The Experts below are selected from a list of 27474 Experts worldwide ranked by ideXlab platform
Herbert Witte - One of the best experts on this subject based on the ideXlab platform.
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Analysis of time-variant Quadratic Phase couplings in the tracé alternant EEG by recursive estimation of 3rd-order time-frequency distributions.
Journal of neuroscience methods, 2006Co-Authors: Marko Helbig, Karin Schwab, Michael Eiselt, Lutz Leistritz, Herbert WitteAbstract:The quantification of transient Quadratic Phase couplings (QPC) by means of time-variant bispectral analysis is a useful approach to explain several interrelations between signal components. A generalized recursive estimation approach for 3rd-order time-frequency distributions (3rd-order TFD) is introduced. Based on 3rd-order TFD, time-variant estimations of biamplitude (BA), bicoherence (BC) and Phase bicoherence (PBC) can be derived. Different smoothing windows and local moment functions for an optimization of the estimation properties are investigated and compared. The methods are applied to signal simulations and EEG signals, and it can be shown that the new time-variant bispectral analysis results in a reliable quantification of QPC in the trace alternant EEG of healthy neonates.
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Time-variant Parametric Estimation of Transient Quadratic Phase Couplings during Electroencephalographic Burst Activity
Methods of information in medicine, 2005Co-Authors: Karin Schwab, Michael Eiselt, C Schelenz, Herbert WitteAbstract:Objectives: Electroencephalographic burst activity characteristic of burst-suppression pattern (BSP) in sedated patients and of burst-interburst pattern (BIP) in the quiet sleep of healthy neonates have similar linear and non-linear signal properties. Strong interrelations between a slow frequency component and rhythmic, spindle-like activities with higher frequencies have been identified in previous studies. Time-varying characteristics of BSP and BIP prevent a definite patternrelated analysis. A continuous estimation of the bispectrum is essential to analyze these patterns. Parametric bispectral approaches provide this opportunity. Methods: The adaptation of an AR model leads to a parametric bispectrum by using the transfer function of the estimated AR filter. Time-variant parametric bispectral approaches require an estimation of AR parameters which consider higher order moments to preserve Phase information. Accordingly, a time-variant parametric estimation of the bispectrum was introduced. Data driven simulations were performed to provide optimal parameters. BSP (12 patients) and BIP (6 neonates) were analyzed using this novel approach. Results: Significant differences in the time course of burst pattern during BSP and burst-like pattern before the onset of BSP could be shown. A rhythmic Quadratic Phase coupling (period 10 sec) was identified during BIP in all neonates. Conclusion: Quadratic Phase couplings during BSP increases in the time course depending on depth of sedation. The visually detected burst activity in BIP is only the temporarily observable EEG correlate of a hidden neural process. Time-variant bispectral approaches offer the possibility of a better characterization of underlying neural processes leading to improved diagnostic tools used in clinical routine.
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On the rhythmicity of Quadratic Phase coupling in the tracé alternant EEG in healthy neonates.
Neuroscience letters, 2004Co-Authors: Karin Schwab, Michael Eiselt, P Putsche, Marko Helbig, Herbert WitteAbstract:Abstract The time-variant Quadratic Phase coupling (QPC) in trace alternant (TA) EEG patterns in healthy full-term neonates (quiet sleep) was investigated by means of time-variant bispectral analysis. The frequency plain 1–1.5 Hz ⇔ 3.5–4.5 Hz was used as the region-of-interest. QPC rhythms with a frequency of approximately 0.1 Hz were found in all neonates ( n =6). It can be demonstrated that the QPC rhythm of the TA is generated by a pattern-spanning time-variant Phase-locking process characterising early functional interactions in the immature brain.
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Technique for the quantification of transient Quadratic Phase couplings between heart rate components.
Biomedizinische Technik. Biomedical engineering, 2001Co-Authors: Herbert Witte, Michael Eiselt, P Putsche, K Schmidt, Matthias Arnold, Bärbel SchackAbstract:A technique for the time-variant analysis of Quadratic Phase coupling (QPC) in heart rate data is introduced and tested in 6 human neonates during quiet sleep. The set up of the approach is based up on the assumption that QPCs in the heart rate variability (HRV) are related to amplitude modulation effects. The application of the biamplitude deals with the detection of the coupling pattern and the bicoherence is used for the statistical quantification of coupling. By means of the results of bispectral analysis the time-variant processing has been adapted. The frequency-selective complex demodulation of the HRV leads to the envelope of the respiratory sinus arrhythmia (RSA), this has been used as one input for a time-variant coherence analysis. The other input is the low-pass filtered 10-second-rhythm of the HRV. A time-continuous quantification of the QPC, caused by amplitude modulation (10-second-rhythm modulates the RSA), is possible using this approach. According to our observed results in neonatal HRV both a Phase co-ordination between the 10-second-rhythm and RSA as well as a non-linear coupling (amplitude modulation) between these HRV components can be seen.
Karin Schwab - One of the best experts on this subject based on the ideXlab platform.
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Time-variant parametric estimation of transient Quadratic Phase couplings between heart rate components in healthy neonates
Medical and Biological Engineering and Computing, 2006Co-Authors: Karin Schwab, Michael Eiselt, M Helbig, P Putsche, H WitteAbstract:The heart rate variability (HRV) can be taken as an indicator of the coordination of the cardio-respiratory rhythms. Bispectral analysis using a direct (fast Fourier transform based) and time-invariant approach has shown the occurrence of a Quadratic Phase coupling (QPC) between a low-frequency (LF: 0.1 Hz) and a high-frequency (HF: 0.4–0.6 Hz) component of the HRV during quiet sleep in healthy neonates. The low-frequency component corresponds to the Mayer–Traube–Hering waves in blood pressure and the high-frequency component to the respiratory sinus arrhythmia (RSA). Time-variant, parametric estimation of the bispectrum provides the possibility of quantifying QPC in the time course. Therefore, the aim of this work was a parametric, time-variant bispectral analysis of the neonatal HRV in the same neonates used in the direct, time-invariant approach. For the first time rhythms in the time course of QPC between the HF component and the LF component could be shown in the neonatal HRV.
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Analysis of time-variant Quadratic Phase couplings in the tracé alternant EEG by recursive estimation of 3rd-order time-frequency distributions.
Journal of neuroscience methods, 2006Co-Authors: Marko Helbig, Karin Schwab, Michael Eiselt, Lutz Leistritz, Herbert WitteAbstract:The quantification of transient Quadratic Phase couplings (QPC) by means of time-variant bispectral analysis is a useful approach to explain several interrelations between signal components. A generalized recursive estimation approach for 3rd-order time-frequency distributions (3rd-order TFD) is introduced. Based on 3rd-order TFD, time-variant estimations of biamplitude (BA), bicoherence (BC) and Phase bicoherence (PBC) can be derived. Different smoothing windows and local moment functions for an optimization of the estimation properties are investigated and compared. The methods are applied to signal simulations and EEG signals, and it can be shown that the new time-variant bispectral analysis results in a reliable quantification of QPC in the trace alternant EEG of healthy neonates.
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Time-variant Parametric Estimation of Transient Quadratic Phase Couplings during Electroencephalographic Burst Activity
Methods of information in medicine, 2005Co-Authors: Karin Schwab, Michael Eiselt, C Schelenz, Herbert WitteAbstract:Objectives: Electroencephalographic burst activity characteristic of burst-suppression pattern (BSP) in sedated patients and of burst-interburst pattern (BIP) in the quiet sleep of healthy neonates have similar linear and non-linear signal properties. Strong interrelations between a slow frequency component and rhythmic, spindle-like activities with higher frequencies have been identified in previous studies. Time-varying characteristics of BSP and BIP prevent a definite patternrelated analysis. A continuous estimation of the bispectrum is essential to analyze these patterns. Parametric bispectral approaches provide this opportunity. Methods: The adaptation of an AR model leads to a parametric bispectrum by using the transfer function of the estimated AR filter. Time-variant parametric bispectral approaches require an estimation of AR parameters which consider higher order moments to preserve Phase information. Accordingly, a time-variant parametric estimation of the bispectrum was introduced. Data driven simulations were performed to provide optimal parameters. BSP (12 patients) and BIP (6 neonates) were analyzed using this novel approach. Results: Significant differences in the time course of burst pattern during BSP and burst-like pattern before the onset of BSP could be shown. A rhythmic Quadratic Phase coupling (period 10 sec) was identified during BIP in all neonates. Conclusion: Quadratic Phase couplings during BSP increases in the time course depending on depth of sedation. The visually detected burst activity in BIP is only the temporarily observable EEG correlate of a hidden neural process. Time-variant bispectral approaches offer the possibility of a better characterization of underlying neural processes leading to improved diagnostic tools used in clinical routine.
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On the rhythmicity of Quadratic Phase coupling in the tracé alternant EEG in healthy neonates.
Neuroscience letters, 2004Co-Authors: Karin Schwab, Michael Eiselt, P Putsche, Marko Helbig, Herbert WitteAbstract:Abstract The time-variant Quadratic Phase coupling (QPC) in trace alternant (TA) EEG patterns in healthy full-term neonates (quiet sleep) was investigated by means of time-variant bispectral analysis. The frequency plain 1–1.5 Hz ⇔ 3.5–4.5 Hz was used as the region-of-interest. QPC rhythms with a frequency of approximately 0.1 Hz were found in all neonates ( n =6). It can be demonstrated that the QPC rhythm of the TA is generated by a pattern-spanning time-variant Phase-locking process characterising early functional interactions in the immature brain.
Michael Eiselt - One of the best experts on this subject based on the ideXlab platform.
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Time-variant parametric estimation of transient Quadratic Phase couplings between heart rate components in healthy neonates
Medical and Biological Engineering and Computing, 2006Co-Authors: Karin Schwab, Michael Eiselt, M Helbig, P Putsche, H WitteAbstract:The heart rate variability (HRV) can be taken as an indicator of the coordination of the cardio-respiratory rhythms. Bispectral analysis using a direct (fast Fourier transform based) and time-invariant approach has shown the occurrence of a Quadratic Phase coupling (QPC) between a low-frequency (LF: 0.1 Hz) and a high-frequency (HF: 0.4–0.6 Hz) component of the HRV during quiet sleep in healthy neonates. The low-frequency component corresponds to the Mayer–Traube–Hering waves in blood pressure and the high-frequency component to the respiratory sinus arrhythmia (RSA). Time-variant, parametric estimation of the bispectrum provides the possibility of quantifying QPC in the time course. Therefore, the aim of this work was a parametric, time-variant bispectral analysis of the neonatal HRV in the same neonates used in the direct, time-invariant approach. For the first time rhythms in the time course of QPC between the HF component and the LF component could be shown in the neonatal HRV.
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Analysis of time-variant Quadratic Phase couplings in the tracé alternant EEG by recursive estimation of 3rd-order time-frequency distributions.
Journal of neuroscience methods, 2006Co-Authors: Marko Helbig, Karin Schwab, Michael Eiselt, Lutz Leistritz, Herbert WitteAbstract:The quantification of transient Quadratic Phase couplings (QPC) by means of time-variant bispectral analysis is a useful approach to explain several interrelations between signal components. A generalized recursive estimation approach for 3rd-order time-frequency distributions (3rd-order TFD) is introduced. Based on 3rd-order TFD, time-variant estimations of biamplitude (BA), bicoherence (BC) and Phase bicoherence (PBC) can be derived. Different smoothing windows and local moment functions for an optimization of the estimation properties are investigated and compared. The methods are applied to signal simulations and EEG signals, and it can be shown that the new time-variant bispectral analysis results in a reliable quantification of QPC in the trace alternant EEG of healthy neonates.
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Time-variant Parametric Estimation of Transient Quadratic Phase Couplings during Electroencephalographic Burst Activity
Methods of information in medicine, 2005Co-Authors: Karin Schwab, Michael Eiselt, C Schelenz, Herbert WitteAbstract:Objectives: Electroencephalographic burst activity characteristic of burst-suppression pattern (BSP) in sedated patients and of burst-interburst pattern (BIP) in the quiet sleep of healthy neonates have similar linear and non-linear signal properties. Strong interrelations between a slow frequency component and rhythmic, spindle-like activities with higher frequencies have been identified in previous studies. Time-varying characteristics of BSP and BIP prevent a definite patternrelated analysis. A continuous estimation of the bispectrum is essential to analyze these patterns. Parametric bispectral approaches provide this opportunity. Methods: The adaptation of an AR model leads to a parametric bispectrum by using the transfer function of the estimated AR filter. Time-variant parametric bispectral approaches require an estimation of AR parameters which consider higher order moments to preserve Phase information. Accordingly, a time-variant parametric estimation of the bispectrum was introduced. Data driven simulations were performed to provide optimal parameters. BSP (12 patients) and BIP (6 neonates) were analyzed using this novel approach. Results: Significant differences in the time course of burst pattern during BSP and burst-like pattern before the onset of BSP could be shown. A rhythmic Quadratic Phase coupling (period 10 sec) was identified during BIP in all neonates. Conclusion: Quadratic Phase couplings during BSP increases in the time course depending on depth of sedation. The visually detected burst activity in BIP is only the temporarily observable EEG correlate of a hidden neural process. Time-variant bispectral approaches offer the possibility of a better characterization of underlying neural processes leading to improved diagnostic tools used in clinical routine.
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On the rhythmicity of Quadratic Phase coupling in the tracé alternant EEG in healthy neonates.
Neuroscience letters, 2004Co-Authors: Karin Schwab, Michael Eiselt, P Putsche, Marko Helbig, Herbert WitteAbstract:Abstract The time-variant Quadratic Phase coupling (QPC) in trace alternant (TA) EEG patterns in healthy full-term neonates (quiet sleep) was investigated by means of time-variant bispectral analysis. The frequency plain 1–1.5 Hz ⇔ 3.5–4.5 Hz was used as the region-of-interest. QPC rhythms with a frequency of approximately 0.1 Hz were found in all neonates ( n =6). It can be demonstrated that the QPC rhythm of the TA is generated by a pattern-spanning time-variant Phase-locking process characterising early functional interactions in the immature brain.
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Technique for the quantification of transient Quadratic Phase couplings between heart rate components.
Biomedizinische Technik. Biomedical engineering, 2001Co-Authors: Herbert Witte, Michael Eiselt, P Putsche, K Schmidt, Matthias Arnold, Bärbel SchackAbstract:A technique for the time-variant analysis of Quadratic Phase coupling (QPC) in heart rate data is introduced and tested in 6 human neonates during quiet sleep. The set up of the approach is based up on the assumption that QPCs in the heart rate variability (HRV) are related to amplitude modulation effects. The application of the biamplitude deals with the detection of the coupling pattern and the bicoherence is used for the statistical quantification of coupling. By means of the results of bispectral analysis the time-variant processing has been adapted. The frequency-selective complex demodulation of the HRV leads to the envelope of the respiratory sinus arrhythmia (RSA), this has been used as one input for a time-variant coherence analysis. The other input is the low-pass filtered 10-second-rhythm of the HRV. A time-continuous quantification of the QPC, caused by amplitude modulation (10-second-rhythm modulates the RSA), is possible using this approach. According to our observed results in neonatal HRV both a Phase co-ordination between the 10-second-rhythm and RSA as well as a non-linear coupling (amplitude modulation) between these HRV components can be seen.
John T. Sheridan - One of the best experts on this subject based on the ideXlab platform.
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Low photon count based digital holography for Quadratic Phase cryptography.
Optics letters, 2017Co-Authors: Inbarasan Muniraj, John J. Healy, Changliang Guo, Ra'ed Malallah, James P. Ryle, Byung-geun Lee, John T. SheridanAbstract:Recently, the vulnerability of the linear canonical transform-based double random Phase encryption system to attack has been demonstrated. To alleviate this, we present for the first time, to the best of our knowledge, a method for securing a two-dimensional scene using a Quadratic Phase encoding system operating in the photon-counted imaging (PCI) regime. Position-Phase-shifting digital holography is applied to record the photon-limited encrypted complex samples. The reconstruction of the complex wavefront involves four sparse (undersampled) dataset intensity measurements (interferograms) at two different positions. Computer simulations validate that the photon-limited sparse-encrypted data has adequate information to authenticate the original data set. Finally, security analysis, employing iterative Phase retrieval attacks, has been performed.
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Security analysis of Quadratic Phase based cryptography
Optics and Photonics for Information Processing X, 2016Co-Authors: Inbarasan Muniraj, John J. Healy, Changliang Guo, Ra'ed Malallah, John T. SheridanAbstract:The linear canonical transform (LCT) is essential in modeling a coherent light field propagation through first-order optical systems. Recently, a generic optical system, known as a Quadratic Phase Encoding System (QPES), for encrypting a two-dimensional (2D) image has been reported. It has been reported together with two Phase keys the individual LCT parameters serve as keys of the cryptosystem. However, it is important that such the encryption systems also satisfies some dynamic security properties. Therefore, in this work, we examine some cryptographic evaluation methods, such as Avalanche Criterion and Bit Independence, which indicates the degree of security of the cryptographic algorithms on QPES. We compare our simulation results with the conventional Fourier and the Fresnel transform based DRPE systems. The results show that the LCT based DRPE has an excellent avalanche and bit independence characteristics than that of using the conventional Fourier and Fresnel based encryption systems.
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Generalized Yamaguchi correlation factor for coherent Quadratic Phase speckle metrology systems with an aperture
Optics letters, 2006Co-Authors: Damien P. Kelly, Jennifer E. Ward, Unnikrishnan Gopinathan, Bryan M. Hennelly, Feidhlim T. O'neill, John T. SheridanAbstract:In speckle-based metrology systems, a finite range of possible motion or deformation can be measured. When coherent imaging systems with a single limiting aperture are used in speckle metrology, the observed decorrelation effects that ultimately define this range are described by the well-known Yamaguchi correlation factor. We extend this result to all coherent Quadratic Phase paraxial optical systems with a single aperture and provide experimental results to support our theoretical conclusions.
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New fast algorithm for the numerical computation of Quadratic-Phase integrals
Advanced Signal Processing Algorithms Architectures and Implementations XVI, 2006Co-Authors: John J. Healy, John T. SheridanAbstract:Paraxial optical systems implemented entirely with thin lenses and propagation through free space and/or Graded Index (GRIN) media are Quadratic Phase systems (QPS). The effect of any arbitrary QPS on an input wavefield can be described using Linear Canonical Transform (LCT). In this paper, we examine a novel numerical implementation of Fast Linear Canonical Transform (FLCT). We then apply the results in various optical signal processing applications.
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Generalized Yamaguchi correlation factor forcoherent Quadratic Phase speckle metrologysystems with an aperture
2006Co-Authors: Damien P. Kelly, Jennifer E. Ward, Unnikrishnan Gopinathan, Bryan M. Hennelly, Feidhlim T. O'neill, John T. SheridanAbstract:In speckle-based metrology systems, a finite range of possible motion or deformation can be measured. When coherent imaging systems with a single limiting aperture are used in speckle metrology, the observed de correlation effects that ultimately define this range are described by the well-known Yamaguchi correlation factor. We extend this result to all coherent Quadratic Phase paraxial optical systems with a single aperture and provide experimental results to support our theoretical conclusions.
Yunhe Cao - One of the best experts on this subject based on the ideXlab platform.
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Dynamic Analysis of Spin Satellites Through the Quadratic Phase Estimation in Multiple-Station Radar Images
IEEE Transactions on Computational Imaging, 2020Co-Authors: Yejian Zhou, Lei Zhang, Shaopeng Wei, Yunhe CaoAbstract:Dynamic analysis of in-orbit satellites is of interest for space situation applications. Some exploratory methods have been presented to analyze the state of attitude-steadied satellites in the complex space situation, but effectively estimating the dynamic parameters of spinning satellites remains a significant and interesting challenge nowadays. With decoupling target spin estimation from its trajectory motion, this paper proposes a novel dynamic estimation approach by using multiple-station inverse synthetic aperture radar (ISAR) images. In brief, Quadratic Phase characteristic, which is usually regarded as a negative factor for ISAR imagery in conventional algorithms, is now directly exploited to build an explicit expression of the relative motion between the spin in-orbit satellite and radar. Then, based on the developed image refocusing algorithm, these Phase coefficients are extracted from the multiple-station images and substituted into the optimization of target dynamic estimation. In the end, target dynamic parameters, including its instantaneous attitude vector and spin speed, are estimated through particle swarm optimization. Experiment results illustrate the feasibility of the proposed algorithm. To some degree, this work also reflects the advantages of multiple-station ISAR system in some space applications.
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Attitude Estimation for Space Targets by Exploiting the Quadratic Phase Coefficients of Inverse Synthetic Aperture Radar Imagery
IEEE Transactions on Geoscience and Remote Sensing, 2019Co-Authors: Yejian Zhou, Lei Zhang, Yunhe CaoAbstract:This paper proposes a novel approach to interpreting the satellite attitude based on inverse synthetic aperture radar (ISAR) images. In the conventional viewpoint, Quadratic and higher order Phase terms of ISAR imagery are regarded as negative factors causing the defocusing phenomenon. In this paper, we introduce how to apply Quadratic Phase coefficients to estimate target attitude from the ISAR imagery. A geometric projection model of ISAR imaging is built according to radar line of sight, and an explicit expression is also derived to connect target attitude parameters and the image defocusing property. With the accommodation of Broyden–Fletcher–Goldfarb–Shanno algorithm, spatial-variant Quadratic Phase coefficients together with attitude parameters are determined by an image contrast maximization. We also extend the proposed algorithm to multistatic ISAR applications, where the Quadratic Phase information lying in simultaneous multistatic ISAR images can be mined to enhance the performance of target attitude estimation. Experimental results illustrate the feasibility of the proposed algorithm.
