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Sample records for interaural time-delay sensitivity

  1. Dynamic binaural sound localization based on variations of interaural time delays and system rotations.

    PubMed

    Baumann, Claude; Rogers, Chris; Massen, Francis

    2015-08-01

    This work develops the mathematical model for a steerable binaural system that determines the instantaneous direction of a sound source in space. The model combines system angular speed and interaural time delays (ITDs) in a differential equation, which allows monitoring the change of source position in the binaural reference frame and therefore resolves the confusion about azimuth and elevation. The work includes the analysis of error propagation and presents results from a real-time application that was performed on a digital signal processing device. Theory and experiments demonstrate that the azimuthal angle to the sound source is accurately yielded in the case of horizontal rotations, whereas the elevation angle is estimated with large uncertainty. This paper also proves the equivalence of the ITD derivative and the Doppler shift appearing between the binaurally captured audio signals. The equation of this Doppler shift is applicable for any kind of motion. It shows that weak binaural pitch differences may represent an additional cue in localization of sound. Finally, the paper develops practical applications from this relationship, such as the synthesizing of binaural images of pure and complex tones emitted by a moving source, and the generation of multiple frequency images for binaural beat experiments. PMID:26328682

  2. The across frequency independence of equalization of interaural time delay in the equalization-cancellation model of binaural unmasking

    NASA Astrophysics Data System (ADS)

    Akeroyd, Michael A.

    2004-08-01

    The equalization stage in the equalization-cancellation model of binaural unmasking compensates for the interaural time delay (ITD) of a masking noise by introducing an opposite, internal delay [N. I. Durlach, in Foundations of Modern Auditory Theory, Vol. II., edited by J. V. Tobias (Academic, New York, 1972)]. Culling and Summerfield [J. Acoust. Soc. Am. 98, 785-797 (1995)] developed a multi-channel version of this model in which equalization was ``free'' to use the optimal delay in each channel. Two experiments were conducted to test if equalization was indeed free or if it was ``restricted'' to the same delay in all channels. One experiment measured binaural detection thresholds, using an adaptive procedure, for 1-, 5-, or 17-component tones against a broadband masking noise, in three binaural configurations (N0S180, N180S0, and N90S270). The thresholds for the 1-component stimuli were used to normalize the levels of each of the 5- and 17-component stimuli so that they were equally detectable. If equalization was restricted, then, for the 5- and 17-component stimuli, the N90S270 and N180S0 configurations would yield a greater threshold than the N0S180 configurations. No such difference was found. A subsequent experiment measured binaural detection thresholds, via psychometric functions, for a 2-component complex tone in the same three binaural configurations. Again, no differential effect of configuration was observed. An analytic model of the detection of a complex tone showed that the results were more consistent with free equalization than restricted equalization, although the size of the differences was found to depend on the shape of the psychometric function for detection.

  3. Sensitivity to spectral interaural intensity difference cues in space-specific neurons of the barn owl.

    PubMed

    Arthur, B J

    2004-02-01

    Barn owls use interaural intensity differences to localize sounds in the vertical plane. At a given elevation the magnitude of the interaural intensity difference cue varies with frequency, creating an interaural intensity difference spectrum of cues which is characteristic of that direction. To test whether space-specific cells are sensitive to spectral interaural intensity difference cues, pure-tone interaural intensity difference tuning curves were taken at multiple different frequencies for single neurons in the external nucleus of the inferior colliculus. For a given neuron, the interaural intensity differences eliciting the maximum response (the best interaural intensity differences) changed with the frequency of the stimulus by an average maximal difference of 9.4+/-6.2 dB. The resulting spectral patterns of these neurally preferred interaural intensity differences exhibited a high degree of similarity to the acoustic interaural intensity difference spectra characteristic of restricted regions in space. Compared to stimuli whose interaural intensity difference spectra matched the preferred spectra, stimuli with inverted spectra elicited a smaller response, showing that space-specific neurons are sensitive to the shape of the spectrum. The underlying mechanism is an inhibition for frequency-specific interaural intensity differences which differ from the preferred spectral pattern. Collectively, these data show that space-specific neurons are sensitive to spectral interaural intensity difference cues and support the idea that behaving barn owls use such cues to precisely localize sounds. PMID:14669025

  4. Sensitivity to Envelope Interaural Time Differences at High Modulation Rates

    PubMed Central

    Bleeck, Stefan; McAlpine, David

    2015-01-01

    Sensitivity to interaural time differences (ITDs) conveyed in the temporal fine structure of low-frequency tones and the modulated envelopes of high-frequency sounds are considered comparable, particularly for envelopes shaped to transmit similar fidelity of temporal information normally present for low-frequency sounds. Nevertheless, discrimination performance for envelope modulation rates above a few hundred Hertz is reported to be poor—to the point of discrimination thresholds being unattainable—compared with the much higher (>1,000 Hz) limit for low-frequency ITD sensitivity, suggesting the presence of a low-pass filter in the envelope domain. Further, performance for identical modulation rates appears to decline with increasing carrier frequency, supporting the view that the low-pass characteristics observed for envelope ITD processing is carrier-frequency dependent. Here, we assessed listeners’ sensitivity to ITDs conveyed in pure tones and in the modulated envelopes of high-frequency tones. ITD discrimination for the modulated high-frequency tones was measured as a function of both modulation rate and carrier frequency. Some well-trained listeners appear able to discriminate ITDs extremely well, even at modulation rates well beyond 500 Hz, for 4-kHz carriers. For one listener, thresholds were even obtained for a modulation rate of 800 Hz. The highest modulation rate for which thresholds could be obtained declined with increasing carrier frequency for all listeners. At 10 kHz, the highest modulation rate at which thresholds could be obtained was 600 Hz. The upper limit of sensitivity to ITDs conveyed in the envelope of high-frequency modulated sounds appears to be higher than previously considered. PMID:26721926

  5. Effects of time delay and pitch control sensitivity in the flared landing

    NASA Technical Reports Server (NTRS)

    Berthe, C. J.; Chalk, C. R.; Wingarten, N. C.; Grantham, W.

    1986-01-01

    Between December 1985 and January 1986, a flared landing program was conducted, using the USAF Total In-Flight simulator airplane, to examine time delay effects in a formal manner. Results show that as pitch sensitivity is increased, tolerance to time delay decreases. With the proper selection of pitch sensitivity, Level I performance was maintained with time delays ranging from 150 milliseconds to greater than 300 milliseconds. With higher sensitivity, configurations with Level I performance at 150 milliseconds degraded to level 2 at 200 milliseconds. When metrics of time delay and pitch sensitivity effects are applied to enhance previously developed predictive criteria, the result is an improved prediction technique which accounts for significant closed loop items.

  6. Direction-dependent spectral sensitivity and interaural spectral difference in a dolphin: evoked potential study.

    PubMed

    Supin AYa; Popov, V V

    1993-06-01

    Sensitivity and interaural intensity difference (IID) dependence on sound frequency and direction was measured in an Amazon river dolphin Inia geoffrensis by recording the auditory nerve evoked response from the body surface. The maximal sensitivity in the horizontal plane was found when the sound direction was 5 degrees to 10 degrees ipsilateral to the recorded ear; the direction dependence of sensitivity was more pronounced at higher frequencies than at lower ones. The IID reached its peak at small azimuthal angles (7.5 degrees to 15 degrees) and higher sound frequencies (100 kHz), or at large azimuthal angles (30 degrees to 45 degrees) and lower sound frequencies (20 to 30 kHz). Each sound direction featured its specific pattern of spectral sensitivity and of interaural spectral difference. The interaural spectral difference fluctuated within a range of more than 20 dB depending on sound direction. The data indicate that interaural intensity as well as spectral difference may be cues for binaural localization of sound direction by dolphins. PMID:8326074

  7. Envelope enhancement increases cortical sensitivity to interaural envelope delays with acoustic and electric hearing.

    PubMed

    Hartley, Douglas E H; Isaiah, Amal

    2014-01-01

    Evidence from human psychophysical and animal electrophysiological studies suggests that sensitivity to interaural time delay (ITD) in the modulating envelope of a high-frequency carrier can be enhanced using half-wave rectified stimuli. Recent evidence has shown potential benefits of equivalent electrical stimuli to deaf individuals with bilateral cochlear implants (CIs). In the current study we assessed the effects of envelope shape on ITD sensitivity in the primary auditory cortex of normal-hearing ferrets, and profoundly-deaf animals with bilateral CIs. In normal-hearing animals, cortical sensitivity to ITDs (±1 ms in 0.1-ms steps) was assessed in response to dichotically-presented i) sinusoidal amplitude-modulated (SAM) and ii) half-wave rectified (HWR) tones (100-ms duration; 70 dB SPL) presented at the best-frequency of the unit over a range of modulation frequencies. In separate experiments, adult ferrets were deafened with neomycin administration and bilaterally-implanted with intra-cochlear electrode arrays. Electrically-evoked auditory brainstem responses (EABRs) were recorded in response to bipolar electrical stimulation of the apical pair of electrodes with singe biphasic current pulses (40 µs per phase) over a range of current levels to measure hearing thresholds. Subsequently, we recorded cortical sensitivity to ITDs (±800 µs in 80-µs steps) within the envelope of SAM and HWR biphasic-pulse trains (40 µs per phase; 6000 pulses per second, 100-ms duration) over a range of modulation frequencies. In normal-hearing animals, nearly a third of cortical neurons were sensitive to envelope-ITDs in response to SAM tones. In deaf animals with bilateral CI, the proportion of ITD-sensitive cortical neurons was approximately a fifth in response to SAM pulse trains. In normal-hearing and deaf animals with bilateral CI the proportion of ITD sensitive units and neural sensitivity to ITDs increased in response to HWR, compared with SAM stimuli. Consequently

  8. Human cortical sensitivity to interaural level differences in low- and high-frequency sounds.

    PubMed

    Salminen, Nelli H

    2015-02-01

    Interaural level difference (ILD) is used as a cue in horizontal sound source localization. In free field, the magnitude of ILD depends on frequency: it is more prominent at high than low frequencies. Here, a magnetoencephalography experiment was conducted to test whether the sensitivity of the human auditory cortex to ILD is also frequency-dependent. Robust cortical sensitivity to ILD was found that could not be explained by monaural level effects, but this sensitivity did not differ between low- and high-frequency stimuli. This is consistent with previous psychoacoustical investigations showing that performance in ILD discrimination is not dependent on frequency. PMID:25698049

  9. Sensitivity to interaural envelope correlation changes in bilateral cochlear-implant users.

    PubMed

    Goupell, Matthew J; Litovsky, Ruth Y

    2015-01-01

    Provision of bilateral cochlear implants (CIs) to people who are deaf is partially justified by improved abilities to understand speech in noise when comparing bilateral vs unilateral listening conditions. However, bilateral CI listeners generally show only monaural head shadow with little improvement in speech understanding due to binaural unmasking. Sensitivity to change in interaural envelope correlation, which is related to binaural speech unmasking, was investigated. Bilateral CI users were tested with bilaterally synchronized processors at single, pitch-matched electrode pairs. First, binaural masking level differences (BMLDs) were measured using 1000 pulse-per-second (pps) carriers, yielding BMLDs of 11.1 ± 6.5 and 8.5 ± 4.2 dB for 10- and 50-Hz bandwidth masking noises, respectively. Second, envelope correlation change just-noticeable differences (JNDs) were measured. Stimuli presented at 1000 pps yielded lower JNDs than those presented at 100 pps. Furthermore, perfectly correlated reference stimuli produced lower JNDs than uncorrelated references, and uncorrelated references generally produced immeasurable JNDs. About 25% of JNDs measured in the CI listeners were in the range of JNDs observed in normal-hearing listeners presented CI simulations. In conclusion, CI listeners can perceive changes in interaural envelope correlation, but the poor performance may be a major limiting factor in binaural unmasking tested to date in realistic listening environments. PMID:25618064

  10. Sensitivity to interaural envelope correlation changes in bilateral cochlear-implant users

    PubMed Central

    Goupell, Matthew J.; Litovsky, Ruth Y.

    2015-01-01

    Provision of bilateral cochlear implants (CIs) to people who are deaf is partially justified by improved abilities to understand speech in noise when comparing bilateral vs unilateral listening conditions. However, bilateral CI listeners generally show only monaural head shadow with little improvement in speech understanding due to binaural unmasking. Sensitivity to change in interaural envelope correlation, which is related to binaural speech unmasking, was investigated. Bilateral CI users were tested with bilaterally synchronized processors at single, pitch-matched electrode pairs. First, binaural masking level differences (BMLDs) were measured using 1000 pulse-per-second (pps) carriers, yielding BMLDs of 11.1 ± 6.5 and 8.5 ± 4.2 dB for 10- and 50-Hz bandwidth masking noises, respectively. Second, envelope correlation change just-noticeable differences (JNDs) were measured. Stimuli presented at 1000 pps yielded lower JNDs than those presented at 100 pps. Furthermore, perfectly correlated reference stimuli produced lower JNDs than uncorrelated references, and uncorrelated references generally produced immeasurable JNDs. About 25% of JNDs measured in the CI listeners were in the range of JNDs observed in normal-hearing listeners presented CI simulations. In conclusion, CI listeners can perceive changes in interaural envelope correlation, but the poor performance may be a major limiting factor in binaural unmasking tested to date in realistic listening environments. PMID:25618064

  11. Robust optimization for nonlinear time-delay dynamical system of dha regulon with cost sensitivity constraint in batch culture

    NASA Astrophysics Data System (ADS)

    Yuan, Jinlong; Zhang, Xu; Liu, Chongyang; Chang, Liang; Xie, Jun; Feng, Enmin; Yin, Hongchao; Xiu, Zhilong

    2016-09-01

    Time-delay dynamical systems, which depend on both the current state of the system and the state at delayed times, have been an active area of research in many real-world applications. In this paper, we consider a nonlinear time-delay dynamical system of dha-regulonwith unknown time-delays in batch culture of glycerol bioconversion to 1,3-propanediol induced by Klebsiella pneumonia. Some important properties and strong positive invariance are discussed. Because of the difficulty in accurately measuring the concentrations of intracellular substances and the absence of equilibrium points for the time-delay system, a quantitative biological robustness for the concentrations of intracellular substances is defined by penalizing a weighted sum of the expectation and variance of the relative deviation between system outputs before and after the time-delays are perturbed. Our goal is to determine optimal values of the time-delays. To this end, we formulate an optimization problem in which the time delays are decision variables and the cost function is to minimize the biological robustness. This optimization problem is subject to the time-delay system, parameter constraints, continuous state inequality constraints for ensuring that the concentrations of extracellular and intracellular substances lie within specified limits, a quality constraint to reflect operational requirements and a cost sensitivity constraint for ensuring that an acceptable level of the system performance is achieved. It is approximated as a sequence of nonlinear programming sub-problems through the application of constraint transcription and local smoothing approximation techniques. Due to the highly complex nature of this optimization problem, the computational cost is high. Thus, a parallel algorithm is proposed to solve these nonlinear programming sub-problems based on the filled function method. Finally, it is observed that the obtained optimal estimates for the time-delays are highly satisfactory

  12. Sensitivity of bilateral cochlear implant users to fine-structure and envelope interaural time differencesa

    PubMed Central

    Noel, Victor A.; Eddington, Donald K.

    2013-01-01

    Bilateral cochlear implant users have poor sensitivity to interaural time differences (ITDs) of high-rate pulse trains, which precludes use of these stimuli to convey fine-structure ITD cues. However, previous reports of single-neuron recordings in cats demonstrated good ITD sensitivity to 1000 pulses-per-second (pps) pulses when the pulses were sinusoidally amplitude modulated. The ability of modulation to restore ITD sensitivity to high-rate pulses in humans was tested by measuring ITD thresholds for three conditions: ITD encoded in the modulated carrier pulses alone, in the envelope alone, and in the whole waveform. Five of six subjects were not sensitive to ITD in the 1000-pps carrier, even with modulation. One subject's 1000-pps carrier ITD sensitivity did significantly improve due to modulation. Sensitivity to ITD encoded in the envelope was also measured as a function of modulation frequency, including at frequencies from 4 to 16 Hz where much of the speech envelope's energy and information resides. Sensitivity was best at the modulation frequency of 100 Hz and degraded rapidly outside of a narrow range. These results provide little evidence to support encoding ITD in the carrier of current bilateral processors, and suggest envelope ITD sensitivity is poor for an important segment of the speech modulation spectrum. PMID:23556598

  13. Human cortical sensitivity to interaural time difference in high-frequency sounds.

    PubMed

    Salminen, Nelli H; Altoè, Alessandro; Takanen, Marko; Santala, Olli; Pulkki, Ville

    2015-05-01

    Human sound source localization relies on various acoustical cues one of the most important being the interaural time difference (ITD). ITD is best detected in the fine structure of low-frequency sounds but it may also contribute to spatial hearing at higher frequencies if extracted from the sound envelope. The human brain mechanisms related to this envelope ITD cue remain unexplored. Here, we tested the sensitivity of the human auditory cortex to envelope ITD in magnetoencephalography (MEG) recordings. We found two types of sensitivity to envelope ITD. First, the amplitude of the auditory cortical N1m response was smaller for zero envelope ITD than for long envelope ITDs corresponding to the sound being in opposite phase in the two ears. Second, the N1m response amplitude showed ITD-specific adaptation for both fine-structure and for envelope ITD. The auditory cortical sensitivity was weaker for envelope ITD in high-frequency sounds than for fine-structure ITD in low-frequency sounds but occurred within a range of ITDs that are encountered in natural conditions. Finally, the participants were briefly tested for their behavioral ability to detect envelope ITD. Interestingly, we found a correlation between the behavioral performance and the neural sensitivity to envelope ITD. In conclusion, our findings show that the human auditory cortex is sensitive to ITD in the envelope of high-frequency sounds and this sensitivity may have behavioral relevance. PMID:25668126

  14. The Role of Conduction Delay in Creating Sensitivity to Interaural Time Differences.

    PubMed

    Carr, Catherine; Ashida, Go; Wagner, Hermann; McColgan, Thomas; Kempter, Richard

    2016-01-01

    Axons from the nucleus magnocellularis (NM) and their targets in nucleus laminaris (NL) form the circuit responsible for encoding interaural time difference (ITD). In barn owls, NL receives bilateral inputs from NM, such that axons from the ipsilateral NM enter NL dorsally, while contralateral axons enter from the ventral side. These afferents act as delay lines to create maps of ITD in NL. Since delay-line inputs are characterized by a precise latency to auditory stimulation, but the postsynaptic coincidence detectors respond to ongoing phase difference, we asked whether the latencies of a local group of axons were identical, or varied by multiples of the inverse of the frequency they respond to, i.e., to multiples of 2π phase. Intracellular recordings from NM axons were used to measure delay-line latencies in NL. Systematic shifts in conduction delay within NL accounted for the maps of ITD, but recorded latencies of individual inputs at nearby locations could vary by 2π or 4π. Therefore microsecond precision is achieved through sensitivity to phase delays, rather than absolute latencies. We propose that the auditory system "coarsely" matches ipsilateral and contralateral latencies using physical delay lines, so that inputs arrive at NL at about the same time, and then "finely" matches latency modulo 2π to achieve microsecond ITD precision. PMID:27080659

  15. The discrimination of interaural level difference sensitivity functions: development of a taxonomic data template for modelling

    PubMed Central

    2013-01-01

    Background A major cue for the position of a high-frequency sound source in azimuth is the difference in sound pressure levels in the two ears, Interaural Level Differences (ILDs), as a sound is presented from different positions around the head. This study aims to use data classification techniques to build a descriptive model of electro-physiologically determined neuronal sensitivity functions for ILDs. The ILDs were recorded from neurons in the central nucleus of the Inferior Colliculus (ICc), an obligatory midbrain auditory relay nucleus. The majority of ICc neurons (~ 85%) show sensitivity to ILDs but with a variety of different forms that are often difficult to unambiguously separate into different information-bearing types. Thus, this division is often based on laboratory-specific and relatively subjective criteria. Given the subjectivity and non-uniformity of ILD classification methods in use, we examined if objective data classification techniques for this purpose. Our key objectives were to determine if we could find an analytical method (A) to validate the presence of four typical ILD sensitivity functions as is commonly assumed in the field, and (B) whether this method produced classifications that mapped on to the physiologically observed results. Methods The three-step data classification procedure forms the basic methodology of this manuscript. In this three-step procedure, several data normalization techniques were first tested to select a suitable normalization technique to our data. This was then followed by PCA to reduce data dimensionality without losing the core characteristics of the data. Finally Cluster Analysis technique was applied to determine the number of clustered data with the aid of the CCC and Inconsistency Coefficient values. Results The outcome of a three-step analytical data classification process was the identification of seven distinctive forms of ILD functions. These seven ILD function classes were found to map to the four

  16. Inhibition sensitive to interaural time difference in the barn owl's inferior colliculus.

    PubMed

    Albeck, Y

    1997-07-01

    In spontaneously active neurons in the external nucleus of the inferior colliculus of the barn owl, a stimulus-driven discharge was followed by a quiescent period lasting tens of milliseconds before the spontaneous activity resumed. The more favorable the interaural time difference, the longer the quiet period. The duration of the quiescent period also depended on stimulus frequency. Frequencies different from the neuron's best frequency induced shorter quiescent periods, although they could elicit similar rates of impulses. Also, the duration of the quiescent period was independent of interaural intensity difference. Thus, the quiet period is not due to an after-hyperpolarization but was an inhibitory effect that depended on the activity of other neurons. In some neurons, discharge continued after the stimulus without a quiescent period and gradually decayed over a period of 50-100 ms past the stimulus offset. The similarity between the quiescent period of the neurons mentioned above and the time course of the poststimulus discharge in these neurons suggests that these neurons serve as inhibitory interneurons. PMID:9259240

  17. Blind people are more sensitive than sighted people to binaural sound-location cues, particularly inter-aural level differences.

    PubMed

    Nilsson, Mats E; Schenkman, Bo N

    2016-02-01

    Blind people use auditory information to locate sound sources and sound-reflecting objects (echolocation). Sound source localization benefits from the hearing system's ability to suppress distracting sound reflections, whereas echolocation would benefit from "unsuppressing" these reflections. To clarify how these potentially conflicting aspects of spatial hearing interact in blind versus sighted listeners, we measured discrimination thresholds for two binaural location cues: inter-aural level differences (ILDs) and inter-aural time differences (ITDs). The ILDs or ITDs were present in single clicks, in the leading component of click pairs, or in the lagging component of click pairs, exploiting processes related to both sound source localization and echolocation. We tested 23 blind (mean age = 54 y), 23 sighted-age-matched (mean age = 54 y), and 42 sighted-young (mean age = 26 y) listeners. The results suggested greater ILD sensitivity for blind than for sighted listeners. The blind group's superiority was particularly evident for ILD-lag-click discrimination, suggesting not only enhanced ILD sensitivity in general but also increased ability to unsuppress lagging clicks. This may be related to the blind person's experience of localizing reflected sounds, for which ILDs may be more efficient than ITDs. On the ITD-discrimination tasks, the blind listeners performed better than the sighted age-matched listeners, but not better than the sighted young listeners. ITD sensitivity declines with age, and the equal performance of the blind listeners compared to a group of substantially younger listeners is consistent with the notion that blind people's experience may offset age-related decline in ITD sensitivity. PMID:26433052

  18. Spectral overlap and interaural time difference sensitivity: Possible role of binaural interference

    PubMed Central

    Brown, Christopher A.; Yost, William A.

    2015-01-01

    A follow-up experiment to those conducted by Brown and Yost [(2011). J. Acoust. Soc. Am. 130, 358–364; (2013). Basic Aspects of Hearing: Physiology and Perception (Springer, London, UK)] examined interaural time difference (ITD) discrimination for a low-frequency target noise band flanked by monotic noise bands that were either lower-frequency than the target band, higher-frequency, or both. The flanking bands were either spectrally contiguous with the target band or spectrally separated. Significant interference in ITD processing occurred in the presence of the high-frequency flanking band. Results are discussed by way of a comparison of the conditions in the present study to those in studies of binaural interference. The possible role of attention is also discussed. PMID:25994736

  19. Cochlear implant speech processor placement and compression effects on sound sensitivity and interaural level difference.

    PubMed

    Ricketts, Todd; Grantham, D Wesley; D'Haese, Patrick; Edwards, Jason; Barco, Amy

    2006-02-01

    The purpose of this investigation was to determine the impact of commonly recommended cochlear implant (CI) speech processor placements on microphone output both with and without single channel front-end compression. The impact of this compression use on interaural level difference (ILD) magnitude was also evaluated for the ear-level position. Finally, pilot localization data collected with and without single channel front-end compression was collected on seven bilateral cochlear implant recipients. The results revealed that differences in signal audibility due to clinical placement of CI speech processors in ear, shoulder, and collar positions can at least partially be offset through the use of front-end compression. These data also revealed that compression impacted ILD cues. Preliminary data indicated that some bilaterally implanted subjects were able to take advantage of the enhanced ILD cues when compression was turned off, while other bilaterally implanted subjects did not localize better in the compression-off condition. PMID:16640065

  20. Spectral overlap and interaural time difference sensitivity: possible role of binaural interference.

    PubMed

    Brown, Christopher A; Yost, William A

    2015-05-01

    A follow-up experiment to those conducted by Brown and Yost [(2011). J. Acoust. Soc. Am. 130, 358-364; (2013). Basic Aspects of Hearing: Physiology and Perception (Springer, London, UK)] examined interaural time difference (ITD) discrimination for a low-frequency target noise band flanked by monotic noise bands that were either lower-frequency than the target band, higher-frequency, or both. The flanking bands were either spectrally contiguous with the target band or spectrally separated. Significant interference in ITD processing occurred in the presence of the high-frequency flanking band. Results are discussed by way of a comparison of the conditions in the present study to those in studies of binaural interference. The possible role of attention is also discussed. PMID:25994736

  1. Electrophysiological and psychophysical asymmetries in sensitivity to interaural correlation gaps and implications for binaural integration time.

    PubMed

    Lüddemann, Helge; Kollmeier, Birger; Riedel, Helmut

    2016-02-01

    Brief deviations of interaural correlation (IAC) can provide valuable cues for detection, segregation and localization of acoustic signals. This study investigated the processing of such "binaural gaps" in continuously running noise (100-2000 Hz), in comparison to silent "monaural gaps", by measuring late auditory evoked potentials (LAEPs) and perceptual thresholds with novel, iteratively optimized stimuli. Mean perceptual binaural gap duration thresholds exhibited a major asymmetry: they were substantially shorter for uncorrelated gaps in correlated and anticorrelated reference noise (1.75 ms and 4.1 ms) than for correlated and anticorrelated gaps in uncorrelated reference noise (26.5 ms and 39.0 ms). The thresholds also showed a minor asymmetry: they were shorter in the positive than in the negative IAC range. The mean behavioral threshold for monaural gaps was 5.5 ms. For all five gap types, the amplitude of LAEP components N1 and P2 increased linearly with the logarithm of gap duration. While perceptual and electrophysiological thresholds matched for monaural gaps, LAEP thresholds were about twice as long as perceptual thresholds for uncorrelated gaps, but half as long for correlated and anticorrelated gaps. Nevertheless, LAEP thresholds showed the same asymmetries as perceptual thresholds. For gap durations below 30 ms, LAEPs were dominated by the processing of the leading edge of a gap. For longer gap durations, in contrast, both the leading and the lagging edge of a gap contributed to the evoked response. Formulae for the equivalent rectangular duration (ERD) of the binaural system's temporal window were derived for three common window shapes. The psychophysical ERD was 68 ms for diotic and about 40 ms for anti- and uncorrelated noise. After a nonlinear Z-transform of the stimulus IAC prior to temporal integration, ERDs were about 10 ms for reference correlations of ±1 and 80 ms for uncorrelated reference. Hence, a physiologically motivated

  2. Interaural intensity and latency difference in the dolphin's auditory system.

    PubMed

    Popov, V V; Supin AYa

    1991-12-01

    Binaural hearing mechanisms were measured in dolphins (Inia geoffrensis) by recording the auditory nerve evoked response from the body surface. The azimuthal position of a sound source at 10-15 degrees from the longitudinal axis elicited interaural intensity disparity up to 20 dB and interaural latency difference as large as 250 microseconds. The latter was many times greater than the acoustical interaural time delay. This latency difference seems to be caused by the intensity disparity. The latency difference seems to be an effective way of coding of intensity disparity. PMID:1816509

  3. Localization by interaural time difference (ITD): Effects of interaural frequency mismatch

    SciTech Connect

    Bonham, B.H.; Lewis, E.R.

    1999-07-01

    A commonly accepted physiological model for lateralization of low-frequency sounds by interaural time delay (ITD) stipulates that binaural comparison neurons receive input from frequency-matched channels from each ear. Here, the effects of hypothetical interaural frequency mismatches on this model are reported. For this study, the cat{close_quote}s auditory system peripheral to the binaural comparison neurons was represented by a neurophysiologically derived model, and binaural comparison neurons were represented by cross-correlators. The results of the study indicate that, for binaural comparison neurons receiving input from one cochlear channel from each ear, interaural CF mismatches may serve to either augment or diminish the effective difference in ipsilateral and contralateral axonal time delays from the periphery to the binaural comparison neuron. The magnitude of this increase or decrease in the effective time delay difference can be up to 400 {mu}s for CF mismatches of 0.2 octaves or less for binaural neurons with CFs between 250 Hz and 2.5 kHz. For binaural comparison neurons with nominal CFs near 500 Hz, the 25-{mu}s effective time delay difference caused by a 0.012-octave CF mismatch is equal to the ITD previously shown to be behaviorally sufficient for the cat to lateralize a low-frequency sound source. {copyright} {ital 1999 Acoustical Society of America.}

  4. VARIABLE TIME DELAY MEANS

    DOEpatents

    Clemensen, R.E.

    1959-11-01

    An electrically variable time delay line is described which may be readily controlled simuitaneously with variable impedance matching means coupied thereto such that reflections are prevented. Broadly, the delay line includes a signal winding about a magnetic core whose permeability is electrically variable. Inasmuch as the inductance of the line varies directly with the permeability, the time delay and characteristic impedance of the line both vary as the square root of the permeability. Consequently, impedance matching means may be varied similariy and simultaneously w:th the electrically variable permeability to match the line impedance over the entire range of time delay whereby reflections are prevented.

  5. Digital time delay

    DOEpatents

    Martin, A.D.

    1986-05-09

    Method and apparatus are provided for generating an output pulse following a trigger pulse at a time delay interval preset with a resolution which is high relative to a low resolution available from supplied clock pulses. A first lumped constant delay provides a first output signal at predetermined interpolation intervals corresponding to the desired high resolution time interval. Latching circuits latch the high resolution data to form a first synchronizing data set. A selected time interval has been preset to internal counters and corrected for circuit propagation delay times having the same order of magnitude as the desired high resolution. Internal system clock pulses count down the counters to generate an internal pulse delayed by an internal which is functionally related to the preset time interval. A second LCD corrects the internal signal with the high resolution time delay. A second internal pulse is then applied to a third LCD to generate a second set of synchronizing data which is complementary with the first set of synchronizing data for presentation to logic circuits. The logic circuits further delay the internal output signal with the internal pulses. The final delayed output signal thereafter enables the output pulse generator to produce the desired output pulse at the preset time delay interval following input of the trigger pulse.

  6. Sensitivity to Interaural Time Differences Conveyed in the Stimulus Envelope: Estimating Inputs of Binaural Neurons Through the Temporal Analysis of Spike Trains.

    PubMed

    Dietz, Mathias; Wang, Le; Greenberg, David; McAlpine, David

    2016-08-01

    Sound-source localization in the horizontal plane relies on detecting small differences in the timing and level of the sound at the two ears, including differences in the timing of the modulated envelopes of high-frequency sounds (envelope interaural time differences (ITDs)). We investigated responses of single neurons in the inferior colliculus (IC) to a wide range of envelope ITDs and stimulus envelope shapes. By a novel means of visualizing neural activity relative to different portions of the periodic stimulus envelope at each ear, we demonstrate the role of neuron-specific excitatory and inhibitory inputs in creating ITD sensitivity (or the lack of it) depending on the specific shape of the stimulus envelope. The underlying binaural brain circuitry and synaptic parameters were modeled individually for each neuron to account for neuron-specific activity patterns. The model explains the effects of envelope shapes on sensitivity to envelope ITDs observed in both normal-hearing listeners and in neural data, and has consequences for understanding how ITD information in stimulus envelopes might be maximized in users of bilateral cochlear implants-for whom ITDs conveyed in the stimulus envelope are the only ITD cues available. PMID:27294694

  7. Angular dependence of Wigner time delay: Relativistic Effects

    NASA Astrophysics Data System (ADS)

    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).

  8. Time-Delay Interferometry

    NASA Astrophysics Data System (ADS)

    Dhurandhar, Sanjeev V.; Tinto, Massimo

    2005-07-01

    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 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 and mathematical foundations of TDI as it will be implemented by the forthcoming space-based interferometers such as the Laser Interferometer Space Antenna (LISA) mission. We have purposely left out from this first version of our "Living Review" article on TDI all the results of more practical and experimental nature, as well as all the aspects of TDI that the data analysts will need to account for when analyzing the LISA TDI data combinations. Our forthcoming "second edition" of this review paper will include these topics.

  9. Binaural interaction in low-frequency neurons in inferior colliculus of the cat. I. Effects of long interaural delays, intensity, and repetition rate on interaural delay function.

    PubMed

    Kuwada, S; Yin, T C

    1983-10-01

    Detailed, quantitative studies were made of the interaural phase sensitivity of 197 neurons with low best frequency in the inferior colliculus (IC) of the barbiturate-anesthetized cat. We analyzed the responses of single cells to interaural delays in which tone bursts were delivered to the two ears via sealed earphones and the onset of the tone to one ear with respect to the other was varied. For most (80%) cells the discharge rate is a cyclic function of interaural delay at a period corresponding to that of the stimulating frequency. The cyclic nature of the interaural delay curve indicates that these cells are sensitive to the interaural phase difference. These cells are distributed throughout the low-frequency zone of the IC, but they are less numerous in the medial and caudal zones. Cells with a wide variety of response patterns will exhibit interaural phase sensitivities at stimulating frequencies up to 3,100 Hz, although above 2,500 Hz the number of such cells decrease markedly. Using dichotic stimuli we could study the cell's sensitivity to the onset delay and interaural phase independently. The large majority of IC cells respond only to changes in interaural phase, with no sensitivity to the onset delay. However, a small number (7%) of cells exhibit a sensitivity to the onset delay as well as to the interaural phase disparity, and most of these cells show an onset response. The effects of changing the stimulus intensity equally to both ears or of changing the interaural intensity difference on the mean interaural phase were studied. While some neurons are not affected by level changes, others exhibit systematic phase shifts for both average and interaural intensity variations, and there is a continuous distribution of sensitivities between these extremes. A few cells also showed systematic changes in the shape of the interaural delay curves as a function of interaural intensity difference, especially at very long delays. These shifts can be interpreted as a

  10. Time Delay of CGM Sensors

    PubMed Central

    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

  11. Comparison of Interaural Electrode Pairing Methods for Bilateral Cochlear Implants

    PubMed Central

    Dietz, Mathias

    2015-01-01

    In patients with bilateral cochlear implants (CIs), pairing matched interaural electrodes and stimulating them with the same frequency band is expected to facilitate binaural functions such as binaural fusion, localization, and spatial release from masking. Because clinical procedures typically do not include patient-specific interaural electrode pairing, it remains the case that each electrode is allocated to a generic frequency range, based simply on the electrode number. Two psychoacoustic techniques for determining interaurally paired electrodes have been demonstrated in several studies: interaural pitch comparison and interaural time difference (ITD) sensitivity. However, these two methods are rarely, if ever, compared directly. A third, more objective method is to assess the amplitude of the binaural interaction component (BIC) derived from electrically evoked auditory brainstem responses for different electrode pairings; a method has been demonstrated to be a potential candidate for bilateral CI users. Here, we tested all three measures in the same eight CI users. We found good correspondence between the electrode pair producing the largest BIC and the electrode pair producing the maximum ITD sensitivity. The correspondence between the pairs producing the largest BIC and the pitch-matched electrode pairs was considerably weaker, supporting the previously proposed hypothesis that whilst place pitch might adapt over time to accommodate mismatched inputs, sensitivity to ITDs does not adapt to the same degree. PMID:26631108

  12. Time delay in molecular photoionization

    NASA Astrophysics Data System (ADS)

    Hockett, P.; Frumker, E.; Villeneuve, D. M.; Corkum, P. B.

    2016-05-01

    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.

  13. Time delays in correlated photoemission processes

    NASA Astrophysics Data System (ADS)

    Pazourek, R.; Nagele, S.; Burgdörfer, J.

    2015-09-01

    We theoretically study time-resolved two-photon double ionization (TPDI) of helium as probed by attosecond streaking. We review recent advances in the understanding of the photoelectric effect in the time domain and discuss the differences between one- and two-photon ionization, as well as one- and two-electron emission. We perform exact ab-initio simulations for attosecond streaking experiments in the sequential TPDI regime and compare the results to the two-electron Eisenbud-Wigner-Smith delay for the process. Our calculations directly show that the timing of the emission process sensitively depends on the energy sharing between the two outgoing electrons. In particular, we identify Fano-like interferences in the relative time delay of the two emitted electrons when the sequential ionization channel occurs via intermediate excited ionic (shake-up) states. Furthermore, we find that the photoemission time delays are only weakly dependent on the relative emission angle of the ejected electrons.

  14. Time delay measurement in the frequency domain

    DOE PAGESBeta

    Durbin, Stephen M.; Liu, Shih -Chieh; Dufresne, Eric M.; Li, Yuelin; Wen, Haidan

    2015-08-06

    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 bymore » simply extending the data acquisition time.« less

  15. Time delay measurement in the frequency domain

    SciTech Connect

    Durbin, Stephen M.; Liu, Shih -Chieh; Dufresne, Eric M.; Li, Yuelin; Wen, Haidan

    2015-08-06

    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.

  16. Synchronization by small time delays

    NASA Astrophysics Data System (ADS)

    Pruessner, G.; Cheang, S.; Jensen, H. J.

    2015-02-01

    Synchronization is a phenomenon observed in all of the living and in much of the non-living world, for example in the heart beat, Huygens' clocks, the flashing of fireflies and the clapping of audiences. Depending on the number of degrees of freedom involved, different mathematical approaches have been used to describe it, most prominently integrate-and-fire oscillators and the Kuramoto model of coupled oscillators. In the present work, we study a very simple and general system of smoothly evolving oscillators, which continue to interact even in the synchronized state. We find that under very general circumstances, synchronization generically occurs in the presence of a (small) time delay. Strikingly, the synchronization time is inversely proportional to the time delay.

  17. PRECISION TIME-DELAY CIRCUIT

    DOEpatents

    Creveling, R.

    1959-03-17

    A tine-delay circuit which produces a delay time in d. The circuit a capacitor, an te back resistance, connected serially with the anode of the diode going to ground. At the start of the time delay a negative stepfunction is applied to the series circuit and initiates a half-cycle transient oscillatory voltage terminated by a transient oscillatory voltage of substantially higher frequency. The output of the delay circuit is taken at the junction of the inductor and diode where a sudden voltage rise appears after the initiation of the higher frequency transient oscillations.

  18. PRECISION TIME-DELAY GENERATOR

    DOEpatents

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

    1959-06-16

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

  19. Time delay and distance measurement

    NASA Technical Reports Server (NTRS)

    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.

  20. Observer weighting of interaural cues in positive and negative envelope slopes of amplitude-modulated waveforms.

    PubMed

    Hsieh, I-Hui; Petrosyan, Agavni; Gonçalves, Óscar F; Hickok, Gregory; Saberi, Kourosh

    2011-07-01

    The auditory system can encode interaural delays in highpass-filtered complex sounds by phase locking to their slowly modulating envelopes. Spectrotemporal analysis of interaurally time-delayed highpass waveforms reveals the presence of a concomitant interaural level cue. The current study systematically investigated the contribution of time and concomitant level cues carried by positive and negative envelope slopes of a modified sinusoidally amplitude-modulated (SAM) high-frequency carrier. The waveforms were generated from concatenation of individual modulation cycles whose envelope peaks were extended by the desired interaural delay, allowing independent control of delays in the positive and negative modulation slopes. In experiment 1, thresholds were measured using a 2-interval forced-choice adaptive task for interaural delays in either the positive or negative modulation slopes. In a control condition, thresholds were measured for a standard SAM tone. In experiment 2, decision weights were estimated using a multiple-observation correlational method in a single-interval forced-choice task for interaural delays carried simultaneously by the positive, and independently, negative slopes of the modulation envelope. In experiment 3, decision weights were measured for groups of 3 modulation cycles at the start, middle, and end of the waveform to determine the influence of onset dominance or recency effects. Results were consistent across experiments: thresholds were equal for the positive and negative modulation slopes. Decision weights were positive and equal for the time cue in the positive and negative envelope slopes. Weights were also larger for modulations cycles near the waveform onset. Weights estimated for the concomitant interaural level cue were positive for the positive envelope slope and negative for the negative slope, consistent with exclusive use of time cues. PMID:21272630

  1. Effects of binaural decorrelation on neural and behavioral processing of interaural level differences in the barn owl (Tyto alba).

    PubMed

    Egnor, S E

    2001-10-01

    The effect of binaural decorrelation on the processing of interaural level difference cues in the barn owl (Tyto alba) was examined behaviorally and electrophysiologically. The electrophysiology experiment measured the effect of variations in binaural correlation on the first stage of interaural level difference encoding in the central nervous system. The responses of single neurons in the posterior part of the ventral nucleus of the lateral lemniscus were recorded to stimulation with binaurally correlated and binaurally uncorrelated noise. No significant differences in interaural level difference sensitivity were found between conditions. Neurons in the posterior part of the ventral nucleus of the lateral lemniscus encode the interaural level difference of binaurally correlated and binaurally uncorrelated noise with equal accuracy and precision. This nucleus therefore supplies higher auditory centers with an undegraded interaural level difference signal for sound stimuli that lack a coherent interaural time difference. The behavioral experiment measured auditory saccades in response to interaural level differences presented in binaurally correlated and binaurally uncorrelated noise. The precision and accuracy of sound localization based on interaural level difference was reduced but not eliminated for binaurally uncorrelated signals. The observation that barn owls continue to vary auditory saccades with the interaural level difference of binaurally uncorrelated stimuli suggests that neurons that drive head saccades can be activated by incomplete auditory spatial information. PMID:11763957

  2. Telepresence, time delay, and adaptation

    NASA Technical Reports Server (NTRS)

    Held, Richard; Durlach, Nathaniel

    1989-01-01

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

  3. Second order Kerr-Newman time delay

    NASA Astrophysics Data System (ADS)

    He, G.; Lin, W.

    2016-01-01

    The explicit form for the post-Newtonian gravitational time delay of light signals propagating on the equatorial plane of a Kerr-Newman black hole is derived. Based on the null geodesic in Kerr-Newman spacetime, we adopt the iterative method to calculate the time delay. Our result reduces to the previous formulation for the Kerr black hole if we drop the contribution from the electrical charge. Our time-delay formula for the Reissner-Nordström geometry is different from the previous publication [Phys. Rev. D 69, 023002 (2004)], in which the largest second order contribution to the time delay is missing.

  4. Time delay plots of unflavoured baryons

    NASA Astrophysics Data System (ADS)

    Kelkar, N. G.; Nowakowski, M.; Khemchandani, K. P.; Jain, S. R.

    2004-01-01

    We explore the usefulness of the existing relations between the S-matrix and time delay in characterizing baryon resonances in pion-nucleon scattering. We draw attention to the fact that the existence of a positive maximum in time delay is a necessary criterion for the existence of a resonance and should be used as a constraint in conventional analyses which locate resonances from poles of the S-matrix and Argand diagrams. The usefulness of the time delay plots of resonances is demonstrated through a detailed analysis of the time delay in several partial waves of πN elastic scattering.

  5. 49 CFR 236.831 - Time, delay.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 4 2012-10-01 2012-10-01 false Time, delay. 236.831 Section 236.831 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Time, delay. As applied to an automatic train stop or train control system, the time which...

  6. 49 CFR 236.831 - Time, delay.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 4 2011-10-01 2011-10-01 false Time, delay. 236.831 Section 236.831 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Time, delay. As applied to an automatic train stop or train control system, the time which...

  7. 49 CFR 236.831 - Time, delay.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 4 2013-10-01 2013-10-01 false Time, delay. 236.831 Section 236.831 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Time, delay. As applied to an automatic train stop or train control system, the time which...

  8. 49 CFR 236.831 - Time, delay.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 4 2014-10-01 2014-10-01 false Time, delay. 236.831 Section 236.831 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Time, delay. As applied to an automatic train stop or train control system, the time which...

  9. 49 CFR 236.831 - Time, delay.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Time, delay. 236.831 Section 236.831 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Time, delay. As applied to an automatic train stop or train control system, the time which...

  10. Switching control and time-delay identification

    NASA Astrophysics Data System (ADS)

    Chen, Qi; Li, Xiang; Qin, Zhi-Chang; Zhong, Shun; Sun, J. Q.

    2014-12-01

    The unknown time delay makes the control design a difficult task. When the lower and upper bounds of an unknown time delay of dynamical systems are specified, one can design a supervisory control that switches among a set of controls designed for the sampled time delays in the given range so that the closed-loop system is stable and the control performance is maintained at a desirable level. In this paper, we propose to design a supervisory control to stabilize the system first. After the supervisory control converges, we start an algorithm to identify the unknown time delay, either on-line or off-line, with the known control being implemented. Examples are shown to demonstrate the stabilization and identification for linear time invariant and periodic systems with a single control time delay.

  11. Annoyance of noise stimuli in relation to the spatial factors extracted from the interaural cross-correlation function

    NASA Astrophysics Data System (ADS)

    Sato, Shin-ichi; Kitamura, Toshihiro; Ando, Yochi

    2004-10-01

    While considering auditory-brain model for subjective responses, effects of spatial factors extracted from the interaural cross-correlation function (IACF) on annoyance of noise stimuli are examined. The previously developed indices to measure sound pressure levels (SPL) and frequency characteristics cannot fully explain the psychological effects of noise. In the first experiment, subjects judged their annoyance by changing fluctuations in the magnitude of interaural cross-correlation function (IACC) and the SPL. In the second, they judged their annoyance by changing fluctuations in the interaural time delay (τIACC) and the SPL. Results show that: (1) annoyance increased by increasing the fluctuations of IACC as well as the SPL, (2) annoyance increased by increasing the fluctuations of τIACC as well as the SPL.

  12. IDENTIFYING ANOMALIES IN GRAVITATIONAL LENS TIME DELAYS

    SciTech Connect

    Congdon, Arthur B.; Keeton, Charles R.; Nordgren, C. Erik E-mail: keeton@physics.rutgers.ed

    2010-02-01

    We examine the ability of gravitational lens time delays to reveal complex structure in lens potentials. In a previous paper, we predicted how the time delay between the bright pair of images in a 'fold' lens scales with the image separation, for smooth lens potentials. Here we show that the proportionality constant increases with the quadrupole moment of the lens potential, and depends only weakly on the position of the source along the caustic. We use Monte Carlo simulations to determine the range of time delays that can be produced by realistic smooth lens models consisting of isothermal ellipsoid galaxies with tidal shear. We can then identify outliers as 'time delay anomalies'. We find evidence for anomalies in close image pairs in the cusp lenses RX J1131 - 1231 and B1422+231. The anomalies in RX J1131 - 1231 provide strong evidence for substructure in the lens potential, while at this point the apparent anomalies in B1422+231 mainly indicate that the time delay measurements need to be improved. We also find evidence for time delay anomalies in larger-separation image pairs in the fold lenses, B1608+656 and WFI 2033 - 4723, and the cusp lens RX J0911+0551. We suggest that these anomalies are caused by some combination of substructure and a complex lens environment. Finally, to assist future monitoring campaigns we use our smooth models with shear to predict the time delays for all known four-image lenses.

  13. Wigner time delay in photodetachment of negative ions

    NASA Astrophysics Data System (ADS)

    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.

  14. Gravitational lens time delays and gravitational waves

    SciTech Connect

    Frieman, J.A. Department of Astronomy Astrophysics, University of Chicago, Chicago, Illinois 60637 ); Harari, D.D.; Surpi, G.C. )

    1994-10-15

    Using Fermat's principle, we analyze the effects of very long wavelength gravitational waves upon the images of a gravitationally lensed quasar. We show that the lens equation in the presence of gravity waves is equivalent to that of a lens with a different alignment between source, deflector, and observer in the absence of gravity waves. Contrary to a recent claim, we conclude that measurements of time delays in gravitational lenses cannot serve as a method to detect or constrain a stochastic background of gravitational waves of cosmological wavelengths, because the wave-induced time delay is observationally indistinguishable from an intrinsic time delay due to the lens geometry.

  15. Resonance Effects in Photoemission Time Delays.

    PubMed

    Sabbar, M; Heuser, S; Boge, R; Lucchini, M; Carette, T; Lindroth, E; Gallmann, L; Cirelli, C; Keller, U

    2015-09-25

    We present measurements of single-photon ionization time delays between the outermost valence electrons of argon and neon using a coincidence detection technique that allows for the simultaneous measurement of both species under identical conditions. The analysis of the measured traces reveals energy-dependent time delays of a few tens of attoseconds with high energy resolution. In contrast to photoelectrons ejected through tunneling, single-photon ionization can be well described in the framework of Wigner time delays. Accordingly, the overall trend of our data is reproduced by recent Wigner time delay calculations. However, besides the general trend we observe resonance features occurring at specific photon energies. These features have been qualitatively reproduced and identified by a calculation using the multiconfigurational Hartree-Fock method, including the influence of doubly excited states and ionization thresholds. PMID:26451550

  16. Time-delayed feedback in neurosystems.

    PubMed

    Schöll, Eckehard; Hiller, Gerald; Hövel, Philipp; Dahlem, Markus A

    2009-03-28

    The influence of time delay in systems of two coupled excitable neurons is studied in the framework of the FitzHugh-Nagumo model. A time delay can occur in the coupling between neurons or in a self-feedback loop. The stochastic synchronization of instantaneously coupled neurons under the influence of white noise can be deliberately controlled by local time-delayed feedback. By appropriate choice of the delay time, synchronization can be either enhanced or suppressed. In delay-coupled neurons, antiphase oscillations can be induced for sufficiently large delay and coupling strength. The additional application of time-delayed self-feedback leads to complex scenarios of synchronized in-phase or antiphase oscillations, bursting patterns or amplitude death. PMID:19218152

  17. Time Delay for the Dirac Equation

    NASA Astrophysics Data System (ADS)

    Naumkin, Ivan; Weder, Ricardo

    2016-07-01

    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.

  18. Interaural attention modulates outer hair cell function.

    PubMed

    Srinivasan, Sridhar; Keil, Andreas; Stratis, Kyle; Osborne, Aaron F; Cerwonka, Colin; Wong, Jennifer; Rieger, Brenda L; Polcz, Valerie; Smith, David W

    2014-12-01

    Mounting evidence suggests that auditory attention tasks may modulate the sensitivity of the cochlea by way of the corticofugal and the medial olivocochlear (MOC) efferent pathways. Here, we studied the extent to which a separate efferent tract, the 'uncrossed' MOC, which functionally connects the two ears, mediates inter-aural selective attention. We compared distortion product otoacoustic emissions (DPOAEs) in one ear with binaurally presented primaries, using an intermodal target detection task in which participants were instructed to report the occurrence of brief target events (visual changes, tones). Three tasks were compared under identical physical stimulation: (i) report brief tones in the ear in which DPOAE responses were recorded; (ii) report brief tones presented to the contralateral, non-recorded ear; and (iii) report brief phase shifts of a visual grating at fixation. Effects of attention were observed as parallel shifts in overall DPOAE contour level, with DPOAEs relatively higher in overall level when subjects ignored the auditory stimuli and attended to the visual stimulus, compared with both of the auditory-attending conditions. Importantly, DPOAE levels were statistically lowest when attention was directed to the ipsilateral ear in which the DPOAE recordings were made. These data corroborate notions that top-down mechanisms, via the corticofugal and medial efferent pathways, mediate cochlear responses during intermodal attention. New findings show attending to one ear can significantly alter the physiological response of the contralateral, unattended ear, probably through the uncrossed-medial olivocochlear efferent fibers connecting the two ears. PMID:25302959

  19. The Strong Lensing Time Delay Challenge (2014)

    NASA Astrophysics Data System (ADS)

    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.

  20. Transformation from a pure time delay to a mixed time and phase delay representation in the auditory forebrain pathway.

    PubMed

    Vonderschen, Katrin; Wagner, Hermann

    2012-04-25

    Birds and mammals exploit interaural time differences (ITDs) for sound localization. Subsequent to ITD detection by brainstem neurons, ITD processing continues in parallel midbrain and forebrain pathways. In the barn owl, both ITD detection and processing in the midbrain are specialized to extract ITDs independent of frequency, which amounts to a pure time delay representation. Recent results have elucidated different mechanisms of ITD detection in mammals, which lead to a representation of small ITDs in high-frequency channels and large ITDs in low-frequency channels, resembling a phase delay representation. However, the detection mechanism does not prevent a change in ITD representation at higher processing stages. Here we analyze ITD tuning across frequency channels with pure tone and noise stimuli in neurons of the barn owl's auditory arcopallium, a nucleus at the endpoint of the forebrain pathway. To extend the analysis of ITD representation across frequency bands to a large neural population, we employed Fourier analysis for the spectral decomposition of ITD curves recorded with noise stimuli. This method was validated using physiological as well as model data. We found that low frequencies convey sensitivity to large ITDs, whereas high frequencies convey sensitivity to small ITDs. Moreover, different linear phase frequency regimes in the high-frequency and low-frequency ranges suggested an independent convergence of inputs from these frequency channels. Our results are consistent with ITD being remodeled toward a phase delay representation along the forebrain pathway. This indicates that sensory representations may undergo substantial reorganization, presumably in relation to specific behavioral output. PMID:22539852

  1. Measurement of Gravitational Lens Time Delays with LSST (SULI Paper)

    SciTech Connect

    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

  2. Electrophysiological study of interaural sound intensity difference in the dolphin Inia geoffrensis.

    PubMed

    Supin AYa; Popov, V V; Klishin, V O

    1991-09-15

    A wave observed in the auditory brainstem responses (ABR), sensitive to the side of sound presentation, is described in a dolphin (Inia geoffrensis). Dependence of the wave threshold on location of the sound source showed that the interaural intensity difference was more than 20 dB. PMID:1915778

  3. Time delay in Swiss cheese gravitational lensing

    SciTech Connect

    Chen, B.; Kantowski, R.; Dai, X.

    2010-08-15

    We compute time delays for gravitational lensing in a flat {Lambda} dominated cold dark matter Swiss cheese universe. We assume a primary and secondary pair of light rays are deflected by a single point mass condensation described by a Kottler metric (Schwarzschild with {Lambda}) embedded in an otherwise homogeneous cosmology. We find that the cosmological constant's effect on the difference in arrival times is nonlinear and at most around 0.002% for a large cluster lens; however, we find differences from time delays predicted by conventional linear lensing theory that can reach {approx}4% for these large lenses. The differences in predicted delay times are due to the failure of conventional lensing to incorporate the lensing mass into the mean mass density of the universe.

  4. Time-Delayed Quantum Feedback Control

    NASA Astrophysics Data System (ADS)

    Grimsmo, Arne L.

    2015-08-01

    A theory of time-delayed coherent quantum feedback is developed. More specifically, we consider a quantum system coupled to a bosonic reservoir creating a unidirectional feedback loop. It is shown that the dynamics can be mapped onto a fictitious series of cascaded quantum systems, where the system is driven by past versions of itself. The derivation of this model relies on a tensor network representation of the system-reservoir time propagator. For concreteness, this general theory is applied to a driven two-level atom scattering into a coherent feedback loop. We demonstrate how delay effects can qualitatively change the dynamics of the atom and how quantum control can be implemented in the presence of time delays.

  5. Time-delayed autosynchronous swarm control.

    PubMed

    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. PMID:22400623

  6. Time-delayed autosynchronous swarm control

    NASA Astrophysics Data System (ADS)

    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.

  7. Time-Delayed Quantum Feedback Control.

    PubMed

    Grimsmo, Arne L

    2015-08-01

    A theory of time-delayed coherent quantum feedback is developed. More specifically, we consider a quantum system coupled to a bosonic reservoir creating a unidirectional feedback loop. It is shown that the dynamics can be mapped onto a fictitious series of cascaded quantum systems, where the system is driven by past versions of itself. The derivation of this model relies on a tensor network representation of the system-reservoir time propagator. For concreteness, this general theory is applied to a driven two-level atom scattering into a coherent feedback loop. We demonstrate how delay effects can qualitatively change the dynamics of the atom and how quantum control can be implemented in the presence of time delays. PMID:26296104

  8. Supervising Remote Humanoids Across Intermediate Time Delay

    NASA Technical Reports Server (NTRS)

    Hambuchen, Kimberly; Bluethmann, William; Goza, Michael; Ambrose, Robert; Rabe, Kenneth; Allan, Mark

    2006-01-01

    The President's Vision for Space Exploration, laid out in 2004, relies heavily upon robotic exploration of the lunar surface in early phases of the program. Prior to the arrival of astronauts on the lunar surface, these robots will be required to be controlled across space and time, posing a considerable challenge for traditional telepresence techniques. Because time delays will be measured in seconds, not minutes as is the case for Mars Exploration, uploading the plan for a day seems excessive. An approach for controlling humanoids under intermediate time delay is presented. This approach uses software running within a ground control cockpit to predict an immersed robot supervisor's motions which the remote humanoid autonomously executes. Initial results are presented.

  9. Inertia, gravitation, and radiation time delays

    SciTech Connect

    Graneau, P.

    1987-05-01

    This note explains how an instantaneous action-at-a-distance theory gives rise to time delays between a cause in one location and its effect at another. The key to this is a suitable law of induction which itself does not produce the time delay, but contains the cause in the form of a time derivative. The many-body solution process for an array of simultaneous induction equations then reveals retardation between cause and effect without the transport of energy at finite velocity. It is suggested that a suitable law of induction of inertia applied to an object in the solar system and the many-body universe may furnish the quantitative connection between inertia and Newtonian gravitation.

  10. Integrated Planning for Telepresence with Time Delays

    NASA Technical Reports Server (NTRS)

    Johnston, Mark D.; Rabe, Kenneth J.

    2006-01-01

    Teleoperation of remote robotic systems over time delays in the range of 2-10 seconds poses a unique set of challenges. In the context of a supervisory control system for the JSC Robonaut humanoid robot, we have developed an 'intelligent assistant' that integrates an Artificial Intelligence planner (JSHOP2) with execution monitoring of the state of both the human supervisor and the remote robot. The assistant reasons simultaneously about the world state on both sides of the time delay, which represents a novel application of this technology. The purpose of the assistant is to provide advice to the human supervisor about current and future activities, derived from a sequence of high-level goals to be achieved. To do this, the assistant must simultaneously monitor and react to various data sources, including actions taken by the supervisor who is issuing commands to the robot (e.g. with a data glove), actions taken by the robot, and the environment of the robot, both as currently perceived over the time delay, along with the current sequence of goals. We have developed a 'leader/follower' software architecture to handle the dual time-shifted streams of execution feedback. In this paper we describe the integrated planner and its executive, and how it operates in normal and anomaly situations.

  11. Critical evaluation of attosecond time delays retrieved from photoelectron streaking measurements

    NASA Astrophysics Data System (ADS)

    Wei, Hui; Morishita, Toru; Lin, C. D.

    2016-05-01

    A photoelectron streaking experiment which was conceived as a means to extract the electron wave packet of single-photon ionization has also been employed to retrieve time delays in the fundamental photoemission processes. The discrepancies between the time delays thus measured and those from many sophisticated theoretical calculations have generated a great deal of controversy in recent years. Here we present a careful examination of the methods that were used to retrieve the time delays and demonstrate the difficulty of achieving an accuracy of the retrieved time delays of a few to tens of attoseconds in typical streaking measurements. The difficulty owes more to the lower sensitivity of the streaking spectra to the phase of the photoionization transition dipole than to the spectral phase of the attosecond light pulse in the experiment. The retrieved time delay contains extra errors when the attochirp of the attosecond pulse is large so that the dipole phase becomes negligible compared to it.

  12. Estimation of time delays from unresolved photometry

    NASA Astrophysics Data System (ADS)

    Hirv, A.; Eenmäe, T.; Liimets, T.; Liivamägi, L. J.; Pelt, J.

    2007-03-01

    Context: Longtime monitoring of gravitational lens systems is often done using telescopes and recording equipment with 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. Aims: In this paper we will develop an algorithm to unscramble this kind of blended data. Methods: 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. Results: We performed a check of feasibility and applicability of the new algorithm. For numerically generated data sets the time delay systems were recovered for a wide range of setups. Application of the new algorithm to the classical double quasar QSO 0957+561 A, B lightcurves shows a clear splitting of one of the images. This is an unexpected result and extremely interesting, especially in the context of the recent controversy about the exact time delay value for the system. Conclusions: .The proposed method allows us to properly analyse the data from low resolution observations that have long time coverages. There are a number of gravitational lens monitoring programmes that can make use of the new algorithm.

  13. Time Delays, Bends, Acceleration and Array Reconfigurations

    SciTech Connect

    Faltens, A.

    2011-06-24

    This note was originally one of the parts of the work on a 50 MeV and 500 MeV Rb{sup +} driver and part of work on delay lines for a 60 GeV U{sup +12} driver. It is slightly expanded here to make it more generally applicable. The emphasis is on beam manipulations such as joining and separating beams at the two ends of a driver and providing various time delays between beams as required by the target.

  14. Integrated Planning for Telepresence with Time Delays

    NASA Technical Reports Server (NTRS)

    Johnston, Mark D.; Rabe, Kenneth J.

    2006-01-01

    Integrated planning and execution of teleoperations in space with time delays is shown. The topics include: 1) The Problem; 2) Future Robot Surgery? 3) Approach Overview; 4) Robonaut; 5) Normal Planning and Execution; 6) Planner Context; 7) Implementation; 8) Use of JSHOP2; 9) Monitoring and Testing GUI; 10) Normal sequence: first the supervisor acts; 11) then the robot; 12) Robot might be late; 13) Supervisor can work ahead; 14) Deviations from Plan; 15) Robot State Change Example; 16) Accomplished goals skipped in replan; 17) Planning continuity; 18) Supervisor Deviation From Plan; 19) Intentional Deviation; and 20) Infeasible states.

  15. SBASI: Actuated pyrotechnic time delay initiator

    NASA Technical Reports Server (NTRS)

    Salter, S. J.; Lundberg, R. E.; Mcdougal, G. L.

    1975-01-01

    A precision pyrotechnic time delay initiator for missile staging was developed and tested. Incorporated in the assembly is a single bridgewire Apollo standard initiator (SBASI) for initiation, a through-bulkhead-initiator to provide isolation of the SBASI output from the delay, the pyrotechnic delay, and an output charge. An attempt was made to control both primary and secondary variables affecting functional performance of the delay initiator. Design and functional limit exploration was performed to establish tolerance levels on manufacturing and assembling operations. The test results demonstrate a 2% coefficient of variation at any one temperature and an overall 2.7% coefficient of variation throughout the temperature range of 30 to 120 F. Tests were conducted at simulated operational altitude from sea level to 200,000 feet.

  16. Relativistic calculations of angle-dependent photoemission time delay

    NASA Astrophysics Data System (ADS)

    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.

  17. 14 CFR 417.221 - Time delay analysis.

    Code of Federal Regulations, 2010 CFR

    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...

  18. 14 CFR 417.221 - Time delay analysis.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 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 elapsed... 14 Aeronautics and Space 4 2011-01-01 2011-01-01 false Time delay analysis. 417.221 Section...

  19. Time delay spectrometry for hydrophone calibrations below 1 MHz.

    PubMed

    Gammell, P M; Harris, G R

    1999-11-01

    Knowing the response of miniature ultrasonic hydrophones at frequencies below 1 MHz is important for assessing the accuracy of acoustic pressure pulse measurements in medical ultrasound applications. Therefore, a time delay spectrometry (TDS) system was developed as an efficient means to measure hydrophone sensitivity in this frequency range. In TDS a swept-frequency signal is transmitted. A tracking receiver distinguishes arrivals with different propagation delays by their frequency offset relative to the signal being transmitted, thus eliminating spurious signals such as those reflected from the water surface or tank walls. Two piezoelectric ceramic source transducers were used: a standard planar disk and a disk with varying thickness to broaden the thickness-resonance. This latter design was preferred for its more uniform response without significant sensitivity loss. TDS is not an absolute method, but it was demonstrated to provide efficient, accurate calibrations via comparison with a reference hydrophone using a substitution technique. PMID:10573913

  20. Integrated Planning for Telepresence With Time Delays

    NASA Technical Reports Server (NTRS)

    Johnston, Mark; Rabe, Kenneth

    2009-01-01

    A conceptual "intelligent assistant" and an artificial-intelligence computer program that implements the intelligent assistant have been developed to improve control exerted by a human supervisor over a robot that is so distant that communication between the human and the robot involves significant signal-propagation delays. The goal of the effort is not only to help the human supervisor monitor and control the state of the robot, but also to improve the efficiency of the robot by allowing the supervisor to "work ahead". The intelligent assistant is an integrated combination of an artificial-intelligence planner and a monitor of states of both the human supervisor and the remote robot. The novelty of the system lies in the way it uses the planner to reason about the states at both ends of the time delay. The purpose served by the assistant is to provide advice to the human supervisor about current and future activities, derived from a sequence of high-level goals to be achieved.

  1. A time delay controller for magnetic bearings

    NASA Technical Reports Server (NTRS)

    Youcef-Toumi, K.; Reddy, S.

    1991-01-01

    The control of systems with unknown dynamics and unpredictable disturbances has raised some challenging problems. This is particularly important when high system performance needs to be guaranteed at all times. Recently, the Time Delay Control has been suggested as an alternative control scheme. The proposed control system does not require an explicit plant model nor does it depend on the estimation of specific plant parameters. Rather, it combines adaptation with past observations to directly estimate the effect of the plant dynamics. A control law is formulated for a class of dynamic systems and a sufficient condition is presented for control systems stability. The derivation is based on the bounded input-bounded output stability approach using L sub infinity function norms. The control scheme is implemented on a five degrees of freedom high speed and high precision magnetic bearing. The control performance is evaluated using step responses, frequency responses, and disturbance rejection properties. The experimental data show an excellent control performance despite the system complexity.

  2. COSMOLOGICAL CONSTRAINTS FROM GRAVITATIONAL LENS TIME DELAYS

    SciTech Connect

    Coe, Dan; Moustakas, Leonidas A.

    2009-11-20

    Future large ensembles of time delay (TD) lenses have the potential to provide interesting cosmological constraints complementary to those of other methods. In a flat universe with constant w including a Planck prior, The Large Synoptic Survey Telescope TD measurements for approx4000 lenses should constrain the local Hubble constant h to approx0.007 (approx1%), OMEGA{sub de} to approx0.005, and w to approx0.026 (all 1sigma precisions). Similar constraints could be obtained by a dedicated gravitational lens observatory (OMEGA) which would obtain precise TD and mass model measurements for approx100 well-studied lenses. We compare these constraints (as well as those for a more general cosmology) to the 'optimistic Stage IV' constraints expected from weak lensing, supernovae, baryon acoustic oscillations, and cluster counts, as calculated by the Dark Energy Task Force. TDs yield a modest constraint on a time-varying w(z), with the best constraint on w(z) at the 'pivot redshift' of z approx 0.31. Our Fisher matrix calculation is provided to allow TD constraints to be easily compared to and combined with constraints from other experiments. We also show how cosmological constraining power varies as a function of numbers of lenses, lens model uncertainty, TD precision, redshift precision, and the ratio of four-image to two-image lenses.

  3. ETD: an extended time delay algorithm for ventricular fibrillation detection.

    PubMed

    Kim, Jungyoon; Chu, Chao-Hsien

    2014-01-01

    Ventricular fibrillation (VF) is the most serious type of heart attack which requires quick detection and first aid to improve patients' survival rates. To be most effective in using wearable devices for VF detection, it is vital that the detection algorithms be accurate, robust, reliable and computationally efficient. Previous studies and our experiments both indicate that the time-delay (TD) algorithm has a high reliability for separating sinus rhythm (SR) from VF and is resistant to variable factors, such as window size and filtering method. However, it fails to detect some VF cases. In this paper, we propose an extended time-delay (ETD) algorithm for VF detection and conduct experiments comparing the performance of ETD against five good VF detection algorithms, including TD, using the popular Creighton University (CU) database. Our study shows that (1) TD and ETD outperform the other four algorithms considered and (2) with the same sensitivity setting, ETD improves upon TD in three other quality measures for up to 7.64% and in terms of aggregate accuracy, the ETD algorithm shows an improvement of 2.6% of the area under curve (AUC) compared to TD. PMID:25571480

  4. A novel online adaptive time delay identification technique

    NASA Astrophysics Data System (ADS)

    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.

  5. Non-commutativity, teleology and GRB time delay

    NASA Astrophysics Data System (ADS)

    Li, Miao; Pang, Yi; Wang, Yi

    2010-01-01

    We propose a model in which an energy-dependent time delay of a photon originates from space-time non-commutativity, the time delay is due to a non-commutative coupling between dilaton and photon. We predict that in our model, high energy photons with different momentum can either be delayed or superluminal, this may be related to a possible time delay reported by the Fermi LAT and Fermi GBM Collaborations.

  6. A Comparison of Two Objective Measures of Binaural Processing: The Interaural Phase Modulation Following Response and the Binaural Interaction Component.

    PubMed

    Haywood, Nicholas R; Undurraga, Jaime A; Marquardt, Torsten; McAlpine, David

    2015-01-01

    There has been continued interest in clinical objective measures of binaural processing. One commonly proposed measure is the binaural interaction component (BIC), which is obtained typically by recording auditory brainstem responses (ABRs)-the BIC reflects the difference between the binaural ABR and the sum of the monaural ABRs (i.e., binaural - (left + right)). We have recently developed an alternative, direct measure of sensitivity to interaural time differences, namely, a following response to modulations in interaural phase difference (the interaural phase modulation following response; IPM-FR). To obtain this measure, an ongoing diotically amplitude-modulated signal is presented, and the interaural phase difference of the carrier is switched periodically at minima in the modulation cycle. Such periodic modulations to interaural phase difference can evoke a steady state following response. BIC and IPM-FR measurements were compared from 10 normal-hearing subjects using a 16-channel electroencephalographic system. Both ABRs and IPM-FRs were observed most clearly from similar electrode locations-differential recordings taken from electrodes near the ear (e.g., mastoid) in reference to a vertex electrode (Cz). Although all subjects displayed clear ABRs, the BIC was not reliably observed. In contrast, the IPM-FR typically elicited a robust and significant response. In addition, the IPM-FR measure required a considerably shorter recording session. As the IPM-FR magnitude varied with interaural phase difference modulation depth, it could potentially serve as a correlate of perceptual salience. Overall, the IPM-FR appears a more suitable clinical measure than the BIC. PMID:26721925

  7. 14 CFR 417.221 - Time delay analysis.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 14 Aeronautics and Space 4 2013-01-01 2013-01-01 false Time delay analysis. 417.221 Section 417.221 Aeronautics and Space COMMERCIAL SPACE TRANSPORTATION, FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.221 Time delay analysis. (a) General. A flight safety analysis must include...

  8. 14 CFR 417.221 - Time delay analysis.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... occurs; (2) A flight safety official's decision and reaction time, including variation in human response... 14 Aeronautics and Space 4 2012-01-01 2012-01-01 false Time delay analysis. 417.221 Section 417... OF TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.221 Time delay analysis....

  9. 14 CFR 417.221 - Time delay analysis.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... occurs; (2) A flight safety official's decision and reaction time, including variation in human response... 14 Aeronautics and Space 4 2014-01-01 2014-01-01 false Time delay analysis. 417.221 Section 417... OF TRANSPORTATION LICENSING LAUNCH SAFETY Flight Safety Analysis § 417.221 Time delay analysis....

  10. Time-delay compensation for stabilization imaging system

    NASA Astrophysics Data System (ADS)

    Chen, Yueting; Xu, Zhihai; Li, Qi; Feng, Huajun

    2014-05-01

    The spatial resolution of imaging systems for airborne and space-borne remote sensing are often limited by image degradation resulting from mechanical vibrations of platforms during image exposure. A straightforward way to overcome this problem is to actively stabilize the optical axis or drive the focal plane synchronous to the motion image during exposure. Thus stabilization imaging system usually consists of digital image motion estimation and micromechanical compensation. The performance of such kind of visual servo system is closely related to precision of motion estimation and time delay. Large time delay results in larger phase delay between motion estimation and micromechanical compensation, and leads to larger uncompensated residual motion and limited bandwidth. The paper analyzes the time delay caused by image acquisition period and introduces a time delay compensation method based on SVM (Support Vector Machine) motion prediction. The main idea to cancel the time delay is to predict the current image motion from delayed measurements. A support vector machine based method is designed to predict the image motion. A prototype of stabilization imaging system has been implemented in the lab. To analyze the influences of time delay on system performance and to verify the proposed time delay cancelation method, comparative experiments over various frequencies of vibration are taken. The experimental results show that, the accuracy of motion compensation and the bandwidth of the system can be significantly improved with time delay cancelation.

  11. Stability of a general SEIV epidemic model with time delay

    NASA Astrophysics Data System (ADS)

    Hikal, M. M.; El-Sheikh, M. M. A.

    2013-10-01

    An SEIV epidemic model with a general nonlinear incidence rate, vaccination and time delay in treatment is considered. Sufficient conditions for the time delay to keep the stability of the endemic equilibria are given. A numerical simulations is given to illustrate our results.

  12. Using Constant Time Delay to Teach Braille Word Recognition

    ERIC Educational Resources Information Center

    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…

  13. Photonic Circuits with Time Delays and Quantum Feedback.

    PubMed

    Pichler, Hannes; Zoller, Peter

    2016-03-01

    We study the dynamics of photonic quantum circuits consisting of nodes coupled by quantum channels. We are interested in the regime where the time delay in communication between the nodes is significant. This includes the problem of quantum feedback, where a quantum signal is fed back on a system with a time delay. We develop a matrix product state approach to solve the quantum stochastic Schrödinger equation with time delays, which accounts in an efficient way for the entanglement of nodes with the stream of emitted photons in the waveguide, and thus the non-Markovian character of the dynamics. We illustrate this approach with two paradigmatic quantum optical examples: two coherently driven distant atoms coupled to a photonic waveguide with a time delay, and a driven atom coupled to its own output field with a time delay as an instance of a quantum feedback problem. PMID:26991174

  14. Photonic Circuits with Time Delays and Quantum Feedback

    NASA Astrophysics Data System (ADS)

    Pichler, Hannes; Zoller, Peter

    2016-03-01

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

  15. Time delay and Doppler tests of the Lorentz symmetry of gravity

    SciTech Connect

    Bailey, Quentin G.

    2009-08-15

    Modifications to the classic time-delay effect and Doppler shift in general relativity (GR) are studied in the context of the Lorentz-violating standard-model extension (SME). We derive the leading Lorentz-violating corrections to the time-delay and Doppler shift signals, for a light ray passing near a massive body. It is demonstrated that anisotropic coefficients for Lorentz violation control a time-dependent behavior of these signals that is qualitatively different from the conventional case in GR. Estimates of sensitivities to gravity-sector coefficients in the SME are given for current and future experiments, including the recent Cassini solar conjunction experiment.

  16. Stability analysis of genetic regulatory networks with multiple time delays.

    PubMed

    Wu, Fang-Xiang

    2007-01-01

    A genetic regulatory network is a dynamic system to describe interactions among genes (mRNA) and its products (proteins). From the statistic thermodynamics and biochemical reaction principle, a genetic regulatory network can be described by a group of nonlinear differential equations with time delays. Stability is one of interesting properties for genetic regulatory network. Previous studies have investigated stability of genetic regulatory networks with a single time delay. In this paper, we investigate properties of genetic regulatory networks with multiple time delays in the notion of delay-independent stability. We present necessary and sufficient condition for the local delay-independent stability of genetic regulatory network with multiple time delays which are independent or commensurate. PMID:18002223

  17. Time-delayed directional beam phased array antenna

    DOEpatents

    Fund, Douglas Eugene; Cable, John William; Cecil, Tony Myron

    2004-10-19

    An antenna comprising a phased array of quadrifilar helix or other multifilar antenna elements and a time-delaying feed network adapted to feed the elements. The feed network can employ a plurality of coaxial cables that physically bridge a microstrip feed circuitry to feed power signals to the elements. The cables provide an incremental time delay which is related to their physical lengths, such that replacing cables having a first set of lengths with cables having a second set of lengths functions to change the time delay and shift or steer the antenna's main beam. Alternatively, the coaxial cables may be replaced with a programmable signal processor unit adapted to introduce the time delay using signal processing techniques applied to the power signals.

  18. Workspace visualization and time-delay telerobotic operations

    NASA Technical Reports Server (NTRS)

    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.

  19. A functional circuit model of interaural time difference processing.

    PubMed

    McColgan, Thomas; Shah, Sahil; Köppl, Christine; Carr, Catherine; Wagner, Hermann

    2014-12-01

    Inputs from the two sides of the brain interact to create maps of interaural time difference (ITD) in the nucleus laminaris of birds. How inputs from each side are matched with high temporal precision in ITD-sensitive circuits is unknown, given the differences in input path lengths from each side. To understand this problem in birds, we modeled the geometry of the input axons and their corresponding conduction velocities and latencies. Consistent with existing physiological data, we assumed a common latency up to the border of nucleus laminaris. We analyzed two biological implementations of the model, the single ITD map in chickens and the multiple maps of ITD in barn owls. For binaural inputs, since ipsi- and contralateral initial common latencies were very similar, we could restrict adaptive regulation of conduction velocity to within the nucleus. Other model applications include the simultaneous derivation of multiple conduction velocities from one set of measurements and the demonstration that contours with the same ITD cannot be parallel to the border of nucleus laminaris in the owl. Physiological tests of the predictions of the model demonstrate its validity and robustness. This model may have relevance not only for auditory processing but also for other computational tasks that require adaptive regulation of conduction velocity. PMID:25185809

  20. How do owls localize interaurally phase-ambiguous signals?

    PubMed

    Saberi, K; Farahbod, H; Konishi, M

    1998-05-26

    Owls and other animals, including humans, use the difference in arrival time of sounds between the ears to determine the direction of a sound source in the horizontal plane. When an interaural time difference (ITD) is conveyed by a narrowband signal such as a tone, human beings may fail to derive the direction represented by that ITD. This is because they cannot distinguish the true ITD contained in the signal from its phase equivalents that are ITD +/- nT, where T is the period of the stimulus tone and n is an integer. This uncertainty is called phase-ambiguity. All ITD-sensitive neurons in birds and mammals respond to an ITD and its phase equivalents when the ITD is contained in narrowband signals. It is not known, however, if these animals show phase-ambiguity in the localization of narrowband signals. The present work shows that barn owls (Tyto alba) experience phase-ambiguity in the localization of tones delivered by earphones. We used sound-induced head-turning responses to measure the sound-source directions perceived by two owls. In both owls, head-turning angles varied as a sinusoidal function of ITD. One owl always pointed to the direction represented by the smaller of the two ITDs, whereas a second owl always chose the direction represented by the larger ITD (i.e., ITD - T). PMID:9600989

  1. Precise inhibition is essential for microsecond interaural time difference coding

    NASA Astrophysics Data System (ADS)

    Brand, Antje; Behrend, Oliver; Marquardt, Torsten; McAlpine, David; Grothe, Benedikt

    2002-05-01

    Microsecond differences in the arrival time of a sound at the two ears (interaural time differences, ITDs) are the main cue for localizing low-frequency sounds in space. Traditionally, ITDs are thought to be encoded by an array of coincidence-detector neurons, receiving excitatory inputs from the two ears via axons of variable length (`delay lines'), to create a topographic map of azimuthal auditory space. Compelling evidence for the existence of such a map in the mammalian lTD detector, the medial superior olive (MSO), however, is lacking. Equally puzzling is the role of a-temporally very precise-glycine-mediated inhibitory input to MSO neurons. Using in vivo recordings from the MSO of the Mongolian gerbil, we found the responses of ITD-sensitive neurons to be inconsistent with the idea of a topographic map of auditory space. Moreover, local application of glycine and its antagonist strychnine by iontophoresis (through glass pipette electrodes, by means of an electric current) revealed that precisely timed glycine-controlled inhibition is a critical part of the mechanism by which the physiologically relevant range of ITDs is encoded in the MSO. A computer model, simulating the response of a coincidence-detector neuron with bilateral excitatory inputs and a temporally precise contralateral inhibitory input, supports this conclusion.

  2. A functional circuit model of interaural time difference processing

    PubMed Central

    McColgan, Thomas; Shah, Sahil; Köppl, Christine; Carr, Catherine

    2014-01-01

    Inputs from the two sides of the brain interact to create maps of interaural time difference (ITD) in the nucleus laminaris of birds. How inputs from each side are matched with high temporal precision in ITD-sensitive circuits is unknown, given the differences in input path lengths from each side. To understand this problem in birds, we modeled the geometry of the input axons and their corresponding conduction velocities and latencies. Consistent with existing physiological data, we assumed a common latency up to the border of nucleus laminaris. We analyzed two biological implementations of the model, the single ITD map in chickens and the multiple maps of ITD in barn owls. For binaural inputs, since ipsi- and contralateral initial common latencies were very similar, we could restrict adaptive regulation of conduction velocity to within the nucleus. Other model applications include the simultaneous derivation of multiple conduction velocities from one set of measurements and the demonstration that contours with the same ITD cannot be parallel to the border of nucleus laminaris in the owl. Physiological tests of the predictions of the model demonstrate its validity and robustness. This model may have relevance not only for auditory processing but also for other computational tasks that require adaptive regulation of conduction velocity. PMID:25185809

  3. The time delay in the twin QSO Q0957 + 561

    SciTech Connect

    Schild, R.E. )

    1990-12-01

    From 10 yr of brightness monitoring of the two gravitational mirage components of Q0957 + 561 A,B it is shown that the time delay is 1.11 yr. An intensive program of daily brightness monitoring suggests a further refinement of the time delay to 404 days. Careful superposition of the phased brightness records shows that small differences are seen. These differences are attributed to microlensing by a star or stars in the lens galaxy. 5 refs.

  4. Next generation strong lensing time delay estimation with Gaussian processes

    NASA Astrophysics Data System (ADS)

    Hojjati, Alireza; Linder, Eric V.

    2014-12-01

    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 light curves is potentially a limiting systematic. Using a large sample of blinded light curves from the Strong Lens Time Delay Challenge we develop and demonstrate a Gaussian process cross correlation 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 one day) for delays from 5-100 days and robust against cadence variations shorter than six days. We study the effects of survey characteristics such as cadence, season, and campaign length, and derive requirements for time delay cosmology: in order not to bias the cosmology determination by 0.5 σ , the mean time delay fit accuracy must be better than 0.2%.

  5. Time Delay for Dispersive Systems in Quantum Scattering Theory

    NASA Astrophysics Data System (ADS)

    Tiedra de Aldecoa, Rafael

    We consider time delay and symmetrized time delay (defined in terms of sojourn times) for quantum scattering pairs {H0 = h(P), H}, where h(P) is a dispersive operator of hypoelliptic-type. For instance, h(P) can be one of the usual elliptic operators such as the Schrödinger operator h(P) = P2 or the square-root Klein-Gordon operator h(P) = √ {1 + P2}. We show under general conditions that the symmetrized time delay exists for all smooth even localization functions. It is equal to the Eisenbud-Wigner time delay plus a contribution due to the non-radial component of the localization function. If the scattering operator S commutes with some function of the velocity operator ∇h(P), then the time delay also exists and is equal to the symmetrized time delay. As an illustration of our results, we consider the case of a one-dimensional Friedrichs Hamiltonian perturbed by a finite rank potential. Our study puts into evidence an integral formula relating the operator of differentiation with respect to the kinetic energy h(P) to the time evolution of localization operators.

  6. Impacts of Time Delays on Distributed Algorithms for Economic Dispatch

    SciTech Connect

    Yang, Tao; Wu, Di; Sun, Yannan; Lian, Jianming

    2015-07-26

    Economic dispatch problem (EDP) is an important problem in power systems. It can be formulated as an optimization problem with the objective to minimize the total generation cost subject to the power balance constraint and generator capacity limits. Recently, several consensus-based algorithms have been proposed to solve EDP in a distributed manner. However, impacts of communication time delays on these distributed algorithms are not fully understood, especially for the case where the communication network is directed, i.e., the information exchange is unidirectional. This paper investigates communication time delay effects on a distributed algorithm for directed communication networks. The algorithm has been tested by applying time delays to different types of information exchange. Several case studies are carried out to evaluate the effectiveness and performance of the algorithm in the presence of time delays in communication networks. It is found that time delay effects have negative effects on the convergence rate, and can even result in an incorrect converge value or fail the algorithm to converge.

  7. Time-delay cosmography: increased leverage with angular diameter distances

    NASA Astrophysics Data System (ADS)

    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.

  8. An adaptive robust controller for time delay maglev transportation systems

    NASA Astrophysics Data System (ADS)

    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.

  9. Electronically variable time delays using magnetostatic wave technology

    NASA Astrophysics Data System (ADS)

    Adkins, L. R.; Glass, H. L.; Jin, K. K.; Stearns, F. S.; Ataiiyn, Y. T.

    1986-03-01

    Variable time delays are necessary in phased array systems to prevent phase squinting and pulse stretching. Methods for providing these time delays include an assortment of fixed cables, ferrite loaded cables, surface acoustic wave (SAW) devices and magnetostatic wave (MSW) devices. Fixed cables are bulky, limiting the number that can be employed per system. Ferrite loaded cables and SAW devices are applicable primarily at frequencies below 1 GHz and provide relatively small delay differentials. MSW wave technology is capable of operating at frequencies up to 20 GHz and providing differential time delays on the order of tens of nanoseconds. An MSW device has recently been demonstrated with a bandwidth greater than 200 MHz centered at 3 GHz. This device has a phase error across the band as low as 8 deg and is capable of providing nearly 50 nS differential delay. Thus, MSW technology appears to be the most promising technique for the next generation of phased array systems.

  10. COSMOGRAIL: Time delays in lensed quasars from Himalayan Chandra Telescope

    NASA Astrophysics Data System (ADS)

    Rathna Kumar, S.; Stalin, C. S.; Tewes, M.; Courbin, F.; Asfandiyarov, I.; Ibrahimov, M.; Eulaers, E.; Meylan, G.; Prabhu, T. P.; Magain, P.

    Estimating H_0 to an accuracy of few percent is an important challenge today as it will offer key insights into various questions in cosmology. By measuring time delays between the photometric variations in lensed quasar images and subsequent modelling of the mass distribution in the lensing galaxy, it is possible to constrain H_0 in a way well complementary to traditional techniques. Time delays are difficult to measure due to the long time span needed to monitor the sources and photometry is challenging due to the small angular separation between the lensed quasar images. These issues are addressed by the COSMOGRAIL (COSmological MOnitoring of GRAvItational Lenses) collaboration, which uses several telescopes in both the hemispheres to monitor a large sample of gravitationally lensed quasars. As part of this collaboration, 6 sources are being monitored using the 2 m Himalayan Chandra Telescope (HCT) in Hanle, India. We present here the preliminary estimates of time delays in these sources.

  11. Strongly Lensed Jets, Time Delays, and the Value of H 0

    NASA Astrophysics Data System (ADS)

    Barnacka, Anna; Geller, Margaret J.; Dell'Antonio, Ian P.; Benbow, Wystan

    2015-01-01

    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 ~50-100 km s-1Mpc-1. Quasars monitored to measure these time delays are multi-component objects. The variability may arise from different components of the quasar or may even originate from a jet. Misidentifying a variable-emitting region in a jet with emission from the core region may introduce an error in the Hubble constant derived from a time delay. Here, we investigate the complex structure of the sources as the underlying physical explanation of the wide spread in values of the Hubble constant based on gravitational lensing. Our Monte Carlo simulations demonstrate that the derived value of the Hubble constant is very sensitive to the offset between the center of the emission and the center of the variable emitting region. Therefore, we propose using the value of H 0 known from other techniques to spatially resolve the origin of the variable emission once the time delay is measured. We particularly advocate this method for gamma-ray astronomy, where the angular resolution of detectors reaches approximately 0.°1 lensed blazars offer the only route for identify the origin of gamma-ray flares. Large future samples of gravitationally lensed sources identified with Euclid, SKA, and LSST will enable a statistical determination of H 0.

  12. Linear stability of a generalized multi-anticipative car following model with time delays

    NASA Astrophysics Data System (ADS)

    Ngoduy, D.

    2015-05-01

    In traffic flow, the multi-anticipative driving behavior describes the reaction of a vehicle to the driving behavior of many vehicles in front where as the time delay is defined as a physiological parameter reflecting the period of time between perceiving a stimulus of leading vehicles and performing a relevant action such as acceleration or deceleration. A lot of effort has been undertaken to understand the effects of either multi-anticipative driving behavior or time delays on traffic flow dynamics. This paper is a first attempt to analytically investigate the dynamics of a generalized class of car-following models with multi-anticipative driving behavior and different time delays associated with such multi-anticipations. To this end, this paper puts forwards to deriving the (long-wavelength) linear stability condition of such a car-following model and study how the combination of different choices of multi-anticipations and time delays affects the instabilities of traffic flow with respect to a small perturbation. It is found that the effect of delays and multi-anticipations are model-dependent, that is, the destabilization effect of delays is suppressed by the stabilization effect of multi-anticipations. Moreover, the weight factor reflecting the distribution of the driver's sensing to the relative gaps of leading vehicles is less sensitive to the linear stability condition of traffic flow than the weight factor for the relative speed of those leading vehicles.

  13. Time-delayed coupled logistic capacity model in population dynamics

    NASA Astrophysics Data System (ADS)

    Cáceres, Manuel O.

    2014-08-01

    This study proposes a delay-coupled system based on the logistic equation that models the interaction of a population with its varying environment. The integro-diferential equations of the model are presented in terms of a distributed time-delayed coupled logistic-capacity equation. The model eliminates the need for a prior knowledge of the maximum saturation environmental carrying capacity value. Therefore the dynamics toward the final attractor in a distributed time-delayed coupled logistic-capacity model is studied. Exact results are presented, and analytical conclusions have been done in terms of the two parameters of the model.

  14. Kernel regression estimates of time delays between gravitationally lensed fluxes

    NASA Astrophysics Data System (ADS)

    AL Otaibi, Sultanah; Tiňo, Peter; Cuevas-Tello, Juan C.; Mandel, Ilya; Raychaudhury, Somak

    2016-06-01

    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 data sets for the same quasar. We develop realistic artificial data sets in order to carry out controlled experiments to test the 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.

  15. Time-delayed operation of a telerobot via geosynchronous relay

    NASA Technical Reports Server (NTRS)

    Wilcox, Brian H.

    1988-01-01

    Operation of a telerobot is compromised if a time delay of more than a few hundred milliseconds exists between the operator and remote manipulator. However, the most economically attractive way to perform telerobotic functions such as assembly, maintenance, and repair in Earth orbit is via geosynchronous relay satellites to a ground-based operator. This induces loop delays from one-half to two seconds, depending on how many relays are involved. Such large delays makes direct master-slave, force-reflecting teleoperated systems infeasible. Research at JPL on a useful telerobot that operates with such time delays is described.

  16. Relativity time-delay experiments utilizing 'Mariner' spacecraft

    NASA Technical Reports Server (NTRS)

    Esposito, P. B.; Anderson, J. D.

    1974-01-01

    Relativity predicts that the transit time of a signal propagated from the earth to a spacecraft and retransmitted back to earth ought to exhibit an additional, variable time delay. The present work describes some of the analytical techniques employed in experiments using Mariner spacecraft designed to test the accuracy of this prediction. Two types of data are analyzed in these relativity experiments; these include phase-coherent, two-way Doppler shift and round-trip, transit-time measurements. Results of Mariner 6 and 7 relativistic time-delay experiments are in agreement with Einstein's theory of general relativity with an uncertainty of 3%.

  17. Time delay in simple one-dimensional systems

    NASA Astrophysics Data System (ADS)

    van Dijk, W.; Kiers, K. A.

    1992-06-01

    The time delay or the time advance in the scattering of simple one-dimensional systems can be evaluated in a straightforward manner for certain potential models. It is found that when the interacting potential is attractive and has a strength such that it nearly supports an additional bound state, the time delay at small scattering energy is very large. On the other hand, if the potential supports a bound state with nearly zero binding energy, the time advance near threshold is anomalously large. The behavior of a wave packet scattering from the double delta-function potential is also investigated.

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

    SciTech Connect

    Pejovic, Milic M.; Denic, Dragan B.; Pejovic, Momcilo M.; Nesic, Nikola T.; Vasovic, Nikola

    2010-10-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  20. Stability Criteria for Differential Equations with Variable Time Delays

    ERIC Educational Resources Information Center

    Schley, D.; Shail, R.; Gourley, S. A.

    2002-01-01

    Time delays are an important aspect of mathematical modelling, but often result in highly complicated equations which are difficult to treat analytically. In this paper it is shown how careful application of certain undergraduate tools such as the Method of Steps and the Principle of the Argument can yield significant results. Certain delay…

  1. Attosecond time-delay spectroscopy of the hydrogen molecule

    NASA Astrophysics Data System (ADS)

    Ivanov, I. A.; Kheifets, A. S.; Serov, Vladislav V.

    2012-12-01

    We apply the concept of photoemission time delay to the process of single-photon one-electron ionization of the H2 molecule. We demonstrate that, by resolving the photoelectron detection in time on the attosecond scale, one can extract differential photoionization cross sections for particular field and molecule orientations from the measurement on a randomly oriented molecule

  2. Use of Constant Time Delay and Attentional Responses with Adolescents.

    ERIC Educational Resources Information Center

    Wolery, Mark; And Others

    1991-01-01

    This study examined effectiveness of a constant time delay (CTD) procedure in teaching social studies and health facts to five adolescents with learning or behavioral disorders. Students were given praise with and without additional information. Results indicated CTD procedures were reliable and effective, and students acquired nontargeted as well…

  3. Influence of time delay and nonlinear diffusion on herbivore outbreak

    NASA Astrophysics Data System (ADS)

    Sun, Gui-Quan; Chakraborty, Amit; Liu, Quan-Xing; Jin, Zhen; Anderson, Kurt E.; Li, Bai-Lian

    2014-05-01

    Herbivore outbreaks, a major form of natural disturbance in many ecosystems, often have devastating impacts on their food plants. Understanding those factors permitting herbivore outbreaks to occur is a long-standing issue in conventional studies of plant-herbivore interactions. These studies are largely concerned with the relative importance of intrinsic biological factors and extrinsic environmental variations in determining the degree of herbivore outbreaks. In this paper, we illustrated that how the time delay associated with plant defense responses to herbivore attacks and the spatial diffusion of herbivore jointly promote outbreaks of herbivore population. Using a reaction-diffusion model, we showed that there exists a threshold of time delay in plant-herbivore interactions; when time delay is below the threshold value, there is no herbivore outbreak. However, when time delay is above the threshold value, periodic outbreak of herbivore emerges. Furthermore, the results confirm that during the outbreak period, plants display much lower density than its normal level but higher in the inter-outbreak periods. Our results are supported by empirical findings.

  4. Investigating Interaural Frequency-Place Mismatches via Bimodal Vowel Integration

    PubMed Central

    Santurette, Sébastien; Chalupper, Josef; Dau, Torsten

    2014-01-01

    For patients having residual hearing in one ear and a cochlear implant (CI) in the opposite ear, interaural place-pitch mismatches might be partly responsible for the large variability in individual benefit. Behavioral pitch-matching between the two ears has been suggested as a way to individualize the fitting of the frequency-to-electrode map but is rather tedious and unreliable. Here, an alternative method using two-formant vowels was developed and tested. The interaural spectral shift was inferred by comparing vowel spaces, measured by presenting the first formant (F1) to the nonimplanted ear and the second (F2) on either side. The method was first evaluated with eight normal-hearing listeners and vocoder simulations, before being tested with 11 CI users. Average vowel distributions across subjects showed a similar pattern when presenting F2 on either side, suggesting acclimatization to the frequency map. However, individual vowel spaces with F2 presented to the implant did not allow a reliable estimation of the interaural mismatch. These results suggest that interaural frequency-place mismatches can be derived from such vowel spaces. However, the method remains limited by difficulties in bimodal fusion of the two formants. PMID:25421087

  5. Investigating interaural frequency-place mismatches via bimodal vowel integration.

    PubMed

    Guérit, François; Santurette, Sébastien; Chalupper, Josef; Dau, Torsten

    2014-01-01

    For patients having residual hearing in one ear and a cochlear implant (CI) in the opposite ear, interaural place-pitch mismatches might be partly responsible for the large variability in individual benefit. Behavioral pitch-matching between the two ears has been suggested as a way to individualize the fitting of the frequency-to-electrode map but is rather tedious and unreliable. Here, an alternative method using two-formant vowels was developed and tested. The interaural spectral shift was inferred by comparing vowel spaces, measured by presenting the first formant (F1) to the nonimplanted ear and the second (F2) on either side. The method was first evaluated with eight normal-hearing listeners and vocoder simulations, before being tested with 11 CI users. Average vowel distributions across subjects showed a similar pattern when presenting F2 on either side, suggesting acclimatization to the frequency map. However, individual vowel spaces with F2 presented to the implant did not allow a reliable estimation of the interaural mismatch. These results suggest that interaural frequency-place mismatches can be derived from such vowel spaces. However, the method remains limited by difficulties in bimodal fusion of the two formants. PMID:25421087

  6. A comparison of cosmological models using time delay lenses

    SciTech Connect

    Wei, Jun-Jie; Wu, Xue-Feng; Melia, Fulvio E-mail: xfwu@pmo.ac.cn

    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.

  7. Adaptive control of systems with unknown time delays

    NASA Astrophysics Data System (ADS)

    Nelson, James P.

    Control systems, on earth or in outer-space, may exhibit time delays in their dynamic behavior. Aerospace control systems must be able to operate in the presence of time delays both internal to the system and in its inputs and outputs. These delays are often introduced via systems controlled through a network, by information, energy or mass transport phenomena, but can also be caused by computer processing time or by the accumulation of time lags in a number of simple dynamic systems connected in series. When a dynamic system is subject to a time delay, unlike other parameters, this affects the temporal characteristics of the system and exact control over system operation cannot be strictly implemented. Systems with significant time delays are difficult to control using standard feedback controllers. The United States Air Force Research Laboratory (AFRL) is considering the use of router-based data networks on-board next generation satellites and in decentralized control architectures. This approach has the potential to introduce non-constant and non-deterministic communications delays into feedback control loops that make use of these data networks. The desire for rapid deployment of new spacecraft architectures will also introduce many other control issues as the rigorous measurement, calibration and performance tests usually conducted on spacecraft systems to develop a highly precise dynamic model will need to be drastically shortened due to the desired abbreviated build and launch schedule. Due to limited testing and system identification, the spacecraft model will have uncertainties/perturbations from the actual plant. This will require a controller that can robustly control the non-linear dynamic model with limited plant knowledge. The problems created by the control of time delay systems and the limited plant knowledge nature of the systems of interest leads us to the concept of adaptive control. Adaptive control makes adjustment of the controllers

  8. Stability and chaotification of vibration isolation floating raft systems with time-delayed feedback control.

    PubMed

    Li, Y L; Xu, D L; Fu, Y M; Zhou, J X

    2011-09-01

    This paper presents a systematic study on the stability of a two-dimensional vibration isolation floating raft system with a time-delayed feedback control. Based on the generalized Sturm criterion, the critical control gain for the delay-independent stability region and critical time delays for the stability switches are derived. The critical conditions can provide a theoretical guidance of chaotification design for line spectra reduction. Numerical simulations verify the correctness of the approach. Bifurcation analyses reveal that chaotification is more likely to occur in unstable region defined by these critical conditions, and the stiffness of the floating raft and mass ratio are the sensitive parameters to reduce critical control gain. PMID:21974650

  9. Emergence of adaptability to time delay in bipedal locomotion.

    PubMed

    Ohgane, Kunishige; Ei, Shin-Ichiro; Kazutoshi, Kudo; Ohtsuki, Tatsuyuki

    2004-02-01

    Based on neurophysiological evidence, theoretical studies have shown that locomotion is generated by mutual entrainment between the oscillatory activities of central pattern generators (CPGs) and body motion. However, it has also been shown that the time delay in the sensorimotor loop can destabilize mutual entrainment and result in the failure to walk. In this study, a new mechanism called flexible-phase locking is proposed to overcome the time delay. It is realized by employing the Bonhoeffer-Van der Pol formalism - well known as a physiologically faithful neuronal model - for neurons in the CPG. The formalism states that neurons modulate their phase according to the delay so that mutual entrainment is stabilized. Flexible-phase locking derives from the phase dynamics related to an asymptotically stable limit cycle of the neuron. The effectiveness of the mechanism is verified by computer simulations of a bipedal locomotion model. PMID:14999479

  10. Delay Independent Criterion for Multiple Time-delay Systems

    NASA Astrophysics Data System (ADS)

    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.

  11. Cross section versus time delay and trapping probability

    NASA Astrophysics Data System (ADS)

    Luna-Acosta, G. A.; Fernández-Marín, A. A.; Méndez-Bermúdez, J. A.; Poli, Charles

    2016-07-01

    We study the behavior of the s-wave partial cross section σ (k), the Wigner-Smith time delay τ (k), and the trapping probability P (k) as function of the wave number k. The s-wave central square well is used for concreteness, simplicity, and to elucidate the controversy whether it shows true resonances. It is shown that, except for very sharp structures, the resonance part of the cross section, the trapping probability, and the time delay, reach their local maxima at different values of k. We show numerically that τ (k) > 0 at its local maxima, occurring just before the resonant part of the cross section reaches its local maxima. These results are discussed in the light of the standard definition of resonance.

  12. Towards Supervising Remote Dexterous Robots Across Time Delay

    NASA Technical Reports Server (NTRS)

    Hambuchen, Kimberly; Bluethmann, William; Goza, Michael; Ambrose, Robert; Wheeler, Kevin; Rabe, Ken

    2006-01-01

    The President s Vision for Space Exploration, laid out in 2004, relies heavily upon robotic exploration of the lunar surface in early phases of the program. Prior to the arrival of astronauts on the lunar surface, these robots will be required to be controlled across space and time, posing a considerable challenge for traditional telepresence techniques. Because time delays will be measured in seconds, not minutes as is the case for Mars Exploration, uploading the plan for a day seems excessive. An approach for controlling dexterous robots under intermediate time delay is presented, in which software running within a ground control cockpit predicts the intention of an immersed robot supervisor, then the remote robot autonomously executes the supervisor s intended tasks. Initial results are presented.

  13. Time Delay Evolution of Five Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Kovačević, A.; Popović, L. Č.; Shapovalova, A. I.; Ilić, D.; Burenkov, A. N.; Chavushyan, V. H.

    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.

  14. Medical ultrasound imager based on time delay spectrometry.

    PubMed

    Heyser, R C; Hestenes, J D; Rooney, J A; Gammell, P M; Le Croissette, D H

    1989-01-01

    A reflection mode proof-of-concept medical ultrasound imager based on time delay spectrometry has been developed and tested. The system uses a broad band swept-frequency signal operating up to 10 MHz. Signal processing using a fast Fourier transform (FFT) permits extraction of range information. The imager has a higher signal-to-noise ratio than pulse-echo systems which allows high resolution at greater depths. The time delay spectrometry (TDS) spread spectrum operates at lower peak intensities than pulse-echo and permits more control of the spectral content and amplitude of the signal. At present, the system is non-real time which degrades in vivo imaging because of averaging over several cardiac cycles and tissue movement. PMID:2643838

  15. Two-actor conflict with time delay: A dynamical model

    NASA Astrophysics Data System (ADS)

    Qubbaj, Murad R.; Muneepeerakul, Rachata

    2012-11-01

    Recent mathematical dynamical models of the conflict between two different actors, be they nations, groups, or individuals, have been developed that are capable of predicting various outcomes depending on the chosen feedback strategies, initial conditions, and the previous states of the actors. In addition to these factors, this paper examines the effect of time delayed feedback on the conflict dynamics. Our analysis shows that under certain initial and feedback conditions, a stable neutral equilibrium of conflict may destabilize for some critical values of time delay, and the two actors may evolve to new emotional states. We investigate the results by constructing critical delay surfaces for different sets of parameters and analyzing results from numerical simulations. These results provide new insights regarding conflict and conflict resolution and may help planners in adjusting and assessing their strategic decisions.

  16. Fullerene valence photoemission time delay near ionization cavity minima

    NASA Astrophysics Data System (ADS)

    Magrakvelidze, Maia; Anstine, Dylan; Dixit, Gopal; Madjet, Mohamed; Chakraborty, Himadri

    2015-05-01

    We investigate photoemission quantum phases and associated Wigner-Smith time delays for HOMO and HOMO-1 electrons of a C60 molecule using time-dependent local density approximation (TDLDA). The interference oscillations in C60 valence emissions 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. Besides fullerenes, the detection of photoemission minima in metal clusters suggests a possible universality of the phenomenon in cluster systems, or even quantum dots, that confine finite-sized electron gas. The work predicts a new research direction to apply attosecond metrology, such as RABITT, in the world of nanosystems. This work was supported by the U.S. National Science Foundation.

  17. Simultaneous Estimation of Time Delays and Quasar Structure

    NASA Astrophysics Data System (ADS)

    Morgan, Christopher W.; Eyler, Michael E.; Kochanek, C. S.; Morgan, Nicholas D.; Falco, Emilio E.; Vuissoz, C.; Courbin, F.; Meylan, G.

    2008-03-01

    We expand our Bayesian Monte Carlo method for analyzing the light curves of gravitationally lensed quasars to simultaneously estimate time delays and the sizes of quasar continuum emission regions including their mutual uncertainties. We apply the method to HE1104-1805 and QJ0158-4325, two doubly imaged quasars with microlensing and intrinsic variability on comparable timescales. For HE1104-1805 the resulting time delay of Δ tAB = tA - tB = 162.2-5.9+6.3 days and accretion disk size estimate of log {(rs/cm) [cos (i)/0.5]1/2} = 15.7-0.5+0.4 at 0.2 μm in the rest frame and for inclination i are consistent with earlier estimates but suggest that existing methods for estimating time delays in the presence of microlensing underestimate the uncertainties. We are unable to measure a time delay for QJ0158-4325, but the accretion disk size is log {(rs/cm) [cos (i)/0.5]1/2} = 14.9 +/- 0.3 at 0.3 μm in the rest frame. Based on observations obtained with the Small and Moderate Aperture Research Telescope System (SMARTS) 1.3 m, which is operated by the SMARTS Consortium, and observations made with the NASA/ESA Hubble Space Telescope for program HST-GO-9744 of the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  18. STRONG LENS TIME DELAY CHALLENGE. I. EXPERIMENTAL DESIGN

    SciTech Connect

    Dobler, Gregory; Fassnacht, Christopher D.; Rumbaugh, Nicholas; Treu, Tommaso; Liao, Kai; Marshall, Phil; Hojjati, Alireza; Linder, Eric

    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.

  19. Time Delay Integration: A Wide-Field Survey Technique

    NASA Astrophysics Data System (ADS)

    Lapointe, Robert; Hill, E.; Leimer, L.; McMillian, K.; Miller, A.; Prindle, A.

    2009-05-01

    The Advanced Placement Physics class of Orange Lutheran High School has conducted a survey-imaging pro-ject using a Time Delay Integration (TDI) technique. TDI enables very wide-field images to be collected in the form of long strips of the sky. A series of five consecutive nights were captured, calibrated and compared to re-veal possible transient phenomena such as supernovae, asteroids, and other events that have a noticeable change over 24-hour intervals.

  20. Across-frequency nonlinear inhibition by GABA in processing of interaural time difference.

    PubMed

    Mori, K

    1997-09-01

    The barn owl uses the interaural time difference (ITD) to determine the azimuth of a sound source. Narrowband ITD-sensitive neurons cannot distinguish a given ITD from those that produce the same interaural phase difference (phase ambiguity). Neurons in the external nucleus of the inferior colliculus (ICx) resolve the ambiguity by gathering ITD information across many frequencies, thereby suppressing false responses (side peaks, SP) relative to the true ITD (the main peak, MP) in a response versus ITD curve. This process was quantitatively studied by comparing the ITD curve for a pair of tones presented simultaneously (two-tone curve) to the simple sum (predicted curve) of the individual ITD curves for the same tones presented separately. Sixteen of the 39 neurons tested did not show a significant difference in MP and SP responses between these curves (category I); 14 neurons showed significant SP suppression (category II). During iontophoretic application of bicuculline methiodide, a GABA(A) antagonist, most (n = 7/8) category II neurons lost nonlinear SP suppression and became linear, whereas category I neurons retained linear summation (n = 3/3). Thus, the nonlinear cross-frequency interaction of ITD responses in ICx neurons was mediated mostly by GABAergic inhibition, which enhanced SP suppression, and helped resolve phase ambiguity. PMID:9307308

  1. Perception and coding of interaural time differences with bilateral cochlear implants.

    PubMed

    Laback, Bernhard; Egger, Katharina; Majdak, Piotr

    2015-04-01

    Bilateral cochlear implantation is increasingly becoming the standard in the clinical treatment of bilateral deafness. The main motivation is to provide users of bilateral cochlear implants (CIs) access to binaural cues essential for localizing sound sources and understanding speech in environments of interfering sounds. One of those cues, interaural level differences, can be perceived well by CI users to allow some basic left versus right localization. However, interaural time differences (ITDs) which are important for localization of low-frequency sounds and spatial release from masking are not adequately represented by clinical envelope-based CI systems. Here, we first review the basic ITD sensitivity of CI users, particularly their dependence on stimulation parameters like stimulation rate and place, modulation rate, and envelope shape in single-electrode stimulation, as well as stimulation level, electrode spacing, and monaural across-electrode timing in multiple-electrode stimulation. Then, we discuss factors involved in ITD perception in electric hearing including the match between highly phase-locked electric auditory nerve response properties and binaural cell properties, the restricted stimulation of apical tonotopic pathways, channel interactions in multiple-electrode stimulation, and the onset age of binaural auditory input. Finally, we present clinically available CI stimulation strategies and experimental strategies aiming at improving listeners' access to ITD cues. This article is part of a Special Issue entitled . PMID:25456088

  2. Quasar optical variability: searching for interband time delays

    NASA Astrophysics Data System (ADS)

    Bachev, R. S.

    2009-01-01

    Aims: The main purpose of this paper is to study time delays between the light variations in different wavebands for a sample of quasars. Measuring a reliable time delay for a large number of quasars may help constraint the models of their central engines. The standard accretion disk irradiation model predicts a delay of the longer wavelengths behind the shorter ones, a delay that depends on the fundamental quasar parameters. Since the black hole masses and the accretion rates are approximately known for the sample we use, one can compare the observed time delays with the expected ones. Methods: We applied the interpolation cross-correlation function (ICCF) method to the Giveon et al. sample of 42 quasars, monitored in two (B and R) colors, to find the time lags represented by the ICCF peaks. Different tests were performed to assess the influence of photometric errors, sampling, etc., on the final result. Results: We found that most of the objects show a delay in the red light curve behind the blue one (a positive lag), which on average for the sample is about +4 days (+3 for the median), although the scatter is significant. These results are broadly consistent with the reprocessing model, especially for the well-sampled objects. The normalized time-lag deviations do not seem to correlate significantly with other quasar properties, including optical, radio, or X-ray measurables. On the other hand, many objects show a clear negative lag, which, if real, may have important consequences for the variability models.

  3. Correlation-induced Time Delay in Atomic Photoionization

    NASA Astrophysics Data System (ADS)

    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.

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

    PubMed

    Goharian, M; Khan, R F H

    2010-04-01

    For the management of mobile tumors, respiratory gating is the ideal option, both during imaging and during therapy. The major advantage of respiratory gating during imaging is that it is possible to create a single artifact-free CT data-set during a selected phase of the patient's breathing cycle. The purpose of the present work is to present a simple technique to measure the time delay during acquisition of a prospectively gated CT. The time delay of a Philips Brilliance BigBore (Philips Medical Systems, Madison, WI) scanner attached to a Varian Real-Time Position Management (RPM) system (Varian Medical Systems, Palo Alto, CA) was measured. Two methods were used to measure the CT time delay: using a motion phantom and using a recorded data file from the RPM system. In the first technique, a rotating wheel phantom was altered by placing two plastic balls on its axis and rim, respectively. For a desired gate, the relative positions of the balls were measured from the acquired CT data and converted into corresponding phases. Phase difference was calculated between the measured phases and the desired phases. Using period of motion, the phase difference was converted into time delay. The Varian RPM system provides an external breathing signal; it also records transistor-transistor logic (TTL) 'X-Ray ON' status signal from the CT scanner in a text file. The TTL 'X-Ray ON' indicates the start of CT image acquisition. Thus, knowledge of the start time of CT acquisition, combined with the real-time phase and amplitude data from the external respiratory signal, provides time-stamping of all images in an axial CT scan. The TTL signal with time-stamp was used to calculate when (during the breathing cycle) a slice was recorded. Using the two approaches, the time delay between the prospective gating signal and CT simulator has been determined to be 367 +/- 40 ms. The delay requires corrections both at image acquisition and while setting gates for the treatment delivery

  5. The range of time delay and the global stability of the equilibrium for an IVGTT model☆

    PubMed Central

    Li, Jiaxu; Wang, Minghu; De Gaetano, Andrea; Palumbo, Pasquale; Panunzi, Simona

    2011-01-01

    Diabetes mellitus has become a prevalent disease in the world. Diagnostic protocol for the onset of diabetes mellitus is the initial step in the treatments. The intravenous glucose tolerance test (IVGTT) has been considered as the most accurate method to determine the insulin sensitivity and glucose effectiveness. It is well known that there exists a time delay in insulin secretion stimulated by the elevated glucose concentration level. However, the range of the length of the delay in the existing IVGTT models are not fully discussed and thus in many cases the time delay may be assigned to a value out of its reasonable range. In addition, several attempts had been made to determine when the unique equilibrium point is globally asymptotically stable. However, all these conditions are delay-independent. In this paper, we discuss the range of the time delay and provide easy-to-check delay-dependent conditions for the global asymptotic stability of the equilibrium point for a recent IVGTT model through Liapunov function approach. Estimates of the upper bound of the delay for global stability are given in corollaries. In addition, the numerical simulation in this paper is fully incorporated with functional initial conditions, which is natural and more appropriate in delay differential equation system. PMID:22123436

  6. Interaural coherence for noise bands: waveforms and envelopes.

    PubMed

    Aaronson, Neil L; Hartmann, William M

    2010-03-01

    This paper reports the results of experiments performed in an effort to find a formulaic relationship between the interaural waveform coherence of a band of noise gamma(W) and the interaural envelope coherence of the noise band gamma(E). An interdependence described by gamma(E)=pi/4+(1-pi/4)(gamma(W))(2.1) is found. This relationship holds true both in a computer experiment and for binaural measurements made in two rooms using a KEMAR manikin. Room measurements are used to derive a measure of reliability for the formula. Ultimately, a user who knows the waveform coherence can predict the envelope coherence with a small degree of uncertainty. PMID:20329836

  7. STRONGLY LENSED JETS, TIME DELAYS, AND THE VALUE OF H {sub 0}

    SciTech Connect

    Barnacka, Anna; Geller, Margaret J.; Benbow, Wystan; Dell'Antonio, Ian P.

    2015-01-20

    In principle, the most straightforward method of estimating the Hubble constant relies on time delays between mirage images of strongly lensed sources. It is a puzzle, then, that the values of H {sub 0} obtained with this method span a range from ∼50-100 km s{sup –1}Mpc{sup –1}. Quasars monitored to measure these time delays are multi-component objects. The variability may arise from different components of the quasar or may even originate from a jet. Misidentifying a variable-emitting region in a jet with emission from the core region may introduce an error in the Hubble constant derived from a time delay. Here, we investigate the complex structure of the sources as the underlying physical explanation of the wide spread in values of the Hubble constant based on gravitational lensing. Our Monte Carlo simulations demonstrate that the derived value of the Hubble constant is very sensitive to the offset between the center of the emission and the center of the variable emitting region. Therefore, we propose using the value of H {sub 0} known from other techniques to spatially resolve the origin of the variable emission once the time delay is measured. We particularly advocate this method for gamma-ray astronomy, where the angular resolution of detectors reaches approximately 0.°1; lensed blazars offer the only route for identify the origin of gamma-ray flares. Large future samples of gravitationally lensed sources identified with Euclid, SKA, and LSST will enable a statistical determination of H {sub 0}.

  8. Anatomical limits on interaural time differences: an ecological perspective

    PubMed Central

    Hartmann, William M.; Macaulay, Eric J.

    2013-01-01

    Human listeners, and other animals too, use interaural time differences (ITD) to localize sounds. If the sounds are pure tones, a simple frequency factor relates the ITD to the interaural phase difference (IPD), for which there are known iso-IPD boundaries, 90°, 180°… defining regions of spatial perception. In this article, iso-IPD boundaries for humans are translated into azimuths using a spherical head model (SHM), and the calculations are checked by free-field measurements. The translated boundaries provide quantitative tests of an ecological interpretation for the dramatic onset of ITD insensitivity at high frequencies. According to this interpretation, the insensitivity serves as a defense against misinformation and can be attributed to limits on binaural processing in the brainstem. Calculations show that the ecological explanation passes the tests only if the binaural brainstem properties evolved or developed consistent with heads that are 50% smaller than current adult heads. Measurements on more realistic head shapes relax that requirement only slightly. The problem posed by the discrepancy between the current head size and a smaller, ideal head size was apparently solved by the evolution or development of central processes that discount large IPDs in favor of interaural level differences. The latter become more important with increasing head size. PMID:24592209

  9. COSMOLOGY FROM GRAVITATIONAL LENS TIME DELAYS AND PLANCK DATA

    SciTech Connect

    Suyu, S. H.; Treu, T.; Sonnenfeld, A.; Hilbert, S.; Spiniello, C.; Auger, M. W.; Collett, T.; Blandford, R. D.; Marshall, P. J.; Courbin, F.; Meylan, G.; Tewes, M.; Fassnacht, C. D.; Koopmans, L. V. E.

    2014-06-20

    Under the assumption of a flat ΛCDM cosmology, recent data from the Planck satellite point toward a Hubble constant that is in tension with that measured by gravitational lens time delays and by the local distance ladder. Prosaically, this difference could arise from unknown systematic uncertainties in some of the measurements. More interestingly—if systematics were ruled out—resolving the tension would require a departure from the flat ΛCDM cosmology, introducing, for example, a modest amount of spatial curvature, or a non-trivial dark energy equation of state. To begin to address these issues, we present an analysis of the gravitational lens RXJ1131–1231 that is improved in one particular regard: we examine the issue of systematic error introduced by an assumed lens model density profile. We use more flexible gravitational lens models with baryonic and dark matter components, and find that the exquisite Hubble Space Telescope image with thousands of intensity pixels in the Einstein ring and the stellar velocity dispersion of the lens contain sufficient information to constrain these more flexible models. The total uncertainty on the time-delay distance is 6.6% for a single system. We proceed to combine our improved time-delay distance measurement with the WMAP9 and Planck posteriors. In an open ΛCDM model, the data for RXJ1131–1231 in combination with Planck favor a flat universe with Ω{sub k}=0.00{sub −0.02}{sup +0.01} (68% credible interval (CI)). In a flat wCDM model, the combination of RXJ1131–1231 and Planck yields w=−1.52{sub −0.20}{sup +0.19} (68% CI)

  10. STRONG LENS TIME DELAY CHALLENGE. II. RESULTS OF TDC1

    SciTech Connect

    Liao, Kai; Treu, Tommaso; Marshall, Phil; Fassnacht, Christopher D.; Rumbaugh, Nick; Dobler, Gregory; Aghamousa, Amir; Bonvin, Vivien; Courbin, Frederic; Meylan, Georges; Hojjati, Alireza; Jackson, Neal; Kashyap, Vinay; Mandel, Kaisey; Rathna Kumar, S.; Prabhu, Tushar P.; Linder, Eric; Meng, Xiao-Li; Moustakas, Leonidas A.; Romero-Wolf, Andrew [Jet Propulsion Laboratory, California Institute of Technology, M 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.

  11. Strong Lens Time Delay Challenge. II. Results of TDC1

    NASA Astrophysics Data System (ADS)

    Liao, Kai; Treu, Tommaso; Marshall, Phil; Fassnacht, Christopher D.; Rumbaugh, Nick; Dobler, Gregory; Aghamousa, Amir; Bonvin, Vivien; Courbin, Frederic; Hojjati, Alireza; Jackson, Neal; Kashyap, Vinay; Rathna Kumar, S.; 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

    2015-02-01

    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 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 χ2, 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 χ2 < 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.

  12. On noise in time-delay integration CMOS image sensors

    NASA Astrophysics Data System (ADS)

    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.

  13. Time-Delayed Models of Gene Regulatory Networks

    PubMed Central

    Parmar, K.; Blyuss, K. B.; Kyrychko, Y. N.; Hogan, S. J.

    2015-01-01

    We discuss different mathematical models of gene regulatory networks as relevant to the onset and development of cancer. After discussion of alternative modelling approaches, we use a paradigmatic two-gene network to focus on the role played by time delays in the dynamics of gene regulatory networks. We contrast the dynamics of the reduced model arising in the limit of fast mRNA dynamics with that of the full model. The review concludes with the discussion of some open problems. PMID:26576197

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  15. On time delay estimation from a sparse linear prediction perspective.

    PubMed

    He, Hongsen; Yang, Tao; Chen, Jingdong

    2015-02-01

    This paper proposes a sparse linear prediction based algorithm to estimate time difference of arrival. This algorithm unifies the cross correlation method without prewhitening and that with prewhitening via an ℓ2/ℓ1 optimization process, which is solved by an augmented Lagrangian alternating direction method. It also forms a set of time delay estimators that make a tradeoff between prewhitening and non-prewhitening through adjusting a regularization parameter. The effectiveness of the proposed algorithm is demonstrated in noisy and reverberant environments. PMID:25698037

  16. Time Delay in Neutron-Alpha Resonant Scattering

    SciTech Connect

    Hoop, Bernard; Hale, Gerald M.

    2011-10-24

    Time delay analysis of neutron-alpha resonant scattering cross sections supports characterization of the lowest 3/2{sup +} level in {sup 5}He as fundamentally an n-{alpha} resonance on the second Riemann energy sheet of both n-{alpha} and deuteron-{sup 3}H channels, with an associated shadow pole on a different unphysical sheet that, through its associated zero on the physical sheet, contributes to the large {sup 4}He(n,d){sup 3}H cross section.

  17. Numerical bifurcation analysis of immunological models with time delays

    NASA Astrophysics Data System (ADS)

    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.

  18. Estimation of nonlinear pilot model parameters including time delay.

    NASA Technical Reports Server (NTRS)

    Schiess, J. R.; Roland, V. R.; Wells, W. R.

    1972-01-01

    Investigation of the feasibility of using a Kalman filter estimator for the identification of unknown parameters in nonlinear dynamic systems with a time delay. The problem considered is the application of estimation theory to determine the parameters of a family of pilot models containing delayed states. In particular, the pilot-plant dynamics are described by differential-difference equations of the retarded type. The pilot delay, included as one of the unknown parameters to be determined, is kept in pure form as opposed to the Pade approximations generally used for these systems. Problem areas associated with processing real pilot response data are included in the discussion.

  19. Detector module for a simplified ultrasonic time delay spectrometry system

    NASA Astrophysics Data System (ADS)

    Gammell, Paul M.; Liu, Yunbo; Maruvada, Subha; Harris, Gerald R.

    2012-05-01

    When setting up a water-tank based ultrasonic system, aligning the transmitting and receiving transducers to maximize the received signal is required. With a digital time delay spectrometry (TDS) system the "dechirped" signal is observed while positional adjustments are being made. Observation is easier if only the envelope, rather than the modulated signal, is displayed. A module is described that provides an envelope (rectified signal) that, when displayed on an oscilloscope, is suitable as an alignment aid for use with the TDS system described elsewhere in these Proceedings.

  20. Optical true time delay unit for multi-beamforming.

    PubMed

    Ye, Xingwei; Zhang, Fangzheng; Pan, Shilong

    2015-04-20

    An optical true time delay (TTD) unit capable of adding independent time delays to multiple RF signals is proposed, which can be used for multi-beamforming in both transmit and receive modes. In the proposed unit, N RF signals with different center frequencies are modulated on an optical frequency comb (OFC). After transmission through a dispersive element, the RF-modulated OFC is split into N paths. In each path, a comb line is selected by a tunable optical filter. Thanks to the chromatic dispersion of the dispersive element, independently-controllable TTDs can be obtained in all paths. Then, a microwave photonic filter (MPF) is incorporated in each path, allowing a designated RF signal to undergo the TTD in that path. A proof-of-concept experiment is carried out. A two-path unit with a low-pass MPF in one path and a high-pass MPF in the other path is built. Controllable TTDs up to ~1.4 ns with a step of ~69 ps are demonstrated based on a 25-GHz-spacing OFC. In addition, a wideband multi-beam phased-array antenna system that can work in both transmit and receive modes is designed using the proposed TTD unit. PMID:25969041

  1. Sleep apnea detection using time-delayed heart rate variability.

    PubMed

    Nano, Marina-Marinela; Xi Long; Werth, Jan; Aarts, Ronald M; Heusdens, Richard

    2015-08-01

    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. PMID:26738071

  2. The VLBI time delay function for synchronous orbits

    NASA Technical Reports Server (NTRS)

    Rosenbaum, B.

    1972-01-01

    The VLBI is a satellite tracking technique that to date was applied largely to the tracking of synchronous orbits. These orbits are favorable for VLBI in that the remote satellite range allows continuous viewing from widely separated stations. The primary observable, geometric time delay is the time difference for signal propagation between satellite and baseline terminals. Extraordinary accuracy in angular position data on the satellite can be obtained by observation from baselines of continental dimensions. In satellite tracking though the common objective is to derive orbital elements. A question arises as to how the baseline vector bears on the accuracy of determining the elements. Our approach to this question is to derive an analytic expression for the time delay function in terms of Kepler elements and station coordinates. The analysis, which is for simplicity based on elliptic motion, shows that the resolution for the inclination of the orbital plane depends on the magnitude of the baseline polar component and the resolution for in-plane elements depends on the magnitude of a projected equatorial baseline component.

  3. A deterministic pseudo-fractal networks with time-delay

    NASA Astrophysics Data System (ADS)

    Xing, Changming; Yang, Lin; Ma, Jun

    2015-08-01

    In this paper, inspired by the pseudo-fractal networks (PFN) and the delayed pseudo-fractal networks (DPFN), we present a novel delayed pseudo-fractal networks model, denoted by NDPFN. Different from the generation algorithm of those two networks, every edge of the novel model has a time-delay to generate new nodes after producing one node. We derive exactly the main structural properties of the novel networks: degree distribution, clustering coefficient, diameter and average path length. Analytical results show that the novel networks have small-world effect and scale-free topology. Comparing topological parameters of these three networks, we find that the degree exponent of the novel networks is the largest while the clustering coefficient and the average path length are the smallest. It means that this kind of delay could weaken the heterogeneity and the small-world features of the network. Particularly, the delay effect in the NDPFN is contrary to that in the DPFN, which illustrates the variety of delay method could produce different effects on the network structure. These present findings may be helpful for a deeper understanding of the time-delay influence on the network topology.

  4. Teleoperation with large time delay using a prevision system

    NASA Astrophysics Data System (ADS)

    Bergamasco, Massimo; De Paolis, Lucio; Ciancio, Stefano; Pinna, Sebastiano

    1997-12-01

    In teleoperation technology various techniques have been proposed in order to alleviate the effects of time delayed communication and to avoid the instability of the system. This paper describes a different approach to robotic teleoperation with large-time delay and a teleoperation system, based on teleprogramming paradigm, has been developed with the intent to improve the slave autonomy and to decrease the amount of information exchanged between master and slave system. The goal concept, specific of AI, has been used. In order to minimize the total task completion time has been introduced a prevision system, called Merlino, able to know in advance the slave's choices taking into account both the operator's actions and the information about the remote environment. The prevision system allows, in case of environment changes, to understand if the slave can solve the goal. Otherwise, Merlino is able to signal a 'fail situation.' Some experiments have been carried out by means of an advanced human-machine interface with force feedback, designed at PERCRO Laboratory of Scuola Superiore S. Anna, which gives a better sensation of presence in the remote environment.

  5. Consensus networks with time-delays over finite fields

    NASA Astrophysics Data System (ADS)

    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.

  6. Performance evaluation of the time delay digital tanlock loop architectures

    NASA Astrophysics Data System (ADS)

    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.

  7. Dynamical analysis of uncertain neural networks with multiple time delays

    NASA Astrophysics Data System (ADS)

    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.

  8. Time delay and integration detectors using charge transfer devices

    NASA Technical Reports Server (NTRS)

    Mccann, D. H.; White, M. H.; Turly, A. P.

    1981-01-01

    An imaging system comprises a multi-channel matrix array of CCD devices wherein a number of sensor cells (pixels) in each channel are subdivided and operated in discrete intercoupled groups of subarrays with a readout CCD shift register terminating each end of the channels. Clock voltages, applied to the subarrays, selectively cause charge signal flow in each subarray in either direction independent of the other subarrays. By selective application of four phase clock voltages, either one, two or all three of the sections subarray sections cause charge signal flow in one direction, while the remainder cause charge signal flow in the opposite direction. This creates a form of selective electronic exposure control which provides an effective variable time delay and integration of three, six or nine sensor cells or integration stages. The device is constructed on a semiconductor sustrate with a buried channel and is adapted for front surface imaging through transparent doped tin oxide gates.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Linearisation via input-output injection of time delay systems

    NASA Astrophysics Data System (ADS)

    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.

  11. Time delay in the Einstein ring PKS 1830-211

    NASA Technical Reports Server (NTRS)

    Van Ommen, T. D.; Jones, D. L.; Preston, R. A.; Jauncey, D. L.

    1995-01-01

    We present radio observations of the gravitational lens PKS 1830-211 at 8.4 and 15 GHz acquired using the Very Large Array. The observations were made over a 13 month period. Significant flux density changes over this period provide strong constraints on the time delay between the two lensed images and suffest a value of 44 +/- 9 days. This offers new direct evidence that this source is indeed a gravitational lens. The lens distance is dependent upon the model chosen, but reasonable limits on the mass of the lensing galaxy suggest that it is unlikely to be at a redshift less than a few tenths, and may well be significantly more distant.

  12. Equilibrium and Disequilibrium Dynamics in Cobweb Models with Time Delays

    NASA Astrophysics Data System (ADS)

    Gori, Luca; Guerrini, Luca; Sodini, Mauro

    2015-06-01

    This paper aims to study price dynamics in two different continuous time cobweb models with delays close to [Hommes, 1994]. In both cases, the stationary equilibrium may be not representative of the long-term dynamics of the model, since it is possible to observe endogenous and persistent fluctuations (supercritical Hopf bifurcations) even if a deterministic context without external shocks is considered. In the model in which markets are in equilibrium every time, we show that the existence of time delays in the expectations formation mechanism may cause chaotic dynamics similar to those obtained in [Hommes, 1994] in a discrete time context. From a mathematical point of view, we apply the Poincaré-Lindstedt perturbation method to study the local dynamic properties of the models. In addition, several numerical experiments are used to investigate global properties of the systems.

  13. Heterogeneity of time delays determines synchronization of coupled oscillators.

    PubMed

    Petkoski, Spase; Spiegler, Andreas; Proix, Timothée; Aram, Parham; Temprado, Jean-Jacques; Jirsa, Viktor K

    2016-07-01

    Network couplings of oscillatory large-scale systems, such as the brain, have a space-time structure composed of connection strengths and signal transmission delays. We provide a theoretical framework, which allows treating the spatial distribution of time delays with regard to synchronization, by decomposing it into patterns and therefore reducing the stability analysis into the tractable problem of a finite set of delay-coupled differential equations. We analyze delay-structured networks of phase oscillators and we find that, depending on the heterogeneity of the delays, the oscillators group in phase-shifted, anti-phase, steady, and non-stationary clusters, and analytically compute their stability boundaries. These results find direct application in the study of brain oscillations. PMID:27575125

  14. On the time delay between ultra-relativistic particles

    NASA Astrophysics Data System (ADS)

    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.

  15. Spectrometer employing optical fiber time delays for frequency resolution

    DOEpatents

    Schuss, Jack J.; Johnson, Larry C.

    1979-01-01

    This invention provides different length glass fibers for providing a broad range of optical time delays for short incident chromatic light pulses for the selective spatial and frequency analysis of the light with a single light detector. To this end, the frequencies of the incident light are orientated and matched with the different length fibers by dispersing the separate frequencies in space according to the respective fiber locations and lengths at the input terminal of the glass fibers. This makes the different length fibers useful in the field of plasma physics. To this end the short light pulses can be scattered by a plasma and then passed through the fibers for analyzing and diagnosing the plasma while it varies rapidly with time.

  16. Heterogeneity of time delays determines synchronization of coupled oscillators

    NASA Astrophysics Data System (ADS)

    Petkoski, Spase; Spiegler, Andreas; Proix, Timothée; Aram, Parham; Temprado, Jean-Jacques; Jirsa, Viktor K.

    2016-07-01

    Network couplings of oscillatory large-scale systems, such as the brain, have a space-time structure composed of connection strengths and signal transmission delays. We provide a theoretical framework, which allows treating the spatial distribution of time delays with regard to synchronization, by decomposing it into patterns and therefore reducing the stability analysis into the tractable problem of a finite set of delay-coupled differential equations. We analyze delay-structured networks of phase oscillators and we find that, depending on the heterogeneity of the delays, the oscillators group in phase-shifted, anti-phase, steady, and non-stationary clusters, and analytically compute their stability boundaries. These results find direct application in the study of brain oscillations.

  17. Lag and anticipating synchronization without time-delay coupling.

    PubMed

    Corron, Ned J; Blakely, Jonathan N; Pethel, Shawn D

    2005-06-01

    We describe a new method for achieving approximate lag and anticipating synchronization in unidirectionally coupled chaotic oscillators. The method uses a specific parameter mismatch between the drive and response that is a first-order approximation to true time-delay coupling. As a result, an adjustable lag or anticipation effect can be achieved without the need for a variable delay line, making the method simpler and more economical to implement in many physical systems. We present a stability analysis, demonstrate the method numerically, and report experimental observation of the effect in radio-frequency electronic oscillators. In the circuit experiments, both lag and anticipation are controlled by tuning a single capacitor in the response oscillator. PMID:16035886

  18. Distinguishing time-delayed causal interactions using convergent cross mapping.

    PubMed

    Ye, Hao; Deyle, Ethan R; Gilarranz, Luis J; Sugihara, George

    2015-01-01

    An important problem across many scientific fields is the identification of causal effects from observational data alone. Recent methods (convergent cross mapping, CCM) have made substantial progress on this problem by applying the idea of nonlinear attractor reconstruction to time series data. Here, we expand upon the technique of CCM by explicitly considering time lags. Applying this extended method to representative examples (model simulations, a laboratory predator-prey experiment, temperature and greenhouse gas reconstructions from the Vostok ice core, and long-term ecological time series collected in the Southern California Bight), we demonstrate the ability to identify different time-delayed interactions, distinguish between synchrony induced by strong unidirectional-forcing and true bidirectional causality, and resolve transitive causal chains. PMID:26435402

  19. Distinguishing time-delayed causal interactions using convergent cross mapping

    NASA Astrophysics Data System (ADS)

    Ye, Hao; Deyle, Ethan R.; Gilarranz, Luis J.; Sugihara, George

    2015-10-01

    An important problem across many scientific fields is the identification of causal effects from observational data alone. Recent methods (convergent cross mapping, CCM) have made substantial progress on this problem by applying the idea of nonlinear attractor reconstruction to time series data. Here, we expand upon the technique of CCM by explicitly considering time lags. Applying this extended method to representative examples (model simulations, a laboratory predator-prey experiment, temperature and greenhouse gas reconstructions from the Vostok ice core, and long-term ecological time series collected in the Southern California Bight), we demonstrate the ability to identify different time-delayed interactions, distinguish between synchrony induced by strong unidirectional-forcing and true bidirectional causality, and resolve transitive causal chains.

  20. Distinguishing time-delayed causal interactions using convergent cross mapping

    PubMed Central

    Ye, Hao; Deyle, Ethan R.; Gilarranz, Luis J.; Sugihara, George

    2015-01-01

    An important problem across many scientific fields is the identification of causal effects from observational data alone. Recent methods (convergent cross mapping, CCM) have made substantial progress on this problem by applying the idea of nonlinear attractor reconstruction to time series data. Here, we expand upon the technique of CCM by explicitly considering time lags. Applying this extended method to representative examples (model simulations, a laboratory predator-prey experiment, temperature and greenhouse gas reconstructions from the Vostok ice core, and long-term ecological time series collected in the Southern California Bight), we demonstrate the ability to identify different time-delayed interactions, distinguish between synchrony induced by strong unidirectional-forcing and true bidirectional causality, and resolve transitive causal chains. PMID:26435402

  1. THE HUBBLE CONSTANT INFERRED FROM 18 TIME-DELAY LENSES

    SciTech Connect

    Paraficz, Danuta; Hjorth, Jens

    2010-04-01

    We present a simultaneous analysis of 18 galaxy lenses with time-delay measurements. For each lens, we derive mass maps using pixelated simultaneous modeling with shared Hubble constant. We estimate the Hubble constant to be 66{sup +6}{sub -4} km s{sup -1} Mpc{sup -1} (for a flat universe with OMEGA{sub m} = 0.3, OMEGA{sub L}AMBDA = 0.7). We have also selected a subsample of five relatively isolated early-type galaxies, and by simultaneous modeling with an additional constraint on isothermality of their mass profiles, we get H{sub 0} = 76{sup +3}{sub -3} km s{sup -1} Mpc{sup -1}.

  2. Extreme fluctuations in stochastic network coordination with time delays

    NASA Astrophysics Data System (ADS)

    Hunt, D.; Molnár, F.; Szymanski, B. K.; Korniss, G.

    2015-12-01

    We study the effects of uniform time delays on the extreme fluctuations in stochastic synchronization and coordination problems with linear couplings in complex networks. We obtain the average size of the fluctuations at the nodes from the behavior of the underlying modes of the network. We then obtain the scaling behavior of the extreme fluctuations with system size, as well as the distribution of the extremes on complex networks, and compare them to those on regular one-dimensional lattices. For large complex networks, when the delay is not too close to the critical one, fluctuations at the nodes effectively decouple, and the limit distributions converge to the Fisher-Tippett-Gumbel density. In contrast, fluctuations in low-dimensional spatial graphs are strongly correlated, and the limit distribution of the extremes is the Airy density. Finally, we also explore the effects of nonlinear couplings on the stability and on the extremes of the synchronization landscapes.

  3. Lensing and time-delay contributions to galaxy correlations

    NASA Astrophysics Data System (ADS)

    Raccanelli, Alvise; Bertacca, Daniele; Maartens, Roy; Clarkson, Chris; Doré, Olivier

    2016-07-01

    Galaxy clustering on very large scales can be probed via the 2-point correlation function in the general case of wide and deep separations, including all the lightcone and relativistic effects. Using our recently developed formalism, we analyze the behavior of the local and integrated contributions and how these depend on redshift range, linear and angular separations and luminosity function. Relativistic corrections to the local part of the correlation can be non-negligible but they remain generally sub-dominant. On the other hand, the additional correlations arising from lensing convergence and time-delay effects can become very important and even dominate the observed total correlation function. We investigate different configurations formed by the observer and the pair of galaxies, and we find that the case of near-radial large-scale separations is where these effects will be the most important.

  4. Digital key for chaos communication performing time delay concealment.

    PubMed

    Nguimdo, Romain Modeste; Colet, Pere; Larger, Laurent; Pesquera, Luís

    2011-07-15

    We introduce a scheme that integrates a digital key in a phase-chaos electro-optical delay system for optical chaos communications. A pseudorandom binary sequence (PRBS) is mixed within the chaotic dynamics in a way that a mutual concealment is performed; e.g., the time delay is hidden by the binary sequence, and the PRBS is also masked by the chaos. In addition to bridging the gap between algorithmic symmetric key cryptography and chaos-based analog encoding, the proposed approach is intended to benefit from the complex algebra mixing between a (pseudorandom) Boolean variable, and another continuous time (chaotic) variable. The scheme also provides a large flexibility allowing for easy reconfigurations to communicate securely at a high bit rate between different systems. PMID:21838363

  5. Digital Key for Chaos Communication Performing Time Delay Concealment

    NASA Astrophysics Data System (ADS)

    Nguimdo, Romain Modeste; Colet, Pere; Larger, Laurent; Pesquera, Luís

    2011-07-01

    We introduce a scheme that integrates a digital key in a phase-chaos electro-optical delay system for optical chaos communications. A pseudorandom binary sequence (PRBS) is mixed within the chaotic dynamics in a way that a mutual concealment is performed; e.g., the time delay is hidden by the binary sequence, and the PRBS is also masked by the chaos. In addition to bridging the gap between algorithmic symmetric key cryptography and chaos-based analog encoding, the proposed approach is intended to benefit from the complex algebra mixing between a (pseudorandom) Boolean variable, and another continuous time (chaotic) variable. The scheme also provides a large flexibility allowing for easy reconfigurations to communicate securely at a high bit rate between different systems.

  6. Tunable Optical True-Time Delay Devices Would Exploit EIT

    NASA Technical Reports Server (NTRS)

    Kulikov, Igor; DiDomenico, Leo; Lee, Hwang

    2004-01-01

    Tunable optical true-time delay devices that would exploit electromagnetically induced transparency (EIT) have been proposed. Relative to prior true-time delay devices (for example, devices based on ferroelectric and ferromagnetic materials) and electronically controlled phase shifters, the proposed devices would offer much greater bandwidths. In a typical envisioned application, an optical pulse would be modulated with an ultra-wideband radio-frequency (RF) signal that would convey the information that one seeks to communicate, and it would be required to couple differently delayed replicas of the RF signal to the radiating elements of a phased-array antenna. One or more of the proposed devices would be used to impose the delays and/or generate the delayed replicas of the RF-modulated optical pulse. The beam radiated or received by the antenna would be steered by use of a microprocessor-based control system that would adjust operational parameters of the devices to tune the delays to the required values. EIT is a nonlinear quantum optical interference effect that enables the propagation of light through an initially opaque medium. A suitable medium must have, among other properties, three quantum states (see Figure 1): an excited state (state 3), an upper ground state (state 2), and a lower ground state (state 1). These three states must form a closed system that exhibits no decays to other states in the presence of either or both of two laser beams: (1) a probe beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 1; and (2) a coupling beam having the wavelength corresponding to the photon energy equal to the energy difference between states 3 and 2. The probe beam is the one that is pulsed and modulated with an RF signal.

  7. Remote Task-level Commanding of Centaur over Time Delay

    NASA Astrophysics Data System (ADS)

    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

  8. Gravitational Lens Time Delays: A Statistical Assessmentof Lens Model Dependences and Implications for the Global Hubble Constant

    SciTech Connect

    Oguri, Masamune; /KIPAC, Menlo Park

    2006-09-29

    Time delays between lensed multiple images have been known to provide an interesting probe of the Hubble constant, but such application is often limited by degeneracies with the shape of lens potentials. We propose a new statistical approach to examine the dependence of time delays on the complexity of lens potentials, such as higher-order perturbations, non-isothermality, and substructures. Specifically, we introduce a reduced time delay of the dimensionless form, and explore its behavior analytically and numerically as a function of the image configuration that is characterized by the asymmetry and opening angle of the image pair. In particular we derive a realistic conditional probability distribution for a given image configuration from Monte-Carlo simulations. We find that the probability distribution is sensitive to the image configuration such that more symmetric and/or smaller opening angle image pairs are more easily affected by perturbations on the primary lens potential. On average time delays of double lenses are less scattered than those of quadruple lenses. Furthermore, the realistic conditional distribution allows a new statistical method to constrain the Hubble constant from observed time delays. We find that 15 published time delay quasars constrain the Hubble constant to be H{sub 0} = 70 {+-} 3km s{sup -1} Mpc{sup -1}. While systematic errors coming from the heterogeneous nature of the quasar sample and the uncertainty of the input distribution of lens potentials should be considered, reasonable agreement with other estimates indicates the usefulness of our new approach as a cosmological and astrophysical probe, particularly in the era of large-scale synoptic surveys.

  9. A novel memristive time-delay chaotic system without equilibrium points

    NASA Astrophysics Data System (ADS)

    Pham, V.-T.; Vaidyanathan, S.; Volos, C. K.; Jafari, S.; Kuznetsov, N. V.; Hoang, T. M.

    2016-02-01

    Memristor and time-delay are potential candidates for constructing new systems with complex dynamics and special features. A novel time-delay system with a presence of memristive device is proposed in this work. It is worth noting that this memristive time-delay system can generate chaotic attractors although it possesses no equilibrium points. In addition, a circuitry implementation of such time-delay system has been introduced to show its feasibility.

  10. Effects of Time Delay on Three Interacting Species System with Noise

    NASA Astrophysics Data System (ADS)

    Su, Yi-Jian; Mei, Dong-Cheng

    2008-09-01

    We study the effects of time delay in three interacting species system with noise. The time evolution and spatiotemporal pattern in the Lotka-Volterra model of three interacting species with noise and time delay were investigated by means of stochastic simulation. Our results indicate that: (i) Time delay induces the synchronously periodic oscillations of the three species densities; (ii) Time delay cause the spatiotemporal pattern to be concentrated.

  11. Time-Delay Discrimination Training: Replication with Different Stimuli and Different Populations.

    ERIC Educational Resources Information Center

    Smeets, Paul M.; And Others

    1990-01-01

    Two time-delay conditions for teaching complex visual discriminations to 14 normal preschoolers, 12 with mild mental retardation, and 11 with moderate mental retardation were compared. Results indicated that for all populations and stimuli, time delay of multiple dynamic distinctive-feature prompts produced learning, while time delay of the single…

  12. Representation of interaural time difference in the central nucleus of the barn owl's inferior colliculus.

    PubMed

    Wagner, H; Takahashi, T; Konishi, M

    1987-10-01

    This paper investigates the role of the central nucleus of the barn owl's inferior colliculus in determination of the sound-source azimuth. The central nucleus contains many neurons that are sensitive to interaural time difference (ITD), the cue for azimuth in the barn owl. The response of these neurons varies in a cyclic manner with the ITD of a tone or noise burst. Response maxima recur at integer multiples of the period of the stimulating tone, or, if the stimulus is noise, at integer multiples of the period corresponding to the neuron's best frequency. Such neurons can signal, by means of their relative spike rate, the phase difference between the sounds reaching the left and right ears. Since an interaural phase difference corresponds to more than one ITD, these neurons represent ITD ambiguously. We call this phenomenon phase ambiguity. The central nucleus is tonotopically organized and its neurons are narrowly tuned to frequency. Neurons in an array perpendicular to isofrequency laminae form a physiological and anatomical unit; only one ITD, the array-specific ITD, activates all neurons in an array at the same relative level. We, therefore, may say that, in the central nucleus, an ITD is conserved in an array of neurons. Array-specific ITDs are mapped and encompass the entire auditory space of the barn owl. Individual space-specific neurons of the external nucleus, which receive inputs from a wide range of frequency channels (Knudsen and Konishi, 1978), are selective for a unique ITD. Space-specific neurons do not show phase ambiguity when stimulated with noise (Takahashi and Konishi, 1986). Space-specific neurons receive inputs from arrays that are selective for the same ITD. The collective response of the neurons in an array may be the basis for the absence of phase ambiguity in space-specific neurons. PMID:3668618

  13. Precision cosmology with time delay lenses: high resolution imaging requirements

    NASA Astrophysics Data System (ADS)

    Meng, Xiao-Lei; Treu, Tommaso; Agnello, Adriano; Auger, Matthew W.; Liao, Kai; Marshall, Philip J.

    2015-09-01

    Lens time delays are a powerful probe of cosmology, provided that the gravitational potential of the main deflector can be modeled with sufficient precision. Recent work has shown that this can be achieved by detailed modeling of the host galaxies of lensed quasars, which appear as ``Einstein Rings'' in high resolution images. The distortion of these arcs and counter-arcs, as measured over a large number of pixels, provides tight constraints on the difference between the gravitational potential between the quasar image positions, and thus on cosmology in combination with the measured time delay. We carry out a systematic exploration of the high resolution imaging required to exploit the thousands of lensed quasars that will be discovered by current and upcoming surveys with the next decade. Specifically, we simulate realistic lens systems as imaged by the Hubble Space Telescope (HST), James Webb Space Telescope (JWST), and ground based adaptive optics images taken with Keck or the Thirty Meter Telescope (TMT). We compare the performance of these pointed observations with that of images taken by the Euclid (VIS), Wide-Field Infrared Survey Telescope (WFIRST) and Large Synoptic Survey Telescope (LSST) surveys. We use as our metric the precision with which the slope γ' of the total mass density profile ρtotpropto 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. However, the exposure time required with upcoming facilitites such as JWST, the Keck Next Generation Adaptive Optics System, and TMT, will only be of

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

    SciTech Connect

    Meng, Xiao -Lei; Treu, Tommaso; Agnello, Adriano; Auger, Matthew W.; Liao, Kai; Marshall, Philip J.

    2015-09-28

    Lens time delays are a powerful probe of cosmology, provided that the gravitational potential of the main deflector can be modeled with sufficient precision. Recent work has shown that this can be achieved by detailed modeling of the host galaxies of lensed quasars, which appear as ``Einstein Rings'' in high resolution images. The distortion of these arcs and counter-arcs, as measured over a large number of pixels, provides tight constraints on the difference between the gravitational potential between the quasar image positions, and thus on cosmology in combination with the measured time delay. We carry out a systematic exploration of the high resolution imaging required to exploit the thousands of lensed quasars that will be discovered by current and upcoming surveys with the next decade. Specifically, we simulate realistic lens systems as imaged by the Hubble Space Telescope (HST), James Webb Space Telescope (JWST), and ground based adaptive optics images taken with Keck or the Thirty Meter Telescope (TMT). We compare the performance of these pointed observations with that of images taken by the Euclid (VIS), Wide-Field Infrared Survey Telescope (WFIRST) and Large Synoptic Survey Telescope (LSST) surveys. We use as our metric the precision with which the slope γ' of the total mass density profile ρtot∝ r–γ' for the main deflector can be measured. Ideally, we require that the statistical error on γ' be less than 0.02, such that it is subdominant to other sources of random and systematic uncertainties. We find that survey data will likely have sufficient depth and resolution to meet the target only for the brighter gravitational lens systems, comparable to those discovered by the SDSS survey. For fainter systems, that will be discovered by current and future surveys, targeted follow-up will be required. Furthermore, the exposure time required with upcoming facilitites such as JWST, the Keck Next Generation Adaptive Optics System, and TMT, will

  15. Discriminability of Prediction Artifacts in a Time Delayed Virtual Environment

    NASA Technical Reports Server (NTRS)

    Adelstein, Bernard D.; Jung, Jae Y.; Ellis, Stephen R.

    2001-01-01

    Overall latency remains an impediment to perceived image stability and consequently to human performance in virtual environment (VE) systems. Predictive compensators have been proposed as a means to mitigate these shortcomings, but they introduce rendering errors because of induced motion overshoot and heightened noise. Discriminability of these compensator artifacts was investigated by a protocol in which head tracked image stability for 35 ms baseline VE system latency was compared against artificially added (16.7 to 100 ms) latency compensated by a previously studied Kalman Filter (K-F) predictor. A control study in which uncompensated 16.7 to 100 ms latencies were compared against the baseline was also performed. Results from 10 subjects in the main study and 8 in the control group indicate that predictive compensation artifacts are less discernible than the disruptions of uncompensated time delay for the shorter but not the longer added latencies. We propose that noise magnification and overshoot are contributory cues to the presence of predictive compensation.

  16. Asymptotic stability for force reflecting teleoperators with time delay

    SciTech Connect

    Anderson, R.J. ); Spong, M.W. )

    1992-04-01

    A bilateral system consists of a local master manipulator and a remotely located slave manipulator. Velocity commands are sent forward from the master to the slave, and force information is reflected back from the slave to the master. Often, there is a transmission delay when communicating between the two subsystems, which causes instability in the force-reflecting teleoperator. Recently, a solution for this problem was found, based on mimicking the behavior of a lossless transmission line. Although the resulting control law was shown to stabilize an actual single-DOF teleoperator system, and although the control law is intuitively stable because of its passivity properties, stability for the system has not yet been proven. In this article the authors extend these results to a nonlinear n-DOF system and prove its stability. Nonlinear, multidimensional networks are used to characterize the nonlinear equations for the master and slave manipulators, the time-delayed communication systems, the human operator, and the environment. Tellegen's theorem and the Lyapunov theory are then applied to prove that the master and slave subsystems have asymptotically stable velocities. In addition, they show how gain scaling can be used without disturbing the stability of the system.

  17. Synthetic LISA: Simulating time delay interferometry in a model LISA

    SciTech Connect

    Vallisneri, Michele

    2005-01-15

    We report on three numerical experiments on the implementation of Time-Delay Interferometry (TDI) for LISA, performed with Synthetic LISA, a C++/Python package that we developed to simulate the LISA science process at the level of scientific and technical requirements. Specifically, we study the laser-noise residuals left by first-generation TDI when the LISA armlengths have a realistic time dependence; we characterize the armlength-measurement accuracies that are needed to have effective laser-noise cancellation in both first- and second-generation TDI; and we estimate the quantization and telemetry bitdepth needed for the phase measurements. Synthetic LISA generates synthetic time series of the LISA fundamental noises, as filtered through all the TDI observables; it also provides a streamlined module to compute the TDI responses to gravitational waves according to a full model of TDI, including the motion of the LISA array and the temporal and directional dependence of the armlengths. We discuss the theoretical model that underlies the simulation, its implementation, and its use in future investigations on system-characterization and data-analysis prototyping for LISA.

  18. Time-Delayed Subsidies: Interspecies Population Effects in Salmon

    PubMed Central

    Nelson, Michelle C.; Reynolds, John D.

    2014-01-01

    Cross-boundary nutrient inputs can enhance and sustain populations of organisms in nutrient-poor recipient ecosystems. For example, Pacific salmon (Oncorhynchus spp.) can deliver large amounts of marine-derived nutrients to freshwater ecosystems through their eggs, excretion, or carcasses. This has led to the question of whether nutrients from one generation of salmon can benefit juvenile salmon from subsequent generations. In a study of 12 streams on the central coast of British Columbia, we found that the abundance of juvenile coho salmon was most closely correlated with the abundance of adult pink salmon from previous years. There was a secondary role for adult chum salmon and watershed size, followed by other physical characteristics of streams. Most of the coho sampled emerged in the spring, and had little to no direct contact with spawning salmon nutrients at the time of sampling in the summer and fall. A combination of techniques suggest that subsidies from spawning salmon can have a strong, positive, time-delayed influence on the productivity of salmon-bearing streams through indirect effects from previous spawning events. This is the first study on the impacts of nutrients from naturally-occurring spawning salmon on juvenile population abundance of other salmon species. PMID:24911974

  19. Principal component analysis for LISA: The time delay interferometry connection

    SciTech Connect

    Romano, J.D.; Woan, G.

    2006-05-15

    Data from the Laser Interferometer Space Antenna (LISA) is expected to be dominated by frequency noise from its lasers. However, the noise from any one laser appears more than once in the data and there are combinations of the data that are insensitive to this noise. These combinations, called time delay interferometry (TDI) variables, have received careful study and point the way to how LISA data analysis may be performed. Here we approach the problem from the direction of statistical inference, and show that these variables are a direct consequence of a principal component analysis of the problem. We present a formal analysis for a simple LISA model and show that there are eigenvectors of the noise covariance matrix that do not depend on laser frequency noise. Importantly, these orthogonal basis vectors correspond to linear combinations of TDI variables. As a result we show that the likelihood function for source parameters using LISA data can be based on TDI combinations of the data without loss of information.

  20. Angular dependence of the attosecond time delay in the H 2 + ion

    NASA Astrophysics Data System (ADS)

    Kheifets, Anatoli; Serov, Vladislav

    2016-05-01

    Angular dependence of attosecond time delay relative to polarization of light can now be measured using combination of RABBITT and COLTRIMS techniques. This dependence brings particularly useful information in molecules where it is sensitive to the orientation of the molecular axis. Here we extend the theoretical studies of and consider a molecular ion H2+in combination of an attosecond pulse train and a dressing IR field which is a characteristic set up of a RABBIT measurement. We solve the time-dependent Schrödinger equation using a fast spherical Bessel transformation (SBT) for the radial variable, a discrete variable representation for the angular variables and a split-step technique for the time evolution. The use of SBT ensures correct phase of the wave function for a long time evolution which is especially important in time delay calculations. To speed up computations, we implement an expanding coordinate (EC) system which allows us to reach space sizes and time periods unavailable by other techniques. Australian Research Council DP120101805.

  1. Resonant control of stochastic spatiotemporal dynamics in a tunnel diode by multiple time-delayed feedback.

    PubMed

    Majer, Niels; Schöll, Eckehard

    2009-01-01

    We study the control of noise-induced spatiotemporal current density patterns in a semiconductor nanostructure (double-barrier resonant tunneling diode) by multiple time-delayed feedback. We find much more pronounced resonant features of noise-induced oscillations compared to single time feedback, rendering the system more sensitive to variations in the delay time tau . The coherence of noise-induced oscillations measured by the correlation time exhibits sharp resonances as a function of tau , and can be strongly increased by optimal choices of tau . Similarly, the peaks in the power spectral density are sharpened. We provide analytical insight into the control mechanism by relating the correlation times and mean frequencies of noise-induced breathing oscillations to the stability properties of the deterministic stationary current density filaments under the influence of the control loop. Moreover, we demonstrate that the use of multiple time delays enlarges the regime in which the deterministic dynamical properties of the system are not changed by delay-induced bifurcations. PMID:19257003

  2. Statistical analysis of the electrical breakdown time delay distributions in krypton

    NASA Astrophysics Data System (ADS)

    Maluckov, Čedomir A.; Karamarković, Jugoslav P.; Radović, Miodrag K.; Pejović, Momčilo M.

    2006-08-01

    The statistical analysis of the experimentally observed electrical breakdown time delay distributions in the krypton-filled diode tube at 2.6mbar is presented. The experimental distributions are obtained on the basis of 1000 successive and independent measurements. The theoretical electrical breakdown time delay distribution is evaluated as the convolution of the statistical time delay with exponential, and discharge formative time with Gaussian distribution. The distribution parameters are estimated by the stochastic modelling of the time delay distributions, and by comparing them with the experimental distributions for different relaxation times, voltages, and intensities of UV radiation. The transition of distribution shapes, from Gaussian-type to the exponential-like, is investigated by calculating the corresponding skewness and excess kurtosis parameters. It is shown that the mathematical model based on the convolution of two random variable distributions describes experimentally obtained time delay distributions and the separation of the total breakdown time delay to the statistical and formative time delay.

  3. Statistical analysis of the electrical breakdown time delay distributions in krypton

    SciTech Connect

    Maluckov, Cedomir A.; Karamarkovic, Jugoslav P.; Radovic, Miodrag K.; Pejovic, Momcilo M.

    2006-08-15

    The statistical analysis of the experimentally observed electrical breakdown time delay distributions in the krypton-filled diode tube at 2.6 mbar is presented. The experimental distributions are obtained on the basis of 1000 successive and independent measurements. The theoretical electrical breakdown time delay distribution is evaluated as the convolution of the statistical time delay with exponential, and discharge formative time with Gaussian distribution. The distribution parameters are estimated by the stochastic modelling of the time delay distributions, and by comparing them with the experimental distributions for different relaxation times, voltages, and intensities of UV radiation. The transition of distribution shapes, from Gaussian-type to the exponential-like, is investigated by calculating the corresponding skewness and excess kurtosis parameters. It is shown that the mathematical model based on the convolution of two random variable distributions describes experimentally obtained time delay distributions and the separation of the total breakdown time delay to the statistical and formative time delay.

  4. Interaural envelope correlation change discrimination in bilateral cochlear implantees: effects of mismatch, centering, and onset of deafness.

    PubMed

    Goupell, Matthew J

    2015-03-01

    Bilateral cochlear implant (CI) listeners can perform binaural tasks, but they are typically worse than normal-hearing (NH) listeners. To understand why this difference occurs and the mechanisms involved in processing dynamic binaural differences, interaural envelope correlation change discrimination sensitivity was measured in real and simulated CI users. In experiment 1, 11 CI (eight late deafened, three early deafened) and eight NH listeners were tested in an envelope correlation change discrimination task. Just noticeable differences (JNDs) were best for a matched place-of-stimulation and increased for an increasing mismatch. In experiment 2, attempts at intracranially centering stimuli did not produce lower JNDs. In experiment 3, the percentage of correct identifications of antiphasic carrier pulse trains modulated by correlated envelopes was measured as a function of mismatch and pulse rate. Sensitivity decreased for increasing mismatch and increasing pulse rate. The experiments led to two conclusions. First, envelope correlation change discrimination necessitates place-of-stimulation matched inputs. However, it is unclear if previous experience with acoustic hearing is necessary for envelope correlation change discrimination. Second, NH listeners presented with CI simulations demonstrated better performance than real CI listeners. If the simulations are realistic representations of electrical stimuli, real CI listeners appear to have difficulty processing interaural information in modulated signals. PMID:25786942

  5. Probability distributed time delays: integrating spatial effects into temporal models

    PubMed Central

    2010-01-01

    Background In order to provide insights into the complex biochemical processes inside a cell, modelling approaches must find a balance between achieving an adequate representation of the physical phenomena and keeping the associated computational cost within reasonable limits. This issue is particularly stressed when spatial inhomogeneities have a significant effect on system's behaviour. In such cases, a spatially-resolved stochastic method can better portray the biological reality, but the corresponding computer simulations can in turn be prohibitively expensive. Results We present a method that incorporates spatial information by means of tailored, probability distributed time-delays. These distributions can be directly obtained by single in silico or a suitable set of in vitro experiments and are subsequently fed into a delay stochastic simulation algorithm (DSSA), achieving a good compromise between computational costs and a much more accurate representation of spatial processes such as molecular diffusion and translocation between cell compartments. Additionally, we present a novel alternative approach based on delay differential equations (DDE) that can be used in scenarios of high molecular concentrations and low noise propagation. Conclusions Our proposed methodologies accurately capture and incorporate certain spatial processes into temporal stochastic and deterministic simulations, increasing their accuracy at low computational costs. This is of particular importance given that time spans of cellular processes are generally larger (possibly by several orders of magnitude) than those achievable by current spatially-resolved stochastic simulators. Hence, our methodology allows users to explore cellular scenarios under the effects of diffusion and stochasticity in time spans that were, until now, simply unfeasible. Our methodologies are supported by theoretical considerations on the different modelling regimes, i.e. spatial vs. delay-temporal, as indicated

  6. Image restoration of hybrid time delay and integration camera system with residual motion

    NASA Astrophysics Data System (ADS)

    Zheng, Zhenzhen; Wu, Jiagu; Feng, Huajun; Xu, Zhihai; Li, Qi; Chen, Yueting

    2011-06-01

    In this paper, we present a hybrid system for time delay and integration (TDI) image restoration. Images are degraded by residual motion, which distorts and blurs the TDI images during exposures and excludes the along-track scanning motion. The motion trajectory is estimated from the image sequence captured by an auxiliary high-speed camera. In order to make the estimated results less sensitive to the imaging conditions and noise, a new method based on cross-correlation is introduced for motion estimation. Then geometric distortion of the TDI image is removed by choosing the correct blurred block according to the central of the corresponding motion trajectory and the final image is restored row by row with the Richardson-Lucy algorithm. Simulated and experimental results are given to prove the effectiveness of our system.

  7. Time-delay concealment and complexity enhancement of an external-cavity laser through optical injection.

    PubMed

    Li, Nianqiang; Pan, Wei; Locquet, A; Citrin, D S

    2015-10-01

    The concealment of the time-delay signature (TDS) of chaotic external-cavity lasers is necessary to ensure the security of optical chaos-based cryptosystems. We show that this signature can be removed simply by optically injecting an external-cavity laser with a large linewidth-enhancement factor into a second, noninjection-locked, semiconductor laser. Concealment is ensured both in the amplitude and in the phase of the optical field, satisfying a sought-after property of optical chaos-based communications. Meanwhile, enhancement of the dynamical complexity, characterized by permutation entropy, coincides with strong TDS suppression over a wide range of parameters, the area for which depends sensitively on the linewidth-enhancement factor. PMID:26421545

  8. Maps of interaural delay in the owl's nucleus laminaris.

    PubMed

    Carr, Catherine E; Shah, Sahil; McColgan, Thomas; Ashida, Go; Kuokkanen, Paula T; Brill, Sandra; Kempter, Richard; Wagner, Hermann

    2015-09-01

    Axons from the nucleus magnocellularis form a presynaptic map of interaural time differences (ITDs) in the nucleus laminaris (NL). These inputs generate a field potential that varies systematically with recording position and can be used to measure the map of ITDs. In the barn owl, the representation of best ITD shifts with mediolateral position in NL, so as to form continuous, smoothly overlapping maps of ITD with iso-ITD contours that are not parallel to the NL border. Frontal space (0°) is, however, represented throughout and thus overrepresented with respect to the periphery. Measurements of presynaptic conduction delay, combined with a model of delay line conduction velocity, reveal that conduction delays can account for the mediolateral shifts in the map of ITD. PMID:26224776

  9. Maps of interaural delay in the owl's nucleus laminaris

    PubMed Central

    Shah, Sahil; McColgan, Thomas; Ashida, Go; Kuokkanen, Paula T.; Brill, Sandra; Kempter, Richard; Wagner, Hermann

    2015-01-01

    Axons from the nucleus magnocellularis form a presynaptic map of interaural time differences (ITDs) in the nucleus laminaris (NL). These inputs generate a field potential that varies systematically with recording position and can be used to measure the map of ITDs. In the barn owl, the representation of best ITD shifts with mediolateral position in NL, so as to form continuous, smoothly overlapping maps of ITD with iso-ITD contours that are not parallel to the NL border. Frontal space (0°) is, however, represented throughout and thus overrepresented with respect to the periphery. Measurements of presynaptic conduction delay, combined with a model of delay line conduction velocity, reveal that conduction delays can account for the mediolateral shifts in the map of ITD. PMID:26224776

  10. Neural coding of interaural time differences with bilateral cochlear implants: effects of congenital deafness.

    PubMed

    Hancock, Kenneth E; Noel, Victor; Ryugo, David K; Delgutte, Bertrand

    2010-10-20

    Human bilateral cochlear implant users do poorly on tasks involving interaural time differences (ITD), a cue that provides important benefits to the normal hearing, especially in challenging acoustic environments, yet the precision of neural ITD coding in acutely deafened, bilaterally implanted cats is essentially normal (Smith and Delgutte, 2007a). One explanation for this discrepancy is that the extended periods of binaural deprivation typically experienced by cochlear implant users degrades neural ITD sensitivity, by either impeding normal maturation of the neural circuitry or altering it later in life. To test this hypothesis, we recorded from single units in inferior colliculus of two groups of bilaterally implanted, anesthetized cats that contrast maximally in binaural experience: acutely deafened cats, which had normal binaural hearing until experimentation, and congenitally deaf white cats, which received no auditory inputs until the experiment. Rate responses of only half as many neurons showed significant ITD sensitivity to low-rate pulse trains in congenitally deaf cats compared with acutely deafened cats. For neurons that were ITD sensitive, ITD tuning was broader and best ITDs were more variable in congenitally deaf cats, leading to poorer ITD coding within the naturally occurring range. A signal detection model constrained by the observed physiology supports the idea that the degraded neural ITD coding resulting from deprivation of binaural experience contributes to poor ITD discrimination by human implantees. PMID:20962228

  11. Synchronization of time-delayed chemically coupled burst-spiking neurons with correlated noises.

    PubMed

    Zhang, X; Yang, J; Wu, F P; Wu, W J; Jiang, M; Chen, L; Wang, H J; Qi, G X; Huang, H B

    2014-06-01

    Synchronization of two time-delayed chemically coupled neurons with burst-spiking states is studied. Different from the previous study by N. Buric et al. (Phys. Rev. E 78, 036211 (2008)), it is found that exactly synchronous burst-spiking dynamics can occur for small coupling strengths and time delays. The results are confirmed by common time delays and non-equal time delays. When common noise is added to the two neurons, synchronization is enhanced as noise strength is increased. But the results are different for larger time delay and smaller time delay. When noises are correlated, it is found that only strong noises with large correlation coefficient can induce exact synchronization. Even one percent of independent noises can influence synchronization much. PMID:24965152

  12. Time delay measurement for linac based treatment delivery in synchronized respiratory gating radiotherapy.

    PubMed

    Jin, Jian-Yue; Yin, Fang-Fang

    2005-05-01

    A time delay in a respiratory gating system could cause an unexpected phase mismatch for synchronized gating radiotherapy. This study presents a method of identifying and measuring the time delay in a gating system. Various port films were taken for a motion phantom at different gating window levels with a very narrow window size. The time delay for the gating system was determined by comparing the motion curve (the position of a moving object versus the gating time) measured in the port films to the motion curve determined by the video cameras. The measured time delay for a linac-based gating system was 0.17+/-0.03 s. This time delay could induce target missing if it was not properly taken into account for the synchronized gating radiotherapy. Measurement/verification of the time delay should be considered as an important part of the accepting/commissioning test before the clinical use of the gating system. PMID:15984681

  13. Computing interaural differences through finite element modeling of idealized human heads

    PubMed Central

    Cai, Tingli; Rakerd, Brad; Hartmann, William M.

    2015-01-01

    Acoustical interaural differences were computed for a succession of idealized shapes approximating the human head-related anatomy: sphere, ellipsoid, and ellipsoid with neck and torso. Calculations were done as a function of frequency (100–2500 Hz) and for source azimuths from 10 to 90 degrees using finite element models. The computations were compared to free-field measurements made with a manikin. Compared to a spherical head, the ellipsoid produced greater large-scale variation with frequency in both interaural time differences and interaural level differences, resulting in better agreement with the measurements. Adding a torso, represented either as a large plate or as a rectangular box below the neck, further improved the agreement by adding smaller-scale frequency variation. The comparisons permitted conjectures about the relationship between details of interaural differences and gross features of the human anatomy, such as the height of the head, and length of the neck. PMID:26428792

  14. Phase velocity spectrum analysis for a time delay comb transducer for guided wave mode excitation

    SciTech Connect

    Quarry, M J; Rose, J L

    2000-09-26

    A theoretical model for the analysis of ultrasonic guided wave mode excitation of a comb transducer with time delay features was developed. Time delay characteristics are included via a Fourier transform into the frequency domain. The phase velocity spectrum can be used to determine the mode excitation on the phase velocity dispersion curves for a given structure. Experimental and theoretical results demonstrate the tuning of guided wave modes using a time delay comb transducer.

  15. Transition from winnerless competition to synchronization in time-delayed neuronal motifs

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Li, P. J.; Wu, F. P.; Wu, W. J.; Jiang, M.; Chen, L.; Qi, G. X.; Huang, H. B.

    2012-03-01

    The dynamics of brain functional motifs are studied. It is shown that different rhythms can occur in the motifs when time delay is taken into account. These rhythms include synchronization, winnerless competition (WLC) and "two plus one" (TPO). The main discovery is that the transition from WLC to synchronization can be induced simply by time delay. It is also concluded that some medium time delay is needed to achieve WLC in the realistic case. The motifs composed of heterogeneous neurons are also considered.

  16. Time-delayed quantum coherent Pyragas feedback control of photon squeezing in a degenerate parametric oscillator

    NASA Astrophysics Data System (ADS)

    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.

  17. In-flight evaluation of pure time delays in pitch and roll

    NASA Technical Reports Server (NTRS)

    Berry, D. T.

    1985-01-01

    An in-flight investigation of the effect of pure time delays in pitch and roll was undertaken. The evaluation tasks consisted of low lift-to-drag-ratio landings of various levels of difficulty and formation flying. The results indicate that the effect of time delay is strongly dependent on the task. In the pitch axis, in calm air, spot landings from a lateral offset were most strongly influenced by time delay. In the roll axis, in calm air, formation flying was most strongly influenced by time delay. However, when landings were made in turbulence, flying qualities in pitch were only slightly degraded, whereas in roll they were severely degraded.

  18. Stability and bifurcation of the Tsodyks-Markram model about short-term synaptic plasticity with time delay

    NASA Astrophysics Data System (ADS)

    Wang, Qiubao

    2014-06-01

    Short-term synaptic plasticity in the Tsodyks-Markram model can lead to unpredictable and complicated network dynamics. In this paper, we present a new Tsodyks-Markram model with time delay as a parameter. The time delay plays a very important role for the dynamics of our model. We report on the existence of Hopf bifurcation in the model for fixed and varied release probability of available neurotransmitters. It is found that there are stability switches, and a supercritical or subcritical Hopf bifurcation occur when the delay passes through a sequence of critical values. We provide numerical results to illustrate our conclusion about stability and obtain the properties of Hopf bifurcation. Moreover, we find the large sensitivity to initial conditions in our model.

  19. Passivity analysis for neural networks of neutral type with Markovian jumping parameters and time delay in the leakage term

    NASA Astrophysics Data System (ADS)

    Balasubramaniam, P.; Nagamani, G.; Rakkiyappan, R.

    2011-11-01

    In this paper, the problem of passivity analysis is investigated for neutral type neural networks with Markovian jumping parameters and time delay in the leakage term. The delay is assumed to be time-varying and belong to a given interval, which means that the lower and upper bounds of interval time-varying delays are available. By constructing proper Lyapunov-Krasovskii functional, new delay-dependent passivity conditions are derived in terms of linear matrix inequalities (LMIs). Moreover, it is well known that the passivity behavior of neural networks is very sensitive to the time delay in the leakage term. Finally, three numerical examples are given to show the effectiveness and less conservatism of the proposed method.

  20. Temporal weighting functions for interaural time and level differences. IV. Effects of carrier frequency

    PubMed Central

    Stecker, G. Christopher

    2014-01-01

    Temporal variation in listeners' sensitivity to interaural time and level differences (ITD and ILD, respectively) was measured for sounds of different carrier frequency using the temporal weighting function (TWF) paradigm [Stecker and Hafter (2002) J. Acoust. Soc. Am. 112,1046–1057]. Listeners made lateralization judgments following brief trains of filtered impulses (Gabor clicks) presented over headphones with overall ITD and/or ILD ranging from ±500 μs ITD and/or ±5 dB ILD across trials. Individual clicks within each train varied by an additional ±100 μs ITD or ±2 dB ILD to allow TWF calculation by multiple regression. In separate conditions, TWFs were measured for carrier frequencies of 1, 2, 4, and 8 kHz. Consistent with past studies, TWFs demonstrated high weight on the first click for stimuli with short interclick interval (ICI = 2 ms), but flatter weighting for longer ICI (5–10 ms). Some conditions additionally demonstrated greater weight for clicks near the offset than near the middle of the train. Results support a primary role of the auditory periphery in emphasizing onset and offset cues in rapidly modulated low-frequency sounds. For slower modulations, sensitivity to ongoing high-frequency ILD and low-frequency ITD cues appears subject to recency effects consistent with the effects of leaky temporal integration of binaural information. PMID:25480069

  1. Synaptic mechanisms underlying interaural level difference selectivity in rat auditory cortex.

    PubMed

    Kyweriga, Michael; Stewart, Whitney; Cahill, Carolyn; Wehr, Michael

    2014-11-15

    The interaural level difference (ILD) is a sound localization cue that is extensively processed in the auditory brain stem and midbrain and is also represented in the auditory cortex. Here, we asked whether neurons in the auditory cortex passively inherit their ILD tuning from subcortical sources or whether their spiking preferences were actively shaped by local inhibition. If inherited, the ILD selectivity of spiking output should match that of excitatory synaptic input. If shaped by local inhibition, by contrast, excitation should be more broadly tuned than spiking output with inhibition suppressing spiking for nonpreferred stimuli. To distinguish between these two processing strategies, we compared spiking responses with excitation and inhibition in the same neurons across a range of ILDs and average binaural sound levels. We found that cells preferring contralateral ILDs (often called EI cells) followed the inheritance strategy. In contrast, cells that were unresponsive to monaural sounds but responded predominantly to near-zero ILDs (PB cells) instead showed evidence of the local processing strategy. These PB cells received excitatory inputs that were similar to those received by the EI cells. However, contralateral monaural sounds and ILDs >0 dB elicited strong inhibition, quenching the spiking output. These results suggest that in the rat auditory cortex, EI cells do not utilize inhibition to shape ILD sensitivity, whereas PB cells do. We conclude that an auditory cortical circuit computes sensitivity for near-zero ILDs. PMID:25185807

  2. Numerical simulation of time delay interferometry for eLISA/NGO

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Ni, Wei-Tou

    2013-03-01

    eLISA/NGO is a new gravitational wave detection proposal with arm length of 106 km and one interferometer down-scaled from LISA. Just like LISA and ASTROD-GW, in order to attain the requisite sensitivity for eLISA/NGO, laser frequency noise must be suppressed to below the secondary noises such as the optical path noise, acceleration noise, etc. In previous papers, we have performed the numerical simulation of the time delay interferometry (TDI) for LISA and ASTROD-GW with one arm dysfunctional by using the CGC 2.7 ephemeris. The results are well below their respective limits in which the laser frequency noise is required to be suppressed. In this paper, we follow the same procedure to simulate the time delay interferometry numerically. To do this, we work out a set of 1000-day optimized mission orbits of the eLISA/NGO spacecraft starting on 1 January 2021 using the CGC 2.7 ephemeris framework. We then use the numerical method to calculate the residual optical path differences in the second-generation TDI solutions as in our previous papers. The maximum path length difference, for all configurations calculated, is below 13 mm (43 ps). It is well below the limit in which the laser frequency noise is required to be suppressed for eLISA/NGO. We compare and discuss the resulting differences due to the different arm lengths for various mission proposals—eLISA/NGO, an NGO-LISA-type mission with a nominal arm length of 2 × 106 km, LISA and ASTROD-GW.

  3. Numerical simulation of time delay interferometry for NGO/eLISA

    NASA Astrophysics Data System (ADS)

    Ni, Wei-Tou; Wang, Gang

    2012-07-01

    NGA/eLISA is a new mission proposal with arm length 106 km and one interferometer down-scaled from LISA (http://elisa-ngo.org/). Just like LISA and ASTROD-GW, in order to attain the requisite sensitivity for NGO/eLISA, laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. In previous papers, we have used the CGC 2.7 ephemeris to numerically simulate the time delay interferometry for LISA and ASTROD-GW with one arm dysfunctional and found that they are both well below the limit under which the laser frequency noise is required to be suppressed. In this paper, we follow the same procedure to simulate the time delay interferometry numerically. To do this, we work out a set of 3-year optimized mission orbits of NGO/eLISA spacecraft starting at January 1, 2021 using the CGC2.7 ephemeris framework. We then use this numerical solution to calculate the residual optical path differences in the second-generation solutions as in our previous papers. The accuracy of this calculation for path differences is better than 0.01 mm (about 0.03 ps). The maximum path length difference, for all configuration calculated, is below 12 mm (40 ps). This is well below the limit under which the laser frequency noise is required to be suppressed for NGO/eLISA. We compare and discuss the resulting differences due to arm lengths for various mission proposals.

  4. Time-delayed feedback control of coherence resonance near subcritical Hopf bifurcation: Theory versus experiment

    SciTech Connect

    Semenov, Vladimir; Feoktistov, Alexey; Vadivasova, Tatyana; Schöll, Eckehard Zakharova, Anna

    2015-03-15

    Using the model of a generalized Van der Pol oscillator in the regime of subcritical Hopf bifurcation, we investigate the influence of time delay on noise-induced oscillations. It is shown that for appropriate choices of time delay, either suppression or enhancement of coherence resonance can be achieved. Analytical calculations are combined with numerical simulations and experiments on an electronic circuit.

  5. The determination for time delay of the CCTV signals relayed by local TV stations.

    NASA Astrophysics Data System (ADS)

    Ren, Yan; Liang, Shuangyou

    1997-06-01

    It is necessary for the users, who need time signals of high precision, to understand the time delay of the received CCTV time signals. The methods for measuring the time delay of CCTV time signals relayed by synchronous satellite position and the measured results are described.

  6. Time-delayed feedback control of coherence resonance near subcritical Hopf bifurcation: theory versus experiment.

    PubMed

    Semenov, Vladimir; Feoktistov, Alexey; Vadivasova, Tatyana; Schöll, Eckehard; Zakharova, Anna

    2015-03-01

    Using the model of a generalized Van der Pol oscillator in the regime of subcritical Hopf bifurcation, we investigate the influence of time delay on noise-induced oscillations. It is shown that for appropriate choices of time delay, either suppression or enhancement of coherence resonance can be achieved. Analytical calculations are combined with numerical simulations and experiments on an electronic circuit. PMID:25833433

  7. Time-delayed feedback control of coherence resonance near subcritical Hopf bifurcation: Theory versus experiment

    NASA Astrophysics Data System (ADS)

    Semenov, Vladimir; Feoktistov, Alexey; Vadivasova, Tatyana; Schöll, Eckehard; Zakharova, Anna

    2015-03-01

    Using the model of a generalized Van der Pol oscillator in the regime of subcritical Hopf bifurcation, we investigate the influence of time delay on noise-induced oscillations. It is shown that for appropriate choices of time delay, either suppression or enhancement of coherence resonance can be achieved. Analytical calculations are combined with numerical simulations and experiments on an electronic circuit.

  8. Pneumatic shutoff and time-delay valve operates at controlled rate

    NASA Technical Reports Server (NTRS)

    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.

  9. Time delay estimation in the ultrasonic flowmeter in the oil well

    NASA Astrophysics Data System (ADS)

    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.

  10. The mean first passage time and stochastic resonance in gene transcriptional system with time delay

    NASA Astrophysics Data System (ADS)

    Feng, Y. L.; Zhu, J.; Zhang, M.; Gao, L. L.; Liu, Y. F.; Dong, J. M.

    2016-04-01

    In this paper, the gene transcriptional dynamics driven by correlated noises are investigated, where the time delay for the synthesis of transcriptional factor is introduced. The effects of the noise correlation strength and time delay on the stationary probability distribution (SPD), the mean first passage time and the stochastic resonance (SR) are analyzed in detail based on the delay Fokker-Planck equation. It is found that both the time delay and noise correlation strength play important roles in the bistable transcriptional system. The effect of the correlation strength reduces but the time delay enhances the mean first passage time (MFPT). Finally, the SR for this gene transcriptional system is found to be enhanced by the time delay.

  11. Programmable multiple true-time-delay elements based on a Fourier-domain optical processor.

    PubMed

    Yi, Xiaoke; Li, Liwei; Huang, Thomas X H; Minasian, Robert A

    2012-02-15

    A new technique to realize an array of multiple true-time-delay elements, which can be independently and continuously tuned, is reported. It is based on a WDM parallel signal processing approach in conjunction with a diffraction-based Fourier-domain optical signal processor. Programmable linear optical phase transfer functions are realized to obtain different electrical true-time delays. The technique can scale to a large number of wideband true-time-delay lines, with continuously tunable programmable delay. Results demonstrate multiple true-time-delay elements with independent tuning control and verify the concept by tuning the free spectral range of a microwave photonic notch filter. To our best knowledge, this is the first demonstration of multiple independently controllable true-time-delay lines for microwave photonic systems. PMID:22344122

  12. Bounded Linear Stability Analysis - A Time Delay Margin Estimation Approach for Adaptive Control

    NASA Technical Reports Server (NTRS)

    Nguyen, Nhan T.; Ishihara, Abraham K.; Krishnakumar, Kalmanje Srinlvas; Bakhtiari-Nejad, Maryam

    2009-01-01

    This paper presents a method for estimating time delay margin for model-reference adaptive control of systems with almost linear structured uncertainty. The bounded linear stability analysis method seeks to represent the conventional model-reference adaptive law by a locally bounded linear approximation within a small time window using the comparison lemma. The locally bounded linear approximation of the combined adaptive system is cast in a form of an input-time-delay differential equation over a small time window. The time delay margin of this system represents a local stability measure and is computed analytically by a matrix measure method, which provides a simple analytical technique for estimating an upper bound of time delay margin. Based on simulation results for a scalar model-reference adaptive control system, both the bounded linear stability method and the matrix measure method are seen to provide a reasonably accurate and yet not too conservative time delay margin estimation.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  14. Temporal weighting functions for interaural time and level differences. III. Temporal weighting for lateral position judgments

    PubMed Central

    Stecker, G. Christopher; Ostreicher, Jennifer D.; Brown, Andrew D.

    2013-01-01

    Temporal variation in listeners' sensitivity to interaural time and level differences (ITD and ILD) was assessed using the temporal weighting function (TWF) paradigm [Stecker and Hafter (2002). J. Acoust. Soc. Am. 112, 1046–1057] in the context of sound-source lateralization. Brief Gabor click trains were presented over headphones with overall ITD and/or ILD ranging ±500 μs ITD and/or ±5 dB ILD across trials; values for individual clicks within each train varied by an additional ±100 μs or ±2 dB to allow TWF calculation by multiple regression. In separate conditions, TWFs were measured for (i) ITD alone, (ii) ILD alone, (iii) ITD and ILD covarying (“in agreement”), and (iv) ITD and ILD varying independently across clicks. Consistent with past studies that measured TWF for binaural discrimination, TWFs demonstrated high weight on the first click for stimuli with short interclick interval (ICI = 2 ms), but flatter weighting for longer ICI (5–10 ms). Some conditions additionally demonstrated greater weight for clicks near the offset than near the middle of the train [Stecker and Hafter (2009). J. Acoust. Soc. Am. 125, 3914–3924]. The latter result was observed only when stimuli carried ILD, and appeared more reliably for 5 ms than for 2 or 10 ms ICI. PMID:23927122

  15. A method to enhance the use of interaural time differences for cochlear implants in reverberant environments.

    PubMed

    Monaghan, Jessica J M; Seeber, Bernhard U

    2016-08-01

    The ability of normal-hearing (NH) listeners to exploit interaural time difference (ITD) cues conveyed in the modulated envelopes of high-frequency sounds is poor compared to ITD cues transmitted in the temporal fine structure at low frequencies. Sensitivity to envelope ITDs is further degraded when envelopes become less steep, when modulation depth is reduced, and when envelopes become less similar between the ears, common factors when listening in reverberant environments. The vulnerability of envelope ITDs is particularly problematic for cochlear implant (CI) users, as they rely on information conveyed by slowly varying amplitude envelopes. Here, an approach to improve access to envelope ITDs for CIs is described in which, rather than attempting to reduce reverberation, the perceptual saliency of cues relating to the source is increased by selectively sharpening peaks in the amplitude envelope judged to contain reliable ITDs. Performance of the algorithm with room reverberation was assessed through simulating listening with bilateral CIs in headphone experiments with NH listeners. Relative to simulated standard CI processing, stimuli processed with the algorithm generated lower ITD discrimination thresholds and increased extents of laterality. Depending on parameterization, intelligibility was unchanged or somewhat reduced. The algorithm has the potential to improve spatial listening with CIs. PMID:27586742

  16. Determination of time delay between ventricles contraction using impedance measurements

    NASA Astrophysics Data System (ADS)

    Lewandowska, M.; Poliński, A.; Wtorek, J.

    2013-04-01

    The paper presents a novel approach to assessment of ventricular dyssynchrony basing on multichannel electrical impedance measurements. Using a proper placement of electrodes, the sensitivity approach allows estimating time difference between chambers contraction from over determined nonlinear system of equations. The theoretical considerations which include Finite Element Method simulations were verified using measurements on healthy 28 year's old woman. The nonlinear least squares method was applied to obtain a time difference between heart chambers contraction. The obtained value was in a good agreement with theoretical values found in literature.

  17. Channel Interaction and Current Level Affect Across-Electrode Integration of Interaural Time Differences in Bilateral Cochlear-Implant Listeners.

    PubMed

    Egger, Katharina; Majdak, Piotr; Laback, Bernhard

    2016-02-01

    Sensitivity to interaural time differences (ITDs) is important for sound localization. Normal-hearing listeners benefit from across-frequency processing, as seen with improved ITD thresholds when consistent ITD cues are presented over a range of frequency channels compared with when ITD information is only presented in a single frequency channel. This study aimed to clarify whether cochlear-implant (CI) listeners can make use of similar processing when being stimulated with multiple interaural electrode pairs transmitting consistent ITD information. ITD thresholds for unmodulated, 100-pulse-per-second pulse trains were measured in seven bilateral CI listeners using research interfaces. Consistent ITDs were presented at either one or two electrode pairs at different current levels, allowing for comparisons at either constant level per component electrode or equal overall loudness. Different tonotopic distances between the pairs were tested in order to clarify the potential influence of channel interaction. Comparison of ITD thresholds between double pairs and the respective single pairs revealed systematic effects of tonotopic separation and current level. At constant levels, performance with double-pair stimulation improved compared with single-pair stimulation but only for large tonotopic separation. Comparisons at equal overall loudness revealed no benefit from presenting ITD information at two electrode pairs for any tonotopic spacing. Irrespective of electrode-pair configuration, ITD sensitivity improved with increasing current level. Hence, the improved ITD sensitivity for double pairs found for a large tonotopic separation and constant current levels seems to be due to increased loudness. The overall data suggest that CI listeners can benefit from combining consistent ITD information across multiple electrodes, provided sufficient stimulus levels and that stimulating electrode pairs are widely spaced. PMID:26377826

  18. On the variation of interaural time differences with frequency.

    PubMed

    Benichoux, Victor; Rébillat, Marc; Brette, Romain

    2016-04-01

    Interaural time difference (ITD) is a major cue to sound localization in humans and animals. For a given subject and position in space, ITD depends on frequency. This variation is analyzed here using a head related transfer functions (HRTFs) database collected from the literature and comprising human HRTFs from 130 subjects and animal HRTFs from six specimens of different species. For humans, the ITD is found to vary with frequency in a way that shows consistent differences with respect to a spherical head model. Maximal ITD values were found to be about 800 μs in low frequencies and 600 μs in high frequencies. The ITD variation with frequency (up to 200 μs for some positions) occurs within the frequency range where ITD is used to judge the lateral position of a sound source. In addition, ITD varies substantially within the bandwidth of a single auditory filter, leading to systematic differences between envelope and fine-structure ITDs. Because the frequency-dependent pattern of ITD does not display spherical symmetries, it potentially provides cues to elevation and resolves front/back confusion. The fact that the relation between position and ITDs strongly depends on the sound's spectrum in turn suggests that humans and animals make use of this relationship for the localization of sounds. PMID:27106329

  19. The time-delay spectrum of GX 5-1 in its horizontal branch

    NASA Astrophysics Data System (ADS)

    Vaughan, B.; van der Klis, M.; Lewin, W. H. G.; Wijers, R. A. M. J.; van Paradijs, J.; Dotani, T.; Mitsuda, K.

    1994-02-01

    Using a cross-spectral technique we investigate time delays between intensity variations of GX 5-1 in 10 X-ray spectral channels. The data were taken during a 1989 Ginga observation during which the source was in its horizontal-branch spectral state. We develope a new method to measure 'time-delay spectra' in fixed Fourier frequency ranges and use it to determine the energy and intensity dependence of time delays in the low-frequency noise (nu less than 2 Hz), the horizontal branch quasi-periodic oscillations (QPO), and the QPO second harmonic. These are the first time-delay spectra of a Z-source in its horizontal branch, and the first detection of time delays in the second harmonic. We consider two mechanisms for the production of the time lags: Comptonization and evolving shots. We perform Monte Carlo simulations of Compton scattering in a homogeneous, isotropic, central corona and show that it qualitatively explain the observed energy and time-delay spectra, but that it cannot explain the differences in the QPO first and second harmonic time-delay spectra, nor the observed dependence of the QPO fractional rms variability upon energy. We consider implications of our results for millisecond pulsar searches in low-mass X-ray binaries.

  20. The time-delay spectrum of GX 5-1 in its horizontal branch

    NASA Technical Reports Server (NTRS)

    Vaughan, B.; Van Der Klis, M.; Lewin, W. H. G.; Wijers, R. A. M. J.; Van Paradijs, J.; Dotani, T.; Mitsuda, K.

    1994-01-01

    Using a cross-spectral technique we investigate time delays between intensity variations of GX 5-1 in 10 X-ray spectral channels. The data were taken during a 1989 Ginga observation during which the source was in its horizontal-branch spectral state. We develope a new method to measure 'time-delay spectra' in fixed Fourier frequency ranges and use it to determine the energy and intensity dependence of time delays in the low-frequency noise (nu less than 2 Hz), the horizontal branch quasi-periodic oscillations (QPO), and the QPO second harmonic. These are the first time-delay spectra of a Z-source in its horizontal branch, and the first detection of time delays in the second harmonic. We consider two mechanisms for the production of the time lags: Comptonization and evolving shots. We perform Monte Carlo simulations of Compton scattering in a homogeneous, isotropic, central corona and show that it qualitatively explain the observed energy and time-delay spectra, but that it cannot explain the differences in the QPO first and second harmomnic time-delay spectra, nor the observed dependence of the QPO fractional rms variability upon energy. We consider implications of our results for millisecond pulsar searches in low-mass X-ray binaries.

  1. Dependence of line shapes in femtosecond broadband stimulated Raman spectroscopy on pump-probe time delay

    PubMed Central

    Yoon, Sangwoon; McCamant, David W.; Kukura, Philipp; Mathies, Richard A.; Zhang, Donghui; Lee, Soo-Y.

    2005-01-01

    The effect of the time delay between the picosecond Raman pump and the femtosecond Stokes probe pulse on the Raman gain line shape in femtosecond broadband stimulated Raman spectroscopy (FSRS) is presented. Experimental data are obtained for cyclohexane to investigate the dependence of the FSRS line shape on this time delay. Theoretical simulations of the line shapes as a function of the time delay using the coupled wave theory agree well with experimental data, recovering broad line shapes at positive time delays and narrower bands with small Raman loss side wings at negative time delays. The analysis yields the lower bounds of the vibrational dephasing times of 2.0 ps and 0.65 ps for the 802 and 1027 cm−1 modes for cyclohexane, respectively. The theoretical description and simulation using the coupled wave theory are also consistent with the observed Raman gain intensity profile over time delay, reaching the maximum at a slightly negative time delay (∼−21 ps), and show that the coupled wave theory is a good model for describing FSRS. PMID:15638596

  2. Dynamics of Time Delay-Induced Multiple Synchronous Behaviors in Inhibitory Coupled Neurons

    PubMed Central

    Gu, Huaguang; Zhao, Zhiguo

    2015-01-01

    The inhibitory synapse can induce synchronous behaviors different from the anti-phase synchronous behaviors, which have been reported in recent studies. In the present paper, synchronous behaviors are investigated in the motif model composed of reciprocal inhibitory coupled neurons with endogenous bursting and time delay. When coupling strength is weak, synchronous behavior appears at a single interval of time delay within a bursting period. When coupling strength is strong, multiple synchronous behaviors appear at different intervals of time delay within a bursting period. The different bursting patterns of synchronous behaviors, and time delays and coupling strengths that can induce the synchronous bursting patterns can be well interpreted by the dynamics of the endogenous bursting pattern of isolated neuron, which is acquired by the fast-slow dissection method, combined with the inhibitory coupling current. For an isolated neuron, when a negative impulsive current with suitable strength is applied at different phases of the bursting, multiple different bursting patterns can be induced. For a neuron in the motif, the inhibitory coupling current, of which the application time and strength is modulated by time delay and coupling strength, can cause single or multiple synchronous firing patterns like the negative impulsive current when time delay and coupling strength is suitable. The difference compared to the previously reported multiple synchronous behaviors that appear at time delays wider than a period of the endogenous firing is discussed. The results present novel examples of synchronous behaviors in the neuronal network with inhibitory synapses and provide a reasonable explanation. PMID:26394224

  3. Robust auditory localization using probabilistic inference and coherence-based weighting of interaural cues.

    PubMed

    Kayser, Hendrik; Hohmann, Volker; Ewert, Stephan D; Kollmeier, Birger; Anemüller, Jörn

    2015-11-01

    Robust sound source localization is performed by the human auditory system even in challenging acoustic conditions and in previously unencountered, complex scenarios. Here a computational binaural localization model is proposed that possesses mechanisms for handling of corrupted or unreliable localization cues and generalization across different acoustic situations. Central to the model is the use of interaural coherence, measured as interaural vector strength (IVS), to dynamically weight the importance of observed interaural phase (IPD) and level (ILD) differences in frequency bands up to 1.4 kHz. This is accomplished through formulation of a probabilistic model in which the ILD and IPD distributions pertaining to a specific source location are dependent on observed interaural coherence. Bayesian computation of the direction-of-arrival probability map naturally leads to coherence-weighted integration of location cues across frequency and time. Results confirm the model's validity through statistical analyses of interaural parameter values. Simulated localization experiments show that even data points with low reliability (i.e., low IVS) can be exploited to enhance localization performance. A temporal integration length of at least 200 ms is required to gain a benefit; this is in accordance with previous psychoacoustic findings on temporal integration of spatial cues in the human auditory system. PMID:26627742

  4. Strong gravitational field time delay for photons coupled to Weyl tensor in a Schwarzschild black hole

    NASA Astrophysics Data System (ADS)

    Lu, Xu; Yang, Feng-Wei; Xie, Yi

    2016-07-01

    We analyze strong gravitational field time delay for photons coupled to the Weyl tensor in a Schwarzschild black hole. By making use of the method of strong deflection limit, we find that these time delays between relativistic images are significantly affected by polarization directions of such a coupling. A practical problem about determination of the polarization direction by observations is investigated. It is found that if the first and second relativistic images can be resolved, the measurement of time delay can more effectively improve detectability of the polarization direction.

  5. Estimation of coupling between time-delay systems from time series

    NASA Astrophysics Data System (ADS)

    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.

  6. Stability analysis of a general family of nonlinear positive discrete time-delay systems

    NASA Astrophysics Data System (ADS)

    Nam, P. T.; Phat, V. N.; Pathirana, P. N.; Trinh, H.

    2016-07-01

    In this paper, we propose a new approach to analyse the stability of a general family of nonlinear positive discrete time-delay systems. First, we introduce a new class of nonlinear positive discrete time-delay systems, which generalises some existing discrete time-delay systems. Second, through a new technique that relies on the comparison and mathematical induction method, we establish explicit criteria for stability and instability of the systems. Three numerical examples are given to illustrate the feasibility of the obtained results.

  7. Time delay and noise explaining the behaviour of the cell growth in fermentation process

    SciTech Connect

    Ayuobi, Tawfiqullah; Rosli, Norhayati; Bahar, Arifah; Salleh, Madihah Md

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  9. Time delay and noise explaining the behaviour of the cell growth in fermentation process

    NASA Astrophysics Data System (ADS)

    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.

  10. Time delay can facilitate coherence in self-driven interacting-particle systems

    NASA Astrophysics Data System (ADS)

    Sun, Yongzheng; Lin, Wei; Erban, Radek

    2014-12-01

    Directional switching in a self-propelled particle model with delayed interactions is investigated. It is shown that the average switching time is an increasing function of time delay. The presented results are applied to studying collective animal behavior. It is argued that self-propelled particle models with time delays can explain the state-dependent diffusion coefficient measured in experiments with locust groups. The theory is further generalized to heterogeneous groups where each individual can respond to its environment with a different time delay.