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1

Joint time-frequency ISAR using adaptive processing  

Microsoft Academic Search

A new joint time-frequency inverse synthetic aperture radar (ISAR) algorithm that combines ISAR processing with the joint time-frequency signal representation is presented as a means of extracting the nonpoint-scattering features from the standard ISAR image. The adaptive Gaussian representation, applied to the range aids of the ISAR image, is used as the time-frequency processing engine. This technique uses Gaussian basis

Luiz C. Trintinalia; Hao Ling

1997-01-01

2

Joint Time-Frequency Spectrum Sensing for Cognitive Radio  

E-print Network

Joint Time-Frequency Spectrum Sensing for Cognitive Radio Wael Guib`ene and Aawatif Hayar EURECOM-frequency plane. Index Terms--Cognitive radio, sensing algorithm, Wigner Ville distribution , algebraic detector, joint time frequency detection. I. INTRODUCTION Cognitive Radio (CR) as introduced by Mitola [1

Paris-Sud XI, Université de

3

Seismic random noise attenuation by time-frequency peak filtering based on joint time-frequency distribution  

NASA Astrophysics Data System (ADS)

Time-Frequency Peak Filtering (TFPF) is an effective method to eliminate pervasive random noise when seismic signals are analyzed. In conventional TFPF, the pseudo Wigner-Ville distribution (PWVD) is used for estimating instantaneous frequency (IF), but is sensitive to noise interferences that mask the borderline between signal and noise and detract the energy concentration on the IF curve. This leads to the deviation of the peaks of the pseudo Wigner-Ville distribution from the instantaneous frequency, which is the cause of undesirable lateral oscillations as well as of amplitude attenuation of the highly varying seismic signal, and ultimately of the biased seismic signal. With the purpose to overcome greatly these drawbacks and increase the signal-to-noise ratio, we propose in this paper a TFPF refinement that is based upon the joint time-frequency distribution (JTFD). The joint time-frequency distribution is obtained by the combination of the PWVD and smooth PWVD (SPWVD). First we use SPWVD to generate a broad time-frequency area of the signal. Then this area is filtered with a step function to remove some divergent time-frequency points. Finally, the joint time-frequency distribution JTFD is obtained from PWVD weighted by this filtered distribution. The objective pursued with all these operations is to reduce the effects of the interferences and enhance the energy concentration around the IF of the signal in the time-frequency domain. Experiments with synthetic and real seismic data demonstrate that TFPF based on the joint time-frequency distribution can effectively suppress strong random noise and preserve events of interest.

Zhang, Chao; Lin, Hong-bo; Li, Yue; Yang, Bao-jun

2013-09-01

4

ISAR motion compensation via adaptive joint time-frequency technique  

Microsoft Academic Search

A novel approach for inverse synthetic aperture radar (ISAR) imaging is presented for both target translational motion and rotational motion nonuniformity compensation. The basic idea is to perform Doppler tracking to individual scatterers via an adaptive joint time-frequency (AJTF) projection technique. After maximizing the projection of the phase function to a set of basis functions in time-frequency plane, the Doppler

Yuanxun Wang; Hao Ling; V. C. Chen

1998-01-01

5

Joint time-frequency analysis of micro-acoustic devices  

NASA Astrophysics Data System (ADS)

In this paper, a novel analysis technique for the performance evaluation of micro-acoustic devices has been proposed. Whereas traditional techniques typically focus solely on the frequency domain characteristics, we employ a Joint Time-Frequency Analysis (JTFA), which has been shown to provide a more complete characterisation of overall device performance and underlying physical phenomena. Although an emphasis is placed on a Flexural Plate Wave (FPW) device, the analysis technique presented is applicable to a wider range of micro-acoustic devices including Surface Acoustic Wave (SAW) structures and Thin-Film Bulk Acoustic Wave Resonators (TFBARs). SAWdevices, and indeed general filters, are typically described by a frequency domain characteristic, whereby the entire time domain information is discarded. This type of analysis assumes that the device has reached quasistationary conditions. By employing JTFA, the device performance can simultaneously be studied as a function of both time and frequency. This type of analysis is typically useful where spurious acoustic modes are generated which may influence the overall filter characteristic. We have investigated the functional properties of various JTFA kernels, including those appearing in the Wigner-Ville, Choi-Williams and Page distributions. A known deficiency associated with JTFA is the appearance of a number of spurious cross-terms in the computations. Whereas the cross-terms are relatively simple to detect for "monochromatic" (single-component) signals, it is not a trivial task to minimise such artifacts for "polychromatic" (multi-component) signals, which are typical in micro-acoustic devices. We propose novel methods for reducing the cross-terms interference appearing in JTFA, thereby improving the performance of the analysis technique. To investigate the application of the proposed technique, the simulated time domain response of a FPW device was investigated. The Finite Element Method (FEM) package ANSYS 8.0 was utilised to obtain the impulse response of the FPW structure under a dynamic transient analysis. A comparison is also made with the spectral domain Green's function to verify the FEM solution, where excellent agreement is obtained. Based on the FEM solutions, the insertion loss characteristics is calculated which represents a commonly applied frequency domain method of analysing micro-acoustic devices. A comparison has been made between the insertion loss characteristics and the proposed approach, where it is clearly demonstrated that the problem-adapted technique provides significantly more detailed information.

Matthews, Glenn I.; Baghai-Wadji, Alireza

2008-12-01

6

Detection and characterization of cultural noise sources in magnetotelluric data: individual and joint analysis of the polarization attributes of the electric and magnetic field time-series in the time-frequency domain  

NASA Astrophysics Data System (ADS)

Magnetotelluric (MT) method is a passive electromagnetic technique, which is currently used to characterize sites for the geological storage of CO2. These later ones are usually located nearby industrialized, urban or farming areas, where man-made electromagnetic (EM) signals contaminate the MT data. The identification and characterization of the artificial EM sources which generate the so-called "cultural noise" is an important challenge to obtain the most reliable results with the MT method. The polarization attributes of an EM signal (tilt angle, ellipticity and phase difference between its orthogonal components) are related to the character of its source. In a previous work (Escalas et al. 2011), we proposed a method to distinguish natural signal from cultural noise in the raw MT data. It is based on the polarization analysis of the MT time-series in the time-frequency domain, using a wavelet scheme. We developed an algorithm to implement the method, and was tested with both synthetic and field data. In 2010, we carried out a controlled-source electromagnetic (CSEM) experiment in the Hontomín site (the Research Laboratory on Geological Storage of CO2 in Spain). MT time-series were contaminated at different frequencies with the signal emitted by a controlled artificial EM source: two electric dipoles (1 km long, arranged in North-South and East-West directions). The analysis with our algorithm of the electric field time-series acquired in this experiment was successful: the polarization attributes of both the natural and artificial signal were obtained in the time-frequency domain, highlighting their differences. The processing of the magnetic field time-series acquired in the Hontomín experiment has been done in the present work. This new analysis of the polarization attributes of the magnetic field data has provided additional information to detect the contribution of the artificial source in the measured data. Moreover, the joint analysis of the polarization attributes of the electric and magnetic field has been crucial to fully characterize the properties and the location of the noise source. Escalas, M., Queralt, P., Ledo, J., Marcuello, A., 2011. Identification of cultural noise sources in magnetotelluric data: estimating polarization attributes in the time-frequency domain using wavelet analysis. Geophysical Research Abstracts Vol. 13, EGU2011-6085. EGU General Assembly 2011.

Escalas, M.; Queralt, P.; Ledo, J.; Marcuello, A.

2012-04-01

7

Body waves separation in the time-frequency domain  

NASA Astrophysics Data System (ADS)

Arrival times of body waves generated by small magnitude microseismic events are usually very close and their limited bandwidth can cause even partial overlap in the time and frequency domains. The separation of P and S waves is then a challenging task that if solved could bring more insights about nature and location of the generating source. Differences in arrival times and frequency content of P and S waves can be seen by using time-frequency decomposition. The traditional time-frequency representation based on the Fourier Transform is limited by its trade-off between time and frequency resolutions, while other alternatives like the Wavelet Transform are still limited by the Heisenberg box. A new derivation of the Continuous Wavelet Transform, called Synchrosqueezing, stretches these boundaries using a mixture of the reassignment method with instantaneous frequency, giving a better frequency representation with improved time localization. Furthermore, all the individual components of the signal are separated in the time domain. This means that we are able to isolate the waveforms of a complex microseismic trace. Each spectral component can then be matched with a body wave plus its associated coda. Proper parameters have to be selected prior to the computation, such as the central frequency and bandwidth of the mother wavelet. We thus include a signal characterization first to find the best matching mother wavelet. In this paper we use the Synchrosqueezing transform to perform the time frequency representation of short brittle events recorded during microseismic experiments. Decomposition results for these examples show that the Synchrosqueezing transform outperforms the Short-Time Fourier Transform. The different components of each body waves (first arrival, coda, frequency components) can then be identified in the time-frequency plane. For some microseismic events, a first P-wave arrival is followed by another arrival at lower frequency that could be a P-wave converted to S-wave (P-S). This arrival is followed by a spectral component at the same frequency potentially corresponding to its coda. The main S-wave comprises a few spectral components of lower frequency. Each signal components can then be extracted by the inverse Synchrosqueezing transform, to be analyzed separately. The same approach could be extrapolated to the time-frequency representation of other seismic signals such as resonance frequencies and long-period events. Microseismic event from a hydraulic fracturing treatment. Zoom in the T-F representations of the STFT (left) and SST (right) of the microseismic event.

Herrera, R. H.; Tary, J.; Van der Baan, M.

2013-12-01

8

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

Santillán-Guzmán, Alina; Heute, Ulrich; Muthuraman, Muthuraman; Stephani, Ulrich; Galka, Andreas

2013-01-01

9

Characterization of Cardio signals by time-frequency domain analysis  

E-print Network

Long term behavior of nonlinear deterministic continuous time signals can be studied in terms of their reconstructed attractors. Reconstructed attractors of a continuous signal are meant to be topologically equivalent representations of the dynamics of the unknown dynamical system which generates the signal. Sometimes, geometry of the attractor or its complexity may give important information on the system of interest. However, if the trajectories of the attractor behave as if they are not coming from continuous system or there exists many spike like structures on the path of the system trajectories, then there is no way to characterize the shape of the attractor. In this article, the traditional attractor reconstruction method is first used for two types of ECG signals: Normal healthy persons (NHP) and Congestive Heart failure patients (CHFP). As common in such a framework, the reconstructed attractors are not at all well formed and hence it is not possible to adequately characterize their geometrical features. Thus, we incorporate frequency domain information to the given time signals. This is done by transforming the signals to a time frequency domain by means of suitable Wavelet transforms (WT). The transformed signal concerns two non homogeneous variables and is still quite difficult to use to reconstruct some dynamics out of it. By applying a suitable mapping, this signal is further converted into integer domain and a new type of 3D plot, called integer lag plot, which characterizes and distinguishes the ECG signals of NHP and CHFP, is finally obtained.

Sayan Mukherjee; Sanjay Kumar Palit; Santo Banerjee; MRK Ariffin; Lamberto Rondoni; Dilip Kumar Bhattacharya

2014-09-04

10

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

11

Heart Rate Tracking Using a Doppler Radar With the Reassigned Joint Time-Frequency Transform  

Microsoft Academic Search

Heart rate variations are tracked using an RF Doppler signal by applying a reassigned joint time-frequency transform (RJTFT). In time-frequency analysis, RJTFT improves the readability of the heart rate on a spectrogram and the heart rate is continuously tracked with it. To verify the result, a heart- beat signal was acquired from a stationary human subject using a Doppler radar

Choonghee Lee; Chiyul Yoon; Hyoun-Joong Kong; Hee Chan Kim; Youngwook Kim

2011-01-01

12

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

13

Broadband interference mitigator for global positioning system using time-frequency domain excision filtering  

NASA Astrophysics Data System (ADS)

This paper explores methods to excise broadband interference signals from a Global Positioning System (GPS) spread spectrum signal using bilinear transformations. The Wigner-Ville Distribution allows for signal and jammer time-frequency characterization. The jammer signals, identified in the Time-Frequency (T-F) domain, are excised by zeroing peak amplitudes above a statistically determined detection threshold. The GPS signal is synthesized using inverse Wigner transform involving least squares amplitude and phase matching. Pre-processing increases Pseudo-Random Noise (PRN) correlator performance due to significant reduction in effective Jammer-to-Signal ratio (JSR). The proposed technique improves receiver robustness for large classes of broadband jammers, not limited to instantaneously narrowband jammers with a constant modulus or well defined instantaneous frequencies, while improving bit-error-performance and GPS Coarse Acquisition (C/A) and tracking in hostile interference environments.

Silvius, Mark D.; Lindsey, Alan R.; Hughes, David H.

2003-12-01

14

Time-frequency domain SNR estimation and its application in seismic data processing  

NASA Astrophysics Data System (ADS)

Based on an approach estimating frequency domain signal-to-noise ratio (FSNR), we propose a method to evaluate time-frequency domain signal-to-noise ratio (TFSNR). This method adopts short-time Fourier transform (STFT) to estimate instantaneous power spectrum of signal and noise, and thus uses their ratio to compute TFSNR. Unlike FSNR describing the variation of SNR with frequency only, TFSNR depicts the variation of SNR with time and frequency, and thus better handles non-stationary seismic data. By considering TFSNR, we develop methods to improve the effects of inverse Q filtering and high frequency noise attenuation in seismic data processing. Inverse Q filtering considering TFSNR can better solve the problem of amplitude amplification of noise. The high frequency noise attenuation method considering TFSNR, different from other de-noising methods, distinguishes and suppresses noise using an explicit criterion. Examples of synthetic and real seismic data illustrate the correctness and effectiveness of the proposed methods.

Zhao, Yan; Liu, Yang; Li, Xuxuan; Jiang, Nansen

2014-08-01

15

Hardware architecture design of image restoration based on time-frequency domain computation  

NASA Astrophysics Data System (ADS)

The image restoration algorithms based on time-frequency domain computation is high maturity and applied widely in engineering. To solve the high-speed implementation of these algorithms, the TFDC hardware architecture is proposed. Firstly, the main module is designed, by analyzing the common processing and numerical calculation. Then, to improve the commonality, the iteration control module is planed for iterative algorithms. In addition, to reduce the computational cost and memory requirements, the necessary optimizations are suggested for the time-consuming module, which include two-dimensional FFT/IFFT and the plural calculation. Eventually, the TFDC hardware architecture is adopted for hardware design of real-time image restoration system. The result proves that, the TFDC hardware architecture and its optimizations can be applied to image restoration algorithms based on TFDC, with good algorithm commonality, hardware realizability and high efficiency.

Wen, Bo; Zhang, Jing; Jiao, Zipeng

2013-10-01

16

Characterizing Long Interval Cortical Inhibition over the Time-Frequency Domain  

PubMed Central

Objective Long-interval cortical inhibition (LICI) can be recorded from motor and non-motor regions of the cortex through combined transcranial magnetic stimulation (TMS) with electroencephalography (EEG). This study aimed to evaluate additional dimensions of LICI characteristics over an extended time-frequency and spatial domain. This was done by introducing two alternative measures of LICI signal amplitude: the Discrete Fourier Transform (DFT) and the Hilbert transform (HT). Both approaches estimate signal amplitude not taking into account the phase. In both cases LICI was measured as the difference between the unconditioned and conditioned activity evoked by the test pulse. Finally, we evaluated whether the topographical patterns of single and paired responses differed beyond the expected variations in amplitude. Materials and Methods LICI was delivered as single and paired pulses to the motor cortex (MC) and dorsolateral prefrontal cortex (DLPFC) in 33 healthy subjects with TMS-EEG. Results Significant differences (p<0.0001) between the unconditioned and conditioned evoked activity were found for both the DLPFC and MC using both methods (i.e., DFT and HT) after correcting for multiple comparisons in the time-frequency domain. The influence of inhibition was found to be significantly larger in space and time than previously considered. Single and paired conditions differ in intensity, but also in their topographic pattern (i.e., the specific spatiotemporal configuration of active sources). Conclusion Similar results were found by both DFT and HT. The effect of inhibition across the cortex was also found to be complex and extended. In particular, it was found that LICI may be measured with high sensitivity in areas that were relatively distant from the stimulation site, which may have important practical applications. The analysis presented in this study overcomes some limitations of previous studies and could serve as a key reference for future studies examining TMS-indices of inhibition/excitation in healthy and diseased states. PMID:24642981

Garcia Dominguez, Luis; Radhu, Natasha; Farzan, Faranak; Daskalakis, Zafiris J.

2014-01-01

17

Maximum likelihood estimator of operational modal analysis for linear time-varying structures in time-frequency domain  

NASA Astrophysics Data System (ADS)

This paper investigates the problem of modal parameter estimation of time-varying structures under unknown excitation. A time-frequency-domain maximum likelihood estimator of modal parameters for linear time-varying structures is presented by adapting the frequency-domain maximum likelihood estimator to the time-frequency domain. The proposed estimator is parametric, that is, the linear time-varying structures are represented by a time-dependent common-denominator model. To adapt the existing frequency-domain estimator for time-invariant structures to the time-frequency methods for time-varying cases, an orthogonal polynomial and z-domain mapping hybrid basis function is presented, which has the advantageous numerical condition and with which it is convenient to calculate the modal parameters. A series of numerical examples have evaluated and illustrated the performance of the proposed maximum likelihood estimator, and a group of laboratory experiments has further validated the proposed estimator.

Zhou, Si-Da; Heylen, Ward; Sas, Paul; Liu, Li

2014-05-01

18

Bandpass variable-bandwidth filter for reconstruction of signals with known boundary in time-frequency domain  

Microsoft Academic Search

A bandpass variable-bandwidth filter (BPVBF) is proposed for the reconstruction of the signal whose boundaries are known in time-frequency domain (TFD). The behaviors of the ideal BPVBF are investigated in TFD. Simulation results show that the ideal BPVBF rejects noise in the outside of a region of interest in TFD and produces the reliable reconstruction of signals.

Heyoung Lee; Zeungnam Bien

2004-01-01

19

Joint Time-Frequency and Kernel Principal Component Based SOM for Machine Maintenance  

Microsoft Academic Search

\\u000a Conventional vibration signals processing techniques are most suitable for stationary processes. However, most mechanical\\u000a faults in machinery reveal themselves through transient events in vibration signals. That is, the vibration generated by industrial\\u000a machines always contains nonlinear and non-stationary signals. It is expected that a desired time-frequency analysis method\\u000a should have good computation efficiency, and have good resolution in both time

Qianjin Guo; Haibin Yu; Yiyong Nie; Aidong Xu

2006-01-01

20

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

21

From phase space to frequency domain: a time-frequency analysis for chaotic time series.  

PubMed

Time-frequency analysis is performed for chaotic flow with a power spectrum estimator based on the phase-space neighborhood. The relation between the reference phase point and its nearest neighbors is demonstrated. The nearest neighbors, representing the state recurrences in the phase space reconstructed by time delay embedding, actually cover data segments with similar wave forms and thus possess redundant information, but recur with no obvious temporal regularity. To utilize this redundant recurrence information, a neighborhood-based spectrum estimator is devised. Then time-frequency analysis with this estimator is performed for the Lorenz time series, the Rössler time series, experimental laser data, and colored noise. Features revealed by the spectrogram can be used to distinguish noisy chaotic flow from colored noise. PMID:17677556

Sun, Junfeng; Zhao, Yi; Nakamura, Tomomichi; Small, Michael

2007-07-01

22

Deriving Lifetime Maps in the Time/Frequency Domain of Coherent Structures in the Turbulent Boundary Layer  

NASA Technical Reports Server (NTRS)

The lifetimes of coherent structures are derived from data correlated over a 3 sensor array sampling streamwise sidewall pressure at high Reynolds number (> 10(exp 8)). The data were acquired at subsonic, transonic and supersonic speeds aboard a Tupolev Tu-144. The lifetimes are computed from a variant of the correlation length termed the lifelength. Characteristic lifelengths are estimated by fitting a Gaussian distribution to the sensors cross spectra and are shown to compare favorably with Efimtsov s prediction of correlation space scales. Lifelength distributions are computed in the time/frequency domain using an interval correlation technique on the continuous wavelet transform of the original time data. The median values of the lifelength distributions are found to be very close to the frequency averaged result. The interval correlation technique is shown to allow the retrieval and inspection of the original time data of each event in the lifelength distributions, thus providing a means to locate and study the nature of the coherent structure in the turbulent boundary layer. The lifelength data are converted to lifetimes using the convection velocity. The lifetime of events in the time/frequency domain are displayed in Lifetime Maps. The primary purpose of the paper is to validate these new analysis techniques so that they can be used with confidence to further characterize the behavior of coherent structures in the turbulent boundary layer.

Palumbo, Dan

2008-01-01

23

Joint discrepancy evaluation of an existing steel bridge using time-frequency and wavelet-based approach  

NASA Astrophysics Data System (ADS)

The objective of this study is to bring out the errors introduced during construction which are overlooked during the physical verification of the bridge. Such errors can be pointed out if the symmetry of the structure is challenged. This paper thus presents the study of downstream and upstream truss of newly constructed steel bridge using time-frequency and wavelet-based approach. The variation in the behavior of truss joints of bridge with variation in the vehicle speed has been worked out to determine their flexibility. The testing on the steel bridge was carried out with the same instrument setup on both the upstream and downstream trusses of the bridge at two different speeds with the same moving vehicle. The nodal flexibility investigation is carried out using power spectral density, short-time Fourier transform, and wavelet packet transform with respect to both the trusses and speed. The results obtained have shown that the joints of both upstream and downstream trusses of the bridge behave in a different manner even if designed for the same loading due to constructional variations and vehicle movement, in spite of the fact that the analytical models present a simplistic model for analysis and design. The difficulty of modal parameter extraction of the particular bridge under study increased with the increase in speed due to decreased excitation time.

Walia, Suresh Kumar; Patel, Raj Kumar; Vinayak, Hemant Kumar; Parti, Raman

2013-12-01

24

Joint Language and Domain Engineering  

NASA Astrophysics Data System (ADS)

In domain-specific development model-driven development environments play an important role. Most of these environments only provide support for language engineering, but do not consider the second dimension which is concerned with domain engineering. In this paper, we join the concerns of language engineering and domain engineering towards a new comprehensive approach of domain-specific development. It allows domain designers to build domain models containing both, types and instances, and it allows language designers for defining language metamodels. Furthermore, based on the integrated description logics the environment provides services for productive modeling in domain and language engineering.

Walter, Tobias; Parreiras, Fernando Silva; Staab, Steffen; Ebert, Jürgen

25

Wavelet denoising for chirp-like signal in time-frequency domain and application to aircraft flight flutter testing  

Microsoft Academic Search

A novel denoising method for chirp-like signal that relies on the time-frequency analysis is described. Because the region of chirp signal in time-frequency (TF) map is well-concentrated relative to the widely distributed noise, the wavelet coefficients corresponding to the true signal can be extracted by a masking operation. And a new procedure is presented to design the mask and reconstruct

Wei Tang; Zhong-Ke Shi; Hong-Chao Li

2005-01-01

26

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

27

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. PMID:22448233

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

2012-01-01

28

Association between P3 Event-Related Potential Amplitude and Externalizing Disorders: A Time Domain and Time Frequency Investigation of 29-Year-Old Adults  

PubMed Central

This study determined whether time-domain P3 amplitude and time-frequency principal component (TF-PC) reductions are present in adulthood (age 29) when participants have largely passed through the age of heaviest substance misuse. Participants were assessed from age 17 through 29 for lifetime externalizing (EXT) disorders. EEG comparisons from three topographic regions were examined for P3 amplitude and TF-PCs at delta and theta frequency ranges. Significant P3 amplitude reductions were found in those with EXT for both regional and site-Pz analyses, with stronger effects observed the greater the EXT comorbidity. Reductions were also observed in all eight TF-PCs extracted, with a delta component yielding frontal effects not apparent in the time-domain. Overall, results suggest that these brain measures continue, at age 29, to provide effective indices of EXT that potentially tap a neural substrate related to behavioral disinhibition. PMID:23614581

Yoon, Henry H.; Malone, Stephen M.; Burwell, Scott J.; Bernat, Edward M.; Iacono, William G.

2013-01-01

29

Joint Frequency Domain and Time Domain Inversion for High Resolution Airborne Monitoring  

NASA Astrophysics Data System (ADS)

Active geophysical monitoring requires high spatial and temporal resolution, in addition to high signal to noise ratios. Airborne electromagnetic (AEM) surveys can be flown relatively cheaply and rapidly, with sampling along line approximately every 3m. This satisfies the first two criteria. However, time domain AEM surveys often have poor resolution in the near surface, while frequency domain surveys are unable to penetrate conductive cover. In addition, each survey type may have its own systematic data biases. Combining frequency and time domain surveys provides the benefits of both methods: collecting high resolution data in both the near surface and at depth. In addition, the use of two independent data collection methods reduces biases in the final reconstructed geology. We present a 3D inversion algorithm that jointly inverts frequency and time domain AEM data. The algorithm uses the moving sensitivity domain method, which makes it applicable to very large scale (1000s line km) surveys. The use of both data types significantly increases the resolution of the final images compared with each system individually. It also reduces the systematic bias from using a single survey. We demonstrate the effectiveness on joint inversion of RESOLVE frequency domain and SkyTEM time domain data along the Murray River, South Australia. The results show sufficient noise reduction and resolution for applications to active geophysical monitoring.

Cox, L.; Zhdanov, M. S.; Sunwall, D.; ENDO, M.

2013-12-01

30

Image compression via joint statistical characterization in the wavelet domain.  

PubMed

We develop a probability model for natural images, based on empirical observation of their statistics in the wavelet transform domain. Pairs of wavelet coefficients, corresponding to basis functions at adjacent spatial locations, orientations, and scales, are found to be non-Gaussian in both their marginal and joint statistical properties. Specifically, their marginals are heavy-tailed, and although they are typically decorrelated, their magnitudes are highly correlated. We propose a Markov model that explains these dependencies using a linear predictor for magnitude coupled with both multiplicative and additive uncertainties, and show that it accounts for the statistics of a wide variety of images including photographic images, graphical images, and medical images. In order to directly demonstrate the power of the model, we construct an image coder called EPWIC (embedded predictive wavelet image coder), in which subband coefficients are encoded one bitplane at a time using a nonadaptive arithmetic encoder that utilizes conditional probabilities calculated from the model. Bitplanes are ordered using a greedy algorithm that considers the MSE reduction per encoded bit. The decoder uses the statistical model to predict coefficient values based on the bits it has received. Despite the simplicity of the model, the rate-distortion performance of the coder is roughly comparable to the best image coders in the literature. PMID:18267447

Buccigrossi, R W; Simoncelli, E P

1999-01-01

31

Polarimetric time-frequency ESPRIT  

Microsoft Academic Search

An ESPRIT (estimation of signal parameters via rotational invariance techniques) like algorithm for estimating the direction-of-arrival (DOA) of nonstationary polarized signals is developed. This algorithm relies on the recently introduced spatial polarimetric time-frequency distributions (SPTFD) as a platform to provide low computational, high resolution direction finding. The use of dual polarizations empowers the SPTFD with additional degrees-of-freedom, and improves the

Baha A. Obeidat; Yimin Zhang; Moeness G. Amin

2003-01-01

32

Electromagnetic Compatibility from a Time-Frequency Perspective  

E-print Network

systems and this is the case for white spaces in the broadcast television (TV) spectrum. To avoid high the impact of time-frequency considerations for radio coexistence. We show that EMC studies are more precise and more representative of the reality when additional parameters relevant to the time domain are taken

Paris-Sud XI, Université de

33

A time frequency analysis of wave packet fractional revivals  

E-print Network

We show that the time frequency analysis of the autocorrelation function is, in many ways, a more appropriate tool to resolve fractional revivals of a wave packet than the usual time domain analysis. This advantage is crucial in reconstructing the initial state of the wave packet when its coherent structure is short-lived and decays before it is fully revived. Our calculations are based on the model example of fractional revivals in a Rydberg wave packet of circular states. We end by providing an analytical investigation which fully agrees with our numerical observations on the utility of time-frequency analysis in the study of wave packet fractional revivals.

Suranjana Ghosh; J. Banerji

2007-06-11

34

Brain connectivity study of joint attention using frequency-domain optical imaging technique  

NASA Astrophysics Data System (ADS)

Autism is a socio-communication brain development disorder. It is marked by degeneration in the ability to respond to joint attention skill task, from as early as 12 to 18 months of age. This trait is used to distinguish autistic from nonautistic populations. In this study, diffuse optical imaging is being used to study brain connectivity for the first time in response to joint attention experience in normal adults. The prefrontal region of the brain was non-invasively imaged using a frequency-domain based optical imager. The imaging studies were performed on 11 normal right-handed adults and optical measurements were acquired in response to joint-attention based video clips. While the intensity-based optical data provides information about the hemodynamic response of the underlying neural process, the time-dependent phase-based optical data has the potential to explicate the directional information on the activation of the brain. Thus brain connectivity studies are performed by computing covariance/correlations between spatial units using this frequency-domain based optical measurements. The preliminary results indicate that the extent of synchrony and directional variation in the pattern of activation varies in the left and right frontal cortex. The results have significant implication for research in neural pathways associated with autism that can be mapped using diffuse optical imaging tools in the future.

Chaudhary, Ujwal; Zhu, Banghe; Godavarty, Anuradha

2010-02-01

35

Blood flow measurement and slow flow detection in retinal vessels with Joint Spectral and Time domain method in ultrahigh speed OCT  

E-print Network

We present an application of the Joint Spectral and Time domain OCT (STdOCT) method for detection of wide range of flows in the retinal vessels. We utilized spectral/Fourier domain OCT (SOCT) technique for development of ...

Gorczynska, I.

36

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

2012-01-01

37

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

38

Time-frequency detection of Gravitational Waves  

E-print Network

We present a time-frequency method to detect gravitational wave signals in interferometric data. This robust method can detect signals from poorly modeled and unmodeled sources. We evaluate the method on simulated data containing noise and signal components. The noise component approximates initial LIGO interferometer noise. The signal components have the time and frequency characteristics postulated by Flanagan and Hughes for binary black hole coalescence. The signals correspond to binaries with total masses between $45 M_\\odot$ to $70 M_\\odot$ and with (optimal filter) signal-to-noise ratios of 7 to 12. The method is implementable in real time, and achieves a coincident false alarm rate for two detectors $\\approx$ 1 per 475 years. At this false alarm rate, the single detector false dismissal rate for our signal model is as low as 5.3% at an SNR of 10. We expect to obtain similar or better detection rates with this method for any signal of similar power that satisfies certain adiabaticity criteria. Because optimal filtering requires knowledge of the signal waveform to high precision, we argue that this method is likely to detect signals that are undetectable by optimal filtering, which is at present the best developed detection method for transient sources of gravitational waves.

Warren G. Anderson; R. Balasubramanian

1999-05-07

39

Superresolved time-frequency processing of wideband radar echo using esprit  

NASA Astrophysics Data System (ADS)

A time-frequency superresolution procedure is presented for processing wideband backscattered data containing both scattering center and natural resonance information. In this procedure, the ESPRIT algorithm is used as the processing engine. The windowed superresolution procedure is performed twice - once in the frequency domain to extract the scattering centers and once in the time domain to extract the resonances. Parametrized models for both scattering centers and resonances are obtained by a weighted average of the results for each segment. The resulting time-frequency image from the present superresolution procedure is not constrained in resolution by the Fourier limit. Superior noise performance is also demonstrated against a similar Prony procedure reported earlier.

Moore, J.; Trintinalia, L. C.; Ling, H.; Xu, G.

1995-05-01

40

Postural tachycardia syndrome: time frequency mapping  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

41

Music: A time-frequency approach Gary W. Don  

E-print Network

Music: A time-frequency approach Gary W. Don Department of Music and Theatre Arts Universityx ) Corresponding author 1 #12;2 Music: A time-frequency approach Gabor transforms and scalograms are used for mathematically analysing music, identifying patterns in the time-frequency structure of music

Walker, James S.

42

The LxVP and PxIxIT NFAT motifs bind jointly to overlapping epitopes on calcineurin's catalytic domain distant to the regulatory domain.  

PubMed

The serine/threonine phosphatase calcineurin (Cn) targets the nuclear factors of activated T cells (NFATs) that activate cytokine genes. Calcium influx activates Cn to dephosphorylate multiple serine residues within the ?200 residue NFAT regulatory domain, which triggers joint nuclear translocation of NFAT and Cn. The dephosphorylation process relies on the interaction between Cn and the conserved motifs PxIxIT and LxVP, which are located N- and C-terminal to the phosphorylation sites in NFAT's regulatory domain. Here, we show that an NFATc1-derived 15-residue peptide segment containing the conserved LxVP motif binds to an epitope on Cn's catalytic domain (CnA), which overlaps with the previously established PxIxIT binding site on CnA and is distant to the regulatory domain (CnB). Both NFAT motifs partially compete for binding but do not fully displace each other on the CnA epitope, revealing that both segments bind simultaneously to the same epitope on the catalytic domain. PMID:24954618

Gal, Maayan; Li, Shuai; Luna, Rafael E; Takeuchi, Koh; Wagner, Gerhard

2014-07-01

43

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

44

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

45

Polarimetric time-frequency music in coherent signal environment  

Microsoft Academic Search

The spatial time-frequency distributions (STFDs) have been developed and successfully applied to high-resolution direction-of-arrival (DOA) estimations and blind recovery of the source waveforms. In [Y. Zhang et al., Aug. 2003], the spatial polarimetric time-frequency distribution (SPTFD) was introduced as a platform for space-time processing for nonstationary source signals with different polarization properties. Based on SPTFD, polarimetric time-frequency MUSIC (PTF-MUSIC) has

Yimin Zhang; Baha A. Obeidat; Moeness G. Amin

2003-01-01

46

WEIGHT FUNCTIONS IN TIME-FREQUENCY ANALYSIS KARLHEINZ GROCHENIG  

E-print Network

WEIGHT FUNCTIONS IN TIME-FREQUENCY ANALYSIS KARLHEINZ GR¨OCHENIG Abstract. We discuss the most common types of weight functions in harmonic analysis and how they occur in time-frequency analysis. As a general rule, sub- multiplicative weights characterize algebra properties, moderate weight charac- terize

Feichtinger, Hans Georg

47

A Coherent Overview of Time-Frequency Reassignment and Synchrosqueezing  

E-print Network

1 A Coherent Overview of Time-Frequency Reassignment and Synchrosqueezing Franc¸ois Auger, Patrick provides a general overview of Time-Frequency reassignment and synchrosqueezing techniques applied to multicomponent signals, covering the theoretical background and applications. We explain how synchrosqueezing can

Meignen, Sylvain

48

THE CIRCULAR NATURE OF DISCRETE-TIME FREQUENCY ESTIMATES Brian C. Lovell Peter J. Kootsookosy Robert C. Williamsonz  

E-print Network

THE CIRCULAR NATURE OF DISCRETE-TIME FREQUENCY ESTIMATES Brian C. Lovell Peter J. Kootsookosy-known that sampling in the time-domain leads to periodicity in the frequency domain, this periodic or circular nature is the sampling frequency. Although the odd behaviour of the DFT is well-documented, the circular nature of some

Botea, Adi

49

Time-frequency analysis of event-related potentials: a brief tutorial.  

PubMed

Event-related potentials (ERPs) reflect cognitive processes and are usually analyzed in the so-called time domain. Additional information on cognitive functions can be assessed when analyzing ERPs in the frequency domain and treating them as event-related oscillations (EROs). This procedure results in frequency spectra but lacks information about the temporal dynamics of EROs. Here, we describe a method-called time-frequency analysis-that allows analyzing both the frequency of an ERO and its evolution over time. In a brief tutorial, the reader will learn how to use wavelet analysis in order to compute time-frequency transforms of ERP data. Basic steps as well as potential artifacts are described. Rather than in terms of formulas, descriptions are in textual form (written text) with numerous figures illustrating the topics. Recommendations on how to present frequency and time-frequency data in journal articles are provided. Finally, we briefly review studies that have applied time-frequency analysis to mismatch negativity paradigms. The deviant stimulus of such a paradigm evokes an ERO in the theta frequency band that is stronger than for the standard stimulus. Conversely, the standard stimulus evokes a stronger gamma-band response than does the deviant. This is interpreted in the context of the so-called match-and-utilization model. PMID:24194116

Herrmann, Christoph S; Rach, Stefan; Vosskuhl, Johannes; Strüber, Daniel

2014-07-01

50

Joint Analyticity and Analytic Continuation of Dirichlet–Neumann Operators on Doubly Perturbed Domains  

Microsoft Academic Search

.  In this paper we take up the question of analyticity properties of Dirichlet–Neumann operators (DNO) which arise in boundary\\u000a value and free boundary problems from a wide variety of applications (e.g., fluid and solid mechanics, electromagnetic and\\u000a acoustic scattering). More specifically, we consider DNO defined on domains inspired by the simulation of ocean waves over\\u000a bathymetry, i.e. domains perturbed independently

David P. Nicholls; Mark Taber

2008-01-01

51

Joint synchronization and calibration of multi-channel transform-domain charge sampling receivers  

E-print Network

and a joint synchronization and calibration technique, based on the Least-mean-squared (LMS) algorithm, is presented to track them. A maximum likelihood (ML) algorithm is used to estimate the frequency offset in carriers which is corrected prior to LMS...

Kotte Prakasam, Pradeep

2010-07-14

52

Joint Entropy for Space and Spatial Frequency Domains Estimated from Psychometric Functions of Achromatic Discrimination  

PubMed Central

We used psychometric functions to estimate the joint entropy for space discrimination and spatial frequency discrimination. Space discrimination was taken as discrimination of spatial extent. Seven subjects were tested. Gábor functions comprising unidimensionalsinusoidal gratings (0.4, 2, and 10 cpd) and bidimensionalGaussian envelopes (1°) were used as reference stimuli. The experiment comprised the comparison between reference and test stimulithat differed in grating's spatial frequency or envelope's standard deviation. We tested 21 different envelope's standard deviations around the reference standard deviation to study spatial extent discrimination and 19 different grating's spatial frequencies around the reference spatial frequency to study spatial frequency discrimination. Two series of psychometric functions were obtained for 2%, 5%, 10%, and 100% stimulus contrast. The psychometric function data points for spatial extent discrimination or spatial frequency discrimination were fitted with Gaussian functions using the least square method, and the spatial extent and spatial frequency entropies were estimated from the standard deviation of these Gaussian functions. Then, joint entropy was obtained by multiplying the square root of space extent entropy times the spatial frequency entropy. We compared our results to the theoretical minimum for unidimensional Gábor functions, 1/4? or 0.0796. At low and intermediate spatial frequencies and high contrasts, joint entropy reached levels below the theoretical minimum, suggesting non-linear interactions between two or more visual mechanisms. We concluded that non-linear interactions of visual pathways, such as the M and P pathways, could explain joint entropy values below the theoretical minimum at low and intermediate spatial frequencies and high contrasts. These non-linear interactions might be at work at intermediate and high contrasts at all spatial frequencies once there was a substantial decrease in joint entropy for these stimulus conditions when contrast was raised. PMID:24466158

Silveira, Vladimir de Aquino; Souza, Givago da Silva; Gomes, Bruno Duarte; Rodrigues, Anderson Raiol; Silveira, Luiz Carlos de Lima

2014-01-01

53

Preamble-based frequency-domain joint CFO and STO estimation for OQAM-based filter bank multicarrier  

NASA Astrophysics Data System (ADS)

Filter bank multicarrier systems, similarly to orthogonal frequency division multiplexing (OFDM), are very sensitive to carrier frequency offset (CFO) and symbol timing offset (STO). In this paper, a low-complexity preamble-based joint CFO and STO technique is presented. It is based on a relatively long preamble in order to improve the CFO estimation performance as well as avoid interference coming from the data following this preamble. After CFO and STO correction, the preamble can be reused to estimate the channel. Unlike most current techniques, the CFO and STO estimation occurs in the frequency domain. This allows for a low-complexity estimation with respect to time-domain techniques and, as will be shown by simulations, provide even better performance in a reasonable range. The drawback however is that the estimation range is shorter. Specifically, for large STOs (and to a smaller extent large CFOs), the performance decreases below time-domain estimations. Two versions of the STO estimation technique will be presented, the second one being an approximation of the first one, making it less complex yet also less precise. The performance is assessed by means of computer simulations, testing for both large and small STOs, and compared with existing techniques.

Caekenberghe, Stijn Van; Bourdoux, André; der Perre, Liesbet Van; Louveaux, Jérôme

2014-12-01

54

Carbon financial markets: A time-frequency analysis of CO2 prices  

NASA Astrophysics Data System (ADS)

We characterize the interrelation of CO2 prices with energy prices (electricity, gas and coal), and with economic activity. Previous studies have relied on time-domain techniques, such as Vector Auto-Regressions. In this study, we use multivariate wavelet analysis, which operates in the time-frequency domain. Wavelet analysis provides convenient tools to distinguish relations at particular frequencies and at particular time horizons. Our empirical approach has the potential to identify relations getting stronger and then disappearing over specific time intervals and frequencies. We are able to examine the coherency of these variables and lead-lag relations at different frequencies for the time periods in focus.

Sousa, Rita; Aguiar-Conraria, Luís; Soares, Maria Joana

2014-11-01

55

Robust acoustic source localization based on modal beamforming and time-frequency processing using circular microphone arrays.  

PubMed

Uniform circular array processing has been shown to be a very useful tool for broadband acoustic source localization over 360°. Specifically, beamforming methods based on circular harmonics have attracted a lot of research attention in the last several years, as modal array signal processing is a very active research topic. On the other hand, due to the sparsity properties of speech, source localization methods in the time-frequency (T-F) domain have also demonstrated their capability to locate several simultaneous sources with high accuracy. In this paper, a localization framework based on circular harmonics beamforming and T-F processing that provides accurate localization performance under very adverse acoustic conditions is presented. Modal processing and sparsity-based localization are jointly addressed to estimate the direction-of-arrival of multiple concurrent speech sources. Experiments in real and simulated environments with different microphone setups are discussed, showing the validity of the proposed approach and comparing its performance with other state-of-the-art methods. PMID:22978880

Torres, Ana M; Cobos, Maximo; Pueo, Basilio; Lopez, Jose J

2012-09-01

56

Focusing ISAR images using fast adaptive time-frequency and 3D motion detection on simulated and experimental radar data ; Focusing inverse synthetic aperture radar images using fast adaptive time-frequency and three-dimensional motion detection on simulated and experimental radar data .  

E-print Network

??Optimization algorithms were developed for use with the Adaptive Joint Time-Frequency (AJFT) algorithm to reduce Inverse Synthetic Aperture Radar (ISAR) image blurring caused by higher-order… (more)

Brinkman, Wade H.

2005-01-01

57

Detailed Vibration Analysis of Pinion Gear with Time-Frequency Methods  

NASA Technical Reports Server (NTRS)

In this paper, the authors show a detailed analysis of the vibration signal from the destructive testing of a spiral bevel gear and pinion pair containing seeded faults. The vibration signal is analyzed in the time domain, frequency domain and with four time-frequency transforms: the Short Time Frequency Transform (STFT), the Wigner-Ville Distribution with the Choi-Williams kernel (WV-CW), the Continuous Wavelet' Transform (CWT) and the Discrete Wavelet Transform (DWT). Vibration data of bevel gear tooth fatigue cracks, under a variety of operating load levels and damage conditions, are analyzed using these methods. A new metric for automatic anomaly detection is developed and can be produced from any systematic numerical representation of the vibration signals. This new metric reveals indications of gear damage with all of the time-frequency transforms, as well as time and frequency representations, on this data set. Analysis with the CWT detects changes in the signal at low torque levels not found with the other transforms. The WV-CW and CWT use considerably more resources than the STFT and the DWT. More testing of the new metric is needed to determine its value for automatic anomaly detection and to develop fault detection methods for the metric.

Mosher, Marianne; Pryor, Anna H.; Lewicki, David G.

2003-01-01

58

Precision frequency synthesizing sources with excellent time/frequency performances  

NASA Technical Reports Server (NTRS)

Precision frequency synthesizing sources are needed in the time / frequency measuring system, atomic frequency standards, telemetry, communication, and radar systems. This kind of frequency synthesizing source possesses high frequency accuracy and excellent long term and short term frequency stability. Several precision frequency synthesizing sources developed by Beijing Institute of Radio Metrology and Measurement (BIRMM) which have been successfully applied to the time / frequency measuring system, atomic frequency standards system, and radar system are described. In addition, the working principle, implementation approach, and the main technical specifications of the frequency synthesizing sources are also given.

Zhou, Liren; Lin, Hai

1994-01-01

59

Electrocardiogram Signal and Linear Time-Frequency Transforms  

NASA Astrophysics Data System (ADS)

The diagnostic analysis of non-stationary multi component signals such as electrocardiogram (ECG) involves the use of time-frequency transforms. So, the application of time-frequency transforms to an ECG signal is an important problem of research. In this paper, initially, linear transforms like short time Fourier transform, continuous wavelet transforms, s-transform etc. are revisited. Then the application of these transforms to normal and abnormal ECG signals is illustrated. It has been observed that s-transform provides better time and frequency resolution compared to other linear transforms. The fractional Fourier transform provides rotation to the spectrogram representation.

Krishna, B. T.

2014-06-01

60

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

61

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

62

Ground roll attenuation using a time-frequency dependent polarization filter based on the S transform  

NASA Astrophysics Data System (ADS)

The ground roll and body wave usually show significant differences in arrival time, frequency content, and polarization characteristics, and conventional polarization filters that operate in either the time or frequency domain cannot consider all these elements. Therefore, we have developed a time-frequency dependent polarization filter based on the S transform to attenuate the ground roll in seismic records. Our approach adopts the complex coefficients of the S transform of the multi-component seismic data to estimate the local polarization attributes and utilizes the estimated attributes to construct the filter function. In this study, we select the S transform to design this polarization filter because its scalable window length can ensure the same number of cycles of a Fourier sinusoid, thereby rendering more precise estimation of local polarization attributes. The results of applying our approach in synthetic and real data examples demonstrate that the proposed polarization filter can effectively attenuate the ground roll and successfully preserve the body wave.

Tan, Yu-Yang; He, Chuan; Wang, Yan-Dong; Zhao, Zhong

2013-06-01

63

A method for constructing orthonormal basis functions with good time-frequency localization  

NASA Astrophysics Data System (ADS)

In this paper we derive an explicit, single expression for a complex-valued, orthonormal basis well localized in time-frequency domain. We construct it from a single real function ?(x) which is a Gaussian divided by the square root of a Jacobi theta ?3 function. Then we simplify ?(x) to the form of inverse square root of a Jacobi theta ?3 function. We show that the shape of ?(x) can be changed from Gaussian-like to rectangular-like with a single parameter. The basis generating function ?(x) and its Fourier transform ? have exponential decay. We also show how to modify a standard I and Q processor to compute complex-valued time-frequency expansion coefficients.

Gertner, Izidor

2013-05-01

64

Time-Frequency Masking for Speech Separation and Its Potential for Hearing Aid Design  

PubMed Central

A new approach to the separation of speech from speech-in-noise mixtures is the use of time-frequency (T-F) masking. Originated in the field of computational auditory scene analysis, T-F masking performs separation in the time-frequency domain. This article introduces the T-F masking concept and reviews T-F masking algorithms that separate target speech from either monaural or binaural mixtures, as well as microphone-array recordings. The review emphasizes techniques that are promising for hearing aid design. This article also surveys recent studies that evaluate the perceptual effects of T-F masking techniques, particularly their effectiveness in improving human speech recognition in noise. An assessment is made of the potential benefits of T-F masking methods for the hearing impaired in light of the processing constraints of hearing aids. Finally, several issues pertinent to T-F masking are discussed. PMID:18974204

Wang, DeLiang

2008-01-01

65

Time-frequency analysis for parametric and non-parametric identification of nonlinear dynamical systems  

NASA Astrophysics Data System (ADS)

This paper points out the differences between linear and nonlinear system identification tasks, shows that time-frequency analysis is most appropriate for nonlinearity identification, and presents advanced signal processing techniques that combine time-frequency decomposition and perturbation methods for parametric and non-parametric identification of nonlinear dynamical systems. Hilbert-Huang transform (HHT) is a recent data-driven adaptive time-frequency analysis technique that combines the use of empirical mode decomposition (EMD) and Hilbert transform (HT). Because EMD does not use predetermined basis functions and function orthogonality for component extraction, HHT provides more concise component decomposition and more accurate time-frequency analysis than the short-time Fourier transform and wavelet transform for extraction of system characteristics and nonlinearities. However, HHT's accuracy seriously suffers from the end effect caused by the discontinuity-induced Gibbs' phenomenon. Moreover, because HHT requires a long set of data obtained by high-frequency sampling, it is not appropriate for online frequency tracking. This paper presents a conjugate-pair decomposition (CPD) method that requires only a few recent data points sampled at a low-frequency for sliding-window point-by-point adaptive time-frequency analysis and can be used for online frequency tracking. To improve adaptive time-frequency analysis, a methodology is developed by combining EMD and CPD for noise filtering in the time domain, reducing the end effect, and dissolving other mathematical and numerical problems in time-frequency analysis. For parametric identification of a nonlinear system, the methodology processes one steady-state response and/or one free damped transient response and uses amplitude-dependent dynamic characteristics derived from perturbation analysis to determine the type and order of nonlinearity and system parameters. For non-parametric identification, the methodology uses the maximum displacement states to determine the displacement-stiffness curve and the maximum velocity states to determine the velocity-damping curve. Numerical simulations and experimental verifications of several nonlinear discrete and continuous systems show that the proposed methodology can provide accurate parametric and non-parametric identifications of different nonlinear dynamical systems.

Frank Pai, P.

2013-04-01

66

A Continuous Time Frequency Translating Delta Sigma Modulator Anurag Pulincherry  

E-print Network

on the delta sigma modulators as well as a wide range of subjects in the analog field. Thanks to my friends.1 Analog-to-Digital Conversion................................................................. 1 1A Continuous Time Frequency Translating Delta Sigma Modulator by Anurag Pulincherry A THESIS

Moon, Un-Ku

67

Linear and quadratic time-frequency signal representations  

Microsoft Academic Search

A tutorial review of both linear and quadratic representations is given. The linear representations discussed are the short-time Fourier transform and the wavelet transform. The discussion of quadratic representations concentrates on the Wigner distribution, the ambiguity function, smoothed versions of the Wigner distribution, and various classes of quadratic time-frequency representations. Examples of the application of these representations to typical problems

F. Hlawatsch; G. F. Boudreaux-Bartels

1992-01-01

68

Classification of digital modulated signals based on time frequency representation  

Microsoft Academic Search

This paper proposes a new method for classifying Digital Modulations, including the typical PSK (Phase Shift Keying), FSK (Frequency Shift Keying), ASK (Amplitude Shift Keying) as well as the present OFDM (Orthogonal Frequency Division Multiplex) modulation. The method is based on the analysis of the time frequency representation of the digitally modulated signals. At first, some experiments have been done

Khandker Nadya Haq; Ali Mansour; Sven Nordholm

2010-01-01

69

Direction finding using spatial polarimetric time-frequency distributions  

Microsoft Academic Search

In this paper, we introduce the spatial polarimetric time-frequency distribution (SPTFD) as a platform to process nonstationary array signals with two orthogonal polarization components, such as horizontal and vertical. The use of dual polarization empowers the STFDs and improves the robustness of the respective signal and noise subspaces. With the additional polarimetric information, improved direction finding performance can be achieved.

Yimin Zhang; Moeness G. Amin; Baha A. Obeidat

2003-01-01

70

CAD OF MICROWAVE OPTICAL SYSTEMS FOR TIME&FREQUENCY APPLICATIONS  

E-print Network

CAD OF MICROWAVE OPTICAL SYSTEMS FOR TIME&FREQUENCY APPLICATIONS Houda Brahimi, LAAS-CNRS, Toulouse this modulator taking into account the effect of the system non-linearity on the transmission of the RF signal Figure 1). This type of system has been studied many times in the literature; using analytical approaches

Boyer, Edmond

71

Time-frequency analysis of extreme-mass-ratio inspiral signals in mock LISA data  

E-print Network

Extreme-mass-ratio inspirals (EMRIs) of ~ 1-10 solar-mass compact objects into ~ million solar-mass massive black holes can serve as excellent probes of strong-field general relativity. The Laser Interferometer Space Antenna (LISA) is expected to detect gravitational wave signals from apprxomiately one hundred EMRIs per year, but the data analysis of EMRI signals poses a unique set of challenges due to their long duration and the extensive parameter space of possible signals. One possible approach is to carry out a search for EMRI tracks in the time-frequency domain. We have applied a time-frequency search to the data from the Mock LISA Data Challenge (MLDC) with promising results. Our analysis used the Hierarchical Algorithm for Clusters and Ridges to identify tracks in the time-frequency spectrogram corresponding to EMRI sources. We then estimated the EMRI source parameters from these tracks. In these proceedings, we discuss the results of this analysis of the MLDC round 1.3 data.

Jonathan R Gair; Ilya Mandel; Linqing Wen

2007-10-27

72

Muscle fatigue detection in EMG using time-frequency methods, ICA and neural networks.  

PubMed

The electromyography (EMG) signals give information about different features of muscle function. Real-time measurements of EMG have been used to observe the dissociation between the electrical and mechanical measures that occurs with fatigue. The purpose of this study was to detect fatigue of biceps brachia muscle using time-frequency methods and independent component analysis (ICA). In order to realize this aim, EMG activity obtained from activated muscle during a phasic voluntary movement was recorded for 14 healthy young persons and EMG signals were observed in time-frequency domain for determination of fatigue. Time-frequency methods are used for the processing of signals that are non-stationary and time varying. The EMG contains transient signals related to muscle activity. The proposed method for the detection of muscle fatigue is automated by using artificial neural networks (ANN). The results show that ANN with ICA separates EMG signals from fresh and fatigued muscles, hence providing a visualization of the onset of fatigue over time. The system is adaptable to different subjects and conditions since the techniques used are not subject or workload regime specific. PMID:20703933

Subasi, Abdulhamit; Kiymik, M Kemal

2010-08-01

73

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

74

Time-frequency and space-wavenumber analysis for damage inspection of thin-walled structures  

NASA Astrophysics Data System (ADS)

This paper presents a dynamics-based methodology for accurate damage inspection of thin-walled structures by combining a boundary-effect evaluation method (BEEM) for space-wavenumber analysis of measured operational deflection shapes (ODSs) and a conjugate-pair decomposition (CPD) method for time-frequency analysis of time traces of measured points. BEEM is for locating and estimating small structural damage by processing ODSs measured by a full-field measurement system (e.g., a scanning laser vibrometer or a camera-based motion measurement system). BEEM is a nondestructive spatial-domain method based on area-by-area processing of ODSs and it works without using any structural model or historical data for comparison. Similar to the short-time Fourier transform and wavelet transform, CPD uses adaptive windowed regular harmonics and function orthogonality to perform time-frequency analysis of time traces by extracting time-localized regular and/or distorted harmonics. Both BEEM and CPD are local spectral analysis based on local, adaptive curve fitting. The first estimation of the wavenumber for BEEM and the frequency for CPD is obtained by using a four-point Teager-Kaiser algorithm based on the use of finite difference. Numerical simulations and experimental results show that the combination of BEEM and CPD for space-wavenumber and time-frequency analysis provides an accurate tool for damage inspection of thin-walled structures.

Pai, P. Frank; Sundaresan, Mannur J.

2011-04-01

75

Time-frequency analysis of laser weld signature  

NASA Astrophysics Data System (ADS)

Reliable monitoring methods are essential for maintaining a high level of quality control in laser welding. In industrial processes, monitoring systems allow for quick decisions on the quality of the weld, allowing for high productions rates and reducing overall cost due to scrap. A monitoring system using infrared, ultraviolet, audible sound, and acoustic emission was implemented for monitoring CO2 laser welds in real-time. The signals were analyzed using time-frequency analysis techniques. The time-frequency distribution using the Choi-Williams kernel was calculated, and the resulting distributions were analyzed using the Renyi information distribution. Results for porosity monitoring showed that an acoustic emission sensor held the most promise with 100% classification in two weld studies. These encouraging results led to a second study for monitoring of weld penetration and in the second case, infrared, ultraviolet, and audible sound showed the most promise with 100% classification for both laboratory and industrial data.

Sun, Allen S.; Kannatey-Asibu, Elijah, Jr.; Williams, William J.; Gartner, Mark

2001-11-01

76

Communication in time-frequency spread media using adaptive equalization  

Microsoft Academic Search

In high-speed communication through a medium with time-frequency spread (such as in HF ionospheric, sonic underwater, and voice-quality telephone line transmission), the transmission speed and system errors are determined by an overall system variance (or equivalent noise). This overall variance comprises: 1) the intersymbol interference variance from time spread (or dispersion in the unit impulse response of the medium); 2)

MICHAEL J. DI TORO

1968-01-01

77

Epileptic Seizure Detection in EEGs Using Time-Frequency Analysis  

Microsoft Academic Search

The detection of recorded epileptic seizure activity in EEG segments is crucial for the localization and classification of epileptic seizures. However, since seizure evolution is typically a dynamic and nonstationary process and the signals are composed of multiple frequencies, visual and conventional frequency-based methods have limited application. In this paper, we demonstrate the suitability of the time-frequency ( t-f) analysis

Alexandros T. Tzallas; Markos G. Tsipouras; Dimitrios I. Fotiadis

2009-01-01

78

Time-Frequency Variability of ENSO and Stochastic Simulations.  

NASA Astrophysics Data System (ADS)

The time-frequency spectral structure of El Niño-Southern Oscillation (ENSO) time series holds much information about the physical dynamics of the ENSO system. The authors have analyzed changes of the spectrum with time of three ENSO indices: the conventional Southern Oscillation index (SOI), Niño3 sea surface temperatures, and a tropical Pacific rain index, over the period 1871-1995. Three methods of time-frequency analysis-windowed Fourier transform, wavelet analysis, and windowed Prony's method-were used, and the results are in good agreement. The time-frequency spectra of all the series show strong multidecadal variations over the past century. In particular, there was reduced activity of ENSO in the 2-3-yr periodicity range during the period 1920-60, compared with both the earlier and later periods. The dominant frequencies in the spectra do not appear to be constrained to certain frequency bands, and there is no evidence that the ENSO system has fixed modes of oscillation.The qualitative behavior of the real SOI time series has been compared with that of time series simulated by an autoregressive stochastic process of order 3 and time series created by phase-randomizing the spectral components of the SOI. The decadal variability of the amplitude and time-frequency spectra was found to be very similar between the observed and simulated SOIs. This suggests that the decadal variability of ENSO can be well simulated by a stochastic model and that stochastic forcing may be an important component of ENSO dynamics.

Kestin, Tahl S.; Karoly, David J.; Yano, Jun-Ichi; Rayner, Nicola A.

1998-09-01

79

Time-Frequency Approach for Stochastic Signal Detection  

SciTech Connect

The detection of events in a stochastic signal has been a subject of great interest. One of the oldest signal processing technique, Fourier Transform of a signal contains information regarding frequency content, but it cannot resolve the exact onset of changes in the frequency, all temporal information is contained in the phase of the transform. On the other hand, Spectrogram is better able to resolve temporal evolution of frequency content, but has a trade-off in time resolution versus frequency resolution in accordance with the uncertainty principle. Therefore, time-frequency representations are considered for energetic characterisation of the non-stationary signals. Wigner Ville Distribution (WVD) is the most prominent quadratic time-frequency signal representation and used for analysing frequency variations in signals.WVD allows for instantaneous frequency estimation at each data point, for a typical temporal resolution of fractions of a second. This paper through simulations describes the way time frequency models are applied for the detection of event in a stochastic signal.

Ghosh, Ripul; Akula, Aparna; Kumar, Satish; Sardana, H. K. [Academy of Scientific and Innovative Research (AcSIR), Central Scientific Instruments Organisation, Chandigarh - 160030 (India)

2011-10-20

80

On context-based Bayesian image segmentation: joint multi-context and multiscale approach and wavelet-domain hidden Markov models  

Microsoft Academic Search

We show that context-based Bayesian image segmentation can be improved by strengthening both contextual modeling and statistical texture characterization. Firstly, we develop a joint multi-context and multiscale segmentation algorithm to achieve more robust contextual modeling by using multiple context models. Secondly, we study statistical texture characterization using wavelet-domain hidden Markov models (HMMs), and in particular, we use an improved HMM,

Guoliang Fan; Xiang-Gen Xia

2001-01-01

81

Performance evaluation of space-time-frequency spreading for MIMO OFDM-CDMA systems  

NASA Astrophysics Data System (ADS)

In this article, we propose a multiple-input-multiple-output, orthogonal frequency division multiplexing, code-division multiple-access (MIMO OFDM-CDMA) scheme. The main objective is to provide extra flexibility in user multiplexing and data rate adaptation, that offer higher system throughput and better diversity gains. This is done by spreading on all the signal domains; i.e, space-time frequency spreading is employed to transmit users' signals. The flexibility to spread on all three domains allows us to independently spread users' data, to maintain increased system throughput and to have higher diversity gains. We derive new accurate approximations for the probability of symbol error and signal-to-interference noise ratio (SINR) for zero forcing (ZF) receiver. This study and simulation results show that MIMO OFDM-CDMA is capable of achieving diversity gains significantly larger than that of the conventional 2-D CDMA OFDM and MIMO MC CDMA schemes.

Dahman, Haysam; Shayan, Yousef

2011-12-01

82

Human Time-Frequency Acuity Beats the Fourier Uncertainty Principle  

NASA Astrophysics Data System (ADS)

The time-frequency uncertainty principle states that the product of the temporal and frequency extents of a signal cannot be smaller than 1/(4?). We study human ability to simultaneously judge the frequency and the timing of a sound. Our subjects often exceeded the uncertainty limit, sometimes by more than tenfold, mostly through remarkable timing acuity. Our results establish a lower bound for the nonlinearity and complexity of the algorithms employed by our brains in parsing transient sounds, rule out simple “linear filter” models of early auditory processing, and highlight timing acuity as a central feature in auditory object processing.

Oppenheim, Jacob N.; Magnasco, Marcelo O.

2013-01-01

83

Time-frequency analysis of the bistatic acoustic scattering from a spherical elastic shell.  

PubMed

The development of low-frequency sonar systems, using, for instance, a network of autonomous systems in unmanned vehicles, provides a practical means for bistatic measurements (i.e., when the source and receiver are widely separated) allowing for multiple viewpoints of the target of interest. Time-frequency analysis, in particular, Wigner-Ville analysis, takes advantage of the evolution time dependent aspect of the echo spectrum to differentiate a man-made target, such as an elastic spherical shell, from a natural object of the similar shape. A key energetic feature of fluid-loaded and thin spherical shell is the coincidence pattern, also referred to as the mid-frequency enhancement (MFE), that results from antisymmetric Lamb-waves propagating around the circumference of the shell. This article investigates numerically the bistatic variations of the MFE with respect to the monostatic configuration using the Wigner-Ville analysis. The observed time-frequency shifts of the MFE are modeled using a previously derived quantitative ray theory by Zhang et al. [J. Acoust. Soc. Am. 91, 1862-1874 (1993)] for spherical shell's scattering. Additionally, the advantage of an optimal array beamformer, based on joint time delays and frequency shifts is illustrated for enhancing the detection of the MFE recorded across a bistatic receiver array when compared to a conventional time-delay beamformer. PMID:22280581

Anderson, Shaun D; Sabra, Karim G; Zakharia, Manell E; Sessarego, Jean-Pierre

2012-01-01

84

A visual parallel-BCI speller based on the time-frequency coding strategy  

NASA Astrophysics Data System (ADS)

Objective. Spelling is one of the most important issues in brain-computer interface (BCI) research. This paper is to develop a visual parallel-BCI speller system based on the time-frequency coding strategy in which the sub-speller switching among four simultaneously presented sub-spellers and the character selection are identified in a parallel mode. Approach. The parallel-BCI speller was constituted by four independent P300+SSVEP-B (P300 plus SSVEP blocking) spellers with different flicker frequencies, thereby all characters had a specific time-frequency code. To verify its effectiveness, 11 subjects were involved in the offline and online spellings. A classification strategy was designed to recognize the target character through jointly using the canonical correlation analysis and stepwise linear discriminant analysis. Main results. Online spellings showed that the proposed parallel-BCI speller had a high performance, reaching the highest information transfer rate of 67.4 bit min-1, with an average of 54.0 bit min-1 and 43.0 bit min-1 in the three rounds and five rounds, respectively. Significance. The results indicated that the proposed parallel-BCI could be effectively controlled by users with attention shifting fluently among the sub-spellers, and highly improved the BCI spelling performance.

Xu, Minpeng; Chen, Long; Zhang, Lixin; Qi, Hongzhi; Ma, Lan; Tang, Jiabei; Wan, Baikun; Ming, Dong

2014-04-01

85

Time-frequency radar processing for meteor detection  

Microsoft Academic Search

In this paper, we present signal processing techniques to detect meteor returns from Arecibo Observatory 430-MHz UHF radar data. We exploit the characteristics of the transmit waveform in the frequency domain as well as in the time domain. Two detection methods are investigated. First, when a meteor is present in the radar return over several interpulse periods, there will be

Chun-Hsien Wen; J. F. Doherty; J. D. Mathews

2004-01-01

86

Faster learning algorithm convergence utilizing a combined time-frequency representation as basis  

NASA Astrophysics Data System (ADS)

Light is capable of directly manipulating and probing molecular dynamics at its most fundamental level. One versatile approach to influencing such dynamics exploits temporally shaped femtosecond laser pulses. Oftentimes the control mechanisms necessary to induce a desired reaction cannot be determined theoretically a priori. However under certain circumstances these mechanisms can be extracted experimentally through trial and error. This can be implemented systematically by using an evolutionary learning algorithm (LA) with closed loop feedback. Most frequently, pulse shaping algorithms operate within either the time or frequency domain, however seldom both. This may influence the physical insight gained due to dependence on the search basis, as well as influence the speed the algorithm takes to converge. As an alternative to the Fourier domain basis, we make use of a combined time-frequency representation known as the von Neumann basis where we observe temporal and spectral effects at the same time. We report on the numerical and experimental results obtained using the Fourier, as well as the von Neumann basis to maximize the second harmonic generation (SHG) output in a non-linear crystal. We show that the von Neumann representation converges faster than the Fourier domain when compared to searches in the Fourier domain. We also show a reduced parameter space is required for the Fourier domain to converge efficiently, but not for von Neumann domain. Finally we show the highest SHG signal is not only a consequence of the shortest pulse, but that the pulse central frequency also plays a key role. Taken together these results suggest that the von Neumann basis can be used as a viable alternative to the Fourier domain with improved convergence time and potentially deeper physical insight.

Hendriks, A. J.; Uys, Hermann; du Plessis, Anton; Steenkamp, Christine

2013-10-01

87

Spatiotemporal and time-frequency analysis of functional near infrared spectroscopy brain signals using independent component analysis.  

PubMed

Functional near infrared spectroscopy (fNIRS) is a noninvasive method to capture brain activities according to the measurements of changes in both oxyhemoglobin and deoxyhemoglobin concentrations. However, fNIRS recordings are the hemodynamic signals that come from the latent neural sources that are spatially and temporally mixed across the brain. The purpose of this work is to extract the temporal and frequency characteristics as well as the spatial activation patterns in the brains using independent component analysis (ICA). In this study, the filtered fNIRS recordings were processed and the time-frequency and spatiotemporal domain independent components (ICs) were identified by ICA. We found that multiple task-related components can be separated by ICA in time-frequency domain, and distinct spatial patterns of brain activity can be derived from ICs that are well correlated with the specific neural events, such as finger tapping tasks. PMID:24150092

Yuan, Zhen

2013-10-01

88

A comparison between advanced time-frequency analyses of non-stationary magnetization dynamics in spin-torque oscillators  

NASA Astrophysics Data System (ADS)

We report re`sults of different time-frequency analyses (Wavelet and Hilbert-Huang Transform (HHT)) of voltage measurements related to a spin-torque oscillator working in a regime of non-stationary dynamics. Our results indicate that the Wavelet analysis identifies the non-stationary magnetization dynamics revealing the existence of intermittent and independent excited modes while the HHT is able to accurately extract the time domain traces of each independent mode. Overall performance indicates a route for a complete characterization of time-frequency domain data of a STO, pointing out that the combined Wavelet-HHT methodology developed is general and can be also used for a variety of other different scenarios.

Siracusano, Giulio; Corte, Aurelio La

2014-02-01

89

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

90

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

91

Time-frequency analysis of functional optical mammographic images  

NASA Astrophysics Data System (ADS)

We have introduced working technology that provides for time-series imaging of the hemoglobin signal in large tissue structures. In this study we have explored our ability to detect aberrant time-frequency responses of breast vasculature for subjects with Stage II breast cancer at rest and in response to simple provocations. The hypothesis being explored is that time-series imaging will be sensitive to the known structural and functional malformations of the tumor vasculature. Mammographic studies were conducted using an adjustable hemisheric measuring head containing 21 source and 21 detector locations (441 source-detector pairs). Simultaneous dual-wavelength studies were performed at 760 and 830 nm at a framing rate of ~2.7 Hz. Optical measures were performed on women lying prone with the breast hanging in a pendant position. Two class of measures were performed: (1) 20- minute baseline measure wherein the subject was at rest; (2) provocation studies wherein the subject was asked to perform some simple breathing maneuvers. Collected data were analyzed to identify the time-frequency structure and central tendencies of the detector responses and those of the image time series. Imaging data were generated using the Normalized Difference Method (Pei et al., Appl. Opt. 40, 5755-5769, 2001). Results obtained clearly document three classes of anomalies when compared to the normal contralateral breast. 1) Breast tumors exhibit altered oxygen supply/demand imbalance in response to an oxidative challenge (breath hold). 2) The vasomotor response of the tumor vasculature is mainly depressed and exhibits an altered modulation. 3) The affected area of the breast wherein the altered vasomotor signature is seen extends well beyond the limits of the tumor itself.

Barbour, Randall L.; Graber, Harry L.; Schmitz, Christoph H.; Tarantini, Frank; Khoury, Georges; Naar, David J.; Panetta, Thomas F.; Lewis, Theophilus; Pei, Yaling

2003-07-01

92

Detection of shockable and non-shockable rhythms in presence of CPR artifacts by time-frequency ECG analysis  

Microsoft Academic Search

Time-frequency domain features of chest compression (CC) artefacts, non-shockable (NShR) and shockable (ShR) rhythms were investigated. The aim was to provide reliable shock advisory analysis during CC by single channel electrocardiogram (ECG) processing. Three frequency bands were suggested to enhance specific components of the CC artefacts, NShR and ShR rhythms: (i) 2-3 Hz to emphasize the similarity of the basic

J. P. Didon; I. Dotsinsky; I. Jekova; V. Krasteva

2009-01-01

93

On the system level prediction of joint time frequency spreading systems with carrier phase noise  

Microsoft Academic Search

Phase noise is a topic of theoretical and practical interest in electronic circuits. Although progress has been made in the characterization of its description, there are still considerable gaps in its effects especially on multi-carrier spreading systems. In this paper, we investigate the impact of a local oscillator phase noise on the multi-carrier 2 dimensional (2D) spreading systems based on

Youssef Nasser; Mathieu Des Noes; Laurent Ros; Geneviève Jourdain

2010-01-01

94

Stochastic joint time-frequency response analysis of nonlinear structural systems  

NASA Astrophysics Data System (ADS)

A novel approximate analytical approach for determining the response evolutionary power spectrum (EPS) of nonlinear/hysteretic structural systems subject to stochastic excitation is developed. Specifically, relying on the theory of locally stationary processes and utilizing a recently proposed representation of non-stationary stochastic processes via wavelets, a versatile formula for determining the nonlinear system response EPS is derived; this is done in conjunction with a stochastic averaging treatment of the problem and by resorting to the orthogonality properties of harmonic wavelets. Further, the nonlinear system non-stationary response amplitude probability density function (PDF), which is required as input for the developed approach, is determined either by utilizing a numerical path integral scheme, or by employing a time-dependent Rayleigh PDF approximation technique. A significant advantage of the approach relates to the fact that it is readily applicable for treating not only separable but non-separable in time and frequency EPS as well. The hardening Duffing and the versatile Preisach (hysteretic) oscillators are considered in the numerical examples section. Comparisons with pertinent Monte Carlo simulations demonstrate the reliability of the approach.

Kougioumtzoglou, Ioannis A.

2013-12-01

95

Comprehensive Joint Time-Frequency Analysis toward Condition Based Maintenance Regimes for Electrical and  

E-print Network

, metrics are proposed for helicopter drivetrain systems and electrical cable. Using principles of time the practical implementation of such technology. A new concept of non-parametric signal detection. Baseline, unbalanced, and misaligned experimental settings of helicopter drive train bearings and shafts

Almor, Amit

96

Crosslinking EEG time-frequency decomposition and fMRI in error monitoring.  

PubMed

Recent studies implicate a common response monitoring system, being active during erroneous and correct responses. Converging evidence from time-frequency decompositions of the response-related ERP revealed that evoked theta activity at fronto-central electrode positions differentiates correct from erroneous responses in simple tasks, but also in more complex tasks. However, up to now it is unclear how different electrophysiological parameters of error processing, especially at the level of neural oscillations are related, or predictive for BOLD signal changes reflecting error processing at a functional-neuroanatomical level. The present study aims to provide crosslinks between time domain information, time-frequency information, MRI BOLD signal and behavioral parameters in a task examining error monitoring due to mistakes in a mental rotation task. The results show that BOLD signal changes reflecting error processing on a functional-neuroanatomical level are best predicted by evoked oscillations in the theta frequency band. Although the fMRI results in this study account for an involvement of the anterior cingulate cortex, middle frontal gyrus, and the Insula in error processing, the correlation of evoked oscillations and BOLD signal was restricted to a coupling of evoked theta and anterior cingulate cortex BOLD activity. The current results indicate that although there is a distributed functional-neuroanatomical network mediating error processing, only distinct parts of this network seem to modulate electrophysiological properties of error monitoring. PMID:23443964

Hoffmann, Sven; Labrenz, Franziska; Themann, Maria; Wascher, Edmund; Beste, Christian

2014-03-01

97

Time-frequency characterization of interdependencies in nonstationary signals: application to epileptic EEG  

PubMed Central

For the past decades, numerous works have been dedicated to the development of signal processing methods aimed at measuring the degree of association between EEG signals. This interdependency parameter, which may be defined in various ways, is often used to characterize a functional coupling between different brain structures or regions during either normal or pathological processes. In this paper we focus on the time-frequency characterization of the interdependency between signals. Particularly, we propose a novel estimator of the linear relationship between nonstationary signals based on the cross correlation of narrow band filtered signals. This estimator is compared to a more classical estimator based on the coherence function. In a simulation framework, results show that it may exhibit better statistical performances (bias and variance or mean square error) when a priori knowledge about time delay between signals is available. On real data (intracerebral EEG signals), results show that this estimator may also enhance the readability of the time-frequency representation of relationship and thus can improve the interpretation of nonstationary interdependencies in EEG signals. Finally, we illustrate the importance of characterizing the relationship in both time and frequency domains by comparing with frequency-independent methods (linear and nonlinear). PMID:16041985

Ansari-Asl, Karim; Bellanger, Jean-Jacques; Bartolomei, Fabrice; Wendling, Fabrice; Senhadji, Lotfi

2005-01-01

98

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

99

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.

2011-04-01

100

Cross Time-Frequency Analysis for Combining Information of Several Sources: Application to Estimation of Spontaneous Respiratory Rate from Photoplethysmography  

PubMed Central

A methodology that combines information from several nonstationary biological signals is presented. This methodology is based on time-frequency coherence, that quantifies the similarity of two signals in the time-frequency domain. A cross time-frequency analysis method, based on quadratic time-frequency distribution, has been used for combining information of several nonstationary biomedical signals. In order to evaluate this methodology, the respiratory rate from the photoplethysmographic (PPG) signal is estimated. The respiration provokes simultaneous changes in the pulse interval, amplitude, and width of the PPG signal. This suggests that the combination of information from these sources will improve the accuracy of the estimation of the respiratory rate. Another target of this paper is to implement an algorithm which provides a robust estimation. Therefore, respiratory rate was estimated only in those intervals where the features extracted from the PPG signals are linearly coupled. In 38 spontaneous breathing subjects, among which 7 were characterized by a respiratory rate lower than 0.15 Hz, this methodology provided accurate estimates, with the median error {0.00; 0.98}?mHz ({0.00; 0.31}%) and the interquartile range error {4.88; 6.59}?mHz ({1.60; 1.92}%). The estimation error of the presented methodology was largely lower than the estimation error obtained without combining different PPG features related to respiration. PMID:24363777

Pelaez-Coca, M. D.; Orini, M.; Lazaro, J.; Bailon, R.; Gil, E.

2013-01-01

101

Time-Frequency Representations for second heart sound analysis.  

PubMed

Several researches have tried to provide a means to analyze the second heart sound (S2) in an attempt to understand the functional mechanisms in its genesis and for diagnosis purposes. In this work we tested Time-Frequency Representation (TFR) for simulated S2 selecting and applying classical and modern TFRs such as the Spectrogram, the Wigner-Ville Distribution, the Time Varying Autoregressive (TVAR) model, the Scalogram, and the Hilbert-Huang Spectrum (HHS) by Empirical Mode Decomposition. Two performance measures are proposed, the first one based on local 2D correlations (rho) between the ideal and the estimated TFRs images, while the second one based on time moments of the TFR images to provide the normalized root-mean-square error (NRMSE). Under no noise conditions, the TFRs by HHS and the TVAR modeling, by the Burg algorithm, resulted in a rho(average) of 0.788 and 0.812, and NRMSE of 0.172 and 0.195, respectively. Therefore, based on the lowest NRMSE, HHS was considered the TFR with the best performance. Afterward, HHS was applied to real S2 acquired at the aortic and pulmonary focal points. PMID:19163492

Reyes, B A; Charleston-Villalobos, S; Gonzalez-Camarena, R; Aljama-Corrales, T

2008-01-01

102

Time frequency analysis of sound from a maneuvering rotorcraft  

NASA Astrophysics Data System (ADS)

The acoustic signatures produced by a full-scale, Bell 430 helicopter during steady-level-flight and transient roll-right maneuvers are analyzed by way of time-frequency analysis. The roll-right maneuvers comprise both a medium and a fast roll rate. Data are acquired using a single ground based microphone that are analyzed by way of the Morlet wavelet transform to extract the spectral properties and sound pressure levels as functions of time. The findings show that during maneuvering operations of the helicopter, both the overall sound pressure level and the blade-vortex interaction sound pressure level are greatest when the roll rate of the vehicle is at its maximum. The reduced inflow in the region of the rotor disk where blade-vortex interaction noise originates is determined to be the cause of the increase in noise. A local decrease in inflow reduces the miss distance of the tip vortex and thereby increases the BVI noise signature. Blade loading and advance ratios are also investigated as possible mechanisms for increased sound production, but are shown to be fairly constant throughout the maneuvers.

Stephenson, James H.; Tinney, Charles E.; Greenwood, Eric; Watts, Michael E.

2014-10-01

103

Environmental sound recognition using time-frequency intersection patterns  

Microsoft Academic Search

Environmental sound recognition is an important function of robots and intelligent computer systems. In this research, we tried to use a multi-stage perceptron type neural network system for environmental sound recognition. The input data is the one-dimensional combination of instantaneous spectrum at power peak and the power pattern in time domain. Since for almost environmental sounds, their spectrum changes are

Xuan Guol; Yoshiyuki Toyoda; Huankang Li; Jie Huang; Shuxue Ding; Yong Liul

2011-01-01

104

Representation of operators by sampling in the time-frequency domain  

E-print Network

f L2 (R) by Vgf(mb0, n0) = f, gmn , m, n Z (1) where the gmn = Mn0 Tmb0 g denote the Gabor atoms to the coefficients Vgf is di- agonal, an approach that leads to accurate approximation for so-called underspread

Torresani, Bruno

105

Representation of operators by sampling in the time-frequency domain  

E-print Network

on the sam- pled short-time Fourier transform (STFT) or Gabor coef- ficients, given for any f L2 (R) by Vgf, the modification consists of a pure multiplication. Thus, the linear operator applied to the coefficients Vgf is di

Paris-Sud XI, Université de

106

Naval Space Surveillance Center uses of time, frequency, and phase  

NASA Technical Reports Server (NTRS)

The Naval Space Surveillance Center (NAVSPASUR) is an operational naval command that has the mission of determining the location of all manmade objects in space and transmitting information on objects of interest to the fleet. NAVSPASUR operates a 217 MHz radar fence that has 9 transmitting and receiving stations deployed in a line across southern Continental United States (CONUS). This surveillance fence provides unalerted detection of satellites overflying CONUS. NAVSPASUR also maintains a space catalog of all orbiting space objects. NAVSPASUR plays an important role as operational alternate to the primary national Space Surveillance Center (SSC) and Space Defence Operations Center (SPADOC). In executing these responsibilities, NAVSPASUR needs precise and/or standardized time and frequency in a number of applications. These include maintenance of the radar fence references to specification, and coordination with other commands and agencies for data receipt and dissemination. Precise time and frequency must be maintained within each site to enable proper operation of the interferometry phasing technique used. Precise time-of-day clocking must exist between sites for proper intersite coordination. Phase may be considered a derivative of time and frequency. Its control within each transmitter or receiver site is of great importance to NAVSPASUR because of the operation of the sensor as an interferometer system, with source direction angles as the primary observable. Determination of the angular position of a satellite is directly dependent on the accuracy with which the differential phase between spaced subarrays can be measured at each receiver site. Various aspects of the NAVSPASUR are discussed with respect to time, frequency, and phase.

Hayden, Carroll C.; Knowles, Stephen H.

1992-01-01

107

Time-frequency analyses of tide-gauge sensor data.  

PubMed

The real world phenomena being observed by sensors are generally non-stationary in nature. The classical linear techniques for analysis and modeling natural time-series observations are inefficient and should be replaced by non-linear techniques of whose theoretical aspects and performances are varied. In this manner adopting the most appropriate technique and strategy is essential in evaluating sensors' data. In this study, two different time-series analysis approaches, namely least squares spectral analysis (LSSA) and wavelet analysis (continuous wavelet transform, cross wavelet transform and wavelet coherence algorithms as extensions of wavelet analysis), are applied to sea-level observations recorded by tide-gauge sensors, and the advantages and drawbacks of these methods are reviewed. The analyses were carried out using sea-level observations recorded at the Antalya-II and Erdek tide-gauge stations of the Turkish National Sea-Level Monitoring System. In the analyses, the useful information hidden in the noisy signals was detected, and the common features between the two sea-level time series were clarified. The tide-gauge records have data gaps in time because of issues such as instrumental shortcomings and power outages. Concerning the difficulties of the time-frequency analysis of data with voids, the sea-level observations were preprocessed, and the missing parts were predicted using the neural network method prior to the analysis. In conclusion the merits and limitations of the techniques in evaluating non-stationary observations by means of tide-gauge sensors records were documented and an analysis strategy for the sequential sensors observations was presented. PMID:22163829

Erol, Serdar

2011-01-01

108

Time-Frequency Analysis in Terahertz-Pulsed Imaging  

Microsoft Academic Search

Recent advances in laser and electro-optical technologies have made the previously underutilized terahertz frequency band\\u000a of the electromagnetic spectrum accessible for practical imaging. Applications are emerging, notably in the biomedical domain.\\u000a In this chapter the technique of terahertz-pulsed imaging is introduced in some detail. The need for special computer vision\\u000a methods, which arises from the use of pulses of radiation

Elizabeth Berry; Roger D Boyle; Anthony J Fitzgerald; James Handley

109

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 PMID:23028544

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

2012-01-01

110

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

111

Ultrashort Pulse Characterization and Coherent Time-Frequency Light Processing  

NASA Astrophysics Data System (ADS)

Over the past several decades ultrafast laser science and technology has evolved into an extensive and diverse yet still one of the most rapidly growing and developing areas of optics. This evolution has been one of mutual interdependence. Each current generation of technological innovations not only solves the specific problems it was designed for, but uncovers new application opportunities and enables the exploration of new basic research areas. In turn, these new challenges will give rise to the next generation of technological improvements born of the currently existing technologies and the advances in fundamental scientific knowledge and understanding. Ultrashort pulse characterization has always been an essential part of this ultrafast optics evolution. The thesis makes yet another contribution to it by describing the principle, design, construction, development and operation of a novel interferometric ultrashort pulse characterization device. It consists of a new implementation of spectral-shearing interferometry for reconstructing the electric field of ultrashort pulses, requiring only a single optical element to encode the temporal field of the pulse under test. The technique relies on an asymmetric group velocity matching type II sum frequency generation process in a single long nonlinear crystal. We analyze the performance of the device for a wide range of experimentally available input pulse parameters. The device --- potential building block for the future generations of ultrashort diagnostics --- proves a practical, elegant, compact, robust, and sensitive option for complete amplitude and phase ultrashort pulse characterization. As the femtosecond systems of increasingly larger bandwidth become a widespread reality, the detrimental effects of dispersion require careful consideration. Dispersive pulse distortion degrades longitudinal resolution of broadband interferometric imaging methods such as optical coherence tomography and low-coherence interferometry. We address the issue with a novel signal processing dispersion compensation method. This numerical technique improves the axial resolution without a priori knowledge of the material dispersive properties of the sample under consideration. The dispersion compensation is based on the generalized temporal fourth order field autoconvolution function computed from the readily available experimental interferometric scans and has an intuitive depiction in the time-frequency phase-space via the Wigner distribution function formalism.

Radunsky, Aleksandr S.

112

Experimental measure of arm stiffness during single reaching movements with a time-frequency analysis  

PubMed Central

We tested an innovative method to estimate joint stiffness and damping during multijoint unfettered arm movements. The technique employs impulsive perturbations and a time-frequency analysis to estimate the arm's mechanical properties along a reaching trajectory. Each single impulsive perturbation provides a continuous estimation on a single-reach basis, making our method ideal to investigate motor adaptation in the presence of force fields and to study the control of movement in impaired individuals with limited kinematic repeatability. In contrast with previous dynamic stiffness studies, we found that stiffness varies during movement, achieving levels higher than during static postural control. High stiffness was associated with elevated reflexive activity. We observed a decrease in stiffness and a marked reduction in long-latency reflexes around the reaching movement velocity peak. This pattern could partly explain the difference between the high stiffness reported in postural studies and the low stiffness measured in dynamic estimation studies, where perturbations are typically applied near the peak velocity point. PMID:23945781

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

2013-01-01

113

Time-Frequency Mixed-Norm Estimates: Sparse M/EEG imaging with non-stationary source activations  

PubMed Central

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 an hypothesis only holds 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 to recently proposed inverse solvers with help of simulations and by analyzing publicly available MEG datasets. PMID:23291276

Gramfort, A.; Strohmeier, D.; Haueisen, J.; Hamalainen, M.; Kowalski, M.

2013-01-01

114

A joint estimation detection of Glaucoma progression in 3D spectral domain optical coherence tomography optic nerve head images  

NASA Astrophysics Data System (ADS)

Glaucoma is an ocular disease characterized by distinctive changes in the optic nerve head (ONH) and visual field. Glaucoma can strike without symptoms and causes blindness if it remains without treatment. Therefore, early disease detection is important so that treatment can be initiated and blindness prevented. In this context, important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, an essential element for glaucoma detection and monitoring. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new framework for detection of glaucoma progression using 3D SD-OCT images. In contrast to previous works that the retinal nerve fiber layer (RNFL) thickness measurement provided by commercially available spectral-domain optical coherence tomograph, we consider the whole 3D volume for change detection. To integrate a priori knowledge and in particular the spatial voxel dependency in the change detection map, we propose the use of the Markov Random Field to handle a such dependency. To accommodate the presence of false positive detection, the estimated change detection map is then used to classify a 3D SDOCT image into the "non-progressing" and "progressing" glaucoma classes, based on a fuzzy logic classifier. We compared the diagnostic performance of the proposed framework to existing methods of progression detection.

Belghith, Akram; Bowd, Christopher; Weinreb, Robert N.; Zangwill, Linda M.

2014-03-01

115

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

116

Time-Frequency Relationships between Heart Rate and Respiration: A Diagnosis Tool for Late  

E-print Network

Time-Frequency Relationships between Heart Rate and Respiration: A Diagnosis Tool for Late Onset of the laboratory tests, including CRP and blood culture, have high predictive accuracy. Heart rate variability (HRV. The objective of this study was to determine if analysis of time-frequency correlations between the heart rate

Paris-Sud XI, Université de

117

Intensity analysis in time-frequency space of surface myoelectric signals by wavelets of specified resolution  

Microsoft Academic Search

Surface myoelectric signals often appear to carry more information than what is resolved in root mean square analysis of the progress curves or in its power spectrum. Time-frequency analysis of myoelectric signals has not yet led to satisfactory results in respect of separating simultaneous events in time and frequency. In this study a time-frequency analysis of the intensities in time

Vinzenz von Tscharner

2000-01-01

118

Diversity in Shallow Water Environments Using Blind Time-Frequency Separation Techniques  

E-print Network

Diversity in Shallow Water Environments Using Blind Time-Frequency Separation Techniques Bertrand-lab.inpg.fr Abstract- The shallow water environment can be character- ized as a time-dispersive system whose time-varying impulse response can be expressed as a superposition of time-frequency components with dispersive

Paris-Sud XI, Université de

119

TIME-FREQUENCY MODELING OF SHALLOW WATER ENVIRONMENTS: RIGID VS. FLUID SEABED  

E-print Network

TIME-FREQUENCY MODELING OF SHALLOW WATER ENVIRONMENTS: RIGID VS. FLUID SEABED Jun Zhang , Bertrand with the ocean bottom and surface, re- sulting in dense dispersion due to the water medium and time- varying (TV the Pekeris model for shallow water environments. In Section 3, we present the time-frequency (TF

Paris-Sud XI, Université de

120

Continuous-variable quantum computing in optical time-frequency modes using quantum memories.  

PubMed

We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate, and measure two-dimensional cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that are a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures. PMID:25302876

Humphreys, Peter C; Kolthammer, W Steven; Nunn, Joshua; Barbieri, Marco; Datta, Animesh; Walmsley, Ian A

2014-09-26

121

Continuous-Variable Quantum Computing in Optical Time-Frequency Modes Using Quantum Memories  

NASA Astrophysics Data System (ADS)

We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate, and measure two-dimensional cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that are a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures.

Humphreys, Peter C.; Kolthammer, W. Steven; Nunn, Joshua; Barbieri, Marco; Datta, Animesh; Walmsley, Ian A.

2014-09-01

122

Continuous-Variable Quantum Computing in Optical Time-Frequency Modes using Quantum Memories  

E-print Network

We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate and measure 2D cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that is a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures.

Peter C. Humphreys; W. Steven Kolthammer; Joshua Nunn; Marco Barbieri; Animesh Datta; Ian A. Walmsley

2014-05-21

123

Time-frequency bandwidth product of a Gaussian LUCAS J. VAN VLIET  

E-print Network

1 Time-frequency bandwidth product of a Gaussian LUCAS J. VAN VLIET Pattern Recognition Group, Lorentzweg 1, 2628CJ Delft, The Netherlands. www.ph.tn.tudelft.nl/~lucas In this note we compute the time

van Vliet, Lucas J.

124

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

125

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

126

Spatial Polarimetric Time-Frequency Distributions and Applications to Direction-of-Arrival Estimation  

Microsoft Academic Search

Time-frequency distributions (TFDs) have evolved to be a powerful technique for nonstationary signal analysis and synthesis. With the use of a multi-sensor array, spatial time-frequency distributions (STFDs) have been developed and successfully applied to high-resolution direction-of-arrival (DOA) estimation and blind recovery of the source waveforms. In this paper, the polarimetric dimension is introduced to the STFDs resulting in the spatial

Yimin Zhang; Moeness G. Amin; Baha A. Obeidat

127

Travels through the time-frequency zone: advanced Doppler ultrasound processing techniques  

Microsoft Academic Search

Doppler ultrasound echoes from cardiac structures is rich in detail and highly nonstationary. The goal of time frequency analysis is to extract features from these echo signals for high confidence visual and machine classification of cardiovascular condition. Presented are side-by-side comparisons of numerous time-frequency representations (TFRs) of Doppler ultrasound data. The techniques illustrated include the short-time Fourier transform, the wavelet

L. Marple; T. Brotherton; R. Barton; E. Lugo; D. Jones

1993-01-01

128

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

Microsoft Academic Search

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

Chuan Li; Ming Liang

2012-01-01

129

Water Peak Suppression: Time-Frequency vs TimeScale Approach  

Microsoft Academic Search

Wavelets are the most popular time-scale analysis tool. A well-known application of wavelets in nuclear magnetic resonance spectroscopy is water peak extraction\\/suppression. However, spectroscopists are more familiar with frequency than scale. So, from a spectroscopist point of view, a time-scale analysis tool (i.e., wavelets) is not natural and a time-frequency approach would be much more satisfactory. We explain a time-frequency

Jean-Pierre Antoine; Alain Coron; Jean-Marie Dereppe

2000-01-01

130

Time-frequency manifold for nonlinear feature extraction in machinery fault diagnosis  

NASA Astrophysics Data System (ADS)

Time-frequency feature is beneficial to representation of non-stationary signals for effective machinery fault diagnosis. The time-frequency distribution (TFD) is a major tool to reveal the synthetic time-frequency pattern. However, the TFD will also face noise corruption and dimensionality reduction issues in engineering applications. This paper proposes a novel nonlinear time-frequency feature based on a time-frequency manifold (TFM) technique. The new TFM feature is generated by mainly addressing manifold learning on the TFDs in a reconstructed phase space. It combines the non-stationary information and the nonlinear information of analyzed signals, and hence exhibits valuable properties. Specifically, the new feature is a quantitative low-dimensional representation, and reveals the intrinsic time-frequency pattern related to machinery health, which can effectively overcome the effects of noise and condition variance issues in sampling signals. The effectiveness and the merits of the proposed TFM feature are confirmed by case study on gear wear diagnosis, bearing defect identification and defect severity evaluation. Results show the value and potential of the new feature in machinery fault pattern representation and classification.

He, Qingbo

2013-02-01

131

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

2012-12-01

132

Comparison of time-frequency-based techniques for estimating instantaneous frequency parameters of nonstationary processes  

NASA Astrophysics Data System (ADS)

The aim of this work is to contrast techniques used to estimate two instantaneous frequency parameters of the surface electromyographic (EMG) signal, the instantaneous median frequency and the instantaneous mean frequency, based on their estimation error. Three methods are compared: Cohen class and Cohen-Posch class time- frequency representations are used to compute both the above- mentioned instantaneous frequency parameters, and a cross-time- frequency based technique is adopted to derive the instantaneous mean frequency. The results demonstrate that the algorithm based on Cohen-Posch class transformations leads to a standard deviation of the instantaneous frequency parameters that is smaller than that obtained using Cohen class representations. However, the cross- time-frequency estimation procedure for instantaneous mean frequency produced the smallest standard deviation compared to the other techniques. The algorithms based on Cohen class and Cohen- Posch class transformations often provided a lower bias than the cross-time-frequency based technique. This advantage was particularly evident when the instantaneous mean frequency varies non-linearly within the epochs used to derive the cross-time- frequency representation of the surface EMG signal.

Bonato, Paolo; Erim, Zeynep; Roy, Serge H.; De Luca, Carlo J.

1999-11-01

133

Spatial polarimetric time-frequency distributions and applications to direction-of-arrival estimation  

NASA Astrophysics Data System (ADS)

Time-frequency distributions (TFDs) have evolved to be a powerful technique for nonstationary signal analysis and synthesis. With the use of a multi-sensor array, spatial time-frequency distributions (STFDs) have been developed and successfully applied to high-resolution direction-of-arrival (DOA) estimation and blind recovery of the source waveforms. In this paper, the polarimetric dimension is introduced to the STFDs resulting in the spatial polarimetric time-frequency distributions (SPTFDs) as a platform for the processing of non-stationary polarized signals. In the SPTFD platform, polarized signals are decomposed (projected) into two orthogonal polarization components, such as horizontal and vertical, and later processed in a manner where their polarization characteristics are exploited. This empowers the STFDs with additional degrees of freedom and improves the robustness of the signal and noise subspaces, and therefore, serving to enhance DOA estimation, signal recovery, and source separation performance. To demonstrate the advantages of the SPTFDs, the polarimetric time-frequency MUSIC (PTF-MUSIC) method for DOA estimation is proposed based on the SPTFD platform and is shown to outperform the time-frequency, polarimetric, and conventional MUSIC methods.

Zhang, Yimin; Amin, Moeness G.; Obeidat, Baha A.

2003-12-01

134

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

2013-12-01

135

Close shock detection using time-frequency Prony modeling Nadine Martin, Pierre Jaussaud and Franois Combet  

E-print Network

1 Close shock detection using time-frequency Prony modeling Nadine Martin, Pierre Jaussaud and their individual identification are not easy. In that paper, we adapt the well-known stationary Prony model to this non stationary context. We propose a method where shocks instants detection and parameters shocks

Paris-Sud XI, Université de

136

Important trait and application of time-frequency to traceable source link  

NASA Astrophysics Data System (ADS)

Taking the traceable source link system of the time-frequency as the typical one from the National Intelligence Standard Research Institute (NIST) of the United States, the article provides its block-diagram and technical indicators reviews its aim and its task. The article also gives the important characters of the traceable source link of the time-frequency, which includes: having the high-accuracy cesium fountain primitive frequency benchmark (accuracy and steady degrees all reach to 1×E-15), keeping ahead in the aspect of time-frequency transform method technology research and development, then reaching the advanced level in the frequency measurement and the analytical system of long-range calibration (FMAS), so as in the quality of the high integration, automatization, intelligent, lightweight of top-level equipment in the traceabel source link system. At last, the article describes the importance and the key technical indicator achieved at present to the high-accuracy synchronous time-frequency system in the field of the astronomy measurement, the guided missile launch, navigation and orientation, etc.

Ni, Guang-Ren; Xu, Lu-Ping; He, Kang-Yuan

2006-03-01

137

Spectrogram analysis of the time–frequency characteristics of ocean wind waves  

Microsoft Academic Search

The spectrogram based on the short-time Fourier transform is proposed as a tool to study the time frequency evolution of the properties of ocean wind waves. After defining the method to determine the spectrogram of wind waves an example of application is given by analyzing the time series from three sea states concerning a swell, a wind sea and a

C. Guedes Soares; Z. Cherneva

2005-01-01

138

RANDOM TIME-FREQUENCY SUBDICTIONARY DESIGN FOR SPARSE REPRESENTATIONS WITH GREEDY ALGORITHMS  

E-print Network

RANDOM TIME-FREQUENCY SUBDICTIONARY DESIGN FOR SPARSE REPRESENTATIONS WITH GREEDY ALGORITHMS Manuel decomposition algorithms. The size of the dictionary, and therefore its resolution, is a key pa- rameter random sequence of subdictionaries in a greedy decomposition process, thus browsing a larger dictionary

Paris-Sud XI, Université de

139

Channel Estimation Based on Space-Time-Frequency Coded Training Sequence for Transmit Diversity System  

NASA Astrophysics Data System (ADS)

A novel transmit diversity scheme with space-time-frequency coded training sequence is proposed to perform channel estimation flexibly over doubly selective channel, which offers a trade-off between maximum delay spread and maximum Doppler spread. Simulation results are presented to verify the effectiveness of the proposed flexible channel estimation method under different propagation conditions.

Yang, Fang; Peng, Kewu; Wang, Jintao; Song, Jian; Yang, Zhixing

140

A MULTIRESOLUTION TIME-FREQUENCY ANALYSIS AND INTERPRETATION OF MUSICAL RHYTHM  

E-print Network

A MULTIRESOLUTION TIME-FREQUENCY ANALYSIS AND INTERPRETATION OF MUSICAL RHYTHM This thesis of such an approach is to provide better models of musical time for machine accompaniment of human musicians in the literature of the characterisation of elements of rhythm. The effect of inter-onset timing, duration, tempo

Kovesi, Peter

141

Periodic wavelet frames and time-frequency localization Elena A. Lebedevaa,1,  

E-print Network

Periodic wavelet frames and time-frequency localization Elena A. Lebedevaa,1, , J¨urgen Prestinb a.com (Elena A. Lebedeva), prestin@math.uni-luebeck.de (J¨urgen Prestin) URL: http://http://www.hmath.spbstu.ru/index.php/staff/9-prepod/56-lebedeva-ea (Elena A. Lebedeva), www.math.uni-luebeck.de/prestin/ (J¨urgen Prestin) 1

Prestin, Jürgen

142

SPATIAL AND COHERENCE CUES BASED TIME-FREQUENCY MASKING FOR BINAURAL REVERBERANT SPEECH SEPARATION  

E-print Network

SPATIAL AND COHERENCE CUES BASED TIME-FREQUENCY MASKING FOR BINAURAL REVERBERANT SPEECH SEPARATION of the binaural source separation algorithms only con- sider the dissimilarities between the recorded mixtures (IC) between the left and right recordings. The binaural room impulse responses measured in four rooms

Jackson, Philip JB

143

A Comparative Study of Time-Frequency Representations for Fault Detection in Wind Turbine  

E-print Network

A Comparative Study of Time-Frequency Representations for Fault Detection in Wind Turbine El of wind energy, minimization and prediction of maintenance operations in wind turbine is of key importance and the easiness of interpretation. Index Terms--Wind turbine, fault detection, broken-rotor bars, signal

Paris-Sud XI, Université de

144

Time-Frequency Characterization and Receiver Waveform Design for Shallow Water  

E-print Network

Time-Frequency Characterization and Receiver Waveform Design for Shallow Water Environments Jun, and the water medium causes a dense dispersion effect due to the time-varying (TV) changes of the ocean-phase conjugation. In [16], time-reversal was applied to multiple-input multiple-output (MIMO) shallow water

Paris-Sud XI, Université de

145

Rapid inversion in shallow water with a single receiver using modal time-frequency pattern  

E-print Network

Rapid inversion in shallow water with a single receiver using modal time-frequency pattern water (0-400 m) for impulsive low-frequency source (0- 200 Hz) using a single static receiver into modes whose arrival times (which are frequency dependant) contain information about environ- ment

Paris-Sud XI, Université de

146

Vibration Sensor Data Denoising Using a Time-Frequency Manifold for Machinery Fault Diagnosis  

PubMed Central

Vibration sensor data from a mechanical system are often associated with important measurement information useful for machinery fault diagnosis. However, in practice the existence of background noise makes it difficult to identify the fault signature from the sensing data. This paper introduces the time-frequency manifold (TFM) concept into sensor data denoising and proposes a novel denoising method for reliable machinery fault diagnosis. The TFM signature reflects the intrinsic time-frequency structure of a non-stationary signal. The proposed method intends to realize data denoising by synthesizing the TFM using time-frequency synthesis and phase space reconstruction (PSR) synthesis. Due to the merits of the TFM in noise suppression and resolution enhancement, the denoised signal would have satisfactory denoising effects, as well as inherent time-frequency structure keeping. Moreover, this paper presents a clustering-based statistical parameter to evaluate the proposed method, and also presents a new diagnostic approach, called frequency probability time series (FPTS) spectral analysis, to show its effectiveness in fault diagnosis. The proposed TFM-based data denoising method has been employed to deal with a set of vibration sensor data from defective bearings, and the results verify that for machinery fault diagnosis the method is superior to two traditional denoising methods. PMID:24379045

He, Qingbo; Wang, Xiangxiang; Zhou, Qiang

2014-01-01

147

Quadratic Time-Frequency Analysis of Hydroacoustic Signals as Applied to Acoustic Emissions of Large Whales  

NASA Astrophysics Data System (ADS)

In order to enrich the set of attributes in setting up a large database of whale signals, as envisioned in the Baleakanta project, we investigate methods of time-frequency analysis. The purpose of establishing the database is to increase and refine knowledge of the emitted signal and of its propagation characteristics, leading to a better understanding of the animal migrations in a non-invasive manner and to characterize acoustic propagation in oceanic media. The higher resolution for signal extraction and a better separation from other signals and noise will be used for various purposes, including improved signal detection and individual animal identification. The quadratic class of time-frequency distributions (TFDs) is the most popular set of time-frequency tools for analysis and processing of non-stationary signals. Two best known and most studied members of this class are the spectrogram and the Wigner-Ville distribution. However, to be used efficiently, i.e. to have highly concentrated signal components while significantly suppressing interference and noise simultaneously, TFDs need to be optimized first. The optimization method used in this paper is based on the Cross-Wigner-Ville distribution, and unlike similar approaches it does not require prior information on the analysed signal. The method is applied to whale signals, which, just like the majority of other real-life signals, can generally be classified as multicomponent non-stationary signals, and hence time-frequency techniques are a natural choice for their representation, analysis, and processing. We present processed data from a set containing hundreds of individual calls. The TFD optimization method results into a high resolution time-frequency representation of the signals. It allows for a simple extraction of signal components from the TFD's dominant ridges. The local peaks of those ridges can then be used for the signal components instantaneous frequency estimation, which in turn can be used as one of the features in any subsequent classification of the whale signals.

Le Bras, Ronan; Victor, Sucic; Damir, Malnar; Götz, Bokelmann

2014-05-01

148

Assessment of time-frequency representation techniques for thoracic sounds analysis.  

PubMed

A step forward in the knowledge about the underlying physiological phenomena of thoracic sounds requires a reliable estimate of their time-frequency behavior that overcomes the disadvantages of the conventional spectrogram. A more detailed time-frequency representation could lead to a better feature extraction for diseases classification and stratification purposes, among others. In this respect, the aim of this study was to look for an omnibus technique to obtain the time-frequency representation (TFR) of thoracic sounds by comparing generic goodness-of-fit criteria in different simulated thoracic sounds scenarios. The performance of ten TFRs for heart, normal tracheal and adventitious lung sounds was assessed using time-frequency patterns obtained by mathematical functions of the thoracic sounds. To find the best TFR performance measures, such as the 2D local (?(mean)) and global (?) central correlation, the normalized root-mean-square error (NRMSE), the cross-correlation coefficient (?(IF)) and the time-frequency resolution (res(TF)) were used. Simulation results pointed out that the Hilbert-Huang spectrum (HHS) had a superior performance as compared with other techniques and then, it can be considered as a reliable TFR for thoracic sounds. Furthermore, the goodness of HHS was assessed using noisy simulated signals. Additionally, HHS was applied to first and second heart sounds taken from a young healthy male subject, to tracheal sound from a middle-age healthy male subject, and to abnormal lung sounds acquired from a male patient with diffuse interstitial pneumonia. It is expected that the results of this research could be used to obtain a better signature of thoracic sounds for pattern recognition purpose, among other tasks. PMID:24680639

Reyes, B A; Charleston-Villalobos, S; González-Camarena, R; Aljama-Corrales, T

2014-05-01

149

Inverse synthetic aperture radar processing using parametric time-frequency estimators Phase I  

SciTech Connect

This report summarizes the work performed for the Office of the Chief of Naval Research (ONR) during the period of 1 September 1997 through 31 December 1997. The primary objective of this research was aimed at developing an alternative time-frequency approach which is recursive-in-time to be applied to the Inverse Synthethic Aperture Radar (ISAR) imaging problem discussed subsequently. Our short term (Phase I) goals were to: 1. Develop an ISAR stepped-frequency waveform (SFWF) radar simulator based on a point scatterer vehicular target model incorporating both translational and rotational motion; 2. Develop a parametric, recursive-in-time approach to the ISAR target imaging problem; 3. Apply the standard time-frequency short-term Fourier transform (STFT) estimator, initially to a synthesized data set; and 4. Initiate the development of the recursive algorithm. We have achieved all of these goals during the Phase I of the project and plan to complete the overall development, application and comparison of the parametric approach to other time-frequency estimators (STFT, etc.) on our synthesized vehicular data sets during the next phase of funding. It should also be noted that we developed a batch minimum variance translational motion compensation (TMC) algorithm to estimate the radial components of target motion (see Section IV). This algorithm is easily extended to recursive solution and will probably become part of the overall recursive processing approach to solve the ISAR imaging problem. Our goals for the continued effort are to: 1. Develop and extend a complex, recursive-in-time, time- frequency parameter estimator based on the recursive prediction error method (RPEM) using the underlying Gauss- Newton algorithms. 2. Apply the complex RPEM algorithm to synthesized ISAR data using the above simulator. 3. Compare the performance of the proposed algorithm to standard time-frequency estimators applied to the same data sets.

Candy, J.V., LLNL

1997-12-31

150

Feature extraction for human identification based on envelogram signal analysis of cardiac sounds in time-frequency domain  

Microsoft Academic Search

Currently there are many security systems relying on tradition biometrics for the purpose of authorization of legal users into a system. However, traditional biometrics systems which commonly use behavioral biometrics have shown serious drawbacks, violating two of the main requirements of a reliable biometrics, namely permanence and circumvention. The paper explores the effectiveness of the features extracted from the envelogram

J. Jasper; K. R. Othman

2010-01-01

151

Ecological prediction with nonlinear multivariate time-frequency functional data models  

USGS Publications Warehouse

Time-frequency analysis has become a fundamental component of many scientific inquiries. Due to improvements in technology, the amount of high-frequency signals that are collected for ecological and other scientific processes is increasing at a dramatic rate. In order to facilitate the use of these data in ecological prediction, we introduce a class of nonlinear multivariate time-frequency functional models that can identify important features of each signal as well as the interaction of signals corresponding to the response variable of interest. Our methodology is of independent interest and utilizes stochastic search variable selection to improve model selection and performs model averaging to enhance prediction. We illustrate the effectiveness of our approach through simulation and by application to predicting spawning success of shovelnose sturgeon in the Lower Missouri River.

Yang, Wen-Hsi; Wikle, Christopher K.; Holan, Scott H.; Wildhaber, Mark L.

2013-01-01

152

Aurally-adequate time-frequency analysis for scattered sound in auditoria  

NASA Astrophysics Data System (ADS)

The goal of this work was to apply an aurally-adequate time-frequency analysis technique to the analysis of sound scattering effects in auditoria. Time-frequency representations were developed as a motivated effort that takes into account binaural hearing, with a specific implementation of interaural cross-correlation process. A model of the human auditory system was implemented in the MATLAB platform based on two previous models [A. Härmä and K. Palomäki, HUTear, Espoo, Finland; and M. A. Akeroyd, A. Binaural Cross-correlogram Toolbox for MATLAB (2001), University of Sussex, Brighton]. These stages include proper frequency selectivity, the conversion of the mechanical motion of the basilar membrane to neural impulses, and binaural hearing effects. The model was then used in the analysis of room impulse responses with varying scattering characteristics. This paper discusses the analysis results using simulated and measured room impulse responses. [Work supported by the Frank H. and Eva B. Buck Foundation.

Norris, Molly K.; Xiang, Ning; Kleiner, Mendel

2005-04-01

153

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 30 min 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

154

Time-Frequency Representation of Microseismic Signals using the Synchrosqueezing Transform  

E-print Network

Resonance frequencies can provide useful information on the deformation occurring during fracturing experiments or $CO_2$ management, complementary to the microseismic event distribution. An accurate time-frequency representation is of crucial importance prior to interpreting the cause of resonance frequencies during microseismic experiments. The popular methods of Short-Time Fourier Transform (STFT) and wavelet analysis have limitations in representing close frequencies and dealing with fast varying instantaneous frequencies and this is often the nature of microseismic signals. The synchrosqueezing transform (SST) is a promising tool to track these resonant frequencies and provide a detailed time-frequency representation. Here we apply the synchrosqueezing transform to microseismic signals and also show its potential to general seismic signal processing applications.

Herrera, Roberto H; van der Baan, Mirko

2013-01-01

155

Time-frequency Analysis of Eye Blinks and Saccades in EOG for EEG Artifact Removal  

Microsoft Academic Search

The electro-oculogram (EOG) is commonly used to detect, reject and remove ocular artifacts (OAs) from the electroencephalogram (EEG). We present a new time-frequency analysis of OAs found in the EOG. Our results indicate that in some tasks and subjects, frequencies up to 181Hz exist. Based on these results, we propose a minimum sampling rate for EOG. In addition, since EOG

Borna Noureddin; Peter D. Lawrence; Gary E. Birch

2007-01-01

156

Dating a tropical ice core by time-frequency analysis of ion concentration depth profiles  

NASA Astrophysics Data System (ADS)

Ice core dating is a key parameter for the interpretation of the ice archives. However, the relationship between ice depth and ice age generally cannot be easily established and requires the combination of numerous investigations and/or modelling efforts. This paper presents a new approach to ice core dating based on time-frequency analysis of chemical profiles at a site where seasonal patterns may be significantly distorted by sporadic events of regional importance, specifically at the summit area of Nevado Illimani (6350 m a.s.l.), located in the eastern Bolivian Andes (16°37' S, 67°46' W). We used ion concentration depth profiles collected along a 100 m deep ice core. The results of Fourier time-frequency and wavelet transforms were first compared. Both methods were applied to a nitrate concentration depth profile. The resulting chronologies were checked by comparison with the multi-proxy year-by-year dating published by de Angelis et al. (2003) and with volcanic tie points. With this first experiment, we demonstrated the efficiency of Fourier time-frequency analysis when tracking the nitrate natural variability. In addition, we were able to show spectrum aliasing due to under-sampling below 70 m. In this article, we propose a method of de-aliasing which significantly improves the core dating in comparison with annual layer manual counting. Fourier time-frequency analysis was applied to concentration depth profiles of seven other ions, providing information on the suitability of each of them for the dating of tropical Andean ice cores.

Gay, M.; De Angelis, M.; Lacoume, J.-L.

2014-09-01

157

Vibration Signal Analysis of Rotor System Based on Time-Frequency Attributes  

Microsoft Academic Search

The time-frequency analysis by Hilbert-Huang transform (HHT) plays on a significant role in the analysis of singularities, which hide in the signal, and is an effective method for non-stationary signal. Based on empirical mode decomposition (EMD), the Hilbert-Huang method can obtain a true instantaneous frequency representation of a signal. The analytical background of the HHT is introduced, and its effectiveness

Ling Xiang; Guiji Tang; Yongli Zhu

2008-01-01

158

Vibration analysis of rotating machinery using time–frequency analysis and wavelet techniques  

Microsoft Academic Search

Time–frequency analysis, including the wavelet transform, is one of the new and powerful tools in the important field of structural health monitoring, using vibration analysis. Commonly-used signal analysis techniques, based on spectral approaches such as the fast Fourier transform, are powerful in diagnosing a variety of vibration-related problems in rotating machinery. Although these techniques provide powerful diagnostic tools in stationary

F. Al-Badour; M. Sunar; L. Cheded

2011-01-01

159

A Method for Fetal Heart Rate Extraction Based on Time-Frequency Analysis  

Microsoft Academic Search

A three-stage method for fetal heart rate extraction, from abdominal ECG recordings, is proposed. In the first stage the maternal R-peaks and fiducial points (QRS onset and offset) are detected, using time-frequency analysis, and the maternal QRS complexes are eliminated. The second stage locates the positions of the candidate fetal R-peaks, using complex wavelets and pattern matching theory techniques. In

E. C. Karvounis; Markos G. Tsipouras; Dimitrios I. Fotiadis; K. K. Naka

2006-01-01

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

The ISAR imaging of ship based on adaptive optimal kernel time-frequency representation  

NASA Astrophysics Data System (ADS)

For ship targets at sea, because of their complicated ship movement, the conventional ISAR imaging algorithm can not be satisfied the needs of ship imaging. On the basis of analyzing the echo's Doppler frequency caused by the complicated ship movements, a new method based on adaptive optimal kernel time-frequency representation for ship imaging is proposed. The instantaneous ship images at different moment are obtained. Simulation and real radar data verify its effectiveness.

Li, Rui; Tao, Jiang; Tang, Zi Yue

2013-03-01

162

Extraction subject-specific motor imagery time–frequency patterns for single trial EEG classification  

Microsoft Academic Search

We introduce a new adaptive time–frequency plane feature extraction strategy for the segmentation and classification of electroencephalogram (EEG) corresponding to left and right hand motor imagery of a brain–computer interface task. The proposed algorithm adaptively segments the time axis by dividing the EEG data into non-uniform time segments over a dyadic tree. This is followed by grouping the expansion coefficients

Nuri F. Ince; Ahmed H. Tewfik; Sami Arica

2007-01-01

163

Inverse synthetic aperture radar processing using parametric time-frequency estimators Phase I  

Microsoft Academic Search

This report summarizes the work performed for the Office of the Chief of Naval Research (ONR) during the period of 1 September 1997 through 31 December 1997. The primary objective of this research was aimed at developing an alternative time-frequency approach which is recursive-in-time to be applied to the Inverse Synthethic Aperture Radar (ISAR) imaging problem discussed subsequently. Our short

Candy

1997-01-01

164

Time-frequency analysis of transient signals - application to cardiovascular control  

NASA Astrophysics Data System (ADS)

A method for time-frequency decomposition (SDA) is presented for the analysis of cardiovascular signals, during steady state as well as under transient conditions. The SDA is applied to a simulated noisy non-stationary signal. It reliably discloses the time evolution of the different spectral components of the signal and does not present noise propagation as other time-frequency methods, such as Wigner-Ville distribution does. A comparison with the well-known short-time Fourier transform is also performed for non-stationary simulated signal showing that the SDA achieves a higher time-frequency resolution. Two physiological applications are then presented in which the SDA is used for the analysis of HR and BP variability, reflecting the activity of the autonomic nervous system. The power spectra of heart rate (HR) and blood pressure (BP) fluctuations during a change of posture from supine to standing are calculated. The decrease of vagal activity on standing is obvious and can be quantified from the spectrum of HR fluctuations. The increase in the LF fluctuations of both BP and HR spectra reflect the enhancement in sympathetic activity on standing. Finally, the power spectrum of fetal HR fluctuations is obtained by SDA. The respiratory peak is observed and can help in evaluating fetal well-being.

Keselbrener, Laurence; Akselrod, Solange

165

Transient analysis with fast Wilson-Daubechies time-frequency transform  

NASA Astrophysics Data System (ADS)

The time-frequency transforms are important tools for identification of transient events in the output of the gravitational-wave detectors. Produced by the terrestrial and possibly by astrophysical sources, the transient events can be identified as patterns on the time-frequency plane with the excess power above stationary detector noise. In this paper we consider a particular case of the Wilson-Daubechies time-frequency transform for use in the gravitational-wave burst analysis. The presented Wilson-Daubechies basis shares some properties with the Gabor frames, but circumvents the Balian-Low theorem. It also shares similarity with the Meyer wavelet, which is actively used in the gravitational-wave burst analysis. The main advantages of the Wilson-Daubechies transform are the low computational cost, spectral leakage control, flexible structure of the frequency sub-bands, and the existence of the analytic time-delay filters, which are important for localization of the gravitational-wave sources in the sky. These properties of the Wilson-Daubechies transform may prove useful not only in the transient analysis, but also in other areas of the gravitational wave data analysis and detector characterization.

Necula, V.; Klimenko, S.; Mitselmakher, G.

2012-06-01

166

20 CFR 1002.104 - Is the employee required to accommodate his or her employer's needs as to the timing, frequency...  

...employer's needs as to the timing, frequency or duration of service? 1002.104...employer's needs as to the timing, frequency or duration of service? No. The...interests or concerns regarding the timing, frequency, or duration of uniformed...

2014-04-01

167

Wavelet based time-frequency comparison of centre of mass time series determined by DORIS, SLR and GNSS techniques  

NASA Astrophysics Data System (ADS)

Wavelet analyzes were applied to determine wide-band dominant oscillations in center of mass time series data obtained by DORIS, GNSS and SLR space geodetic techniques. The time frequency wavelet spectra computed for complex-valued time series reveal seasonal and subseasonal oscillations in these data. Oscillations in these time series usually have variable amplitudes and phases which entail change in the flattening and polarization of the elliptic oscillations in their projections onto XY, XZ and ZY planes of the terrestrial reference frame. The comparison of these center of mass time series using the corresponding Morlet wavelet transform coefficients enabled detection of common variations in the flattening and polarization of the relevant elliptic oscillations. Next, these time series were transformed into time-scale domain using the discrete wavelet transform based on the Shannon wavelet functions. Such a transformation enables computation of the semblance functions between the wavelet transform coefficients of the considered time series determined by different techniques. Assuming a fixed semblance threshold, e.g. 0.1, zero values were assigned to discrete wavelet transform coefficients for which the semblance was below this threshold. The common signals in the compared center of mass time series were then computed using the inverse discrete wavelet transform of the coefficients exceeding the assumed threshold level.

Kosek, W.; Popi?ski, W.; Wnek, A.; Zbylut, M.

2012-04-01

168

Time-frequency representation of a highly nonstationary signal via the modified Wigner distribution  

NASA Technical Reports Server (NTRS)

A new signal analysis technique called the modified Wigner distribution (MWD) is presented. The new signal processing tool has been very successful in determining time frequency representations of highly non-stationary multicomponent signals in both simulations and trials involving actual Space Shuttle Main Engine (SSME) high frequency data. The MWD departs from the classic Wigner distribution (WD) in that it effectively eliminates the cross coupling among positive frequency components in a multiple component signal. This attribute of the MWD, which prevents the generation of 'phantom' spectral peaks, will undoubtedly increase the utility of the WD for real world signal analysis applications which more often than not involve multicomponent signals.

Zoladz, T. F.; Jones, J. H.; Jong, J.

1992-01-01

169

Time-frequency analysis of transient evoked otoacoustic emissions via smoothed pseudo Wigner distribution.  

PubMed

Transient evoked otoacoustic emissions (TEOAEs) can be processed by the smoothed pseudo Wigner distribution (SPWD). With this process, TEOAEs can be transformed into the time-frequency plane to give a three-dimensional pattern. The analyses of shape and localization of TEOAE patterns and the comparisons of pattern differences establish a method for describing otoacoustic emissions. A better understanding and interpretation of the characteristics of TEOAEs can be achieved as well. This method can be used as a powerful tool for monitoring the cochlear condition. PMID:7660060

Cheng, J

1995-01-01

170

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] [Univ. of Washington, Seattle, WA (United States). Dept. of Electrical Engineering; Bernard, G.D. [Boeing Commercial Airplane Group, Seattle, WA (United States)] [Boeing Commercial Airplane Group, Seattle, WA (United States)

1996-09-01

171

Missing data outside the detector range. II. Application to time-frequency entanglement  

NASA Astrophysics Data System (ADS)

In a previous paper, we pointed out the problem of missing data outside the detector range for continuous-variable entanglement verification and quantum key distribution, and we provided a straightforward solution based on entropic separability criteria (as those work better than variance-based criteria). We apply that solution here to the verification of time-frequency entanglement of photon pairs, particularly to the quantum key distribution scheme proposed by Nunn [Opt. ExpressOPEXFF1094-408710.1364/OE.21.015959 21, 15959 (2013)]. We find that the scheme does lead to verifiable entanglement, but that transmission noise quickly destroys the ability to verify the entanglement.

Ray, Megan R.; van Enk, S. J.

2013-12-01

172

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

173

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

2012-11-15

174

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. PMID:20933002

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

2010-01-01

175

Classification of time-frequency representations using improved morphological pattern spectrum for engine fault diagnosis  

NASA Astrophysics Data System (ADS)

Time-frequency representations (TFR) have been intensively employed for analyzing vibration signals in the field of mechanical faults diagnosis. However, in many applications, TFR are simply utilized as a visual aid. It is very attractive to investigate the utility of TFR for automatic classification of vibration signals. A key step for this work is to extract discriminative parameters from TFR as input feature vector for classifiers. This paper contributes to this ongoing investigation by developing an improved morphological pattern spectrum (IMPS) for feature extraction from TFR. The S transform, which combines the separate strengths of the short time Fourier transform and wavelet transforms, is chosen to perform the time-frequency analysis of vibration signals. Then, we present an improved morphological pattern spectrum (IMPS) scheme, which utilizes the first moment replace of the volume measure used in traditional morphological pattern spectrum (MPS) method. The promise of IMPS is illustrated by performing our procedure on vibration signals measured from an engine with five operating states. Experimental results have demonstrated the presented IMPS to be an effective approach for characterizing the TFR of vibration signals in engine fault diagnosis.

Li, Bing; Mi, Shuang-shan; Liu, Peng-yuan; Wang, Zheng-jun

2013-06-01

176

Applying matching pursuit decomposition time-frequency processing to UGS footstep classification  

NASA Astrophysics Data System (ADS)

The challenge of rapid footstep detection and classification in remote locations has long been an important area of study for defense technology and national security. Also, as the military seeks to create effective and disposable unattended ground sensors (UGS), computational complexity and power consumption have become essential considerations in the development of classification techniques. In response to these issues, a research project at the Flexible Display Center at Arizona State University (ASU) has experimented with footstep classification using the matching pursuit decomposition (MPD) time-frequency analysis method. The MPD provides a parsimonious signal representation by iteratively selecting matched signal components from a pre-determined dictionary. The resulting time-frequency representation of the decomposed signal provides distinctive features for different types of footsteps, including footsteps during walking or running activities. The MPD features were used in a Bayesian classification method to successfully distinguish between the different activities. The computational cost of the iterative MPD algorithm was reduced, without significant loss in performance, using a modified MPD with a dictionary consisting of signals matched to cadence temporal gait patterns obtained from real seismic measurements. The classification results were demonstrated with real data from footsteps under various conditions recorded using a low-cost seismic sensor.

Larsen, Brett W.; Chung, Hugh; Dominguez, Alfonso; Sciacca, Jacob; Kovvali, Narayan; Papandreou-Suppappola, Antonia; Allee, David R.

2013-06-01

177

Time-frequency analysis in optical coherence tomography for technical objects examination  

NASA Astrophysics Data System (ADS)

Optical coherence tomography (OCT) is one of the most advanced optical measurement techniques for complex structure visualization. The advantages of OCT have been used for surface and subsurface defect detection in composite materials, polymers, ceramics, non-metallic protective coatings, and many more. Our research activity has been focused on timefrequency spectroscopic analysis in OCT. It is based on time resolved spectral analysis of the backscattered optical signal delivered by the OCT. The time-frequency method gives spectral characteristic of optical radiation backscattered or backreflected from the particular points inside the tested device. This provides more information about the sample, which are useful for further analysis. Nowadays, the applications of spectroscopic analysis for composite layers characterization or tissue recognition have been reported. During our studies we have found new applications of spectroscopic analysis. We have used this method for thickness estimation of thin films, which are under the resolution of OCT. Also, we have combined the spectroscopic analysis with polarization sensitive OCT (PS-OCT). This approach enables to obtain a multiorder retardation value directly and may become a breakthrough in PS-OCT measurements of highly birefringent media. In this work, we present the time-frequency spectroscopic algorithms and their applications for OCT. Also, the theoretical simulations and measurement validation of this method are shown.

StrÄ kowski, Marcin R.; Kraszewski, Maciej; Trojanowski, Micha?; Pluci?ski, Jerzy

2014-05-01

178

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

179

Time-frequency methods and voluntary ramped-frequency breathing: a powerful combination for exploration of human neurophysiological mechanisms.  

PubMed

We experimentally altered the timing of respiratory motoneuron activity as a means to modulate and better understand otherwise hidden human central neural and hemodynamic oscillatory mechanisms. We recorded the electrocardiogram, finger photoplethysmographic arterial pressure, tidal carbon dioxide concentrations, and muscle sympathetic nerve activity in 13 healthy supine young men who gradually increased or decreased their breathing frequencies between 0.05 and 0.25 Hz over 9-min periods. We analyzed results with traditional time- and frequency-domain methods, and also with time-frequency methods (wavelet transform, wavelet phase coherence, and directional coupling). We determined statistical significance and identified frequency boundaries by comparing measurements with randomly generated surrogates. Our results support several major conclusions. First, respiration causally modulates both sympathetic (weakly) and vagal motoneuron (strongly) oscillations over a wide frequency range-one that extends well below the frequency of actual breaths. Second, breathing frequency broadly modulates vagal baroreflex gain, with peak gains registered in the low frequency range. Third, breathing frequency does not influence median levels of sympathetic or vagal activity over time. Fourth, phase relations between arterial pressure and sympathetic and vagal motoneurons are unaffected by breathing, and are therefore likely secondary to intrinsic responsiveness of these motoneurons to other synaptic inputs. Finally, breathing frequency does not affect phase coherence between diastolic pressure and muscle sympathetic oscillations, but it augments phase coherence between systolic pressure and R-R interval oscillations over a limited portion of the usual breathing frequency range. These results refine understanding of autonomic oscillatory processes and those physiological mechanisms known as the human respiratory gate. PMID:24114700

Stankovski, Tomislav; Cooke, William H; Rudas, László; Stefanovska, Aneta; Eckberg, Dwain L

2013-12-01

180

Time-frequency analysis of heart rate variability in elderly people  

NASA Astrophysics Data System (ADS)

Assessment of the ability of the autonomic nervous system (ANS) to regulate blood pressure (BP). This is of particular importance for elderly people, for whom the project was designed. We measure a patient's BP noninvasively under various conditions: deep respiration, passive tilt, etc. The variability of the heart rate in the lower frequency band (LF) (0.04 - 0.15 Hz) is known to have sympathetic- and parasympathetic origin, while in the higher (HF) (0.15 - 0.4 Hz) it is vagally mediated. We do a Time-Frequency analysis for the two frequency bands (Wigner) and eliminate the 'cross-terms' with a novel method due to Qian and Chen. We obtain a clear resolution of the activity in LF and HF over time. Research is ongoing aiming at identifying unambiguously the sympathetic and vagal activity.

Sager, Herbert C.; Guntermann, Juergen

2001-11-01

181

Demonstration of coherent time-frequency Schmidt mode selection using dispersion-engineered frequency conversion  

E-print Network

Time-frequency Schmidt (TFS) modes of ultrafast quantum states are naturally compatible with high bit-rate integrated quantum communication networks. Thus they offer an attractive alternative for the realization of high dimensional quantum optics. Here, we present a quantum pulse gate based on dispersion-engineered ultrafast frequency conversion in a nonlinear optical waveguide, which is a key element for harnessing the potential of TFS modes. We experimentally retrieve the modal spectral-temporal structure of our device and demonstrate a single-mode operation fidelity of 80\\%, which is limited by experimental shortcomings. In addition, we retrieve a conversion efficiency of 87.7\\% with a high signal-to-noise ratio of 8.8 when operating the quantum pulse gate at the single-photon level.

Benjamin Brecht; Andreas Eckstein; Raimund Ricken; Viktor Quiring; Hubertus Suche; Linda Sansoni; Christine Silberhorn

2014-03-18

182

Looking for activity cycles in late-type Kepler stars using time-frequency analysis  

NASA Astrophysics Data System (ADS)

We analyse light curves covering four years of 39 fast-rotating (Prot ? 1 d) late-type active stars from the Kepler data base. Using time-frequency analysis (short-term Fourier transform), we find hints for activity cycles of 300-900 d at nine targets from the changing typical latitude of the starspots, which with the differential rotation of the stellar surface change the observed rotation period over the activity cycle. We also give a lowest estimation for the shear parameter of the differential rotation, which is ?0.001 for the cycling targets. These results populate the less studied, short-period end of the rotation-cycle length relation.

Vida, K.; Oláh, K.; Szabó, R.

2014-07-01

183

Exploiting polarization using multi-frequency SAR data and multi-dimensional time-frequency techniques  

NASA Astrophysics Data System (ADS)

During recent years, Time-Frequency (TF) techniques have been introduced to characterize scene polarimetric behaviours using PolSAR data. In this paper, we apply a TF decomposition approach to the analysis of PolSAR data with different frequency bands and show some polarimetric TF behaviours of various scenes. The PolSAR data may be decomposed in azimuth direction, range direction only and in both directions. Two statistical descriptor, i.e., polarimetric TF stationarity and coherence indicators, are used to depict the features of the scene backscattering response. Their individual performance is assessed. The polarimetric TF features, extracted from the scenes of interest, can show some special relevant information compared to the original full resolution case. Moreover, with the availability of new multi-frequency full-polarization high resolution F-SAR data, the results of same site with respect to different frequency bands are exploited and compared with each other.

Hu, Canbin; Wang, Wei; Zhao, Lingjun; Kuang, Gangyao

2014-03-01

184

Aesthetic appreciation: event-related field and time-frequency analyses  

PubMed Central

Improvements in neuroimaging methods have afforded significant advances in our knowledge of the cognitive and neural foundations of aesthetic appreciation. We used magnetoencephalography (MEG) to register brain activity while participants decided about the beauty of visual stimuli. The data were analyzed with event-related field (ERF) and Time-Frequency (TF) procedures. ERFs revealed no significant differences between brain activity related with stimuli rated as “beautiful” and “not beautiful.” TF analysis showed clear differences between both conditions 400 ms after stimulus onset. Oscillatory power was greater for stimuli rated as “beautiful” than those regarded as “not beautiful” in the four frequency bands (theta, alpha, beta, and gamma). These results are interpreted in the frame of synchronization studies. PMID:22287948

Munar, Enric; Nadal, Marcos; Castellanos, Nazareth P.; Flexas, Albert; Maestu, Fernando; Mirasso, Claudio; Cela-Conde, Camilo J.

2012-01-01

185

Feature extraction using time-frequency/scale analysis and ensemble of feature sets for crackle detection.  

PubMed

Pulmonary crackles are used as indicators for the diagnosis of different pulmonary disorders. Crackles are very common adventitious sounds which have transient characteristic. From the characteristics of crackles such as timing and number of occurrences, the type and the severity of the pulmonary diseases can be obtained. In this study, a novel method is proposed for crackle detection. In this method, various feature sets are extracted using time-frequency and time-scale analysis. The extracted feature sets are fed into support vector machines both individually and as an ensemble of networks. Besides, as a preprocessing stage in order to improve the success of the model, frequency bands containing no-information are removed using dual tree complex wavelet transform, which is a shift invariant transform with limited redundancy and an improved version of discrete wavelet transform. The comparative results of individual feature sets and ensemble of sets with pre-processed and non pre-processed data are proposed. PMID:22255048

Serbes, Gorkem; Sakar, C Okan; Kahya, Yasemin P; Aydin, Nizamettin

2011-01-01

186

On the extraction of instantaneous frequencies from ridges in time-frequency representations of signals  

E-print Network

The extraction of oscillatory components and their properties from different time-frequency representations, such as windowed Fourier transform, wavelet transform or their synchrosqueezed versions, is an important topic in signal processing. The first step in this procedure is to extract the ridge curve: a sequence of amplitude peak positions (ridge points), corresponding to the component of interest. This is not a trivial issue, and the best procedure for extraction is still not settled or agreed. We discuss and develop the procedures that can be used for this task and compare their performance, based on both simulated and real data. We also propose an algorithm for optimization of the path functional over all possible ridge sequences. By achieving this in O(N) steps, it runs much faster than the computationally expensive simulated annealing used previously. Finally, we investigate the advantages and drawbacks that synchrosqueezing offers in relation to curve extraction. The codes used in this work are freel...

Iatsenko, Dmytro; Stefanovska, Aneta

2013-01-01

187

Linear and synchrosqueezed time-frequency representations revisited. Part II: Resolution, reconstruction and concentration  

E-print Network

Having reviewed the aspects of the linear and synchrosqueezed time-frequency representations (TFRs) needed for their understanding and correct use in Part I of this review, we now consider three more subtle issues that are nonetheless of crucial importance for effective application of these methods. (i) What effect do the window/wavelet parameters have on the resultant TFR, and how can they most appropriately be chosen? (ii) What are the errors inherent in the two reconstruction methods (direct and ridge) and which of them is the better? (iii) What are the advantages and drawbacks associated with synchrosqueezing? To answer these questions, we perform a detailed numerical and theoretical study of the TFRs under consideration. We consider the relevant estimates in the presence of the complications that arise in practical applications including interference between components, amplitude modulation, frequency modulation, and noise. Taken together, the results provide an in-depth understanding of the issues in qu...

Iatsenko, Dmytro; Stefanovska, Aneta

2013-01-01

188

Demonstration of coherent time-frequency Schmidt mode selection using dispersion-engineered frequency conversion  

NASA Astrophysics Data System (ADS)

Time-frequency Schmidt (TFS) modes of ultrafast quantum states are naturally compatible with high-bit-rate integrated quantum communication networks. Thus they offer an attractive alternative for the realization of high-dimensional quantum optics. Here, we present a quantum pulse gate based on dispersion-engineered ultrafast frequency conversion in a nonlinear optical waveguide, which is a key element for harnessing the potential of TFS modes. We experimentally retrieve the modal spectral-temporal structure of our device and demonstrate a single-mode operation fidelity of 80%, which is limited by experimental shortcomings. In addition, we retrieve a conversion efficiency of 87.7% with a high signal-to-noise ratio of 8.8 when operating the quantum pulse gate at the single-photon level.

Brecht, Benjamin; Eckstein, Andreas; Ricken, Raimund; Quiring, Viktor; Suche, Hubertus; Sansoni, Linda; Silberhorn, Christine

2014-09-01

189

Time-frequency analysis of fiber-optic temperature data on groundwater-surface water interactions  

NASA Astrophysics Data System (ADS)

Accurate characterization of the hydrogeological framework and groundwater-surface water interactions in particular, is crucial to understanding contaminant transport between aquifers and rivers. Fiber-optic distributed temperature sensing (FODTS) is a novel tool that offers unprecedented resolution for characterizing groundwater-surface water interaction. Time-frequency analysis of FODTS data provides a means to distinguish between a wide range of hydrologic processes at various scales. This work demonstrates the use of the S-Transform to analyze FODTS time series and synchronous river stage time series. Our study focused on improving understanding of the dynamics of groundwater-surface water interaction at the Hanford 300-Area Richland, WA. We used ~1.5 km long fiber optic cable to continuously monitor real time temperature variations along the hyporheic corridor at ~1 m spatial resolution and 5 minutes temporal resolution. It is generally recognized that contaminated groundwater discharge in Hanford site 300-Area is highly controlled by fluctuations in the Columbia River stage. Using S-Transform analysis of the temperature data along the river corridor we investigated in more detail the contributions of periodicity in the river stage to focused groundwater discharge. This time-frequency analysis of the DTS data uniquely identified areas of stage-controlled enhanced exchange along the hyporheic corridor. Dam operations upstream of the site were identified as a factor controlling stage fluctuations with relatively long periods (4 - 8 days). S-Transform analysis was used to map areas of high amplitude in these diagnostic periods indicative of stage-driven exchange along the river corridor.

Mwakanyamale, K. E.; Slater, L. D.; Day-Lewis, F. D.; Alwasif, M. H.; Ntarlagiannis, D.; Johnson, C. D.

2011-12-01

190

The local maxima method for enhancement of time-frequency map and its application to local damage detection in rotating machines  

NASA Astrophysics Data System (ADS)

In this paper a new method of fault detection in rotating machinery is presented. It is based on a vibration time series analysis in time-frequency domain. A raw vibration signal is decomposed via the short-time Fourier transform (STFT). The time-frequency map is considered as matrix (M×N) with N sub-signals with length M. Each sub-signal is considered as a time series and might be interpreted as energy variation for narrow frequency bins. Each sub-signal is processed using a novel approach called the local maxima method. Basically, we search for local maxima because they should appear in the signal if local damage in bearings or gearbox exists. Finally, information for all sub-signals is combined in order to validate impulsive behavior of energy. Due to random character of the obtained time series, each maximum occurrence has to be checked for its significance. If there are time points for which the average number of local maxima for all sub-signals is significantly higher than for the other time instances, then location of these maxima is “weighted” as more important (at this time instance local maxima create for a set of ?f a pattern on the time-frequency map). This information, called vector of weights, is used for enhancement of spectrogram. When vector of weights is applied for spectrogram, non-informative energy is suppressed while informative features on spectrogram are enhanced. If the distribution of local maxima on spectrogram creates a pattern of wide-band cyclic energy growth, the machine is suspected of being damaged. For healthy condition, the vector of the average number of maxima for each time point should not have outliers, aggregation of information from all sub-signals is rather random and does not create any pattern. The method is illustrated by analysis of very noisy both real and simulated signals.

Obuchowski, Jakub; Wy?oma?ska, Agnieszka; Zimroz, Rados?aw

2014-06-01

191

Adaptive diffusion as a versatile tool for time-frequency and time-scale representations processing: a review  

Microsoft Academic Search

Inspired by the work on image processing by Perona and Malik, diffusion-based models were first investigated by Goncalve`s and Payot to improve the readability of Cohen class time-frequency representations. They rely on signal-dependent partial differential equations that yield adaptive smoothed representations with sharpened time-frequency components. Here, we demonstrate the versatility and utility of this family of methods, and we propose

Julien Gosme; Cédric Richard; Paulo Gonçalvès

2005-01-01

192

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

193

Study of wavepacket dynamics in rubidium vapor by means of time-frequency analysis  

NASA Astrophysics Data System (ADS)

Wavepackets are excited in rubidium vapor by intense ultrashort (˜100 fs) pulses centered at a wavelength of 620 nm or 770 nm. The generated atomic wavepackets are optically detected via a pump-probe experiment based on axially phase-matched parametric four-wave mixing (FWM). This nonlinear process results in coherent ultraviolet (UV) or violet emission that carries information about the relative number densities of the excited states. The frequency spectrum of the UV/violet signal intensity, recorded while varying the pump-probe time delay, shows the presence of quantum beats between energy levels involved in the FWM process. The time-frequency analysis of that temporal UV/violet data is done by means of the short-time Fourier transform that leads to retrieval of the temporal evolution of amplitude and phase of the quantum beats. The observed dynamics suggest that not only atomic but also molecular ( Rb*2 ) wavepackets are generated, and that the temporal history of the amplitude of the quantum beats reflects the production of the excited atomic fragments of Rb*2 dissociation. More precisely, changes in the Rb excited state number densities alter the third-order nonlinear susceptibility chi(3) of the Rb vapor, which affects generation of the output signal wave by FWM. Dissociation into several product states is detected, and their branching ratios are estimated. Thus, atomic wavepackets, combined with FWM, appear to be a sensitive new multichannel spectroscopic means to study the fundamental process of molecular dissociation.

Senin, Andrey Aleksandrovich

194

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

NASA Technical Reports Server (NTRS)

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.

2011-01-01

195

Relation between deep bioluminescence and oceanographic variables: A statistical analysis using time-frequency decompositions  

NASA Astrophysics Data System (ADS)

We consider the statistical analysis of a 1.7-year high-frequency sampled time series, between 2009 and 2010, recorded at the ANTARES observatory in the deep NW Mediterranean Sea (2475 m depth). The objective was to estimate relationships between bioluminescence and environmental time series (temperature, salinity and current speed). As this entire dataset is characterized by non-linearity and non-stationarity, two time-frequency decomposition methods (wavelet and Hilbert-Huang) were used. These mathematical methods are dedicated to the analysis of a signal at various time and frequencies scales. This work propose some statistical tools dedicated to the study of relationships between two time series. Our study highlights three events of high bioluminescence activity in March 2009, December 2009 and March 2010. We demonstrate that the two events occurring in March 2009 and 2010 are correlated to the arrival of newly formed deep water masses at frequencies of approximately 4.8×10-7 (period of 24.1 days). In contrast, the event in December 2009 is only correlated with current speed at frequencies of approximately 1.9×10-6 (period of 6.0 days). The use of both wavelet and Hilbert-Huang transformations has proven to be successful for the analysis of multivariate time series. These methods are well-suited in a context of the increasing number of long time series recorded in oceanography.

Martini, S.; Nerini, D.; Tamburini, C.

2014-09-01

196

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. PMID:18356081

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

197

Time-Frequency Analysis of Transient-Evoked Otoacoustic Emissions in Children exposed to Carboplatin Chemotherapy  

PubMed Central

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 peSPL clicks. After WT analysis, TEOAE energy, latency, and normalized energy in the narrow-band frequency components were compared before and during carboplatin (average dose 1693 mg/m2) chemotherapy treatment. On a group basis, no significant differences (p>0.05) in pre- and post-carboplatin TEOAE energy, latency, or normalized energy were observed. There were decreases in normalized energy on an individual basis in 10/18 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

2013-01-01

198

Phase retrieval and time-frequency methods in the measurement of ultrashort laser pulses  

SciTech Connect

Recently several techniques have become available to measure the time- (or frequency-) dependent intensity and phase of ultrashort laser pulses. One of these, Frequency-Resolved Optical Gating (FROG), is rigorous and has achieved single-laser-shot operation. FROG combines the concepts of time-frequency analysis in the form of spectrogram generation (in order to create a two-dimensional problem), and uses a phase-retrieval-based algorithm to invert the experimental data to yield the intensity and phase of the laboratory laser pulse. In FROG it is easy to generate a spectrogram of the unknown signal, and inversion of the spectrogram to recover the signal is the main goal. Because the temporal width of a femtosecond laser pulse is much shorter than anything achievable by electronics, FROG uses the pulse to measure itself. In FROG, the laser pulse is split into two replicas of itself by a partially reflecting beamsplitter, and the two replicas interact with each other in a medium with an instantaneous nonlinear-optical response. This interaction generates a signal field that is then frequency-resolved using a spectrometer. The spectrum of the signal field is measured for all relevant values of the temporal delay between the two pulses. Here, the authors employ FROG and FROG related techniques to measure the time-dependent intensity and phase of an ultrashort laser pulse.

DeLong, K.W.; Fittinghoff, D.N.; Ladera, C.L.; Trebino, R.

1995-02-01

199

Cardiorespiratory Dynamic Response to Mental Stress: A Multivariate Time-Frequency Analysis  

PubMed Central

Mental stress is a growing problem in our society. In order to deal with this, it is important to understand the underlying stress mechanisms. In this study, we aim to determine how the cardiorespiratory interactions are affected by mental arithmetic stress and attention. We conduct cross time-frequency (TF) analyses to assess the cardiorespiratory coupling. In addition, we introduce partial TF spectra to separate variations in the RR interval series that are linearly related to respiration from RR interval variations (RRV) that are not related to respiration. The performance of partial spectra is evaluated in two simulation studies. Time-varying parameters, such as instantaneous powers and frequencies, are derived from the computed spectra. Statistical analysis is carried out continuously in time to evaluate the dynamic response to mental stress and attention. The results show an increased heart and respiratory rate during stress and attention, compared to a resting condition. Also a fast reduction in vagal activity is noted. The partial TF analysis reveals a faster reduction of RRV power related to (3?s) than unrelated to (30?s) respiration, demonstrating that the autonomic response to mental stress is driven by mechanisms characterized by different temporal scales. PMID:24386006

Orini, Michele; Van Huffel, Sabine

2013-01-01

200

Toward an EEG-based recognition of music liking using time-frequency analysis.  

PubMed

Affective phenomena, as reflected through brain activity, could constitute an effective index for the detection of music preference. In this vein, this paper focuses on the discrimination between subjects' electroencephalogram (EEG) responses to self-assessed liked or disliked music, acquired during an experimental procedure, by evaluating different feature extraction approaches and classifiers to this end. Feature extraction is based on time-frequency (TF) analysis by implementing three TF techniques, i.e., spectrogram, Zhao-Atlas-Marks distribution and Hilbert-Huang spectrum (HHS). Feature estimation also accounts for physiological parameters that relate to EEG frequency bands, reference states, time intervals, and hemispheric asymmetries. Classification is performed by employing four classifiers, i.e., support vector machines, k-nearest neighbors (k -NN), quadratic and Mahalanobis distance-based discriminant analyses. According to the experimental results across nine subjects, best classification accuracy {86.52 (±0.76)%} was achieved using k-NN and HHS-based feature vectors ( FVs) representing a bilateral average activity, referred to a resting period, in ? (13-30 Hz) and ? (30-49 Hz) bands. Activity in these bands may point to a connection between music preference and emotional arousal phenomena. Furthermore, HHS-based FVs were found to be robust against noise corruption. The outcomes of this study provide early evidence and pave the way for the development of a generalized brain computer interface for music preference recognition. PMID:23033323

Hadjidimitriou, Stelios K; Hadjileontiadis, Leontios J

2012-12-01

201

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

202

Optical phase noise from atmospheric fluctuations and its impact on optical time-frequency transfer  

NASA Astrophysics Data System (ADS)

The time of flight for a laser beam through the atmosphere will fluctuate as the path-averaged index of refraction varies with atmospheric turbulence, air temperature, and pressure. We measure these fluctuations by transmitting optical pulses from a frequency comb across a 2-km horizontal path and detecting variations in their time of flight through linear optical sampling. This technique is capable of continuous measurements, with femtosecond resolution, over time scales of many hours despite turbulence-induced signal fading. The power spectral density for the time of flight, or equivalently for the optical phase, follows a simple power-law response of ?f-2.3 measured down to Fourier frequencies, f, of 100 ?Hz. There is no evidence of a roll-off at low frequencies associated with an outer scale for turbulence. Both of these results depart from the predictions of turbulence theory, but are consistent with some other results in the literature. We discuss the implications for the stability and accuracy of one-way optical time-frequency transfer.

Sinclair, L. C.; Giorgetta, F. R.; Swann, W. C.; Baumann, E.; Coddington, I.; Newbury, N. R.

2014-02-01

203

Long-term polar motion prediction using normal time-frequency transform  

NASA Astrophysics Data System (ADS)

This paper presents normal time-frequency transform (NTFT) application in harmonic/quasi-harmonic signal prediction. Particularly, we use the normal wavelet transform (a special NTFT) to make long-term polar motion prediction. Instantaneous frequency, phase and amplitude of Chandler wobble, prograde and retrograde annual wobbles of Earth's polar motion are analyzed via the NTFT. Results show that the three main wobbles can be treated as quasi-harmonic processes. Current instantaneous harmonic information of the three wobbles can be acquired by the NTFT that has a kernel function constructed with a normal half-window function. Based on this information, we make the polar motion predictions with lead times of 1 year and 5 years. Results show that our prediction skills are very good with long lead time. An abnormality in the predictions occurs during the second half of 2005 and first half of 2006. Finally, we provide the future (starting from 2013) polar motion predictions with 1- and 5-year leads. These predictions will be used to verify the effectiveness of the method proposed in this paper.

Su, Xiaoqing; Liu, Lintao; Houtse, Hsu; Wang, Guocheng

2014-02-01

204

Continuous Time-Frequency Transform for Unevenly Sampled Time Series and Significance Testing  

NASA Astrophysics Data System (ADS)

Spectral analysis is a common approach for the interpretation of climate time series. In particular, the continuous wavelet transform and the Gabor transform are generally well-suited for non-stationary, multi-periodic and highly noisy data. The purpose of this contribution is to propose a rigorous framework to estimate the significance of wavelet spectra given unevenly sampled data. To this end, we expand the theory developed by G. Foster [1], originally targeted for astronomical data, as follows: (i) Define the model: Significance testing is always based on a model, that needs to be properly defined. (ii) Define the parametric hypotheses H0 (null case) and H1 (alternative case), and attempt to find an appropriate statistical summary. The idea is to obtain a well-known distribution under H0, allowing an analytical approach and avoiding most of Monte-Carlo simulations which can be expensive in time. We also discuss the choice to be done for the analysis function of the time-frequency transform. Indeed, Morlet wavelet is often chosen, but it is not always the best option. Some examples of paleoclimate time series analysis will be given. Finally, we investigate whether considering the interpolated data to get a constant time step and using the traditional tools may lead to significant errors. Reference: [1] G. Foster. Wavelets for period analysis of unevenly sampled time series. The Astronomical Journal, 112(4):1709-1729, 1996.

Lenoir, Guillaume; Crucifix, Michel

2014-05-01

205

Applying Time-Frequency Analysis to Assist Identification of Hydrogeological Structure of Groundwater Aquifers  

NASA Astrophysics Data System (ADS)

Due to global warming, climate change, and economic development, the stability of water supply is challenged using only surface water resources. Hence, groundwater becomes an important water resource for increasing water supply reliability. However, groundwater extraction many introduce damages such as land subsidence and seawater intrusion. To accurately evaluate the response of groundwater aquifers, correct hydrogeological structure is a key factor. In the past, the evaluation of the hydrogeological structure relies on subjective judgment which is arbitrarily made based on available information of core sampling record, fossils, geological dating, etc. This study develops a quantitative method to provide objective information for improving the judgment. This method uses observed groundwater water level and time-frequency analysis. Precisely, the signal strength of the groundwater level is evaluated using Fast Fourier Transform (FFT) which is done by a commercially available software named Visual Signal. Two signal frequencies, daily and annual frequency, are studied. This method is applied to Lanyang Plain in Taiwan. The groundwater level record of shallow wells is selected for the signal processing. Therefore, higher signal strength of an annual signal indicates higher recharge which is an indicator of unconfined aquifer. In the case of Lanyang Plain, the low signal strength area includes fan top area and scatter areas at fan central and fantail areas. This signal information along with core sampling information can provide a complete picture of the hydrogeological structure and characteristics for the studied area Ilan shallow water wells in different frequencies

shiuan, C. W.; Chang, L.

2013-12-01

206

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

207

Acoustic emission source location in plates using wavelet analysis and cross time frequency spectrum.  

PubMed

In this study, the theories of wavelet transform and cross-time frequency spectrum (CTFS) are used to locate AE source with frequency-varying wave velocity in plate-type structures. A rectangular array of four sensors is installed on the plate. When an impact is generated by an artificial AE source such as Hsu-Nielsen method of pencil lead breaking (PLB) at any position of the plate, the AE signals will be detected by four sensors at different times. By wavelet packet decomposition, a packet of signals with frequency range of 0.125-0.25MHz is selected. The CTFS is calculated by the short-time Fourier transform of the cross-correlation between considered packets captured by AE sensors. The time delay is calculated when the CTFS reaches the maximum value and the corresponding frequency is extracted per this maximum value. The resulting frequency is used to calculate the group velocity of wave velocity in combination with dispersive curve. The resulted locating error shows the high precision of proposed algorithm. PMID:25063341

Mostafapour, A; Davoodi, S; Ghareaghaji, M

2014-12-01

208

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

209

Non-identical smoothing operators for estimating time-frequency interdependence in electrophysiological recordings  

NASA Astrophysics Data System (ADS)

Synchronization of neural activity from distant parts of the brain is crucial for the coordination of cognitive activities. Because neural synchronization varies both in time and frequency, time-frequency (T-F) coherence is commonly employed to assess interdependences in electrophysiological recordings. T-F coherence entails smoothing the cross and power spectra to ensure statistical consistency of the estimate, which reduces its T-F resolution. This trade-off has been described in detail when the cross and power spectra are smoothed using identical smoothing operators, which may yield spurious coherent frequencies. In this article, we examine the use of non-identical smoothing operators for the estimation of T-F interdependence, i.e., phase synchronization is characterized by phase locking between signals captured by the cross spectrum and we may hence improve the trade-off by selectively smoothing the auto spectra. We first show that the frequency marginal density of the present estimate is bound within [0,1] when using non-identical smoothing operators. An analytic calculation of the bias and variance of present estimators is performed and compared with the bias and variance of standard T-F coherence using Monte Carlo simulations. We then test the use of non-identical smoothing operators on simulated data, whose T-F properties are known through construction. Finally, we analyze empirical data from eyes-closed surface electroencephalography recorded in human subjects to investigate alpha-band synchronization. These analyses show that selectively smoothing the auto spectra reduces the bias of the estimator and may improve the detection of T-F interdependence in electrophysiological data at high temporal resolution.

Mehrkanoon, Saeid; Breakspear, Michael; Daffertshofer, Andreas; Boonstra, Tjeerd W.

2013-12-01

210

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

211

Diesel Engine Condition Classification Based on Mechanical Dynamics and Time-Frequency Image Processing  

Microsoft Academic Search

\\u000a In this research, mechanical structure dynamics for diesel engine working process are investigated in detail for diesel engine\\u000a vibration signal analysis and pattern recognition. Time domain vibration signal can be looked on as several impulse forces’\\u000a responses according to mechanical dynamics analysis. Different part vibration signal can be used for different components’\\u000a fault diagnoses. It is very useful to determine

Hongkun Li; Zhixin Zhang

212

Study of the time-frequency characteristics of continuous gravity data sequence  

NASA Astrophysics Data System (ADS)

The continuous gravity measurements contained much valuable signal which was maybe caused by internal and external change of the Earth, which offered abundant information to study activities of the Earth. In the past decades, researchers mostly focused on discussing the relationship between the gravity variation and geodynamical processes. Here we studied the temporal variation of the gravity field through the continuous gravity records. Our goal was to detect certain geophysical signal on the order of a few tens of micro-Gal from the gravity data sequence. The gravity data sequences were recorded by the Scintrex g-Phone relative gravimeters those were located at the numerous observation stations of mainland China which had well-controlled observation systems. We presented a two-step procedure to study the signal of gravity variation. Firstly, we developed a Linear Similarity filtering technique which could reduce the drift of gravity instrument effectively by using two relative gravimeters at the same station by the reason of the short-term liner drift feature of gravimeters. Based on the method above, we gained non-tidal gravity variation more accurate that contained much geophysical signal which was associated with geodynamical phenomena. Secondly, we employed the time-frequency analysis techniques to analyze the feature of different temporal variation signal and tried to find some periodic and non-periodic characteristics of the continuous gravity data sequence. Moreover, we compared the results to the mobile repeated gravity measurements on ground and acquired the spatial and temporal gravity variation at last. We also expected to find some anomaly signal related to the activities of tectogenesis and fault movement prior to the destructive earthquakes from the continuous gravity data sequence. Acknowledgment: We acknowledge the financial support of the Basic Scientific Research Foundation of Institute of Geophysics CEA (DQJB12B20, DQJB12C03 and DQJB12B14), the Scientific and Technological Support Foundation of CEA (2012BAK19B01-05-02) and the National Natural Science Foundation of China (41104046).

Weimin, X.; Shi, C.; Lei, S.; Hongyan, L.

2013-12-01

213

Abstract--Time-frequency analysis of heart rate variability (HRV) makes it easier to evaluate how the balance  

E-print Network

spectrogram. The analysis of heart rate variability (HRV) is important when studying the autonomic nervousAbstract--Time-frequency analysis of heart rate variability (HRV) makes it easier to evaluate how the balance between the sympathetic and parasympathetic influences on heart rhythm varies with time. The auto

Carvalho, João Luiz

214

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

215

A Practical Guide to Time—Frequency Analysis in the Study of Human Motor Behavior: The Contribution of Wavelet Transform  

Microsoft Academic Search

The authors present a practical guide for studying nonstationary data on human motor behavior in a time-frequency representation. They explain the limits of classical methods founded exclusively on the time or frequency basis and then answer those limits with the windowed Fourier transform and the wavelet transform (WT) methods, both of which are founded on timefrequency bases. The authors stress

Johann Issartel; Ludovic Marin; Philippe Gaillot; Thomas Bardainne; Marielle Cadopi

2006-01-01

216

Time–frequency analysis and estimation of muscle fiber conduction velocity from surface EMG signals during explosive dynamic contractions  

Microsoft Academic Search

Time–frequency analysis of the surface electromyographic (EMG) signal is used to assess muscle fiber membrane properties during dynamic contractions. The aim of this study was to compare the direct estimation of average muscle fiber conduction velocity (CV) with instantaneous mean frequency (iMNF) of surface EMG signals in isometric and explosive dynamic contractions. The muscles investigated were the vastus lateralis and

Enrico Merlo; Marco Pozzo; Guglielmo Antonutto; Pietro E. di Prampero; Roberto Merletti; Dario Farina

2005-01-01

217

Joint Occupancy.  

ERIC Educational Resources Information Center

This annotated bibliography includes summaries of 15 articles and reports dealing with the joint use of buildings and facilities by schools and other public or private organizations. An introductory section describes the historical origins and development of the joint occupancy concept and examines the various economic and philosophical arguments…

Higham, Charlene Ellison

218

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

219

Frequency Domain Load Calculation for Offshore Wind Turbines (TURBU Offshore)  

Microsoft Academic Search

The design of offshore wind turbines requires to assess a huge amount of different sea-states and wind conditions. Therefor the calculational efficiency of a comb ined time\\/frequency domain approach is attractive. This was the reason for the development of the frequency domain tool TURBU Offshore. In addition, such a tool is very feasible for parameter studies; the dynamics of large

T. G. van Engelen

220

Point Process Time-Frequency Analysis Of Dynamic Respiratory Patterns During Meditation Practice  

PubMed Central

Respiratory sinus arrhythmia (RSA) is largely mediated by the autonomic nervous system through its modulating influence on the heart beats. We propose a robust algorithm for quantifying instantaneous RSA as applied to heart beat intervals and respiratory recordings under dynamic breathing patterns. The blood volume pressure derived heart beat series (pulse intervals, PIs) are modeled as an inverse gaussian point process, with the instantaneous mean PI modeled as a bivariate regression incorporating both past PIs and respiration values observed at the beats. A point process maximum likelihood algorithm is used to estimate the model parameters, and instantaneous RSA is estimated via a frequency domain transfer function evaluated at instantaneous respiratory frequency where high coherence between respiration and PIs is observed. The model is statistically validated using Kolmogorov-Smirnov (KS) goodness-of-fit analysis, as well as independence tests. The algorithm is applied to subjects engaged in meditative practice, with distinctive dynamics in the respiration patterns elicited as a result. The presented analysis confirms the ability of the algorithm to track important changes in cardiorespiratory interactions elicited during meditation, otherwise not evidenced in control resting states, reporting statistically significant increase in RSA gain as measured by our paradigm. PMID:22350435

Kodituwakku, Sandun; Lazar, Sara W; Indic, Premananda; Chen, Zhe; Brown, Emery N; Barbieri, Riccardo

2012-01-01

221

Time-frequency analysis of non-stationary fusion plasma signals using an improved Hilbert-Huang transform  

NASA Astrophysics Data System (ADS)

An improved Hilbert-Huang transform method is developed to the time-frequency analysis of non-stationary signals in tokamak plasmas. Maximal overlap discrete wavelet packet transform rather than wavelet packet transform is proposed as a preprocessor to decompose a signal into various narrow-band components. Then, a correlation coefficient based selection method is utilized to eliminate the irrelevant intrinsic mode functions obtained from empirical mode decomposition of those narrow-band components. Subsequently, a time varying vector autoregressive moving average model instead of Hilbert spectral analysis is performed to compute the Hilbert spectrum, i.e., a three-dimensional time-frequency distribution of the signal. The feasibility and effectiveness of the improved Hilbert-Huang transform method is demonstrated by analyzing a non-stationary simulated signal and actual experimental signals in fusion plasmas.

Liu, Yangqing; Tan, Yi; Xie, Huiqiao; Wang, Wenhao; Gao, Zhe

2014-07-01

222

A Recursive Method of Time-Frequency Analysis for the Signal Processing of Flutter Test with Progression Variable Speed  

Microsoft Academic Search

Focused on the non-stationarity and real-time analysis of signal in flutter test with progression variable speed (FTPVS), a new method of recursive time-frequency analysis is presented. The time varying system is tracked on-line by building a time-varying parameter model, and then the relevant parameter spectrum can be obtained. The feasibility and advantages of the met hod are examined by digital

Shu-biao SONG; Cheng-ming PEI

2005-01-01

223

A method for time-frequency feature extraction from vibration signal based on Hilbert-Huang Transform  

Microsoft Academic Search

Based on the Hilbert-Huang transform (HHT), a method for time-frequency feature extraction from vibration signals was introduced into fault diagnosis of rotors. Firstly, the empirical mode decomposition (EMD) was implemented on vibration signals measured by sensors. As a result, a set of components with different time scales, i.e. intrinsic mode function (IMF), was extracted. Then, the Hilbert Transformation (HT) was

Weidong Jiao

2008-01-01

224

Time-frequency representation based on time-varying autoregressive model with applications to non-stationary rotor vibration analysis  

Microsoft Academic Search

A parametric time-frequency representation is presented based on time-varying autoregressive model (TVAR), followed by applications\\u000a to non-stationary vibration signal processing. The identification of time-varying model coefficients and the determination\\u000a of model order, are addressed by means of neural networks and genetic algorithms, respectively. Firstly, a simulated signal\\u000a which mimic the rotor vibration during run-up stages was processed for a comparative

Long Zhang; Guoliang Xiong; Hesheng Liu; Huijun Zou; Weizhong Guo

2010-01-01

225

On-Silicon Neural Activity Monitoring and Time-Frequency Analysis for Early Detection of Epileptic Seizures  

Microsoft Academic Search

We present an architecture and very-large-scale integration (VLSI) implementation of a microsystem for neural activity monitoring and time-frequency analysis. The key functional blocks of the microsystem, the integrated neural interface and the wavelet transform processor, have been prototyped in a 0.35-m standard complementary metal- oxide-semiconductor (CMOS) technology. Its utility is vali- dated in autonomous early detection of epileptic seizures in

Joseph N. Y. Aziz; Rafal Karakiewicz; Roman Genov; Alan W. L. Chiu; Berj L. Bardakjian; Miron Derchansky; Peter L. Carlen

226

Classification of single trial motor imagery EEG recordings with subject adapted non-dyadic arbitrary time frequency tilings  

Microsoft Academic Search

We describe a new technique for the classification of motor imagery electroencephalogram (EEG) recordings in a brain computer interface (BCI) task. The technique is based on an adaptive time-frequency analysis of EEG signals computed using local discriminant bases (LDB) derived from local cosine packets (LCP). In an offline step, the EEG data obtained from the C3\\/C4 electrode locations of the

Nuri Finodotrat Ince; Sami Arica; Ahmed Tewfik

2006-01-01

227

Time-Frequency Analysis of GALLEX and GNO Solar Neutrino Data: Evidence Suggestive of Asymmetric and Variable Nuclear Burning  

E-print Network

Time-frequency analysis of data from the GALLEX and GNO solar neutrino experiments shows that some features in power-spectrum analyses of those datasets are due to aliasing. We normalize data for each of the four experiments in the GALLEX series, concatenate the resulting normalized data, and then form time-frequency displays. We also form time-frequency displays of the two principal modulations found in the data, at 11.87 yr-1 and at 13.63 yr-1, and of the datasets formed by subtracting these modulations from the actual (normalized) data. The results suggest that the true modulation is that at 11.87 yr-1, consistent with the results of our earlier analysis of Homestake solar neutrino data. Comparison with helioseismology data indicates that modulation is occurring either in the radiative zone just below the tachocline, presumably by the RSFP (resonant spin-flavor precession) process, or in the core, presumably due to inhomogeneities and fluctuations in the nuclear-burning process.

P. A. Sturrock

2008-02-22

228

Time-frequency analyses of transient-evoked stimulus-frequency and distortion-product otoacoustic emissions: Testing cochlear model predictions  

NASA Astrophysics Data System (ADS)

Time-frequency representations (TFRs) of otoacoustic emissions (OAEs) provide information simultaneously in time and frequency that may be obscured in waveform or spectral analyses. TFRs were applied to transient-evoked stimulus-frequency (SF) and distortion-product (DP) OAEs to test cochlear model predictions. SFOAEs and DPOAEs were elicited in 18 normal-hearing subjects using gated tones and tone pips. Synchronous spontaneous (SS) OAEs were measured to assess their contributions to SFOAEs and DPOAEs. A common form of TFR of measured OAEs was a collection of frequency-specific components often aligned with SSOAE sites, with each component characterized by one or more brief segments or a single long-duration segment. The spectral envelope of evoked OAEs differed from that of the evoking stimulus. Strong emission regions or cochlear ``hot spots'' were detected, and sometimes accounted for OAE energy observed outside the stimulus bandwidth. Contributions of hot spots and multiple internal reflections to the OAE, and differences between measured and predicted OAE spectra, increased as stimulus level decreased, consistent with level-dependent changes in the estimated cochlear reflectance. Suppression and frequency-pulling effects between components were observed. A recursive formulation was described for the linear coherent reflection emission theory [Zweig and Shera, J. Acoust. Soc. Am. 98, 2018-2047 (1995)] that is well suited for time-domain calculations.

Konrad-Martin, Dawn; Keefe, Douglas H.

2003-10-01

229

Affective Domain  

NSDL National Science Digital Library

The affective domain can significantly enhance, inhibit or even prevent student learning. The affective domain includes factors such as student motivation, attitudes, perceptions and values. Teachers can increase their effectiveness by considering the affective domain in planning courses, delivering lectures and activities, and assessing student learning. This module contains information and resources for incorporating the affective domain into teaching.

230

Large-alphabet time-frequency entangled quantum key distribution by means of time-to-frequency conversion  

NASA Astrophysics Data System (ADS)

We introduce a novel time-frequency quantum key distribution (TFQKD) scheme based on photon pairs entangled in these two conjugate degrees of freedom. The scheme uses spectral detection and phase modulation to enable measurements in the temporal basis by means of time-to-frequency conversion. This allows large-alphabet encoding to be implemented with realistic components. A general security analysis for TFQKD with binned measurements reveals a close connection with finite-dimensional QKD protocols and enables analysis of the effects of dark counts on the secure key size.

Nunn, J.; Wright, L. J.; Söller, C.; Zhang, L.; Walmsley, I. A.; Smith, B. J.

2013-07-01

231

A new time-frequency method to reveal quantum dynamics of atomic hydrogen in intense laser pulses: Synchrosqueezing Transform  

E-print Network

This study introduces a new adaptive time-frequency (TF) analysis technique, synchrosqueezing transform (SST), to explore the dynamics of a laser-driven hydrogen atom at an {\\it ab initio} level, upon which we have demonstrated its versatility as a new viable venue for further exploring quantum dynamics. For a signal composed of oscillatory components which can be characterized by instantaneous frequency, the SST enables rendering the decomposed signal based on the phase information inherited in the linear TF representation with mathematical support. Compared with the classical type TF methods, the SST clearly depicts several intrinsic quantum dynamical processes such as selection rules, AC Stark effects, and high harmonic generation.

Sheu, Yae-lin; Wu, Hau-tieng; Li, Peng-Cheng; Chu, Shih-I

2014-01-01

232

Joint hypermobility  

Microsoft Academic Search

Joint hypermobility is an area of neglect in rheumatology. That is not to say it is overlooked by rheumatologists. It is spotted when sought, but for many unfortunate patients, here the story ends. The act of recognition becomes the goal in itself rather than the medium through which effective therapy can be provided. This chapter serves to reinforce the clinical

Rodney Grahame

2003-01-01

233

Effects of the air-sea coupling time frequency on the ocean response during Mediterranean intense events  

NASA Astrophysics Data System (ADS)

The near-sea surface meteorological conditions associated with the Mediterranean heavy precipitation events constitute, on a short time scale, a strong forcing on the ocean mixed layer. This study addresses the question of the optimal time frequency of the atmospheric forcing to drive an ocean model in order to make it able to capture the fine scale ocean mixed layer response to severe meteorological conditions. The coupling time frequency should allow the ocean model to reproduce the formation of internal low-salty boundary layers due to sudden input of intense precipitation, as well as the cooling and deepening of the ocean mixed layer through large latent heat fluxes and stress under the intense low-level jet associated with these events. In this study, the one-dimensional ocean model is driven by 2.4-km atmospheric simulated fields on a case of Mediterranean heavy precipitation, varying the time resolution of the atmospheric forcing. The results show that using a finer temporal resolution than 1 h for the atmospheric forcing is not necessary, but a coarser temporal resolution (3 or 6 h) modifies the event course and intensity perceived by the ocean. Consequently, when using a too coarse temporal resolution forcing, typically 6 h, the ocean model fails to reproduce the ocean mixed layer fine scale response under the heavy rainfall pulses and the strong wind gusts.

Lebeaupin Brossier, Cindy; Ducrocq, Véronique; Giordani, Hervé

2009-08-01

234

A Novel Approach to Predict Sudden Cardiac Death (SCD) Using Nonlinear and Time-Frequency Analyses from HRV Signals  

PubMed Central

Investigations show that millions of people all around the world die as the result of sudden cardiac death (SCD). These deaths can be reduced by using medical equipment, such as defibrillators, after detection. We need to propose suitable ways to assist doctors to predict sudden cardiac death with a high level of accuracy. To do this, Linear, Time-Frequency (TF) and Nonlinear features have been extracted from HRV of ECG signal. Finally, healthy people and people at risk of SCD are classified by k-Nearest Neighbor (k-NN) and Multilayer Perceptron Neural Network (MLP). To evaluate, we have compared the classification rates for both separate and combined Nonlinear and TF features. The results show that HRV signals have special features in the vicinity of the occurrence of SCD that have the ability to distinguish between patients prone to SCD and normal people. We found that the combination of Time-Frequency and Nonlinear features have a better ability to achieve higher accuracy. The experimental results show that the combination of features can predict SCD by the accuracy of 99.73%, 96.52%, 90.37% and 83.96% for the first, second, third and forth one-minute intervals, respectively, before SCD occurrence. PMID:24504331

Ebrahimzadeh, Elias; Pooyan, Mohammad; Bijar, Ahmad

2014-01-01

235

Joint Replacement (Finger and Wrist Joints)  

MedlinePLUS

... A-Z Hand Anatomy Find a Hand Surgeon Joint Replacement Email to a friend * required fields From * To * ... be possible to treat arthritic joints surgically, including “joint replacement” procedures. What does it mean to have a “ ...

236

Joint hypermobility.  

PubMed

Joint hypermobility is an area of neglect in rheumatology. That is not to say it is overlooked by rheumatologists. It is spotted when sought, but for many unfortunate patients, here the story ends. The act of recognition becomes the goal in itself rather than the medium through which effective therapy can be provided. This chapter serves to reinforce the clinical and epidemiological importance of a common disorder whose significance is under-appreciated and impact largely ignored. In contradistinction to our earlier chapter, published in 2000, which took for its remit the heritable disorders of connective tissue in general, the current one focuses on the commonly encountered (so-called benign) joint hypermobility syndrome, its recognition, epidemiology, clinical features and management according to the most recent literature. PMID:15123047

Hakim, Alan; Grahame, Rodney

2003-12-01

237

A time-frequency convolutional neural network for the offline classification of steady-state visual evoked potential responses  

Microsoft Academic Search

A new convolutional neural network architecture is presented. It includes the fast Fourier transform between two hidden layers to switch the signal analysis from the time domain to the frequency domain inside the network. This technique allows the signal classification without any special pre-processing and uses knowledge from the problem in the network topology. The first step allows the creation

Hubert Cecotti

2011-01-01

238

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

239

Linear and synchrosqueezed time-frequency representations revisited. Part I: Overview, standards of use, related issues and algorithms  

E-print Network

Time-frequency representations (TFRs) of signals, such as windowed Fourier transform (WFT), wavelet transform (WT) and their synchrosqueezed variants (SWFT, SWT), provide powerful analysis tools. However, there are many important issues related to the practical use of TFRs that need to be clarified. Here we present a thorough review of these TFRs, summarizing all theoretical, practical and numerical aspects of their use, reconsidering some conventions and introducing new concepts and procedures. The purposes of this work are: (i) to provide a consistent overview of the computation, properties, and use of the (S)WFT/(S)WT methods; (ii) to establish general standards related to their use, both theoretical and practical; and (iii) to provide clean and optimized algorithms and MatLab codes, appropriate for any window or wavelet.

Iatsenko, Dmytro; Stefanovska, Aneta

2013-01-01

240

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

2012-07-30

241

A multivariate time-frequency method to characterize the influence of respiration over heart period and arterial pressure  

NASA Astrophysics Data System (ADS)

Respiratory activity introduces oscillations both in arterial pressure and heart period, through mechanical and autonomic mechanisms. Respiration, arterial pressure, and heart period are, generally, non-stationary processes and the interactions between them are dynamic. In this study we present a methodology to robustly estimate the time course of cross spectral indices to characterize dynamic interactions between respiratory oscillations of heart period and blood pressure, as well as their interactions with respiratory activity. Time-frequency distributions belonging to Cohen's class are used to estimate time-frequency (TF) representations of coherence, partial coherence and phase difference. The characterization is based on the estimation of the time course of cross spectral indices estimated in specific TF regions around the respiratory frequency. We used this methodology to describe the interactions between respiration, heart period variability (HPV) and systolic arterial pressure variability (SAPV) during tilt table test with both spontaneous and controlled respiratory patterns. The effect of selective autonomic blockade was also studied. Results suggest the presence of common underling mechanisms of regulation between cardiovascular signals, whose interactions are time-varying. SAPV changes followed respiratory flow both in supine and standing positions and even after selective autonomic blockade. During head-up tilt, phase differences between respiration and SAPV increased. Phase differences between respiration and HPV were comparable to those between respiration and SAPV during supine position, and significantly increased during standing. As a result, respiratory oscillations in SAPV preceded respiratory oscillations in HPV during standing. Partial coherence was the most sensitive index to orthostatic stress. Phase difference estimates were consistent among spontaneous and controlled breathing patterns, whereas coherence was higher in spontaneous breathing. Parasympathetic blockade did not affect interactions between respiration and SAPV, reduced the coherence between SAPV and HPV and between respiration and HPV. Our results support the hypothesis that non-autonomic, possibly mechanically mediated, mechanisms also contributes to the respiratory oscillations in HPV. A small contribution of sympathetic activity on HPV-SAPV interactions around the respiratory frequency was also observed.

Orini, Michele; Bailón, Raquel; Laguna, Pablo; Mainardi, Luca T.; Barbieri, Riccardo

2012-12-01

242

A time-frequency analysis of the dynamics of cortical networks of sleep spindles from MEG-EEG recordings  

PubMed Central

Sleep spindles are a hallmark of NREM sleep. They result from a widespread thalamo-cortical loop and involve synchronous cortical networks that are still poorly understood. We investigated whether brain activity during spindles can be characterized by specific patterns of functional connectivity among cortical generators. For that purpose, we developed a wavelet-based approach aimed at imaging the synchronous oscillatory cortical networks from simultaneous MEG-EEG recordings. First, we detected spindles on the EEG and extracted the corresponding frequency-locked MEG activity under the form of an analytic ridge signal in the time-frequency plane (Zerouali et al., 2013). Secondly, we performed source reconstruction of the ridge signal within the Maximum Entropy on the Mean framework (Amblard et al., 2004), yielding a robust estimate of the cortical sources producing observed oscillations. Lastly, we quantified functional connectivity among cortical sources using phase-locking values. The main innovations of this methodology are (1) to reveal the dynamic behavior of functional networks resolved in the time-frequency plane and (2) to characterize functional connectivity among MEG sources through phase interactions. We showed, for the first time, that the switch from fast to slow oscillatory mode during sleep spindles is required for the emergence of specific patterns of connectivity. Moreover, we show that earlier synchrony during spindles was associated with mainly intra-hemispheric connectivity whereas later synchrony was associated with global long-range connectivity. We propose that our methodology can be a valuable tool for studying the connectivity underlying neural processes involving sleep spindles, such as memory, plasticity or aging. PMID:25389381

Zerouali, Younes; Lina, Jean-Marc; Sekerovic, Zoran; Godbout, Jonathan; Dube, Jonathan; Jolicoeur, Pierre; Carrier, Julie

2014-01-01

243

Numerical Simulation and Laboratory Testing of Time-Frequency MUSIC Beamforming for Identifying Continuous and Impulsive Ground Targets from a Mobile Aerial Platform  

E-print Network

and laboratory experiments are presented that validate a proposed time-frequency beamforming method based on the Multiple Signal Classification (MUSIC) algorithm to detect these acoustic sources from a mobile aerial platform. In the numerical simulations three...

Silva, Ramon Alejandro

2013-04-25

244

Joint Sealants for Horizontal Pavement Joints—Specifically Bridge Joints  

Microsoft Academic Search

The various types of materials that have been used to seal bridge joints have been reviewed. Some of the bridge engineers joint material requirements have been listed together with the advantages and disadvantages of the three most widely used bridge joint sealants being specified and used today. It is felt that the cold applied two component asphalt-modified polyurethane sealants come

Thomas J. Green

1969-01-01

245

TFT-Bootstrap: Resampling time series in the frequency domain to obtain replicates  

E-print Network

TFT-Bootstrap: Resampling time series in the frequency domain to obtain replicates in the time domain Claudia Kirch and Dimitris N. Politis December 23, 2010 Abstract A new time series bootstrap scheme, the Time Frequency Toggle (TFT)-Bootstrap, is proposed. Its basic idea is to bootstrap

Politis, Dimitris N.

246

Timing, Frequency and Environmental Conditions Associated with Mainstem–Tributary Movement by a Lowland River Fish, Golden Perch (Macquaria ambigua)  

PubMed Central

Tributary and mainstem connections represent important links for the movement of fish and other biota throughout river networks. We investigated the timing, frequency and environmental conditions associated with movements by adult golden perch (Macquaria ambigua) between the mainstem of the mid-Murray River and a tributary, the Goulburn River, in south-eastern Australia, using acoustic telemetry over four years (2007–2011). Fish were tagged and released in autumn 2007–2009 in the mid-Murray (n?=?42) and lower Goulburn (n?=?37) rivers within 3–6 km of the mid-Murray-lower Goulburn junction. 38% of tagged fish undertook mainstem–tributary movements, characterised mostly by temporary occupation followed by return of fish to the original capture river. Approximately 10% of tagged fish exhibited longer-term shifts between the mainstem and tributary. Movement of fish from the tributary into the mainstem occurred primarily during the spawning season and in some years coincided with the presence of golden perch eggs/larvae in drift samples in the mainstem. Many of the tributary-to-mainstem movements occurred during or soon after changes in flow. The movements of fish from the mainstem into the tributary were irregular and did not appear to be associated with spawning. The findings show that golden perch moved freely across the mainstem–tributary interface. This demonstrates the need to consider the spatial, behavioural and demographic interdependencies of aquatic fauna across geographic management units such as rivers. PMID:24788137

Koster, Wayne M.; Dawson, David R.; O’Mahony, Damien J.; Moloney, Paul D.; Crook, David A.

2014-01-01

247

Time-frequency analysis of short-lasting modulation of EEG induced by TMS during wake, sleep deprivation and sleep  

PubMed Central

The occurrence of dynamic changes in spontaneous electroencephalogram (EEG) rhythms in the awake state or sleep is highly variable. These rhythms can be externally modulated during transcranial magnetic stimulation (TMS) with a perturbation method to trigger oscillatory brain activity. EEG-TMS co-registration was performed during standard wake, during wake after sleep deprivation and in sleep in six healthy subjects. Dynamic changes in the regional neural oscillatory activity of the cortical areas were characterized using time-frequency analysis based on the wavelet method, and the modulation of induced oscillations were related to different vigilance states. A reciprocal synchronizing/desynchronizing effect on slow and fast oscillatory activity was observed in response to focal TMS after sleep deprivation and sleep. We observed a sleep-related slight desynchronization of alpha mainly over the frontal areas, and a widespread increase in theta synchronization. These findings could be interpreted as proof of the interference external brain stimulation can exert on the cortex, and how this could be modulated by the vigilance state. Potential clinical applications may include evaluation of hyperexcitable states such as epilepsy or disturbed states of consciousness such as minimal consciousness. PMID:24302903

Manganotti, Paolo; Formaggio, Emanuela; Del Felice, Alessandra; Storti, Silvia F.; Zamboni, Alessandro; Bertoldo, Alessandra; Fiaschi, Antonio; Toffolo, Gianna M.

2013-01-01

248

Spacesuit mobility joints  

NASA Technical Reports Server (NTRS)

Joints for use in interconnecting adjacent segments of an hermetically sealed spacesuit which have low torques, low leakage and a high degree of reliability are described. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics. Linkages which restrain the joint from longitudinal distension and a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli are featured. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints.

Vykukal, H. C. (inventor)

1978-01-01

249

Spacesuit mobility knee joints  

NASA Technical Reports Server (NTRS)

Pressure suit mobility joints are for use in interconnecting adjacent segments of an hermetically sealed spacesuit in which low torques, low leakage and a high degree of reliability are required. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics and includes linkages which restrain the joint from longitudinal distension and includes a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints.

Vykukal, H. C. (inventor)

1979-01-01

250

Temporal Features of Spike Trains in the Moth Antennal Lobe Revealed by a Comparative Time-Frequency Analysis  

PubMed Central

The discrimination of complex sensory stimuli in a noisy environment is an immense computational task. Sensory systems often encode stimulus features in a spatiotemporal fashion through the complex firing patterns of individual neurons. To identify these temporal features, we have developed an analysis that allows the comparison of statistically significant features of spike trains localized over multiple scales of time-frequency resolution. Our approach provides an original way to utilize the discrete wavelet transform to process instantaneous rate functions derived from spike trains, and select relevant wavelet coefficients through statistical analysis. Our method uncovered localized features within olfactory projection neuron (PN) responses in the moth antennal lobe coding for the presence of an odor mixture and the concentration of single component odorants, but not for compound identities. We found that odor mixtures evoked earlier responses in biphasic response type PNs compared to single components, which led to differences in the instantaneous firing rate functions with their signal power spread across multiple frequency bands (ranging from 0 to 45.71 Hz) during a time window immediately preceding behavioral response latencies observed in insects. Odor concentrations were coded in excited response type PNs both in low frequency band differences (2.86 to 5.71 Hz) during the stimulus and in the odor trace after stimulus offset in low (0 to 2.86 Hz) and high (22.86 to 45.71 Hz) frequency bands. These high frequency differences in both types of PNs could have particular relevance for recruiting cellular activity in higher brain centers such as mushroom body Kenyon cells. In contrast, neurons in the specialized pheromone-responsive area of the moth antennal lobe exhibited few stimulus-dependent differences in temporal response features. These results provide interesting insights on early insect olfactory processing and introduce a novel comparative approach for spike train analysis applicable to a variety of neuronal data sets. PMID:24465391

Capurro, Alberto; Baroni, Fabiano; Kuebler, Linda S.; Karpati, Zsolt; Dekker, Teun; Lei, Hong; Hansson, Bill S.; Pearce, Timothy C.; Olsson, Shannon B.

2014-01-01

251

Effect of fatigue on the intra-cycle acceleration in front crawl swimming: A time-frequency analysis  

E-print Network

The present study analyzes the changes in acceleration produced by swimmers before and after fatiguing effort. The subjects (n=15) performed a 25-meter crawl series at maximum speed without fatigue, and a second series with fatigue. The data were registered with a synchronized system that consisted in a position transducer (1 kHz) and a video photogrametry (50Hz). The acceleration (ms-2) was obtained by the derivative analysis of the variation of the position with time. The amplitude in the time domain was calculated with the root mean square (RMS); while the peak power (PP), the peak power frequency (PPF) and the spectrum area (SA) was calculated in the frequency domain with Fourier analysis. On one hand, the results of the temporal domain show that the RMS change percentage between series was 67.5% (p<0.001). On the other hand, PP, PPF, and SA show significant changes (p<0.001). PP and SA were reduced by 63.1% and 59.5%, respectively. Our results show that the acceleration analysis of the swimmer with...

Tella, V; Gallach, J E; Benavent, J; Gonzalez, L M; Arellano, R

2008-01-01

252

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

253

Proprioception and joint stability  

Microsoft Academic Search

In the present paper the current clinical knowledge about proprioception is given for the shoulder, knee, ankle, elbow and the radiocarpal joint. Proprioceptive capabilities are decreased after joint injuries such as ACL or meniscus tears, shoulder dislocation, ankle sprain and in joints with degenerative joint disease. Some surgical procedures seem to restore the proprioceptive abilities; others do not. Elastic knee

J. Jerosch; M. Prymka

1996-01-01

254

Frequency Domain Computation of the Feedback Filter of the Hybrid Decision Feedback Equalizer  

Microsoft Academic Search

The hybrid decision feedback equalizer is a combined time-frequency domain implementation of the classical decision feedback equalizer. In the original hybrid decision feedback equalizer, independently proposed by Falconer et al. and by Benvenuto and Tomasin, the computation of the feedforward filter is done in the frequency-domain, while the impulse response of the feedback filter is computed in the time-domain. In

Maurizio Magarini; Arnaldo Spalvieri

2009-01-01

255

Time-, frequency-, and wavevector-resolved x-ray diffraction from single molecules Kochise Bennett, Jason D. Biggs, Yu Zhang, Konstantin E. Dorfman, and Shaul Mukamel  

E-print Network

(2005); 10.1063/1.1844291 Time-resolved x-ray photoabsorption and diffraction on timescales from nsTime-, frequency-, and wavevector-resolved x-ray diffraction from single molecules Kochise Bennett soft X-ray scattering map of cysteine J. Chem. Phys. 138, 034306 (2013); 10.1063/1.4774059 Resonant

Mukamel, Shaul

256

One System, Many Domains: Open-Domain Statistical Machine Translation via Feature Augmentation  

E-print Network

Count TargetGivenSource ... news_LanguageModel news_WordCount news_TargetGivenSource ... web_LanguageModel web_WordCount web_TargetGivenSource news_LanguageModel news_WordCount news_TargetGivenSource ... Domain-Agnostic Independent Domain-Specific Joint Domain-Specific (This Work) Figure 1: A comparison of feature sets from

Lavie, Alon

257

Butt Joint Tool Commissioning  

SciTech Connect

ITER Central Solenoid uses butt joints for connecting the pancakes in the CS module. The principles of the butt joining of the CICC were developed by the JAPT during CSMC project. The difference between the CSMC butt joint and the CS butt joint is that the CS butt joint is an in-line joint, while the CSMC is a double joint through a hairpin jumper. The CS butt joint has to carry the hoop load. The straight length of the joint is only 320 mm, and the vacuum chamber around the joint has to have a split in the clamp shell. These requirements are challenging. Fig.1 presents a CSMC joint, and Fig.2 shows a CS butt joint. The butt joint procedure was verified and demonstrated. The tool is capable of achieving all specified parameters. The vacuum in the end was a little higher than the target, which is not critical and readily correctable. We consider, tentatively that the procedure is established. Unexpectedly, we discover significant temperature nonuniformity in the joint cross section, which is not formally a violation of the specs, but is a point of concern. All testing parameters are recorded for QA purposes. We plan to modify the butt joining tool to improve its convenience of operation and provide all features necessary for production of butt joints by qualified personnel.

Martovetsky, N N

2007-12-06

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

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

260

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 ...

261

A time-frequency approach to distinguish diurnal and lunar variations in measurements of ground magnetic and TEC data.  

NASA Astrophysics Data System (ADS)

Here, we explore the diurnal and lunar variations in measurements of ground magnetic and TEC data by using gapped wavelet technique. We analyze the last solar minimum period of solar cycle 23, which presented unusually low and prolonged solar activity, providing a good opportunity to investigate the impact of wave activity on the system thermosphere-ionosphere. It is well-known that wavelets are localized in both the time and frequency domains because wavelets have limited time duration and frequency bandwidth. For instance the Morlet wavelet has a long support in physical space and a short support in Fourier space as expected by the Heisenberg's uncertainty principle. For this reason, here we applied the Morlet wavelet with different temporal parameters to improve the frequency resolution (bandwidth), and also, to distinguish the physical phenomena of our interest. We try to determine the dominant timescales related to the signature of 12 h (semidiurnal variations) and 12.42 h (semilunar variations), therefore the appropriate choices of temporal parameter allow us to determine which kinds of information can be extracted.

Klausner, Virginia; Fontes Gomes, Anna Karina; Candido, Claudia; Frick, Peter; Mendes, Odim; Reinaldo Rodriguez Papa, Andres; Oliveira Domingues, Margarete; Negreti, Patricia M. S.

262

Arch & Chord Joint Detail; Crossbracing Center Joint Detail; Chord, ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Arch & Chord Joint Detail; Crossbracing Center Joint Detail; Chord, Panel Post, Tie & Diagonal Brace Joint Detail; Chord, Panel Post, Tie & Crossbracing Joint Detail - Dunlapsville Covered Bridge, Spanning East Fork Whitewater River, Dunlapsville, Union County, IN

263

Jointly Poisson processes  

Microsoft Academic Search

What constitutes jointly Poisson processes remains an unresolved issue. This report reviews the current state of the theory and indicates how the accepted but unproven model equals that resulting from the small time-interval limit of jointly Bernoulli processes. One intriguing consequence of these models is that jointly Poisson processes can only be positively correlated as measured by the correlation coefficient

D. H. Johnson; I. N. Goodman

2009-01-01

264

Magnetic domains  

NASA Astrophysics Data System (ADS)

Recently a Nahm transform has been discovered for magnetic bags, which are conjectured to arise in the large n limit of magnetic monopoles of charge n. We interpret these ideas using string theory and present evidence for this conjecture. Our main result concerns the extension of the notion of bags and their Nahm transform to higher gauge theories and arbitrary domains. Bags in four dimensions conjecturally describe the large n limit of n self-dual strings. We show that the corresponding Basu-Harvey equation is the large n limit of an equation describing n M2-branes, and that it has a natural interpretation in loop space. We also formulate our Nahm equations using strong homotopy Lie algebras.

Harland, Derek; Palmer, Sam; Sämann, Christian

2012-10-01

265

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

SciTech Connect

Time-lapse resistivity imaging is increasingly used to monitor hydrologic processes. Compared to conventional hydrologic measurements, surface time-lapse resistivity provides (1) superior spatial coverage in two or three dimensions, (2) potentially high-resolution information in time, and (3) 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 time-series conductivity datasets. Here, we use three-dimensional (3D) surface time-lapse electrical imaging to monitor subsurface electrical conductivity variations associated with stage-driven groundwater/surface-water interaction along a stretch of the Columbia River adjacent to the Hanford 300 Area, Hanford WA, USA. We reduce the resulting 3D conductivity time series using both correlation and time-frequency analysis to isolate a paleochannel causing enhanced groundwater/river-water interaction. Correlation analysis on the time-lapse imaging results concisely represents enhanced ground water/surface-water interaction within the paleochannel, and provides information concerning groundwater flow velocities. Time-frequency analysis using the Stockwell (S) Transform provides additional information by 1) identifying the stage periodicities driving ground water/river-water interaction due to upstream dam operations, 2) 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, Timothy C.; Slater, Lee; Ntarlagiannis, Dimitrios; Day-Lewis, Frederick D.; Elwaseif, Mehrez

2012-08-22

266

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

USGS Publications Warehouse

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, Timothy C.; Slater, Lee D.; Ntarlagiannis, Dimitris; Day-Lewis, Frederick D.; Elwaseif, Mehrez

2012-01-01

267

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

268

DMBC: Domain Names & Web Hosting Domain Names  

E-print Network

DMBC: Domain Names & Web Hosting Domain Names Top Level Domains · .com · .net · .org · .edu · .gov.9% of the web-viewing audience is used to typing in. Chances are, a visitor will type in ".com" even if you tell and simple · Try to avoid dashes or underscores in the domain name unless there is no other option Web

Stowell, Michael

269

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

270

Joint Power Allocation for Nonregenerative MIMO-OFDM Relay Links  

Microsoft Academic Search

We consider a two-hop MIMO-OFDM communication scheme with a source, a relay, and a destination. The relay is assumed to be nonregenerative (or amplify-and-forward (AF)). We assume channel state information at each transmitter (CSIT), source and relay. We present a jointly optimized power allocation (PA) over the subchannels in space and frequency domain at source and relay with a joint

I. Hammerstrom; Armin Wittneben

2006-01-01

271

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

272

Campylobacter Prosthetic Joint Infection  

PubMed Central

A 75-year-old man was diagnosed with probable Campylobacter jejuni prosthetic knee infection after a diarrheal illness. Joint aspirate and operative cultures were negative, but PCR of prosthesis sonicate fluid was positive, as was stool culture. Nineteen additional cases of Campylobacter prosthetic joint infection reported in the literature are reviewed. PMID:24523462

Vasoo, Shawn; Schwab, Jeramy J.; Cunningham, Scott A.; Robinson, Trisha J.; Cass, Joseph R.; Berbari, Elie F.; Walker, Randall C.; Osmon, Douglas R.

2014-01-01

273

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

274

PH domains, FYVE domains, ENTH domains, C2 do-mains, Tubby domains, and PX domains, and the list  

E-print Network

domain and the second SH3 domain (yellow), while the Selected Reading C-terminal tail interacts with the first SH3 domain. Phosphorylation of serine and threonine residues in the C-terminal tail liberates., Tempst, P., Thuring, J.W., Cooper,space and time, and thereby prevent inadvertent dam- M.A., Lim, Z

275

Hip joint replacement - series (image)  

MedlinePLUS

... pain that limits what you can do. Hip joint replacement is usually done in people age 60 and ... Hip joint replacement is surgery to replace all or part of the hip joint with a man-made or artificial ...

276

Pressure vessel flex joint  

NASA Technical Reports Server (NTRS)

An airtight, flexible joint is disclosed for the interfacing of two pressure vessels such as between the Space Station docking tunnel and the Space Shuttle Orbiter bulkhead adapter. The joint provides for flexibility while still retaining a structural link between the two vessels required due to the loading created by the internal/external pressure differential. The joint design provides for limiting the axial load carried across the joint to a specific value, a function returned in the Orbiter/Station tunnel interface. The flex joint comprises a floating structural segment which is permanently attached to one of the pressure vessels through the use of an inflatable seal. The geometric configuration of the joint causes the tension between the vessels created by the internal gas pressure to compress the inflatable seal. The inflation pressure of the seal is kept at a value above the internal/external pressure differential of the vessels in order to maintain a controlled distance between the floating segment and pressure vessel. The inflatable seal consists of either a hollow torus-shaped flexible bladder or two rolling convoluted diaphragm seals which may be reinforced by a system of straps or fabric anchored to the hard structures. The joint acts as a flexible link to allow both angular motion and lateral displacement while it still contains the internal pressure and holds the axial tension between the vessels.

Kahn, Jon B. (inventor)

1992-01-01

277

Acromioclavicular joint dislocations.  

PubMed

Acromioclavicular (AC) dislocation is a common injury especially among sportsmen. There is still a lack of consensus on whether to conserve or operate type III AC joint dislocations. Even among surgeons inclined to operate AC joint dislocations there is no unanimity on which surgical technique. There are a plethora of choices between mechanical fixation or synthetic materials or biologic anatomic reconstructions. Even among surgeons, there is a choice between open repairs and the latest-arthroscopic reconstructions. This review of AC joint dislocations intends to analyze the available surgical options, a critical analysis of existing literature, actual technique of anatomic repair, and also accompanying complications. PMID:24431027

Babhulkar, Ashish; Pawaskar, Aditya

2014-03-01

278

Anterior glenohumeral joint dislocations.  

PubMed

The glenohumeral joint is the most mobile articulation in the body and the most commonly dislocated diarthroidal joint. Anterior dislocation is by far the most common direction and can lead to instability of the glenohumeral joint, which ranges from subtle increased laxity to recurrent dislocation. Overtime, understanding of anterior shoulder dislocations and the resulting instability has improved. Likewise, significant advances in arthroscopic equipment have allowed use of the arthroscope to address anatomically the various lesions that cause instability. This article reviews the anatomy, pathophysiology, clinical evaluation, and treatment of anterior shoulder instability. PMID:18803980

Dodson, Christopher C; Cordasco, Frank A

2008-10-01

279

Improved orthopedic arm joint  

NASA Technical Reports Server (NTRS)

Joint permits smooth and easy movement of disabled arm and is smaller, lighter and less expensive than previous models. Device is interchangeable and may be used on either arm at the shoulder or at the elbow.

Dane, D. H.

1971-01-01

280

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

281

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

282

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

283

JOINT SEMINAR FINAL REPORT  

E-print Network

evolving from the Joint Seminar. - Peer-reviewed publications (journals, contribution to anthologies, working papers, proceedings, etc.) - Non peer-reviewed publications (journals, contribution to anthologies Application guidelines Length Clarity Intelligibility Procedures (submission, review, decision) Advising

Fuchs, Clemens

284

Culture - joint fluid  

MedlinePLUS

Joint fluid culture ... fungi, or viruses grow. This is called a culture. If such microorganisms are detected, other tests may ... is no special preparation needed for the lab culture. For information on preparing for the removal of ...

285

Joint hypermobility syndrome pain  

Microsoft Academic Search

Joint hypermobility syndrome (JHS) was initially defined as the occurrence of musculoskeletal symptoms in the presence of\\u000a joint laxity and hypermobility in otherwise healthy individuals. It is now perceived as a commonly overlooked, underdiagnosed,\\u000a multifaceted, and multisystemic heritable disorder of connective tissue (HDCT), which shares many of the phenotypic features\\u000a of other HDCTs such as Marfan syndrome and Ehlers-Danlos syndrome.

Rodney Grahame

2009-01-01

286

Panel Post & Diagonal Brace Joint Detail; Crossbracing Center Joint ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Panel Post & Diagonal Brace Joint Detail; Crossbracing Center Joint Detail; Chord, Panel Post, Tie Bar, & Diagonal Brace Joint Detail; Chord, Tie Bar, & Crossbracing Joint Detail - Medora Bridge, Spanning East Fork of White River at State Route 235, Medora, Jackson County, IN

287

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

288

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

289

ROBUST VIDEO RESTORATION BY JOINT SPARSE AND LOW RANK MATRIX APPROXIMATION  

E-print Network

ROBUST VIDEO RESTORATION BY JOINT SPARSE AND LOW RANK MATRIX APPROXIMATION HUI JI, SIBIN HUANG, ZUOWEI SHEN, AND YUHONG XU Abstract. This paper presents a new video restoration scheme based domain, we formulate the video restoration problem as a joint sparse and low-rank matrix approximation

Shen, Zuowei

290

Dissimilar metals joint evaluation  

NASA Technical Reports Server (NTRS)

Dissimilar metals tubular joints between 2219-T851 aluminum alloy and 304L stainless steel were fabricated and tested to evaluate bonding processes. Joints were fabricated by four processes: (1) inertia (friction) weldings, where the metals are spun and forced together to create the weld; (2) explosive welding, where the metals are impacted together at high velocity; (3) co-extrusion, where the metals are extruded in contact at high temperature to promote diffusion; and (4) swaging, where residual stresses in the metals after a stretching operation maintain forced contact in mutual shear areas. Fifteen joints of each type were prepared and evaluated in a 6.35 cm (2.50 in.) O.D. size, with 0.32 cm (0.13 in.) wall thickness, and 7.6 cm (3.0 in) total length. The joints were tested to evaluate their ability to withstand pressure cycle, thermal cycle, galvanic corrosion and burst tests. Leakage tests and other non-destructive test techniques were used to evaluate the behavior of the joints, and the microstructure of the bond areas was analyzed.

Wakefield, M. E.; Apodaca, L. E.

1974-01-01

291

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. PMID:23162140

Thomas, Binu P; Sreekanth, Raveendran

2012-01-01

292

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. PMID:24023542

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

2013-01-01

293

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

294

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. PMID:20969891

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

2010-01-01

295

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

296

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. PMID:21319875

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

2010-01-01

297

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

298

Heterogeneous domain adaptation and classification by exploiting the correlation subspace.  

PubMed

We present a novel domain adaptation approach for solving cross-domain pattern recognition problems, i.e., the data or features to be processed and recognized are collected from different domains of interest. Inspired by canonical correlation analysis (CCA), we utilize the derived correlation subspace as a joint representation for associating data across different domains, and we advance reduced kernel techniques for kernel CCA (KCCA) if nonlinear correlation subspace are desirable. Such techniques not only makes KCCA computationally more efficient, potential over-fitting problems can be alleviated as well. Instead of directly performing recognition in the derived CCA subspace (as prior CCA-based domain adaptation methods did), we advocate the exploitation of domain transfer ability in this subspace, in which each dimension has a unique capability in associating cross-domain data. In particular, we propose a novel support vector machine (SVM) with a correlation regularizer, named correlation-transfer SVM, which incorporates the domain adaptation ability into classifier design for cross-domain recognition. We show that our proposed domain adaptation and classification approach can be successfully applied to a variety of cross-domain recognition tasks such as cross-view action recognition, handwritten digit recognition with different features, and image-to-text or text-to-image classification. From our empirical results, we verify that our proposed method outperforms state-of-the-art domain adaptation approaches in terms of recognition performance. PMID:24710401

Yeh, Yi-Ren; Huang, Chun-Hao; Wang, Yu-Chiang Frank

2014-05-01

299

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

300

Joint Durability The problem?  

E-print Network

;Interfacial Zone? #12;Walking a Cliff Edge · In situ air content · w/cm · Saturation · Salts #12;Base Permeability #12;An Example #12;So · Water has to be prevented from saturating the concrete · Prevent water from ponding in the joint · Prevent water from penetrating from the base · Permeability of the concrete

301

Joint global motion estimation and coding for scalable H.264\\/SVC high-definition video streams  

Microsoft Academic Search

This paper presents a joint indexing-coding approach applied to global camera motion detection in the scalable H.264\\/SVC compressed domain. Our goal is to facilitate and to improve indexing in the MPEG compressed domain, if necessary by modifying the original coded stream, without losing compatibility with the standard. In frames with very noisy motion vector fields, we use the global motion

Christian Käs; Henri Nicolas

2008-01-01

302

Stochastic quantification of the electric power generated by a piezoelectric energy harvester using a time-frequency analysis under non-stationary random vibrations  

NASA Astrophysics Data System (ADS)

Vibration energy, which is widely available, can be converted into electric energy using a piezoelectric energy harvester that generates alternating current in response to applied mechanical strain. For the last decade, there has been a strong surge of interest in developing an electromechanically-coupled analytical model of a piezoelectric energy harvester. Such a model is of great importance to enable understanding of the first principle of the piezoelectric transduction and to quantify harvestable electric power under a given vibration condition. However, existing analytical models that operate under an assumption of deterministic excitations cannot deal with the random nature present in realistic vibrations, even though this randomness considerably affects the variation in harvestable electric power. Furthermore, even when random vibrations are taken into account, existing stochastic analytical models can only be applied to stationary excitations, such as in the case of white Gaussian noise. This paper thus proposes a three-step framework for stochastic quantification of the electric power generated by a piezoelectric energy harvester under non-stationary random vibrations. First, we propose estimation of the time-varying power spectral density (PSD) of the input non-stationary random vibration using a statistical time-frequency analysis. The second step is to employ an existing electromechanical model as the linear operator for calculating the output voltage response. The final step is to estimate the time-varying PSD of the output voltage response. Following this three-step process, the expected electric power can be estimated from the autocorrelation function which is the inverse Fourier transform of the time-varying PSD of the output voltage response. The merits of the proposed framework are two-fold in that it enables: (i) quantification of the time-varying electric power generated under non-stationary random vibrations and (ii) consideration of the randomness in the design process of the energy harvester. Four case studies are used to demonstrate the effectiveness of the proposed framework.

Yoon, Heonjun; Youn, Byeng D.

2014-04-01

303

Joints in a Cornstarch Analog  

NSDL National Science Digital Library

Joints are very important to problems in applied geology (fluid flow, slope stability), but three-dimensional exposures of simple joint sets are not readily accessible from my campus. I developed this exercise based on the experiments of Miller (2001) to give students hands-on practice describing and interpreting joints. For the exercise, I prepare a cornstarch-water mixture a few days in advance and pour it into plastic petri dishes. I add a "flaw" to each dish (typically a small pebble). As the cornstarch dries, vertical joints develop. In class, each group of 3-4 students is provided a petri dish of desiccated cornstarch. Students are asked to draw a map of the joints, paying particular attention to intersection angles. (The joints curve to intersect at 90 degrees.) They determine relative ages of the joints using abutting relationships. (Typically 3-6 generations of joints.) Students next dissect the sample and describe the surface textures of the larger joints and the location of the flaw. The cornstarch produces beautiful plumose structure (hackles). Students then interpret the joint propagation direction from the surface textures, and note the origin of the joint. (Typically, a first- or second-generation joint initiates at the flaw.) Students discuss the role of flaws in the initiation of joints in their groups.

Crider, Juliet

304

MIGRATION DES JOINTS DE GRAINS LA MIGRATION DES JOINTS INTERGRANULAIRES  

E-print Network

MIGRATION DES JOINTS DE GRAINS LA MIGRATION DES JOINTS INTERGRANULAIRES O. DIMITROV Centre d nombre de faits fondamentaux concernant la migration des joints de grains sont brièvement rappelés considérant les forces qui provoquent ou qui freinent la migration. L'évolution des modèles proposés pour

Boyer, Edmond

305

Decoupled Control of Flexure Jointed Hexapods Using Estimated Joint Space  

E-print Network

1 Decoupled Control of Flexure Jointed Hexapods Using Estimated Joint Space Mass-Inertia Matrix of flexure jointed hexapods (or Stewart platforms), a new decoupling method is proposed. The new decoupling. Keywords Vibration isolation, decoupling control, Stewart platform, precision robots, hexapod, symmetric

Chen, Yixin

306

Shoulder Joint For Protective Suit  

NASA Technical Reports Server (NTRS)

Shoulder joint allows full range of natural motion: wearer senses little or no resisting force or torque. Developed for space suit, joint offers advantages in protective garments for underwater work, firefighting, or cleanup of hazardous materials.

Kosmo, Joseph J.; Smallcombe, Richard D.

1994-01-01

307

Rolling contact orthopaedic joint design  

E-print Network

Arthroplasty, the practice of rebuilding diseased biological joints using engineering materials, is often used to treat severe arthritis of the knee and hip. Prosthetic joints have been created in a "biomimetic" manner to ...

Slocum, Alexander Henry, Jr

2013-01-01

308

Estimating Average Domain Scores.  

ERIC Educational Resources Information Center

A simulation study was performed to determine whether a group's average percent correct in a content domain could be accurately estimated for groups taking a single test form and not the entire domain of items. Six Item Response Theory (IRT) -based domain score estimation methods were evaluated, under conditions of few items per content area per…

Pommerich, Mary; Nicewander, W. Alan

309

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

310

Phase 1 Program Joint Report  

NASA Technical Reports Server (NTRS)

This report consists of inputs from each of the Phase I Program Joint Working Groups. The Working Groups were tasked to describe the organizational structure and work processes that they used during the program, joint accomplishments, lessons learned, and applications to the International Space Station Program. This report is a top-level joint reference document that contains information of interest to both countries.

Nield, George C. (Editor); Vorobiev, Pavel Mikhailovich (Editor)

1999-01-01

311

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

312

Joint hypermobility syndrome pain.  

PubMed

Joint hypermobility syndrome (JHS) was initially defined as the occurrence of musculoskeletal symptoms in the presence of joint laxity and hypermobility in otherwise healthy individuals. It is now perceived as a commonly overlooked, underdiagnosed, multifaceted, and multisystemic heritable disorder of connective tissue (HDCT), which shares many of the phenotypic features of other HDCTs such as Marfan syndrome and Ehlers-Danlos syndrome. Whereas the additional flexibility can confer benefits in terms of mobility and agility, adverse effects of tissue laxity and fragility can give rise to clinical consequences that resonate far beyond the confines of the musculoskeletal system. There is hardly a clinical specialty to be found that is not touched in one way or another by JHS. Over the past decade, it has become evident that of all the complications that may arise in JHS, chronic pain is arguably the most menacing and difficult to treat. PMID:19889283

Grahame, Rodney

2009-12-01

313

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

314

Jointly Poisson processes  

Microsoft Academic Search

What constitutes jointly Poisson processes remains an unresolved issue. This\\u000areport reviews the current state of the theory and indicates how the accepted\\u000abut unproven model equals that resulting from the small time-interval limit of\\u000ajointly Bernoulli processes. One intriguing consequence of these models is that\\u000ajointly Poisson processes can only be positively correlated as measured by the\\u000acorrelation coefficient

Don H. Johnson; Ilan N. Goodman

2009-01-01

315

Prosthetic elbow joint  

NASA Technical Reports Server (NTRS)

An artificial, manually positionable elbow joint for use in an upper extremity, above-elbow, prosthetic is described. The prosthesis provides a locking feature that is easily controlled by the wearer. The instant elbow joint is very strong and durable enough to withstand the repeated heavy loadings encountered by a wearer who works in an industrial, construction, farming, or similar environment. The elbow joint of the present invention comprises a turntable, a frame, a forearm, and a locking assembly. The frame generally includes a housing for the locking assembly and two protruding ears. The forearm includes an elongated beam having a cup-shaped cylindrical member at one end and a locking wheel having a plurality of holes along a circular arc on its other end with a central bore for pivotal attachment to the protruding ears of the frame. The locking assembly includes a collar having a central opening with a plurality of internal grooves, a plurality of internal cam members each having a chamfered surface at one end and a V-shaped slot at its other end; an elongated locking pin having a crown wheel with cam surfaces and locking lugs secured thereto; two coiled compression springs; and a flexible filament attached to one end of the elongated locking pin and extending from the locking assembly for extending and retracting the locking pin into the holes in the locking wheel to permit selective adjustment of the forearm relative to the frame. In use, the turntable is affixed to the upper arm part of the prosthetic in the conventional manner, and the cup-shaped cylindrical member on one end of the forearm is affixed to the forearm piece of the prosthetic in the conventional manner. The elbow joint is easily adjusted and locked between maximum flex and extended positions.

Weddendorf, Bruce C. (inventor)

1994-01-01

316

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

317

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

318

49 CFR 213.121 - Rail joints.  

Code of Federal Regulations, 2013 CFR

...Transportation 4 2013-10-01 2013-10-01 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...

2013-10-01

319

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

320

49 CFR 213.121 - Rail joints.  

Code of Federal Regulations, 2010 CFR

...Transportation 4 2010-10-01 2010-10-01 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...

2010-10-01

321

Multiscale texture segmentation using wavelet-domain hidden Markov models  

Microsoft Academic Search

Wavelet-domain hidden Markov tree (HMT) models are powerful tools for modeling the statistical properties of wavelet transforms. By characterizing the joint statistics of the wavelet coefficients, HMTs efficiently capture the characteristics of a large class of real-world signals and images. In this paper, we apply this multiscale statistical description to the texture segmentation problem. Using the inherent tree structure of

Hyeokho Choi; Richard Baraniuk

1998-01-01

322

Multiscale Image Segmentation Using Wavelet-Domain Hidden Markov Models  

Microsoft Academic Search

A new image segmentation algorithm based wavelet-domain, referred to as joint adaptive context and multiscale segmentation (JACMS) is developed. Towards achieving lower computational complexity, we propose a fast training algorithm, when applied to image segmentation, this technique provides a reliable initial segmentation. The contextual labeling tree which is used for the context-based Bayesian interscale fusion is studied. In order to

Jixiang Zhang; Xiangling Zhang

2008-01-01

323

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

324

New plastic joints for plastic orthoses.  

PubMed

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 appropriate flexibility and toughness. PMID:7079105

Watanabe, H; Kutsuna, T; Morinaga, H; Okabe, T

1982-04-01

325

Joint attention studies in normal and autistic children using NIRS  

NASA Astrophysics Data System (ADS)

Autism is a socio-communication brain development disorder. It is marked by degeneration in the ability to respond to joint attention skill task, from as early as 12 to 18 months of age. This trait is used to distinguish autistic from nonautistic. In this study Near infrared spectroscopy (NIRS) is being applied for the first time to study the difference in activation and connectivity in the frontal cortex of typically developing (TD) and autistic children between 4-8 years of age in response to joint attention task. The optical measurements are acquired in real time from frontal cortex using Imagent (ISS Inc.) - a frequency domain based NIRS system in response to video clips which engenders a feeling of joint attention experience in the subjects. A block design consisting of 5 blocks of following sequence 30 sec joint attention clip (J), 30 sec non-joint attention clip (NJ) and 30 sec rest condition is used. Preliminary results from TD child shows difference in brain activation (in terms of oxy-hemoglobin, HbO) during joint attention interaction compared to the nonjoint interaction and rest. Similar activation study did not reveal significant differences in HbO across the stimuli in, unlike in an autistic child. Extensive studies are carried out to validate the initial observations from both brain activation as well as connectivity analysis. The result has significant implication for research in neural pathways associated with autism that can be mapped using NIRS.

Chaudhary, Ujwal; Hall, Michael; Gutierrez, Anibal; Messinger, Daniel; Rey, Gustavo; Godavarty, Anuradha

2011-03-01

326

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. PMID:24187603

Gelman, Susan A.; Noles, Nicholaus S.

2013-01-01

327

Imaye Restoration Usinr a Hybrid Fourier-Wavelet Domain Hidden Markov Model  

Microsoft Academic Search

We propose an efficient hybrid Fourier-Wavelet domain hidden Markov model. Fourier regularized deconvolution algorithm performs noise regularization using scalar shrinkage in the Fourier domain. The Fourier shrinkage exploit the Fourier transform's economical representation of the colored noise inherent in deconvolution, whereas the hidden Markov tree (HMT) model captures the key features of the joint probability density of the wavelet coefficients

A. Suliman; R. Li

2007-01-01

328

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

329

Joint services electronics program  

NASA Astrophysics Data System (ADS)

This report is the Annual Progress Report for Joint Services Electronics Program Contract N00014-84-K-0327 for the Faculty of the Edward L. Ginzton Laboratory of Stanford University (S.E. Harris, Director). The report includes contributions on four units: (1) (Unit 85-1: Processor D.M. Bloom) Picosecond Optical Measurements; (2) Unit 85-2: Processor R.L. Byer) Optical and Nonlinear Optical Studies of Single Crystal Fibers; (3) (Unit 85-3: Professor G.S. Kino) Very High Frequency Signal Processing Techniques; (4) Unit 85-4: Professor C.F. Quate) Metal-Vacuum-Metal Tunneling or scanned Tunneling Microscopy.

Harris, S. E.; Bloom, D. M.; Byer, R. L.; Kino, G. S.; Quate, C. F.

1985-07-01

330

Ferroelectric domain wall injection.  

PubMed

Ferroelectric domain wall injection has been demonstrated by engineering of the local electric field, using focused ion beam milled defects in thin single crystal lamellae of KTiOPO4 (KTP). The electric field distribution (top) displays localized field hot-spots, which correlate with nucleation events (bottom). Designed local field variations can also dictate subsequent domain wall mobility, demonstrating a new paradigm in ferroelectric domain wall control. PMID:24136810

Whyte, Jonathan R; McQuaid, Raymond G P; Sharma, Pankaj; Canalias, Carlota; Scott, James F; Gruverman, Alexei; Gregg, J Marty

2014-01-15

331

Internet Domain Survey  

NSDL National Science Digital Library

The Internet Domain Survey is published on a biannual basis and has been conducted since 1987. Sponsored by the Internet Software Consortium, the survey "attempts to discover every host on the Internet by doing a complete search of the Domain Name System." In doing so, it serves as a key indicator of the growth of the Internet. This Web site provides results from each iteration of the survey. Additionally, the general methodology used to conduct the domain name search is explained. The number of hosts representing each domain (e.g. .com, .net, etc.) is also included.

332

Learning and Domain Adaptation  

NASA Astrophysics Data System (ADS)

Domain adaptation is a fundamental learning problem where one wishes to use labeled data from one or several source domains to learn a hypothesis performing well on a different, yet related, domain for which no labeled data is available. This generalization across domains is a very significant challenge for many machine learning applications and arises in a variety of natural settings, including NLP tasks (document classification, sentiment analysis, etc.), speech recognition (speakers and noise or environment adaptation) and face recognition (different lighting conditions, different population composition).

Mansour, Yishay

333

Jointly Sponsored Research Program  

SciTech Connect

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 energy systems that meet the nation's requirements for clean fuels, chemicals, and electricity in the 21st century. The EERC in partnership with its nonfederal partners jointly performed 131 JSRP projects for which the total DOE cost share was $22,716,634 (38%) and the nonfederal share was $36,776,573 (62%). Summaries of these projects are presented in this report for six program areas: (1) resource characterization and waste management, (2) air quality assessment and control, (3) advanced power systems, (4) advanced fuel forms, (5) value-added coproducts, and (6) advanced materials. The work performed under this agreement addressed DOE goals for reductions in CO{sub 2} emissions through efficiency, capture, and sequestration; near-zero emissions from highly efficient coal-fired power plants; environmental control capabilities for SO{sub 2}, NO{sub x}, fine respirable particulate (PM{sub 2.5}), and mercury; alternative transportation fuels including liquid synfuels and hydrogen; and synergistic integration of fossil and renewable resources.

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

2009-03-31

334

Joint collaborative technology experiment  

NASA Astrophysics Data System (ADS)

Use of unmanned systems is rapidly growing within the military and civilian sectors in a variety of roles including reconnaissance, surveillance, explosive ordinance disposal (EOD), and force-protection and perimeter security. As utilization of these systems grows at an ever increasing rate, the need for unmanned systems teaming and inter-system collaboration becomes apparent. Collaboration provides a means of enhancing individual system capabilities through relevant data exchange that contributes to cooperative behaviors between systems and enables new capabilities not possible if the systems operate independently. A collaborative networked approach to development holds the promise of adding mission capability while simultaneously reducing the workload of system operators. The Joint Collaborative Technology Experiment (JCTE) joins individual technology development efforts within the Air Force, Navy, and Army to demonstrate the potential benefits of interoperable multiple system collaboration in a force-protection application. JCTE participants are the Air Force Research Laboratory, Materials and Manufacturing Directorate, Airbase Technologies Division, Force Protection Branch (AFRL/RXQF); the Army Aviation and Missile Research, Development, and Engineering Center Software Engineering Directorate (AMRDEC SED); and the Space and Naval Warfare Systems Center - Pacific (SSC Pacific) Unmanned Systems Branch operating with funding provided by the Joint Ground Robotics Enterprise (JGRE). This paper will describe the efforts to date in system development by the three partner organizations, development of collaborative behaviors and experimentation in the force-protection application, results and lessons learned at a technical demonstration, simulation results, and a path forward for future work.

Wills, Michael; Ciccimaro, Donny; Yee, See; Denewiler, Thomas; Stroumtsos, Nicholas; Messamore, John; Brown, Rodney; Skibba, Brian; Clapp, Daniel; Wit, Jeff; Shirts, Randy J.; Dion, Gary N.; Anselmo, Gary S.

2009-05-01

335

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.

Lasecki, John V. (Livonia, MI); Novak, Robert F. (Farmington Hills, MI); McBride, James R. (Ypsilanti, MI)

1991-01-01

336

Visualizing domain wall and reverse domain superconductivity.  

PubMed

In magnetically coupled, planar ferromagnet-superconductor (F/S) hybrid structures, magnetic domain walls can be used to spatially confine the superconductivity. In contrast to a superconductor in a uniform applied magnetic field, the nucleation of the superconducting order parameter in F/S structures is governed by the inhomogeneous magnetic field distribution. The interplay between the superconductivity localized at the domain walls and far from the walls leads to effects such as re-entrant superconductivity and reverse domain superconductivity with the critical temperature depending upon the location. Here we use scanning tunnelling spectroscopy to directly image the nucleation of superconductivity at the domain wall in F/S structures realized with Co-Pd multilayers and Pb thin films. Our results demonstrate that such F/S structures are attractive model systems that offer the possibility to control the strength and the location of the superconducting nucleus by applying an external magnetic field, potentially useful to guide vortices for computing application. PMID:25164004

Iavarone, M; Moore, S A; Fedor, J; Ciocys, S T; Karapetrov, G; Pearson, J; Novosad, V; Bader, S D

2014-01-01

337

Rotary Joint for Heat Transfer  

NASA Technical Reports Server (NTRS)

Rotary joint exchanges heat between two heat pipes - one rotating and one stationary. Joint accommodates varying heat loads with little temperature drop across interface. According to concept, heat pipe enters center of disklike stationary section of joint. There, wicks in central artery of heat pipe separate into multiple strands that lead to concentric channels on rotaryinterface side of stationary disk. Thin layer of liquid sodium/potassium alloy carries heat from one member of rotary joint to other. Liquid conducts heat efficiently while permitting relative motion between members. Polypropylene rings contain liquid without interfering with rotation.

Shauback, R.

1986-01-01

338

Space Domain Awareness for Manned GEO Servicing  

NASA Astrophysics Data System (ADS)

The Defense Advanced Research Projects Agency (DARPA) is embarking on a joint program to service spacecraft in Geosynchronous (GEO) Orbit. This ambitious program, known as R5 (Rendezvous, Refuel, Refurbish, Repair, and Reposition), will develop the technologies required to extend the life of billions of dollars of invested in building, launching and operating GEO spacecraft. Inherent in the R5 program, is the need for high quality awareness of the space domain at GEO. Servicing non-operational spacecraft in GEO will require enhanced debris detect/track and space weather monitoring for crew safety, as well as high resolution characterization of the spacecraft to understand the status of the spacecraft to manifest the repair mission. This paper will briefly describe the GEO space domain sensor and data processing requirements to support the R5 program and outline DARPA’s program plans to develop these capabilities. Distribution Statement A (Approved for Public Release, Distribution Unlimited). DISTAR case 15410.

Blake, T.

2010-09-01

339

Magnetic domains in gadolinium  

Microsoft Academic Search

The bitter patterns of ferromagnetic domains on a (1120) ; crystallographic plane of a gadolinium single crystal are presented. A ; suspension of magnetite particles in xylene, stabilized with a ten millimolar ; concentration of sodium di(ethylhexyl) sulfosuccinate was employed at -5 c- ; C. On the application of a magnetic field, the walls separating adjacent ; domains were observed

R. R. Birss; P. M. Wallis

1963-01-01

340

Support vector domain description  

Microsoft Academic Search

This paper shows the use of a data domain description method, inspired by the support vector machine by Vapnik, called the support vector domain description (SVDD). This data description can be used for novelty or outlier de- tection. A spherically shaped decision boundary around a set of objects is constructed by a set of support vectors describing the sphere boundary.

David M. J. Tax; Robert P. W. Duin

1999-01-01

341

Biased domain walls  

NASA Astrophysics Data System (ADS)

Domain walls form naturally in the early Universe whenever a discrete symmetry is spontaneously broken at some phase transition. When each vacuum is populated equally, it is well known that the domain wall network comes to dominate the energy density of the Universe and causes excessive anisotropy in the cosmic microwave background. We present results for the initial conditions and dynamical evolution of domain wall networks in which one of the degenerate vacua has a population bias over the other. The initial distribution of domain walls is well described by percolation theory. We find that such networks, although they show evidence of a limited scaling regime for a range of biases, do not persist indefinitely. It follows that biased domain wall networks avoid the energy density and anisotropy problems.

Coulson, D.; Lalak, Z.; Ovrut, B.

1996-04-01

342

Protein Domain Histochemistry (PDH)  

PubMed Central

Specialized protein domains bind to posttranslational modifications (PTMs) of proteins, such as phosphorylation or glycosylation. When such PTM-binding protein domains are used as analytical tools, the functional states of cells and tissues can be determined with high precision. Here, we describe the use of recombinant CLEC10A (CD301), a human glycoreceptor of the C-type lectin family, for the detection of ligands in sections from formalin-fixed, paraffin-embedded normal and cancerous mammary tissues. A construct, in which part of the carbohydrate recognition domain (CRD) was deleted, was used as a negative control. In comparison to normal mammary glands, a pronounced staining of tumor tissues was observed. Because the construct with the truncated CRD did not show any tissue staining, the binding of the wild-type glycoreceptor can be attributed to its carbohydrate recognition domain. To distinguish our novel approach from immunohistochemistry, we propose the designation “protein domain histochemistry” (PDH). PMID:23275449

Nollau, Peter; Wolters-Eisfeld, Gerrit; Mortezai, Naghmeh; Kurze, Anna-Katharina; Klampe, Birgit; Debus, Annegret; Bockhorn, Maximilian; Niendorf, Axel

2013-01-01

343

[Prosthetics of metacarpophalangeal joints].  

PubMed

Only a few of the large number of implants developed during the last decades for replacement of the metacarpophalangeal (MCP) joint have proven to be reliable. The rates of loosening and mechanical failure of almost all types of constrained prostheses are so high that their use cannot be recommended at present. For more than 40 years silicone arthroplasty according to Swanson has been regarded as the gold standard in the prosthetic replacement of the MCP joint. In long-term studies this device provided good pain relief and a lasting correction of preoperative ulnar deviation. The degree of patient satisfaction continues to be high after more than 10 years. With the NeuFlex spacer, a modification of the original Swanson implant, a better range of motion and a reduction of wear-related problems is expected. In this study the results of 130 NeuFlex spacers after a mean time of 3.6 years were examined and 82% of the patients were completely pain free. The mobility of the joints improved from 40 degrees preoperatively to 54 degrees after 3.6 years. Radiologically periprosthetic erosions or osteolyses were seen in approximately 15% of implants. A minimal sinking of the stems developed in 24%, a massive one in 6% and 13% of the spacers were broken. Thus the use of the NeuFlex implant resulted in a better range of motion compared to the Swanson spacer, but the problem of radiological appearance remained unchanged. For unlinked prostheses sufficient soft tissue stability is mandatory as well as wear-resistant surface materials. The pyrocarbon prosthesis according to Beckenbaugh is the only implant for which long-term results are available. In a prospective study we evaluated 28 Ascension pyrocarbon prostheses with a mean follow-up of 4 years. Stability was not found to be a problem. Subjective results were satisfactory, the range of motion remained unchanged, however 46% of prosthesis stems exhibited radiolucent seams, 7 prostheses (25%) were rated as loose and 5 of those had to be replaced by a silicone implant. Use of the implant was abandoned, as it was unreliable regarding bony fixation. There are promising concepts in some new prostheses but independent data are still lacking. PMID:17717677

Hilker, A; Miehlke, R-K; Schmidt, K

2007-09-01

344

Healthy Joints Matter What exactly is a joint?  

E-print Network

diet, avoiding injuries, and getting plenty of sleep will help you stay healthy and keep your joints be triggered by an injury to a joint, such as a knee injury that damages the cartilage. · Rheumatoid arthritis arthritis is a term often used to describe arthritis in children. Children can develop almost all types

Baker, Chris I.

345

Passive Ball Capture Joint  

NASA Technical Reports Server (NTRS)

A passive ball capture joint has a sleeve with a plurality of bores distributed about a circumference thereof and formed therethrough at an acute angle relative to the sleeve's longitudinal axis. A spring-loaded retainer is slidingly fitted in each bore and is biased such that, if allowed, will extend at least partially into the sleeve to retain a ball therein. A ring, rotatably mounted about the bores, has an interior wall defining a plurality of shaped races that bear against the spring-loaded retainers. A mechanized rotational force producer is coupled to the ring. The ring can be rotated from a first position (that presses the retainers into the sleeve to lock the ball in place) to a second position (that allows the retainers to springback out of the sleeve to release the ball).

Cloyd, Richard A. (Inventor); Bryan, Thomas C. (Inventor)

2003-01-01

346

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

347

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

348

Teflon-packed flexible joint  

NASA Technical Reports Server (NTRS)

Teflon-packed flexible joint separates the movement of the shaker from the liquid nitrogen hose during the ground testing of cryogenic zero-g equipment. The joint allows the hose to lie on the floor in a stationary position as the shaker moves back and forth, thus, the hose is not subject to violent motion.

Belmont, G. E.

1969-01-01

349

Joint mobility and motor development  

Microsoft Academic Search

The association of joint hypermobility and motor development was sequentially investigated in 715 infants from the ages of 8 to 14 months. Seven joints were evaluated for mobility, and each infant underwent a physical and neurological examination. Parents were given a Denver Developmental Parents' Questionnaire. All subjects with a general developmental delay, systemic illness or syndrome were excluded. The infants

M Jaffe; E Tirosh; A Cohen; Y Taub

1988-01-01

350

Light alloys plates welded joints  

Microsoft Academic Search

In the field described by the topics of the title, there are different ways to achieve the joint. One of them is the spot cold pressure welding. First, the paper presents the experimental results regarding the sharing strength test of the spot cold welded joints. The purpose of the research was to analyze different variant of welding, in order to

Valeriu Georgescu; Mihaela Iordachescu; Bogdan Georgescu

351

Exercise and the Knee Joint.  

ERIC Educational Resources Information Center

This report by the President's Council on Physical Fitness and Sports examines the effects of various forms of physical exercise on the knee joint which, because of its vulnerability, is especially subject to injury. Discussion centers around the physical characteristics of the joint, commonly used measurements for determining knee stability,…

Clarke, H. Harrison, Ed.

1976-01-01

352

Micromechanical model for anisotropic rock joints  

Microsoft Academic Search

Force-deformation relationships of rock joints are important in the study of mechanical behavior of fractured or jointed rocks. Experimental studies have shown that rock joints often exhibit deformation hardening and anisotropic behavior under shearing loads. This paper focuses upon the mathematical modeling of force-deformation behavior of anisotropic rock joints by explicitly considering interaction of asperities on a joint surface. Elastic

Anil Misra

1999-01-01

353

Space Station alpha joint bearing  

NASA Technical Reports Server (NTRS)

Perhaps the most critical structural system aboard the Space Station is the Solar Alpha Rotary Joint which helps align the power generation system with the sun. The joint must provide structural support and controlled rotation to the outboard transverse booms as well as power and data transfer across the joint. The Solar Alpha Rotary Joint is composed of two transition sections and an integral, large diameter bearing. Alpha joint bearing design presents a particularly interesting problem because of its large size and need for high reliability, stiffness, and on orbit maintability. The discrete roller bearing developed is a novel refinement to cam follower technology. It offers thermal compensation and ease of on-orbit maintenance that are not found in conventional rolling element bearings. How the bearing design evolved is summarized. Driving requirements are reviewed, alternative concepts assessed, and the selected design is described.

Everman, Michael R.; Jones, P. Alan; Spencer, Porter A.

1987-01-01

354

Supersymmetric Domain Walls  

E-print Network

We classify the half-supersymmetric "domain walls", i.e. branes of codimension one, in toroidally compactified IIA/IIB string theory and show to which gauged supergravity theory each of these domain walls belong. We use as input the requirement of supersymmetric Wess-Zumino terms, the properties of the E11 Kac-Moody algebra and the embedding tensor formalism. We show that the number of half-supersymmetric domain walls is a multiple of the number of corresponding central charges in the supersymmetry algebra, where the multiplicity is related to the degeneracy of the BPS conditions.

Eric A. Bergshoeff; Axel Kleinschmidt; Fabio Riccioni

2012-06-25

355

Visualizing Knowledge Domains.  

ERIC Educational Resources Information Center

Reviews visualization techniques for scientific disciplines and information retrieval and classification. Highlights include historical background of scientometrics, bibliometrics, and citation analysis; map generation; process flow of visualizing knowledge domains; measures and similarity calculations; vector space model; factor analysis;…

Borner, Katy; Chen, Chaomei; Boyack, Kevin W.

2003-01-01

356

Psychomotor Domain Taxonomy  

NSDL National Science Digital Library

Pennsylvania State University's "Teaching and Learning with Technology" program presents an overview of Bloom's Psychomotor Domain Taxonomy, which is characterized by progressive levels of behaviors from observation to mastery of a physical skill. Definitions and examples are given of the four levels, along with behavioral verbs appropriate for the psychomotor domain. The site also features an extensive directory of links to ideas that will assist in the development of high-quality instruction.

University, Pennsylvania S.

357

Domain wall Skyrmions  

NASA Astrophysics Data System (ADS)

Skyrmions of different dimensions are related by domain walls. We obtain explicit full numerical solutions of various Skyrmion configurations trapped inside a domain wall. We find for the quadratic mass term that multi-Skyrmions are ring shaped and conjecture for the linear mass term, that the lowest-energy state of multi-Skyrmions will consist of charge-2 rings accommodated in a lattice.

Gudnason, Sven Bjarke; Nitta, Muneto

2014-04-01

358

Introduction Joints and the muscle articulation  

E-print Network

: biomechanics, Cephalopoda, electromyography, mus the joint. The morphology of the articulating surfaces and joint capsule controls the range of motion segments of smaller insects use this mechanism. The joint studied here, termed a `muscle articulation

Kier, William M.

359

11 CFR 9034.8 - Joint fundraising.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Joint fundraising. 9034.8 Section 9034.8 Federal... ENTITLEMENTS § 9034.8 Joint fundraising. (a) General. Nothing...this subchapter may engage in joint fundraising with other candidates, political...

2011-01-01

360

11 CFR 9034.8 - Joint fundraising.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Joint fundraising. 9034.8 Section 9034.8 Federal... ENTITLEMENTS § 9034.8 Joint fundraising. (a) General. Nothing...this subchapter may engage in joint fundraising with other candidates, political...

2010-01-01

361

Musculoskeletal US: examining the joints.  

PubMed

Musculoskeletal ultrasound (US) is an excellent tool to diagnose muscle, tendon and ligament injuries, cystic structures and peripheral nerve compression, as well as soft tissue masses, without the risk of ionizing radiation. Musculoskeletal US is now routinely used by a growing number of rheumatology and sports medicine centres throughout UK. In standard clinical practice, US has an extremely useful application in differentiating fluid from soft tissue and identifying the severity of joint inflammation. The work described in this article was carried out to assess patients' feedback regarding the use of US guidance for intra-articular injections and/or the removal of fluid from their inflamed knee joints in a nurse-led clinic. Nineteen patients who had US-guided knee joint injection/aspiration in the clinic were asked to complete a questionnaire regarding their satisfaction with the procedure, and to rate their joint pain and patient global assessment (using numerical visual analogue scale) before the US-guided procedure, and 1 month after. Results revealed a significant improvement (p<0.001) of the joint injection outcome measures and the patients' satisfaction of the US-guided procedure. Therefore, musculoskeletal US can improve two fundamental clinical skills: the clinical diagnosis of joint inflammation, and the accuracy of joint injection/aspiration. This study supports the concept that incorporating musculoskeletal US into clinical practice leads to significant improvements in patient care. It also reveals that US-guided procedures are appreciated by patients. PMID:22584929

El Miedany, Yasser

362

Common Bolted Joint Analysis Tool  

NASA Technical Reports Server (NTRS)

Common Bolted Joint Analysis Tool (comBAT) is an Excel/VB-based bolted joint analysis/optimization program that lays out a systematic foundation for an inexperienced or seasoned analyst to determine fastener size, material, and assembly torque for a given design. Analysts are able to perform numerous what-if scenarios within minutes to arrive at an optimal solution. The program evaluates input design parameters, performs joint assembly checks, and steps through numerous calculations to arrive at several key margins of safety for each member in a joint. It also checks for joint gapping, provides fatigue calculations, and generates joint diagrams for a visual reference. Optimum fastener size and material, as well as correct torque, can then be provided. Analysis methodology, equations, and guidelines are provided throughout the solution sequence so that this program does not become a "black box:" for the analyst. There are built-in databases that reduce the legwork required by the analyst. Each step is clearly identified and results are provided in number format, as well as color-coded spelled-out words to draw user attention. The three key features of the software are robust technical content, innovative and user friendly I/O, and a large database. The program addresses every aspect of bolted joint analysis and proves to be an instructional tool at the same time. It saves analysis time, has intelligent messaging features, and catches operator errors in real time.

Imtiaz, Kauser

2011-01-01

363

Compliant Prosthetic Or Robotic Joint  

NASA Technical Reports Server (NTRS)

Rotation partly free and partly restrained by resilience and damping. Joint includes U-shaped x- and y-axis frames joined by cables that cross in at center piece. The y-axis frame rotates about y-axis on roller bearing within predetermined angular range. The y-axis frame rotates slightly farther when arm strikes stop, because cables can twist. This mimics compliant resistance of knee joint reaching limit of its forward or backward motion. Used in prosthetic device to replace diseased or damage human joint, or in robot linkage to limit movement and cushion overloads.

Kerley, James J.; Eklund, Wayne D.

1989-01-01

364

Imaging of the patellofemoral joint.  

PubMed

The patellofemoral (PF) joint is a complex articulation, with interplay between the osseous and soft tissue structures to maintain the balance between knee mobility and stability. Disorders of the PF joint can be a source of anterior knee pain (AKP). In this article, radiographic and magnetic resonance imaging of the PF joint are reviewed, including normal anatomy, imaging techniques, and imaging-based measurements. Common imaging findings associated with AKP are reviewed, including symptomatic normal variants, tendinopathy, apophysitis, osteoarthritis, chondromalacia patella, trochlear dysplasia, excessive lateralization of tibial tuberosity, patellar maltracking, patellar dislocation and fractures, anterior bursitis, Morel-Lavallée effusions, and fat pad edema. PMID:24993408

Thomas, Stephen; Rupiper, David; Stacy, G Scott

2014-07-01

365

Time Domain Time Domain Description of Linear Systems  

E-print Network

Time Domain Time Domain Description of Linear Systems #12;Time Domain Definition A behavior B: the future of every trajectory is completely determined by its past. #12;Time Domain Theorem Let P() R if it is of the form w(t) = N k=1 rk (t)ek t with rk () C[] an arbitrary polynomial of degree less than nk . #12;Time

Vellekoop, Michel

366

The complexity of joint computation  

E-print Network

Joint computation is the ubiquitous scenario in which a computer is presented with not one, but many computational tasks to perform. A fundamental question arises: when can we cleverly combine computations, to perform them ...

Drucker, Andrew Donald

2012-01-01

367

Joint probabilities and quantum cognition  

E-print Network

In this paper we discuss the existence of joint probability distributions for quantum-like 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.

J. Acacio de Barros

2012-06-26

368

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

369

Biofluid lubrication for artificial joints  

E-print Network

. [33]. It is comprised of three areas as follows: lubrication, friction, and wear. In the natural human joint during lubrication, the same principle applies. The frictional patterns of bearing are adapted by the existence of a lubricant [33.... [33]. It is comprised of three areas as follows: lubrication, friction, and wear. In the natural human joint during lubrication, the same principle applies. The frictional patterns of bearing are adapted by the existence of a lubricant [33...

Pendelton, Alice Mae

2009-05-15

370

Ontology of Domain Analysis Concepts in Software System Design Domain  

Microsoft Academic Search

\\u000a The aim of domain analysis is to extract, identify, capture, organize, and make reusable information used in developing new\\u000a information systems. Many different concepts are used in the area of domain analysis, such as concerns, features, aspects,\\u000a subjects, intentions, roles. Metamodeling of domain concepts by constructing domain ontologies (ontology engineering), taxonomies,\\u000a and meta-models of domain concepts supports flexible, concise, and

Robertas Damasevicius

2010-01-01

371

Optimal domain decomposition strategies  

NASA Technical Reports Server (NTRS)

The primary interest of the authors is in the area of grid generation, in particular, optimal domain decomposition about realistic configurations. A grid generation procedure with optimal blocking strategies has been developed to generate multi-block grids for a circular-to-rectangular transition duct. The focus of this study is the domain decomposition which optimizes solution algorithm/block compatibility based on geometrical complexities as well as the physical characteristics of flow field. The progress realized in this study is summarized in this paper.

Yoon, Yonghyun; Soni, Bharat K.

1995-01-01

372

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

373

49 CFR 213.351 - Rail joints.  

Code of Federal Regulations, 2010 CFR

...Transportation 4 2010-10-01 2010-10-01 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...

2010-10-01

374

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

375

49 CFR 213.351 - Rail joints.  

Code of Federal Regulations, 2013 CFR

...Transportation 4 2013-10-01 2013-10-01 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...

2013-10-01

376

Simplified procedures for designing composite bolted joints  

NASA Technical Reports Server (NTRS)

Simplified procedures are described to design and analyze single and multi-bolt composite joints. Numerical examples illustrate the use of these methods. Factors affecting composite bolted joints are summarized. References are cited where more detailed discussion is presented on specific aspects of composite bolted joints. Design variables associated with these joints are summarized in the appendix.

Chamis, Christos C.

1988-01-01

377

Management of acromioclavicular joint injuries.  

PubMed

Acromioclavicular joint injuries are among the most common shoulder girdle injuries in athletes and most commonly result from a direct force to the acromion with the arm in an adducted position. Acromioclavicular joint injuries often present with associated injuries to the glenohumeral joint, including an increased incidence of superior labrum anterior posterior (SLAP) tears that may warrant further evaluation and treatment. Anteroposterior stability of the acromioclavicular joint is conferred by the capsule and acromioclavicular ligaments, of which the posterior and superior ligaments are the strongest. Superior-inferior stability is maintained by the coracoclavicular (conoid and trapezoid) ligaments. Type-I or type-II acromioclavicular joint injuries have been treated with sling immobilization, early shoulder motion, and physical therapy, with favorable outcomes. Return to activity can occur when normal shoulder motion and strength are obtained and the shoulder is asymptomatic as compared with the contralateral normal extremity. The management of type-III injuries remains controversial and is individualized. While a return to the previous level of functional activity with nonsurgical treatment has been documented in a number of case series, surgical reduction and coracoclavicular ligament reconstruction has been associated with a favorable outcome and can be considered in patients who place high functional demands on their shoulders or in athletes who participate in overhead sports. Surgical management is indicated for high-grade (?type IV) acromioclavicular joint injuries to achieve anatomic reduction of the acromioclavicular joint, reconstruction of the coracoclavicular ligaments, and repair of the deltotrapezial fascia. Outcomes after surgical reconstruction of the coracoclavicular ligaments have been satisfactory with regard to achieving pain relief and return to functional activities, but further improvements in the biomechanical strength of these constructs are necessary to avoid loss of reduction and creep with cyclic loading. PMID:24382728

Li, Xinning; Ma, Richard; Bedi, Asheesh; Dines, David M; Altchek, David W; Dines, Joshua S

2014-01-01

378

Time-domain imaging  

NASA Technical Reports Server (NTRS)

The quest for the highest resolution microwave imaging and principle of time-domain imaging has been the primary motivation for recent developments in time-domain techniques. With the present technology, fast time varying signals can now be measured and recorded both in magnitude and in-phase. It has also enhanced our ability to extract relevant details concerning the scattering object. In the past, the interface of object geometry or shape for scattered signals has received substantial attention in radar technology. Various scattering theories were proposed to develop analytical solutions to this problem. Furthermore, the random inversion, frequency swept holography, and the synthetic radar imaging, have two things in common: (1) the physical optic far-field approximation, and (2) the utilization of channels as an extra physical dimension, were also advanced. Despite the inherent vectorial nature of electromagnetic waves, these scalar treatments have brought forth some promising results in practice with notable examples in subsurface and structure sounding. The development of time-domain techniques are studied through the theoretical aspects as well as experimental verification. The use of time-domain imaging for space robotic vision applications has been suggested.

Tolliver, C. L.

1989-01-01

379

Cellulose binding domain proteins  

DOEpatents

A cellulose binding domain (CBD) having a high affinity for crystalline cellulose and chitin is disclosed, along with methods for the molecular cloning and recombinant production. Fusion products comprising the CBD and a second protein are likewise described. A wide range of applications are contemplated for both the CBD and the fusion products, including drug delivery, affinity separations, and diagnostic techniques. 16 figs.

Shoseyov, O.; Shpiegl, I.; Goldstein, M.; Doi, R.

1998-11-17

380

Cellulose binding domain proteins  

DOEpatents

A cellulose binding domain (CBD) having a high affinity for crystalline cellulose and chitin is disclosed, along with methods for the molecular cloning and recombinant production thereof. Fusion products comprising the CBD and a second protein are likewise described. A wide range of applications are contemplated for both the CBD and the fusion products, including drug delivery, affinity separations, and diagnostic techniques.

Shoseyov, Oded (Karmey Yosef, IL); Shpiegl, Itai (Rehovot, IL); Goldstein, Marc (Davis, CA); Doi, Roy (Davis, CA)

1998-01-01

381

Joint Key-frame Extraction and Object Segmentation for Content-based Video Analysis  

E-print Network

to enrich the semantical meaning of key-frames by incorporating certain templates or domain knowledge [2, 3 semantic levels and involve different features. In this work, we propose a joint key-frame extraction.fan@okstate.edu. Guoliang Fan is the contact author. 1 #12;1 Introduction How to bridge the semantic gap between low

Fan, Guoliang

382

On the Central Limit Theorem for Lozenge Tilings of Sawtooth Domains  

E-print Network

In this note, we consider the distribution of vertical tiles on a horizontal slice through a uniformly random lozenge tiling of a large sawtooth domain. We conjecture that the joint distribution of vertical tiles asymptotically coincides with the joint distribution of eigenvalues of a GUE random matrix if and only if the height of the slice is negligible in comparison to the square root of the height of the domain. We prove that this conjecture holds with respect to a natural family of observables playing the role of moments.

Jonathan Novak

2014-07-28

383

Wavelet-domain hidden Markov models for signal detection and classification  

NASA Astrophysics Data System (ADS)

This paper addresses the problem of detection and classification of complicated signals in noise. Classical detection methods such as energy detectors and linear discriminant analysis do not perform well in many situations of practical interest. We introduce a new approach based on hidden Markov modeling in the wavelet domain. Using training data, we fit a hidden Markov model (HMM) to the wavelet transform to concisely represent its probabilistic time- frequency structure. The HMM provides a natural framework for performing likelihood ratio tests used in signal detection and classification. We compare our approach with classical methods for classification of nonlinear processes, change-point detection, and detection with unknown delay.

Crouse, Matthew S.; Nowak, Robert D.; Mhirsi, K.; Baraniuk, Richard G.

1997-10-01

384

Joint attention and language evolution  

NASA Astrophysics Data System (ADS)

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 (checking attention, following attention, and directing attention) substantially increase the performance of agents in these language games. In particular, the rates of improved performance for the individual attentional mechanisms have the same ordering as that of the emergence of these mechanisms in infants' development. These results suggest that language evolution and joint attentional mechanisms have developed in a co-evolutionary way, and that the evolutionary emergence of the individual attentional mechanisms is ordered just like their developmental emergence.

Kwisthout, Johan; Vogt, Paul; Haselager, Pim; Dijkstra, Ton

2008-06-01

385

[Divorce and joint physical custody].  

PubMed

This work first recalls the definition of joint physical custody, as well as the current legal procedure for obtaining it, its practical implementation, the financial implications for parents, and finally some statistics. Some psychological and psychopathological reflections on the impact of divorce on children are then presented before considering the question of joint physically custody with regard to attachment theory and depending on the age of the child (a great caution seems to be required before three years). The article concludes with a brief discussion of parental alienation syndrome. PMID:24630624

Golse, B

2014-04-01

386

Dual and Joint Degrees Dual and Joint Degrees  

E-print Network

Education plus major program overlap · Use existing degree for simpler approval ­ Argues against joint Degrees Conservative: Security and Simplicity · Protect institutional brand integrity ­ Reputation of institutional education ­ Retain control of institution's degree programs · Maintain (relative) simplicity

387

General joint hypermobility and temporomandibular joint derangement in adolescents  

Microsoft Academic Search

Joint mobility was assessed in each member of an epidemiological sample of 96 girls and 97 boys, 17 years old, and graded by means of the hypermobility score of Beighton et al. Twenty two per cent of the girls and 3% of the boys could perform five or more of the nine manoeuvres. The prevalence of symptoms and signs of

L Westling; A Mattiasson

1992-01-01

388

Technique and application for quantifying dynamic shoulder joint kinematics and glenohumeral joint contact patterns  

E-print Network

The shoulder (glenohumeral) joint has the greatest range of motion of all human joints; as a result, it is particularly vulnerable to dislocation and injury. The ability to accurately measure dynamic in-vivo joint kinematics ...

Massimini, Daniel Frank

2014-01-01

389

Frequency domain measurement systems  

NASA Technical Reports Server (NTRS)

Stable frequency sources and signal processing blocks were characterized by their noise spectra, both discrete and random, in the frequency domain. Conventional measures are outlined, and systems for performing the measurements are described. Broad coverage of system configurations which were found useful is given. Their functioning and areas of application are discussed briefly. Particular attention is given to some of the potential error sources in the measurement procedures, system configurations, double-balanced-mixer-phase-detectors, and application of measuring instruments.

Eischer, M. C.

1978-01-01

390

Bayesian Wavelet Domain Segmentation  

NASA Astrophysics Data System (ADS)

We have recently demonstrated that fully unsupervised segmentations of still images and 2D+T sequences is possible by Bayesian methods, on the basis of a Hidden Markovian Model (HMM) and a Potts-Markov Random Field (PMRF), in the pixel domain. The use of a high number of iterations to reach convergence in a segmentation where the number of segments, or "classes" labels, is important makes the algorithm rather slow for the processing of a large quantity of data like in image sequences. We more recently have worked out a new version of this algorithm by first operating our segmentation in the wavelet transform domain rather than in the direct domain. Doing so, we take advantage of the local decay property, or "peaky" distribution of the wavelet coefficients, in an orthogonal decomposition. This decomposition is a fast pyramidal. O(N2), decomposition, so the Bayesian segmentation is performed only once on the first coarse image then on all sub-bands up to the highest resolution level. Moreover, we have improved our Potts-Markov model in order to take into account the three main orientations of the wavelets band-pass, or so-called, detail, subbands. The main advantage of such an algorithm, in comparison with the direct domain Bayesian segmentation, is that the high frequency coefficients, i.e. the coefficients of all sub-bands except the coarsest, are segmented in only 2 classes : 1 for the weak energy coefficients and 2 for the few, and most representative, high energy coefficients, thus enabling to speed up the convergence process of the segmentation.

Brault, Patrice; Mohammad-Djafari, Ali

2004-11-01

391

FRF based joint dynamics modeling and identification  

NASA Astrophysics Data System (ADS)

Complex structures, such as machine tools, are comprised of several substructures connected to each other through joints to form the assembled structures. Joints can have significant contributions on the behavior of the overall assembly and ignoring joint effects in the design stage may result in considerable deviations from the actual dynamic behavior. The identification of joint dynamics enables us to accurately predict overall assembled dynamics by mathematically combining substructure dynamics through the equilibrium and compatibility conditions at the joint. The essence of joint identification is the determination of the difference between the measured overall dynamics and the rigidly coupled substructure dynamics. In this study, we investigate the inverse receptance coupling (IRC) method and the point-mass joint model, which considers the joint as lumped mass, damping and stiffness elements. The dynamic properties of the joint are investigated using both methods through a finite element (FE) simulation and experimental tests. `100

Mehrpouya, Majid; Graham, Eldon; Park, Simon S.

2013-08-01

392

ECG Feature Extraction using Time Frequency Analysis  

Microsoft Academic Search

\\u000a The proposed algorithm is a novel method for the feature extraction of ECG beats based on Wavelet Transforms. A combination\\u000a of two well-accepted methods, Pan Tompkins algorithm and Wavelet decomposition, this system is implemented with the help of\\u000a MATLAB. The focus of this work is to implement the algorithm, which can extract the features of ECG beats with high accuracy.

Mahesh A. Nair

2009-01-01

393

ECG Feature Extraction using Time Frequency Analysis  

NASA Astrophysics Data System (ADS)

The proposed algorithm is a novel method for the feature extraction of ECG beats based on Wavelet Transforms. A combination of two well-accepted methods, Pan Tompkins algorithm and Wavelet decomposition, this system is implemented with the help of MATLAB. The focus of this work is to implement the algorithm, which can extract the features of ECG beats with high accuracy. The performance of this system is evaluated in a pilot study using the MIT-BIH Arrhythmia database.

Nair, Mahesh A.

394

ECG Feature Extraction using Time Frequency Analysis  

Microsoft Academic Search

The proposed algorithm is a novel method for the feature extraction of ECG beats based on Wavelet Transforms. A combination of two well-accepted methods, Pan Tompkins algorithm and Wavelet decomposition, this system is implemented with the help of MATLAB. The focus of this work is to implement the algorithm, which can extract the features of ECG beats with high accuracy.

Mahesh A. Nair

2010-01-01

395

Time-Frequency Analysis as Probabilistic Inference  

E-print Network

statistically optimal description of the signal (or family of signals). This yields a principled approach for adapting the parameters of the representation. One strategy is to maximize the likelihood (2). In the GTF model, the marginal distribution of the signal... of the uncertainty, which may often be sum- marized by standard deviations for each (or more briefly by the total variance or entropy of the posterior) will depend on the parameters of the noise model, the parameters of the prior, and sometimes (but not always...

Turner, Richard E.

2014-11-06

396

Multi-Domain Learning: When Do Domains Matter? Mahesh Joshi  

E-print Network

- guage processing. A mismatch between training and test domains can negatively impact system accuracy, these algorithms are traditionally evaluated in a balanced la- bel setting, although in practice many multi- domain of these two issues presents a clearer idea about where the field has had success in multi- domain learning

Dredze, Mark

397

Domain Specific vs Domain General: Implications for Dynamic Assessment  

ERIC Educational Resources Information Center

The article responds to the need for evidence-based dynamic assessment. The article is divided into two sections: In Part 1 we examine the scientific answer to the question of how far human mental activities and capabilities are domain general (DG) / domain specific (DS). A highly complex answer emerges from the literature review of domains such…

Kaniel, Shlomo

2010-01-01

398

The temporal relationship between joints and faults  

NASA Astrophysics Data System (ADS)

Examples are presented of three temporal relationships between joints and faults: joints that pre-date faults; joints that are precursors to, or synchronous with, faults; and joints that post-date faults. Emphasis is placed on strike-slip faults in carbonate beds, but other examples are used. General rules are given for identifying the three temporal relationships between joints and faults. Joints that formed before faults can be dilated, sheared or affected by pressure solution during faulting, depending on their orientation in relation to the applied stress system. Faulted joints can preserve some original geometry of a joint pattern, with pinnate joints or veins commonly developing where faulted joints interact. Joints formed synchronously with faults reflect the same stress system that caused the faulting, and tend to increase in frequency toward faults. In contrast, joints that pre- or post-date faults tend not to increase in frequency towards the fault. Joints that post-date a fault may cut across or abut the fault and fault-related veins, without being displaced by the fault. They may also lack dilation near the fault, even if the fault has associated veins. Joints formed either syn- or post-faulting may curve into the fault, indicating stress perturbation around the fault. Different joint patterns may exist across the fault because of mechanical variations. Geometric features may therefore be used in the field to identify the temporal relationships between faults and joints, especially where early joints affect or control fault development, or where the distribution of late joints are influenced by faults.

Peacock, D. C. P.

2001-02-01

399

Unsupervised spatial event detection in targeted domains with applications to civil unrest modeling.  

PubMed

Twitter has become a popular data source as a surrogate for monitoring and detecting events. Targeted domains such as crime, election, and social unrest require the creation of algorithms capable of detecting events pertinent to these domains. Due to the unstructured language, short-length messages, dynamics, and heterogeneity typical of Twitter data streams, it is technically difficult and labor-intensive to develop and maintain supervised learning systems. We present a novel unsupervised approach for detecting spatial events in targeted domains and illustrate this approach using one specific domain, viz. civil unrest modeling. Given a targeted domain, we propose a dynamic query expansion algorithm to iteratively expand domain-related terms, and generate a tweet homogeneous graph. An anomaly identification method is utilized to detect spatial events over this graph by jointly maximizing local modularity and spatial scan statistics. Extensive experiments conducted in 10 Latin American countries demonstrate the effectiveness of the proposed approach. PMID:25350136

Zhao, Liang; Chen, Feng; Dai, Jing; Hua, Ting; Lu, Chang-Tien; Ramakrishnan, Naren

2014-01-01

400

Unsupervised Spatial Event Detection in Targeted Domains with Applications to Civil Unrest Modeling  

PubMed Central

Twitter has become a popular data source as a surrogate for monitoring and detecting events. Targeted domains such as crime, election, and social unrest require the creation of algorithms capable of detecting events pertinent to these domains. Due to the unstructured language, short-length messages, dynamics, and heterogeneity typical of Twitter data streams, it is technically difficult and labor-intensive to develop and maintain supervised learning systems. We present a novel unsupervised approach for detecting spatial events in targeted domains and illustrate this approach using one specific domain, viz. civil unrest modeling. Given a targeted domain, we propose a dynamic query expansion algorithm to iteratively expand domain-related terms, and generate a tweet homogeneous graph. An anomaly identification method is utilized to detect spatial events over this graph by jointly maximizing local modularity and spatial scan statistics. Extensive experiments conducted in 10 Latin American countries demonstrate the effectiveness of the proposed approach. PMID:25350136

Zhao, Liang; Chen, Feng; Dai, Jing; Hua, Ting; Lu, Chang-Tien; Ramakrishnan, Naren

2014-01-01

401

Long-term outcome of multiple joint procedures in haemophilia.  

PubMed

In elderly people with haemophilia (PWH), surgery of more than one joint of the lower extremities might be needed. Multiple joint procedures (MJP) were introduced in 1995, defined as any combination of Total Knee or Total Hip Arthroplasty or Ankle Arthrodesis during one in-hospital stay. The expectation is that by means of such procedures this specific population is able to physically function better for an extended period of time. Thus, they will participate in their society in an optimal way. In this study, we tried to describe an outcome after MJP, including pre- and post-operative pain and range of motion (ROM), and recommend measurement tools. 22 of 37 PWH who underwent MJP between 1995 and 2012 were available for assessment. Pain (WFH score) and range of motion were compared pre and postoperatively. Current outcome was described by VAS per joint, nocturnal and overall pain, MACTAR, Hemophilia Activity List, SF36, and EQ-5D. Mean age at surgery was 50, 3 years (SD 8, 3); mean follow-up 12 years (1-18 years). Pain (VAS) decreased post-surgery (Median 1 - 1, 5), but moderate pain remained. Extension of knees slightly increased, but both knee flexion and ankle plantar and dorsal flexion decreased. PWH reported the ability to stand longer but also pointed at specific problems, e.g. riding a bike (MACTAR). The HAL showed limited activities (functional domains), especially in the 'complex lower extremity' (22, 8/100). The SF36 and EQ-5D showed a mix of physical problems of our population, while experiencing moderate pain and reasonable physical functioning. This led us to the conclusion that adequate follow-up is needed: ROM of all joints, VAS of all joints as well as nocturnal and overall pain, HAL, SF36 and EQ5D. Performance based activities and participation need further attention. PMID:24533953

de Kleijn, P; Sluiter, D; Vogely, H Ch; Lindeman, E; Fischer, K

2014-03-01

402

Flexible joints for thrust vector control  

NASA Technical Reports Server (NTRS)

Flexible joints have been used to achieve thrust vector control over a wide range of sizes of nozzles and have been demonstrated successfully in bench tests and static firings, and are operational on two motors. From these many joints the problems of flexible joints have been defined as establishment of the movable nozzle envelope, definition of the actuation power requirements, definition of the mechanical properties of joint materials, adhesive bonding, test methods, and quality control. These data and problem solutions are contained in a large number of reports. Data relating to joint configuration, design requirements, materials selection, joint design, structural analysis, manufacture, and testing are summarized.

Woodberry, R. F. H.

1975-01-01

403

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

404

Solders in Real Electronic Joints  

NASA Astrophysics Data System (ADS)

Undercooling and recalescence were studied using the differential scanning calorimetry (DSC) method on real electronic systems. Two solder pastes, Sn62.5Pb36.5Ag1 and Sn96.5Ag3Cu0.5, were used for preparation of electronic joints. Various combinations of these solders and soldering pads with different surface finishes such as Cu, Cu-Ni-Au, Cu-Sn, and Cu-Sn99Cu1 were used. During melting of both pastes, the Sn and Sn99Cu1 surface finishes immediately dissolved in the solder and the Cu surface coating was exposed to the melt. Therefore, practically the same undercooling was found for the Cu, Cu-Sn, and Cu-Sn99Cu1 coatings. The lowest undercooling was found for the Cu-Ni-Au surface finish for both solder pastes. If two separated electronic joints were made on the sample, two separate peaks were found in the DSC signal during solidification. In the sample with only one joint, only one exothermic peak was found. These findings were observed for all paste/surface finish combinations. These data were analyzed, showing that this effect is a consequence of undercooling and recalescence: Latent heat released during solidification of the joint increases the surrounding temperature and influences all the processes taking place.

Rudajevová, A.; Dušek, K.

2014-07-01

405

Sea Lion Skeleton (Gliding Joint)  

NSDL National Science Digital Library

Sea lions are vertebrates with both backbones and ribs. The backbone is a gliding joint, allowing the animal to be flexible, while the ribs main function is to protect it's inner organs. The short tail helps to balance the animal while walking on land.

Ketan Patel (California State University, Fullerton;Student, B)

2007-07-14

406

Joint strength in RCS frames  

E-print Network

As part of a National Science Foundation (NSF) program ics. on composite and hybrid systems at Texas A&M University, the objective of this thesis is to investigate the joint strength in reinforced column-steel beam (RCS) special moment frames...

Kirby, Cynthia Dawn

2012-06-07

407

Fellows Celebrated at Joint Assembly  

NASA Astrophysics Data System (ADS)

The 2007 AGU Fellows were presented at the recent Joint Assembly in Acapulco, Mexico. A formal ceremony was held on 25 May 2007, where President Tim Killeen introduced each Fellow and read a brief statement of the achievements for which each had been selected. The presentations were followed by an honors fiesta at which family members and close colleagues further feted the honorees.

2007-06-01

408

JD MADR Joint Degree Description  

E-print Network

schools has been to seek out or offer additional work in alternative dispute resolution to facilitate. In addition, Law School courses LEX 7016 (Alternative Dispute Resolution) and LEX 7616 (NegotiationJD ­ MADR Joint Degree Description Current trends in the legal profession emphasize alternatives

Berdichevsky, Victor

409

Biofluid lubrication for artificial joints  

Microsoft Academic Search

This research investigated biofluid lubrication related to artificial joints using tribological and rheological approaches. Biofluids studied here represent two categories of fluids, base fluids and nanostructured biofluids. Base fluids were studied through comparison of synthetic fluids (simulated body fluid and hyaluronic acid) as well as natural biofluids (from dogs, horses, and humans) in terms of viscosity and fluid shear stress.

Alice Mae Pendleton

2008-01-01

410

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. PMID:24043640

Myers, K. R.; Sgaglione, N. A.; Grande, D. A.

2013-01-01

411

Internet Domain Survey: July 1997  

NSDL National Science Digital Library

Network Wizards recently released their latest Internet Domain Survey (July 1997). Included is information on hosts and domains, distributions of top level domains by hostcount and name, top 100 host names, and a glossary of survey definitions. Users should read the Survey Notes and Observations section for caveats about the data. Archives of previous surveys, as well as links to related domain name information, are available at the web site.

1997-01-01

412

Scientific Reasoning across Different Domains.  

ERIC Educational Resources Information Center

This study seeks to establish which scientific reasoning skills are primarily domain-general and which appear to be domain-specific. The subjects, 12 university undergraduates, each participated in self-directed experimentation with three different content domains. The experimentation contexts were computer-based laboratories in d.c. circuits…

Glaser, Robert; And Others

413

Graph Laplacians and Nodal Domains Turker Biyikoglu  

E-print Network

Graph Laplacians and Nodal Domains T�urker Biyikoglu Graph Laplacians and Nodal Domains � p.1 domains The number of nodal domains of trees hypercubes cographs Graph Laplacians and Nodal Domains � p.2 78 9 10 11 12 Graph Laplacians and Nodal Domains � p.3/20 #12;Nodal Domains x=(-1,4.5,3,-2

Wien, Universität

414

Teachers' Domain: Ionic Bonding  

NSDL National Science Digital Library

This Flash interactive tutorial explores ionic bondingâa type of chemical bond formed between two ions with opposite charges. Learners investigate how the transfer of electrons between atoms creates ions and how the mutual attraction of these charged particles forms ionic bonds. It also discusses trends in the periodic table to help learners comprehend how the structure of an ionic compound relates to its formula. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-08-16

415

Teachers' Domain: Heat Transfer  

NSDL National Science Digital Library

This item is an interactive Flash animation for Grades 5-8 on the topic of heat. Users explore methods of heat transfer and classify examples from everyday life. Three methods of heat transfer are depicted: conduction, convection, and radiation. Teachers' Domain is an NSF-funded pathway of the National Science Digital Library (NSDL). It is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2008-10-21

416

Teachers' Domain: The Atom  

NSDL National Science Digital Library

This Flash interactive activity explores atomic structure at a pace that middle school students can easily understand. It contains 26 animated pages that depict the atomic nucleus and the three primary subatomic particles: electrons, protons, and neutrons. It was designed to give learners a taste of the particles' properties, such as charge and mass, without introducing advanced terminology. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-07-24

417

F-IF Domains  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: For the functions in (a)–(f), List the algebraic operations in order of evaluation. What restrictions does each operation place on the domain of ...

418

Runaway dilatonic domain walls  

SciTech Connect

We explore the stability of domain wall and bubble solutions in theories with compact extra dimensions. The energy density stored inside of the wall can destabilize the volume modulus of a compactification, leading to solutions containing either a timelike singularity or a region where space decompactifies, depending on the metric ansatz. We determine the structure of such solutions both analytically and using numerical simulations, and analyze how they arise in compactifications of Einstein-Maxwell theory and type IIB string theory. The existence of instabilities has important implications for the formation of networks of topological defects and the population of vacua during eternal inflation.

Aguirre, Anthony [SCIPP, University of California, Santa Cruz, California 95064 (United States); Johnson, Matthew C. [California Institute of Technology, Pasadena, California 91125 (United States); Larfors, Magdalena [Arnold Sommerfeld Center fuer Theoretische Physik, Ludwig Maximilians Universitaet, Muenchen (Germany)

2010-02-15

419

Dynamic Ball & Socket Joint Force Simulator  

E-print Network

The stability of an implant in the bone, one factor in joint replacement survival, is usually tested using biaxial fatigue loading. These loading protocols do not replicate physiological loading conditions. The Dynamic Ball and Socket Joint Force...

Farmer, Ryan Neal

2011-07-26

420

26 - LMFBR Flexible Pipe Joint Development.  

National Technical Information Service (NTIS)

Objective is the qualification of a PLBR-size primary loop flexible piping joint to the ASME Band PVC rules. Progress and activities are reported for: Class 1 flexible joint code approval support, engineering and design, material development, component te...

R. V. Anderson

1978-01-01

421

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

422

Older Person's Guide to Joint Replacement  

MedlinePLUS

... Osteoporosis Related Documents PDF Older Person’s Guide to Joint Replacement Download Join our e-newsletter! Resources Older Person’s Guide to Joint Replacement Tools and Tips Printer-friendly PDF Click here ...

423

United States Bone and Joint Decade  

MedlinePLUS

... President's Corner USBJI Board Staff Global Bone & Joint Decade Contact Us Bylaws Members & Friends Founding Members Participating ... Meeting 2012 Resources Musculoskeletal Summits Bone and Joint Decade Global Network Conference 2009 2011 Musculoskeletal Summit 2013 ...

424

38 CFR 4.45 - The joints.  

...weight-bearing are related considerations. For the purpose of rating disability from arthritis, the shoulder, elbow, wrist, hip, knee, and ankle are considered major joints; multiple involvements of the interphalangeal, metacarpal and carpal joints of the...

2014-07-01

425

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

426

of Concrete Pavements Joint PerformanCe  

E-print Network

practitioners under- stand how to optimize concrete pavement joint perfor- mance through the identificationof Concrete Pavements Joint PerformanCe interim Guide for optimum JUNE 2012 #12;#12;Interim Guide for Optimum Joint Performance of Concrete Pavements i Technical Report Documentation Page 1. Report No. 2

427

Navigating Joint Projects in Telephone Conversations  

ERIC Educational Resources Information Center

Conversation coordinates joint activities and the joint projects that compose them. Participants coordinate (1) vertical transitions on entering and exiting joint projects; and (2) horizontal transitions in continuing within them. Transitions are coordinated using project markers such as uh-huh, yeah, right, and okay. In the authors' proposal,…

Bangerter, Adrian; Clark, Herbert H.; Katz, Anna R.

2004-01-01

428

Sealing of Small Movement Bridge Expansion Joints.  

National Technical Information Service (NTIS)

Sealing of bridge expansion joint systems is important to protect the structural components below the joint from damage due to water, salt, and other roadway debris. A new elastomeric foam-type joint sealant has been developed for sealing small-movement b...

R. B. Malla, M. T. Shaw, M. R. Shrestha, S. Boob

2006-01-01

429

Joints in deployable space truss structures  

NASA Technical Reports Server (NTRS)

Since the response of deployable structural concepts being considered for the Large Deployable Reflector (LDR) backup structure will be dominated by the response of joints, the joint characteristics are significant. An overview is given of the research activities at LaRC on the static behavior of joints for deployable space truss structures. Since a pin-clevis-type joint will be utilized in deployable structures, an experimental research program to characterize the joint parameters which affect stiffness was conducted. An experimental research program was conducted on a second type of joint, referred to as a near-center latch joint. It was used in the center of members on the deployable truss structure for the Control of Flexible Structures (COFS) flight experiment. The test results of the near-center latch joint and the member with the joints indicated that the stiffness of the near-center joint is linear and stiffer than the stiffness of the total member, and that non-linearities in the stiffness characteristics of the total member were due to bending introduced at the ends of the member. The resulting data indicates that stiff linear folding joints can be designed and that bending load paths should be avoided whenever possible. In summary, for deployable structures, special attention to the joint and the structure design is required to minimize the undesirable structural non-linearities.

Rhodes, M.

1988-01-01

430

Joint Invariant Signatures Peter J. Olver  

E-print Network

Joint Invariant Signatures Peter J. Olver School of Mathematics University of Minnesota Minneapolis­Carlo Rota Abstract. A new, algorithmic theory of moving frames is applied to classify joint invariants and joint differential invariants of transformation groups. Equivalence and sym- metry properties

Olver, Peter

431

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

432

International Joint Ventures: A Welfare Analysis  

Microsoft Academic Search

We examine the welfare implications of joint venture formation between an MNC and a firm from a less developed country (LDC). For symmetric firms greater the market size, greater is the incentive for joint venture formation. Moreover, joint venture formation is welfare reducing for both high, as well as low levels of demand. However, if the MNC is more efficient

Indrani Roy Chowdhury; Prabla Roy Chowdhury

2002-01-01

433

49 CFR 234.233 - Rail joints.  

Code of Federal Regulations, 2013 CFR

... 4 2013-10-01 2013-10-01 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...

2013-10-01

434

49 CFR 234.233 - Rail joints.  

Code of Federal Regulations, 2010 CFR

... 4 2010-10-01 2010-10-01 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...

2010-10-01

435

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

436

Continuous Domain Theory in Logical Form School of Computer Science, University of Birmingham  

E-print Network

birthday Abstract. In 1987 Samson Abramsky presented Domain Theory in Log- ical Form in the Logic interesting objects to study. It was only during my period as a post-doc working for Samson at Imperial Science, edited jointly by him, Dov Gabbay and Tom Maibaum. I accepted but admittedly had little idea

Jung, Achim

437

Shift-invariant denoising using wavelet-domain hidden Markov trees  

Microsoft Academic Search

Wavelet-domain hidden Markov models have proven to be useful tools for statistical signal and image processing. The hidden Markov tree (HMT) model captures the key features of the joint statistics of the wavelet coefficients of real-world data. One potential drawback to the HMT framework is the need for computationally expensive iterative training (using the EM algorithm, for example). We use

Justin K. Romberg; Hyeokho Choi; Richard G. Baraniuk

1999-01-01

438

Laser speckle images research based on wavelet-domain hidden Markov models  

Microsoft Academic Search

Wavelet-domain hidden Markov models have proven to be useful tools for statistical signal and image processing. The hidden Markov tree (HMT) model captures the key features of the joint probability density of the wavelet coefficients of laser speckle images. In this paper, considering both the characteristics of laser speckle images after log- transformed and the statistical features of wavelet transformed

Wang Junli; Yin Fuchang; Song Zhengxun

2011-01-01

439

Bayesian tree-structured image modeling using wavelet-domain hidden Markov models  

Microsoft Academic Search

Wavelet-domain hidden Markov models have proven to be useful tools for statistical signal and image processing. The hidden Markov tree (HMT) model captures the key features of the joint probability density of the wavelet coefficients of real-world data. One potential drawback to the HMT framework is the need for computationally expensive iterative training to fit an HMT model to a

Justin K. Romberg; Hyeokho Choi; Richard G. Baraniuk

2001-01-01

440

Inspection of plastic weld joints with terahertz imaging  

NASA Astrophysics Data System (ADS)

Polymers cover the whole range from commodities to high-tech applications. Plastic products have also gained in importance for construction purposes. This draws the attention to joining techniques like welding. Common evaluation of the weld quality is mostly mechanical and destructive. Existing non-destructive techniques are mostly not entirely reliable or economically inefficient. Here, we demonstrate the potential of terahertz time-domain spectroscopy imaging as a non-destructive testing tool for the inspection of plastic weld joints. High-density polyethylene sheets welded in a lap joint with varying quality serve as samples for terahertz transmission measurements. Imperfections within the weld contact area can clearly be detected by displaying the transmitted intensity in a limited frequency range. Contaminations such as metal or sand are identified since they differ significantly from the polymer in the terahertz image. Furthermore, this new and promising technique is capable of detecting the boundaries of a weld contact area. Aside from revealing a contrast between a proper weld joint and no material connection, the size of an air gap between two plastic sheets can be determined by considering the characteristic frequency-dependent transmission through the structure: The spectral positions of the maxima and minima allow for the calculation of the air layer thickness.

Wietzke, S.; Krumbholz, N.; Jördens, C.; Baudrit, B.; Bastian, M.; Koch, M.

2007-06-01

441

Foldable self-erecting joint  

NASA Technical Reports Server (NTRS)

The invention relates to a foldable self erecting joint which may be used to deploy the tetratruss frame of the proposed shuttle launched triangular space station. The frame must be folded into the payload bay of the space shuttle orbiter. To deploy the frame the tubes are automatically unfolded and once in position should remain safely. A pair of hinged, tubular members in which the hinging is located at corresponding portions of the members are used. The opposite edge portions are connected by spring-based toggle links which in the unfolded position of the members are nested against one of the members in substantial alignment and over-center for securely locking the joint in the unfolded position.

Pelischek, T. E. (inventor)

1986-01-01

442

Joint stabilizing projects in defense  

SciTech Connect

Joint defensive projects could increase stability and decrease the alert rates of strategic forces. Areas include the defense of the US, Commonwealth of Independent States (CIS), and their allies against third world threats; protection against each other`s accidental or unauthorized launches; and defense against intentional attacks. The most promising area appears to be defining interfaces for the handover of satellite warning and trajectory information, which applies to most phases of theater defense and mutual protection. 19 refs.

Canavan, G.H.; Browne, J.C.; Joseph, R.J.

1992-06-01

443

Joint stabilizing projects in defense  

SciTech Connect

Joint defensive projects could increase stability and decrease the alert rates of strategic forces. Areas include the defense of the US, Commonwealth of Independent States (CIS), and their allies against third world threats; protection against each other's accidental or unauthorized launches; and defense against intentional attacks. The most promising area appears to be defining interfaces for the handover of satellite warning and trajectory information, which applies to most phases of theater defense and mutual protection. 19 refs.

Canavan, G.H.; Browne, J.C.; Joseph, R.J.

1992-06-01

444

Hydraulic fracturing of jointed formations  

SciTech Connect

Measured by volume, North America's largest hydraulic fracturing operations have been conducted at Fenton Hill, New Mexico to create geothermal energy reservoirs. In the largest operation 21,000 m/sup 3/ of water were injected into jointed granitic rock at a depth of 3.5 km. Microearthquakes induced by this injection were measured with geophones placed in five wells drilled into, or very close, to the reservoir, as well as 11 surface seismometers. The large volume of rock over which the microearthquakes were distributed indicates a mechanism of hydraulic stimulation which is at odds with conventional fracturing theory, which predicts failure along a plane which is perpendicular to the least compressive earth stress. A coupled rock mechanics/fluid flow model provides much of the explanation. Shear slippage along pre-existing joints in the rock is more easily induced than conventional tensile failure, particularly when the difference between minimum and maximum earth stresses is large and the joints are oriented at angles between 30 and 60 degrees to the principal earth stresses, and a low viscosity fluid like water is injected. Shear slippage results in local redistribution of stresses, which allows a branching, or dendritic, stimulation pattern to evolve, in agreement with the patterns of microearthquake locations. These results are qualitatively similar to the controversial process known as ''Kiel'' fracturing, in which sequential injections and shut-ins are repeated to create dendritic fractures for enhanced oil and gas recovery. However, we believe that the explanation is shear slippage of pre-existing joints and stress redistribution, not proppant bridging and fluid blocking as suggested by Kiel. 15 refs., 10 figs.

Murphy, H.D.; Fehler, M.C.

1986-01-01

445

The Joint Damping Experiment (JDX)  

NASA Technical Reports Server (NTRS)

The Joint Damping Experiment (JDX), flown on the Shuttle STS-69 Mission, is designed to measure the influence of gravity on the structural damping of a high precision three bay truss. Principal objectives are: (1) Measure vibration damping of a small-scale, pinjointed truss to determine how pin gaps give rise to gravity-dependent damping rates; (2) Evaluate the applicability of ground and low-g aircraft tests for predicting on-orbit behavior; and (3) Evaluate the ability of current nonlinear finite element codes to model the dynamic behavior of the truss. Damping of the truss was inferred from 'Twang' tests that involve plucking the truss structure and recording the decay of the oscillations. Results are summarized as follows. (1) Damping, rates can change by a factor of 3 to 8 through changing the truss orientation; (2) The addition of a few pinned joints to a truss structure can increase the damping by a factor as high as 30; (3) Damping is amplitude dependent; (4) As gravity induced preloads become large (truss long axis perpendicular to gravity vector) the damping is similar to non-pinjointed truss; (5) Impacting in joints drives higher modes in structure; (6) The torsion mode disappears if gravity induced preloads are low.

Folkman, Steven L.; Bingham, Jeff G.; Crookston, Jess R.; Dutson, Joseph D.; Ferney, Brook D.; Ferney, Greg D.; Rowsell, Edwin A.

1997-01-01

446

CDD: a conserved domain database for interactive domain family analysis  

Microsoft Academic Search

The conserved domain database (CDD) is part of NCBI's Entrez database system and serves as a primary resource for the annotation of conserved domain footprints on protein sequences in Entrez. Entrez's global query interface can be accessed at http:\\/\\/www.ncbi.nlm.nih.gov\\/Entrez and will search CDD and many other databases. Domain annota- tion for proteins in Entrez has been pre-computed and is readily

Aron Marchler-bauer; John B. Anderson; Myra K. Derbyshire; Carol Deweese-scott; Noreen R. Gonzales; Marc Gwadz; Luning Hao; Siqian He; David I. Hurwitz; John D. Jackson; Zhaoxi Ke; Dmitri M. Krylov; Christopher J. Lanczycki; Cynthia A. Liebert; Chunlei Liu; Fu Lu; Shennan Lu; Gabriele H. Marchler; Mikhail Mullokandov; James S. Song; Narmada Thanki; Roxanne A. Yamashita; Jodie J. Yin; Dachuan Zhang; Stephen H. Bryant

2007-01-01

447

Domain-domain interaction in cytochrome P450BM3  

Microsoft Academic Search

The influence of ionic strength on the interactions between individually expressed functional domains of cytochrome P450BM-3 and the domains in the holoenzyme has been analyzed by spectrophotometric and fluorometric techniques. High ionic strength facilitated electron transfer from NADPH to the FMN moiety of the reductase domain (BMR) of P450BM-3 and did not affect the first electron transfer from FMN to

I. Sevrioukova; J. A. Peterson

1996-01-01

448

Benefits of multi-domain feature of mismatch negativity extracted by non-negative tensor factorization from EEG collected by low-density array.  

PubMed

Through exploiting temporal, spectral, time-frequency representations, and spatial properties of mismatch negativity (MMN) simultaneously, this study extracts a multi-domain feature of MMN mainly using non-negative tensor factorization. In our experiment, the peak amplitude of MMN between children with reading disability and children with attention deficit was not significantly different, whereas the new feature of MMN significantly discriminated the two groups of children. This is because the feature was derived from multi-domain information with significant reduction of the heterogeneous effect of datasets. PMID:23186274

Cong, Fengyu; Phan, Anh Huy; Zhao, Qibin; Huttunen-Scott, Tiina; Kaartinen, Jukka; Ristaniemi, Tapani; Lyytinen, Heikki; Cichocki, Andrzej

2012-12-01

449

Analysis of NSTX TF Joint Voltage Measurements  

SciTech Connect

This report presents findings of analyses of recorded current and voltage data associated with 72 electrical joints operating at high current and high mechanical stress. The analysis goal was to characterize the mechanical behavior of each joint and thus evaluate its mechanical supports. The joints are part of the toroidal field (TF) magnet system of the National Spherical Torus Experiment (NSTX) pulsed plasma device operating at the Princeton Plasma Physics Laboratory (PPPL). Since there is not sufficient space near the joints for much traditional mechanical instrumentation, small voltage probes were installed on each joint and their voltage monitoring waveforms have been recorded on sampling digitizers during each NSTX ''shot''.

Woolley R

2005-10-07

450

Ultrasonic Probing Of Complexly Shaped Joints  

NASA Technical Reports Server (NTRS)

Technique developed involves use of ultrasonics to inspect first bond surfaces of solid-rocket-motor joints. By fitting pieces of insulating materials to mate exactly with complicated shapes of affected parts of insulation, complicated shapes redefined into simpler ones probed more easily. When technique used to insonify from insulation side, one readily detects difference between disbond and good bond. Same technique applied to field tang joints, field clevis joints, and aft-dome-to-fixed-nozzle-housing attachment points. Although developed for inspecting joints in solid rocket motors, also applicable to nondestructive evaluation of other complicated joints.

Madaras, Eric I.

1993-01-01

451

Gap Domain Wall Fermions  

E-print Network

I demonstrate that the chiral properties of Domain Wall Fermions (DWF) in the large to intermediate lattice spacing regime of QCD, 1 to 2 GeV, are significantly improved by adding to the action two standard Wilson fermions with supercritical mass equal to the negative DWF five dimensional mass. Using quenched DWF simulations I show that the eigenvalue spectrum of the transfer matrix Hamiltonian develops a substantial gap and that the residual mass decreases appreciatively. Furthermore, I confirm that topology changing remains active and that the hadron spectrum of the added Wilson fermions is above the lattice cutoff and therefore is irrelevant. I argue that this result should also hold for dynamical DWF and furthermore that it should improve the chiral properties of related fermion methods.

Pavlos M. Vranas

2006-06-22

452

Teachers' Domain: Barfing Pumpkin  

NSDL National Science Digital Library

This 2-minute video demonstrates chemical reaction in an amusing and highly visual way. Water, dish soap, and potassium iodide are mixed and placed inside a carved plastic pumpkin. Hydrogen peroxide is added last. The reaction is immediate and dramatic: soap bubbles come pouring out of the mouth, nose and eyes of the pumpkin. Resource also includes teacher's guide and assessment. Editor's Note: In a chemical reaction, properties of the original substances change as new substances with different properties are formed. The molecular structure of the substances is altered irreversibly. This video is part of "Lessons in Matter and Energy" by WOSU Public Media. See related materials for a link to the full collection, also available for iTunes viewing. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-06-23

453

Teachers' Domain: Banana Hammer  

NSDL National Science Digital Library

This 3-minute video demonstrates simple physical change as a banana is frozen in liquid nitrogen and used to hammer a nail into a piece of wood. Resource also includes teacher's guide, assessment, and background information. Editor's Note: Physical changes in matter are reversible and can include changes in color, shape, size, texture and state of matter. This video is part of "Lessons in Matter and Energy" by WOSU Public Media. See related materials for a link to the full collection, also available as a podcast. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-06-23

454

Teachers' Domain: Dust Explosion  

NSDL National Science Digital Library

This video package illustrates the hazard of dust explosionsâspecifically, how a material that is not generally flammable suddenly becomes combustible when its surface area is increased. The featured chemical is lycopodium powder, which is not especially flammable in normal circumstances. But disperse it into the air, bring a flame close by and.....KABOOM. (Video may be viewed in slow motion.) Editor's Note: When a substance rapidly reacts with oxygen, energy is released in the form of heat and/or light. This type of exothermic reaction is known as combustion. This resource will be especially useful in helping students see that many factors can affect combustion: temperature, the concentration of the reactants, and surface area of the fuel. Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-06-27

455

Teachers' Domain: Biotechnology  

NSDL National Science Digital Library

Funded by the Amgen Foundation, the Teachers' Domain Biotechnology website provides resources on this broad field for educators to use in their classrooms. The materials are divided into four primary areas, including "Applications", "Careers", and "Tools and Techniques". In the "Applications" area, visitors will find over fifteen activities that include "Animal Cloning 101" and "DNA Extraction". Each resource contains an interactive component, and visitors are free to use them as they see fit. In the "Careers" area, visitors can listen to scientists like Andres Berrio talk about his work in biotechnology. The "Tools and Techniques" area contains some rather useful links on how to prepare agarose gel for use in gel electrophoresis and an interactive activity about gene cloning. The site is rounded out by the inclusion of a lesson plan that will help students learn how biotechnology can be used to detect and treat disease.

456

Teachers' Domain: Virtual Pendulum  

NSDL National Science Digital Library

This interactive Shockwave simulation, produced by PBS Zoom, lets users explore pendulum motion in a unique game-like format. Swing it back and forth from different heights and change the length of the string. But now it gets more complicated: the user can jump to another planet to see how changing gravity affects the motion of the pendulum. Users can also explore why the pendulum traces out a flower-shaped pattern rather than a straight line. (This occurs because of Earth's rotation -- making it seem as though the pendulum is turning when, actually, the earth is turning.) The simulation can change the rate of planetary rotation to show what the pattern would look like on a fast or slow-spinning planet. The game ends by putting all four variables together. Don't miss the supplementary background information and warm-up questions provided by Teachers' Domain to accompany this activity.

2010-10-12

457

Space Domain Awareness (SDA)  

NASA Astrophysics Data System (ADS)

While Space Domain Awareness (SDA), including all of space surveillance and characterization of all space objects and environments, is critical for national and economic security, SDA capabilities cannot be developed independent of cost. This presentation will describe a new approach to SDA being developed by the Defense Advanced Projects Agency (DARPA) and other agencies. This approach endeavors to integrate the data from a wide range of current and future SDA capabilities for a fraction of the current costs by utilizing a new methodology for obtaining data. This approach will not just provide more SDA data for a reduced cost, but has the potential to also increase the amount of knowledge gained from the data. Distribution Statement: A (Approved for Public Release, Distribution Unlimited)

Blake, T.

2011-09-01

458

Teachers' Domain: Gooey Gak  

NSDL National Science Digital Library

This module explores complex fluids, mixtures that have characteristics of more than one phase of matter. It features a video of cornstarch "coming to life" -- when combined with water, the resulting mixture becomes a non-Newtonian fluid with properties of both a solid and a liquid, depending on the amount of pressure or force applied to it. In a related hands-on activity, learners make a polymer called "Gak" from borax powder, glue, and water. The experiment is a springboard for teaching about polymers, long-chained molecules consisting of smaller repeating molecule units (known as monomers). Teachers' Domain is a growing collection of more than 1,000 free educational resources compiled by researchers and experienced teachers to promote the use of digital resources in the classroom.

2011-08-18

459

Domain Filtering Consistencies  

E-print Network

Enforcing local consistencies is one of the main features of constraint reasoning. Which level of local consistency should be used when searching for solutions in a constraint network is a basic question. Arc consistency and partial forms of arc consistency have been widely studied, and have been known for sometime through the forward checking or the MAC search algorithms. Until recently, stronger forms of local consistency remained limited to those that change the structure of the constraint graph, and thus, could not be used in practice, especially on large networks. This paper focuses on the local consistencies that are stronger than arc consistency, without changing the structure of the network, i.e., only removing inconsistent values from the domains. In the last five years, several such local consistencies have been proposed by us or by others. We make an overview of all of them, and highlight some relations between them. We compare them both theoretically and experimentally, considering their pruning e...

Bessiere, C; 10.1613/jair.834

2011-01-01

460

ModelingModeling Domain InterplayDomain Interplay  

E-print Network

Schizophrenia Cognitions (altered processing) Mood Mania Aggression Impulsivity Bipolar depression Anxiety Activity Mood Mania Cognitions OCD Aggression Impulsivity #12;Domain interplay concept Kalueff et al

Kalueff, Allan V.

461

Multifunctionalities driven by ferroic domains  

NASA Astrophysics Data System (ADS)

Considerable attention has been paid to ferroic systems in pursuit of advanced applications in past decades. Most recently, the emergence and development of multiferroics, which exhibit the coexistence of different ferroic natures, has offered a new route to create functionalities in the system. In this manuscript, we step from domain engineering to explore a roadmap for discovering intriguing phenomena and multifunctionalities driven by periodic domain patters. As-grown periodic domains, offering exotic order parameters, periodic local perturbations and the capability of tailoring local spin, charge, orbital and lattice degrees of freedom, are introduced as modeling templates for fundamental studies and novel applications. We discuss related significant findings on ferroic domain, nanoscopic domain walls, and conjunct heterostructures based on the well-organized domain patterns, and end with future prospects and challenges in the field.

Yang, J. C.; Huang, Y. L.; He, Q.; Chu, Y. H.

2014-08-01

462

Multi-Domain Learning: When Do Domains Matter? Mahesh Joshi  

E-print Network

of domains in statistical natural lan- guage processing. A mismatch between training and test domains can, these algorithms are traditionally evaluated in a balanced class la- bel setting, although in practice many multi? An under- standing of these two issues presents a clearer idea about where the field has had success

Cohen, William W.

463

Stabilization of the sacroiliac joint.  

PubMed

Lower back pain and pain involving the area of the posterior iliac spine are extremely common. Degeneration of the sacroiliac joint (SIJ) is one potential cause for lower back pain and pain radiating into the groin or buttocks. Degenerative changes to the lumbar spine and sacroiliac joints are common. A recent study evaluating SIJ abnormalities in a primary low back pain population d