The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Rufin Vanrullen - One of the best experts on this subject based on the ideXlab platform.
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on the cyclic nature of perception in vision versus audition
Philosophical Transactions of the Royal Society B, 2014Co-Authors: Rufin Vanrullen, Benedikt Zoefel, Barkin IlhanAbstract:Does our perceptual awareness consist of a continuous stream, or a discrete sequence of perceptual cycles, possibly associated with the rhythmic structure of brain activity? This has been a long-standing question in neuroscience. We review recent psychophysical and electrophysiological studies indicating that part of our visual awareness proceeds in approximately 7–13 Hz cycles rather than continuously. On the other hand, experimental attempts at applying similar tools to demonstrate the discreteness of auditory awareness have been largely unsuccessful. We argue and demonstrate experimentally that visual and auditory perception are not equally affected by temporal subSampling of their respective input streams: video sequences remain intelligible at Sampling rates of two to three frames per second, whereas audio inputs lose their fine temporal structure, and thus all significance, below 20–30 samples per second. This does not mean, however, that our auditory perception must proceed continuously. Instead, we propose that audition could still involve perceptual cycles, but the Periodic Sampling should happen only after the stage of auditory feature extraction. In addition, although visual perceptual cycles can follow one another at a spontaneous pace largely independent of the visual input, auditory cycles may need to sample the input stream more flexibly, by adapting to the temporal structure of the auditory inputs.
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the dynamics of attentional Sampling during visual search revealed by fourier analysis of Periodic noise interference
Journal of Vision, 2014Co-Authors: Rufin Vanrullen, Laura DugueAbstract:What are the temporal dynamics of perceptual Sampling during visual search tasks, and how do they differ between a difficult (or inefficient) and an easy (or efficient) task? Does attention focus intermittently on the stimuli, or are the stimuli processed continuously over time? We addressed these questions by way of a new paradigm using Periodic fluctuations of stimulus information during a difficult (color-orientation conjunction) and an easy (+ among Ls) search task. On each stimulus, we applied a dynamic visual noise that oscillated at a given frequency (2-20 Hz, 2-Hz steps) and phase (four cardinal phase angles) for 500 ms. We estimated the dynamics of attentional Sampling by computing an inverse Fourier transform on subjects' d-primes. In both tasks, the Sampling function presented a significant peak at 2 Hz; we showed that this peak could be explained by nonPeriodic search strategies such as increased sensitivity to stimulus onset and offset. Specifically in the difficult task, however, a second, higher-frequency peak was observed at 9 to 10 Hz, with a similar phase for all subjects; this isolated frequency component necessarily entails oscillatory attentional dynamics. In a second experiment, we presented difficult search arrays with dynamic noise that was modulated by the previously obtained grand-average attention Sampling function or by its converse function (in both cases omitting the 2 Hz component to focus on genuine oscillatory dynamics). We verified that performance was higher in the latter than in the former case, even for subjects who had not participated in the first experiment. This study supports the idea of a Periodic Sampling of attention during a difficult search task. Although further experiments will be needed to extend these findings to other search tasks, the present report validates the usefulness of this novel paradigm for measuring the temporal dynamics of attention.
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spontaneous eeg oscillations reveal Periodic Sampling of visual attention
Proceedings of the National Academy of Sciences of the United States of America, 2010Co-Authors: Niko A Busch, Rufin VanrullenAbstract:An important effect of sustained attention is the facilitation of perception. Although the term “sustained” suggests that this beneficial effect endures continuously as long as something is attended, we present electrophysiological evidence that perception at attended locations is actually modulated Periodically. Subjects detected brief light flashes that were presented peripherally at locations that were either attended or unattended. We analyzed the correlation between detection performance for attended and unattended stimuli and the phase of ongoing EEG oscillations, which relate to subsecond fluctuations of neuronal excitability. Although on average, detection performance was improved by attention—indicated by reduced detection thresholds at attended locations—we found that detection performance for attended stimuli actually fluctuated over time along with the phase of spontaneous oscillations in the θ (≈7 Hz) frequency band just before stimulus onset. This fluctuation was absent for unattended stimuli. This pattern of results suggests that “sustained” attention in fact exerts its facilitative effect on perception in a Periodic fashion.
Alan R. Lax - One of the best experts on this subject based on the ideXlab platform.
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areawide field study on effect of three chitin synthesis inhibitor baits on populations of coptotermes formosanus and reticulitermes flavipes isoptera rhinotermitidae
Journal of Economic Entomology, 2011Co-Authors: Mary L Cornelius, Alan R. LaxAbstract:ABSTRACT Periodic Sampling of 43 independent monitors, initially active with Formosan subterranean termite, Coptotermes formosanus Shiraki, or the eastern subterranean termite, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), was conducted to evaluate the effects of cellulose baits containing one of three chitin synthesis inhibitors (CSIs)—diflubenzuron, hexaflumuron, or chlorfluazuron—on termite populations. Diflubenzuron at 0.1% active ingredient (AI, wt:wt) had no noticeable effect on termite populations. Chlorfluazuron (0.25% [AI]) significantly reduced termite populations in ≈3 yr. Chlorfluazuron used after >2-yr diflubenzuron treatment significantly reduced termite populations within months. This suggests diflubenzuron exposure increased the termite's sensitivity to chlorfluazuron accelerating population collapse. Hexaflumuron (0.5% [AI] ) also reduced termite populations in ≈2 yr. The process of removing most detectable termite populations from the ≈460,000-m2 campus of the Southern Re...
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effects of flooding on field populations of formosan subterranean termites isoptera rhinotermitidae in new orleans louisiana
Journal of Economic Entomology, 2008Co-Authors: Weste L. A. Osbrink, Mary L Cornelius, Alan R. LaxAbstract:Hurricane Katrina (2005) resulted in extensive flooding in the city of New Orleans, LA. Periodic Sampling of monitors before the flood, and of different monitors in the same areas after the flood, was used to evaluate the effects of long-term flooding on populations of Formosan subterranean termites, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Monitors were located adjacent to buildings and in urban forests. Significant population reductions occurred in areas that flooded 2-3 wk with brackish water, with termite populations associated with pine (Pinus spp.) trees and buildings slower to recover than populations associated with oak trees. Alate production in flooded areas showed no reduction from previous years.
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effect of imidacloprid soil treatments on occurrence of formosan subterranean termites isoptera rhinotermitidae in independent monitors
Journal of Economic Entomology, 2005Co-Authors: Weste L. A. Osbrink, Mary L Cornelius, Alan R. LaxAbstract:Abstract Periodic Sampling of 30 independent monitors, initially active with the Formosan subterranean termite, Coptotermes formosanus Shiraki, was conducted to evaluate the effects of soil treated with imidacloprid on nearby termite activity. Monitors were located adjacent (1–3 m) to the buildings. Soil around and under the buildings was treated with 0.05% imidacloprid. None of the termites collected showed latent mortality attributed to imidacloprid intoxication. Imidacloprid soil treatments did not measurably reduce C. formosanus populations adjacent to the treatments. Imidacloprid does not seem to fit the liquid-bait model.
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effect of imidacloprid tree treatments on the occurrence of formosan subterranean termites coptotermes formosanus shiraki isoptera rhinotermitidae in independent monitors
Journal of Economic Entomology, 2003Co-Authors: Weste L. A. Osbrink, Alan R. LaxAbstract:Periodic Sampling of 87 independent monitors, initially active with the Formosan subterranean termite, Coptotermes formosanus Shiraki, was conducted. Monitors, located in eight sectors adjacent to seven buildings, were various distances (1–46 m) from 57 trees treated with 0.1% imidacloprid foam. Termites collected from six of the eight sectors showed latent mortality attributed to imidacloprid intoxication at all monitor-tree distances. Approximately 6 mo after treatment, termite populations had recovered in these sectors. Another sector showed termite population suppression for ≈15 mo, followed by recovery. Imidacloprid tree treatments did not control C. formosanus populations in independent monitors adjacent to the treatments.
Xiankui Wang - One of the best experts on this subject based on the ideXlab platform.
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application of active disturbance rejection control to variable spindle speed noncircular turning process
International Journal of Machine Tools & Manufacture, 2009Co-Authors: Dan Wu, Tong Zhao, Ken Chen, Xiankui WangAbstract:In application of variable spindle speed machining to noncircular turning process, the tracking control of the fast tool servo yields a Periodic Sampling rate in the real-time domain. However, in the view of the angle domain, the Sampling rate is constant. Moreover, the reference acceleration signal is easily available. This implies that it is advantageous to design the control system from the angle domain perspective, but the plant for a linear time-invariant system will become a Periodically time-varying system. In this paper, the active disturbance rejection control strategy is applied to actively estimate the time-varying dynamics and other disturbances and compensate for them in the control law. The acceleration feed-forward strategy is employed to achieve better tracking performance. The stability analysis based on the lifting technique is proposed. Experimental machining results demonstrate the tracking performance of the proposed design, as well as the ability to increase machining stability using variable spindle speed machining.
Benjamin W Abbott - One of the best experts on this subject based on the ideXlab platform.
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unexpected spatial stability of water chemistry in headwater stream networks
Ecology Letters, 2018Co-Authors: Benjamin W Abbott, Jay P Zarnetske, Florentina Moatar, Lou Barbe, Zahra Thomas, Ophélie Fovet, Gerard Gruau, Tamara KolbeAbstract:Understanding how water and solutes enter and propagate through freshwater landscapes in the Anthropocene is critical to protecting and restoring aquatic ecosystems and ensuring human water security. However, high hydrochemical variability in headwater streams, where most carbon and nutrients enter river networks, has hindered effective modelling and management. We developed an analytical framework informed by landscape ecology and catchment hydrology to quantify spatiotemporal variability across scales, which we tested in 56 headwater catchments, sampled Periodically over 12 years in western France. Unexpectedly, temporal variability in dissolved carbon, nutrients and major ions was preserved moving downstream and spatial patterns of water chemistry were stable on annual to decadal timescales, partly because of synchronous variation in solute concentrations. These findings suggest that while concentration and flux cannot be extrapolated among subcatchments, Periodic Sampling of headwaters provides valuable information about solute sources and subcatchment resilience to disturbance.
David J Hill - One of the best experts on this subject based on the ideXlab platform.
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decentralized event triggered frequency control with guaranteed l gain for multi area power systems
IEEE Control Systems Letters, 2021Co-Authors: Luwei Yang, Tao Liu, David J HillAbstract:This letter proposes a novel decentralized event-triggered control algorithm to replace the conventional Periodic Sampling/communication mechanism of automatic generation control (AGC) for multi-area power systems. For each control area, event-triggering rules that only rely on local measurements are designed to decide the Sampling/communication instants. Further, a strictly positive dwell time is introduced to exclude Zeno behaviours. The $\mathcal {L}_{\infty }$ -stability of the multi-area power system with the developed event-triggered control law and essentially bounded net load disturbances is studied, and a sufficient stability criterion is established. Finally, case studies demonstrate the effectiveness and efficiency of the proposed method.
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decentralized event triggered frequency regulation for multi area power systems
Automatica, 2021Co-Authors: Luwei Yang, Tao Liu, David J HillAbstract:Abstract To achieve a better frequency control performance for multi-area power systems, this paper proposes a novel decentralized event-triggered control (ETC) algorithm for automatic generation control (AGC) to replace the traditional Periodic Sampling/communication mechanism. For each control area, decentralized event-triggering conditions that only depend on locally available information are designed for the control center to determine time instants when to sample the frequency and for each communication channel to decide instants when to broadcast corresponding information. Further, a strictly positive dwell time is introduced to prevent Zeno behaviors. Small disturbance frequency stability of the interconnected power network under the developed ETC law is analyzed, and a sufficient stability criterion on the selection of event-triggered parameters is established. Case studies on a three-area test system illustrate the effectiveness and efficiency of our method.
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decentralized Periodic event triggered frequency regulation for multi area power systems
Power Systems Computation Conference, 2018Co-Authors: Luwei Yang, Tao Liu, David J HillAbstract:In order to improve the control performance of load frequency control for multi-area power systems, this paper proposes a decentralized Periodic event-triggered control (DPETC) approach to replace the traditional Periodic Sampling mechanism in automatic generation control (AGC) for communication scheduling. In each control area, the communication is enforced via two unidirectional communication channels, i.e., one is to transfer the local measurements from the power plants to the control center and the other is to transfer the updated control signals from the control center to the power plants. A decentralized event-triggering condition is designed for each communication channel, which is evaluated Periodically and only depends on the local measurements. However, AGC executes the unidirectional communication only when the corresponding event-triggering condition is fulfilled. Small disturbance frequency stability of the system under the proposed DPETC method is investigated, and a sufficient stability criterion is established. Simulation studies on a three-area interconnected system validate the effectiveness of the proposed method.
