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1

Joint Time-Frequency Domain Interference Mitigation for Galileo L1 Band Receivers  

Microsoft Academic Search

In this paper we address the problem of interference mitigation (IM) for the Galileo system. In particular, a joint domain technique is investigated by coupling the mitigation effects in both time and frequency dimensions, against interference concurrently variable in more than one domain. The proposed technique is based on an open loop adaptive filter, which creates an infinite notch in

Marco Villanti; Raffaella Pedone; Giovanni E. Corazza; Rodolfo Crescimbeni

2006-01-01

2

Factors influencing intelligibility of whisper in joint time-frequency domain based on real-valued Discrete Gabor transform  

Microsoft Academic Search

Intelligibility improvement of the enhancement algorithm proposed in our previous paper is evaluated in this paper. Joint time-frequency spectrum of the noisy whisper and clean whisper are computed based on real-valued Discrete Gabor transformation respectively. The Gaussian window is used as the kernel function which assures the best utilization of the information area for it possess the smallest product of

Kang Qi; Xiao Lu; Jian Zhou; Liang Tao

2011-01-01

3

Joint time-frequency and finite-difference time-domain analysis of precursor fields in dispersive media.  

PubMed

Superluminal group velocities, defined as group velocities exceeding the speed of light in vacuum, c, have been theoretically predicted and experimentally observed in various types of dispersive media, such as passive and active Lorentzian media, one-dimensional photonic crystals, and undersized waveguides. Though superluminal group velocities have been found in these media, it has been suggested that the pulse "front" and associated transient field oscillations, known as the precursors or forerunners, will never travel faster than c, and hence relativistic causality is always preserved. Until now, few rigorous studies of these transient fields in structures exhibiting superluminal group velocities have been performed. In this paper, we present the dynamic evolution of these earliest field oscillations in one-dimensional photonic crystals (1DPC), using finite-difference time-domain (FDTD) techniques in conjunction with joint time-frequency analysis (JTFA). Our study clearly shows that the precursor fields associated with superluminal pulse propagation travel at subluminal speeds, and thus, the arrival of these precursor fields must be associated with the arrival of "genuine information." Our study demonstrates the expected result that abnormal group velocities do not contradict Einstein causality. This work also shows that FDTD analysis and JTFA can be combined to study the dynamic evolution of the transient and steady state pulse propagation in dispersive media. PMID:16906992

Safian, Reza; Sarris, Costas D; Mojahedi, Mohammad

2006-06-02

4

Transionospheric signal recognition by joint time-frequency representation  

NASA Astrophysics Data System (ADS)

A challenging problem in signal processing is the detection of impulsive signals which are dispersed by the ionosphere and received by RF satellite sensors. One example of this type of signal is the so-called transionospheric pulse pair (TIPP), thought to be associated with lightning discharges. Since these dispersed events occur sporadically and typically persist for less than 100 ?s, the first objective is to detect or trigger on the signal of interest, thereby reducing the amount of data relayed back to Earth. Difficulties in detecting transionospheric impulses arise from the dispersion of the original signal, which lowers the signal-to-noise ratio (SNR), and the need for continuous, real-time observation. The energy content of TIPPs has been measured from 25 MHz to more than 100 MHz, requiring sampling rates of at least 150 MHz to capture the events. Although these transionospheric signals are easily recognized in the joint time-frequency domain, the computation involved in time-frequency transformations prohibits application to a real-time detector with this sampling rate. Using a joint time-frequency representation allows us to derive a robust time convolution template to fit transionospheric signals. This template can be used to design matched chirp filter banks, which are optimum with respect to SNR, for detection of transionospheric signals. We believe that a realistic matched filter bank could have a sparse spacing while maintaining good detection ability. This type of detector is also amenable to real-time analog hardware implementation in conventional finite impulse response (FIR) filter structures. Our work shows that transionospheric signals encountered in real data are effectively detected by matched filter banks. While a specific application is treated here, the methods described are general, and applicable to many problems in signal detection and recognition which treat nonlinearly dispersed signals.

Qian, Shie; Dunham, Mark E.; Freeman, Matthew J.

1995-11-01

5

Joint Time-Frequency Analysis of High Power Microwave Signals  

NASA Astrophysics Data System (ADS)

We report a new technique for the study of high power microwave sources utilizing joint-time-frequency (JTF) analysis of heterodyne mixer signals (C. W. Peters et al., Phys. Rev. E, to be published, 1998). Reduced-interference-distributions (RIDs) are used to avoid the spectrogram windowing effect (W. J. Williams, Proc. IEEE 84, 1264 (1996)). JTF analysis of coaxial gyrotron heterodyne signals shows, with unprecedented clarity, the following effects under different conditions: 1)Frequency modulation by e-beam voltage fluctuations, 2) Mode hopping, and 3) Mode competition. Microwave signals from other microwave sources (MILO, RKO) and simulations are being analyzed. This technique is expected to open up a new paradigm to investigate HPM pulse shortening, mode competition, noise and unwanted frequencies in RF generation.

Peters, C. W.; Jaynes, R. L.; Gilgenbach, R. M.; Lau, Y. Y.; Williams, W. J.; Hochman, J. M.; Cohen, W. E.; Rintamaki, J. I.; Vollers, D. E.; Luginsland, J. W.; Haworth, M. D.; Hendricks, K. J.; Spencer, T. A.

1998-11-01

6

DBS artifact suppression using a time-frequency domain filter.  

PubMed

Electroencephalogram (EEG) is a useful tool for brain research. However, during Deep-Brain Stimulation (DBS), there are large artifacts that obscure the physiological EEG signals. In this paper, we aim at suppressing the DBS artifacts by means of a time-frequency-domain filter. As a pre-processing step, Empirical-Mode Decomposition (EMD) is applied to detrend the raw data. The detrended signals are then filtered iteratively until, by visual inspection, the quality is good enough for interpretation. The proposed algorithm is demonstrated by an application to a clinical DBS-EEG data set in resting state and in finger-tapping condition. Moreover, a comparison with a Low-Pass filter (LPF) is provided, by visual inspection and by a quantitative measure. PMID:24110812

Santillan-Guzman, Alina; Heute, Ulrich; Muthuraman, Muthuraman; Stephani, Ulrich; Galka, Andreas

2013-07-01

7

Joint DOD/DOA estimation in MIMO radar exploiting time-frequency signal representations  

NASA Astrophysics Data System (ADS)

In this article, we consider the joint estimation of direction-of-departure (DOD) and direction-of-arrival (DOA) information of maneuvering targets in a bistatic multiple-input multiple-output (MIMO) radar system that exploits spatial time-frequency distribution (STFD). STFD has been found useful in solving various array processing problems, such as direction finding and blind source separation, where nonstationary signals with time-varying spectral characteristics are encountered. The STFD approach to array processing has been primarily limited to conventional problems for passive radar platform that deals with signal arrivals, while its use in a MIMO radar configuration has received much less attention. This paper examines the use of STFD in MIMO radar systems with application to direction finding of moving targets with nonstationary signatures. Within this framework, we consider the use of joint transmit and receive apertures for the improved estimation of both target time-varying Doppler signatures and joint DOD/DOA. It is demonstrated that the STFD is an effective tool in MIMO radar processing when moving targets produce Doppler signatures that are highly localized in the time-frequency domain.

Zhang, Yimin D.; Amin, Moeness G.; Himed, Braham

2012-12-01

8

Algorithm based on joint time-frequency analysis to eliminate noise from stratospheric laser data  

NASA Astrophysics Data System (ADS)

The difficulties in extracting useful information from the noise-corrupted stratospheric laser echoes have elevated application of digital signal processing techniques to the atmospheric research. This paper focuses on the problem of noise elimination from the transient returns of stratospheric laser echoes, proposes a new solution approach to it. Unlike related methods which address signal modeling in time domain only, we formulate the problem in both time and frequency domain, present a new modeling environment for the joint time-frequency analysis and use a non-linear median filter for noise elimination. Experiments with various patterns of spectral clouds demonstrate that such an approach significantly increases readability and accuracy of results in terms of the back-scattering function and depolarization.

Boyo, Henry; Fujiwara, Motowo; Moshnyaga, Vasily G.; Boyo, Adenike

2003-04-01

9

Seismic waveform tomography in the time-frequency domain with applications to the Australian upper mantle  

Microsoft Academic Search

We present a novel approach to full waveform tomography based on misfits in the time-frequency domain and adjoint methods. Our focus is on theoretical developments and synthetic inversions for heterogeneities in the Australian upper mantle. The centrepieces of our methodology are envelope and instantaneous phase misfits defined on time-frequency transforms of the seismograms. These misfits allow us to extract the

A. Fichtner; P. Bunge; H. Igel; B. Kennett

2007-01-01

10

Bubble Pulse Cancelation in the Time-Frequency Domain Using Warping Operators  

NASA Astrophysics Data System (ADS)

The received shock waves produced by explosive charges are often polluted by bubble pulses in underwater acoustic experiments. A method based on warping operators is proposed to cancel the bubble pulses in the time-frequency domain. This is applied to the explosive data collected during the Yellow Sea experiment in November 2000. The original received signal is first transformed into a warped signal by warping operators. Then, the warped signal is analyzed in the time-frequency domain. Due to the different features between the shock waves and the bubble pulses in the time-frequency domain for the warped signal, the bubble pulses can be easily filtered out. Furthermore, the shock waves in the original time domain can be retrieved by the inverse warping transformation. The autocorrelation functions and the time-frequency representation show that the bubble pulses can be canceled effectively.

Niu, Hai-Qiang; Zhang, Ren-He; Li, Zheng-Lin; Guo, Yong-Gang; He, Li

2013-08-01

11

Asymptotically exact localized expansions for signals in the time-frequency domain  

NASA Astrophysics Data System (ADS)

Based on a unique waveform with strong exponential localization property, an exact mathematical method for solving problems in signal analysis in the time-frequency domain is presented. An analogue of the Gabor frame exposes the non-commutative geometry of the time-frequency plane. Signals are visualized using the constructed graphical representation. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.

Muzhikyan, Aramazd H.; Avanesyan, Gagik T.

2012-06-01

12

Joint Time-Frequency Analysis: A tool for exploratory analysis and filtering of non-stationary time series  

Microsoft Academic Search

It is the purpose of the paper to describe the virtues of time-frequency methods for signal processing applications, having astronomical time series in mind. Different methods are considered and their potential usefulness respectively drawbacks are discussed and illustrated by examples. As areas where one can hope for a successful application of joint time-frequency analysis (JTFA), we describe specifically the problem

R. Vio; W. Wamsteker

2002-01-01

13

Adaptive Emotional Information Retrieval From EEG Signals in the Time-Frequency Domain  

Microsoft Academic Search

This paper aims at developing adaptive methods for electroencephalogram (EEG) signal segmentation in the time-frequency domain, in order to effectively retrieve the emotion-related information within the EEG recordings. Using the multidimensional directed information analysis supported by the frontal brain asymmetry in the case of emotional reaction, a criterion, namely asymmetry index $(AsI)$ , is used to realize the proposed segmentation

Panagiotis C. Petrantonakis; Leontios J. Hadjileontiadis

2012-01-01

14

Measuring high-frequency wave propagation in railroad tracks by joint time-frequency analysis  

NASA Astrophysics Data System (ADS)

The behavior of high-frequency elastic waves propagating in railroad tracks is relevant to the field of rail noise generation and long-range rail inspection. While a large amount of theoretical and numerical work exists to predict transient vibrations propagating in rails, obtaining experimental data has been particularly challenging due to the multimode and dispersive behavior of the waves. In this work a joint time-frequency analysis based on the Gabor wavelet transform is employed for characterizing longitudinal, lateral and vertical vibrational modes propagating in rails in the 1000-7000Hz range. The Gabor transform optimizes the time-frequency resolution of the measurements and theoretically requires a single excitation point and a single measurement point. These features make the analysis well-suited for the study of wave propagation in rails. The theory of the wavelet transform is reviewed in the context of dispersive measurements. Accelerometer data were taken from a section of rail subject to impulse dynamic testing in the laboratory. The group (energy) velocity dispersion curves and the frequency-dependent attenuation of the waves were successfully extracted from the wavelet scalograms of the accelerometer signals.

Lanza di Scalea, F.; McNamara, J.

2004-06-01

15

Encoding scheme for 2-D time/frequency domain optical CDMA system  

NASA Astrophysics Data System (ADS)

Applying CDMA techniques to optical communications and combining CDMA techniques with optical communication has its advantages, which not only keeps the characteristics of CDMA techniques in wireless communication, such as interference immunity, secrecy, soft capacity and simple network protocol, but also make use of the huge bandwidth of fiber. Therefore, optical CDMA communication system has the virtue of asynchronism, broad band and reliable. In this paper, we have done tasks as below: first we thoroughly study the development and recent progress in 2-D time / frequency domain optical CDMA encoding schemes. Then we put forward an implement encoding/ decoding scheme based on optical time spreading/ frequency hopping to solve the problem in current schemes. The scheme adopts 2-D time / frequency domain combination codes as address codes, by assigning two orthogonal address codes to each user and encoding "1" and "0" to these address codes respectively, in sink side differential detection technique is adopted. The scheme has the advantage of increasing power efficiency and improving system performance. While under the condition that two branches are balance, the best judge threshold of system is not variety with the environment, so the scheme also has the merit of lower systemic complexity.

Wei, Lin Qi; Gui, Feng

2005-12-01

16

Joint time-frequency transform processing for linear and sinusoidal FM coherent ladars  

NASA Astrophysics Data System (ADS)

We examine the signal processing of both linear and sinusoidal frequency modulation (FM) coherent ladar returns from resolved and unresolved targets, which are spread in Doppler. The Doppler spread may be due to target spin, tumbling, or vibration as well as to the applied linear or sinusoidal-FM on the transmitted E-field. Monte Carlo realizations of the target surface random phasor reflector elements interact with the incident Efield producing laser speckle, and the speckled returns are analyzed in this study. The speckle signals are processed (1) using several spectrum (periodogram based) estimators, (2) the conventional "spectrogram" approach, and (3) ten joint time-frequency transforms (JTFT). We show that the Born-Jordan JTFT is superior to the other spectral estimators tested here in suppressing local oscillator laser noise and accurately estimating the target"s spectrum for signal processing under speckle target return conditions pertaining to coherent laser radar. A new algorithm which sums particular pixels of the JTFT image is introduced and is shown to be much more robust in low CNR conditions than the JTFT maxima or JTFT centroid processing when utilizing the applied linear or sinusoidal-FM modulation waveform.

Youmans, Douglas G.

2003-09-01

17

Iterative Receiver in Time--Frequency Domain for Shallow Water Acoustic Channel  

NASA Astrophysics Data System (ADS)

Inter-symbol interference (ISI) caused by multi-path propagation, especially in shallow water channel, degrades the performance of underwater acoustic (UWA) communication systems. In this paper, we combine soft minimum mean squared error (MMSE) equalization and the serially concatenated trellis coded modulation (SCTCM) decoding to develop an iterative receiver in time--frequency domain (TFD) for underwater acoustic point to point communications. Based on sound speed profile (SSP) measured in the lake and finite-element ray (FER) tracing method (Bellhop), the shallow water channel is constructed to evaluate the performance of the proposed iterative receiver. The results suggest that the proposed iterative receiver can reduce the calculation complexity of the equalizer and obtain better performance using less receiving elements.

Zhao, Liang; Ge, Jianhua

2012-03-01

18

Wavelet-transform-based time-frequency domain reflectometry for reduction of blind spot  

NASA Astrophysics Data System (ADS)

In this paper, wavelet-transform-based time-frequency domain reflectometry (WTFDR) is proposed to reduce the blind spot in reflectometry. TFDR has a blind spot problem when the time delay between the reference signal and the reflected signal is short enough compared with the time duration of the reference signal. To solve the blind spot problem, the wavelet transform (WT) is used because the WT has linearity. Using the characteristics of the WT, the overlapped reference signal at the measured signal can be separated and the blind spot is reduced by obtaining the difference of the wavelet coefficients for the reference and reflected signals. In the proposed method, the complex wavelet is utilized as a mother wavelet because the reference signal in WTFDR has a complex form. Finally, the computer simulations and the real experiments are carried out to confirm the effectiveness and accuracy of the proposed method.

Lee, Sin Ho; Park, Jin Bae; Choi, Yoon Ho

2012-06-01

19

Review of time-frequency domain concepts with application to ultrashort laser pulses  

NASA Astrophysics Data System (ADS)

We review the application of time-frequency concepts in the field of ultrashort laser science. We consider the Wigner distribution, the spectrogram, and the sonogram, and show how each of these distributions are used in ultrafast laser science. We also plot four example pulses in each of the three representations.

Delong, Kenneth W.; Trebino, Rick P.; Fittinghoff, David N.; Ladera, Celso L.

1995-04-01

20

Position domain joint tracking  

Microsoft Academic Search

It was shown that the Vector Delay Lock Loop (VDLL) enhances the robustness of a GNSS receiver by exploiting the spatial correlation of the received signals. But due to the periodicity of the carrier, the VDLL only operates on the codephase and the carrier-frequency. In contrast to the VDLL, the Joint Tracking receiver manages to sustain the carrier-phase lock even

Kaspar Giger; C. Gu?nther

2010-01-01

21

Measurement of load impedance in power cables using wavelet-transform-based time–frequency domain reflectometry  

NASA Astrophysics Data System (ADS)

In this paper, wavelet-transform-based time–frequency domain reflectometry (WTFDR) is proposed for load impedance measurement. In order to measure the load impedance, the energy of the measured signal in the time–frequency domain, the phase difference between the reference signal and the reflected signal, the characteristic impedance, and the attenuation factor of the measured cable must all be known. Since the complex wavelet transform is composed of real and imaginary parts, the phase difference is easily obtained using the ratio of the real coefficient to the imaginary coefficient. In addition, the wavelet energy denotes the sum of the square of the modulus of the wavelet transform and describes the energy of the measured signal in the time and frequency domains. To accurately determine the characteristic impedance and attenuation factors, the power cable should be estimated as a coaxial cable. Using WTFDR with the complex mother wavelet and the estimated power cable, the load impedance can be obtained simply and accurately. Finally, real experiments for the evaluation of various load impedances are carried out to confirm the effectiveness and accuracy of the proposed method compared to the conventional time–frequency domain reflectometry.

Lee, Sin Ho; Park, Jin Bae; Choi, Yoon Ho

2013-09-01

22

Oscillatory brain activity in the time frequency domain associated to change blindness and change detection awareness.  

PubMed

Despite the importance of change detection (CD) for visual perception and for performance in our environment, observers often miss changes that should be easily noticed. In the present study, we employed time-frequency analysis to investigate the neural activity associated with CD and change blindness (CB). Observers were presented with two successive visual displays and had to look for a change in orientation in any one of four sinusoid gratings between both displays. Theta power increased widely over the scalp after the second display when a change was consciously detected. Relative to no-change and CD, CB was associated with a pronounced theta power enhancement at parietal-occipital and occipital sites and broadly distributed alpha power suppression during the processing of the prechange display. Finally, power suppressions in the beta band following the second display show that, even when a change is not consciously detected, it might be represented to a certain degree. These results show the potential of time-frequency analysis to deepen our knowledge of the temporal curse of the neural events underlying CD. The results further reveal that the process resulting in CB begins even before the occurrence of the change itself. PMID:21671737

Darriba, Alvaro; Pazo-Álvarez, Paula; Capilla, Almudena; Amenedo, Elena

2011-06-14

23

A method for efficient fractional sample delay generation for real-time frequency-domain beamformers  

SciTech Connect

This paper presents an efficient method for fractional delay filter generation for frequency-domain beamformers. A common misunderstanding regarding frequency-domain beamforming is that any fractional time shift can be achieved using the delay property of the discrete Fourier transform (DFT). Blind application of the DFT delay property introduces circular convolution errors that may adversely affect the beam`s time series. The method presented avoids these errors while enabling real-time processing.

Breeding, J.E.; Karnowski, T.P.

1995-07-01

24

Joint time-frequency analysis of EEG signals based on a phase-space interpretation of the recording process  

NASA Astrophysics Data System (ADS)

Time-frequency transforms are used to identify events in clinical EEG data. Data are recorded as part of a study for correlating the performance of human subjects during a memory task with pathological events in the EEG, called spikes. The spectrogram and the scalogram are reviewed as tools for evaluating spike activity. A statistical evaluation of the continuous wavelet transform across trials is used to quantify phase-locking events. For simultaneously improving the time and frequency resolution, and for representing the EEG of several channels or trials in a single time-frequency plane, a multichannel matching pursuit algorithm is used. Fundamental properties of the algorithm are discussed as well as preliminary results, which were obtained with clinical EEG data.

Testorf, M. E.; Jobst, B. C.; Kleen, J. K.; Titiz, A.; Guillory, S.; Scott, R.; Bujarski, K. A.; Roberts, D. W.; Holmes, G. L.; Lenck-Santini, P.-P.

2012-10-01

25

Measuring Multi-Joint Stiffness during Single Movements: Numerical Validation of a Novel Time-Frequency Approach  

PubMed Central

This study presents and validates a Time-Frequency technique for measuring 2-dimensional multijoint arm stiffness throughout a single planar movement as well as during static posture. It is proposed as an alternative to current regressive methods which require numerous repetitions to obtain average stiffness on a small segment of the hand trajectory. The method is based on the analysis of the reassigned spectrogram of the arm's response to impulsive perturbations and can estimate arm stiffness on a trial-by-trial basis. Analytic and empirical methods are first derived and tested through modal analysis on synthetic data. The technique's accuracy and robustness are assessed by modeling the estimation of stiffness time profiles changing at different rates and affected by different noise levels. Our method obtains results comparable with two well-known regressive techniques. We also test how the technique can identify the viscoelastic component of non-linear and higher than second order systems with a non-parametrical approach. The technique proposed here is very impervious to noise and can be used easily for both postural and movement tasks. Estimations of stiffness profiles are possible with only one perturbation, making our method a useful tool for estimating limb stiffness during motor learning and adaptation tasks, and for understanding the modulation of stiffness in individuals with neurodegenerative diseases.

Piovesan, Davide; Pierobon, Alberto; DiZio, Paul; Lackner, James R.

2012-01-01

26

Fast broadband macromodeling technique of sampled time\\/frequency data using z-domain vector-fitting method  

Microsoft Academic Search

The vector-fitting algorithm has been used as the main macromodeling tool for approximating frequency domain responses of complex interconnects and electrical packages (Gustavsen, 1999). In this paper, a new methodology is proposed to fit transfer functions of frequency response data obtained from numerical electromagnetic simulation or measured frequency-domain or time-domain response data. This new method, z-domain vector-fitting (ZDVF), is a

Yidnek S. Mekonnen; J. E. Schutt-Aine

2008-01-01

27

A novel flexible model for the extraction of features from brain signals in the time-frequency domain.  

PubMed

Electrophysiological signals such as the EEG, MEG, or LFPs have been extensively studied over the last decades, and elaborate signal processing algorithms have been developed for their analysis. Many of these methods are based on time-frequency decomposition to account for the signals' spectral properties while maintaining their temporal dynamics. However, the data typically exhibit intra- and interindividual variability. Existing algorithms often do not take into account this variability, for instance by using fixed frequency bands. This shortcoming has inspired us to develop a new robust and flexible method for time-frequency analysis and signal feature extraction using the novel smooth natural Gaussian extension (snaGe) model. The model is nonlinear, and its parameters are interpretable. We propose an algorithm to derive initial parameters based on dynamic programming for nonlinear fitting and describe an iterative refinement scheme to robustly fit high-order models. We further present distance functions to be able to compare different instances of our model. The method's functionality and robustness are demonstrated using simulated as well as real data. The snaGe model is a general tool allowing for a wide range of applications in biomedical data analysis. PMID:23401674

Heideklang, R; Ivanova, G

2013-01-21

28

Unsaturated zone characterization in soil through transient wetting and drying using GPR joint time-frequency analysis and grayscale images  

NASA Astrophysics Data System (ADS)

This paper describes an experimental method to characterize the soil's unsaturated zone by constructing a scenario in which transient downward water infiltration took place from the topsoil to the bottom soil continuously. During the water infiltration, GPR waveforms and side-view grayscale images of the soil column were simultaneously and continuously captured. The GPR wavelets associated with the wetting front were analyzed using short time fourier transform (STFT) algorithm. The downward wetting front and the stretch of unsaturated transition zone decelerated and eased the wetting front's reflection in the time domain; as well as reduced the peak frequency and attenuated the frequency spectra in the frequency domain. The subsequent drying process further attenuated but accelerated the wetting front's reflection in both time and frequency domains. These observations were correlated with the image pixel profiles, from which GPR velocity profiles at different lapsed times were generated after computation via a complex refractive index model (CRIM). The CRIM method is entirely non-invasive and not only offers very detailed measurement of the water saturation profile of the transition zone in laboratory scale, but also is potentially useful for the further study of a variety of vadose zone properties.

Lai, W. L.; Kou, S. C.; Poon, C. S.

2012-07-01

29

A hybrid time\\/frequency domain approach for efficient coupled analysis of vessel\\/mooring\\/riser dynamics  

Microsoft Academic Search

The dynamic analysis of a deepwater floating structure is complex due to dynamic coupling between the platform and the moorings\\/risers. Furthermore, the system response at the incident wave frequency and at the resonant low frequency is coupled due to geometric and hydrodynamic nonlinearities. As such, it is generally held that a fully coupled time-domain analysis should be used for an

Y. M. Low; R. S. Langley

2008-01-01

30

GNSS Signal Interference Classified by Means of a Supervised Learning Method Applied in the Time-Frequency Domain  

Microsoft Academic Search

Global Navigation Satellite System (GNSS) signals received by an occulting Low Earth Orbiter (LEO) often reflect on the Earth's surface, thus interfering with the direct ray. For certain remote sensing applications, the identification and classification of the reflection events is required. We have taken advantage of the fact that interference patterns in the time-domain (oscillation of both received amplitude and

Estel Cardellach; Santiago Oliveras; Antonio Rius

2009-01-01

31

Prediction of extreme responses of floating structures using a hybrid time\\/frequency domain coupled analysis approach  

Microsoft Academic Search

The dynamic analysis of a deepwater floating system has many complexities, which include the dynamic coupling between the platform and the moorings\\/risers, coupling between the first-order wave frequency (WF) and second-order low-frequency (LF) motions, hydrodynamic\\/geometric nonlinearities and non-Gaussian response statistics. These complexities can be automatically captured in a fully coupled time domain analysis, but at the expense of an enormous

Y. M. Low

2008-01-01

32

Fast computation of critically sampled time frequency signal representations  

NASA Astrophysics Data System (ADS)

An algorithm is proposed to compute samples of any bilinear joint time-frequency representation of the Cohen's class. The computation is performed on a decimated sampling grid, mapping N equals 3BD signal samples into N equals K X L critical samples of the joint representation in the time-frequency domain. This is in contrast with the usual approaches that perform the computation on a much denser grid, mapping N signal samples into N X N samples in the time-frequency plane. The algorithm is based on the discrete Zak transform and represents an extension of the work by Auslander et al. on fast computation of the ambiguity function. For a number of popular representations, the algorithm is shown to have computational complexity about the same as an ordinary FFT.

Marinovich, Nenad M.

1994-10-01

33

Joint time-frequency and finite-difference time-domain analysis of precursor fieldsin dispersive media  

Microsoft Academic Search

Superluminal group velocities, defined as group velocities exceeding the speed of light in vacuum, c , have been theoretically predicted and experimentally observed in various types of dispersive media, such as passive and active Lorentzian media, one-dimensional photonic crystals, and undersized waveguides. Though superluminal group velocities have been found in these media, it has been suggested that the pulse ``front''

Reza Safian; Costas D. Sarris; Mohammad Mojahedi

2006-01-01

34

Time-Frequency-Power Adaptive Interference Mitigation for Galileo L1 Band Receivers  

Microsoft Academic Search

This paper proposes a method for interference mitigation (IM) in the Galileo system based on a joint time-frequency domain (TFD) technique. In particular, the proposed approach is based on the use of an adaptive finite impulse response (FIR) filter, which introduces a notch in correspondence of the instantaneous frequency (IF) of the jammer. The filter coefficients are adapted to both

Chiara Togni; Raffaella Pedone; Marco Villanti; Matteo Iubatti; Giovanni E. Corazza

2007-01-01

35

Precambrian basement control on joint domains in northwestern Ohio  

SciTech Connect

Joint attitudes in Upper Silurian and Lower Devonian carbonates in northwestern Ohio reveal a marked north-south-trending joint domain boundary in Lucas and Wood Counties. East of the domain boundary, first-formed systematic joints trend N45/sup 0/W; west of this boundary, first-formed systematics trend N40/sup 0/E. The line of change in joint trends follows the Lucas County monocline-Bowling Green fault complex and the projected position of the Grenville front from the Canadian shield. Basement well information and gravity and magnetic data indicate a major change in Precambrian rock types across the domain boundary that is coincident with the projected position of the Grenville front. Observed joint patterns are interpreted to result from extensional tectonics associated with the evolution of the Findlay arch and Michigan basin. Recurrent movements on the Bowling Green fault during the early and middle Paleozoic may have been caused by reactivation of Grenville-age faults, which ultimately localized the joint domain boundary along the Lucas County monocline-Bowling Green fault trend.

Dean, S.L.; Armstrong, W.B.; Kulander, B.R.

1986-08-01

36

Time-frequency analysis of human motion during rhythmic exercises.  

PubMed

Biomechanical signals due to human movements during exercise are represented in time-frequency domain using Wigner Distribution Function (WDF). Analysis based on WDF reveals instantaneous spectral and power changes during a rhythmic exercise. Investigations were carried out on 11 healthy subjects who performed 5 cycles of sun salutation, with a body-mounted Inertial Measurement Unit (IMU) as a motion sensor. Variance of Instantaneous Frequency (I.F) and Instantaneous Power (I.P) for performance analysis of the subject is estimated using one-way ANOVA model. Results reveal that joint Time-Frequency analysis of biomechanical signals during motion facilitates a better understanding of grace and consistency during rhythmic exercise. PMID:22254550

Omkar, S N; Vyas, Khushi; Vikranth, H N

2011-01-01

37

JPEG image steganalysis using joint discrete cosine transform domain features  

NASA Astrophysics Data System (ADS)

A JPEG image steganalysis scheme based on joint discrete cosine transform (DCT) domain features is proposed. Intrinsic characteristics of DCT coefficients, such as histogram, intrablock correlation, and interblock correlation, are exploited to construct three feature sets. Support vector machine is utilized to learn and discriminate the difference of features between cover and stego images. First, the three feature sets are investigated separately to reveal their individual capability of attacking steganographic methods. Second, the feature sets are combined to form a joint feature set with better performance. Experimental results demonstrate that all three feature sets individually succeed in attacking the four typical steganographic tools to some extent, with the intrablock feature set performing the best. Furthermore, the comparison experiments show that the jointed feature set not only outperforms the three individual feature sets but also proves to be better than a previous state-of-the-art steganalysis method.

Xia, Zhihua; Sun, Xingming; Liang, Wei; Qin, Jiaohua; Li, Feng

2010-04-01

38

METAS Time & Frequency Metrology Report.  

National Technical Information Service (NTIS)

METAS is the National Metrology Institute (NMI) for Switzerland. The Time & Frequency Laboratory (TFL) is responsible for the generation and dissemination of precise time and performs calibrations for customers. This paper reports on current or recent act...

A. Stefanov C. Schlunegger L. Bernier

2009-01-01

39

METAS Time & Frequency Metrology Report.  

National Technical Information Service (NTIS)

METAS is the Swiss Federal Office of Metrology and Accreditation. The METAS Time & Frequency Laboratory (T&F Lab) operates a cesium primary standard, maintains the Swiss national time scales, disseminates precise time and performs calibrations for custome...

C. Schlunegger G. Dudle L. Bernier

2005-01-01

40

Sparse time-frequency representations  

PubMed Central

Auditory neurons preserve exquisite temporal information about sound features, but we do not know how the brain uses this information to process the rapidly changing sounds of the natural world. Simple arguments for effective use of temporal information led us to consider the reassignment class of time-frequency representations as a model of auditory processing. Reassigned time-frequency representations can track isolated simple signals with accuracy unlimited by the time-frequency uncertainty principle, but lack of a general theory has hampered their application to complex sounds. We describe the reassigned representations for white noise and show that even spectrally dense signals produce sparse reassignments: the representation collapses onto a thin set of lines arranged in a froth-like pattern. Preserving phase information allows reconstruction of the original signal. We define a notion of “consensus,” based on stability of reassignment to time-scale changes, which produces sharp spectral estimates for a wide class of complex mixed signals. As the only currently known class of time-frequency representations that is always “in focus” this methodology has general utility in signal analysis. It may also help explain the remarkable acuity of auditory perception. Many details of complex sounds that are virtually undetectable in standard sonograms are readily perceptible and visible in reassignment.

Gardner, Timothy J.; Magnasco, Marcelo O.

2006-01-01

41

Nonblind and semiblind space-time-frequency multiuser detection for space-time block-coded MC-CDMA  

Microsoft Academic Search

In this paper, a novel space-time-frequency minimum mean squared error (STF-MMSE)-based parallel interference cancellation receiver is proposed for space-time block-coded multicarrier code division multiple access systems in time-varying fading channels. The signal processing of this new detector is jointly implemented in space, time, and frequency domains, which leads to a powerful capability of combating interference coming from different sources. An

Zexian Li; Matti Latva-aho

2005-01-01

42

Velocity noise reduction by using enhanced joint spectral and time domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

The unbiased complex algorithm for flow velocity measurements with enhanced joint spectral and time domain OCT (enhSTdOCT) is verified statistically and experimentally to find the optimal parameters for maximal velocity noise reduction.

Walther, Julia; Koch, Edmund

2013-06-01

43

Multiridge detection and time-frequency reconstruction  

Microsoft Academic Search

The ridges of the wavelet transform, the Gabor transform, or any time-frequency representation of a signal contain crucial information on the characteristics of the signal. Indeed, they mark the regions of the time-frequency plane where the signal concentrates most of its energy. We introduce a new algorithm to detect and identify these ridges. The procedure is based on an original

R. A. Carmona; Wen L. Hwang; B. Torresani

1999-01-01

44

Linear and Quadratic Time-Frequency Representations.  

National Technical Information Service (NTIS)

This report is reviewing both linear and quadratic time-frequency representations. The linear representations discussed are Short-Time Fourier Transform and S-transform. The quadratic representation discussed is Wigner distribution. We outline the motivat...

T. Thayaparan

2000-01-01

45

Tools for Time-Frequency Analysis.  

National Technical Information Service (NTIS)

Together with students and postdocs, the PI has worked on the mathematical aspects and applications of various tools in time frequency or time scale analysis. they have brought a deeper understanding to the geometry of redundant representations (frames), ...

I. Daubechies

1997-01-01

46

Wave propagation across non-linear rock joints based on time-domain recursive method  

NASA Astrophysics Data System (ADS)

Studying wave propagation across joints is crucial in geophysics, mining and underground construction. Limited analyses are available for oblique incidence across non-linear joints. In this paper, the time-domain recursive method (TDRM) proposed by Li et al. is extended to analyse wave propagation across a set of non-linear joints. The Barton-Bandis model (B-B model) and the Coulomb-slip model are adopted to describe the non-linear normal and shear properties of the joints, respectively. With the displacement discontinuity model and the time shifting function, the wave propagation equation is established for incident longitudinal-(P-) or transverse-(S-)wave across the joints with arbitrary impinging angles. Comparison between the results from the TDRM and the existing methods is carried out for two specific cases to verify the derived wave propagation equation. The effects of some parameters, such as the incident angle, the joint spacing, the amplitude of incidence and the joint maximum allowable normal closure, on wave propagation are discussed.

Li, J. C.

2013-05-01

47

On Iterative EM-Based Frequency Domain Joint Estimation of Synchronization Parameter and Channel Impulse Response  

Microsoft Academic Search

In this paper, an iterative EM-based frequency domain joint estimation algorithm of synchronization parameter and channel impulse response (CIR) in direct sequence code division multiple access (DS-CDMA) system is proposed. This algorithm is based on the expectation-maximization (EM) method. A complete Cramer-Rao lower bound (CRLB) analysis of the proposed algorithms is also given in this paper. Because this algorithm can

Cheng Li; Tianqi Wang; Hsiao-hwa Chen

2007-01-01

48

Postural tachycardia syndrome: time frequency mapping  

Microsoft Academic Search

Orthostatic tachycardia is common but its specificity remains uncertain. Our preliminary work suggested that using autonomic function testing in conjunction with time–frequency mapping (TFM), it might be possible to characterize a subset of the postural tachycardia syndrome (POTS), that is due to a restricted autonomic neuropathy. We describe 20 patients (17 women and 3 men, aged 14–43 years) with florid

Vera Novak; Peter Novak; Tonette L Opfer-Gehrking; Phillip A Low

1996-01-01

49

Simultaneous time-frequency control of bifurcation and chaos  

NASA Astrophysics Data System (ADS)

Control scheme facilitated either in the time- or frequency-domain alone is insufficient in controlling route-to-chaos, where the corresponding response deteriorates in the time and frequency domains simultaneously. A novel chaos control scheme is formulated by addressing the fundamental characteristics inherent of chaotic response. The proposed control scheme has its philosophical basis established in simultaneous time-frequency control, on-line system identification, and adaptive control. Physical features that embody the concept include multiresolution analysis, adaptive Finite Impulse Response (FIR) filter, and Filtered-x Least Mean Square (FXLMS) algorithm. A non-stationary Duffing oscillator is investigated to demonstrate the effectiveness of the control methodology. Results presented herein indicate that for the control of dynamic instability including chaos to be deemed viable, mitigation has to be adaptive and engaged in the time and frequency domains at the same time.

Liu, Meng-Kun; Suh, C. Steve

2012-06-01

50

Channel estimation using time-frequency techniques  

Microsoft Academic Search

We propose the use of time-varying signals and time-frequency techniques to estimate fast fading channels with unknown state information. Specifically, we apply the reassigned spectrogram to estimate multiple sinusoids resulting from transmitting and processing two linear frequency-modulated (FM) chirp pilots. The estimation procedure is complicated by the need to pair sinusoids resulting from the same multipath. This problem is overcome

Hao Shen; Antonia Papandreou-Suppappola

2005-01-01

51

Uncertainty, information, and time-frequency distributions  

Microsoft Academic Search

ABSTRACT The well-known uncertaintly principle is of- ten invoked in signal processing. It is also often considered to have the same implications in sig- nal analysis as does the uncertainty principle in quantum,mechanics. The uncertainty principle is often incorrectly interpreted to mean that one cannot locate the time-frequency coordi- nates of a signal with arbitrarily good precision, since, in quantum

W. J. Williams; M. L. Brown; A. O. Hero

1991-01-01

52

Time/Frequency Analysis of Terrestrial Impack Crater Records  

NASA Astrophysics Data System (ADS)

The terrestrial impact cratering record recently has been examined in the time domain by Chang & Moon (2005). It was found that the ˜ 26 Myr periodicity in the impact cratering rate exists over the last ˜ 250 Myrs. Such a periodicity can be found regardless of the lower limit of the diameter up to D ˜ 35 km. It immediately called pros and cons. The aim of this paper is two-fold: (1) to test if reported periodicities can be obtained with an independent method, (2) to see, as attempted earlier, if the phase is modulated. To achieve these goals we employ the time/frequency analysis and for the first time apply this method to the terrestrial impact cratering records. We have confirmed that without exceptions noticeable peaks appear around ˜ 25 Myr, corresponding to a frequency of ˜ 0.04 (Myr)^{-1}. We also find periodicities in the data base including small impact craters, which are longer. Though the time/frequency analysis allows us to observe directly phase variations, we cannot find any indications of such changes. Instead, modes display slow variations of power in time. The time/frequency analysis shows a nonstationary behavior of the modes. The power can grow from just above the noise level and then decrease back to its initial level in a time of order of 10 Myrs.

Chang, Heon-Young

2006-09-01

53

Computer-aided classification of rheumatoid arthritis in finger joints using frequency domain optical tomography  

NASA Astrophysics Data System (ADS)

Novel methods that can help in the diagnosis and monitoring of joint disease are essential for efficient use of novel arthritis therapies that are currently emerging. Building on previous studies that involved continuous wave imaging systems we present here first clinical data obtained with a new frequency-domain imaging system. Three-dimensional tomographic data sets of absorption and scattering coefficients were generated for 107 fingers. The data were analyzed using ANOVA, MANOVA, Discriminant Analysis DA, and a machine-learning algorithm that is based on self-organizing mapping (SOM) for clustering data in 2-dimensional parameter spaces. Overall we found that the SOM algorithm outperforms the more traditional analysis methods in terms of correctly classifying finger joints. Using SOM, healthy and affected joints can now be separated with a sensitivity of 0.97 and specificity of 0.91. Furthermore, preliminary results suggest that if a combination of multiple image properties is used, statistical significant differences can be found between RA-affected finger joints that show different clinical features (e.g. effusion, synovitis or erosion).

Klose, C. D.; Kim, H. K.; Netz, U.; Blaschke, S.; Zwaka, P. A.; Mueller, G. A.; Beuthan, J.; Hielscher, A. H.

2009-02-01

54

Joint Electrical and Time Domain Electromagnetism (TDEM) Data Inversion Applied to the Super Sauze Earthflow (France)  

NASA Astrophysics Data System (ADS)

In order to evaluate the risk of an earthflow to evolve abruptly into torrential surge, knowledge of its internal structure is necessary. This study deals with the internal structure of the Super Sauze earthflow developed in black marls in the southern French Alps. Difficulties in this study area are a rough topography, surface heterogeneities and a large thickness variability of the earthflow mass. These conditions hamper the application of geotechnical methods as a preferred investigation mean. Moreover, they pose problems to geophysical investigations and their interpretation.This paper shows the advantage offered by the joint inversion of Time Domain ElectroMagne-tism data (TDEM) and data obtained from Direct Current soundings (DC). The results of the joint inversions are checked using geotechnical data. The internal structure of the earthflow interpreted on the basis of joint inversion data is comparable to that obtained from geotechnical results. Moreover, contrary to separate electrical and TDEM inversions, a satisfactory joint inversion model can be derived without supplying additional a priori information.

Schmutz, Myriam; Albouy, Yves; Guérin, Roger; et al.

55

Joints  

NSDL National Science Digital Library

Hinge joints move only in one direction, ball-and-socket joints are free to rotate in all directions, and gliding joints are able to move forward, backward, and side to side, but do not rotate freely.

Olivia Worland (Purdue University;Biological Sciences)

2008-06-06

56

True velocity mapping using joint spectral and time domain optical coherence tomography  

NASA Astrophysics Data System (ADS)

We present both axial and transverse components estimation using joint Spectral and Time domain Optical Coherence Tomography (STdOCT) method. Whereas axial component of velocity vector can be determined from the time-dependent Doppler beating frequency, the transverse component can be assessed by the analysis of the broadening of flow velocity profiles (Doppler bandwidth). This enables us to quantitatively determine the absolute value of the velocity vector. The accurate analyses are performed using well-defined flow of Intralipid solution in the glass capillary. This enables performing in vivo imaging and allows to calculate velocity maps of the retinal vasculature.

Grulkowski, Ireneusz; Szkulmowski, Maciej; Bukowska, Danuta; Tamborski, Szymon; Gorczynska, Iwona; Kowalczyk, Andrzej; Wojtkowski, Maciej

2010-02-01

57

Constructing Time-Frequency Dictionaries for Source Separation via Time-Frequency Masking and Source Localisation  

Microsoft Academic Search

We describe a new localisation and source separation algorithm which is based upon the accurate construction of time-frequency\\u000a spatial signatures. We present a technique for constructing time-frequency spatial signatures with the required accuracy.\\u000a This algorithm for multi-channel source separation and localisation allows arbitrary placement of microphones yet achieves\\u000a good performance. We demonstrate the efficacy of the technique using source location

Ruairí De Fréin; Scott T. Rickard; Barak A. Pearlmutter

2009-01-01

58

Copula-based positive time-frequency distributions of the phonocardiogram.  

PubMed

This paper introduces a method for time-frequency analysis of the phonocardiogram. The proposed method is a modified version of the copula-based technique, which constructs positive time-frequency distributions, so as to be suitable for the analysis of periodically stationary random processes. The copula-based time-frequency distributions have some desirable properties: positivity, correct marginals and low computational cost. We use averaged spectrogram as a template in copula-based technique in order to construct a positive time-frequency distribution of the phonocardiogram. Results clearly show that the copula-based time-frequency distributions have much better resolution in time and frequency domain than the spectrogram does. Positivity and high resolution depend on the marginals of the distributions will offer excellent potential for estimating local parameters of the distributions, like a instantaneous frequency or instantaneous equivalent bandwidths using Renyi's divergence formulated by the authors. PMID:17271693

Yoshida, Hisashi; Ikegami, Tadashi; Kikkawa, Sho

2004-01-01

59

Multipixel system for gigahertz frequency-domain optical imaging of finger joints  

NASA Astrophysics Data System (ADS)

Frequency-domain optical imaging systems have shown great promise for characterizing blood oxygenation, hemodynamics, and other physiological parameters in human and animal tissues. However, most of the frequency domain systems presented so far operate with source modulation frequencies below 150 MHz. At these low frequencies, their ability to provide accurate data for small tissue geometries such as encountered in imaging of finger joints or rodents is limited. Here, we present a new system that can provide data up to 1 GHz using an intensity modulated charged coupled device camera. After data processing, the images show the two-dimensional distribution of amplitude and phase of the light modulation on the finger surface. The system performance was investigated and test measurements on optical tissue phantoms were taken to investigate whether higher frequencies yield better signal-to-noise ratios (SNRs). It could be shown that local changes in optical tissue properties, as they appear in the initial stages of rheumatoid arthritis in a finger joint, are detectable by simple image evaluation, with the range of modulation frequency around 500 MHz proving to yield the highest SNR.

Netz, Uwe J.; Beuthan, Jürgen; Hielscher, Andreas H.

2008-03-01

60

Time-frequency characterisation of paediatric heart sounds  

NASA Astrophysics Data System (ADS)

The operation of the heart can be monitored by the sounds it emits. Structural defects or malfunction of the heart valves will cause additional abnormal sounds such as murmurs and ejection clicks. This thesis aims to characterise the heart sounds of three groups of children who either have an Atrial Septal Defect (ASD), a Ventricular Septal Defect (VSD), or are normal. Two aspects of heart sounds have been specifically investigated; the time-frequency analysis of systolic murmurs and the identification of splitting patterns in the second heart sound. The analysis is based on 42 paediatric heart sound recordings. Murmurs are sounds generated by turbulent flow of blood in the heart. They can be found in patients with both pathological and non-pathological conditions. The acoustic quality of the murmurs generated in each heart condition are different. The first aspect of this work is to characterise the three types of murmurs in the time- frequency domain. Modern time-frequency methods including, the Wigner-Ville Distribution, Smoothed Pseudo Wigner-Ville Distribution, Choi-Williams Distribution and spectrogram have been applied to characterise the murmurs. It was found that the three classes of murmurs exhibited different signatures in their time-frequency representations. By performing Discriminant Analysis, it was shown that spectral features extracted from the time- frequency representations can be used to distinguish between the three classes. The second aspect of the research is to identify splitting patterns in the second heart sound, which consists of two acoustic components due to the closure of the aortic valve and pulmonary valve. The aortic valve usually closes before the pulmonary valve, introducing a time delay known as 'split'. The split normally varies in duration over the respiratory cycle. In certain pathologies such as the ASD, the split becomes fixed over the respiration cycle. A technique based on adaptive signal decomposition is developed to measure the split and hence to identify the splitting pattern as either 'variable' or 'fixed'. This work has successfully characterised the murmurs and splitting patterns in the three groups of patients. Features extracted can be used for diagnostic purposes.

Leung, Terence Sze-Tat

1998-08-01

61

A method for ventricular late potentials detection using time-frequency representation and wavelet denoising.  

PubMed

This study proposes a method for ventricular late potentials (VLPs) detection using time-frequency representation and wavelet denoising in high-resolution electrocardiography (HRECG). The analysis is performed both with the signal averaged electrocardiography (SAECG) and in real time. A comparison between the temporal and the time-frequency analysis is also reported. In the first analysis the standard parameters QRSd, LAS40, and RMS40 were used; in the second normalized energy in time-frequency domain was calculated. The algorithm was tested adding artificial VLPs to real ECGs. PMID:22957271

Gadaleta, Matteo; Giorgio, Agostino

2012-08-26

62

Radon transformation of time-frequency distributions for analysis of multicomponent signals  

Microsoft Academic Search

The Radon transform of a time-frequency distribution produces local areas of signal concentration that facilitate interpretation of multicomponent signals. The Radon-Wigner transform can be efficiently implemented with dechirping in the time domain, however, only half of the possible projections through the time-frequency plane can be realized because of aliasing. We show here that the frequency dual to dechirping exists, so

John C. Wood; Daniel T. Barry

1994-01-01

63

Accurate time-frequency-wavenumber analysis to study coda waves  

NASA Astrophysics Data System (ADS)

An accurate method is developed to characterize the seismic coda phases recorded by small-aperture arrays. The coda is modelled as a superposition of several interfering wavelets identified by their arrival time, frequency content, backazimuth and apparent velocity of propagation. The wavelets are caused by the diffraction and refraction of the direct wavefield by heterogeneities of the propagation medium. The deterministic modelling is different from the statistical one generally used to retrieve mean parameters of the medium. As the complexity of the medium increases, separation of interfering wavelets needs an accurate time-frequency-wavenumber decomposition method that consists of detection and characterization of the different coherent wavelets propagating through the array. Detection is realized by mean time-frequency decomposition, based on the ridges algorithm. The MUltiple SIgnal Classification (MUSIC) algorithm, allowing a higher separation of simultaneous wavelets in the wavenumber domain, is then used to characterize the propagation parameters of the detected components. An optimal use of the MUSIC algorithm assumes the knowledge of the number of sources that simultaneously propagate through the array. The new iterative technique presented here allows the automatic determination of this number of sources. This methodology is applied to synthetic signals simulated in a heterogeneous medium. Results obtained show that: (i) the diffracted wavefield may be more energetic than the primary direct one and (ii) the relative energy diffracted by each heterogeneity is strongly dependent on the location of the array within the medium. The well-controlled results obtained for the synthetic examples allow interpretations of the observations made during the Annot experiment in the southern French Alps in 1998, where four small-aperture arrays were deployed, with small distances between each array (~10 km). The time-azimuth-velocity evolutions determined for the earthquakes recorded during this experiment are used to characterize the heterogeneous structures of the medium.

Schisselé, Estelle; Guilbert, Jocelyn; Gaffet, Stéphane; Cansi, Yves

2004-08-01

64

Time-frequency analysis of the dispersion of Lamb modes.  

PubMed

Accurate knowledge of the velocity dispersion of Lamb modes is important for ultrasonic nondestructive evaluation methods used in detecting and locating flaws in thin plates and in determining their elastic stiffness coefficients. Lamb mode dispersion is also important in the acoustic emission technique for accurately triangulating the location of emissions in thin plates. In this research, the ability to characterize Lamb mode dispersion through a time-frequency analysis (the pseudo-Wigner-Ville distribution) was demonstrated. A major advantage of time-frequency methods is the ability to analyze acoustic signals containing multiple propagation modes, which overlap and superimpose in the time domain signal. By combining time-frequency analysis with a broadband acoustic excitation source, the dispersion of multiple Lamb modes over a wide frequency range can be determined from as little as a single measurement. In addition, the technique provides a direct measurement of the group velocity dispersion. The technique was first demonstrated in the analysis of a simulated waveform in an aluminum plate in which the Lamb mode dispersion was well known. Portions of the dispersion curves of the A0, A1, S0, and S2 Lamb modes were obtained from this one waveform. The technique was also applied for the analysis of experimental waveforms from a unidirectional graphite/epoxy composite plate. Measurements were made both along and perpendicular to the fiber direction. In this case, the signals contained only the lowest order symmetric and antisymmetric modes. A least squares fit of the results from several source to detector distances was used. Theoretical dispersion curves were calculated and are shown to be in good agreement with experimental results. PMID:10335617

Prosser, W H; Seale, M D; Smith, B T

1999-05-01

65

Time-Frequency Analysis of Long Range Ultrasonic Signals  

NASA Astrophysics Data System (ADS)

Long range ultrasonic testing (LRUT) is a relatively new development within the non-destructive testing sector. Traditionally, conventional ultrasonic testing (UT) is performed at high frequencies, in the MHz range, and is capable of detecting small flaws within a range of millimetres; whereas long range ultrasonic inspection is carried out at lower frequencies, typically between 20 and 100kHz, and is capable of highlighting structural detail and discontinuities tens of metres from a test position. Conventional ultrasonic testing relies on the transmission of bulk waves, the velocities of which are independent of frequency and can usually be predicted easily if the elastic properties of the material under test are known. The dynamics of guided waves, however, are dependent upon frequency making the analysis of received data from a specimen complex. This paper will serve as an introduction to time-frequency representation and may allow a clearer understanding of the non-stationary raw signals produced by this inspection process. Currently, LRUT data are assessed in the time or distance domain using the amplitude vs. time 'A-Scan', therefore structural features and potential flaws are highlighted on a time-of-flight basis. However, as the data obtained are dynamic in time and frequency (non-stationary), time-frequency distributions could provide a mode identification or de-noising process to deal with the problem of coherent noise.

Thornicroft, Keith; Mares, Cristinel; Mudge, Peter

2012-08-01

66

Joint Tomlinson-Harashima Precoding and Frequency-Domain Equalization for Broadband Single-Carrier Transmission  

NASA Astrophysics Data System (ADS)

The performance of single-carrier (SC) transmission in a frequency-selective fading channel degrades due to a severe inter-symbol interference (ISI). Using frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion can improve the bit error rate (BER) performance of SC transmission. However, the residual ISI after FDE limits the performance improvement. In this paper, we propose a joint use of Tomlinson-Harashima precoding (THP) and FDE to remove the residual ISI. An approximate conditional BER analysis is presented for the given channel condition. The achievable average BER performance is evaluated by Monte-Carlo numerical computation method using the derived conditional BER. The BER analysis is confirmed by computer simulation of the signal transmission.

Takeda, Kazuki; Tomeba, Hiromichi; Adachi, Fumiyuki

67

Adaptive harmonic time-frequency decomposition of audio using shift-invariant PLCA  

Microsoft Academic Search

Numerous methods have been developed for the time-frequency analysis and smart decomposition of audio signals. However, these techniques are not consistently suitable for real music signals where each note presents continuous variations of both pitch and spectral envelope. This paper presents a new model for analyzing the harmonic structures of an audio signal that can jointly handle those two types

Benoit Fuentes; Roland Badeau; Gael Richard

2011-01-01

68

CFAR detection and extraction of unknown signal in noise with time-frequency Gabor transform  

NASA Astrophysics Data System (ADS)

Detection and extraction of unknown signal in noise is an important issue in radar. When signal is an unknown transient, the representation in terms of basis functions which are localized in both time and frequency, such as Gabor representation, is very useful for signal detection. By taking time-frequency decomposition, the noise tends to spread its energy into entire time-frequency domain, while the signal often concentrates its energy within a small region with a limited time interval and frequency band. Therefore, the signal embedded in noise is much easier to be recognized in the time-frequency domain than that in either time or frequency domain. Constant false alarm rate (CFAR) processing is an optimal way to set up a threshold for detecting signals in noise environment. In this paper, we extend the CFAR processing to the time-frequency domain. By setting a CFAR threshold for the time-frequency Gabor coefficients, we can examine the Gabor coefficients and determine whether there is a signal. Then, the signal can be extracted by using the detected signal's Gabor coefficients. Therefore, the time location, the time duration, the frequency range, and other parameters of the unknown signal can be measured. The SNR of the extracted signal is improved about 10 - 12 dB over the observed noisy signal.

Chen, Victor C.; Qian, Shie

1996-03-01

69

Enabling time-frequency agility: wavelet packet modulation in practice  

NASA Astrophysics Data System (ADS)

We describe the implementation of a novel adaptive wireless communications waveform for interference avoidance (IA) in re-configurable logic devices. While other transform domain-based IA waveforms have been suggested, the wavelet packet modulation (WPM) system described here is unique in its multiplexing of complex quadrature amplitude modulation symbols onto orthogonal wavelet packets for unrivaled time-frequency agility. We examine the realization aspects of dynamically instantiating the transmit side inverse discrete wavelet packet transform (DWPT) and receive side DWPT filter bank structures, and the WPM symbol timing recovery, in Field Programmable Gate Array (FPGA) devices. This work applies Trenas' re-configurable wavelet packet transform (WPT) architecture to a wireless communications system, draws upon Jones' theoretical foundation for orthogonally multiplexed communications, and utilizes Lindsey's WPM supersymbol tuning and Kjeldsen's WPM symbol synchronization algorithms.

Kjeldsen, Erik H.; Lindsey, Alan R.

2003-11-01

70

Wavelets and Affine Distributions: A Time-Frequency Perspective.  

National Technical Information Service (NTIS)

OUTLINE: * The notion of time-frequency analysis * Linear and quadratic time-frequency analysis * Short-time Fourier transform and wavelet transform; spectrogram and scalogram * Constant-bandwidth analysis vs. constant- Q analysis * The affine class * Aff...

H. Hlawatsch

2005-01-01

71

Time-frequency analysis of the endocavitarian signal in paroxysmal atrial fibrillation.  

PubMed

We apply the time-frequency analysis to the endocavitarian signal of patients suffering from paroxysmal atrial fibrillation. The time-frequency spectrum reveals the components of the endocavitarian signal. These components are located in the regions of the time-frequency domain that differ for in-rhythm and in-atrial fibrillation signals. By using experimental data, we perform a statistical study of these regions, and we obtain their average value. The difference in the shape of these regions is caused by the re-entry circuits that characterize atrial fibrillation. We propose a propagation model for atrial fibrillation based on the re-entry circuits, which explains the shape of the time-frequency spectrum. PMID:22875240

Pagana, Guido; Galleani, Lorenzo; Gross, Stefano; Roch, Massimo Ruo; Pastore, Erica; Poggio, Mauro; Quaranta, Greta

2012-08-03

72

Postural tachycardia syndrome: time frequency mapping.  

PubMed

Orthostatic tachycardia is common but its specificity remains uncertain. Our preliminary work suggested that using autonomic function testing in conjunction with time-frequency mapping (TFM), it might be possible to characterize a subset of the postural tachycardia syndrome (POTS), that is due to a restricted autonomic neuropathy. We describe 20 patients (17 women and 3 men, aged 14-43 years) with florid POTS and 20 controls (14 women and 6 men, aged 20-41 years). Autonomic failure was quantified by its distribution (cardiovagal, adrenergic and sudomotor) and severity, a symptom profile was generated, and spectral indices, based on modified Wigner distribution during rest and head-up tilt (80 degrees) were evaluated. During tilt-up POTS patients differed from controls by an excessive heart rate (> 130 bpm) (P < 0.001), and higher diastolic pressure (P < 0.01). During rest, cardiovagal oscillations (at respiratory frequencies [RF]) and slow rhythms at nonrespiratory frequencies (NONRF) (from 0.01 to 0.07 Hz) in R-R intervals (RRI) (P < 0.01) were reduced. Both RF and NONRF rhythms in RRI were further blunted with tilt-up (P < 0.001). Slow adrenergic vasomotor rhythms in blood pressure (BP) (approximately 0.07 Hz) surged with tilt-up and returned to normal levels afterwards. The index of sympatho-vagal balance (NONRF-Systolic BP (SBP)/RF-RRI) was dramatically increased in POTS (P < 0.001). Distal postganglionic sudomotor failure was observed, and impairment of the BP responses to the Valsalva maneuver (phase II) suggested peripheral adrenergic dysfunction. Persistent orthostatic dizziness, tiredness, gastrointestinal symptoms and palpitations were common in POTS patients. It is possible to identify a subset of POTS patients who have a length-dependent autonomic neuropathy, affecting the peripheral adrenergic and cardiovagal fibers, with relative preservation of cardiac adrenergic fibers. PMID:8988490

Novak, V; Novak, P; Opfer-Gehrking, T L; Low, P A

1996-12-14

73

Enhanced joint spectral and time domain optical coherence tomography for quantitative flow velocity measurement  

NASA Astrophysics Data System (ADS)

Recently, a new method called joint spectral and time domain optical coherence tomography (STdOCT) for flow velocity measurement in spectral domain OCT (SD OCT) was presented. This method analyzes the detected timeresolved interference fringe spectra by using a two-dimensional fast Fourier transformation (2D FFT) to determine directly the Doppler frequency shift instead of calculating the phase difference at each depth position of adjacent A-scans. There, it was found that STdOCT is more robust for measurements with low signal to noise ratio than the classic phase-resolved Doppler OCT (DOCT) making it attractive first for imaging fast flow velocities at which a strong Doppler angle dependent signal damping occurs due to interference fringe washout and second for investigating large blood vessels with a big diameter and a highly damped signal of blood with increasing depth due to strong scattering and absorption in the near-infrared wavelength range. In the present study, we would like to introduce an enhanced algorithm for STdOCT permitting a more precise flow velocity measurement in comparison to the conventional STdOCT. The new method determines the amplitude of the broadened Doppler frequency shift by calculating the center of gravity via the complex analytical signal as a result of the second FFT instead of detecting the maximum intensity signal. Furthermore, the comparison with phase-resolved DOCT was done experimentally by using a flow phantom consisting of a 1% Intralipid emulsion and a 320 ?m glass capillary. As a result, the enhanced STdOCT and DOCT processed data are completely equivalent.

Walther, Julia; Koch, Edmund

2011-06-01

74

Bionic wavelet transform: a new time-frequency method based on an auditory model  

Microsoft Academic Search

A new adaptive wavelet transform, named bionic wavelet transform (BWT), is developed based on a model of the active auditory system. The most distinguishing characteristic of BWT is that its resolution in the time-frequency domain can be adaptively adjusted not only by the signal frequency but also by the signal instantaneous amplitude and its first-order differential. The automatically adjusted resolution,

Jun Yao; Yuan-Ting Zhang

2001-01-01

75

Heart Rate Variability Characterization Using a Time-Frequency Based Instantaneous Frequency Estimation Technique  

Microsoft Academic Search

In this paper, a new method for characterizing the newborn heart rate variability (HRV) is proposed. The central of the method is the newly proposed technique for instantaneous frequency (IF) estimation specifically designed for nonstationary multicomponent signals such as HRV. The new method attempts to characterize the newborn HRV using features extracted from the time-frequency (TF) domain of the signal.

MB Malarvili; L. Rankine; M. Mesbah; P. B. Colditz; B. Boashash

76

Blind separation of speech mixtures via time-frequency masking  

Microsoft Academic Search

Binary time-frequency masks are powerful tools for the separation of sources from a single mixture. Perfect demixing via binary time-frequency masks is possible provided the time-frequency representations of the sources do not overlap: a condition we call W-disjoint orthogonality. We introduce here the concept of approximate W-disjoint orthogonality and present experimental results demonstrating the level of approximate W-disjoint orthogonality of

O. Yilmaz; Scott Rickard

2004-01-01

77

[Application of time-frequency filter of wavelet to single-trail ERP extracting].  

PubMed

A new approach to extracting single-trail event-related potential(ERP) in combination with the correlation analysis has been proposed. This approach, called time-frequency filter, is based on the concept that multiresolution wavelet transforms. At first, an investigation of the properties in time and frequency domain was carried out on the ERP. On the basis of the findings, the time-frequency filter of wavelet was designed and used for single-trail ERP extracting. The results and related discussion are presented in this paper. PMID:12548895

Li, L; Ma, R; Cheng, H; Ni, H; Cheng, J

1998-06-01

78

Time-frequency-distribution analysis of frequency dispersive targets  

NASA Astrophysics Data System (ADS)

In the analysis of scattering targets, it is common to obtain time domain profiles by a Fourier transformation of the frequency response. In this process, wide-band frequency data are used to generate an approximation of the impulse response of the target via an inverse Fourier transform (IFT). The peaks in this impulse response then correspond to scattering centers of the target. In this paper, the authors show that an analysis of scattering from frequency dispersive structures can be accomplished by time-frequency distribution (TFD) techniques. Three TFDs are investigated, and applied to the scattering analysis of a circular waveguide cavity. This paper comprises a brief description of the applied TFDs, and a detailed comparison of the TFD results for scattering analysis. We shall show that for some targets, such as the cavity, TFD is an effective method for description of the properties of the target. For the waveguide cavity, propagating modes and cutoff frequencies can readily be determined from the TFD, whereas neither time nor frequency representations will provide such information.

Walton, E. K.; Moghaddar, A.

1993-01-01

79

Broadband Time-Frequency Analysis Using a Multicomputer.  

National Technical Information Service (NTIS)

Time-frequency analysis techniques are used to produce a plot of a signal's power spectrum as a function of time. The most well-known time- frequency representation is the spectrogram. Although relatively simple to compute, it suffers from having a signif...

J. Saunders

2004-01-01

80

Study on the Time-Frequency Two Dimensional CFAR Algorithm for Moving Targets on Ground in PRC-CW Radar  

Microsoft Academic Search

PRC-CW radar is mainly used to detect moving targets on ground. Ground clutter heaves fiercely, and its distribution is complex, which makes it difficult to detect targets correctly from time domain. The characteristics of moving targets and ground clutter differ in frequency domain. And the spectrum of targets may change with time, so, this paper designs the time-frequency two dimensional

Han Ning; Liu Limin; Han Zhuangzhi; Shang Chaoxuan

2010-01-01

81

Blind Signal Separation of Convolutive Mixtures: A Time-Domain Joint-Diagonalization Approach  

Microsoft Academic Search

We address the blind source separation (BSS) problem for the convolutive mixing case. Second-order statistical methods are em- ployed assuming the source signals are non-stationary and possibly also non-white. The proposed algorithm is based on a joint-diagonalization approach, where we search for a single polynomial matrix that jointly diagonalizes a set of measured spatiotemporal correlation matrices. In contrast to most

Marcel Joho

2004-01-01

82

Time-Frequency Analysis in Radar Backscatter Problems.  

National Technical Information Service (NTIS)

Time frequency techniques provide new and unique insights for analyzing electromagnetic scattering problems. These techniques transform functions of time or frequency into two dimensional functions of both time and frequency to reveal nonstationary charac...

C. J. McCormack W. J. Williams V. V. Liepa

1997-01-01

83

Time-frequency analysis of polarimetric SAR images  

Microsoft Academic Search

This article demonstrates the usefulness of time-frequency tools in SAR imagery through two applications. A new method is proposed to analyse moving targets. It uses a two dimensional matching-pursuit algorithm, over a time-frequency dictionary. Point targets speed and scattering characteristics (frequency comportment, angular and polarimetric behaviour) can be retrieved, thus permitting a better knowledge of the target. Urban areas analysis

Paul Leducq; Laurent Ferro-Famil; Eric Pottier

2005-01-01

84

Adaptive Interference Mitigation for Galileo L1 Band Receivers in Time and Frequency Domains  

Microsoft Academic Search

This paper proposes a method for interference mitigation (IM) in the Galileo system based on a joint time- frequency domain (TFD) technique. In particular, the proposed approach is based on the use of an open loop adaptive filter, which introduces a notch in correspondence of the instantaneous frequency (IF) of the jammer. The filter coefficients are adapted to both jammer

Chiara Togni; Raffaella Pedone; Marco Villanti; Matteo Iubatti; Giovanni E. Corazza

85

Speckle reduction by energy time-frequency filtering.  

PubMed

Structural noise is a very important limitation to the visibility of flaw echoes in ultrasonic testing and evaluation of highly scattering materials. In order to enhance the signal-to-noise ratio, different algorithms have been developed. One of these techniques is based on filtering the spectrum low band of the received echo to obtain a significant improvement of the defect visibility. Based on this idea, in this work a new time-frequency technique is presented. In this method, block-processing autoregressive techniques are used to estimate the instantaneous center frequency of the traveling wave. From this information, a time-frequency filter is designed tuned at half the estimated instantaneous center frequency. Experimental results and the comparison with the non-time-frequency filtering technique are also included, showing that the proposed method has an excellent performance on SNR enhancement. PMID:15047394

Izquierdo, M A G; Hernández, M G; Anaya, J J; Martinez, O

2004-04-01

86

Estimation of the power spectral density in nonstationary cardiovascular time series: assessing the role of the time-frequency representations (TFR).  

PubMed

Spectral analysis of cardiovascular series has been proposed as a noninvasive tool for investigating the autonomic control of the cardiovascular system. The analysis of such series during autonomic tests requires high resolution estimators that are capable to track the transients of the tests. A comparative evaluation has been made among classical (FFT based), autoregressive (both block and sequential mode) and time-frequency representation (TFR) based power spectral estimators. The evaluation has been performed on artificial data that have typical patterns of the nonstationary series. The results documented the superiority of the TFR approach when a sharp time resolution is required. Moreover, the test on a RR-like series has shown that the smoothing operation is effective for rejecting TFR cross-terms when a simple, two-three components series is concerned. Finally, the preliminary application of the selected methods to real RR interval time series obtained during some autonomic tests has shown that the TFR are capable to correctly represent the transient of the series in the joint time-frequency domain. PMID:8567005

Pola, S; Macerata, A; Emdin, M; Marchesi, C

1996-01-01

87

[The research on time-frequency detection method of respiratory component in ballistocardiogram signal].  

PubMed

Based on the fact that the respiratory component modulates the cardiac cycle component in the ballistocardiogram (BCG) signal, we propose a method that detects respiratory with time-frequency analysis for the sitting ballistocardiography system. Firstly, we demodulated the BCG signal by using the variable frequency complex demodulation (VFCDM) to obtain the output for different center frequency of interest. Then we calculated the instantaneous frequencies and the instantaneous amplitudes by the time-frequency representation. We reconstructed the time-domain waveform of respiratory at last. In order to verify the feasibility and accuracy of this method, we applied wavelet transform and nasal thermistor signal to compare qualitatively and quantitatively. The simulation results showed that the proposed method could detect the respiratory rate from BCG signal more accurately, which provided meaningful attempt for monitoring the multiple physiological parameters synchronously and unconsciously. PMID:22826926

Jiang, Fangfang; Wang, Xu; Yang, Dan

2012-06-01

88

Instantaneous frequency and time-frequency signature estimation using compressive sensing  

NASA Astrophysics Data System (ADS)

This paper considers compressive sensing for time-frequency signal representation (TFSR) of nonstationary radar signals which can be considered as instantaneously narrowband. Under-sampling and random sampling of the signal stem from avoiding aliasing and relaxing Nyquist sampling constraints. Unlike previous work on compressive sensing (CS) and TFSR based on the ambiguity function, reduced observations in the underlying problem are time-domain data. In the reconstruction process, Orthogonal Matching Pursuit (OMP) is used. Since the frequency index in the first iteration of OMP is the same as the one obtained by finding the frequency position of the highest Spectrogram peak, it becomes necessary to consider several OMP iterations to improve over Spectrograms performance. We examine various methods for estimating IF from higher number of OMP iterations, including the S-method. The paper also applies CS for signal time-frequency signature estimations corresponding to human gait radar returns.

Jokanovi?, Branka; Amin, Moeness; Stankovi?, Srdjan

2013-05-01

89

Character Recognition Method by Time-Frequency Analyses Using Writing Pressure  

NASA Astrophysics Data System (ADS)

With the development of information and communication technology, personal verification becomes more and more important. In the future ubiquitous society, the development of terminals handling personal information requires the personal verification technology. The signature is one of the personal verification methods; however, the number of characters is limited in the case of the signature and therefore false signature is used easily. Thus, personal identification is difficult from handwriting. This paper proposes a “haptic pen” that extracts the writing pressure, and shows a character recognition method by time-frequency analyses. Although the figures of characters written by different amanuenses are similar, the differences appear in the time-frequency domain. As a result, it is possible to use the proposed character recognition for personal identification more exactly. The experimental results showed the viability of the proposed method.

Watanabe, Tatsuhito; Katsura, Seiichiro

90

The Separate, Relative, and Joint Effects of Employee Job Performance Domains on Supervisors' Willingness to Mentor  

ERIC Educational Resources Information Center

|The purpose of our study was to further elucidate how employees should behave at work to increase their chances of being mentored by their immediate supervisor. To that end, we experimentally tested how three domains of employee performance [task performance (TP), organizational citizenship behavior (OCB) targeting the supervisor, and…

Lapierre, Laurent M.; Bonaccio, Silvia; Allen, Tammy D.

2009-01-01

91

Doppler time-frequency estimators: cost\\/benefit analysis  

Microsoft Academic Search

We apply a selection criterion for Doppler spectral estimators that takes into account the accuracy of the estimation, benefit, and also the “cost” in computation power required. This cost\\/benefit criterion is used to compare four time-frequency distributions including the conventional short-term Fourier transform

Jose C. Cardoso; Peter J. Fish; M. Graga Ruano

1996-01-01

92

Solar Millimeter Wave Bursts: Time-Frequency Analysis.  

National Technical Information Service (NTIS)

Analysis of low-frequency (LF) fluctuations of solar flare emission at 22 and 37 GHz is performed. Three microwave bursts observed at Metashovi Radio Observatory with the time resolution of 100 and 50 ms are investigated. To find time-frequency diagram fo...

V.V. Zaitsev A.G. Kislyakov S. Urpo A.V. Stepanov E.I. Shkelev

2003-01-01

93

Time-Frequency Analysis of EEGs Recorded during Meditation  

Microsoft Academic Search

Time-frequency analysis is one of the most important and commonly used analytical tools for evaluating physiological signals. In the past, many researchers investigated the effect of meditation on stress relief and disease improvement. In this research, we select 10 normal adults as the subjects, and divided them into two groups: more than 10 years of meditation experience and no experience.

Shih-Feng Wang; Yu-Hao Lee; Yung-Jong Shiah; Ming-Shing Young

2011-01-01

94

Time-frequency energy distributions meet compressed sensing  

Microsoft Academic Search

In the case of multicomponent signals with amplitude and frequency modulations, the idealized representation which consists of weighted trajectories on the time-frequency (TF) plane, is intrinsically sparse. Recent advances in optimal recovery from sparsity constraints thus suggest to revisit the issue of TF localization by exploiting sparsity, as adapted to the specific context of (quadratic) TF distributions. Based on classical

Patrick Flandrin; Pierre Borgnat

2010-01-01

95

Time-Frequency Localization via the Weyl Correspondence.  

National Technical Information Service (NTIS)

A technique of producing signals whose energy is concentrated in a given region of the time-frequency plane is examined. The degree to which a particular signal is concentrated is measured by integrating the Wigner distribution over the given region. This...

J. Ramanathan P. Topiwala

1992-01-01

96

Time-frequency Wiener filtering for structural noise reduction.  

PubMed

In order to enhance the defect in relation to background noise of large grained materials different algorithms have been developed. Wiener filtering techniques have proved to be efficient for the SNR enhancement of ultrasonic signals coming from highly scattering materials. These processing algorithms are based on designing a filter that has large gain at frequencies where the SNR is high and low gain at frequencies where SNR is small. However, this technique does not consider two important ultrasonic effects: the finite-time duration of the flaw UT signal coming from a defect and the distortion of the frequency components of the traveling wave-front due to the dispersion. In this work, a time-frequency Wiener filter is proposed that takes into account these two characteristics. Experimental results are presented, showing that the proposed time-frequency algorithm has an excellent performance on SNR enhancement. PMID:12159944

Izquierdo, M A G; Hernández, M G; Graullera, O; Ullate, L G

2002-05-01

97

High-spectral-resolution time-frequency distribution kernels  

NASA Astrophysics Data System (ADS)

A new class of time-frequency kernels is introduced. Members in this class satisfy the desired time-frequency distribution properties and simultaneously provide local autocorrelation functions (LAF) which are amenable to high resolution techniques over periods of stationarities. These high spectral resolution kernels map the sinusoids in time into damped/undamped sinusoidal bilinear data products over the LAF lag variable. The damped sinusoids represent cross-terms. Using SVD-based backward linear prediction techniques, the signal zeros, the cross-term zeros, and the extraneous zeros, respectively, lie on, outside, and inside the unit circle, providing a mechanism to distinguish between different types of components. It is shown that the binomial kernel introduced is a member of this class.

Amin, Moeness G.; Williams, William J.

1992-11-01

98

Time-frequency dynamics in neurally mediated syncope  

Microsoft Academic Search

In this study, the responses during syncope were determined by noninvasive beat-to-beat analysis during passive orthostasis. Twenty patients with recurrent unexplained syncope (13 men and seven women) and ten healthy age-matched control subjects were studied during 80° head-up tilt for 25 min. Time-frequency mapping of R-R intervals, systolic and diastolic pressures and respiration was used to determine the responses to

Vera Lepicovska; Peter Novak; Réginald Nadeau

1992-01-01

99

Hard target penetration acceleration signals Time-frequency Analysis  

Microsoft Academic Search

The hard target penetration process is very complex and the various missile vibration signals are very rich. So Hard target penetration acceleration signals are non-stationary signals. We use the Hilbert-Huang transform (HHT) for Time­ frequency Analysis non-stationary signals in noisy environments. Empirical Mode Decomposition (EMD) is hard core of HHT so these maybes bring Mode Mixing. We put forward a

Huiyan Hao; Hui Zhao

2011-01-01

100

Airborne collision avoidance and other applications of time\\/frequency  

Microsoft Academic Search

Time\\/frequency technology provides a reliable aircraft collision avoidance system (CAS) that can operate in either synchronous or asynchronous modes. Precision time-ordered techniques of CAS provide both range and range-rate measurements in a one-way sense to all aircraft as well as ground stations within range of transmitted microwave signals. The cooperative system utilizes exact frequency references coupled with precise synchronization: control

R. E. Perkinson; F. D. Watson

1972-01-01

101

Time-frequency manifold correlation matching for periodic fault identification in rotating machines  

NASA Astrophysics Data System (ADS)

For rotating machines, the localized faults of key components generally represent as periodic transient impulses in vibration signals. The existence of background noise will corrupt transient impulses in practice, and will thus increase the difficulty to identify specific faults. This paper combines the concepts of time-frequency manifold (TFM) and image template matching, and proposes a novel TFM correlation matching method to enhance identification of the periodic faults. This method is to conduct correlation matching of a vibration signal in the time-frequency domain by using the TFM with a short duration as a template. By this method, the time-frequency distribution (TFD) of a vibration signal is firstly achieved by the Smoothed Pseudo-Wigner-Ville distribution (SPWVD) method. Then the TFM template is learned to do correlation matching with the TFD of the analyzed signal. Finally, the ridge is extracted from the correlation matching image and the ridge coefficients are analyzed for periodic fault identification. The proposed method takes advantages of the TFM in noise suppression and template matching in object enhancement, and can enhance the fault impulses of interest in a unified scale. The novel method is verified to be superior to traditional enveloping method with providing smoother and clearer fault impulse component via applications to gearbox fault detection and bearing defect identification.

He, Qingbo; Wang, Xiangxiang

2013-05-01

102

Degraded time-frequency acuity to time-reversed notes.  

PubMed

Time-reversal symmetry breaking is a key feature of many classes of natural sounds, originating in the physics of sound production. While attention has been paid to the response of the auditory system to "natural stimuli," very few psychophysical tests have been performed. We conduct psychophysical measurements of time-frequency acuity for stylized representations of "natural"-like notes (sharp attack, long decay) and the time-reversed versions of these notes (long attack, sharp decay). Our results demonstrate significantly greater precision, arising from enhanced temporal acuity, for such sounds over their time-reversed versions, without a corresponding decrease in frequency acuity. These data inveigh against models of auditory processing that include tradeoffs between temporal and frequency acuity, at least in the range of notes tested and suggest the existence of statistical priors for notes with a sharp-attack and a long-decay. We are additionally able to calculate a minimal theoretical bound on the sophistication of the nonlinearities in auditory processing. We find that among the best studied classes of nonlinear time-frequency representations, only matching pursuit, spectral derivatives, and reassigned spectrograms are able to satisfy this criterion. PMID:23799012

Oppenheim, Jacob N; Isakov, Pavel; Magnasco, Marcelo O

2013-06-17

103

Time-frequency analysis of synthetic aperture radar signals  

SciTech Connect

Synthetic aperture radar (SAR) has become an important tool for remote sensing of the environment. SAR is a set of digital signal processing algorithms that are used to focus the signal returned to the radar because radar systems in themselves cannot produce the high resolution images required in remote sensing applications. To reconstruct an image, several parameters must be estimated and the quality of output image depends on the degree of accuracy of these parameters. In this thesis, we derive the fundamental SAR algorithms and concentrate on the estimation of one of its critical parameters. We show that the common technique for estimating this particular parameter can sometimes lead to erroneous results and reduced quality images. We also employ time-frequency analysis techniques to examine variations in the radar signals caused by platform motion and show how these results can be used to improve output image quality.

Johnston, B.

1996-08-01

104

High-resolution signal synthesis for time-frequency distributions  

SciTech Connect

Bilinear time-frequency distributions (TFDs) offer improved resolution over linear nine-frequency representations (TFRs), but many TFDs are costly to evaluate and are not associated with signal synthesis algorithms. Recently, the spectrogram (SP) decomposition and weighted reversal correlator decomposition have been used to define low-cost, high-resolution TFDs. In this paper, we show that the vector-valued square-root'' of a TFD (VVTFR) provides a representational underpinning for the TFD. By synthesizing signals from modified VVTFRs, we define high-resolution signal synthesis algorithms associated with TFDs. The signal analysis and synthesis packages can be implemented as weighted sums of SP/short-time Fourier Transform signal analysis and synthesis packages, which are widely available, allowing the interested non-specialist easy access to high-resolution methods.

Cunningham, G.S. (Los Alamos National Lab., NM (United States)); Williams, W.J. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Electrical Engineering and Computer Science)

1993-01-01

105

High-resolution signal synthesis for time-frequency distributions  

SciTech Connect

Bilinear time-frequency distributions (TFDs) offer improved resolution over linear nine-frequency representations (TFRs), but many TFDs are costly to evaluate and are not associated with signal synthesis algorithms. Recently, the spectrogram (SP) decomposition and weighted reversal correlator decomposition have been used to define low-cost, high-resolution TFDs. In this paper, we show that the vector-valued ``square-root`` of a TFD (VVTFR) provides a representational underpinning for the TFD. By synthesizing signals from modified VVTFRs, we define high-resolution signal synthesis algorithms associated with TFDs. The signal analysis and synthesis packages can be implemented as weighted sums of SP/short-time Fourier Transform signal analysis and synthesis packages, which are widely available, allowing the interested non-specialist easy access to high-resolution methods.

Cunningham, G.S. [Los Alamos National Lab., NM (United States); Williams, W.J. [Michigan Univ., Ann Arbor, MI (United States). Dept. of Electrical Engineering and Computer Science

1993-03-01

106

OFDM, Laurent operators, and time-frequency localization  

NASA Astrophysics Data System (ADS)

Orthogonal frequency division multiplexing (OFDM) has gained considerable interest as an efficient technology for high- date-data transmission over wireless channels. The design of pulse shapes that are well-localized in the time-frequency plane is of great importance in order to combat intersymbol interference and interchannel interference caused by the mobile radio channel. Recently proposed methods to construct such well-localized functions are utilizing the link between OFDM and Gabor systems. We derive a theoretical framework that shows why and under which conditions these methods will yield well-localized pulse shapes. In our analysis we exploit the connection between Gabor systems, Laurent operators and the classical work of Gelfand, Raikov, and Shilov on commutative Banach algebras. In the language of Gabor analysis we derive a general condition under which the dual window and the canonical tight window inherit the decay properties of the analysis window.

Strohmer, Thomas

2000-12-01

107

Parametric Time-frequency Modeling of Nonstationary Signals by Adaptive Decomposition Based on Time-shearing Gabor Atoms  

Microsoft Academic Search

A kind of localized four parameters Gabor atom (dialating, time-shearing, modulating and translating of Gaussian function)\\u000a was derived. Based on it, a parametric adaptive time-frequency distribution (PAD) is proposed by using adaptive signal decomposition\\u000a method in frequency domain, which is a non-negative energy distribution and free of cross-term interference for multi-component\\u000a signals and is suitable to model the dispersion components

Shiwei Ma; Zhongjie Liu; Weibin Liang

108

Content based audio classification and retrieval using joint time-frequency analysis  

Microsoft Academic Search

We present an audio classification and retrieval technique that exploits the non-stationary behavior of music signals and extracts features that characterize their spectral change over time. Audio classification provides a solution to incorrect and inefficient manual labelling of audio files on computers by allowing users to extract music files based on content similarity rather than labels. In our technique, classification

S. Esmaili; S. Krishnan; K. Raahemifar

2004-01-01

109

Joint time-frequency transform processing for linear and sinusoidal FM coherent ladars  

Microsoft Academic Search

We examine the signal processing of both linear and sinusoidal frequency modulation (FM) coherent ladar returns from resolved and unresolved targets, which are spread in Doppler. The Doppler spread may be due to target spin, tumbling, or vibration as well as to the applied linear or sinusoidal-FM on the transmitted E-field. Monte Carlo realizations of the target surface random phasor

Douglas G. Youmans

2003-01-01

110

Bump time-frequency toolbox: a toolbox for time-frequency oscillatory bursts extraction in electrophysiological signals  

PubMed Central

Background oscillatory activity, which can be separated in background and oscillatory burst pattern activities, is supposed to be representative of local synchronies of neural assemblies. Oscillatory burst events should consequently play a specific functional role, distinct from background EEG activity – especially for cognitive tasks (e.g. working memory tasks), binding mechanisms and perceptual dynamics (e.g. visual binding), or in clinical contexts (e.g. effects of brain disorders). However extracting oscillatory events in single trials, with a reliable and consistent method, is not a simple task. Results in this work we propose a user-friendly stand-alone toolbox, which models in a reasonable time a bump time-frequency model from the wavelet representations of a set of signals. The software is provided with a Matlab toolbox which can compute wavelet representations before calling automatically the stand-alone application. Conclusion The tool is publicly available as a freeware at the address:

Vialatte, Francois B; Sole-Casals, Jordi; Dauwels, Justin; Maurice, Monique; Cichocki, Andrzej

2009-01-01

111

Bionic wavelet transform: a new time-frequency method based on an auditory model.  

PubMed

In this paper, a new adaptive wavelet transform, named bionic wavelet transform (BWT), is developed based on a model of the active auditory system. The most distinguishing characteristic of BWT is that its resolution in the time-frequency domain can be adaptively adjusted not only by the signal frequency but also by the signal instantaneous amplitude and its first-order differential. The automatically adjusted resolution, even in a fixed frequency along the time-axis, is achieved by introducing the active control of the auditory system into the wavelet transform (WT). Other properties of BWT include that: 1) BWT is a nonlinear transform that has high sensitivity and frequency selectivity; 2) BWT represents the signal with a concentrated energy distribution; and 3) the inverse BWT can reconstruct the original signal from its time-frequency representation. In order to compare these three properties between BWT and WT, experiments were conducted on both constructed signals and real speech signals. The results show that BWT performs better than WT in these three aspects, and that BWT is appropriate for speech signal processing, especially for cochlear implants. PMID:11499523

Yao, J; Zhang, Y T

2001-08-01

112

Time-frequency signal analysis for gearbox fault diagnosis using a generalized synchrosqueezing transform  

NASA Astrophysics Data System (ADS)

The vibration data, especially those collected during the system run-up and run-down periods, contain rich information for gearbox condition monitoring. Time-frequency (TF) signal analysis is an effective tool to detect gearbox faults under varying shaft speed. However, the feature of the amplitude modulated-frequency modulated (AM-FM) gearbox fault signal usually cannot be directly extracted from the blurred time-frequency representation (TFR) caused by the time-varying frequency and noisy multicomponent measurement. As such, we propose to use a generalized synchrosqueezing transform (GST)-based TF method to detect and diagnose gearbox faults. With this method, the original vibration signal is first mapped into another analytical signal to facilitate synchrosqueezing of the TF picture. A time-scale domain restoration process is then applied to recover the instantaneous frequency profile with concentrated TFR. The gearbox fault, if any, can then be detected by observing the presence of the meshing frequency and sideband components in the TFR. The faulty gear can be identified via frequency relation analysis of AM-FM components. The proposed method is evaluated using both simulated and experimental gearbox vibration signals. The results show that the proposed approach is effective for gearbox condition monitoring.

Li, Chuan; Liang, Ming

2012-01-01

113

Seismic attenuation qualitative characterizing method based on adaptive optimal-kernel time–frequency representation  

NASA Astrophysics Data System (ADS)

The main issue of seismic attenuation characterizing method based on time–frequency analyzing method is the time–frequency resolution. The adaptive optimal-kernel time–frequency representation, which has high time–frequency resolution comparing with commonly used time–frequency analyzing method, is investigated. The seismic attenuation qualitative characterizing method based on adaptive optimal-kernel time–frequency representation is proposed. The synthetic data example and 3D field-data example reveal that the proposed method can qualitatively characterize seismic attenuation, and the attenuated anomaly of this field-data example coincides with gas reservoir well.

Wang, Xiaokai; Gao, Jinghuai; Chen, Wenchao; Zhao, Wei; Jiang, Xiudi; Zhu, Zhenyu

2013-02-01

114

Wind turbine gearbox health monitoring using time-frequency features from multiple sensors  

NASA Astrophysics Data System (ADS)

As wind energy plays an increasingly important role in the US and world electricity supply, maintenance of wind turbines emerges as a critical issue. Because of the remote nature of wind turbines, autonomous and robust health monitoring techniques are necessary. Detecting faults in complex systems such as wind turbine gearboxes remains challenging, even with the recently significant advancement of sensing and signal processing technologies. In this paper, we collect time domain signals from a gearbox test bed on which either a healthy or a faulty gear is installed. Then a harmonic wavelet based method is used to extract time-frequency features. We also develop a speed profile masking technique to account for tachometer readings and gear meshing relationship. Features from multiple sources are then fused together through a statistical weighting approach based on principal component analysis. Using the fused timefrequency features, we demonstrate that different gear faults can be effectively identified through a simple decision making algorithm.

Lu, Y.; Tang, J.

2011-03-01

115

Time-frequency effects in wireless communication systems  

NASA Astrophysics Data System (ADS)

Time-frequency effects in wireless communication systems caused by narrowband resonances and coupled with device nonlinearities are revealed as new sources of co-site interference, exploited for the metrology of bandpass circuits, and employed to linearize amplitude-modulated transmissions. The transient properties of bandpass filters are found to last much longer than traditional time/bandwidth rules-of-thumb. The cause of this long-tail behavior is attributed to the coupled-resonator structure of the filter circuit. A solution method which uses lowpass prototyping is developed to reduce, by a factor of two, the complexity of the differential equation set describing a narrowband filter's transient response. Pulse overlap caused by the frequency dependence of long tails produced by filters is shown to cause intersymbol interference and intermodulation distortion in RF front-ends during frequency-hopped communications. The same properties which cause the ISI and IMD are used to develop three new transient methods for measuring resonant circuit parameters and a one-port method for extracting the operating band of a filter. A new signal-processing technique which combines time- and frequency-selectivity, Linear Amplification by Time-Multiplexed Spectrum, is developed to reduce IMD associated with amplitude modulation. Distortion reduction is demonstrated experimentally for multisines up to 20 tones.

Mazzaro, Gregory James

116

Analysis and synthesis of room reverberation based on a statistical time-frequency model  

Microsoft Academic Search

This paper reviews a statistical time-frequency model of late reverberation decays, and describes an associated analysis procedure for deriving the time-frequency envelope of the reverberation from a measured impulse response, based on the notion of \\

Jean-Marc Jot; Laurent Cerveau; Olivier Warusfel

1997-01-01

117

Time-frequency analysis of heart murmurs. Part II: Optimisation of time-frequency representations and performance evaluation.  

PubMed

The basic parameters of the spectrogram, the Choi-Williams, and the Bessel distributions are adjusted to provide the best time-frequency representations (TFRs) of the simulated murmur signals of mitral stenosis, mitral regurgitation, aortic stenosis, aortic regurgitation, and of two musical murmurs. The initial adjustment of the parameters of each TFR technique is performed by computing and minimising the relative averaged absolute error between the frequency contours at -3 dB and -10 dB of each TFR of the simulated murmurs and those of the theoretical distribution of the same signals. The results show that the spectrogram generally provides very good to excellent performance in representing the TFRs of stenotic and regurgitant murmurs. Improvements provided by the Choi-Williams and the Bessel distributions are minor but not systematic for the two signal-to-noise ratios tested (0 and 30 dB) and for the two frequency contours estimated. The Bessel and the Choi-Williams distributions provide the best performance for the musical murmurs. The study shows that although a single technique cannot be optimal for all six murmurs, the spectrogram using a Hamming window of 30 ms is an acceptable compromise to detect the six simulated heart murmurs. PMID:9374051

Debiais, F; Durand, L G; Guo, Z; Guardo, R

1997-09-01

118

Choosing the best hardware form-factor for the airborne domain of the Joint Tactical Terminal (JTT) and Joint Tactical Radio System (JTRS)  

Microsoft Academic Search

Shrinking budgets, shortened design cycles, and the ready availability of commercial off-the-shelf (COTS) products and technology encourage future intelligence and tactical terminals, such as the JTT and the JTRS, to embrace widely- accepted, commercial standards and practices. Deployment of COTS products must however be balanced by any requirements for a robust environment, especially in the airborne domain which shows a

Ernie Franke

2001-01-01

119

Characterization and Robust Classification of EEG Signal from Image RSVP Events with Independent Time-Frequency Features  

PubMed Central

This paper considers the problem of automatic characterization and detection of target images in a rapid serial visual presentation (RSVP) task based on EEG data. A novel method that aims to identify single-trial event-related potentials (ERPs) in time-frequency is proposed, and a robust classifier with feature clustering is developed to better utilize the correlated ERP features. The method is applied to EEG recordings of a RSVP experiment with multiple sessions and subjects. The results show that the target image events are mainly characterized by 3 distinct patterns in the time-frequency domain, i.e., a theta band (4.3 Hz) power boosting 300–700 ms after the target image onset, an alpha band (12 Hz) power boosting 500–1000 ms after the stimulus onset, and a delta band (2 Hz) power boosting after 500 ms. The most discriminant time-frequency features are power boosting and are relatively consistent among multiple sessions and subjects. Since the original discriminant time-frequency features are highly correlated, we constructed the uncorrelated features using hierarchical clustering for better classification of target and non-target images. With feature clustering, performance (area under ROC) improved from 0.85 to 0.89 on within-session tests, and from 0.76 to 0.84 on cross-subject tests. The constructed uncorrelated features were more robust than the original discriminant features and corresponded to a number of local regions on the time-frequency plane. Availability: The data and code are available at: http://compgenomics.cbi.utsa.edu/rsvp/index.html

Meng, Jia; Merino, Lenis Mauricio; Shamlo, Nima Bigdely; Makeig, Scott; Robbins, Kay; Huang, Yufei

2012-01-01

120

Hybrid time-frequency domain analysis for inverter-fed induction motor fault detection  

Microsoft Academic Search

The detection of faults in an induction motor is important as a part of preventive maintenance. Stator current is one of the most popular signals used for utility-supplied induction motor fault detection as a current sensor can be installed nonintrusively. In variable speeds operation, the use of an inverter to drive the induction motor introduces noise into the stator current

T. W. Chua; W. W. Tan; Z.-X. Wang; C. S. Chang

2010-01-01

121

Compressive sensing for sparse time-frequency representation of nonstationary signals in the presence of impulsive noise  

NASA Astrophysics Data System (ADS)

A modified robust two-dimensional compressive sensing algorithm for reconstruction of sparse time-frequency representation (TFR) is proposed. The ambiguity function domain is assumed to be the domain of observations. The two-dimensional Fourier bases are used to linearly relate the observations to the sparse TFR, in lieu of the Wigner distribution. We assume that a set of available samples in the ambiguity domain is heavily corrupted by an impulsive type of noise. Consequently, the problem of sparse TFR reconstruction cannot be tackled using standard compressive sensing optimization algorithms. We introduce a two-dimensional L-statistics based modification into the transform domain representation. It provides suitable initial conditions that will produce efficient convergence of the reconstruction algorithm. This approach applies sorting and weighting operations to discard an expected amount of samples corrupted by noise. The remaining samples serve as observations used in sparse reconstruction of the time-frequency signal representation. The efficiency of the proposed approach is demonstrated on numerical examples that comprise both cases of monocomponent and multicomponent signals.

Orovi?, Irena; Stankovi?, Srdjan; Amin, Moeness

2013-05-01

122

Assessment of the flow velocity of blood cells in a microfluidic device using joint spectral and time domain optical coherence tomography.  

PubMed

Although Doppler optical coherence tomography techniques have enabled the imaging of blood flow in mid-sized vessels in biological tissues, the generation of velocity maps of capillary networks remains a challenge. To better understand the origin and information content of the Doppler signal from small vessels and limitations of such measurements, we used joint spectral and time domain optical coherence tomography to monitor the flow in a model, semitransparent microchannel device. The results obtained for Intralipid, whole blood, as well as separated red blood cells indicate that the technique is suitable to record velocity profiles in vitro, in a range of microchannel configurations. PMID:24104312

Bukowska, Danuta M; Derzsi, Ladislav; Tamborski, Szymon; Szkulmowski, Maciej; Garstecki, Piotr; Wojtkowski, Maciej

2013-10-01

123

Time-frequency mixed-norm estimates: sparse M/EEG imaging with non-stationary source activations.  

PubMed

Magnetoencephalography (MEG) and electroencephalography (EEG) allow functional brain imaging with high temporal resolution. While solving the inverse problem independently at every time point can give an image of the active brain at every millisecond, such a procedure does not capitalize on the temporal dynamics of the signal. Linear inverse methods (minimum-norm, dSPM, sLORETA, beamformers) typically assume that the signal is stationary: regularization parameter and data covariance are independent of time and the time varying signal-to-noise ratio (SNR). Other recently proposed non-linear inverse solvers promoting focal activations estimate the sources in both space and time while also assuming stationary sources during a time interval. However such a hypothesis holds only for short time intervals. To overcome this limitation, we propose time-frequency mixed-norm estimates (TF-MxNE), which use time-frequency analysis to regularize the ill-posed inverse problem. This method makes use of structured sparse priors defined in the time-frequency domain, offering more accurate estimates by capturing the non-stationary and transient nature of brain signals. State-of-the-art convex optimization procedures based on proximal operators are employed, allowing the derivation of a fast estimation algorithm. The accuracy of the TF-MxNE is compared with recently proposed inverse solvers with help of simulations and by analyzing publicly available MEG datasets. PMID:23291276

Gramfort, A; Strohmeier, D; Haueisen, J; Hämäläinen, M S; Kowalski, M

2013-01-04

124

Time-frequency transform techniques for seabed and buried target classification  

NASA Astrophysics Data System (ADS)

An approach for processing sonar signals with the ultimate goal of ocean bottom sediment classification and underwater buried target classification is presented in this paper. Work reported for sediment classification is based on sonar data collected by one of the AN/AQS-20's sonars. Synthetic data, simulating data acquired by parametric sonar, is employed for target classification. The technique is based on the Fractional Fourier Transform (FrFT), which is better suited for sonar applications because FrFT uses linear chirps as basis functions. In the first stage of the algorithm, FrFT requires finding the optimum order of the transform that can be estimated based on the properties of the transmitted signal. Then, the magnitude of the Fractional Fourier transform for optimal order applied to the backscattered signal is computed in order to approximate the magnitude of the bottom impulse response. Joint time-frequency representations of the signal offer the possibility to determine the timefrequency configuration of the signal as its characteristic features for classification purposes. The classification is based on singular value decomposition of the time-frequency distributions applied to the impulse response. A set of the largest singular values provides the discriminant features in a reduced dimensional space. Various discriminant functions are employed and the performance of the classifiers is evaluated. Of particular interest for underwater under-sediment classification applications are long targets such as cables of various diameters, which need to be identified as different from other strong reflectors or point targets. Synthetic test data are used to exemplify and evaluate the proposed technique for target classification. The synthetic data simulates the impulse response of cylindrical targets buried in the seafloor sediments. Results are presented that illustrate the processing procedure. An important characteristic of this method is that good classification accuracy of an unknown target is achieved having only the response of a known target in the free field. The algorithm shows an accurate way to classify buried objects under various scenarios, with high probability of correct classification.

Barbu, Madalina; Kaminsky, Edit; Trahan, Russell E., Jr.

2007-04-01

125

Study on the Fault Location Method for Power Cables using the Time-frequency Analysis  

NASA Astrophysics Data System (ADS)

The pulse radar method is one of fault location methods for power cables. It locates the breakdown point by measuring the delay time of the echo or the discharge signal coming from the breakdown point. The equipment for the pulse radar method is more compact compared with the Murray loop bridge, and its operation is more simple because sensitive adjustments of proportion are not needed. However the signal propagating through the cable is distorted depending on the distance and frequency, leading to a poor accuracy for the location. In this report, signal processing in the time-frequency domain is proposed to solve this problem. The pulse waveforms received at two different terminals of the cable were extracted by a window function, and subsequently Fourier transformed in order to calculate the phase difference at an appropriate frequency. A special care was taken for un-wrapping the folded phase spectrum. The phase difference was interpreted as the time lag at an identical frequency. The technique was applied to the fault location for a full size XLPE cable line.

Kobayashi, Shin'ichi; Morimoto, Nozomi; Miyajima, Kazuhisa; Hozumi, Naohiro

126

Acoustic modeling, phantom echolocation experiments, and time-frequency analysis of dolphin sonar for improved technological sonar systems  

NASA Astrophysics Data System (ADS)

Dolphin echolocation has been demonstrated to be a remarkable natural sonar system, one which may greatly exceed the performance of technological sonar systems in terms of detection and discrimination of targets. A dolphin's ability to discriminate targets may depend on the characteristics of echo highlights within a received signal. Previous experiments with dolphins varied the physical parameters of targets, but did not fully investigate how changes in individual echo components within the scattered waveforms affected the dolphin's subsequent response. The experiments utilize a phantom echo system to test a dolphin's detection response to relative amplitude differences of echo highlights and time separation differences between echo highlights. By electronically manipulating the amplitude and temporal separation of the highlights, the underlying acoustic cues are more efficiently investigated. Based on the dolphin's performance, the animal is sensitive to changes in the relative amplitudes and temporal separations of the highlights. Center frequency and rms bandwidth are calculated for the clicks collected during the experiments and the clicks are clustered into four classes using model based clustering. Echo signatures are obtained from elastic, isotropic spheres for each class of clicks with an acoustic scattering model. The results from the model are compared with experimentally obtained results. The joint time-frequency content of the resulting echo signals are obtained by the reduced interference distribution (RID). The RIDs are examined for each signal class for four different spherical targets. RID correlation values are obtained for a standard target versus comparison targets using a time-frequency correlator. Matching pursuit decomposition is applied to the signals to study frequency changes within the dolphin's functional bandwidth during discrimination tasks. The matching pursuit algorithm extracts subtle frequency differences that traditional time-frequency analysis techniques do not reveal. Furthermore, ROC analysis is applied to the relative energies of the matched waveforms to determine probability of discrimination. The results support the hypothesis that dolphins may discriminate by altering outgoing clicks and utilizing the time-frequency information returned by the targets. In a similar manner, by altering transmission signals and incorporating time-frequency signal processing algorithms, it may be possible to improve technological sonar models.

Muller, Mark W.

127

Unconventional Signal Processing Using the Cone Kernel Time-Frequency Representation.  

National Technical Information Service (NTIS)

In phase I of this project, the applicability of the cone kernel time-frequency representation (CK-TFR) to underwater acoustic signal analysis was explored. The Cohen class of time-frequency distributions is described and the theoretical basis for improve...

J. Carothers E. W. Swenson

1992-01-01

128

IGS/BIPM pilot project: GPS carrier phase for time/frequency transfer and timescale formation  

NASA Astrophysics Data System (ADS)

The development within the International GPS Service (IGS) of a suite of clock products, for both satellites and tracking receivers, offers some experiences which mirror the operations of the Bureau International des Poids et Mesures (BIPM) in its formation of TAI/UTC but some aspects differ markedly. The IGS relies exclusively on the carrier phase-based geodetic technique whereas BIPM time/frequency transfers use only common-view and two-way satellite (TWSTFT) methods. The carrier-phase approach has the potential of very high precision but suitable instrumental calibration procedures are only in the initial phases of deployment; the current BIPM techniques are more mature and widely used among timing labs, but are either less precise (common-view) or much more expensive (TWSTFT). In serving its geodetic users, the essential requirement for IGS clock products is that they be fully self-consistent in relative terms and also fully consistent with all other IGS products, especially the satellite orbits, in order to permit an isolated user to apply them with accuracy of a few centimetres. While there is no other strong requirement for the IGS timescale except to be reasonably close to broadcast GPS time, it is nonetheless very desirable for the IGS clock products to possess additional properties, such as being highly stable and being accurately relatable to UTC. These qualities enhance the value of IGS clock products for applications other than pure geodesy, especially for timing operations. The jointly sponsored `IGS/BIPM Pilot Project to Study Accurate Time and Frequency Comparisons using GPS Phase and Code Measurements' is developing operational strategies to exploit geodetic GPS methods for improved global time/frequency comparisons to the mutual benefit of both organizations. While helping the IGS to refine its clock products and link them to UTC, this collaboration will also provide new time transfer results for the BIPM that may eventually improve the formation of TAI and allow meaningful comparisons of new cold atom clocks. Thus far, geodetic receivers have been installed at many timing labs, a new internally realized IGS timescale has been produced using a weighted ensemble algorithm, and instrumental calibration procedures developed. Formulating a robust frequency ensemble from a globally distributed network of clocks presents unique challenges compared with intra-laboratory timescales. We have used these products to make a detailed study of the observed time transfer performance for about 30 IGS stations equipped with H-maser frequency standards. The results reveal a large dispersion in quality which can often be related to differences in local station factors. The main elements of the Project's original plan are now largely completed or in progress. In major ways, the experiences of this joint effort can serve as a useful model for future distributed timing systems, for example, Galileo and other GNSS operations.

Ray, J.; Senior, K.

2003-06-01

129

Time-Frequency Analysis of Chemosensory Event-Related Potentials to Characterize the Cortical Representation of Odors in Humans  

PubMed Central

Background The recording of olfactory and trigeminal chemosensory event-related potentials (ERPs) has been proposed as an objective and non-invasive technique to study the cortical processing of odors in humans. Until now, the responses have been characterized mainly using across-trial averaging in the time domain. Unfortunately, chemosensory ERPs, in particular, olfactory ERPs, exhibit a relatively low signal-to-noise ratio. Hence, although the technique is increasingly used in basic research as well as in clinical practice to evaluate people suffering from olfactory disorders, its current clinical relevance remains very limited. Here, we used a time-frequency analysis based on the wavelet transform to reveal EEG responses that are not strictly phase-locked to onset of the chemosensory stimulus. We hypothesized that this approach would significantly enhance the signal-to-noise ratio of the EEG responses to chemosensory stimulation because, as compared to conventional time-domain averaging, (1) it is less sensitive to temporal jitter and (2) it can reveal non phase-locked EEG responses such as event-related synchronization and desynchronization. Methodology/Principal Findings EEG responses to selective trigeminal and olfactory stimulation were recorded in 11 normosmic subjects. A Morlet wavelet was used to characterize the elicited responses in the time-frequency domain. We found that this approach markedly improved the signal-to-noise ratio of the obtained EEG responses, in particular, following olfactory stimulation. Furthermore, the approach allowed characterizing non phase-locked components that could not be identified using conventional time-domain averaging. Conclusion/Significance By providing a more robust and complete view of how odors are represented in the human brain, our approach could constitute the basis for a robust tool to study olfaction, both for basic research and clinicians.

Huart, Caroline; Legrain, Valery; Hummel, Thomas; Rombaux, Philippe; Mouraux, Andre

2012-01-01

130

Performance comparison of ISAR imaging method based on time frequency transforms  

NASA Astrophysics Data System (ADS)

Inverse synthetic aperture radar (ISAR) can image the moving target, especially the target in the air, so it is important in the air defence and missile defence system. Time-frequency Transform was applied to ISAR imaging process widely. Several time frequency transforms were introduced. Noise jamming methods were analysed, and when these noise jamming were added to the echo of the ISAR receiver, the image can become blur even can't to be identify. But the effect is different to the different time frequency analysis. The results of simulation experiment show the Performance Comparison of the method.

Xie, Chunjian; Guo, Chenjiang; Xu, Jiadong

2013-03-01

131

Orthonormal-basis partitioning and time-frequency representation of cardiac rhythm dynamics.  

PubMed

Although a number of time-frequency representations have been proposed for the estimation of time-dependent spectra, the time-frequency analysis of multicomponent physiological signals, such as beat-to-beat variations of cardiac rhythm or heart rate variability (HRV), is difficult. We thus propose a simple method for 1) detecting both abrupt and slow changes in the structure of the HRV signal, 2) segmenting the nonstationary signal into the less nonstationary portions, and 3) exposing characteristic patterns of the changes in the time-frequency plane. The method, referred to as orthonormal-basis partitioning and time-frequency representation (OPTR), is validated using simulated signals and actual HRV data. Here we show that OPTR can be applied to long multicomponent ambulatory signals to obtain the signal representation along with its time-varying spectrum. PMID:15887537

Aysin, Benhur; Chaparro, Luis F; Gravé, Ilan; Shusterman, Vladimir

2005-05-01

132

Time-frequency analysis of nonlinear and non-stationary weak signals of corona discharge  

NASA Astrophysics Data System (ADS)

It is very useful to study the signals radiated from corona discharges for the purposes of high-voltage line monitoring. Time-frequency analysis can clearly reveal the time-varying spectrum characteristics of such signals, which is very useful for analyzing and processing the non-linear and non-stationary weak signals, such as the signals radiated from corona discharges. Several time-frequency analysis methods, such as the Short-Time Fourier Transform (STFT), Wigner-Ville distribution and the Hilbert-Huang Transform (HHT) and so on, are used in this paper. The simulation data with the same and different amplitudes are comparatively analyzed by these time-frequency distribution methods. It can be concluded that the time-frequency analysis method based on HHT is more efficient to identify and suitable for the non-linear and non-stationary weak signals.

Wang, Lei; Liu, Shanghe; Wei, Ming; Hu, Xiao Feng

2013-03-01

133

Time-Frequency Analysis of Beach Bacteria Variations and its Implication for Recreational Water Quality Modeling  

EPA Science Inventory

This paper explores the potential of time-frequency wavelet analysis in resolving beach bacteria concentration and possible explanatory variables across multiple time scales with temporal information still preserved. The wavelet scalograms of E. coli concentrations and the explan...

134

Classification of Underwater Mammals using Feature Extraction Based on Time-Frequency Analysis and BCM Theory.  

National Technical Information Service (NTIS)

Underwater mammal sounds classification is demonstrated using a novel application of wavelet time/frequency decomposition and feature extraction using the BCM neuron. The system achieves outstanding classification performance even when tested with mammal ...

Q. Q. Huynh L. N. Cooper N. Intrator H. Shouval

1996-01-01

135

Basic Research on Sound Recognition of Traffic Accident using Visualization Method with Time-Frequency Analysis  

NASA Astrophysics Data System (ADS)

Conciderable skill is needed to detect traffic accident sound which was recorded in the intersection. In this paper, we proposed detection method of accident sound data using time-frequency analysis and correlation method in a short time.

Yamagami, Noriko; Hasegawa, Shinji

136

Time-Frequency Analysis of the Delta Modulation and PWM Control for the Asynchronous Motors  

Microsoft Academic Search

This work presents some considerations on a control method for a three-phase asynchronous motor and a time-frequency analysis of the proposed system. The control method uses the delta modulation principle to generate the command signals for a full bridge power inverter that drives three phase asynchronous motor. The time-frequency analysis can bring more new information that could be used to

Daniel N. Trip; Comelia Gordan; M. I. Gordan; A. Schiop; R. Reiz

2005-01-01

137

Spatial polarimetric time-frequency distributions for direction-of-arrival estimations  

Microsoft Academic Search

Time-frequency distributions (TFDs) are traditionally applied to a single antenna receiver with a single polarization. Recently, spatial time-frequency distributions (STFDs) have been developed for receivers with multiple single-polarized antennas and successfully applied for direction-of-arrival (DOA) estimation of nonstationary signals. In this paper, we consider dual-polarized antenna arrays and extend the STFD to utilize the source polarization properties. The spatial polarimetric

Yimin Zhang; Baha Adnan Obeidat; Moeness G. Amin

2006-01-01

138

Application of time frequency and wavelet analysis to the diagnosis of epilepsy  

NASA Astrophysics Data System (ADS)

Wavelet transforms and time-frequency distributions are powerful techniques for analysis of nonstationary biomedical signals. This paper investigates three applications of these techniques to multichannel electroencephalography (EEG) for the diagnosis of epilepsy. Wavelet transforms are utilized to detect the onset of seizures at different sites of subdural electrodes, and to extract spike patterns from EEG data recorded from the scalp. Time-frequency distributions are applied to characterize the early activity of seizures.

Sun, Mingui; Pon, Lin-Sen; Scheuer, Mark L.; Sclabassi, Robert J.

2000-04-01

139

Jamming interference suppression and multiuser detection for DSSS systems in time-frequency selective channels  

Microsoft Academic Search

In this paper, we propose a receiver structure that reduces multiple degradation on the transmitted signal in time-frequency selective direct sequence spread spectrum systems. The structure incorporates time-frequency diversity within a minimum mean square estimation technique based on orthonormal projections. It also uses time-varying signal processing techniques to mitigate additive wideband jamming interference. Simulations demonstrate that the simpler structure of

H. Shen; A. A. Papandreou-Suppappola

2003-01-01

140

Effect of excessive Internet use on the time–frequency characteristic of EEG  

Microsoft Academic Search

We examined the effect of excessive Internet use on the time–frequency characteristic of the electroencephalogram by wavelet transformed and non-negative matrix factorization (NMF). The event-related potentials (ERP) of normal subjects and excessive Internet users were acquired using the oddball paradigm experiment. We applied the wavelet transformed and event-related spectral perturbation to ERP in order to extract the time–frequency values. The

Hongqiang Yu; Xin Zhao; Ning Li; Mingshi Wang; Peng Zhou

2009-01-01

141

Muscle activation of patients suffering from asymmetric ankle osteoarthritis during isometric contractions and level walking - a time-frequency analysis.  

PubMed

Asymmetric osteoarthritis (OA) is a common type of OA in the ankle joint. OA also influences the muscles surrounding a joint, however, little is known about the muscle activation in asymmetric ankle OA. Therefore, the aim of this study was to characterize the patients' muscle activation during isometric ankle torque measurements and level walking. Surface electromyography (EMG) was measured of gastrocnemius medialis (GM) and lateralis (GL), soleus (SO), tibialis anterior (TA), and peroneus longus (PL) in 12 healthy subjects and 12 ankle OA patients. To obtain time and frequency components of the EMG power a wavelet transformation was performed. Furthermore, entropy was introduced to characterize the homogeneity of the wavelet patterns. Patients produced lower plantar- and dorsiflexion torques and their TA wavelet spectrum was shifted towards lower frequencies. While walking, the patients' muscles were active with a lower intensity and over a broader time-frequency region. In contrast to controls and varus OA patients, maximal GM activity of valgus OA patients lagged behind the activity of GL and SO. In both tasks, PL of the valgus patients contained more low frequency power. The results of this study will help to assess whether surgical interventions of ankle OA can reestablish the muscle activation patterns. PMID:22742975

Nüesch, Corina; Huber, Cora; Pagenstert, Geert; von Tscharner, Vinzenz; Valderrabano, Victor

2012-06-26

142

Time-frequency data fusion technique with application to vibration signal analysis  

NASA Astrophysics Data System (ADS)

To overcome the inherent deficiencies of conventional time-frequency analysis (TFA) methods, i.e., different TFA methods or the same TFA method with different control parameters will present different results for the same target signal, a novel scheme named as the time-frequency data fusion (TFDF) is developed in this study by extending the idea of data fusion technique. By combining the results produced by two or more different TFA methods, the TFDF technique can present a more accurate time-frequency presentation for the target signal than what can be achieved by any individual TFA method. Therefore, the TFDF has potential to render a significantly improved time-frequency representation and greatly facilitates extracting time-frequency features of target signals. This will promote the applications of TFA in engineering practices and make TFA methods more acceptable to field engineers. The effectiveness of the TFDF technique is validated by three numerical case studies and the analysis of a rubbing-impact signal collected from a rotor test rig.

Peng, Z. K.; Zhang, W. M.; Lang, Z. Q.; Meng, G.; Chu, F. L.

2012-05-01

143

Automated condition classification of a reciprocating compressor using time frequency analysis and an artificial neural network  

NASA Astrophysics Data System (ADS)

The purpose of this study is to develop an automated system for condition classification of a reciprocating compressor. Various time-frequency analysis techniques will be examined for decomposition of the vibration signals. Because a time-frequency distribution is a 3D data map, data reduction is indispensable for subsequent analysis. The extraction of the system characteristics using three indices, namely the time index, frequency index, and amplitude index, will be presented and examined for their applicability. The probability neural network is applied for automated condition classification using a combination of the three indices. The study reveals that a proper choice of the index combination and the time-frequency band can provide excellent classification accuracy for the machinery conditions examined in this work.

Lin, Yih-Hwang; Wu, Hsien-Chang; Wu, Chung-Yung

2006-12-01

144

Fault diagnosis for diesel valve trains based on time frequency images  

NASA Astrophysics Data System (ADS)

In this paper, the Wigner Ville distributions (WVD) of vibration acceleration signals which were acquired from the cylinder head in eight different states of valve train were calculated and displayed in grey images; and the probabilistic neural networks (PNN) were directly used to classify the time frequency images after the images were normalized. By this way, the fault diagnosis of valve train was transferred to the classification of time frequency images. As there is no need to extract further fault features (such as eigenvalues or symptom parameters) from time frequency distributions before classification, the fault diagnosis process is highly simplified. The experimental results show that the faults of diesel valve trains can be classified accurately by the proposed methods.

Wang, Chengdong; Zhang, Youyun; Zhong, Zhenyuan

2008-11-01

145

Automatic classification of sleep stages based on the time-frequency image of EEG signals.  

PubMed

In this paper, a new method for automatic sleep stage classification based on time-frequency image (TFI) of electroencephalogram (EEG) signals is proposed. Automatic classification of sleep stages is an important part for diagnosis and treatment of sleep disorders. The smoothed pseudo Wigner-Ville distribution (SPWVD) based time-frequency representation (TFR) of EEG signal has been used to obtain the time-frequency image (TFI). The segmentation of TFI has been performed based on the frequency-bands of the rhythms of EEG signals. The features derived from the histogram of segmented TFI have been used as an input feature set to multiclass least squares support vector machines (MC-LS-SVM) together with the radial basis function (RBF), Mexican hat wavelet, and Morlet wavelet kernel functions for automatic classification of sleep stages from EEG signals. The experimental results are presented to show the effectiveness of the proposed method for classification of sleep stages from EEG signals. PMID:24008250

Bajaj, Varun; Pachori, Ram Bilas

2013-09-02

146

Identification of a multicomponent signal by a TEA scheme operating in the time-frequency plane  

NASA Astrophysics Data System (ADS)

In this paper, a method for signal component separation, operating in the Time-Frequency (TF) plane and employing a Turbo Estimation Algorithm (TEA), is described. A novel 2D distribution is proposed, named Two Window Spectrogram (TWS), which is free from crossterms and able to yield good time and frequency resolution. Then, a set of parameters is defined in the time-frequency plane, which are able to carry the relevant information on the signal components. An algorithm of estimation of these parameters is proposed, making use of a TEA scheme to yield improved performance. The algorithm has been tested by simulation, yielding very encouraging performance.

Lo Presti, Letizia; Olmo, Gabriella; Galleani, Lorenzo

1999-11-01

147

Damage Classification Structural Health Monitoring in Bolted Structures Using Time-frequency Techniques  

Microsoft Academic Search

The analysis, detection, and classification of damage in complex bolted structures is an important component of structural health monitoring. In this article, an advanced signal processing and classification method is introduced based on time-frequency techniques. The time-varying signals collected from sensors are decomposed into linear combinations of highly localized Gaussian functions using the matching pursuit decomposition algorithm. These functions are

Debejyo Chakraborty; Narayan Kovvali; Jun Wei; Antonia Papandreou-Suppappola; Douglas Cochran; Aditi Chattopadhyay

2009-01-01

148

Blind Separation for Estimation of Near-Surface Interface by GPR with Time-Frequency Distribution  

Microsoft Academic Search

SUMMARY In this paper, the time-frequency separation al- gorithm (TFS) proposed by Belouchrani and Amin (1) is applied to ground penetrating radar (GPR) data to reduce ground clut- ter, that hides reflected waves from a near-surface planar inter- face. We formulated the problem with several assumptions so that narrow band signals, whose center frequency and baseband signal depend on propagation

Satoshi EBIHARA

2003-01-01

149

Canonical time-frequency processing for broadband signaling over dispersive channels  

Microsoft Academic Search

Even though broadband signaling and reception is often employed in practice for communication over time- and frequency-dispersive channels, existing receiver designs do not fully exploit the advantage of broadband signaling. We introduce a framework for time-frequency processing that is dictated by a canonical characterization of linear dispersive channels and fully utilizes the advantage of broadband signaling. The framework is based

Akbar M. Sayeed

1998-01-01

150

Wheeze detection based on time-frequency analysis of breath sounds  

Microsoft Academic Search

Abnormal breath sounds like wheezes are observed in patients with obstructive pulmonary diseases. The aim of this study was to construct an automatic technique for wheeze detection and monitoring using spectral analysis. Wheezes from 13 patients with diagnosed asthma, chronic obstructive pulmonary disease and pneumonia were recorded and a time-frequency wheeze detector (TF-WD) based on TF wheeze characteristics was constructed.

Styliani A. Taplidou; Leontios J. Hadjileontiadis

2007-01-01

151

Feature extraction of frictional vibration based on CWT time-frequency image  

Microsoft Academic Search

A method to extract features of frictional vibration signals was developed, using continuous wavelet transform (CWT) time-frequency image (TFI) and image processing to analyze the vibration signals, since the frictional vibration signals contain a wealth of information about the interface's fault state and friction wear state. TFIs were generated by CWT theory from the vibration signals produced by cylinder and

Chaoming Huang; Hongliang Yu; Delin Guan; Guobin Li; Qili Wu

2010-01-01

152

Characterization and analysis of marine mammal sounds using time-frequency and time-prony techniques  

Microsoft Academic Search

This paper presents the application of time-frequency signal processing techniques to the analysis of marine mammal sounds. In general, the analysis of marine mammal sounds are compared to a baseline in order to assess the animal's reaction to a stimulus such as man made sound sources in the ocean environment. A particular area of interest is the effect that low

Dale Groutage; Jim Schempp; L. Cohen

1994-01-01

153

Automated segmentation of linear time-frequency representations of marine-mammal sounds.  

PubMed

Many marine mammals produce highly nonlinear frequency modulations. Determining the time-frequency support of these sounds offers various applications, which include recognition, localization, and density estimation. This study introduces a low parameterized automated spectrogram segmentation method that is based on a theoretical probabilistic framework. In the first step, the background noise in the spectrogram is fitted with a Chi-squared distribution and thresholded using a Neyman-Pearson approach. In the second step, the number of false detections in time-frequency regions is modeled as a binomial distribution, and then through a Neyman-Pearson strategy, the time-frequency bins are gathered into regions of interest. The proposed method is validated on real data of large sequences of whistles from common dolphins, collected in the Bay of Biscay (France). The proposed method is also compared with two alternative approaches: the first is smoothing and thresholding of the spectrogram; the second is thresholding of the spectrogram followed by the use of morphological operators to gather the time-frequency bins and to remove false positives. This method is shown to increase the probability of detection for the same probability of false alarms. PMID:23968052

Dadouchi, Florian; Gervaise, Cedric; Ioana, Cornel; Huillery, Julien; Mars, Jérôme I

2013-09-01

154

A Novel Algorithm for Automatic Ship and Oil Spill Detection Based on Time-Frequency Methods  

Microsoft Academic Search

A novel method for automatic ship detection based on the Wavelet Transform (WT) has been recently presented. The results obtained point out the potential of the use of a multiresolution time-frequency framework for the analysis of SAR imagery. On the one hand, this paper aims at reviewing the algorithm for automatic spot detection on speckled images. On the other hand,

M. Tello; C. López-Martínez; J. J. Mallorqui

2006-01-01

155

Feature Extraction From Underwater Signals Using Time-Frequency Warping Operators  

Microsoft Academic Search

Processing marine-mammal signals for passive oceanic acoustic tomography or species classification and monitoring are problems that have recently attracted attention in scientific literature. For these purposes, it is necessary to use a method which could be able to extract the useful information about the processed data, knowing that the underwater environment is highly nonstationary. In this context, time-frequency (TF) or

Cornel Ioana; André QUINQUIS; Yann Stephan

2006-01-01

156

Mechanical signature analysis using time-frequency signal processing: application to internal combustion engine knock detection  

Microsoft Academic Search

Signature analysis consists of the extraction of information from measured signal patterns. The work presented in this paper illustrates the use of time-frequency (TF) analysis methods for the purpose of mechanical signature analysis. Mechanical signature analysis is a mature and developed field; however, TF analysis methods are relatively new to the field of mechanical signal processing, having mostly been developed

B. Samimy; G. Rizzoni

1996-01-01

157

Considering the influence of artificial environmental noise to study cough time-frequency features  

NASA Astrophysics Data System (ADS)

In general the study of the cough mechanism and sound in both animal and human is performed by eliciting coughing in a reproducible way by nebulization of an irritating substance. Due to ventilation the controlled evaporation-protocol causes artificial noises from a mechanical origin. The resulting environmental low-frequency noises complicate cough time-frequency features. In order to optimize the study of the cough-sound the research described in this paper attempts on the one hand to characterize and model the environmental noises and on the other hand to evaluate the influence of the noise on the time-frequency representation for the intended cough sounds by comparing different de-noising approaches. Free field acoustic sound is continuously registered during 30min citric acid cough-challenges on individual Belgian Landrace piglets and during respiratory infection experiments, with a duration of about 10 days, where room-ventilation was present.

van Hirtum, A.; Berckmans, D.

2003-09-01

158

Evaluation of the modified S-transform for time-frequency synchrony analysis and source localisation  

NASA Astrophysics Data System (ADS)

This article considers the problem of phase synchrony and coherence analysis using a modified version of the S-transform, referred to here as the Modified S-transform (MST). This is a novel and important time-frequency approach to study the phase coupling between two or more different spatially recorded entities with non-stationary characteristics. The basic method includes a cross-spectral analysis to study the phase synchrony of non-stationary signals, and relies on some properties of the MST, such as phase preservation. We demonstrate the usefulness of the technique using simulated examples and real newborn EEG data. The results show the advantage of using the cross-MST in the study of the connectivity between different signals using the time-frequency coherence. The MST led to improvements in resolution of almost twofold over the standard S-Transform in the examples presented in the article.

Assous, Said; Boashash, Boualem

2012-12-01

159

DOA estimation of wide-band signals based on time-frequency analysis  

Microsoft Academic Search

A numerical study on an approach based on the time-frequency analysis is performed for the high-resolution direction finding applications of wide-band signals. In this method, the direction of arrival (DOA) is estimated using a subband of the incoming signal instead of the whole signal spectrum. This treatment forces the DOA of the wide-band signals to be similar to that of

Sathish Chandran; Mohammad K. Ibrahim

1999-01-01

160

Time selection for ISAR imaging based on time-frequency analysis  

NASA Astrophysics Data System (ADS)

Because of target's complicated movement, conventional ISAR imaging algorithm can not meet the demands of maneuvering target imaging. On the basis of analyzing the phase model of target scatterer, a new time selection method for maneuvering target imaging is proposed. Based on adaptive optimal kernel (AOK) time-frequency representation, instantaneous Doppler frequencies of echoes in range bins are estimated. According to the estimated Doppler frequencies, imaging time can be selected. Raw radar data verify the effectiveness of the proposed method.

Li, Rui; Tao, Jiang; Shi, Wang D.

2013-03-01

161

Space-time-frequency coded OFDM over frequency-selective fading channels  

Microsoft Academic Search

This paper proposes novel space-time-frequency (STF) coding for multi-antenna orthogonal frequency-division multiplexing (OFDM) transmissions over frequency-selective Rayleigh fading channels. Incorporating subchannel grouping and choosing appropriate system parameters, we first convert our system into a set of group STF (GSTF) systems. This enables simplification of STF coding within each GSTF system. We derive design criteria for STF coding and exploit existing

Zhiqiang Liu; Yan Xin; Georgios B. Giannakis

2002-01-01

162

A new method of radar target recognition based on time-frequency analysis  

Microsoft Academic Search

In this paper, focused on three targets with simple structure, such as cone, sphere and cone, cylinder and cone, dynamic RCS echo signals is predicted with the improved Greco software. The Dynamic RCS echo signals of targets with micro-movement are preprocessed by using short time Fourier transform, and high-resolution time-frequency distribution images are obtained. A new radar target recognition method

Weixing Sheng; Kang Pan; Fang Wang; Xiaofeng Ma; Hao Wang

2010-01-01

163

The T-class of time–frequency distributions: Time-only kernels with amplitude estimation  

Microsoft Academic Search

This paper presents a class of time–frequency distributions (TFDs) characterized by time-lag kernels which are functions of time only. If the parameters of the time-only kernels are properly chosen, their corresponding TFDs, the T-distributions, are more efficient than their two-dimensional counterparts in terms of cross-terms suppression while keeping a high-energy concentration (resolution) around the IF law of non-stationary signals. The

Zahir M. Hussain

2006-01-01

164

Performance comparison of time-frequency distributions for ultrasonic nondestructive testing  

Microsoft Academic Search

In the nondestructive testing of materials ultrasonic backscattered echoes often exhibit critical time and frequency information. The time-frequency (t-f) analysis of ultrasonic signals instantaneously reveals the frequency and time of arrival of target echoes which help to characterize the target. But varying results are obtained by applying different t-f algorithms to ultrasonic signals. Performance evaluation of t-f algorithms for ultrasonic

M. A. Malik; J. Saniie

1996-01-01

165

Output only modal identifi cation and structural damage detection using time frequency & wavelet techniques  

Microsoft Academic Search

The primary objective of this paper is to develop output only modal identifi cation and structural damage detection. Identifi cation of multi-degree of freedom (MDOF) linear time invariant (LTI) and linear time variant (LTV—due to damage) systems based on Time-frequency (TF) techniques—such as short-time Fourier transform (STFT), empirical mode decomposition (EMD), and wavelets—is proposed. STFT, EMD, and wavelet methods developed

S. Nagarajaiah; B. Basu

2009-01-01

166

Sources Separation of Instantaneous Mixtures Using a Linear Time-Frequency Representation and Vectors Clustering  

Microsoft Academic Search

In this paper, we address the problem of separating N unknown sources using as many observed mixtures. The sources considered here are assumed to be of a non-stationary nature, i.e., their spectral contents are assumed to be time-varying. Using linear time-frequency (TF) representations of the mixtures along with a classification procedure based on vector clustering yield an effective way to

Braham Barkat; Farook Sattar; Karim Abed-Meraim

2006-01-01

167

Time-frequency analysis reveals decreased high-frequency oscillations in writer's cramp  

Microsoft Academic Search

High-frequency oscillations (HFO) have been suggested to reflect the activity of thalamocortical and\\/or intracortical neurons bursting at high frequencies. These circuits seem to be involved in pathophysiological mechanisms of focal dystonia. In healthy subjects, we characterized the spectrotemporal properties of HFO patterns evoked by dominant-hand median-nerve stimulation, using magnetoencephalography coupled with time-frequency analysis. Then, we investigated HFO in patients with

Zoe Cimatti; D. P Schwartz; F. Bourdain; S. Meunier; J.-P. Bleton; M. Vidailhet; B. Renault; L. Garnero

2006-01-01

168

Time-frequency coherence analysis of atrial fibrillation termination during procainamide administration  

Microsoft Academic Search

A time-frequency coherence estimator is developed and applied to study changes in signal characteristics as atrial fibrillation\\u000a converts to sinus rhythm during administration of procainamide. A coherence spectrogram (CS) using multiple sinusoidal tapers\\u000a is used in this study to assess phase relations between electrogram recordings at multiple atrial sites of seven patients\\u000a who received procainamide to terminate atrial fibrillation. CSs

Eric G. Lovett; Kristina M. Ropella

1997-01-01

169

Comparing the applications of EMD and EEMD on time-frequency analysis of seismic signal  

NASA Astrophysics Data System (ADS)

The Hilbert-Huang transform (HHT) is a novel signal analysis method in seismic exploration. It integrates empirical mode decomposition (EMD) and classical Hilbert transform (HT), which can express the intrinsic essence using simple and understandable algorithm. But there is a serious mode mixing phenomenon in EMD. To solve the mode mixing problem, a noise-assisted data analysis method called ensemble empirical mode decomposition (EEMD) is adopted instead of EMD. In this paper, the applications of EMD and EEMD on time-frequency analyzing behaviors were compared, and the results show that (1) EMD decomposes an original nonlinear and non-stationary signal into a series of simple intrinsic mode functions (IMFs), but with the mode mixing phenomenon. (2) EEMD skillfully solves the mode mixing problem by adding a white noise to the original signal. (3) The synthetic signal example reveals the remarkable ability of EEMD to decompose the signal into different IMFs and analyze the time-frequency distribution of the signal. (4) The time-frequency spectrum obtained by EEMD more realistically reflects the real geology than by EMD.

Wang, Tong; Zhang, Mingcai; Yu, Qihao; Zhang, Huyuan

2012-08-01

170

Automatic Seizure Detection Based on Time-Frequency Analysis and Artificial Neural Networks  

PubMed Central

The recording of seizures is of primary interest in the evaluation of epileptic patients. Seizure is the phenomenon of rhythmicity discharge from either a local area or the whole brain and the individual behavior usually lasts from seconds to minutes. Since seizures, in general, occur infrequently and unpredictably, automatic detection of seizures during long-term electroencephalograph (EEG) recordings is highly recommended. As EEG signals are nonstationary, the conventional methods of frequency analysis are not successful for diagnostic purposes. This paper presents a method of analysis of EEG signals, which is based on time-frequency analysis. Initially, selected segments of the EEG signals are analyzed using time-frequency methods and several features are extracted for each segment, representing the energy distribution in the time-frequency plane. Then, those features are used as an input in an artificial neural network (ANN), which provides the final classification of the EEG segments concerning the existence of seizures or not. We used a publicly available dataset in order to evaluate our method and the evaluation results are very promising indicating overall accuracy from 97.72% to 100%.

Tzallas, A. T.; Tsipouras, M. G.; Fotiadis, D. I.

2007-01-01

171

Time-frequency analysis as a tool for improving neural detectors for low probability of false alarm  

Microsoft Academic Search

This paper deals with the application of time-frequency analysis for transforming the received radar echoes in order to facilitate a neural network classification task. So as to compress the time-frequency representations maintaining most of the information, a feature extractor is designed. The proposed detector is compared with a single Multilayer Perceptron (MLP). The results show that time-frequency decompositions improve the

Pilar Jarabo Amores; Manuel Rosa Zurera; F. L. Ferreras; M. U. Manso

2001-01-01

172

Signal analysis by means of time-frequency (Wigner-type) distributions -- Applications to sonar and radar echoes  

SciTech Connect

Time series data have been traditionally analyzed in either the time or the frequency domains. For signals with a time-varying frequency content, the combined time-frequency (TF) representations, based on the Cohen class of (generalized) Wigner distributions (WD`s) offer a powerful analysis tool. Using them, it is possible to: (1) trace the time-evolution of the resonance features usually present in a standard sonar cross section (SCS), or in a radar cross section (RCS) and (2) extract target information that may be difficult to even notice in an ordinary SCS or RCS. After a brief review of the fundamental properties of the WD, the authors discuss ways to reduce or suppress the cross term interference that appears in the WD of multicomponent systems. These points are illustrated with a variety of three-dimensional (3-D) plots of Wigner and pseudo-Wigner distributions (PWD), in which the strength of the distribution is depicted as the height of a Wigner surface with height scales measured by various color shades or pseudocolors. The authors also review studies they have made of the echoes returned by conducting or dielectric targets in the atmosphere, when they are illuminated by broadband radar pings. A TF domain analysis of these impulse radar returns demonstrates their superior informative content. These plots allow the identification of targets in an easier and clearer fashion than by the conventional RCS of narrowband systems. The authors show computed and measured plots of WD and PWD of various types of aircraft to illustrate the classification advantages of the approach at any aspect angle. They also show analogous results for metallic objects buried underground, in dielectric media, at various depths.

Gaunaurd, G. [Naval Surface Warfare Center, Silver Spring, MD (United States). Carderock Div.; Strifors, H.C. [National Defense Research Establishment, Stockholm (Sweden)

1996-09-01

173

Determination of the Potential Benefit of Time-Frequency Gain Manipulation  

PubMed Central

Objective The purpose of this study was to determine the maximum benefit provided by a time-frequency gain-manipulation algorithm for noise-reduction (NR) based on an ideal detector of speech energy. The amount of detected energy necessary to show benefit using this type of NR algorithm was examined, as well as the necessary speed and frequency resolution of the gain manipulation. Design NR was performed using time-frequency gain manipulation, wherein the gains of individual frequency bands depended on the absence or presence of speech energy within each band. Three different experiments were performed: (1) NR using ideal detectors, (2) NR with nonideal detectors, and (3) NR with ideal detectors and different processing speeds and frequency resolutions. All experiments were performed using the Hearing-in-Noise test (HINT). A total of 6 listeners with normal hearing and 14 listeners with hearing loss were tested. Results HINT thresholds improved for all listeners with NR based on the ideal detectors used in Experiment I. The nonideal detectors of Experiment II required detection of at least 90% of the speech energy before an improvement was seen in HINT thresholds. The results of Experiment III demonstrated that relatively high temporal resolution (<100 msec) was required by the NR algorithm to improve HINT thresholds. Conclusions The results indicated that a single-microphone NR system based on time-frequency gain manipulation improved the HINT thresholds of listeners. However, to obtain benefit in speech intelligibility, the detectors used in such a strategy were required to detect an unrealistically high percentage of the speech energy and to perform the gain manipulations on a fast temporal basis.

Anzalone, Michael C.; Calandruccio, Lauren; Doherty, Karen A.; Carney, Laurel H.

2008-01-01

174

Applications of time-frequency analysis to signals from manufacturing and machine monitoring sensors  

SciTech Connect

Manufacturing industries are now demanding substantial increases in flexibility, productivity and reliability from their process machines as well as increased quality and value of their products. One important strategy to support this goal is sensor-based, on-line, real-time evaluation of key characteristics of both machines and products, throughout the manufacturing process. Recent advances in time-frequency (TF) analysis are particularly well suited to extracting key vibrational characteristics from monitoring sensors. Thus this paper presents applications of TF analysis to several important manufacturing and machine monitoring tasks, to show the value of these forms of digital signal processing applied to manufacturing.

Atlas, L.E.; Narayanan, S.B. [Univ. of Washington, Seattle, WA (United States). Dept. of Electrical Engineering; Bernard, G.D. [Boeing Commercial Airplane Group, Seattle, WA (United States)

1996-09-01

175

Audio source separation with multiple microphones on time-frequency representations  

NASA Astrophysics Data System (ADS)

This paper presents various source separation methods that utilize multiple microphones. We classify them into two classes. Methods that fall into the first class apply independent component analysis (ICA) or Gaussian mixture model (GMM) to frequency bin-wise observations, and then solve the permutation problem to reconstruct separated signals. The second type of method extends non-negative matrix factorization (NMF) to a multimicrophone situation, in which NMF bases are clustered according to their spatial properties. We have a unified understanding that all methods analyze a time-frequency representation with an additional microphone axis.

Sawada, Hiroshi

2013-05-01

176

Time-frequency analysis using damped-oscillator pseudo-wavelets: application to electrophysiological recordings  

PubMed Central

The damped-oscillator pseudo-wavelet is presented as a method of time-frequency analysis along with a new spectral density measure, the data power. An instantaneous phase can be defined for this pseudo-wavelet, and it is easily inverted. The data power measure is tested on both computer generated data and in vivo intrahippocampal electrophysiological recordings from a rat. The data power spectral density is found to give better time and frequency resolution than the more conventional total energy measure, and additionally shows intricate time-frequency structure in the rat that is altered in association with the emergence of epilepsy. With epileptogenesis, the baseline theta oscillation is severely degraded and is absorbed into a broader gamma band. There are also broad 600 Hz and 2000 Hz bands which localize to hippocampal layers that are distinct from those of the theta and gamma bands. The 600 Hz band decreases in prominence with epileptogenesis while the 2000 Hz band increases in prominence. The origins of these high frequency bands await further study. In general, we find that the damped-oscillator pseudo-wavelet is easy to use and is particularly suitable for problems where a wide range of oscillator frequencies is expected.

Hsu, David; Hsu, Murielle; Grabenstatter, Heidi L.; Worrell, Gregory A.; Sutula, Thomas P.

2010-01-01

177

Analysis of damped tissue vibrations in time-frequency space: a wavelet-based approach.  

PubMed

There is evidence that vibrations of soft tissue compartments are not appropriately described by a single sinusoidal oscillation for certain types of locomotion such as running or sprinting. This paper discusses a new method to quantify damping of superimposed oscillations using a wavelet-based time-frequency approach. This wavelet-based method was applied to experimental data in order to analyze the decay of the overall power of vibration signals over time. Eight healthy subjects performed sprinting trials on a 30 m runway on a hard surface and a soft surface. Soft tissue vibrations were quantified from the tissue overlaying the muscle belly of the medial gastrocnemius muscle. The new methodology determines damping coefficients with an average error of 2.2% based on a wavelet scaling factor of 0.7. This was sufficient to detect differences in soft tissue compartment damping between the hard and soft surface. On average, the hard surface elicited a 7.02 s(-1) lower damping coefficient than the soft surface (p<0.05). A power spectral analysis of the muscular vibrations occurring during sprinting confirmed that vibrations during dynamic movements cannot be represented by a single sinusoidal function. Compared to the traditional sinusoidal approach, this newly developed method can quantify vibration damping for systems with multiple vibration modes that interfere with one another. This new time-frequency analysis may be more appropriate when an acceleration trace does not follow a sinusoidal function, as is the case with multiple forms of human locomotion. PMID:22995145

Enders, Hendrik; von Tscharner, Vinzenz; Nigg, Benno M

2012-09-18

178

Time-frequency analysis of accelerometry data for detection of myoclonic seizures.  

PubMed

Four time-frequency and time-scale methods are studied for their ability of detecting myoclonic seizures from accelerometric data. Methods that are used are: the short-time Fourier transform (STFT), the Wigner distribution (WD), the continuous wavelet transform (CWT) using a Daubechies wavelet, and a newly introduced model-based matched wavelet transform (MOD). Real patient data are analyzed using these four time-frequency and time-scale methods. To obtain quantitative results, all four methods are evaluated in a linear classification setup. Data from 15 patients are used for training and data from 21 patients for testing. Using features based on the CWT and MOD, the success rate of the classifier was 80%. Using STFT or WD-based features, the classification success is reduced. Analysis of the false positives revealed that they were either clonic seizures, the onset of tonic seizures, or sharp peaks in "normal" movements indicating that the patient was making a jerky movement. All these movements are considered clinically important to detect. Thus, the results show that both CWT and MOD are useful for the detection of myoclonic seizures. On top of that, MOD has the advantage that it consists of parameters that are related to seizure duration and intensity that are physiologically meaningful. Furthermore, in future work, the model can also be useful for the detection of other motor seizure types. PMID:20667813

Nijsen, Tamara M E; Aarts, Ronald M; Cluitmans, Pierre J M; Griep, Paul A M

2010-07-26

179

An evaluation of objective measures for intelligibility prediction of time-frequency weighted noisy speech.  

PubMed

Existing objective speech-intelligibility measures are suitable for several types of degradation, however, it turns out that they are less appropriate in cases where noisy speech is processed by a time-frequency weighting. To this end, an extensive evaluation is presented of objective measure for intelligibility prediction of noisy speech processed with a technique called ideal time frequency (TF) segregation. In total 17 measures are evaluated, including four advanced speech-intelligibility measures (CSII, CSTI, NSEC, DAU), the advanced speech-quality measure (PESQ), and several frame-based measures (e.g., SSNR). Furthermore, several additional measures are proposed. The study comprised a total number of 168 different TF-weightings, including unprocessed noisy speech. Out of all measures, the proposed frame-based measure MCC gave the best results (??=?0.93). An additional experiment shows that the good performing measures in this study also show high correlation with the intelligibility of single-channel noise reduced speech. PMID:22087929

Taal, Cees H; Hendriks, Richard C; Heusdens, Richard; Jensen, Jesper

2011-11-01

180

Time-frequency based feature selection for discrimination of non-stationary biosignals  

NASA Astrophysics Data System (ADS)

This research proposes a generic methodology for dimensionality reduction upon time-frequency representations applied to the classification of different types of biosignals. The methodology directly deals with the highly redundant and irrelevant data contained in these representations, combining a first stage of irrelevant data removal by variable selection, with a second stage of redundancy reduction using methods based on linear transformations. The study addresses two techniques that provided a similar performance: the first one is based on the selection of a set of the most relevant time-frequency points, whereas the second one selects the most relevant frequency bands. The first methodology needs a lower quantity of components, leading to a lower feature space; but the second improves the capture of the time-varying dynamics of the signal, and therefore provides a more stable performance. In order to evaluate the generalization capabilities of the methodology proposed it has been applied to two types of biosignals with different kinds of non-stationary behaviors: electroencephalographic and phonocardiographic biosignals. Even when these two databases contain samples with different degrees of complexity and a wide variety of characterizing patterns, the results demonstrate a good accuracy for the detection of pathologies, over 98 %.The results open the possibility to extrapolate the methodology to the study of other biosignals.

D Martínez-Vargas, Juan; I Godino-Llorente, Juan; Castellanos-Dominguez, Germán

2012-12-01

181

Time-frequency analysis of heart murmurs. Part I: Parametric modelling and numerical simulations.  

PubMed

The object of this study is to compare the performance of two new bilinear time-frequency representation techniques with the spectrogram to characterise the behaviour of heart murmurs produced by bioprosthetic heart valves implanted in the mitral or aortic position. The murmurs are those of mitral stenosis, mitral regurgitation, aortic stenosis, aortic regurgitation, a diastolic musical murmur and a systolic musical murmur. In the first part of the study, the general characteristics of the amplitude and the spectral content of these murmurs are determined by visual observation of the spectrogram of phonocardiograms obtained from several patients with known valvular pathology complemented with a literature review. A parametric model is then generated for each murmur signal. Stenotic and regurgitant murmurs are modelled as the sequential output of a bank of low-pass filters excited by a white noise input signal. The basic parameters of each filter are selected to simulate, as a function of time, the basic characteristics of random heart murmurs. Musical murmurs are modelled as a frequency-modulated deterministic sinusoid of constant amplitude. Numerical simulations of these random and musical heart murmurs are then generated and will be used in Part II to determine the best of three time-frequency representation techniques for analysing heart murmur signals. PMID:9374050

Debiais, F; Durand, L G; Pibarot, P; Guardo, R

1997-09-01

182

Large dynamic range time-frequency signal analysis with application to helicopter Doppler radar data  

NASA Astrophysics Data System (ADS)

Despite the enhanced time-frequency analysis (TFA) detailing capability of quadratic TFAs like the Wigner and Cohen representations, their performance with signals of large dynamic range (DNR in excess of 40 dB) is not acceptable due to the inability to totally suppress the cross-term artifacts which typically are much stronger than the weakest signal components that they obscure. AMTI and GMTI radar targets exhibit such high dynamic range when microDoppler is present, with the aspects of interest being the weakest components. This paper presents one of two modifications of linear TFA to provide the enhanced detailing behavior of quadratic TFAs without introducing cross terms, making it possible to see the time-frequency detail of extremely weak signal components. The technique described here is based on subspace-enhanced linear predictive extrapolation of the data within each analysis window to create a longer data sequence for conventional STFT TFA. The other technique, based on formation of a special two-dimensional transformed data matrix analyzed by high-definition two-dimensional spectral analysis methods such as 2-D AR or 2-D minimum variance, is compared to the new technique using actual AMTI and GMTI radar data.

Marple, Stanley L., Jr.; Marino, Claudio S.; Strange, Shawn

2003-12-01

183

Determination of transient disturbance energy flow in electric power systems via cross time-frequency distribution  

NASA Astrophysics Data System (ADS)

In electric power systems, the flow of electric power is an important issue for the control and management of the system. However, under transient-states caused by electrical disturbances, it is not a simple task to determine the flow of transient disturbance energy in an analytic way with high accuracy. The proposed algorithm for the determination of transient disturbance energy flow is based on cross time-frequency analysis that provides time- and frequency- localized phase difference information. Hence, based on the cross time-frequency distribution of the transient voltage and current, the classical parameters in power systems are modified for transient analysis. The transient power factor angle will determine the direction of transient disturbance energy (real and reactive) flows in power distribution system networks. For the verification of the proposed algorithm, a practical model of a power system is simulated by EMTP (Electromagnetic Transient Program). In addition, knowledge of this nature should greatly facilitate automatic identification of transient events and determination of the physical location of the source of various transient disturbances.

Shin, Yong-June; Powers, Edward J.; Grady, W. M.; Arapostathis, Ari

2004-10-01

184

Improved time-frequency analysis of ASDEX Upgrade reflectometry data using the reassigned spectrogram technique.  

PubMed

The spectrogram is one of the best-known time-frequency distributions suitable to analyze signals whose energy varies both in time and frequency. In reflectometry, it has been used to obtain the frequency content of FM-CW signals for density profile inversion and also to study plasma density fluctuations from swept and fixed frequency data. Being implemented via the short-time Fourier transform, the spectrogram is limited in resolution, and for that reason several methods have been developed to overcome this problem. Among those, we focus on the reassigned spectrogram technique that is both easily automated and computationally efficient requiring only the calculation of two additional spectrograms. In each time-frequency window, the technique reallocates the spectrogram coordinates to the region that most contributes to the signal energy. The application to ASDEX Upgrade reflectometry data results in better energy concentration and improved localization of the spectral content of the reflected signals. When combined with the automatic (data driven) window length spectrogram, this technique provides improved profile accuracy, in particular, in regions where frequency content varies most rapidly such as the edge pedestal shoulder. PMID:21061480

Varela, P; Silva, A; da Silva, F; da Graça, S; Manso, M E; Conway, G D

2010-10-01

185

{chi}{sup 2} time-frequency discriminator for gravitational wave detection  

SciTech Connect

Searches for known waveforms in gravitational wave detector data are often done using matched filtering. When used on real instrumental data, matched filtering often does not perform as well as might be expected, because nonstationary and non-Gaussian detector noise produces large spurious filter outputs (events). This paper describes a {chi}{sup 2} time-frequency test which is one way to discriminate such spurious events from the events that would be produced by genuine signals. The method works well only for broadband signals. The case where the filter-template does not exactly match the signal waveform is also considered, and upper bounds are found for the expected value of {chi}{sup 2}.

Allen, Bruce [Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, Wisconsin 53201 (United States)

2005-03-15

186

Time-frequency spectral signature of Pelotas Basin deep water gas hydrates system  

NASA Astrophysics Data System (ADS)

Pelotas Basin has the largest gas hydrate occurrence of the Brazilian coast. The reserves are estimated in 780 trillion cubic feet, covering an area of 45,000 km2. In this work we apply spectral decomposition technique in order to better understand a gas hydrate deep water system, performing a continuous time-frequency analysis of seismic trace, where frequency spectrum is the output for each time sample of the seismic trace. This allows a continuous analysis on the effects of the geologic structures and lithology over frequency content of the seismic wave. Spectral anomalies found were interpreted as variations of hydrates concentration inside the Gas Hydrate Stability Zone (GHSZ), as well free gas accumulations beneath and Below the GHSZ and gas chimneys. We concluded that this technique has a good potential to assist seismic study of structures associated with gas hydrates accumulations.

Oliveira, Sérgio; Vilhena, Odilla; da Costa, Emanuel

2010-03-01

187

Time-frequency analysis methods for detecting effects of diabetic neuropathy.  

PubMed

There have been several research studies on efficient methods for analysis and classification of electromyography (EMG) signals and adoption of wavelet functions, which is a promising approach for determining the spectral distribution of the signal. This study compares distinct time-frequency analysis methods for investigating the EMG activity of the thigh and calf muscles during gait among non-diabetic subjects and diabetic neuropathic patients. It also attempts to verify, by adaptive optimal kernel and discrete wavelet transform, whether there are EMG alterations related to diabetic neuropathy in the lower limb muscles during gait. The results show that diabetics might not keep up with the mechanical demands of walking by changing muscle fibre recruitment strategies, as seen in the control group. Moreover, principal components analysis indicates more alterations in diabetic motor strategies, and we identify that diabetic subjects need other strategies with different muscle energy production and frequencies to carry out their daily activities. Copyright ©?2013 John Wiley & Sons, Ltd. PMID:23620093

Weiderpass, H A; Pachi, C G F; Yamamoto, J F; Hamamoto, A; Onodera, A N; Sacco, I C N

2013-04-26

188

Event-related EEG time-frequency analysis and the Orienting Reflex to auditory stimuli.  

PubMed

Sokolov's classic works discussed electroencephalogram (EEG) alpha desynchronization as a measure of the Orienting Reflex (OR). Early studies confirmed that this reduced with repeated auditory stimulation, but without reliable stimulus-significance effects. We presented an auditory habituation series with counterbalanced indifferent and significant (counting) instructions. Time-frequency analysis of electrooculogram (EOG)-corrected EEG was used to explore prestimulus levels and the timing and amplitude of event-related increases and decreases in 4 classic EEG bands. Decrement over trials and response recovery were substantial for the transient increase (in delta, theta, and alpha) and subsequent desynchronization (in theta, alpha, and beta). There was little evidence of dishabituation and few effects of counting. Expected effects in stimulus-induced alpha desynchronization were confirmed. Two EEG response patterns over trials and conditions, distinct from the full OR pattern, warrant further research. PMID:22524168

Barry, Robert J; Steiner, Genevieve Z; De Blasio, Frances M

2012-04-23

189

Ultrasonic sensing and time-frequency analysis for detecting plastic deformation in an aluminum plate  

NASA Astrophysics Data System (ADS)

We investigate the use of low frequency (10-70 MHz) laser ultrasound for the detection of fatigue damage. While high frequency ultrasonics have been utilized in earlier work, unlike contacting transducers, laser-based techniques allow for simultaneous interrogation of the longitudinal and shear moduli of the fatigued material. The differential attenuation changes with the degree of damage, indicating the presence of plasticity. In this paper, we describe a structural damage identification approach based on ultrasonic sensing and time-frequency techniques. A parsimonious representation is first constructed for the ultrasonic signals using the modified matching pursuit decomposition (MMPD) method. This decomposition is then employed to compute projections onto the various damage classes, and classification is performed based on the magnitude of these projections. Results are presented for the detection of fatigue damage in Al-6061 and Al-2024 plates tested under 3-point bending.

Channels, Lindsey; Chakraborty, Debejyo; Simon, Donna; Kovvali, Narayan; Spicer, James; Papandreou-Suppappola, Antonia; Cochran, Douglas; Peralta, Pedro; Chattopadhyay, Aditi

2008-04-01

190

Recent advances in time-frequency analysis methods for machinery fault diagnosis: A review with application examples  

NASA Astrophysics Data System (ADS)

Nonstationary signal analysis is one of the main topics in the field of machinery fault diagnosis. Time-frequency analysis can identify the signal frequency components, reveals their time variant features, and is an effective tool to extract machinery health information contained in nonstationary signals. Various time-frequency analysis methods have been proposed and applied to machinery fault diagnosis. These include linear and bilinear time-frequency representations (e.g., wavelet transform, Cohen and affine class distributions), adaptive parametric time-frequency analysis (based on atomic decomposition and time-frequency auto-regressive moving average models), adaptive non-parametric time-frequency analysis (e.g., Hilbert-Huang transform, local mean decomposition, and energy separation), and time varying higher order spectra. This paper presents a systematic review of over 20 major such methods reported in more than 100 representative articles published since 1990. Their fundamental principles, advantages and disadvantages, and applications to fault diagnosis of machinery have been examined. Some examples have also been provided to illustrate their performance.

Feng, Zhipeng; Liang, Ming; Chu, Fulei

2013-07-01

191

Models of the Joint Structure of Domain-Related and Global Distress: Implications for the Reconciliation of Quality of Life and Mental Health Perspectives  

ERIC Educational Resources Information Center

|Research on subjective wellbeing includes studies of both domain-related and global distress. The mental health literature, though, focuses almost exclusively on global distress. This seems to be partly due to a common belief that psychological distress, and the moods that comprise distress, necessarily lack referential content. However, if that…

Magee, William; St-Arnaud, Sebastien

2012-01-01

192

Pulse transformation and time-frequency filtering with electromagnetically induced transparency  

NASA Astrophysics Data System (ADS)

A simple analytical solution for the propagation of a weak Gaussian pulse in a dense absorptive medium with electromagnetically induced transparency is found. This solution is applied to the analysis of three regimes: (1) and (2) the pulse spectrum is narrower than the transparency window [which is narrow (1) or wide (2) with respect to the width of the absorption line] and (3) the pulse spectrum is broader than the transparency window. It is shown that the pulse maintains its area in all three regimes and maintains its Gaussian shape but narrows in spectrum in regime 1. In regime 2, the pulse begins to distort after a certain distance. In regime 3, the pulse is split into two parts. One part is an adiabatic part with a spectrum defined by the effective width of the transparency window for a thick medium and the other is an oscillating nonadiabatic part of short duration. The adiabatic part propagates slowly and the nonadiabatic part propagates with a velocity close to the speed of light. Thus in regime 3, the medium acts as a time-frequency filter, separating the narrow and wide spectrum components of the pulse in time at the output of the absorber.

Shakhmuratov, R. N.; Odeurs, J.

2005-01-01

193

A procedure based on proper orthogonal decomposition for time-frequency analysis of time series  

NASA Astrophysics Data System (ADS)

A procedure for time-frequency analysis of time series is described, which is mainly inspired by singular-spectrum analysis, but it presents some modifications that allow checking the convergence of the results and extracting the detected spectral components through a more efficient technique, especially for real applications. This technique is adaptive, completely data dependent with no a priori assumption and applicable to non-stationary signals. The principal components are extracted from the signals and sorted by their fluctuating energy; moreover, the time variation of their amplitude and frequency is characterized. The technique is first assessed for multi-component computer-generated signals and then applied to experimental velocity signals. The latter are acquired in proximity of the wake generated from a triangular prism placed vertically on a plane, with a vertical edge against the incoming flow. From these experimental signals, three different spectral components, connected to the dynamics of different vorticity structures, are detected, and the time histories of their amplitudes and frequencies are characterized.

Iungo, Giacomo Valerio; Lombardi, Edoardo

2011-10-01

194

Detection of transient, regional cardiac repolarization alternans by time-frequency analysis of synthetic electrograms.  

PubMed

Repolarization alternans (RA), originating at the cellular level, is thought to produce an arrhythmogenic substrate, and surface ECG T-wave alternans (TWA) is a marker of risk for sudden cardiac death. In this paper we study RA in the unipolar electrograms (EGM), which represent the electrical activity of the heart at the tissue level. We first describe a simple analytical model to study how RA, simulated as alternating variations of action potential duration, affects EGM-TWA, and then we propose a novel methodology based on time-frequency analysis to detect EGM-TWA which occurs intermittently in few consecutive beats. In a simulation study, we used a 257-node whole heart model to reproduce several patterns of RA. RA involved specific subsets of adjacent nodes (11, 65 and 257), exhibited different amplitudes (0.25, 0.5 and 1 ms) and lasted for 40 consecutive beats of a 80-beat-long test sequence. Results show a relationship between the spatial distribution of RA and EGM-TWA: the smaller the region where RA occurs, the higher the extent of EGM-TWA. With the proposed methodology, we localized those portions of myocardium which exhibited EGM-TWA with an accuracy higher than 90%. PMID:24110552

Orini, Michele; Hanson, Ben; Taggart, Peter; Lambiase, Pier

2013-07-01

195

Automated extraction and classification of time-frequency contours in humpback vocalizations.  

PubMed

A time-frequency contour extraction and classification algorithm was created to analyze humpback whale vocalizations. The algorithm automatically extracted contours of whale vocalization units by searching for gray-level discontinuities in the spectrogram images. The unit-to-unit similarity was quantified by cross-correlating the contour lines. A library of distinctive humpback units was then generated by applying an unsupervised, cluster-based learning algorithm. The purpose of this study was to provide a fast and automated feature selection tool to describe the vocal signatures of animal groups. This approach could benefit a variety of applications such as species description, identification, and evolution of song structures. The algorithm was tested on humpback whale song data recorded at various locations in Hawaii from 2002 to 2003. Results presented in this paper showed low probability of false alarm (0%-4%) under noisy environments with small boat vessels and snapping shrimp. The classification algorithm was tested on a controlled set of 30 units forming six unit types, and all the units were correctly classified. In a case study on humpback data collected in the Auau Chanel, Hawaii, in 2002, the algorithm extracted 951 units, which were classified into 12 distinctive types. PMID:23297903

Ou, Hui; Au, Whitlow W L; Zurk, Lisa M; Lammers, Marc O

2013-01-01

196

Frequency and time-frequency analysis of intraoperative ECoG during awake brain stimulation.  

PubMed

Electrocortical stimulation remains the standard for functional brain mapping of eloquent areas to prevent postoperative functional deficits. The aim of this study was to investigate whether the short-train technique (monopolar stimulation) and Penfield's technique (bipolar stimulation) would induce different effects on brain oscillatory activity in awake patients, as quantified by electrocorticography (ECoG). The study population was seven patients undergoing brain tumor surgery. Intraoperative bipolar and monopolar electrical stimulation for cortical mapping was performed during awake surgery. ECoG was recorded using 1 × 8 electrode strip. Spectral estimation was calculated using a parametric approach based on an autoregressive model. Wavelet-based time-frequency analysis was then applied to evaluate the temporal evolution of brain oscillatory activity. Both monopolar and bipolar stimulation produced an increment in delta and a decrease in beta powers for the motor and the sensory channels. These phenomena lasted about 4 s. Comparison between monopolar and bipolar stimulation showed no significant difference in brain activity. Given the importance of quantitative signal analysis for evaluating response accuracy, ECoG recording during electrical stimulation is necessary to characterize the dynamic processes underlying changes in cortical responses in vivo. This study is a preliminary approach to the quantitative analysis of post-stimulation ECoG signals. PMID:23443302

Formaggio, Emanuela; Storti, Silvia F; Tramontano, Vincenzo; Casarin, Agnese; Bertoldo, Alessandra; Fiaschi, Antonio; Talacchi, Andrea; Sala, Francesco; Toffolo, Gianna M; Manganotti, Paolo

2013-02-25

197

Time-frequency analysis of transient-evoked otoacoustic emissions in children exposed to carboplatin chemotherapy.  

PubMed

The aims of this study were to characterize and quantify time-frequency changes in transient-evoked otoacoustic emissions (TEOAEs) recorded in children diagnosed with retinoblastoma who were receiving carboplatin chemotherapy. A signal processing technique, the wavelet transform (WT), was used to analyze TEOAE waveforms in narrow-band frequency components. Ten children (aged 3-72 months) diagnosed with unilateral or bilateral retinoblastoma were enrolled in the study. TEOAEs were acquired from the children with linear sequences of 70 dB peak equivalent SPL clicks. After WT analysis, TEOAE energy, latency and normalized energy in the narrow-band frequency components were compared before and during carboplatin chemotherapy treatment (average dose 1693 mg/m2). On a group basis, no significant differences (p>0.05) in the TEOAE energy, latency or normalized energy before and after carboplatin treatment were observed. There were decreases in normalized energy on an individual basis in 10 out of 18 ears in the sample. Exposure to carboplatin chemotherapy did not cause significant changes in TEOAE energy, latency and normalized energy during treatment. However, long-term monitoring of hearing with measurements of TEOAEs is warranted, given the risks of delayed hearing loss in some children receiving carboplatin chemotherapy. PMID:23147804

Bhagat, Shaum; Bass, Johnnie; Qaddoumi, Ibrahim; Brennan, Rachel; Wilson, Matthew; Wu, Jianrong; Galindo, Carlos-Rodriguez; Paglialonga, Alessia; Tognola, Gabriella

2012-11-06

198

Time-frequency model for echo-delay resolution in wideband biosonar  

NASA Astrophysics Data System (ADS)

A time/frequency model of the bat's auditory system was developed to examine the basis for the fine (~2 ?s) echo-delay resolution of big brown bats (Eptesicus fuscus), and its performance at resolving closely spaced FM sonar echoes in the bat's 20-100-kHz band at different signal-to-noise ratios was computed. The model uses parallel bandpass filters spaced over this band to generate envelopes that individually can have much lower bandwidth than the bat's ultrasonic sonar sounds and still achieve fine delay resolution. Because fine delay separations are inside the integration time of the model's filters (~250-300 ?s), resolving them means using interference patterns along the frequency dimension (spectral peaks and notches). The low bandwidth content of the filter outputs is suitable for relay of information to higher auditory areas that have intrinsically poor temporal response properties. If implemented in fully parallel analog-digital hardware, the model is computationally extremely efficient and would improve resolution in military and industrial sonar receivers.

Neretti, Nicola; Sanderson, Mark I.; Intrator, Nathan; Simmons, James A.

2003-04-01

199

Source localization of non-stationary acoustic data using time-frequency analysis  

NASA Astrophysics Data System (ADS)

An improvement in temporal locality of the generalized cross-correlation (GCC) for angle of arrival (AOA) estimation can be achieved by employing 2-D cross-correlation of infrasonic sensor data transformed to its time-frequency (TF) representation. Intermediate to the AOA evaluation is the time delay between pairs of sensors. The signal class of interest includes far field sources which are partially coherent across the array, nonstationary, and wideband. In addition, signals can occur as multiple short bursts, for which TF representations may be more appropriate for time delay estimation. The GCC tends to smooth out such temporal energy bursts. Simulation and experimental results will demonstrate the improvement in using a TF-based GCC, using the Cohen class, over the classic GCC method. Comparative demonstration of the methods will be performed on data captured on an infrasonic sensor array located at NASA Langley Research Center (LaRC). The infrasonic data sources include Delta IV and Space Shuttle launches from Kennedy Space Center which belong to the stated signal class. Of interest is to apply this method to the AOA estimation of atmospheric turbulence. [Work supported by NASA LaRC Creativity and Innovation project: Infrasonic Detection of Clear Air Turbulence and Severe Storms.

Stoughton, Jack; Edmonson, William

2005-04-01

200

Time-Frequency Analysis of Rocket Nozzle Wall Pressures during Start-up Transients  

NASA Astrophysics Data System (ADS)

Surveys of the fluctuating wall pressure were conducted on a sub-scale, thrust-optimized parabolic nozzle in order to develop a physical intuition for its Fourier-azimuthal mode behavior during fixed and transient start-up conditions. These unsteady signatures are driven by shock wave turbulent boundary layer interactions which depend on the nozzle pressure ratio and nozzle geometry. The focus however, is on the degree of similarity between the spectral footprints of these modes obtained from transient start-ups as opposed to a sequence of fixed nozzle pressure ratio conditions. For the latter, statistically converged spectra are computed using conventional Fourier analyses techniques, whereas the former are investigated by way of time-frequency analysis. The findings suggest that at low nozzle pressure ratios -where the flow resides in a Free Shock Separation state- strong spectral similarities occur between fixed and transient conditions. Conversely, at higher nozzle pressure ratios -where the flow resides in Restricted Shock Separation- stark differences are observed between the fixed and transient conditions and depends greatly on the ramping rate of the transient period. And so, it appears that an understanding of the dynamics during transient start-up conditions cannot be furnished by a way of fixed flow analysis.

Baars, Woutijn J.; Tinney, Charles E.; Ruf, Joseph H.

2011-12-01

201

Perceptual learning for speech in noise after application of binary time-frequency masks.  

PubMed

Ideal time-frequency (TF) masks can reject noise and improve the recognition of speech-noise mixtures. An ideal TF mask is constructed with prior knowledge of the target speech signal. The intelligibility of a processed speech-noise mixture depends upon the threshold criterion used to define the TF mask. The study reported here assessed the effect of training on the recognition of speech in noise after processing by ideal TF masks that did not restore perfect speech intelligibility. Two groups of listeners with normal hearing listened to speech-noise mixtures processed by TF masks calculated with different threshold criteria. For each group, a threshold criterion that initially produced word recognition scores between 0.56-0.69 was chosen for training. Listeners practiced with one set of TF-masked sentences until their word recognition performance approached asymptote. Perceptual learning was quantified by comparing word-recognition scores in the first and last training sessions. Word recognition scores improved with practice for all listeners with the greatest improvement observed for the same materials used in training. PMID:23464038

Ahmadi, Mahnaz; Gross, Vauna L; Sinex, Donal G

2013-03-01

202

Prediction of nociceptive responses during sedation by time-frequency representation.  

PubMed

The level of sedation in patients undergoing medical procedures evolves continuously, such as the effect of the anesthetic and analgesic agents is counteracted by pain stimuli. The monitors of depth of anesthesia, based on the analysis of the electroencephalogram (EEG), have been progressively introduced into the daily practice to provide additional information about the state of the patient. However, the quantification of analgesia still remains an open problem. The purpose of this work is to analyze the capability of prediction of nociceptive responses based on the time-frequency representation (TFR) of EEG signal. Functions of spectral entropy, instantaneous power and instantaneous frequency were calculated in order to predict the presence or absence of the nociceptive responses to different stimuli during sedation in endoscopy procedure. Values of prediction probability of Pk above 0.75 and percentages of sensitivity and specificity above 70% and 65% respectively were achieved combining TFR functions with bispectral index (BIS) and with concentrations of propofol (CeProp) and remifentanil (CeRemi). PMID:24110246

Melia, Umberto; Vallverdu, Montserrat; Jospin, Mathieu; Jensen, Erik W; Valencia, Jose Fernando; Claria, Francesc; Gambus, Pedro L; Caminal, Pere

2013-07-01

203

Application Of The Time-Frequency Polarization Analysis Of The Wavefield For Seismic Noise Array Processing  

NASA Astrophysics Data System (ADS)

Microzonation studies using ambient noise measurements constitute an extended and useful procedure for determine the local soil characteristics and its response due to an earthquake. Several methods exist for analyzing the noise measurements, being the most popular the horizontal-to-vertical spectral ratio (H/V) and the array techniques, i.e. the frequency-wavenumber (F-K) transform. Many works exist about this topic and it stills being an ongoing debate about ambient noise composition, whether body or surface waves constitute most of it, showing the importance of identifying the different kinds of waves presents in a seismic record. In this work we utilize a new method of time-frequency polarization analysis, based on the stationary wavelet packet transform, to investigate how the polarization characteristics of the wavefield influence in the application of ambient noise techniques. The signals are divided in different bands, according to their reciprocal ellipticity values and then the H/V method and the F-K array analysis are computed for each band. The qualitative and quantitative comparison between the original curve and the obtained for the analyzed intervals provide information about the signals composition, showing that the major components of the seismic noise present reciprocal ellipticity values lower than 0.5. The efficient application of the studied techniques by using just the main a part of the entire signal, [0 - 0.5], is also evaluated, showing favorable results.

Galiana-Merino, J. J.; Rosa-Cintas, S.; Rosa-Herranz, J. L.; Molina-Palacios, S.; Martinez-Espla, J. J.

2011-12-01

204

Five-dimensional neuroimaging: Localization of the time-frequency dynamics of cortical activity  

PubMed Central

The spatiotemporal dynamics of cortical oscillations across human brain regions remain poorly understood because of a lack of adequately validated methods for reconstructing such activity from noninvasive electrophysiological data. In this paper, we present a novel adaptive spatial filtering algorithm optimized for robust source time-frequency reconstruction from magnetoencephalography (MEG) and electroencephalography (EEG) data. The efficacy of the method is demonstrated with simulated sources and is also applied to real MEG data from a self-paced finger movement task. The algorithm reliably reveals modulations both in the beta band (12–30 Hz) and high gamma band (65–90 Hz) in sensorimotor cortex. The performance is validated by both across-subjects statistical comparisons and by intracranial electrocorticography (ECoG) data from two epilepsy patients. Interestingly, we also reliably observed high frequency activity (30–300 Hz) in the cerebellum, though with variable locations and frequencies across subjects. The proposed algorithm is highly parallelizable and runs efficiently on modern high performance computing clusters. This method enables the ultimate promise of MEG and EEG for five-dimensional imaging of space, time, and frequency activity in the brain and renders it applicable for widespread studies of human cortical dynamics during cognition.

Dalal, Sarang S.; Guggisberg, Adrian G.; Edwards, Erik; Sekihara, Kensuke; Findlay, Anne M.; Canolty, Ryan T.; Berger, Mitchel S.; Knight, Robert T.; Barbaro, Nicholas M.; Kirsch, Heidi E.; Nagarajan, Srikantan S.

2008-01-01

205

Frequency and time-frequency analysis of intraoperative ECoG during awake brain stimulation  

PubMed Central

Electrocortical stimulation remains the standard for functional brain mapping of eloquent areas to prevent postoperative functional deficits. The aim of this study was to investigate whether the short-train technique (monopolar stimulation) and Penfield's technique (bipolar stimulation) would induce different effects on brain oscillatory activity in awake patients, as quantified by electrocorticography (ECoG). The study population was seven patients undergoing brain tumor surgery. Intraoperative bipolar and monopolar electrical stimulation for cortical mapping was performed during awake surgery. ECoG was recorded using 1 × 8 electrode strip. Spectral estimation was calculated using a parametric approach based on an autoregressive model. Wavelet-based time-frequency analysis was then applied to evaluate the temporal evolution of brain oscillatory activity. Both monopolar and bipolar stimulation produced an increment in delta and a decrease in beta powers for the motor and the sensory channels. These phenomena lasted about 4 s. Comparison between monopolar and bipolar stimulation showed no significant difference in brain activity. Given the importance of quantitative signal analysis for evaluating response accuracy, ECoG recording during electrical stimulation is necessary to characterize the dynamic processes underlying changes in cortical responses in vivo. This study is a preliminary approach to the quantitative analysis of post-stimulation ECoG signals.

Formaggio, Emanuela; Storti, Silvia F.; Tramontano, Vincenzo; Casarin, Agnese; Bertoldo, Alessandra; Fiaschi, Antonio; Talacchi, Andrea; Sala, Francesco; Toffolo, Gianna M.; Manganotti, Paolo

2013-01-01

206

Time-frequency analysis of transient pressure signals for a mechanical heart valve cavitation study.  

PubMed

A series of transient pressure signals (TPSs) can be measured using a miniature pressure transducer mounted near the tip of the inflow side of a mechanical heart valve (MHV) occluder during closure. A relationship appears to exist between the intensity and pattern of the TPS and the cavitation potential of a MHV. To study the relationship between MHV cavitation and the TPSs, we installed an MHV in a valve testing chamber of a digitally controlled burst test loop. A charge coupled device (CCD) camera and a personal computer based image grabbing program was used to visualize cavitation bubbles appearing on or near the occluder surface. One bileaflet MHV was used as the model for this study. Cavitation bubbles were observed within 300 microsec of the leaflet/housing impact. The valve was tested at various driving pressures between 100 and 1,300 mmHg. MHV cavitation bubble intensities were qualitatively classified into three categories: 1) strong, 2) weak, and 3) none. Digital images of the MHV occluder inflow surface were recorded simultaneously with the TPSs. TPSs were studied by the time-frequency analysis method (spectrogram) and correlated to MHV cavitation potential. The intensity of the cavitation bubbles was found to be associated with burst test loop driving pressures during leaflet closure. PMID:9804476

Yu, A A; White, J A; Hwang, N H

207

Models of the Joint Structure of Domain-Related and Global Distress: Implications for the Reconciliation of Quality of Life and Mental Health Perspectives  

Microsoft Academic Search

Research on subjective wellbeing includes studies of both domain-related and global distress. The mental health literature,\\u000a though, focuses almost exclusively on global distress. This seems to be partly due to a common belief that psychological distress,\\u000a and the moods that comprise distress, necessarily lack referential content. However, if that were the case it would make little\\u000a sense for any study

William Magee; Sébastien St-Arnaud

2012-01-01

208

Automated sleep stage identification system based on time-frequency analysis of a single EEG channel and random forest classifier.  

PubMed

In this work, an efficient automated new approach for sleep stage identification based on the new standard of the American academy of sleep medicine (AASM) is presented. The propose approach employs time-frequency analysis and entropy measures for feature extraction from a single electroencephalograph (EEG) channel. Three time-frequency techniques were deployed for the analysis of the EEG signal: Choi-Williams distribution (CWD), continuous wavelet transform (CWT), and Hilbert-Huang Transform (HHT). Polysomnographic recordings from sixteen subjects were used in this study and features were extracted from the time-frequency representation of the EEG signal using Renyi's entropy. The classification of the extracted features was done using random forest classifier. The performance of the new approach was tested by evaluating the accuracy and the kappa coefficient for the three time-frequency distributions: CWD, CWT, and HHT. The CWT time-frequency distribution outperformed the other two distributions and showed excellent performance with an accuracy of 0.83 and a kappa coefficient of 0.76. PMID:22178068

Fraiwan, Luay; Lweesy, Khaldon; Khasawneh, Natheer; Wenz, Heinrich; Dickhaus, Hartmut

2011-12-16

209

Detection of Heart Blocks in ECG Signals by Spectrum and Time-Frequency Analysis  

Microsoft Academic Search

The electrocardiogram (ECG) is a non-invasive test that records the electrical activity of the heart and is important in the investigation of cardiac abnormalities. Each portion of the ECG waveform carries various types of information for the cardiologists analyzing patient's heart condition. ECG interpretation at the present time remains dependent manually in time domain. It is difficult for the cardiologists

Norhashimah Mohd Saad; Abdul Rahim Abdullah; Yin Fen Low

2006-01-01

210

Specific Movement Detection in EEG Signal Using Time-Frequency Analysis  

Microsoft Academic Search

Recent research in BCI focuses not only on developing a new communication channel for severely handicapped people but also on applications for rehabilitation, multimedia, communication, virtual reality, entertainment and relaxation. Most of them fall in the domain of human-computer interfaces (HCIs) designed for interaction between brain, eyes, body and computer or robot. For brain signal acquisition several technologies have been

Haller Piroska; Szalai János

2008-01-01

211

Kernel design for time-frequency signal analysis using the Radon transform  

Microsoft Academic Search

The authors present a kernel design technique based on using the Radon transform of the modulus of the ambiguity function of the signal for determination of angles and distances of radially distributed contents of the autoterms in the ambiguity domain. The proposed kernel effectively reduces the cross-terms and noise for linear FM signals. The result is a tool for high-resolution

B. Ristic; B. Boashash

1993-01-01

212

Condition monitoring of wooden railway sleepers using time-frequency techniques and pattern classification  

Microsoft Academic Search

Railway sleepers are a key engineering element of all railways. Lack of much sophistication in monitoring railway sleepers makes it a key problem within the rail transportation domain. Current day condition monitoring applications involving wooden railway sleepers are mostly carried out through visual inspection and if necessary some impact acoustic examination is carried out. Decision making is largely based on

Siril Yella; Samira Ghiamati; Marc Dougherty

2009-01-01

213

Adaptive multicarrier modulation: a convenient framework for time-frequency processing in wireless communications  

Microsoft Academic Search

A historical perspective of orthogonal frequency-division multiplexing (OFDM) is given with reference to its literature. Its advantages and disadvantages are reviewed, and its performance is characterized over highly dispersive channels. The effects of both time- and frequency-domain synchronization errors are quantified, and a range of solutions proposed in the recent literature are reviewed. One of the main objectives of this

THOMAS KELLER; LAJOS HANZO

2000-01-01

214

Astrophysically motivated time frequency clustering for burst gravitational wave search: application to TAMA300 data  

NASA Astrophysics Data System (ADS)

We have developed a method of 'time frequency (TF) clustering' to find burst gravitational waves for TAMA data analysis. The TF clustering method on the sonogram (spectrogram) shows some characteristics of short-duration signals. Burst gravitational waveforms from stellar-core collapse of supernovae that are predicted by Dimmelmeier et al [1, 2] (DFM waveforms) have short durations on the order of 10 ms and have a large spike and ringing tail in time series. On the other hand, typical detector instrumental noise transients of the same timescale have different waveforms as like as simpler spikes. Since the numerically predicted waveforms may not be reliable given conditions and model dependency, using one search algorithm is not robust to differentiate gravitational waves from instrumental noises. Our proposal for performing the separation is to compare many parameters of the cluster that represent the signal waveform. This approach will be useful for cases when the difference between gravitational waves and noise is not clear for one parameter. We employ TF clustering to represent the waveform characteristics. We calculated the parameters of each respective cluster, such as the magnitude and the Nth momentum around the center of a power distribution of the cluster. Using these parameters, we can efficiently identify some predicted gravitational waveforms and can exclude the TAMA detector's typical unstable spike-like noises due to the instruments. Our selection criteria for TF cluster shape parameters achieved an average efficiency of roughly 50% for injected DFM waveforms of h_rss\\sim 2 \\times 10^{-20}\\; {Hz^{-1/2}} (source distance of 350 pc) with false alarm rate of ~1 Hz. In addition, the false alarm rate for larger noises, such as SNR > 100, is improved 10-fold by applying the selection criteria for TF cluster parameters.

Honda, Ryota; Yamagishi, Shougo; Kanda, Nobuyuki; TAMA Collaboration

2008-09-01

215

Time frequency analysis of sea level anomaly data corrected for centre of Earth mass variations model  

NASA Astrophysics Data System (ADS)

The accuracy of the Earth centre of mass coordinates has a significant influence on altimetric measurements accuracy because altimetric satellites orbit around temporary Earth centre of mass meanwhile orbits of these satellites are determined in the terrestrial reference frame with fixed origin (currently ITRF2008). The systematic errors in sea level variations are caused by systematic errors of altimetric satellites orbits and station coordinates determined in the ITRF. The investigations have shown that the determination of the centre of mass of the Earth estimated from SLR and GNSS measurements is so accurate that it is possible to model it with a precision of 1 mm. The common signal in the centre of mass time series has been found using the wavelet based semblance filtering. The highest amplitude of the annual retrograde oscillation in this signal is of the order of 5mm in the equatorial plane. The wavelet based semblance filtering model, can be then used to correct the global sea level anomalies (SLA) data available from AVISO for systematic errors due to centre of mass variations. The time-frequency analysis of the SLA data and corrected SLA for centre of mass variations were carried out. The amplitudes and phases of oscillations in the SLA data as a function of geographic latitude and longitude with periods ranging from about 30 to 400 days were computed using the Fourier transform band pass filter and other spectro-temporal analyzes based on the wavelet transform. It was shown that in the equatorial region the amplitudes of the annual oscillation in the SLA data were slightly changed after applying the Earth centre of mass correction.

Zbylut, Maria; Kosek, Wies?aw; Wn?k, Agnieszka; Niedzielski, Tomasz

2013-04-01

216

A comparative study on hydrocarbon detection using three EMD-based time–frequency analysis methods  

NASA Astrophysics Data System (ADS)

Due to strong heterogeneity of marine carbonate reservoir, seismic signals become more complex, thus, it is very difficult for hydrocarbon detection. In hydrocarbon reservoir, there usually exist some changes in seismic wave energy and frequency. In their instantaneous spectrums there often exist such phenomena that show the characteristics of attenuation of high frequency energy and enhancement of low-frequency energy. The three EMD-based time-frequency analysis methods' instantaneous spectra all have certain oil and gas detection capability. In this paper, we introduced the Normalized Hilbert Transform (NHT) and a new method named the HU method for hydrocarbon detection. The model results in the Jingbian Gas Field which is located in the eastern Ordos Basin, China, show that NHT and HU methods can be adopted. They also detect the gas-bearing reservoir efficiently as the HHT method does. The three EMD-based methods, that is, the Hilbert–Huang transformation (HHT) and NHT and HU methods, were respectively applied to analyze the seismic data from the Jingbian Gas Field. Firstly, the seismic signals were decomposed into a finite number of intrinsic mode functions (IMFs) by empirical mode decomposition (EMD) method. The second IMF signal (IMF2) of the original seismic section better indicates the distribution of the reservoir. Information on hydrocarbon-bearing reservoir is mainly in IMF2. Secondly, the HHT, NHT and HU methods were respectively used to obtain different frequency division sections from IMF2. Hydrocarbon detection was realized from the energy distribution of the different frequency division sections with these three EMD-based methods. The practical application results show that the three EMD-based methods can all be employed to hydrocarbon detection. Frequency division section of IMF2 using NHT method was better for the seismic data from the Jingbian Gas Field than when using the HHT method and HU method.

Xue, Ya-juan; Cao, Jun-xing; Tian, Ren-fei

2013-02-01

217

Space Object Characterization Using Time-Frequency Analysis of Multispectral Measurements from the Magdalena Ridge Observatory  

NASA Astrophysics Data System (ADS)

The interactions between the surface materials and the body dynamics complicate the characterization of space objects from their optical signatures. One method for decoupling these two effects on the observed signature is to obtain simultaneous measurements using multiple spectral filter bands. The advantage of this approach is that it provides spectral resolution between the filter bands to identify the different materials based on their optical properties as a function of wavelength and temporal resolution between samples to identify the periodic, quasi-periodic, and transient fluctuations characteristic of the object motions, including attitude control, maneuvers, and station-keeping. We have developed algorithms to extract and to analyze light curve data from unresolved resident space objects (RSO) collected at the Magdalena Ridge Observatory (MRO) using the Multi Lens Array (MLA) camera coupled to the 2.4-m telescope. The MLA camera produces 16 spectrally-filtered and temporally synchronous sub-images ranging from 414 nm to 845 nm. We have developed a filter band calibration using a set of stellar observations to remove the atmospheric refraction and absorption effects and differences in the optical paths across the different filter bands using catalogued spectrophotometric data. We apply wavelet analysis to the RSO optical signature light curves to obtain the time-frequency characteristics of the signal for each band. This information allows us to obtain information about the body motions as a function of time. We next attempt to correlate these characteristics across the different MLA filter bands to derive constraints on the types of surface materials. In this presentation, we will present results from several case studies to demonstrate the effectiveness of our approach and to provide guidance on the effectiveness of different spectral bands for space object characterization.

Alcala, C.; Brown, J.

218

Output only modal identification and structural damage detection using time frequency & wavelet techniques  

NASA Astrophysics Data System (ADS)

The primary objective of this paper is to develop output only modal identification and structural damage detection. Identification of multi-degree of freedom (MDOF) linear time invariant (LTI) and linear time variant (LTV—due to damage) systems based on Time-frequency (TF) techniques—such as short-time Fourier transform (STFT), empirical mode decomposition (EMD), and wavelets—is proposed. STFT, EMD, and wavelet methods developed to date are reviewed in detail. In addition a Hilbert transform (HT) approach to determine frequency and damping is also presented. In this paper, STFT, EMD, HT and wavelet techniques are developed for decomposition of free vibration response of MDOF systems into their modal components. Once the modal components are obtained, each one is processed using Hilbert transform to obtain the modal frequency and damping ratios. In addition, the ratio of modal components at different degrees of freedom facilitate determination of mode shape. In cases with output only modal identification using ambient/random response, the random decrement technique is used to obtain free vibration response. The advantage of TF techniques is that they are signal based; hence, can be used for output only modal identification. A three degree of freedom 1:10 scale model test structure is used to validate the proposed output only modal identification techniques based on STFT, EMD, HT, wavelets. Both measured free vibration and forced vibration (white noise) response are considered. The secondary objective of this paper is to show the relative ease with which the TF techniques can be used for modal identification and their potential for real world applications where output only identification is essential. Recorded ambient vibration data processed using techniques such as the random decrement technique can be used to obtain the free vibration response, so that further processing using TF based modal identification can be performed.

Nagarajaiah, S.; Basu, B.

2009-12-01

219

Speckle suppression in Fourier domain optical coherence tomography by fractional Fourier domain compounding  

NASA Astrophysics Data System (ADS)

We propose a new numerical method for speckle reduction in Fourier domain OCT based on incoherent averaging of fractional Fourier domains of a single A-scan. Fractional Fourier transforms represent projections in the time-frequency space and thus, this method simultaneously compensates for group velocity dispersion.

Lippok, Norman; Vanholsbeeck, Frédérique; Nielsen, Poul

2013-06-01

220

Using wavelets to decompose the time frequency effects of monetary policy  

NASA Astrophysics Data System (ADS)

Central banks have different objectives in the short and long run. Governments operate simultaneously at different timescales. Many economic processes are the result of the actions of several agents, who have different term objectives. Therefore, a macroeconomic time series is a combination of components operating on different frequencies. Several questions about economic time series are connected to the understanding of the behavior of key variables at different frequencies over time, but this type of information is difficult to uncover using pure time-domain or pure frequency-domain methods. To our knowledge, for the first time in an economic setup, we use cross-wavelet tools to show that the relation between monetary policy variables and macroeconomic variables has changed and evolved with time. These changes are not homogeneous across the different frequencies.

Aguiar-Conraria, Luís; Azevedo, Nuno; Soares, Maria Joana

2008-05-01

221

Applying time, frequency and nonlinear features from nocturnal oximetry to OSA diagnosis  

Microsoft Academic Search

This study is aimed to improve the diagnostic ability of blood oxygen saturation (SaO2) in obstructive sleep apnea (OSA) detection. We studied 74 patients suspected of suffering from OSA. Ten characteristics were derived from each SaO2 recording: arithmetic mean, variance, skewness and kurtosis from both time and frequency domains, central tendency measure and Lempel-Ziv complexity. The diagnostic ability of each

Daniel Alvarez; Roberto Hornero; J. Victor Marcos; Felix del Campo; Carlos Zamarron; Miguel Lopez

2008-01-01

222

Moment tensor inversion of waveforms: a two-step time-frequency approach  

NASA Astrophysics Data System (ADS)

We present a moment tensor inversion of waveforms, which is more robust and yields more stable and more accurate results than standard approaches. The inversion is performed in two steps and combines inversions in time and frequency domains. First, the inversion for the source-time function is performed in the frequency domain using complex spectra. Second, the time-domain inversion for the moment tensor is performed using the source-time function calculated in the first step. In this way, we can consider a realistic, complex source-time function and still keep the final moment tensor inversion linear. Using numerical modelling, we compare the efficiency and accuracy of the proposed approach with standard waveform inversions. We study the sensitivity of the retrieved double-couple and non-double-couple components of the moment tensors to noise in the data, to inaccuracies of the location and of the velocity model, and to the type of the focal mechanism. Finally, the proposed moment tensor inversion is tested on real data observed in a complex 3-D inhomogeneous geological environment: a production blast and a rockburst in the Pyhäsalmi ore mine, Finland.

Vavry?uk, Václav; Kühn, Daniela

2012-09-01

223

Identification of Damaged Wheat Kernels and Cracked-Shell Hazelnuts with Impact Acoustics Time-Frequency Patterns  

Technology Transfer Automated Retrieval System (TEKTRAN)

A new adaptive time-frequency (t-f) analysis and classification procedure is applied to impact acoustic signals for detecting hazelnuts with cracked shells and three types of damaged wheat kernels. Kernels were dropped onto a steel plate, and the resulting impact acoustic signals were recorded with ...

224

Identification of Different Types of Partial Discharge Sources from Acoustic Emission Signals in the Time-Frequency Representation  

Microsoft Academic Search

The subject matter of this paper is to introduce the time-frequency representation in analyzing the acoustic emission signals emitted by partial discharge sources. Three different types of partial discharge sources used to generate the acoustic emission signals during the partial discharge (PD) occurrences are created in an experimental tank filled with transformer oil. These partial discharge sources are the plain

M. L. Chai; Y. H. M. Thayoob; P. S. Ghosh; A. Z. Sha'ameri; M. A. Talib

2006-01-01

225

Space–time–frequency analysis of EEG data using within-subject statistical tests followed by sequential PCA  

Microsoft Academic Search

A new method is developed for analyzing the time-varying spectral content of EEG data collected in cognitive tasks. The goal is to extract and summarize the most salient features of numerical results, which span space, time, frequency, task conditions, and multiple subjects. Direct generalization of an established approach for analyzing event-related potentials, which uses sequential PCA followed by ANOVA to

Thomas C. Ferree; Matthew R. Brier; John Hart Jr; Michael A. Kraut

2009-01-01

226

Use of the cross time-frequency distribution for the analysis of the class of PSK signals  

Microsoft Academic Search

Phase Shift- Keying (PSK) modulation has been applied widely in most of the data communication system nowadays due to its noise immunity and bandwidth efficiency capability. Analysis of digital modulation is an important component of spectrum monitoring. Furthermore, it has been identified recently that spectrum sensing is part of the function in cognitive radio. Works on bilinear time-frequency distribution (TFD)

Chee Yen Mei; A. Z. Sha'ameri

2010-01-01

227

Applications of time-frequency and time-scale transforms to ultra-wideband radar transient signal detection  

NASA Astrophysics Data System (ADS)

In this paper we use a non-stationary approach and analyze ultra-wideband (UWB) radar data using time-frequency and time-scale transformations. The time-frequency transformations considered are the Short-Time Fourier Transform (STFT), the Wigner-Ville Distribution (WD), the Instantaneous Power Spectrum (IPS), and the ZAM transform. Two discrete implementations of the Wavelet Transform (DWT) are also investigated: the decimated A- trous algorithm proposed by Holschneider et al, which uses non-orthogonal wavelets; and the Mallat algorithm, which employs orthogonal wavelets. The transients under study are UWB radar returns from a boat (with and without corner reflector) in the presence of sea clutter, multipath, and radio frequency interferences (RFI). Results show that all time-frequency and time-scale transforms clearly detect the transient radar returns corresponding to the boat with a corner reflector. However, as the radar cross section of the target decreases (boat without a corner reflector), results change drastically as the RFI component dominates the signal. Simulations show that the Instantaneous Power Spectrum may be better adapted for localizing the transient among the time-frequency techniques studied. The decimated A-trous algorithm has the best time resolution of the techniques studied as the return appears better localized in the scalogram.

Fargues, Monique P.; Brooks, William A.

1993-11-01

228

Target ranging and the role of time-frequency structure of synthetic echoes in big brown bats, Eptesicus fuscus  

Microsoft Academic Search

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.

Annemarie Surlykke

1992-01-01

229

Time-Frequency-Wavenumber Analysis of Surface Waves Using the Continuous Wavelet Transform  

NASA Astrophysics Data System (ADS)

A modified approach to surface wave dispersion analysis using active sources is proposed. The method is based on continuous recordings, and uses the continuous wavelet transform to analyze the phase velocity dispersion of surface waves. This gives the possibility to accurately localize the phase information in time, and to isolate the most significant contribution of the surface waves. To extract the dispersion information, then, a hybrid technique is applied to the narrowband filtered seismic recordings. The technique combines the flexibility of the slant stack method in identifying waves that propagate in space and time, with the resolution of f- k approaches. This is particularly beneficial for higher mode identification in cases of high noise levels. To process the continuous wavelet transform, a new mother wavelet is presented and compared to the classical and widely used Morlet type. The proposed wavelet is obtained from a raised-cosine envelope function (Hanning type). The proposed approach is particularly suitable when using continuous recordings (e.g., from seismological-like equipment) since it does not require any hardware-based source triggering. This can be subsequently done with the proposed method. Estimation of the surface wave phase delay is performed in the frequency domain by means of a covariance matrix averaging procedure over successive wave field excitations. Thus, no record stacking is necessary in the time domain and a large number of consecutive shots can be used. This leads to a certain simplification of the field procedures. To demonstrate the effectiveness of the method, we tested it on synthetics as well on real field data. For the real case we also combine dispersion curves from ambient vibrations and active measurements.

Poggi, V.; Fäh, D.; Giardini, D.

2013-03-01

230

Classification of the intention to generate a shoulder versus elbow torque by means of a time frequency synthesized spatial patterns BCI algorithm  

NASA Astrophysics Data System (ADS)

In this paper, we attempt to determine a subject's intention of generating torque at the shoulder or elbow, two neighboring joints, using scalp electroencephalogram signals from 163 electrodes for a brain-computer interface (BCI) application. To achieve this goal, we have applied a time-frequency synthesized spatial patterns (TFSP) BCI algorithm with a presorting procedure. Using this method, we were able to achieve an average recognition rate of 89% in four healthy subjects, which is comparable to the highest rates reported in the literature but now for tasks with much closer spatial representations on the motor cortex. This result demonstrates, for the first time, that the TFSP BCI method can be applied to separate intentions between generating static shoulder versus elbow torque. Furthermore, in this study, the potential application of this BCI algorithm for brain-injured patients was tested in one chronic hemiparetic stroke subject. A recognition rate of 76% was obtained, suggesting that this BCI method can provide a potential control signal for neural prostheses or other movement coordination improving devices for patients following brain injury.

Deng, Jie; Yao, Jun; Dewald, Julius P. A.

2005-12-01

231

Ceramic joints  

DOEpatents

Butt joints between materials having different coefficients of thermal expansion are prepared having a reduced probability of failure of stress facture. This is accomplished by narrowing/tapering the material having the lower coefficient of thermal expansion in a direction away from the joint interface and not joining the narrow-tapered surface to the material having the higher coefficient of thermal expansion.

Miller, Bradley J. (Worcester, MA); Patten, Jr., Donald O. (Sterling, MA)

1991-01-01

232

High-resolution time-frequency representations based on the local polynomial Fourier transform for over-the-horizon radars  

NASA Astrophysics Data System (ADS)

In this paper, we consider resolving over-the-horizon radar (OTHR) Doppler returns. A high-resolution time-frequency (TF) representation of the received signal is obtained by using the local polynomial Fourier transform (LPFT). From the optimally concentrated LPFT, multicomponent Doppler signatures, which are only several frequency bins apart, are extracted using an instantaneous frequency estimation method based on the Viterbi algorithm. The performance of the proposed method is validated using real data.

Djurovic, Igor; Djukanovic, Slobodan; Amin, Moeness G.; Zhang, Yimin D.; Himed, Braham

2012-05-01

233

Joint Replacement (Finger and Wrist Joints)  

MedlinePLUS

... mean to have a “joint replacement” or an “artificial joint”? The abnormal bone and lining structures of ... When should joint replacement surgery NOT be done? Artificial joints should not be done when: There is ...

234

Joint Multi-Pitch Detection Using Harmonic Envelope Estimation for Polyphonic Music Transcription  

Microsoft Academic Search

In this paper, a method for automatic transcrip- tion of music signals based on joint multiple-F0 estimation is proposed. As a time-frequency representation, the constant-Q resonator time-frequency image is employed, while a novel noise suppression technique based on pink noise assumption is applied in a preprocessing step. In the multiple-F0 estimation stage, the optimal tuning and inharmonicity parameters are computed

Emmanouil Benetos; Simon Dixon

2011-01-01

235

Real-time, frequency-translated holographic visualization of surface acoustic wave interactions with surface-breaking defects.  

PubMed

A real-time, frequency-translated holographic imaging system has been developed by use of bacteriorhodopsin film. The system provides a capability for imaging surface acoustic waves and has been utilized to detect and characterize surface-breaking defects through near-field ultrasonic scattering effects. Frequency-plane filtering was used to discriminate between ultrasonic standing-wave and near-field scattering features, dramatically enhancing the holographic visualization of the defect sites. A detailed description of the system is presented, along with representative holographic images showing the interaction of surface acoustic waves with surface-breaking cracks and small notches in aluminum and titanium substrates. PMID:18026353

Blackshire, James L; Sathish, Shamachary; Duncan, Bradley D; Millard, Mike

2002-06-15

236

Normal and hypoacoustic infant cry signal classification using time-frequency analysis and general regression neural network.  

PubMed

Crying is the most noticeable behavior of infancy. Infant cry signals can be used to identify physical or psychological status of an infant. Recently, acoustic analysis of infant cry signal has shown promising results and it has been proven to be an excellent tool to investigate the pathological status of an infant. This paper proposes short-time Fourier transform (STFT) based time-frequency analysis of infant cry signals. Few statistical features are derived from the time-frequency plot of infant cry signals and used as features to quantify infant cry signals. General Regression Neural Network (GRNN) is employed as a classifier for discriminating infant cry signals. Two classes of infant cry signals are considered such as normal cry signals and pathological cry signals from deaf infants. To prove the reliability of the proposed features, two neural network models such as Multilayer Perceptron (MLP) and Time-Delay Neural Network (TDNN) trained by scaled conjugate gradient algorithm are also used as classifiers. The experimental results show that the GRNN classifier gives very promising classification accuracy compared to MLP and TDNN and the proposed method can effectively classify normal and pathological infant cries. PMID:21824676

Hariharan, M; Sindhu, R; Yaacob, Sazali

2011-08-07

237

Time-frequency integration characteristics of hearing are optimized for perception of speech-like acoustic patterns.  

PubMed

Several psychoacoustic phenomena such as loudness perception, absolute thresholds of hearing, and perceptual grouping in time are affected by temporal integration of the signal in the auditory system. Similarly, the frequency resolution of the hearing system, often expressed in terms of critical bands, implies signal integration across neighboring frequencies. Although progress has been made in understanding the neurophysiological mechanisms behind these processes, the underlying reasons for the observed integration characteristics have remained poorly understood. The current work proposes that the temporal and spectral integration are a result of a system optimized for pattern detection from ecologically relevant acoustic inputs. This argument is supported by a simulation where the average time-frequency structure of speech that is derived from a large set of speech signals shows a good match to the time-frequency characteristics of the human auditory system. The results also suggest that the observed integration characteristics are learnable from acoustic inputs of the auditory environment using a Hebbian-like learning rule. PMID:23862817

Räsänen, Okko; Laine, Unto K

2013-07-01

238

RAPID COMMUNICATION: A novel time frequency-based 3D Lissajous figure method and its application to the determination of oxygen saturation from the photoplethysmogram  

NASA Astrophysics Data System (ADS)

We present a novel time-frequency method for the measurement of oxygen saturation using the photoplethysmogram (PPG) signals from a standard pulse oximeter machine. The method utilizes the time-frequency transformation of the red and infrared PPGs to derive a 3D Lissajous figure. By selecting the optimal Lissajous, the method provides an inherently robust basis for the determination of oxygen saturation as regions of the time-frequency plane where high- and low-frequency signal artefacts are to be found are automatically avoided.

Addison, Paul S.; Watson, James N.

2004-11-01

239

Teaching Children with Autism to Respond to Joint Attention Initiations  

Microsoft Academic Search

Children with autism fail to develop joint attention skills appropriate to developmental age. Joint attention is a predictor of ability in several core domains of autism including language, social development, affective sharing, and theory of mind capacity, thus establishing the significance of teaching joint attention. However, there is limited research to assist clinicians with methods to teach this skill. The

Megan P. Martins; Sandra L. Harris

2006-01-01

240

Comparison of Time-Frequency Responses and the Event-Related Potential to Auditory Speech Stimuli in Human Cortex  

PubMed Central

We recorded the electrocorticogram directly from the exposed cortical surface of awake neurosurgical patients during the presentation of auditory syllable stimuli. All patients were unanesthetized as part of a language-mapping procedure for subsequent left-hemisphere tumor resection. Time–frequency analyses showed significant high-gamma (?high: 70–160 Hz) responses from the left superior temporal gyrus, but no reliable response from the left inferior frontal gyrus. Alpha suppression (?: 7–14 Hz) and event-related potential responses exhibited a more widespread topography. Across electrodes, the ? suppression from 200 to 450 ms correlated with the preceding (50–200 ms) ?high increase. The results are discussed in terms of the different physiological origins of these electrocortical signals.

Edwards, Erik; Soltani, Maryam; Kim, Won; Dalal, Sarang S.; Nagarajan, Srikantan S.; Berger, Mitchel S.; Knight, Robert T.

2009-01-01

241

Performance analysis for time-frequency MUSIC algorithm in presence of both additive noise and array calibration errors  

NASA Astrophysics Data System (ADS)

This article deals with the application of Spatial Time-Frequency Distribution (STFD) to the direction finding problem using the Multiple Signal Classification (MUSIC)algorithm. A comparative performance analysis is performed for the method under consideration with respect to that using data covariance matrix when the received array signals are subject to calibration errors in a non-stationary environment. An unified analytical expression of the Direction Of Arrival (DOA) error estimation is derived for both methods. Numerical results show the effect of the parameters intervening in the derived expression on the algorithm performance. It is particularly observed that for low Signal to Noise Ratio (SNR) and high Signal to sensor Perturbation Ratio (SPR) the STFD method gives better performance, while for high SNR and for the same SPR both methods give similar performance.

Khodja, Mohamed; Belouchrani, Adel; Abed-Meraim, Karim

2012-12-01

242

Probing neural activations from continuous EEG in a real-world task: time-frequency independent component analysis.  

PubMed

It is of fundamental significance to study human brain functions using neuroimaging technologies, such as electroencephalograph (EEG) and functional magnetic resonance imaging (fMRI), in real-world tasks. The present study explores the feasibility of using EEG to identify networked brain activations when subjects perform a realistic task. To robustly identify physiologically plausible EEG patterns related to brain activations involved in the task, a novel data-driven method, i.e., time-frequency independent component analysis (tfICA), is developed to analyze high-density EEG data, which combines the time-frequency analysis and complex-valued ICA method. Six classes of independent components (ICs) of various spatio-temporal-spectral patterns were identified across subjects, relating to frontal, motor, premotor, supplementary motor, secondary somatosensory, and occipital cortices, which suggest a networked brain activation involving visual perception and processing, movement planning and execution, working memory, performance monitoring, and decision making to accomplish the task. Our results indicate that temporal patterns of these ICs are consistent, show causal relationship among them, and of significant correlation to behavioral performance data recorded in same task sessions. Furthermore, the time-on-task effect that indicates the phenomenon of mental fatigue in sustained tasks for a long duration (i.e., 1h) was observed. The present study demonstrates the capability of the tfICA method in distinguishing various brain processes from continuous EEG data obtained in a realistic task and it is thus promising to address real-world problems, such as time-on-task fatigue. PMID:22659004

Shou, Guofa; Ding, Lei; Dasari, Deepika

2012-05-30

243

TIME-FREQUENCY ANALYSIS OF THE SUPERORBITAL MODULATION OF THE X-RAY BINARY SMC X-1 USING THE HILBERT-HUANG TRANSFORM  

SciTech Connect

The high-mass X-ray binary SMC X-1 exhibits a superorbital modulation with a dramatically varying period ranging between {approx}40 days and {approx}60 days. This research studies the time-frequency properties of the superorbital modulation of SMC X-1 based on the observations made by the All-Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE). We analyzed the entire ASM database collected since 1996. The Hilbert-Huang transform (HHT), developed for non-stationary and nonlinear time-series analysis, was adopted to derive the instantaneous superorbital frequency. The resultant Hilbert spectrum is consistent with the dynamic power spectrum as it shows more detailed information in both the time and frequency domains. The RXTE observations show that the superorbital modulation period was mostly between {approx}50 days and {approx}65 days, whereas it changed to {approx}45 days around MJD 50,800 and MJD 54,000. Our analysis further indicates that the instantaneous frequency changed to a timescale of hundreds of days between {approx}MJD 51,500 and {approx}MJD 53,500. Based on the instantaneous phase defined by HHT, we folded the ASM light curve to derive a superorbital profile, from which an asymmetric feature and a low state with barely any X-ray emissions (lasting for {approx}0.3 cycles) were observed. We also calculated the correlation between the mean period and the amplitude of the superorbital modulation. The result is similar to the recently discovered relationship between the superorbital cycle length and the mean X-ray flux for Her X-1.

Hu, Chin-Ping; Chou, Yi; Yang, Ting-Chang; Su, Yi-Hao [Graduate Institute of Astronomy, National Central University, Jhongli 32001, Taiwan (China); Wu, Ming-Chya, E-mail: m929011@astro.ncu.edu.tw, E-mail: yichou@astro.ncu.edu.tw [Research Center for Adaptive Data Analysis, National Central University, Jhongli 32001, Taiwan (China)

2011-10-20

244

Time-frequency Analysis of the Superorbital Modulation of the X-Ray Binary SMC X-1 Using the Hilbert-Huang Transform  

NASA Astrophysics Data System (ADS)

The high-mass X-ray binary SMC X-1 exhibits a superorbital modulation with a dramatically varying period ranging between ~40 days and ~60 days. This research studies the time-frequency properties of the superorbital modulation of SMC X-1 based on the observations made by the All-Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE). We analyzed the entire ASM database collected since 1996. The Hilbert-Huang transform (HHT), developed for non-stationary and nonlinear time-series analysis, was adopted to derive the instantaneous superorbital frequency. The resultant Hilbert spectrum is consistent with the dynamic power spectrum as it shows more detailed information in both the time and frequency domains. The RXTE observations show that the superorbital modulation period was mostly between ~50 days and ~65 days, whereas it changed to ~45 days around MJD 50,800 and MJD 54,000. Our analysis further indicates that the instantaneous frequency changed to a timescale of hundreds of days between ~MJD 51,500 and ~MJD 53,500. Based on the instantaneous phase defined by HHT, we folded the ASM light curve to derive a superorbital profile, from which an asymmetric feature and a low state with barely any X-ray emissions (lasting for ~0.3 cycles) were observed. We also calculated the correlation between the mean period and the amplitude of the superorbital modulation. The result is similar to the recently discovered relationship between the superorbital cycle length and the mean X-ray flux for Her X-1.

Hu, Chin-Ping; Chou, Yi; Wu, Ming-Chya; Yang, Ting-Chang; Su, Yi-Hao

2011-10-01

245

Increasing sensitivity in the measurement of heart rate variability: the method of non-stationary RR time-frequency analysis.  

PubMed

A novel method of the time-frequency analysis of non-stationary heart rate variability (HRV) is developed which introduces the fragmentary spectrum as a measure that brings together the frequency content, timing and duration of HRV segments. The fragmentary spectrum is calculated by the similar basis function algorithm. This numerical tool of the time to frequency and frequency to time Fourier transformations accepts both uniform and non-uniform sampling intervals, and is applicable to signal segments of arbitrary length. Once the fragmentary spectrum is calculated, the inverse transform recovers the original signal and reveals accuracy of spectral estimates. Numerical experiments show that discontinuities at the boundaries of the succession of inter-beat intervals can cause unacceptable distortions of the spectral estimates. We have developed a measure that we call the "RR deltagram" as a form of the HRV data that minimises spectral errors. The analysis of the experimental HRV data from real-life and controlled breathing conditions suggests transient oscillatory components as functionally meaningful elements of highly complex and irregular patterns of HRV. PMID:22306071

Melkonian, D; Korner, A; Meares, R; Bahramali, H

2012-02-10

246

Recognition of speech in noise after application of time-frequency masks: dependence on frequency and threshold parameters.  

PubMed

Binary time-frequency (TF) masks can be applied to separate speech from noise. Previous studies have shown that with appropriate parameters, ideal TF masks can extract highly intelligible speech even at very low speech-to-noise ratios (SNRs). Two psychophysical experiments provided additional information about the dependence of intelligibility on the frequency resolution and threshold criteria that define the ideal TF mask. Listeners identified AzBio Sentences in noise, before and after application of TF masks. Masks generated with 8 or 16 frequency bands per octave supported nearly-perfect identification. Word recognition accuracy was slightly lower and more variable with 4 bands per octave. When TF masks were generated with a local threshold criterion of 0 dB SNR, the mean speech reception threshold was -9.5 dB SNR, compared to -5.7 dB for unprocessed sentences in noise. Speech reception thresholds decreased by about 1 dB per dB of additional decrease in the local threshold criterion. Information reported here about the dependence of speech intelligibility on frequency and level parameters has relevance for the development of non-ideal TF masks for clinical applications such as speech processing for hearing aids. PMID:23556604

Sinex, Donal G

2013-04-01

247

Compressive sampling of swallowing accelerometry signals using time-frequency dictionaries based on modulated discrete prolate spheroidal sequences  

NASA Astrophysics Data System (ADS)

Monitoring physiological functions such as swallowing often generates large volumes of samples to be stored and processed, which can introduce computational constraints especially if remote monitoring is desired. In this article, we propose a compressive sensing (CS) algorithm to alleviate some of these issues while acquiring dual-axis swallowing accelerometry signals. The proposed CS approach uses a time-frequency dictionary where the members are modulated discrete prolate spheroidal sequences (MDPSS). These waveforms are obtained by modulation and variation of discrete prolate spheroidal sequences (DPSS) in order to reflect the time-varying nature of swallowing acclerometry signals. While the modulated bases permit one to represent the signal behavior accurately, the matching pursuit algorithm is adopted to iteratively decompose the signals into an expansion of the dictionary bases. To test the accuracy of the proposed scheme, we carried out several numerical experiments with synthetic test signals and dual-axis swallowing accelerometry signals. In both cases, the proposed CS approach based on the MDPSS yields more accurate representations than the CS approach based on DPSS. Specifically, we show that dual-axis swallowing accelerometry signals can be accurately reconstructed even when the sampling rate is reduced to half of the Nyquist rate. The results clearly indicate that the MDPSS are suitable bases for swallowing accelerometry signals.

Sejdi?, Ervin; Can, Azime; Chaparro, Luis F.; Steele, Catriona M.; Chau, Tom

2012-12-01

248

Muscle fatigue during cross country sprint assessed by activation patterns and electromyographic signals time-frequency analysis.  

PubMed

The aims of this study were as follows: (i) analysis of activation patterns during the spurt of two heats of a cross country skiing sprint with the double poling technique and (ii) quantification of muscle fatigue of the investigated muscles. Eight elite skiers were tested and surface electromyographic signals (EMG) were recorded from seven muscles of the upper and lower limbs. For each subject and each muscle, the activation intervals were calculated for relying on a double-threshold statistical detector and the average rectified value was calculated on each activation interval. The detected activations were processed by a time-frequency algorithm in order to assess the progression of muscle fatigue. The EMG activation patterns and EMG amplitude highlighted no significant difference between the two spurts, despite a generally lower speed in the second spurt. The frequency analysis showed that upper body muscles are the first to be affected by fatigue and that clear signs of muscle fatigue appear right from the first spurt of the sprint simulation (i.e., biceps and triceps brachii) with a decrease in the instantaneous mean frequency. Biceps brachii activations and fatigue demonstrated the involvement of this muscle in propulsion. PMID:20492586

Zory, R; Molinari, F; Knaflitz, M; Schena, F; Rouard, A

2010-05-12

249

Joint multipath-Doppler diversity in fast fading channels  

Microsoft Academic Search

We present a new framework for code-division multiple access (CDMA) communication over fast fading mobile wireless channels. The performance of the RAKE receiver, which is at the heart of existing CDMA systems, degrades substantially under fast fading encountered in many mobile scenarios. Due to the time-varying nature of the fast fading channel, we employ joint time-frequency processing, which is a

Akbar Sayeed; Behnaam Aazhang

1998-01-01

250

Decoding a bistable percept with integrated time-frequency representation of single-trial local field potential  

NASA Astrophysics Data System (ADS)

Bistable perception emerges when a stimulus under continuous view is perceived as the alternation of two mutually exclusive states. Such a stimulus provides a unique opportunity for understanding the neural basis of visual perception because it dissociates the perception from the visual input. In this paper we analyze the dynamic activity of local field potential (LFP), simultaneously collected from multiple channels in the middle temporal (MT) visual cortex of a macaque monkey, for decoding its bistable structure-from-motion (SFM) perception. Based on the observation that the discriminative information of neuronal population activity evolves and accumulates over time, we propose to select features from the integrated time-frequency representation of LFP using a relaxation (RELAX) algorithm and a sequential forward selection (SFS) algorithm with maximizing the Mahalanobis distance as the criterion function. The integrated-spectrogram based feature selection is much more robust and can achieve significantly better features than the instantaneous-spectrogram based feature selection. We exploit the support vector machines (SVM) classifier and the linear discriminant analysis (LDA) classifier based on the selected features to decode the reported perception on a single trial basis. Our results demonstrate the excellent performance of the integrated-spectrogram based feature selection and suggest that the features in the gamma frequency band (30-100 Hz) of LFP within specific temporal windows carry the most discriminative information for decoding bistable perception. The proposed integrated-spectrogram based feature selection approach may have potential for a myriad of applications involving multivariable time series such as brain-computer interfaces (BCI).

Wang, Zhisong; Logothetis, Nikos K.; Liang, Hualou

2008-12-01

251

Stage level, volume, and time-frequency information content of Lake Tana using stochastic and wavelet analysis methods  

NASA Astrophysics Data System (ADS)

Lake Tana is the largest fresh water body situated in the north western highlands of Ethiopia. It serves for local transport, electric power generation, fishing, ecological restoration, recreational purposes, and dry season irrigation supply. Evidence show, the lake has dried at least once at about 15 000-17 000 BP (before present) due to a combination of high evaporation and low precipitation events. Past attempts to observe historical fluctuation of Lake Tana based on simplistic water balance approach of inflow, out-flow and storage have failed to capture well known events of drawdown and rise of the lake that have happened in the last 44 years. This study is aimed at simulating the lake level, specifically extreme events of the lake variation using stochastic approaches. Fourty-four years of daily, monthly and mean annual lake level data has showed a Gaussian variation with goodness of fit at 0.01 significant levels of the Konglomorov-Simrnov test. Three stochastic methods were employed, namely perturbations approach, Monte-Carlo methods and wavelet analysis, and the results were compared with the stage level measurements. The stochastic simulations predicted the lake stage level of the 1972, 1984 and 2002/2003 historical droughts 99% of the time. The information content (frequency) of fluctuation of Lake Tana for various periods was resolved using Wigner's Time-Frequency Decomposition method. The wavelet analysis agreed with the perturbations and Monte Carlo simulations resolving the time (1970s, 1980s and 2000s) in which low frequency and high spectral power fluctuation has occurred. In summary, the Monte-Carlo and perturbations methods have shown their superiority for risk analysis over deterministic methods while wavelet analysis has met reconstructing stage level historical record at multiple time scales. A further study is recommended on dynamic forecasting of the Lake Tana stage level using a combined approach of the perturbation and wavelet analysis methods.

Chebud, Y.; Melesse, A.

2010-08-01

252

CONVENTIONAL TIME DOMAIN REFLECTOMETRY SYSTEMS  

Technology Transfer Automated Retrieval System (TEKTRAN)

This chapter in a book to be published by the International Atomic Energy Agency/FAO Joint Division provides detailed information on how to accurately sense soil water content and bulk electrical conductivity with the conventional time domain reflectometry (TDR) method. Attention is given to integra...

253

Magnetic domains  

NASA Astrophysics Data System (ADS)

At the recently concluded International Association of Geomagnetism and Aeronomy Assembly in Exeter, U.K., magnetic domain observations on magnetite imaged for the first time by the magneto-optic Kerr effect were reported. The picture (Figure 1) shows domains on a synthetic magnetite grain where magnetic contrast is achieved by the longitudinal Kerr effect using a polarizing light microscope with an attached high-sensitivity video camera, a digital video processor and a graphics computer.Previous domain studies on magnetite were done by the Bitter technique, where magnetic colloids are attracted by magnetic gradients over domain walls. Results were at odds with theoretical predictions concerning domain sizes, and it has been questioned whether the colloid actually leaves the domains themselves unaffected or whether there are (Néel-type) domain walls that are not associated with a significant gradient.

Worm, H.-U.; Banerjee, S. K.; Ryan, P. J.; Hoffmann, V.; Appel, E.; Soffel, H.

254

Jointness: A Selected Bibliography.  

National Technical Information Service (NTIS)

JDEIS is the Joint Doctrine, Education and Training Community Electronic Information System. It encompasses a searchable Joint Doctrine Database, a Joint Education section that includes the JPME Prospective Research Topics Database, as well as award-winni...

L. Garder

2010-01-01

255

Revised concepts for estimation of spawning fraction in multiple batch spawning fish considering temperature-dependent duration of spawning markers and spawning time frequency distribution  

Microsoft Academic Search

A generalized method to accurately estimate the spawning fraction (S) of multiple batch spawning fish considering the duration of histological spawning markers over a wide range of ambient temperature, spawning time frequency distribution of the population, and sampling time was developed. The concept of the variable “fraction of the daily spawning females with spawning markers at a sampling time t

Yutaka Kurita

256

Heart Rate Variability Analysis of Ischemic and Heart Rate Related ST-segment Deviation Episodes Based on Time-frequency Method  

Microsoft Academic Search

ST-segment deviation is the routine method for the diagnosis of coronary heart diseases. However, other phenomena, such as heart rate changes and a posture change can cause similar manifestations in the ST segment, lowing the sensitivity and specificity of the detection. In this study, a different method, based on time-frequency analysis of heart rate variability, was proposed to evaluate the

Wang Xing; Xu Liang; Sun Zhongwei; Yang Zibin; Peng Yi

2007-01-01

257

Joint spectrogram segmentation and ridge-extraction method for separating multimodal guided waves in long bones  

NASA Astrophysics Data System (ADS)

Ultrasonic guided waves (GWs) can be used to evaluate long bones effectively because of the ability to provide the information of the whole bone. In this study, a joint spectrogram segmentation and ridge-extraction (JSSRE) method was proposed to separate multiple modes in long bones. First, the Gabor time-frequency transform was applied to obtain the spectrogram of multimodal signals. Then, a multi-class image segmentation algorithm was used to find the corresponding region of each mode in the spectrogram, including an improved watershed transform and a region growing procedure. Finally, the ridges were extracted and the time domain signals representing individual modes were reconstructed from these ridges in each region. The validations of this method were discussed by simulated multimodal signals with different signal-to-noise ratios (SNR). The correlation coefficients between the original signals without noise and the reconstructed signals were calculated to analyze the results quantitatively. The results showed that the extracted ridges were in good agreement with generated theoretical dispersion curves, and the reconstructed signals were highly related to the original signals, even under the SNR=3 dB situation.

Zhang, ZhengGang; Xu, KaiLiang; Ta, DeAn; Wang, WeiQi

2013-07-01

258

Kalman filter methods for real-time frequency and mode number estimation of MHD activity in tokamak plasmas  

NASA Astrophysics Data System (ADS)

Magnetohydrodynamic (MHD) activity in magnetically confined fusion experiments is often associated with detrimental effects such as increased radial transport and consequent loss of confinement. In particular, the (2,1) neoclassical tearing mode (NTM), when proceeding to mode-locking, is a potentially disruptive instability hence with the potential to compromise the mechanical integrity of the machine. It is therefore quite significant to be able to characterize in real-time the most virulent and performance limiting instabilities such that adequate mitigation or complete stabilization using feedback control methods are employed during the plasma discharge. This work proposes a Kalman filter (KF) based mechanism for providing, in real-time, the amplitude and phase evolution of instabilities within a predefined set of mode numbers. The method relies on two KF implementations: a non-linear KF isolating the non-stationary dominant signal component of a sensor measurement and subsequently a linear KF which projects the former, for a collection of sensors, onto a predefined set of mode numbers. A basic overview of algorithms commonly used for real-time mode number analysis is also presented along with applications of the proposed algorithm to recently recorded data of the Joint European Torus (JET) tokamak.

Alves, D.; Coelho, R.; JET EFDA contributors, the

2013-10-01

259

Domains in multiferroics with magnetically induced ferroelectricity  

NASA Astrophysics Data System (ADS)

Two types of multiferroics are distinguished. In the split-order-parameter multiferroics magnetic and ferroelectric order evolve independently while in the joint-order-parameter multiferroics the emergence of the spontaneous polarization is a direct consequence of the magnetic order. The latter type is particularly interesting because of the inherent giant magnetoelectric effects. In the joint-order-parameter multiferroics any magnetoelectric interaction is, at its root, an interaction of its magnetic and ferroelectric domains. Yet, very little is known about the topology of these domains. In my talk I will discuss the domain topology and its magnetoelectric manipulation in a variety of joint-order-parameter multiferroics: MnWO4, RMn2O5, RMnO3, CuO, CuCrO2. Domains are resolved by optical second harmonic generation. Two types of unusual and fundamentally different domains will be distinguished: (i) hybrid-multiferroic domains in which hallmarks of magnetic and ferroelectric domains are inseparably entangled; (ii) incommensurate translation domains whose walls correspond to discontinuities in the incommensurate magnetic wave vector.

Fiebig, Manfred

2010-03-01

260

Time–frequency analysis of variabilities of heart rate, systolic blood pressure and pulse transit time before and after exercise using the recursive autoregressive model  

Microsoft Academic Search

Time–frequency (T–F) analysis is often used to study the non-stationary cardiovascular oscillations such as heart rate and blood pressure variabilities in dynamic situations. This study intends to use the T–F recursive autoregressive technique to investigate variability in pulse transit time (PTT), which is a cardiovascular parameter of emerging interest due to its potential to estimate blood pressure non-invasively, continuously and

Q. Liu; C. C. Y. Poon; Y. T. Zhang

2011-01-01

261

The time-frequency analysis of variabilities of heart rate, systolic blood pressure and pulse transit time on normotensive subjects after exercise  

Microsoft Academic Search

Spectral components of cardiovascular oscillations are related to complex autonomic control mechanisms. Since these oscillations are non-stationary, time-frequency (T-F) analysis has been used in studying cardiovascular oscillations such as variabilities of heart rate and blood pressure; however, few studies have extended the T-F analysis to other cardiovascular signals such as pulse transit time (PTT). In this preliminary study, a T-F

Q. Liu; C. C. Y. Poon; M. Y. M. Wong; Y. T. Zhang

2009-01-01

262

A methodology for time-frequency image processing applied to the classification of non-stationary multichannel signals using instantaneous frequency descriptors with application to newborn EEG signals  

NASA Astrophysics Data System (ADS)

This article presents a general methodology for processing non-stationary signals for the purpose of classification and localization. The methodology combines methods adapted from three complementary areas: time-frequency signal analysis, multichannel signal analysis and image processing. The latter three combine in a new methodology referred to as multichannel time-frequency image processing which is applied to the problem of classifying electroencephalogram (EEG) abnormalities in both adults and newborns. A combination of signal related features and image related features are used by merging key instantaneous frequency descriptors which characterize the signal non-stationarities. The results obtained show that, firstly, the features based on time-frequency image processing techniques such as image segmentation, improve the performance of EEG abnormalities detection in the classification systems based on multi-SVM and neural network classifiers. Secondly, these discriminating features are able to better detect the correlation between newborn EEG signals in a multichannel-based newborn EEG seizure detection for the purpose of localizing EEG abnormalities on the scalp.

Boashash, Boualem; Boubchir, Larbi; Azemi, Ghasem

2012-12-01

263

Domain Representations  

NSDL National Science Digital Library

This lesson from Illuminations asks students to use graphs, tables, number lines, verbal descriptions, and symbols to represent the domain of various functions. The material allows students to examine and utilize connections between a functionâÂÂs symbolic representation, a functionâÂÂs graphical representation, and a functionâÂÂs domain. The lesson is intended for grades 9-12 and should require 1 class period to complete.

2011-01-14

264

Experimental and theoretical studies of a bolted joint excited by a torsional dynamic load  

Microsoft Academic Search

This paper presents the experimental work on a single joint rig and the analytical models for representing the experimental results. A bolted joint connecting two beams is shaken at two resonant frequencies. These experiments have illustrated microslip and macroslip phenomena from measurements taken locally to the joint interface in the time domain. Hysteresis loops of the torque versus the relative

H. Ouyang; M. J. Oldfield; J. E. Mottershead

2006-01-01

265

Joint Injection/Aspiration  

MedlinePLUS

... osteoarthritis. What usually is injected into the joint space? Corticosteroids (such as methylprednisolone and triamcinolone formulated to ... for producing inflammation and pain within the joint space. Although corticosteroids may also be successfully used in ...

266

Arthritis: Metacarpophalangeal (MP) Joint  

MedlinePLUS

... activities. Arthritis is the wearing away of the cartilage at a joint. Cartilage is the coating layer of tissue on the ... that acts as a shock-absorber. Loss of cartilage can lead to joint destruction and a shift ...

267

Large displacement spherical joint  

DOEpatents

A new class of spherical joints has a very large accessible full cone angle, a property which is beneficial for a wide range of applications. Despite the large cone angles, these joints move freely without singularities.

Bieg, Lothar F. (Albuquerque, NM); Benavides, Gilbert L. (Albuquerque, NM)

2002-01-01

268

Collapsible mechanical joint  

NASA Astrophysics Data System (ADS)

A mechanical joint that can be configured to be either flexible or rigid is presented. The mechanical joint comprises three members which are flexibly attached to each other with a cable. When the cable is tightened, the three members come together to form a rigid joint capable of withstanding structural loads.

Robertson, Glen A.

1993-11-01

269

Bolted Hybrid Joints.  

National Technical Information Service (NTIS)

The report presents the results of an analytical study of hybrid steel butt joints of A36, A440 and A514 steel. The joints were fastened by either A325 or A490 bolts. The studies were designed to determine the effect of various variables on the joint stre...

R. Kormanik J. W. Fisher

1966-01-01

270

Monitoring groundwater-surface water interaction using time-series and time-frequency analysis of transient three-dimensional electrical resistivity changes  

NASA Astrophysics Data System (ADS)

Time-lapse resistivity imaging is increasingly used to monitor hydrologic processes. Compared to conventional hydrologic measurements, surface time-lapse resistivity provides superior spatial coverage in two or three dimensions, potentially high-resolution information in time, and information in the absence of wells. However, interpretation of time-lapse electrical tomograms is complicated by the ever-increasing size and complexity of long-term, three-dimensional (3-D) time series conductivity data sets. Here we use 3-D surface time-lapse electrical imaging to monitor subsurface electrical conductivity variations associated with stage-driven groundwater-surface water interactions along a stretch of the Columbia River adjacent to the Hanford 300 near Richland, Washington, USA. We reduce the resulting 3-D conductivity time series using both time-series and time-frequency analyses to isolate a paleochannel causing enhanced groundwater-surface water interactions. Correlation analysis on the time-lapse imaging results concisely represents enhanced groundwater-surface water interactions within the paleochannel, and provides information concerning groundwater flow velocities. Time-frequency analysis using the Stockwell (S) transform provides additional information by identifying the stage periodicities driving groundwater-surface water interactions due to upstream dam operations, and identifying segments in time-frequency space when these interactions are most active. These results provide new insight into the distribution and timing of river water intrusion into the Hanford 300 Area, which has a governing influence on the behavior of a uranium plume left over from historical nuclear fuel processing operations.

Johnson, T. C.; Slater, L. D.; Ntarlagiannis, D.; Day-Lewis, F. D.; Elwaseif, M.

2012-07-01

271

A new statistical test based on the wavelet cross-spectrum to detect time–frequency dependence between non-stationary signals: Application to the analysis of cortico-muscular interactions  

Microsoft Academic Search

The study of the correlations that may exist between neurophysiological signals is at the heart of modern techniques for data analysis in neuroscience. Wavelet coherence is a popular method to construct a time–frequency map that can be used to analyze the time–frequency correlations between two time series. Coherence is a normalized measure of dependence, for which it is possible to

Jérémie Bigot; Marieke Longcamp; Fabien Dal Maso; David Amarantini

2011-01-01

272

Probabilistic Domains  

Microsoft Academic Search

We show the equivalence of several different axiomatizations of the notion of (abstract) probabilistic domain in the category of dcpo's and continuous functions. The axiomatization with the richest set of operations provides probabilistic selection among a finite number of possibilities with arbitrary probabilities, whereas the poorest one has binary choice with equal probabilities as the only operation. The remaining theories

Reinhold Heckmann

1994-01-01

273

Belief propagation estimation of protein and domain interactions using the sum-product algorithm  

Microsoft Academic Search

In this paper, a novel framework is presented to estimate protein-protein interactions (PPIs) and domain-domain interactions (DDIs) based on a belief propagation estimation method that efficiently computes interaction probabilities. Experimental interactions, domain architecture, and gene ontology (GO) annotations are used to create a factor graph representation of the joint probability distribution of pairwise protein and domain interactions. Bound structures are

Faruck Morcos; Marcin Sikora; Mark S. Alber; Dale Kaiser; Jesús A. Izaguirre

2010-01-01

274

Event-Related EEG Time-Frequency Analysis: An Overview of Measures and An Analysis of Early Gamma Band Phase Locking in Schizophrenia  

PubMed Central

An increasing number of schizophrenia studies have been examining electroencephalography (EEG) data using time-frequency analysis, documenting illness-related abnormalities in neuronal oscillations and their synchronization, particularly in the gamma band. In this article, we review common methods of spectral decomposition of EEG, time-frequency analyses, types of measures that separately quantify magnitude and phase information from the EEG, and the influence of parameter choices on the analysis results. We then compare the degree of phase locking (ie, phase-locking factor) of the gamma band (36–50 Hz) response evoked about 50 milliseconds following the presentation of standard tones in 22 healthy controls and 21 medicated patients with schizophrenia. These tones were presented as part of an auditory oddball task performed by subjects while EEG was recorded from their scalps. The results showed prominent gamma band phase locking at frontal electrodes between 20 and 60 milliseconds following tone onset in healthy controls that was significantly reduced in patients with schizophrenia (P?=?.03). The finding suggests that the early-evoked gamma band response to auditory stimuli is deficiently synchronized in schizophrenia. We discuss the results in terms of pathophysiological mechanisms compromising event-related gamma phase synchrony in schizophrenia and further attempt to reconcile this finding with prior studies that failed to find this effect.

Roach, Brian J.; Mathalon, Daniel H.

2008-01-01

275

[Age-related changes in time-frequency structure of sleep spindles in EEG in rats with genetic predisposition to absence epilepsy (Wag/Rij)].  

PubMed

It is known that sleep spindles are produced by thalamo-cortical system spontaneously during the slow-wave sleep; pathological processes in thalamo-cortical network might cause absence epilepsy. The aim of this study was to examine age-dependent changes in time-frequency structure of sleep spindles in parallel to a progressive increase in amount of absence seizures in WAG/Rij rat model. EEG was consistently recorded at the age of 5, 7 and 9 months by means of epidural electrodes implanted in the frontal cortex. Continuous wavelet transform was used for automatic identification and further time-frequency analysis of sleep spindles in EEG. It was found that the mean duration of epileptic discharges and total duration of epileptic activity increased with age, whereas the length of sleep spindles decreased. Mean frequency of oscillations within a spindle was used as a criterion for dividing sleep spindles in three categories: "slow" (9.3 Hz), "tr ansitional" (11.4 Hz) and "fast" (13.5 Hz). "Slow" and "transitional" spindles in 5-months animals displayed an increase in frequency from the beginning towards the end. It was shown that the higher incidence of epilepsy corresponded to the lower duration of sleep spindles (all types). Mean frequency of "transitional" and "fast" spindles was higher in rats with more intensive epileptic discharges. In general, high epileptic activity in WAG/Rij rats corresponded to the most substantial changes within "transitional" spindles, whereas changes within slow and fast spindles were moderate. PMID:23530451

Sitnikova, E Iu; Grubov, V V; Khramov, A E; Koronovski?, A A

276

A generalized time-frequency subtraction method for robust speech enhancement based on wavelet filter banks modeling of human auditory system.  

PubMed

We present a new speech enhancement scheme for a single-microphone system to meet the demand for quality noise reduction algorithms capable of operating at a very low signal-to-noise ratio. A psychoacoustic model is incorporated into the generalized perceptual wavelet denoising method to reduce the residual noise and improve the intelligibility of speech. The proposed method is a generalized time-frequency subtraction algorithm, which advantageously exploits the wavelet multirate signal representation to preserve the critical transient information. Simultaneous masking and temporal masking of the human auditory system are modeled by the perceptual wavelet packet transform via the frequency and temporal localization of speech components. The wavelet coefficients are used to calculate the Bark spreading energy and temporal spreading energy, from which a time-frequency masking threshold is deduced to adaptively adjust the subtraction parameters of the proposed method. An unvoiced speech enhancement algorithm is also integrated into the system to improve the intelligibility of speech. Through rigorous objective and subjective evaluations, it is shown that the proposed speech enhancement system is capable of reducing noise with little speech degradation in adverse noise environments and the overall performance is superior to several competitive methods. PMID:17702286

Shao, Yu; Chang, Chip-Hong

2007-08-01

277

Common time-frequency analysis of local field potential and pyramidal cell activity in seizure-like events of the rat hippocampus  

NASA Astrophysics Data System (ADS)

To study cell-field dynamics, physiologists simultaneously record local field potentials and the activity of individual cells from animals performing cognitive tasks, during various brain states or under pathological conditions. However, apart from spike shape and spike timing analyses, few studies have focused on elucidating the common time-frequency structure of local field activity relative to surrounding cells across different periods of phenomena. We have used two algorithms, multi-window time frequency analysis and wavelet phase coherence (WPC), to study common intracellular-extracellular (I-E) spectral features in spontaneous seizure-like events (SLEs) from rat hippocampal slices in a low magnesium epilepsy model. Both algorithms were applied to 'pairs' of simultaneously observed I-E signals from slices in the CA1 hippocampal region. Analyses were performed over a frequency range of 1-100 Hz. I-E spectral commonality varied in frequency and time. Higher commonality was observed from 1 to 15 Hz, and lower commonality was observed in the 15-100 Hz frequency range. WPC was lower in the non-SLE region compared to SLE activity; however, there was no statistical difference in the 30-45 Hz band between SLE and non-SLE modes. This work provides evidence of strong commonality in various frequency bands of I-E SLEs in the rat hippocampus, not only during SLEs but also immediately before and after.

Cotic, M.; Chiu, A. W. L.; Jahromi, S. S.; Carlen, P. L.; Bardakjian, B. L.

2011-08-01

278

Comparing Predictive Inference Methods for Discrete Domains  

Microsoft Academic Search

Predictive inference is seen here as the process of determining the predictive distribution of a discretevariable, given a data set of training examples and the values for the other problem domain variables. Weconsider three approaches for computing this predictive distribution, and assume that the joint probabilitydistribution for the variables belongs to a set of distributions determined by a set of

Henry Tirri; Peter Grunwald; Petri Kontkanen; Petri Myllymaki; Tomi Sil

1997-01-01

279

Joint warfare system (JWARS)  

Microsoft Academic Search

The Joint Warfare System (JWARS) is a campaign-level model of military operations that is currently being developed under contract by the Office of the Secretary of Defense (OSD) for use by OSD, the Joint Staff, the Services, and the War fighting Commands. The behavior of military forces can be simulated from ports of embarkation through to their activities in combat.

A. Simlote

2003-01-01

280

Joint Seal Materials.  

National Technical Information Service (NTIS)

Three major experimental field installations of approximately 7 types of joint sealing materials were used to compare and evaluate the products of numerous sealant manufacturers. The sealants were placed in contraction joints (3/8 in. x 2 in.) which were ...

J. G. F. Hiss J. R. Lambert W. M. McCarty

1968-01-01

281

Joint remote state preparation  

Microsoft Academic Search

Alice, Bob and Charlie are three remote parties. Alice and Bob share the classical knowledge of a secret qubit state. We consider the following question: 'how can Alice and Bob jointly prepare the qubit state for Charlie?' Two different protocols are proposed for such a joint remote state preparation. The first protocol uses a single GHZ state while the second

Ba An Nguyen; Jaewan Kim

2008-01-01

282

Joint spacing criterion for equivalent continuum model  

SciTech Connect

Currently, the Yucca Mountain Site Characterization Project is investigating the feasibility of the disposal of high-level radioactive waste in the unsaturated Topopah Spring formation. The Topopah Spring formation is a heavily fractured, predominantly vertically jointed, welded tuff, and the potential disposal area is cut by the Ghost Dance fault and bounded by several other faults structures. The joints in the tuff and the faults may have an impact on the emplacement drift or borehole stability, as well as on the movement of fluids through the rock mass. The design of the repository drifts and layout, the waste emplacement scheme, and the thermomechanical performance of the rock mass will be analyzed using various numerical models. These models may be based on different assumptions regarding the representation of the fracture behavior under given applied stresses, and will range from discrete models where individual mechanically active fractures are treated distinctly, to continuum models where the joint behavior is smeared over a representative volume. There is always the question of applicability of a model with respect to a given material domain to be analyzed. For the mechanical analysis of the rock mass response around a repository drift, the applicability of an equivalent continuum model is dependent on the joint spacing in the rock mass. Considering the joint spacings that may be encountered at the potential repository site, a ratio of joint spacing to the planned drift diameter may be adopted as a criterion for evaluating the applicability of the Compliant Joint Model (CJM) in the Yucca Mountain Site Characterization Project. In this paper, this criterion is established by reviewing basic continuum concepts and numerical approximation implications used to build the CJM and by examining rock mass conditions that may be encountered at the potential Yucca Mountain repository site.

Tsai, F.C.

1995-12-31

283

Transforming Logistics: Joint Theater Logistics.  

National Technical Information Service (NTIS)

Effective and efficient management of joint theater logistics is a challenge for theater commanders. Current doctrine for joint theater logistics management provides broad non-directive guidance for developing a joint theater logistics system that can opt...

S. W. Pate

2006-01-01

284

From domain modeling to collaborative domain construction  

Microsoft Academic Search

Domain-oriented systems offer many potential benefits for end-users such as more intuitive interfaces, better task support, and knowledge-based assistance. A key challenge for system developers constructing domain-oriented systems is determining what the current domain is and what the future domain should be; i.e. what entities should the system embody and how should they be represented. Determining an appropriate domain model

Gerhard Fischer; Stefanie N. Lindstaedt; Jonathan L. Ostwald; Markus Stolze; Tamara Sumner; Beatrix Zimmermann

1995-01-01

285

ASCO/FDA JOINT  

Center for Drug Evaluation (CDER)

Text VersionPage 1. ASCO/FDA JOINT LUNG CANCER PANEL 2002-2003 Paul Bunn, MD (NCE-Chair) University of Colorado Cancer Center Denver, CO ... More results from www.fda.gov/downloads/drugs/developmentapprovalprocess

286

Joint Agency Turbulence Experiment.  

National Technical Information Service (NTIS)

Doppler radar data acquired during the 1981 Joint Agency Turbulence Experiment are presented. Pulse-pair processed reflectivity factor and Doppler spectrum mean data collected during volume scan periods are displayed over constant height surfaces at aircr...

A. R. Bohne

1983-01-01

287

Joint fluid Gram stain  

MedlinePLUS

... and shape of the cells help identify the bacteria. ... Abnormal results mean bacteria were seen on the Gram stain. This may be a sign of a joint infection, for example, gonococcal arthritis or arthritis due to Staphylococcus aureus.

288

Joint aspiration and injection.  

PubMed

Joint aspiration/injection is an invaluable procedure for the diagnosis and treatment of joint disease. The knee is the commonest site to require aspiration although any non-axial joint is accessible for obtaining synovial fluid. Septic arthritis and crystal arthritis can be readily diagnosed by aspirating synovial fluid. Intra-articular injection of long-acting insoluble corticosteroids produces rapid resolution of inflammation in most injected joints and is a well established procedure in rheumatological practice. The technique involves only a knowledge of basic anatomy and should not be unduly painful for the patient. Provided sterile equipment and a sensible, aseptic approach are used it is a safe procedure. This chapter addresses the indications, technical principals, expected benefits and risks of intra-articular corticosteroid injection. The use of other intra-articular injections including osmic acid, radioisotopes and hyaluronic acid, which are less universally utilised than intra-articular corticosteroid, will also be addressed. PMID:15939363

Courtney, Philip; Doherty, Michael

2005-06-01

289

Joint Healthcare Manpower Standards.  

National Technical Information Service (NTIS)

The purpose of the Standard is to ensure that the peacetime staffing requirements of the Military Health Services System (MHSS) provide quality medical care in a productive environment. The Joint Healthcare Manpower Standards (JHMS) provide the Department...

V. Melidosian

1989-01-01

290

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

An annual report of the JSEP (Joint Services Electronics Program) in solid state electronics, quantum electronics, information electronics, control and optimization, and electromagnetic phenomena is presented. Results of the research to date are summarize...

M. Tinkham

1991-01-01

291

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

An annual report of the JSEP (Joint Services Electronics Program) in solid state electronics, quantum electronics, information electronics, control and optimization, and electromagnetic phenomena is presented. Results of the research to date are summarize...

M. Tinkham

1987-01-01

292

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

This annual report of the JSEP (Joint Services Electronic Program) in solid state electronics, quantum electronics, information electronics, control and optimization, and electromagnetic phenomenon is presented. Results of the research to date are summari...

M. Tinkham

1985-01-01

293

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

An annual report of the JSEP (Joint Services Electronics Program) in Electromagnetics, Quantum Electronics, Solid State Electronics, Materials and Devices and Information System is presented. In addition, results of the research to date are summarized and...

W. G. Oldham

1986-01-01

294

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

An annual report of the JSEP (Joint Services Electronic Program) in solid state electronics, quantum electronics, information electronics control and optimization and electromagnetic phenomenon is presented. Results of the research to date are summarized ...

M. Tinkham

1985-01-01

295

Joint Services Electronics Program.  

National Technical Information Service (NTIS)

An annual report of the JSEP (Joint Services Electronics Program) in solid state electronics, quantum electronics, information electronics, control and optimization, and electromagnetic phenomena is presented. Results of the research to date are summarize...

M. Tinkham

1986-01-01

296

Prosthetic Joint Infections  

PubMed Central

Prosthetic joint infections represent a major therapeutic challenge for both healthcare providers and patients. This paper reviews the predisposing factors, pathogenesis, microbiology, diagnosis, treatment and prophylaxis of prosthetic joint infection. The most optimal management strategy should be identified based on a number of considerations including type and duration of infection, antimicrobial susceptibility of the infecting pathogen, condition of infected tissues and bone stock, patient wishes and functional status.

Aslam, Saima; Darouiche, Rabih O.

2012-01-01

297

Joint remote state preparation  

NASA Astrophysics Data System (ADS)

Alice, Bob and Charlie are three remote parties. Alice and Bob share the classical knowledge of a secret qubit state. We consider the following question: 'how can Alice and Bob jointly prepare the qubit state for Charlie?' Two different protocols are proposed for such a joint remote state preparation. The first protocol uses a single GHZ state while the second one uses a pair of EPR states as the quantum channel whose entanglement is not necessarily maximal.

Nguyen, Ba An; Kim, Jaewan

2008-05-01

298

High pressure ceramic joint  

DOEpatents

Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

Ward, Michael E. (Poway, CA); Harkins, Bruce D. (San Diego, CA)

1993-01-01

299

Modeling Macro-Cognitive Influence on Information Sharing between Members of a Joint Team.  

National Technical Information Service (NTIS)

Research exploring the effectiveness of joint military teams lacks the empirical robustness found in similar multicultural team research from the business domain. This research study broadens the study of effective military teams through an assessment of ...

S. F. Burnett

2006-01-01

300

Time-frequency characterization of electrocorticographic recordings of epileptic patients using Frequency-Entropy Similarity: A comparison to other bi-variate measures  

PubMed Central

Expert evaluation of electrocorticographic (ECoG) recordings forms the linchpin of seizure onset zone localization in the evaluation of epileptic patients for surgical resection. Numerous methods have been developed to analyze these complex recordings, including uni-variate (characterizing single channels), bi-variate (comparing channel pairs) and multivariate measures. Developing reliable algorithms may be helpful in clinical tasks such as localization of epileptogenic zones and seizure anticipation, as well as enabling better understanding of neuronal function and dynamics. Recently we have developed the Frequency-Entropy (F-E) similarity measure, and have tested its capability in mapping the epileptogenic zones. The F-E similarity measure compares time-frequency characterizations of two recordings. In this study, we examine the method's principles and utility and compare it to previously described bi-variate correspondence measures such as correlation, coherence, mean phase coherence and spectral comparison methods. Specially designed synthetic signals were used for illuminating theoretical differences between the measures. Intracranial recordings of four epileptic patients were then used for the measures' comparative analysis by creating a mean inter-electrode matrix for each of the correspondence measures and comparing the structure of these matrices during the inter-ictal and ictal periods. We found that the F-E similarity measure is able to discover spectral and temporal features in data which are hidden for the other measures and are important for foci localization.

Gazit, T.; Doron, I.; Sagher, O.; Kohrman, M.H.; Towle, V.L.; Teicher, M.; Ben Jacob, E.

2010-01-01

301

Time-frequency characterization of electrocorticographic recordings of epileptic patients using frequency-entropy similarity: a comparison to other bi-variate measures.  

PubMed

Expert evaluation of electrocorticographic (ECoG) recordings forms the linchpin of seizure onset zone localization in the evaluation of epileptic patients for surgical resection. Numerous methods have been developed to analyze these complex recordings, including uni-variate (characterizing single channels), bi-variate (comparing channel pairs) and multivariate measures. Developing reliable algorithms may be helpful in clinical tasks such as localization of epileptogenic zones and seizure anticipation, as well as enabling better understanding of neuronal function and dynamics. Recently we have developed the frequency-entropy (F-E) similarity measure, and have tested its capability in mapping the epileptogenic zones. The F-E similarity measure compares time-frequency characterizations of two recordings. In this study, we examine the method's principles and utility and compare it to previously described bi-variate correspondence measures such as correlation, coherence, mean phase coherence and spectral comparison methods. Specially designed synthetic signals were used for illuminating theoretical differences between the measures. Intracranial recordings of four epileptic patients were then used for the measures' comparative analysis by creating a mean inter-electrode matrix for each of the correspondence measures and comparing the structure of these matrices during the inter-ictal and ictal periods. We found that the F-E similarity measure is able to discover spectral and temporal features in data which are hidden for the other measures and are important for foci localization. PMID:20969891

Gazit, T; Doron, I; Sagher, O; Kohrman, M H; Towle, V L; Teicher, M; Ben-Jacob, E

2010-10-20

302

Time-frequency analysis of short-lasting modulation of EEG induced by intracortical and transcallosal paired TMS over motor areas.  

PubMed

Dynamic changes in spontaneous electroencephalogram (EEG) rhythms can be seen to occur with a high rate of variability. An innovative method to study brain function is by triggering oscillatory brain activity with transcranial magnetic stimulation (TMS). EEG-TMS coregistration was performed on five healthy subjects during a 1-day experimental session that involved four steps: baseline acquisition, unconditioned single-pulse TMS, intracortical inhibition (ICI, 3 ms) paired-pulse TMS, and transcallosal stimulation over left and right primary motor cortex (M1). A time-frequency analysis based on the wavelet method was used to characterize rapid modifications of oscillatory EEG rhythms induced by TMS. Single, paired, and transcallosal TMS applied on the sensorimotor areas induced rapid desynchronization over the frontal and central-parietal electrodes mainly in the alpha and beta bands, followed by a rebound of synchronization, and rapid synchronization of delta and theta activity. Wavelet analysis after a perturbation approach is a novel way to investigate modulation of oscillatory brain activity. The main findings are consistent with the concept that the human motor system may be based on networklike oscillatory cortical activity and might be modulated by single, paired, and transcallosal magnetic pulses applied to M1, suggesting a phenomenon of fast brain activity resetting and triggering of slow activity. PMID:22298825

Manganotti, Paolo; Formaggio, Emanuela; Storti, Silvia Francesca; De Massari, Daniele; Zamboni, Alessandro; Bertoldo, Alessandra; Fiaschi, Antonio; Toffolo, Gianna Maria

2012-02-01

303

Ridge extraction from the time-frequency representation (TFR) of signals based on an image processing approach: application to the analysis of uterine electromyogram AR TFR.  

PubMed

Time-frequency representations (TFRs) of signals are increasingly being used in biomedical research. Analysis of such representations is sometimes difficult, however, and is often reduced to the extraction of ridges, or local energy maxima. In this paper, we describe a new ridge extraction method based on the image processing technique of active contours or snakes. We have tested our method on several synthetic signals and for the analysis of uterine electromyogram or electrohysterogram (EHG) recorded during gestation in monkeys. We have also evaluated a postprocessing algorithm that is especially suited for EHG analysis. Parameters are evaluated on real EHG signals in different gestational periods. The presented method gives good results when applied to synthetic as well as EHG signals. We have been able to obtain smaller ridge extraction errors when compared to two other methods specially developed for EHG. The gradient vector flow (GVF) snake method, or GVF-snake method, appears to be a good ridge extraction tool, which could be used on TFR of mono or multicomponent signals with good results. PMID:18440895

Terrien, Jérémy; Marque, Catherine; Germain, Guy

2008-05-01

304

Spatially variable stage-driven groundwater-surface water interaction inferred from time-frequency analysis of distributed temperature sensing data  

NASA Astrophysics Data System (ADS)

Characterization of groundwater-surface water exchange is essential for improving understanding of contaminant transport between aquifers and rivers. Fiber-optic distributed temperature sensing (FODTS) provides rich spatiotemporal datasets for quantitative and qualitative analysis of groundwater-surface water exchange. We demonstrate how time-frequency analysis of FODTS and synchronous river stage time series from the Columbia River adjacent to the Hanford 300-Area, Richland, Washington, provides spatial information on the strength of stage-driven exchange of uranium contaminated groundwater in response to subsurface heterogeneity. Although used in previous studies, the stage-temperature correlation coefficient proved an unreliable indicator of the stage-driven forcing on groundwater discharge in the presence of other factors influencing river water temperature. In contrast, S-transform analysis of the stage and FODTS data definitively identifies the spatial distribution of discharge zones and provided information on the dominant forcing periods (?2 d) of the complex dam operations driving stage fluctuations and hence groundwater-surface water exchange at the 300-Area.

Mwakanyamale, Kisa; Slater, Lee; Day-Lewis, Frederick; Elwaseif, Mehrez; Johnson, Carole

2012-03-01

305

Time frequency analysis of laser Doppler flowmetry signals recorded in response to a progressive pressure applied locally on anaesthetized healthy rats  

NASA Astrophysics Data System (ADS)

The laser Doppler flowmetry technique has recently been used to report a significant transient increase of the cutaneous blood flow signal, in response to a local non-noxious pressure applied progressively on the skin of both healthy humans and rats. This phenomenon is not entirely understood yet. In the present work, a time-frequency analysis is applied to signals recorded on anaesthetized healthy rats, at rest and during a cutaneous pressure-induced vasodilation (PIV). The comparison, at rest and during PIV, of the scalogram relative energies and scalogram relative amplitudes in five bands, corresponding to five characteristic frequencies, shows an increased contribution for the endothelial related metabolic activity in PIV signals, till 400 s after the beginning of the progressive pressure application. The other subsystems (heart, respiration, myogenic and neurogenic activities) contribute relatively less during PIV than at rest. The differences are statistically significant for all the relative activities in the interval 0-200 s following the beginning of the pressure. These results and others obtained on patients, such as diabetics, could increase the understanding of some cutaneous pathologies involved in various neurological diseases and in the pathophysiology of decubitus ulcers.

Humeau, Anne; Koïtka, Audrey; Abraham, Pierre; Saumet, Jean-Louis; L'Huillier, Jean-Pierre

2004-03-01

306

Optimized fusion method based on adaptation of the RMS time-frequency criterion for simultaneous compression and encryption of multiple images  

NASA Astrophysics Data System (ADS)

An extension of the recently proposed method of simultaneous compression and encryption of multiple images [Opt. Lett. 35, 1914-1916 (2010)] is developed. This analysis allows us to find a compromise between compression rate and quality of the reconstructed images for target detection applications. This spectral compression method can significantly reduce memory size and can be easily implemented with a VanderLugt correlator (VLC). For that purpose, we determine the size of the useful spectra for each target image by exploiting the root-mean-square time-frequency criterion. This parameter is used to determine the allowed area of each target image within the compressed spectrum. Moreover, this parameter is adapted in order to minimize overlapping between the different spectra. For that purpose we add a shift function adapted to each spectra. Finally, the spectra are merged together by making use of a segmentation criterion. The latter compares the local energy relative to each pixel for each spectrum. Furthermore, it optimizes assignment of the considered pixel by taking into account the adjacent areas to the considered pixel. This permits to avoid the presence of isolated areas and small sized areas (less than 10 pixels). In this paper, we analyse and optimize the shift function needed to separate the different spectra. We use mean square error (MSE) for comparing compression rates. A series of tests with several video sequences show the benefit of this shift function on the quality of reconstructed images and compression rate.

Aldossari, M.; Alfalou, A.; Brosseau, C.

2013-03-01

307

Externalizing Psychopathology and Gain/Loss Feedback in a Simulated Gambling Task: Dissociable Components of Brain Response Revealed by Time-Frequency Analysis  

PubMed Central

Externalizing is a broad construct that reflects propensity toward a variety of impulse control problems, including antisocial personality disorder and substance use disorders. Two event-related potential responses known to be reduced among individuals high in externalizing proneness are the P300, which reflects post-perceptual processing of a stimulus, and the error-related negativity (ERN), which indexes performance monitoring based on endogenous representations. The current study employed a simulated gambling task to examine the relationship between externalizing proneness and the feedback-related negativity (FRN), a brain response that indexes performance monitoring related to exogenous cues, which is thought to be highly related to the ERN. Time-frequency (TF) analysis was used to disentangle the FRN from the accompanying P300 response to feedback cues by parsing the overall feedback-locked potential into distinctive theta (4–7 Hz) and delta (< 3 Hz) TF components. Whereas delta-P300 amplitude was reduced among individuals high in externalizing proneness, theta-FRN response was unrelated to externalizing. These findings suggest that, in contrast with previously reported deficits in endogenously-based performance monitoring (as indexed by the ERN), individuals high in externalizing tendencies show intact monitoring of exogenous cues (as indexed by the FRN). The results also contribute to a growing body of evidence indicating that the P300 is attenuated across a broad range of task conditions in high-externalizing individuals.

Bernat, Edward M.; Nelson, Lindsay D.; Steele, Vaughn R.; Gehring, William J.; Patrick, Christopher J.

2010-01-01

308

A safe joint with a joint torque sensor  

Microsoft Academic Search

In this study, a safe joint with a joint torque sensor is presented. The safe joint, named “Spring-Clutch”, is a simple passive mechanism that consists of a spring, a cam, and a joint torque sensor. When the torque applied is less than a pre-set threshold, the Spring-Clutch acts as a rigid joint between the input and output. However, if the

Dong-Eun Choi; Gi-Hun Yang; Junho Choi; Woosub Lee; Changhyun Cho; Sungchul Kang

2011-01-01

309

New plastic joints for plastic orthoses  

Microsoft Academic Search

Plastic joints for orthoses have more advantages than metal joints. They are lightweight, noiseless comfortable to use, rust proof, corrosion free, and radiolucent. Two types of plastic joints were developed by the authors, one for the ankle joint and the other for the knee joint, elbow joint or hip joint. Polypropylene was chosen as the joint material because of its

H. WATANABE; T. KUTSUNA; H. MORINAGA; T. OKABE

310

INDICATIONS FOR SACROILIAC JOINT FUSION  

Microsoft Academic Search

Sacroiliac joint fusion remains a useful piece of the surgical armamentarium. Newer percutaneous techniques for fusion supplement the older established procedures. The sacroiliac joint functions in the transmission of forces from the spine to the lower extremities and vice versa. It is a diarthrodial synovial joint that connects the sacrum to the ilium. The sacroiliac joint is unusual in that

Christopher A. Iobst; John A. Glaser

311

Joint impingement syndrome: clinical features  

Microsoft Academic Search

Joint impingement is a painful syndrome caused by the friction of joint tissues, which is both the cause and the effect of altered joint biomechanics. From the anatomical and clinical viewpoints, these syndromes are classified as bone impingement, soft tissue impingement and entrapment neuropathy, depending on what joint portion impinges on the others. We considered the most important impingement syndromes

Andrea Billi; Alessia Catalucci; Antonio Barile; Carlo Masciocchi

1998-01-01

312

Damage detection of truss bridge joints using Artificial Neural Networks  

Microsoft Academic Search

Recent developments in Artificial Neural Networks (ANNs) have opened up new possibilities in the domain of inverse problems. For inverse problems like structural identification of large structures (such as bridges) where in situ measured data are expected to be imprecise and often incomplete, ANNs may hold greater promise. This study presents a method for estimating the damage intensities of joints

M. Mehrjoo; N. Khaji; H. Moharrami; A. Bahreininejad

2008-01-01

313

Chinese seal imprint recognition with joint transform correlators  

Microsoft Academic Search

We design an optimized synthetic reference function for detecting rotated seal images with equal correlation peak. The method to minimize the average cross-correlation intensity on the joint transform correlator (JTC) has been utilized. The reference function can be implemented in the spatial domain of the JTC. Correlation results are presented. The system has the ability to recognize the rotated seal

Jian-Shuen Fang; Chulung Chen

2001-01-01

314

Distal radioulnar joint injuries.  

PubMed

Distal radioulnar joint is a trochoid joint relatively new in evolution. Along with proximal radioulnar joint, forearm bones and interosseous membrane, it allows pronosupination and load transmission across the wrist. Injuries around distal radioulnar joint are not uncommon, and are usually associated with distal radius fractures,fractures of the ulnar styloid and with the eponymous Galeazzi or Essex_Lopresti fractures. The injury can be purely involving the soft tissue especially the triangular fibrocartilage or the radioulnar ligaments. The patients usually present with ulnar sided wrist pain, features of instability, or restriction of rotation. Difficulty in carrying loads in the hand is a major constraint for these patients. Thorough clinical examination to localize point of tenderness and appropriate provocative tests help in diagnosis. Radiology and MRI are extremely useful, while arthroscopy is the gold standard for evaluation. The treatment protocols are continuously evolving and range from conservative, arthroscopic to open surgical methods. Isolated dislocation are uncommon. Basal fractures of the ulnar styloid tend to make the joint unstable and may require operative intervention. Chronic instability requires reconstruction of the stabilizing ligaments to avoid onset of arthritis. Prosthetic replacement in arthritis is gaining acceptance in the management of arthritis. PMID:23162140

Thomas, Binu P; Sreekanth, Raveendran

2012-09-01

315

Distal radioulnar joint injuries  

PubMed Central

Distal radioulnar joint is a trochoid joint relatively new in evolution. Along with proximal radioulnar joint, forearm bones and interosseous membrane, it allows pronosupination and load transmission across the wrist. Injuries around distal radioulnar joint are not uncommon, and are usually associated with distal radius fractures,fractures of the ulnar styloid and with the eponymous Galeazzi or Essex_Lopresti fractures. The injury can be purely involving the soft tissue especially the triangular fibrocartilage or the radioulnar ligaments. The patients usually present with ulnar sided wrist pain, features of instability, or restriction of rotation. Difficulty in carrying loads in the hand is a major constraint for these patients. Thorough clinical examination to localize point of tenderness and appropriate provocative tests help in diagnosis. Radiology and MRI are extremely useful, while arthroscopy is the gold standard for evaluation. The treatment protocols are continuously evolving and range from conservative, arthroscopic to open surgical methods. Isolated dislocation are uncommon. Basal fractures of the ulnar styloid tend to make the joint unstable and may require operative intervention. Chronic instability requires reconstruction of the stabilizing ligaments to avoid onset of arthritis. Prosthetic replacement in arthritis is gaining acceptance in the management of arthritis.

Thomas, Binu P; Sreekanth, Raveendran

2012-01-01

316

Periprosthetic Joint Infections  

PubMed Central

Implantation of joint prostheses is becoming increasingly common, especially for the hip and knee. Infection is considered to be the most devastating of prosthesis-related complications, leading to prolonged hospitalization, repeated surgical intervention, and even definitive loss of the implant. The main risk factors to periprosthetic joint infections (PJIs) are advanced age, malnutrition, obesity, diabetes mellitus, HIV infection at an advanced stage, presence of distant infectious foci, and antecedents of arthroscopy or infection in previous arthroplasty. Joint prostheses can become infected through three different routes: direct implantation, hematogenic infection, and reactivation of latent infection. Gram-positive bacteria predominate in cases of PJI, mainly Staphylococcus aureus and Staphylococcus epidermidis. PJIs present characteristic signs that can be divided into acute and chronic manifestations. The main imaging method used in diagnosing joint prosthesis infections is X-ray. Computed tomography (CT) scan may assist in distinguishing between septic and aseptic loosening. Three-phase bone scintigraphy using technetium has high sensitivity, but low specificity. Positron emission tomography using fluorodeoxyglucose (FDG-PET) presents very divergent results in the literature. Definitive diagnosis of infection should be made by isolating the microorganism through cultures on material obtained from joint fluid puncturing, surgical wound secretions, surgical debridement procedures, or sonication fluid. Success in treating PJI depends on extensive surgical debridement and adequate and effective antibiotic therapy. Treatment in two stages using a spacer is recommended for most chronic infections in arthroplasty cases. Treatment in a single procedure is appropriate in carefully selected cases.

Lima, Ana Lucia L.; Oliveira, Priscila R.; Carvalho, Vladimir C.; Saconi, Eduardo S.; Cabrita, Henrique B.; Rodrigues, Marcelo B.

2013-01-01

317

Use of high and low frequency dielectric measurements in the NDE of adhesively bonded composite joints  

NASA Astrophysics Data System (ADS)

Dielectric spectroscopy has been developed as a non-destructive technique for assessment of moisture content and structural integrity of adhesively bonded joints. Knowledge of these parameters is particularly crucial for the aerospace industry, since environmental degradation of adhesive joints presents a major limit on their utilization. High and low frequency measurements have been carried out on joints assembled from CFRP adherend, and a commercially available adhesive (AF 163-2K). The samples have been aged in deionised water at 75oC to chart the effect water ingress has on bond durability. In addition, some joints have been exposed to cryogenic temperatures to mimic the conditions joints experience whilst an aircraft is in flight. In this way it has been possible to determine the extent of degradation caused by freezing of water within the joint structure. Dielectric behaviour of the joints was studied in both the frequency and in the time domain. Frequency domain analysis allows the amount and effects of moisture ingress in the bondline to be assessed, whereas the time domain highlights the onset of joint defects with increasing exposure time. Mechanical testing of the joints has been carried out to enable correlation between changes in strength and failure mechanism due to moisture ingress, with changes in the dielectric data. In addition, dielectric studies of the neat adhesive have been undertaken, as have gravimetric and dynamic mechanical thermal analysis. These have helped reveal the effects of ageing upon the adhesive layer itself.

Pethrick, R. A.; Hayward, D.; McConnell, B. K.; Crane, R. L.

2005-05-01

318

[Knee joint cyst].  

PubMed

Ninety cases of knee joint cysts were treated surgically. This included 50 patients with rheumatoid arthritis, 22 patients with degenerative-deforming changes, ten children with true cysts, and eight ones with post-traumatic cysts. Double-contrast X-ray examination with Lipiodol Ultra-fluid and air is of the best diagnostic value. All cases of knee joint cysts were treated surgically with a careful plastic closure of cyst gate. For this purpose the authors used the arcus tendon of the semi-membranous muscle. In cases of rheumatoid arthritis and degenerative changes cyst removal was preceded by synovectomy of the knee joint. Early and remote were good, no recurrence was observed. PMID:1299044

Noczy?ski, L; Benarz, W; Wojczys, R

1992-11-01

319

Joint polar satellite system  

NASA Astrophysics Data System (ADS)

The Joint Polar Satellite System (JPSS) is a joint NOAA/NASA mission comprised of a series of polar orbiting weather and climate monitoring satellites which will fly in a sun-synchronous orbit, with a 1330 equatorial crossing time. JPSS resulted from the decision to reconstitute the National Polar-orbiting Operational Environmental Satellite System (NPOESS) into two separate programs, one to be run by the Department of Defense (DOD) and the other by NOAA. This decision was reached in early 2010, after numerous development issues caused a series of unacceptable delays in launching the NPOESS system.

Trenkle, Timothy; Driggers, Phillip

2011-10-01

320

Joint reversible data hiding and image encryption  

NASA Astrophysics Data System (ADS)

Image encryption process is jointed with reversible data hiding in this paper, where the data to be hided are modulated by different secret keys selected for encryption. To extract the hided data from the cipher-text, the different tentative decrypted results are tested against typical random distribution in both spatial and frequency domain and the goodnessof- fit degrees are compared to extract one hided bit. The encryption based data hiding process is inherently reversible. Experiments demonstrate the proposed scheme's effectiveness on natural and textural images, both in gray-level and binary forms.

Yang, Bian; Busch, Christoph; Niu, Xiamu

2010-02-01

321

Mapping knowledge domains: Characterizing PNAS  

PubMed Central

A review of data mining and analysis techniques that can be used for the mapping of knowledge domains is given. Literature mapping techniques can be based on authors, documents, journals, words, and/or indicators. Most mapping questions are related to research assessment or to the structure and dynamics of disciplines or networks. Several mapping techniques are demonstrated on a data set comprising 20 years of papers published in PNAS. Data from a variety of sources are merged to provide unique indicators of the domain bounded by PNAS. By using funding source information and citation counts, it is shown that, on an aggregate basis, papers funded jointly by the U.S. Public Health Service (which includes the National Institutes of Health) and non-U.S. government sources outperform papers funded by other sources, including by the U.S. Public Health Service alone. Grant data from the National Institute on Aging show that, on average, papers from large grants are cited more than those from small grants, with performance increasing with grant amount. A map of the highest performing papers over the 20-year period was generated by using citation analysis. Changes and trends in the subjects of highest impact within the PNAS domain are described. Interactions between topics over the most recent 5-year period are also detailed.

Boyack, Kevin W.

2004-01-01

322

New Joint Sealants. Criteria, Design and Materials.  

ERIC Educational Resources Information Center

|Contents include--(1) sealing concrete joints, (2) sealing glass and metal joints, (3) metal and glass joint sealants from a fabricator's viewpoint, (4) a theory of adhesion for joint sealants, (5) geometry of simple joint seals under strain, (6) joint sealant specifications from a manufacturer's viewpoint, (7) joint sealant requirements from an…

Building Research Inst., Inc., Washington, DC.

323

Joint Fires Training Guide for a Corps Joint Task Force.  

National Technical Information Service (NTIS)

A detailed analysis of responsibilities, inputs, processes, outputs, and interactions was conducted for the staff elements and cells involved in joint fires at the Corps Joint Task Force level. This research product documents that analysis. The purpose of...

J. F. Love

1998-01-01

324

First metatarsophalangeal joint arthrodesis.  

PubMed

First MTP joint arthrodesis continues to be a time-honored, effective, and valuable procedure as a primary or secondary surgery for various pathologies afflicting the first ray segment. Though commonly thought of as a salvage procedure, it has proven beneficial in the management of primary hallux limitus and rigidus, geriatric hallux valgus deformity, severe arthritis of any etiology, and conditions in which joint instability or deformity are not readily correctable by more traditional approaches. Since its initial description in the 1800s, the procedure has continued to be popular among orthopedic and podiatric surgeons. Success of the procedure is highly dependent on the position of fusion. Though surgeons are often fascinated and at times obsessed with a particular fixation technique, it cannot be over-emphasized that this takes a back seat to the importance of achieving proper position to meet the needs of an individual patient. Unlike joint resection or implant arthroplasty procedures, which commonly leave the hallux lacking stability and propulsion, first MPJ fusion has been shown to be effective during weight bearing and propulsion. The success enjoyed by the senior author continues to reinforce that motion is not necessary at the first MTP joint for good, pain-free function. PMID:15012033

Yu, Gerard V; Gorby, Paul O

2004-01-01

325

Clad metal joint closure  

SciTech Connect

A plasma arc spray overlay of cladding metals is used over joints between clad metal pieces to provide a continuous cladding metal surface. The technique permits applying an overlay of a high melting point cladding metal to a cladding metal surface without excessive heating of the backing metal.

Siebert, O.W.

1985-04-09

326

Dolphin Skeleton (Gliding Joint)  

NSDL National Science Digital Library

The dolphin is built to be sleek. Its body is made of almost entirely backbone (a gliding joint) which makes it very flexible under water. The ribs protect the inner organs of the dolphin and the tail beats from side to side, thrusting the animal forward.

Ketan Patel (California State University, Fullerton;)

2007-07-14

327

Joint Criminal Enterprise  

Microsoft Academic Search

The Joint Criminal Enterprise (JCE) doctrine has made an impressive appearance on the stage of the International Criminal Tribunal for the former Yugoslavia. However, the initial enthusiasm has faded somewhat recently as doubts about the doctrine's broad applicability have started to dominate the discussion. In this article, the author argues that we should not deplore the partial demise of the

Harmen van der Wilt

2007-01-01

328

Imaging the temporomandibular joint  

SciTech Connect

This book encompasses all imaging modalities as they apply to the Temporomandibular Joint and its disorders. The volume employs correlative line drawings to elaborate on diagnostic images. It helps teach methods of TMJ imaging and describes findings identified by different imaging modalities to both radiologists and dental clinicians.

Katzberg, R.W.; Manzione, J.V.; Westesson, P.L.

1988-01-01

329

BETTER BRAZED JOINTS  

Microsoft Academic Search

Brazing is presented as a technique for making high quality joints for ; use in corrosive environments and at elevated temperatures. The characteristics ; of an ideal, as well as commercially available brazing alloys based on silver, ; nickel, palladium, and gold are discussed. The conditions and equipment required ; for this type of brazing are described, as are the

1963-01-01

330

Evolving flexible joint morphologies  

Microsoft Academic Search

Transferring virtual robotic designs into physical robots has become possible with the development of 3D printers. Accurately simulating the performance of real robots in a virtual environment requires modeling a variety of conditions, including the physical composition of the robots themselves. In this paper, we investigate how modeling material flexibility through the use of a passive joint affects the resulting

Jared M. Moore; Philip K. McKinley

2012-01-01

331

Bladder Operated Robotic Joint.  

National Technical Information Service (NTIS)

This invention is a robotic joint which is operated by inflatable bladders and which can be used in applications where it is desired to move or hold an object. A support block supports an elongated plate to which is pivotally attached a finger. A tension ...

G. A. Robertson

1992-01-01

332

Lubrication of Fretting Joints.  

National Technical Information Service (NTIS)

The performance and optimum application domains of antifretting lubricants were assessed, using a specially designed test apparatus. Over 70 tests were carried out on 5, 11 and 18 mm samples, with steel, titanium and aluminum substrates. Results show that...

M. Maillat H. E. Hintermann H. Boving H. R. Kocher G. Mondin

1983-01-01

333

On-line identification of new coal type using joint probability density arbiter  

Microsoft Academic Search

A new approach for on-line identification of new coal type as well as existing coal types by combining the principal component analysis (PCA) technique and the joint probability density arbiter is presented. The flame features were extracted in the time domain and frequency domain from each flame oscillation signal and formed an original feature vector. The principal component analysis technique

Lijun Xu; Cheng Tan; Xiaomin Li; Chenfeng Xu

2010-01-01

334

Joint Laser Designation Procedures (JLASER).  

National Technical Information Service (NTIS)

This publication provides joint procedures for employing laser designators with target acquisition systems and laser-guided weapons to enhance the combat effectiveness of joint US forces. Application Procedures established in this publication apply to the...

1991-01-01

335

Collaborative Domain Construction  

Microsoft Academic Search

Domain-oriented systems offer many potential benefits for end-users such as more intuitive interfaces, better task support, and knowledge-based assistance. A key challenge for system developers constructing domain-oriented systems is determining what the current domain is and what the future domain should be; i.e. what entities should the system embody and how should they be represented. Determining an appropriate domain model

Gerhard Fischer; Stefanie Lindstaedt; Jonathan Ostwald; Markus Stolze; Tamara Sumner; Beatrix Zimmermann

336

Sacroiliac joint abnormalities in paraplegics  

Microsoft Academic Search

We studied 186 paraplegic patients to clarify the pathogenesis of the sacroiliac (SI) joint abnormalities reported in these patients. Partial or complete fusion of SI joints was noted in 47 patients (25%), and milder degrees of abnormalities of these joints were present in 27 patients (15%). The abnormalities differed from those seen in ankylosing spondylitis and were found more commonly

M A Khan; I Kushner; A A Freehafer

1979-01-01

337

Joint Experimentation: A Systems Approach.  

National Technical Information Service (NTIS)

The Secretary of Defense charged the United States Atlantic Command (USACOM) on I October 1998 to conduct Joint Experimentation (JE) in support of the Defense of Department (DoD) Joint Vision 2010 concept. Since a common definition of joint experimentatio...

K. T. Royar

2000-01-01

338

Double slotted socket spherical joint  

DOEpatents

A new class of spherical joints is disclosed. These spherical joints are capable of extremely large angular displacements (full cone angles in excess of 270.degree.), while exhibiting no singularities or dead spots in their range of motion. These joints can improve or simplify a wide range of mechanical devices.

Bieg, Lothar F. (Albuquerque, NM); Benavides, Gilbert L. (Albuquerque, NM)

2001-05-22

339

The Challenges of Joint Attention  

Microsoft Academic Search

This paper discusses the concept of joint at- tention and the dierent skills underlying its development. We argue that joint attention is much more than gaze following or simul- taneous looking because it implies a shared intentional relation to the world. The current state-of-the-art in robotic and computational models of the dierent prerequisites of joint attention is discussed in relation

Frederic Kaplan; Verena V. Hafner

2004-01-01

340

Formation of tough composite joints  

SciTech Connect

Joints which exhibit tough fracture behavior were formed in a composite with a Si/SiC matrix reinforced with Textron SCS-6 fibers with either boron nitride or silicon nitride fiber coatings. In composites with BN coatings fibers were aligned uniaxially, while composites with Si{sub 3}N{sub 4}-coated fibers had a 0/90{degree} architecture. Lapped joints (joints with overlapping fingers) were necessary to obtain tough behavior. Geometrical requirements necessary to avoid brittle joint failure have been proposed. Joints with a simple overlap geometry (only a few fingers) would have to be very long in order to prevent brittle failure. Typical failure in these joints is caused by a crack propagating along the interfaces between the joint fingers. Joints of the same overall length, but with geometry changed to be symmetric about the joint centerline and with an extra shear surface exhibited tough fractures accompanied with extensive fiber pullout. The initial matrix cracking of these joints was relatively low because cracks propagated easily through the ends of the fingers. Joints with an optimized stepped sawtooth geometry produced composite-like failures with the stress/strain curves containing an elastic region followed by a region of rising stress with an increase of strain. Increasing the fiber/matrix interfacial strength from 9 to 25 MPa, by changing the fiber coating, increased matrix cracking and ultimate strength of the composite significantly. The best joints had matrix cracking stress and ultimate strength of 138 and 240 MPa, respectively. Joint failure was preceded by multiple matrix cracking in the entire composite. The high strength of the joints will permit building of structures containing joints with only a minor reduction of design stresses.

Brun, M.K. [GE Corporate Research and Development, Schenectady, NY (United States)

1997-05-01

341

Metalceramic joint assembly  

Microsoft Academic Search

A metal-ceramic joint assembly in which a brazing alloy is situated between metallic and ceramic members. The metallic member is either an aluminum-containing stainless steel, a high chromium-content ferritic stainless steel or an iron nickel alloy with a corrosion protection coating. The brazing alloy, in turn, is either an Au-based or Ni-based alloy with a brazing temperature in the range

Jian

2002-01-01

342

Charcot joint of shoulder  

Microsoft Academic Search

Neuropathic arthropathy involving the shoulder is a relatively rare chronic disorder characterized by the destruction of the\\u000a joint which is also associated with decreased sensory innervation (Lequesne et al. in Rev Rhum Mal Osteoartic 49(6):427–437,\\u000a 1982; Yan?k et al. in Rheumatol Int 24(4):238–241, 2004). Here, we report a case of neuropathic arthropathy of the shoulder (charcot shoulder), secondary to syringomyelia

Korhan Ozkan; Umut Yavuz; Budak Akman; Namik Kemal Ozkan; Levent Eralp

2008-01-01

343

Joint Venture Marketing  

Microsoft Academic Search

Joint venture marketing links a for profit organization with a non-profit organization for their mutual benefit. Since American Express launched its 1981 Statue of Liberty\\/Ellis Island campaign, the strategy has proliferated among all types of health care organizations, manufacturers and even financial and educational institutions. With the successes have come concerns about non-profits having to compromise their integrity, the elimination

Nora Ganin Barnes

1991-01-01

344

Jointly Sponsored Research Program  

Microsoft Academic Search

U.S. Department of Energy (DOE) Cooperative Agreement DE-FC26-98FT40321 funded through the Office of Fossil Energy and administered at the National Energy Technology Laboratory (NETL) supported the performance of a Jointly Sponsored Research Program (JSRP) at the Energy & Environmental Research Center (EERC) with a minimum 50% nonfederal cost share to assist industry in commercializing and effectively applying highly efficient, nonpolluting

Everett A. Sondreal; John G. Hendrikson; Thomas A. Erickson

2009-01-01

345

38 CFR 4.45 - The joints.  

Code of Federal Regulations, 2010 CFR

...vertebrae, are considered groups of minor joints, ratable on a parity with major joints. The lumbosacral articulation and both sacroiliac joints are considered to be a group of minor joints, ratable on disturbance of lumbar spine...

2009-07-01

346

49 CFR 213.121 - Rail joints.  

Code of Federal Regulations, 2012 CFR

...Transportation 4 2012-10-01 2012-10-01 false Rail joints. 213.121 Section 213.121 Transportation...SAFETY STANDARDS Track Structure § 213.121 Rail joints. (a) Each rail joint, insulated joint, and compromise...

2012-10-01

347

49 CFR 213.121 - Rail joints.  

Code of Federal Regulations, 2011 CFR

...Transportation 4 2011-10-01 2011-10-01 false Rail joints. 213.121 Section 213.121 Transportation...SAFETY STANDARDS Track Structure § 213.121 Rail joints. (a) Each rail joint, insulated joint, and compromise...

2011-10-01

348

Metacarpophalangeal joint arthritis.  

PubMed

Arthritis of the metacarpophalangeal joint can result in considerable disability and pain. Inflammatory, posttraumatic, crystalline, and osteoarthritis are common etiologies of joint disease. A variety of nonsurgical treatment options have been shown to be effective, including activity modification, anti-inflammatory medications, splinting, and cortisone injections. In addition, newer generation disease-modifying antirheumatic drugs geared toward the treatment of rheumatoid arthritis have shown promise in retarding the inflammatory process. Another, relatively newer, conservative treatment option includes topical anti-inflammatories such as diclofenac sodium that are now approved by the Federal Drug Administration. Surgical treatment options most commonly include arthroplasty and arthrodesis. In the treatment of thumb metacarpophalangeal arthritis, arthrodesis is a popular and generally reliable surgical solution. In the fingers, arthroplasty remains the most common treatment option. Traditional constrained silicone joint replacements remain the most commonly used. Newer generation, unconstrained, surface replacement arthroplasties have shown promise in the treatment of osteoarthritis and select cases of inflammatory arthritis in which there is good bone stock, no or minimal deformity, adequate supporting soft tissues, and good disease control. PMID:21276901

Rizzo, Marco

2011-02-01

349

Dynamic glenohumeral joint stability.  

PubMed

Stability of the glenohumeral joint with an anterior, posterior, and inferior displacement force of 50 N was measured in a dynamic shoulder model. Controlled hydrodynamic actuator forces were applied to the deltoid muscle and to the rotator cuff in seven anatomic specimens. During elevation of the arm the position of the humerus was measured with a six-degree-of-freedom ultrasonic sensor device. The rotational center of the humeral head was used as a reference point for translation. A displacement force of 50 N led to significant humeral head displacement anteriorly and posteriorly but not inferiorly. A 50% reduction of rotator cuff forces increased anterior displacement by 46% and posterior displacement by 31%. Venting of the glenohumeral joint space and of the subacromial bursa resulted in a 50% increase of anterior displacement, a 19% increase of posterior displacement, and significant inferior displacement. This study demonstrates that in addition to passive stabilizers and negative intraarticular pressure, rotator cuff force significantly contributes to stabilization of the glenohumeral joint during arm motion. Muscle strength and coordination should gain more emphasis in the diagnosis and treatment of shoulder instability. PMID:9524340

Wuelker, N; Korell, M; Thren, K

350

Performance of MIMO with Frequency Domain Packet Scheduling in UTRAN LTE Downlink  

Microsoft Academic Search

This paper addresses the performance of spatial division multiplexing (SDM) multiple-input multiple-output (MIMO) techniques together with frequency domain packet scheduling (FDPS) based on UTRAN long term evolution (LTE) downlink. Two SDM concepts currently considered in 3GPP are the single-user (SU-) and the multi-user (MU-) MIMO. For MU-MIMO, multiple users can be scheduled on different streams on the same time-frequency resource,

Na Wei; Akhilesh Pokhariyal; Troels B. Sørensen; Troels E. Kolding; Preben E. Mogensen

2007-01-01

351

Laboratory characterization of rock joints  

SciTech Connect

A laboratory characterization of the Apache Leap tuff joints under cyclic pseudostatic and dynamic loads has been undertaken to obtain a better understanding of dynamic joint shear behavior and to generate a complete data set that can be used for validation of existing rock-joint models. Study has indicated that available methods for determining joint roughness coefficient (JRC) significantly underestimate the roughness coefficient of the Apache Leap tuff joints, that will lead to an underestimation of the joint shear strength. The results of the direct shear tests have indicated that both under cyclic pseudostatic and dynamic loadings the joint resistance upon reverse shearing is smaller than that of forward shearing and the joint dilation resulting from forward shearing recovers during reverse shearing. Within the range of variation of shearing velocity used in these tests, the shearing velocity effect on rock-joint behavior seems to be minor, and no noticeable effect on the peak joint shear strength and the joint shear strength for the reverse shearing is observed.

Hsiung, S.M.; Kana, D.D.; Ahola, M.P.; Chowdhury, A.H.; Ghosh, A. [Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

1994-05-01

352

Joint slip in steel electric transmission towers  

Microsoft Academic Search

Joint slip is the relative displacement of a bolted joint under shear. It is greater in transmission towers as bolt diameters are small, members joined are thin, bearing type joints with a lower clamping force are used, and coefficient of friction of galvanized faying surfaces is low. This study on behaviour of such joints, incorporated 36 joint tests, generated joint

N Ungkurapinan; S. R. De S Chandrakeerthy; R. K. N. D Rajapakse; S. B Yue

2003-01-01

353

Evolutionary conservation of domain-domain interactions  

Microsoft Academic Search

Background  Recently, there has been much interest in relating domain-domain interactions (DDIs) to protein-protein interactions (PPIs)\\u000a and vice versa, in an attempt to understand the molecular basis of PPIs.\\u000a \\u000a \\u000a \\u000a \\u000a Results  Here we map structurally derived DDIs onto the cellular PPI networks of different organisms and demonstrate that there is\\u000a a catalog of domain pairs that is used to mediate various interactions in

Zohar Itzhaki; Eyal Akiva; Yael Altuvia; Hanah Margalit

2007-01-01

354

Lower Bag Domains  

Microsoft Academic Search

Two lower bag domain constructions are introduced: the initial construction which gives free lower monoids, and the final co nstruction which is defined explicitly in terms of second order functions. The latter is analyzed closely. For sober dcpo's, the elements of the final lower bag domains can be described concretely as bags. For continuous domains, init ial and final lower

Reinhold Heckmann

1995-01-01

355

Visualizing latent domain knowledge  

Microsoft Academic Search

Knowledge discovery and data mining commonly rely on finding salient patterns of association from a vast amount of data. Traditional citation analysis of scientific literature draws insights from strong citation patterns. Latent domain knowledge, in contrast to the mainstream domain knowledge, often consists of highly relevant but relatively infrequently cited scientific works. Visualizing latent domain knowledge presents a significant chal-

Chaomei Chen; Jasna Kuljis; Ray J. Paul

2001-01-01

356

Closure domains in magnetite  

Microsoft Academic Search

We have observed clear arrays of closure domains at internal and external boundaries, such as crystal edges, cracks, and chemically altered regions, in a single crystal of magnetite, using the Bitter colloid technique with a (110) viewing plane. The common occurrence of closure domains in magnetite confirms the controlling role of magnetostatic energy in determining domain structures in strongly magnetic

Ozden Ozdemir; Song Xu; David J. Dunlop

1995-01-01

357

Joint hypermobility syndrome.  

PubMed

Although perceived as a rare condition, joint hypermobility syndrome is common. Its prevalence in rheumatology clinics is extremely high. Early estimates suggest that it may be the most common of all rheumatologic conditions. The problem lies in the general lack of awareness of the syndrome, its means of recognition, and the resultant failure to diagnose it correctly when present. It is a worldwide problem. This article provides an overview of hypermobility and hypermobility syndrome, stressing its multisystemic nature and the negative impact that it may have on quality of life, with particular reference to gastrointestinal involvement. PMID:23597972

Fikree, Asma; Aziz, Qasim; Grahame, Rodney

2013-05-01

358

An intermediate complexity marine ecosystem model for the global domain  

Microsoft Academic Search

A new marine ecosystem model designed for the global domain is presented, and model output is compared with field data from nine different locations. Field data were collected as part of the international Joint Global Ocean Flux Study (JGOFS) program, and from historical time series stations. The field data include a wide variety of marine ecosystem types, including nitrogen- and

J. Keith Moore; Scott C. Doney; Joanie A. Kleypas; David M. Glover; Inez Y. Fung

2001-01-01

359

On representations for joint moments using a joint coordinate system.  

PubMed

In studies of the biomechanics of joints, the representation of moments using the joint coordinate system has been discussed by several authors. The primary purpose of this technical brief is to emphasize that there are two distinct, albeit related, representations for moment vectors using the joint coordinate system. These distinct representations are illuminated by exploring connections between the Euler and dual Euler bases, the "nonorthogonal projections" presented in a recent paper by Desroches et al. (2010, "Expression of Joint Moment in the Joint Coordinate System," ASME J. Biomech. Eng., 132(11), p. 11450) and seminal works by Grood and Suntay (Grood and Suntay, 1983, "A Joint Coordinate System for the Clinical Description of Three-Dimensional Motions: Application to the Knee," ASME J. Biomech. Eng., 105(2), pp. 136-144) and Fujie et al. (1996, "Forces and Moment in Six-DOF at the Human Knee Joint: Mathematical Description for Control," Journal of Biomechanics, 29(12), pp. 1577-1585) on the knee joint. It is also shown how the representation using the dual Euler basis leads to straightforward definition of joint stiffnesses. PMID:24008987

O'Reilly, Oliver M; Sena, Mark P; Feeley, Brian T; Lotz, Jeffrey C

2013-11-01

360

Restructuring speech representations using a pitch-adaptive time-frequency smoothing and an instantaneous-frequency-based F0 extraction: Possible role of a repetitive structure in sounds  

Microsoft Academic Search

A set of simple new procedures has been developed to enable the real-time manipulation of speech parame- ters. The proposed method uses pitch-adaptive spec- tral analysis combined with a surface reconstruction method in the time-frequency region, and an excita- tion source design based on group delay manipulation. It also consists of a fundamental frequency (F0) ex- traction method using instantaneous

Hideki Kawahara; Ikuyo Masuda-katsuse; Alain De Cheveigné

1999-01-01

361

Metal to ceramic sealed joint  

DOEpatents

A metal to ceramic sealed joint which can withstand wide variations in temperature and maintain a good seal is provided for use in a device adapted to withstand thermal cycling from about 20 to about 1000 degrees C. The sealed joint includes a metal member, a ceramic member having an end portion, and an active metal braze forming a joint to seal the metal member to the ceramic member. The joint is positioned remote from the end portion of the ceramic member to avoid stresses at the ends or edges of the ceramic member. The sealed joint is particularly suited for use to form sealed metal to ceramic joints in a thermoelectric generator such as a sodium heat engine where a solid ceramic electrolyte is joined to metal parts in the system. 11 figures.

Lasecki, J.V.; Novak, R.F.; McBride, J.R.

1991-08-27

362

Interpolation function for approximating knee joint behavior in human gait  

NASA Astrophysics Data System (ADS)

Starting from the importance of analyzing the kinematic data of the lower limb in gait movement, especially the angular variation of the knee joint, the paper propose an approximation function that can be used for processing the correlation among a multitude of knee cycles. The approximation of the raw knee data was done by Lagrange polynomial interpolation on a signal acquired using Zebris Gait Analysis System. The signal used in approximation belongs to a typical subject extracted from a lot of ten investigated subjects, but the function domain of definition belongs to the entire group. The study of the knee joint kinematics plays an important role in understanding the kinematics of the gait, this articulation having the largest range of motion in whole joints, in gait. The study does not propose to find an approximation function for the adduction-abduction movement of the knee, this being considered a residual movement comparing to the flexion-extension.

Toth-Ta?c?u, Mirela; Pater, Flavius; Stoia, Dan Ioan

2013-10-01

363

A Design Pattern for Asynchronous Web Services in Secure, Cross-Domain Information Sharing  

Microsoft Academic Search

Cross-domain information sharing is the cornerstone of joint operations. This is particularly true in the context of intelligence activities, where raw data must be collected, distributed, analyzed, validated, and annotated before any usable information product can be created. A significant barrier to rapid, efficient, and effective data distribution and analysis is the tiered, multi-domain access paradigm employed by the DOD

Robert Dourandish; Nina Zumel; Michael Manno

2007-01-01

364

CRUCIFORM CONTROL ROD JOINT  

DOEpatents

An invention is described which relates to nuclear reactor control rod components and more particularly to a joint between cruciform control rod members and cruciform control rod follower members. In one embodiment this invention provides interfitting crossed arms at adjacent ends of a control rod and its follower in abutting relation. This holds the members against relative opposite longitudinal movement while a compression member keys the arms against relative opposite rotation around a common axis. Means are also provided for centering the control rod and its follower on a common axis and for selectively releasing the control rod from its follower for the insertion of a replacement of the control rod and reuse of the follower. (AEC)

Thorp, A.G. II

1962-08-01

365

Smart material joint band  

NASA Astrophysics Data System (ADS)

The present invention relates to an improved connector for joining two tubular members together. The connector is formed by a plurality of longitudinally extending fingers extending from an end of one of the tubular members and at least one locking groove in the other of the tubular members for receiving the fingers. The connector further includes a circumferentially extending wire member which is received in a notch in a head portion of each of the plurality of fingers. The wire member is preferably formed from a shape memory alloy and has an original circumference less than the circumference of a circle formed by the notches in the head portions of the fingers. The connector includes apertures through which electric wires may be connected to the shape memory alloy ring member so as to cause the shape memory alloy ring member to return to its original shape and allow release of the joint connection.

Tucchio, Michael A.; Stoodt, Robert A.; Livsey, Robert A.

1993-12-01

366

Joint Targeting Planning Training Guide.  

National Technical Information Service (NTIS)

This guide resulted from an effort to develop a new approach to assessment and diagnostic training feedback in joint training. The guide resulted from a front-end analysis of joint targeting for an air campaign planning simulation. The analysis generated ...

J. F. Love

1998-01-01

367

Managing International Joint Venture Relationships  

Microsoft Academic Search

The purpose of the study is to describe and analyze the formation and development of international joint venture processes and relationships between the partners over time. Moreover, the study analyzes how far foreign partners have been successful in developing new contacts and in expanding their activities in local markets. We have carried out two case studies on joint ventures between

Akmal S. Hyder; Pervez N. Ghauri

2000-01-01

368

Articulated Joint for Deployable Structures.  

National Technical Information Service (NTIS)

A joint is described for connecting a pair of beams to pivot them between positions in alignment or beside one another, which is of light weight and which operates in a controlled manner. The joint includes a pair of fittings and at least one center link ...

N. D. Craighead R. J. Preliasco T. D. Hult

1983-01-01

369

International retail joint venture learning  

Microsoft Academic Search

Where retail entry mode decision-making is examined in the literature, it has almost exclusively focused upon international store acquisitions and franchising growth and expansion. In contrast, international joint venture decision-making processes are visibly absent in the international retail literature. This article explores three retail multinationals' international retail joint venturing experiences, extracting some of the salient lessons learned at each stage

Mark Palmer

2006-01-01

370

Industrial robots with seven joints  

Microsoft Academic Search

In a physical 3-dimensional free space at most six degrees of freedom can be independent, i.e. three for position and three for orientation. Intuitively robots with six joints are adequate to execute any tasks. However, in reality, constraints often exist under the complex environment so that six joints are not quite enough for the robots. An insertion of an additional

J. Y. S. Luh; Y. L. Gu

1985-01-01

371

Joint attention and language evolution  

Microsoft Academic Search

This study investigates how more advanced joint attentional mechanisms, rather than only shared attention between two agents and an object, can be implemented and how they influence the results of language games played by these agents. We present computer simulations with language games showing that adding constructs that mimic the three stages of joint attention identified in children's early development

Johan Kwisthout; Paul Vogt; Pim Haselager; Ton Dijkstra

2008-01-01

372

High pressure tubular swivel joint  

Microsoft Academic Search

A swivel joint and connection for abutting high pressure hydraulic manifolds are described. The joint consists of 2 flanged nonrotating swivel bodies, with one of the nonrotating swivel bodies having a rotating swivel body journaled in it. A flanged tubular sleeve is secured between the adjacent end faces of the 2 nonrotating swivel bodies. A static annular seal is disposed

Kendrick

1976-01-01

373

High pressure tubular swivel joint  

Microsoft Academic Search

A swivel joint and connection for abutting high pressure hydraulic manifolding are described. The joint consists of 2 flanged nonrotating swivel bodies, with one of the nonrotating swivel bodies having a rotating swivel body journaled in it. A flanged tubular sleeve is secured between the adjacent end faces of the 2 nonrotating swivel bodies, with the opposite ends of the

W. D. Kendrick; B. J. Frazier

1976-01-01

374

Detailed FDTD analysis of electromagnetic fields penetrating narrow slots and lapped joints in thick conducting screens  

Microsoft Academic Search

The physics of electromagnetic-wave transmission through narrow slots and tapped joints in thick conducting screens is examined in detail by applying numerical models to compute both field distributions within the slots and joints, and fields transmitted to the shadow region. The modeling tools used is the finite-difference time-domain (FD-TD) method, using a Faraday's-law contour integral approach to modify the basic

Allen Taflove; Fady Harfoush; Korada R. Umashankar; Benjamin Beker; Kane S. Yee

1988-01-01

375

Joint torque sensory feedback in the control of a PUMA manipulator  

Microsoft Academic Search

The design of a joint torque sensor for a PUMA 500 and its characteristics are described. Using this sensor, a joint torque servomechanism is designed and implemented. A model of the actuator-transmission-load system, including flexibility, is developed and verified using both time- and frequency-domain techniques. Compensators based on this model are designed and tested. Experimental results obtained from pure torque

L. E. Pfeffer; O. Khatib; J. Hake

1989-01-01

376

Domains and Naive Theories  

PubMed Central

Human cognition entails domain-specific cognitive processes that influence memory, attention, categorization, problem-solving, reasoning, and knowledge organization. This review examines domain-specific causal theories, which are of particular interest for permitting an examination of how knowledge structures change over time. We first describe the properties of commonsense theories, and how commonsense theories differ from scientific theories, illustrating with children’s classification of biological and non-biological kinds. We next consider the implications of domain-specificity for broader issues regarding cognitive development and conceptual change. We then examine the extent to which domain-specific theories interact, and how people reconcile competing causal frameworks. Future directions for research include examining how different content domains interact, the nature of theory change, the role of context (including culture, language, and social interaction) in inducing different frameworks, and the neural bases for domain-specific reasoning.

Gelman, Susan A.; Noles, Nicholaus S.

2013-01-01

377

Joint Tactics, Techniques, and Procedures for Joint Logistics Over the Shore.  

National Technical Information Service (NTIS)

1. Purpose. This publication sets forth joint doctrine and joint tactics, techniques, and procedures for conducting Joint Logistics Over The Shore (JLOTS) operations by the US Military Services during the conduct of joint operations. It provides basic doc...

1991-01-01

378

Ubiquitin-binding domains  

PubMed Central

The covalent modification of proteins by ubiquitination is a major regulatory mechanism of protein degradation and quality control, endocytosis, vesicular trafficking, cell-cycle control, stress response, DNA repair, growth-factor signalling, transcription, gene silencing and other areas of biology. A class of specific ubiquitin-binding domains mediates most of the effects of protein ubiquitination. The known membership of this group has expanded rapidly and now includes at least sixteen domains: UBA, UIM, MIU, DUIM, CUE, GAT, NZF, A20 ZnF, UBP ZnF, UBZ, Ubc, UEV, UBM, GLUE, Jab1/MPN and PFU. The structures of many of the complexes with mono-ubiquitin have been determined, revealing interactions with multiple surfaces on ubiquitin. Inroads into understanding polyubiquitin specificity have been made for two UBA domains, whose structures have been characterized in complex with Lys48-linked di-ubiquitin. Several ubiquitin-binding domains, including the UIM, CUE and A20 ZnF (zinc finger) domains, promote auto-ubiquitination, which regulates the activity of proteins that contain them. At least one of these domains, the A20 ZnF, acts as a ubiquitin ligase by recruiting a ubiquitin–ubiquitin-conjugating enzyme thiolester adduct in a process that depends on the ubiquitin-binding activity of the A20 ZnF. The affinities of the mono-ubiquitin-binding interactions of these domains span a wide range, but are most commonly weak, with Kd>100 ?M. The weak interactions between individual domains and mono-ubiquitin are leveraged into physiologically relevant high-affinity interactions via several mechanisms: ubiquitin polymerization, modification multiplicity, oligomerization of ubiquitinated proteins and binding domain proteins, tandem-binding domains, binding domains with multiple ubiquitin-binding sites and co-operativity between ubiquitin binding and binding through other domains to phospholipids and small G-proteins.

Hurley, James H.; Lee, Sangho; Prag, Gali

2006-01-01

379

Domain wall nanoelectronics  

NASA Astrophysics Data System (ADS)

Domains in ferroelectrics were considered to be well understood by the middle of the last century: They were generally rectilinear, and their walls were Ising-like. Their simplicity stood in stark contrast to the more complex Bloch walls or Néel walls in magnets. Only within the past decade and with the introduction of atomic-resolution studies via transmission electron microscopy, electron holography, and atomic force microscopy with polarization sensitivity has their real complexity been revealed. Additional phenomena appear in recent studies, especially of magnetoelectric materials, where functional properties inside domain walls are being directly measured. In this paper these studies are reviewed, focusing attention on ferroelectrics and multiferroics but making comparisons where possible with magnetic domains and domain walls. An important part of this review will concern device applications, with the spotlight on a new paradigm of ferroic devices where the domain walls, rather than the domains, are the active element. Here magnetic wall microelectronics is already in full swing, owing largely to the work of Cowburn and of Parkin and their colleagues. These devices exploit the high domain wall mobilities in magnets and their resulting high velocities, which can be supersonic, as shown by Kreines’ and co-workers 30 years ago. By comparison, nanoelectronic devices employing ferroelectric domain walls often have slower domain wall speeds, but may exploit their smaller size as well as their different functional properties. These include domain wall conductivity (metallic or even superconducting in bulk insulating or semiconducting oxides) and the fact that domain walls can be ferromagnetic while the surrounding domains are not.

Catalan, G.; Seidel, J.; Ramesh, R.; Scott, J. F.

2012-01-01

380

Symbolic Domain Decomposition  

Microsoft Academic Search

Decomposing the domain of a function into parts has many uses in mathematics.\\u000aA domain may naturally be a union of pieces, a function may be defined by\\u000acases, or different boundary conditions may hold on different regions. For any\\u000aparticular problem the domain can be given explicitly, but when dealing with a\\u000afamily of problems given in terms of

Jacques Carette; Alan P. Sexton; Volker Sorge; Stephen M. Watt

2010-01-01

381

Provocative sacroiliac joint maneuvers and sacroiliac joint block are unreliable for diagnosing sacroiliac joint pain  

Microsoft Academic Search

Mapping studies of pain elicited by injections into the sacroiliac joints (SIJs) suggest that sacroiliac joint syndrome (SIJS) may manifest as low back pain, sciatica, or trochanteric pain. Neither patient-reported symptoms nor provocative SIJ maneuvers are sensitive or specific for SIJS when SIJ block is used as the diagnostic gold standard. This has led to increasing diagnostic use of SIJ

Jean-Marie Berthelot; Jean-Jacques Labat; Benoît Le Goff; François Gouin; Yves Maugars

2006-01-01

382

Applications Of The Universal Joint Task List To Joint Exercise Results  

Microsoft Academic Search

The foundation of readiness is training. The Chairman, Joint Chiefs of Staff (CJCS) Joint Training Program institutes methods for identifying training requirements through review of the Commander-in-Chief's (CINC) missions and the compilation of Joint Mission Essential Task Lists. The Universal Joint Task List comprehensively outlines these joint essential tasks, providing a summary of CINC missions, joint tasks, and corresponding supporting

Sam H. Parry; Michael C. McAneny; Richard J. Dromerhauser

1997-01-01

383

Applications of the universal joint task list to joint exercise results  

Microsoft Academic Search

The foundation of readiness is training. The Chairman, Joint Chiefs of Staff (CJCS) Joint Training Program institutes methods for identifying training requirements through review of the Commander-in-Chief's (CINC) missions and the compilation of Joint Mission Essential Task Lists. The Universal Joint Task List comprehen- sively outlines these joint essential tasks, providing a summary of CINC missions, joint tasks, and corre-

Sam H. Parry; Michael C. McAneny; Richard J. Dromerhauser

1997-01-01

384

Regenerative Medicine and Restoration of Joint Function.  

National Technical Information Service (NTIS)

Currently amputation, arthrodesis (joint fusion), or joint replacement are used to treat a joint with an intra-articular fracture or destroyed by a combat injury. Generation of personalized, anatomically shaped biological implants formed using techniques ...

E. Toyserkani M. Hurtig P. Zalzal R. Kandel R. Pilliar

2012-01-01

385

Evaluation of Joint Sealants of Concrete Pavements.  

National Technical Information Service (NTIS)

This report document investigation of concrete pavement joint sealants which began with project 1371 'Evaluation of Joint Sealants.' The purpose of the continued investigation is to propose specification and test protocol for joint sealants in concrete pa...

A. H. Gurjar T. Tang D. G. Zollinger

1997-01-01

386

Standing Joint Force Headquarters: A Planning Multiplier.  

National Technical Information Service (NTIS)

The Standing Joint Force Headquarters (SJFHQ) provides a planning multiplier by bringing both joint and regional expertise to the Joint Task Force Headquarters (JTFHQ), thereby increasing its capabilities. These capabilities assist in the rapid establishm...

C. A. Barkley

2006-01-01

387

Quantitative Continuous Domains  

Microsoft Academic Search

We relate two approaches to Quantitative Domain Theory, the partial metrics of Steve Matthews and the measurements of Keye Martin, by showing that stable partial metrics are in one-to-one correspondence to weakly modular measurements. It is shown that every ?-algebraic domain admits a partial metric whose associated measurement assigns zero precisely to the set of maximal elements, a condition which

Pawel Waszkiewicz

2003-01-01

388

Domain wall filters  

SciTech Connect

We propose using the extra dimension separating the domain walls carrying lattice quarks of opposite handedness to gradually filter out the ultraviolet fluctuations of the gauge fields that are felt by the fermionic excitations living in the bulk. This generalization of the homogeneous domain wall construction has some theoretical features that seem nontrivial.

Oliver Baer; Rajamani Narayanan; Herbert Neuberger; Oliver Witzel

2007-03-15

389

Modeling Protein Domain Function  

ERIC Educational Resources Information Center

|This simple but effective laboratory exercise helps students understand the concept of protein domain function. They use foam beads, Styrofoam craft balls, and pipe cleaners to explore how domains within protein active sites interact to form a functional protein. The activity allows students to gain content mastery and an understanding of the…

Baker, William P.; Jones, Carleton "Buck"; Hull, Elizabeth

2007-01-01

390

Joint services electronics program  

NASA Astrophysics Data System (ADS)

The transfer of the compact range and target identification technology initiated under JSEP support for time domain studies continues to make large advances. Using other sources of support, design for a mini-chamber has now been generated and has been constructed. This range is designed to study smaller targets at higher frequencies. The research has proven to be of intense interest to DoD and the aerospace industry and our compact range consortium represents a major cross section of the aerospace and electronic industries, including additional major support from several DoD agencies. In fact, the total support in these experimental studies substantially exceeds our JSEP support. This research is truly guiding a major portion of this technology in the USA and has been extremely important for stealth technology advances.

Peters, Leon, Jr.

1990-11-01

391

Sac phosphatase domain proteins.  

PubMed Central

Advances in our understanding of the roles of phosphatidylinositol phosphates in controlling cellular functions such as endocytosis, exocytosis and the actin cytoskeleton have included new insights into the phosphatases that are responsible for the interconversion of these lipids. One of these is an entirely novel class of phosphatase domain found in a number of well characterized proteins. Proteins containing this Sac phosphatase domain include the yeast Saccharomyces cerevisiae proteins Sac1p and Fig4p. The Sac phosphatase domain is also found within the mammalian phosphoinositide 5-phosphatase synaptojanin and the yeast synaptojanin homologues Inp51p, Inp52p and Inp53p. These proteins therefore contain both Sac phosphatase and 5-phosphatase domains. This review describes the Sac phosphatase domain-containing proteins and their actions, with particular reference to the genetic and biochemical insights provided by study of the yeast Saccharomyces cerevisiae.

Hughes, W E; Cooke, F T; Parker, P J

2000-01-01

392

Soldering of mild steels: functional joints  

SciTech Connect

In recent years, adhesive joints have replaced numerous soldered joints, especially in applications where electrical conductivity is not required from the members of the joint. Nevertheless, soldered joints are still used in applications ranging from electronics to high-technology components. The present work seeks to demonstrate that soldered joints, which can be considered as functional joints, have very good mechanical properties and can provide more than acceptable levels of leak tightness. Hence, microstructural characterisation studies have been carried out on the filler metals used to solder mild steel, the surface preparation required to achieve the best final properties has been assessed, the joints characterised by means of radiography and the mechanical properties of the joints determined. The results obtained for soldered joints have been compared with those obtained from adhesive and hybrid joints. Finally, scanning electron microscopy has been performed on the fracture surfaces of the soldered joint.

Molleda, F.; Mora, J.; Molleda, F.J.; Carillo, E.; Mellor, B.G

2003-12-15

393

Lumbar Zygapophysial (Facet) Joint Injections  

MedlinePLUS

... arthritis) in the facet joints may contribute to low back pain and may be visualized on diagnostic imaging. However, ... sometimes called “block”) may be performed. If the low back pain pain is reduced or relieved after an anesthetic ...

394

Joint Service Family Support Network.  

National Technical Information Service (NTIS)

The Joint Service Family Support Network is an Office of the Secretary of Defense pilot program in the Pacific Region, working in concert with civilian agencies, intended to establish a comprehensive multi-agency approach for community support and service...

J. Chambers

2007-01-01

395

Joint Infection (Beyond the Basics)  

MedlinePLUS

... The Basics) Patient information: Septic arthritis (The Basics) Pseudomonas aeruginosa skin, soft tissue, and bone infections Septic arthritis ... Clinical manifestations and diagnosis of prosthetic joint infections Pseudomonas aeruginosa skin, soft tissue, and bone infections Septic arthritis ...

396

Joint Measurement Operations Controller (JMOC).  

National Technical Information Service (NTIS)

The increasingly complex interactions of systems of systems for training today's military means that supporting joint training exercises includes supporting live, virtual and constructive simulations. Capturing and integrating observer-based measures with...

B. Schaab J. Ayers J. Feeney M. Puglisi W. Salter

2011-01-01

397

Joint probabilities and quantum cognition  

NASA Astrophysics Data System (ADS)

In this paper we discuss the existence of joint probability distributions for quantumlike response computations in the brain. We do so by focusing on a contextual neural-oscillator model shown to reproduce the main features of behavioral stimulus-response theory. We then exhibit a simple example of contextual random variables not having a joint probability distribution, and describe how such variables can be obtained from neural oscillators, but not from a quantum observable algebra.

de Barros, J. Acacio

2012-12-01

398

Joint probabilities and quantum cognition  

SciTech Connect

In this paper we discuss the existence of joint probability distributions for quantumlike response computations in the brain. We do so by focusing on a contextual neural-oscillator model shown to reproduce the main features of behavioral stimulus-response theory. We then exhibit a simple example of contextual random variables not having a joint probability distribution, and describe how such variables can be obtained from neural oscillators, but not from a quantum observable algebra.

Acacio de Barros, J. [Liberal Studies, 1600 Holloway Ave., San Francisco State University, San Francisco, CA 94132 (United States)

2012-12-18

399

Joint services electronics program  

NASA Astrophysics Data System (ADS)

The central theme of our work at Ginzton is the development of new material and device technologies, along with novel techniques for characterization and measurement, that will allow ultra-high speed electronic and optical processing of information. The different work units of this proposal interconnect the physics and technology of linear and nonlinear optical materials and fibers with new measurement tools which provide unprecedented spatial and temporal resolution. The following paragraphs summarize each of these work units. Professor Bloom's work has been concerned with developing laser techniques for obtaining both time and frequency domain measurements of high speed electrical circuits. His efforts have been concerned with both electrooptic voltage sampling in gallium arsenide and with real time charge sampling in silicon. Using these techniques Bloom and his students have demonstrated 2 ps time resolution, and circuits with response into the 100 GHz range. A particularly exciting achievement during this contract period was the development of the charge sensing technique in silicon. This concept has in turn allowed the development of a very simple silicon optical modulator with extraordinary potential.

Bloom, D. M.; Byer, R. L.; Harris, S. E.; Kino, G. S.; Quate, C. F.

1987-10-01

400

Edge-preserving image deconvolution with nonlocal domain transform  

NASA Astrophysics Data System (ADS)

In this paper, we propose a new approach for performing efficient edge-preserving image deconvolution algorithm based on a nonlocal domain transform (NLDT). We present the geodesic distance-preserving transforming procedure of a 1D signal embedded in 2D space into a new 1D domain via a transformation for simplicity. The nonlocal domain transform derives from the (1D) nonlocal means filter kernel and iteratively and separably applies 1D edge-aware operations. In order to solve the main issue with noisy images that is finding robust estimates for their derivatives, we develop an efficient joint nonlocal domain transform filter in the deblurring process. Furthermore, we derive the discrepancy principle to automatically adjust the regularization parameter at each iteration. We compare our deconvolution algorithm with many competitive deconvolution techniques in terms of ISNR and visual quality.

Yang, Hang; Zhang, Zhongbo; Zhu, Ming; Huang, Heyan

2013-12-01

401

Domain and Antidomain Semigroups  

NASA Astrophysics Data System (ADS)

We axiomatise and study operations for relational domain and antidomain on semigroups and monoids. We relate this approach with previous axiomatisations for semirings, partial transformation semigroups and dynamic predicate logic.

Desharnais, Jules; Jipsen, Peter; Struth, Georg

402

Bubble Domain Structures.  

National Technical Information Service (NTIS)

The patent application provides a film of nickel/iron alloy evaporated onto a substrate at an angle of from 45 degrees to 80 degrees, and having bubble domains formed therein by an applied magnetic field.

I. Puchalska-Hibner

1974-01-01

403

49 CFR 213.351 - Rail joints.  

Code of Federal Regulations, 2011 CFR

...Transportation 4 2011-10-01 2011-10-01 false Rail joints. 213.351 Section 213.351 Transportation...Operations at Track Classes 6 and Higher § 213.351 Rail joints. (a) Each rail joint, insulated joint, and compromise...

2011-10-01

404

49 CFR 213.351 - Rail joints.  

Code of Federal Regulations, 2012 CFR

...Transportation 4 2012-10-01 2012-10-01 false Rail joints. 213.351 Section 213.351 Transportation...Operations at Track Classes 6 and Higher § 213.351 Rail joints. (a) Each rail joint, insulated joint, and compromise...

2012-10-01

405

Synovial chondromatosis of the acromioclavicular joint  

Microsoft Academic Search

Synovial chondromatosis involving the acromioclavicular joint is very rare. We report a case of synovial chondromatosis of the acromioclavicular joint associated with synovial cyst formation. Arthrography of the acromioclavicular joint revealed that the loose bodies lay within a synovial cyst which was in communication with the acromioclavicular joint. Synovectomy including removal of the synovial cyst and the loose bodies relieved

J. Ozaki; Y. Tomita; Y. Nakagawa; O. Kisanuki; S. Tamai

1993-01-01

406

Degenerative joint disease in captive waterfowl  

Microsoft Academic Search

A retrospective study was conducted to evaluate degenerative joint disease (DJD) in captive waterfowl that died or were euthanized at Fresno's Chaffee Zoo in Fresno, California, USA from 2001 to 2005. Of these, 16 out of 33 birds (48%) had DJD in one or both stifle (femoral–tibiotarsal joint; n = 13), hock (tibiotarsal–tarsometatarsal joint; n = 4), or toe joints

L. A. Degernes; P. S. Lynch; H. L. Shivaprasad

2011-01-01

407

Interface failure in lead free solder joints  

Microsoft Academic Search

The phenomenon of interface failure in lead free solder joints was explored using solder joint array tensile testing. The effects of pad metallization, solder alloy, reflow conditions, and post reflow thermal aging were quantified. The joint strength ranged from 5 to 115MPa. The joint ductility dropped to zero in some cases. The interface microstructure and failure mode were characterized for

Robert Darveaux; Corey Reichman; Nokibul Islam

2006-01-01

408

Jointness and the Impact of the War.  

National Technical Information Service (NTIS)

Operations during World War II clearly and repeatedly demonstrated the advantages of jointness and the penalties for failing to achieve it. At war's end, the Joint Chiefs of Staff (JCS) supported jointness in principle, but the progress of jointness was s...

D. A. Armstrong

1995-01-01

409

Time–frequency Analysis for Biosystems Engineering  

Microsoft Academic Search

Many biological and agricultural systems naturally emit a number of signals which may be easily gathered and then used to monitor or control the system. For example, signals consisting of measurements of the temperature or heart rate of animals may be used to assess the health of the individuals. The interpretation of these signals is relatively simple since the value

B. P. Marchant

2003-01-01

410

Compact continuous L-domains  

Microsoft Academic Search

The purpose of this paper is to study the structure of compact continuous L-domains. It is proved that FS-domains, continuous B-domains, and compact continuous dcpos are all equivalent for L-domains. A basic notion of property W is introduced and some characterizations of compact continuous L-domains and of continuous L-domains are given by means of the continuity of function spaces and

K. Keimel

1999-01-01

411

Perlecan Immunolocalizes to Perichondrial Vessels and Canals in Human Fetal Cartilaginous Primordia in Early Vascular and Matrix Remodeling Events Associated with Diarthrodial Joint Development  

Microsoft Academic Search

The aim of this study was to ascertain how perlecan was localized in human fetal cartilaginous joint rudiment tissues. Perlecan was immunolocalized in human fetal (12–14-week-old) toe, finger, knee, elbow, shoulder, and hip joint rudiments using a monoclonal antibody to domain-1 of perlecan (MAb A76). Perlecan had a widespread distribution in the cartilaginous joint rudiments and growth plates and was

James Melrose; Susan Smith; John Whitelock

2004-01-01

412

Twist-joints and double twist-joints in RNA structure.  

PubMed

Analysis of available RNA crystal structures has allowed us to identify a new family of RNA arrangements that we call double twist-joints, or DTJs. Each DTJ is composed of a double helix that contains two bulges incorporated into different strands and separated from each other by 2 or 3 bp. At each bulge, the double helix is over-twisted, while the unpaired nucleotides of both bulges form a complex network of stacking and hydrogen-bonding with nucleotides of helical regions. In total, we identified 14 DTJ cases, which can be combined in three groups based on common structural characteristics. One DTJ is found in a functional center of the ribosome, another DTJ mediates binding of the pre-tRNA to the RNase P, and two more DTJs form the sensing domains in the glycine riboswitch. PMID:23060425

Boutorine, Yury I; Steinberg, Sergey V

2012-10-11

413

Development of cryogenic rotatable heat transfer joints  

Microsoft Academic Search

A summary of cryogenic rotatable heat transfer joint technology development, at Rockwell International Space Division, is presented. Starting with the flight qualified radiative joint on the RM-20B IR sensor of the early 70's, leading to rotatable heat pipe joint, gas conductive joints, rolling-contact-conductance joints, and the more recent work on development and evaluation of cryogenic rotatable seals and mechanical interfaces.

J. A. Sadunas; Z. F. Backovsky; D. E. Wilson

1992-01-01

414

Prosthetic Joint Infections in Elderly Patients  

Microsoft Academic Search

Although prosthetic joint infections (PJIs) occur in a small proportion of patients following total joint arthroplasty, they\\u000a have catastrophic consequences on morbidity and joint function and carry a high economic burden in the elderly patients.\\u000a \\u000a Clinical presentation of prosthetic joint infection is highly variable, and differentiating a painful joint arthroplasty secondary\\u000a to mechanical loosening from an indolent infection can be

Camelia E Marculescu; Elie F. Berbari; Douglas R. Osmon

415

Optimal key mask design for optical encryption based on joint transform correlator architecture  

Microsoft Academic Search

We examine perfect recovery in the optical encryption system based on joint transform correlator architecture, which requires the key mask to be space-limited and phase-only in the frequency domain. Accordingly, a discrete sinc function interpolation is used to generate a binary phase difference mask for image encryption and decryption. Furthermore, the optimal binary phase difference mask is derived from the

Li-Chien Lin; Chau-Jern Cheng

2006-01-01

416

Removing Ocular Movement Artefacts by a Joint Smoothened Subspace Estimator  

PubMed Central

To cope with the severe masking of background cerebral activity in the electroencephalogram (EEG) by ocular movement artefacts, we present a method which combines lower-order, short-term and higher-order, long-term statistics. The joint smoothened subspace estimator (JSSE) calculates the joint information in both statistical models, subject to the constraint that the resulting estimated source should be sufficiently smooth in the time domain (i.e., has a large autocorrelation or self predictive power). It is shown that the JSSE is able to estimate a component from simulated data that is superior with respect to methodological artefact suppression to those of FastICA, SOBI, pSVD, or JADE/COM1 algorithms used for blind source separation (BSS). Interference and distortion suppression are of comparable order when compared with the above-mentioned methods. Results on patient data demonstrate that the method is able to suppress blinking and saccade artefacts in a fully automated way.

Phlypo, Ronald; Boon, Paul; D'Asseler, Yves; Lemahieu, Ignace

2007-01-01

417

Domains in Ferroelectric Nanostructures  

NASA Astrophysics Data System (ADS)

Ferroelectric materials have great potential in influencing the future of small scale electronics. At a basic level, this is because ferroelectric surfaces are charged, and so interact strongly with charge-carrying metals and semiconductors - the building blocks for all electronic systems. Since the electrical polarity of the ferroelectric can be reversed, surfaces can both attract and repel charges in nearby materials, and can thereby exert complete control over both charge distribution and movement. It should be no surprise, therefore, that microelectronics industries have already looked very seriously at harnessing ferroelectric materials in a variety of applications, from solid state memory chips (FeRAMs) to field effect transistors (FeFETs). In all such applications, switching the direction of the polarity of the ferroelectric is a key aspect of functional behavior. The mechanism for switching involves the field-induced nucleation and growth of domains. Domain coarsening, through domain wall propagation, eventually causes the entire ferroelectric to switch its polar direction. It is thus the existence and behavior of domains that determine the switching response, and ultimately the performance of the ferroelectric device. A major issue, associated with the integration of ferroelectrics into microelectronic devices, has been that the fundamental properties associated with ferroelectrics, when in bulk form, appear to change quite dramatically and unpredictably when at the nanoscale: new modes of behaviour, and different functional characteristics from those seen in bulk appear. For domains, in particular, the proximity of surfaces and boundaries have a dramatic effect: surface tension and depolarizing fields both serve to increase the equilibrium density of domains, such that minor changes in scale or morphology can have major ramifications for domain redistribution. Given the importance of domains in dictating the overall switching characteristics of a device, the need to fully understand how size and morphology affect domain behaviour in small scale ferroelectrics is obvious. In this talk, observations from a programme of study examining domains in meso and nano-scale BaTiO3 shapes, that have been cut directly from bulk single crystal using focused ion beam milling, will be presented. In general, the equilibrium static domain configurations that occur appear to be the result of a simultaneous desire to minimize both the macroscopic strain and depolarizing fields developed on cooling through the Curie Temperature. While such governing factors might be obvious, the specific patterns that result as a function of morphology are often non-intuitive, and a series of images of domains in nanodots, rods and wires will be presented and rationalised. In addition, the nature in which morphological factors influence domain dynamics during switching will be discussed, with particular focus on axial switching in nanowires, and the manner in which local surface perturbations (such as notches and antinotches) affect domain wall propagation. In collaboration with Alina Schilling, Li-Wu Chang, Mark McMillen, Raymond McQuaid, and Leo McGilly, Queen's University Belfast; Gustau Catalan, Universitat Autonoma de Barcelona; and James Scott, University of Cambridge.

Gregg, Marty

2010-03-01

418

Just how versatile are domains?  

PubMed Central

Background Creating new protein domain arrangements is a frequent mechanism of evolutionary innovation. While some domains always form the same combinations, others form many different arrangements. This ability, which is often referred to as versatility or promiscuity of domains, its a random evolutionary model in which a domain's promiscuity is based on its relative frequency of domains. Results We show that there is a clear relationship across genomes between the promiscuity of a given domain and its frequency. However, the strength of this relationship differs for different domains. We thus redefine domain promiscuity by defining a new index, DV I ("domain versatility index"), which eliminates the effect of domain frequency. We explore links between a domain's versatility, when unlinked from abundance, and its biological properties. Conclusion Our results indicate that domains occurring as single domain proteins and domains appearing frequently at protein termini have a higher DV I. This is consistent with previous observations that the evolution of domain re-arrangements is primarily driven by fusion of pre-existing arrangements and single domains as well as loss of domains at protein termini. Furthermore, we studied the link between domain age, defined as the first appearance of a domain in the species tree, and the DV I. Contrary to previous studies based on domain promiscuity, it seems as if the DV I is age independent. Finally, we find that contrary to previously reported findings, versatility is lower in Eukaryotes. In summary, our measure of domain versatility indicates that a random attachment process is sufficient to explain the observed distribution of domain arrangements and that several views on domain promiscuity need to be revised.

2008-01-01

419

An analysis of a joint shear model for jointed media with orthogonal joint sets; Yucca Mountain Site Characterization Project  

SciTech Connect

This report describes a joint shear model used in conjunction with a computational model for jointed media with orthogonal joint sets. The joint shear model allows nonlinear behavior for both joint sets. Because nonlinear behavior is allowed for both joint sets, a great many cases must be considered to fully describe the joint shear behavior of the jointed medium. An extensive set of equations is required to describe the joint shear stress and slip displacements that can occur for all the various cases. This report examines possible methods for simplifying this set of equations so that the model can be implemented efficiently form a computational standpoint. The shear model must be examined carefully to obtain a computationally efficient implementation that does not lead to numerical problems. The application to fractures in rock is discussed. 5 refs., 4 figs.

Koteras, J.R.

1991-10-01

420

Understanding the role of domain-domain linkers in the spatial orientation of domains in multi-domain proteins.  

PubMed

Inter-domain linkers (IDLs)' bridge flanking domains and support inter-domain communication in multi-domain proteins. Their sequence and conformational preferences enable them to carry out varied functions. They also provide sufficient flexibility to facilitate domain motions and, in conjunction with the interacting interfaces, they also regulate the inter-domain geometry (IDG). In spite of the basic intuitive understanding of the inter-domain orientations with respect to linker conformations and interfaces, we still do not entirely understand the precise relationship among the three. We show that IDG is evolutionarily well conserved and is constrained by the domain-domain interface interactions. The IDLs modulate the interactions by varying their lengths, conformations and local structure, thereby affecting the overall IDG. Results of our analysis provide guidelines in modelling of multi-domain proteins from the tertiary structures of constituent domain components. PMID:23249395

Bhaskara, Ramachandra M; de Brevern, Alexandre G; Srinivasan, Narayanaswamy

2012-12-19

421

Breathing and temporomandibular joint disease.  

PubMed

Temporomandibular joint disease (TMD) refers to a collection of pain related conditions in the masticatory muscles and temporomandibular joint. Occlusal factors have been implicated in TMD pathogenesis, yet despite decades of research no causal relationship between occlusion and TMD has been found. The significance of psychosocial factors in both the assessment and the long-term management of patients with TMD is receiving increased recognition. The teaching of relaxation skills and coping strategies are effective, proven TMD therapies. The role of breathing re-education in temporomandibular joint (TMJ) disorders is rarely mentioned. A focus on breathing patterns and their disorders potentially explains how biomechanical factors associated with psychosocial influences might lead to pathophysiological changes within the TMJ as well as in the associated muscles. Attention to factors such as breathing and postural rehabilitation provides health professionals valuable, additional tools to help care for patients with TMD. PMID:21665104

Bartley, Jim

2010-06-25

422

Periprosthetic joint infection: Current concept.  

PubMed

Periprosthetic joint infection (PJI) is one of the most devastating and costly complications following total joint arthroplasty (TJA). Diagnosis and management of PJI is challenging for surgeons. There is no "gold standard" for diagnosis of PJI, making distinction between septic and aseptic failures difficult. Additionally, some of the greatest difficulties and controversies involve choosing the optimal method to treat the infected joint. Currently, there is significant debate as to the ideal treatment strategy for PJI, and this has led to considerable international variation in both surgical and nonsurgical management of PJI. In this review, we will discuss diagnosis and management of PJI following TJA and highlight some recent advances in this field. PMID:23531512

Aggarwal, Vinay K; Rasouli, Mohammad R; Parvizi, Javad

2013-01-01

423

Arthroscopy of the Sternoclavicular Joint  

PubMed Central

Traditionally, an open approach has been required to undertake any surgical intervention for intra-articular sternoclavicular joint pathology. This in itself carries a certain operative morbidity, including damage to the underlying mediastinal structures and damage to the sternoclavicular and costoclavicular ligaments, with subsequent joint instability and unsightly scarring. This technical note describes an arthroscopic approach to the sternoclavicular joint that reduces this morbidity. The evolution of the technique including the rationale for portal placement and the angle of instrument insertion is explained. Experience of over 50 arthroscopic procedures including diagnostic arthroscopy, discectomy, excision of loose bodies, and washout and debridement after infection and excision of the medial end of the clavicle for osteoarthritis is detailed.

Tytherleigh-Strong, Graham

2013-01-01

424

Joint inversion of MRS and TEM data  

NASA Astrophysics Data System (ADS)

In this study we present a joint inversion of Magnetic resonance Sounding (MRS) and time domain electromagnetic (TEM) data. The joint scheme offers a better resolution of the model parameters than a traditional independent inversion of MRS and TEM. MRS is a non-invasive geophysical technique applied to groundwater investigations. The method offers a direct quantification of water content from surface measurements. TEM measures the conductivity of the formation which is only indirectly related to the water content. Though, TEM is essential for the interpretation of the MRS data as the conductivity of the formation highly influences the MRS kernel calculation. Based on the physical principle of nuclear magnetic resonance (NMR), protons of the water molecules in the subsurface are excited at the specific Larmor frequency. Although the NMR signal is relatively weak, a large investigated volume of water in the subsurface makes it possible to measure the NMR signals using a loop on the surface. The typical loop sizes are 50 x 50 m2 and 100 x 100 m2. An alternating current is passed through a large transmitter loop deployed on the surface, and the superposition of signals from all precessing protons within the investigated volume is measured in a receiver loop. The observed data are inverted directly for the water content of the subsurface. In cases where the inversion of TEM data does not represent the true conductivity structure accurate because of equivalent models, the MRS response will be biased due to the wrong estimation of the magnetic field. In these cases, the MRS inversion does not retrieve the correct model parameters, such as water content. In this study we present a joint inversion scheme of MRS and TEM data, where the resistivity structure is inverted simultaneously with the MRS parameters. The model space thus consist of resistivity, water content, relaxation time, layer thickness and the spectral information of the layers. The resistivity structure is adapted for each calculation of the MRS forward response in the iterative inversion procedure leading to a more reliable and robust determination of aquifer characteristics than single MRS inversion. The inversion scheme uses a new MRS forward routine where data are the full free induction decays (FID), and a stretched exponential model is used for description of multi-exponential behavior of the MRS signal. The MRS forward response is calculated in an efficient numerical manner which speeds up the computation time considerably, reduces the model space but maintains the numerical accuracy.

Behroozmand, A.; Auken, E.; Fiandaca, G.; Christiansen, A. V.

2011-12-01

425

A new finger joint prosthesis.  

PubMed

A new finger joint prosthesis is being developed for the proximal and distal interphalangeal positions. Currently available "joint spacer" prostheses provide relief from pain and cosmetic improvement, but relatively poor long-term function. The new prosthesis employs a mechanical hinge at the joint. It is fabricated from titanium alloy (6A14V). The hinge mechanism avoids direct metal to metal contact by using high density polyethylene bearings. In vitro tests of the hinge mechanism have passed 75 million cycles of continuous flexure without failure (n = 12). The hinge also incorporates a mechanical limit stop to prevent hyperextension. The hinge mechanism is enclosed in a sealed elastomeric jacket that isolates the hinge from connective tissue ingrowth. The jacket, equivalent to an artificial synovial membrane, has an integrally textured exterior surface designed to promote tissue attachment to the implant to stabilize tissue capsule formation around the joint. To test the in vivo efficacy of the new design, a series of 12 devices were implanted in the knee joint position of adult rabbits. A jacketed prosthesis was implanted on one side, whereas 2 weeks later an unjacketed control was implanted contralaterally. The animals then were maintained for an 8 week period. At sacrifice, the implants were removed, and the response of the surrounding tissues was studied histologically. At the time of implantation, the range of motion of the joints was approximately 100-105 degrees. There was a progressive loss in range of motion observed in both groups. The fibrous tissue capsule around the jacketed implants, however, was significantly reduced in thickness compared with the controls (mean thickness, 1.5 mm vs. 4.5 mm).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8268583

Whalen, R L; Bowen, M A; Sarrasin, M J; Fukumura, F; Harasaki, H

426

Putting the 'O' in Joint DOTMLPF: Organizational Capabilities for Joint Task Force Command and Control.  

National Technical Information Service (NTIS)

Across the defense establishment joint transformation is beginning to take hold though unevenly. Sweeping changes concerning joint doctrine training leader development acquisition, and facilities have taken effect under joint purview and direction through...

J. F. Dickens

2005-01-01

427

Temporomandibular joint disorders in children.  

PubMed

A child's difficulty in verbalizing the precise location and nature of facial pain and jaw dysfunction often results in a nondefinitive history, increasing the importance of the dentist's awareness of the early signs and symptoms of temporomandibular joint disorders (TMD). A focused examination of the masticatory musculature, the temporomandibular joints, and associated capsular and ligamentous structures can reveal if a patient's symptoms are TMD in origin. An accurate differential diagnosis enables timely referral to appropriate health care providers and minimizes the use of diagnostic imaging. PMID:23174613

Howard, James A

2013-01-01

428

Joint bioaccumulation and joint biological activity as ecotoxicological risk indicators  

Microsoft Academic Search

In this contribution, mathematical formulae for the estima- tion of thusly defined indicators are presented. Strategies for assessing biological activity from simultaneous mea- surements of biological effects and internal exposure are given special attention. Relevance of transformation products The question which of the known or suspected transforma- tion products should be included in an assessment of joint persistence (4), secondary

J. Ranke

429

Knee joint replacement - series (image)  

MedlinePLUS

The knee is a complex joint. It contains the distal end of the femur (the femoral condyles) and the ... The most common cause of knee damage that leads to knee replacement ... is a degenerative disease of the bones of the knee. It causes ...

430

DYNAMIC FRACTURE OF WELDED JOINTS  

Microsoft Academic Search

This paper presents an experimental and analytical investigation of dynamic fracture of T-shaped welded joints (stiffener on a plate) in a high strength steel. A fracture test was designed in which strain rates of several thousand per second can be reached in the weldment region by loading the specimen with tamped explosive. Test conditions can be reliably controlled by adjusting

J. H. GIOVANOLA; R. W. KLOPP; S. W. KIRKPATRICK; W. W. McDONALD

1991-01-01

431

The Strength of Adhesive Joints  

Microsoft Academic Search

The main rules pertaining to the strength of adhesive joints are: (1) This strength is a mechanical (or rheological) property. The local stress which causes the extension of a pre-existing crack can be determined only if the stress pattern in the whole adhint is known and the intensification of stress at flaws is taken into account. (2) The rupture occurs

J. J. Bikerman

1972-01-01

432

Joint Operational Access Concept (JOAC).  

National Technical Information Service (NTIS)

This paper proposes a concept for how joint forces will achieve operational access in the face of armed opposition by a variety of potential enemies and under a variety of conditions, as part of a broader national approach. Operational access is the abili...

2012-01-01

433

Automatic Locking Knee Brace Joint.  

National Technical Information Service (NTIS)

This invention is an apparatus for controlling the pivotal movement of a knee brace comprising a tang-and-clevis joint that has been uniquely modified. Both the tang and the clevis have a set of teeth that, when engaged, can lock the tang and the clevis t...

B. Weddendorf

1995-01-01

434

Trends in biological joint resurfacing  

PubMed Central

The treatment of osteochondral lesions and osteoarthritis remains an ongoing clinical challenge in orthopaedics. This review examines the current research in the fields of cartilage regeneration, osteochondral defect treatment, and biological joint resurfacing, and reports on the results of clinical and pre-clinical studies. We also report on novel treatment strategies and discuss their potential promise or pitfalls. Current focus involves the use of a scaffold providing mechanical support with the addition of chondrocytes or mesenchymal stem cells (MSCs), or the use of cell homing to differentiate the organism’s own endogenous cell sources into cartilage. This method is usually performed with scaffolds that have been coated with a chemotactic agent or with structures that support the sustained release of growth factors or other chondroinductive agents. We also discuss unique methods and designs for cell homing and scaffold production, and improvements in biological joint resurfacing. There have been a number of exciting new studies and techniques developed that aim to repair or restore osteochondral lesions and to treat larger defects or the entire articular surface. The concept of a biological total joint replacement appears to have much potential. Cite this article: Bone Joint Res 2013;2:193–9.

Myers, K. R.; Sgaglione, N. A.; Grande, D. A.

2013-01-01

435

Human Zygapophyseal Joint Synovial Folds  

Microsoft Academic Search

The structure of human zygapophyseal joint synovial folds as seen by high-power light microscopy and transmission electron microscopy is described. Small myelinated nerves are demonstrated in association with some capillaries in the synovial folds. This may have clinical significance in the field of spinal pain.Copyright © 1986 S. Karger AG, Basel

L. G. F. Giles; J. R. Taylor; A. Cockson

1986-01-01

436

Cryopumping field joint can testing  

NASA Astrophysics Data System (ADS)

For long installations, vacuum jacketed piping often comes in 40 foot sections that are butt welded together in the field. A short can is then welded over the bare pipe connection to allow for insulation to be protected from the environment. Traditionally, the field joint is insulated with multilayer insulation and a vacuum is pulled on the can to minimize heat leak through the bare section and prevent frost from forming on the pipe section. The vacuum jacketed lines for the Ares I mobile launch platform were to be a combined 2000 feet long, with 60+ pipe sections and field joint cans. Historically, Kennedy Space Center has drilled a hole in the long sections to create a common vacuum with the field joint can to minimize maintenance on the vacuum jacketed piping. However, this effort looked at ways to use a passive system that didn't require a vacuum, but may cryopump to create its own vacuum. Various forms of aerogel, multilayer insulations, and combinations thereof were tested to determine the best method of insulating the field joint while minimizing maintenance and thermal losses.

Johnson, Wesley; Fesmire, James; Meneghelli, Barry

2012-06-01

437

The Rationale for Joint Mobilization.  

ERIC Educational Resources Information Center

|This paper presents an overview of the functions of connective tissue and the mechanisms of joint injury and contracture formation in relation to therapeutic exercise. The components of connective tissue operation are explained, including fibroblasts, macrophages, plasma cells, and collagen. An examination of the histology of connective tissue as…

Burkhardt, Sandy

438

Joint Civilian Orientation Conference Program.  

National Technical Information Service (NTIS)

We reviewed whether the Assistant Secretary of Defense (Public Affairs) (ASD(PA)) administered the Joint Civilian Orientation Conference (JCOC) program in accordance with public law and DoD policies. This is the third in a series of audits conducted at th...

2009-01-01

439

Deterministic joint remote state preparation  

Microsoft Academic Search

We put forward a new nontrivial three-step strategy to execute joint remote state preparation via Einstein-Podolsky-Rosen pairs deterministically. At variance with all existing protocols, in ours the receiver contributes actively in both preparation and reconstruction steps, although he knows nothing about the quantum state to be prepared.

Nguyen Ba An; Cao Thi Bich; Nung Van Don

2011-01-01

440

Deterministic joint remote state preparation  

Microsoft Academic Search

We put forward a new nontrivial three-step strategy to execute joint remote state preparation via Einstein–Podolsky–Rosen pairs deterministically. At variance with all existing protocols, in ours the receiver contributes actively in both preparation and reconstruction steps, although he knows nothing about the quantum state to be prepared.

Nguyen Ba An; Cao Thi Bich; Nung Van Don

2011-01-01

441

Deterministic joint remote state preparation  

NASA Astrophysics Data System (ADS)

We put forward a new nontrivial three-step strategy to execute joint remote state preparation via Einstein-Podolsky-Rosen pairs deterministically. At variance with all existing protocols, in ours the receiver contributes actively in both preparation and reconstruction steps, although he knows nothing about the quantum state to be prepared.

An, Nguyen Ba; Bich, Cao Thi; Don, Nung Van

2011-09-01

442

Arthrodesis of the Trapeziometacarpal Joint  

Microsoft Academic Search

Over a 10-year period, 32 trapeziometacarpal (TM) joint fusions were performed in 29 patients, and reviewed. Pin fixation with tension band wiring was used in 14 cases, screws in eight cases, a plate in six cases, K-wires in three cases and staple fixation in one case. None was bone grafted. Splinting was applied for 4 to 5 weeks. There were

A. CHAMAY; F. PIAGET-MOREROD

1994-01-01

443

Joint calibration of multiple sensors  

Microsoft Academic Search

Many calibration methods calibrate a pair of sensors at a time. For robotic systems with many sensors, they are often time-consuming to use, and can also lead to inaccurate results. In this paper, we combine a number of ideas in the literature to derive a unified framework that jointly calibrates many sensors a large system. Key to our approach are

Quoc V. Le; Andrew Y. Ng

2009-01-01

444

In vivo estimation of the short-range stiffness of cross-bridges from joint rotation.  

PubMed

Short-range stiffness (SRS) is a mechanical property of muscles that is characterized by a disproportionally high stiffness within a short length range during both lengthening and shortening movements. SRS is attributed to the cross-bridges and is beneficial for stabilizing a joint during, e.g., postural conditions. Thus far, SRS has been estimated mainly on isolated mammalian muscles. In this study we presented a method to estimate SRS in vivo in the human wrist joint. SRS was estimated at joint level in the angular domain (Nm/rad) for both flexion and extension rotations of the human wrist in nine healthy subjects. Wrist rotations of 0.15rad at 3rad/s were imposed at eight levels of voluntary contraction ranging from 0 to 2.1Nm by means of a single axis manipulator. Flexion and extension SRS of the wrist joint was estimated consistently and accurately using a dynamic nonlinear model that was fitted onto the recorded wrist torque. SRS increased monotonically with torque in a way consistent with previous studies on isolated muscles. It is concluded that in vivo measurement of joint SRS represents the population of coupled cross-bridges in wrist flexor and extensor muscles. In its current form, the presented technique can be used for clinical applications in many neurological and muscular diseases where altered joint torque and (dissociated) joint stiffness are important clinical parameters. PMID:20541761

van Eesbeek, Stijn; de Groot, Jurriaan H; van der Helm, Frans C T; de Vlugt, Erwin

2010-06-11

445

Mapping the Moral Domain  

Microsoft Academic Search

The moral domain is broader than the empathy and justice concerns assessed by existing measures of moral competence, and it is not just a subset of the values assessed by value inventories. To fill the need for reliable and theoretically grounded measurement of the full range of moral concerns, we developed the Moral Foundations Questionnaire on the basis of a

Jesse Graham; Brian A. Nosek; Jonathan Haidt; Ravi Iyer; Spassena Koleva; Peter H. Ditto

2011-01-01

446

Dynamic dilatonic domain walls  

Microsoft Academic Search

Motivated by the “universe as a brane” idea, we investigate the motion of a (D?2)-brane (or domain wall) that couples to bulk matter. Usually one would expect the space-time outside such a wall to be time dependent however we show that in certain cases it can be static, with consistency of the Israel equations yielding relationships between the bulk metric

H. A. Chamblin; H. S. Reall

1999-01-01

447

Stripe domain light deflector  

Microsoft Academic Search

A fast two dimensional solid-state light deflector with a very large number of resolvable spots is needed. It is critical not only for optical memories but also for displays, communication beam steerers, optical radar, optical processors and a host of other devices. The stripe domain light deflector is the newest type of light deflector; it is a solid state, fast,

D. L. Fleming; T. R. Johansen; F. G. Hewitt; E. J. Torok

1975-01-01

448

Modulation domain texture decomposition  

Microsoft Academic Search

We introduce a novel texture analysis algorithm capable of extracting visually meaningful and locally coherent sub-textural components from images. The algorithm operates in the modulation domain where texture is represented by locally coherent amplitude and frequency modulation functions. The texture components are iteratively extracted based on a new quantitative coherency measure. The effectiveness of the algorithm is demonstrated on several

Chuong T. Nguyen; Joseph P. Havlicek

2010-01-01

449

Domain Knowledge Integration  

Microsoft Academic Search

\\u000a In this chapter we focus on the theoretical underpinning and enabling technologies which ensure that the knowledge about the\\u000a domain embedded in the software system remains current and is understood by the members of the VE.

Iain Duncan Stalker; Martin Carpenter; Nikolay Mehandjiev; Ali Owrak; Georg Weichhart

450

Comparing Categories of Domains  

Microsoft Academic Search

We discuss some of the reasons for the proliferation of categories of domains suggested for the mathematical foundations of the Scott-Strachey theory of programming semantics. Five general conditions are presented which such a category should satisfy and they are used to motivate a number of examples. An attempt is made to survey some of the methods whereby these examples may

Carl A. Gunter

1985-01-01

451

UPDATING ACTION DOMAIN DESCRIPTIONS  

Microsoft Academic Search

Incorporating new information into a knowledge base is an important problem which has been widely considered. In this paper, we study the problem in a formal framework for reasoning about action and change, in which action domains are described in an action language that has a transition-based semantics. Going beyond previous works, we consider (i) a richer action language that

Thomas Eiter; Esra Erdem; Michael Fink

2008-01-01

452

Expanding community psychology's domain  

Microsoft Academic Search

Community psychology's twin goals of prevention and empowerment are ill-served when researchers and practitioners restrict their activities to traditional mental health settings. This paper echoes the call of the Swampscott conference for expanding community psychology's domain of inquiry and action. It reviews examples from the research literature of efforts at prevention and empowerment in five classes of behavior settings identified

Marybeth Shinn

1987-01-01

453

Function of stiff joints may be restored by Ilizarov joint distraction.  

PubMed

Three patients with joint stiffness caused by trauma or infection are reported. The involved joints are the interphalangeal joint of the thumb, patellofemoral joint, and ankle joint. As an alternative for the indicated arthrodesis in these patients, treatment with articulating joint distraction was performed. By use of adapted Ilizarov external ring fixators, gradual distraction was applied to loosen the joint, followed after loosening by a period of exercise during distraction. In all three patients this experimental approach led to a decrease in pain and improvement of joint function that persisted for at least 2 years after treatment. With the use of Ilizarov joint distraction, joint function in cases of joint stiffness may be restored, and the need for an arthrodesis can be postponed. PMID:9553556

van Roermund, P M; van Valburg, A A; Duivemann, E; van Melkebeek, J; Lafeber, F P; Bijlsma, J W; Verbout, A J

1998-03-01

454

An Empirical Study of Automated Dictionary Construction for Information Extraction in Three Domains  

Microsoft Academic Search

this paper, we describe experiments with AutoSlog intwo additional domains: joint ventures and microelectronics. Wecompare the performance of AutoSlog across the three domains,discuss the lessons learned about the generality of this approach,and present results from two experiments which demonstrate thatnovice users can generate effective dictionaries using AutoSlog.1 IntroductionPortability is a crucial concern for researchers in knowledge-based naturallanguage processing (NLP)....

Ellen Riloff

1996-01-01

455

29 CFR 791.2 - Joint employment.  

Code of Federal Regulations, 2013 CFR

...REGULATIONS JOINT EMPLOYMENT RELATIONSHIP UNDER FAIR LABOR STANDARDS ACT OF 1938 § 791.2 Joint employment. ...two or more employers at the same time under the Fair Labor Standards Act of 1938, since there is nothing in the...

2013-07-01

456

Simplifying Bridge Expansion Joint Design and Maintenance.  

National Technical Information Service (NTIS)

This report presents a study focused on identifying the most durable expansion joints for the South Carolina Department of Transportation. This is performed by proposing a degradation model for the expansion joints and updating it based on bridge inspecti...

D. Rizos G. Wieger J. M. Caicedo P. Ziehl

2011-01-01

457

30 CFR 36.24 - Engine joints.  

Code of Federal Regulations, 2013 CFR

...PERMISSIBLE MOBILE DIESEL-POWERED TRANSPORTATION EQUIPMENT Construction and Design Requirements § 36.24 Engine joints. (a) Cylinder head. The joint between the cylinder head and block of the engine shall be...

2013-07-01

458

38 CFR 4.66 - Sacroiliac joint.  

Code of Federal Regulations, 2010 CFR

...changes from arthritis in this location are decrease or obliteration of the joint space, with the appearance of increased bone density of the sacrum and ilium and sharpening of the margins of the joint. Disability is manifest from erector spinae...

2010-07-01

459

38 CFR 4.66 - Sacroiliac joint.  

Code of Federal Regulations, 2010 CFR

...changes from arthritis in this location are decrease or obliteration of the joint space, with the appearance of increased bone density of the sacrum and ilium and sharpening of the margins of the joint. Disability is manifest from erector spinae...

2009-07-01

460

38 CFR 4.66 - Sacroiliac joint.  

Code of Federal Regulations, 2013 CFR

...changes from arthritis in this location are decrease or obliteration of the joint space, with the appearance of increased bone density of the sacrum and ilium and sharpening of the margins of the joint. Disability is manifest from erector spinae...

2013-07-01

461

49 CFR 583.15 - Joint ownership.  

Code of Federal Regulations, 2012 CFR

...Transportation (Continued) NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) AUTOMOBILE PARTS CONTENT LABELING § 583.15 Joint ownership. (a) A carline jointly owned and/or produced by more...

2012-10-01

462

Predicting variability in joint frequencies from boreholes  

NASA Astrophysics Data System (ADS)

Joints in rock are not evenly spaced, but commonly show clustering. This suggests that boreholes that are a short distance apart can intersect very different numbers of joints. A simple 1D model is used to illustrate variability in joint frequencies from vertical wells intersecting steeply dipping joints. The model indicates that raw joint frequencies logged from core or borehole images can give unreliable inputs into reservoir models, especially when the joints are clustered and variations occur over scales that are much smaller than the resolution of seismic surveys or the grid blocks used in reservoir simulations. Variability in joint frequencies from deviated or horizontal wells can be used, however, to test the variability in joint frequencies from vertical wells.

Peacock, D. C. P.

2006-02-01

463

Joint Operations and the Vicksburg Campaign.  

National Technical Information Service (NTIS)

This historical study investigates why Union joint operations between army and navy forces on the Mississippi and other western rivers were effective. It examines the development of a joint doctrine at the strategic, operational, and tactical levels of wa...

J. W. Tindall

1993-01-01

464

Joint Lessons Learned System and Interoperability.  

National Technical Information Service (NTIS)

This study analyzes the evolution of the Joint Lessons Learned System. It examines historical evidence of interoperability issues in US joint military operations from World War II to the present. Three major conflicts: World War II, Korea, and Vietnam, ar...

A. D. Landry

1989-01-01

465

Bone, Joint, and Muscle Infections in Children  

MedlinePLUS

... American Academy of Orthopaedic Surgeons Bone, Joint, and Muscle Infections in Children Children can develop infections in their bones, joints, or muscles. Often referred to as "deep" infections, the technical ...

466

Joint Operations at Vicksburg: The Decisive Force.  

National Technical Information Service (NTIS)

The joint operations employed in the Civil War provide valuable lessons to all military leaders involved in planning and executing future campaigns. This paper analyzes the extent and results of the joint operations developed and implemented by the Union ...

C. A. Hazard

2002-01-01

467

Strength of profile-adhesive joints  

Microsoft Academic Search

The current article presents an attempt to describe the strength of profile-adhesive joints. Its main objective was to develop\\u000a mathematical models describing phenomena occurring in bent mortise joints prevalent in constructions of skeleton furniture,\\u000a but also to determine factors influencing the strength of profile-adhesive joints. The presented cases of gluing of a mortise\\u000a joint reveal that mutual interactions of compressed

J. Smardzewski

2002-01-01

468

Predictions of solder joint fatigue life  

Microsoft Academic Search

Procedures used to predict solder-joint life from calculations of the joint strains and low-cycle fatigue data are described. The fatigue lives of chip-carrier\\/printed-wiring-board joints are predicted and compared to measured values. This prediction utilizes a finite-element analysis of the string distributions in a typical joint acted upon by an imposed displacement. These strains are then used to determine the fatigue

H. D. Solomon; V. Brzozowski; D. G. Thompson

1990-01-01

469

Coarsening of the Sn-Pb Solder Microstructure in Constitutive Model-Based Predictions of Solder Joint Thermal Mechanical Fatigue  

SciTech Connect

Thermal mechanical fatigue (TMF) is an important damage mechanism for solder joints exposed to cyclic temperature environments. Predicting the service reliability of solder joints exposed to such conditions requires two knowledge bases: first, the extent of fatigue damage incurred by the solder microstructure leading up to fatigue crack initiation, must be quantified in both time and space domains. Secondly, fatigue crack initiation and growth must be predicted since this metric determines, explicitly, the loss of solder joint functionality as it pertains to its mechanical fastening as well as electrical continuity roles. This paper will describe recent progress in a research effort to establish a microstructurally-based, constitutive model that predicts TMF deformation to 63Sn-37Pb solder in electronic solder joints up to the crack initiation step. The model is implemented using a finite element setting; therefore, the effects of both global and local thermal expansion mismatch conditions in the joint that would arise from temperature cycling.

Vianco, P.T.; Burchett, S.N.; Neilsen, M.K.; Rejent, J.A.; Frear, D.R.

1999-04-12

470

Radioulnar joint fusion for distal radioulnar joint instability.  

PubMed

Each one of this small group of patients illustrates a rare indication for the radioulnar joint fusion procedure in distal radioulnar joint instability. The case histories tell of a last ditch effort to salvage function in an extremity crippled by painful radioulnar instability after excision of the distal ulna. The fusions healed slowly and two required repeat surgery to achieve union. Today we would routinely add iliac bone graft to the fusion area to hasten healing. Rarely indicated, this is a salvage procedure that is done after failure of other procedures geared to preserve the rotation of the forearm. These patients all had successful salvage of their extremities for activities of daily living, but only one returned to his labor job. All were worker's compensation cases in physical jobs. Two patients had had prior radiocarpal fusions, making them even more restricted in function. This procedure should be kept in mind to be used in the rare cases of painful instability of the distal radioulnar joint when traditional motion-preserving procedures have failed. PMID:1880172

Schneider, L H; Imbriglia, J E

1991-05-01

471

Seismic response of rock joints and jointed rock mass  

SciTech Connect

Long-term stability of emplacement drifts and potential near-field fluid flow resulting from coupled effects are among the concerns for safe disposal of high-level nuclear waste (HLW). A number of factors can induce drift instability or change the near-field flow patterns. Repetitive seismic loads from earthquakes and thermal loads generated by the decay of emplaced waste are two significant factors. One of two key technical uncertainties (KTU) that can potentially pose a high risk of noncompliance with the performance objectives of 10 CFR Part 60 is the prediction of thermal-mechanical (including repetitive seismic load) effects on stability of emplacement drifts and the engineered barrier system. The second KTU of concern is the prediction of thermal-mechanical-hydrological (including repetitive seismic load) effects on the host rock surrounding the engineered barrier system. The Rock Mechanics research project being conducted at the Center for Nuclear Waste Regulatory Analyses (CNWRA) is intended to address certain specific technical issues associated with these two KTUs. This research project has two major components: (i) seismic response of rock joints and a jointed rock mass and (ii) coupled thermal-mechanical-hydrological (TMH) response of a jointed rock mass surrounding the engineered barrier system (EBS). This final report summarizes the research activities concerned with the repetitive seismic load aspect of both these KTUs.

Ghosh, A.; Hsiung, S.M.; Chowdhury, A.H. [Southwest Research Inst., San Antonio, TX (United States). Center for Nuclear Waste Regulatory Analyses

1996-06-01

472

Exploratory visual analysis of conserved domains on multiple sequence alignments  

PubMed Central

Background Multiple alignment of protein sequences can provide insight into sequence conservation across many species and thus allow identification of those sections of the sequence most critical to protein function. This insight can be augmented by joint display of conserved domains along the sequences. By fusing this metadata visually, biologists can analyze sequence conservation and functional motifs simultaneously and efficiently. Results We present MSAVis, a new approach combining luminance and hue for simultaneous visualization of conserved motifs and sequence alignment. Input for the algorithm is a multiple sequence alignment in a standard format. The NCBI Conserved Domain Database (CDD) is used for finding conserved domains along the alignment. The visualization quickly identifies conserved domains, and allows both macro (sequence-long) and micro (small amino-acid neighborhood) views. Conclusion MSAVis utilizes two visual cues, luminance and hue, to facilitate at-a-glance summary of the conservation of a user-provided protein alignment while enabling multiple comparisons among functional domains. These visual cues are preattentive and separable so that the relationship between conservation strength and domain membership can be understood. The MSAVis software, written in Python and using BioPython and OpenGL, can be found at http://agbase.msstate.edu/tools/MSAVis.html.

2009-01-01

473

Radiofrequency sacroiliac joint denervation for sacroiliac syndrome  

Microsoft Academic Search

Background and Objectives: Radiofrequency (RF) denervation of the sacroiliac (SI) joint has been advocated for the treatment of sacroiliac syndrome, yet no clinical studies or case series support its use. Methods: We report the results of a consecutive series of 50 SI joint RF denervations performed in 33 patients with sacroiliac syndrome. All patients underwent diagnostic SI joint injections with

F. Michael Ferrante; Lawrence F. King; Elizabeth A. Roche; Philip S. Kim; Margaret Aranda; Leslie R. DeLaney; Issam A. Mardini; Andrew J. Mannes

2001-01-01

474

Analysis of Adhesively Bonded Riveted Joints  

Microsoft Academic Search

This paper represents the analysis and modeling of adhesively bonded single lap riveted joints. The present work aimed at recommending appropriate configuration and characterization of these joints for maximum utilization. The present study includes the effectiveness of bond line thickness, the bonded layer configuration, and the situation of dissimilar thickness joints. The finite-element technique was used throughout the analysis of

Ali M. Al-Samhan

475

The frictional properties of joints in rock  

Microsoft Academic Search

Summary The conditions for sliding over artificial joint surfaces have been studied experimentally by cutting rock cylinders at various angles to their axes and studying slip over these surfaces in a triaxial testing apparatus. The types of joint used were: (i) filled with plaster to simulate a soft joint filling, (ii) bare surfaces ground approximately flat, and (iii) natural surfaces

J. C. Jaeger

1959-01-01

476

17 CFR 300.105 - Joint accounts.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Joint accounts. 300.105 Section 300.105 ...SECURITIES INVESTOR PROTECTION CORPORATION Accounts of âseparateâ Customers of Sipc Members § 300.105 Joint accounts. (a) A joint account shall be...

2013-04-01

477

49 CFR 234.233 - Rail joints.  

Code of Federal Regulations, 2011 CFR

... 4 2011-10-01 2011-10-01 false Rail joints. 234.233 Section 234.233 Transportation...Testing Maintenance Standards § 234.233 Rail joints. Each non-insulated rail joint located within the limits of a...

2011-10-01

478

49 CFR 234.233 - Rail joints.  

Code of Federal Regulations, 2012 CFR

... 4 2012-10-01 2012-10-01 false Rail joints. 234.233 Section 234.233 Transportation...Testing Maintenance Standards § 234.233 Rail joints. Each non-insulated rail joint located within the limits of a...

2012-10-01

479

Septic arthritis of the acromioclavicular joint  

Microsoft Academic Search

A patient with isolated pyogenous arthritis of the acromioclavicular joint (A-C joint) caused by Streptococcus viridans is described. The patient had no underlying disease. Minor trauma preceded shortly the development of the septic process. The patient was treated successfully with surgical drainage and antibiotics. To our knowledge this is the first case report of septic arthritis of the A-C joint

A. Blankstein; J. L. Amsallem; E. Rubinstein; H. Horoszowski; I. Farin

1985-01-01

480