The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Annemarie Surlykke - One of the best experts on this subject based on the ideXlab platform.
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Target ranging and the role of time-Frequency Structure of synthetic echoes in big brown bats, Eptesicus fuscus
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1992Co-Authors: Annemarie SurlykkeAbstract:Echolocating bats judge the distance to a target on basis of the delay between the emitted cry and the returning echo. In a phantom echo set-up it was investigated how changes in the time-Frequency Structure of synthetic echoes affect ranging accuracy of big brown bats, Eptesicus fuscus.
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Target ranging and the role of time-Frequency Structure of synthetic echoes in big brown bats, Eptesicus fuscus
Journal of Comparative Physiology A, 1992Co-Authors: Annemarie SurlykkeAbstract:Echolocating bats judge the distance to a target on basis of the delay between the emitted cry and the returning echo. In a phantom echo set-up it was investigated how changes in the time-Frequency Structure of synthetic echoes affect ranging accuracy of big brown bats, Eptesicus fuscus . A one channel phantom target simulator and a Y/N paradigm was used. Five Eptesicus fuscus were trained to discriminate between phantom targets with different virtual distances (delays). The phantom echo was stored in a memory and broadcast from a loudspeaker after a certain delay following the bat's triggering of the system via a trigger microphone. The ranging accuracy was compared using 5 different signals with equal energy as phantom echoes: a standard cry (a natural bat cry), two kinds of noise signals, a high pass, and a low pass filtered version of the standard cry. The standard cry was recorded from one of the bats while judging the distance to a real target. The duration was 1.1 ms, the first harmonic swept down from 55 to 25 kHz and there was energy also in the second and third harmonic. Both noise signals had the same duration, power spectrum, and energy as the standard cry. One noise signal was stored in a memory and hence was exactly the same each time the bat triggered the system. The other variable noise signal was produced by storing the envelope of the standard cry and multiplying on-line with band pass filtered noise. The time-Frequency Structure (e.g. rise time) of this noise signal changed from triggering to triggering. The filtered signals were produced by either 40 kHz high pass or 40 kHz low pass filtering of the standard cry. The range difference thresholds for the 5 bats were around 1–2 cm (51–119 us) using the standard cry as echo. The range difference threshold with both noise signals was 7–8 cm (around 450 μs delay difference). The 40 kHz high pass filtered cry increased the threshold to approximately twice the threshold with the standard cry. With the 40 kHz low pass filtered cry the threshold was increased 2.5–3 times relative to the threshold with the standard cry. A single bat was tested with a signal filtered with a 55 kHz low pass filter leaving the whole first harmonic. The threshold was the same as that with the standard signal. The reduced ranging accuracy with the filtered signals indicates that the full band width of the first harmonic is utilised for ranging by the bats. The substantial reduction in accuracy with the noise signals indicates that not only the full band width but also the orderly time-Frequency Structure (the FM sweep) of the cry is important for ranging in echolocating bats.
A.c. Pugh - One of the best experts on this subject based on the ideXlab platform.
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Spectral Structures of the generalized companion form and applications
Systems & Control Letters, 2002Co-Authors: A.c. PughAbstract:In this note, we investigate the relationship between the finite and infinite Frequency Structure of a regular polynomial matrix and that of a particular linearization, called the generalized companion matrix. A special resolvent decomposition of the regular polynomial matrix is proposed which is based on the Weierstrass canonical form of this generalized companion matrix and the solution of a regular polynomial matrix description (PMD) is thus formulated from this resolvent decomposition. Both the initial conditions of the pseudostate and the input are considered.
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Properties of the generalised companion form and application to the solution of regular PMDs
Proceedings of the 1999 American Control Conference (Cat. No. 99CH36251), 1999Co-Authors: A.c. PughAbstract:We investigate the relationship between the finite and infinite Frequency Structure of a regular polynomial matrix and that of a particular linearization, called the generalised companion matrix. A special resolvent decomposition of the regular polynomial matrix is proposed which is based on the Weierstrass canonical form of this generalised companion matrix and the solution of the regular polynomial matrix descriptions (PMDs) is thus formulated from this resolvent decomposition. Both the initial conditions of the pseudo state and the input are considered.
Christian Brosseau - One of the best experts on this subject based on the ideXlab platform.
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exploiting root mean square time Frequency Structure for multiple image optical compression and encryption
Optics Letters, 2010Co-Authors: Ayman Alfalou, Christian BrosseauAbstract:We report on a new algorithm to compress and encrypt simultaneously multiple images (target images). This method, which is based upon a specific spectral multiplexing (fusion without overlapping) of the multiple images, aims to achieve a single encrypted image, at the output plane of our system, that contains all information needed to reconstruct the target images. For that purpose, we divide the Fourier plane of the image to transmit into two types of area, i.e., specific and common areas to each target image. A segmentation criterion taking into account the rootmean- square duration of each target image spectrum is proposed. This approach, which consists of merging the input target images together (in the Fourier plane) allows us to reduce the information to be stored and/or transmitted (compression) and induce noise on the output image (encryption). To achieve a good encryption level, a first key image (containing biometric information and providing the intellectual property of the target images) is used. A second encryption key is inserted in the Fourier plane to ensure a relevant phase distribution of the different merged spectra. We also discuss how the encoding information can be optimized by minimizing the number of bits required to encode each pixel. © 2010 Optical Society of America
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exploiting root mean square time Frequency Structure for multiple image optical compression and encryption
Optics Letters, 2010Co-Authors: Ayman Alfalou, Christian BrosseauAbstract:We report on an algorithm to compress and encrypt simultaneously multiple images (target images). This method, which is based upon a specific spectral multiplexing (fusion without overlapping) of the multiple images, aims to achieve a single encrypted image, at the output plane of our system, that contains all information needed to reconstruct the target images. For that purpose, we divide the Fourier plane of the image to transmit into two types of area, i.e., specific and common areas to each target image. A segmentation criterion taking into account the rms duration of each target image spectrum is proposed. This approach, which consists of merging the input target images together (in the Fourier plane) allows us to reduce the information to be stored and/or transmitted (compression) and induce noise on the output image (encryption). To achieve a good encryption level, a first key image (containing biometric information and providing the intellectual property of the target images) is used. A second encryption key is inserted in the Fourier plane to ensure a relevant phase distribution of the different merged spectra. We also discuss how the encoding information can be optimized by minimizing the number of bits required to encode each pixel.
Stephen W Morris - One of the best experts on this subject based on the ideXlab platform.
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Frequency Structure of the nonlinear instability of a dragged viscous thread
Physical Review E, 2012Co-Authors: Robert L Welch, Billy Szeto, Stephen W MorrisAbstract:A thread of viscous fluid falling onto a moving surface exhibits a spectacular variety of types of motion as the surface speed and nozzle height are varied. For modest nozzle heights, four clear regimes are observed. For large surface speed, the thread is dragged into a stretched centenary configuration which is confined to a plane. As the surface speed is lowered, the thread exhibits a supercritical bifurcation to a meandering state. At very low surface speeds, the state resembles the usual coiling motion of a viscous thread falling on a stationary surface. In between the meandering and coiling regimes, a window containing a novel multiFrequency state, previously called "figures of eight," is found. Using an improved visualization technique and a fully automated apparatus, we made detailed measurements of the longitudinal and transverse motion of the thread in all these states. We found that the multiFrequency state is characterized by a complex pattern of motion whose main frequencies are locked in a 3:2 ratio. This state appears and disappears with finite amplitude at sharp bifurcations without measurable hysteresis.
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Frequency Structure of the nonlinear instability of a dragged viscous thread
Bulletin of the American Physical Society, 2011Co-Authors: Stephen W Morris, Robert L Welch, Billy SzetoAbstract:A thread of viscous fluid falling onto a moving surface exhibits a spectacular variety of types of motion as the surface speed and nozzle height are varied. For modest nozzle heights, four clear regimes are observed. For large surface speed, the thread is dragged into a stretched centenary configuration which is confined to a plane. As the surface speed is lowered, this exhibits a supercritical bifurcation to a meandering state. At very low surface speeds, the state resembles the usual coiling motion of a viscous thread falling on a stationary surface. In between the meandering and coiling regimes, a window containing a novel multiFrequency state, previously called “figures of eight” is found. Using an improved visualization technique and a fully automated apparatus, we made detailed measurements of the longitudinal and transverse motion of the thread in all these states. We found that the multiFrequency state is characterized by a complex pattern of motion whose main frequencies are locked in a 3:2 ratio. This state appears and disappears with finite amplitude at sharp bifurcations without measurable hysteresis.
Stephanie J. Lent - One of the best experts on this subject based on the ideXlab platform.
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High resolution spectral analysis of plasma adrenocorticotropin reveals a multifactorial Frequency Structure.
Endocrinology, 1991Co-Authors: Molly Carnes, Brian M. Goodman, Stephanie J. LentAbstract:Time series of plasma ACTH concentrations were analyzed with a high resolution spectral analysis program based on digital Fourier transforms. Both coherent signal and stochastic aspects of the time series were analyzed. Samples were collected at 2- and 15-min intervals in control rats and rats immunoneutralized against CRH. The individual and composite spectral distributions revealed significant Structure at both the higher and lower ranges of frequencies studied, with multiple periodicities between 4-220 min in both groups. CRH immunoneutralization consistently reduced the amplitude by 82% and compressed the Frequency distribution for waveforms with periods longer than 15 min by 23%. A systematic break in the slopes of the background continua occurred between 10 and 15 min in the 2-min time series. This break was unaffected by CRH immunoneutralization. Digital Fourier transform analysis of our ACTH time series suggests a system with a more complex high Frequency Structure than has previously been appreci...
