frequency shift due to the time delay is also investigated. We show that the sign of the time delay in the lens models is the same as that of the deflection angle of light. The size of the time delay decreases with increase in the parameter $n$. We discuss also possible parameter ranges that are relevant to pulsar timing measurements in our galaxy.
Workspace visualization and time-delay telerobotic operations
Schenker, P. S.; Bejczy, A. K.
1990-01-01
The paper examines the performance of telerobotic tasks where the operator and robot are physically separated, and a comunication time delay of up to several seconds between them exists. This situation is applicable to space robotic servicing-assembly-maintenance operations on low earth or geosynchronous orbits with a ground-based command station. Attention is given to two developments which address advanced time-delay teleoperations for unstructured tasks: (1) the 'phantom robot', a real-time predictive graphics simulator developed to allow teleoperator eye-to-hand coordination or robot free-space kinematics under a time delay of several seconds; and (2) shared compliance control, a modified form of automatic electromechanical impedance control employed in parallel with manual position control to permit soft contact and grasp compliance with workpiece geometry under a time delay of several seconds.
New delay-dependent stability criteria for neural networks with time-varying interval delay
Energy Technology Data Exchange (ETDEWEB)
Chen Jie, E-mail: chenjie@bit.edu.c [School of Automation, Beijing Institute of Technology, Beijing, 100081 (China); Sun Jian, E-mail: helios1225@yahoo.com.c [School of Automation, Beijing Institute of Technology, Beijing, 100081 (China); Liu, G.P., E-mail: gpliu@glam.ac.u [Faculty of Advanced Technology, University of Glamorgan, Pontypridd CF37 1DL (United Kingdom); CTGT Center in Harbin Institute of Technology, Harbin, 150001 (China); Rees, D., E-mail: drees@glam.ac.u [Faculty of Advanced Technology, University of Glamorgan, Pontypridd CF37 1DL (United Kingdom)
2010-09-27
The problem of stability analysis of neural networks with time-varying delay in a given range is investigated in this Letter. By introducing a new Lyapunov functional which uses the information on the lower bound of the delay sufficiently and an augmented Lyapunov functional which contains some triple-integral terms, some improved delay-dependent stability criteria are derived using the free-weighting matrices method. Numerical examples are presented to illustrate the less conservatism of the obtained results and the effectiveness of the proposed method.
Delay-Dependent H∞ Filtering for Singular Time-Delay Systems
Directory of Open Access Journals (Sweden)
Zhenbo Li
2011-01-01
Full Text Available This paper deals with the problem of delay-dependent H∞ filtering for singular time-delay systems. First, a new delay-dependent condition which guarantees that the filter error system has a prescribed H∞ performance γ is given in terms of linear matrix inequalities (LMIs. Then, the sufficient condition is obtained for the existence of the H∞ filter, and the explicit expression for the desired H∞ filter is presented by using LMIs and the cone complementarity linearization iterative algorithm. A numerical example is provided to illustrate the effectiveness of the proposed method.
Directory of Open Access Journals (Sweden)
Zhong-Da Tian
2015-01-01
Full Text Available The random time delay in a networked control system can usually deteriorate the control performance and stability of the networked control system. In order to solve this problem, this paper puts forward a networked control system random time-delay compensation method based on time-delay prediction and improved implicit generalized predictive control (GPC. The least squares support vector machine is used to predict the future time delay of network. The parameters of the least squares support vector machine time-delay prediction model are difficult to determine, and the genetic algorithm is used for least squares support vector machine optimal prediction parameter optimization. Then, an improved implicit generalized predictive control method is adopted to compensate for the time delay. The simulation results show that the method in this paper has high prediction accuracy and a good compensation effect for the random time delay of the networked control system, has a small amount of on-line calculation and that the output response and control stability of the system are improved.
Coulomb time delays in high harmonic generation
Smirnova, Olga
2016-01-01
Measuring the time it takes to remove an electron from an atom or molecule during photoionization using newly developed attosecond spectroscopies has been a focus of many recent experiments. However, the outcome of such measurement depends on measurement protocols and specific observables available in each particular experiment. One of such protocols relies on high harmonic generation. First, we derive rigorous and general expressions for ionization and recombination times in high harmonic generation experiments. We show that these times are different from, but related to ionization times measured in photo-electron spectroscopy, i.e. using attosecond streak camera, RABBITT and atto-clock methods. Second, we use the Analytical R-Matrix theory (ARM) to calculate these times and compare them with experimental values.
Coulomb time delays in high harmonic generation
Torlina, Lisa; Smirnova, Olga
2017-02-01
Measuring the time it takes to remove an electron from an atom or molecule during photoionization has been the focus of a number of recent experiments using newly developed attosecond spectroscopies. The interpretation of such measurements, however, depends critically on the measurement protocol and the specific observables available in each experiment. One such protocol relies on high harmonic generation. In this paper, we derive rigorous and general expressions for ionisation and recombination times in high harmonic generation experiments. We show that these times are different from, but related to, ionisation times measured in photoelectron spectroscopy: that is, those obtained using the attosecond streak camera, RABBITT and attoclock methods. We then proceed to use the analytical R-matrix theory to calculate these times and compare them with experimental values.
Walsh, J. R.; Wetherington, R. D.
1975-01-01
The results of a study on time delays in communication systems applicable to the teleoperator program are presented. Time delay data for 11 specific orbits of interest are shown. These data can be used in the MSFC teleoperator simulator to investigate the effect of time delays in the communications link on the teleoperator control functions.
Energy Technology Data Exchange (ETDEWEB)
Pyragas, V. [Semiconductor Physics Institute, Center for Physical Sciences and Technology, A. Gostauto 11, LT-01108 Vilnius (Lithuania); Pyragas, K. [Semiconductor Physics Institute, Center for Physical Sciences and Technology, A. Gostauto 11, LT-01108 Vilnius (Lithuania)
2011-10-24
We propose a simple adaptive delayed feedback control algorithm for stabilization of unstable periodic orbits with unknown periods. The state dependent time delay is varied continuously towards the period of controlled orbit according to a gradient-descent method realized through three simple ordinary differential equations. We demonstrate the efficiency of the algorithm with the Roessler and Mackey-Glass chaotic systems. The stability of the controlled orbits is proven by computation of the Lyapunov exponents of linearized equations. -- Highlights: → A simple adaptive modification of the delayed feedback control algorithm is proposed. → It enables the control of unstable periodic orbits with unknown periods. → The delay time is varied continuously according to a gradient descend method. → The algorithm is embodied by three simple ordinary differential equations. → The validity of the algorithm is proven by computation of the Lyapunov exponents.
Synchronization of time-delay coupled pulse oscillators
Energy Technology Data Exchange (ETDEWEB)
Klinshov, V.V., E-mail: vklin@mail.r [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov Str., 603950 Nizhny Novgorod (Russian Federation); Nekorkin, V.I. [Institute of Applied Physics, Russian Academy of Sciences, 46 Ulyanov Str., 603950 Nizhny Novgorod (Russian Federation)
2011-01-15
Research highlights: Oscillators can be synchronized via coupling with arbitrary large delay. Imposing of coupling delay may either result in delay-induced synchronization or delay-induced desynchronization. In-phase and antiphase synchronization zones alternate in parameter space. Two types of transitions between the in-phase and antiphase synchronization, i.e. phase-flip bifurcation and soft switching. - Abstract: We present a detailed study of the dynamics of pulse oscillators with time-delayed coupling. We get the return maps, obtain strict solutions and analyze their stability. For the case of two oscillators, a periodical structure of synchronization regions is found in parameter space, and the regions corresponding to in-phase and antiphase regimes alternate with growth of time delay. Two types of switching between in-phase and antiphase regimes are studied. We also show that for different parameters coupling delay may have synchronizing or desynchronizing effect. Another novel result is that phase locked regimes exist for arbitrary large values. The specificity of system dynamics with large delay is studied.
Crilly, Julia; Keijzers, Gerben; Tippett, Vivienne; O'Dwyer, John; Lind, James; Bost, Nerolie; O'Dwyer, Marilla; Shiels, Sue; Wallis, Marianne
2015-06-01
To describe and compare characteristics and outcomes of patients who arrive by ambulance to the ED. We aimed to (i) compare patients with a delayed ambulance offload time (AOT) >30 min with those who were not delayed; and (ii) identify predictors of an ED length of stay (LOS) of >4 h for ambulance-arriving patients. A retrospective, multi-site cohort study was undertaken in Australia using 12 months of linked health data (September 2007-2008). Outcomes of AOT delayed and non-delayed presentations were compared. Logistic regression analysis was undertaken to identify predictors of an ED LOS of >4 h. Of the 40 783 linked, analysable ambulance presentations, AOT delay of >30 min was experienced by 15%, and 63% had an ED LOS of >4 h. Patients with an AOT ambulance time at hospital; time to see healthcare professional; proportion seen within recommended triage time frame; and ED LOS for both admitted and non-admitted patients. In-hospital mortality did not differ. Strong predictors of an ED LOS >4 h included: hospital admission, older age, triage category, and offload delay >30 min. Patients arriving to the ED via ambulance and offloaded within 30 min experience better outcomes than those delayed. Given that offload delay is a modifiable predictor of an ED LOS of >4 h, targeted improvements in the ED arrival process for ambulance patients might be useful. © 2015 The Authors. Emergency Medicine Australasia published by Wiley Publishing Asia Pty Ltd on behalf of Australasian College for Emergency Medicine and Australasian Society for Emergency Medicine.
Analysis and synthesis of singular systems with time-delays
Wu, Zheng-Guang; Shi, Peng; Chu, Jian
2013-01-01
Singular time-delay systems are very suitable to describe a lot of practical systems such as manufacturing systems, networked control systems, power systems and electrical circuits. Thus, the past two decades have witnessed a significant progress on the theory of singular time-delay systems, and many fundamental and important topics have been successfully investigated including stability analysis, stabilization, guaranteed cost control, filtering, observer design, sliding mode control and so on. The main objective of this book is to present the latest developments and references in the analysis and synthesis of singular time-delay systems with or without Markov jumping parameters in a unified framework. The materials adopted in this book are mainly based on research results of the authors. This book will be of interest to academic researchers working in singular systems, time-delay systems and Markov jump systems and to graduate students interested in systems and control theory.
Complex synchronization manifold in coupled time-delayed systems
Energy Technology Data Exchange (ETDEWEB)
Hoang, Thang Manh, E-mail: hmt@mail.hut.edu.v [Signal and Information Processing Laboratory, Faculty of Electronics and Telecommunications, Hanoi University of Science and Technology, 1 Dai Co Viet, Hanoi (Viet Nam)
2011-01-15
Research highlights: The complex synchronization manifold in coupled multiple time delay systems is demonstrated for the first time. The complex synchronization manifold is in the form of sum of multiple simple manifolds. The equation for driving signal is the sum of nonlinearly transformed components of delayed state variable. - Abstract: In the present paper, the complex synchronization manifold generated in coupled multiple time delay systems is demonstrated for the first time. There, the manifold is in the form of sum of multiple simple manifolds. The structure of master is identical to that of slave. The equation for driving signal is the sum of nonlinearly transformed components of delayed state variable. The specific examples will demonstrate and verify the effectiveness of the proposed model.
Exact synchronization bound for coupled time-delay systems
Senthilkumar, D. V.; Pesquera, Luis; Banerjee, Santo; Ortín, Silvia; Kurths, J.
2013-04-01
We obtain an exact bound for synchronization in coupled time-delay systems using the generalized Halanay inequality for the general case of time-dependent delay, coupling, and coefficients. Furthermore, we show that the same analysis is applicable to both uni- and bidirectionally coupled time-delay systems with an appropriate evolution equation for their synchronization manifold, which can also be defined for different types of synchronization. The exact synchronization bound assures an exponential stabilization of the synchronization manifold which is crucial for applications. The analytical synchronization bound is independent of the nature of the modulation and can be applied to any time-delay system satisfying a Lipschitz condition. The analytical results are corroborated numerically using the Ikeda system.
Backstepping tracking control for nonlinear time-delay systems
Institute of Scientific and Technical Information of China (English)
Chen Weisheng; Li Junmin
2006-01-01
Two design approaches of state feedback and output feedback tracking controllers are proposed for a class of strict feedback nonlinear time-delay systems by using backstepping technique. When the states of system cannot be observed, the time-delay state observer is designed to estimate the system states. Domination method is used to deal with nonlinear time-delay function under the assumption that the nonlinear time-delay functions of systems satisfy Lipschitz condition. The global asymptotical tracking of the references signal is achieved and the bound of all signals of the resultant closed-loop system is also guaranteed. By constructing a Lyapunov-Krasoviskii functional, the stability of the closed-loop system is proved. The feasibility of the proposed approach is illustrated by a simulation example.
Delay-Dependent Asymptotic Stability of Cohen-Grossberg Models with Multiple Time-Varying Delays
Directory of Open Access Journals (Sweden)
Xiaofeng Liao
2007-01-01
Full Text Available Dynamical behavior of a class of Cohen-Grossberg models with multiple time-varying delays is studied in detail. Sufficient delay-dependent criteria to ensure local and global asymptotic stabilities of the equilibrium of this network are derived by constructing suitable Lyapunov functionals. The obtained conditions are shown to be less conservative and restrictive than those reported in the known literature. Some numerical examples are included to demonstrate our results.
Time Delay in the Kuramoto Model of Coupled Oscillators
Yeung, M K S; Strogatz, Steven H.
1999-01-01
We generalize the Kuramoto model of coupled oscillators to allow time-delayed interactions. New phenomena include bistability between synchronized and incoherent states, and unsteady solutions with time-dependent order parameters. We derive exact formulas for the stability boundaries of the incoherent and synchronized states, as a function of the delay, in the special case where the oscillators are identical. The experimental implications of the model are discussed for populations of chirping crickets, where the finite speed of sound causes communication delays, and for physical systems such as coupled phase-locked loops or lasers.
Reducing time delays in the management of ischemic stroke patients in Northern Italy.
Vidale, Simone; Arnaboldi, Marco; Bezzi, Giacomo; Bono, Giorgio; Grampa, Giampiero; Guidotti, Mario; Perrone, Patrizia; Salmaggi, Andrea; Zarcone, Davide; Zoli, Alberto; Agostoni, Elio
2016-07-15
Thrombolysis represents the best therapy for ischemic stroke but the main limitation of its administration is time. The avoidable delay is a concept reflecting the effectiveness of management pathway. For this reason, we projected a study concerning the detection of main delays with following introduction of corrective factors. In this paper we describe the results after these corrections. Consecutive patients admitted for ischemic stroke during a 3-months period to 35 hospitals of a macro-area of Northern Italy were enrolled. Each time of management was registered, identifying three main intervals: pre-hospital, in-hospital and total times. Previous corrective interventions were: 1.increasing of population awareness to use the Emergency Medical Service (EMS); 2.pre-notification of Emergency Department; 3.use of high urgency codes; 4.use of standardised operational algorithm. Statistical analysis was conducted using time-to-event analysis and Cox proportional hazard regression. 1084 patients were enrolled. EMS was alerted for 56.3% of subjects, mainly in females and severe strokes (p<0.001). Thrombolytic treatment was performed in 4.7% of patients. Median pre-hospital and in-hospital times were 113 and 105min, while total time was 240. High urgency codes at transport contributed to reduce pre-hospital and in-hospital time (p<0.05). EMS use and high urgency codes promoted thrombolysis. Treatment within 4.5hours from symptom onset was performed in 14% of patients more than the first phase of study. The implementation of an organizational system based on EMS and concomitant high urgency codes use was effective to reduce avoidable delay and to increase thrombolysis. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Disturbance Rejection for Fractional-Order Time-Delay Systems
Hai-Peng Jiang; Yong-Qiang Liu
2016-01-01
This paper presents an equivalent-input-disturbance (EID-) based disturbance rejection method for fractional-order time-delay systems. First, a modified state observer is applied to reconstruct the state of the fractional-order time-delay plant. Then, a disturbance estimator is designed to actively compensate for the disturbances. Under such a construction of the system, by constructing a novel monochromatic Lyapunov function and using direct Lyapunov approach, the stability analysis and cont...
Time Delay Evolution of Five Active Galactic Nuclei
Indian Academy of Sciences (India)
A. Kovačević; L. Č. Popović; A. I. Shapovalova; D. Ilić; A. N. Burenkov; V. H. Chavushyan
2015-12-01
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 observed AGN light curves, we apply Gaussian kernel-based estimator to capture variation of local patterns of their time evolving delays. The largest variations of time delays of all objects occur in the period when continuum or emission lines luminosity is the highest. However, Gaussian kernel-based method shows instability in the case of NGC 5548, 3C 390.3, E1821+643 and NGC 4051 possibly due to numerical discrepancies between damped random walk (DRW) time scale of light curves and sliding time windows of the method. The temporal variations of time lags of Arp 102B can correspond to the real nature of the time lag evolution.
On the time delay evolution of five Active Galactic Nuclei
Kovacevic, Andjelka; Shapovalova, Alla I; Ilic, Dragana; Burenkov, Aleksandr N; Chavushyan, Vahram H
2015-01-01
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 observed AGN light curves we apply Gaussian-kernel based estimator to capture variation of local patterns of their time evolving delays. The largest variations of time delays of all objects occur in the period when continuum or emission lines luminosity is the highest. However, Gaussian kernel based method shows instability in the case of NGC 5548, 3C 390.3, E1821+643 and NGC 4051 possible due to numerical discrepancies between Damped Random Walk (DRW) time scale of light curves and sliding time windows of the method. The temporal variations of time lags of Arp 102B can correspond to the real nature of the time lag evolution.
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...
Truncated predictor feedback for time-delay systems
Zhou, Bin
2014-01-01
This book provides a systematic approach to the design of predictor based controllers for (time-varying) linear systems with either (time-varying) input or state delays. Differently from those traditional predictor based controllers, which are infinite-dimensional static feedback laws and may cause difficulties in their practical implementation, this book develops a truncated predictor feedback (TPF) which involves only finite dimensional static state feedback. Features and topics: A novel approach referred to as truncated predictor feedback for the stabilization of (time-varying) time-delay systems in both the continuous-time setting and the discrete-time setting is built systematically Semi-global and global stabilization problems of linear time-delay systems subject to either magnitude saturation or energy constraints are solved in a systematic manner Both stabilization of a single system and consensus of a group of systems (multi-agent systems) are treated in a unified manner by applying the truncated pre...
An adaptive robust controller for time delay maglev transportation systems
Milani, Reza Hamidi; Zarabadipour, Hassan; Shahnazi, Reza
2012-12-01
For engineering systems, uncertainties and time delays are two important issues that must be considered in control design. Uncertainties are often encountered in various dynamical systems due to modeling errors, measurement noises, linearization and approximations. Time delays have always been among the most difficult problems encountered in process control. In practical applications of feedback control, time delay arises frequently and can severely degrade closed-loop system performance and in some cases, drives the system to instability. Therefore, stability analysis and controller synthesis for uncertain nonlinear time-delay systems are important both in theory and in practice and many analytical techniques have been developed using delay-dependent Lyapunov function. In the past decade the magnetic and levitation (maglev) transportation system as a new system with high functionality has been the focus of numerous studies. However, maglev transportation systems are highly nonlinear and thus designing controller for those are challenging. The main topic of this paper is to design an adaptive robust controller for maglev transportation systems with time-delay, parametric uncertainties and external disturbances. In this paper, an adaptive robust control (ARC) is designed for this purpose. It should be noted that the adaptive gain is derived from Lyapunov-Krasovskii synthesis method, therefore asymptotic stability is guaranteed.
Switched Control of a Time Delayed Compass Gait Robot
Directory of Open Access Journals (Sweden)
Elyes Maherzi
2016-07-01
Full Text Available the analysis and control of delayed systems are becoming more and more research topics in progress. This is mainly due to the fact that the delay is frequently encountered in technological systems. Most control command laws are based on current digital computers and delays are intrinsic to the process or in the control loop caused by the transmission time control sequences, or computing time. In other hand, the controls of humanoid walking robot present a common problem in robotics because it involves physical interaction between an articulated system and its environment. This close relationship is actually a common set of fundamental problems such as the implementation of robust stable dynamic control. This paper presents acomplete approach, based on switched system theory, for the stabilization of a compass gait robot subject to time delays transmission. The multiple feedback gains designed are based on multiple linear systems governed by a switching control law. The establishment of control law in real time is affected by the unknown pounded random delay. The results obtained from this method show that the control law stabilize the compass robot walk despite a varying delay reaching six times sampling period.
Finite-time Lyapunov exponents in time-delayed nonlinear dynamical systems.
Kanno, Kazutaka; Uchida, Atsushi
2014-03-01
We introduce a method for the calculation of finite-time Lyapunov exponents in time-delayed nonlinear dynamical systems. We apply the method to the Mackey-Glass model with time-delayed feedback. We investigate the standard deviation of the probability distribution of the finite-time Lyapunov exponents when the finite time or the delay time is changed. It is found that the standard deviation decreases in a power-law scaling with the exponent ∼0.5 as the finite time or the delay time is increased. Similar results are obtained for the finite-time Lyapunov spectrum.
New Delay-Dependent Stability of Uncertain Discrete-Time Switched Systems with Time-Varying Delays
Institute of Scientific and Technical Information of China (English)
Liang Lin XIONG; Shou Ming ZHONG; Mao YE
2011-01-01
This paper deals with the issues of robust stability for uncertain discrete-time switched systems with mode-dependent time delays. Based on a novel difference inequality and a switched Lyapunov function, new delay-dependent stability criteria are formulated in terms of linear matrix inequalities (LMIs) which are not contained in known literature. A numerical example is given to demonstrate that the proposed criteria improves some existing results significantly with much less computational effort.
Unsignaled delay of reinforcement, relative time, and resistance to change.
Shahan, Timothy A; Lattal, Kennon A
2005-05-01
Two experiments with pigeons examined the effects of unsignaled, nonresetting delays of reinforcement on responding maintained by different reinforcement rates. In Experiment 1, 3-s unsignaled delays were introduced into each component of a multiple variable-interval (VI) 15-s VI 90-s VI 540-s schedule. When considered as a proportion of the preceding immediate reinforcement baseline, responding was decreased similarly for the three multiple-schedule components in both the first six and last six sessions of exposure to the delay. In addition, the relation between response rates and reinforcement rates was altered such that both parameters of the single-response version of the matching law (i.e., k and Re) were decreased. Experiment 2 examined the effects of unsignaled delays ranging from 0.5 s to 8.0 s on responding maintained by a multiple VI 20-s VI 120-s schedule of reinforcement. Response rates in both components increased with brief unsignaled delays and decreased with longer delays. As in Experiment 1, response rates as a proportion of baseline were affected similarly for the two components in both the first six and last six sessions of exposure to the delay. Unlike delays imposed between two stimulus events, the effects of delays between responses and reinforcers do not appear to be attenuated when the average time between reinforcers is longer. In addition, the disruptions produced by unsignaled delays appear to be inconsistent with the general finding that responding maintained by higher rates of reinforcement is less resistant to change.
Complete chaotic synchronization in mutually coupled time-delay systems.
Landsman, Alexandra S; Schwartz, Ira B
2007-02-01
Complete chaotic synchronization of end lasers has been observed in a line of mutually coupled, time-delayed system of three lasers, with no direct communication between the end lasers. The present paper uses ideas from generalized synchronization to explain the complete synchronization in the presence of long coupling delays, applied to a model of mutually coupled semiconductor lasers in a line. These ideas significantly simplify the analysis by casting the stability in terms of the local dynamics of each laser. The variational equations near the synchronization manifold are analyzed, and used to derive the synchronization condition that is a function of parameters. The results explain and predict the dependence of synchronization on various parameters, such as time delays, strength of coupling and dissipation. The ideas can be applied to understand complete synchronization in other chaotic systems with coupling delays and no direct communication between synchronized subsystems.
Complex Time-Delay Systems Theory and Applications
Atay, Fatihcan M
2010-01-01
Time delays in dynamical systems arise as an inevitable consequence of finite speeds of information transmission. Realistic models increasingly demand the inclusion of delays in order to properly understand, analyze, design, and control real-life systems. The goal of this book is to present the state-of-the-art in research on time-delay dynamics in the framework of complex systems and networks. While the mathematical theory of delay equations is quite mature, its application to the particular problems of complex systems and complexity is a newly emerging field, and the present volume aims to play a pioneering role in this perspective. The chapters in this volume are authored by renowned experts and cover both theory and applications in a wide range of fields, with examples extending from neuroscience and biology to laser physics and vehicle traffic. Furthermore, all chapters include sufficient introductory material and extensive bibliographies, making the book a self-contained reference for both students and ...
Time-delay cosmography: increased leverage with angular diameter distances
Jee, I.; Komatsu, E.; Suyu, S. H.; Huterer, D.
2016-04-01
Strong lensing time-delay systems constrain cosmological parameters via the so-called time-delay distance and the angular diameter distance to the lens. In previous studies, only the former information was used in forecasting cosmographic constraints. In this paper, we show that the cosmological constraints improve significantly when the latter information is also included. Specifically, the angular diameter distance plays a crucial role in breaking the degeneracy between the curvature of the Universe and the time-varying equation of state of dark energy. Using a mock sample of 55 bright quadruple lens systems based on expectations for ongoing/future imaging surveys, we find that adding the angular diameter distance information to the time-delay distance information and the Planck's measurements of the cosmic microwave background anisotropies improves the constraint on the constant equation of state by 30%, on the time variation in the equation of state by a factor of two, and on the Hubble constant in the flat ΛCDM model by a factor of two. Therefore, previous forecasts for the statistical power of time-delay systems were overly pessimistic, i.e., time-delay systems are more powerful than previously appreciated.
Robust stability of discrete-time nonlinear system with time-delay
Institute of Scientific and Technical Information of China (English)
LIU Xin-ge; WU Min
2005-01-01
The robustly asymptotical stability problem for discrete-time nonlinear systems with time-delay was investigated. Positive definite matrix are constructed through Lyapunov functional. With the identity transform, property of matrix inverse and S-procedure, a new sufficient condition independent of the size of time-delay for robust stability of discrete-time nonlinear systems with time-delay is established. With Schur complement, another equivalent sufficient condition for robust stability of discrete-time nonlinear systems with time-delay is given. Finally, a sufficient condition dependent on the size of time-delay for robust stability of discrete-time nonlinear systems with time-delay is obtained. A unified approach is used to cast the robust stability problem into a convex optimization involving linear matrix inequalities.
Improved Stabilization Criteria for Neutral Time-Delay Systems
Lianglin Xiong; Haiyang Zhang; Yongkun Li; Zixin Liu
2016-01-01
This paper addresses the stabilization conditions for neutral systems with mixed time delays. By constructing a novel class of Lyapunov functionals which contains an augmented Lyapunov functional, using a new class of improved Jensen’s like inequalities, two improved delay-dependent stability criteria are firstly established. Next, state feedback controllers are designed according to the stability conditions in different cases. Finally, five numerical examples are provided to demonstrate the ...
STABILITY OF TIME VARYING SINGULAR DIFFERENTIAL SYSTEMS WITH DELAY
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
In this paper, stability of time varying singular differential systems with delay is considered. Based on variation formula and Gronwall-Bellman integral inequality, we obtain the exponential estimation of the solution and the sufficient conditions under which the considered system is stable and exponentially asymptotically stable. These results will be very useful to further research on Roust stability and control design of uncertain singular control systems with delay.
Microwave component time delays for the 70-meter antennas
Hartop, R.
1987-05-01
The X-band feed assemblies in the 64 meter antennas were redesigned to accommodate the upgrading to 70 meters and the associated surface reshaping. To maintain time delay data logs, new calculations were made of the microwave component delays for the XRO Mod IV X-band (8.4 to 8.45 GHz) feed assembly that was installed at DSS-63, and will soon be implemented at DSS-43 and DSS-14.
Visual prediction: psychophysics and neurophysiology of compensation for time delays.
Nijhawan, Romi
2008-04-01
A necessary consequence of the nature of neural transmission systems is that as change in the physical state of a time-varying event takes place, delays produce error between the instantaneous registered state and the external state. Another source of delay is the transmission of internal motor commands to muscles and the inertia of the musculoskeletal system. How does the central nervous system compensate for these pervasive delays? Although it has been argued that delay compensation occurs late in the motor planning stages, even the earliest visual processes, such as phototransduction, contribute significantly to delays. I argue that compensation is not an exclusive property of the motor system, but rather, is a pervasive feature of the central nervous system (CNS) organization. Although the motor planning system may contain a highly flexible compensation mechanism, accounting not just for delays but also variability in delays (e.g., those resulting from variations in luminance contrast, internal body temperature, muscle fatigue, etc.), visual mechanisms also contribute to compensation. Previous suggestions of this notion of "visual prediction" led to a lively debate producing re-examination of previous arguments, new analyses, and review of the experiments presented here. Understanding visual prediction will inform our theories of sensory processes and visual perception, and will impact our notion of visual awareness.
$H_0$ from 11 well measured time-delay lenses
Kumar, S Rathna; Prabhu, T P
2014-01-01
In this work, we present a homogeneous curve-shifting analysis of the publicly available light curves of 24 gravitationally lensed quasars, for which time delays have been reported in the literature till date, using the difference-smoothing technique. The uncertainty of each measured time delay was estimated using realistic simulated light curves. The recipe for generating such simulated light curves with known time delays in a plausible range around the measured time delay is introduced here. We identified 18 gravitationally lensed quasars that have light curves of sufficiently good quality to enable the measurement of at least one time delay between the images, adjacent to each other in terms of arrival-time order, to a precision of better than 33.3% (including systematic errors). We modelled the mass distribution of 11 of those systems, which have known lens redshifts, accurate astrometric data and sufficiently simple mass distribution, using the publicly available PixeLens code to infer a value of $H_0$ o...
Modified active disturbance rejection control for time-delay systems.
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.
Hybrid discretization method for time-delay nonlinear systems
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Zhang, Zheng [Xi' an Jiaotong University, Xi' an (China); Zhang, Yuanliang; Kil Chong, To [Chonbuk National University, Jeonju (Korea, Republic of); Kostyukova, Olga [3Institute of Mathematics National Academy of Science of Belarus, Minsk (Belarus)
2010-03-15
A hybrid discretization scheme that combines the virtues of the Taylor series and Matrix exponential integration methods is proposed. In the algorithm, each sampling time interval is divided into two subintervals to be considered according to the time delay and sampling period. The algorithm is not too expensive computationally and lends itself to be easily inserted into large simulation packages. The mathematical structure of the new discretization scheme is explored and described in detail. The performance of the proposed discretization procedure is evaluated by employing case studies. Various input signals, sampling rates, and time-delay values are considered to test the proposed method. The results demonstrate that the proposed discretization scheme is better than previous Taylor series method for nonlinear time-delay systems, especially when a large sampling period is inevitable
Wigner time delay in photodetachment of negative ions
Saha, S.; Deshmukh, P. C.; Jose, J.; Kkeifets, A. S.; Manson, S. T.
2016-05-01
In recent years, there has been much interest in studies on Wigner time delay in atomic photoionization using various experimental techniques and theoretical methodologies. In the present work, we report time delay in the photodetachment of negative ions using the relativistic-random-phase approximation (RRPA), which includes relativistic and important correlation effects. Time delay is obtained as energy derivative of phase of the photodetachment complex transition amplitude. We investigate the time delay in the dipole n p --> ɛd channels in the photodetachment of F- and Cl-, and in n f --> ɛg channels in the photodetachment of Tm-. In photodetachment of the negative ions, the photoelectron escapes in the field of the neutral atom and thus does not experience the nuclear Coulomb field; hence the phase is devoid of the Coulomb component. The systems chosen are well suited to examine the sensitivity of the photodetachment time delay to the centrifugal potential. The ions chosen have closed shells, and thus amenable to the RPA. Work supported by DOE, Office of Chemical Sciences, DST (India), and the Australian Research Council.
Effect of multiple time-delay on vibrational resonance.
Jeevarathinam, C; Rajasekar, S; Sanjuán, M A F
2013-03-01
We report our investigation on the effect of multiple time-delay on vibrational resonance in a single Duffing oscillator and in a system of n Duffing oscillators coupled unidirectionally and driven by both a low- and a high-frequency periodic force. For the single oscillator, we obtain analytical expressions for the response amplitude Q and the amplitude g of the high-frequency force at which resonance occurs. The regions in parameter space of enhanced Q at resonance, as compared to the case in absence of time-delay, show a bands-like structure. For the two-coupled oscillators, we explain all the features of variation of Q with the control parameter g. For the system of n-coupled oscillators with a single time-delay coupling, the response amplitudes of the oscillators are shown to be independent of the time-delay. In the case of a multi time-delayed coupling, undamped signal propagation takes place for coupling strength (δ) above a certain critical value (denoted as δu). Moreover, the response amplitude approaches a limiting value QL with the oscillator number i. We obtain analytical expressions for both δu and QL.
Angular dependence of photoemission time delay in helium
Heuser, Sebastian; Jiménez Galán, Álvaro; Cirelli, Claudio; Marante, Carlos; Sabbar, Mazyar; Boge, Robert; Lucchini, Matteo; Gallmann, Lukas; Ivanov, Igor; Kheifets, Anatoli S.; Dahlström, J. Marcus; Lindroth, Eva; Argenti, Luca; Martín, Fernando; Keller, Ursula
2016-12-01
Time delays of electrons emitted from an isotropic initial state with the absorption of a single photon and leaving behind an isotropic ion are angle independent. Using an interferometric method involving XUV attosecond pulse trains and an IR-probe field in combination with a detection scheme, which allows for full three-dimensional momentum resolution, we show that measured time delays between electrons liberated from the 1 s2 spherically symmetric ground state of helium depend on the emission direction of the electrons relative to the common linear polarization axis of the ionizing XUV light and the IR-probing field. Such time delay anisotropy, for which we measure values as large as 60 as, is caused by the interplay between final quantum states with different symmetry and arises naturally whenever the photoionization process involves the exchange of more than one photon. With the support of accurate theoretical models, the angular dependence of the time delay is attributed to small phase differences that are induced in the laser-driven continuum transitions to the final states. Since most measurement techniques tracing attosecond electron dynamics involve the exchange of at least two photons, this is a general and significant effect that must be taken into account in all measurements of time delays involving photoionization processes.
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.
On pole-placement controllers for linear time-delay systems with commensurate point delays
Directory of Open Access Journals (Sweden)
de la Sen M.
2005-01-01
Full Text Available We investigate the exact and approximate spectrum assignment properties associated with realizable output-feedback pole-placement-type controllers for single-input single-output linear time-invariant time-delay systems with commensurate point delays. The controller synthesis problem is discussed through the solvability of a set of coupled Diophantine equations of polynomials. An extra complexity is incorporated in the above design to cancel extra unsuitable dynamics being generated when solving the above Diophantine equations. Thus, the complete controller tracks any arbitrary prefixed (either finite or delay-dependent closed-loop spectrum. However, if the controller is simplified by deleting the above-mentioned extra complexity, then robust stability and approximated spectrum assignment are still achievable for a certain sufficiently small amount of delayed dynamics. Finally, the approximate spectrum assignment and robust stability problems are revisited under plant disturbances if the nominal controller is maintained. In the current approach, the finite spectrum assignment is only considered as a particular case of the designer's choice of a (delay-dependent arbitrary spectrum assignment objective.
Quantum time delay in chaotic scattering: a semiclassical approach
Energy Technology Data Exchange (ETDEWEB)
Vallejos, R.O.; Ozorio de Almeida, A.M. [Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro (Brazil); Lewenkopf, C.H. [Instituto de Fisica, UERJ, Rio de Janeiro (Brazil)
1998-05-29
We study the universal fluctuations of the Wigner-Smith time delay for systems which exhibit chaotic dynamics in their classical limit. We present a new derivation of the semiclassical relation of the quantum time delay to properties of the set of trapped periodic orbits in the repeller. As an application, we calculate the energy correlator in the crossover regime between preserved and fully broken time reversal symmetry. We discuss the range of validity of our results and compare them with the predictions of random matrix theories. (author)
Quantum mechanical time-delay matrix in chaotic scattering
Brouwer, P W; Beenakker, C W J
1997-01-01
We calculate the probability distribution of the matrix Q = -i \\hbar S^{-1} dS/dE for a chaotic system with scattering matrix S at energy E. The eigenvalues \\tau_j of Q are the so-called proper delay times, introduced by E. P. Wigner and F. T. Smith to describe the time-dependence of a scattering process. The distribution of the inverse delay times turns out to be given by the Laguerre ensemble from random-matrix theory.
Quantum Mechanical Time-Delay Matrix in Chaotic Scattering
Energy Technology Data Exchange (ETDEWEB)
Brouwer, P.W.; Frahm, K.M.; Beenakker, C.W. [Instituut-Lorentz, Leiden University, P.O. Box 9506, 2300 RA Leiden (The Netherlands)
1997-06-01
We calculate the probability distribution of the matrix Q=-i{h_bar}S{sup -1}{partial_derivative}S/{partial_derivative}E for a chaotic system with scattering matrix S at energy E . The eigenvalues {tau}{sub j} of Q are the so-called proper delay times, introduced by Wigner and Smith to describe the time dependence of a scattering process. The distribution of the inverse delay times turns out to be given by the Laguerre ensemble from random-matrix theory. {copyright} {ital 1997} {ital The American Physical Society}
Kalman filtering for time-delayed linear systems
Institute of Scientific and Technical Information of China (English)
LU Xiao; WANG Wei
2006-01-01
This paper is to study the linear minimum variance estimation for discrete- time systems. A simple approach to the problem is presented by developing re-organized innovation analysis for the systems with instantaneous and double time-delayed measurements. It is shown that the derived estimator involves solving three different standard Kalman filtering with the same dimension as the original system. The obtained results form the basis for solving some complicated problems such as H∞ fixed-lag smoothing, preview control, H∞ filtering and control with time delays.
Different Types of Synchronization in Time-Delayed Systems
Institute of Scientific and Technical Information of China (English)
FENG Cun-Fang; ZHANG Yan; WANG Ying-Hai
2007-01-01
@@ We investigate different types of synchronization between two unidirectionally nonlinearly coupled identical delaydifferential systems related to optical bistable or hybrid optical bistable devices. This system can represent some kinds of delay-differential models, I.e. Ikeda model, Vallée model, sine-square model, Mackey-Glass model, and so on. We find existence and sufficient stability conditions by theoretical analysis and test the correctness by numerical simulations. Lag, complete and anticipating synchronization are observed, respectively. It is found that the time-delay system can be divided into two parts, one is the instant term and the other is the delay term.Synchronization between two identical chaotic systems can be derived by adding a coupled term to the delay term in the driven system.
Linearisation via input-output injection of time delay systems
García-Ramírez, Eduardo; Moog, Claude H.; Califano, Claudia; Alejandro Márquez-Martínez, Luis
2016-06-01
This paper deals with the problem of linearisation of systems with constant commensurable delays by input-output injection using algebraic control tools based on the theory of non-commutative rings. Solutions for the problem of linearisation free of delays, and with delays of an observable nonlinear time-delay systems are presented based on the analysis of the input-output equation. These results are achieved by means of constructive algorithms that use the nth derivative of the output expressed in terms of the state-space variables instead of the explicit computation of the input-output representation of the system. Necessary and sufficient conditions are established in both cases by means of an invertible change of coordinates.
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.
Discrete-Time Sliding Mode Control for Uncertain Networked System Subject to Time Delay
Directory of Open Access Journals (Sweden)
Saulo C. Garcia
2015-01-01
Full Text Available We deal with uncertain systems with networked sliding mode control, subject to time delay. To minimize the degenerative effects of the time delay, a simpler format of state predictor is proposed in the control law. Some ultimate bounded stability analyses and stabilization conditions are provided for the uncertain time delay system with proposed discrete-time sliding mode control strategy. A numerical example is presented to corroborate the analyses.
Global Exponential Stability of Discrete-Time Neural Networks with Time-Varying Delays
Directory of Open Access Journals (Sweden)
S. Udpin
2013-01-01
Full Text Available This paper presents some global stability criteria of discrete-time neural networks with time-varying delays. Based on a discrete-type inequality, a new global stability condition for nonlinear difference equation is derived. We consider nonlinear discrete systems with time-varying delays and independence of delay time. Numerical examples are given to illustrate the effectiveness of our theoretical results.
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.
Finite-Time Stability of Nonautonomous Delayed Systems
Institute of Scientific and Technical Information of China (English)
孙武军; 孔德兴
2003-01-01
The finite-time stability to linear discontinuous time-varying delayed system was investigated. By applying the method of upper and lower solutions, some sufficient conditions of this kind of stability were obtained.Furthermore, it also developed a monotone iterative technique for obtaining solutions which are obtained as limits of monotone sequences
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.
Sensitivity analysis of dynamic biological systems with time-delays.
Wu, Wu Hsiung; Wang, Feng Sheng; Chang, Maw Shang
2010-10-15
Mathematical modeling has been applied to the study and analysis of complex biological systems for a long time. Some processes in biological systems, such as the gene expression and feedback control in signal transduction networks, involve a time delay. These systems are represented as delay differential equation (DDE) models. Numerical sensitivity analysis of a DDE model by the direct method requires the solutions of model and sensitivity equations with time-delays. The major effort is the computation of Jacobian matrix when computing the solution of sensitivity equations. The computation of partial derivatives of complex equations either by the analytic method or by symbolic manipulation is time consuming, inconvenient, and prone to introduce human errors. To address this problem, an automatic approach to obtain the derivatives of complex functions efficiently and accurately is necessary. We have proposed an efficient algorithm with an adaptive step size control to compute the solution and dynamic sensitivities of biological systems described by ordinal differential equations (ODEs). The adaptive direct-decoupled algorithm is extended to solve the solution and dynamic sensitivities of time-delay systems describing by DDEs. To save the human effort and avoid the human errors in the computation of partial derivatives, an automatic differentiation technique is embedded in the extended algorithm to evaluate the Jacobian matrix. The extended algorithm is implemented and applied to two realistic models with time-delays: the cardiovascular control system and the TNF-α signal transduction network. The results show that the extended algorithm is a good tool for dynamic sensitivity analysis on DDE models with less user intervention. By comparing with direct-coupled methods in theory, the extended algorithm is efficient, accurate, and easy to use for end users without programming background to do dynamic sensitivity analysis on complex biological systems with time-delays.
Birthrates and delay times of Type Ia supernovae
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
Type Ia supernovae (SNe Ia) play an important role in diverse areas of astrophysics, from the chemical evolution of galaxies to observational cosmology. However, the nature of the progenitors of SNe Ia is still unclear. In this paper, according to a detailed binary population synthesis study, we obtained SN Ia birthrates and delay times from different progenitor models, and compared them with observations. We find that the Galactic SN Ia birthrate from the double-degenerate (DD) model is close to those inferred from observations, while the birthrate from the single-degenerate (SD) model accounts for only about 1/2-2/3 of the observations. If a single starburst is assumed, the distribution of the delay times of SNe Ia from the SD model is a weak bimodality, where the WD + He channel contributes to the SNe Ia with delay times shorter than 100 Myr, and the WD + MS and WD + RG channels to those with age longer than 1 Gyr.
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.
Finite-Time Stability of Neutral Fractional Time-Delay Systems via Generalized Gronwalls Inequality
Directory of Open Access Journals (Sweden)
Pang Denghao
2014-01-01
Full Text Available This paper studies the finite-time stability of neutral fractional time-delay systems. With the generalized Gronwall inequality, sufficient conditions of the finite-time stability are obtained for the particular class of neutral fractional time-delay systems.
Further triple integral approach to mixed-delay-dependent stability of time-delay neutral systems.
Wang, Ting; Li, Tao; Zhang, Guobao; Fei, Shumin
2017-09-01
This paper studies the asymptotic stability for a class of neutral systems with mixed time-varying delays. Through utilizing some Wirtinger-based integral inequalities and extending the convex combination technique, the upper bound on derivative of Lyapunov-Krasovskii (L-K) functional can be estimated more tightly and three mixed-delay-dependent criteria are proposed in terms of linear matrix inequalities (LMIs), in which the nonlinearity and parameter uncertainties are also involved, respectively. Different from those existent works, based on the interconnected relationship between neutral delay and state one, some novel triple integral functional terms are constructed and the conservatism can be effectively reduced. Finally, two numerical examples are given to show the benefits of the proposed criteria. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.
Reconstruction of ensembles of coupled time-delay systems from time series.
Sysoev, I V; Prokhorov, M D; Ponomarenko, V I; Bezruchko, B P
2014-06-01
We propose a method to recover from time series the parameters of coupled time-delay systems and the architecture of couplings between them. The method is based on a reconstruction of model delay-differential equations and estimation of statistical significance of couplings. It can be applied to networks composed of nonidentical nodes with an arbitrary number of unidirectional and bidirectional couplings. We test our method on chaotic and periodic time series produced by model equations of ensembles of diffusively coupled time-delay systems in the presence of noise, and apply it to experimental time series obtained from electronic oscillators with delayed feedback coupled by resistors.
Reconstruction of ensembles of coupled time-delay systems from time series
Sysoev, I. V.; Prokhorov, M. D.; Ponomarenko, V. I.; Bezruchko, B. P.
2014-06-01
We propose a method to recover from time series the parameters of coupled time-delay systems and the architecture of couplings between them. The method is based on a reconstruction of model delay-differential equations and estimation of statistical significance of couplings. It can be applied to networks composed of nonidentical nodes with an arbitrary number of unidirectional and bidirectional couplings. We test our method on chaotic and periodic time series produced by model equations of ensembles of diffusively coupled time-delay systems in the presence of noise, and apply it to experimental time series obtained from electronic oscillators with delayed feedback coupled by resistors.
Robust output regulation problem for linear time-delay systems
Lu, Maobin; Huang, Jie
2015-06-01
In this paper, we study the robust output regulation problem for linear systems with input time-delay. By extending the internal model design method to linear time-delay systems, we have established solvability conditions for the problem by both dynamic state feedback control and dynamic output feedback control. The advantages of internal model approach over the feedforward design approach are that it can handle perturbations of the uncertain parameters in the plant and the control law, and it does not need to solve the regulator equations.
Extracting the relevant delays in time series modelling
DEFF Research Database (Denmark)
Goutte, Cyril
1997-01-01
selection, and more precisely stepwise forward selection. The method is compared to other forward selection schemes, as well as to a nonparametric tests aimed at estimating the embedding dimension of time series. The final application extends these results to the efficient estimation of FIR filters on some......In this contribution, we suggest a convenient way to use generalisation error to extract the relevant delays from a time-varying process, i.e. the delays that lead to the best prediction performance. We design a generalisation-based algorithm that takes its inspiration from traditional variable...
Time delayed laser networks: phase versus chaos synchronization
Reidler, I; Aviad, Y; Guberman, S; Friesem, A A; Rosenbluh, M; Davidson, N; Kanter, I
2013-01-01
The synchronization of chaotic lasers and the optical phase synchronization of light originating in multiple coupled lasers have both been extensively studied, however, the interplay between these two phenomena, especially at the network level is unexplored. Here we experimentally compare chaos synchronization of laser networks with heterogeneous coupling delay times to phase synchronization of similar networks. While chaotic lasers exhibit deterioration in synchronization as the network time delay heterogeneity increases, phase synchronization is found to be independent of heterogeneity. The experimental results are found to be in agreement with numerical simulations for semiconductor lasers.
Time Delay Properties of a Fabry-Perot Interferometer
Institute of Scientific and Technical Information of China (English)
YUAN Shi; MAN Wei-Ning; YU Jin; GAO Jin-Yue
2001-01-01
The time delay properties of a Fabry-Perot interferometer are investigated. We found that the group velocity of light through a Fabry-Perot interferometer can be reduced to 10-4 of the light speed in vacuum and the time delay is 210ns, when the reflectivity is 0.999 and the distance between two mirrors is 1 cm. The system is analogous to the recently proposed one-dimensional photonic band-gap structures with a defect [Zhu et al. Opt.Commun. 174(2000)139].
Kernel regression estimates of time delays between gravitationally lensed fluxes
Otaibi, Sultanah AL; Cuevas-Tello, Juan C; Mandel, Ilya; Raychaudhury, Somak
2015-01-01
Strongly lensed variable quasars can serve as precise cosmological probes, provided that time delays between the image fluxes can be accurately measured. A number of methods have been proposed to address this problem. In this paper, we explore in detail a new approach based on kernel regression estimates, which is able to estimate a single time delay given several datasets for the same quasar. We develop realistic artificial data sets in order to carry out controlled experiments to test of performance of this new approach. We also test our method on real data from strongly lensed quasar Q0957+561 and compare our estimates against existing results.
Generalized Synchronization of Time-Delayed Differential Systems
Institute of Scientific and Technical Information of China (English)
JING Jian-Yi; MIN Le-Quan
2009-01-01
We establish two theorems for two time-delayed (chaotic) differential equation systems to achieve time-delayed generalized synchronization (TDGS). The theorems uncover general forms of two TDGS systems via a prescribed differentiable transformation. Based on the theorems, we use two-coupled Ikeda equations as the driving system to construct TDGS driven systems via two prescribed transformations. Numerical simulations demonstrate the effectiveness of the proposed theorems. It may be expected that our theorems provide new tools for understanding and studying TDGS phenomena.
Singular perturbation methods for nonlinear dynamic systems with time delays
Energy Technology Data Exchange (ETDEWEB)
Hu, H.Y. [MOE Key Laboratory of Structure Mechanics and Control for Aircraft, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing (China)], E-mail: hhyae@nuaa.edu.cn; Wang, Z.H. [MOE Key Laboratory of Structure Mechanics and Control for Aircraft, Nanjing University of Aeronautics and Astronautics, 210016 Nanjing (China)
2009-04-15
This review article surveys the recent advances in the dynamics and control of time-delay systems, with emphasis on the singular perturbation methods, such as the method of multiple scales, the method of averaging, and two newly developed methods, the energy analysis and the pseudo-oscillator analysis. Some examples are given to demonstrate the advantages of the methods. The comparisons with other methods show that these methods lead to easier computations and higher accurate prediction on the local dynamics of time-delay systems near a Hopf bifurcation.
Zhong, Qishui; Cheng, Jun; Zhao, Yuqing
2015-07-01
In this paper, a novel method is developed for delay-dependent finite-time boundedness of a class of Markovian switching neural networks with time-varying delays. New sufficient condition for stochastic boundness of Markovian jumping neural networks is presented and proved by an newly augmented stochastic Lyapunov-Krasovskii functional and novel activation function conditions, the state trajectory remains in a bounded region of the state space over a given finite-time interval. Finally, a numerical example is given to illustrate the efficiency and less conservative of the proposed method.
Delays and the Capacity of Continuous-time Channels
Khanna, Sanjeev
2011-01-01
Any physical channel of communication offers two potential reasons why its capacity (the number of bits it can transmit in a unit of time) might be unbounded: (1) Infinitely many choices of signal strength at any given instant of time, and (2) Infinitely many instances of time at which signals may be sent. However channel noise cancels out the potential unboundedness of the first aspect, leaving typical channels with only a finite capacity per instant of time. The latter source of infinity seems less studied. A potential source of unreliability that might restrict the capacity also from the second aspect is delay: Signals transmitted by the sender at a given point of time may not be received with a predictable delay at the receiving end. Here we examine this source of uncertainty by considering a simple discrete model of delay errors. In our model the communicating parties get to subdivide time as microscopically finely as they wish, but still have to cope with communication delays that are macroscopic and va...
Determination of Uncalibrated Phase Delays for Real-Time PPP
Hinterberger, Fabian; Weber, Robert; Huber, Katrin; Lesjak, Roman
2014-05-01
Today PPP is a well-known technique of GNSS based positioning used for a wide range of post-processing applications. Using observations of a single GNSS receiver and applying precise orbit and clock information derived from global GNSS networks highly precise positions can be obtained. The atmospheric delays are usually mitigated by linear combination (ionosphere) and parameter estimation (troposphere). Within the last years also the demand for real-time PPP increased. In 2012, the IGS real-time working group started a pilot project to broadcast real-time precise orbits and clock correction streams. Nevertheless, real-time PPP is in its starting phase and currently only few applications make use of the technique although SSR-Messages are already implemented in RTCM3.1. The problems of still limited accuracy compared to Network-RTK as well as long convergence times might be solved by almost instantaneous integer ambiguity resolution at zero-difference level which is a major topic of current scientific investigations. Therefore a national consortium has carried out over the past 2 years the research project PPP-Serve (funded by the Austrian Research Promotion Agency - FFG), which aimed at the development of appropriate algorithms for real-time PPP with special emphasis on the ambiguity resolution of zero-difference observations. We have established a module which calculates based on GPS-reference station data-streams of a dense network (obtained from IGS via BKG) so-called wide-lane and narrow-lane satellite specific calibration phase delays. While the wide-lane phase delays are almost stable over longer periods, the estimation of narrow-lane phase delays has to be re-established every 24 hours. These phase-delays are submitted via a real-time module to the rover where they are used for point positioning via a PPP-model. This presentation deals with the process and obstacles of calculating the wide-lane and narrow-lane phase-delays (based on SD -observations between
Institute of Scientific and Technical Information of China (English)
Back-Song; Lee; Jong-Dug; Shin; Boo-Gyoun; Kim
2003-01-01
We proposed an optical true time delay (TTD) for phased array antennas (PAAs) composed of 2×2 optical MEMS switches, single-mode fiber delay lines, and a fixed wavelength laser diode. A 3-bit TTD for 10 GHz PAAs was implemented with a time delay error less than ± 0.2 ps.
A new approach to consensus problems in discrete-time multiagent systems with time-delays
Institute of Scientific and Technical Information of China (English)
WANG Long; XIAO Feng
2007-01-01
In this paper, consensus problems in discrete-time multiagent systems with timeinvariant delays are considered. In order to characterize the structures of communication topologies, the concept of "pre-leader-follower" decomposition is introduced.Then, a necessary and sufficient condition for state consensus is established. By this method, consensus problems in networks with a single time-delay, as well as with multiple time-delays, are studied, and some necessary and sufficient conditions for solvability of consensus problems are obtained.
Directory of Open Access Journals (Sweden)
Moretti M
2015-10-01
Full Text Available Maurizio Moretti,1 Stefano Fagnani2 1Respiratory Unit, Massa-Carrara Hospital and University of Pisa, Pisa, Italy; 2Medical Department, Edmond Pharma Srl, Paderno Dugnano, Milan, Italy Purpose: Mucolytics can improve disease outcome in patients with acute exacerbations of chronic obstructive pulmonary disease (AECOPD. The objectives of this study were to investigate the effects of erdosteine (ER, a mucolytic agent with antioxidant activity, on systemic inflammation, symptoms, recurrence of exacerbation, and time to first exacerbation postdischarge in hospitalized patients with AECOPD. Patients and methods: Patients admitted to hospital with AECOPD were randomized to receive either ER 900 mg daily (n=20 or a matching control (n=20. Treatment was continued for 10 days until discharge. Patients also received standard treatment with steroids, nebulized bronchodilators, and antibiotics as appropriate. Serum C-reactive protein levels, lung function, and breathlessness–cough–sputum scale were measured on hospital admission and thereafter at days 10 and 30 posttreatment. Recurrence of AECOPD-requiring antibiotics and/or oral steroids and time to first exacerbation in the 2 months (days 30 and 60 postdischarge were also assessed. Results: Mean serum C-reactive protein levels were lower in both groups at days 10 and 30, compared with those on admission, with significantly lower levels in the ER group at day 10. Improvements in symptom score and forced expiratory volume in 1 second were greater in the ER than the control group, which reached statistical significance on day 10. ER was associated with a 39% lower risk of exacerbations and a significant delay in time to first exacerbation (log-rank test P=0.009 and 0.075 at days 30 and 60, respectively compared with controls. Conclusion: Results confirm that the addition of ER (900 mg/d to standard treatment improves outcomes in patients with AECOPD. ER significantly reduced airway inflammation, improved
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.
Control of time stability of scintillation spectrometer of delayed coincidences
Morozov, V A
2002-01-01
Paper describes a system to control time stability of a two-detector plastic scintillation spectrometer of three-dimensional coincides. A two-reference control system incorporates a light guide base delay optical line, two light diodes and a two-channel generator of nanosecond pulses. A distinguishing feature of the design system is application of one delay line to form both advance and delay time signal as to the real coincidences in the studied radioactive source. The designed system of control enables to measure periods of half-decay of nuclei excited states within 40-100 ns range ensuring control of position of coincidence curve gravity centers within 4 ps limits
Efficient Training of Recurrent Neural Network with Time Delays.
Marom, Emanuel; Saad, David; Cohen, Barak
1997-01-01
Training recurrent neural networks to perform certain tasks is known to be difficult. The possibility of adding synaptic delays to the network properties makes the training task more difficult. However, the disadvantage of tough training procedure is diminished by the improved network performance. During our research of training neural networks with time delays we encountered a robust method for accomplishing the training task. The method is based on adaptive simulated annealing algorithm (ASA) which was found to be superior to other training algorithms. It requires no tuning and is fast enough to enable training to be held on low end platforms such as personal computers. The implementation of the algorithm is presented over a set of typical benchmark tests of training recurrent neural networks with time delays. Copyright 1996 Elsevier Science Ltd.
Low-complexity controllers for time-delay systems
Özbay, Hitay; Bonnet, Catherine; Mounier, Hugues
2014-01-01
This volume in the newly established series Advances in Delays and Dynamics (ADD@S) provides a collection of recent results on the design and analysis of Low Complexity Controllers for Time Delay Systems. A widely used indirect method to obtain low order controllers for time delay systems is to design a controller for the reduced order model of the plant. In the dual indirect approach, an infinite dimensional controller is designed first for the original plant model; then, the controller is approximated by keeping track of the degradation in performance and stability robustness measures. The present volume includes new techniques used at different stages of the indirect approach. It also includes new direct design methods for fixed structure and low order controllers. On the other hand, what is meant by low complexity controller is not necessarily low order controller. For example, Smith predictor or similar type of controllers include a copy of the plant internally in the controller, so they are technically ...
Time delays across saddles as a test of modified gravity
Magueijo, Joao
2012-01-01
Modified gravity theories can produce strong signals in the vicinity of the saddles of the total gravitational potential. In a sub-class of these models this translates into diverging time-delays for echoes crossing the saddles. Such models arise from the possibility that gravity might be infrared divergent or confined, and if suitably designed they are very difficult to rule out. We show that Lunar Laser Ranging during an eclipse could probe the time-delay effect within meters of the saddle, thereby proving or excluding these models. Very Large Baseline Interferometry, instead, could target delays across the Jupiter-Sun saddle. Such experiments would shed light on the infrared behaviour of gravity and examine the puzzling possibility that there might be well-hidden regions of strong gravity and even singularities inside the solar system.
Noise-enhanced phase synchronization in time-delayed systems.
Senthilkumar, D V; Shrii, M Manju; Kurths, J
2012-02-01
We investigate the phenomenon of noise-enhanced phase synchronization (PS) in coupled time-delay systems, which usually exhibit non-phase-coherent attractors with complex topological properties. As a delay system is essentially an infinite dimensional in nature with multiple characteristic time scales, it is interesting and crucial to understand the interplay of noise and the time scales in achieving PS. In unidirectionally coupled systems, the response system adjust all its time scales to that of the drive, whereas both subsystems adjust their rhythms to a single (main time scale of the uncoupled system) time scale in bidirectionally coupled systems. We find similar effects for both a common and an independent additive Gaussian noise.
Corticomuscular Coherence With Time Lag With Application to Delay Estimation.
Xu, Yuhang; McClelland, Verity M; Cvetkovic, Zoran; Mills, Kerry R
2017-03-01
Functional coupling between the motor cortex and muscle activity is usually detected and characterized using the spectral method of corticomuscular coherence (CMC). This functional coupling occurs with a time delay, which, if not properly accounted for, may decrease the coherence and make the synchrony difficult to detect. In this paper, we introduce the concept of CMC with time lag (CMCTL), that is the coherence between segments of motor cortex electroencephalogram (EEG) and electromyography (EMG) signals displaced from a central observation point. This concept is motivated by the need to compensate for the unknown delay between coupled cortex and muscle processes. We demonstrate using simulated data that under certain conditions the time lag between EEG and EMG segments at points of local maxima of CMCTL corresponds to the average delay along the involved corticomuscular conduction pathways. Using neurophysiological data, we then show that CMCTL with appropriate time lag enhances the coherence between cortical and muscle signals, and that time lags which correspond to local maxima of CMCTL provide estimates of delays involved in corticomuscular coupling that are consistent with the underlying physiology.
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.
POLE PLACEMENT CONTROLLERS FOR LINEAR TIME-DELAY SYSTEMS WITH COMMENSURATE POINT DELAYS
Institute of Scientific and Technical Information of China (English)
M. de la Sen
2004-01-01
This paper investigates the exact and approximate spectrum assignment properties associated with realizable output-feedback pole-placement type controllers for single-input single-output linear time-invariant time-delay systems with commensurate point delays. The controller synthesis problem is discussed through the solvability of a set of coupled diophantine equations of polynomials. An extra complexity is incorporated to the above design to cancel extra unsuitable dynamics being generated when solving the above diophantine equations. Thus, the complete controller tracks any arbitrary prefixed (either finite or delaydependent) closed-loop spectrum. However, if the controller is simplified by deleting the above mentioned extra complexity, then the robust stability and approximated spectrum assignment are still achievable for a certain sufficiently small amount of delayed dynamics. Finally, the approximate spectrum assignment and robust stability problems are revisited under plant disturbances if the nominal controller is maintained. In the current approach, the finite spectrum assignment is only considered as a particular case to the designer's choice of a (delay-dependent) arbitrary spectrum assignment objective.
Stability analysis in a car-following model with reaction-time delay and delayed feedback control
Jin, Yanfei; Xu, Meng
2016-10-01
The delayed feedback control in terms of both headway and velocity differences has been proposed to guarantee the stability of a car-following model including the reaction-time delay of drivers. Using Laplace transformation and transfer function, the stable condition is derived and appropriate choices of time delay and feedback gains are designed to stabilize traffic flow. Meanwhile, an upper bound on explicit time delay is determined with respect to the response of desired acceleration. To ensure the string stability, the explicit time delay cannot over its upper bound. Numerical simulations indicate that the proposed control method can restraint traffic congestion and improve control performance.
OSCILLATION FOR NONAUTONOMOUS NEUTRAL DYNAMIC DELAY EQUATIONS ON TIME SCALES
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The article is concerned with oscillation of nonautonomous neutral dynamic delay equations on time scales. Sufficient conditions are established for the existence of bounded positive solutions and for oscillation of all solutions of this equation. Some results extend known results for difference equations when the time scale is the set Z+ of positive integers and for differential equations when the time scale is the set R of real numbers.
SLEEP TIMING AND CIRCADIAN PHASE IN DELAYED SLEEP PHASE
2009-01-01
Delayed sleep phase syndrome (DSPS) is a circadian rhythm sleep disorder in which the timing of the sleep episode occurs later than desired and is associated with difficulty falling asleep, problems awakening on time (e.g., to meet work or school obligations), and daytime sleepiness. The phase relationship between the timing of sleep and endogenous circadian rhythms is critical to the initiation and maintenance of sleep, and significant alteration leads to impairment of sleep quality and dura...
Controlling Beam Halo-Chaos via Time-Delayed Feedback
Institute of Scientific and Technical Information of China (English)
FANG Jin-Qing; WENG Jia-Qiang; ZHU Lun-Wu; LUO Xiao-Shu
2004-01-01
The study of controlling high-current proton beam halo-chaos has become a key concerned issue for many important applications. In this paper, time-delayed feedback control method is proposed for beam halo-chaos. Particle in cell simulation results show that the method is very effective and has some advantages for high-current beam experiments and engineering.
Stabilization of a Class of Stochastic Systems with Time Delays
Directory of Open Access Journals (Sweden)
Jian Wang
2014-01-01
Full Text Available The problem of exponential stability is investigated for a class of stochastic time-delay systems. By using the decomposition technique and Lyapunov stability theory, two improved exponential stability criteria are derived. Finally, a numerical example is given to illustrate the effectiveness and the benefit of the proposed method.
How accurate are the time delay estimates in gravitational lensing?
Cuevas-Tello, J C; Tino, P; Cuevas-Tello, Juan C.; Raychaudhury, Somak; Tino, Peter
2006-01-01
We present a novel approach to estimate the time delay between light curves of multiple images in a gravitationally lensed system, based on Kernel methods in the context of machine learning. We perform various experiments with artificially generated irregularly-sampled data sets to study the effect of the various levels of noise and the presence of gaps of various size in the monitoring data. We compare the performance of our method with various other popular methods of estimating the time delay and conclude, from experiments with artificial data, that our method is least vulnerable to missing data and irregular sampling, within reasonable bounds of Gaussian noise. Thereafter, we use our method to determine the time delays between the two images of quasar Q0957+561 from radio monitoring data at 4 cm and 6 cm, and conclude that if only the observations at epochs common to both wavelengths are used, the time delay gives consistent estimates, which can be combined to yield 408\\pm 12 days. The full 6 cm dataset, ...
Introduction to time-delay systems analysis and control
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...
Strong Lens Time Delay Challenge: I. Experimental Design
Dobler, Gregory; Treu, Tommaso; Marshall, Phillip J; Liao, Kai; Hojjati, Alireza; Linder, Eric; Rumbaugh, Nicholas
2013-01-01
The time delays between point-like images in gravitational lens systems can be used to measure cosmological parameters as well as probe the dark matter (sub-)structure within the lens galaxy. The number of lenses with measured time delays is growing rapidly as a result of some dedicated efforts; the upcoming Large Synoptic Survey Telescope (LSST) will monitor ~1000 lens systems consisting of a foreground elliptical galaxy producing multiple images of a background quasar. In an effort to assess the present capabilities of the community to accurately measure the time delays in strong gravitational lens systems, and to provide input to dedicated monitoring campaigns and future LSST cosmology feasibility studies, we invite the community to take part in a "Time Delay Challenge" (TDC). The challenge is organized as a set of "ladders", each containing a group of simulated datasets to be analyzed blindly by participating independent analysis teams. Each rung on a ladder consists of a set of realistic mock observed le...
STABILITY ANALYSIS OF HOPFIELD NEURAL NETWORKS WITH TIME DELAY
Institute of Scientific and Technical Information of China (English)
王林山; 徐道义
2002-01-01
The global asymptotic stability for Hopfield neural networks with time delay was investigated. A theorem and two corollaries were obtained, in which the boundedness and differentiability offjon R in some articles were deleted. Some sufficient conditions for the existence of global asymptotic stable equilibrium of the networks in this paper are better than the sufficient conditions in quoted articles.
GLOBAL STABILITY IN HOPFIELD NEURAL NETWORKS WITH DISTRIBUTED TIME DELAYS
Institute of Scientific and Technical Information of China (English)
Zhang Jiye; Wu Pingbo; Dai Huanyun
2001-01-01
In this paper, without assuming the boundedness, monotonicity and differentiability of the activation functions, the conditions ensuring existence, uniqueness, and global asymptotical stability of the equilibrium point of Hopfield neural network models with distributed time delays are studied. Using M-matrix theory and constructing proper Liapunov functionals, the sufficient conditions for global asymptotic stability are obtained.
Time delays in PG1115+080: new estimates
Vakulik, V G; Schild, R E; Tsvetkova, V S; Dudinov, V N; Minakov, A A; Nuritdinov, S N; Artamonov, B P; Kochetov, A Ye; Smirnov, G V; Sergeyev, A A; Konichek, V V; Sinelnikov, I Ye; Bruevich, V V; Akhunov, T; Burkhonov, O
2009-01-01
We report new estimates of the time delays in the quadruple gravitationally lensed quasar PG1115+080, obtained from the monitoring data in filter R with the 1.5-m telescope at the Maidanak Mountain (Uzbekistan, Central Asia) in 2004-2006. The time delays are 16.4 days between images C and B, and 12 days between C and A1+A2, with image C being leading for both pairs. The only known estimates of the time delays in PG1115 are those based on observations by Schechter et al. (1997) -- 23.7 and 9.4 days between images C and B, C and A1+A2, respectively, as calculated by Schechter et al., and 25 and 13.3 days as revised by Barkana (1997) for the same image components with the use of another method. The new values of time delays in PG 1115+080 may be expected to provide larger estimates of the Hubble constant thus decreasing a diversity between the H_0 estimates taken from gravitationally lensed quasars and with other methods.
An identification algorithm for linear stochastic systems with time delays
Leondes, C. T.; Wong, E. C.
1982-01-01
Linear discrete stochastic control systems containing unknown multiple time delays, plant parameters and noise variances are considered. An algorithm is established which uses the maximum-likelihood technique to identify the unknown parameters. An estimated likelihood function is evaluated based on the previous parameter estimates, which in turn generates a new descent direction vector to update the unknown parameters. The delays and plant parameters are identified in their respective parameter spaces. An example of a second-order stochastic system has been implemented by digital simulation to demonstrate the applicability of the algorithm.
Numerical bifurcation analysis of immunological models with time delays
Luzyanina, Tatyana; Roose, Dirk; Bocharov, Gennady
2005-12-01
In recent years, a large number of mathematical models that are described by delay differential equations (DDEs) have appeared in the life sciences. To analyze the models' dynamics, numerical methods are necessary, since analytical studies can only give limited results. In turn, the availability of efficient numerical methods and software packages encourages the use of time delays in mathematical modelling, which may lead to more realistic models. We outline recently developed numerical methods for bifurcation analysis of DDEs and illustrate the use of these methods in the analysis of a mathematical model of human hepatitis B virus infection.
Dynamic Server Allocation over Time Varying Channels with Switchover Delay
Celik, Güner D; Modiano, Eytan
2012-01-01
We consider a dynamic server allocation problem over parallel queues with randomly varying connectivity and server switchover delay between the queues. At each time slot the server decides either to stay with the current queue or switch to another queue based on the current connectivity and the queue length information. Switchover delay occurs in many telecommunications applications and is a new modeling component of this problem that has not been previously addressed. We show that the simultaneous presence of randomly varying connectivity and switchover delay changes the system stability region and the structure of optimal policies. In the first part of the paper, we consider a system of two parallel queues, and develop a novel approach to explicitly characterize the stability region of the system using state-action frequencies which are stationary solutions to a Markov Decision Process (MDP) formulation. We then develop a frame-based dynamic control (FBDC) policy, based on the state-action frequencies, and ...
Spatio-temporal phenomena in complex systems with time delays
Yanchuk, Serhiy; Giacomelli, Giovanni
2017-03-01
Real-world systems can be strongly influenced by time delays occurring in self-coupling interactions, due to unavoidable finite signal propagation velocities. When the delays become significantly long, complicated high-dimensional phenomena appear and a simple extension of the methods employed in low-dimensional dynamical systems is not feasible. We review the general theory developed in this case, describing the main destabilization mechanisms, the use of visualization tools, and commenting on the most important and effective dynamical indicators as well as their properties in different regimes. We show how a suitable approach, based on a comparison with spatio-temporal systems, represents a powerful instrument for disclosing the very basic mechanism of long-delay systems. Various examples from different models and a series of recent experiments are reported.
Dynamical analysis of uncertain neural networks with multiple time delays
Arik, Sabri
2016-02-01
This paper investigates the robust stability problem for dynamical neural networks in the presence of time delays and norm-bounded parameter uncertainties with respect to the class of non-decreasing, non-linear activation functions. By employing the Lyapunov stability and homeomorphism mapping theorems together, a new delay-independent sufficient condition is obtained for the existence, uniqueness and global asymptotic stability of the equilibrium point for the delayed uncertain neural networks. The condition obtained for robust stability establishes a matrix-norm relationship between the network parameters of the neural system, which can be easily verified by using properties of the class of the positive definite matrices. Some constructive numerical examples are presented to show the applicability of the obtained result and its advantages over the previously published corresponding literature results.
A comparison of cosmological models using time delay lenses
Energy Technology Data Exchange (ETDEWEB)
Wei, Jun-Jie; Wu, Xue-Feng; Melia, Fulvio, E-mail: jjwei@pmo.ac.cn, E-mail: xfwu@pmo.ac.cn, E-mail: fmelia@email.arizona.edu [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)
2014-06-20
The use of time-delay gravitational lenses to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 12 lens systems, which have thus far been used solely for optimizing the parameters of ΛCDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between competing models. The currently available sample indicates a likelihood of ∼70%-80% that the R {sub h} = ct universe is the correct cosmology versus ∼20%-30% for the standard model. This possibly interesting result reinforces the need to greatly expand the sample of time-delay lenses, e.g., with the successful implementation of the Dark Energy Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope. In anticipation of a greatly expanded catalog of time-delay lenses identified with these surveys, we have produced synthetic samples to estimate how large they would have to be in order to rule out either model at a ∼99.7% confidence level. We find that if the real cosmology is ΛCDM, a sample of ∼150 time-delay lenses would be sufficient to rule out R {sub h} = ct at this level of accuracy, while ∼1000 time-delay lenses would be required to rule out ΛCDM if the real universe is instead R {sub h} = ct. This difference in required sample size reflects the greater number of free parameters available to fit the data with ΛCDM.
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
Measurement of Gravitational Lens Time Delays with LSST (SULI Paper)
Energy Technology Data Exchange (ETDEWEB)
Kirkby, Lowry Anna; /Oxford U. /SLAC
2006-01-04
The proposed Large Synoptic Survey Telescope will be the first to explore multiple dark energy probes simultaneously, including baryon acoustic oscillations, weak lensing, and strong gravitational lensing. The large data sample, covering the entire visible sky every few nights, will allow an unprecedented survey of deep supernova sources and their lensed images. The latter have not yet been observed. Notably, LSST will measure the time delays between different strong-lensed images of the same supernova. This will provide a unique probe of dark matter, dark energy, and the expansion rate of the Universe. By simulating LSST observations under realistic conditions, we determined the time delay precision of multiple images from a representative strong-lensed Type Ia supernova. The output of the simulation was a set of light curves according to field and filter, which were subsequently analyzed to determine the experimental time delays. We find that a time delay precision of better then 10% can be achieved under suitable conditions. Firstly, a minimum observed peak-magnitude of 22 is required for the lensed image, corresponding to an intrinsic source magnitude of about 24. The number of such supernova sources expected for LSST is under investigation, but it could amount to several thousand. Secondly, a minimum of about 50 visits per field is required, and, moreover, these visits must be evenly distributed over the duration of the event. The visit frequency should be approximately once per week, or better. Thirdly, the sky brightness should be below 21 magnitude arcsec{sup -2} to allow sufficient sensitivity to distance sources. Under the nominal LSST visiting schedule and field conditions, 15% of all fields satisfy these criteria, and allow time delay measurements of better than 10% precision. This performance can be further improved by fitting the predicted supernova light curves to the observations, rather than using the simple weighted mean as in the present study
The generalized Burgers equation with and without a time delay
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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, 0
Ignition delay time measurements of primary reference fuel blends
Alabbad, Mohammed
2017-02-07
Ignition delay times of four different primary reference fuels (PRF), mixtures of n-heptane and iso-octane, were measured behind reflected shock waves in a high-pressure shock tube facility. The PRFs were formulated to match the RON of two high-octane gasolines (RON 95 and 91) and two prospective low-octane naphtha fuels (RON 80 and 70). Experiments were carried out over a wide range of temperatures (700–1200K), pressures (10, 20, and 40bar) and equivalence ratios (0.5 and 1). Kinetic modeling predictions from four chemical kinetic mechanisms are compared with the experimental data. Ignition delay correlations are developed to reproduce the measured ignition delay times. Brute force sensitivity analyses are carried out to identify reactions that affect ignition delay times at specific temperature, pressure and equivalence ratio. The large experimental data set provided in the current work will serve as a benchmark for the validation of chemical kinetic mechanisms of primary reference fuel blends.
Time Delay Circuits: A Quality Criterion for Delay Variations versus Frequency
Garakoui, Seyed Kasra; Klumperink, Eric A.M.; Nauta, Bram; Vliet, van Frank E.
2010-01-01
This paper shows that the group delay of a delay circuit does not give sufficient information to predict the delay vs. frequency. A new criterion (fϕ=0) is proposed that characterizes the delay variations over a specified frequency range. The mathematical derivation of fϕ=0 for a single delay block
Axo: Masking Delay Faults in Real-Time Control Systems
Maaz, Mashood Mohiuddin; Saab, Wajeb; Bliudze, Simon; Le Boudec, Jean-Yves
2016-01-01
We consider real-time control systems that consist of a controller that computes and sends setpoints to be implemented in physical processes through process agents. We focus on systems that use commercial off-the-shelf hardware and software components. Setpoints of these systems have strict real-time constraints: Implementing a setpoint after its deadline, or not receiving setpoints within a deadline, can cause failure. In this paper, we address delay faults: faults that cause setpoints to vi...
Absolute Stability of Discrete-Time Systems with Delay
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Rigoberto Medina
2008-02-01
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 Ã¢Â€ÂœfreezingÃ¢Â€Â technique to discrete-time systems, we derive explicit conditions for the absolute stability of the zero solution of such systems.
Receding horizon H∞ control for constrained time-delay systems
Institute of Scientific and Technical Information of China (English)
Lu Mei; Jin Chengbo; Shao Huihe
2009-01-01
A receding horizon H∞ control algorithm is presented for linear discrete time-delay system in the presence of constrained input and disturbances. Disturbance attenuation level is optimized at each time instant, and the receding optimization problem includes several linear matrix inequality constraints. When the convex hull is applied to denote the saturating input, the algorithm has better performance. The numerical example can verify this result.
Compact cascadable gm-C all-pass true time delay cell with reduced delay variation over frequency
Garakoui, Seyed Kasra; Klumperink, Eric A.M.; Nauta, Bram; Vliet, van Frank E.
2015-01-01
At low-GHz frequencies, analog time-delay cells realized by LC delay lines or transmission lines are unpractical in CMOS, due to their large size. As an alternative, delays can be approximated by all-pass filters exploiting transconductors and capacitors (g m -C filters). This paper presents an easi
A Stability Condition with Delay-Dependence for a Class of Switched Large-Scale Time-Delay Systems
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Chi-Jo Wang
2013-01-01
Full Text Available By using the time-switched method and the comparison theorem, we derived a criterion of delay-dependent stability for the switched large-scale time-delay systems. To guarantee the exponential stability for the switched large-scale time-delay systems with stability margin λ, the total activation time ratio of the switching law is determined. An example is used to illustrate the effectiveness of our result.
Time delay and partial coherence analyses to identify cortical connectivities
Govindan, R B; Deuschl, G; Kopper, F; Raethjen, J
2005-01-01
Recently it has been demonstrated by Albo that partial coherence analysis is sensitive to signal to noise ratio (SNR) and that it will always identify the signal with the highest SNR among the three signals as the main (driving) influence. We propose to use time delay analysis in parallel to partial coherence analysis to identify the connectivities between the multivariate time series. Both are applied to a theoretical model (used by Albo) to analyse the connections introduced in the model. Time delay analysis identifies the connections correctly. We also apply these analyses to the electroencephalogram (EEG) and electromyogram (EMG) of essential tremor patients and EEG of normal subjects while bimanually tapping their index fingers. Biologically plausible cortico-muscular and cortico-cortical connections are identified by these methods.
Time-delay Cosmography: Increased Leverage with Angular Diameter Distances
Jee, Inh; Suyu, Sherry H; Huterer, Dragan
2015-01-01
Strong lensing time-delay systems constrain cosmological parameters via the so-called time-delay distance and the angular diameter distance to the lens. In previous studies, only the former information was used. In this paper, we show that the cosmological constraints improve significantly when the latter information is also included. Specifically, the angular diameter distance plays a crucial role in breaking the degeneracy between the curvature of the Universe and the time-varying equation of state of dark energy. Using a mock sample of 55 bright quadruple lens systems based on expectations for ongoing/future imaging surveys, we find that adding the angular diameter distance information to the time-delay distance information and the cosmic microwave background data of Planck improves the constraint on the constant equation of state by 30%, on the time variation in the equation of state by a factor of two, and on the Hubble constant in the flat $\\Lambda$CDM model by a factor of two. Therefore, previous forec...
A new delay-independent condition for global robust stability of neural networks with time delays.
Samli, Ruya
2015-06-01
This paper studies the problem of robust stability of dynamical neural networks with discrete time delays under the assumptions that the network parameters of the neural system are uncertain and norm-bounded, and the activation functions are slope-bounded. By employing the results of Lyapunov stability theory and matrix theory, new sufficient conditions for the existence, uniqueness and global asymptotic stability of the equilibrium point for delayed neural networks are presented. The results reported in this paper can be easily tested by checking some special properties of symmetric matrices associated with the parameter uncertainties of neural networks. We also present a numerical example to show the effectiveness of the proposed theoretical results.
Delay time for the onset of beam plasma discharge
Parish, J. L.; Denig, W. F.; Raitt, W. J.
1987-01-01
The interaction of a nonrelativistic electron beam with a neutral gas in a large chamber is considered, and the time interval before ignition of beam plasma discharge (BPD) is studied. A new theoretical expression for the time delay before BPD ignition is found as a function of the critical current necessary for BPD to be established. There are two parameters in the theoretical expression, and both are derived from two different experiments. These parameters are used to write the time evolution equation for plasma density as a function of time.
Estimation of coupling between time-delay systems from time series.
Prokhorov, M D; Ponomarenko, V I
2005-07-01
We propose a method for estimation of coupling between the systems governed by scalar time-delay differential equations of the Mackey-Glass type from the observed time series data. The method allows one to detect the presence of certain types of linear coupling between two time-delay systems, to define the type, strength, and direction of coupling, and to recover the model equations of coupled time-delay systems from chaotic time series corrupted by noise. We verify our method using both numerical and experimental data.
A Tool to Recover Scalar Time-Delay Systems from Experimental Time Series
Bünner, M J; Meyer, T; Kittel, A; Parisi, J; Meyer, Th.
1996-01-01
We propose a method that is able to analyze chaotic time series, gained from exp erimental data. The method allows to identify scalar time-delay systems. If the dynamics of the system under investigation is governed by a scalar time-delay differential equation of the form $dy(t)/dt = h(y(t),y(t-\\tau_0))$, the delay time $\\tau_0$ and the functi on $h$ can be recovered. There are no restrictions to the dimensionality of the chaotic attractor. The method turns out to be insensitive to noise. We successfully apply the method to various time series taken from a computer experiment and two different electronic oscillators.
Identification of optimal inspection interval via delay-time concept
Directory of Open Access Journals (Sweden)
Glauco Ricardo Simões Gomes
2016-06-01
Full Text Available This paper presents an application of mathematical modeling aimed at managing maintenance based on the delay-time concept. The study scenario was the manufacturing sector of an industrial unit, which operates 24 hours a day in a continuous flow of production. The main idea was to use the concepts of this approach to determine the optimal time of preventive action by the maintenance department in order to ensure the greatest availability of equipment and facilities at appropriate maintenance costs. After a brief introduction of the subject, the article presents topics that illustrate the importance of mathematical modeling in maintenance management and the delay-time concept. It also describes the characteristics of the company where the study was conducted, as well as the data related to the production process and maintenance actions. Finally, the results obtained after applying the delay-time concept are presented and discussed, as well as the limitations of the article and the proposals for future research.
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
In this paper, using the theory of topological degree and Liapunov functional methods, the authors study the competitive neural networks with time delays and different time scales and present some criteria of global robust stability for this neural network model.
Béavogui, Kézély; Koïvogui, Akoï; Loua, Tokpagnan Oscar; Baldé, Ramata; Diallo, Boubacar; Diallo, Aminata Rougui; Béavogui, Zézé; Goumou, Koué; Guilavogui, Vamala; Sylla, N’famara; Chughtai, Morad; Qureshi, Adnan I.; Diallo, Aissatou Taran; Camara, Naby Daouda
2015-01-01
Background Traumatic brain injury related to road traffic accidents poses a major challenge in resource-poor settings within Guinea. Objective To analyze the impact of treatment delay, access to healthcare, and patient's financial capacity on duration of hospital stay and in-hospital mortality. Methodology Data from patients with traumatic brain injury secondary to motor vehicle accident admitted to a reference hospital (public or private) in Guinea during 2009 were analyzed. The association between various factors (treatment delay, access to healthcare, and patient's financial capacity) and prolonged hospital stay (>21 days) and in-hospital mortality were analyzed using two multivariate logistic regression models. Results The mean (±standard deviation) duration of hospital stay was 8.0 (±8.1) days. The risk of prolonged hospital stay increased by 60% when the time interval between accident and hospital arrival was greater than 12 hours compared with those in whom the time interval was less than 6 hours (adjusted odds ratio [OR] = 1.6, 95% confidence interval [CI] = 1.0–2.6, p = 0.03). Compared with patients with low-financial capacity, patients with medium-financial capacity (adjusted OR = 0.6, 95% CI = 0.4–0.8, p = 0.001) and those with high capacity (adjusted OR = 0.6, 95% CI = 0.4–0.9, p = 0.02) were less likely to have a prolonged hospital stay. The risk of in-hospital mortality was 2.6 times higher in patients with time interval between accident and hospital arrival greater than 12 hours compared with those in whom the time interval was less than 6 hours (adjusted OR = 2.6, 95% CI = 1.1–6.2 p = 0.03). In-hospital mortality was not related to patient’s financial capacity. Conclusion Prolonged hospital stay and higher in-hospital mortality was associated with longer time interval between accident and hospital arrival. This delay is attributed to inadequate condition of intercity roads and lack of emergency medical services. PMID:26576213
Multipath time delay estimation of underwater acoustic sinusoidal signals
Institute of Scientific and Technical Information of China (English)
TONG Feng; XU Xiaomei; FANG Shiliang
2009-01-01
To overcome the performance limitation of multipath time-delay estimation posed by underwater acoustic sinusoidal signals, an approach incorporating the frequency-domain weighting of the highly oscillatory Nonlinear Least Squares (NLS) cost function with the evolutionary optimization was proposed to facilitate the accurate estimation of the multipath timedelay of sinusoidal signals. In the described method, the number of the effective multipath signals, which is included into the parameter model as well as the multipath time-delay and amplitude factor, can be estimated simultaneously thus avoiding the requirement of additional computation. The experimental results performed with numerical simulation and sea-trial data are provided, demonstrating the effectiveness and precision enhancement of the proposed algorithm.
Robust adaptive control for interval time-delay systems
Institute of Scientific and Technical Information of China (English)
Yizhong WANG; Huaguang ZHANG; Jun YANG
2006-01-01
This paper focuses on the robust adaptive control problems for a class of interval time-delay systems and a class of large-scale interconnected systems. The nonlinear uncertainties of the systems under study are bounded by high-order polynomial functions with unknown gains. Firstly, the adaptive feedback controller which can guarantee the stability of the closed-loop system in the sense of uniform ultimate boundedness is proposed. Then the proposed adaptive idea is extended to robust stabilizing designing method for a class of large-scale interconnected systems. Here, another problem we address is to design a decentralized feedback adaptive controller such that the closed-loop system is stable in the sense of uniform ultimate boundedness for all admissible uncertainties and time-delay. Finally, an illustrative example is given to show the validity of the proposed approach.
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.
Time delay in double micro-ring resonator with grating
Li, Qiliang; Chen, Xin; Song, Junfeng; Bi, Meihua; Hu, Miao; Li, Shuqin
2016-10-01
In this paper, using the transfer matrix which is obtained by coupled mode theory, we have studied the transmission and time delay characteristics of the micro-ring resonator with the grating. We find that fast- and slow-light can occur in double ring resonator which contains the grating. We also study the effect of coupling coefficient on transmission characteristics. The results reveal that the increase of the coupling coefficient can lead to the change of the time delay at various ports at the resonant point. Thus by adjusting the frequency of the incident light and selecting the device with different coupling coefficient, we can realize the output of the fast and slow light.
Ignition Delay Times of Kerosene(Jet-A)/Air Mixtures
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.
Time Delay Systems Methods, Applications and New Trends
Vyhlídal, Tomáš; Niculescu, Silviu-Iulian; Pepe, Pierdomenico
2012-01-01
This volume is concerned with the control and dynamics of time delay systems; a research field with at least six-decade long history that has been very active especially in the past two decades. In parallel to the new challenges emerging from engineering, physics, mathematics, and economics, the volume covers several new directions including topology induced stability, large-scale interconnected systems, roles of networks in stability, and new trends in predictor-based control and consensus dynamics. The associated applications/problems are described by highly complex models, and require solving inverse problems as well as the development of new theories, mathematical tools, numerically-tractable algorithms for real-time control. The volume, which is targeted to present these developments in this rapidly evolving field, captures a careful selection of the most recent papers contributed by experts and collected under five parts: (i) Methodology: From Retarded to Neutral Continuous Delay Models, (ii) Systems, S...
Adaptive control method for nonlinear time-delay processes
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Two complex properties,varying time-delay and block-oriented nonlinearity,are very common in chemical engineering processes and not easy to be controlled by routine control methods.Aimed at these two complex properties,a novel adaptive control algorithm the basis of nonlinear OFS(orthonormal functional series) model is proposed.First,the hybrid model which combines OFS and Volterra series is introduced.Then,a stable state feedback strategy is used to construct a nonlinear adaptive control algorithm that can guarantee the closed-loop stability and can track the set point curve without steady-state errors.Finally,control simulations and experiments on a nonlinear process with varying time-delay are presented.A number of experimental results validate the efficiency and superiority of this algorithm.
Construction of New Delay-Tolerant Space-Time Codes
Sarkiss, Mireille; Damen, Mohamed Oussama; Belfiore, Jean-Claude
2010-01-01
Perfect Space-Time Codes (STC) are optimal codes in their original construction for Multiple Input Multiple Output (MIMO) systems. Based on Cyclic Division Algebras (CDA), they are full-rate, full-diversity codes, have Non-Vanishing Determinants (NVD) and hence achieve Diversity-Multiplexing Tradeoff (DMT). In addition, these codes have led to optimal distributed space-time codes when applied in cooperative networks under the assumption of perfect synchronization between relays. However, they loose their diversity when delays are introduced and thus are not delay-tolerant. In this paper, using the cyclic division algebras of perfect codes, we construct new codes that maintain the same properties as perfect codes in the synchronous case. Moreover, these codes preserve their full-diversity in asynchronous transmission.
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.
Modular Timing Constraints for Delay-Insensitive Systems
Institute of Scientific and Technical Information of China (English)
Hoon Park; Anping He; Marly Roncken; Xiaoyu Song; Ivan Sutherland
2016-01-01
This paper introduces ARCtimer, a framework for modeling, generating, verifying, and enforcing timing con-straints for individual self-timed handshake components. The constraints guarantee that the component’s gate-level cir-cuit implementation obeys the component’s handshake protocol specification. Because the handshake protocols are delay-insensitive, self-timed systems built using ARCtimer-verified components are also delay-insensitive. By carefully considering time locally, we can ignore time globally. ARCtimer comes early in the design process as part of building a library of verified components for later system use. The library also stores static timing analysis (STA) code to validate and enforce the com-ponent’s constraints in any self-timed system built using the library. The library descriptions of a handshake component’s circuit, protocol, timing constraints, and STA code are robust to circuit modifications applied later in the design process by technology mapping or layout tools. In addition to presenting new work and discussing related work, this paper identifies critical choices and explains what modular timing verification entails and how it works.
Dispatching policy for manufacturing jobs and time-delay plots
2007-01-01
Abstract In this paper, the concepts of chaos and non-linear dynamics are briefly introduced and the tools used in the characterization of a chaotic or non-linear system are discussed for studying the performance of dispatching policies in manufacturing systems. The scheduling of a simple manufacturing system with the help of common assignment rules has been simulated first. The results are studied and analysed with the help of time-delay plots. Some conclusions are drawn and, base...
Parametric time delay modeling for floating point units
Fahmy, Hossam A. H.; Liddicoat, Albert A.; Flynn, Michael J.
2002-12-01
A parametric time delay model to compare floating point unit implementations is proposed. This model is used to compare a previously proposed floating point adder using a redundant number representation with other high-performance implementations. The operand width, the fan-in of the logic gates and the radix of the redundant format are used as parameters to the model. The comparison is done over a range of operand widths, fan-in and radices to show the merits of each implementation.
STRONG LENS TIME DELAY CHALLENGE. I. EXPERIMENTAL DESIGN
Energy Technology Data Exchange (ETDEWEB)
Dobler, Gregory [Kavli Institute for Theoretical Physics, University of California Santa Barbara, Santa Barbara, CA 93106 (United States); Fassnacht, Christopher D.; Rumbaugh, Nicholas [Department of Physics, University of California, 1 Shields Avenue, Davis, CA 95616 (United States); Treu, Tommaso; Liao, Kai [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Marshall, Phil [Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 20450, MS29, Stanford, CA 94309 (United States); Hojjati, Alireza [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1 (Canada); Linder, Eric, E-mail: tt@astro.ucla.edu [Lawrence Berkeley National Laboratory and University of California, Berkeley, CA 94720 (United States)
2015-02-01
The time delays between point-like images in gravitational lens systems can be used to measure cosmological parameters. The number of lenses with measured time delays is growing rapidly; the upcoming Large Synoptic Survey Telescope (LSST) will monitor ∼10{sup 3} strongly lensed quasars. In an effort to assess the present capabilities of the community, to accurately measure the time delays, and to provide input to dedicated monitoring campaigns and future LSST cosmology feasibility studies, we have invited the community to take part in a ''Time Delay Challenge'' (TDC). The challenge is organized as a set of ''ladders'', each containing a group of simulated data sets to be analyzed blindly by participating teams. Each rung on a ladder consists of a set of realistic mock observed lensed quasar light curves, with the rungs' data sets increasing in complexity and realism. The initial challenge described here has two ladders, TDC0 and TDC1. TDC0 has a small number of data sets, and is designed to be used as a practice set by the participating teams. The (non-mandatory) deadline for completion of TDC0 was the TDC1 launch date, 2013 December 1. The TDC1 deadline was 2014 July 1. Here we give an overview of the challenge, we introduce a set of metrics that will be used to quantify the goodness of fit, efficiency, precision, and accuracy of the algorithms, and we present the results of TDC0. Thirteen teams participated in TDC0 using 47 different methods. Seven of those teams qualified for TDC1, which is described in the companion paper.
Fuzzy Association Degree with Delayed Time in Temporal Data Model
Institute of Scientific and Technical Information of China (English)
刘惟一; 郭陵芝; 宋宁
2001-01-01
This paper presents an expression of the semantic proximity. Based on the temporal data model, a method of the temporal approximation is given. Using these concepts, this paper provides an evaluated method of fuzzy and dynamic association degree with delayed time and a superposition method of association degrees. Particularly, by means of the fuzzy and dynamic association degree, the connection between the weather data of two regions can be discovered.
State Predictive Model Following Control System for Linear Time Delays
Institute of Scientific and Technical Information of China (English)
Da-Zhong Wang; Shu-Jing Wu; Shigenori Okubo
2009-01-01
In this paper, we propose a new state predictive model following control system (MFCS). The considered system has linear time delays. With the MFCS method, we obtain a simple input control law. The bounded property of the internal states for the control is given and the utility of this control design is guaranteed. Finally, an example is given to illustrate the effectiveness of the proposed method.
Hubble Constant, Lensing, and Time Delay in Relativistic MOND
2012-01-01
Time delay in galaxy gravitational lensing systems has been used to determine the value of Hubble constant. As in other dynamical phenomena at the scale of galaxy, dark matter is often invoked in gravitational lensing to account for the "missing mass" (the apparent discrepancy between the dynamical mass and the luminous mass). Alternatively, modified gravity can be used to explain the discrepancy. In this paper we adopt the Tensor-Vector-Scalar gravity (TeVeS), a relativistic version of MOdif...
Numerical Investigation of Noise Enhanced Stability Phenomenon in a Time-Delayed Metastable System
Institute of Scientific and Technical Information of China (English)
JIA Zheng-Lin
2008-01-01
@@ The transient properties of a time-delayed metastable system subjected to the additive white noise are investigated by means of the stochastic simulation method. The noise enhanced stability phenomenon (NES) can be observed in this system and the effect of the delay time on the NES shows a critical behaviour, i.e., there is a critical value of the delay time Tc ≈ 1, above which the time delay enhances the NES effect with the delay time increasing and below which the time delay weakens the NES effect as the delay time increases.
Incomplete phase-space method to reveal time delay from scalar time series
Zhu, Shengli; Gan, Lu
2016-11-01
A computationally quick and conceptually simple method to recover time delay of the chaotic system from scalar time series is developed in this paper. We show that the orbits in the incomplete two-dimensional reconstructed phase-space will show local clustering phenomenon after the component reordering procedure proposed in this work. We find that information captured by the incomplete two-dimensional reconstructed phase-space is related to the time delay τ0 present in the system, and will be transferred to the reordered component by the procedure of component reordering. We then propose the segmented mean variance (SMV) from the reordered component to identify the time delay τ0 of the system. The proposed SMV shows clear maximum when the embedding delay τ of the incomplete reconstruction matches the time delay τ0 of the chaotic system. Numerical data generated by a time-delay system based on the Mackey-Glass equation operating in the chaotic regime are used to illustrate the effectiveness of the proposed SMV. Experimental results show that the proposed SMV is robust to additive observational noise and is able to recover the time delay of the chaotic system even though the amount of data is relatively small and the feedback strength is weak. Moreover, the time complexity of the proposed method is quite low.
Fullerene photoemission time delay explores molecular cavity in attoseconds
Magrakvelidze, Maia; Dixit, Gopal; Madjet, Mohamed El-Amine; Chakraborty, Himadri S
2014-01-01
Time-resolved photoelectron spectroscopy can probe interference oscillations in C60 valence emissions that produce series of minima whose energy separation depends on the molecular size. We show that the quantum phase associated with these minima exhibits rapid variations due to electron correlations, causing rich structures in the photoemission time delay. These findings provide a way to utilize temporal information to access the fullerene cavity size, that is making the time to "see" the space, and can be generalized to photoemissions from clusters and nanostructures.
Time domain passivity controller for 4-channel time-delay bilateral teleoperation.
Rebelo, Joao; Schiele, Andre
2015-01-01
This paper presents an extension of the time-domain passivity control approach to a four-channel bilateral controller under the effects of time delays. Time-domain passivity control has been used successfully to stabilize teleoperation systems with position-force and position-position controllers; however, the performance with such control architectures is sub-optimal both with and without time delays. This work extends the network representation of the time-domain passivity controller to the four-channel architecture, which provides perfect transparency to the user without time delay. The proposed architecture is based on modelling the controllers as dependent voltage sources and using only series passivity controllers. The obtained results are shown on a one degree-of-freedom setup and illustrate the stabilization behaviour of the proposed controller when time delay is present in the communication channel.
Correlation-induced Time Delay in Atomic Photoionization
Keating, David A.; Manson, Steven T.; Deshmukh, Pranawa C.; Kheifets, Anatoli S.
2016-05-01
Interchannel coupling has been seen to result in structures in the photoionization cross sections of outer shell electrons in the vicinity of inner-shell thresholds, a result which leads us to ask if the same would be true for the time delay of outer shell electrons near inner-shell thresholds. Using the relativistic-random-phase approximation (RRPA) methodology, a theoretical study of neon, argon, krypton, and xenon were performed to search for these correlation-induced effects. Calculations were performed both with coupling and without coupling to verify that the structures found in the time delay were in fact due to interchannel coupling. Using this method to study the effects of interchannel coupling reveals how much of an impact the coupling has on the time delay, in some cases over a broad energy range. In cases where the spin-orbit doublets' respective thresholds are far enough apart, effects can be found in the j = l + 1/2channels due to interchannel coupling with the j = l-1/2 channels. These structures are purely a relativistic effect and are related to spin-obit activated interchannel coupling effects. Work supported by DOE, Office of Chemical Sciences, DST (India), and the Australian Research Council.
Negative Time Delay in Strongly Naked Singularity Lensing
DeAndrea, Justin P
2014-01-01
We model the supermassive galactic center of the Milky Way galaxy as a strongly naked singularity lens described by the Janis-Newman-Winicour metric. This metric has an ordinary mass and a massless scalar charge parameters. For very accurate results, we use Virbhadra-Ellis lens equation for computations. The galactic center serving as gravitational lens gives rise to 4 images: 2 images on the same side as the source and 2 images on the opposite side of the source from the optic axis. We compute positions and time delays of these images for many values of the angular source position. The time delays of primary images decrease with increase in the angular source position and is always negative. The time delays of the other 3 images are negative for small angular source position; however, they increase with an increase in angular source position. Such observations would support strongly naked singularity interpretation of the galactic center and, if ever observed, would disprove the cosmic censorship hypothesis ...
Time Delay for Aerial Ammonia Concentration Measurements in Livestock Buildings
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. PMID:22399896
Strong lensing, time delays, and the value of H$_0$
Barnacka, Anna; Dell'antonio, Ian P; Benbow, Wystan
2014-01-01
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$_0$ obtained with this method span a range from $\\sim 50 - 100$ km s$^{-1}$Mpc$^{-1}$. 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 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 the potentially large impact of the position of the variable emitting region on H$_0$ determination. The derived value of the Hubble constant is very sensitive to the offset between the cen...
A Comparison of Cosmological Models Using Time Delay Lenses
Wei, Jun-Jie; Melia, Fulvio
2014-01-01
The use of time-delay gravitational lenses to examine the cosmological expansion introduces a new standard ruler with which to test theoretical models. The sample suitable for this kind of work now includes 12 lens systems, which have thus far been used solely for optimizing the parameters of $\\Lambda$CDM. In this paper, we broaden the base of support for this new, important cosmic probe by using these observations to carry out a one-on-one comparison between {\\it competing} models. The currently available sample indicates a likelihood of $\\sim 70-80%$ that the $R_{\\rm h}=ct$ Universe is the correct cosmology versus $\\sim 20-30%$ for the standard model. This possibly interesting result reinforces the need to greatly expand the sample of time-delay lenses, e.g., with the successful implementation of the Dark Energy Survey, the VST ATLAS survey, and the Large Synoptic Survey Telescope. In anticipation of a greatly expanded catalog of time-delay lenses identified with these surveys, we have produced synthetic sa...
Sleep timing and circadian phase in delayed sleep phase syndrome.
Chang, Anne-Marie; Reid, Kathryn J; Gourineni, Ramadevi; Zee, Phyllis C
2009-08-01
Delayed sleep phase syndrome (DSPS) is a circadian rhythm sleep disorder in which the timing of the sleep episode occurs later than desired and is associated with difficulty falling asleep, problems awakening on time (e.g., to meet work or school obligations), and daytime sleepiness. The phase relationship between the timing of sleep and endogenous circadian rhythms is critical to the initiation and maintenance of sleep, and significant alteration leads to impairment of sleep quality and duration. The aim of this retrospective study was to determine the phase relationship between sleep-wake times and physiological markers of circadian timing in clinic patients with DSPS. Objective and subjective measures of sleep timing and circadian phase markers (core body temperature and melatonin) were measured in patients with DSPS and compared with age-matched controls. As expected, significant delays in the timing of the major sleep episode and circadian phase of body temperature and melatonin rhythms were seen in the DSPS group when allowed to sleep at their own habitual schedules, but the phase relationship between sleep-wake times and circadian phase was similar between the 2 groups. These results suggest that the symptoms of insomnia and excessive daytime sleepiness in DSPS patients living under entrained real-life conditions cannot be explained by an alteration in the phase relationship between sleep-wake patterns and other physiological circadian rhythms.
Network delay predictive compensation based on time-delay modelling as disturbance
Florin Caruntu, Constantin; Lazar, Corneliu
2014-10-01
In this paper, a control design methodology that can assure the closed-loop performances of a physical plant, while compensating the network-induced time-varying delays, is proposed. First, the error caused by the time-varying delays is modelled as a disturbance and a novel method of bounding the disturbance is proposed. Second, a robust one step ahead predictive controller based on flexible control Lyapunov functions is designed, which explicitly takes into account the bounds of the disturbances and guarantees also the input-to-state stability of the system in a non-conservative way. The methodology was tested on a vehicle drivetrain controlled through controller area network, with the aim of damping driveline oscillations. The comparison with a proportional-integral-derivative (PID) controller using TrueTime simulator shows that the proposed control scheme can outperform classical controllers and it can handle the performance/physical constraints. Moreover, the handling of the strict limitations on the computational complexity was tested using a real-time test-bench.
On Delay Independent Stabilization Analysis for a Class of Switched Large-Scale Time-Delay Systems
Directory of Open Access Journals (Sweden)
Chi-Jo Wang
2013-01-01
Full Text Available In view of the state-driven switching method, the sufficient stability conditions with delay independence will be derived for the switched large-scale time-delay systems. A new stability criterion of switched large-scale time-delay systems is deduced by Lyapunov stability theorem. The method can be applied to cases when all individual switched systems are unstable. Finally, one example is exploited to illustrate the proposed schemes.
Directory of Open Access Journals (Sweden)
Saffet Ayasun
2014-01-01
Full Text Available This paper investigates the effect of time delays on the stability of a generator excitation control system compensated with a stabilizing transformer known as rate feedback stabilizer to damp out oscillations. The time delays are due to the use of measurement devices and communication links for data transfer. An analytical method is presented to compute the delay margin for stability. The delay margin is the maximum amount of time delay that the system can tolerate before it becomes unstable. First, without using any approximation, the transcendental characteristic equation is converted into a polynomial without the transcendentality such that its real roots coincide with the imaginary roots of the characteristic equation exactly. The resulting polynomial also enables us to easily determine the delay dependency of the system stability and the sensitivities of crossing roots with respect to the time delay. Then, an expression in terms of system parameters and imaginary root of the characteristic equation is derived for computing the delay margin. Theoretical delay margins are computed for a wide range of controller gains and their accuracy is verified by performing simulation studies. Results indicate that the addition of a stabilizing transformer to the excitation system increases the delay margin and improves the system damping significantly.
Sleep apnea detection using time-delayed heart rate variability.
Nano, Marina-Marinela; Xi Long; Werth, Jan; Aarts, Ronald M; Heusdens, Richard
2015-01-01
Sleep apnea is a sleep disorder distinguished by repetitive absence of breathing. Compared with the traditional expensive and cumbersome methods, sleep apnea diagnosis or screening with physiological information that can be easily acquired is needed. This paper describes algorithms using heart rate variability (HRV) to automatically detect sleep apneas as long as it can be easily acquired with unobtrusive sensors. Because the changes in cardiac activity are usually hysteretic than the presence of apneas with a few minutes, we propose to use the delayed HRV features to identify the episodes with sleep apneic events. This is expected to help improve the apnea detection performance. Experiments were conducted with a data set of 23 sleep apnea patients using support vector machine (SVM) classifiers and cross validations. Results show that using eleven HRV features with a time delay of 1.5 minutes rather than the features without time delay for SA detection, the overall accuracy increased from 74.9% to 76.2% and the Cohen's Kappa coefficient increased from 0.49 to 0.52. Further, an accuracy of 94.5% and a Kappa of 0.89 were achieved when applying subject-specific classifiers.
Parameter identification of linear discrete stochastic systems with time delays
Wong, E. C.
1980-01-01
An identification algorithm that uses the maximum likelihood technique to identify the unknown time delays, plant parameters, and noise covariances of linear discrete stochastic systems is presented. Cases of additive white noise and colored measurement noises are considered. The likelihood function is evaluated using either a minimum-variance (Kalman) filter or a minimal-order observer. The Kalman filter is used in the identification algorithm to provide minimum-variance estimates. The minimal-order observer is a lower-dimensional and computationally simpler filter, and is advantageous especially for systems with long delays. It provides a less optimal solution to the minimum-mean-square state estimation problem. The colored-noise observer algorithm has the disadvantage of having to compute an extra error covariance matrix of lower order.
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.
Complex systems fractionality, time-delay and synchronization
Sun, Jian-Qiao
2012-01-01
"Complex Systems: Fractionality, Time-delay and Synchronization" covers the most recent developments and advances in the theory and application of complex systems in these areas. Each chapter was written by scientists highly active in the field of complex systems. The book discusses a new treatise on fractional dynamics and control, as well as the new methods for differential delay systems and control. Lastly, a theoretical framework for the complexity and synchronization of complex system is presented. The book is intended for researchers in the field of nonlinear dynamics in mathematics, physics and engineering. It can also serve as a reference book for graduate students in physics, applied mathematics and engineering. Dr. Albert C.J. Luo is a Professor at Southern Illinois University Edwardsville, USA. Dr. Jian-Qiao Sun is a Professor at the University of California, Merced, USA.
On the time delay between ultra-relativistic particles
Fleury, Pierre
2016-09-01
The time delay between the receptions of ultra-relativistic particles emitted simultaneously is a useful observable for both fundamental physics and cosmology. The expression of the delay when the particles travel through an arbitrary spacetime has been derived recently by Fanizza et al., using a particular coordinate system and self-consistent assumptions. The present article shows that this formula enjoys a simple physical interpretation: the relative velocity between two ultra-relativistic particles is constant. This result reveals an interesting kinematical property of general relativity, namely that the tidal forces experienced by ultra-relativistic particles in the direction of their motion are much smaller than those experienced orthogonally to their motion.
Remote Task-level Commanding of Centaur over Time Delay
Schreckenghost, Debra; Ngo, Tam; Burridge, Robert; Wang, Lui; Izygon, Michel
2008-01-01
Remote operation of robots on the lunar surface by ground controllers poses unique human-robot interaction challenges due to time delay and constrained bandwidth. One strategy for addressing these challenges is to provide task-level commanding of robots by a ground controller. Decision-support tools are being developed at JSC for remote task-level commanding over time-delay. The approach is to provide ground procedures that guide a controller when executing task-level command sequences and aid awareness of the state of command execution in the robot. This approach is being evaluated using the Centaur robot at JSC. The Centaur Central Commander provides a task-level command interface that executes on the robot side of the delay. Decision support tools have been developed for a human Supervisor in the JSC Cockpit to use when interacting with the Centaur Central Commander. Commands to the Central Commander are defined as instructions in a procedure. Sequences of these instructions are grouped into procedures for the Cockpit Supervisor. When a Supervisor is ready to perform a task, a procedure is loaded into the decision support tool. From this tool, the Supervisor can view command sequences and dispatch individual commands to Centaur. Commands are queued for execution on the robot side of the delay. Reliable command sequences can be dispatched automatically upon approval by the Supervisor. The decision support tool provides the Supervisor with feedback about which commands are waiting for execution and which commands have finished. It also informs the Supervisor when a command fails to have its intended effect. Cockpit procedures are defined using the Procedure Representation Language (PRL) developed at JSC for mission operations. The decision support tool is based on a Procedure Sequencer and multi-agent software developed for human-robot interaction. In this paper the approach for remote task-level commanding of robots is described and the results of the evaluation
Effects of Time Delay on Intracellular Ca2+ Concentration Oscillations
Institute of Scientific and Technical Information of China (English)
YING Yang-Jun; HUANG Zu-Qia
2001-01-01
Based on the SS-model [Somogyi R and Stucki J W J. Biol. Chem. 266 (1991) 11 068] for the generation of intracellular Ca2+ concentration oscillations, we consider a time delay for the binding kinetics of the Ca2+ channel and find a significant phenomenon that the oscillation takes two quite different modes when a parameter of the system crosses a threshold. One is a quick oscillation mode and the other is a slow oscillation mode. The oscillation frequencies of these modes differ from each other by more than ten times. The change of oscillation form with parameters and its critical behaviour are illustrated by numerical simulation results.
DISCRETE VARIABLE STRUCTURE CONTROL OF LINEAR TIME-INVARIANT SYSTEMS WITH TIME DELAY
Institute of Scientific and Technical Information of China (English)
蔡国平; 黄金枝
2002-01-01
A discrete variable structure control(DVSC) method for the linear time-invariant systems with time delay was presented. The continuous time-delay systems are first transformed into the standard discrete form which contains no time delay by augmenting the state variables. Then the switching surface is determined by using the ideal quasi-sliding mode. As it is difficult for the state trajectory to reach the switching surface exactly, the reaching condition in the form of approach law is used to design the controller. The deduced switching surface and controller contain not only the current step of state feedback but also some former steps of controls. Stability analysis with and without time-delay information is also investigated in this paper. Numerical simulation was carried out to demonstrate the effectiveness and feasibility of the presented control method.
A delay-time model with safety constraint
Energy Technology Data Exchange (ETDEWEB)
Aven, Terje [University of Stavanger, 4036 Stavanger (Norway)], E-mail: terje.aven@uis.no; Castro, I.T. [Departamento de Matematicas, Escuela Politecnica, Universidad de Extremadura, 10071 Caceres (Spain)], E-mail: inmatorres@unex.es
2009-02-15
We consider the basic delay-time model in which a system has three states, the perfect functioning state, a defective state and the failure state. The system is deteriorating and to reduce the number of failures, preventive replacements are carried out when the system is in the defective state. The time in the defective state is referred to as the delay time. Inspections are required to check whether the system is in the defective state. System failures are safety critical and to control the risk, management considers two types of safety constraints: (i) the probability of at least one failure in the interval [0,A] should not exceed a fixed probability {omega}{sub 1} and (ii) the fraction of time the system is in the defective state should not exceed a fixed limit {omega}{sub 2}. The problem is to determine optimal inspection intervals T, minimizing the expected discounted costs under the safety constraints. Conditions are established for when the safety constraints affect the optimal inspection time and causes increased costs.
Predictive active disturbance rejection control for processes with time delay.
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.
Robust Continuous-time Generalized Predictive Control for Large Time-delay System
Institute of Scientific and Technical Information of China (English)
WEI Huan; PAN Li-deng; ZHEN Xin-ping
2008-01-01
A simple delay-predictive continuous-time generalized predictive controller with filter (F - SDCGPC) is proposed. By using modified predictive output signal and cost function, the delay compensator is incorporated in the control law with observer structure, and a filter is added for enhancing robustness. The design of filter does not affect the nominal set-point response, and it is more flexible than the design of observer polynomial. The analysis and simulation results show that the F - SDCGPC has better robustness than the observer structure without filter when large time-delay error is considered.
Time-delay interferometry for LISA with one arm dysfunctional
Energy Technology Data Exchange (ETDEWEB)
Dhurandhar, S V [IUCAA, Postbag 4, Ganeshkind, Pune, 411 007 (India); Nayak, K Rajesh [IISER-Kolkata, PO: BCKV Campus Main Office, Mohanpur, 741252 (India); Vinet, J-Y, E-mail: rajesh@iiserkol.ac.i [ARTEMIS, Observatoire de la Cote d' Azur, BP 4229, 06304 Nice (France)
2010-07-07
In order to attain the requisite sensitivity for LISA (Laser Interferometric Space Antenna)-a joint space mission of the ESA and NASA-the laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. By combining six appropriately time-delayed data streams containing fractional Doppler shifts-a technique called time-delay interferometry (TDI)-the laser frequency noise may be adequately suppressed. We consider the general model of LISA where the armlengths vary with time, so that second-generation TDI are relevant. However, we must envisage the possibility that not all the optical links of LISA will be operating at all times, and therefore, we here consider the case of LISA operating with two arms only. As shown earlier in the literature, obtaining even approximate solutions of TDI to the general problem is very difficult. Since here only four optical links are relevant, the algebraic problem simplifies considerably. We are then able to exhibit a large number of solutions (from a mathematical point of view an infinite number) and further present an algorithm to generate these solutions.
Directory of Open Access Journals (Sweden)
YaJun Li
2015-01-01
Full Text Available The passivity problem for a class of stochastic neural networks systems (SNNs with varying delay and leakage delay has been further studied in this paper. By constructing a more effective Lyapunov functional, employing the free-weighting matrix approach, and combining with integral inequality technic and stochastic analysis theory, the delay-dependent conditions have been proposed such that SNNs are asymptotically stable with guaranteed performance. The time-varying delay is divided into several subintervals and two adjustable parameters are introduced; more information about time delay is utilised and less conservative results have been obtained. Examples are provided to illustrate the less conservatism of the proposed method and simulations are given to show the impact of leakage delay on stability of SNNs.
Delay-dependent robust passivity control for uncertain time-delay systems
Institute of Scientific and Technical Information of China (English)
Li Guifang; Li Huiying; Yang Chengwu
2007-01-01
The robust passivity control problem is addressed for a class of uncertain delayed systems with timevarying delay. The parameter uncertainties are norm-bounded. First, the delay-dependent stability sufficient condition is obtained for the nominal system, and then, based-on the former, the delay-dependent robust passivity criteria is provided and the corresponding controller is designed in terms of linear matrix inequalities. Finally, a numerical example is given to demonstrate the validity of the proposed approach.
Effects of time delay on stochastic resonance of the stock prices in financial system
Energy Technology Data Exchange (ETDEWEB)
Li, Jiang-Cheng [Department of Physics, Yunnan University, Kunming, 650091 (China); Li, Chun [Department of Computer Science, Puer Teachers' College, Puer 665000 (China); Mei, Dong-Cheng, E-mail: meidch@ynu.edu.cn [Department of Physics, Yunnan University, Kunming, 650091 (China)
2014-06-13
The effect of time delay on stochastic resonance of the stock prices in finance system was investigated. The time delay is introduced into the Heston model driven by the extrinsic and intrinsic periodic information for stock price. The signal power amplification (SPA) was calculated by numerical simulation. The results indicate that an optimal critical value of delay time maximally enhances the reverse-resonance in the behaviors of SPA as a function of long-run variance of volatility or cross correlation coefficient between noises for both cases of intrinsic and extrinsic periodic information. Moreover, in both cases, being a critical value in the delay time, when the delay time takes value below the critical value, reverse-resonance increases with the delay time increasing, however, when the delay time takes value above the critical value, the reverse-resonance decrease with the delay time increasing. - Highlights: • The effects of delay time on stochastic resonance of the stock prices was investigated. • There is an optimal critical value of delay time maximally enhances the reverse-resonance • The reverse-resonance increases with the delay time increasing as the delay time takes value below the critical value • The reverse-resonance decrease with the delay time increasing as the delay time takes value above the critical value.
On noise in time-delay integration CMOS image sensors
Levski, Deyan; Choubey, Bhaskar
2016-05-01
Time delay integration sensors are of increasing interest in CMOS processes owing to their low cost, power and ability to integrate with other circuit readout blocks. This paper presents an analysis of the noise contributors in current day CMOS Time-Delay-Integration image sensors with various readout architectures. An analysis of charge versus voltage domain readout modes is presented, followed by a noise classification of the existing Analog Accumulator Readout (AAR) and Digital Accumulator Readout (DAR) schemes for TDI imaging. The analysis and classification of existing readout schemes include, pipelined charge transfer, buffered direct injection, voltage as well as current-mode analog accumulators and all-digital accumulator techniques. Time-Delay-Integration imaging modes in CMOS processes typically use an N-number of readout steps, equivalent to the number of TDI pixel stages. In CMOS TDI sensors, where voltage domain readout is used, the requirements over speed and noise of the ADC readout chain are increased due to accumulation of the dominant voltage readout and ADC noise with every stage N. Until this day, the latter is the primary reason for a leap-back of CMOS TDI sensors as compared to their CCD counterparts. Moreover, most commercial CMOS TDI implementations are still based on a charge-domain readout, mimicking a CCD-like operation mode. Thus, having a good understanding of each noise contributor in the signal chain, as well as its magnitude in different readout architectures, is vital for the design of future generation low-noise CMOS TDI image sensors based on a voltage domain readout. This paper gives a quantitative classification of all major noise sources for all popular implementations in the literature.
STRONG LENS TIME DELAY CHALLENGE. II. RESULTS OF TDC1
Energy Technology Data Exchange (ETDEWEB)
Liao, Kai [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Treu, Tommaso [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Marshall, Phil [Kavli Institute for Particle Astrophysics and Cosmology, P.O. Box 20450, MS29, Stanford, CA 94309 (United States); Fassnacht, Christopher D.; Rumbaugh, Nick [Department of Physics, University of California, 1 Shields Avenue, Davis, CA 95616 (United States); Dobler, Gregory [Kavli Institute for Theoretical Physics, University of California Santa Barbara, Santa Barbara, CA 93106 (United States); Aghamousa, Amir [Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784 (Korea, Republic of); Bonvin, Vivien; Courbin, Frederic; Meylan, Georges [EPFL, Lausanne (Switzerland); Hojjati, Alireza [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Jackson, Neal [University of Manchester, School of Physics and Astronomy, Jodrell Bank Centre for Astrophysics, Manchester M13 9PL (United Kingdom); Kashyap, Vinay; Mandel, Kaisey [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Rathna Kumar, S.; Prabhu, Tushar P. [Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560034 (India); Linder, Eric [Lawrence Berkeley National Laboratory and University of California, Berkeley, CA 94720 (United States); Meng, Xiao-Li [Department of Statistics, Harvard University, 1 Oxford Street, Cambridge, MA 02138 (United States); Moustakas, Leonidas A.; Romero-Wolf, Andrew [Jet Propulsion Laboratory, California Institute of Technology, M/S 169-506, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); and others
2015-02-10
We present the results of the first strong lens time delay challenge. The motivation, experimental design, and entry level challenge are described in a companion paper. This paper presents the main challenge, TDC1, which consisted of analyzing thousands of simulated light curves blindly. The observational properties of the light curves cover the range in quality obtained for current targeted efforts (e.g., COSMOGRAIL) and expected from future synoptic surveys (e.g., LSST), and include simulated systematic errors. Seven teams participated in TDC1, submitting results from 78 different method variants. After describing each method, we compute and analyze basic statistics measuring accuracy (or bias) A, goodness of fit χ{sup 2}, precision P, and success rate f. For some methods we identify outliers as an important issue. Other methods show that outliers can be controlled via visual inspection or conservative quality control. Several methods are competitive, i.e., give |A| < 0.03, P < 0.03, and χ{sup 2} < 1.5, with some of the methods already reaching sub-percent accuracy. The fraction of light curves yielding a time delay measurement is typically in the range f = 20%-40%. It depends strongly on the quality of the data: COSMOGRAIL-quality cadence and light curve lengths yield significantly higher f than does sparser sampling. Taking the results of TDC1 at face value, we estimate that LSST should provide around 400 robust time-delay measurements, each with P < 0.03 and |A| < 0.01, comparable to current lens modeling uncertainties. In terms of observing strategies, we find that A and f depend mostly on season length, while P depends mostly on cadence and campaign duration.
Robust H∞ Control of Uncertain T-S Fuzzy Time-Delay System: A Delay Decomposition Approach
Cheng Gong; Chunsong Han
2013-01-01
This paper is concerned with the problem of robust H∞ control for a class of uncertain time-delay fuzzy systems with norm-bounded parameter uncertainties. By utilizing the instrumental idea of delay decomposition, the decomposed Lyapunov-Krasovskii functional is introduced to uncertain T-S fuzzy system, and some delay-dependent conditions for the existence of robust controller are formulated in the form of linear matrix inequalities (LMIs). When these LMIs are feasible, a controller is presen...
Distributed Load Shedding over Directed Communication Networks with Time Delays
Energy Technology Data Exchange (ETDEWEB)
Yang, Tao; Wu, Di
2016-07-25
When generation is insufficient to support all loads under emergencies, effective and efficient load shedding needs to be deployed in order to maintain the supply-demand balance. This paper presents a distributed load shedding algorithm, which makes efficient decision based on the discovered global information. In the global information discovery process, each load only communicates with its neighboring load via directed communication links possibly with arbitrarily large but bounded time varying communication delays. We propose a novel distributed information discovery algorithm based on ratio consensus. Simulation results are used to validate the proposed method.
Equation and test of possible delay time of Newton force
Diósi, Lajos
2014-01-01
Recently, a simple heuristic modification of the Newton potential with a non-zero delay-time $\\tau_G$ has been proposed. Our modification is largely suppressed for purely gravitational interactions, it becomes relevant under non-gravitational accelerations of the sources. We illustrate how the choice $\\tau_G\\sim1$ms may already influence the 5th digit of G determined by Cavendish experiments. Re-evaluation of old Cavendish experiments and implementing slightly modified new ones may confirm the proposal or, at least, put a stronger upper limit on $\\tau_G$.
Delayed choice experiments, the arrow of time, and quantum measurement
Schulman, L. S.
2011-11-01
By a radical modification of statistical mechanics the measurement process of quantum mechanics can be described in terms of pure, unitary time evolution, with no wave function collapse or many-world ideas. The key notion is "special states," rare microscopic states of a complex system. Recovering the standard probabilities requires of this theory the appearance of Cauchy-distributed noise in some measurement processes. This article treats experimental situations where such noise might be detected and correlated with the need or absence of need for special states. Included in this possibility are "delayed choice" experiments, in which the correlation contravenes conventional ideas on causality. Background material on all topics is provided.
Multiple integral inequalities and stability analysis of time delay systems
Gyurkovics, Eva; Takacs, Tibor
2016-01-01
This paper is devoted to stability analysis of continuous-time delay systems based on a set of Lyapunov-Krasovskii functionals. New multiple integral inequalities are derived that involve the famous Jensen's and Wirtinger's inequalities, as well as the recently presented Bessel-Legendre inequalities of A. Seuret and F. Gouaisbaut, (2015) and the Wirtinger-based multiple-integral inequalities of M. Park et al. (2015) and T.H. Lee et al. (2015). The present paper aims at showing that the propos...
Topology Identification of General Dynamical Network with Distributed Time Delays
Institute of Scientific and Technical Information of China (English)
WU Zhao-Yan; FU Xin-Chu
2009-01-01
General dynamical networks with distributed time delays are studied. The topology of the networks are viewed as unknown parameters, which need to be identified. Some auxiliary systems (also called the network estimators)are designed to achieve this goal. Both linear feedback control and adaptive strategy are applied in designing these network estimators. Based on linear matrix inequalities and the Lyapunov function method, the sufficient condition for the achievement of topology identification is obtained. This method can also better monitor the switching topology of dynamical networks. Illustrative examples are provided to show the effectiveness of this method.
Discrete-Time Approximation for Nonlinear Continuous Systems with Time Delays
Directory of Open Access Journals (Sweden)
Bemri H’mida
2016-05-01
Full Text Available This paper is concerned with the discretization of nonlinear continuous time delay systems. Our approach is based on Taylor-Lie series. The main idea aims to minimize the effect of the delay and neglects the importance of nonlinear parameter by the linearization of the system study in an attempt to make its handling and easier programming as possible. We investigate a new method based on the development of new theoretical methods for the time discretization of nonlinear systems with time delay .The performance of these proposed discretization methods was validated by doing the numerical simulation using a nonlinear system with state delay. Some illustrative examples are given to show the effectiveness of the obtained results.
Senthilkumar, D V; Lakshmanan, M
2007-03-01
Existence of a new type of oscillating synchronization that oscillates between three different types of synchronizations (anticipatory, complete, and lag synchronizations) is identified in unidirectionally coupled nonlinear time-delay systems having two different time-delays, that is feedback delay with a periodic delay time modulation and a constant coupling delay. Intermittent anticipatory, intermittent lag, and complete synchronizations are shown to exist in the same system with identical delay time modulations in both the delays. The transition from anticipatory to complete synchronization and from complete to lag synchronization as a function of coupling delay with suitable stability condition is discussed. The intermittent anticipatory and lag synchronizations are characterized by the minimum of the similarity functions and the intermittent behavior is characterized by a universal asymptotic -32 power law distribution. It is also shown that the delay time carved out of the trajectories of the time-delay system with periodic delay time modulation cannot be estimated using conventional methods, thereby reducing the possibility of decoding the message by phase space reconstruction.
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.
Constraints on interacting dark energy from time delay lenses
Pan, Yu; Cao, Shuo; Li, Li
2016-10-01
We use the time delay measurements between multiple images of lensed sources in 18 strongly gravitationally lensed (SGL) systems to put additional constraints on three phenomenological interaction models for dark energy (DE) and dark matter (DM). The compatibility among the fits on the three models seems to imply that the coupling between DE and DM is a small value close to zero, which is compatible with the previous results for constraining interacting DE parameters. We find that, among the three interacting DE models, the γmIDE model with the interaction term Q proportional to the energy density of DM provides relatively better fits to recent observations. However, the coincidence problem is still very severe in the framework of three interacting DE models, since the fitting results do not show any preference for a nonzero coupling between DE and DM. More importantly, we have studied the significance of the current strong lensing data in deriving the interacting information between dark sectors, which highlights the importance of strong lensing time delay measurements to provide additional observational fits on alternative cosmological models.
Minimizing Maximum Response Time and Delay Factor in Broadcast Scheduling
Chekuri, Chandra; Moseley, Benjamin
2009-01-01
We consider online algorithms for pull-based broadcast scheduling. In this setting there are n pages of information at a server and requests for pages arrive online. When the server serves (broadcasts) a page p, all outstanding requests for that page are satisfied. We study two related metrics, namely maximum response time (waiting time) and maximum delay-factor and their weighted versions. We obtain the following results in the worst-case online competitive model. - We show that FIFO (first-in first-out) is 2-competitive even when the page sizes are different. Previously this was known only for unit-sized pages [10] via a delicate argument. Our proof differs from [10] and is perhaps more intuitive. - We give an online algorithm for maximum delay-factor that is O(1/eps^2)-competitive with (1+\\eps)-speed for unit-sized pages and with (2+\\eps)-speed for different sized pages. This improves on the algorithm in [12] which required (2+\\eps)-speed and (4+\\eps)-speed respectively. In addition we show that the algori...
Robust generalized H2 control:time-delay case
Institute of Scientific and Technical Information of China (English)
刘飞
2004-01-01
Generalized H2 control problem is considered for a class of linear time-delay systems covering linear timeinvariant (LTI) case and time-varying but norm-bounded linear differential inclusion (NLDI) case. The issues focus on the synthesis of so-called generalized H2 controller, which guarantees internal/robust stability and a certain performance level of generalized H2 norm of resulting closed-loop system. By using Lyapunov functional technique, sufficient conditions for the existence of such a kind of controllers are obtained in terms of two linear matrix inequalities (LMIs).In the state space, for memoryless state feedback case, we treat the controller design in a unified framework for both LTI and NLDI. The presented results are illustrated by numerical examples.
Wang, Leimin; Shen, Yi; Sheng, Yin
2016-04-01
This paper is concerned with the finite-time robust stabilization of delayed neural networks (DNNs) in the presence of discontinuous activations and parameter uncertainties. By using the nonsmooth analysis and control theory, a delayed controller is designed to realize the finite-time robust stabilization of DNNs with discontinuous activations and parameter uncertainties, and the upper bound of the settling time functional for stabilization is estimated. Finally, two examples are provided to demonstrate the effectiveness of the theoretical results.
Real-Time Tropospheric Delay Estimation using IGS Products
Stürze, Andrea; Liu, Sha; Söhne, Wolfgang
2014-05-01
The Federal Agency for Cartography and Geodesy (BKG) routinely provides zenith tropospheric delay (ZTD) parameter for the assimilation in numerical weather models since more than 10 years. Up to now the results flowing into the EUREF Permanent Network (EPN) or E-GVAP (EUMETNET EIG GNSS water vapour programme) analysis are based on batch processing of GPS+GLONASS observations in differential network mode. For the recently started COST Action ES1206 about "Advanced Global Navigation Satellite Systems tropospheric products for monitoring severe weather events and climate" (GNSS4SWEC), however, rapid updates in the analysis of the atmospheric state for nowcasting applications require changing the processing strategy towards real-time. In the RTCM SC104 (Radio Technical Commission for Maritime Services, Special Committee 104) a format combining the advantages of Precise Point Positioning (PPP) and Real-Time Kinematic (RTK) is under development. The so-called State Space Representation approach is defining corrections, which will be transferred in real-time to the user e.g. via NTRIP (Network Transport of RTCM via Internet Protocol). Meanwhile messages for precise orbits, satellite clocks and code biases compatible to the basic PPP mode using IGS products are defined. Consequently, the IGS Real-Time Service (RTS) was launched in 2013 in order to extend the well-known precise orbit and clock products by a real-time component. Further messages e.g. with respect to ionosphere or phase biases are foreseen. Depending on the level of refinement, so different accuracies up to the RTK level shall be reachable. In co-operation of BKG and the Technical University of Darmstadt the real-time software GEMon (GREF EUREF Monitoring) is under development. GEMon is able to process GPS and GLONASS observation and RTS product data streams in PPP mode. Furthermore, several state-of-the-art troposphere models, for example based on numerical weather prediction data, are implemented. Hence, it
Delayed feedback control of time-delayed chaotic systems: Analytical approach at Hopf bifurcation
Energy Technology Data Exchange (ETDEWEB)
Vasegh, Nastaran [Faculty of Electrical Engineering, K.N. Toosi University of Technology, PO Box 16315-1355, Tehran (Iran, Islamic Republic of)], E-mail: vasegh@eetd.kntu.ac.ir; Sedigh, Ali Khaki [Faculty of Electrical Engineering, K.N. Toosi University of Technology, PO Box 16315-1355, Tehran (Iran, Islamic Republic of)
2008-07-28
This Letter is concerned with bifurcation and chaos control in scalar delayed differential equations with delay parameter {tau}. By linear stability analysis, the conditions under which a sequence of Hopf bifurcation occurs at the equilibrium points are obtained. The delayed feedback controller is used to stabilize unstable periodic orbits. To find the controller delay, it is chosen such that the Hopf bifurcation remains unchanged. Also, the controller feedback gain is determined such that the corresponding unstable periodic orbit becomes stable. Numerical simulations are used to verify the analytical results.
Directory of Open Access Journals (Sweden)
Zupanc Andrea
2009-06-01
Full Text Available Abstract Background Hospital physicians' time is a critical resource in medical care. Two aspects are of interest. First, the time spent in direct patient contact – a key principle of effective medical care. Second, simultaneous task performance ('multitasking' which may contribute to medical error, impaired safety behaviour, and stress. There is a call for instruments to assess these aspects. A preliminary study to gain insight into activity patterns, time allocation and simultaneous activities of hospital physicians was carried out. Therefore an observation instrument for time-motion-studies in hospital settings was developed and tested. Methods 35 participant observations of internists and surgeons of a German municipal 300-bed hospital were conducted. Complete day shifts of hospital physicians on wards, emergency ward, intensive care unit, and operating room were continuously observed. Assessed variables of interest were time allocation, share of direct patient contact, and simultaneous activities. Inter-rater agreement of Kappa = .71 points to good reliability of the instrument. Results Hospital physicians spent 25.5% of their time at work in direct contact with patients. Most time was allocated to documentation and conversation with colleagues and nursing staff. Physicians performed parallel simultaneous activities for 17–20% of their work time. Communication with patients, documentation, and conversation with colleagues and nursing staff were the most frequently observed simultaneous activities. Applying logit-linear analyses, specific primary activities increase the probability of particular simultaneous activities. Conclusion Patient-related working time in hospitals is limited. The potential detrimental effects of frequently observed simultaneous activities on performance outcomes need further consideration.
Delay-Dependent Absolute Stability ofUncertain Lur′e Systems with Time-Delays1）
Institute of Scientific and Technical Information of China (English)
CHENWu-Hua; GUANZhi-Hong; LUXiao-Mei; YANGXuan-Fang
2004-01-01
This paper is concerned with delay dependent absolute stability for a class of uncertain Lur′e systems with multiple time-delays. By using a descriptor model transformation of the sys-tem and by applying a recent result on bounding of cross products of vectors, a new type of Lya-punov-Krasovskii functional is constructed. Based on the new functional, delay-dependent suffi-cient conditions for absolute stability are derived in terms of linear matrix inequalities. These con-ditions do not require any parameter tuning, and can be solved numerically using the software LMI Lab. A numerical example is presented which shows that the proposed method can substantiallyimprove the delay bound for absolute stability of Lur′e system with time-delays, compared to theexisting ones.
Directory of Open Access Journals (Sweden)
Zhang Xinhua
2011-01-01
Full Text Available Abstract In this paper, a class of impulsive bidirectional associative memory (BAM fuzzy cellular neural networks (FCNNs with time delays in the leakage terms and distributed delays is formulated and investigated. By establishing an integro-differential inequality with impulsive initial conditions and employing M-matrix theory, some sufficient conditions ensuring the existence, uniqueness and global exponential stability of equilibrium point for impulsive BAM FCNNs with time delays in the leakage terms and distributed delays are obtained. In particular, the estimate of the exponential convergence rate is also provided, which depends on the delay kernel functions and system parameters. It is believed that these results are significant and useful for the design and applications of BAM FCNNs. An example is given to show the effectiveness of the results obtained here.
Institute of Scientific and Technical Information of China (English)
Wang Shen-Quan; Feng Jian; Zhao Qing
2012-01-01
In this paper,the problem of delay-distribution-dependent stability is investigated for continuous-time recurrent neural networks (CRNNs) with stochastic delay.Different from the common assumptions on time delays,it is assumed that the probability distribution of the delay taking values in some intervals is known a priori.By making full use of the information concerning the probability distribution of the delay and by using a tighter bounding technique (the reciprocally convex combination method),less conservative asymptotic mean-square stable sufficient conditions are derived in terms of linear matrix inequalities (LMIs).Two numerical examples show that our results are better than the existing ones.
Contagion effects in a chartist fundamentalist model with time delays
Dibeh, Ghassan
2007-08-01
In this paper two models of speculative markets are developed to study the effects of feedback mechanisms in financial markets. In the first model, a crash market model couples a linear chartist-fundamentalist model with time delays with a log-periodic market index I(t) through direct coupling. Numerical solutions to the model show that asset prices exhibit significant persistence as a result of the coupling to the log-periodic market index. An extension to include endogenous wealth dynamics shows that the chartists benefit from the persistent dynamics induced by the coupling. The second model is a two-asset model represented by a 2-dimensional delay-differential equation. Asset one price exhibits limit cycle dynamics while in the second market asset prices follow stable damped oscillations. The markets are coupled through a diffusive coupling term. Solutions to the coupled model show that the dynamics of asset two changes fundamentally with the price now exhibiting a limit cycle. The stable converging dynamics is replaced with limit cycle oscillations around the fundamental.
Nonlocal Mechanism for Synchronization of Time Delay Networks
Kanter, Ido; Kopelowitz, Evi; Vardi, Roni; Zigzag, Meital; Cohen, Dana; Kinzel, Wolfgang
2011-11-01
We present the interplay between synchronization of networks with heterogeneous delays and the greatest common divisor (GCD) of loops composing the network. We distinguish between two types of networks; (I) chaotic networks and (II) population dynamic networks with periodic activity driven by external stimuli. For type (I), in the weak chaos region, the units of a chaotic network characterized by GCD=1 are in a chaotic zero-lag synchronization, whereas for GCD>1, the network splits into GCD-clusters in which clustered units are in zero-lag synchronization. These results are supported by simulations of chaotic systems, self-consistent and mixing arguments, as well as analytical solutions of Bernoulli maps. Type (II) is exemplified by simulations of Hodgkin Huxley population dynamic networks with unidirectional connectivity, synaptic noise and distribution of delays within neurons belonging to a node and between connecting nodes. For a stimulus to one node, the network splits into GCD-clusters in which cluster neurons are in zero-lag synchronization. For complex external stimuli, the network splits into clusters equal to the greatest common divisor of loops composing the network (spatial) and the periodicity of the external stimuli (temporal). The results suggest that neural information processing may take place in the transient to synchronization and imply a much shorter time scale for the inference of a perceptual entity.
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.
An all-optical time-delay relay based n a bacteriorhodopsin film
Institute of Scientific and Technical Information of China (English)
Chen Gui-Ying; Xu Xu-Xu; Zhang Chun-Ping; Qi Shen-Wen; Song Qi-Wang
2008-01-01
Using a special property of dynamic complementary-suppression-modulated transmission (DCSMT) in the bacteriorhodopsin (bR) film,we have demonstrated an all-optical time-delay relay.To extend our work,the relationship between the delay time of the all-optical time-delay relay and parameters of a bR film is numerically studied.We show how the delay time changes with the product of concentration and thickness (PCT) of a bR film.Furthermore,the shortest and longest delay times are given for the relay of 'switch off'.The saturable delay time and maximum delaytime of 'switch on' are also given.How the wavelengths (632.8,568,533 and 412 nm) and intensities of the illuminating light influence the delay time is also discussed.The simulation results are useful for optimizing the design of all-optical time-delay relays.
Semi-Discretization for Time-Delay Systems
Insperger, Tamás
2011-01-01
This book presents the recently introduced and already widely referred semi-discretization method for the stability analysis of delayed dynamical systems. Delay differential equations often come up in different fields of engineering, like feedback control systems, machine tool vibrations, balancing/stabilization with reflex delay. The behavior of such systems is often counter-intuitive and closed form analytical formulas can rarely be given even for the linear stability conditions. If parametric excitation is coupled with the delay effect, then the governing equation is a delay differential eq
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.
Robust passive filtering for continuous-time polytopic uncertain time-delay systems
Institute of Scientific and Technical Information of China (English)
LU Ling-ling; DUAN Guang-ren; WU Ai-guo
2008-01-01
To obtain a stable and proper linear filter to make the filtering error system robustly and strictly passive,the problem of full-order robust passive filtering for continuous-time polytopie uncertain time-delay systems was investigated.A criterion for the passivity of time-delay systems was firstly provided in terms of linear matrix inequalities(LMI).Then an LMI sufficient condition for the existence of a robust filter was established and a design procedure was proposed for this type of systems.A numerical example demonstrated the feasibility of the filtering design procedure.
DEFF Research Database (Denmark)
Xue, Weiqi; Mørk, Jesper
2010-01-01
We experimentally demonstrate microwave time delays in a semiconductor optical amplifier by cross gain modulation. In the counter-propagation configuration, ~10.5ps tunable true time delay over a microwave bandwidth of several tens of GHz is obtained.......We experimentally demonstrate microwave time delays in a semiconductor optical amplifier by cross gain modulation. In the counter-propagation configuration, ~10.5ps tunable true time delay over a microwave bandwidth of several tens of GHz is obtained....
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
This paper focuses on the H∞ controller design for linear systems with time-varying delays and norm bounded parameter perturbetions in the system state and control/disturbance. On the existence of delayed/undelayed full state feedback controllers, we present a sufficient condition and give a design method in the form of Riccati equation. The controller can not only stabilize the time-delay system, but also make the H∞ norm of the closed-loop system be less than a given bound. This result practically generalizes the related results in current literature.
A high-resolution time interpolator based on a delay locked loop and an RC delay line
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).
Time-Delay Interferometry with optical frequency comb
Tinto, Massimo
2015-01-01
Heterodyne laser phase measurements in a space-based gravitational wave interferometer are degraded by the phase fluctuations of the onboard clocks, resulting in unacceptable sensitivity performance levels of the interferometric data. In order to calibrate out the clock phase noises it has been previously suggested that additional inter-spacecraft phase measurements must be performed by modulating the laser beams. This technique, however, considerably increases system complexity and probability of subsystem failure. With the advent of self-referenced optical frequency combs, it is possible to generate the heterodyne microwave signal that is coherently referenced to the onboard laser. We show in this case that the microwave noise can be cancelled directly by applying modified second-generation Time-Delay Interferometric combinations to the heterodyne phase measurements. This approach avoids use of modulated laser beams as well as the need of additional ultra-stable oscillator clocks.
Time delay between cardiac and brain activity during sleep transitions
Long, Xi; Arends, Johan B.; Aarts, Ronald M.; Haakma, Reinder; Fonseca, Pedro; Rolink, Jérôme
2015-04-01
Human sleep consists of wake, rapid-eye-movement (REM) sleep, and non-REM (NREM) sleep that includes light and deep sleep stages. This work investigated the time delay between changes of cardiac and brain activity for sleep transitions. Here, the brain activity was quantified by electroencephalographic (EEG) mean frequency and the cardiac parameters included heart rate, standard deviation of heartbeat intervals, and their low- and high-frequency spectral powers. Using a cross-correlation analysis, we found that the cardiac variations during wake-sleep and NREM sleep transitions preceded the EEG changes by 1-3 min but this was not the case for REM sleep transitions. These important findings can be further used to predict the onset and ending of some sleep stages in an early manner.
Precision cosmology with time delay lenses: high resolution imaging requirements
Meng, Xiao-Lei; Agnello, Adriano; Auger, Matthew W; Liao, Kai; Marshall, Philip J
2015-01-01
Lens time delays are a powerful probe of cosmology, provided that the gravitational potential of the main deflector can be modeled with sufficient precision. Recent work has shown that this can be achieved by detailed modeling of the host galaxies of lensed quasars, which appear as "Einstein Rings" in high resolution images. 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 $\\gamma'$ of the...
Direct Tunneling Delay Time Measurement in an Optical Lattice.
Fortun, A; Cabrera-Gutiérrez, C; Condon, G; Michon, E; Billy, J; Guéry-Odelin, D
2016-07-01
We report on the measurement of the time required for a wave packet to tunnel through the potential barriers of an optical lattice. The experiment is carried out by loading adiabatically a Bose-Einstein condensate into a 1D optical lattice. A sudden displacement of the lattice by a few tens of nanometers excites the micromotion of the dipole mode. We then directly observe in momentum space the splitting of the wave packet at the turning points and measure the delay between the reflected and the tunneled packets for various initial displacements. Using this atomic beam splitter twice, we realize a chain of coherent micron-size Mach-Zehnder interferometers at the exit of which we get essentially a wave packet with a negative momentum, a result opposite to the prediction of classical physics.
The delayed time distribution of massive double compact star mergers
Mennekens, N
2016-01-01
In order to investigate the temporal evolution of binary populations in general, double compact star binaries and mergers in particular within a galactic evolution context, a most straightforward method is obviously the implementation of a detailed binary evolutionary model in a galactic chemical evolution code. To our knowledge, only the Brussels galactic code explicitly accounts for binaries. With a galactic code that does not explicitly include binaries, the temporal evolution of the population of double compact star binaries and mergers can be estimated with reasonable accuracy if the delayed time distribution (DTD) for these mergers is available. The DTD for supernovae type Ia has been studied extensively the last decade. In the present paper we present the DTD for merging double neutron star binaries and mixed systems consisting of a neutron star and a black hole. The latter mergers are very promising sites for the production of r-process elements and the DTDs can be used to study the galactic evolution...
Strong Lens Time Delay Challenge: II. Results of TDC1
Liao, Kai; Marshall, Phil; Fassnacht, Christopher D; Rumbaugh, Nick; Dobler, Gregory; Aghamousa, Amir; Bonvin, Vivien; Courbin, Frederic; Hojjati, Alireza; Jackson, Neal; Kashyap, Vinay; Kumar, S Rathna; Linder, Eric; Mandel, Kaisey; Meng, Xiao-Li; Meylan, Georges; Moustakas, Leonidas A; Prabhu, Tushar P; Romero-Wolf, Andrew; Shafieloo, Arman; Siemiginowska, Aneta; Stalin, Chelliah S; Tak, Hyungsuk; Tewes, Malte; van Dyk, David
2014-01-01
We present the results of the first strong lens time delay challenge. The motivation, experimental design, and entry level challenge are described in a companion paper. This paper presents the main challenge, TDC1, which consisted in analyzing thousands of simulated light curves blindly. The observational properties of the light curves cover the range in quality obtained for current targeted efforts (e.g. COSMOGRAIL) and expected from future synoptic surveys (e.g. LSST), and include "evilness" in the form of simulated systematic errors. 7 teams participated in TDC1, submitting results from 78 different method variants. After a describing each method, we compute and analyze basic statistics measuring accuracy (or bias) $A$, goodness of fit $\\chi^2$, precision $P$, and success rate $f$. For some methods we identify outliers as an important issue. Other methods show that outliers can be controlled via visual inspection or conservative quality control. Several methods are competitive, i.e. give $|A|<0.03$, $P&...
Time delayed K sup + N reactions and exotic baryon resonances
Kelkar, N G; Khemchandani, K P
2003-01-01
Evidence and hints, from both the theoretical and experimental sides, of exotic baryon resonances with B = S, have been with us for the last 30 years. The poor status of the general acceptance of these Z* resonances is partly due to the prejudice against penta-quark baryons and partly due to the opinion that a proof of the existence of exotic states must be rigorous. This can refer to the quality and amount of data gathered, and also to the analytical methods applied in the study of these resonances. It then seems mandatory that all possibilities and aspects be exploited. We do that by analysing the time delay in K sup + N scattering, encountering clear signals of the exotic Z* resonances close to the pole values found in partial wave analyses.
Performance evaluation of the time delay digital tanlock loop architectures
Al-Kharji Al-Ali, Omar; Anani, Nader; Al-Qutayri, Mahmoud; Al-Araji, Saleh; Ponnapalli, Prasad
2016-01-01
This article presents the architectures, theoretical analyses and testing results of modified time delay digital tanlock loop (TDTLs) system. The modifications to the original TDTL architecture were introduced to overcome some of the limitations of the original TDTL and to enhance the overall performance of the particular systems. The limitations addressed in this article include the non-linearity of the phase detector, the restricted width of the locking range and the overall system acquisition speed. Each of the modified architectures was tested by subjecting the system to sudden positive and negative frequency steps and comparing its response with that of the original TDTL. In addition, the performance of all the architectures was evaluated under noise-free as well as noisy environments. The extensive simulation results using MATLAB/SIMULINK demonstrate that the new architectures overcome the limitations they addressed and the overall results confirmed significant improvements in performance compared to the conventional TDTL system.
A time-delayed model for radiation reaction in electrodynamics
Faci, Sofiane; Satheeshkumar, V H
2016-01-01
The dynamics of a radiating charge is one of the oldest unsettled problems in classical physics. The standard Lorentz-Abraham-Dirac (LAD) equation of motion is known to suffer from several pathologies and ambiguities. This paper briefly reviews these issues, and reports on a new model that fixes these difficulties in a natural way. This model is based on a hypothesis that there is an infinitesimal time delay between action and reaction. This can be related to Feynman's regularization scheme, leading to a quasi-local QED with a natural UV cutoff, hence without the need for renormalization as the divergences are absent. Besides leading to a pathology-free equation of motion, the new model predicts a modification of the Larmor formula that is testable with current and near future ultra-intense lasers.
Complex-Vector Time-Delay Control of Power Converters
DEFF Research Database (Denmark)
Blaabjerg, Frede; Loh, P. C.; Tang, Y.;
2008-01-01
Precise controlling of current produced by power converters is an important topic that has attracted interests over the last few decades. With the recent proliferation of grid-tied converters where the control of power flow is indirectly governed by the accuracy of current tracking, motivation...... 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...... precision and disturbance rejection. In principle, the proposed scheme can either be implemented solely in the stationary frame or in a "mixed" stationary and synchronous frame, termed as mixed frame in the paper. Regardless of the frame orientation chosen, the scheme always exhibits ease of implementation...
An HBV model with diffusion and time delay.
Xu, Rui; Ma, Zhien
2009-04-07
In this paper, a hepatitis B virus (HBV) model with spatial diffusion and saturation response of the infection rate is investigated, in which the intracellular incubation period is modelled by a discrete time delay. By analyzing the corresponding characteristic equations, the local stability of an infected steady state and an uninfected steady state is discussed. By comparison arguments, it is proved that if the basic reproductive number is less than unity, the uninfected steady state is globally asymptotically stable. If the basic reproductive number is greater than unity, by successively modifying the coupled lower-upper solution pairs, sufficient conditions are obtained for the global stability of the infected steady state. Numerical simulations are carried out to illustrate the main results.
New delay-dependent criterion for the stability of recurrent neural networks with time-varying delay
Institute of Scientific and Technical Information of China (English)
ZHANG HuaGuang; WANG ZhanShan
2009-01-01
This paper is concerned with the global asymptotic stability of a class of recurrent neural networks with interval time-varying delay. By constructing a suitable Lyapunov functional, a new criterion is established to ensure the global asymptotic stability of the concerned neural networks, which can be expressed in the form of linear matrix inequality and independent of the size of derivative of time varying delay. Two numerical examples show the effectiveness of the obtained results.
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.
Embedding and Distributing Constant Time Delay in Circle Time and Transitions.
Wolery, Mark; Anthony, Leslie; Caldwell, Nicola K.; Snyder, Erin D.; Morgante, James D.
2002-01-01
This study evaluated embedding and distributing constant time delay instructional trials into circle time and transitions between activities in a summer camp program. Three boys (ages 5-8) with disabilities or behavior problems participated. Results indicated the children acquired the behaviors they were taught and generalized the learned…
A delay-range-partition approach to analyse stability of linear systems with time-varying delays
Xue, Y.; Zhang, X.; Han, Y. Y.; Shi, M.
2016-12-01
In this paper, the stability analysis of linear systems with an interval time-varying delay is investigated. First, augmented Lyapunov-Krasovskii functionals are constructed, which include more information of the delay's range and the delay's derivative. Second, two improved integral inequalities, which are less conservative than Jensen's integral inequalities, and delay-range-partition approach are utilised to estimate the upper bounds of the derivatives of the augmented Lyapunov-Krasovskii functionals. Then, less conservative stability criteria are proposed no matter whether the lower bound of delay is zero or not. Finally, to illustrate the effectiveness of the stability criteria proposed in this paper, two numerical examples are given and their results are compared with the existing results.
On a cellular automaton with time delay for modelling cancer tumors
Energy Technology Data Exchange (ETDEWEB)
Iarosz, K C; Martins, C C; Batista, A M [Departamento de Matematica e EstatIstica, Universidade Estadual de Ponta Grossa, 84030-900, Ponta Grossa, PR (Brazil); Viana, R L; Lopes, S R [Departamento de Fisica, Universidade Federal do Parana, 81531-990, Curitiba, PR (Brazil); Caldas, I L [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66316, 05315-970, Sao Paulo, SP (Brazil); Penna, T J P, E-mail: antoniomarcosbatista@gmail.com [Instituto de Fisica, Universidade Federal Fluminense, 24210-340, Niteroi, RJ (Brazil)
2011-03-01
In this work we considered cellular automaton model with time delay. Time delay included in this model reflects the delay between the time in which the site is affected and the time in which its variable is updated. We analyzed the effect of the rules on the dynamics through the cluster counting. According to this cluster counting, the dynamics behavior is investigated. We verified periodic oscillations same as delay differential equation. We also studied the relation between the time delay in the cell cycle and the time to start the metastasis, using suitable numerical diagnostics.
Simple In-Hospital Interventions to Reduce Door-to-CT Time in Acute Stroke
Taheraghdam, Aliakbar; Rikhtegar, Reza; Mehrvar, Kaveh; Mehrara, Mehrdad; Hassasi, Rogayyeh; Aliyar, Hannane; Farzi, Mohammadamin; Hasaneh Tamar, Somayyeh
2016-01-01
Background. Intravenous tissue plasminogen activator, a time dependent therapy, can reduce the morbidity and mortality of acute ischemic stroke. This study was designed to assess the effect of simple in-hospital interventions on reducing door-to-CT (DTC) time and reaching door-to-needle (DTN) time of less than 60 minutes. Methods. Before any intervention, DTC time was recorded for 213 patients over a one-year period at our center. Five simple quality-improvement interventions were implemented, namely, call notification, prioritizing patients for CT scan, prioritizing patients for lab analysis, specifying a bed for acute stroke patients, and staff education. After intervention, over a course of 44 months, DTC time was recorded for 276 patients with the stroke code. Furthermore DTN time was recorded for 106 patients who were treated with IV thrombolytic therapy. Results. The median DTC time significantly decreased in the postintervention period comparing to the preintervention period [median (IQR); 20 (12–30) versus 75 (52.5–105), P DTC time and resulted in an acceptable DTN time. These interventions are feasible in most hospitals and should be considered. PMID:27478641
Delay-dependent robust H∞ control for uncertain discrete time-delay fuzzy systems
Institute of Scientific and Technical Information of China (English)
Gong Cheng; Su Baoku
2009-01-01
The robust H∞ control problem of norm bounded uncertain discrete Takagi-Sugeno (T-S) fuzzy tems with state delay is addressed. First, by constructing an appropriate basis-dependent Lyapunov-Krasovskii function, a new delay-dependent sufficient condition on robust H∞-disturbance attenuation is presented, in which both robust stability and prescribed H∞ performance are guaranteed to be achieved. Then based on the condition, a delay-dependent robust H∞ controller design scheme is developed in term of a convex algorithm. Finally, examples are given to illustrate the effectiveness of the proposed method.
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.
Energy Technology Data Exchange (ETDEWEB)
Yan, J.-J. [Department of Computer and Communication, Shu-Te University, Kaohsiung 824, Taiwan (China)]. E-mail: jjyan@mail.stu.edu.tw; Hung, M.-L. [Department of Electrical Engineering, Far-East College, No. 49, Jung-Haw Road, Hsin-Shih Town, Tainan 744, Taiwan (China)
2006-09-15
This paper investigates a novel stability criterion for interval time-delay chaotic systems via the evolutionary programming (EP) approach. First a delay-dependent criterion is derived for ensuring the stability of degenerate time-delay systems, and then by solving eigenvalue location optimization problems, which will be defined later, the robust stability of interval time-delay systems can be guaranteed. An example is given to verify our method that yields less conservative results than those appeared in the literature.
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.
Logistic map with a delayed feedback: Stability of a discrete time-delay control of chaos.
Buchner, T; Zebrowski, J J
2001-01-01
The logistic map with a delayed feedback is studied as a generic model. The stability of the model and its bifurcation scheme is analyzed as a function of the feedback amplitude and of the delay. Stability analysis is performed semianalytically. A relation between the delay and the periodicity of the orbit, which explains why some terms used in chaos control are ineffective, was found. The consequences for chaos control are discussed. The structure of bifurcations is found to depend strongly on the parity and on the length of the delay. Boundary crisis, the tangent, the Neimark, as well as the period-doubling bifurcations occur in this system. The effective dimension of the model is also discussed.
On the controllability and observability of discrete-time linear time-delay systems
Liu, Yuan-Ming; Fong, I.-Kong
2012-04-01
This article studies the controllability and observability of discrete-time linear time-delay systems, so that the two properties can play a more fundamental role in system analysis before controller and observer design is engaged. Complete definitions of controllability and observability, which imply the stabilisability and detectability, respectively, and determine the feasibility of eigenvalue assignment, are proposed for systems with delays in both state variables and input/output signals. Necessary and sufficient criteria are developed to check the controllability and observability efficiently. The proofs are based on the equivalent expanded system, but the criteria only involve the delays and matrices of the same dimension as the original system. Finally, the duality between the suggested controllability and observability is presented.
Pola, Giordano; Di Benedetto, Maria Domenica
2010-01-01
Time-delay systems are an important class of dynamical systems that provide a solid mathematical framework to deal with many application domains of interest. In this paper we focus on nonlinear control systems with unknown and time-varying delay signals and we propose one approach to the control design of such systems, which is based on the construction of symbolic models. Symbolic models are abstract descriptions of dynamical systems in which one symbolic state and one symbolic input correspond to an aggregate of states and an aggregate of inputs. We first introduce the notion of incremental input-delay-to-state stability and characterize it by means of Liapunov-Krasovskii functionals. We then derive sufficient conditions for the existence of symbolic models that are shown to be alternating approximately bisimilar to the original system. Further results are also derived which prove the computability of the proposed symbolic models in a finite number of steps.
Effect of Time Delay on Recognition Memory for Pictures: The Modulatory Role of Emotion
Wang, Bo
2014-01-01
This study investigated the modulatory role of emotion in the effect of time delay on recognition memory for pictures. Participants viewed neutral, positive and negative pictures, and took a recognition memory test 5 minutes, 24 hours, or 1 week after learning. The findings are: 1) For neutral, positive and negative pictures, overall recognition accuracy in the 5-min delay did not significantly differ from that in the 24-h delay. For neutral and positive pictures, overall recognition accuracy in the 1-week delay was lower than in the 24-h delay; for negative pictures, overall recognition in the 24-h and 1-week delay did not significantly differ. Therefore negative emotion modulates the effect of time delay on recognition memory, maintaining retention of overall recognition accuracy only within a certain frame of time. 2) For the three types of pictures, recollection and familiarity in the 5-min delay did not significantly differ from that in the 24-h and the 1-week delay. Thus emotion does not appear to modulate the effect of time delay on recollection and familiarity. However, recollection in the 24-h delay was higher than in the 1-week delay, whereas familiarity in the 24-h delay was lower than in the 1-week delay. PMID:24971457
ACTIVE CONTROL OF A FLEXIBLE CANTILEVER PLATE WITH MULTIPLE TIME DELAYS
Institute of Scientific and Technical Information of China (English)
Longxiang Chen; Ji Pan; Guoping Cai
2008-01-01
Active control of a flexible cantilever plate with multiple time delays is investigated using the discrete optimal control method.A controller with multiple time delays is presented.In this controller,time delay effect is incorporated in the mathematical model of the dynamic system throughout the control design and no approximations and assumptions are made in the controller derivation,so the system stability is easily guaranteed.Furthermore,this controller is available for both small time delays and large time delays.The feasibility and efficiency of the proposed controller are verified through numerical simulations in the end of this paper.
The time delay in strong gravitational lensing with Gauss-Bonnet correction
Energy Technology Data Exchange (ETDEWEB)
Man, Jingyun; Cheng, Hongbo, E-mail: jingyunman@mail.ecust.edu.cn, E-mail: hbcheng@ecust.edu.cn [Department of Physics, East China University of Science and Technology, Shanghai 200237 (China)
2014-11-01
The time delay between two relativistic images in the strong gravitational lensing governed by Gauss-Bonnet gravity is studied. We make a complete analytical derivation of the expression of time delay in presence of Gauss-Bonnet coupling. With respect to Schwarzschild, the time delay decreases as a consequence of the shrinking of the photon sphere. As the coupling increases, the second term in the time delay expansion becomes more relevant. Thus time delay in strong limit encodes some new information about geometry in five-dimensional spacetime with Gauss-Bonnet correction.
Complete synchronization and generalized synchronization of one-way coupled time-delay systems.
Zhan, Meng; Wang, Xingang; Gong, Xiaofeng; Wei, G W; Lai, C-H
2003-09-01
The complete synchronization and generalized synchronization (GS) of one-way coupled time-delay systems are studied. We find that GS can be achieved by a single scalar signal, and its synchronization threshold for different delay times shows the parameter resonance effect, i.e., we can obtain stable synchronization at a smaller coupling if the delay time of the driven system is chosen such that it is in resonance with the driving system. Near chaos synchronization, the desynchronization dynamics displays periodic bursts with the period equal to the delay time of the driven system. These features can be easily applied to the recovery of time-delay systems.
Directory of Open Access Journals (Sweden)
Weihua Mao
2012-01-01
Full Text Available This paper discusses the mean-square exponential stability of uncertain neutral linear stochastic systems with interval time-varying delays. A new augmented Lyapunov-Krasovskii functional (LKF has been constructed to derive improved delay-dependent robust mean-square exponential stability criteria, which are forms of linear matrix inequalities (LMIs. By free-weight matrices method, the usual restriction that the stability conditions only bear slow-varying derivative of the delay is removed. Finally, numerical examples are provided to illustrate the effectiveness of the proposed method.
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 ρ_{tot}∝ r–γ' for the main deflector can be measured. Ideally, we require that the statistical error on γ' be less than 0.02, such that it is subdominant to other sources of random and systematic uncertainties. We find that survey data will likely have sufficient depth and resolution to meet the target only for the brighter gravitational lens systems, comparable to those discovered by the SDSS survey. For fainter systems, that will be discovered by current and future surveys, targeted follow-up will be required. Furthermore, the exposure time required with upcoming facilitites such as JWST, the Keck Next Generation Adaptive
Su, Huan; Mao, Xuerong; Li, Wenxue
2016-11-01
This paper is concerned with the asymptotical stabilization for a class of unstable delay differential equations. Continuous-time delayed feedback controller (C-TDFC) and discrete-time delayed feedback controller (D-TDFC) are presented and studied, respectively. To our best knowledge, applying Hopf bifurcation theory to delay differential equations with D-TDFC is original and meaningful. The difficulty brought by the introduction of sampling period has been overcome. An effective control range which ensures the asymptotical stability of equilibrium for the system with C-TDFC is obtained. Sequently, another effective control range for the system with D-TDFC is gotten, which approximates the one of C-TDFCS provided that the sampling period is sufficiently small. Meanwhile, efforts are paid to estimate a bound on sampling period. Finally, the theoretical results are applied to a physiological system to illustrate the effectiveness of the two control ranges.
Wideband RF beamforming: architectures, time-delays and CMOS implementations
Garakoui, Seyed Kasra
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 effec
More relaxed condition for dynamics of discrete time delayed Hopfield neural networks
Institute of Scientific and Technical Information of China (English)
Zhang Qiang
2008-01-01
The dynamics of discrete time delayed Hopfield neural networks is investigated.By using a difference inequality combining with the linear matrix inequality,a sufficient condition ensuring global exponential stability of the unique equilibrium point of the networks is found.The result obtained holds not only for constant delay but also for time-varying delays.
Estimating the Lyapunov spectrum of time delay feedback systems from scalar time series.
Hegger, R
1999-08-01
On the basis of a recently developed method for modeling time delay systems, we propose a procedure to estimate the spectrum of Lyapunov exponents from a scalar time series. It turns out that the spectrum is approximated very well and allows for good estimates of the Lyapunov dimension even if the sampling rate of the time series is so low that the infinite dimensional tangent space is spanned quite sparsely.
Synchronization transitions in coupled time-delay electronic circuits with a threshold nonlinearity.
Srinivasan, K; Senthilkumar, D V; Murali, K; Lakshmanan, M; Kurths, J
2011-06-01
Experimental observations of typical kinds of synchronization transitions are reported in unidirectionally coupled time-delay electronic circuits with a threshold nonlinearity and two time delays, namely feedback delay τ(1) and coupling delay τ(2). We have observed transitions from anticipatory to lag via complete synchronization and their inverse counterparts with excitatory and inhibitory couplings, respectively, as a function of the coupling delay τ(2). The anticipating and lag times depend on the difference between the feedback and the coupling delays. A single stability condition for all the different types of synchronization is found to be valid as the stability condition is independent of both the delays. Further, the existence of different kinds of synchronizations observed experimentally is corroborated by numerical simulations and from the changes in the Lyapunov exponents of the coupled time-delay systems.
Theory and numerics of vibrational resonance in Duffing oscillators with time-delayed feedback.
Jeevarathinam, C; Rajasekar, S; Sanjuán, M A F
2011-06-01
The influence of linear time-delayed feedback on vibrational resonance is investigated in underdamped and overdamped Duffing oscillators with double-well and single-well potentials driven by both low frequency and high frequency periodic forces. This task is performed through both theoretical approach and numerical simulation. Theoretically determined values of the amplitude of the high frequency force and the delay time at which resonance occurs are in very good agreement with the numerical simulation. A major consequence of time-delayed feedback is that it gives rise to a periodic or quasiperiodic pattern of vibrational resonance profile with respect to the time-delayed parameter. An appropriate time delay is shown to induce a resonance in an overdamped single-well system which is otherwise not possible. For a range of values of the time-delayed parameters, the response amplitude is found to be larger than in delay-time feedback-free systems.
Delay-dependent H2 control for discrete time-delay systems with D-stability constraints
Institute of Scientific and Technical Information of China (English)
Man Sun; Yingmin Jia; Junping Du; Shiying Yuan
2008-01-01
This paper studies the problem of H2 control for a class of discrete time-delay systems with D-stability constraints. The corresponding sufficient conditions are given in terms of linear matrix inequalities. In particular, the conditions are delay-dependent, and so they are less conservative. The obtained controller can provide an upper bound for the H2 cost function. A numerical example is given to illustrate the proposed method.
Liu, Pin-Lin
2013-11-01
This paper provides an improved delay-range-dependent stability criterion for linear systems with interval time-varying delays. No model transformation and no slack matrix variable are introduced. Furthermore, overly bounding for some cross term is avoided. The resulting criterion has advantages over some previous ones in that it involves fewer matrix variables but has less conservatism, which is established theoretically. Finally, two numerical examples are given to show the effectiveness of the proposed results.
Large-time dynamics of the asymptotic Lohe model with a small time-delay
Choi, Sun-Ho; Ha, Seung-Yeal
2015-10-01
We study the asymptotic behavior of an ensemble of identical Lohe oscillators on the unit sphere {{{S}}}d in the presence of small time delay interaction effects. When there is no time delay, the ensemble of identical Lohe oscillators collapses asymptotically to a one-cluster ensemble on the sphere; its asymptotic dynamics are governed by linear motion on the unit sphere with a constant natural velocity. We show that the presence of a small time delay can induce rich dynamical features such as asymptotic changes in the velocity and asymptotic low-dimensional dynamics in high-dimensional cases. For d = 1, the Lohe dynamics is equivalent to the Kuramoto dynamics via polar coordinates. In this case, the modified asymptotic frequency is uniquely determined by an implicit relation based on the natural frequency, coupling strength, and time delay. For d = 3, we show that the dynamics of identical Lohe oscillators converges to the Kuramoto dynamics for properly chosen initial configurations. We also provide several numerical simulations to confirm our analytical results.
LONG-TIME BEHAVIOR OF A CLASS OF REACTION DIFFUSION EQUATIONS WITH TIME DELAYS
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The present paper devotes to the long-time behavior of a class of reaction diffusion equations with delays under Dirichlet boundary conditions. The stability and global attractability for the zero solution are provided, and the existence, stability and attractability for the positive stationary solution are also obtained.
Directory of Open Access Journals (Sweden)
Ewa Smoleń
2017-02-01
Full Text Available Background: Working time is a non-renewable and important element in the management of an organization. The implementation of changes in the structure of working time may be facilitated by the insight into activities undertaken by employees during work. Such an approach plays an important role since the effective use of time improves the quality of care, prevents timewasting and optimizes the use of the full potential of employees, including nurses. The objective of the study was to determine the structure of working time of pediatric nurses in hospital wards of 2 referential levels. Material and Methods: The study was conducted in 2 wards (2nd and 3rd levels of reference in the Regional Specialist Children’s Hospital in Olsztyn. The research method involved the measurement of working time, as well as continuous and snap-shot observation techniques. Standardized research instruments were used in the study; 8 continuous observations and 2333 snap-shot observations were carried out. Results: In the structure of working time of pediatric nurses indirect nursing-related activities predominated (52.2%. Direct nursing made 28.7% of the working time. The nurses devoted the smallest amount of time to coordination and organization – 8%. The percentage of time associated with non-duty activities and breaks at work was 11.1%. In direct nursing activities associated with diagnosing (9% and treatment (11.7% prevailed. In indirect nursing activities pertaining to documentation of activities related to direct nursing made 24.6%. Conclusions: Pediatric nurses devote insufficient amount of time to direct nursing. Activities associated with documentation of activities related to direct nursing, preparation for direct nursing, as well as treatment and diagnosing predominate in the working time structure of nurses. Med Pr 2017;68(1:95–103
On Extended Dissipativity of Discrete-Time Neural Networks With Time Delay.
Feng, Zhiguang; Zheng, Wei Xing
2015-12-01
In this brief, the problem of extended dissipativity analysis for discrete-time neural networks with time-varying delay is investigated. The definition of extended dissipativity of discrete-time neural networks is proposed, which unifies several performance measures, such as the H∞ performance, passivity, l2 - l∞ performance, and dissipativity. By introducing a triple-summable term in Lyapunov function, the reciprocally convex approach is utilized to bound the forward difference of the triple-summable term and then the extended dissipativity criterion for discrete-time neural networks with time-varying delay is established. The derived condition guarantees not only the extended dissipativity but also the stability of the neural networks. Two numerical examples are given to demonstrate the reduced conservatism and effectiveness of the obtained results.
Global exponential stability conditions for generalized state-space systems with time-varying delays
Energy Technology Data Exchange (ETDEWEB)
Yu, K.-W. [Department of Marine Engineering, National Kaohsiung Marine University, Kaohsiung 811, Taiwan (China)], E-mail: kwyu@mail.nkmu.edu.tw; Lien, C.-H. [Department of Marine Engineering, National Kaohsiung Marine University, Kaohsiung 811, Taiwan (China)], E-mail: chlien.ee@msa.hinet.net
2008-05-15
A unified approach is proposed to deal with the exponential stability for generalized state-space systems with time-varying delays. Many systems models can be regarded as special cases of the considered systems; such as neutral time-delay systems and delayed cellular neural networks. Delay-dependent stability criteria are proposed to guarantee the global exponential stability for generalized state-space systems with two cases of uncertainties. Two numerical examples are given to show the effectiveness of our method.
Zhu, Quanxin; Cao, Jinde
2011-04-01
This paper is concerned with the adaptive synchronization problem for a class of stochastic delayed neural networks. Based on the LaSalle invariant principle of stochastic differential delay equations and the stochastic analysis theory as well as the adaptive feedback control technique, a linear matrix inequality approach is developed to derive some novel sufficient conditions achieving complete synchronization of unidirectionally coupled stochastic delayed neural networks. In particular, the synchronization criterion considered in this paper is the globally almost surely asymptotic stability of the error dynamical system, which has seldom been applied to investigate the synchronization problem. Moreover, the delays proposed in this paper are time-varying delays and distributed delays, which have rarely been used to study the synchronization problem for coupled stochastic delayed neural networks. Therefore, the results obtained in this paper are more general and useful than those given in the previous literature. Finally, two numerical examples and their simulations are provided to demonstrate the effectiveness of the theoretical results.
Nurses' daily life: gender relations from the time spent in hospital
Directory of Open Access Journals (Sweden)
Audrey Vidal Pereira
2015-10-01
Full Text Available Objective: to analyze the everyday life of nurses through the sexual work division as well as through interdependence relations and the time in hospital.Method: quanti-qualitative study, based on the Time Use Survey and in Norbert Elias's Configuration Theory of Interdependencies. Daily shifts distribution record, directed by 42 participants - with self-confrontation - by interviews which drew dialogues on subjective aspects of the everyday experiences related to use of time, based on a job at a university hospital. The theoretical intake that founded data analysis was based on concepts of conflicts of interest, power struggles, sexual work division and polychronic-monochronic concepts - whether the work environment demands multitasking nurses or not.Results: time records allowed to observe differences between the groups studied, useful to identify conflicts, tensions, power struggles and gender inequalities in interviewees' everyday affairs that do not only affect physical and mental health, but also their way of life.Conclusion: the analytical path pointed out the need for public policies that promote equity in gender relations, keeping at sight the exercise of plural discourses and tolerant stances capable to respect differences between individual and collective time.
Nurses' daily life: gender relations from the time spent in hospital1
Pereira, Audrey Vidal
2015-01-01
Objective: to analyze the everyday life of nurses through the sexual work division as well as through interdependence relations and the time in hospital. Method: quanti-qualitative study, based on the Time Use Survey and in Norbert Elias's Configuration Theory of Interdependencies. Daily shifts distribution record, directed by 42 participants - with self-confrontation - by interviews which drew dialogues on subjective aspects of the everyday experiences related to use of time, based on a job at a university hospital. The theoretical intake that founded data analysis was based on concepts of conflicts of interest, power struggles, sexual work division and polychronic-monochronic concepts - whether the work environment demands multitasking nurses or not. Results: time records allowed to observe differences between the groups studied, useful to identify conflicts, tensions, power struggles and gender inequalities in interviewees' everyday affairs that do not only affect physical and mental health, but also their way of life. Conclusion: the analytical path pointed out the need for public policies that promote equity in gender relations, keeping at sight the exercise of plural discourses and tolerant stances capable to respect differences between individual and collective time. PMID:26487146
Delay-dependent H-infinity filtering for neutral time-delay systems
Institute of Scientific and Technical Information of China (English)
Huiying LI; Guifang LI; Chengwu YANG
2006-01-01
This paper deals with the robust delay-dependent H-infinity filtering problem for neutral delay differential systems. The resulting filter is of the Luenberger observer type, and it guarantees that the filtering systems remains asymptotically stable and satisfies a prescribed H-infinity performance level. The Lyapunov stability theory and the descriptor model transformation are used for analysis of the system and are expected to be least conservative as compared with existing design methods. Some examples are provided to demonstrate the validity of proposed design approach.
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.
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.
Anticontrol of chaos in continuous-time systems via time-delay feedback.
Wang, Xiao Fan; Chen, Guanrong; Yu, Xinghuo
2000-12-01
In this paper, a systematic design approach based on time-delay feedback is developed for anticontrol of chaos in a continuous-time system. This anticontrol method can drive a finite-dimensional, continuous-time, autonomous system from nonchaotic to chaotic, and can also enhance the existing chaos of an originally chaotic system. Asymptotic analysis is used to establish an approximate relationship between a time-delay differential equation and a discrete map. Anticontrol of chaos is then accomplished based on this relationship and the differential-geometry control theory. Several examples are given to verify the effectiveness of the methodology and to illustrate the systematic design procedure. (c) 2000 American Institute of Physics.
Fundamental and Subharmonic Resonances of Harmonically Oscillation with Time Delay State Feedback
Directory of Open Access Journals (Sweden)
A.F. EL-Bassiouny
2006-01-01
Full Text Available Time delays occur in many physical systems. In particular, when automatic control is used with structural or mechanical systems, there exists a delay between measurement of the system state and corrective action. The concept of an equivalent damping related to the delay feedback is proposed and the appropriate choice of the feedback gains and the time delay is discussed from the viewpoint of vibration control. We investigate the fundamental resonance and subharmonic resonance of order one-half of a harmonically oscillation under state feedback control with a time delay. By using the multiple scale perturbation technique, the first order approximation of the resonances are derived and the effect of time delay on the resonances is investigated. The fixed points correspond to a periodic motion for the starting system and we show the external excitation-response and frequency-response curves. We analyze the effect of time delay and the other different parameters on these oscillations.
The effect of distributed time-delays on the synchronization of neuronal networks
Kachhvah, Ajay Deep
2017-01-01
Here we investigate the synchronization of networks of FitzHugh-Nagumo neurons coupled in scale-free, small-world and random topologies, in the presence of distributed time delays in the coupling of neurons. We explore how the synchronization transition is affected when the time delays in the interactions between pairs of interacting neurons are non-uniform. We find that the presence of distributed time-delays does not change the behavior of the synchronization transition significantly, vis-a-vis networks with constant time-delay, where the value of the constant time-delay is the mean of the distributed delays. We also notice that a normal distribution of delays gives rise to a transition at marginally lower coupling strengths, vis-a-vis uniformly distributed delays. These trends hold across classes of networks and for varying standard deviations of the delay distribution, indicating the generality of these results. So we conclude that distributed delays, which may be typically expected in real-world situations, do not have a notable effect on synchronization. This allows results obtained with constant delays to remain relevant even in the case of randomly distributed delays.
Stability Analysis of Uncertain Discrete-Time Piecewise Linear Systems with Time Delays
Institute of Scientific and Technical Information of China (English)
Ou Ou; Hong-Bin Zhang; Jue-Bang Yu
2009-01-01
This paper considers the stability analysis of uncertain discrete-time piecewise linear systems with time delays based on piecewise Lyapunov-Krasovskii functionals. It is shown that the stability can be established for the control systems if there is a piecewise Lyapunov-Krasovskii functional, and moreover, the functional can be obtained by solving a set of linear matrix inequalities (LMIs) that are numerically feasible. A numerical example is given to demonstrate the efficiency and advantage of the proposed method.
Wu, Yuanyuan; Cao, Jinde; Alofi, Abdulaziz; Al-Mazrooei, Abdullah; Elaiw, Ahmed
2015-09-01
This paper deals with the finite-time boundedness and stabilization problem for a class of switched neural networks with time-varying delay and parametric uncertainties. Based on Lyapunov-like function method and average dwell time technique, some sufficient conditions are derived to guarantee the finite-time boundedness of considered uncertain switched neural networks. Furthermore, the state feedback controller is designed to solve the finite-time stabilization problem. Moreover, the proposed sufficient conditions can be simplified into the form of linear matrix equalities for conveniently using Matlab LMI toolbox. Finally, two numerical examples are given to show the effectiveness of the main results.
MSW (Magnetostatic Wave) Variable Time-Delay Techniques.
1983-09-01
calculated value of 68 nS/GHz is believed to be due to experi- mental tolerances in assembling the delay lines, particularly the FVW delay line with its...ContoCommunicatiofl and IntetUigence (C31) activitieIs Teehnicoat a2nd en-netng auppouz- £V’-hWb 44e2 o6 tecnica ~t competenee i6 p’cowided to ESV Ptog-oam
Delayed sequence intubation: is it ready for prime time?
Taylor, John A; Hohl, Corinne Michele
2017-01-01
Clinical question Does delayed sequence intubation (DSI) improve preoxygenation and safety when intubating otherwise uncooperative patients? Article chosen Weingart SD, Trueger S, Wong N, et al. Delayed sequence intubation: a prospective observational study. Ann Emerg Med 2015;65(4):349-55. doi:10.1016/j.annemergmed.2014.09.025 OBJECTIVE: To investigate whether the administration of ketamine 3 minutes prior to the administration of a muscle relaxant allows for optimal preoxygenation in uncooperative patients undergoing intubation.
Delay-dependent asymptotic stability for neural networks with time-varying delays
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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.
Synchronization of High-order Discrete-time Linear Complex Networks with Time-varying Delays
Institute of Scientific and Technical Information of China (English)
HaiLong Li; JianXiang Xi; YaoQing Cao; DuoSheng Wu
2014-01-01
Synchronization of high-order discrete-time complex networks with undirected topologies is studied and the impacts of time delays are investigated. Firstly, by the state decomposition, synchronization problems are transformed into asymptotic stability ones of multiple lower dimensional time-delayed subsystems. Then, linear matrix inequality ( LMI) criteria for synchronization are given, which can guarantee the scalability of complex networks since they only include three LMI constraints independent of the number of agents. Moreover, an explicit expression of the synchronization function is presented, which can describe the synchronization behavior of all agents in complex networks. Finally, a numerical example is given to demonstrate the theoretical results, where it is shown that if the gain matrices of synchronization protocols satisfy LMI criteria for synchronization, synchronization can be achieved.
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...... using past and present estimates of the Kalman filter and calculating an optimal gain for this extrapolated measurement...... there is at hand, the designer has to make trade offs between optimality and computational burden of the filter. In this paper various methods in the literature along with a new method proposed by the authors will be presented and compared. The new method is based on “extrapolating” the measurement to present time...
Local Stability of AIDS Epidemic Model Through Treatment and Vertical Transmission with Time Delay
Novi W, Cascarilla; Lestari, Dwi
2016-02-01
This study aims to explain stability of the spread of AIDS through treatment and vertical transmission model. Human with HIV need a time to positively suffer AIDS. The existence of a time, human with HIV until positively suffer AIDS can be delayed for a time so that the model acquired is the model with time delay. The model form is a nonlinear differential equation with time delay, SIPTA (susceptible-infected-pre AIDS-treatment-AIDS). Based on SIPTA model analysis results the disease free equilibrium point and the endemic equilibrium point. The disease free equilibrium point with and without time delay are local asymptotically stable if the basic reproduction number is less than one. The endemic equilibrium point will be local asymptotically stable if the time delay is less than the critical value of delay, unstable if the time delay is more than the critical value of delay, and bifurcation occurs if the time delay is equal to the critical value of delay.
Attochirp-corrected photo ionization time delays using coincidence attosecond streaking
Sabbar, M; Boge, R; Lucchini, M; Gallmann, L; Cirelli, C; Keller, U
2014-01-01
Recent measurements have demonstrated the possibility of probing single-photon ionization time delays of electrons originating from different initial states [1,2]. Here, we show for the first time the importance of the temporal structure of the ionizing single attosecond pulse (i.e. attochirp) in the extraction of time delays in attosecond streaking experiments. We have demonstrated this by measuring the time delay between valence electrons from different atomic species by combining attosecond streaking with a coincidence detection scheme. This novel technique allows for the simultaneous measurement of both species under identical conditions. We find that the attochirp introduces an artificial time delay that may exceed the atomic time delay and present a general procedure, which corrects for this contribution. Our analysis, exemplarily applied to argon (Ar) and neon (Ne), reveals an energy-dependent atomic time delay of a few tens of attoseconds in agreement with theoretical predictions.
Stability Tests of Positive Fractional Continuous-time Linear Systems with Delays
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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.
Shen, Nicole T; Maw, Anna; Tmanova, Lyubov L; Pino, Alejandro; Ancy, Kayley; Crawford, Carl V; Simon, Matthew S; Evans, Arthur T
2017-06-01
Systematic reviews have provided evidence for the efficacy of probiotics in preventing Clostridium difficile infection (CDI), but guidelines do not recommend probiotic use for prevention of CDI. We performed an updated systematic review to help guide clinical practice. We searched MEDLINE, EMBASE, International Journal of Probiotics and Prebiotics, and The Cochrane Library databases for randomized controlled trials evaluating use of probiotics and CDI in hospitalized adults taking antibiotics. Two reviewers independently extracted data and assessed risk of bias and overall quality of the evidence. Primary and secondary outcomes were incidence of CDI and adverse events, respectively. Secondary analyses examined the effects of probiotic species, dose, timing, formulation, duration, and study quality. We analyzed data from 19 published studies, comprising 6261 subjects. The incidence of CDI in the probiotic cohort, 1.6% (54 of 3277), was lower than of controls, 3.9% (115 of 2984) (P probiotic users was 0.42 (95% confidence interval, 0.30-0.57; I(2) = 0.0%). Meta-regression analysis demonstrated that probiotics were significantly more effective if given closer to the first antibiotic dose, with a decrement in efficacy for every day of delay in starting probiotics (P = .04); probiotics given within 2 days of antibiotic initiation produced a greater reduction of risk for CDI (relative risk, 0.32; 95% confidence interval, 0.22-0.48; I(2) = 0%) than later administration (relative risk, 0.70; 95% confidence interval, 0.40-1.23; I(2) = 0%) (P = .02). There was no increased risk for adverse events among patients given probiotics. The overall quality of the evidence was high. In a systematic review with meta-regression analysis, we found evidence that administration of probiotics closer to the first dose of antibiotic reduces the risk of CDI by >50% in hospitalized adults. Future research should focus on optimal probiotic dose, species, and formulation. Systematic
Institute of Scientific and Technical Information of China (English)
Renji Han; Wei Jiang
2009-01-01
The problem of delay-dependent robust stability for uncertain linear singular neu-tral systems with time-varying and distributed delays is investigated. The uncertain-ties under consideration are norm bounded, and possibly time varying. Some new stability criteria, which are simpler and less conservative than existing results, are derived based on a new class of Lyapunov-Krasovskii functionals combined with the descriptor model transformation and the decomposition technique of coefficient matrix and formulated in the form of a linear matrix inequalitys (LMIs). Also, the criteria can be easily checked by the Matlab LMI toolbox.
Dynamical behaviors in time-delay systems with delayed feedback and digitized coupling
Mitra, Chiranjit; Ambika, G.; Banerjee, Soumitro
2014-12-01
We consider a network of delay dynamical systems connected in a ring via unidirectional positive feedback with constant delay in coupling. For the specific case of Mackey-Glass systems on the ring topology, we capture the phenomena of amplitude death, isochronous synchronization and phase-flip bifurcation as the relevant parameters are tuned. Using linear stability analysis and master stability function approach, we predict the region of amplitude death and synchronized states respectively in the parameter space and study the nature of transitions between the different states. For a large number of systems in the same dynamical configuration, we observe splay states, mixed splay states and phase locked clusters. We extend the study to the case of digitized coupling and observe that these emergent states still persist. However, the sampling and quantization reduce the regions of amplitude death and induce phase-flip bifurcation.
On Delay-independent Stability Criteria for Linear Time-delay Systems
Institute of Scientific and Technical Information of China (English)
Ai-Guo Wu; Guang-Ren Duan
2007-01-01
Several LMI representations for delay-independence stability are proposed by applying Projection Lemma and the socalled "Small Scalar Method". These criteria realize the elimination of the products coupling the system matrices and Lyapunov matrices by introducing some additional matrices. When they are applied to robust stability analysis for polytopic uncertain systems,the vertex-dependent Lyapunov functions are allowed, so less conservative results can be obtained. A numerical example is employed to illustrate the effect of these proposed criteria.
Institute of Scientific and Technical Information of China (English)
Yang Dai; YunZe Cai; Xiao-Ming Xu
2009-01-01
Exponential estimates and sufficient conditions for the exponential synchronization of complex dynamical networks with bounded time-varying delays are given in terms of linear matrix inequalities (LMIs). A generalized complex networks model involving both neutral delays and retarded ones is presented. The exponential synchronization problem of the complex networks is converted equivalently into the exponential stability problem of a group of uncorrelated delay functional differential equations with mixed time-varying delays. By utilizing the free weighting matrix technique, a less conservative delay-dependent synchronization criterion is derived. An illustrative example is provided to demonstrate the effectiveness of the proposed method.
Zhang, Wei; Li, Chuandong; Huang, Tingwen; He, Xing
2015-12-01
Synchronization of an array of linearly coupled memristor-based recurrent neural networks with impulses and time-varying delays is investigated in this brief. Based on the Lyapunov function method, an extended Halanay differential inequality and a new delay impulsive differential inequality, some sufficient conditions are derived, which depend on impulsive and coupling delays to guarantee the exponential synchronization of the memristor-based recurrent neural networks. Impulses with and without delay and time-varying delay are considered for modeling the coupled neural networks simultaneously, which renders more practical significance of our current research. Finally, numerical simulations are given to verify the effectiveness of the theoretical results.
Spatial Patterns of a Predator-Prey System of Leslie Type with Time Delay
Wang, Caiyun; Chang, Lili; Liu, Huifeng
2016-01-01
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. PMID:26930573
A NEW SLIDING MODE CONTROL FOR A CLASS OF UNCERTAIN TIME-DELAY CHAOTIC SYSTEMS
Institute of Scientific and Technical Information of China (English)
LI LI-XIANG; PENG HAI-PENG; GUAN BAO-ZHU; XU JIN-MING
2001-01-01
We propose a new sliding mode control scheme for a class of uncertain time-delay chaotic systems. It is shown that a linear time invariant system with the desired system dynamics is used as a reference model for the output of a time-delay chaotic system to track. A sliding mode controller is then designed to drive the output of the time-delay chaotic system to track the desired linear system. On the sliding mode, the output of the controlled time-delay chaotic system can behave like the desired linear system. A simulation example is given in support of the proposed control scheme.
Time Delay of a Chirped Light Pulse After Transmitting a Fabry-Pérot Interferometer
Institute of Scientific and Technical Information of China (English)
夏光琼; 吴正茂; 陈建国
2002-01-01
We have theoretically investigated the time delay of a chirped light pulse, defined as the temporal difference of for an interferometer of known parameters, the chirp of the light pulse makes the time delay become intensively smaller. The mismatch between the central frequency of the light pulse and the resonance frequency of the interferometer also has an influence on the time delay. Under some circumstances, this mismatch will induce a time delay smaller than t0 that is defined as the one-way traverse time of the light inside the interferometer.
Spatial Patterns of a Predator-Prey System of Leslie Type with Time Delay.
Wang, Caiyun; Chang, Lili; Liu, Huifeng
2016-01-01
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.
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.
Synthesis of nonlinear discrete control systems via time-delay affine Takagi-Sugeno fuzzy models.
Chang, Wen-Jer; Chang, Wei
2005-04-01
The affine Takagi-Sugeno (TS) fuzzy model played a more important role in nonlinear control because it can be used to approximate the nonlinear systems more than the homogeneous TS fuzzy models. Besides, it is known that the time delays exist in physical systems and the previous works did not consider the time delay effects in the analysis of affine TS fuzzy models. Hence a parallel distributed compensation based fuzzy controller design issue for discrete time-delay affine TS fuzzy models is considered in this paper. The time-delay effect is considered in the discrete affine TS fuzzy models and the stabilization issue is developed for the nonlinear time-delay systems. Finally, a numerical simulation for a time-delayed nonlinear truck-trailer system is given to show the applications of the present approach.
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.
Liu, Hongjian; Wang, Zidong; Shen, Bo; Alsaadi, Fuad E.
2016-07-01
This paper deals with the robust H∞ state estimation problem for a class of memristive recurrent neural networks with stochastic time-delays. The stochastic time-delays under consideration are governed by a Bernoulli-distributed stochastic sequence. The purpose of the addressed problem is to design the robust state estimator such that the dynamics of the estimation error is exponentially stable in the mean square, and the prescribed ? performance constraint is met. By utilizing the difference inclusion theory and choosing a proper Lyapunov-Krasovskii functional, the existence condition of the desired estimator is derived. Based on it, the explicit expression of the estimator gain is given in terms of the solution to a linear matrix inequality. Finally, a numerical example is employed to demonstrate the effectiveness and applicability of the proposed estimation approach.
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.
Compensation for time-delayed feedback bang-bang control of quasi-integrable Hamiltonian systems
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The stochastic averaging method for quasi-integrable Hamiltonian systems with time-delayed feedback bang-bang control is first introduced. Then, two time delay compensation methods, namely the method of changing control force amplitude (CFA) and the method of changing control delay time (CDT), are proposed. The conditions applicable to each compensation method are discussed. Finally, an example is worked out in detail to illustrate the application and effectiveness of the proposed methods and the two compensation methods in combination.
Simple stability conditions of linear discrete time systems with multiple delay
Directory of Open Access Journals (Sweden)
Stojanović Sreten B.
2010-01-01
Full Text Available In this paper we have established a new Lyapunov-Krasovskii method for linear discrete time systems with multiple time delay. Based on this method, two sufficient conditions for delay-independent asymptotic stability of the linear discrete time systems with multiple delays are derived in the shape of Lyapunov inequality. Numerical examples are presented to demonstrate the applicability of the present approach.
Real-time random delay compensation with prediction-based digital redesign.
Zhang, Yongpeng; Cofie, Penrose; Ajuzie, Augustine N; Zhang, Jian; Akujuobi, Cajetan M
2011-04-01
Today's technological demands require challenging control solutions such as real-time applications of Networked Control System (NCS). However, due to communication protocol and shared data bus, NCS experiences uncertain and unpredictable time delays in both input and output channels. These delays cause asynchronization between the controller and the plant thereby degrading the performance of closed-loop control systems. To address this problem, this paper proposes to utilize digital redesign technique to provide real-time random delay compensation.
CAN LARGE TIME DELAYS OBSERVED IN LIGHT CURVES OF CORONAL LOOPS BE EXPLAINED IN IMPULSIVE HEATING?
Energy Technology Data Exchange (ETDEWEB)
Lionello, Roberto; Linker, Jon A.; Mikić, Zoran [Predictive Science, Inc., 9990 Mesa Rim Rd., Ste. 170, San Diego, CA 92121-3933 (United States); Alexander, Caroline E.; Winebarger, Amy R., E-mail: lionel@predsci.com, E-mail: linkerj@predsci.com, E-mail: mikicz@predsci.com, E-mail: caroline.e.alexander@nasa.gov, E-mail: amy.r.winebarger@nasa.gov [NASA Marshall Space Flight Center, ZP 13, Huntsville, AL 35805 (United States)
2016-02-20
The light curves of solar coronal loops often peak first in channels associated with higher temperatures and then in those associated with lower temperatures. The delay times between the different narrowband EUV channels have been measured for many individual loops and recently for every pixel of an active region observation. The time delays between channels for an active region exhibit a wide range of values. The maximum time delay in each channel pair can be quite large, i.e., >5000 s. These large time delays make-up 3%–26% (depending on the channel pair) of the pixels where a trustworthy, positive time delay is measured. It has been suggested that these time delays can be explained by simple impulsive heating, i.e., a short burst of energy that heats the plasma to a high temperature, after which the plasma is allowed to cool through radiation and conduction back to its original state. In this paper, we investigate whether the largest observed time delays can be explained by this hypothesis by simulating a series of coronal loops with different heating rates, loop lengths, abundances, and geometries to determine the range of expected time delays between a set of four EUV channels. We find that impulsive heating cannot address the largest time delays observed in two of the channel pairs and that the majority of the large time delays can only be explained by long, expanding loops with photospheric abundances. Additional observations may rule out these simulations as an explanation for the long time delays. We suggest that either the time delays found in this manner may not be representative of real loop evolution, or that the impulsive heating and cooling scenario may be too simple to explain the observations, and other potential heating scenarios must be explored.
Travelling wave solutions for some time-delayed equations through factorizations
Energy Technology Data Exchange (ETDEWEB)
Fahmy, E.S. [King Saud University, Women Students Medical Studies and Sciences Sections, Mathematics Department, P.O. Box 22452, Riyadh 11495 (Saudi Arabia)], E-mail: esfahmy@operamail.com
2008-11-15
In this work, we use factorization method to find explicit particular travelling wave solutions for the following important nonlinear second-order partial differential equations: The generalized time-delayed Burgers-Huxley, time-delayed convective Fishers, and the generalized time-delayed Burgers-Fisher. Using the particular solutions for these equations we find the general solutions, two-parameter solution, as special cases.
Synchronization of Different Fractional Order Time-Delay Chaotic Systems Using Active Control
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.
Chaos control via TDFC in time-delayed systems: The harmonic balance approach
Energy Technology Data Exchange (ETDEWEB)
Vasegh, Nastaran [Faculty of Electrical Engineering, K.N. Toosi University of Technology, PO Box 16315-1355, Tehran (Iran, Islamic Republic of)], E-mail: vasegh@eetd.kntu.ac.ir; Khaki Sedigh, Ali [Faculty of Electrical Engineering, K.N. Toosi University of Technology, PO Box 16315-1355, Tehran (Iran, Islamic Republic of)
2009-01-12
This Letter deals with the problem of designing time-delayed feedback controllers (TDFCs) to stabilize unstable equilibrium points and periodic orbits for a class of continuous time-delayed chaotic systems. Harmonic balance approach is used to select the appropriate controller parameters: delay time and feedback gain. The established theoretical results are illustrated via a case study of the well-known Logistic model.
OUTPUT VARIABLE STRUCTURE CONTROL FOR TIME-INVARIANT LINEAR TIME-DELAY SINGULAR SYSTEM
Institute of Scientific and Technical Information of China (English)
Jifeng GUO; Cunchen GAO
2007-01-01
Synthesis and design of output variable structure controller for time-invariant linear time-delay singular system are studied. In the case that the system is regular and the system index is one, switching function with integral compensator and variable structure controller are designed, which guarantee that the sliding mode is asymptotically stable and the solution trajectory of the system arrives at the switching manifold in limited time. The design method is applicable to the systems which can be regularized. Finally, a numerical example is given to demonstrate effectiveness and simplicity of the design method.
Data-based controllability analysis of discrete-time linear time-delay systems
Liu, Yang; Chen, Hong-Wei; Lu, Jian-Quan
2014-11-01
In this paper, a data-based method is used to analyse the controllability of discrete-time linear time-delay systems. By this method, one can directly construct a controllability matrix using the measured state data without identifying system parameters. Hence, one can save time in practice and avoid corresponding identification errors. Moreover, its calculation precision is higher than some other traditional approaches, which need to identify unknown parameters. Our methods are feasible to the study of characteristics of deterministic systems. A numerical example is given to show the advantage of our results.
Finite-time synchronization of fractional-order memristor-based neural networks with time delays.
Velmurugan, G; Rakkiyappan, R; Cao, Jinde
2016-01-01
In this paper, we consider the problem of finite-time synchronization of a class of fractional-order memristor-based neural networks (FMNNs) with time delays and investigated it potentially. By using Laplace transform, the generalized Gronwall's inequality, Mittag-Leffler functions and linear feedback control technique, some new sufficient conditions are derived to ensure the finite-time synchronization of addressing FMNNs with fractional order α:1neural networks. Finally, three numerical examples are presented to show the effectiveness of our proposed theoretical results.
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.
A Sliding Mode Control for Uncertain Time-delay Systems
Institute of Scientific and Technical Information of China (English)
WU Jun-sheng; WENG Zheng-xin; TIAN Zuo-hua; SHI Song-jiao
2008-01-01
By means of the feasibility of some linear matrix inequalities (LMIs), delay dependeat sufficient condition is derived for the existence of a linear sliding surface, which guarantees quadratic stability of the reduced-order equivalent system restricted to the sliding surface. And a reaching motion controller is proposed. A numerical simulation shows the effectiveness of the approach.
Semistability of Nonlinear Systems Having a Continuum of Equilibria and Time-Varying Delays
Hui, Qing
2010-01-01
In this paper, we develop a semistability analysis framework for nonlinear systems with time-varying delays with applications to stability analysis of multiagent dynamic networks with consensus protocols in the presence of unknown heterogeneous time-varying delays along the communication links. We show that for such a nonlinear system having a continuum of equilibria, if the system asymptotically converges to a constant time-delay system and this new system is semistable, then the original time-varying delay system is semistable, provided that the delays are just bounded, not necessarily differentiable. In proving our results, we extend the limiting equation approach to the time-varying delay systems and also develop some new convergence results for functional differential equations.
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....
The time delay in strong gravitational lensing with Gauss-Bonnet correction
Man, Jingyun
2014-01-01
The time delay between two relativistic images in the strong gravitational lensing governed by Gauss-Bonnet gravity is studied. We derive and calculate the expression of time delay due to the Gauss-Bonnet coupling. It is shown that the time delay for two images with larger space each other is longer. We also find that the ratio of Gauss-Bonnet coefficient and the mass of gravitational source changes in the region like $\\frac{\\alpha}{M}\\in[0,2)$. The time delay is divergent with $\\frac{\\alpha}{M}\\longrightarrow 2$.
Effects of Nonlinear Time-Delay on a Stochastic Asymmetric System
Institute of Scientific and Technical Information of China (English)
WANG Jiu-Yun; ZHU Chun-Lian; JIA Ya; LI Jia-Rong
2006-01-01
We numerically investigate the effects of nonlinear time-delay on the stochastic system. With the delay time increasing, it is found that the peak of probability distribution in low steady states is decreased, and the peak of probability distribution in high steady states is increased. The mean of state variable, the normalized variance, and the normalized autocorrelation function which quantifies the concentrated degree are slowly varied for small delay time. However, the mean of state variable is rapidly increased, and the normalized variance and the normalized autocorrelation function is rapidJy decreased for large delay time.
Containment consensus with measurement noises and time-varying communication delays
Institute of Scientific and Technical Information of China (English)
周峰; 王正杰; 范宁军
2015-01-01
In this paper, we consider the containment consensus control problem for multi-agent systems with measurement noises and time-varying communication delays under directed networks. By using stochastic analysis tools and algebraic graph theory, we prove that the followers can converge to the convex hull spanned by the leaders in the sense of mean square if the allowed upper bound of the time-varying delays satisfies a certain sufficient condition. Moreover, the time-varying delays are asymmetric for each follower agent, and the time-delay-dependent consensus condition is derived. Finally, numerical simulations are provided to illustrate the effectiveness of the obtained theoretical results.
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....
Attosecond time delay in valence photoionization and photorecombination of argon: a TDLDA study
Magrakvelidze, Maia; Dixit, Gopal; Ivanov, Misha; Chakraborty, Himadri S
2015-01-01
We determine and analyze the quantum phases and time delays in photoionization and photorecombination of valence 3p and 3s electrons of argon using the Kohn-Sham local density functional approach. The time-dependent local density approximation (TDLDA) is used to account for the electron correlation. Resulting attosecond Wigner-Smith time delays show excellent agreements with two recent independent experiments on argon that measured the relative 3s-3p time delay in photoionization [Physical Review Letters {\\bf 106}, 143002 (2011)] and the delay in 3p photorecombination [Physical Review Letters {\\bf 112}, 153002 (2014)
Stability analysis of fractional-order Hopfield neural networks with time delays.
Wang, Hu; Yu, Yongguang; Wen, Guoguang
2014-07-01
This paper investigates the stability for fractional-order Hopfield neural networks with time delays. Firstly, the fractional-order Hopfield neural networks with hub structure and time delays are studied. Some sufficient conditions for stability of the systems are obtained. Next, two fractional-order Hopfield neural networks with different ring structures and time delays are developed. By studying the developed neural networks, the corresponding sufficient conditions for stability of the systems are also derived. It is shown that the stability conditions are independent of time delays. Finally, numerical simulations are given to illustrate the effectiveness of the theoretical results obtained in this paper.
Extracting messages masked by chaotic signals of time-delay systems.
Zhou, C; Lai, C H
1999-07-01
We show how to extract messages masked by a chaotic signal of a time-delay system with very high dimensions and many positive Lyapunov exponents. Using a special embedding coordinate, the infinite-dimensional phase space of the time-delay system is projected onto a special three-dimensional space, which enables us to identify the time delay of the system from the transmitted signal and reconstruct the chaotic dynamics to unmask the hidden message successfully. The message extraction procedure is illustrated by simulations with the Mackey-Glass time-delay system for two types of masking schemes and different kinds of messages.
Stability and Performance of First-Order Linear Time-Delay Feedback Systems: An Eigenvalue Approach
Directory of Open Access Journals (Sweden)
Shu-An He
2011-01-01
Full Text Available Linear time-delay systems with transcendental characteristic equations have infinitely many eigenvalues which are generally hard to compute completely. However, the spectrum of first-order linear time-delay systems can be analyzed with the Lambert function. This paper studies the stability and state feedback stabilization of first-order linear time-delay system in detail via the Lambert function. The main issues concerned are the rightmost eigenvalue locations, stability robustness with respect to delay time, and the response performance of the closed-loop system. Examples and simulations are presented to illustrate the analysis results.
On Robust Stability of a Class of Uncertain Nonlinear Systems with Time-Varying Delay
Institute of Scientific and Technical Information of China (English)
NIAN Xiao-hong
2002-01-01
The problem of robust stability of a class of uncertain nonlinear dynamical systems with time-delay is considered. Based on the assumption that the nominal system is stable, some sufficient conditions onrobust stability of uncertain nonlinear dynamical systems with time-delay are derived. Some analytical methods and a type of Lyapunov functional are used to investigate such sufficient conditions. The results obtained in this paper are applicable to perturbed time-delay systems with unbounded time-varying delay.Some previous results are improved and a numerical example is given to demonstrate the validity of our results.
Kraft, Manuel; Hein, Sven M.; Lehnert, Judith; Schöll, Eckehard; Hughes, Stephen; Knorr, Andreas
2016-08-01
Quantum coherent feedback control is a measurement-free control method fully preserving quantum coherence. In this paper we show how time-delayed quantum coherent feedback can be used to control the degree of squeezing in the output field of a cavity containing a degenerate parametric oscillator. We focus on the specific situation of Pyragas-type feedback control where time-delayed signals are fed back directly into the quantum system. Our results show how time-delayed feedback can enhance or decrease the degree of squeezing as a function of time delay and feedback strength.
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.
Institute of Scientific and Technical Information of China (English)
无
2011-01-01
This paper proposed a design method for delay-dependent robust H-infinity filter of linear systems with uncertainty and time-varying interval delay.The proposed method was shown to be much simpler than existing ones while giving significant improvement to the existing results.The key step in the method was to construct a special type of Lyapunov functional for the filter design problem.Unlike the existing techniques,the proposed method employed neither free weighting matrices nor any model transformation,le...
Time delay estimation in the ultrasonic flowmeter in the oil well
Sun, Jian; Lin, Weijun; Zhang, Chengyu; Shen, Zhihui; Zhang, Hailan
2010-01-01
A new prototype of ultrasonic flowmeter used in the oil well is presented. The flowmeter depends on the time delay between the propagating times of the downstream and upstream ultrasonic pulses. The ultrasonic passageway is slanted to prevent the disadvantage introduced by the high viscosity of the oil. Two method of time delay estimation: threshold and cross-correlation are both studied and realized.
Pneumatic shutoff and time-delay valve operates at controlled rate
Horning, J. L.; Tomlinson, L. E.
1966-01-01
Shutoff and time delay valve, which incorporates a metering spool that moves at constant velocity under pneumatic pressure and spring compression, increases fluid-flow area at a uniform rate. Diaphragm areas, control cavity volume, and bleed-orifice size may be varied to give any desired combination of time delay and spool travel time.
The effect of distributed time-delays on the synchronization of neuronal networks
Kachhvah, Ajay Deep
2016-01-01
Here we investigate the synchronization of networks of FitzHugh-Nagumo neurons coupled in scale-free, small-world and random topologies, in the presence of distributed time delays in the coupling of neurons. We explore how the synchronization transition is affected when the time delays in the interactions between pairs of interacting neurons are non-uniform. We find that the presence of distributed time-delays does not change the behavior of the synchronization transition significantly, vis-a-vis networks with constant time-delay, where the value of the constant time-delay is the mean of the distributed delays. We also notice that a normal distribution of delays gives rise to a transition at marginally lower coupling strengths, vis-a-vis uniformly distributed delays. These trends hold across classes of networks and for varying standard deviations of the delay distribution, indicating the generality of these results. So we conclude that distributed delays, which may be typically expected in real-world situatio...
Revathi, V M; Balasubramaniam, P
2016-04-01
In this paper, the [Formula: see text] filtering problem is treated for N coupled genetic oscillator networks with time-varying delays and extrinsic molecular noises. Each individual genetic oscillator is a complex dynamical network that represents the genetic oscillations in terms of complicated biological functions with inner or outer couplings denote the biochemical interactions of mRNAs, proteins and other small molecules. Throughout the paper, first, by constructing appropriate delay decomposition dependent Lyapunov-Krasovskii functional combined with reciprocal convex approach, improved delay-dependent sufficient conditions are obtained to ensure the asymptotic stability of the filtering error system with a prescribed [Formula: see text] performance. Second, based on the above analysis, the existence of the designed [Formula: see text] filters are established in terms of linear matrix inequalities with Kronecker product. Finally, numerical examples including a coupled Goodwin oscillator model are inferred to illustrate the effectiveness and less conservatism of the proposed techniques.
Energy Technology Data Exchange (ETDEWEB)
Rezaie, B; Motlagh, M R Jahed; Analoui, M [Iran University of Science and Technology, Narmak, Tehran (Iran, Islamic Republic of); Khorsandi, S [Amirkabir University of Technology, Hafez St., Tehran (Iran, Islamic Republic of)], E-mail: brezaie@iust.ac.ir
2009-10-02
This paper deals with the problem of Hopf bifurcation control for a class of nonlinear time-delay systems. A dynamic delayed feedback control method is utilized for stabilizing unstable fixed points near Hopf bifurcation. Using a linear stability analysis, we show that under certain conditions of the control parameters, and without changing the operating point of the system, the onset of Hopf bifurcation is delayed. Meanwhile, by applying the center manifold theorem and the normal form theory, we obtain formulas for determining the direction of the Hopf bifurcation and the stability of bifurcating periodic solutions of the closed loop system. Numerical simulations are given to justify the validity of the analytical results for the system controlled by the proposed method.
Temporal Dynamics of the Interaction between Reward and Time Delay during Intertemporal Choice
Gui, Dan-Yang; Li, Jin-Zhen; Li, Xiaoli; Luo, Yue-jia
2016-01-01
Intertemporal choice involves the processes of valuation and choice. Choice is often the result of subjective valuation, in which reward is integrated with time delay. Here, using event-related potential (ERP) signals as temporal hallmarks, we aim to investigate temporal dynamics of how reward interacts with time delay during a delayed discounting task. We found that participants preferred immediate rewards when delayed rewards were small or over long-term delays. Our ERP results suggested that the P200 component reflected an initial valuation of reward and time delay, while the frontal N2 component correlated with individual choices of immediate option of rewards. The LPP component was modulated by the N2 component. These findings demonstrate that the N2 component is the key component in temporal dynamics of the interaction between reward and time valuation.
Finite-time stabilization control for discontinuous time-delayed networks: New switching design.
Zhang, Ling-Ling; Huang, Li-Hong; Cai, Zuo-Wei
2016-03-01
This paper discusses the finite-time stabilization problem for time-varying delayed neural networks (DNNs) with discontinuous activation functions. By using fixed point theory and set-valued analysis, we establish the existence theorem of equilibrium point. In order to stabilize the states of this class of discontinuous DNNs in finite time, we design two different kinds of switching controllers which are described by discontinuous functions. Under the framework of Filippov solutions, several new and effective criteria are derived to realize finite-time stabilization of discontinuous DNNs based on the famous finite-time stability theory. Besides, the upper bounds of the settling time of stabilization are estimated. Numerical examples are finally provided to illustrate the correctness of the proposed design method and theoretical results.
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.
Synchronization in coupled time-delayed systems with parameter mismatch and noise perturbation
Sun, Yongzheng; Ruan, Jiong
2009-12-01
In this paper, a design of coupling and effective sufficient condition for stable complete synchronization and antisynchronization of a class of coupled time-delayed systems with parameter mismatch and noise perturbation are established. Based on the LaSalle-type invariance principle for stochastic differential equations, sufficient conditions guaranteeing complete synchronization and antisynchronization with constant time delay are developed. Also delay-dependent sufficient conditions for the case of time-varying delay are derived by using the Lyapunov approach for stochastic differential equations. Numerical examples fully support the analytical results.
Mean Square Exponential Stability of Stochastic Switched System with Interval Time-Varying Delays
Directory of Open Access Journals (Sweden)
Manlika Rajchakit
2012-01-01
Full Text Available This paper is concerned with mean square exponential stability of switched stochastic system with interval time-varying delays. The time delay is any continuous function belonging to a given interval, but not necessary to be differentiable. By constructing a suitable augmented Lyapunov-Krasovskii functional combined with Leibniz-Newton’s formula, a switching rule for the mean square exponential stability of switched stochastic system with interval time-varying delays and new delay-dependent sufficient conditions for the mean square exponential stability of the switched stochastic system are first established in terms of LMIs. Numerical example is given to show the effectiveness of the obtained result.
Time delay and noise explaining the behaviour of the cell growth in fermentation process
Energy Technology Data Exchange (ETDEWEB)
Ayuobi, Tawfiqullah; Rosli, Norhayati [Faculty of Industrial Sciences and Technology, Universiti Malaysia Pahang, Lebuhraya Tun Razak, 26300 Gambang, Pahang (Malaysia); Bahar, Arifah [Department of Mathematical Sciences, Faculty of Science, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Salleh, Madihah Md [Department of Biotechnology Industry, Faculty of Biosciences and Bioengineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia)
2015-02-03
This paper proposes to investigate the interplay between time delay and external noise in explaining the behaviour of the microbial growth in batch fermentation process. Time delay and noise are modelled jointly via stochastic delay differential equations (SDDEs). The typical behaviour of cell concentration in batch fermentation process under this model is investigated. Milstein scheme is applied for solving this model numerically. Simulation results illustrate the effects of time delay and external noise in explaining the lag and stationary phases, respectively for the cell growth of fermentation process.
Lag synchronization of chaotic systems with time-delayed linear terms via impulsive control
Indian Academy of Sciences (India)
Ranchao Wu; Dongxu Cao
2013-11-01
In this paper, the lag synchronization of chaotic systems with time-delayed linear terms via impulsive control is investigated. Based on the stability theory of impulsive delayed differential equations, some sufficient conditions are obtained guaranteeing the synchronized behaviours between two delayed chaotic systems. 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.
Time delay and noise explaining the behaviour of the cell growth in fermentation process
Ayuobi, Tawfiqullah; Rosli, Norhayati; Bahar, Arifah; Salleh, Madihah Md
2015-02-01
This paper proposes to investigate the interplay between time delay and external noise in explaining the behaviour of the microbial growth in batch fermentation process. Time delay and noise are modelled jointly via stochastic delay differential equations (SDDEs). The typical behaviour of cell concentration in batch fermentation process under this model is investigated. Milstein scheme is applied for solving this model numerically. Simulation results illustrate the effects of time delay and external noise in explaining the lag and stationary phases, respectively for the cell growth of fermentation process.
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.
Stability analysis and design of amplitude death induced by a time-varying delay connection
Energy Technology Data Exchange (ETDEWEB)
Konishi, Keiji, E-mail: konishi@eis.osakafu-u.ac.j [Department of Electrical and Information Systems, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan); Kokame, Hideki; Hara, Naoyuki [Department of Electrical and Information Systems, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531 (Japan)
2010-01-18
The present Letter considers amplitude death in a pair of oscillators coupled by a time-varying delay connection. A linear stability analysis is used to derive the boundary curves for amplitude death in a connection parameters space. The delay time can be arbitrarily long for certain amplitude of delay variation and coupling strength. A simple systematic procedure for designing such variation and strength is provided. The theoretical results are verified by a numerical simulation.
Global exponential stabilisation of a class of nonlinear time-delay systems
Benabdallah, Amel; Echi, Nadhem
2016-12-01
This paper deals with the state and output feedback stabilisation problems for a family of nonlinear time-delay systems satisfying some relaxed triangular-type condition. The delay is supposed to be constant. Parameter-dependent control laws are used to compensate for the nonlinearities. Based on the Lyapunov-Krasovskii functionals, global exponential stability of the closed-loop systems is achieved. Finally, an extension to nonlinear time-varying delay systems is given.
Hopf Bifurcation of a Differential-Algebraic Bioeconomic Model with Time Delay
Directory of Open Access Journals (Sweden)
Xiaojian Zhou
2012-01-01
Full Text Available We investigate the dynamics of a differential-algebraic bioeconomic model with two time delays. Regarding time delay as a bifurcation parameter, we show that a sequence of Hopf bifurcations occur at the positive equilibrium as the delay increases. Using the theories of normal form and center manifold, we also give the explicit algorithm for determining the direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions. Numerical tests are provided to verify our theoretical analysis.
True Time Delay Scheme for X-band Phased Array Radar
Institute of Scientific and Technical Information of China (English)
LI Zheng
2007-01-01
The system of a true-time delay line for X-band and 8-unit phased array antennas is introduced. Changing the length of a chirp grating with piezotranslator(PZT), the variable delay is obtained. The scheme is applied to X-band phased array radar whose searching data rate is 56/s. It is simulated that the beam squinting is influenced by the error of real time delay. The relation between the beamforming mode and its modifying volt is discussed.
Stochastic stability of linear time-delay system with Markovian jumping parameters
Directory of Open Access Journals (Sweden)
K. Benjelloun
1997-01-01
Full Text Available This paper deals with the class of linear time-delay systems with Markovian jumping parameters (LTDSMJP. We mainly extend the stability results of the deterministic class of linear systems with time-delay to this class of systems. A delay-independent necessary condition and sufficient conditions for checking the stochastic stability are established. A sufficient condition is also given. Some numerical examples are provided to show the usefulness of the proposed theoretical results.
Delay decomposition at a single server queue with constant service time and multiple inputs
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.
Institute of Scientific and Technical Information of China (English)
Su Weiwei; Chen Yiming
2008-01-01
Delay-dependent robust stability of cellular neural networks with time-varying discrete and distributed time-varying delays is considered. Based on Lyapunov stability theory and the linear matrix inequality (LMIs) technique, delay-dependent stability criteria are derived in terms of LMIs avoiding bounding certain cross terms, which often leads to conservatism. The effectiveness of the proposed stability criteria and the improvement over the existing results are illustrated in the numerical examples.
Correcting for Interstellar Scattering Delay in High-precision Pulsar Timing: Simulation Results
Palliyaguru, Nipuni; McLaughlin, Maura; Demorest, Paul; Jones, Glenn
2015-01-01
Light travel time changes due to gravitational waves 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 gravitational wave. Cyclic spectroscopy, first described in an astronomical context by Demorest (2011), is a potenti...
Wang, Qi; Gong, Yubing; Wu, Yanan
2015-04-01
Autapse is a special synapse that connects a neuron to itself. In this work, we numerically study the effect of chemical autapse on the synchronization of Newman-Watts Hodgkin-Huxley neuron network with time delays. It is found that the neurons exhibit synchronization transitions as autaptic self-feedback delay is varied, and the phenomenon enhances when autaptic self-feedback strength increases. Moreover, this phenomenon becomes strongest when network time delay or coupling strength is optimal. It is also found that the synchronization transitions by network time delay can be enhanced by autaptic activity and become strongest when autaptic delay is optimal. These results show that autaptic delayed self-feedback activity can intermittently enhance and reduce the synchronization of the neuronal network and hence plays an important role in regulating the synchronization of the neurons. These findings could find potential implications for the information processing and transmission in neural systems.
Institute of Scientific and Technical Information of China (English)
Zhang Min-Min; Wang Can-Jun; Mei Dong-Cheng
2011-01-01
The effects of the time delay on the upper bound of the time derivative of information entropy are investigated in a time-delayed dynamical system driven by correlated noise.Using the Markov approximation of the stochastic delay differential equations and the Schwartz inequality principle,we obtain an analytical expression for the upper bound UB(t) of the time derivative of the information entropy.The results show that there is a critical value of T (delay time),and UB(t) presents opposite behaviours on difference sides of the critical value.For the case of the weak additive noise,T can induce a reentrance transition.Delay time T also causes a reversal behaviour in UB(t)-λ plot,where λ denotes the decree of the correlation between the two noises.
Xie, Huijuan; Gong, Yubing; Wang, Qi
2016-06-01
In this paper, we numerically study how time delay induces multiple coherence resonance (MCR) and synchronization transitions (ST) in adaptive Hodgkin-Huxley neuronal networks with spike-timing dependent plasticity (STDP). It is found that MCR induced by time delay STDP can be either enhanced or suppressed as the adjusting rate Ap of STDP changes, and ST by time delay varies with the increase of Ap, and there is optimal Ap by which the ST becomes strongest. It is also found that there are optimal network randomness and network size by which ST by time delay becomes strongest, and when Ap increases, the optimal network randomness and optimal network size increase and related ST is enhanced. These results show that STDP can either enhance or suppress MCR and optimal STDP can enhance ST induced by time delay in the adaptive neuronal networks. These findings provide a new insight into STDP's role for the information processing and transmission in neural systems.
2012-01-01
Background Noise, nonlinear interactions, positive and negative feedbacks within signaling pathways, time delays, protein oligomerization, and crosstalk between different pathways are main characters in the regulatory of gene expression. However, only a single noise source or only delay time in the deterministic model is considered in the gene transcriptional regulatory system in previous researches. The combined effects of correlated noise and time delays on the gene regulatory model still remain not to be fully understood. Results The roles of time delay on gene switch and stochastic resonance are systematically explored based on a famous gene transcriptional regulatory model subject to correlated noise. Two cases, including linear time delay appearing in the degradation process (case I) and nonlinear time delay appearing in the synthesis process (case II) are considered, respectively. For case I: Our theoretical results show that time delay can induce gene switch, i.e., the TF-A monomer concentration shifts from the high concentration state to the low concentration state ("on"→"off"). With increasing the time delay, the transition from "on" to "off" state can be further accelerated. Moreover, it is found that the stochastic resonance can be enhanced by both the time delay and correlated noise intensity. However, the additive noise original from the synthesis rate restrains the stochastic resonance. It is also very interesting that a resonance bi-peaks structure appears under large additive noise intensity. The theoretical results by using small-delay time-approximation approach are consistent well with our numerical simulation. For case II: Our numerical simulation results show that time delay can also induce the gene switch, however different with case I, the TF-A monomer concentration shifts from the low concentration state to the high concentration state ("off"→"on"). With increasing time delay, the transition from "on" to "off" state can be further
An Electroluminescence Delay Time Model of Bilayer Organic Light-Emitting Diodes
Institute of Scientific and Technical Information of China (English)
LI Hong-Jian; ZHU Ru-Hui; LI Xue-Yong; YANG Bing-Chu
2007-01-01
@@ Based on the mechanism of injection, transport and recombination of the charge carriers, we develop a model to calculate the delay time of electroluminescence (EL) from bilayer organic light emitting diodes. The effect of injection, transport and recombination processes on the EL delay time is discussed, and the relationship between the internal interface barrier and the recombination time is revealed. The results show that the EL delay time is dominated by the recombination process at lower applied voltage and by the transport process at higher applied voltage. When the internal interface barrier varies from 0.15 eV to 0.3 eV, the recombination delay time increases rapidly, while the internal interface barrier exceeds about 0.3eV, the dependence of the recombination delay time on applied voltage is almost undiversified, which may serve as a guideline for designing of a high-speed EL response device.
Song, Haiyu; Yu, Li; Zhang, Dan; Zhang, Wen-An
2012-12-01
This paper is concerned with the finite-time quantized H∞ control problem for a class of discrete-time switched time-delay systems with time-varying exogenous disturbances. By using the sector bound approach and the average dwell time method, sufficient conditions are derived for the switched system to be finite-time bounded and ensure a prescribed H∞ disturbance attenuation level, and a mode-dependent quantized state feedback controller is designed by solving an optimization problem. Two illustrative examples are provided to demonstrate the effectiveness of the proposed theoretical results.