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Sample records for waveform cross-correlation techniques

  1. Auto-correlation based intelligent technique for complex waveform presentation and measurement

    International Nuclear Information System (INIS)

    Rana, K P S; Singh, R; Sayann, K S

    2009-01-01

    Waveform acquisition and presentation forms the heart of many measurement systems. Particularly, data acquisition and presentation of repeating complex signals like sine sweep and frequency-modulated signals introduces the challenge of waveform time period estimation and live waveform presentation. This paper presents an intelligent technique, for waveform period estimation of both the complex and simple waveforms, based on the normalized auto-correlation method. The proposed technique is demonstrated using LabVIEW based intensive simulations on several simple and complex waveforms. Implementation of the technique is successfully demonstrated using LabVIEW based virtual instrumentation. Sine sweep vibration waveforms are successfully presented and measured for electrodynamic shaker system generated vibrations. The proposed method is also suitable for digital storage oscilloscope (DSO) triggering, for complex signals acquisition and presentation. This intelligence can be embodied into the DSO, making it an intelligent measurement system, catering wide varieties of the waveforms. The proposed technique, simulation results, robustness study and implementation results are presented in this paper.

  2. Remote detection of weak aftershocks of the DPRK underground explosions using waveform cross correlation

    Science.gov (United States)

    Le Bras, R.; Rozhkov, M.; Bobrov, D.; Kitov, I. O.; Sanina, I.

    2017-12-01

    Association of weak seismic signals generated by low-magnitude aftershocks of the DPRK underground tests into event hypotheses represent a challenge for routine automatic and interactive processing at the International Data Centre (IDC) of the Comprehensive Nuclear-Test-Ban Treaty Organization, due to the relatively low station density of the International Monitoring System (IMS) seismic network. Since 2011, as an alternative, the IDC has been testing various prototype techniques of signal detection and event creation based on waveform cross correlation. Using signals measured by seismic stations of the IMS from DPRK explosions as waveform templates, the IDC detected several small (estimated mb between 2.2 and 3.6) seismic events after two DPRK tests conducted on September 9, 2016 and September 3, 2017. The obtained detections were associated with reliable event hypothesis and then used to locate these events relative to the epicenters of the DPRK explosions. We observe high similarity of the detected signals with the corresponding waveform templates. The newly found signals also correlate well between themselves. In addition, the values of the signal-to-noise ratios (SNR) estimated using the traces of cross correlation coefficients, increase with template length (from 5 s to 150 s), providing strong evidence in favour of their spatial closeness, which allows interpreting them as explosion aftershocks. We estimated the relative magnitudes of all aftershocks using the ratio of RMS amplitudes of the master and slave signal in the cross correlation windows characterized by the highest SNR. Additional waveform data from regional non-IMS stations MDJ and SEHB provide independent validation of these aftershock hypotheses. Since waveform templates from any single master event may be sub-efficient at some stations, we have also developed a method of joint usage of the DPRK and the biggest aftershocks templates to build more robust event hypotheses.

  3. Generating Correlated QPSK Waveforms By Exploiting Real Gaussian Random Variables

    KAUST Repository

    Jardak, Seifallah

    2012-11-01

    The design of waveforms with specified auto- and cross-correlation properties has a number of applications in multiple-input multiple-output (MIMO) radar, one of them is the desired transmit beampattern design. In this work, an algorithm is proposed to generate quadrature phase shift- keying (QPSK) waveforms with required cross-correlation properties using real Gaussian random-variables (RV’s). This work can be considered as the extension of what was presented in [1] to generate BPSK waveforms. This work will be extended for the generation of correlated higher-order phase shift-keying (PSK) and quadrature amplitude modulation (QAM) schemes that can better approximate the desired beampattern.

  4. Generating Correlated QPSK Waveforms By Exploiting Real Gaussian Random Variables

    KAUST Repository

    Jardak, Seifallah; Ahmed, Sajid; Alouini, Mohamed-Slim

    2012-01-01

    The design of waveforms with specified auto- and cross-correlation properties has a number of applications in multiple-input multiple-output (MIMO) radar, one of them is the desired transmit beampattern design. In this work, an algorithm is proposed to generate quadrature phase shift- keying (QPSK) waveforms with required cross-correlation properties using real Gaussian random-variables (RV’s). This work can be considered as the extension of what was presented in [1] to generate BPSK waveforms. This work will be extended for the generation of correlated higher-order phase shift-keying (PSK) and quadrature amplitude modulation (QAM) schemes that can better approximate the desired beampattern.

  5. MIMO-OFDM Chirp Waveform Diversity Design and Implementation Based on Sparse Matrix and Correlation Optimization

    Directory of Open Access Journals (Sweden)

    Wang Wen-qin

    2015-02-01

    Full Text Available The waveforms used in Multiple-Input Multiple-Output (MIMO Synthetic Aperture Radar (SAR should have a large time-bandwidth product and good ambiguity function performance. A scheme to design multiple orthogonal MIMO SAR Orthogonal Frequency Division Multiplexing (OFDM chirp waveforms by combinational sparse matrix and correlation optimization is proposed. First, the problem of MIMO SAR waveform design amounts to the associated design of hopping frequency and amplitudes. Then a iterative exhaustive search algorithm is adopted to optimally design the code matrix with the constraints minimizing the block correlation coefficient of sparse matrix and the sum of cross-correlation peaks. And the amplitudes matrix are adaptively designed by minimizing the cross-correlation peaks with the genetic algorithm. Additionally, the impacts of waveform number, hopping frequency interval and selectable frequency index are also analyzed. The simulation results verify the proposed scheme can design multiple orthogonal large time-bandwidth product OFDM chirp waveforms with low cross-correlation peak and sidelobes and it improves ambiguity performance.

  6. Generation of correlated finite alphabet waveforms using gaussian random variables

    KAUST Repository

    Jardak, Seifallah

    2014-09-01

    Correlated waveforms have a number of applications in different fields, such as radar and communication. It is very easy to generate correlated waveforms using infinite alphabets, but for some of the applications, it is very challenging to use them in practice. Moreover, to generate infinite alphabet constant envelope correlated waveforms, the available research uses iterative algorithms, which are computationally very expensive. In this work, we propose simple novel methods to generate correlated waveforms using finite alphabet constant and non-constant-envelope symbols. To generate finite alphabet waveforms, the proposed method map the Gaussian random variables onto the phase-shift-keying, pulse-amplitude, and quadrature-amplitude modulation schemes. For such mapping, the probability-density-function of Gaussian random variables is divided into M regions, where M is the number of alphabets in the corresponding modulation scheme. By exploiting the mapping function, the relationship between the cross-correlation of Gaussian and finite alphabet symbols is derived. To generate equiprobable symbols, the area of each region is kept same. If the requirement is to have each symbol with its own unique probability, the proposed scheme allows us that as well. Although, the proposed scheme is general, the main focus of this paper is to generate finite alphabet waveforms for multiple-input multiple-output radar, where correlated waveforms are used to achieve desired beampatterns. © 2014 IEEE.

  7. Perspectives of Cross-Correlation in Seismic Monitoring at the International Data Centre

    Science.gov (United States)

    Bobrov, Dmitry; Kitov, Ivan; Zerbo, Lassina

    2014-03-01

    We demonstrate that several techniques based on waveform cross-correlation are able to significantly reduce the detection threshold of seismic sources worldwide and to improve the reliability of arrivals by a more accurate estimation of their defining parameters. A master event and the events it can find using waveform cross-correlation at array stations of the International Monitoring System (IMS) have to be close. For the purposes of the International Data Centre (IDC), one can use the spatial closeness of the master and slave events in order to construct a new automatic processing pipeline: all qualified arrivals detected using cross-correlation are associated with events matching the current IDC event definition criteria (EDC) in a local association procedure. Considering the repeating character of global seismicity, more than 90 % of events in the reviewed event bulletin (REB) can be built in this automatic processing. Due to the reduced detection threshold, waveform cross-correlation may increase the number of valid REB events by a factor of 1.5-2.0. Therefore, the new pipeline may produce a more comprehensive bulletin than the current pipeline—the goal of seismic monitoring. The analysts' experience with the cross correlation event list (XSEL) shows that the workload of interactive processing might be reduced by a factor of two or even more. Since cross-correlation produces a comprehensive list of detections for a given master event, no additional arrivals from primary stations are expected to be associated with the XSEL events. The number of false alarms, relative to the number of events rejected from the standard event list 3 (SEL3) in the current interactive processing—can also be reduced by the use of several powerful filters. The principal filter is the difference between the arrival times of the master and newly built events at three or more primary stations, which should lie in a narrow range of a few seconds. In this study, one event at a

  8. Study of water flowrate using time transient and cross-correlation techniques with 82Br radiotracer

    International Nuclear Information System (INIS)

    Salgado, William L.; Brandao, Luiz E.B.

    2013-01-01

    This paper aims to determinate the water flowrate using Time Transient and Cross-Correlation techniques. The detection system uses two NaI (T1) detectors adequately positioned on the outside of pipe and a gamma-ray source ( 82 Br radiotracer). The water flowrate measurements using Time Transient and Cross-Correlation techniques were compared to invasive conventional measurements of the flowrate previously installed in pipeline. Discrepancies between Time Transient and Cross-Correlation techniques flowmeter previously installed in pipeline. Discrepancies between Time Transient and Cross-Correlation techniques flowrate values were found to be less than 3% in relation to conventional ones. (author)

  9. Generation of correlated finite alphabet waveforms using gaussian random variables

    KAUST Repository

    Jardak, Seifallah; Ahmed, Sajid; Alouini, Mohamed-Slim

    2014-01-01

    , the proposed scheme is general, the main focus of this paper is to generate finite alphabet waveforms for multiple-input multiple-output radar, where correlated waveforms are used to achieve desired beampatterns. © 2014 IEEE.

  10. A technique for plasma velocity-space cross-correlation

    Science.gov (United States)

    Mattingly, Sean; Skiff, Fred

    2018-05-01

    An advance in experimental plasma diagnostics is presented and used to make the first measurement of a plasma velocity-space cross-correlation matrix. The velocity space correlation function can detect collective fluctuations of plasmas through a localized measurement. An empirical decomposition, singular value decomposition, is applied to this Hermitian matrix in order to obtain the plasma fluctuation eigenmode structure on the ion distribution function. A basic theory is introduced and compared to the modes obtained by the experiment. A full characterization of these modes is left for future work, but an outline of this endeavor is provided. Finally, the requirements for this experimental technique in other plasma regimes are discussed.

  11. Correlation between the respiratory waveform measured using a respiratory sensor and 3D tumor motion in gated radiotherapy

    International Nuclear Information System (INIS)

    Tsunashima, Yoshikazu; Sakae, Takeji; Shioyama, Yoshiyuki; Kagei, Kenji; Terunuma, Toshiyuki; Nohtomi, Akihiro; Akine, Yasuyuki

    2004-01-01

    Purpose: The purpose of this study is to investigate the correlation between the respiratory waveform measured using a respiratory sensor and three-dimensional (3D) tumor motion. Methods and materials: A laser displacement sensor (LDS: KEYENCE LB-300) that measures distance using infrared light was used as the respiratory sensor. This was placed such that the focus was in an area around the patient's navel. When the distance from the LDS to the body surface changes as the patient breathes, the displacement is detected as a respiratory waveform. To obtain the 3D tumor motion, a biplane digital radiography unit was used. For the tumor in the lung, liver, and esophagus of 26 patients, the waveform was compared with the 3D tumor motion. The relationship between the respiratory waveform and the 3D tumor motion was analyzed by means of the Fourier transform and a cross-correlation function. Results: The respiratory waveform cycle agreed with that of the cranial-caudal and dorsal-ventral tumor motion. A phase shift observed between the respiratory waveform and the 3D tumor motion was principally in the range 0.0 to 0.3 s, regardless of the organ being measured, which means that the respiratory waveform does not always express the 3D tumor motion with fidelity. For this reason, the standard deviation of the tumor position in the expiration phase, as indicated by the respiratory waveform, was derived, which should be helpful in suggesting the internal margin required in the case of respiratory gated radiotherapy. Conclusion: Although obtained from only a few breathing cycles for each patient, the correlation between the respiratory waveform and the 3D tumor motion was evident in this study. If this relationship is analyzed carefully and an internal margin is applied, the accuracy and convenience of respiratory gated radiotherapy could be improved by use of the respiratory sensor.Thus, it is expected that this procedure will come into wider use

  12. New Frontiers in Characterization of Sub-Catalog Microseismicity: Utilizing Inter-Event Waveform Cross Correlation for Estimating Precise Locations, Magnitudes, and Focal Mechanisms of Tiny Earthquakes

    Science.gov (United States)

    Ellsworth, W. L.; Shelly, D. R.; Hardebeck, J.; Hill, D. P.

    2017-12-01

    Microseismicity often conveys the most direct information about active processes in the earth's subsurface. However, routine network processing typically leaves most earthquakes uncharacterized. These "sub-catalog" events can provide critical clues to ongoing processes in the source region. To address this issue, we have developed waveform-based processing that leverages the existing routine catalog of earthquakes to detect and characterize "sub-catalog" events (those absent in routine catalogs). By correlating waveforms of cataloged events with the continuous data stream, we 1) identify events with similar waveform signatures in the continuous data across multiple stations, 2) precisely measure relative time lags across these stations for both P- and S-wave time windows, and 3) estimate the relative polarity between events by the sign of the peak absolute value correlations and its height above the secondary peak. When combined, these inter-event comparisons yield robust measurements, which enable sensitive event detection, relative relocation, and relative magnitude estimation. The most recent addition, focal mechanisms derived from correlation-based relative polarities, addresses a significant shortcoming in microseismicity analyses (see Shelly et al., JGR, 2016). Depending on the application, we can characterize 2-10 times as many events as included in the initial catalog. This technique is particularly well suited for compact zones of active seismicity such as seismic swarms. Application to a 2014 swarm in Long Valley Caldera, California, illuminates complex patterns of faulting that would have otherwise remained obscured. The prevalence of such features in other environments remains an important, as yet unresolved, question.

  13. MIMO-Radar Waveform Design for Beampattern Using Particle-Swarm-Optimisation

    KAUST Repository

    Ahmed, Sajid

    2012-07-31

    Multiple input multiple output (MIMO) radars have many advantages over their phased-array counterparts: improved spatial resolution; better parametric identifiably and greater flexibility to acheive the desired transmit beampattern. The desired transmit beampatterns using MIMO-radar requires the waveforms to have arbitrary auto- and cross-correlations. To design such waveforms, generally a waveform covariance matrix, R, is synthesised first then the actual waveforms are designed. Synthesis of the covariance matrix, R, is a constrained optimisation problem, which requires R to be positive semidefinite and all of its diagonal elements to be equal. To simplify the first constraint the covariance matrix is synthesised indirectly from its square-root matrix U, while for the second constraint the elements of the m-th column of U are parameterised using the coordinates of the m-hypersphere. This implicitly fulfils both of the constraints and enables us to write the cost-function in closed form. Then the cost-function is optimised using a simple particle-swarm-optimisation (PSO) technique, which requires only the cost-function and can optimise any choice of norm cost-function. © 2012 IEEE.

  14. Generation of correlated finite alphabet waveforms using gaussian random variables

    KAUST Repository

    Ahmed, Sajid

    2016-01-13

    Various examples of methods and systems are provided for generation of correlated finite alphabet waveforms using Gaussian random variables in, e.g., radar and communication applications. In one example, a method includes mapping an input signal comprising Gaussian random variables (RVs) onto finite-alphabet non-constant-envelope (FANCE) symbols using a predetermined mapping function, and transmitting FANCE waveforms through a uniform linear array of antenna elements to obtain a corresponding beampattern. The FANCE waveforms can be based upon the mapping of the Gaussian RVs onto the FANCE symbols. In another example, a system includes a memory unit that can store a plurality of digital bit streams corresponding to FANCE symbols and a front end unit that can transmit FANCE waveforms through a uniform linear array of antenna elements to obtain a corresponding beampattern. The system can include a processing unit that can encode the input signal and/or determine the mapping function.

  15. Generation of correlated finite alphabet waveforms using gaussian random variables

    KAUST Repository

    Ahmed, Sajid; Alouini, Mohamed-Slim; Jardak, Seifallah

    2016-01-01

    Various examples of methods and systems are provided for generation of correlated finite alphabet waveforms using Gaussian random variables in, e.g., radar and communication applications. In one example, a method includes mapping an input signal comprising Gaussian random variables (RVs) onto finite-alphabet non-constant-envelope (FANCE) symbols using a predetermined mapping function, and transmitting FANCE waveforms through a uniform linear array of antenna elements to obtain a corresponding beampattern. The FANCE waveforms can be based upon the mapping of the Gaussian RVs onto the FANCE symbols. In another example, a system includes a memory unit that can store a plurality of digital bit streams corresponding to FANCE symbols and a front end unit that can transmit FANCE waveforms through a uniform linear array of antenna elements to obtain a corresponding beampattern. The system can include a processing unit that can encode the input signal and/or determine the mapping function.

  16. Full waveform inversion using envelope-based global correlation norm

    Science.gov (United States)

    Oh, Ju-Won; Alkhalifah, Tariq

    2018-05-01

    To increase the feasibility of full waveform inversion on real data, we suggest a new objective function, which is defined as the global correlation of the envelopes of modelled and observed data. The envelope-based global correlation norm has the advantage of the envelope inversion that generates artificial low-frequency information, which provides the possibility to recover long-wavelength structure in an early stage. In addition, the envelope-based global correlation norm maintains the advantage of the global correlation norm, which reduces the sensitivity of the misfit to amplitude errors so that the performance of inversion on real data can be enhanced when the exact source wavelet is not available and more complex physics are ignored. Through the synthetic example for 2-D SEG/EAGE overthrust model with inaccurate source wavelet, we compare the performance of four different approaches, which are the least-squares waveform inversion, least-squares envelope inversion, global correlation norm and envelope-based global correlation norm. Finally, we apply the envelope-based global correlation norm on the 3-D Ocean Bottom Cable (OBC) data from the North Sea. The envelope-based global correlation norm captures the strong reflections from the high-velocity caprock and generates artificial low-frequency reflection energy that helps us recover long-wavelength structure of the model domain in the early stages. From this long-wavelength model, the conventional global correlation norm is sequentially applied to invert for higher-resolution features of the model.

  17. Data mining technique for fast retrieval of similar waveforms in Fusion massive databases

    International Nuclear Information System (INIS)

    Vega, J.; Pereira, A.; Portas, A.; Dormido-Canto, S.; Farias, G.; Dormido, R.; Sanchez, J.; Duro, N.; Santos, M.; Sanchez, E.; Pajares, G.

    2008-01-01

    Fusion measurement systems generate similar waveforms for reproducible behavior. A major difficulty related to data analysis is the identification, in a rapid and automated way, of a set of discharges with comparable behaviour, i.e. discharges with 'similar' waveforms. Here we introduce a new technique for rapid searching and retrieval of 'similar' signals. The approach consists of building a classification system that avoids traversing the whole database looking for similarities. The classification system diminishes the problem dimensionality (by means of waveform feature extraction) and reduces the searching space to just the most probable 'similar' waveforms (clustering techniques). In the searching procedure, the input waveform is classified in any of the existing clusters. Then, a similarity measure is computed between the input signal and all cluster elements in order to identify the most similar waveforms. The inner product of normalized vectors is used as the similarity measure as it allows the searching process to be independent of signal gain and polarity. This development has been applied recently to TJ-II stellarator databases and has been integrated into its remote participation system

  18. Analysis of correlation between full-waveform metrics, scan geometry and land-cover: an application over forests

    Directory of Open Access Journals (Sweden)

    F. Pirotti

    2013-10-01

    Full Text Available For a correct use of metrics derived from processing of the full-waveform return signal from airborne laser scanner sensors any correlation which is not related to properties of the reflecting target must be known and, if possible, removed. In the following article we report on an analysis of correlation between several metrics extracted from the full-waveform return signal and scan characteristics (mainly range and type of land-cover (urban, grasslands, forests. The metrics taken in consideration are the amplitude, normalized amplitude, width (full width at half maximum, asymmetry indicators, left and right energy content, and the cross-section calculated from width and normalized amplitude considering the range effect. The results show that scan geometry in this case does not have a significant impact scans over forest cover, except for range affecting amplitude and width distribution. Over complex targets such as vegetation canopy, other factors such as incidence angle have little meaning, therefore corrections of range effect are the most meaningful. A strong correlation with the type of land-cover is also shown by the distribution of the values of the metrics in the different areas taken in consideration.

  19. Data mining technique for fast retrieval of similar waveforms in Fusion massive databases

    Energy Technology Data Exchange (ETDEWEB)

    Vega, J. [Asociacion EURATOM/CIEMAT Para Fusion, Madrid (Spain)], E-mail: jesus.vega@ciemat.es; Pereira, A.; Portas, A. [Asociacion EURATOM/CIEMAT Para Fusion, Madrid (Spain); Dormido-Canto, S.; Farias, G.; Dormido, R.; Sanchez, J.; Duro, N. [Departamento de Informatica y Automatica, UNED, Madrid (Spain); Santos, M. [Departamento de Arquitectura de Computadores y Automatica, UCM, Madrid (Spain); Sanchez, E. [Asociacion EURATOM/CIEMAT Para Fusion, Madrid (Spain); Pajares, G. [Departamento de Arquitectura de Computadores y Automatica, UCM, Madrid (Spain)

    2008-01-15

    Fusion measurement systems generate similar waveforms for reproducible behavior. A major difficulty related to data analysis is the identification, in a rapid and automated way, of a set of discharges with comparable behaviour, i.e. discharges with 'similar' waveforms. Here we introduce a new technique for rapid searching and retrieval of 'similar' signals. The approach consists of building a classification system that avoids traversing the whole database looking for similarities. The classification system diminishes the problem dimensionality (by means of waveform feature extraction) and reduces the searching space to just the most probable 'similar' waveforms (clustering techniques). In the searching procedure, the input waveform is classified in any of the existing clusters. Then, a similarity measure is computed between the input signal and all cluster elements in order to identify the most similar waveforms. The inner product of normalized vectors is used as the similarity measure as it allows the searching process to be independent of signal gain and polarity. This development has been applied recently to TJ-II stellarator databases and has been integrated into its remote participation system.

  20. Big Data solution for CTBT monitoring: CEA-IDC joint global cross correlation project

    Science.gov (United States)

    Bobrov, Dmitry; Bell, Randy; Brachet, Nicolas; Gaillard, Pierre; Kitov, Ivan; Rozhkov, Mikhail

    2014-05-01

    Waveform cross-correlation when applied to historical datasets of seismic records provides dramatic improvements in detection, location, and magnitude estimation of natural and manmade seismic events. With correlation techniques, the amplitude threshold of signal detection can be reduced globally by a factor of 2 to 3 relative to currently standard beamforming and STA/LTA detector. The gain in sensitivity corresponds to a body wave magnitude reduction by 0.3 to 0.4 units and doubles the number of events meeting high quality requirements (e.g. detected by three and more seismic stations of the International Monitoring System (IMS). This gain is crucial for seismic monitoring under the Comprehensive Nuclear-Test-Ban Treaty. The International Data Centre (IDC) dataset includes more than 450,000 seismic events, tens of millions of raw detections and continuous seismic data from the primary IMS stations since 2000. This high-quality dataset is a natural candidate for an extensive cross correlation study and the basis of further enhancements in monitoring capabilities. Without this historical dataset recorded by the permanent IMS Seismic Network any improvements would not be feasible. However, due to the mismatch between the volume of data and the performance of the standard Information Technology infrastructure, it becomes impossible to process all the data within tolerable elapsed time. To tackle this problem known as "BigData", the CEA/DASE is part of the French project "DataScale". One objective is to reanalyze 10 years of waveform data from the IMS network with the cross-correlation technique thanks to a dedicated High Performance Computer (HPC) infrastructure operated by the Centre de Calcul Recherche et Technologie (CCRT) at the CEA of Bruyères-le-Châtel. Within 2 years we are planning to enhance detection and phase association algorithms (also using machine learning and automatic classification) and process about 30 terabytes of data provided by the IDC to

  1. Application of multi-source waveform inversion to marine streamer data using the global correlation norm

    KAUST Repository

    Choi, Yun Seok

    2012-05-02

    Conventional multi-source waveform inversion using an objective function based on the least-square misfit cannot be applied to marine streamer acquisition data because of inconsistent acquisition geometries between observed and modelled data. To apply the multi-source waveform inversion to marine streamer data, we use the global correlation between observed and modelled data as an alternative objective function. The new residual seismogram derived from the global correlation norm attenuates modelled data not supported by the configuration of observed data and thus, can be applied to multi-source waveform inversion of marine streamer data. We also show that the global correlation norm is theoretically the same as the least-square norm of the normalized wavefield. To efficiently calculate the gradient, our method employs a back-propagation algorithm similar to reverse-time migration based on the adjoint-state of the wave equation. In numerical examples, the multi-source waveform inversion using the global correlation norm results in better inversion results for marine streamer acquisition data than the conventional approach. © 2012 European Association of Geoscientists & Engineers.

  2. Cardiac-driven Pulsatile Motion of Intracranial Cerebrospinal Fluid Visualized Based on a Correlation Mapping Technique.

    Science.gov (United States)

    Yatsushiro, Satoshi; Sunohara, Saeko; Hayashi, Naokazu; Hirayama, Akihiro; Matsumae, Mitsunori; Atsumi, Hideki; Kuroda, Kagayaki

    2018-04-10

    A correlation mapping technique delineating delay time and maximum correlation for characterizing pulsatile cerebrospinal fluid (CSF) propagation was proposed. After proofing its technical concept, this technique was applied to healthy volunteers and idiopathic normal pressure hydrocephalus (iNPH) patients. A time-resolved three dimensional-phase contrast (3D-PC) sampled the cardiac-driven CSF velocity at 32 temporal points per cardiac period at each spatial location using retrospective cardiac gating. The proposed technique visualized distributions of propagation delay and correlation coefficient of the PC-based CSF velocity waveform with reference to a waveform at a particular point in the CSF space. The delay time was obtained as the amount of time-shift, giving the maximum correlation for the velocity waveform at an arbitrary location with that at the reference location. The validity and accuracy of the technique were confirmed in a flow phantom equipped with a cardiovascular pump. The technique was then applied to evaluate the intracranial CSF motions in young, healthy (N = 13), and elderly, healthy (N = 13) volunteers and iNPH patients (N = 13). The phantom study demonstrated that root mean square error of the delay time was 2.27%, which was less than the temporal resolution of PC measurement used in this study (3.13% of a cardiac cycle). The human studies showed a significant difference (P correlation coefficient between the young, healthy group and the other two groups. A significant difference (P correlation coefficients in intracranial CSF space among all groups. The result suggests that the CSF space compliance of iNPH patients was lower than that of healthy volunteers. The correlation mapping technique allowed us to visualize pulsatile CSF velocity wave propagations as still images. The technique may help to classify diseases related to CSF dynamics, such as iNPH.

  3. Two-detector cross-correlation noise technique and its application in measuring reactor kinetic parameters

    International Nuclear Information System (INIS)

    Lu Guiping; Peng Feng; Yi Jieyi

    1988-01-01

    The two-detector cross-correlation noise technique is a new method of measuring reactor kinetic parameters developed in the sixties. It has the advantages of non-perturbation in core, high signal to noise ratio, low space dependent effect, and simple and reliable in measurement. A special set of cross-correlation analyzer has been prepared for measuring kinetic parameters of several reactor assemblies, such as the High Flux Engineering Test Reactor, its zero power mock up facility and a low enriched uranium light water lattice zero power facility

  4. Rapid and Robust Cross-Correlation-Based Seismic Phase Identification Using an Approximate Nearest Neighbor Method

    Science.gov (United States)

    Tibi, R.; Young, C. J.; Gonzales, A.; Ballard, S.; Encarnacao, A. V.

    2016-12-01

    The matched filtering technique involving the cross-correlation of a waveform of interest with archived signals from a template library has proven to be a powerful tool for detecting events in regions with repeating seismicity. However, waveform correlation is computationally expensive, and therefore impractical for large template sets unless dedicated distributed computing hardware and software are used. In this study, we introduce an Approximate Nearest Neighbor (ANN) approach that enables the use of very large template libraries for waveform correlation without requiring a complex distributed computing system. Our method begins with a projection into a reduced dimensionality space based on correlation with a randomized subset of the full template archive. Searching for a specified number of nearest neighbors is accomplished by using randomized K-dimensional trees. We used the approach to search for matches to each of 2700 analyst-reviewed signal detections reported for May 2010 for the IMS station MKAR. The template library in this case consists of a dataset of more than 200,000 analyst-reviewed signal detections for the same station from 2002-2014 (excluding May 2010). Of these signal detections, 60% are teleseismic first P, and 15% regional phases (Pn, Pg, Sn, and Lg). The analyses performed on a standard desktop computer shows that the proposed approach performs the search of the large template libraries about 20 times faster than the standard full linear search, while achieving recall rates greater than 80%, with the recall rate increasing for higher correlation values. To decide whether to confirm a match, we use a hybrid method involving a cluster approach for queries with two or more matches, and correlation score for single matches. Of the signal detections that passed our confirmation process, 52% were teleseismic first P, and 30% were regional phases.

  5. Flaw characterization through nonlinear ultrasonics and wavelet cross-correlation algorithms

    Science.gov (United States)

    Bunget, Gheorghe; Yee, Andrew; Stewart, Dylan; Rogers, James; Henley, Stanley; Bugg, Chris; Cline, John; Webster, Matthew; Farinholt, Kevin; Friedersdorf, Fritz

    2018-04-01

    Ultrasonic measurements have become increasingly important non-destructive techniques to characterize flaws found within various in-service industrial components. The prediction of remaining useful life based on fracture analysis depends on the accurate estimation of flaw size and orientation. However, amplitude-based ultrasonic measurements are not able to estimate the plastic zones that exist ahead of crack tips. Estimating the size of the plastic zone is an advantage since some flaws may propagate faster than others. This paper presents a wavelet cross-correlation (WCC) algorithm that was applied to nonlinear analysis of ultrasonically guided waves (GW). By using this algorithm, harmonics present in the waveforms were extracted and nonlinearity parameters were used to indicate both the tip of the cracks and size of the plastic zone. B-scans performed with the quadratic nonlinearities were sensitive to micro-damage specific to plastic zones.

  6. Coordination analysis of players' distribution in football using cross-correlation and vector coding techniques.

    Science.gov (United States)

    Moura, Felipe Arruda; van Emmerik, Richard E A; Santana, Juliana Exel; Martins, Luiz Eduardo Barreto; Barros, Ricardo Machado Leite de; Cunha, Sergio Augusto

    2016-12-01

    The purpose of this study was to investigate the coordination between teams spread during football matches using cross-correlation and vector coding techniques. Using a video-based tracking system, we obtained the trajectories of 257 players during 10 matches. Team spread was calculated as functions of time. For a general coordination description, we calculated the cross-correlation between the signals. Vector coding was used to identify the coordination patterns between teams during offensive sequences that ended in shots on goal or defensive tackles. Cross-correlation showed that opponent teams have a tendency to present in-phase coordination, with a short time lag. During offensive sequences, vector coding results showed that, although in-phase coordination dominated, other patterns were observed. We verified that during the early stages, offensive sequences ending in shots on goal present greater anti-phase and attacking team phase periods, compared to sequences ending in tackles. Results suggest that the attacking team may seek to present a contrary behaviour of its opponent (or may lead the adversary behaviour) in the beginning of the attacking play, regarding to the distribution strategy, to increase the chances of a shot on goal. The techniques allowed detecting the coordination patterns between teams, providing additional information about football dynamics and players' interaction.

  7. Efficient blind search for similar-waveform earthquakes in years of continuous seismic data

    Science.gov (United States)

    Yoon, C. E.; Bergen, K.; Rong, K.; Elezabi, H.; Bailis, P.; Levis, P.; Beroza, G. C.

    2017-12-01

    Cross-correlating an earthquake waveform template with continuous seismic data has proven to be a sensitive, discriminating detector of small events missing from earthquake catalogs, but a key limitation of this approach is that it requires advance knowledge of the earthquake signals we wish to detect. To overcome this limitation, we can perform a blind search for events with similar waveforms, comparing waveforms from all possible times within the continuous data (Brown et al., 2008). However, the runtime for naive blind search scales quadratically with the duration of continuous data, making it impractical to process years of continuous data. The Fingerprint And Similarity Thresholding (FAST) detection method (Yoon et al., 2015) enables a comprehensive blind search for similar-waveform earthquakes in a fast, scalable manner by adapting data-mining techniques originally developed for audio and image search within massive databases. FAST converts seismic waveforms into compact "fingerprints", which are efficiently organized and searched within a database. In this way, FAST avoids the unnecessary comparison of dissimilar waveforms. To date, the longest duration of continuous data used for event detection with FAST was 3 months at a single station near Guy-Greenbrier, Arkansas, which revealed microearthquakes closely correlated with stages of hydraulic fracturing (Yoon et al., 2017). In this presentation we introduce an optimized, parallel version of the FAST software with improvements to the fingerprinting algorithm and the ability to detect events using continuous data from a network of stations (Bergen et al., 2016). We demonstrate its ability to detect low-magnitude earthquakes within several years of continuous data at locations of interest in California.

  8. Towards full waveform ambient noise inversion

    Science.gov (United States)

    Sager, Korbinian; Ermert, Laura; Boehm, Christian; Fichtner, Andreas

    2018-01-01

    In this work we investigate fundamentals of a method—referred to as full waveform ambient noise inversion—that improves the resolution of tomographic images by extracting waveform information from interstation correlation functions that cannot be used without knowing the distribution of noise sources. The fundamental idea is to drop the principle of Green function retrieval and to establish correlation functions as self-consistent observables in seismology. This involves the following steps: (1) We introduce an operator-based formulation of the forward problem of computing correlation functions. It is valid for arbitrary distributions of noise sources in both space and frequency, and for any type of medium, including 3-D elastic, heterogeneous and attenuating media. In addition, the formulation allows us to keep the derivations independent of time and frequency domain and it facilitates the application of adjoint techniques, which we use to derive efficient expressions to compute first and also second derivatives. The latter are essential for a resolution analysis that accounts for intra- and interparameter trade-offs. (2) In a forward modelling study we investigate the effect of noise sources and structure on different observables. Traveltimes are hardly affected by heterogeneous noise source distributions. On the other hand, the amplitude asymmetry of correlations is at least to first order insensitive to unmodelled Earth structure. Energy and waveform differences are sensitive to both structure and the distribution of noise sources. (3) We design and implement an appropriate inversion scheme, where the extraction of waveform information is successively increased. We demonstrate that full waveform ambient noise inversion has the potential to go beyond ambient noise tomography based on Green function retrieval and to refine noise source location, which is essential for a better understanding of noise generation. Inherent trade-offs between source and structure

  9. Doppler waveform of hepatic vein in patients with chronic hepatitis B; Correlation with histologic grade and stage

    International Nuclear Information System (INIS)

    Eom, Kyeong Tae; Namkung, Sook; Bae, Sang Hoon; Choi, Young Hee

    1999-01-01

    To evaluate the relationship between the waveform of the right hepatic vein and the histological grade and stage in patients with chronic hepatitis B. Eighty-seven patients with chronic hepatitis B were examined prospectively by one sonographer. In each patient, Doppler waveform of the right hepatic vein was obtained. Doppler waveform was classified into 3 type, type 0; normal triphasic pattern, type 1; reduced amplitude of phasic oscillation and no reverse flow phase, and type 2; completely flat flow pattern. In the same session, an ultrasound guided liver biopsy was performed and submitted to one pathologist for grading and staging. Duplex doppler ultrasonography of the right hepatic vein was also performed in 12 control subjects with no evidence of liver or heart disease. The doppler waveform was compared with the histologic severity and a statistical analysis was performed. In the control group, all cases had type 0 waveform. In the hepatitis group, there were type 0 waveform in 61 cases (70.1%), type 1 waveform in 22 cases (25.3%) and type 2 waveform in 4 cases (4.6%). The frequency of abnormal waveform is significantly higher in patients with grade 3-4 and stage 3-4 than grade and stage 1-2 (p>0.005). In the hepatitis group, the venous pulsatility index (VPI) was 0.17-0.69 (mean 0.41), and decreased in the highest and mean values when increasing the histologic scores. However, it was nor significant statistically (p>0.05). The frequency of abnormal waveform was correlated with the histologic severity in patients with chronic hepatitis B. The highest and mean values of the VPI were also correlated. However 70.1% of the patients with chronic hepatitis B showed normal waveform. So doppler ultrasonogram of the hepatic vein may be useful for the diagnosis and the differential diagnosis from cirrhosis in patients with chronic hepatitis B by combination of doppler waveform and venous pulsatility index.

  10. Design of pulse waveform for waveform division multiple access UWB wireless communication system.

    Science.gov (United States)

    Yin, Zhendong; Wang, Zhirui; Liu, Xiaohui; Wu, Zhilu

    2014-01-01

    A new multiple access scheme, Waveform Division Multiple Access (WDMA) based on the orthogonal wavelet function, is presented. After studying the correlation properties of different categories of single wavelet functions, the one with the best correlation property will be chosen as the foundation for combined waveform. In the communication system, each user is assigned to different combined orthogonal waveform. Demonstrated by simulation, combined waveform is more suitable than single wavelet function to be a communication medium in WDMA system. Due to the excellent orthogonality, the bit error rate (BER) of multiuser with combined waveforms is so close to that of single user in a synchronous system. That is to say, the multiple access interference (MAI) is almost eliminated. Furthermore, even in an asynchronous system without multiuser detection after matched filters, the result is still pretty ideal and satisfactory by using the third combination mode that will be mentioned in the study.

  11. Waveform correlation and coherence of short-period seismic noise within Gauribidanur array with implications for event detection

    International Nuclear Information System (INIS)

    Bhadauria, Y.S.; Arora, S.K.

    1995-01-01

    In continuation with our effort to model the short-period micro seismic noise at the seismic array at Gauribidanur (GBA), we have examined in detail time-correlation and spectral coherence of the noise field within the array space. This has implications of maximum possible improvement in signal-to-noise ratio (SNR) relevant to event detection. The basis of this study is about a hundred representative wide-band noise samples collected from GBA throughout the year 1992. Both time-structured correlation as well as coherence of the noise waveforms are found to be practically independent of the inter element distances within the array, and they exhibit strong temporal and spectral stability. It turns out that the noise is largely incoherent at frequencies ranging upwards from 2 Hz; the coherency coefficient tends to increase in the lower frequency range attaining a maximum of 0.6 close to 0.5 Hz. While the maximum absolute cross-correlation also diminishes with increasing frequency, the zero-lag cross-correlation is found to be insensitive to frequency filtering regardless of the pass band. An extremely small value of -0.01 of the zero-lag correlation and a comparatively higher year-round average estimate at 0.15 of the maximum absolute time-lagged correlation yields an SNR improvement varying between a probable high of 4.1 and a low of 2.3 for the full 20-element array. 19 refs., 6 figs

  12. Estimation of Spatial Trends in LAI in Heterogeneous Semi-arid Ecosystems using Full Waveform Lidar

    Science.gov (United States)

    Glenn, N. F.; Ilangakoon, N.; Spaete, L.; Dashti, H.

    2017-12-01

    Leaf area index (LAI) is a key structural trait that is defined by the plant functional type (PFT) and controlled by prevailing climate- and human-driven ecosystem stresses. Estimates of LAI using remote sensing techniques are limited by the uncertainties of vegetation inter and intra-gap fraction estimates; this is especially the case in sparse, low stature vegetated ecosystems. Small footprint full waveform lidar digitizes the total amount of return energy with the direction information as a near continuous waveform at a high vertical resolution (1 ns). Thus waveform lidar provides additional data matrices to capture vegetation gaps as well as PFTs that can be used to constrain the uncertainties of LAI estimates. In this study, we calculated a radiometrically calibrated full waveform parameter called backscatter cross section, along with other data matrices from the waveform to estimate vegetation gaps across plots (10 m x 10 m) in a semi-arid ecosystem in the western US. The LAI was then estimated using empirical relationships with directional gap fraction. Full waveform-derived gap fraction based LAI showed a high correlation with field observed shrub LAI (R2 = 0.66, RMSE = 0.24) compared to discrete return lidar based LAI (R2 = 0.01, RMSE = 0.5). The data matrices derived from full waveform lidar classified a number of deciduous and evergreen tree species, shrub species, and bare ground with an overall accuracy of 89% at 10 m. A similar analysis was performed at 1m with overall accuracy of 80%. The next step is to use these relationships to map the PFTs LAI at 10 m spatial scale across the larger study regions. The results show the exciting potential of full waveform lidar to identify plant functional types and LAI in low-stature vegetation dominated semi-arid ecosystems, an ecosystem in which many other remote sensing techniques fail. These results can be used to assess ecosystem state, habitat suitability as well as to constrain model uncertainties in

  13. A quantum accurate waveform synthesizer as a voltage reference for an electronic primary thermometer

    Science.gov (United States)

    Pollarolo, Alessio; Benz, Samuel; Rogalla, Horst; Dresselhaus, Paul

    2014-03-01

    We are using a quantum voltage noise source (QVNS) for use as an intrinsically accurate voltage reference for a new type of electronic temperature standard. In Johnson Noise Thermometry (JNT) the noise of a resistor is used to measure temperature or Boltzmann's constant k, because the Nyquist equation =4kTR Δf shows that the power spectral density is proportional to k, temperature T, resistance R and measurement bandwidth Δf . The QVNS is a digital to analog converter used to synthesize a voltage waveform that resembles pseudo-random noise comparable in amplitude to the resistor noise. The signal generated is a frequency comb of harmonics tones that are equally spaced in frequency, all having identical amplitudes but random phases. The QVNS is an array superconducting Josephson junctions that are biased with a pulsed waveform clocked at 10 GHz. The accuracy of the voltage waveform derives from the identical voltage pulses produced by each junction that are perfectly quantized because their time-integrals are always equal to flux quantum h/2 e. The time-dependent output voltage waveform is determined by the number of pulses and their density in time. The measurement electronics exploits cross-correlation techniques to reduce the uncorrelated measurement noise so as to reveal the resistor noise, both of which are on the order of 2 nV/ √Hz. With this technique we have measured k with an uncertainty of about one part in 105, which we hope to improve by another order of magnitude with further research.

  14. Semiautomated tremor detection using a combined cross-correlation and neural network approach

    Science.gov (United States)

    Horstmann, Tobias; Harrington, Rebecca M.; Cochran, Elizabeth S.

    2013-01-01

    Despite observations of tectonic tremor in many locations around the globe, the emergent phase arrivals, low‒amplitude waveforms, and variable event durations make automatic detection a nontrivial task. In this study, we employ a new method to identify tremor in large data sets using a semiautomated technique. The method first reduces the data volume with an envelope cross‒correlation technique, followed by a Self‒Organizing Map (SOM) algorithm to identify and classify event types. The method detects tremor in an automated fashion after calibrating for a specific data set, hence we refer to it as being “semiautomated”. We apply the semiautomated detection algorithm to a newly acquired data set of waveforms from a temporary deployment of 13 seismometers near Cholame, California, from May 2010 to July 2011. We manually identify tremor events in a 3 week long test data set and compare to the SOM output and find a detection accuracy of 79.5%. Detection accuracy improves with increasing signal‒to‒noise ratios and number of available stations. We find detection completeness of 96% for tremor events with signal‒to‒noise ratios above 3 and optimal results when data from at least 10 stations are available. We compare the SOM algorithm to the envelope correlation method of Wech and Creager and find the SOM performs significantly better, at least for the data set examined here. Using the SOM algorithm, we detect 2606 tremor events with a cumulative signal duration of nearly 55 h during the 13 month deployment. Overall, the SOM algorithm is shown to be a flexible new method that utilizes characteristics of the waveforms to identify tremor from noise or other seismic signals.

  15. Correlation of Electropenetrography Waveforms From Lygus lineolaris (Hemiptera: Miridae) Feeding on Cotton Squares With Chemical Evidence of Inducible Tannins.

    Science.gov (United States)

    Cervantes, Felix A; Backus, Elaine A; Godfrey, Larry; Wallis, Christopher; Akbar, Waseem; Clark, Thomas L; Rojas, Maria G

    2017-10-01

    Probing behavior of Lygus lineolaris (Palisot de Beauvois) has previously been characterized with electropenetrography (EPG). Cell rupturing (CR) and ingestion (I) EPG waveforms were identified as the two main stylet-probing behaviors by adult L. lineolaris. However, characterization and identification of EPG waveforms are not complete until specific events of a particular waveform are correlated to insect probing. With the use of EPG, histology, microscopy, and chemical analysis, probing behavior of L. lineolaris on pin-head cotton squares was studied. Occurrences of waveforms CR and I were artificially terminated during the EPG recording. Histological samples of probed cotton squares were prepared and analyzed to correlate specific types and occurrences of feeding damage location and plant responses to insect feeding. Both CR and I occurred in the staminal column of the cotton square. Cell rupturing events elicited the production of dark-red deposits seen in histological staining that were demonstrated via chemical analysis to contain condensed tannins. We hypothesize that wounding and saliva secreted during CR triggered release of tannins, because tannin production was positively correlated with the number of probes with single CR events performed by L. lineolaris. Degraded plant tissue and tannins were removed from the staminal column during occurrence of waveform I. These results conclude the process of defining CR and I as probing waveforms performed by L. lineolaris on pin-head cotton squares. These biological definitions will now allow EPG to be used to quantitatively compare L. lineolaris feeding among different plant treatments, with the goal of improving pest management tactics against this pest. Published by Oxford University Press on behalf of Entomological Society of America 2017. This work is written by (a) US Government employee(s) and is in the public domain in the US.

  16. Changes in waveform on hepatic venous doppler in patients with chronic hepatic B: Correlation with histologic findings

    International Nuclear Information System (INIS)

    Ko, Joon Seok; Kim, Hak Soo; Chung, Dong Hae

    2001-01-01

    To evaluate changes of the waveform of the hepatic vein on doppler ultrasound (US) in patients with chronic hepatic B and to correlate them with histologic findings. Thirty three patients with chronic hepatic B were prospectively examined with doppler US, and liver biopsy was done at the same time. The right hepatic vein was examined on doppler US, and a liver biopsy was performed in the right lobe of the liver. Doppler waveform was considered abnormal if it showed either reduction in the amplitude of phasic oscillation without the reversed flow phase or the presence of completely flow. Specimens obtained from the biopsy were classified according to the predetermined histologic scoring criteria. It was technically possible to performed Doppler US of the right hepatic vein and liver biopsy simultaneously in all thirty three patients. Waveforms of the right hepatic vein were abnormal in fourteen (42.4%), biphasic in 12 (36.4%) and flat in two (6.0%) patients. Only the steatosis exhibited statistically significant correlation between changes of doppler waveform (p,0.05) of the normal and abnormal groups. Doppler US patterns of the hepatic vein in chronic hepatitis B were different from those of the normal group. The abnormal flow pattern on hepatic venous doppler appeared to be mainly influenced by the intrahepatic fat deposition rather than the degree of fibrosis.

  17. Psychoacoustical evaluation of the pitch-synchronous overlap-and-add speech-waveform manipulation technique using single-format stimuli

    NARCIS (Netherlands)

    Kortekaas, R.W.L.; Kohlrausch, A.G.

    1997-01-01

    This article presents two experiments dealing with a psychoacoustical evaluation of the pitch synchronous overlap-and-add (PSOLA) technique. This technique has been developed for modification of duration and fundamental frequency of speech and is based on simple waveform manipulations. Both

  18. Determining carotid artery pressure from scaled diameter waveforms: comparison and validation of calibration techniques in 2026 subjects

    International Nuclear Information System (INIS)

    Vermeersch, S J; Verdonck, P R; Segers, P; Rietzschel, E R; De Buyzere, M L; Gillebert, T C; De Bacquer, D; De Backer, G; Van Bortel, L M

    2008-01-01

    Calibrated diameter distension waveforms could provide an alternative for local arterial pressure assessment more widely applicable than applanation tonometry. We compared linearly and exponentially calibrated carotid diameter waveforms to tonometry readings. Local carotid pressures measured by tonometry and diameter waveforms measured by ultrasound were obtained in 2026 subjects participating in the Asklepios study protocol. Diameter waveforms were calibrated using a linear and an exponential calibration scheme and compared to measured tonometry waveforms by examining the mean root-mean-squared error (RMSE), carotid systolic blood pressure (SBP car ) and augmentation index (AIx) of calibrated and measured pressures. Mean RMSE was 5.2(3.3) mmHg (mean(stdev)) for linear and 4.6(3.6) mmHg for exponential calibration. Linear calibration yielded an underestimation of SBP car by 6.4(4.1) mmHg which was strongly correlated to values of brachial pulse pressure (PP bra ) (R = 0.4, P car by 1.9(3.9) mmHg, independent of PP bra . AIx was overestimated by linear calibration by 1.9(10.1)%, the difference significantly increasing with increasing AIx (R = 0.25, P < 0.001) and by exponential calibration by 5.4(10.6)%, independently of the value of AIx. Properly calibrated diameter waveforms offer a viable alternative for local pressure estimation at the carotid artery. Compared to linear calibration, exponential calibration significantly improves the pressure estimation

  19. Estimation of Correlation Functions by the Random Decrement Technique

    DEFF Research Database (Denmark)

    Brincker, Rune; Krenk, Steen; Jensen, Jakob Laigaard

    responses simulated by two SDOF ARMA models loaded by the same bandlimited white noise. The speed and the accuracy of the RDD technique is compared to the Fast Fourier Transform (FFT) technique. The RDD technique does not involve multiplications, but only additions. Therefore, the technique is very fast......The Random Decrement (RDD) Technique is a versatile technique for characterization of random signals in the time domain. In this paper a short review of the theoretical basis is given, and the technique is illustrated by estimating auto-correlation functions and cross-correlation functions on modal...

  20. Estimation of Correlation Functions by the Random Decrement Technique

    DEFF Research Database (Denmark)

    Brincker, Rune; Krenk, Steen; Jensen, Jacob Laigaard

    1991-01-01

    responses simulated by two SDOF ARMA models loaded by the same band-limited white noise. The speed and the accuracy of the RDD technique is compared to the Fast Fourier Transform (FFT) technique. The RDD technique does not involve multiplications, but only additions. Therefore, the technique is very fast......The Random Decrement (RDD) Technique is a versatile technique for characterization of random signals in the time domain. In this paper a short review of the theoretical basis is given, and the technique is illustrated by estimating auto-correlation functions and cross-correlation functions on modal...

  1. Estimation of Correlation Functions by the Random Decrement Technique

    DEFF Research Database (Denmark)

    Brincker, Rune; Krenk, Steen; Jensen, Jakob Laigaard

    1992-01-01

    responses simulated by two SDOF ARMA models loaded by the same bandlimited white noise. The speed and the accuracy of the RDD technique is compared to the Fast Fourier Transform (FFT) technique. The RDD technique does not involve multiplications, but only additions. Therefore, the technique is very fast......The Random Decrement (RDD) Technique is a versatile technique for characterization of random signals in the time domain. In this paper a short review of the theoretical basis is given, and the technique is illustrated by estimating auto-correlation functions and cross-correlation functions on modal...

  2. Cross-correlation analysis of Ge/Li/ spectra

    International Nuclear Information System (INIS)

    MacDonald, R.; Robertson, A.; Kennett, T.J.; Prestwich, W.V.

    1974-01-01

    A sensitive technique is proposed for activation analysis using cross-correlation and improved spectral orthogonality achieved through use of a rectangular zero area digital filter. To test the accuracy and reliability of the cross-correlation procedure five spectra obtained with a Ge/Li detector were combined in different proportions. Gaussian distributed statistics were then added to the composite spectra by means of a pseudo-random number generator. The basis spectra used were 76 As, 82 Br, 72 Ga, 77 Ge, and room background. In general, when the basis spectra were combined in roughly comparable proportions the accuracy of the techique proved to be excelent (>1%). However, of primary importance was the ability of the correlation technique to identify low intensity components in the presence of high intensity components. It was found that the detection threshold for Ge, for example, was not reached until the Ge content in the unfiltered spectrum was <0.16%. (T.G.)

  3. Development of comprehensive image processing technique for differential diagnosis of liver disease by using multi-modality images. Pixel-based cross-correlation method using a profile

    International Nuclear Information System (INIS)

    Inoue, Akira; Okura, Yasuhiko; Akiyama, Mitoshi; Ishida, Takayuki; Kawashita, Ikuo; Ito, Katsuyoshi; Matsunaga, Naofumi; Sanada, Taizo

    2009-01-01

    Imaging techniques such as high magnetic field imaging and multidetector-row CT have been markedly improved recently. The final image-reading systems easily produce more than a thousand diagnostic images per patient. Therefore, we developed a comprehensive cross-correlation processing technique using multi-modality images, in order to decrease the considerable time and effort involved in the interpretation of a radiogram (multi-formatted display and/or stack display method, etc). In this scheme, the criteria of an attending radiologist for the differential diagnosis of liver cyst, hemangioma of liver, hepatocellular carcinoma, and metastatic liver cancer on magnetic resonance images with various sequences and CT images with and without contrast enhancement employ a cross-correlation coefficient. Using a one-dimensional cross-correlation method, comprehensive image processing could be also adapted for various artifacts (some depending on modality imaging, and some on patients), which may be encountered at the clinical scene. This comprehensive image-processing technique could assist radiologists in the differential diagnosis of liver diseases. (author)

  4. Big Data Solution for CTBT Monitoring Using Global Cross Correlation

    Science.gov (United States)

    Gaillard, P.; Bobrov, D.; Dupont, A.; Grenouille, A.; Kitov, I. O.; Rozhkov, M.

    2014-12-01

    Due to the mismatch between data volume and the performance of the Information Technology infrastructure used in seismic data centers, it becomes more and more difficult to process all the data with traditional applications in a reasonable elapsed time. To fulfill their missions, the International Data Centre of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO/IDC) and the Département Analyse Surveillance Environnement of Commissariat à l'Energie atomique et aux énergies alternatives (CEA/DASE) collect, process and produce complex data sets whose volume is growing exponentially. In the medium term, computer architectures, data management systems and application algorithms will require fundamental changes to meet the needs. This problem is well known and identified as a "Big Data" challenge. To tackle this major task, the CEA/DASE takes part during two years to the "DataScale" project. Started in September 2013, DataScale gathers a large set of partners (research laboratories, SMEs and big companies). The common objective is to design efficient solutions using the synergy between Big Data solutions and the High Performance Computing (HPC). The project will evaluate the relevance of these technological solutions by implementing a demonstrator for seismic event detections thanks to massive waveform correlations. The IDC has developed an expertise on such techniques leading to an algorithm called "Master Event" and provides a high-quality dataset for an extensive cross correlation study. The objective of the project is to enhance the Master Event algorithm and to reanalyze 10 years of waveform data from the International Monitoring System (IMS) network thanks to a dedicated HPC infrastructure operated by the "Centre de Calcul Recherche et Technologie" at the CEA of Bruyères-le-Châtel. The dataset used for the demonstrator includes more than 300,000 seismic events, tens of millions of raw detections and more than 30 terabytes of continuous seismic data

  5. Applications of multiscale waveform inversion to marine data using a flooding technique and dynamic early-arrival windows

    KAUST Repository

    Boonyasiriwat, Chaiwoot

    2010-11-01

    A recently developed time-domain multiscale waveform tomography (MWT) method is applied to synthetic and field marine data. Although the MWT method was already applied to synthetic data, the synthetic data application leads to a development of a hybrid method between waveform tomography and the salt flooding technique commonly use in subsalt imaging. This hybrid method can overcome a convergence problem encountered by inversion with a traveltime velocity tomogram and successfully provides an accurate and highly resolved velocity tomogram for the 2D SEG/EAGE salt model. In the application of MWT to the field data, the inversion process is carried out using a multiscale method with a dynamic early-arrival muting window to mitigate the local minima problem of waveform tomography and elastic effects. With the modified MWT method, reasonably accurate results as verified by comparison of migration images and common image gathers were obtained. The hybrid method with the salt flooding technique is not used in this field data example because there is no salt in the subsurface according to our interpretation. However, we believe it is applicable to field data applications. © 2010 Society of Exploration Geophysicists.

  6. DFT-Based Closed-form Covariance Matrix and Direct Waveforms Design for MIMO Radar to Achieve Desired Beampatterns

    KAUST Repository

    Bouchoucha, Taha

    2017-01-23

    In multiple-input multiple-out (MIMO) radar, for desired transmit beampatterns, appropriate correlated waveforms are designed. To design such waveforms, conventional MIMO radar methods use two steps. In the first step, the waveforms covariance matrix, R, is synthesized to achieve the desired beampattern. While in the second step, to realize the synthesized covariance matrix, actual waveforms are designed. Most of the existing methods use iterative algorithms to solve these constrained optimization problems. The computational complexity of these algorithms is very high, which makes them difficult to use in practice. In this paper, to achieve the desired beampattern, a low complexity discrete-Fourier-transform based closed-form covariance matrix design technique is introduced for a MIMO radar. The designed covariance matrix is then exploited to derive a novel closed-form algorithm to directly design the finite-alphabet constant-envelope waveforms for the desired beampattern. The proposed technique can be used to design waveforms for large antenna array to change the beampattern in real time. It is also shown that the number of transmitted symbols from each antenna depends on the beampattern and is less than the total number of transmit antenna elements.

  7. A correlation-based pulse detection technique for gamma-ray/neutron detectors

    International Nuclear Information System (INIS)

    Faisal, Muhammad; Schiffer, Randolph T.; Flaska, Marek; Pozzi, Sara A.; Wentzloff, David D.

    2011-01-01

    We present a correlation-based detection technique that significantly improves the probability of detection for low energy pulses. We propose performing a normalized cross-correlation of the incoming pulse data to a predefined pulse template, and using a threshold correlation value to trigger the detection of a pulse. This technique improves the detector sensitivity by amplifying the signal component of incoming pulse data and rejecting noise. Simulation results for various different templates are presented. Finally, the performance of the correlation-based detection technique is compared to the current state-of-the-art techniques.

  8. Machine Learning Techniques for Arterial Pressure Waveform Analysis

    Directory of Open Access Journals (Sweden)

    João Cardoso

    2013-05-01

    Full Text Available The Arterial Pressure Waveform (APW can provide essential information about arterial wall integrity and arterial stiffness. Most of APW analysis frameworks individually process each hemodynamic parameter and do not evaluate inter-dependencies in the overall pulse morphology. The key contribution of this work is the use of machine learning algorithms to deal with vectorized features extracted from APW. With this purpose, we follow a five-step evaluation methodology: (1 a custom-designed, non-invasive, electromechanical device was used in the data collection from 50 subjects; (2 the acquired position and amplitude of onset, Systolic Peak (SP, Point of Inflection (Pi and Dicrotic Wave (DW were used for the computation of some morphological attributes; (3 pre-processing work on the datasets was performed in order to reduce the number of input features and increase the model accuracy by selecting the most relevant ones; (4 classification of the dataset was carried out using four different machine learning algorithms: Random Forest, BayesNet (probabilistic, J48 (decision tree and RIPPER (rule-based induction; and (5 we evaluate the trained models, using the majority-voting system, comparatively to the respective calculated Augmentation Index (AIx. Classification algorithms have been proved to be efficient, in particular Random Forest has shown good accuracy (96.95% and high area under the curve (AUC of a Receiver Operating Characteristic (ROC curve (0.961. Finally, during validation tests, a correlation between high risk labels, retrieved from the multi-parametric approach, and positive AIx values was verified. This approach gives allowance for designing new hemodynamic morphology vectors and techniques for multiple APW analysis, thus improving the arterial pulse understanding, especially when compared to traditional single-parameter analysis, where the failure in one parameter measurement component, such as Pi, can jeopardize the whole evaluation.

  9. Full-waveform seismic tomography of the Vrancea, Romania, subduction region

    Science.gov (United States)

    Baron, Julie; Morelli, Andrea

    2017-12-01

    The Vrancea region is one of the few locations of deep seismicity in Europe. Seismic tomography has been able to map lithospheric downwelling, but has not been able yet to clearly discriminate between competing geodynamic interpretations of the geological and geophysical evidence available. We study the seismic structure of the Vrancea subduction zone, using adjoint-based, full-waveform tomography to map the 3D vP and vS structure in detail. We use the database that was built during the CALIXTO (Carpathian Arc Lithosphere X-Tomography) temporary experiment, restricted to the broadband sensors and local intermediate-depth events. We fit waveforms with a cross-correlation misfit criterion in separate time windows around the expected P and S arrivals, and perform 17 iterations of vP and vS model updates (altogether, requiring about 16 million CPU hours) before reaching stable convergence. Among other features, our resulting model shows a nearly vertical, high-velocity body, that overlaps with the distribution of seismicity in its northeastern part. In its southwestern part, a slab appears to dip less steeply to the NW, and is suggestive of ongoing - or recently concluded - subduction geodynamic processes. Joint inversion for vP and vS allow us to address the vP/vS ratio distribution, that marks high vP/vS in the crust beneath the Focsani sedimentary basin - possibly due to high fluid pressure - and a low vP/vS edge along the lower plane of the subducting lithosphere, that in other similar environment has been attributed to dehydration of serpentine in the slab. In spite of the restricted amount of data available, and limitations on the usable frequency pass-band, full-waveform inversion reveals its potential to improve the general quality of imaging with respect to other tomographic techniques - although at a sensible cost in terms of computing resources. Our study also shows that re-analysis of legacy data sets with up-to-date techniques may bring new, useful

  10. Current cross-correlations in double quantum dot Cooper pair splitter

    Energy Technology Data Exchange (ETDEWEB)

    Wrzesniewski, Kacper; Trocha, Piotr; Weymann, Ireneusz [Faculty of Physics, Adam Mickiewicz University, 61-614 Poznan (Poland)

    2016-07-01

    We investigate theoretically transport properties of a quantum dot (QD) system working as a Cooper pair splitter. The device is coupled to one superconducting and two ferromagnetic leads. Presented results are calculated using real-time diagrammatic technique in the sequential tunneling approximation with respect to the coupling to ferromagnetic leads. The transport properties are evaluated within the superconductor subgap regime taking into account Andreev reflection processes solely. We focus on the analysis of current and current cross-correlations, both in linear and nonlinear responses. Current cross-correlations give additional information about dynamics of transport processes. We identify both positive and negative signs of current cross-correlations and discuss mechanisms leading to those results. Strong negative cross-correlations are found when the occupation number of QD system becomes degenerate and near the emergence of the triplet blockade, while positive ones occur in the most range where current flows due to crossed Andreev processes. Finally, we consider ferromagnetic leads polarization and temperature influences on aforementioned features.

  11. Sparse Frequency Waveform Design for Radar-Embedded Communication

    Directory of Open Access Journals (Sweden)

    Chaoyun Mai

    2016-01-01

    Full Text Available According to the Tag application with function of covert communication, a method for sparse frequency waveform design based on radar-embedded communication is proposed. Firstly, sparse frequency waveforms are designed based on power spectral density fitting and quasi-Newton method. Secondly, the eigenvalue decomposition of the sparse frequency waveform sequence is used to get the dominant space. Finally the communication waveforms are designed through the projection of orthogonal pseudorandom vectors in the vertical subspace. Compared with the linear frequency modulation waveform, the sparse frequency waveform can further improve the bandwidth occupation of communication signals, thus achieving higher communication rate. A certain correlation exists between the reciprocally orthogonal communication signals samples and the sparse frequency waveform, which guarantees the low SER (signal error rate and LPI (low probability of intercept. The simulation results verify the effectiveness of this method.

  12. Colocated MIMO Radar: Beamforming, Waveform design, and Target Parameter Estimation

    KAUST Repository

    Jardak, Seifallah

    2014-04-01

    Thanks to its improved capabilities, the Multiple Input Multiple Output (MIMO) radar is attracting the attention of researchers and practitioners alike. Because it transmits orthogonal or partially correlated waveforms, this emerging technology outperformed the phased array radar by providing better parametric identifiability, achieving higher spatial resolution, and designing complex beampatterns. To avoid jamming and enhance the signal to noise ratio, it is often interesting to maximize the transmitted power in a given region of interest and minimize it elsewhere. This problem is known as the transmit beampattern design and is usually tackled as a two-step process: a transmit covariance matrix is firstly designed by minimizing a convex optimization problem, which is then used to generate practical waveforms. In this work, we propose simple novel methods to generate correlated waveforms using finite alphabet constant and non-constant-envelope symbols. To generate finite alphabet waveforms, the proposed method maps easily generated Gaussian random variables onto the phase-shift-keying, pulse-amplitude, and quadrature-amplitude modulation schemes. For such mapping, the probability density function of Gaussian random variables is divided into M regions, where M is the number of alphabets in the corresponding modulation scheme. By exploiting the mapping function, the relationship between the cross-correlation of Gaussian and finite alphabet symbols is derived. The second part of this thesis covers the topic of target parameter estimation. To determine the reflection coefficient, spatial location, and Doppler shift of a target, maximum likelihood estimation yields the best performance. However, it requires a two dimensional search problem. Therefore, its computational complexity is prohibitively high. So, we proposed a reduced complexity and optimum performance algorithm which allows the two dimensional fast Fourier transform to jointly estimate the spatial location

  13. Investigation of a Cross-Correlation Based Optical Strain Measurement Technique for Detecting radial Growth on a Rotating Disk

    Science.gov (United States)

    Clem, Michelle M.; Woike, Mark R.

    2013-01-01

    The Aeronautical Sciences Project under NASA`s Fundamental Aeronautics Program is extremely interested in the development of novel measurement technologies, such as optical surface measurements in the internal parts of a flow path, for in situ health monitoring of gas turbine engines. In situ health monitoring has the potential to detect flaws, i.e. cracks in key components, such as engine turbine disks, before the flaws lead to catastrophic failure. In the present study, a cross-correlation imaging technique is investigated in a proof-of-concept study as a possible optical technique to measure the radial growth and strain field on an already cracked sub-scale turbine engine disk under loaded conditions in the NASA Glenn Research Center`s High Precision Rotordynamics Laboratory. The optical strain measurement technique under investigation offers potential fault detection using an applied high-contrast random speckle pattern and imaging the pattern under unloaded and loaded conditions with a CCD camera. Spinning the cracked disk at high speeds induces an external load, resulting in a radial growth of the disk of approximately 50.0-im in the flawed region and hence, a localized strain field. When imaging the cracked disk under static conditions, the disk will be undistorted; however, during rotation the cracked region will grow radially, thus causing the applied particle pattern to be .shifted`. The resulting particle displacements between the two images will then be measured using the two-dimensional cross-correlation algorithms implemented in standard Particle Image Velocimetry (PIV) software to track the disk growth, which facilitates calculation of the localized strain field. In order to develop and validate this optical strain measurement technique an initial proof-of-concept experiment is carried out in a controlled environment. Using PIV optimization principles and guidelines, three potential speckle patterns, for future use on the rotating disk, are developed

  14. On the accuracy and precision of numerical waveforms: effect of waveform extraction methodology

    Science.gov (United States)

    Chu, Tony; Fong, Heather; Kumar, Prayush; Pfeiffer, Harald P.; Boyle, Michael; Hemberger, Daniel A.; Kidder, Lawrence E.; Scheel, Mark A.; Szilagyi, Bela

    2016-08-01

    We present a new set of 95 numerical relativity simulations of non-precessing binary black holes (BBHs). The simulations sample comprehensively both black-hole spins up to spin magnitude of 0.9, and cover mass ratios 1-3. The simulations cover on average 24 inspiral orbits, plus merger and ringdown, with low initial orbital eccentricities e\\lt {10}-4. A subset of the simulations extends the coverage of non-spinning BBHs up to mass ratio q = 10. Gravitational waveforms at asymptotic infinity are computed with two independent techniques: extrapolation and Cauchy characteristic extraction. An error analysis based on noise-weighted inner products is performed. We find that numerical truncation error, error due to gravitational wave extraction, and errors due to the Fourier transformation of signals with finite length of the numerical waveforms are of similar magnitude, with gravitational wave extraction errors dominating at noise-weighted mismatches of ˜ 3× {10}-4. This set of waveforms will serve to validate and improve aligned-spin waveform models for gravitational wave science.

  15. Experimental validation of waveform relaxation technique for power ...

    Indian Academy of Sciences (India)

    damping controller drawn our attention to a potential convergence problem which ... method was originally proposed as a method of parallelizing the numerical integration of very. Figure 2 ..... to it the features of an industrial real-time operating system. ..... Odeh F and Ruehli A 1985 Waveform relaxation: Theory and practice.

  16. Propagation compensation by waveform predistortion

    Science.gov (United States)

    Halpin, Thomas F.; Urkowitz, Harry; Maron, David E.

    Certain modifications of the Cobra Dane radar are considered, particularly modernization of the waveform generator. For wideband waveforms, the dispersive effects of the ionosphere become increasingly significant. The technique of predistorting the transmitted waveform so that a linear chirp is received after two-way passage is one way to overcome that dispersion. This approach is maintained for the modified system, but with a specific predistortion waveform well suited to the modification. The appropriate form of predistortion was derived in an implicit form of time as a function of frequency. The exact form was approximated by Taylor series and pseudo-Chebyshev approximation. The latter proved better, as demonstrated by the resulting smaller loss in detection sensitivity, less coarsening of range resolution, and a lower peak sidelobe. The effects of error in determining the plasma delay constant were determined and are given in graphical form. A suggestion for in-place determination of the plasma delay constant is given.

  17. Two-receiver measurements of phase velocity: cross-validation of ambient-noise and earthquake-based observations

    NARCIS (Netherlands)

    Kästle, Emanuel D.; Soomro, Riaz; Weemstra, C.; Boschi, Lapo; Meier, Thomas

    2016-01-01

    Phase velocities derived from ambient-noise cross-correlation are compared with phase velocities calculated from cross-correlations of waveform recordings of teleseismic earthquakes whose epicentres are approximately on the station–station great circle. The comparison is conducted both for Rayleigh

  18. Waveform LiDAR across forest biomass gradients

    Science.gov (United States)

    Montesano, P. M.; Nelson, R. F.; Dubayah, R.; Sun, G.; Ranson, J.

    2011-12-01

    Detailed information on the quantity and distribution of aboveground biomass (AGB) is needed to understand how it varies across space and changes over time. Waveform LiDAR data is routinely used to derive the heights of scattering elements in each illuminated footprint, and the vertical structure of vegetation is related to AGB. Changes in LiDAR waveforms across vegetation structure gradients can demonstrate instrument sensitivity to land cover transitions. A close examination of LiDAR waveforms in footprints across a forest gradient can provide new insight into the relationship of vegetation structure and forest AGB. In this study we use field measurements of individual trees within Laser Vegetation Imaging Sensor (LVIS) footprints along transects crossing forest to non-forest gradients to examine changes in LVIS waveform characteristics at sites with low (field AGB measurements to original and adjusted LVIS waveforms to detect the forest AGB interval along a forest - non-forest transition in which the LVIS waveform lose the ability to discern differences in AGB. Our results help identify the lower end the forest biomass range that a ~20m footprint waveform LiDAR can detect, which can help infer accumulation of biomass after disturbances and during forest expansion, and which can guide the use of LiDAR within a multi-sensor fusion biomass mapping approach.

  19. Sodium boiling detection in LMFBRs by acoustic-neutronic cross correlation

    International Nuclear Information System (INIS)

    Wright, S.A.

    1977-01-01

    The acoustic and neutronic noise signals caused by boiling are the signals primarily considered likely to detect sodium boiling in an LMFBR. Unfortunately, these signals may have serious signal-to-noise problems due to strong background noise sources. Neutronic-acoustic cross correlation techniques are expected to provide a means of improving the signal-to-noise ratio. This technique can improve the signal-to-noise ratio because the neutronic and acoustic signals due to boiling are highly correlated near the bubble repetition frequency, while the background noise sources are expected to be uncorrelated (or at most weakly correlated). An experiment was designed to show that the neutronic and acoustic noise signals are indeed highly correlated. The experiment consisted of simulating the void and pressure effects of local sodium boiling in the core of a zero-power reactor (ARK). The analysis showed that the neutronic and acoustic noise signals caused by boiling are almost perfectly correlated in a wide frequency band about the bubble repetition frequency. The results of the experiments were generalized to full-scale reactors to compare the inherent effectiveness of the methods which use the neutronic or acoustic signals alone with a hybrid method, which cross correlates the neutronic and acoustic signals. It was concluded that over a zone of the reactor where the void coefficient is sufficiently large (approximately 85 percent the core volume), the cross correlation method can provide a more rapid detection system for a given signal-to-noise ratio. However, where the void coefficient is small, one must probably rely on the acoustic method alone

  20. High-speed technique based on a parallel projection correlation procedure for digital image correlation

    Science.gov (United States)

    Zaripov, D. I.; Renfu, Li

    2018-05-01

    The implementation of high-efficiency digital image correlation methods based on a zero-normalized cross-correlation (ZNCC) procedure for high-speed, time-resolved measurements using a high-resolution digital camera is associated with big data processing and is often time consuming. In order to speed-up ZNCC computation, a high-speed technique based on a parallel projection correlation procedure is proposed. The proposed technique involves the use of interrogation window projections instead of its two-dimensional field of luminous intensity. This simplification allows acceleration of ZNCC computation up to 28.8 times compared to ZNCC calculated directly, depending on the size of interrogation window and region of interest. The results of three synthetic test cases, such as a one-dimensional uniform flow, a linear shear flow and a turbulent boundary-layer flow, are discussed in terms of accuracy. In the latter case, the proposed technique is implemented together with an iterative window-deformation technique. On the basis of the results of the present work, the proposed technique is recommended to be used for initial velocity field calculation, with further correction using more accurate techniques.

  1. Statistical analysis of correlated experimental data and neutron cross section evaluation

    International Nuclear Information System (INIS)

    Badikov, S.A.

    1998-01-01

    The technique for evaluation of neutron cross sections on the basis of statistical analysis of correlated experimental data is presented. The most important stages of evaluation beginning from compilation of correlation matrix for measurement uncertainties till representation of the analysis results in the ENDF-6 format are described in details. Special attention is paid to restrictions (positive uncertainty) on covariation matrix of approximate parameters uncertainties generated within the method of least square fit which is derived from physical reasons. The requirements for source experimental data assuring satisfaction of the restrictions mentioned above are formulated. Correlation matrices of measurement uncertainties in particular should be also positively determined. Variants of modelling the positively determined correlation matrices of measurement uncertainties in a situation when their consequent calculation on the basis of experimental information is impossible are discussed. The technique described is used for creating the new generation of estimates of dosimetric reactions cross sections for the first version of the Russian dosimetric file (including nontrivial covariation information)

  2. A new methodology of spatial cross-correlation analysis.

    Science.gov (United States)

    Chen, Yanguang

    2015-01-01

    Spatial correlation modeling comprises both spatial autocorrelation and spatial cross-correlation processes. The spatial autocorrelation theory has been well-developed. It is necessary to advance the method of spatial cross-correlation analysis to supplement the autocorrelation analysis. This paper presents a set of models and analytical procedures for spatial cross-correlation analysis. By analogy with Moran's index newly expressed in a spatial quadratic form, a theoretical framework is derived for geographical cross-correlation modeling. First, two sets of spatial cross-correlation coefficients are defined, including a global spatial cross-correlation coefficient and local spatial cross-correlation coefficients. Second, a pair of scatterplots of spatial cross-correlation is proposed, and the plots can be used to visually reveal the causality behind spatial systems. Based on the global cross-correlation coefficient, Pearson's correlation coefficient can be decomposed into two parts: direct correlation (partial correlation) and indirect correlation (spatial cross-correlation). As an example, the methodology is applied to the relationships between China's urbanization and economic development to illustrate how to model spatial cross-correlation phenomena. This study is an introduction to developing the theory of spatial cross-correlation, and future geographical spatial analysis might benefit from these models and indexes.

  3. Cross-Correlation-Function-Based Multipath Mitigation Method for Sine-BOC Signals

    Directory of Open Access Journals (Sweden)

    H. H. Chen

    2012-06-01

    Full Text Available Global Navigation Satellite Systems (GNSS positioning accuracy indoor and urban canyons environments are greatly affected by multipath due to distortions in its autocorrelation function. In this paper, a cross-correlation function between the received sine phased Binary Offset Carrier (sine-BOC modulation signal and the local signal is studied firstly, and a new multipath mitigation method based on cross-correlation function for sine-BOC signal is proposed. This method is implemented to create a cross-correlation function by designing the modulated symbols of the local signal. The theoretical analysis and simulation results indicate that the proposed method exhibits better multipath mitigation performance compared with the traditional Double Delta Correlator (DDC techniques, especially the medium/long delay multipath signals, and it is also convenient and flexible to implement by using only one correlator, which is the case of low-cost mass-market receivers.

  4. Individual Biometric Identification Using Multi-Cycle Electrocardiographic Waveform Patterns

    Directory of Open Access Journals (Sweden)

    Wonki Lee

    2018-03-01

    Full Text Available The electrocardiogram (ECG waveform conveys information regarding the electrical property of the heart. The patterns vary depending on the individual heart characteristics. ECG features can be potentially used for biometric recognition. This study presents a new method using the entire ECG waveform pattern for matching and demonstrates that the approach can potentially be employed for individual biometric identification. Multi-cycle ECG signals were assessed using an ECG measuring circuit, and three electrodes can be patched on the wrists or fingers for considering various measurements. For biometric identification, our-fold cross validation was used in the experiments for assessing how the results of a statistical analysis will generalize to an independent data set. Four different pattern matching algorithms, i.e., cosine similarity, cross correlation, city block distance, and Euclidean distances, were tested to compare the individual identification performances with a single channel of ECG signal (3-wire ECG. To evaluate the pattern matching for biometric identification, the ECG recordings for each subject were partitioned into training and test set. The suggested method obtained a maximum performance of 89.9% accuracy with two heartbeats of ECG signals measured on the wrist and 93.3% accuracy with three heartbeats for 55 subjects. The performance rate with ECG signals measured on the fingers improved up to 99.3% with two heartbeats and 100% with three heartbeats of signals for 20 subjects.

  5. Individual Biometric Identification Using Multi-Cycle Electrocardiographic Waveform Patterns.

    Science.gov (United States)

    Lee, Wonki; Kim, Seulgee; Kim, Daeeun

    2018-03-28

    The electrocardiogram (ECG) waveform conveys information regarding the electrical property of the heart. The patterns vary depending on the individual heart characteristics. ECG features can be potentially used for biometric recognition. This study presents a new method using the entire ECG waveform pattern for matching and demonstrates that the approach can potentially be employed for individual biometric identification. Multi-cycle ECG signals were assessed using an ECG measuring circuit, and three electrodes can be patched on the wrists or fingers for considering various measurements. For biometric identification, our-fold cross validation was used in the experiments for assessing how the results of a statistical analysis will generalize to an independent data set. Four different pattern matching algorithms, i.e., cosine similarity, cross correlation, city block distance, and Euclidean distances, were tested to compare the individual identification performances with a single channel of ECG signal (3-wire ECG). To evaluate the pattern matching for biometric identification, the ECG recordings for each subject were partitioned into training and test set. The suggested method obtained a maximum performance of 89.9% accuracy with two heartbeats of ECG signals measured on the wrist and 93.3% accuracy with three heartbeats for 55 subjects. The performance rate with ECG signals measured on the fingers improved up to 99.3% with two heartbeats and 100% with three heartbeats of signals for 20 subjects.

  6. A New Methodology of Spatial Cross-Correlation Analysis

    Science.gov (United States)

    Chen, Yanguang

    2015-01-01

    Spatial correlation modeling comprises both spatial autocorrelation and spatial cross-correlation processes. The spatial autocorrelation theory has been well-developed. It is necessary to advance the method of spatial cross-correlation analysis to supplement the autocorrelation analysis. This paper presents a set of models and analytical procedures for spatial cross-correlation analysis. By analogy with Moran’s index newly expressed in a spatial quadratic form, a theoretical framework is derived for geographical cross-correlation modeling. First, two sets of spatial cross-correlation coefficients are defined, including a global spatial cross-correlation coefficient and local spatial cross-correlation coefficients. Second, a pair of scatterplots of spatial cross-correlation is proposed, and the plots can be used to visually reveal the causality behind spatial systems. Based on the global cross-correlation coefficient, Pearson’s correlation coefficient can be decomposed into two parts: direct correlation (partial correlation) and indirect correlation (spatial cross-correlation). As an example, the methodology is applied to the relationships between China’s urbanization and economic development to illustrate how to model spatial cross-correlation phenomena. This study is an introduction to developing the theory of spatial cross-correlation, and future geographical spatial analysis might benefit from these models and indexes. PMID:25993120

  7. Adaptive phase k-means algorithm for waveform classification

    Science.gov (United States)

    Song, Chengyun; Liu, Zhining; Wang, Yaojun; Xu, Feng; Li, Xingming; Hu, Guangmin

    2018-01-01

    Waveform classification is a powerful technique for seismic facies analysis that describes the heterogeneity and compartments within a reservoir. Horizon interpretation is a critical step in waveform classification. However, the horizon often produces inconsistent waveform phase, and thus results in an unsatisfied classification. To alleviate this problem, an adaptive phase waveform classification method called the adaptive phase k-means is introduced in this paper. Our method improves the traditional k-means algorithm using an adaptive phase distance for waveform similarity measure. The proposed distance is a measure with variable phases as it moves from sample to sample along the traces. Model traces are also updated with the best phase interference in the iterative process. Therefore, our method is robust to phase variations caused by the interpretation horizon. We tested the effectiveness of our algorithm by applying it to synthetic and real data. The satisfactory results reveal that the proposed method tolerates certain waveform phase variation and is a good tool for seismic facies analysis.

  8. Needlet estimation of cross-correlation between CMB lensing maps and LSS

    Energy Technology Data Exchange (ETDEWEB)

    Bianchini, Federico [Astrophysics Sector, SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Renzi, Alessandro; Marinucci, Domenico, E-mail: fbianchini@sissa.it, E-mail: renzi@mat.uniroma2.it, E-mail: marinucc@mat.uniroma2.it [Dipartimento di Matematica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133 Roma (Italy)

    2016-11-01

    In this paper we develop a novel needlet-based estimator to investigate the cross-correlation between cosmic microwave background (CMB) lensing maps and large-scale structure (LSS) data. We compare this estimator with its harmonic counterpart and, in particular, we analyze the bias effects of different forms of masking. In order to address this bias, we also implement a MASTER-like technique in the needlet case. The resulting estimator turns out to have an extremely good signal-to-noise performance. Our analysis aims at expanding and optimizing the operating domains in CMB-LSS cross-correlation studies, similarly to CMB needlet data analysis. It is motivated especially by next generation experiments (such as Euclid) which will allow us to derive much tighter constraints on cosmological and astrophysical parameters through cross-correlation measurements between CMB and LSS.

  9. IMPROVING CORRELATION FUNCTION FITTING WITH RIDGE REGRESSION: APPLICATION TO CROSS-CORRELATION RECONSTRUCTION

    International Nuclear Information System (INIS)

    Matthews, Daniel J.; Newman, Jeffrey A.

    2012-01-01

    Cross-correlation techniques provide a promising avenue for calibrating photometric redshifts and determining redshift distributions using spectroscopy which is systematically incomplete (e.g., current deep spectroscopic surveys fail to obtain secure redshifts for 30%-50% or more of the galaxies targeted). In this paper, we improve on the redshift distribution reconstruction methods from our previous work by incorporating full covariance information into our correlation function fits. Correlation function measurements are strongly covariant between angular or spatial bins, and accounting for this in fitting can yield substantial reduction in errors. However, frequently the covariance matrices used in these calculations are determined from a relatively small set (dozens rather than hundreds) of subsamples or mock catalogs, resulting in noisy covariance matrices whose inversion is ill-conditioned and numerically unstable. We present here a method of conditioning the covariance matrix known as ridge regression which results in a more well behaved inversion than other techniques common in large-scale structure studies. We demonstrate that ridge regression significantly improves the determination of correlation function parameters. We then apply these improved techniques to the problem of reconstructing redshift distributions. By incorporating full covariance information, applying ridge regression, and changing the weighting of fields in obtaining average correlation functions, we obtain reductions in the mean redshift distribution reconstruction error of as much as ∼40% compared to previous methods. We provide a description of POWERFIT, an IDL code for performing power-law fits to correlation functions with ridge regression conditioning that we are making publicly available.

  10. Solving seismological problems using sgraph program: II-waveform modeling

    International Nuclear Information System (INIS)

    Abdelwahed, Mohamed F.

    2012-01-01

    One of the seismological programs to manipulate seismic data is SGRAPH program. It consists of integrated tools to perform advanced seismological techniques. SGRAPH is considered a new system for maintaining and analyze seismic waveform data in a stand-alone Windows-based application that manipulate a wide range of data formats. SGRAPH was described in detail in the first part of this paper. In this part, I discuss the advanced techniques including in the program and its applications in seismology. Because of the numerous tools included in the program, only SGRAPH is sufficient to perform the basic waveform analysis and to solve advanced seismological problems. In the first part of this paper, the application of the source parameters estimation and hypocentral location was given. Here, I discuss SGRAPH waveform modeling tools. This paper exhibits examples of how to apply the SGRAPH tools to perform waveform modeling for estimating the focal mechanism and crustal structure of local earthquakes.

  11. Nuclear techniques and cross-correlation methods for spectral analysis in two-phase flow measurements in mineral pipelines

    Energy Technology Data Exchange (ETDEWEB)

    Brandao, Luis E.B.; Salgado, Cesar M., E-mail: brandaos@ien.gov.br, E-mail: otero@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Divisao de Radiofarmacos; Sicilliano, Umberto C.C.S., E-mail: umberto.cassara@poli.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, RJ (Brazil). Dept. de Metalurgia

    2013-07-01

    In mineral industry is common to use water to transport pellets inside pipes. In these units, the correct measurement of flow (both solid and liquid phase) is important to guarantee a safe operation. Cross correlation flow meters are devices specially suited to be used in dual-phase flow and they are based on measure the transit time due the disturbances registered between two points, in our case gamma attenuation from radioactive sources. The emphasis of this work is the application of gamma transmission and scattering technique associated with spectral analysis methods to measure the flow of solid phase in a liquid fluid in side the pipe. The detectors and the sources are out side of the tube and are positioned 10.0 cm distant one from the other. The photons of transmission/scattering gamma radiation were registered, and across-correlation method was applied to measure the flow and spectral analysis was used to study the flow profile inside the pipe. (author)

  12. Mixed-correlated ARFIMA processes for power-law cross-correlations

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav

    2013-01-01

    Roč. 392, č. 24 (2013), s. 6484-6493 ISSN 0378-4371 R&D Projects: GA ČR GA402/09/0965 Institutional support: RVO:67985556 Keywords : power-law cross-correlations * long - term memory * econophysics Subject RIV: AH - Economics Impact factor: 1.722, year: 2013 http://library.utia.cas.cz/separaty/2013/E/kristoufek-mixed-correlated arfima processes for power-law cross-correlations.pdf

  13. WFCatalog: A catalogue for seismological waveform data

    Science.gov (United States)

    Trani, Luca; Koymans, Mathijs; Atkinson, Malcolm; Sleeman, Reinoud; Filgueira, Rosa

    2017-09-01

    This paper reports advances in seismic waveform description and discovery leading to a new seismological service and presents the key steps in its design, implementation and adoption. This service, named WFCatalog, which stands for waveform catalogue, accommodates features of seismological waveform data. Therefore, it meets the need for seismologists to be able to select waveform data based on seismic waveform features as well as sensor geolocations and temporal specifications. We describe the collaborative design methods and the technical solution showing the central role of seismic feature catalogues in framing the technical and operational delivery of the new service. Also, we provide an overview of the complex environment wherein this endeavour is scoped and the related challenges discussed. As multi-disciplinary, multi-organisational and global collaboration is necessary to address today's challenges, canonical representations can provide a focus for collaboration and conceptual tools for agreeing directions. Such collaborations can be fostered and formalised by rallying intellectual effort into the design of novel scientific catalogues and the services that support them. This work offers an example of the benefits generated by involving cross-disciplinary skills (e.g. data and domain expertise) from the early stages of design, and by sustaining the engagement with the target community throughout the delivery and deployment process.

  14. Multifractal temporally weighted detrended cross-correlation analysis to quantify power-law cross-correlation and its application to stock markets

    Science.gov (United States)

    Wei, Yun-Lan; Yu, Zu-Guo; Zou, Hai-Long; Anh, Vo

    2017-06-01

    A new method—multifractal temporally weighted detrended cross-correlation analysis (MF-TWXDFA)—is proposed to investigate multifractal cross-correlations in this paper. This new method is based on multifractal temporally weighted detrended fluctuation analysis and multifractal cross-correlation analysis (MFCCA). An innovation of the method is applying geographically weighted regression to estimate local trends in the nonstationary time series. We also take into consideration the sign of the fluctuations in computing the corresponding detrended cross-covariance function. To test the performance of the MF-TWXDFA algorithm, we apply it and the MFCCA method on simulated and actual series. Numerical tests on artificially simulated series demonstrate that our method can accurately detect long-range cross-correlations for two simultaneously recorded series. To further show the utility of MF-TWXDFA, we apply it on time series from stock markets and find that power-law cross-correlation between stock returns is significantly multifractal. A new coefficient, MF-TWXDFA cross-correlation coefficient, is also defined to quantify the levels of cross-correlation between two time series.

  15. Frequency-domain waveform inversion using the unwrapped phase

    KAUST Repository

    Choi, Yun Seok

    2011-01-01

    Phase wrapping in the frequency-domain (or cycle skipping in the time-domain) is the major cause of the local minima problem in the waveform inversion. The unwrapped phase has the potential to provide us with a robust and reliable waveform inversion, with reduced local minima. We propose a waveform inversion algorithm using the unwrapped phase objective function in the frequency-domain. The unwrapped phase, or what we call the instantaneous traveltime, is given by the imaginary part of dividing the derivative of the wavefield with respect to the angular frequency by the wavefield itself. As a result, the objective function is given a traveltime-like function, which allows us to smooth it and reduce its nonlinearity. The gradient of the objective function is computed using the back-propagation algorithm based on the adjoint-state technique. We apply both our waveform inversion algorithm using the unwrapped phase and the conventional waveform inversion and show that our inversion algorithm gives better convergence to the true model than the conventional waveform inversion. © 2011 Society of Exploration Geophysicists.

  16. Hidden cross-correlation patterns in stock markets based on permutation cross-sample entropy and PCA

    Science.gov (United States)

    Lin, Aijing; Shang, Pengjian; Zhong, Bo

    2014-12-01

    In this article, we investigate the hidden cross-correlation structures in Chinese stock markets and US stock markets by performing PCSE combined with PCA approach. It is suggested that PCSE can provide a more faithful and more interpretable description of the dynamic mechanism between time series than cross-correlation matrix. We show that this new technique can be adapted to observe stock markets especially during financial crisis. In order to identify and compare the interactions and structures of stock markets during financial crisis, as well as in normal periods, all the samples are divided into four sub-periods. The results imply that the cross-correlations between Chinese group are stronger than the US group in the most sub-periods. In particular, it is likely that the US stock markets are more integrated with each other during global financial crisis than during Asian financial crisis. However, our results illustrate that Chinese stock markets are not immune from the global financial crisis, although less integrated with other markets if they are compared with US stock markets.

  17. Visualization of synchronization of the uterine contraction signals: running cross-correlation and wavelet running cross-correlation methods.

    Science.gov (United States)

    Oczeretko, Edward; Swiatecka, Jolanta; Kitlas, Agnieszka; Laudanski, Tadeusz; Pierzynski, Piotr

    2006-01-01

    In physiological research, we often study multivariate data sets, containing two or more simultaneously recorded time series. The aim of this paper is to present the cross-correlation and the wavelet cross-correlation methods to assess synchronization between contractions in different topographic regions of the uterus. From a medical point of view, it is important to identify time delays between contractions, which may be of potential diagnostic significance in various pathologies. The cross-correlation was computed in a moving window with a width corresponding to approximately two or three contractions. As a result, the running cross-correlation function was obtained. The propagation% parameter assessed from this function allows quantitative description of synchronization in bivariate time series. In general, the uterine contraction signals are very complicated. Wavelet transforms provide insight into the structure of the time series at various frequencies (scales). To show the changes of the propagation% parameter along scales, a wavelet running cross-correlation was used. At first, the continuous wavelet transforms as the uterine contraction signals were received and afterwards, a running cross-correlation analysis was conducted for each pair of transformed time series. The findings show that running functions are very useful in the analysis of uterine contractions.

  18. Signal processing in noise waveform radar

    CERN Document Server

    Kulpa, Krzysztof

    2013-01-01

    This book is devoted to the emerging technology of noise waveform radar and its signal processing aspects. It is a new kind of radar, which use noise-like waveform to illuminate the target. The book includes an introduction to basic radar theory, starting from classical pulse radar, signal compression, and wave radar. The book then discusses the properties, difficulties and potential of noise radar systems, primarily for low-power and short-range civil applications. The contribution of modern signal processing techniques to making noise radar practical are emphasized, and application examples

  19. Multiscale Detrended Cross-Correlation Analysis of STOCK Markets

    Science.gov (United States)

    Yin, Yi; Shang, Pengjian

    2014-06-01

    In this paper, we employ the detrended cross-correlation analysis (DCCA) to investigate the cross-correlations between different stock markets. We report the results of cross-correlated behaviors in US, Chinese and European stock markets in period 1997-2012 by using DCCA method. The DCCA shows the cross-correlated behaviors of intra-regional and inter-regional stock markets in the short and long term which display the similarities and differences of cross-correlated behaviors simply and roughly and the persistence of cross-correlated behaviors of fluctuations. Then, because of the limitation and inapplicability of DCCA method, we propose multiscale detrended cross-correlation analysis (MSDCCA) method to avoid "a priori" selecting the ranges of scales over which two coefficients of the classical DCCA method are identified, and employ MSDCCA to reanalyze these cross-correlations to exhibit some important details such as the existence and position of minimum, maximum and bimodal distribution which are lost if the scale structure is described by two coefficients only and essential differences and similarities in the scale structures of cross-correlation of intra-regional and inter-regional markets. More statistical characteristics of cross-correlation obtained by MSDCCA method help us to understand how two different stock markets influence each other and to analyze the influence from thus two inter-regional markets on the cross-correlation in detail, thus we get a richer and more detailed knowledge of the complex evolutions of dynamics of the cross-correlations between stock markets. The application of MSDCCA is important to promote our understanding of the internal mechanisms and structures of financial markets and helps to forecast the stock indices based on our current results demonstrated the cross-correlations between stock indices. We also discuss the MSDCCA methods of secant rolling window with different sizes and, lastly, provide some relevant implications and

  20. Cross-correlations and influence in world gold markets

    Science.gov (United States)

    Lin, Min; Wang, Gang-Jin; Xie, Chi; Stanley, H. Eugene

    2018-01-01

    Using the detrended cross-correlation analysis (DCCA) coefficient and the detrended partial cross-correlation analysis (DPCCA) coefficient, we investigate cross-correlations and net cross-correlations among five major world gold markets (London, New York, Shanghai, Tokyo, and Mumbai) at different time scales. We propose multiscale influence measures for examining the influence of individual markets on other markets and on the entire system. We find (i) that the cross-correlations, net cross-correlations, and net influences among the five gold markets vary across time scales, (ii) that the cross-market correlation between London and New York at each time scale is intense and inherent, meaning that the influence of other gold markets on the London-New York market is negligible, (iii) that the remaining cross-market correlations (i.e., those other than London-New York) are greatly affected by other gold markets, and (iv) that the London gold market significantly affects the other four gold markets and dominates the world-wide gold market. Our multiscale findings give market participants and market regulators new information on cross-market linkages in the world-wide gold market.

  1. Two-dimensional multifractal cross-correlation analysis

    International Nuclear Information System (INIS)

    Xi, Caiping; Zhang, Shuning; Xiong, Gang; Zhao, Huichang; Yang, Yonghong

    2017-01-01

    Highlights: • We study the mathematical models of 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Present the definition of the two-dimensional N 2 -partitioned multiplicative cascading process. • Do the comparative analysis of 2D-MC by 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Provide a reference on the choice and parameter settings of these methods in practice. - Abstract: There are a number of situations in which several signals are simultaneously recorded in complex systems, which exhibit long-term power-law cross-correlations. This paper presents two-dimensional multifractal cross-correlation analysis based on the partition function (2D-MFXPF), two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) and two-dimensional multifractal cross-correlation analysis based on the detrended moving average analysis (2D-MFXDMA). We apply these methods to pairs of two-dimensional multiplicative cascades (2D-MC) to do a comparative study. Then, we apply the two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) to real images and unveil intriguing multifractality in the cross correlations of the material structures. At last, we give the main conclusions and provide a valuable reference on how to choose the multifractal algorithms in the potential applications in the field of SAR image classification and detection.

  2. The effect of inlet waveforms on computational hemodynamics of patient-specific intracranial aneurysms.

    Science.gov (United States)

    Xiang, J; Siddiqui, A H; Meng, H

    2014-12-18

    Due to the lack of patient-specific inlet flow waveform measurements, most computational fluid dynamics (CFD) simulations of intracranial aneurysms usually employ waveforms that are not patient-specific as inlet boundary conditions for the computational model. The current study examined how this assumption affects the predicted hemodynamics in patient-specific aneurysm geometries. We examined wall shear stress (WSS) and oscillatory shear index (OSI), the two most widely studied hemodynamic quantities that have been shown to predict aneurysm rupture, as well as maximal WSS (MWSS), energy loss (EL) and pressure loss coefficient (PLc). Sixteen pulsatile CFD simulations were carried out on four typical saccular aneurysms using 4 different waveforms and an identical inflow rate as inlet boundary conditions. Our results demonstrated that under the same mean inflow rate, different waveforms produced almost identical WSS distributions and WSS magnitudes, similar OSI distributions but drastically different OSI magnitudes. The OSI magnitude is correlated with the pulsatility index of the waveform. Furthermore, there is a linear relationship between aneurysm-averaged OSI values calculated from one waveform and those calculated from another waveform. In addition, different waveforms produced similar MWSS, EL and PLc in each aneurysm. In conclusion, inlet waveform has minimal effects on WSS, OSI distribution, MWSS, EL and PLc and a strong effect on OSI magnitude, but aneurysm-averaged OSI from different waveforms has a strong linear correlation with each other across different aneurysms, indicating that for the same aneurysm cohort, different waveforms can consistently stratify (rank) OSI of aneurysms. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Measurement of correlated b quark cross sections at CDF

    International Nuclear Information System (INIS)

    Gerdes, D.

    1994-09-01

    Using data collected during the 1992--93 collider run at Fermilab, CDF has made measurements of correlated b quark cross section where one b is detected from a muon from semileptonic decay and the second b is detected with secondary vertex techniques. We report on measurements of the cross section as a function of the momentum of the second b and as a function of the azimuthal separation of the two b quarks, for transverse momentum of the initial b quark greater than 15 GeV. Results are compared to QCD predictions

  4. Measurement of spatial correlation functions using image processing techniques

    International Nuclear Information System (INIS)

    Berryman, J.G.

    1985-01-01

    A procedure for using digital image processing techniques to measure the spatial correlation functions of composite heterogeneous materials is presented. Methods for eliminating undesirable biases and warping in digitized photographs are discussed. Fourier transform methods and array processor techniques for calculating the spatial correlation functions are treated. By introducing a minimal set of lattice-commensurate triangles, a method of sorting and storing the values of three-point correlation functions in a compact one-dimensional array is developed. Examples are presented at each stage of the analysis using synthetic photographs of cross sections of a model random material (the penetrable sphere model) for which the analytical form of the spatial correlations functions is known. Although results depend somewhat on magnification and on relative volume fraction, it is found that photographs digitized with 512 x 512 pixels generally have sufficiently good statistics for most practical purposes. To illustrate the use of the correlation functions, bounds on conductivity for the penetrable sphere model are calculated with a general numerical scheme developed for treating the singular three-dimensional integrals which must be evaluated

  5. A 32-channel photon counting module with embedded auto/cross-correlators for real-time parallel fluorescence correlation spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gong, S.; Labanca, I.; Rech, I.; Ghioni, M. [Dipartimento di Elettronica, Informazione e Bioingegneria, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2014-10-15

    Fluorescence correlation spectroscopy (FCS) is a well-established technique to study binding interactions or the diffusion of fluorescently labeled biomolecules in vitro and in vivo. Fast FCS experiments require parallel data acquisition and analysis which can be achieved by exploiting a multi-channel Single Photon Avalanche Diode (SPAD) array and a corresponding multi-input correlator. This paper reports a 32-channel FPGA based correlator able to perform 32 auto/cross-correlations simultaneously over a lag-time ranging from 10 ns up to 150 ms. The correlator is included in a 32 × 1 SPAD array module, providing a compact and flexible instrument for high throughput FCS experiments. However, some inherent features of SPAD arrays, namely afterpulsing and optical crosstalk effects, may introduce distortions in the measurement of auto- and cross-correlation functions. We investigated these limitations to assess their impact on the module and evaluate possible workarounds.

  6. A 32-channel photon counting module with embedded auto/cross-correlators for real-time parallel fluorescence correlation spectroscopy

    International Nuclear Information System (INIS)

    Gong, S.; Labanca, I.; Rech, I.; Ghioni, M.

    2014-01-01

    Fluorescence correlation spectroscopy (FCS) is a well-established technique to study binding interactions or the diffusion of fluorescently labeled biomolecules in vitro and in vivo. Fast FCS experiments require parallel data acquisition and analysis which can be achieved by exploiting a multi-channel Single Photon Avalanche Diode (SPAD) array and a corresponding multi-input correlator. This paper reports a 32-channel FPGA based correlator able to perform 32 auto/cross-correlations simultaneously over a lag-time ranging from 10 ns up to 150 ms. The correlator is included in a 32 × 1 SPAD array module, providing a compact and flexible instrument for high throughput FCS experiments. However, some inherent features of SPAD arrays, namely afterpulsing and optical crosstalk effects, may introduce distortions in the measurement of auto- and cross-correlation functions. We investigated these limitations to assess their impact on the module and evaluate possible workarounds

  7. Detrended cross-correlation analysis of electroencephalogram

    International Nuclear Information System (INIS)

    Wang Jun; Zhao Da-Qing

    2012-01-01

    In the paper we use detrended cross-correlation analysis (DCCA) to study the electroencephalograms of healthy young subjects and healthy old subjects. It is found that the cross-correlation between different leads of a healthy young subject is larger than that of a healthy old subject. It was shown that the cross-correlation relationship decreases with the aging process and the phenomenon can help to diagnose whether the subject's brain function is healthy or not. (interdisciplinary physics and related areas of science and technology)

  8. Random matrix theory analysis of cross-correlations in the US stock market: Evidence from Pearson’s correlation coefficient and detrended cross-correlation coefficient

    Science.gov (United States)

    Wang, Gang-Jin; Xie, Chi; Chen, Shou; Yang, Jiao-Jiao; Yang, Ming-Yan

    2013-09-01

    In this study, we first build two empirical cross-correlation matrices in the US stock market by two different methods, namely the Pearson’s correlation coefficient and the detrended cross-correlation coefficient (DCCA coefficient). Then, combining the two matrices with the method of random matrix theory (RMT), we mainly investigate the statistical properties of cross-correlations in the US stock market. We choose the daily closing prices of 462 constituent stocks of S&P 500 index as the research objects and select the sample data from January 3, 2005 to August 31, 2012. In the empirical analysis, we examine the statistical properties of cross-correlation coefficients, the distribution of eigenvalues, the distribution of eigenvector components, and the inverse participation ratio. From the two methods, we find some new results of the cross-correlations in the US stock market in our study, which are different from the conclusions reached by previous studies. The empirical cross-correlation matrices constructed by the DCCA coefficient show several interesting properties at different time scales in the US stock market, which are useful to the risk management and optimal portfolio selection, especially to the diversity of the asset portfolio. It will be an interesting and meaningful work to find the theoretical eigenvalue distribution of a completely random matrix R for the DCCA coefficient because it does not obey the Marčenko-Pastur distribution.

  9. Harmonic arbitrary waveform generator

    Science.gov (United States)

    Roberts, Brock Franklin

    2017-11-28

    High frequency arbitrary waveforms have applications in radar, communications, medical imaging, therapy, electronic warfare, and charged particle acceleration and control. State of the art arbitrary waveform generators are limited in the frequency they can operate by the speed of the Digital to Analog converters that directly create their arbitrary waveforms. The architecture of the Harmonic Arbitrary Waveform Generator allows the phase and amplitude of the high frequency content of waveforms to be controlled without taxing the Digital to Analog converters that control them. The Harmonic Arbitrary Waveform Generator converts a high frequency input, into a precision, adjustable, high frequency arbitrary waveform.

  10. Progress of a Cross-Correlation Based Optical Strain Measurement Technique for Detecting Radial Growth on a Rotating Disk

    Science.gov (United States)

    Clem, Michelle M.; Abdul-Aziz, Ali; Woike, Mark R.; Fralick, Gustave C.

    2015-01-01

    The modern turbine engine operates in a harsh environment at high speeds and is repeatedly exposed to combined high mechanical and thermal loads. The cumulative effects of these external forces lead to high stresses and strains on the engine components, such as the rotating turbine disks, which may eventually lead to a catastrophic failure if left undetected. The operating environment makes it difficult to use conventional strain gauges, therefore, non-contact strain measurement techniques is of interest to NASA and the turbine engine community. This presentation describes one such approach; the use of cross correlation analysis to measure strain experienced by the engine turbine disk with the goal of assessing potential faults and damage.

  11. Analyzing the Cross-Correlation Between Onshore and Offshore RMB Exchange Rates Based on Multifractal Detrended Cross-Correlation Analysis (MF-DCCA)

    Science.gov (United States)

    Xie, Chi; Zhou, Yingying; Wang, Gangjin; Yan, Xinguo

    We use the multifractal detrended cross-correlation analysis (MF-DCCA) method to explore the multifractal behavior of the cross-correlation between exchange rates of onshore RMB (CNY) and offshore RMB (CNH) against US dollar (USD). The empirical data are daily prices of CNY/USD and CNH/USD from May 1, 2012 to February 29, 2016. The results demonstrate that: (i) the cross-correlation between CNY/USD and CNH/USD is persistent and its fluctuation is smaller when the order of fluctuation function is negative than that when the order is positive; (ii) the multifractal behavior of the cross-correlation between CNY/USD and CNH/USD is significant during the sample period; (iii) the dynamic Hurst exponents obtained by the rolling windows analysis show that the cross-correlation is stable when the global economic situation is good and volatile in bad situation; and (iv) the non-normal distribution of original data has a greater effect on the multifractality of the cross-correlation between CNY/USD and CNH/USD than the temporary correlation.

  12. Flow velocity measurement by using zero-crossing polarity cross correlation method

    International Nuclear Information System (INIS)

    Xu Chengji; Lu Jinming; Xia Hong

    1993-01-01

    Using the designed correlation metering system and a high accurate hot-wire anemometer as a calibration device, the experimental study of correlation method in a tunnel was carried out. The velocity measurement of gas flow by using zero-crossing polarity cross correlation method was realized and the experimental results has been analysed

  13. Classification of morphologic changes in photoplethysmographic waveforms

    Directory of Open Access Journals (Sweden)

    Tigges Timo

    2016-09-01

    Full Text Available An ever increasing number of research is examining the question to what extent physiological information beyond the blood oxygen saturation could be drawn from the photoplethysmogram. One important approach to elicit that information from the photoplethysmogram is the analysis of its waveform. One prominent example for the value of photoplethysmographic waveform analysis in cardiovascular monitoring that has emerged is hemodynamic compensation assessment in the peri-operative setting or trauma situations, as digital pulse waveform dynamically changes with alterations in vascular tone or pulse wave velocity. In this work, we present an algorithm based on modern machine learning techniques that automatically finds individual digital volume pulses in photoplethysmographic signals and sorts them into one of the pulse classes defined by Dawber et al. We evaluate our approach based on two major datasets – a measurement study that we conducted ourselves as well as data from the PhysioNet MIMIC II database. As the results are satisfying we could demonstrate the capabilities of classification algorithms in the automated assessment of the digital volume pulse waveform measured by photoplethysmographic devices.

  14. Programmable waveform controller

    International Nuclear Information System (INIS)

    Yeh, H.T.

    1979-01-01

    A programmable waveform controller (PWC) was developed for voltage waveform generation in the laboratory. It is based on the Intel 8080 family of chips. The hardware uses the modular board approach, sharing a common 44-pin bus. The software contains two separate programs: the first generates a single connected linear ramp waveform and is capable of bipolar operation, linear interpolation between input data points, extended time range, and cycling; the second generates four independent square waveforms with variable duration and amplitude

  15. Three dimensional winds: A maximum cross-correlation application to elastic lidar data

    Energy Technology Data Exchange (ETDEWEB)

    Buttler, William Tillman [Univ. of Texas, Austin, TX (United States)

    1996-05-01

    Maximum cross-correlation techniques have been used with satellite data to estimate winds and sea surface velocities for several years. Los Alamos National Laboratory (LANL) is currently using a variation of the basic maximum cross-correlation technique, coupled with a deterministic application of a vector median filter, to measure transverse winds as a function of range and altitude from incoherent elastic backscatter lidar (light detection and ranging) data taken throughout large volumes within the atmospheric boundary layer. Hourly representations of three-dimensional wind fields, derived from elastic lidar data taken during an air-quality study performed in a region of complex terrain near Sunland Park, New Mexico, are presented and compared with results from an Environmental Protection Agency (EPA) approved laser doppler velocimeter. The wind fields showed persistent large scale eddies as well as general terrain-following winds in the Rio Grande valley.

  16. Multifractal detrended cross-correlation analysis in the MENA area

    Science.gov (United States)

    El Alaoui, Marwane; Benbachir, Saâd

    2013-12-01

    In this paper, we investigated multifractal cross-correlations qualitatively and quantitatively using a cross-correlation test and the Multifractal detrended cross-correlation analysis method (MF-DCCA) for markets in the MENA area. We used cross-correlation coefficients to measure the level of this correlation. The analysis concerns four stock market indices of Morocco, Tunisia, Egypt and Jordan. The countries chosen are signatory of the Agadir agreement concerning the establishment of a free trade area comprising Arab Mediterranean countries. We computed the bivariate generalized Hurst exponent, Rényi exponent and spectrum of singularity for each pair of indices to measure quantitatively the cross-correlations. By analyzing the results, we found the existence of multifractal cross-correlations between all of these markets. We compared the spectrum width of these indices; we also found which pair of indices has a strong multifractal cross-correlation.

  17. Testing Cross-Sectional Correlation in Large Panel Data Models with Serial Correlation

    Directory of Open Access Journals (Sweden)

    Badi H. Baltagi

    2016-11-01

    Full Text Available This paper considers the problem of testing cross-sectional correlation in large panel data models with serially-correlated errors. It finds that existing tests for cross-sectional correlation encounter size distortions with serial correlation in the errors. To control the size, this paper proposes a modification of Pesaran’s Cross-sectional Dependence (CD test to account for serial correlation of an unknown form in the error term. We derive the limiting distribution of this test as N , T → ∞ . The test is distribution free and allows for unknown forms of serial correlation in the errors. Monte Carlo simulations show that the test has good size and power for large panels when serial correlation in the errors is present.

  18. Josephson Arbitrary Waveform Synthesis With Multilevel Pulse Biasing

    Science.gov (United States)

    Brevik, Justus A.; Flowers-Jacobs, Nathan E.; Fox, Anna E.; Golden, Evan B.; Dresselhaus, Paul D.; Benz, Samuel P.

    2017-01-01

    We describe the implementation of new commercial pulse-bias electronics that have enabled an improvement in the generation of quantum-accurate waveforms both with and without low-frequency compensation biases. We have used these electronics to apply a multilevel pulse bias to the Josephson arbitrary waveform synthesizer and have generated, for the first time, a quantum-accurate bipolar sinusoidal waveform without the use of a low-frequency compensation bias current. This uncompensated 1 kHz waveform was synthesized with an rms amplitude of 325 mV and maintained its quantum accuracy over a1.5 mA operating current range. The same technique and equipment was also used to synthesize a quantum-accurate 1 MHz sinusoid with a 1.2 mA operating margin. In addition, we have synthesized a compensated 1 kHz sinusoid with an rms amplitude of 1 V and a 2.7 mA operating margin. PMID:28736494

  19. Analysis of thermal fluctuations in the semiscale tests to determine flow transit delay times using a transfer function cross-correlation technique

    International Nuclear Information System (INIS)

    Raptis, A.C.; Popper, G.F.

    1977-08-01

    On April 14, 1976, EG and G performed the Semiscale Blowdown 29-1 experiment to try to establish the feasibility of using a transit time flowmeter (TTF) to measure transient blowdown two-phase flow rates. The recorded signals from that experiment were made available to and analyzed by the Argonne National Laboratory using the transfer function cross-correlation technique. The theoretical background for the transfer function method of analysis and the results of the data analysis are presented. Histograms of transit time during the blowdown are shown and topics for further investigation are identified

  20. Multifractal Detrended Cross-Correlation Analysis of agricultural futures markets

    International Nuclear Information System (INIS)

    He Lingyun; Chen Shupeng

    2011-01-01

    Highlights: → We investigated cross-correlations between China's and US agricultural futures markets. → Power-law cross-correlations are found between the geographically far but correlated markets. → Multifractal features are significant in all the markets. → Cross-correlation exponent is less than averaged GHE when q 0. - Abstract: We investigated geographically far but temporally correlated China's and US agricultural futures markets. We found that there exists a power-law cross-correlation between them, and that multifractal features are significant in all the markets. It is very interesting that the geographically far markets show strong cross-correlations and share much of their multifractal structure. Furthermore, we found that for all the agricultural futures markets in our studies, the cross-correlation exponent is less than the averaged generalized Hurst exponents (GHE) when q 0.

  1. Statistical tests for power-law cross-correlated processes

    Science.gov (United States)

    Podobnik, Boris; Jiang, Zhi-Qiang; Zhou, Wei-Xing; Stanley, H. Eugene

    2011-12-01

    For stationary time series, the cross-covariance and the cross-correlation as functions of time lag n serve to quantify the similarity of two time series. The latter measure is also used to assess whether the cross-correlations are statistically significant. For nonstationary time series, the analogous measures are detrended cross-correlations analysis (DCCA) and the recently proposed detrended cross-correlation coefficient, ρDCCA(T,n), where T is the total length of the time series and n the window size. For ρDCCA(T,n), we numerically calculated the Cauchy inequality -1≤ρDCCA(T,n)≤1. Here we derive -1≤ρDCCA(T,n)≤1 for a standard variance-covariance approach and for a detrending approach. For overlapping windows, we find the range of ρDCCA within which the cross-correlations become statistically significant. For overlapping windows we numerically determine—and for nonoverlapping windows we derive—that the standard deviation of ρDCCA(T,n) tends with increasing T to 1/T. Using ρDCCA(T,n) we show that the Chinese financial market's tendency to follow the U.S. market is extremely weak. We also propose an additional statistical test that can be used to quantify the existence of cross-correlations between two power-law correlated time series.

  2. 100 GHz pulse waveform measurement based on electro-optic sampling

    Science.gov (United States)

    Feng, Zhigang; Zhao, Kejia; Yang, Zhijun; Miao, Jingyuan; Chen, He

    2018-05-01

    We present an ultrafast pulse waveform measurement system based on an electro-optic sampling technique at 1560 nm and prepare LiTaO3-based electro-optic modulators with a coplanar waveguide structure. The transmission and reflection characteristics of electrical pulses on a coplanar waveguide terminated with an open circuit and a resistor are investigated by analyzing the corresponding time-domain pulse waveforms. We measure the output electrical pulse waveform of a 100 GHz photodiode and the obtained rise times of the impulse and step responses are 2.5 and 3.4 ps, respectively.

  3. Arbitrary magnetic field gradient waveform correction using an impulse response based pre-equalization technique.

    Science.gov (United States)

    Goora, Frédéric G; Colpitts, Bruce G; Balcom, Bruce J

    2014-01-01

    The time-varying magnetic fields used in magnetic resonance applications result in the induction of eddy currents on conductive structures in the vicinity of both the sample under investigation and the gradient coils. These eddy currents typically result in undesired degradations of image quality for MRI applications. Their ubiquitous nature has resulted in the development of various approaches to characterize and minimize their impact on image quality. This paper outlines a method that utilizes the magnetic field gradient waveform monitor method to directly measure the temporal evolution of the magnetic field gradient from a step-like input function and extracts the system impulse response. With the basic assumption that the gradient system is sufficiently linear and time invariant to permit system theory analysis, the impulse response is used to determine a pre-equalized (optimized) input waveform that provides a desired gradient response at the output of the system. An algorithm has been developed that calculates a pre-equalized waveform that may be accurately reproduced by the amplifier (is physically realizable) and accounts for system limitations including system bandwidth, amplifier slew rate capabilities, and noise inherent in the initial measurement. Significant improvements in magnetic field gradient waveform fidelity after pre-equalization have been realized and are summarized. Copyright © 2013 Elsevier Inc. All rights reserved.

  4. Characterization of Direct Current-Electrical Penetration Graph Waveforms and Correlation With the Probing Behavior of Matsumuratettix hiroglyphicus (Hemiptera: Cicadellidae), the Insect Vector of Sugarcane White Leaf Phytoplasma.

    Science.gov (United States)

    Roddee, J; Kobori, Y; Yorozuya, H; Hanboonsong, Y

    2017-06-01

    The leafhopper Matsumuratettix hiroglyphicus (Matsumura) (Hemiptera: Cicadellidae) is an important vector of phytoplasma causing white leaf disease in sugarcane. Thus, the aim of our study was to understand and describe the stylet-probing activities of this vector while feeding on sugarcane plants, by using direct current (DC) electrical penetration graph (EPG) monitoring. The EPG signals were classified into six distinct waveforms, according to amplitude, frequency, voltage level, and electrical origin of the observed traces during stylet penetration into the host plant tissues (probing). These six EPG waveforms of probing behavior comprise no stylet penetration (NP); stylet pathway through epidermis, mesophyll, and parenchymal cells (waveform A); contact at the bundle sheath layer (waveform B); salivation into phloem sieve elements (waveform C); phloem sap ingestion (waveform D); and short ingestion time of xylem sap (waveform E). The above waveform patterns were correlated with histological data of salivary sheath termini in plant tissue generated from insect stylet tips. The key findings of this study were that M. hiroglyphicus ingests the phloem sap at a relatively higher rate and for longer duration from any other cell type, suggesting that M. hiroglyphicus is mainly a phloem-feeder. Quantitative comparison of probing behavior revealed that females typically probe more frequently and longer in the phloem than males. Thus, females may acquire and inoculate greater amounts of phytoplasma than males, enhancing the efficiency of phytoplasma transmission and potentially exacerbating disease spreading. Overall, our study provides basic information on the probing behavior and transmission mechanism of M. hiroglyphicus. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  5. Bunches of random cross-correlated sequences

    International Nuclear Information System (INIS)

    Maystrenko, A A; Melnik, S S; Pritula, G M; Usatenko, O V

    2013-01-01

    The statistical properties of random cross-correlated sequences constructed by the convolution method (likewise referred to as the Rice or the inverse Fourier transformation) are examined. We clarify the meaning of the filtering function—the kernel of the convolution operator—and show that it is the value of the cross-correlation function which describes correlations between the initial white noise and constructed correlated sequences. The matrix generalization of this method for constructing a bunch of N cross-correlated sequences is presented. Algorithms for their generation are reduced to solving the problem of decomposition of the Fourier transform of the correlation matrix into a product of two mutually conjugate matrices. Different decompositions are considered. The limits of weak and strong correlations for the one-point probability and pair correlation functions of sequences generated by the method under consideration are studied. Special cases of heavy-tailed distributions of the generated sequences are analyzed. We show that, if the filtering function is rather smooth, the distribution function of generated variables has the Gaussian or Lévy form depending on the analytical properties of the distribution (or characteristic) functions of the initial white noise. Anisotropic properties of statistically homogeneous random sequences related to the asymmetry of a filtering function are revealed and studied. These asymmetry properties are expressed in terms of the third- or fourth-order correlation functions. Several examples of the construction of correlated chains with a predefined correlation matrix are given. (paper)

  6. Frequency-domain elastic full waveform inversion using encoded simultaneous sources

    Science.gov (United States)

    Jeong, W.; Son, W.; Pyun, S.; Min, D.

    2011-12-01

    Currently, numerous studies have endeavored to develop robust full waveform inversion and migration algorithms. These processes require enormous computational costs, because of the number of sources in the survey. To avoid this problem, the phase encoding technique for prestack migration was proposed by Romero (2000) and Krebs et al. (2009) proposed the encoded simultaneous-source inversion technique in the time domain. On the other hand, Ben-Hadj-Ali et al. (2011) demonstrated the robustness of the frequency-domain full waveform inversion with simultaneous sources for noisy data changing the source assembling. Although several studies on simultaneous-source inversion tried to estimate P- wave velocity based on the acoustic wave equation, seismic migration and waveform inversion based on the elastic wave equations are required to obtain more reliable subsurface information. In this study, we propose a 2-D frequency-domain elastic full waveform inversion technique using phase encoding methods. In our algorithm, the random phase encoding method is employed to calculate the gradients of the elastic parameters, source signature estimation and the diagonal entries of approximate Hessian matrix. The crosstalk for the estimated source signature and the diagonal entries of approximate Hessian matrix are suppressed with iteration as for the gradients. Our 2-D frequency-domain elastic waveform inversion algorithm is composed using the back-propagation technique and the conjugate-gradient method. Source signature is estimated using the full Newton method. We compare the simultaneous-source inversion with the conventional waveform inversion for synthetic data sets of the Marmousi-2 model. The inverted results obtained by simultaneous sources are comparable to those obtained by individual sources, and source signature is successfully estimated in simultaneous source technique. Comparing the inverted results using the pseudo Hessian matrix with previous inversion results

  7. CCFpams: Atmospheric stellar parameters from cross-correlation functions

    Science.gov (United States)

    Malavolta, Luca; Lovis, Christophe; Pepe, Francesco; Sneden, Christopher; Udry, Stephane

    2017-07-01

    CCFpams allows the measurement of stellar temperature, metallicity and gravity within a few seconds and in a completely automated fashion. Rather than performing comparisons with spectral libraries, the technique is based on the determination of several cross-correlation functions (CCFs) obtained by including spectral features with different sensitivity to the photospheric parameters. Literature stellar parameters of high signal-to-noise (SNR) and high-resolution HARPS spectra of FGK Main Sequence stars are used to calibrate the stellar parameters as a function of CCF areas.

  8. A seamless acquisition digital storage oscilloscope with three-dimensional waveform display

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Kuojun, E-mail: kuojunyang@gmail.com; Guo, Lianping [School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu (China); School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore); Tian, Shulin; Zeng, Hao [School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu (China); Qiu, Lei [School of Electrical and Electronic Engineering, Nanyang Technological University (Singapore)

    2014-04-15

    In traditional digital storage oscilloscope (DSO), sampled data need to be processed after each acquisition. During data processing, the acquisition is stopped and oscilloscope is blind to the input signal. Thus, this duration is called dead time. With the rapid development of modern electronic systems, the effect of infrequent events becomes significant. To capture these occasional events in shorter time, dead time in traditional DSO that causes the loss of measured signal needs to be reduced or even eliminated. In this paper, a seamless acquisition oscilloscope without dead time is proposed. In this oscilloscope, three-dimensional waveform mapping (TWM) technique, which converts sampled data to displayed waveform, is proposed. With this technique, not only the process speed is improved, but also the probability information of waveform is displayed with different brightness. Thus, a three-dimensional waveform is shown to the user. To reduce processing time further, parallel TWM which processes several sampled points simultaneously, and dual-port random access memory based pipelining technique which can process one sampling point in one clock period are proposed. Furthermore, two DDR3 (Double-Data-Rate Three Synchronous Dynamic Random Access Memory) are used for storing sampled data alternately, thus the acquisition can continue during data processing. Therefore, the dead time of DSO is eliminated. In addition, a double-pulse test method is adopted to test the waveform capturing rate (WCR) of the oscilloscope and a combined pulse test method is employed to evaluate the oscilloscope's capture ability comprehensively. The experiment results show that the WCR of the designed oscilloscope is 6 250 000 wfms/s (waveforms per second), the highest value in all existing oscilloscopes. The testing results also prove that there is no dead time in our oscilloscope, thus realizing the seamless acquisition.

  9. A seamless acquisition digital storage oscilloscope with three-dimensional waveform display

    Science.gov (United States)

    Yang, Kuojun; Tian, Shulin; Zeng, Hao; Qiu, Lei; Guo, Lianping

    2014-04-01

    In traditional digital storage oscilloscope (DSO), sampled data need to be processed after each acquisition. During data processing, the acquisition is stopped and oscilloscope is blind to the input signal. Thus, this duration is called dead time. With the rapid development of modern electronic systems, the effect of infrequent events becomes significant. To capture these occasional events in shorter time, dead time in traditional DSO that causes the loss of measured signal needs to be reduced or even eliminated. In this paper, a seamless acquisition oscilloscope without dead time is proposed. In this oscilloscope, three-dimensional waveform mapping (TWM) technique, which converts sampled data to displayed waveform, is proposed. With this technique, not only the process speed is improved, but also the probability information of waveform is displayed with different brightness. Thus, a three-dimensional waveform is shown to the user. To reduce processing time further, parallel TWM which processes several sampled points simultaneously, and dual-port random access memory based pipelining technique which can process one sampling point in one clock period are proposed. Furthermore, two DDR3 (Double-Data-Rate Three Synchronous Dynamic Random Access Memory) are used for storing sampled data alternately, thus the acquisition can continue during data processing. Therefore, the dead time of DSO is eliminated. In addition, a double-pulse test method is adopted to test the waveform capturing rate (WCR) of the oscilloscope and a combined pulse test method is employed to evaluate the oscilloscope's capture ability comprehensively. The experiment results show that the WCR of the designed oscilloscope is 6 250 000 wfms/s (waveforms per second), the highest value in all existing oscilloscopes. The testing results also prove that there is no dead time in our oscilloscope, thus realizing the seamless acquisition.

  10. A seamless acquisition digital storage oscilloscope with three-dimensional waveform display

    International Nuclear Information System (INIS)

    Yang, Kuojun; Guo, Lianping; Tian, Shulin; Zeng, Hao; Qiu, Lei

    2014-01-01

    In traditional digital storage oscilloscope (DSO), sampled data need to be processed after each acquisition. During data processing, the acquisition is stopped and oscilloscope is blind to the input signal. Thus, this duration is called dead time. With the rapid development of modern electronic systems, the effect of infrequent events becomes significant. To capture these occasional events in shorter time, dead time in traditional DSO that causes the loss of measured signal needs to be reduced or even eliminated. In this paper, a seamless acquisition oscilloscope without dead time is proposed. In this oscilloscope, three-dimensional waveform mapping (TWM) technique, which converts sampled data to displayed waveform, is proposed. With this technique, not only the process speed is improved, but also the probability information of waveform is displayed with different brightness. Thus, a three-dimensional waveform is shown to the user. To reduce processing time further, parallel TWM which processes several sampled points simultaneously, and dual-port random access memory based pipelining technique which can process one sampling point in one clock period are proposed. Furthermore, two DDR3 (Double-Data-Rate Three Synchronous Dynamic Random Access Memory) are used for storing sampled data alternately, thus the acquisition can continue during data processing. Therefore, the dead time of DSO is eliminated. In addition, a double-pulse test method is adopted to test the waveform capturing rate (WCR) of the oscilloscope and a combined pulse test method is employed to evaluate the oscilloscope's capture ability comprehensively. The experiment results show that the WCR of the designed oscilloscope is 6 250 000 wfms/s (waveforms per second), the highest value in all existing oscilloscopes. The testing results also prove that there is no dead time in our oscilloscope, thus realizing the seamless acquisition

  11. Shaping the spectrum of random-phase radar waveforms

    Science.gov (United States)

    Doerry, Armin W.; Marquette, Brandeis

    2017-05-09

    The various technologies presented herein relate to generation of a desired waveform profile in the form of a spectrum of apparently random noise (e.g., white noise or colored noise), but with precise spectral characteristics. Hence, a waveform profile that could be readily determined (e.g., by a spoofing system) is effectively obscured. Obscuration is achieved by dividing the waveform into a series of chips, each with an assigned frequency, wherein the sequence of chips are subsequently randomized. Randomization can be a function of the application of a key to the chip sequence. During processing of the echo pulse, a copy of the randomized transmitted pulse is recovered or regenerated against which the received echo is correlated. Hence, with the echo energy range-compressed in this manner, it is possible to generate a radar image with precise impulse response.

  12. Comparison of correlation analysis techniques for irregularly sampled time series

    Directory of Open Access Journals (Sweden)

    K. Rehfeld

    2011-06-01

    Full Text Available Geoscientific measurements often provide time series with irregular time sampling, requiring either data reconstruction (interpolation or sophisticated methods to handle irregular sampling. We compare the linear interpolation technique and different approaches for analyzing the correlation functions and persistence of irregularly sampled time series, as Lomb-Scargle Fourier transformation and kernel-based methods. In a thorough benchmark test we investigate the performance of these techniques.

    All methods have comparable root mean square errors (RMSEs for low skewness of the inter-observation time distribution. For high skewness, very irregular data, interpolation bias and RMSE increase strongly. We find a 40 % lower RMSE for the lag-1 autocorrelation function (ACF for the Gaussian kernel method vs. the linear interpolation scheme,in the analysis of highly irregular time series. For the cross correlation function (CCF the RMSE is then lower by 60 %. The application of the Lomb-Scargle technique gave results comparable to the kernel methods for the univariate, but poorer results in the bivariate case. Especially the high-frequency components of the signal, where classical methods show a strong bias in ACF and CCF magnitude, are preserved when using the kernel methods.

    We illustrate the performances of interpolation vs. Gaussian kernel method by applying both to paleo-data from four locations, reflecting late Holocene Asian monsoon variability as derived from speleothem δ18O measurements. Cross correlation results are similar for both methods, which we attribute to the long time scales of the common variability. The persistence time (memory is strongly overestimated when using the standard, interpolation-based, approach. Hence, the Gaussian kernel is a reliable and more robust estimator with significant advantages compared to other techniques and suitable for large scale application to paleo-data.

  13. The use of joint time frequency analysis to quantify the effect of ventilation on the pulse oximeter waveform.

    Science.gov (United States)

    Shelley, Kirk H; Awad, Aymen A; Stout, Robert G; Silverman, David G

    2006-04-01

    In the process of determining oxygen saturation, the pulse oximeter functions as a photoelectric plethysmograph. By analyzing how the frequency spectrum of the pulse oximeter waveform changes over time, new clinically relevant features can be extracted. Thirty patients undergoing general anesthesia for abdominal surgery had their pulse oximeter, airway pressure and CO(2) waveforms collected (50 Hz). The pulse oximeter waveform was analyzed with a short-time Fourier transform using a moving 4096 point Hann window of 82 seconds duration. The frequency signal created by positive pressure ventilation was extracted using a peak detection algorithm in the frequency range of ventilation (0.08-0.4 Hz = 5-24 breaths/minute). The respiratory rate derived in this manner was compared to the respiratory rate as determined by CO(2) detection. In total, 52 hours of telemetry data were analyzed. The respiratory rate measured from the pulse oximeter waveform was found to have a 0.89 linear correlation when compared to CO(2) detection and airway pressure change. the bias was 0.03 breath/min, SD was 0.557 breath/min and the upper and lower limits of agreement were 1.145 and -1.083 breath/min respectively. The presence of motion artifact proved to be the primary cause of failure of this technique. Joint time frequency analysis of the pulse oximeter waveform can be used to determine the respiratory rate of ventilated patients and to quantify the impact of ventilation on the waveform. In addition, when applied to the pulse oximeter waveform new clinically relevant features were observed.

  14. Stochastic systems with cross-correlated Gaussian white noises

    International Nuclear Information System (INIS)

    Wang Cheng-Yu; Song Yu-Min; Zhou Peng; Yang Hai; Gao Yun

    2010-01-01

    This paper theoretically investigates three stochastic systems with cross-correlation Gaussian white noises. Both steady state properties of the stochastic nonlinear systems and the nonequilibrium transitions induced by the cross-correlated noises are studied. The stationary solutions of the Fokker—Planck equation for three specific examples are analysed. It is shown explicitly that the cross-correlation of white noises can induce nonequilibrium transitions

  15. Cross-correlation of long-range correlated series

    International Nuclear Information System (INIS)

    Arianos, Sergio; Carbone, Anna

    2009-01-01

    A method for estimating the cross-correlation C xy (τ) of long-range correlated series x(t) and y(t), at varying lags τ and scales n, is proposed. For fractional Brownian motions with Hurst exponents H 1 and H 2 , the asymptotic expression for C xy (τ) depends only on the lag τ (wide-sense stationarity) and scales as a power of n with exponent H 1 +H 2 for τ→0. The method is illustrated on: (i) financial series, to show the leverage effect; (ii) genomic sequences, to estimate the correlations between structural parameters along the chromosomes

  16. Phase-space topography characterization of nonlinear ultrasound waveforms.

    Science.gov (United States)

    Dehghan-Niri, Ehsan; Al-Beer, Helem

    2018-03-01

    Fundamental understanding of ultrasound interaction with material discontinuities having closed interfaces has many engineering applications such as nondestructive evaluation of defects like kissing bonds and cracks in critical structural and mechanical components. In this paper, to analyze the acoustic field nonlinearities due to defects with closed interfaces, the use of a common technique in nonlinear physics, based on a phase-space topography construction of ultrasound waveform, is proposed. The central idea is to complement the "time" and "frequency" domain analyses with the "phase-space" domain analysis of nonlinear ultrasound waveforms. A nonlinear time series method known as pseudo phase-space topography construction is used to construct equivalent phase-space portrait of measured ultrasound waveforms. Several nonlinear models are considered to numerically simulate nonlinear ultrasound waveforms. The phase-space response of the simulated waveforms is shown to provide different topographic information, while the frequency domain shows similar spectral behavior. Thus, model classification can be substantially enhanced in the phase-space domain. Experimental results on high strength aluminum samples show that the phase-space transformation provides a unique detection and classification capabilities. The Poincaré map of the phase-space domain is also used to better understand the nonlinear behavior of ultrasound waveforms. It is shown that the analysis of ultrasound nonlinearities is more convenient and informative in the phase-space domain than in the frequency domain. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Fragmentation of the C60 molecule in collision with light ions studied by a multi-correlation technique. Cross-sections, electron spectroscopy

    International Nuclear Information System (INIS)

    Rentenier, A.

    2004-04-01

    A quantitative study of the C60 fullerenes fragmentation in collision with light ions (H n + with n=1,2,3, He q+ with q=1,2) in the velocity range 0,1 - 2,3 u.a.) is presented. The multi-correlation technique, developed between fragment ions and electrons with well defined energy, has enlightened some of the dependences and properties of fragmentation mechanisms (cross sections, electron spectroscopy, size distributions, kinetic energy of fragment ions, Campi's scatter plot, activation energies). The deposited energy hence appeared as an important parameter. Cross sections have been measured, for the first time, for all the collisional processes. Ionisation and capture only depends on the collision velocity. On the other hand, scaling laws with the deposited energy have been observed for the cross sections of multifragmentation, which depends on the collision energy and the nature of the projectile. The deposited energy has also been found as an essential parameter to understand the evolution of the charged fragment size distributions. The electron spectroscopy, achieved at an emission angle of 35 degrees, showed spectra peaked at important energies (from 5 to 20 eV). The spectra shape depends on the collision velocity. A first theoretical analysis points out the link between the observed energy distribution and the presence of a centrifugal potential barrier. Finally, correlation experiments between produced ions and electron energy reveal that electron energy increases with internal energy. (author)

  18. Signal Digitizer and Cross-Correlation Application Specific Integrated Circuit

    Science.gov (United States)

    Baranauskas, Dalius (Inventor); Baranauskas, Gytis (Inventor); Zelenin, Denis (Inventor); Kangaslahti, Pekka (Inventor); Tanner, Alan B. (Inventor); Lim, Boon H. (Inventor)

    2017-01-01

    According to one embodiment, a cross-correlator comprises a plurality of analog front ends (AFEs), a cross-correlation circuit and a data serializer. Each of the AFEs comprises a variable gain amplifier (VGA) and a corresponding analog-to-digital converter (ADC) in which the VGA receives and modifies a unique analog signal associates with a measured analog radio frequency (RF) signal and the ADC produces digital data associated with the modified analog signal. Communicatively coupled to the AFEs, the cross-correlation circuit performs a cross-correlation operation on the digital data produced from different measured analog RF signals. The data serializer is communicatively coupled to the summing and cross-correlating matrix and continuously outputs a prescribed amount of the correlated digital data.

  19. Wavelet-Based Signal Processing of Electromagnetic Pulse Generated Waveforms

    National Research Council Canada - National Science Library

    Ardolino, Richard S

    2007-01-01

    This thesis investigated and compared alternative signal processing techniques that used wavelet-based methods instead of traditional frequency domain methods for processing measured electromagnetic pulse (EMP) waveforms...

  20. Pseudo LRM waveforms from CryoSat SARin acquisition

    Science.gov (United States)

    Scagliola, Michele; Fornari, Marco; Bouffard, Jerome; Parrinello, Tommaso; Féménias, Pierre

    2016-04-01

    CryoSat was launched on the 8th April 2010 and is the first European ice mission dedicated to the monitoring of precise changes in the thickness of polar ice sheets and floating sea ice. The main payload of CryoSat is a Ku-band pulsewidth limited radar altimeter, called SIRAL (Synthetic interferometric radar altimeter). When commanded in SARIn (synthetic aperture radar interferometry) mode, through coherent along-track processing of the returns received from two antennas, the interferometric phase related to the first arrival of the echo is used to retrieve the angle of arrival of the scattering in the across-track direction. When SIRAL operates in SAR or SARin mode, the obtained waveforms have an along-track resolution and a speckle reduction which is increased with respect to the pulse-limited waveforms. Anyway, in order to analyze the continuity of the geophysical retrieved parameters among different acquisition modes, techniques to transform SARin mode data to pseudo-LRM mode data are welcome. The transformation process is known as SAR reduction and it is worth recalling here that only approximate pseudo-LRM waveforms can be obtained in case of closed burst acquisitions, as SIRAL operates. A SAR reduction processing scheme has been developed to obtain pseudo-LRM waveforms from CryoSat SARin acquisition. As a trade-off between the along-track length on Earth surface contributing to one SARin pseudo-LRM waveform and the noisiness of the waveform itself, it has been chosen a SAR reduction approach based on the averaging of all the SARin echoes received each 20Hz, resulting in one pseudo-LRM waveform for each SARin burst given the SARin burst repetition period. SARin pseudo-LRM waveforms have been produced for CryoSat acquisition both on ice and sea surfaces, aiming at verifying the continuity of the retracked surface height over the ellipsoid between genuine LRM products and pseudo-LRM products. Moreover, the retracked height from the SARin pseudo-LRM has been

  1. Adaptive Waveform Design for Cognitive Radar in Multiple Targets Situations

    Directory of Open Access Journals (Sweden)

    Xiaowen Zhang

    2018-02-01

    Full Text Available In this paper, the problem of cognitive radar (CR waveform optimization design for target detection and estimation in multiple extended targets situations is investigated. This problem is analyzed in signal-dependent interference, as well as additive channel noise for extended targets with unknown target impulse response (TIR. To address this problem, an improved algorithm is employed for target detection by maximizing the detection probability of the received echo on the promise of ensuring the TIR estimation precision. In this algorithm, an additional weight vector is introduced to achieve a trade-off among different targets. Both the estimate of TIR and transmit waveform can be updated at each step based on the previous step. Under the same constraint on waveform energy and bandwidth, the information theoretical approach is also considered. In addition, the relationship between the waveforms that are designed based on the two criteria is discussed. Unlike most existing works that only consider single target with temporally correlated characteristics, waveform design for multiple extended targets is considered in this method. Simulation results demonstrate that compared with linear frequency modulated (LFM signal, waveforms designed based on maximum detection probability and maximum mutual information (MI criteria can make radar echoes contain more multiple-target information and improve radar performance as a result.

  2. Correlation techniques for the improvement of signal-to-noise ratio in measurements with stochastic processes

    CERN Document Server

    Reddy, V R; Reddy, T G; Reddy, P Y; Reddy, K R

    2003-01-01

    An AC modulation technique is described to convert stochastic signal variations into an amplitude variation and its retrieval through Fourier analysis. It is shown that this AC detection of signals of stochastic processes when processed through auto- and cross-correlation techniques improve the signal-to-noise ratio; the correlation techniques serve a similar purpose of frequency and phase filtering as that of phase-sensitive detection. A few model calculations applied to nuclear spectroscopy measurements such as Angular Correlations, Mossbauer spectroscopy and Pulse Height Analysis reveal considerable improvement in the sensitivity of signal detection. Experimental implementation of the technique is presented in terms of amplitude variations of harmonics representing the derivatives of normal spectra. Improved detection sensitivity to spectral variations is shown to be significant. These correlation techniques are general and can be made applicable to all the fields of particle counting where measurements ar...

  3. Simultaneous inversion of seismic velocity and moment tensor using elastic-waveform inversion of microseismic data: Application to the Aneth CO2-EOR field

    Science.gov (United States)

    Chen, Y.; Huang, L.

    2017-12-01

    Moment tensors are key parameters for characterizing CO2-injection-induced microseismic events. Elastic-waveform inversion has the potential to providing accurate results of moment tensors. Microseismic waveforms contains information of source moment tensors and the wave propagation velocity along the wavepaths. We develop an elastic-waveform inversion method to jointly invert the seismic velocity model and moment tensor. We first use our adaptive moment-tensor joint inversion method to estimate moment tensors of microseismic events. Our adaptive moment-tensor inversion method jointly inverts multiple microseismic events with similar waveforms within a cluster to reduce inversion uncertainty for microseismic data recorded using a single borehole geophone array. We use this inversion result as the initial model for our elastic-waveform inversion to minimize the cross-correlated-based data misfit between observed data and synthetic data. We verify our method using synthetic microseismic data and obtain improved results of both moment tensors and seismic velocity model. We apply our new inversion method to microseismic data acquired at a CO2-enhanced oil recovery field in Aneth, Utah, using a single borehole geophone array. The results demonstrate that our new inversion method significantly reduces the data misfit compared to the conventional ray-theory-based moment-tensor inversion.

  4. Application of digital waveform processing to position-sensitive proportional counter

    International Nuclear Information System (INIS)

    Takenaka, Yasuto; Uritani, Akira; Mori, Chizuo

    1995-01-01

    In a charge-division type position-sensitive proportional counter (PSPC) with an anode wire of small resistance, a reflected component from an opposite end and thermal noise involved in signals deteriorate the position resolution of the PSPC. A digital waveform processing method was applied to the reduction of these undesirable effects by skillfully utilizing their signal characteristics that can be observed as inversely correlative signals between two-output signals from both sides of the PSPC. The digital waveform processing could improve the position resolution compared to a conventional pulse height processing method with analog filters. When the digital waveform processing was applied to signals of an equivalent circuit simulating the PSPC, the position resolutions defined by the full width at half maximum were improved to about 30% of those of conventional analog pulse processing. In the case of an actual PSPC, the position resolutions by the digital waveform processing were improved by 4-10% as compared with those of conventional pulse height processing. (author)

  5. Improving waveform inversion using modified interferometric imaging condition

    Science.gov (United States)

    Guo, Xuebao; Liu, Hong; Shi, Ying; Wang, Weihong; Zhang, Zhen

    2018-02-01

    Similar to the reverse-time migration, full waveform inversion in the time domain is a memory-intensive processing method. The computational storage size for waveform inversion mainly depends on the model size and time recording length. In general, 3D and 4D data volumes need to be saved for 2D and 3D waveform inversion gradient calculations, respectively. Even the boundary region wavefield-saving strategy creates a huge storage demand. Using the last two slices of the wavefield to reconstruct wavefields at other moments through the random boundary, avoids the need to store a large number of wavefields; however, traditional random boundary method is less effective at low frequencies. In this study, we follow a new random boundary designed to regenerate random velocity anomalies in the boundary region for each shot of each iteration. The results obtained using the random boundary condition in less illuminated areas are more seriously affected by random scattering than other areas due to the lack of coverage. In this paper, we have replaced direct correlation for computing the waveform inversion gradient by modified interferometric imaging, which enhances the continuity of the imaging path and reduces noise interference. The new imaging condition is a weighted average of extended imaging gathers can be directly used in the gradient computation. In this process, we have not changed the objective function, and the role of the imaging condition is similar to regularization. The window size for the modified interferometric imaging condition-based waveform inversion plays an important role in this process. The numerical examples show that the proposed method significantly enhances waveform inversion performance.

  6. Importance of Preserving Cross-correlation in developing Statistically Downscaled Climate Forcings and in estimating Land-surface Fluxes and States

    Science.gov (United States)

    Das Bhowmik, R.; Arumugam, S.

    2015-12-01

    Multivariate downscaling techniques exhibited superiority over univariate regression schemes in terms of preserving cross-correlations between multiple variables- precipitation and temperature - from GCMs. This study focuses on two aspects: (a) develop an analytical solutions on estimating biases in cross-correlations from univariate downscaling approaches and (b) quantify the uncertainty in land-surface states and fluxes due to biases in cross-correlations in downscaled climate forcings. Both these aspects are evaluated using climate forcings available from both historical climate simulations and CMIP5 hindcasts over the entire US. The analytical solution basically relates the univariate regression parameters, co-efficient of determination of regression and the co-variance ratio between GCM and downscaled values. The analytical solutions are compared with the downscaled univariate forcings by choosing the desired p-value (Type-1 error) in preserving the observed cross-correlation. . For quantifying the impacts of biases on cross-correlation on estimating streamflow and groundwater, we corrupt the downscaled climate forcings with different cross-correlation structure.

  7. Cross-correlation enhanced stability in a tumor cell growth model with immune surveillance driven by cross-correlated noises

    International Nuclear Information System (INIS)

    Zeng Chunhua; Zhou Xiaofeng; Tao Shufen

    2009-01-01

    The transient properties of a tumor cell growth model with immune surveillance driven by cross-correlated multiplicative and additive noises are investigated. The explicit expression of extinction rate from the state of a stable tumor to the state of extinction is obtained. Based on the numerical computations, we find the following: (i) the intensity of multiplicative noise D and the intensity of additive noise α enhance the extinction rate for the case of λ ≤ 0 (i.e. λ denotes cross-correlation intensity between two noises), but for the case of λ > 0, a critical noise intensity D or α exists at which the extinction rate is the smallest; D and α at first weaken the extinction rate and then enhance it. (ii) The immune rate β and the cross-correlation intensity λ play opposite roles on the extinction rate, i.e. β enhances the extinction rate of the tumor cell, while λ weakens the extinction rate of the tumor cell. Namely, the immune rate can enhance the extinction of the tumor cell and the cross-correlation between two noises can enhance stability of the cancer state.

  8. Cross-correlation Doppler global velocimetry (CC-DGV)

    Science.gov (United States)

    Cadel, Daniel R.; Lowe, K. Todd

    2015-08-01

    A flow velocimetry method, cross-correlation Doppler global velocimetry (CC-DGV), is presented as a robust, simplified, and high dynamic range implementation of the Doppler global/planar Doppler velocimetry technique. A sweep of several gigahertz of the vapor absorption spectrum is used for each velocity sample, with signals acquired from both Doppler-shifted scattered light within the flow and a non-Doppler shifted reference beam. Cross-correlation of these signals yields the Doppler shift between them, averaged over the duration of the scan. With presently available equipment, velocities from 0 ms-1 to over 3000 ms-1 can notionally be measured simultaneously, making the technique ideal for high speed flows. The processing routine is shown to be robust against large changes in the vapor pressure of the iodine cell, benefiting performance of the system in facilities where ambient conditions cannot be easily regulated. Validation of the system was performed with measurements of a model wind turbine blade boundary layer made in a 1.83 m by 1.83 m subsonic wind tunnel for which laser Doppler velocimetry (LDV) measurements were acquired alongside the CC-DGV results. CC-DGV uncertainties of ±1.30 ms-1, ±0.64 ms-1, and ±1.11 ms-1 were determined for the orthogonal stream-wise, transverse-horizontal, and transverse-vertical velocity components, and root-mean-square deviations of 2.77 ms-1 and 1.34 ms-1 from the LDV validation results were observed for Reynolds numbers of 1.5 million and 2 million, respectively. Volumetric mean velocity measurements are also presented for a supersonic jet, with velocity uncertainties of ±4.48 ms-1, ±16.93 ms-1, and ±0.50 ms-1 for the orthogonal components, and self-validation done by collapsing the data with a physical scaling.

  9. Bottomside sinusoidal irregularities in the equatorial F region. II - Cross-correlation and spectral analysis

    Science.gov (United States)

    Cragin, B. L.; Hanson, W. B.; Mcclure, J. P.; Valladares, C. E.

    1985-01-01

    Equatorial bottomside sinusoidal (BSS) irregularities have been studied by applying techniques of cross-correlation and spectral analysis to the Atmosphere Explorer data set. The phase of the cross-correlations of the plasma number density is discussed and the two drift velocity components observed using the retarding potential analyzer and ion drift meter on the satellite are discussed. Morphology is addressed, presenting the geographical distributions of the occurrence of BSS events for the equinoxes and solstices. Physical processes including the ion Larmor flux, interhemispheric plasma flows, and variations in the lower F region Pedersen conductivity are invoked to explain the findings.

  10. Measuring time-of-flight in an ultrasonic LPS system using generalized cross-correlation.

    Science.gov (United States)

    Villladangos, José Manuel; Ureña, Jesús; García, Juan Jesús; Mazo, Manuel; Hernández, Alvaro; Jiménez, Ana; Ruíz, Daniel; De Marziani, Carlos

    2011-01-01

    In this article, a time-of-flight detection technique in the frequency domain is described for an ultrasonic local positioning system (LPS) based on encoded beacons. Beacon transmissions have been synchronized and become simultaneous by means of the DS-CDMA (direct-sequence code Division multiple access) technique. Every beacon has been associated to a 255-bit Kasami code. The detection of signal arrival instant at the receiver, from which the distance to each beacon can be obtained, is based on the application of the generalized cross-correlation (GCC), by using the cross-spectral density between the received signal and the sequence to be detected. Prior filtering to enhance the frequency components around the carrier frequency (40 kHz) has improved estimations when obtaining the correlation function maximum, which implies an improvement in distance measurement precision. Positioning has been achieved by using hyperbolic trilateration, based on the time differences of arrival (TDOA) between a reference beacon and the others.

  11. New techniques for multi-level cross section calculation and fitting

    International Nuclear Information System (INIS)

    Froehner, F.H.

    1980-09-01

    A number of recent developments in multi-level cross section work are described. A new iteration scheme for the conversion of Reich-Moore resonance parameters to Kapur-Peierls parameters allows application of Turing's method for Gaussian broadening of meromorphic functions directly to multi-level cross section expressions, without recourse to the Voigt profiles psi and chi. This makes calculation of Doppler-broadened Reich-Moore and MLBW cross sections practically as fast as SLBW and Adler-Adler cross section calculations involving the Voigt profiles. A convenient distant-level treatment utilizing average resonance parameters is presented. Apart from effectively dealing with edge effects in resonance fitting work it also leads to a simple prescription for the determination of bound levels which reproduce the thermal cross sections correctly. A brief discussion of improved resonance shape fitting techniques is included, with empahsis on the importance of correlated errors and proper use of prior information by application of Bayes' theorem. (orig.) [de

  12. New techniques for multi-level cross section calculation and fitting

    International Nuclear Information System (INIS)

    Froehner, F.H.

    1981-01-01

    A number of recent developments in multi-level cross section work are described. A new iteration scheme for the conversion of Reich-Moore resonance parameters to Kapur-Peierls parameters allows application of Turing's method for Gaussian broadening of meromorphic functions directly to multi-level cross section expressions, without recourse to the Voigt profiles psi and chi. This makes calculation of Doppler-broadened Reich-Moore and MLBW cross sections practically as fast as SLBW and Adler-Adler cross section calculations involving the Voigt profiles. A convenient distant-level treatment utilizing average resonance parameters is presented. Apart from effectively dealing with edge effects in resonance fitting work it also leads to a simple prescription for the determination of bound levels which reproduce the thermal cross sections correctly. A brief discussion of improved resonance shape fitting techniques is included, with emphasis on the importance of correlated errors and proper use of prior information by application of Bayes' theorem

  13. Full–waveform inversion using the excitation representation of the source wavefield

    KAUST Repository

    Kalita, Mahesh

    2016-09-06

    Full waveform inversion (FWI) is an iterative method of data-fitting, aiming at high resolution recovery of the unknown model parameters. However, it is a cumbersome process, requiring a long computational time and large memory space/disc storage. One of the reasons for this computational limitation is the gradient calculation step. Based on the adjoint state method, it involves the temporal cross-correlation of the forward propagated source wavefield with the backward propagated residuals, in which we usually need to store the source wavefield, or include an extra extrapolation step to propagate the source wavefield from its storage at the boundary. We propose, alternatively, an amplitude excitation gradient calculation based on the excitation imaging condition concept that represents the source wavefield history by a single, specifically the most energetic arrival. An excitation based Born modeling allows us to derive the adjoint operation. In this case, the source wavelet is injected by a cross-correlation step applied to the data residual directly. Representing the source wavefield through the excitation amplitude and time, we reduce the large requirements for both storage and the computational time. We demonstrate the application of this approach on a 2-layer model with an anomaly and the Marmousi II model.

  14. Full–waveform inversion using the excitation representation of the source wavefield

    KAUST Repository

    Kalita, Mahesh; Alkhalifah, Tariq Ali

    2016-01-01

    Full waveform inversion (FWI) is an iterative method of data-fitting, aiming at high resolution recovery of the unknown model parameters. However, it is a cumbersome process, requiring a long computational time and large memory space/disc storage. One of the reasons for this computational limitation is the gradient calculation step. Based on the adjoint state method, it involves the temporal cross-correlation of the forward propagated source wavefield with the backward propagated residuals, in which we usually need to store the source wavefield, or include an extra extrapolation step to propagate the source wavefield from its storage at the boundary. We propose, alternatively, an amplitude excitation gradient calculation based on the excitation imaging condition concept that represents the source wavefield history by a single, specifically the most energetic arrival. An excitation based Born modeling allows us to derive the adjoint operation. In this case, the source wavelet is injected by a cross-correlation step applied to the data residual directly. Representing the source wavefield through the excitation amplitude and time, we reduce the large requirements for both storage and the computational time. We demonstrate the application of this approach on a 2-layer model with an anomaly and the Marmousi II model.

  15. Multisource waveform inversion of marine streamer data using normalized wavefield

    KAUST Repository

    Choi, Yun Seok

    2013-09-01

    Multisource full-waveform inversion based on the L1- and L2-norm objective functions cannot be applied to marine streamer data because it does not take into account the unmatched acquisition geometries between the observed and modeled data. To apply multisource full-waveform inversion to marine streamer data, we construct the L1- and L2-norm objective functions using the normalized wavefield. The new residual seismograms obtained from the L1- and L2-norms using the normalized wavefield mitigate the problem of unmatched acquisition geometries, which enables multisource full-waveform inversion to work with marine streamer data. In the new approaches using the normalized wavefield, we used the back-propagation algorithm based on the adjoint-state technique to efficiently calculate the gradients of the objective functions. Numerical examples showed that multisource full-waveform inversion using the normalized wavefield yields much better convergence for marine streamer data than conventional approaches. © 2013 Society of Exploration Geophysicists.

  16. Cross-correlation interference effects in multiaccess optical communications

    Science.gov (United States)

    Peterson, G. D.; Gardner, C. S.

    1981-03-01

    An analysis is presented of the cross correlation between user codes in an optical code-division multiple-access communication system. The system model is a multiaccess satellite repeater, where the uplink and downlink channels are direct-detection optical-polarization modulation links. The error probability is obtained in terms of the cross correlation between the intended and interfering user codes. It is demonstrated that the system error rate can be minimized by the use of code sequences in which the normalized second moment of the cross correlation between codes is small.

  17. Full Waveform Inversion for Reservoir Characterization - A Synthetic Study

    KAUST Repository

    Zabihi Naeini, E.; Kamath, N.; Tsvankin, I.; Alkhalifah, Tariq Ali

    2017-01-01

    Most current reservoir-characterization workflows are based on classic amplitude-variation-with-offset (AVO) inversion techniques. Although these methods have generally served us well over the years, here we examine full-waveform inversion (FWI

  18. PyCCF: Python Cross Correlation Function for reverberation mapping studies

    Science.gov (United States)

    Sun, Mouyuan; Grier, C. J.; Peterson, B. M.

    2018-05-01

    PyCCF emulates a Fortran program written by B. Peterson for use with reverberation mapping. The code cross correlates two light curves that are unevenly sampled using linear interpolation and measures the peak and centroid of the cross-correlation function. In addition, it is possible to run Monto Carlo iterations using flux randomization and random subset selection (RSS) to produce cross-correlation centroid distributions to estimate the uncertainties in the cross correlation results.

  19. Cross-correlations between RMB exchange rate and international commodity markets

    Science.gov (United States)

    Lu, Xinsheng; Li, Jianfeng; Zhou, Ying; Qian, Yubo

    2017-11-01

    This paper employs multifractal detrended analysis (MF-DFA) and multifractal detrended cross-correlation analysis (MF-DCCA) to study cross-correlation behaviors between China's RMB exchange rate market and four international commodity markets, using a comprehensive set of data covering the period from 22 July 2005 to 15 March 2016. Our empirical results from MF-DFA indicate that the RMB exchange rate is the most inefficient among the 4 selected markets. The results from quantitative analysis have testified the existence of cross-correlations and the result from MF-DCCA have further confirmed a strong multifractal behavior between RMB exchange rate and international commodity markets. We also demonstrate that the recent financial crisis has significant impact on the cross-correlated behavior. Through the rolling window analysis, we find that the RMB exchange rates and international commodity prices are anti-persistent cross-correlated. The main sources of multifractality in the cross-correlations are long-range correlations between RMB exchange rate and the aggregate commodity, energy and metals index.

  20. Evaluation of surface-wave waveform modeling for lithosphere velocity structure

    Science.gov (United States)

    Chang, Tao-Ming

    Surface-waveform modeling methods will become standard tools for studying the lithosphere structures because they can place greater constraints on earth structure and because of interest in the three-dimensional earth. The purpose of this study is to begin to learn the applicabilities and limitations of these methods. A surface-waveform inversion method is implemented using generalized seismological data functional theory. The method has been tested using synthetic and real seismic data and show that this method is well suited for teleseismic and regional seismograms. Like other linear inversion problems, this method also requires a good starting model. To ease reliance on good starting models, a global search technique, the genetic algorithm, has been applied to surface waveform modeling. This method can rapidly find good models for explaining surface-wave waveform at regional distance. However, this implementation also reveals that criteria which are widely used in seismological studies are not good enough to indicate the goodness of waveform fit. These two methods with the linear waveform inversion method, and traditional surface wave dispersion inversion method have been applied to a western Texas earthquake to test their abilities. The focal mechanism of the Texas event has been reestimated using a grid search for surface wave spectral amplitudes. A comparison of these four algorithms shows some interesting seismic evidences for lithosphere structure.

  1. Analysis of two-phase flow velocity measurements by cross-correlation techniques and the applicability of the drift flux model for their interpretation

    International Nuclear Information System (INIS)

    Analytis, G.Th.; Luebbesmeyer, D.

    1982-11-01

    An extensive and detailed investigation of two-phase flow velocity measurements by cross-correlating noise signals of information carriers (neutrons, gammas, visible light) modulated by the two-phase flow and registered by two axially placed detectors outside the flow is pursued. To this end, a detailed analysis of velocity measurements in experimental loops and a large number of velocity measurements in a commercial BWR is undertaken, and the applicability and limitations of the drift flux model for their interpretation is investigated. On the basis of this extensive analysis, the authors propose a physically plausible explanation for the deviations in the upper part of the core, expound on why the drift flux model is, to a great extent, not suitable for interpreting two-phase flow velocity measurements by cross-correlation techniques reported in the present work, and conclude that due to the large number of uncertainties and the lack of detailed knowledge about the kind of microstructures of the flow which the detectors prefer to ''sample'', one can safely assume that at least in the lower half of the core the velocity measured can be well approximated by the velocity of the centre of volume, from which the mass fluxes can readily be computed. (Auth.)

  2. Photoplethysmographic signal waveform index for detection of increased arterial stiffness

    International Nuclear Information System (INIS)

    Pilt, K; Meigas, K; Ferenets, R; Temitski, K; Viigimaa, M

    2014-01-01

    The aim of this research was to assess the validity of the photoplethysmographic (PPG) waveform index PPGAI for the estimation of increased arterial stiffness. For this purpose, PPG signals were recorded from 24 healthy subjects and from 20 type II diabetes patients. The recorded PPG signals were processed with the analysis algorithm developed and the waveform index PPGAI similar to the augmentation index (AIx) was calculated. As a reference, the aortic AIx was assessed and normalized for a heart rate of 75 bpm (AIx@75) by a SphygmoCor device. A strong correlation (r = 0.85) between the PPGAI and the aortic AIx@75 and a positive correlation of both indices with age were found. Age corrections for the indices PPGAI and AIx@75 as regression models from the signals of healthy subjects were constructed. Both indices revealed a significant difference between the groups of diabetes patients and healthy controls. However, the PPGAI provided the best statistical discrimination for the group of subjects with increased arterial stiffness. The waveform index PPGAI based on the inexpensive PPG technology can be considered as a perspective measure of increased arterial stiffness estimation in clinical screenings. (paper)

  3. Background Noise Reduction Using Adaptive Noise Cancellation Determined by the Cross-Correlation

    Science.gov (United States)

    Spalt, Taylor B.; Brooks, Thomas F.; Fuller, Christopher R.

    2012-01-01

    Background noise due to flow in wind tunnels contaminates desired data by decreasing the Signal-to-Noise Ratio. The use of Adaptive Noise Cancellation to remove background noise at measurement microphones is compromised when the reference sensor measures both background and desired noise. The technique proposed modifies the classical processing configuration based on the cross-correlation between the reference and primary microphone. Background noise attenuation is achieved using a cross-correlation sample width that encompasses only the background noise and a matched delay for the adaptive processing. A present limitation of the method is that a minimum time delay between the background noise and desired signal must exist in order for the correlated parts of the desired signal to be separated from the background noise in the crosscorrelation. A simulation yields primary signal recovery which can be predicted from the coherence of the background noise between the channels. Results are compared with two existing methods.

  4. A new detrended semipartial cross-correlation analysis: Assessing the important meteorological factors affecting API

    International Nuclear Information System (INIS)

    Shen, Chen-Hua

    2015-01-01

    To analyze the unique contribution of meteorological factors to the air pollution index (API), a new method, the detrended semipartial cross-correlation analysis (DSPCCA), is proposed. Based on both a detrended cross-correlation analysis and a DFA-based multivariate-linear-regression (DMLR), this method is improved by including a semipartial correlation technique, which is used to indicate the unique contribution of an explanatory variable to multiple correlation coefficients. The advantages of this method in handling nonstationary time series are illustrated by numerical tests. To further demonstrate the utility of this method in environmental systems, new evidence of the primary contribution of meteorological factors to API is provided through DMLR. Results show that the most important meteorological factors affecting API are wind speed and diurnal temperature range, and the explanatory ability of meteorological factors to API gradually strengthens with increasing time scales. The results suggest that DSPCCA is a useful method for addressing environmental systems. - Highlights: • A detrended multiple linear regression is shown. • A detrended semipartial cross correlation analysis is proposed. • The important meteorological factors affecting API are assessed. • The explanatory ability of meteorological factors to API gradually strengthens with increasing time scales.

  5. A new detrended semipartial cross-correlation analysis: Assessing the important meteorological factors affecting API

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Chen-Hua, E-mail: shenandchen01@163.com [College of Geographical Science, Nanjing Normal University, Nanjing 210046 (China); Jiangsu Center for Collaborative Innovation in Geographical Information Resource, Nanjing 210046 (China); Key Laboratory of Virtual Geographic Environment of Ministry of Education, Nanjing 210046 (China)

    2015-12-04

    To analyze the unique contribution of meteorological factors to the air pollution index (API), a new method, the detrended semipartial cross-correlation analysis (DSPCCA), is proposed. Based on both a detrended cross-correlation analysis and a DFA-based multivariate-linear-regression (DMLR), this method is improved by including a semipartial correlation technique, which is used to indicate the unique contribution of an explanatory variable to multiple correlation coefficients. The advantages of this method in handling nonstationary time series are illustrated by numerical tests. To further demonstrate the utility of this method in environmental systems, new evidence of the primary contribution of meteorological factors to API is provided through DMLR. Results show that the most important meteorological factors affecting API are wind speed and diurnal temperature range, and the explanatory ability of meteorological factors to API gradually strengthens with increasing time scales. The results suggest that DSPCCA is a useful method for addressing environmental systems. - Highlights: • A detrended multiple linear regression is shown. • A detrended semipartial cross correlation analysis is proposed. • The important meteorological factors affecting API are assessed. • The explanatory ability of meteorological factors to API gradually strengthens with increasing time scales.

  6. A semi-automatic method for peak and valley detection in free-breathing respiratory waveforms

    International Nuclear Information System (INIS)

    Lu Wei; Nystrom, Michelle M.; Parikh, Parag J.; Fooshee, David R.; Hubenschmidt, James P.; Bradley, Jeffrey D.; Low, Daniel A.

    2006-01-01

    The existing commercial software often inadequately determines respiratory peaks for patients in respiration correlated computed tomography. A semi-automatic method was developed for peak and valley detection in free-breathing respiratory waveforms. First the waveform is separated into breath cycles by identifying intercepts of a moving average curve with the inspiration and expiration branches of the waveform. Peaks and valleys were then defined, respectively, as the maximum and minimum between pairs of alternating inspiration and expiration intercepts. Finally, automatic corrections and manual user interventions were employed. On average for each of the 20 patients, 99% of 307 peaks and valleys were automatically detected in 2.8 s. This method was robust for bellows waveforms with large variations

  7. Pick- and waveform-based techniques for real-time detection of induced seismicity

    Science.gov (United States)

    Grigoli, Francesco; Scarabello, Luca; Böse, Maren; Weber, Bernd; Wiemer, Stefan; Clinton, John F.

    2018-05-01

    The monitoring of induced seismicity is a common operation in many industrial activities, such as conventional and non-conventional hydrocarbon production or mining and geothermal energy exploitation, to cite a few. During such operations, we generally collect very large and strongly noise-contaminated data sets that require robust and automated analysis procedures. Induced seismicity data sets are often characterized by sequences of multiple events with short interevent times or overlapping events; in these cases, pick-based location methods may struggle to correctly assign picks to phases and events, and errors can lead to missed detections and/or reduced location resolution and incorrect magnitudes, which can have significant consequences if real-time seismicity information are used for risk assessment frameworks. To overcome these issues, different waveform-based methods for the detection and location of microseismicity have been proposed. The main advantages of waveform-based methods is that they appear to perform better and can simultaneously detect and locate seismic events providing high-quality locations in a single step, while the main disadvantage is that they are computationally expensive. Although these methods have been applied to different induced seismicity data sets, an extensive comparison with sophisticated pick-based detection methods is still missing. In this work, we introduce our improved waveform-based detector and we compare its performance with two pick-based detectors implemented within the SeiscomP3 software suite. We test the performance of these three approaches with both synthetic and real data sets related to the induced seismicity sequence at the deep geothermal project in the vicinity of the city of St. Gallen, Switzerland.

  8. Principles of femtosecond X-ray/optical cross-correlation with X-ray induced transient optical reflectivity in solids

    Energy Technology Data Exchange (ETDEWEB)

    Eckert, S., E-mail: sebastian.eckert@helmholtz-berlin.de, E-mail: martin.beye@helmholtz-berlin.de; Beye, M., E-mail: sebastian.eckert@helmholtz-berlin.de, E-mail: martin.beye@helmholtz-berlin.de; Pietzsch, A.; Quevedo, W.; Hantschmann, M. [Institute for Methods and Instrumentation in Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Ochmann, M.; Huse, N. [Institute for Nanostructure and Solid State Physics, University of Hamburg, Jungiusstr. 11, 20355 Hamburg, Germany and Max Planck Institute for the Structure and Dynamics of Matter, Center for Free-Electron Laser Science, Luruper Chaussee 149, 22761 Hamburg (Germany); Ross, M.; Khalil, M. [Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 (United States); Minitti, M. P.; Turner, J. J.; Moeller, S. P.; Schlotter, W. F.; Dakovski, G. L. [LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); Föhlisch, A. [Institute for Methods and Instrumentation in Synchrotron Radiation Research, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam (Germany)

    2015-02-09

    The discovery of ultrafast X-ray induced optical reflectivity changes enabled the development of X-ray/optical cross correlation techniques at X-ray free electron lasers worldwide. We have now linked through experiment and theory the fundamental excitation and relaxation steps with the transient optical properties in finite solid samples. Therefore, we gain a thorough interpretation and an optimized detection scheme of X-ray induced changes to the refractive index and the X-ray/optical cross correlation response.

  9. Assessing the blood pressure waveform of the carotid artery using an ultrasound image processing method

    Energy Technology Data Exchange (ETDEWEB)

    Soleimani, Effat; Mokhtari-Dizaji, Manijhe [Dept. of Medical Physics, Tarbiat Modares University, Tehran (Iran, Islamic Republic of); Fatouraee, Nasser [Dept. of Medical Engineering, Amirkabir University of Technology, Tehran (Iran, Islamic Republic of); Saben, Hazhir [Dept. Radiology, Imaging Center of Imam Khomaini Hospital, Tehran Medical Sciences University, Tehran (Iran, Islamic Republic of)

    2017-04-15

    The aim of this study was to introduce and implement a noninvasive method to derive the carotid artery pressure waveform directly by processing diagnostic sonograms of the carotid artery. Ultrasound image sequences of 20 healthy male subjects (age, 36±9 years) were recorded during three cardiac cycles. The internal diameter and blood velocity waveforms were extracted from consecutive sonograms over the cardiac cycles by using custom analysis programs written in MATLAB. Finally, the application of a mathematical equation resulted in time changes of the arterial pressure. The resulting pressures were calibrated using the mean and the diastolic pressure of the radial artery. A good correlation was found between the mean carotid blood pressure obtained from the ultrasound image processing and the mean radial blood pressure obtained using a standard digital sphygmomanometer (R=0.91). The mean absolute difference between the carotid calibrated pulse pressures and those measured clinically was -1.333±6.548 mm Hg. The results of this study suggest that consecutive sonograms of the carotid artery can be used for estimating a blood pressure waveform. We believe that our results promote a noninvasive technique for clinical applications that overcomes the reproducibility problems of common carotid artery tonometry with technical and anatomical causes.

  10. Assessing the blood pressure waveform of the carotid artery using an ultrasound image processing method

    International Nuclear Information System (INIS)

    Soleimani, Effat; Mokhtari-Dizaji, Manijhe; Fatouraee, Nasser; Saben, Hazhir

    2017-01-01

    The aim of this study was to introduce and implement a noninvasive method to derive the carotid artery pressure waveform directly by processing diagnostic sonograms of the carotid artery. Ultrasound image sequences of 20 healthy male subjects (age, 36±9 years) were recorded during three cardiac cycles. The internal diameter and blood velocity waveforms were extracted from consecutive sonograms over the cardiac cycles by using custom analysis programs written in MATLAB. Finally, the application of a mathematical equation resulted in time changes of the arterial pressure. The resulting pressures were calibrated using the mean and the diastolic pressure of the radial artery. A good correlation was found between the mean carotid blood pressure obtained from the ultrasound image processing and the mean radial blood pressure obtained using a standard digital sphygmomanometer (R=0.91). The mean absolute difference between the carotid calibrated pulse pressures and those measured clinically was -1.333±6.548 mm Hg. The results of this study suggest that consecutive sonograms of the carotid artery can be used for estimating a blood pressure waveform. We believe that our results promote a noninvasive technique for clinical applications that overcomes the reproducibility problems of common carotid artery tonometry with technical and anatomical causes

  11. Onboard Processing on PWE OFA/WFC (Onboard Frequency Analyzer/Waveform Capture) aboard the ERG (ARASE) Satellite

    Science.gov (United States)

    Matsuda, S.; Kasahara, Y.; Kojima, H.; Kasaba, Y.; Yagitani, S.; Ozaki, M.; Imachi, T.; Ishisaka, K.; Kurita, S.; Ota, M.; Kumamoto, A.; Tsuchiya, F.; Yoshizumi, M.; Matsuoka, A.; Teramoto, M.; Shinohara, I.

    2017-12-01

    Exploration of energization and Radiation in Geospace (ERG) is a mission for understanding particle acceleration, loss mechanisms, and the dynamic evolution of space storms in the context of cross-energy and cross-regional coupling [Miyoshi et al., 2012]. The ERG (ARASE) satellite was launched on December 20, 2016, and successfully inserted into an orbit. The Plasma Wave Experiment (PWE) is one of the science instruments on board the ERG satellite to measure electric field and magnetic field in the inner magnetosphere. PWE consists of three sub-components, EFD (Electric Field Detector), OFA/WFC (Onboard Frequency Analyzer and Waveform Capture), and HFA (High Frequency Analyzer). Especially, OFA/WFC measures electric and magnetic field spectrum and waveform from a few Hz to 20 kHz. OFA/WFC processes signals detected by a couple of dipole wire-probe antenna (WPT) and tri-axis magnetic search coils (MSC) installed onboard the satellite. The PWE-OFA subsystem calculates and produces three kind of data; OFA-SPEC (power spectrum), OFA-MATRIX (spectrum matrix), and OFA-COMPLEX (complex spectrum). They are continuously processed 24 hours per day and all data are sent to the ground. OFA-MATRIX and OFA-COMPLEX are used for polarization analyses and direction finding of the plasma waves. The PWE-WFC subsystem measures raw (64 kHz sampled) and down-sampled (1 kHz sampled) burst waveform detected by the WPT and the MSC sensors. It activates by a command, automatic triggering, and scheduling. The initial check-out process of the PWE successfully completed, and initial data has been obtained. In this presentation, we introduce onboard processing technique on PWE OFA/WFC and its initial results.

  12. BER Performance Simulation of Generalized MC DS-CDMA System with Time-Limited Blackman Chip Waveform

    Directory of Open Access Journals (Sweden)

    I. Develi

    2010-09-01

    Full Text Available Multiple access interference encountered in multicarrier direct sequence-code division multiple access (MC DS-CDMA is the most important difficulty that depends mainly on the correlation properties of the spreading sequences as well as the shape of the chip waveforms employed. In this paper, bit error rate (BER performance of the generalized MC DS-CDMA system that employs time-limited Blackman chip waveform is presented for Nakagami-m fading channels. Simulation results show that the use of Blackman chip waveform can improve the BER performance of the generalized MC DS-CDMA system, as compared to the performances achieved by using timelimited chip waveforms in the literature.

  13. Characteristics of angular cross correlations studied by light scattering from two-dimensional microsphere films

    Science.gov (United States)

    Schroer, M. A.; Gutt, C.; Grübel, G.

    2014-07-01

    Recently the analysis of scattering patterns by angular cross-correlation analysis (CCA) was introduced to reveal the orientational order in disordered samples with special focus to future applications on x-ray free-electron laser facilities. We apply this CCA approach to ultra-small-angle light-scattering data obtained from two-dimensional monolayers of microspheres. The films were studied in addition by optical microscopy. This combined approach allows to calculate the cross-correlations of the scattering patterns, characterized by the orientational correlation function Ψl(q), as well as to obtain the real-space structure of the monolayers. We show that CCA is sensitive to the orientational order of monolayers formed by the microspheres which are not directly visible from the scattering patterns. By mixing microspheres of different radii the sizes of ordered monolayer domains is reduced. For these samples it is shown that Ψl(q) quantitatively describes the degree of hexagonal order of the two-dimensional films. The experimental CCA results are compared with calculations based on the microscopy images. Both techniques show qualitatively similar features. Differences can be attributed to the wave-front distortion of the laser beam in the experiment. This effect is discussed by investigating the effect of different wave fronts on the cross-correlation analysis results. The so-determined characteristics of the cross-correlation analysis will be also relevant for future x-ray-based studies.

  14. Hepatic vein Doppler waveform in patients with diffuse fatty infiltration of the liver

    International Nuclear Information System (INIS)

    Oguzkurt, Levent; Yildirim, Tulin; Torun, Dilek; Tercan, Fahri; Kizilkilic, Osman; Niron, E. Alp

    2005-01-01

    Objective: To determine the incidence of abnormal hepatic vein Doppler waveform in patients with diffuse fatty infiltration of the liver (FIL). Materials and methods: In this prospective study, 40 patients with diffuse FIL and 50 normal healthy adults who served as control group underwent hepatic vein (HV) Doppler ultrasonography. The patients with the diagnosis of FIL were 23 men (57.5%) and 17 women aged 30-62 years (mean age ± S.D., 42 ± 12 years). Subjects in the control group were 27 men (54%) and 23 women aged 34-65 years (mean age ± S.D., 45 ± 14 years). The diagnosis of FIL was confirmed with computed tomography density measurements. The waveforms of HV were classified into three groups: regular triphasic waveform, biphasic waveform without a reverse flow, and monophasic or flat waveform. Etiological factors for FIL were diabetes mellitus (DM), hyperlipidemia and obesity (body mass index > 25). Serum lipid profile was obtained from all the patients with FIL. Results: Seventeen of the 40 patients (43%) with FIL had an abnormal HV Doppler waveform, whereas only one of the 50 (2%) healthy subjects had an abnormal waveform. The difference in the distribution of normal Doppler waveform pattern between the patients and the control group was significant (P 0.05). There was not any correlation between the degree of fat infiltration and the hepatic vein waveform pattern (P = 0.60). Conclusion: Patients with fatty liver has a high rate of an abnormal hepatic vein Doppler waveform pattern which can be biphasic or monophasic. We could not find a relation between the etiological factors for FIL and the occurrence of an abnormal HV Doppler waveform

  15. Surrogate waveform models

    Science.gov (United States)

    Blackman, Jonathan; Field, Scott; Galley, Chad; Scheel, Mark; Szilagyi, Bela; Tiglio, Manuel

    2015-04-01

    With the advanced detector era just around the corner, there is a strong need for fast and accurate models of gravitational waveforms from compact binary coalescence. Fast surrogate models can be built out of an accurate but slow waveform model with minimal to no loss in accuracy, but may require a large number of evaluations of the underlying model. This may be prohibitively expensive if the underlying is extremely slow, for example if we wish to build a surrogate for numerical relativity. We examine alternate choices to building surrogate models which allow for a more sparse set of input waveforms. Research supported in part by NSERC.

  16. Multifractal detrended cross-correlation analysis for epileptic patient in seizure and seizure free status

    International Nuclear Information System (INIS)

    Ghosh, Dipak; Dutta, Srimonti; Chakraborty, Sayantan

    2014-01-01

    Highlights: • We analyze EEG of patients during seizure and in seizure free interval. • Data from different sections of the brain and seizure activity was analyzed. • Assessment of cross-correlation in seizure and seizure free interval using MF-DXA technique. - Abstract: This paper reports a study of EEG data of epileptic patients in terms of multifractal detrended cross-correlation analysis (MF-DXA). The EEG clinical data were obtained from the EEG Database available with the Clinic of Epileptology of the University Hospital of Bonn, Germany. The data sets (C, D, and E) were taken from five epileptic patients undergoing presurgical evaluations. The data sets consist of intracranial EEG recordings during seizure-free intervals (interictal periods) from within the epileptogenic zone (D) and from the hippocampal formation of the opposite hemisphere of the epileptic patients’ brain, respectively (C). The data set (E) was recorded during seizure activity (ictal periods). MF-DXA is a very rigorous and robust tool for assessment of cross-correlation among two nonlinear time series. The study reveals the degree of cross-correlation is more among seizure and seizure free interval in epileptogenic zone. These data are very significant for diagnosis, onset and prognosis of epileptic patients

  17. Classification of Pulse Waveforms Using Edit Distance with Real Penalty

    Directory of Open Access Journals (Sweden)

    Zhang Dongyu

    2010-01-01

    Full Text Available Abstract Advances in sensor and signal processing techniques have provided effective tools for quantitative research in traditional Chinese pulse diagnosis (TCPD. Because of the inevitable intraclass variation of pulse patterns, the automatic classification of pulse waveforms has remained a difficult problem. In this paper, by referring to the edit distance with real penalty (ERP and the recent progress in -nearest neighbors (KNN classifiers, we propose two novel ERP-based KNN classifiers. Taking advantage of the metric property of ERP, we first develop an ERP-induced inner product and a Gaussian ERP kernel, then embed them into difference-weighted KNN classifiers, and finally develop two novel classifiers for pulse waveform classification. The experimental results show that the proposed classifiers are effective for accurate classification of pulse waveform.

  18. Strong anticipation and long-range cross-correlation: Application of detrended cross-correlation analysis to human behavioral data

    Science.gov (United States)

    Delignières, Didier; Marmelat, Vivien

    2014-01-01

    In this paper, we analyze empirical data, accounting for coordination processes between complex systems (bimanual coordination, interpersonal coordination, and synchronization with a fractal metronome), by using a recently proposed method: detrended cross-correlation analysis (DCCA). This work is motivated by the strong anticipation hypothesis, which supposes that coordination between complex systems is not achieved on the basis of local adaptations (i.e., correction, predictions), but results from a more global matching of complexity properties. Indeed, recent experiments have evidenced a very close correlation between the scaling properties of the series produced by two coordinated systems, despite a quite weak local synchronization. We hypothesized that strong anticipation should result in the presence of long-range cross-correlations between the series produced by the two systems. Results allow a detailed analysis of the effects of coordination on the fluctuations of the series produced by the two systems. In the long term, series tend to present similar scaling properties, with clear evidence of long-range cross-correlation. Short-term results strongly depend on the nature of the task. Simulation studies allow disentangling the respective effects of noise and short-term coupling processes on DCCA results, and suggest that the matching of long-term fluctuations could be the result of short-term coupling processes.

  19. CROSS-CORRELATIONS AS A COSMOLOGICAL CARBON MONOXIDE DETECTOR

    International Nuclear Information System (INIS)

    Pullen, Anthony R.; Doré, Olivier; Chang, Tzu-Ching; Lidz, Adam

    2013-01-01

    We present a new procedure to measure the large-scale carbon monoxide (CO) emissions across cosmic history. As a tracer of large-scale structure (LSS), the CO gas content as a function of redshift can be quantified by its three-dimensional fluctuation power spectra. Furthermore, cross-correlating CO emission with other LSS tracers offers a way to measure the emission as a function of scale and redshift. Here we introduce the model relevant for such a cross-correlation measurement between CO and other LSS tracers, and between different CO rotational lines. We propose a novel use of cosmic microwave background (CMB) data and attempt to extract redshifted CO emissions embedded in the Wilkinson Microwave Anisotropy Probe (WMAP) data set. We cross-correlate the all-sky WMAP7 data with LSS data sets, namely, the photometric quasar sample and the luminous red galaxy sample from the Sloan Digital Sky Survey Data Releases 6 and 7, respectively. We are unable to detect a cross-correlation signal with either CO(1-0) or CO(2-1) lines, mainly due to the instrumental noise in the WMAP data. However, we are able to rule out models more than three times greater than our more optimistic model. We discuss the cross-correlation signal from the thermal Sunyaev-Zeldovich effect and dust as potential contaminants, and quantify their impact for our CO measurements. We discuss forecasts for current CMB experiments and a hypothetical future CO-focused experiment, and propose to cross-correlate CO temperature data with the Hobby-Eberly Telescope Dark Energy Experiment Lyα-emitter sample, for which a signal-to-noise ratio of 58 is possible.

  20. Cross-correlation time-of-flight analysis of molecular beam scattering

    International Nuclear Information System (INIS)

    Nowikow, C.V.; Grice, R.

    1979-01-01

    The theory of the cross-correlation method of time-of-flight analysis is presented in a form which highlights its formal similarity to the conventional method. A time-of-flight system for the analysis of crossed molecular beam scattering is described, which is based on a minicomputer interface and can operate in both the cross-correlation and conventional modes. The interface maintains the synchronisation of chopper disc rotation and channel advance indefinitely in the cross-correlation method and can acquire data in phase with the beam modulation in both methods. The shutter function of the cross-correlation method is determined and the deconvolution analysis of the data is discussed. (author)

  1. Expanding the frontiers of waveform imaging with Salvus

    Science.gov (United States)

    Afanasiev, M.; Boehm, C.; van Driel, M.; Krischer, L.; Fichtner, A.

    2017-12-01

    Mechanical waves are natural harbingers of information. From medical ultrasound to the normal modes of Sun, wave motion is often our best window into the character of some underlying continuum. For over a century, geophysicists have been using this window to peer deep into the Earth, developing techniques that have gone on to underlie much of world's energy economy. As computers and numerical techniques have become more powerful over the last several decades, seismologists have begun to scale back classical simplifying approximations of wave propagation physics. As a result, we are now approaching the ideal of `full-waveform inversion'; maximizing the aperture of our window by taking the full complexity of wave motion into account.Salvus is a modern high-performance software suite which aims to bring recent developments in geophysical waveform inversion to new and exciting domains. In this short presentation we will look at the connections between these applications, with examples from non-destructive testing, medical imaging, seismic exploration, and (extra-) planetary seismology.

  2. Overview of intelligent data retrieval methods for waveforms and images in massive fusion databases

    Energy Technology Data Exchange (ETDEWEB)

    Vega, J. [JET-EFDA, Culham Science Center, OX14 3DB Abingdon (United Kingdom); Asociacion EURATOM/CIEMAT para Fusion, Avda. Complutense 22, 28040 Madrid (Spain)], E-mail: jesus.vega@ciemat.es; Murari, A. [JET-EFDA, Culham Science Center, OX14 3DB Abingdon (United Kingdom); Consorzio RFX-Associazione EURATOM ENEA per la Fusione, I-35127 Padua (Italy); Pereira, A.; Portas, A.; Ratta, G.A.; Castro, R. [JET-EFDA, Culham Science Center, OX14 3DB Abingdon (United Kingdom); Asociacion EURATOM/CIEMAT para Fusion, Avda. Complutense 22, 28040 Madrid (Spain)

    2009-06-15

    JET database contains more than 42 Tbytes of data (waveforms and images) and it doubles its size about every 2 years. ITER database is expected to be orders of magnitude above this quantity. Therefore, data access in such huge databases can no longer be efficiently based on shot number or temporal interval. Taking into account that diagnostics generate reproducible signal patterns (structural shapes) for similar physical behaviour, high level data access systems can be developed. In these systems, the input parameter is a pattern and the outputs are the shot numbers and the temporal locations where similar patterns appear inside the database. These pattern oriented techniques can be used for first data screening of any type of morphological aspect of waveforms and images. The article shows a new technique to look for similar images in huge databases in a fast an efficient way. Also, previous techniques to search for similar waveforms and to retrieve time-series data or images containing any kind of patterns are reviewed.

  3. Efficient full waveform inversion using the excitation representation of the source wavefield

    KAUST Repository

    Kalita, Mahesh

    2017-05-16

    Full waveform inversion (FWI) is an iterative method of data-fitting, aiming at high-resolution recovery of the unknown model parameters. However, its conventional implementation is a cumbersome process, requiring a long computational time and large memory space/disk storage. One of the reasons for this computational limitation is the gradient calculation step. Based on the adjoint state method, it involves the temporal cross-correlation of the forward propagated sourcewavefield with the backward propagated residuals, inwhichwe usually need to store the source wavefield, or include an extra extrapolation step to propagate the source wavefield from its storage at the boundary. We propose, alternatively, an amplitude excitation gradient calculation based on the excitation imaging condition concept that represents the source wavefield history by a single, specifically the most energetic arrival. An excitation based Born modelling allows us to derive the adjoint operation. In this case, the source wavelet is injected by a cross-correlation step applied to the data residual directly. Representing the source wavefield through the excitation amplitude and time, we reduce the large requirements for both storage and the computational time. We demonstrate the application of this approach on a two-layer model with an anomaly, the Marmousi II model and a marine data set acquired by CGG.

  4. Categorisation of full waveform data provided by laser scanning devices

    Science.gov (United States)

    Ullrich, Andreas; Pfennigbauer, Martin

    2011-11-01

    In 2004, a laser scanner device for commercial airborne laser scanning applications, the RIEGL LMS-Q560, was introduced to the market, making use of a radical alternative approach to the traditional analogue signal detection and processing schemes found in LIDAR instruments so far: digitizing the echo signals received by the instrument for every laser pulse and analysing these echo signals off-line in a so-called full waveform analysis in order to retrieve almost all information contained in the echo signal using transparent algorithms adaptable to specific applications. In the field of laser scanning the somewhat unspecific term "full waveform data" has since been established. We attempt a categorisation of the different types of the full waveform data found in the market. We discuss the challenges in echo digitization and waveform analysis from an instrument designer's point of view and we will address the benefits to be gained by using this technique, especially with respect to the so-called multi-target capability of pulsed time-of-flight LIDAR instruments.

  5. Detecting PM2.5's Correlations between Neighboring Cities Using a Time-Lagged Cross-Correlation Coefficient.

    Science.gov (United States)

    Wang, Fang; Wang, Lin; Chen, Yuming

    2017-08-31

    In order to investigate the time-dependent cross-correlations of fine particulate (PM2.5) series among neighboring cities in Northern China, in this paper, we propose a new cross-correlation coefficient, the time-lagged q-L dependent height crosscorrelation coefficient (denoted by p q (τ, L)), which incorporates the time-lag factor and the fluctuation amplitude information into the analogous height cross-correlation analysis coefficient. Numerical tests are performed to illustrate that the newly proposed coefficient ρ q (τ, L) can be used to detect cross-correlations between two series with time lags and to identify different range of fluctuations at which two series possess cross-correlations. Applying the new coefficient to analyze the time-dependent cross-correlations of PM2.5 series between Beijing and the three neighboring cities of Tianjin, Zhangjiakou, and Baoding, we find that time lags between the PM2.5 series with larger fluctuations are longer than those between PM2.5 series withsmaller fluctuations. Our analysis also shows that cross-correlations between the PM2.5 series of two neighboring cities are significant and the time lags between two PM2.5 series of neighboring cities are significantly non-zero. These findings providenew scientific support on the view that air pollution in neighboring cities can affect one another not simultaneously but with a time lag.

  6. Strongly correlated systems experimental techniques

    CERN Document Server

    Mancini, Ferdinando

    2015-01-01

    The continuous evolution and development of experimental techniques is at the basis of any fundamental achievement in modern physics. Strongly correlated systems (SCS), more than any other, need to be investigated through the greatest variety of experimental techniques in order to unveil and crosscheck the numerous and puzzling anomalous behaviors characterizing them. The study of SCS fostered the improvement of many old experimental techniques, but also the advent of many new ones just invented in order to analyze the complex behaviors of these systems. Many novel materials, with functional properties emerging from macroscopic quantum behaviors at the frontier of modern research in physics, chemistry and materials science, belong to this class of systems. The volume presents a representative collection of the modern experimental techniques specifically tailored for the analysis of strongly correlated systems. Any technique is presented in great detail by its own inventor or by one of the world-wide recognize...

  7. Cross-correlations between agricultural commodity futures markets in the US and China

    Science.gov (United States)

    Li, Zhihui; Lu, Xinsheng

    2012-08-01

    This paper examines the cross-correlation properties of agricultural futures markets between the US and China using a cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). The results show that the cross-correlations between the two geographically distant markets for four pairs of important agricultural commodities futures are significantly multifractal. By introducing the concept of a “crossover”, we find that the multifractality of cross-correlations between the two markets is not long lasting. The cross-correlations in the short term are more strongly multifractal, but they are weakly so in the long term. Moreover, cross-correlations of small fluctuations are persistent and those of large fluctuations are anti-persistent in the short term while cross-correlations of all kinds of fluctuations for soy bean and soy meal futures are persistent and for corn and wheat futures are anti-persistent in the long term. We also find that cross-correlation exponents are less than the averaged generalized Hurst exponent when q0 in the short term, while in the long term they are almost the same.

  8. Pulsed Field Waveforms for Magnetization of HTS Gd-Ba-Cu-O Bulk Magnets

    International Nuclear Information System (INIS)

    Ida, T; Matsuzaki, H; Morita, E; Sakashita, H; Harada, T; Ogata, H; Kimura, Y; Miki, M; Kitano, M; Izumi, M

    2006-01-01

    Progress in pulse magnetization technique for high-temperature superconductor bulks of melt-textured RE-Ba-Cu-O with large diameter is important for the realization of power applications. We studied the pulsed power source and pulsed field waveforms to enhance to improve the magnetization properties for Gd-Ba-Cu-O bulk. The risetime and duration of pulse waveform effectively varied distribution of magnetic flux

  9. Biomagnetic and bioelectric detection of gastric slow wave activity in normal human subjects—a correlation study

    International Nuclear Information System (INIS)

    Somarajan, S; Muszynski, N D; Obioha, C; Bradshaw, L A; Richards, W O

    2012-01-01

    We measured gastric slow wave activity simultaneously with a Superconducting Quantum Interference Device (SQUID) magnetometer, mucosal electrodes and cutaneous electrodes in 18 normal human subjects (11 women and 7 men). We processed signals with Fourier spectral analysis and SOBI blind-source separation techniques. We observed a high waveform correlation between the mucosal electromyogram (EMG) and multichannel SQUID magnetogastrogram (MGG). There was a lower waveform correlation between the mucosal EMG and cutaneous electrogastrogram (EGG), but the correlation improved with the application of SOBI. There was also a high correlation between the frequency of the electrical activity recorded in the MGG and in mucosal electrodes (r = 0.97). We concluded that SQUID magnetometers noninvasively record gastric slow wave activity that is highly correlated with the activity recorded by invasive mucosal electrodes. (paper)

  10. Eruption mass estimation using infrasound waveform inversion and ash and gas measurements: Evaluation at Sakurajima Volcano, Japan [Comparison of eruption masses at Sakurajima Volcano, Japan calculated by infrasound waveform inversion and ground-based sampling

    International Nuclear Information System (INIS)

    Fee, David; Izbekov, Pavel; Kim, Keehoon; Yokoo, Akihiko; Lopez, Taryn

    2017-01-01

    Eruption mass and mass flow rate are critical parameters for determining the aerial extent and hazard of volcanic emissions. Infrasound waveform inversion is a promising technique to quantify volcanic emissions. Although topography may substantially alter the infrasound waveform as it propagates, advances in wave propagation modeling and station coverage permit robust inversion of infrasound data from volcanic explosions. The inversion can estimate eruption mass flow rate and total eruption mass if the flow density is known. However, infrasound-based eruption flow rates and mass estimates have yet to be validated against independent measurements, and numerical modeling has only recently been applied to the inversion technique. Furthermore we present a robust full-waveform acoustic inversion method, and use it to calculate eruption flow rates and masses from 49 explosions from Sakurajima Volcano, Japan.

  11. Cross-correlations between Renminbi and four major currencies in the Renminbi currency basket

    Science.gov (United States)

    Wang, Gang-Jin; Xie, Chi

    2013-03-01

    We investigate the cross-correlations between Renminbi (CNY) and four major currencies (USD, EUR, JPY, and KRW) in the Renminbi currency basket, i.e., the cross-correlations of CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW. Qualitatively, using a statistical test in analogy to the Ljung-Box test, we find that cross-correlations significantly exist in CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW. Quantitatively, employing the detrended cross-correlation analysis (DCCA) method, we find that the cross-correlations of CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW are weakly persistent. We use the DCCA cross-correlation coefficient ρ to quantify the level of cross-correlations and find the currency weight in the Renminbi currency basket is arranged in the order of USD>EUR>JPY >KRW. Using the method of rolling windows, which can capture the time-varying cross-correlation scaling exponents, we find that: (i) CNY and USD are positively cross-correlated over time, but the cross-correlations of CNY-USD are anti-persistent during the US sub-prime crisis and the European debt crisis. (ii) The cross-correlation scaling exponents of CNY-EUR have the cyclical fluctuation with a nearly two-year cycle. (iii) CNY-JPY has long-term negative cross-correlations, during the European debt crisis, but CNY and KRW are positively cross-correlated.

  12. Seismic Broadband Full Waveform Inversion by shot/receiver refocusing

    NARCIS (Netherlands)

    Haffinger, P.R.

    2013-01-01

    Full waveform inversion is a tool to obtain high-resolution property models of the subsurface from seismic data. However, the technique is computationally expens- ive and so far no multi-dimensional implementation exists to achieve a resolution that can directly be used for seismic interpretation

  13. A survey of techniques applied to non-stationary waveforms in electrical power systems

    NARCIS (Netherlands)

    Rodrigues, R.P.; Silveira, P.M.; Ribeiro, P.F.

    2010-01-01

    The well-known and ever-present time-varying and non-stationary nature of waveforms in power systems requires a comprehensive and precise analytical basis that needs to be incorporated in the system studies and analyses. This time-varying behavior is due to continuous changes in system

  14. Austenitic stainless steel weld inspection

    International Nuclear Information System (INIS)

    Mech, S.J.; Emmons, J.S.; Michaels, T.E.

    1978-01-01

    Analytical techniques applied to ultrasonic waveforms obtained from inspection of austenitic stainless steel welds are described. Experimental results obtained from a variety of geometric and defect reflectors are presented. Specifically, frequency analyses parameters, such as simple moments of the power spectrum, cross-correlation techniques, and adaptive learning network analysis, all represent improvements over conventional time domain analysis of ultrasonic waveforms. Results for each of these methods are presented, and the overall inspection difficulties of austenitic stainless steel welds are discussed

  15. Strategies for the characteristic extraction of gravitational waveforms

    International Nuclear Information System (INIS)

    Babiuc, M. C.; Bishop, N. T.; Szilagyi, B.; Winicour, J.

    2009-01-01

    We develop, test, and compare new numerical and geometrical methods for improving the accuracy of extracting waveforms using characteristic evolution. The new numerical method involves use of circular boundaries to the stereographic grid patches which cover the spherical cross sections of the outgoing null cones. We show how an angular version of numerical dissipation can be introduced into the characteristic code to damp the high frequency error arising form the irregular way the circular patch boundary cuts through the grid. The new geometric method involves use of the Weyl tensor component Ψ 4 to extract the waveform as opposed to the original approach via the Bondi news function. We develop the necessary analytic and computational formula to compute the O(1/r) radiative part of Ψ 4 in terms of a conformally compactified treatment of null infinity. These methods are compared and calibrated in test problems based upon linearized waves.

  16. What is the best site for measuring the effect of ventilation on the pulse oximeter waveform?

    Science.gov (United States)

    Shelley, Kirk H; Jablonka, Denis H; Awad, Aymen A; Stout, Robert G; Rezkanna, Hoda; Silverman, David G

    2006-08-01

    The cardiac pulse is the predominant feature of the pulse oximeter (plethysmographic) waveform. Less obvious is the effect of ventilation on the waveform. There have been efforts to measure the effect of ventilation on the waveform to determine respiratory rate, tidal volume, and blood volume. We measured the relative strength of the effect of ventilation on the reflective plethysmographic waveform at three different sites: the finger, ear, and forehead. The plethysmographic waveforms from 18 patients undergoing positive pressure ventilation during surgery and 10 patients spontaneously breathing during renal dialysis were collected. The respiratory signal was isolated from the waveform using spectral analysis. It was found that the respiratory signal in the pulse oximeter waveform was more than 10 times stronger in the region of the head when compared with the finger. This was true with both controlled positive pressure ventilation and spontaneous breathing. A significant correlation was demonstrated between the estimated blood loss from surgical procedures and the impact of ventilation on ear plethysmographic data (r(s) = 0.624, P = 0.006).

  17. Quantum optical arbitrary waveform manipulation and measurement in real time.

    Science.gov (United States)

    Kowligy, Abijith S; Manurkar, Paritosh; Corzo, Neil V; Velev, Vesselin G; Silver, Michael; Scott, Ryan P; Yoo, S J B; Kumar, Prem; Kanter, Gregory S; Huang, Yu-Ping

    2014-11-17

    We describe a technique for dynamic quantum optical arbitrary-waveform generation and manipulation, which is capable of mode selectively operating on quantum signals without inducing significant loss or decoherence. It is built upon combining the developed tools of quantum frequency conversion and optical arbitrary waveform generation. Considering realistic parameters, we propose and analyze applications such as programmable reshaping of picosecond-scale temporal modes, selective frequency conversion of any one or superposition of those modes, and mode-resolved photon counting. We also report on experimental progress to distinguish two overlapping, orthogonal temporal modes, demonstrating over 8 dB extinction between picosecond-scale time-frequency modes, which agrees well with our theory. Our theoretical and experimental progress, as a whole, points to an enabling optical technique for various applications such as ultradense quantum coding, unity-efficiency cavity-atom quantum memories, and high-speed quantum computing.

  18. Testing power-law cross-correlations: Rescaled covariance test

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav

    2013-01-01

    Roč. 86, č. 10 (2013), 418-1-418-15 ISSN 1434-6028 R&D Projects: GA ČR GA402/09/0965 Institutional support: RVO:67985556 Keywords : power-law cross-correlations * testing * long-term memory Subject RIV: AH - Economics Impact factor: 1.463, year: 2013 http://library.utia.cas.cz/separaty/2013/E/kristoufek-testing power-law cross-correlations rescaled covariance test.pdf

  19. Frequency-Dependent Blanking with Digital Linear Chirp Waveform Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Andrews, John M. [General Atomics Aeronautical Systems, Inc., San Diego, CA (United States)

    2014-07-01

    Wideband radar systems, especially those that operate at lower frequencies such as VHF and UHF, are often restricted from transmitting within or across specific frequency bands in order to prevent interference to other spectrum users. Herein we describe techniques for notching the transmitted spectrum of a generated and transmitted radar waveform. The notches are fully programmable as to their location, and techniques are given that control the characteristics of the notches.

  20. Mergers of Black-Hole Binaries with Aligned Spins: Waveform Characteristics

    Science.gov (United States)

    Kelly, Bernard J.; Baker, John G.; vanMeter, James R.; Boggs, William D.; McWilliams, Sean T.; Centrella, Joan

    2011-01-01

    "We apply our gravitational-waveform analysis techniques, first presented in the context of nonspinning black holes of varying mass ratio [1], to the complementary case of equal-mass spinning black-hole binary systems. We find that, as with the nonspinning mergers, the dominant waveform modes phases evolve together in lock-step through inspiral and merger, supporting the previous model of the binary system as an adiabatically rigid rotator driving gravitational-wave emission - an implicit rotating source (IRS). We further apply the late-merger model for the rotational frequency introduced in [1], along with a new mode amplitude model appropriate for the dominant (2, plus or minus 2) modes. We demonstrate that this seven-parameter model performs well in matches with the original numerical waveform for system masses above - 150 solar mass, both when the parameters are freely fit, and when they are almost completely constrained by physical considerations."

  1. RECONSTRUCTING REDSHIFT DISTRIBUTIONS WITH CROSS-CORRELATIONS: TESTS AND AN OPTIMIZED RECIPE

    International Nuclear Information System (INIS)

    Matthews, Daniel J.; Newman, Jeffrey A.

    2010-01-01

    Many of the cosmological tests to be performed by planned dark energy experiments will require extremely well-characterized photometric redshift measurements. Current estimates for cosmic shear are that the true mean redshift of the objects in each photo-z bin must be known to better than 0.002(1 + z), and the width of the bin must be known to ∼0.003(1 + z) if errors in cosmological measurements are not to be degraded significantly. A conventional approach is to calibrate these photometric redshifts with large sets of spectroscopic redshifts. However, at the depths probed by Stage III surveys (such as DES), let alone Stage IV (LSST, JDEM, and Euclid), existing large redshift samples have all been highly (25%-60%) incomplete, with a strong dependence of success rate on both redshift and galaxy properties. A powerful alternative approach is to exploit the clustering of galaxies to perform photometric redshift calibrations. Measuring the two-point angular cross-correlation between objects in some photometric redshift bin and objects with known spectroscopic redshift, as a function of the spectroscopic z, allows the true redshift distribution of a photometric sample to be reconstructed in detail, even if it includes objects too faint for spectroscopy or if spectroscopic samples are highly incomplete. We test this technique using mock DEEP2 Galaxy Redshift survey light cones constructed from the Millennium Simulation semi-analytic galaxy catalogs. From this realistic test, which incorporates the effects of galaxy bias evolution and cosmic variance, we find that the true redshift distribution of a photometric sample can, in fact, be determined accurately with cross-correlation techniques. We also compare the empirical error in the reconstruction of redshift distributions to previous analytic predictions, finding that additional components must be included in error budgets to match the simulation results. This extra error contribution is small for surveys that sample

  2. A quantitative correlation between the mobility and crystallinity of photo-cross-linkable P3HT

    KAUST Repository

    Woo, Claire; Piliego, Claudia; Holcombe, Thomas W.; Toney, Michael F.; Frechet, Jean

    2012-01-01

    The performance of polymer field effect transistors (FETs) can vary by orders of magnitude by applying different processing conditions. Although it is generally believed that a higher degree of crystallinity results in a higher mobility, the correlation is not straightforward. In addition, the effect of cross-linking on polymer thin film microstructural order is relatively unknown. This study investigates the effect of thermal annealing and UV-initiated photo-cross-linking on the FET performance and microstructural order of a photo-cross-linkable P3HT derivative. Our results demonstrate that while cross-linking did not disrupt the overall crystallinity of the polymer thin film, the photo-cross-linking process likely induced doping in the semiconductor layer, leading to the absence of saturation behavior in the FET. Annealing after cross-linking slightly improved the FET performance but only minimally affected the microstructural order of the polymer film since the 3D morphology had been "locked in" during the first cross-linking step. Importantly, annealing and cross-linking simultaneously was a successful method to preserve polymer crystallinity while also achieving effective cross-linking. Using newly developed quantitative X-ray analysis techniques, our study established a quantitative correlation between FET charge mobility and thin film crystallinity. © 2012 American Chemical Society.

  3. A quantitative correlation between the mobility and crystallinity of photo-cross-linkable P3HT

    KAUST Repository

    Woo, Claire

    2012-04-10

    The performance of polymer field effect transistors (FETs) can vary by orders of magnitude by applying different processing conditions. Although it is generally believed that a higher degree of crystallinity results in a higher mobility, the correlation is not straightforward. In addition, the effect of cross-linking on polymer thin film microstructural order is relatively unknown. This study investigates the effect of thermal annealing and UV-initiated photo-cross-linking on the FET performance and microstructural order of a photo-cross-linkable P3HT derivative. Our results demonstrate that while cross-linking did not disrupt the overall crystallinity of the polymer thin film, the photo-cross-linking process likely induced doping in the semiconductor layer, leading to the absence of saturation behavior in the FET. Annealing after cross-linking slightly improved the FET performance but only minimally affected the microstructural order of the polymer film since the 3D morphology had been "locked in" during the first cross-linking step. Importantly, annealing and cross-linking simultaneously was a successful method to preserve polymer crystallinity while also achieving effective cross-linking. Using newly developed quantitative X-ray analysis techniques, our study established a quantitative correlation between FET charge mobility and thin film crystallinity. © 2012 American Chemical Society.

  4. Triplicated P-wave measurements for waveform tomography of the mantle transition zone

    Directory of Open Access Journals (Sweden)

    S. C. Stähler

    2012-11-01

    Full Text Available Triplicated body waves sample the mantle transition zone more extensively than any other wave type, and interact strongly with the discontinuities at 410 km and 660 km. Since the seismograms bear a strong imprint of these geodynamically interesting features, it is highly desirable to invert them for structure of the transition zone. This has rarely been attempted, due to a mismatch between the complex and band-limited data and the (ray-theoretical modelling methods. Here we present a data processing and modelling strategy to harness such broadband seismograms for finite-frequency tomography. We include triplicated P-waves (epicentral distance range between 14 and 30° across their entire broadband frequency range, for both deep and shallow sources. We show that is it possible to predict the complex sequence of arrivals in these seismograms, but only after a careful effort to estimate source time functions and other source parameters from data, variables that strongly influence the waveforms. Modelled and observed waveforms then yield decent cross-correlation fits, from which we measure finite-frequency traveltime anomalies. We discuss two such data sets, for North America and Europe, and conclude that their signal quality and azimuthal coverage should be adequate for tomographic inversion. In order to compute sensitivity kernels at the pertinent high body wave frequencies, we use fully numerical forward modelling of the seismic wavefield through a spherically symmetric Earth.

  5. Processing and evaluation of riverine waveforms acquired by an experimental bathymetric LiDAR

    Science.gov (United States)

    Kinzel, P. J.; Legleiter, C. J.; Nelson, J. M.

    2010-12-01

    Accurate mapping of fluvial environments with airborne bathymetric LiDAR is challenged not only by environmental characteristics but also the development and application of software routines to post-process the recorded laser waveforms. During a bathymetric LiDAR survey, the transmission of the green-wavelength laser pulses through the water column is influenced by a number of factors including turbidity, the presence of organic material, and the reflectivity of the streambed. For backscattered laser pulses returned from the river bottom and digitized by the LiDAR detector, post-processing software is needed to interpret and identify distinct inflections in the reflected waveform. Relevant features of this energy signal include the air-water interface, volume reflection from the water column itself, and, ideally, a strong return from the bottom. We discuss our efforts to acquire, analyze, and interpret riverine surveys using the USGS Experimental Advanced Airborne Research LiDAR (EAARL) in a variety of fluvial environments. Initial processing of data collected in the Trinity River, California, using the EAARL Airborne Lidar Processing Software (ALPS) highlighted the difficulty of retrieving a distinct bottom signal in deep pools. Examination of laser waveforms from these pools indicated that weak bottom reflections were often neglected by a trailing edge algorithm used by ALPS to process shallow riverine waveforms. For the Trinity waveforms, this algorithm had a tendency to identify earlier inflections as the bottom, resulting in a shallow bias. Similarly, an EAARL survey along the upper Colorado River, Colorado, also revealed the inadequacy of the trailing edge algorithm for detecting weak bottom reflections. We developed an alternative waveform processing routine by exporting digitized laser waveforms from ALPS, computing the local extrema, and fitting Gaussian curves to the convolved backscatter. Our field data indicate that these techniques improved the

  6. 2D acoustic-elastic coupled waveform inversion in the Laplace domain

    KAUST Repository

    Bae, Hoseuk

    2010-04-01

    Although waveform inversion has been intensively studied in an effort to properly delineate the Earth\\'s structures since the early 1980s, most of the time- and frequency-domain waveform inversion algorithms still have critical limitations in their applications to field data. This may be attributed to the highly non-linear objective function and the unreliable low-frequency components. To overcome the weaknesses of conventional waveform inversion algorithms, the acoustic Laplace-domain waveform inversion has been proposed. The Laplace-domain waveform inversion has been known to provide a long-wavelength velocity model even for field data, which may be because it employs the zero-frequency component of the damped wavefield and a well-behaved logarithmic objective function. However, its applications have been confined to 2D acoustic media.We extend the Laplace-domain waveform inversion algorithm to a 2D acoustic-elastic coupled medium, which is encountered in marine exploration environments. In 2D acoustic-elastic coupled media, the Laplace-domain pressures behave differently from those of 2D acoustic media, although the overall features are similar to each other. The main differences are that the pressure wavefields for acoustic-elastic coupled media show negative values even for simple geological structures unlike in acoustic media, when the Laplace damping constant is small and the water depth is shallow. The negative values may result from more complicated wave propagation in elastic media and at fluid-solid interfaces.Our Laplace-domain waveform inversion algorithm is also based on the finite-element method and logarithmic wavefields. To compute gradient direction, we apply the back-propagation technique. Under the assumption that density is fixed, P- and S-wave velocity models are inverted from the pressure data. We applied our inversion algorithm to the SEG/EAGE salt model and the numerical results showed that the Laplace-domain waveform inversion

  7. Calibration of the Dodewaard downcomer thermocouple cross-correlation flow-rate measurements

    Energy Technology Data Exchange (ETDEWEB)

    Stekelenburg, A J.C. [Technische Univ. Delft (Netherlands). Interfacultair Reactor Inst.; Hagen, T.H.J.J. van der [Technische Univ. Delft (Netherlands). Interfacultair Reactor Inst.; Akker, H.E.A. van den [Technische Univ. Delft (Netherlands). Lab. voor Fysische Technologie

    1992-12-01

    The cross-correlation flow measurement technique, applied for measuring the coolant flow rate in a nuclear reactor, was calibrated with the use of numerical simulations of turbulent flow. The three-dimensional domain was collapsed into two dimensions. With a two-dimensional calculation of steady-state flow with transient thermal characteristics the response of thermocouples to a temperature variation was calculated. By cross-correlating the calculated thermocouple responses, the link between total flow rate and measured transit times was made. Three calibration points were taken in the range of 579 kg/s to 1477 kg/s. In this range, the product of the calculated transit time and the mass flow-rate is constant up to +3.5% and -2.4%. The reliability of the calibration was estimated at {+-}4.6%. The influence of the inlet boundary conditions, and the modelling of the flow in the upper part of the downcomer channel on the calibration result is shown to be small. A measured velocity profile effect was successfully predicted. (orig.).

  8. Ultrafast chirped optical waveform recorder using a time microscope

    Science.gov (United States)

    Bennett, Corey Vincent

    2015-04-21

    A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

  9. High resolution aquifer characterization using crosshole GPR full-waveform tomography

    Science.gov (United States)

    Gueting, N.; Vienken, T.; Klotzsche, A.; Van Der Kruk, J.; Vanderborght, J.; Caers, J.; Vereecken, H.; Englert, A.

    2016-12-01

    Limited knowledge about the spatial distribution of aquifer properties typically constrains our ability to predict subsurface flow and transport. Here, we investigate the value of using high resolution full-waveform inversion of cross-borehole ground penetrating radar (GPR) data for aquifer characterization. By stitching together GPR tomograms from multiple adjacent crosshole planes, we are able to image, with a decimeter scale resolution, the dielectric permittivity and electrical conductivity of an alluvial aquifer along cross-sections of 50 m length and 10 m depth. A logistic regression model is employed to predict the spatial distribution of lithological facies on the basis of the GPR results. Vertical profiles of porosity and hydraulic conductivity from direct-push, flowmeter and grain size data suggest that the GPR predicted facies classification is meaningful with regard to porosity and hydraulic conductivity, even though the distributions of individual facies show some overlap and the absolute hydraulic conductivities from the different methods (direct-push, flowmeter, grain size) differ up to approximately one order of magnitude. Comparison of the GPR predicted facies architecture with tracer test data suggests that the plume splitting observed in a tracer experiment was caused by a hydraulically low-conductive sand layer with a thickness of only a few decimeters. Because this sand layer is identified by GPR full-waveform inversion but not by conventional GPR ray-based inversion we conclude that the improvement in spatial resolution due to full-waveform inversion is crucial to detect small-scale aquifer structures that are highly relevant for solute transport.

  10. Automated vessel segmentation using cross-correlation and pooled covariance matrix analysis.

    Science.gov (United States)

    Du, Jiang; Karimi, Afshin; Wu, Yijing; Korosec, Frank R; Grist, Thomas M; Mistretta, Charles A

    2011-04-01

    Time-resolved contrast-enhanced magnetic resonance angiography (CE-MRA) provides contrast dynamics in the vasculature and allows vessel segmentation based on temporal correlation analysis. Here we present an automated vessel segmentation algorithm including automated generation of regions of interest (ROIs), cross-correlation and pooled sample covariance matrix analysis. The dynamic images are divided into multiple equal-sized regions. In each region, ROIs for artery, vein and background are generated using an iterative thresholding algorithm based on the contrast arrival time map and contrast enhancement map. Region-specific multi-feature cross-correlation analysis and pooled covariance matrix analysis are performed to calculate the Mahalanobis distances (MDs), which are used to automatically separate arteries from veins. This segmentation algorithm is applied to a dual-phase dynamic imaging acquisition scheme where low-resolution time-resolved images are acquired during the dynamic phase followed by high-frequency data acquisition at the steady-state phase. The segmented low-resolution arterial and venous images are then combined with the high-frequency data in k-space and inverse Fourier transformed to form the final segmented arterial and venous images. Results from volunteer and patient studies demonstrate the advantages of this automated vessel segmentation and dual phase data acquisition technique. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Application of multi-source waveform inversion to marine streamer data using the global correlation norm

    KAUST Repository

    Choi, Yun Seok; Alkhalifah, Tariq Ali

    2012-01-01

    Conventional multi-source waveform inversion using an objective function based on the least-square misfit cannot be applied to marine streamer acquisition data because of inconsistent acquisition geometries between observed and modelled data

  12. Cross-correlations between crude oil and exchange markets for selected oil rich economies

    Science.gov (United States)

    Li, Jianfeng; Lu, Xinsheng; Zhou, Ying

    2016-07-01

    Using multifractal detrended cross-correlation analysis (MF-DCCA), this paper studies the cross-correlation behavior between crude oil market and five selected exchange rate markets. The dataset covers the period of January 1,1996-December 31,2014, and contains 4,633 observations for each of the series, including daily closing prices of crude oil, Australian Dollars, Canadian Dollars, Mexican Pesos, Russian Rubles, and South African Rand. Our empirical results obtained from cross-correlation statistic and cross-correlation coefficient have confirmed the existence of cross-correlations, and the MF-DCCA results have demonstrated a strong multifractality between cross-correlated crude oil market and exchange rate markets in both short term and long term. Using rolling window analysis, we have also found the persistent cross-correlations between the exchange rates and crude oil returns, and the cross-correlation scaling exponents exhibit volatility during some time periods due to its sensitivity to sudden events.

  13. General renormalized statistical approach with finite cross-field correlations

    International Nuclear Information System (INIS)

    Vakulenko, M.O.

    1992-01-01

    The renormalized statistical approach is proposed, accounting for finite correlations of potential and magnetic fluctuations. It may be used for analysis of a wide class of nonlinear model equations describing the cross-correlated plasma states. The influence of a cross spectrum on stationary potential and magnetic ones is investigated. 10 refs. (author)

  14. Some techniques of correlation experiments

    International Nuclear Information System (INIS)

    Allas, R.G.

    1976-01-01

    Some general remarks concerning correlation techniques are made. Most of the remarks are limited to correlated pairs of charged particles. The relatively simple system 3 He + 3 H → A + B + C, where all possible charged particle pairs A,B are detected and particle C is left undetected either charged or neutral, is considered. (G.T.H.)

  15. Preliminary assessment of the waveform inversion method for interpretation of cross-well seismic data from the thermal production test, JAPEX/JNOC/GSC et al. Mallik 5L-38 gas hydrate production research well

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, T. [Nagoya Univ., Nagoya (Japan). Research Center for Seismology and Volcanology; Shimizu, S. [Japan National Oil Co., Chiba (Japan); Asakawa, E. [JGI Inc., Tokyo (Japan); Kamei, R.; Matsuoka, T. [Kyoto Univ., Kyoto (Japan). Dept. of Civil and Earth Resources Engineering

    2005-07-01

    The JAPEX/JNOC/GSC et al. Mallik 3L-38 and 4L-38 test wells were subjected to repeated cross-well seismic surveys before and during the gas production test from the gas-hydrate-bearing layer at a depth of about 905 to 920 m. High-resolution velocity images in the gas-hydrate-bearing layer were obtained using the frequency-domain nonlinear waveform inversion method. An acoustic waveform inversion method was used along with the frequency-domain approach in order to detect the change in acoustic properties of the gas-hydrate-bearing layer resulting from gas production. The layered structures with small lateral heterogeneities were reconstructed by tomography analysis of preprocessed waveform data using a smaller number of source-receiver pairs. Preliminary results reveal high velocity and very high attenuation in the gas-hydrate-bearing layers. No obvious velocity decreases were noted. Information for further detailed processing was also gathered.

  16. Extracting More Data from LiDAR in Forested Areas by Analyzing Waveform Shape

    Directory of Open Access Journals (Sweden)

    Peter Beets

    2012-03-01

    Full Text Available Light Detection And Ranging (LiDAR in forested areas is used for constructing Digital Terrain Models (DTMs, estimating biomass carbon and timber volume and estimating foliage distribution as an indicator of tree growth and health. All of these purposes are hindered by the inability to distinguish the source of returns as foliage, stems, understorey and the ground except by their relative positions. The ability to separate these returns would improve all analyses significantly. Furthermore, waveform metrics providing information on foliage density could improve forest health and growth estimates. In this study, the potential to use waveform LiDAR was investigated. Aerial waveform LiDAR data were acquired for a New Zealand radiata pine plantation forest, and Leaf Area Density (LAD was measured in the field. Waveform peaks with a good signal-to-noise ratio were analyzed and each described with a Gaussian peak height, half-height width, and an exponential decay constant. All parameters varied substantially across all surface types, ruling out the potential to determine source characteristics for individual returns, particularly those with a lower signal-to-noise ratio. However, pulses on the ground on average had a greater intensity, decay constant and a narrower peak than returns from coniferous foliage. When spatially averaged, canopy foliage density (measured as LAD varied significantly, and was found to be most highly correlated with the volume-average exponential decay rate. A simple model based on the Beer-Lambert law is proposed to explain this relationship, and proposes waveform decay rates as a new metric that is less affected by shadowing than intensity-based metrics. This correlation began to fail when peaks with poorer curve fits were included.

  17. Spatiotemporal Ultrafast-Plasmon Control Based on Response Functions of Nanostructures Measured by Interferometric Cross-Correlation Microscopy

    Directory of Open Access Journals (Sweden)

    Kusaba Miyuki

    2013-03-01

    Full Text Available We demonstrate an electrical-field cross-correlation imaging technique to obtain a response function of localized plasmon generated by femtosecond laser pulses on gold nanostructures. Based on the measured response functions, we spatiotemporally control the plasmon by shaping the femtosecond excitation laser pulses.

  18. Seismic waveform classification using deep learning

    Science.gov (United States)

    Kong, Q.; Allen, R. M.

    2017-12-01

    MyShake is a global smartphone seismic network that harnesses the power of crowdsourcing. It has an Artificial Neural Network (ANN) algorithm running on the phone to distinguish earthquake motion from human activities recorded by the accelerometer on board. Once the ANN detects earthquake-like motion, it sends a 5-min chunk of acceleration data back to the server for further analysis. The time-series data collected contains both earthquake data and human activity data that the ANN confused. In this presentation, we will show the Convolutional Neural Network (CNN) we built under the umbrella of supervised learning to find out the earthquake waveform. The waveforms of the recorded motion could treat easily as images, and by taking the advantage of the power of CNN processing the images, we achieved very high successful rate to select the earthquake waveforms out. Since there are many non-earthquake waveforms than the earthquake waveforms, we also built an anomaly detection algorithm using the CNN. Both these two methods can be easily extended to other waveform classification problems.

  19. Ascending-ramp biphasic waveform has a lower defibrillation threshold and releases less troponin I than a truncated exponential biphasic waveform.

    Science.gov (United States)

    Huang, Jian; Walcott, Gregory P; Ruse, Richard B; Bohanan, Scott J; Killingsworth, Cheryl R; Ideker, Raymond E

    2012-09-11

    We tested the hypothesis that the shape of the shock waveform affects not only the defibrillation threshold but also the amount of cardiac damage. Defibrillation thresholds were determined for 11 waveforms-3 ascending-ramp waveforms, 3 descending-ramp waveforms, 3 rectilinear first-phase biphasic waveforms, a Gurvich waveform, and a truncated exponential biphasic waveform-in 6 pigs with electrodes in the right ventricular apex and superior vena cava. The ascending, descending, and rectilinear waveforms had 4-, 8-, and 16-millisecond first phases and a 3.5-millisecond rectilinear second phase that was half the voltage of the first phase. The exponential biphasic waveform had a 60% first-phase and a 50% second-phase tilt. In a second study, we attempted to defibrillate after 10 seconds of ventricular fibrillation with a single ≈30-J shock (6 pigs successfully defibrillated with 8-millisecond ascending, 8-millisecond rectilinear, and truncated exponential biphasic waveforms). Troponin I blood levels were determined before and 2 to 10 hours after the shock. The lowest-energy defibrillation threshold was for the 8-milliseconds ascending ramp (14.6±7.3 J [mean±SD]), which was significantly less than for the truncated exponential (19.6±6.3 J). Six hours after shock, troponin I was significantly less for the ascending-ramp waveform (0.80±0.54 ng/mL) than for the truncated exponential (1.92±0.47 ng/mL) or the rectilinear waveform (1.17±0.45 ng/mL). The ascending ramp has a significantly lower defibrillation threshold and at ≈30 J causes 58% less troponin I release than the truncated exponential biphasic shock. Therefore, the shock waveform affects both the defibrillation threshold and the amount of cardiac damage.

  20. A Cross-Wavelet Transform Aided Rule Based Approach for Early Prediction of Lean Blow-out in Swirl-Stabilized Dump Combustor

    Directory of Open Access Journals (Sweden)

    Debangshu Dey

    2015-03-01

    Full Text Available Lean or ultralean combustion is one of the popular strategies to achieve very low emission levels. However, it is extremely susceptible to lean blow-out (LBO. The present work explores a Cross-wavelet transform (XWT aided rule based scheme for early prediction of lean blowout. XWT can be considered as an advancement of wavelet analysis which gives correlation between two waveforms in time-frequency space. In the present scheme a swirl-stabilized dump combustor is used as a laboratory-scale model of a generic gas turbine combustor with LPG as fuel. Various time series data of CH chemiluminescence signal are recorded for different flame conditions by varying equivalence ratio, flow rate and level of air-fuel premixing. Some features are extracted from the cross-wavelet spectrum of the recorded waveforms and a reference wave. The extracted features are observed to classify the flame condition into three major classes: near LBO, moderate and healthy. Moreover, a Rough Set based technique is also applied on the extracted features to generate a rule base so that it can be fed to a real time controller or expert system to take necessary control action to prevent LBO. Results show that the proposed methodology performs with an acceptable degree of accuracy.

  1. Analysis of classical time-trial performance and technique-specific physiological determinants in elite female cross-country skiers

    Directory of Open Access Journals (Sweden)

    Øyvind Sandbakk

    2016-08-01

    Full Text Available The present study investigated the contribution of performance on uphill, flat, and downhill sections to overall performance in an international 10-km classical time-trial in elite female cross-country skiers, as well as the relationships between performance on snow and laboratory-measured physiological variables in the double poling (DP and diagonal (DIA techniques. Ten elite female cross-country skiers were continuously measured by a global positioning system device during an international 10-km cross-country skiing time-trial in the classical technique. One month prior to the race, all skiers performed a 5-min submaximal and 3-min self-paced performance test while roller skiing on a treadmill, both in the DP and DIA techniques. The time spent on uphill (r=0.98 and flat (r=0.91 sections of the race correlated most strongly with the overall 10-km performance (both p<0.05. Approximately 56% of the racing time was spent uphill, and stepwise multiple regression revealed that uphill time explained 95.5% of the variance in overall performance (p<0.001. Distance covered during the 3-min roller-skiing test and body-mass normalized peak oxygen uptake (VO2peak in both techniques showed the strongest correlations with overall time-trial performance (r=0.66-0.78, with DP capacity tending to have greatest impact on the flat and DIA capacity on uphill terrain (all p<0.05. Our present findings reveal that the time spent uphill most strongly determine classical time-trial performance, and that the major portion of the performance differences among elite female cross-country skiers can be explained by variations in technique-specific aerobic power.

  2. Salvus: A scalable software suite for full-waveform modelling & inversion

    Science.gov (United States)

    Afanasiev, M.; Boehm, C.; van Driel, M.; Krischer, L.; Fichtner, A.

    2017-12-01

    Full-waveform inversion (FWI), whether at the lab, exploration, or planetary scale, requires the cooperation of five principal components. (1) The geometry of the domain needs to be properly discretized and an initial guess of the model parameters must be projected onto it; (2) Large volumes of recorded waveform data must be collected, organized, and processed; (3) Synthetic waveform data must be efficiently and accurately computed through complex domains; (4) Suitable misfit functions and optimization techniques must be used to relate discrepancies in data space to perturbations in the model; and (5) Some form of workflow management must be employed to schedule and run (1) - (4) in the correct order. Each one of these components can represent a formidable technical challenge which redirects energy from the true task at hand: using FWI to extract new information about some underlying continuum.In this presentation we give an overview of the current status of the Salvus software suite, which was introduced to address the challenges listed above. Specifically, we touch on (1) salvus_mesher, which eases the discretization of complex Earth models into hexahedral meshes; (2) salvus_seismo, which integrates with LASIF and ObsPy to streamline the processing and preparation of seismic data; (3) salvus_wave, a high-performance and scalable spectral-element solver capable of simulating waveforms through general unstructured 2- and 3-D domains, and (4) salvus_opt, an optimization toolbox specifically designed for full-waveform inverse problems. Tying everything together, we also discuss (5) salvus_flow: a workflow package designed to orchestrate and manage the rest of the suite. It is our hope that these developments represent a step towards the automation of large-scale seismic waveform inversion, while also lowering the barrier of entry for new applications. We include several examples of Salvus' use in (extra-) planetary seismology, non-destructive testing, and medical

  3. Perceptually informed synthesis of bandlimited classical waveforms using integrated polynomial interpolation.

    Science.gov (United States)

    Välimäki, Vesa; Pekonen, Jussi; Nam, Juhan

    2012-01-01

    Digital subtractive synthesis is a popular music synthesis method, which requires oscillators that are aliasing-free in a perceptual sense. It is a research challenge to find computationally efficient waveform generation algorithms that produce similar-sounding signals to analog music synthesizers but which are free from audible aliasing. A technique for approximately bandlimited waveform generation is considered that is based on a polynomial correction function, which is defined as the difference of a non-bandlimited step function and a polynomial approximation of the ideal bandlimited step function. It is shown that the ideal bandlimited step function is equivalent to the sine integral, and that integrated polynomial interpolation methods can successfully approximate it. Integrated Lagrange interpolation and B-spline basis functions are considered for polynomial approximation. The polynomial correction function can be added onto samples around each discontinuity in a non-bandlimited waveform to suppress aliasing. Comparison against previously known methods shows that the proposed technique yields the best tradeoff between computational cost and sound quality. The superior method amongst those considered in this study is the integrated third-order B-spline correction function, which offers perceptually aliasing-free sawtooth emulation up to the fundamental frequency of 7.8 kHz at the sample rate of 44.1 kHz. © 2012 Acoustical Society of America.

  4. Seismic reflection response from cross-correlations of ambient vibrations on non-conventional hidrocarbon reservoir

    Science.gov (United States)

    Huerta, F. V.; Granados, I.; Aguirre, J.; Carrera, R. Á.

    2017-12-01

    Nowadays, in hydrocarbon industry, there is a need to optimize and reduce exploration costs in the different types of reservoirs, motivating the community specialized in the search and development of alternative exploration geophysical methods. This study show the reflection response obtained from a shale gas / oil deposit through the method of seismic interferometry of ambient vibrations in combination with Wavelet analysis and conventional seismic reflection techniques (CMP & NMO). The method is to generate seismic responses from virtual sources through the process of cross-correlation of records of Ambient Seismic Vibrations (ASV), collected in different receivers. The seismic response obtained is interpreted as the response that would be measured in one of the receivers considering a virtual source in the other. The acquisition of ASV records was performed in northern of Mexico through semi-rectangular arrays of multi-component geophones with instrumental response of 10 Hz. The in-line distance between geophones was 40 m while in cross-line was 280 m, the sampling used during the data collection was 2 ms and the total duration of the records was 6 hours. The results show the reflection response of two lines in the in-line direction and two in the cross-line direction for which the continuity of coherent events have been identified and interpreted as reflectors. There is certainty that the events identified correspond to reflections because the time-frequency analysis performed with the Wavelet Transform has allowed to identify the frequency band in which there are body waves. On the other hand, the CMP and NMO techniques have allowed to emphasize and correct the reflection response obtained during the correlation processes in the frequency band of interest. The results of the processing and analysis of ASV records through the seismic interferometry method have allowed us to see interesting results in light of the cross-correlation process in combination with

  5. Reliability of pressure waveform analysis to determine correct epidural needle placement in labouring women.

    Science.gov (United States)

    Al-Aamri, I; Derzi, S H; Moore, A; Elgueta, M F; Moustafa, M; Schricker, T; Tran, D Q

    2017-07-01

    Pressure waveform analysis provides a reliable confirmatory adjunct to the loss-of-resistance technique to identify the epidural space during thoracic epidural anaesthesia, but its role remains controversial in lumbar epidural analgesia during labour. We performed an observational study in 100 labouring women of the sensitivity and specificity of waveform analysis to determine the correct location of the epidural needle. After obtaining loss-of-resistance, the anaesthetist injected 5 ml saline through the epidural needle (accounting for the volume already used in the loss-of-resistance). Sterile extension tubing, connected to a pressure transducer, was attached to the needle. An investigator determined the presence or absence of a pulsatile waveform, synchronised with the heart rate, on a monitor screen that was not in the view of the anaesthetist or the parturient. A bolus of 4 ml lidocaine 2% with adrenaline 5 μg.ml -1 was administered, and the epidural block was assessed after 15 min. Three women displayed no sensory block at 15 min. The results showed: epidural block present, epidural waveform present 93; epidural block absent, epidural waveform absent 2; epidural block present, epidural waveform absent 4; epidural block absent, epidural waveform present 1. Compared with the use of a local anaesthetic bolus to ascertain the epidural space, the sensitivity, specificity, positive and negative predictive values of waveform analysis were 95.9%, 66.7%, 98.9% and 33.3%, respectively. Epidural waveform analysis provides a simple adjunct to loss-of-resistance for confirming needle placement during performance of obstetric epidurals, however, further studies are required before its routine implementation in clinical practice. © 2017 The Association of Anaesthetists of Great Britain and Ireland.

  6. [Correlation and conversion of plasma cholinesterase activity values using three techniques].

    Science.gov (United States)

    Carmona-Fonseca, Jaime

    2007-07-01

    To determine mathematical correlations of three quantitative techniques to measure plasma cholinesterase, using reference values already established for two populations in the department of Antioquia, Colombia. In this descriptive, cross-sectional, prospective study, two independent, representative samples of working adults (18 to 65 years old) were examined. In both samples the adults worked for businesses associated with Colombia's Social Security system. Adults in the two samples had not been exposed to cholinesterase-inhibiting pesticides. The samples were from two neighboring regions of the department of Antioquia: one sample (415 adults) was from the Aburrá Valley, and the other (412 adults) was from Oriente Antioqueño (Eastern Antioquia). Plasma cholinesterase (EC 3.1.1.8) was measured using three quantitative methods: Michel, EQM, and Monotest. Linear regression equations were developed to correlate results of these three techniques. Six simple linear regression equations were defined to show the relationship of three measurement techniques for plasma cholinesterase. There was a moderate correlation of the three techniques (r = 0.686 to 0.771), but it increased (r = 0.744 to 0.811) when 12 (1.5%) outliers were eliminated. Associations among the three techniques were highly significant (P EQM (U/mL) = 0.40773 + 1.8757 (Michel [delta pH/h]); Michel (delta pH/h) = 0.25799 + 0.33871 (EQM [U/mL]); Monotest (U/L) = 462.0 + 4 565.0 (Michel [delta pH/h]); Michel (delta pH/h) = 0.42956 + 0.00012125 (Monotest [U/L]); EQM (U/mL) = 0.75333 + 0.00031056 (Monotest [U/L]); and Monotest (U/L) = 262.0 + 2 118.0 (EQM [U/mL]). The proposed mathematical models allow conversion of cholinesterase activity values using the Michel, EQM, and Monotest techniques. These models can be of assistance in Colombia and other countries where a variety of measurement techniques are used, and where it becomes difficult to compare the results of different studies. Having mathematical models

  7. Stationary-phase integrals in the cross correlation of ambient noise

    NARCIS (Netherlands)

    Boschi, L.; Weemstra, C.

    2015-01-01

    The cross correlation of ambient signal allows seismologists to collect data even in the absence of seismic events. “Seismic interferometry” shows that the cross correlation of simultaneous recordings of a random wavefield made at two locations is formally related to the impulse response between

  8. Spatially-Variant Tikhonov Regularization for Double-Difference Waveform Inversion

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Youzuo [Los Alamos National Laboratory; Huang, Lianjie [Los Alamos National Laboratory; Zhang, Zhigang [Los Alamos National Laboratory

    2011-01-01

    Double-difference waveform inversion is a potential tool for quantitative monitoring for geologic carbon storage. It jointly inverts time-lapse seismic data for changes in reservoir geophysical properties. Due to the ill-posedness of waveform inversion, it is a great challenge to obtain reservoir changes accurately and efficiently, particularly when using time-lapse seismic reflection data. Regularization techniques can be utilized to address the issue of ill-posedness. The regularization parameter controls the smoothness of inversion results. A constant regularization parameter is normally used in waveform inversion, and an optimal regularization parameter has to be selected. The resulting inversion results are a trade off among regions with different smoothness or noise levels; therefore the images are either over regularized in some regions while under regularized in the others. In this paper, we employ a spatially-variant parameter in the Tikhonov regularization scheme used in double-difference waveform tomography to improve the inversion accuracy and robustness. We compare the results obtained using a spatially-variant parameter with those obtained using a constant regularization parameter and those produced without any regularization. We observe that, utilizing a spatially-variant regularization scheme, the target regions are well reconstructed while the noise is reduced in the other regions. We show that the spatially-variant regularization scheme provides the flexibility to regularize local regions based on the a priori information without increasing computational costs and the computer memory requirement.

  9. Photonic arbitrary waveform generator based on Taylor synthesis method

    DEFF Research Database (Denmark)

    Liao, Shasha; Ding, Yunhong; Dong, Jianji

    2016-01-01

    Arbitrary waveform generation has been widely used in optical communication, radar system and many other applications. We propose and experimentally demonstrate a silicon-on-insulator (SOI) on chip optical arbitrary waveform generator, which is based on Taylor synthesis method. In our scheme......, a Gaussian pulse is launched to some cascaded microrings to obtain first-, second- and third-order differentiations. By controlling amplitude and phase of the initial pulse and successive differentiations, we can realize an arbitrary waveform generator according to Taylor expansion. We obtain several typical...... waveforms such as square waveform, triangular waveform, flat-top waveform, sawtooth waveform, Gaussian waveform and so on. Unlike other schemes based on Fourier synthesis or frequency-to-time mapping, our scheme is based on Taylor synthesis method. Our scheme does not require any spectral disperser or large...

  10. Statistical properties of cross-correlation in the Korean stock market

    Science.gov (United States)

    Oh, G.; Eom, C.; Wang, F.; Jung, W.-S.; Stanley, H. E.; Kim, S.

    2011-01-01

    We investigate the statistical properties of the cross-correlation matrix between individual stocks traded in the Korean stock market using the random matrix theory (RMT) and observe how these affect the portfolio weights in the Markowitz portfolio theory. We find that the distribution of the cross-correlation matrix is positively skewed and changes over time. We find that the eigenvalue distribution of original cross-correlation matrix deviates from the eigenvalues predicted by the RMT, and the largest eigenvalue is 52 times larger than the maximum value among the eigenvalues predicted by the RMT. The β_{473} coefficient, which reflect the largest eigenvalue property, is 0.8, while one of the eigenvalues in the RMT is approximately zero. Notably, we show that the entropy function E(σ) with the portfolio risk σ for the original and filtered cross-correlation matrices are consistent with a power-law function, E( σ) σ^{-γ}, with the exponent γ 2.92 and those for Asian currency crisis decreases significantly.

  11. Wavelet Analysis of Ultrasonic Echo Waveform and Application to Nondestructive Evaluation

    International Nuclear Information System (INIS)

    Park, Ik Keun; Park, Un Su; Ahn, Hyung Keun; Kwun, Sook In; Byeon, Jai Won

    2000-01-01

    Recently, advanced signal analysis which is called 'time-frequency analysis' has been used widely in nondestructive evaluation applications. Wavelet transform(WT) and Wigner Distribution are the most advanced techniques for processing signals with time-varying spectra. Wavelet analysis method is an attractive technique for evaluation of material characterization nondestructively. Wavelet transform is applied to the time-frequency analysis of ultrasonic echo waveform obtained by an ultrasonic pulse-echo technique. In this study, the feasibility of noise suppression of ultrasonic flaw signal and frequency-dependent ultrasonic group velocity and attenuation coefficient using wavelet analysis of ultrasonic echo waveform have been verified experimentally. The Gabor function is adopted the analyzing wavelet. The wavelet analysis shows that the variations of ultrasonic group velocity and attenuation coefficient due to the change of material characterization can be evaluated at each frequency. Furthermore, to assure the enhancement of detectability and new sizing performance, both computer simulated results and experimental measurements using wavelet signal processing are used to demonstrate the effectiveness of the noise suppression of ultrasonic flaw signal obtained from austenitic stainless steel weld including EDM notch

  12. Image processing by use of the digital cross-correlator

    International Nuclear Information System (INIS)

    Katou, Yoshinori

    1982-01-01

    We manufactured for trial an instrument which achieved the image processing using digital correlators. A digital correlator perform 64-bit parallel correlation at 20 MH. The output of a digital correlator is a 7-bit word representing. An A-D converter is used to quantize it a precision of six bits. The resulting 6-bit word is fed to six correlators, wired in parallel. The image processing achieved in 12 bits, whose digital outputs converted an analog signal by a D-A converter. This instrument is named the digital cross-correlator. The method which was used in the image processing system calculated the convolution with the digital correlator. It makes various digital filters. In the experiment with the image processing video signals from TV camera were used. The digital image processing time was approximately 5 μs. The contrast was enhanced and smoothed. The digital cross-correlator has the image processing of 16 sorts, and was produced inexpensively. (author)

  13. Retrieving rupture history using waveform inversions in time sequence

    Science.gov (United States)

    Yi, L.; Xu, C.; Zhang, X.

    2017-12-01

    The rupture history of large earthquakes is generally regenerated using the waveform inversion through utilizing seismological waveform records. In the waveform inversion, based on the superposition principle, the rupture process is linearly parameterized. After discretizing the fault plane into sub-faults, the local source time function of each sub-fault is usually parameterized using the multi-time window method, e.g., mutual overlapped triangular functions. Then the forward waveform of each sub-fault is synthesized through convoluting the source time function with its Green function. According to the superposition principle, these forward waveforms generated from the fault plane are summarized in the recorded waveforms after aligning the arrival times. Then the slip history is retrieved using the waveform inversion method after the superposing of all forward waveforms for each correspond seismological waveform records. Apart from the isolation of these forward waveforms generated from each sub-fault, we also realize that these waveforms are gradually and sequentially superimposed in the recorded waveforms. Thus we proposed a idea that the rupture model is possibly detachable in sequent rupture times. According to the constrained waveform length method emphasized in our previous work, the length of inverted waveforms used in the waveform inversion is objectively constrained by the rupture velocity and rise time. And one essential prior condition is the predetermined fault plane that limits the duration of rupture time, which means the waveform inversion is restricted in a pre-set rupture duration time. Therefore, we proposed a strategy to inverse the rupture process sequentially using the progressively shift rupture times as the rupture front expanding in the fault plane. And we have designed a simulation inversion to test the feasibility of the method. Our test result shows the prospect of this idea that requiring furthermore investigation.

  14. Full-waveform inversion of GPR data for civil engineering applications

    Science.gov (United States)

    van der Kruk, Jan; Kalogeropoulos, Alexis; Hugenschmidt, Johannes; Klotzsche, Anja; Busch, Sebastian; Vereecken, Harry

    2014-05-01

    Conventional GPR ray-based techniques are often limited in their capability to image complex structures due to the pertaining approximations. Due to the increased computational power, it is becoming more easy to use modeling and inversion tools that explicitly take into account the detailed electromagnetic wave propagation characteristics. In this way, new civil engineering application avenues are opening up that enable an improved high resolution imaging of quantitative medium properties. In this contribution, we show recent developments that enable the full-waveform inversion of off-ground, on-ground and crosshole GPR data. For a successful inversion, a proper start model must be used that generates synthetic data that overlaps the measured data with at least half a wavelength. In addition, the GPR system must be calibrated such that an effective wavelet is obtained that encompasses the complexity of the GPR source and receiver antennas. Simple geometries such as horizontal layers can be described with a limited number of model parameters, which enable the use of a combined global and local search using the Simplex search algorithm. This approach has been implemented for the full-waveform inversion of off-ground and on-ground GPR data measured over horizontally layered media. In this way, an accurate 3D frequency domain forward model of Maxwell's equation can be used where the integral representation of the electric field is numerically evaluated. The full-waveform inversion (FWI) for a large number of unknowns uses gradient-based optimization methods where a 3D to 2D conversion is used to apply this method to experimental data. Off-ground GPR data, measured over homogeneous concrete specimens, were inverted using the full-waveform inversion. In contrast to traditional ray-based techniques we were able to obtain quantitative values for the permittivity and conductivity and in this way distinguish between moisture and chloride effects. For increasing chloride

  15. Detrended cross-correlation analysis on RMB exchange rate and Hang Seng China Enterprises Index

    Science.gov (United States)

    Ruan, Qingsong; Yang, Bingchan; Ma, Guofeng

    2017-02-01

    In this paper, we investigate the cross-correlations between the Hang Seng China Enterprises Index and RMB exchange markets on the basis of a cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). MF-DCCA has, at best, serious limitations for most of the signals describing complex natural processes and often indicates multifractal cross-correlations when there are none. In order to prevent these false multifractal cross-correlations, we apply MFCCA to verify the cross-correlations. Qualitatively, we find that the return series of the Hang Seng China Enterprises Index and RMB exchange markets were, overall, significantly cross-correlated based on the statistical analysis. Quantitatively, we find that the cross-correlations between the stock index and RMB exchange markets were strongly multifractal, and the multifractal degree of the onshore RMB exchange markets was somewhat larger than the offshore RMB exchange markets. Moreover, we use the absolute return series to investigate and confirm the fact of multifractality. The results from the rolling windows show that the short-term cross-correlations between volatility series remain high.

  16. 3D elastic full waveform inversion using P-wave excitation amplitude: Application to OBC field data

    KAUST Repository

    Oh, Juwon; Kalita, Mahesh; Alkhalifah, Tariq Ali

    2017-01-01

    We propose an efficient elastic full waveform inversion (FWI) based on the P-wave excitation amplitude (maximum energy arrival) approximation in the source wavefields. Because, based on the P-wave excitation approximation (ExA), the gradient direction is approximated by the cross-correlation of source and receiver wavefields at only excitation time, it estimates the gradient direction faster than its conventional counterpart. In addition to this computational speedup, the P-wave excitation approximation automatically ignores SP and SS correlations in the approximated gradient direction. In elastic FWI for ocean bottom cable (OBC) data, the descent direction for the S-wave velocity is often degraded by undesired long-wavelength features from the SS correlation. For this reason, the P-wave excitation approach increases the convergence rate of multi-parameter FWI compared to the conventional approach. The modified 2D Marmousi model with OBC acquisition is used to verify the differences between the conventional method and ExA. Finally, the feasibility of the proposed method is demonstrated on a real OBC data from North Sea.

  17. 3D elastic full waveform inversion using P-wave excitation amplitude: Application to OBC field data

    KAUST Repository

    Oh, Juwon

    2017-12-05

    We propose an efficient elastic full waveform inversion (FWI) based on the P-wave excitation amplitude (maximum energy arrival) approximation in the source wavefields. Because, based on the P-wave excitation approximation (ExA), the gradient direction is approximated by the cross-correlation of source and receiver wavefields at only excitation time, it estimates the gradient direction faster than its conventional counterpart. In addition to this computational speedup, the P-wave excitation approximation automatically ignores SP and SS correlations in the approximated gradient direction. In elastic FWI for ocean bottom cable (OBC) data, the descent direction for the S-wave velocity is often degraded by undesired long-wavelength features from the SS correlation. For this reason, the P-wave excitation approach increases the convergence rate of multi-parameter FWI compared to the conventional approach. The modified 2D Marmousi model with OBC acquisition is used to verify the differences between the conventional method and ExA. Finally, the feasibility of the proposed method is demonstrated on a real OBC data from North Sea.

  18. Generation of Quasi-Gaussian Pulses Based on Correlation Techniques

    Directory of Open Access Journals (Sweden)

    POHOATA, S.

    2012-02-01

    Full Text Available The Gaussian pulses have been mostly used within communications, where some applications can be emphasized: mobile telephony (GSM, where GMSK signals are used, as well as the UWB communications, where short-period pulses based on Gaussian waveform are generated. Since the Gaussian function signifies a theoretical concept, which cannot be accomplished from the physical point of view, this should be expressed by using various functions, able to determine physical implementations. New techniques of generating the Gaussian pulse responses of good precision are approached, proposed and researched in this paper. The second and third order derivatives with regard to the Gaussian pulse response are accurately generated. The third order derivates is composed of four individual rectangular pulses of fixed amplitudes, being easily to be generated by standard techniques. In order to generate pulses able to satisfy the spectral mask requirements, an adequate filter is necessary to be applied. This paper emphasizes a comparative analysis based on the relative error and the energy spectra of the proposed pulses.

  19. Cross correlation measurement of low frequency conductivity noise

    Science.gov (United States)

    Jain, Aditya Kumar; Nigudkar, Himanshu; Chakraborti, Himadri; Udupa, Aditi; Gupta, Kantimay Das

    2018-04-01

    In order to study the low frequency noise(1/f noise)an experimental technique based on cross correlation of two channels is presented. In this method the device under test (DUT)is connected to the two independently powered preamplifiers in parallel. The amplified signals from the two preamplifiers are fed to two channels of a digitizer. Subsequent data processing largelyeliminates the uncorrelated noise of the two channels. This method is tested for various commercial carbon/metal film resistors by measuring equilibrium thermal noise (4kBTR). The method is then modified to study the non-equilibrium low frequency noise of heterostructure samples using fiveprobe configuration. Five contact probes allow two parts of the sample to become two arms of a balanced bridge. This configuration helps in suppressing the effect of power supply fluctuations, bath temperature fluctuations and contact resistances.

  20. Mini-batch optimized full waveform inversion with geological constrained gradient filtering

    Science.gov (United States)

    Yang, Hui; Jia, Junxiong; Wu, Bangyu; Gao, Jinghuai

    2018-05-01

    High computation cost and generating solutions without geological sense have hindered the wide application of Full Waveform Inversion (FWI). Source encoding technique is a way to dramatically reduce the cost of FWI but subject to fix-spread acquisition setup requirement and slow convergence for the suppression of cross-talk. Traditionally, gradient regularization or preconditioning is applied to mitigate the ill-posedness. An isotropic smoothing filter applied on gradients generally gives non-geological inversion results, and could also introduce artifacts. In this work, we propose to address both the efficiency and ill-posedness of FWI by a geological constrained mini-batch gradient optimization method. The mini-batch gradient descent optimization is adopted to reduce the computation time by choosing a subset of entire shots for each iteration. By jointly applying the structure-oriented smoothing to the mini-batch gradient, the inversion converges faster and gives results with more geological meaning. Stylized Marmousi model is used to show the performance of the proposed method on realistic synthetic model.

  1. Advances in waveform-agile sensing for tracking

    CERN Document Server

    Sira, Sandeep Prasad

    2009-01-01

    Recent advances in sensor technology and information processing afford a new flexibility in the design of waveforms for agile sensing. Sensors are now developed with the ability to dynamically choose their transmit or receive waveforms in order to optimize an objective cost function. This has exposed a new paradigm of significant performance improvements in active sensing: dynamic waveform adaptation to environment conditions, target structures, or information features. The manuscript provides a review of recent advances in waveform-agile sensing for target tracking applications. A dynamic wav

  2. Full Waveform Inversion Using Nonlinearly Smoothed Wavefields

    KAUST Repository

    Li, Y.; Choi, Yun Seok; Alkhalifah, Tariq Ali; Li, Z.

    2017-01-01

    The lack of low frequency information in the acquired data makes full waveform inversion (FWI) conditionally converge to the accurate solution. An initial velocity model that results in data with events within a half cycle of their location in the observed data was required to converge. The multiplication of wavefields with slightly different frequencies generates artificial low frequency components. This can be effectively utilized by multiplying the wavefield with itself, which is nonlinear operation, followed by a smoothing operator to extract the artificially produced low frequency information. We construct the objective function using the nonlinearly smoothed wavefields with a global-correlation norm to properly handle the energy imbalance in the nonlinearly smoothed wavefield. Similar to the multi-scale strategy, we progressively reduce the smoothing width applied to the multiplied wavefield to welcome higher resolution. We calculate the gradient of the objective function using the adjoint-state technique, which is similar to the conventional FWI except for the adjoint source. Examples on the Marmousi 2 model demonstrate the feasibility of the proposed FWI method to mitigate the cycle-skipping problem in the case of a lack of low frequency information.

  3. Full Waveform Inversion Using Nonlinearly Smoothed Wavefields

    KAUST Repository

    Li, Y.

    2017-05-26

    The lack of low frequency information in the acquired data makes full waveform inversion (FWI) conditionally converge to the accurate solution. An initial velocity model that results in data with events within a half cycle of their location in the observed data was required to converge. The multiplication of wavefields with slightly different frequencies generates artificial low frequency components. This can be effectively utilized by multiplying the wavefield with itself, which is nonlinear operation, followed by a smoothing operator to extract the artificially produced low frequency information. We construct the objective function using the nonlinearly smoothed wavefields with a global-correlation norm to properly handle the energy imbalance in the nonlinearly smoothed wavefield. Similar to the multi-scale strategy, we progressively reduce the smoothing width applied to the multiplied wavefield to welcome higher resolution. We calculate the gradient of the objective function using the adjoint-state technique, which is similar to the conventional FWI except for the adjoint source. Examples on the Marmousi 2 model demonstrate the feasibility of the proposed FWI method to mitigate the cycle-skipping problem in the case of a lack of low frequency information.

  4. WAVEFORM ANALYSIS FOR THE EXTRACTION OF POST-FIRE VEGETATION CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    F. Pirotti

    2012-08-01

    Full Text Available Full-waveform is becoming increasingly available in today's LiDAR systems and the analysis of the full return signal can provide additional information on the reflecting surfaces. In this paper we present the results of an assessment on full-waveform analysis, as opposed to the more classic discrete return analysis, for discerning vegetation cover classes related to post-fire renovation. In the spring of 2011 an OPTECH ALTM sensor was used to survey an Alpine area of almost 20 km2 in the north of Italy. A forest fire event several years ago burned large patches of vegetation for a total of about 1.5 km2 . The renovation process in the area is varied because of the different interventions ranging from no intervention to the application of re-forestation techniques to accelerate the process of re-establishing protection forest. The LiDAR data was used to divide the study site into areas with different conditions in terms of re-establishment of the natural vegetation condition. The LiDAR survey provided both the full-waveform data in Optech's CSD+DGT (corrected sensor data and NDF+IDX (digitizer data with index file formats, and the discrete return in the LAS format. The method applied to the full-waveform uses canopy volume profiles obtained by modelling, whereas the method applied to discrete return uses point geometry and density indexes. The results of these two methods are assessed by ground truth obtained from sampling and comparison shows that the added information from the full-waveform does give a significant better discrimination of the vegetation cover classes.

  5. Quantifying the range of cross-correlated fluctuations using a q- L dependent AHXA coefficient

    Science.gov (United States)

    Wang, Fang; Wang, Lin; Chen, Yuming

    2018-03-01

    Recently, based on analogous height cross-correlation analysis (AHXA), a cross-correlation coefficient ρ×(L) has been proposed to quantify the levels of cross-correlation on different temporal scales for bivariate series. A limitation of this coefficient is that it cannot capture the full information of cross-correlations on amplitude of fluctuations. In fact, it only detects the cross-correlation at a specific order fluctuation, which might neglect some important information inherited from other order fluctuations. To overcome this disadvantage, in this work, based on the scaling of the qth order covariance and time delay L, we define a two-parameter dependent cross-correlation coefficient ρq(L) to detect and quantify the range and level of cross-correlations. This new version of ρq(L) coefficient leads to the formation of a ρq(L) surface, which not only is able to quantify the level of cross-correlations, but also allows us to identify the range of fluctuation amplitudes that are correlated in two given signals. Applications to the classical ARFIMA models and the binomial multifractal series illustrate the feasibility of this new coefficient ρq(L) . In addition, a statistical test is proposed to quantify the existence of cross-correlations between two given series. Applying our method to the real life empirical data from the 1999-2000 California electricity market, we find that the California power crisis in 2000 destroys the cross-correlation between the price and the load series but does not affect the correlation of the load series during and before the crisis.

  6. SCA Waveform Development for Space Telemetry

    Science.gov (United States)

    Mortensen, Dale J.; Kifle, Multi; Hall, C. Steve; Quinn, Todd M.

    2004-01-01

    The NASA Glenn Research Center is investigating and developing suitable reconfigurable radio architectures for future NASA missions. This effort is examining software-based open-architectures for space based transceivers, as well as common hardware platform architectures. The Joint Tactical Radio System's (JTRS) Software Communications Architecture (SCA) is a candidate for the software approach, but may need modifications or adaptations for use in space. An in-house SCA compliant waveform development focuses on increasing understanding of software defined radio architectures and more specifically the JTRS SCA. Space requirements put a premium on size, mass, and power. This waveform development effort is key to evaluating tradeoffs with the SCA for space applications. Existing NASA telemetry links, as well as Space Exploration Initiative scenarios, are the basis for defining the waveform requirements. Modeling and simulations are being developed to determine signal processing requirements associated with a waveform and a mission-specific computational burden. Implementation of the waveform on a laboratory software defined radio platform is proceeding in an iterative fashion. Parallel top-down and bottom-up design approaches are employed.

  7. Doppler waveforms of the hepatic veins in children with diffuse fatty infiltration of the liver

    International Nuclear Information System (INIS)

    Uzun, Hakan; Yazici, Burhan; Erdogmus, Besir; Kocabay, Kenan; Buyukkaya, Ramazan; Buyukkaya, Ayla; Yazgan, Omer

    2009-01-01

    Objective: The aim of this study was to investigate the effect of fatty infiltration of the liver (FIL) on the Doppler waveform pattern in the hepatic veins of obese children. Methods: In this prospective study, 59 patients with diffuse FIL and 45 normal healthy children who served as control group underwent hepatic vein B-mod and duplex Doppler sonography. The Doppler sonography spectrum of the right hepatic vein was classified into three groups: triphasic waveform, biphasic waveform, and monophasic or flat waveform. Results: There was a statistically significant difference in the phasicity of hepatic venous flow between patients and control subjects (p < 0.001). The Doppler flow pattern in the right hepatic vein was triphasic in 28 (47.5%), biphasic in 28 (47.5%), and monophasic in 3 (5%) children with fatty liver, while it was triphasic in 43 (95.6%) and biphasic in 2 (4.4%) control subjects. There was an inverse correlation between the sonographic grade of fatty infiltration of the liver and the phasicity of hepatic venous flow (r = -0.479, p < 0.001). Conclusions: Abnormal right hepatic vein Doppler waveform, biphasic as well as monophasic, can be seen in healthy obese children with diffuse FIL.

  8. A Robust Gold Deconvolution Approach for LiDAR Waveform Data Processing to Characterize Vegetation Structure

    Science.gov (United States)

    Zhou, T.; Popescu, S. C.; Krause, K.; Sheridan, R.; Ku, N. W.

    2014-12-01

    Increasing attention has been paid in the remote sensing community to the next generation Light Detection and Ranging (lidar) waveform data systems for extracting information on topography and the vertical structure of vegetation. However, processing waveform lidar data raises some challenges compared to analyzing discrete return data. The overall goal of this study was to present a robust de-convolution algorithm- Gold algorithm used to de-convolve waveforms in a lidar dataset acquired within a 60 x 60m study area located in the Harvard Forest in Massachusetts. The waveform lidar data was collected by the National Ecological Observatory Network (NEON). Specific objectives were to: (1) explore advantages and limitations of various waveform processing techniques to derive topography and canopy height information; (2) develop and implement a novel de-convolution algorithm, the Gold algorithm, to extract elevation and canopy metrics; and (3) compare results and assess accuracy. We modeled lidar waveforms with a mixture of Gaussian functions using the Non-least squares (NLS) algorithm implemented in R and derived a Digital Terrain Model (DTM) and canopy height. We compared our waveform-derived topography and canopy height measurements using the Gold de-convolution algorithm to results using the Richardson-Lucy algorithm. Our findings show that the Gold algorithm performed better than the Richardson-Lucy algorithm in terms of recovering the hidden echoes and detecting false echoes for generating a DTM, which indicates that the Gold algorithm could potentially be applied to processing of waveform lidar data to derive information on terrain elevation and canopy characteristics.

  9. Multifractal detrended Cross Correlation Analysis of Foreign Exchange and SENSEX fluctuation in Indian perspective

    Science.gov (United States)

    Dutta, Srimonti; Ghosh, Dipak; Chatterjee, Sucharita

    2016-12-01

    The manuscript studies autocorrelation and cross correlation of SENSEX fluctuations and Forex Exchange Rate in respect to Indian scenario. Multifractal detrended fluctuation analysis (MFDFA) and multifractal detrended cross correlation analysis (MFDXA) were employed to study the correlation between the two series. It was observed that the two series are strongly cross correlated. The change of degree of cross correlation with time was studied and the results are interpreted qualitatively.

  10. Modeling CMB lensing cross correlations with CLEFT

    Energy Technology Data Exchange (ETDEWEB)

    Modi, Chirag; White, Martin [Department of Physics, University of California, Berkeley, CA 94720 (United States); Vlah, Zvonimir, E-mail: modichirag@berkeley.edu, E-mail: mwhite@berkeley.edu, E-mail: zvlah@stanford.edu [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, CA 94306 (United States)

    2017-08-01

    A new generation of surveys will soon map large fractions of sky to ever greater depths and their science goals can be enhanced by exploiting cross correlations between them. In this paper we study cross correlations between the lensing of the CMB and biased tracers of large-scale structure at high z . We motivate the need for more sophisticated bias models for modeling increasingly biased tracers at these redshifts and propose the use of perturbation theories, specifically Convolution Lagrangian Effective Field Theory (CLEFT). Since such signals reside at large scales and redshifts, they can be well described by perturbative approaches. We compare our model with the current approach of using scale independent bias coupled with fitting functions for non-linear matter power spectra, showing that the latter will not be sufficient for upcoming surveys. We illustrate our ideas by estimating σ{sub 8} from the auto- and cross-spectra of mock surveys, finding that CLEFT returns accurate and unbiased results at high z . We discuss uncertainties due to the redshift distribution of the tracers, and several avenues for future development.

  11. The effects of common risk factors on stock returns: A detrended cross-correlation analysis

    Science.gov (United States)

    Ruan, Qingsong; Yang, Bingchan

    2017-10-01

    In this paper, we investigate the cross-correlations between Fama and French three factors and the return of American industries on the basis of cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). Qualitatively, we find that the return series of Fama and French three factors and American industries were overall significantly cross-correlated based on the analysis of a statistic. Quantitatively, we find that the cross-correlations between three factors and the return of American industries were strongly multifractal, and applying MF-DCCA we also investigate the cross-correlation of industry returns and residuals. We find that there exists multifractality of industry returns and residuals. The result of correlation coefficients we can verify that there exist other factors which influence the industry returns except Fama three factors.

  12. Cross-Correlations between Energy and Emissions Markets: New Evidence from Fractal and Multifractal Analysis

    Directory of Open Access Journals (Sweden)

    Gang-Jin Wang

    2014-01-01

    Full Text Available We supply a new perspective to describe and understand the behavior of cross-correlations between energy and emissions markets. Namely, we investigate cross-correlations between oil and gas (Oil-Gas, oil and CO2 (Oil-CO2, and gas and CO2 (Gas-CO2 based on fractal and multifractal analysis. We focus our study on returns of the oil, gas, and CO2 during the period of April 22, 2005–April 30, 2013. In the empirical analysis, by using the detrended cross-correlation analysis (DCCA method, we find that cross-correlations for Oil-Gas, Oil-CO2, and Gas-CO2 obey a power-law and are weakly persistent. Then, we adopt the method of DCCA cross-correlation coefficient to quantify cross-correlations between energy and emissions markets. The results show that their cross-correlations are diverse at different time scales. Next, based on the multifractal DCCA method, we find that cross-correlated markets have the nonlinear and multifractal nature and that the multifractality strength for three cross-correlated markets is arranged in the order of Gas-CO2 > Oil-Gas > Oil-CO2. Finally, by employing the rolling windows method, which can be used to investigate time-varying cross-correlation scaling exponents, we analyze short-term and long-term market dynamics and find that the recent global financial crisis has a notable influence on short-term and long-term market dynamics.

  13. Cross-correlating the γ-ray Sky with Catalogs of Galaxy Clusters

    Science.gov (United States)

    Branchini, Enzo; Camera, Stefano; Cuoco, Alessandro; Fornengo, Nicolao; Regis, Marco; Viel, Matteo; Xia, Jun-Qing

    2017-01-01

    We report the detection of a cross-correlation signal between Fermi Large Area Telescope diffuse γ-ray maps and catalogs of clusters. In our analysis, we considered three different catalogs: WHL12, redMaPPer, and PlanckSZ. They all show a positive correlation with different amplitudes, related to the average mass of the objects in each catalog, which also sets the catalog bias. The signal detection is confirmed by the results of a stacking analysis. The cross-correlation signal extends to rather large angular scales, around 1°, that correspond, at the typical redshift of the clusters in these catalogs, to a few to tens of megaparsecs, I.e., the typical scale-length of the large-scale structures in the universe. Most likely this signal is contributed by the cumulative emission from active galactic nuclei (AGNs) associated with the filamentary structures that converge toward the high peaks of the matter density field in which galaxy clusters reside. In addition, our analysis reveals the presence of a second component, more compact in size and compatible with a point-like emission from within individual clusters. At present, we cannot distinguish between the two most likely interpretations for such a signal, I.e., whether it is produced by AGNs inside clusters or if it is a diffuse γ-ray emission from the intracluster medium. We argue that this latter, intriguing, hypothesis might be tested by applying this technique to a low-redshift large-mass cluster sample.

  14. CROSS-CORRELATING THE γ -RAY SKY WITH CATALOGS OF GALAXY CLUSTERS

    Energy Technology Data Exchange (ETDEWEB)

    Branchini, Enzo [Dipartimento di Matematica e Fisica, Università degli Studi “Roma Tre,” via della Vasca Navale 84, I-00146 Roma (Italy); Camera, Stefano [Jodrell Bank Centre for Astrophysics, The University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom); Cuoco, Alessandro [Institute for Theoretical Particle Physics and Cosmology, RWTH Aachen University, D-52056 Aachen (Germany); Fornengo, Nicolao; Regis, Marco [Dipartimento di Fisica, Università di Torino, via P. Giuria 1, I–10125 Torino (Italy); Viel, Matteo [INAF Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34141, Trieste (Italy); Xia, Jun-Qing, E-mail: xiajq@bnu.edu.cn, E-mail: branchin@fis.uniroma3.it, E-mail: stefano.camera@manchester.ac.uk, E-mail: cuoco@physik.rwth-aachen.de, E-mail: fornengo@to.infn.it, E-mail: regis@to.infn.it, E-mail: viel@oats.inaf.it [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)

    2017-01-01

    We report the detection of a cross-correlation signal between Fermi Large Area Telescope diffuse γ -ray maps and catalogs of clusters. In our analysis, we considered three different catalogs: WHL12, redMaPPer, and PlanckSZ. They all show a positive correlation with different amplitudes, related to the average mass of the objects in each catalog, which also sets the catalog bias. The signal detection is confirmed by the results of a stacking analysis. The cross-correlation signal extends to rather large angular scales, around 1°, that correspond, at the typical redshift of the clusters in these catalogs, to a few to tens of megaparsecs, i.e., the typical scale-length of the large-scale structures in the universe. Most likely this signal is contributed by the cumulative emission from active galactic nuclei (AGNs) associated with the filamentary structures that converge toward the high peaks of the matter density field in which galaxy clusters reside. In addition, our analysis reveals the presence of a second component, more compact in size and compatible with a point-like emission from within individual clusters. At present, we cannot distinguish between the two most likely interpretations for such a signal, i.e., whether it is produced by AGNs inside clusters or if it is a diffuse γ -ray emission from the intracluster medium. We argue that this latter, intriguing, hypothesis might be tested by applying this technique to a low-redshift large-mass cluster sample.

  15. Pulsatile pipe flow transition: Flow waveform effects

    Science.gov (United States)

    Brindise, Melissa C.; Vlachos, Pavlos P.

    2018-01-01

    Although transition is known to exist in various hemodynamic environments, the mechanisms that govern this flow regime and their subsequent effects on biological parameters are not well understood. Previous studies have investigated transition in pulsatile pipe flow using non-physiological sinusoidal waveforms at various Womersley numbers but have produced conflicting results, and multiple input waveform shapes have yet to be explored. In this work, we investigate the effect of the input pulsatile waveform shape on the mechanisms that drive the onset and development of transition using particle image velocimetry, three pulsatile waveforms, and six mean Reynolds numbers. The turbulent kinetic energy budget including dissipation rate, production, and pressure diffusion was computed. The results show that the waveform with a longer deceleration phase duration induced the earliest onset of transition, while the waveform with a longer acceleration period delayed the onset of transition. In accord with the findings of prior studies, for all test cases, turbulence was observed to be produced at the wall and either dissipated or redistributed into the core flow by pressure waves, depending on the mean Reynolds number. Turbulent production increased with increasing temporal velocity gradients until an asymptotic limit was reached. The turbulence dissipation rate was shown to be independent of mean Reynolds number, but a relationship between the temporal gradients of the input velocity waveform and the rate of turbulence dissipation was found. In general, these results demonstrated that the shape of the input pulsatile waveform directly affected the onset and development of transition.

  16. On the Empirical Estimation of Utility Distribution Damping Parameters Using Power Quality Waveform Data

    Directory of Open Access Journals (Sweden)

    Irene Y. H. Gu

    2007-01-01

    Full Text Available This paper describes an efficient yet accurate methodology for estimating system damping. The proposed technique is based on linear dynamic system theory and the Hilbert damping analysis. The proposed technique requires capacitor switching waveforms only. The detected envelope of the intrinsic transient portion of the voltage waveform after capacitor bank energizing and its decay rate along with the damped resonant frequency are used to quantify effective X/R ratio of a system. Thus, the proposed method provides complete knowledge of system impedance characteristics. The estimated system damping can also be used to evaluate the system vulnerability to various PQ disturbances, particularly resonance phenomena, so that a utility may take preventive measures and improve PQ of the system.

  17. Time-dependent phase error correction using digital waveform synthesis

    Science.gov (United States)

    Doerry, Armin W.; Buskirk, Stephen

    2017-10-10

    The various technologies presented herein relate to correcting a time-dependent phase error generated as part of the formation of a radar waveform. A waveform can be pre-distorted to facilitate correction of an error induced into the waveform by a downstream operation/component in a radar system. For example, amplifier power droop effect can engender a time-dependent phase error in a waveform as part of a radar signal generating operation. The error can be quantified and an according complimentary distortion can be applied to the waveform to facilitate negation of the error during the subsequent processing of the waveform. A time domain correction can be applied by a phase error correction look up table incorporated into a waveform phase generator.

  18. Stationary echo canceling in velocity estimation by time-domain cross-correlation

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    1993-01-01

    The application of stationary echo canceling to ultrasonic estimation of blood velocities using time-domain cross-correlation is investigated. Expressions are derived that show the influence from the echo canceler on the signals that enter the cross-correlation estimator. It is demonstrated...

  19. Extension of frequency-based dissimilarity for retrieving similar plasma waveforms

    International Nuclear Information System (INIS)

    Hochin, Teruhisa; Koyama, Katsumasa; Nakanishi, Hideya; Kojima, Mamoru

    2008-01-01

    Some computer-aided assistance in finding the waveforms similar to a waveform has become indispensable for accelerating data analysis in the plasma experiments. For the slowly-varying waveforms and those having time-sectional oscillation patterns, the methods using the Fourier series coefficients of waveforms in calculating the dissimilarity have successfully improved the performance in retrieving similar waveforms. This paper treats severely-varying waveforms, and proposes two extensions to the dissimilarity of waveforms. The first extension is to capture the difference of the importance of the Fourier series coefficients of waveforms against frequency. The second extension is to consider the outlines of waveforms. The correctness of the extended dissimilarity is experimentally evaluated by using the metrics used in evaluating that of the information retrieval, i.e. precision and recall. The experimental results show that the extended dissimilarity could improve the correctness of the similarity retrieval of plasma waveforms

  20. Multifunction waveform generator for EM receiver testing

    Science.gov (United States)

    Chen, Kai; Jin, Sheng; Deng, Ming

    2018-01-01

    In many electromagnetic (EM) methods - such as magnetotelluric, spectral-induced polarization (SIP), time-domain-induced polarization (TDIP), and controlled-source audio magnetotelluric (CSAMT) methods - it is important to evaluate and test the EM receivers during their development stage. To assess the performance of the developed EM receivers, controlled synthetic data that simulate the observed signals in different modes are required. In CSAMT and SIP mode testing, the waveform generator should use the GPS time as the reference for repeating schedule. Based on our testing, the frequency range, frequency precision, and time synchronization of the currently available function waveform generators on the market are deficient. This paper presents a multifunction waveform generator with three waveforms: (1) a wideband, low-noise electromagnetic field signal to be used for magnetotelluric, audio-magnetotelluric, and long-period magnetotelluric studies; (2) a repeating frequency sweep square waveform for CSAMT and SIP studies; and (3) a positive-zero-negative-zero signal that contains primary and secondary fields for TDIP studies. In this paper, we provide the principles of the above three waveforms along with a hardware design for the generator. Furthermore, testing of the EM receiver was conducted with the waveform generator, and the results of the experiment were compared with those calculated from the simulation and theory in the frequency band of interest.

  1. Analysis of LFM-waveform Libraries for Cognitive Tracking Maneuvering Targets

    Directory of Open Access Journals (Sweden)

    Wang Hongyan

    2016-01-01

    Full Text Available Based on the idea of the waveform agility in cognitive radars,the waveform libraries for maneuvering target tracking are discussed. LFM-waveform libraries are designed according to different combinations of chirp parameters and FrFT rotation angles. By applying the interact multiple model (IMM algorithm in tracking maneuvering targets, transmitted waveform is called real time from the LFM-waveform libraries. The waveforms are selected from the library according to the criterion of maximum mutual information between the current state of knowledge of the model and the measurement. Simulation results show that waveform library containing certain amount LFM-waveforms can improve the performance of cognitive tracking radar.

  2. KiDS-450: tomographic cross-correlation of galaxy shear with Planck lensing

    Science.gov (United States)

    Harnois-Déraps, Joachim; Tröster, Tilman; Chisari, Nora Elisa; Heymans, Catherine; van Waerbeke, Ludovic; Asgari, Marika; Bilicki, Maciej; Choi, Ami; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Joudaki, Shahab; Kuijken, Konrad; Merten, Julian; Miller, Lance; Robertson, Naomi; Schneider, Peter; Viola, Massimo

    2017-10-01

    We present the tomographic cross-correlation between galaxy lensing measured in the Kilo Degree Survey (KiDS-450) with overlapping lensing measurements of the cosmic microwave background (CMB), as detected by Planck 2015. We compare our joint probe measurement to the theoretical expectation for a flat Λ cold dark matter cosmology, assuming the best-fitting cosmological parameters from the KiDS-450 cosmic shear and Planck CMB analyses. We find that our results are consistent within 1σ with the KiDS-450 cosmology, with an amplitude re-scaling parameter AKiDS = 0.86 ± 0.19. Adopting a Planck cosmology, we find our results are consistent within 2σ, with APlanck = 0.68 ± 0.15. We show that the agreement is improved in both cases when the contamination to the signal by intrinsic galaxy alignments is accounted for, increasing A by ∼0.1. This is the first tomographic analysis of the galaxy lensing - CMB lensing cross-correlation signal, and is based on five photometric redshift bins. We use this measurement as an independent validation of the multiplicative shear calibration and of the calibrated source redshift distribution at high redshifts. We find that constraints on these two quantities are strongly correlated when obtained from this technique, which should therefore not be considered as a stand-alone competitive calibration tool.

  3. Volatility-constrained multifractal detrended cross-correlation analysis: Cross-correlation among Mainland China, US, and Hong Kong stock markets

    Science.gov (United States)

    Cao, Guangxi; Zhang, Minjia; Li, Qingchen

    2017-04-01

    This study focuses on multifractal detrended cross-correlation analysis of the different volatility intervals of Mainland China, US, and Hong Kong stock markets. A volatility-constrained multifractal detrended cross-correlation analysis (VC-MF-DCCA) method is proposed to study the volatility conductivity of Mainland China, US, and Hong Kong stock markets. Empirical results indicate that fluctuation may be related to important activities in real markets. The Hang Seng Index (HSI) stock market is more influential than the Shanghai Composite Index (SCI) stock market. Furthermore, the SCI stock market is more influential than the Dow Jones Industrial Average stock market. The conductivity between the HSI and SCI stock markets is the strongest. HSI was the most influential market in the large fluctuation interval of 1991 to 2014. The autoregressive fractionally integrated moving average method is used to verify the validity of VC-MF-DCCA. Results show that VC-MF-DCCA is effective.

  4. Implementation of isotope correlation technique for safeguards

    International Nuclear Information System (INIS)

    Persiani, P.J.; Bucher, R.G.

    1989-01-01

    The isotopic correlation technique (ICT) is based on the fundamental physics principle that the isotopic compositions of nuclear material in the fuel cycle systems contain information regarding the design and history of nuclear material flow from fuel fabrication, reactor operation, and through input to the reprocessing plant. Isotopic Correlation in conjunction with the gravimetric (or Pu/U) method for mass determination can be developed to provide an independent in-field verification of the reprocessing input accountancy at the dissolver and/or accountancy stage of the reprocessing plant. The Argonne National Laboratory program in isotope correlation techniques is based on three-dimensional reactor physics calculations of characteristic geometries/composition in each reactor class. 10 refs., 1 fig., 3 tabs

  5. Flow pumping system for physiological waveforms.

    Science.gov (United States)

    Tsai, William; Savaş, Omer

    2010-02-01

    A pulsatile flow pumping system is developed to replicate flow waveforms with reasonable accuracy for experiments simulating physiological blood flows at numerous points in the body. The system divides the task of flow waveform generation between two pumps: a gear pump generates the mean component and a piston pump generates the oscillatory component. The system is driven by two programmable servo controllers. The frequency response of the system is used to characterize its operation. The system has been successfully tested in vascular flow experiments where sinusoidal, carotid, and coronary flow waveforms are replicated.

  6. Exploiting Cross Correlations and Joint Analyses

    Energy Technology Data Exchange (ETDEWEB)

    Rhodes, J. [Caltech; Allen, S. [SLAC; Benson, B. A. [Chicago U., Astron. Astrophys. Ctr.; Chang, T. [Taipei, Inst. Astron. Astrophys.; de Putter, R. [Caltech; Dodelson, S. [Chicago U., Astron. Astrophys. Ctr.; Doré, O. [Caltech; Honscheid, K. [Ohio State U., CCAPP; Linder, E. [UC, Berkeley; Ménard, B. [Tokyo U., IPMU; Newman, J. [Pittsburgh U.; Nord, B. [Fermilab; Rozo, E. [SLAC; Rykoff, E. [SLAC; Vallinotto, A. [LBL, Berkeley; Weinberg, D. [Ohio State U., CCAPP

    2014-02-28

    In this report, we present a wide variety of ways in which information from multiple probes of dark energy may be combined to obtain additional information not accessible when they are considered separately. Fundamentally, because all major probes are affected by the underlying distribution of matter in the regions studied, there exist covariances between them that can provide information on cosmology. Combining multiple probes allows for more accurate (less contaminated by systematics) and more precise (since there is cosmological information encoded in cross-correlation statistics) measurements of dark energy. The potential of cross-correlation methods is only beginning to be realized. By bringing in information from other wavelengths, the capabilities of the existing probes of dark energy can be enhanced and systematic effects can be mitigated further. We present a mixture of work in progress and suggestions for future scientific efforts. Given the scope of future dark energy experiments, the greatest gains may only be realized with more coordination and cooperation between multiple project teams; we recommend that this interchange should begin sooner, rather than later, to maximize scientific gains.

  7. Femtosecond laser ablation of polymethylmethacrylate via dual-color synthesized waveform

    International Nuclear Information System (INIS)

    Yang, Chan-Shan; Zaytsev, Alexey; Lin, Chih-Hsuan; Teng, Kuei-Chung; Her, Tsing-Hua; Pan, Ci-Ling

    2015-01-01

    We have demonstrated the laser ablation of PMMA using dual-color waveform synthesis of the fundamental (ω) and its second-harmonic (2ω) of a femtosecond Ti:Sapphire laser. A modest and yet clear modulation (∼22%) in ablated area versus relative phase between the 2ω and ω beams with a power-ratio of 15% (28/183 mW) is revealed. This is explained qualitatively by the dependence of ablation on multiphoton ionization of which the rate is related to the relative phase of the synthesized waveform. At higher peak power ratios, the modulation decreases rapidly, as the two-photon-ionization rate of the 2ω dominates over that of the three- to four- photon ionization of the ω beam. This technique demonstrates the feasibility of phase-controlled laser processing of materials

  8. Statistical gravitational waveform models: What to simulate next?

    Science.gov (United States)

    Doctor, Zoheyr; Farr, Ben; Holz, Daniel E.; Pürrer, Michael

    2017-12-01

    Models of gravitational waveforms play a critical role in detecting and characterizing the gravitational waves (GWs) from compact binary coalescences. Waveforms from numerical relativity (NR), while highly accurate, are too computationally expensive to produce to be directly used with Bayesian parameter estimation tools like Markov-chain-Monte-Carlo and nested sampling. We propose a Gaussian process regression (GPR) method to generate reduced-order-model waveforms based only on existing accurate (e.g. NR) simulations. Using a training set of simulated waveforms, our GPR approach produces interpolated waveforms along with uncertainties across the parameter space. As a proof of concept, we use a training set of IMRPhenomD waveforms to build a GPR model in the 2-d parameter space of mass ratio q and equal-and-aligned spin χ1=χ2. Using a regular, equally-spaced grid of 120 IMRPhenomD training waveforms in q ∈[1 ,3 ] and χ1∈[-0.5 ,0.5 ], the GPR mean approximates IMRPhenomD in this space to mismatches below 4.3 ×10-5. Our approach could in principle use training waveforms directly from numerical relativity. Beyond interpolation of waveforms, we also present a greedy algorithm that utilizes the errors provided by our GPR model to optimize the placement of future simulations. In a fiducial test case we find that using the greedy algorithm to iteratively add simulations achieves GPR errors that are ˜1 order of magnitude lower than the errors from using Latin-hypercube or square training grids.

  9. Dynamic evolution of cross-correlations in the Chinese stock market.

    Directory of Open Access Journals (Sweden)

    Fei Ren

    Full Text Available The analysis of cross-correlations is extensively applied for the understanding of interconnections in stock markets and the portfolio risk estimation. Current studies of correlations in Chinese market mainly focus on the static correlations between return series, and this calls for an urgent need to investigate their dynamic correlations. Our study aims to reveal the dynamic evolution of cross-correlations in the Chinese stock market, and offer an exact interpretation for the evolution behavior. The correlation matrices constructed from the return series of 367 A-share stocks traded on the Shanghai Stock Exchange from January 4, 1999 to December 30, 2011 are calculated over a moving window with a size of 400 days. The evolutions of the statistical properties of the correlation coefficients, eigenvalues, and eigenvectors of the correlation matrices are carefully analyzed. We find that the stock correlations are significantly increased in the periods of two market crashes in 2001 and 2008, during which only five eigenvalues significantly deviate from the random correlation matrix, and the systemic risk is higher in these volatile periods than calm periods. By investigating the significant contributors of the deviating eigenvectors in different time periods, we observe a dynamic evolution behavior in business sectors such as IT, electronics, and real estate, which lead the rise (drop before (after the crashes. Our results provide new perspectives for the understanding of the dynamic evolution of cross-correlations in the Chines stock markets, and the result of risk estimation is valuable for the application of risk management.

  10. Dynamic evolution of cross-correlations in the Chinese stock market.

    Science.gov (United States)

    Ren, Fei; Zhou, Wei-Xing

    2014-01-01

    The analysis of cross-correlations is extensively applied for the understanding of interconnections in stock markets and the portfolio risk estimation. Current studies of correlations in Chinese market mainly focus on the static correlations between return series, and this calls for an urgent need to investigate their dynamic correlations. Our study aims to reveal the dynamic evolution of cross-correlations in the Chinese stock market, and offer an exact interpretation for the evolution behavior. The correlation matrices constructed from the return series of 367 A-share stocks traded on the Shanghai Stock Exchange from January 4, 1999 to December 30, 2011 are calculated over a moving window with a size of 400 days. The evolutions of the statistical properties of the correlation coefficients, eigenvalues, and eigenvectors of the correlation matrices are carefully analyzed. We find that the stock correlations are significantly increased in the periods of two market crashes in 2001 and 2008, during which only five eigenvalues significantly deviate from the random correlation matrix, and the systemic risk is higher in these volatile periods than calm periods. By investigating the significant contributors of the deviating eigenvectors in different time periods, we observe a dynamic evolution behavior in business sectors such as IT, electronics, and real estate, which lead the rise (drop) before (after) the crashes. Our results provide new perspectives for the understanding of the dynamic evolution of cross-correlations in the Chines stock markets, and the result of risk estimation is valuable for the application of risk management.

  11. Use of paravascular admittance waveforms to monitor relative change in arterial blood pressure

    Science.gov (United States)

    Zielinski, Todd M.; Hettrick, Doug; Cho, Yong

    2010-04-01

    Non-invasive methods to monitor ambulatory blood pressure often have limitations that can affect measurement accuracy and patient adherence [1]. Minimally invasive measurement of a relative blood pressure surrogate with an implantable device may provide a useful chronic diagnostic and monitoring tool. We assessed a technique that uses electrocardiogram and paravascular admittance waveform morphology analysis to one, measure a time duration (vascular tone index, VTI in milliseconds) change from the electrocardiogram R-wave to admittance waveform peak and two, measure the admittance waveform minimum, maximum and magnitude as indicators of change in arterial compliance/distensibility or pulse pressure secondary to change in afterload. Methods: Five anesthetized domestic pigs (32 ± 4.2 kg) were used to study the effects of phenylephrine (1-5 ug/kg/min) on femoral artery pressure and admittance waveform morphology measured with a quadrapolar electrode array catheter placed next to the femoral artery to assess the relative change in arterial compliance due to change in peripheral vascular tone. Results: Statistical difference was observed (p blood pressure may be suitable for implantable devices to detect progression of cardiovascular disease such as hypertension.

  12. Waveform design and diversity for advanced radar systems

    CERN Document Server

    Gini, Fulvio

    2012-01-01

    In recent years, various algorithms for radar signal design, that rely heavily upon complicated processing and/or antenna architectures, have been suggested. These techniques owe their genesis to several factors, including revolutionary technological advances (new flexible waveform generators, high speed signal processing hardware, digital array radar technology, etc.) and the stressing performance requirements, often imposed by defence applications in areas such as airborne early warning and homeland security.Increasingly complex operating scenarios calls for sophisticated algorithms with the

  13. Gaseous isotope correlation technique for safeguards at reprocessing facilities

    International Nuclear Information System (INIS)

    Ohkubo, Michiaki.

    1988-03-01

    The isotope correlation technique based on gaseous stable fission products can be used as a means of verifying the input measurement to fuel reprocessing plants. This paper reviews the theoretical background of the gaseous fission product isotope correlation technique. The correlations considered are those between burnup and various isotopic ratios of Kr and Xe nuclides. The feasibility of gaseous ICT application to Pu input accountancy of reprocessing facilities is also discussed. The technique offers the possibility of in situ measurement verification by the inspector. (author). 16 refs, 7 figs

  14. Cross Correlation versus Normalized Mutual Information on Image Registration

    Science.gov (United States)

    Tan, Bin; Tilton, James C.; Lin, Guoqing

    2016-01-01

    This is the first study to quantitatively assess and compare cross correlation and normalized mutual information methods used to register images in subpixel scale. The study shows that the normalized mutual information method is less sensitive to unaligned edges due to the spectral response differences than is cross correlation. This characteristic makes the normalized image resolution a better candidate for band to band registration. Improved band-to-band registration in the data from satellite-borne instruments will result in improved retrievals of key science measurements such as cloud properties, vegetation, snow and fire.

  15. Cross-correlation redshift calibration without spectroscopic calibration samples in DES Science Verification Data

    Science.gov (United States)

    Davis, C.; Rozo, E.; Roodman, A.; Alarcon, A.; Cawthon, R.; Gatti, M.; Lin, H.; Miquel, R.; Rykoff, E. S.; Troxel, M. A.; Vielzeuf, P.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Doel, P.; Drlica-Wagner, A.; Fausti Neto, A.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Giannantonio, T.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Jeltema, T.; Krause, E.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; March, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Ogando, R. L. C.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.; Wechsler, R. H.

    2018-06-01

    Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogues with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty of Δz ˜ ±0.01. We forecast that our proposal can, in principle, control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Our results provide strong motivation to launch a programme to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.

  16. Waveform Catalog, Extreme Mass Ratio Binary (Capture)

    Data.gov (United States)

    National Aeronautics and Space Administration — Numerically-generated gravitational waveforms for circular inspiral into Kerr black holes. These waveforms were developed using Scott Hughes' black hole perturbation...

  17. High precision Cross-correlated imaging in Few-mode fibers

    DEFF Research Database (Denmark)

    Muliar, Olena; Usuga Castaneda, Mario A.; Kristensen, Torben

    2017-01-01

    us to distinguishing differential time delays between HOMs in the picosecond timescale. Broad wavelength scanning in combination with spectral shaping, allows us to estimate the modal behavior of FMF without prior knowledge of the fiber parameters. We performed our demonstration at wavelengths from...... existing approaches for modal content analysis, several methods as S2, C2 in time and frequency domain are available. In this contribution we will present an improved time-domain cross-correlated (C2) imaging technique for the experimental evaluation of modal properties in HOM fibers over a broad range......) in a few-mode fiber (FMF) are used as multiple spatial communication channels, comes in this context as a viable approach to enable the optimization of high-capacity links. From this perspective, it becomes highly necessary to possess a diagnostic tool for the precise modal characterization of FMFs. Among...

  18. Detrended fluctuation analysis made flexible to detect range of cross-correlated fluctuations

    Science.gov (United States)

    Kwapień, Jarosław; Oświecimka, Paweł; DroŻdŻ, Stanisław

    2015-11-01

    The detrended cross-correlation coefficient ρDCCA has recently been proposed to quantify the strength of cross-correlations on different temporal scales in bivariate, nonstationary time series. It is based on the detrended cross-correlation and detrended fluctuation analyses (DCCA and DFA, respectively) and can be viewed as an analog of the Pearson coefficient in the case of the fluctuation analysis. The coefficient ρDCCA works well in many practical situations but by construction its applicability is limited to detection of whether two signals are generally cross-correlated, without the possibility to obtain information on the amplitude of fluctuations that are responsible for those cross-correlations. In order to introduce some related flexibility, here we propose an extension of ρDCCA that exploits the multifractal versions of DFA and DCCA: multifractal detrended fluctuation analysis and multifractal detrended cross-correlation analysis, respectively. The resulting new coefficient ρq not only is able to quantify the strength of correlations but also allows one to identify the range of detrended fluctuation amplitudes that are correlated in two signals under study. We show how the coefficient ρq works in practical situations by applying it to stochastic time series representing processes with long memory: autoregressive and multiplicative ones. Such processes are often used to model signals recorded from complex systems and complex physical phenomena like turbulence, so we are convinced that this new measure can successfully be applied in time-series analysis. In particular, we present an example of such application to highly complex empirical data from financial markets. The present formulation can straightforwardly be extended to multivariate data in terms of the q -dependent counterpart of the correlation matrices and then to the network representation.

  19. Compressive full waveform lidar

    Science.gov (United States)

    Yang, Weiyi; Ke, Jun

    2017-05-01

    To avoid high bandwidth detector, fast speed A/D converter, and large size memory disk, a compressive full waveform LIDAR system, which uses a temporally modulated laser instead of a pulsed laser, is studied in this paper. Full waveform data from NEON (National Ecological Observatory Network) are used. Random binary patterns are used to modulate the source. To achieve 0.15 m ranging resolution, a 100 MSPS A/D converter is assumed to make measurements. SPIRAL algorithm with canonical basis is employed when Poisson noise is considered in the low illuminated condition.

  20. Progress of a Cross-Correlation Based Optical Strain Measurement Technique for Detecting Radial Growth on a Rotating Disk

    Science.gov (United States)

    Clem, Michelle M.; Woike, Mark R.; Abdul-Aziz, Ali

    2014-01-01

    The Aeronautical Sciences Project under NASA's Fundamental Aeronautics Program is interested in the development of novel measurement technologies, such as optical surface measurements for the in situ health monitoring of critical constituents of the internal flow path. In situ health monitoring has the potential to detect flaws, i.e. cracks in key components, such as engine turbine disks, before the flaws lead to catastrophic failure. The present study, aims to further validate and develop an optical strain measurement technique to measure the radial growth and strain field of an already cracked disk, mimicking the geometry of a sub-scale turbine engine disk, under loaded conditions in the NASA Glenn Research Center's High Precision Rotordynamics Laboratory. The technique offers potential fault detection by imaging an applied high-contrast random speckle pattern under unloaded and loaded conditions with a CCD camera. Spinning the cracked disk at high speeds (loaded conditions) induces an external load, resulting in a radial growth of the disk of approximately 50.0-µm in the flawed region and hence, a localized strain field. When imaging the cracked disk under static conditions, the disk will be undistorted; however, during rotation the cracked region will grow radially, thus causing the applied particle pattern to be 'shifted'. The resulting particle displacements between the two images is measured using the two-dimensional cross-correlation algorithms implemented in standard Particle Image Velocimetry (PIV) software to track the disk growth, which facilitates calculation of the localized strain field. A random particle distribution is adhered onto the surface of the cracked disk and two bench top experiments are carried out to evaluate the technique's ability to measure the induced particle displacements. The disk is shifted manually using a translation stage equipped with a fine micrometer and a hotplate is used to induce thermal growth of the disk, causing the

  1. A Denoising Method for LiDAR Full-Waveform Data

    Directory of Open Access Journals (Sweden)

    Xudong Lai

    2015-01-01

    Full Text Available Decomposition of LiDAR full-waveform data can not only enhance the density and positioning accuracy of a point cloud, but also provide other useful parameters, such as pulse width, peak amplitude, and peak position which are important information for subsequent processing. Full-waveform data usually contain some random noises. Traditional filtering algorithms always cause distortion in the waveform. λ/μ filtering algorithm is based on Mean Shift method. It can smooth the signal iteratively and will not cause any distortion in the waveform. In this paper, an improved λ/μ filtering algorithm is proposed, and several experiments on both simulated waveform data and real waveform data are implemented to prove the effectiveness of the proposed algorithm.

  2. Full Waveform Analysis for Long-Range 3D Imaging Laser Radar

    Directory of Open Access Journals (Sweden)

    Wallace AndrewM

    2010-01-01

    Full Text Available The new generation of 3D imaging systems based on laser radar (ladar offers significant advantages in defense and security applications. In particular, it is possible to retrieve 3D shape information directly from the scene and separate a target from background or foreground clutter by extracting a narrow depth range from the field of view by range gating, either in the sensor or by postprocessing. We discuss and demonstrate the applicability of full-waveform ladar to produce multilayer 3D imagery, in which each pixel produces a complex temporal response that describes the scene structure. Such complexity caused by multiple and distributed reflection arises in many relevant scenarios, for example in viewing partially occluded targets, through semitransparent materials (e.g., windows and through distributed reflective media such as foliage. We demonstrate our methodology on 3D image data acquired by a scanning time-of-flight system, developed in our own laboratories, which uses the time-correlated single-photon counting technique.

  3. Multifractal detrended cross-correlation analysis on gold, crude oil and foreign exchange rate time series

    Science.gov (United States)

    Pal, Mayukha; Madhusudana Rao, P.; Manimaran, P.

    2014-12-01

    We apply the recently developed multifractal detrended cross-correlation analysis method to investigate the cross-correlation behavior and fractal nature between two non-stationary time series. We analyze the daily return price of gold, West Texas Intermediate and Brent crude oil, foreign exchange rate data, over a period of 18 years. The cross correlation has been measured from the Hurst scaling exponents and the singularity spectrum quantitatively. From the results, the existence of multifractal cross-correlation between all of these time series is found. We also found that the cross correlation between gold and oil prices possess uncorrelated behavior and the remaining bivariate time series possess persistent behavior. It was observed for five bivariate series that the cross-correlation exponents are less than the calculated average generalized Hurst exponents (GHE) for q0 and for one bivariate series the cross-correlation exponent is greater than GHE for all q values.

  4. Discharge dynamics of self-oriented microplasma coupling between cross adjacent cavities in micro-structure device driven by a bipolar pulse waveform

    Science.gov (United States)

    Wang, Yaogong; Zhang, Xiaoning; Liu, Lingguang; Zhou, Xuan; Liu, Chunliang; Zhang, Qiaogen

    2018-04-01

    The excitation dynamics and self-oriented plasma coupling of a micro-structure plasma device with a rectangular cross-section are investigated. The device consists of 7 × 7 microcavity arrays, which are blended into a unity by a 50 μm-thick bulk area above them. The device is operated in argon with a pressure of 200 Torr, driven by a bipolar pulse waveform of 20 kHz. The discharge evolution is characterized by means of electrical measurements and optical emission profiles. It has been found that different emission patterns are observed within microcavities. The formation of these patterns induced by the combined action between the applied electric field and surface deactivation is discussed. The microplasma distribution in some specific regions along the diagonal direction of cavities in the bulk area is observed, and self-oriented microplasma coupling is explored, while the plasma interaction occurred between cross adjacent cavities, contributed by the ionization wave propagation. The velocity of ionization wave propagation is measured to be 1.2 km/s to 3.5 km/s. The exploration of this plasma interaction in the bulk area is of value to applications in electromagnetics and signal processing.

  5. Fast and Accurate Prediction of Numerical Relativity Waveforms from Binary Black Hole Coalescences Using Surrogate Models.

    Science.gov (United States)

    Blackman, Jonathan; Field, Scott E; Galley, Chad R; Szilágyi, Béla; Scheel, Mark A; Tiglio, Manuel; Hemberger, Daniel A

    2015-09-18

    Simulating a binary black hole coalescence by solving Einstein's equations is computationally expensive, requiring days to months of supercomputing time. Using reduced order modeling techniques, we construct an accurate surrogate model, which is evaluated in a millisecond to a second, for numerical relativity (NR) waveforms from nonspinning binary black hole coalescences with mass ratios in [1, 10] and durations corresponding to about 15 orbits before merger. We assess the model's uncertainty and show that our modeling strategy predicts NR waveforms not used for the surrogate's training with errors nearly as small as the numerical error of the NR code. Our model includes all spherical-harmonic _{-2}Y_{ℓm} waveform modes resolved by the NR code up to ℓ=8. We compare our surrogate model to effective one body waveforms from 50M_{⊙} to 300M_{⊙} for advanced LIGO detectors and find that the surrogate is always more faithful (by at least an order of magnitude in most cases).

  6. Signal averaging technique for noninvasive recording of late potentials in patients with coronary artery disease

    Science.gov (United States)

    Abboud, S.; Blatt, C. M.; Lown, B.; Graboys, T. B.; Sadeh, D.; Cohen, R. J.

    1987-01-01

    An advanced non invasive signal averaging technique was used to detect late potentials in two groups of patients: Group A (24 patients) with coronary artery disease (CAD) and without sustained ventricular tachycardia (VT) and Group B (8 patients) with CAD and sustained VT. Recorded analog data were digitized and aligned using a cross correlation function with fast Fourier transform schema, averaged and band pass filtered between 60 and 200 Hz with a non-recursive digital filter. Averaged filtered waveforms were analyzed by computer program for 3 parameters: (1) filtered QRS (fQRS) duration (2) interval between the peak of the R wave peak and the end of fQRS (R-LP) (3) RMS value of last 40 msec of fQRS (RMS). Significant change was found between Groups A and B in fQRS (101 -/+ 13 msec vs 123 -/+ 15 msec; p < .0005) and in R-LP vs 52 -/+ 11 msec vs 71-/+18 msec, p <.002). We conclude that (1) the use of a cross correlation triggering method and non-recursive digital filter enables a reliable recording of late potentials from the body surface; (2) fQRS and R-LP durations are sensitive indicators of CAD patients susceptible to VT.

  7. A Time Domain Waveform for Testing General Relativity

    International Nuclear Information System (INIS)

    Huwyler, Cédric; Jetzer, Philippe; Porter, Edward K

    2015-01-01

    Gravitational-wave parameter estimation is only as good as the theory the waveform generation models are based upon. It is therefore crucial to test General Relativity (GR) once data becomes available. Many previous works, such as studies connected with the ppE framework by Yunes and Pretorius, rely on the stationary phase approximation (SPA) to model deviations from GR in the frequency domain. As Fast Fourier Transform algorithms have become considerably faster and in order to circumvent possible problems with the SPA, we test GR with corrected time domain waveforms instead of SPA waveforms. Since a considerable amount of work has been done already in the field using SPA waveforms, we establish a connection between leading-order-corrected waveforms in time and frequency domain, concentrating on phase-only corrected terms. In a Markov Chain Monte Carlo study, whose results are preliminary and will only be available later, we will assess the ability of the eLISA detector to measure deviations from GR for signals coming from supermassive black hole inspirals using these corrected waveforms. (paper)

  8. Frequency Adaptability and Waveform Design for OFDM Radar Space-Time Adaptive Processing

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Satyabrata [ORNL; Glover, Charles Wayne [ORNL

    2012-01-01

    We propose an adaptive waveform design technique for an orthogonal frequency division multiplexing (OFDM) radar signal employing a space-time adaptive processing (STAP) technique. We observe that there are inherent variabilities of the target and interference responses in the frequency domain. Therefore, the use of an OFDM signal can not only increase the frequency diversity of our system, but also improve the target detectability by adaptively modifying the OFDM coefficients in order to exploit the frequency-variabilities of the scenario. First, we formulate a realistic OFDM-STAP measurement model considering the sparse nature of the target and interference spectra in the spatio-temporal domain. Then, we show that the optimal STAP-filter weight-vector is equal to the generalized eigenvector corresponding to the minimum generalized eigenvalue of the interference and target covariance matrices. With numerical examples we demonstrate that the resultant OFDM-STAP filter-weights are adaptable to the frequency-variabilities of the target and interference responses, in addition to the spatio-temporal variabilities. Hence, by better utilizing the frequency variabilities, we propose an adaptive OFDM-waveform design technique, and consequently gain a significant amount of STAP-performance improvement.

  9. Multiscale properties of DNA primary structure: cross-scale correlations

    International Nuclear Information System (INIS)

    Altajskij, M.V.; Ivanov, V.V.; Polozov, R.V.

    2000-01-01

    Cross-scale correlations of wavelet coefficients of the DNA coding sequences are calculated and compared to that of the generated random sequence of the same length. The coding sequences are shown to have strong correlation between large and small scale structures, while random sequences have not

  10. Evaluation of frequency-dependent ultrasound attenuation in transparent medium using focused shadowgraph technique

    Science.gov (United States)

    Iijima, Yukina; Kudo, Nobuki

    2017-07-01

    Acoustic fields of a short-pulsed ultrasound propagating through a transparent medium with ultrasound attenuation were visualized by the focused shadowgraph technique. A brightness waveform and its spatial integrations were derived from a visualized field image and compared with a pressure waveform measured by a membrane hydrophone. The experimental results showed that first-order integration of the brightness wave has good agreement with the pressure waveforms. Frequency-dependent attenuation of the pulse propagating through castor oil was derived from brightness and pressure waveforms, and attenuation coefficients determined from focused shadowgraphy and hydrophone techniques showed good agreement. The results suggest the usefulness of the shadowgraph technique not only for the visualization of ultrasound fields but also for noncontact estimation of rough pressure waveforms and correct ultrasound attenuation.

  11. Bayesian and Classical Machine Learning Methods: A Comparison for Tree Species Classification with LiDAR Waveform Signatures

    Directory of Open Access Journals (Sweden)

    Tan Zhou

    2017-12-01

    Full Text Available A plethora of information contained in full-waveform (FW Light Detection and Ranging (LiDAR data offers prospects for characterizing vegetation structures. This study aims to investigate the capacity of FW LiDAR data alone for tree species identification through the integration of waveform metrics with machine learning methods and Bayesian inference. Specifically, we first conducted automatic tree segmentation based on the waveform-based canopy height model (CHM using three approaches including TreeVaW, watershed algorithms and the combination of TreeVaW and watershed (TW algorithms. Subsequently, the Random forests (RF and Conditional inference forests (CF models were employed to identify important tree-level waveform metrics derived from three distinct sources, such as raw waveforms, composite waveforms, the waveform-based point cloud and the combined variables from these three sources. Further, we discriminated tree (gray pine, blue oak, interior live oak and shrub species through the RF, CF and Bayesian multinomial logistic regression (BMLR using important waveform metrics identified in this study. Results of the tree segmentation demonstrated that the TW algorithms outperformed other algorithms for delineating individual tree crowns. The CF model overcomes waveform metrics selection bias caused by the RF model which favors correlated metrics and enhances the accuracy of subsequent classification. We also found that composite waveforms are more informative than raw waveforms and waveform-based point cloud for characterizing tree species in our study area. Both classical machine learning methods (the RF and CF and the BMLR generated satisfactory average overall accuracy (74% for the RF, 77% for the CF and 81% for the BMLR and the BMLR slightly outperformed the other two methods. However, these three methods suffered from low individual classification accuracy for the blue oak which is prone to being misclassified as the interior live oak due

  12. Elastic reflection waveform inversion with variable density

    KAUST Repository

    Li, Yuanyuan; Li, Zhenchun; Alkhalifah, Tariq Ali; Guo, Qiang

    2017-01-01

    Elastic full waveform inversion (FWI) provides a better description of the subsurface than those given by the acoustic assumption. However it suffers from a more serious cycle skipping problem compared with the latter. Reflection waveform inversion

  13. A new strategy for earthquake focal mechanisms using waveform-correlation-derived relative polarities and cluster analysis: Application to the 2014 Long Valley Caldera earthquake swarm

    Science.gov (United States)

    Shelly, David R.; Hardebeck, Jeanne L.; Ellsworth, William L.; Hill, David P.

    2016-01-01

    In microseismicity analyses, reliable focal mechanisms can typically be obtained for only a small subset of located events. We address this limitation here, presenting a framework for determining robust focal mechanisms for entire populations of very small events. To achieve this, we resolve relative P and S wave polarities between pairs of waveforms by using their signed correlation coefficients—a by-product of previously performed precise earthquake relocation. We then use cluster analysis to group events with similar patterns of polarities across the network. Finally, we apply a standard mechanism inversion to the grouped data, using either catalog or correlation-derived P wave polarity data sets. This approach has great potential for enhancing analyses of spatially concentrated microseismicity such as earthquake swarms, mainshock-aftershock sequences, and industrial reservoir stimulation or injection-induced seismic sequences. To demonstrate its utility, we apply this technique to the 2014 Long Valley Caldera earthquake swarm. In our analysis, 85% of the events (7212 out of 8494 located by Shelly et al. [2016]) fall within five well-constrained mechanism clusters, more than 12 times the number with network-determined mechanisms. Of the earthquakes we characterize, 3023 (42%) have magnitudes smaller than 0.0. We find that mechanism variations are strongly associated with corresponding hypocentral structure, yet mechanism heterogeneity also occurs where it cannot be resolved by hypocentral patterns, often confined to small-magnitude events. Small (5–20°) rotations between mechanism orientations and earthquake location trends persist when we apply 3-D velocity models and might reflect a geometry of en echelon, interlinked shear, and dilational faulting.

  14. Waveform Design for Wireless Power Transfer

    Science.gov (United States)

    Clerckx, Bruno; Bayguzina, Ekaterina

    2016-12-01

    Far-field Wireless Power Transfer (WPT) has attracted significant attention in recent years. Despite the rapid progress, the emphasis of the research community in the last decade has remained largely concentrated on improving the design of energy harvester (so-called rectenna) and has left aside the effect of transmitter design. In this paper, we study the design of transmit waveform so as to enhance the DC power at the output of the rectenna. We derive a tractable model of the non-linearity of the rectenna and compare with a linear model conventionally used in the literature. We then use those models to design novel multisine waveforms that are adaptive to the channel state information (CSI). Interestingly, while the linear model favours narrowband transmission with all the power allocated to a single frequency, the non-linear model favours a power allocation over multiple frequencies. Through realistic simulations, waveforms designed based on the non-linear model are shown to provide significant gains (in terms of harvested DC power) over those designed based on the linear model and over non-adaptive waveforms. We also compute analytically the theoretical scaling laws of the harvested energy for various waveforms as a function of the number of sinewaves and transmit antennas. Those scaling laws highlight the benefits of CSI knowledge at the transmitter in WPT and of a WPT design based on a non-linear rectenna model over a linear model. Results also motivate the study of a promising architecture relying on large-scale multisine multi-antenna waveforms for WPT. As a final note, results stress the importance of modeling and accounting for the non-linearity of the rectenna in any system design involving wireless power.

  15. System and Method for Generating a Frequency Modulated Linear Laser Waveform

    Science.gov (United States)

    Pierrottet, Diego F. (Inventor); Petway, Larry B. (Inventor); Amzajerdian, Farzin (Inventor); Barnes, Bruce W. (Inventor); Lockard, George E. (Inventor); Hines, Glenn D. (Inventor)

    2017-01-01

    A system for generating a frequency modulated linear laser waveform includes a single frequency laser generator to produce a laser output signal. An electro-optical modulator modulates the frequency of the laser output signal to define a linear triangular waveform. An optical circulator passes the linear triangular waveform to a band-pass optical filter to filter out harmonic frequencies created in the waveform during modulation of the laser output signal, to define a pure filtered modulated waveform having a very narrow bandwidth. The optical circulator receives the pure filtered modulated laser waveform and transmits the modulated laser waveform to a target.

  16. Correlation of EPG waveforms from Lygus lineolaris feeding on cotton squares and chemical evidence of inducible tannins

    Science.gov (United States)

    Probing behavior of Lygus lineolaris (Palisot de Beauvois), one of the most important pests affecting cotton production in mid-southern United States, has previously been characterized with electropenetrography (EPG). Cell rupturing (CR) and Ingestion (I) EPG waveforms were identified as two of the ...

  17. Brief communication: Landslide motion from cross correlation of UAV-derived morphological attributes

    Science.gov (United States)

    Peppa, Maria V.; Mills, Jon P.; Moore, Phil; Miller, Pauline E.; Chambers, Jonathan E.

    2017-12-01

    Unmanned aerial vehicles (UAVs) can provide observations of high spatio-temporal resolution to enable operational landslide monitoring. In this research, the construction of digital elevation models (DEMs) and orthomosaics from UAV imagery is achieved using structure-from-motion (SfM) photogrammetric procedures. The study examines the additional value that the morphological attribute of openness, amongst others, can provide to surface deformation analysis. Image-cross-correlation functions and DEM subtraction techniques are applied to the SfM outputs. Through the proposed integrated analysis, the automated quantification of a landslide's motion over time is demonstrated, with implications for the wider interpretation of landslide kinematics via UAV surveys.

  18. Cross-Correlation Asymmetries and Causal Relationships between Stock and Market Risk

    Science.gov (United States)

    Borysov, Stanislav S.; Balatsky, Alexander V.

    2014-01-01

    We study historical correlations and lead-lag relationships between individual stock risk (volatility of daily stock returns) and market risk (volatility of daily returns of a market-representative portfolio) in the US stock market. We consider the cross-correlation functions averaged over all stocks, using 71 stock prices from the Standard & Poor's 500 index for 1994–2013. We focus on the behavior of the cross-correlations at the times of financial crises with significant jumps of market volatility. The observed historical dynamics showed that the dependence between the risks was almost linear during the US stock market downturn of 2002 and after the US housing bubble in 2007, remaining at that level until 2013. Moreover, the averaged cross-correlation function often had an asymmetric shape with respect to zero lag in the periods of high correlation. We develop the analysis by the application of the linear response formalism to study underlying causal relations. The calculated response functions suggest the presence of characteristic regimes near financial crashes, when the volatility of an individual stock follows the market volatility and vice versa. PMID:25162697

  19. Cross-correlation asymmetries and causal relationships between stock and market risk.

    Science.gov (United States)

    Borysov, Stanislav S; Balatsky, Alexander V

    2014-01-01

    We study historical correlations and lead-lag relationships between individual stock risk (volatility of daily stock returns) and market risk (volatility of daily returns of a market-representative portfolio) in the US stock market. We consider the cross-correlation functions averaged over all stocks, using 71 stock prices from the Standard & Poor's 500 index for 1994-2013. We focus on the behavior of the cross-correlations at the times of financial crises with significant jumps of market volatility. The observed historical dynamics showed that the dependence between the risks was almost linear during the US stock market downturn of 2002 and after the US housing bubble in 2007, remaining at that level until 2013. Moreover, the averaged cross-correlation function often had an asymmetric shape with respect to zero lag in the periods of high correlation. We develop the analysis by the application of the linear response formalism to study underlying causal relations. The calculated response functions suggest the presence of characteristic regimes near financial crashes, when the volatility of an individual stock follows the market volatility and vice versa.

  20. Angle-correlated cross sections in the framework of the continuum shell model

    International Nuclear Information System (INIS)

    Moerschel, K.P.

    1984-01-01

    In the present thesis in the framework of the continuum shell modell a concept for the treatment of angle-correlated cross sections was developed by which coincidence experiments on electron scattering on nuclei are described. For this the existing Darmstadt continuum-shell-model code had to be extended to the calculation of the correlation coefficients in which nuclear dynamics enter and which determine completely the angle-correlated cross sections. Under inclusion of the kinematics a method for the integration over the scattered electron was presented and used for the comparison with corresponding experiments. As application correlation coefficients for the proton channel in 12 C with 1 - and 2 + excitations were studied. By means of these coefficients finally cross sections for the reaction 12 C (e,p) 11 B could be calculated and compared with the experiment whereby the developed methods were proved as suitable to predict correctly both the slope and the quantity of the experimental cross sections. (orig.) [de

  1. Measurements of timing resolution of ultra-fast silicon detectors with the SAMPIC waveform digitizer

    Energy Technology Data Exchange (ETDEWEB)

    Breton, D. [CNRS/IN2P3/LAL Orsay, Université Paris-Saclay, F-91898 Orsay (France); De Cacqueray, V.; Delagnes, E. [IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Grabas, H. [Santa Cruz Institute for Particle Physics UC Santa Cruz, CA 95064 (United States); Maalmi, J. [CNRS/IN2P3/LAL Orsay, Université Paris-Saclay, F-91898 Orsay (France); Minafra, N. [Dipartimento Interateneo di Fisica di Bari, Bari (Italy); CERN, Geneva (Switzerland); Royon, C. [University of Kansas, Lawrence (United States); Saimpert, M., E-mail: matthias.saimpert@cern.ch [IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France)

    2016-11-01

    The SAMpler for PICosecond time (SAMPIC) chip has been designed by a collaboration including CEA/IRFU/SEDI, Saclay and CNRS/LAL/SERDI, Orsay. It benefits from both the quick response of a time to digital converter and the versatility of a waveform digitizer to perform accurate timing measurements. Thanks to the sampled signals, smart algorithms making best use of the pulse shape can be used to improve time resolution. A software framework has been developed to analyse the SAMPIC output data and extract timing information by using either a constant fraction discriminator or a fast cross-correlation algorithm. SAMPIC timing capabilities together with the software framework have been tested using pulses generated by a signal generator or by a silicon detector illuminated by a pulsed infrared laser. Under these ideal experimental conditions, the SAMPIC chip has proven to be capable of timing resolutions down to 4 ps with synthesized signals and 40 ps with silicon detector signals.

  2. The Dynamic Cross-Correlations between Mass Media News, New Media News, and Stock Returns

    Directory of Open Access Journals (Sweden)

    Zuochao Zhang

    2018-01-01

    Full Text Available We investigate the dynamic cross-correlations between mass media news, new media news, and stock returns for the SSE 50 Index in Chinese stock market by employing the MF-DCCA method. The empirical results show that (1 there exist power-law cross-correlations between two types of news as well as between news and its corresponding SSE 50 Index return; (2 the cross-correlations between mass media news and SSE 50 Index returns show larger multifractality and more complicated structures; (3 mass media news and new media news have both complementary and competitive relationships; (4 with the rolling window analysis, we further find that there is a general increasing trend for the cross-correlations between the two types of news as well as the cross-correlations between news and returns and this trend becomes more persistent over time.

  3. Atmospheric stellar parameters from cross-correlation functions

    Science.gov (United States)

    Malavolta, L.; Lovis, C.; Pepe, F.; Sneden, C.; Udry, S.

    2017-08-01

    The increasing number of spectra gathered by spectroscopic sky surveys and transiting exoplanet follow-up has pushed the community to develop automated tools for atmospheric stellar parameters determination. Here we present a novel approach that allows the measurement of temperature (Teff), metallicity ([Fe/H]) and gravity (log g) within a few seconds and in a completely automated fashion. Rather than performing comparisons with spectral libraries, our technique is based on the determination of several cross-correlation functions (CCFs) obtained by including spectral features with different sensitivity to the photospheric parameters. We use literature stellar parameters of high signal-to-noise (SNR), high-resolution HARPS spectra of FGK main-sequence stars to calibrate Teff, [Fe/H] and log g as a function of CCF parameters. Our technique is validated using low-SNR spectra obtained with the same instrument. For FGK stars we achieve a precision of σ _{{T_eff}} = 50 K, σlog g = 0.09 dex and σ _{{{[Fe/H]}}} =0.035 dex at SNR = 50, while the precision for observation with SNR ≳ 100 and the overall accuracy are constrained by the literature values used to calibrate the CCFs. Our approach can easily be extended to other instruments with similar spectral range and resolution or to other spectral range and stars other than FGK dwarfs if a large sample of reference stars is available for the calibration. Additionally, we provide the mathematical formulation to convert synthetic equivalent widths to CCF parameters as an alternative to direct calibration. We have made our tool publicly available.

  4. Biomechanical comparison of the double-push technique and the conventional skate skiing technique in cross-country sprint skiing.

    Science.gov (United States)

    Stöggl, Thomas; Müller, Erich; Lindinger, Stefan

    2008-09-01

    The aims of the study were to: (1) adapt the "double-push" technique from inline skating to cross-country skiing; (2) compare this new skiing technique with the conventional skate skiing cross-country technique; and (3) test the hypothesis that the double-push technique improves skiing speed in a short sprint. 13 elite skiers performed maximum-speed sprints over 100 m using the double-push skate skiing technique and using the conventional "V2" skate skiing technique. Pole and plantar forces, knee angle, cycle characteristics, and electromyography of nine lower body muscles were analysed. We found that the double-push technique could be successfully transferred to cross-country skiing, and that this new technique is faster than the conventional skate skiing technique. The double-push technique was 2.9 +/- 2.2% faster (P push technique had a longer cycle length and a lower cycle rate, and it was characterized by higher muscle activity, higher knee extension amplitudes and velocities, and higher peak foot forces, especially in the first phase of the push-off. Also, the foot was more loaded laterally in the double-push technique than in the conventional skate skiing technique.

  5. Time stepping free numerical solution of linear differential equations: Krylov subspace versus waveform relaxation

    NARCIS (Netherlands)

    Bochev, Mikhail A.; Oseledets, I.V.; Tyrtyshnikov, E.E.

    2013-01-01

    The aim of this paper is two-fold. First, we propose an efficient implementation of the continuous time waveform relaxation method based on block Krylov subspaces. Second, we compare this new implementation against Krylov subspace methods combined with the shift and invert technique.

  6. Optimal current waveforms for brushless permanent magnet motors

    Science.gov (United States)

    Moehle, Nicholas; Boyd, Stephen

    2015-07-01

    In this paper, we give energy-optimal current waveforms for a permanent magnet synchronous motor that result in a desired average torque. Our formulation generalises previous work by including a general back-electromotive force (EMF) wave shape, voltage and current limits, an arbitrary phase winding connection, a simple eddy current loss model, and a trade-off between power loss and torque ripple. Determining the optimal current waveforms requires solving a small convex optimisation problem. We show how to use the alternating direction method of multipliers to find the optimal current in milliseconds or hundreds of microseconds, depending on the processor used, which allows the possibility of generating optimal waveforms in real time. This allows us to adapt in real time to changes in the operating requirements or in the model, such as a change in resistance with winding temperature, or even gross changes like the failure of one winding. Suboptimal waveforms are available in tens or hundreds of microseconds, allowing for quick response after abrupt changes in the desired torque. We demonstrate our approach on a simple numerical example, in which we give the optimal waveforms for a motor with a sinusoidal back-EMF, and for a motor with a more complicated, nonsinusoidal waveform, in both the constant-torque region and constant-power region.

  7. LPI Radar Waveform Recognition Based on Time-Frequency Distribution

    Directory of Open Access Journals (Sweden)

    Ming Zhang

    2016-10-01

    Full Text Available In this paper, an automatic radar waveform recognition system in a high noise environment is proposed. Signal waveform recognition techniques are widely applied in the field of cognitive radio, spectrum management and radar applications, etc. We devise a system to classify the modulating signals widely used in low probability of intercept (LPI radar detection systems. The radar signals are divided into eight types of classifications, including linear frequency modulation (LFM, BPSK (Barker code modulation, Costas codes and polyphase codes (comprising Frank, P1, P2, P3 and P4. The classifier is Elman neural network (ENN, and it is a supervised classification based on features extracted from the system. Through the techniques of image filtering, image opening operation, skeleton extraction, principal component analysis (PCA, image binarization algorithm and Pseudo–Zernike moments, etc., the features are extracted from the Choi–Williams time-frequency distribution (CWD image of the received data. In order to reduce the redundant features and simplify calculation, the features selection algorithm based on mutual information between classes and features vectors are applied. The superiority of the proposed classification system is demonstrated by the simulations and analysis. Simulation results show that the overall ratio of successful recognition (RSR is 94.7% at signal-to-noise ratio (SNR of −2 dB.

  8. Measurement of morphing wing deflection by a cross-coherence fiber optic interferometric technique

    Science.gov (United States)

    Tomić, Miloš C.; Djinović, Zoran V.; Scheerer, Michael; Petricevic, Slobodan J.

    2018-01-01

    A fiber-optic interferometric technique aimed at measuring the deflection of aircrafts’ morphing wings is presented. The wing deflection induces a strain in the sensing fiber optic coils that are firmly fixed onto the wing. A change of the phase angle of the light propagating through the fiber is measured by an ‘all-in-fiber’ Michelson interferometer based on a 3 × 3 fiber-optic coupler. Two light sources of different coherence lengths and wavelengths are simultaneously used to ensure a wide measurement range and high accuracy. A new technique for determination of the zero deflection point using the cross-correlation of the two interferograms is proposed. The experiments performed on a specimen made of a carbon-fiber-reinforced plastic honeycomb structure demonstrated a relative uncertainty morphing wing deflection.

  9. The Atacama Cosmology Telescope: cross correlation with Planck maps

    Energy Technology Data Exchange (ETDEWEB)

    Louis, Thibaut; Calabrese, Erminia; Dunkley, Joanna; Næss, Sigurd [Department of Astrophysics, Oxford University, Oxford OX1 3RH (United Kingdom); Addison, Graeme E.; Hincks, Adam D. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z4 (Canada); Hasselfield, Matthew; Hlozek, Renée [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Bond, J. Richard; Hajian, Amir [Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, ON M5S 3H8 (Canada); Das, Sudeep [Argonne National Laboratory, 9700 S. Cass Ave., Lemont, IL 60439 (United States); Devlin, Mark J. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104, U.S.A (United States); Dünner, Rolando; Infante, Leopoldo [Departamento de Astronomía y Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile); Gralla, Megan; Marriage, Tobias A. [Dept. of Physics and Astronomy, The Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218-2686 (United States); Huffenberger, Kevin [Department of Physics, Florida State University, Keen Physics Building, 77 Chieftan Way, Tallahassee, Florida (United States); Kosowsky, Arthur [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA, 15260 (United States); Moodley, Kavilan [Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, Durban, 4041 (South Africa); Niemack, Michael D., E-mail: Thibaut.Louis@astro.ox.ac.uk [Joseph Henry Laboratories of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); and others

    2014-07-01

    We present the temperature power spectrum of the Cosmic Microwave Background obtained by cross-correlating maps from the Atacama Cosmology Telescope (ACT) at 148 and 218 GHz with maps from the Planck satellite at 143 and 217 GHz, in two overlapping regions covering 592 square degrees. We find excellent agreement between the two datasets at both frequencies, quantified using the variance of the residuals between the ACT power spectra and the ACT × Planck cross-spectra. We use these cross-correlations to measure the calibration of the ACT data at 148 and 218 GHz relative to Planck, to 0.7% and 2% precision respectively. We find no evidence for anisotropy in the calibration parameter. We compare the Planck 353 GHz power spectrum with the measured amplitudes of dust and cosmic infrared background (CIB) of ACT data at 148 and 218 GHz. We also compare planet and point source measurements from the two experiments.

  10. Random matrix approach to cross correlations in financial data

    Science.gov (United States)

    Plerou, Vasiliki; Gopikrishnan, Parameswaran; Rosenow, Bernd; Amaral, Luís A.; Guhr, Thomas; Stanley, H. Eugene

    2002-06-01

    We analyze cross correlations between price fluctuations of different stocks using methods of random matrix theory (RMT). Using two large databases, we calculate cross-correlation matrices C of returns constructed from (i) 30-min returns of 1000 US stocks for the 2-yr period 1994-1995, (ii) 30-min returns of 881 US stocks for the 2-yr period 1996-1997, and (iii) 1-day returns of 422 US stocks for the 35-yr period 1962-1996. We test the statistics of the eigenvalues λi of C against a ``null hypothesis'' - a random correlation matrix constructed from mutually uncorrelated time series. We find that a majority of the eigenvalues of C fall within the RMT bounds [λ-,λ+] for the eigenvalues of random correlation matrices. We test the eigenvalues of C within the RMT bound for universal properties of random matrices and find good agreement with the results for the Gaussian orthogonal ensemble of random matrices-implying a large degree of randomness in the measured cross-correlation coefficients. Further, we find that the distribution of eigenvector components for the eigenvectors corresponding to the eigenvalues outside the RMT bound display systematic deviations from the RMT prediction. In addition, we find that these ``deviating eigenvectors'' are stable in time. We analyze the components of the deviating eigenvectors and find that the largest eigenvalue corresponds to an influence common to all stocks. Our analysis of the remaining deviating eigenvectors shows distinct groups, whose identities correspond to conventionally identified business sectors. Finally, we discuss applications to the construction of portfolios of stocks that have a stable ratio of risk to return.

  11. The cross-correlation analysis of multi property of stock markets based on MM-DFA

    Science.gov (United States)

    Yang, Yujun; Li, Jianping; Yang, Yimei

    2017-09-01

    In this paper, we propose a new method called DH-MXA based on distribution histograms of Hurst surface and multiscale multifractal detrended fluctuation analysis. The method allows us to investigate the cross-correlation characteristics among multiple properties of different stock time series. It may provide a new way of measuring the nonlinearity of several signals. It also can provide a more stable and faithful description of cross-correlation of multiple properties of stocks. The DH-MXA helps us to present much richer information than multifractal detrented cross-correlation analysis and allows us to assess many universal and subtle cross-correlation characteristics of stock markets. We show DH-MXA by selecting four artificial data sets and five properties of four stock time series from different countries. The results show that our proposed method can be adapted to investigate the cross-correlation of stock markets. In general, the American stock markets are more mature and less volatile than the Chinese stock markets.

  12. Fast Prediction and Evaluation of Gravitational Waveforms Using Surrogate Models

    Science.gov (United States)

    Field, Scott E.; Galley, Chad R.; Hesthaven, Jan S.; Kaye, Jason; Tiglio, Manuel

    2014-07-01

    We propose a solution to the problem of quickly and accurately predicting gravitational waveforms within any given physical model. The method is relevant for both real-time applications and more traditional scenarios where the generation of waveforms using standard methods can be prohibitively expensive. Our approach is based on three offline steps resulting in an accurate reduced order model in both parameter and physical dimensions that can be used as a surrogate for the true or fiducial waveform family. First, a set of m parameter values is determined using a greedy algorithm from which a reduced basis representation is constructed. Second, these m parameters induce the selection of m time values for interpolating a waveform time series using an empirical interpolant that is built for the fiducial waveform family. Third, a fit in the parameter dimension is performed for the waveform's value at each of these m times. The cost of predicting L waveform time samples for a generic parameter choice is of order O(mL+mcfit) online operations, where cfit denotes the fitting function operation count and, typically, m ≪L. The result is a compact, computationally efficient, and accurate surrogate model that retains the original physics of the fiducial waveform family while also being fast to evaluate. We generate accurate surrogate models for effective-one-body waveforms of nonspinning binary black hole coalescences with durations as long as 105M, mass ratios from 1 to 10, and for multiple spherical harmonic modes. We find that these surrogates are more than 3 orders of magnitude faster to evaluate as compared to the cost of generating effective-one-body waveforms in standard ways. Surrogate model building for other waveform families and models follows the same steps and has the same low computational online scaling cost. For expensive numerical simulations of binary black hole coalescences, we thus anticipate extremely large speedups in generating new waveforms with a

  13. Health monitoring of Ceramic Matrix Composites from waveform-based analysis of Acoustic Emission

    Directory of Open Access Journals (Sweden)

    Maillet Emmanuel

    2015-01-01

    Full Text Available Ceramic Matrix Composites (CMCs are anticipated for use in the hot section of aircraft engines. Their implementation requires the understanding of the various damage modes that are involved and their relation to life expectancy. Acoustic Emission (AE has been shown to be an efficient technique for monitoring damage evolution in CMCs. However, only a waveform-based analysis of AE can offer the possibility to validate and precisely examine the recorded AE data with a view to damage localization and identification. The present work fully integrates wave initiation, propagation and acquisition in the analysis of Acoustic Emission waveforms recorded at various sensors, therefore providing more reliable information to assess the relation between Acoustic Emission and damage modes. The procedure allows selecting AE events originating from damage, accurate determination of their location as well as the characterization of effects of propagation on the recorded waveforms. This approach was developed using AE data recorded during tensile tests on carbon/carbon composites. It was then applied to melt-infiltrated SiC/SiC composites.

  14. Detrended partial cross-correlation analysis of two nonstationary time series influenced by common external forces

    Science.gov (United States)

    Qian, Xi-Yuan; Liu, Ya-Min; Jiang, Zhi-Qiang; Podobnik, Boris; Zhou, Wei-Xing; Stanley, H. Eugene

    2015-06-01

    When common factors strongly influence two power-law cross-correlated time series recorded in complex natural or social systems, using detrended cross-correlation analysis (DCCA) without considering these common factors will bias the results. We use detrended partial cross-correlation analysis (DPXA) to uncover the intrinsic power-law cross correlations between two simultaneously recorded time series in the presence of nonstationarity after removing the effects of other time series acting as common forces. The DPXA method is a generalization of the detrended cross-correlation analysis that takes into account partial correlation analysis. We demonstrate the method by using bivariate fractional Brownian motions contaminated with a fractional Brownian motion. We find that the DPXA is able to recover the analytical cross Hurst indices, and thus the multiscale DPXA coefficients are a viable alternative to the conventional cross-correlation coefficient. We demonstrate the advantage of the DPXA coefficients over the DCCA coefficients by analyzing contaminated bivariate fractional Brownian motions. We calculate the DPXA coefficients and use them to extract the intrinsic cross correlation between crude oil and gold futures by taking into consideration the impact of the U.S. dollar index. We develop the multifractal DPXA (MF-DPXA) method in order to generalize the DPXA method and investigate multifractal time series. We analyze multifractal binomial measures masked with strong white noises and find that the MF-DPXA method quantifies the hidden multifractal nature while the multifractal DCCA method fails.

  15. Facies Constrained Elastic Full Waveform Inversion

    KAUST Repository

    Zhang, Z.

    2017-05-26

    Current efforts to utilize full waveform inversion (FWI) as a tool beyond acoustic imaging applications, for example for reservoir analysis, face inherent limitations on resolution and also on the potential trade-off between elastic model parameters. Adding rock physics constraints does help to mitigate these issues. However, current approaches to add such constraints are based on averaged type rock physics regularization terms. Since the true earth model consists of different facies, averaging over those facies naturally leads to smoothed models. To overcome this, we propose a novel way to utilize facies based constraints in elastic FWI. A so-called confidence map is calculated and updated at each iteration of the inversion using both the inverted models and the prior information. The numerical example shows that the proposed method can reduce the cross-talks and also can improve the resolution of inverted elastic properties.

  16. Facies Constrained Elastic Full Waveform Inversion

    KAUST Repository

    Zhang, Z.; Zabihi Naeini, E.; Alkhalifah, Tariq Ali

    2017-01-01

    Current efforts to utilize full waveform inversion (FWI) as a tool beyond acoustic imaging applications, for example for reservoir analysis, face inherent limitations on resolution and also on the potential trade-off between elastic model parameters. Adding rock physics constraints does help to mitigate these issues. However, current approaches to add such constraints are based on averaged type rock physics regularization terms. Since the true earth model consists of different facies, averaging over those facies naturally leads to smoothed models. To overcome this, we propose a novel way to utilize facies based constraints in elastic FWI. A so-called confidence map is calculated and updated at each iteration of the inversion using both the inverted models and the prior information. The numerical example shows that the proposed method can reduce the cross-talks and also can improve the resolution of inverted elastic properties.

  17. The q-dependent detrended cross-correlation analysis of stock market

    Science.gov (United States)

    Zhao, Longfeng; Li, Wei; Fenu, Andrea; Podobnik, Boris; Wang, Yougui; Stanley, H. Eugene

    2018-02-01

    Properties of the q-dependent cross-correlation matrices of the stock market have been analyzed by using random matrix theory and complex networks. The correlation structures of the fluctuations at different magnitudes have unique properties. The cross-correlations among small fluctuations are much stronger than those among large fluctuations. The large and small fluctuations are dominated by different groups of stocks. We use complex network representation to study these q-dependent matrices and discover some new identities. By utilizing those q-dependent correlation-based networks, we are able to construct some portfolios of those more independent stocks which consistently perform better. The optimal multifractal order for portfolio optimization is around q  =  2 under the mean-variance portfolio framework, and q\\in[2, 6] under the expected shortfall criterion. These results have deepened our understanding regarding the collective behavior of the complex financial system.

  18. Waveform digitizing at 500 MHz

    International Nuclear Information System (INIS)

    Atiya, M.; Ito, M.; Haggerty, J.; Ng, C.; Sippach, F.W.

    1988-01-01

    Experiment E787 at Brookhaven National Laboratory is designed to study the decay K + → π + ν/bar /nu// to a sensitivity of 2 /times/ 10 -10 . To achieve acceptable muon rejection it is necessary to couple traditional methods (range/energy/momentum correlation) with observation of the (π + → μ + ν, μ + → e + ν/bar /nu//) decay sequence in scintillator. We report on the design and construction of 200 channels of relatively low cost solid state waveform digitizers. The distinguishing features are: 8 bits dynamic range, 500 MHz sampling, zero suppression on the fly, deep memory (up to .5 msec), and fast readout time (100 μsec for the entire system). We report on data obtained during the February-May 1988 run showing performance of the system for the observation of the above decay. 8 figs

  19. Waveform digitizing at 500 MHz

    International Nuclear Information System (INIS)

    Atiya, M.; Ito, M.; Haggerty, J.; Ng, C.; Sippach, F.W.

    1988-01-01

    Experiment E787 at Brookhaven National Laboratory is designed to study the decay K + → π + ν/bar /nu// to a sensitivity of 2 /times/ 10/sup /minus/10/. To achieve acceptable muon rejection it is necessary to couple traditional methods (range/energy/momentum correlation) with observation of the π + → μ + → e + ν/bar /nu// decay sequence in scintillator. We report on the design and construction of over 200 channels of relatively low cost solid state waveform digitizers. The distinguishing features are: 8 bits dynamic range, 500 MHz sampling, zero suppression on the fly, deep memory (up to .5 msec), and fast readout time (100 μsec for the entire system). We report on data obtained during the February--May 1988 run showing performance of the system for the observation of the above decay. 9 figs

  20. Structure of a financial cross-correlation matrix under attack

    Science.gov (United States)

    Lim, Gyuchang; Kim, SooYong; Kim, Junghwan; Kim, Pyungsoo; Kang, Yoonjong; Park, Sanghoon; Park, Inho; Park, Sang-Bum; Kim, Kyungsik

    2009-09-01

    We investigate the structure of a perturbed stock market in terms of correlation matrices. For the purpose of perturbing a stock market, two distinct methods are used, namely local and global perturbation. The former involves replacing a correlation coefficient of the cross-correlation matrix with one calculated from two Gaussian-distributed time series while the latter reconstructs the cross-correlation matrix just after replacing the original return series with Gaussian-distributed time series. Concerning the local case, it is a technical study only and there is no attempt to model reality. The term ‘global’ means the overall effect of the replacement on other untouched returns. Through statistical analyses such as random matrix theory (RMT), network theory, and the correlation coefficient distributions, we show that the global structure of a stock market is vulnerable to perturbation. However, apart from in the analysis of inverse participation ratios (IPRs), the vulnerability becomes dull under a small-scale perturbation. This means that these analysis tools are inappropriate for monitoring the whole stock market due to the low sensitivity of a stock market to a small-scale perturbation. In contrast, when going down to the structure of business sectors, we confirm that correlation-based business sectors are regrouped in terms of IPRs. This result gives a clue about monitoring the effect of hidden intentions, which are revealed via portfolios taken mostly by large investors.

  1. Reversible conduction block in peripheral nerve using electrical waveforms.

    Science.gov (United States)

    Bhadra, Niloy; Vrabec, Tina L; Bhadra, Narendra; Kilgore, Kevin L

    2018-01-01

    Electrical nerve block uses electrical waveforms to block action potential propagation. Two key features that distinguish electrical nerve block from other nonelectrical means of nerve block: block occurs instantly, typically within 1 s; and block is fully and rapidly reversible (within seconds). Approaches for achieving electrical nerve block are reviewed, including kilohertz frequency alternating current and charge-balanced polarizing current. We conclude with a discussion of the future directions of electrical nerve block. Electrical nerve block is an emerging technique that has many significant advantages over other methods of nerve block. This field is still in its infancy, but a significant expansion in the clinical application of this technique is expected in the coming years.

  2. CROSS-CORRELATION MODELLING OF SURFACE WATER – GROUNDWATER INTERACTION USING THE EXCEL SPREADSHEET APPLICATION

    Directory of Open Access Journals (Sweden)

    Kristijan Posavec

    2017-01-01

    Full Text Available Modelling responses of groundwater levels in aquifer systems, which occur as a reaction to changes in aquifer system boundary conditions such as river or stream stages, is commonly being studied using statistical methods, namely correlation, cross-correlation and regression methods. Although correlation and regression analysis tools are readily available in Microsoft Excel, a widely applied spreadsheet industry standard, the cross-correlation analysis tool is missing. As a part of research of groundwater pressure propagation into alluvial aquifer systems of the Sava and Drava/Danube River catchments following river stages rise, focused on estimating groundwater pressure travel times in aquifers, an Excel spreadsheet data analysis application for cross-correlation modelling has been designed and used in modelling surface water – groundwater interaction. Examples of fi eld data from the Zagreb aquifer system and the Kopački rit Nature Park aquifer system are used to illustrate the usefulness of the cross-correlation application.

  3. Design of a 9-loop quasi-exponential waveform generator.

    Science.gov (United States)

    Banerjee, Partha; Shukla, Rohit; Shyam, Anurag

    2015-12-01

    We know in an under-damped L-C-R series circuit, current follows a damped sinusoidal waveform. But if a number of sinusoidal waveforms of decreasing time period, generated in an L-C-R circuit, be combined in first quarter cycle of time period, then a quasi-exponential nature of output current waveform can be achieved. In an L-C-R series circuit, quasi-exponential current waveform shows a rising current derivative and thereby finds many applications in pulsed power. Here, we have described design and experiment details of a 9-loop quasi-exponential waveform generator. In that, design details of magnetic switches have also been described. In the experiment, output current of 26 kA has been achieved. It has been shown that how well the experimentally obtained output current profile matches with the numerically computed output.

  4. Measurement of angle-correlated differential (n,2n) reaction cross section with pencil-beam DV neutron source

    International Nuclear Information System (INIS)

    Takaki, S.; Kondo, K.; Shido, S.; Miyamaru, H.; Murata, I.; Ochiai, Kentaro; Nishitani, Takeo

    2006-01-01

    Angle-correlated differential cross-section for 9 Be(n,2n) reaction has been measured with the coincidence detection technique and a pencil-beam DT neutron source at FNS, JAEA. Energy spectra of two emitted neutrons were obtained for azimuthal and polar direction independently. It was made clear from the experiment that there are noise signals caused by inter-detector scattering. The ratio of the inter-detector scattering components in the detected signals was estimated by MCNP calculation to correct the measured result. By considering the inter-detector scattering components, the total 9 Be(n,2n) reaction cross-section agreed with the evaluated nuclear data within the experimental error. (author)

  5. Developed vibration waveform monitoring unit for CBM

    International Nuclear Information System (INIS)

    Hamada, T.; Hotsuta, K.; Hirose, I.; Morita, E.

    2007-01-01

    In nuclear power plants, many rotating machines such as pumps and fans are in use. Shikoku Research Institute Inc. has recently developed easy-to-use tools to facilitate the maintenance of such equipment. They include a battery-operated vibration waveform monitoring unit which allows unmanned vibration monitoring on a regular basis and data collection even from intermittently operating equipment, a waveform data collector which can be used for easy collection, storage, control, and analysis of raw vibration waveform data during normal operation, and vibration analysis and evaluation tools. A combination of these tools has a high potential for optimization of rotating equipment maintenance. (author)

  6. Source-independent elastic waveform inversion using a logarithmic wavefield

    KAUST Repository

    Choi, Yun Seok

    2012-01-01

    The logarithmic waveform inversion has been widely developed and applied to some synthetic and real data. In most logarithmic waveform inversion algorithms, the subsurface velocities are updated along with the source estimation. To avoid estimating the source wavelet in the logarithmic waveform inversion, we developed a source-independent logarithmic waveform inversion algorithm. In this inversion algorithm, we first normalize the wavefields with the reference wavefield to remove the source wavelet, and then take the logarithm of the normalized wavefields. Based on the properties of the logarithm, we define three types of misfit functions using the following methods: combination of amplitude and phase, amplitude-only, and phase-only. In the inversion, the gradient is computed using the back-propagation formula without directly calculating the Jacobian matrix. We apply our algorithm to noise-free and noise-added synthetic data generated for the modified version of elastic Marmousi2 model, and compare the results with those of the source-estimation logarithmic waveform inversion. For the noise-free data, the source-independent algorithms yield velocity models close to true velocity models. For random-noise data, the source-estimation logarithmic waveform inversion yields better results than the source-independent method, whereas for coherent-noise data, the results are reversed. Numerical results show that the source-independent and source-estimation logarithmic waveform inversion methods have their own merits for random- and coherent-noise data. © 2011.

  7. Cross-correlations in volume space: Differences between buy and sell volumes

    Science.gov (United States)

    Lee, Sun Young; Hwang, Dong Il; Kim, Min Jae; Koh, In Gyu; Kim, Soo Yong

    2011-03-01

    We study the cross-correlations of buy and sell volumes on the Korean stock market in high frequency. We observe that the pulling effects of volumes are as small as that of returns. The properties of the correlations of buy and sell volumes differ. They are explained by the degree of synchronization of stock volumes. Further, the pulling effects on the minimal spanning tree are studied. In minimal spanning trees with directed links, the large pulling effects are clustered at the center, not uniformly distributed. The Epps effect of buy and sell volumes are observed. The reversal of the cross-correlations of buy and sell volumes is also detected.

  8. Autocorrelation and cross-correlation in time series of homicide and attempted homicide

    Science.gov (United States)

    Machado Filho, A.; da Silva, M. F.; Zebende, G. F.

    2014-04-01

    We propose in this paper to establish the relationship between homicides and attempted homicides by a non-stationary time-series analysis. This analysis will be carried out by Detrended Fluctuation Analysis (DFA), Detrended Cross-Correlation Analysis (DCCA), and DCCA cross-correlation coefficient, ρ(n). Through this analysis we can identify a positive cross-correlation between homicides and attempted homicides. At the same time, looked at from the point of view of autocorrelation (DFA), this analysis can be more informative depending on time scale. For short scale (days), we cannot identify auto-correlations, on the scale of weeks DFA presents anti-persistent behavior, and for long time scales (n>90 days) DFA presents a persistent behavior. Finally, the application of this new type of statistical analysis proved to be efficient and, in this sense, this paper can contribute to a more accurate descriptive statistics of crime.

  9. A new optimization approach for source-encoding full-waveform inversion

    NARCIS (Netherlands)

    Moghaddam, P.P.; Keers, H.; Herrmann, F.J.; Mulder, W.A.

    2013-01-01

    Waveform inversion is the method of choice for determining a highly heterogeneous subsurface structure. However, conventional waveform inversion requires that the wavefield for each source is computed separately. This makes it very expensive for realistic 3D seismic surveys. Source-encoding waveform

  10. World currency exchange rate cross-correlations

    Science.gov (United States)

    Droå¼dż, S.; Górski, A. Z.; Kwapień, J.

    2007-08-01

    World currency network constitutes one of the most complex structures that is associated with the contemporary civilization. On a way towards quantifying its characteristics we study the cross correlations in changes of the daily foreign exchange rates within the basket of 60 currencies in the period December 1998 May 2005. Such a dynamics turns out to predominantly involve one outstanding eigenvalue of the correlation matrix. The magnitude of this eigenvalue depends however crucially on which currency is used as a base currency for the remaining ones. Most prominent it looks from the perspective of a peripheral currency. This largest eigenvalue is seen to systematically decrease and thus the structure of correlations becomes more heterogeneous, when more significant currencies are used as reference. An extreme case in this later respect is the USD in the period considered. Besides providing further insight into subtle nature of complexity, these observations point to a formal procedure that in general can be used for practical purposes of measuring the relative currencies significance on various time horizons.

  11. Multiparameter Elastic Full Waveform Inversion With Facies Constraints

    KAUST Repository

    Zhang, Zhendong; Alkhalifah, Tariq Ali; Naeini, Ehsan Zabihi

    2017-01-01

    Full waveform inversion (FWI) aims fully benefit from all the data characteristics to estimate the parameters describing the assumed physics of the subsurface. However, current efforts to utilize full waveform inversion as a tool beyond acoustic

  12. Multi-source waveform inversion of marine streamer data using the normalized wavefield

    KAUST Repository

    Choi, Yun Seok

    2012-01-01

    Even though the encoded multi-source approach dramatically reduces the computational cost of waveform inversion, it is generally not applicable to marine streamer data. This is because the simultaneous-sources modeled data cannot be muted to comply with the configuration of the marine streamer data, which causes differences in the number of stacked-traces, or energy levels, between the modeled and observed data. Since the conventional L2 norm does not account for the difference in energy levels, multi-source inversion based on the conventional L2 norm does not work for marine streamer data. In this study, we propose the L2, approximated L2, and L1 norm using the normalized wavefields for the multi-source waveform inversion of marine streamer data. Since the normalized wavefields mitigate the different energy levels between the observed and modeled wavefields, the multi-source waveform inversion using the normalized wavefields can be applied to marine streamer data. We obtain the gradient of the objective functions using the back-propagation algorithm. To conclude, the gradient of the L2 norm using the normalized wavefields is exactly the same as that of the global correlation norm. In the numerical examples, the new objective functions using the normalized wavefields generate successful results whereas conventional L2 norm does not.

  13. Audio Quality Assurance : An Application of Cross Correlation

    DEFF Research Database (Denmark)

    Jurik, Bolette Ammitzbøll; Nielsen, Jesper Asbjørn Sindahl

    2012-01-01

    We describe algorithms for automated quality assurance on content of audio files in context of preservation actions and access. The algorithms use cross correlation to compare the sound waves. They are used to do overlap analysis in an access scenario, where preserved radio broadcasts are used in...

  14. Nonreciprocal Green’s function retrieval by cross correlation

    NARCIS (Netherlands)

    Wapenaar, C.P.A.

    2006-01-01

    The cross correlation of two recordings of a diffuse acoustic wave field at different receivers yields the Green’s function between these receivers. In nearly all cases considered so far the wave equation obeys time-reversal invariance and the Green’s function obeys source-receiver reciprocity. Here

  15. Multiples waveform inversion

    KAUST Repository

    Zhang, Dongliang

    2013-01-01

    To increase the illumination of the subsurface and to eliminate the dependency of FWI on the source wavelet, we propose multiples waveform inversion (MWI) that transforms each hydrophone into a virtual point source with a time history equal to that of the recorded data. These virtual sources are used to numerically generate downgoing wavefields that are correlated with the backprojected surface-related multiples to give the migration image. Since the recorded data are treated as the virtual sources, knowledge of the source wavelet is not required, and the subsurface illumination is greatly enhanced because the entire free surface acts as an extended source compared to the radiation pattern of a traditional point source. Numerical tests on the Marmousi2 model show that the convergence rate and the spatial resolution of MWI is, respectively, faster and more accurate then FWI. The potential pitfall with this method is that the multiples undergo more than one roundtrip to the surface, which increases attenuation and reduces spatial resolution. This can lead to less resolved tomograms compared to conventional FWI. The possible solution is to combine both FWI and MWI in inverting for the subsurface velocity distribution.

  16. Workflows for Full Waveform Inversions

    Science.gov (United States)

    Boehm, Christian; Krischer, Lion; Afanasiev, Michael; van Driel, Martin; May, Dave A.; Rietmann, Max; Fichtner, Andreas

    2017-04-01

    Despite many theoretical advances and the increasing availability of high-performance computing clusters, full seismic waveform inversions still face considerable challenges regarding data and workflow management. While the community has access to solvers which can harness modern heterogeneous computing architectures, the computational bottleneck has fallen to these often manpower-bounded issues that need to be overcome to facilitate further progress. Modern inversions involve huge amounts of data and require a tight integration between numerical PDE solvers, data acquisition and processing systems, nonlinear optimization libraries, and job orchestration frameworks. To this end we created a set of libraries and applications revolving around Salvus (http://salvus.io), a novel software package designed to solve large-scale full waveform inverse problems. This presentation focuses on solving passive source seismic full waveform inversions from local to global scales with Salvus. We discuss (i) design choices for the aforementioned components required for full waveform modeling and inversion, (ii) their implementation in the Salvus framework, and (iii) how it is all tied together by a usable workflow system. We combine state-of-the-art algorithms ranging from high-order finite-element solutions of the wave equation to quasi-Newton optimization algorithms using trust-region methods that can handle inexact derivatives. All is steered by an automated interactive graph-based workflow framework capable of orchestrating all necessary pieces. This naturally facilitates the creation of new Earth models and hopefully sparks new scientific insights. Additionally, and even more importantly, it enhances reproducibility and reliability of the final results.

  17. SURFACE FITTING FILTERING OF LIDAR POINT CLOUD WITH WAVEFORM INFORMATION

    Directory of Open Access Journals (Sweden)

    S. Xing

    2017-09-01

    Full Text Available Full-waveform LiDAR is an active technology of photogrammetry and remote sensing. It provides more detailed information about objects along the path of a laser pulse than discrete-return topographic LiDAR. The point cloud and waveform information with high quality can be obtained by waveform decomposition, which could make contributions to accurate filtering. The surface fitting filtering method with waveform information is proposed to present such advantage. Firstly, discrete point cloud and waveform parameters are resolved by global convergent Levenberg Marquardt decomposition. Secondly, the ground seed points are selected, of which the abnormal ones are detected by waveform parameters and robust estimation. Thirdly, the terrain surface is fitted and the height difference threshold is determined in consideration of window size and mean square error. Finally, the points are classified gradually with the rising of window size. The filtering process is finished until window size is larger than threshold. The waveform data in urban, farmland and mountain areas from “WATER (Watershed Allied Telemetry Experimental Research” are selected for experiments. Results prove that compared with traditional method, the accuracy of point cloud filtering is further improved and the proposed method has highly practical value.

  18. The use of diameter distension waveforms as an alternative for tonometric pressure to assess carotid blood pressure

    International Nuclear Information System (INIS)

    Kips, Jan; Mahieu, Dries; Fabry, Isabelle; Van Bortel, Luc; Vanmolkot, Floris; De Hoon, Jan; Vermeersch, Sebastian; Segers, Patrick

    2010-01-01

    Proper non-invasive assessment of carotid artery pressure ideally uses waveforms recorded at two anatomical locations: the brachial and the carotid artery. Calibrated diameter distension waveforms could provide a more widely applicable alternative for local arterial pressure assessment than applanation tonometry. This approach might be of particular use at the brachial artery, where the feasibility of a reliable tonometric measurement has been questioned. The aim of this study was to evaluate an approach based on distension waveforms obtained at the brachial and carotid arteries. This approach will be compared to traditional pulse pressures obtained through tonometry at both the carotid and brachial arteries (used as a reference) and the more recently proposed approach of combining tonometric readings at the brachial artery with linearly or exponentially calibrated distension curves at the carotid artery. Local brachial and carotid diameter distension and tonometry waveforms were recorded in 148 subjects (119 women; aged 19–59 years). The morphology of the waveforms was compared by the form factor and the root-mean-squared error. The difference between the reference carotid PP and the PP obtained from brachial and carotid distension waveforms was smaller (0.9 (4.9) mmHg or 2.3%) than the difference between the reference carotid PP and the estimates obtained using a tonometric and a distension waveform (−4.8 (2.5) mmHg for the approach using brachial tonometry and linearly scaled carotid distension, and 2.7 (6.8) mmHg when using exponentially scaled carotid distension waves). We therefore recommend to stick to one technique on both the brachial and the carotid artery, either tonometry or distension, when assessing carotid blood pressure non-invasively

  19. 3D Electric Waveforms of Solar Wind Turbulence

    Science.gov (United States)

    Kellogg, P. J.; Goetz, K.; Monson, S. J.

    2018-01-01

    Electric fields provide the major coupling between the turbulence of the solar wind and particles. A large part of the turbulent spectrum of fluctuations in the solar wind is thought to be kinetic Alfvén waves; however, whistlers have recently been found to be important. In this article, we attempt to determine the mode identification of individual waveforms using the three-dimensional antenna system of the SWaves experiments on the STEREO spacecraft. Samples are chosen using waveforms with an apparent periodic structure, selected visually. The short antennas of STEREO respond to density fluctuations and to electric fields. Measurement of four quantities using only three antennas presents a problem. Methods to overcome or to ignore this difficulty are presented. We attempt to decide whether the waveforms correspond to the whistler mode or the Alfvén mode by using the direction of rotation of the signal. Most of the waveforms are so oblique—nearly linearly polarized—that the direction cannot be determined. However, about one third of the waveforms can be identified, and whistlers and Alfvén waves are present in roughly equal numbers. The selected waveforms are very intense but intermittent and are orders of magnitude stronger than the average, yet their accumulated signal accounts for a large fraction of the average. The average, however, is supposed to be the result of a turbulent mixture of many waves, not short coherent events. This presents a puzzle for future work.

  20. Bistatic High Frequency Radar Ocean Surface Cross Section for an FMCW Source with an Antenna on a Floating Platform

    Directory of Open Access Journals (Sweden)

    Yue Ma

    2016-01-01

    Full Text Available The first- and second-order bistatic high frequency radar cross sections of the ocean surface with an antenna on a floating platform are derived for a frequency-modulated continuous wave (FMCW source. Based on previous work, the derivation begins with the general bistatic electric field in the frequency domain for the case of a floating antenna. Demodulation and range transformation are used to obtain the range information, distinguishing the process from that used for a pulsed radar. After Fourier-transforming the autocorrelation and comparing the result with the radar range equation, the radar cross sections are derived. The new first- and second-order antenna-motion-incorporated bistatic radar cross section models for an FMCW source are simulated and compared with those for a pulsed source. Results show that, for the same radar operating parameters, the first-order radar cross section for the FMCW waveform is a little lower than that for a pulsed source. The second-order radar cross section for the FMCW waveform reduces to that for the pulsed waveform when the scattering patch limit approaches infinity. The effect of platform motion on the radar cross sections for an FMCW waveform is investigated for a variety of sea states and operating frequencies and, in general, is found to be similar to that for a pulsed waveform.

  1. CROSS-CORRELATION BETWEEN X-RAY AND OPTICAL/NEAR-INFRARED BACKGROUND INTENSITY FLUCTUATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell-Wynne, Ketron; Cooray, Asantha [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Xue, Yongquan [CAS Key Laboratory for Researches in Galaxies and Cosmology, Center for Astrophysics, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Luo, Bin [School of Astronomy and Space Science, Nanjing University, Nanjing, 210093 (China); Brandt, William [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA, 16802 (United States); Koekemoer, Anton [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2016-12-01

    Angular power spectra of optical and infrared background anisotropies at wavelengths between 0.5 and 5 μ m are a useful probe of faint sources present during reionization, in addition to faint galaxies and diffuse signals at low redshift. The cross-correlation of these fluctuations with backgrounds at other wavelengths can be used to separate some of these signals. A previous study on the cross-correlation between X-ray and Spitzer fluctuations at 3.6 μ m and 4.5 μ m has been interpreted as evidence for direct collapse black holes present at z  > 12. Here we return to this cross-correlation and study its wavelength dependence from 0.5 to 4.5 μ m using Hubble and Spitzer data in combination with a subset of the 4 Ms Chandra observations in GOODS-S/ECDFS. Our study involves five Hubble bands at 0.6, 0.7, 0.85, 1.25, and 1.6 μ m, and two Spitzer -IRAC bands at 3.6 μ m and 4.5 μ m. We confirm the previously seen cross-correlation between 3.6 μ m (4.5 μ m) and X-rays with 3.7 σ (4.2 σ ) and 2.7 σ (3.7 σ ) detections in the soft [0.5–2] keV and hard [2–8] keV X-ray bands, respectively, at angular scales above 20 arcsec. The cross-correlation of X-rays with Hubble is largely anticorrelated, ranging between the levels of 1.4 σ –3.5 σ for all the Hubble and X-ray bands. This lack of correlation in the shorter optical/NIR bands implies the sources responsible for the cosmic infrared background at 3.6 and 4.5 μ m are at least partly dissimilar to those at 1.6 μ m and shorter.

  2. Multi-dimensional modeling of two-phase flow in rod bundles and interpretation of velocities measured in BWRs by the cross-correlation technique

    International Nuclear Information System (INIS)

    Analytis, G.Th.; Luebbesmeyer, D.

    1984-04-01

    The authors present an as precise as possible interpretation of velocity measurements in BWRs by the cross-correlation technique, which is based on the radially non-uniform quality and velocity distribution in BWR type bundles, as well as on our knowledge about the spatial 'field of view' of the in-core neutron detectors. After formulating the three-dimensional two-fluid model volume/time averaged equations and pointing out some problems associated with averaging, they expound a little on the turbulence mixing and void drift effects, as well as on the way they are modelled in advanced subchannel analysis codes like THERMIT or COBRA-TF. Subsequently, some comparisons are made between axial velocities measured in a commercial BWR by neutron noise analysis, and the steam velocities of the four subchannels nearest to the instrument tube of one of the four bundles as predicted by COBRA-III and by THERMIT. Although as expected, for well-known reasons, COBRA-III predicts subchannel steam velocities which are close to each other, THERMIT correctly predicts in the upper half of the core three largely different steam velocities in the three different types of BW0 subchannels (corner, edge and interior). (Auth.)

  3. Corrections for frequency domain transformations of Winfrith binary cross correlator responses

    International Nuclear Information System (INIS)

    Cummins, J.D.

    1968-04-01

    This report considers the corrections for frequency domain transformations of Winfrith binary cross correlator responses; (i) for the finite bandwidth of the equivalent input signal; (2) for the finite time required for the actuator to move between the two positions appropriate to the two levels of the periodic binary chain code input and (3) for the averaging of experimental determinations of the system frequency response and calculations of the standard deviations of the modulus and phase of the frequency responses determined from the cross correlator responses. (author)

  4. Nuclear material safeguards surveillance and accountancy by isotope correlation techniques

    International Nuclear Information System (INIS)

    Persiani, P.J.; Goleb, J.A.; Kroc, T.K.

    1981-11-01

    The purpose of this study is to investigate the applicability of isotope correlation techniques (ICT) to the Light Water Reactor (LWR) and the Liquid Metal Fast Breeder Reactor (LMFBR) fuel cycles for nuclear material accountancy and safeguards surveillance. The isotopic measurement of the inventory input to the reprocessing phase of the fuel cycle is the primary direct determination that an anomaly may exist in the fuel management of nuclear material. The nuclear materials accountancy gap which exists between the fabrication plant output and the input to the reprocessing plant can be minimized by using ICT at the dissolver stage of the reprocessing plant. The ICT allows a level of verification of the fabricator's fuel content specifications, the irradiation history, the fuel and blanket assemblies management and scheduling within the reactor, and the subsequent spent fuel assembly flows to the reprocessing plant. The investigation indicates that there exist relationships between isotopic concentration which have predictable, functional behavior over a range of burnup. Several cross-correlations serve to establish the initial core assembly-averaged composition. The selection of the more effective functionals will depend not only on the level of reliability of ICT for verification, but also on the capability, accuracy and difficulty of developing measurement methods. The propagation of measurement errors on the correlation functions and respective sensitivities to isotopic compositional changes have been examined and found to be consistent with current measurement methods

  5. Ocular pressure waveform reflects ventricular bigeminy and aortic insufficiency

    Directory of Open Access Journals (Sweden)

    Jean B Kassem

    2015-01-01

    Full Text Available Ocular pulse amplitude (OPA is defined as the difference between maximum and minimum intraocular pressure (IOP during a cardiac cycle. Average values of OPA range from 1 to 4 mmHg. The purpose of this investigation is to determine the source of an irregular IOP waveform with elevated OPA in a 48-year-old male. Ocular pressure waveforms had an unusual shape consistent with early ventricular contraction. With a normal IOP, OPA was 9 mmHg, which is extraordinarily high. The subject was examined by a cardiologist and was determined to be in ventricular bigeminy. In addition, he had bounding carotid pulses and echocardiogram confirmed aortic insufficiency. After replacement of the aortic valve, the bigeminy resolved and the ocular pulse waveform became regular in appearance with an OPA of 1.6-2.0 mmHg. The ocular pressure waveform is a direct reflection of hemodynamics. Evaluating this waveform may provide an additional opportunity for screening subjects for cardiovascular anomalies and arrhythmias.

  6. Gravitational Waveforms in the Early Inspiral of Binary Black Hole Systems

    Science.gov (United States)

    Barkett, Kevin; Kumar, Prayush; Bhagwat, Swetha; Brown, Duncan; Scheel, Mark; Szilagyi, Bela; Simulating eXtreme Spacetimes Collaboration

    2015-04-01

    The inspiral, merger and ringdown of compact object binaries are important targets for gravitational wave detection by aLIGO. Detection and parameter estimation will require long, accurate waveforms for comparison. There are a number of analytical models for generating gravitational waveforms for these systems, but the only way to ensure their consistency and correctness is by comparing with numerical relativity simulations that cover many inspiral orbits. We've simulated a number of binary black hole systems with mass ratio 7 and a moderate, aligned spin on the larger black hole. We have attached these numerical waveforms to analytical waveform models to generate long hybrid gravitational waveforms that span the entire aLIGO frequency band. We analyze the robustness of these hybrid waveforms and measure the faithfulness of different hybrids with each other to obtain an estimate on how long future numerical simulations need to be in order to ensure that waveforms are accurate enough for use by aLIGO.

  7. A study on Improvisation in a Musical performance using Multifractal Detrended Cross Correlation Analysis

    Science.gov (United States)

    Sanyal, Shankha; Banerjee, Archi; Patranabis, Anirban; Banerjee, Kaushik; Sengupta, Ranjan; Ghosh, Dipak

    2016-11-01

    MFDFA (the most rigorous technique to assess multifractality) was performed on four Hindustani music samples played on same 'raga' sung by the same performer. Each music sample was divided into six parts and 'multifractal spectral width' was determined for each part corresponding to the four samples. The results obtained reveal that different parts of all the four sound signals possess spectral width of widely varying values. This gives a cue of the so called 'musical improvisation' in all music samples, keeping in mind they belong to the bandish part of the same raga. Formal compositions in Hindustani raga are juxtaposed with the improvised portions, where an artist manoeuvers his/her own creativity to bring out a mood that is specific for that particular performance, which is known as 'improvisation'. Further, this observation hints at the association of different emotions even in the same bandish of the same raga performed by the same artist, this interesting observation cannot be revealed unless rigorous non-linear technique explores the nature of musical structure. In the second part, we applied MFDXA technique to explore more in-depth about 'improvisation' and association with emotion. This technique is applied to find the degree of cross-correlation (γx) between the different parts of the samples. Pronounced correlation has been observed in the middle parts of the all the four samples evident from higher values of γx ​whereas the other parts show weak correlation. This gets further support from the values of spectral width from different parts of the sample - width of those parts is significantly different from other parts. This observation is extremely new both in respect of musical structure of so called improvisation and associated emotion. The importance of this study in application area of cognitive music therapy is immense.

  8. Performance Prediction of Constrained Waveform Design for Adaptive Radar

    Science.gov (United States)

    2016-11-01

    the famous Woodward quote, having a ubiquitous feeling for all radar waveform design (and performance prediction) researchers , that is found at the end...discuss research that develops performance prediction models to quantify the impact on SINR when an amplitude constraint is placed on a radar waveform...optimize the radar perfor- mance for the particular scenario and tasks. There have also been several survey papers on various topics in waveform design for

  9. Use of the Kalman Filter for Aortic Pressure Waveform Noise Reduction.

    Science.gov (United States)

    Lam, Frank; Lu, Hsiang-Wei; Wu, Chung-Che; Aliyazicioglu, Zekeriya; Kang, James S

    2017-01-01

    Clinical applications that require extraction and interpretation of physiological signals or waveforms are susceptible to corruption by noise or artifacts. Real-time hemodynamic monitoring systems are important for clinicians to assess the hemodynamic stability of surgical or intensive care patients by interpreting hemodynamic parameters generated by an analysis of aortic blood pressure (ABP) waveform measurements. Since hemodynamic parameter estimation algorithms often detect events and features from measured ABP waveforms to generate hemodynamic parameters, noise and artifacts integrated into ABP waveforms can severely distort the interpretation of hemodynamic parameters by hemodynamic algorithms. In this article, we propose the use of the Kalman filter and the 4-element Windkessel model with static parameters, arterial compliance C , peripheral resistance R , aortic impedance r , and the inertia of blood L , to represent aortic circulation for generating accurate estimations of ABP waveforms through noise and artifact reduction. Results show the Kalman filter could very effectively eliminate noise and generate a good estimation from the noisy ABP waveform based on the past state history. The power spectrum of the measured ABP waveform and the synthesized ABP waveform shows two similar harmonic frequencies.

  10. Krylov subspace acceleration of waveform relaxation

    Energy Technology Data Exchange (ETDEWEB)

    Lumsdaine, A.; Wu, Deyun [Univ. of Notre Dame, IN (United States)

    1996-12-31

    Standard solution methods for numerically solving time-dependent problems typically begin by discretizing the problem on a uniform time grid and then sequentially solving for successive time points. The initial time discretization imposes a serialization to the solution process and limits parallel speedup to the speedup available from parallelizing the problem at any given time point. This bottleneck can be circumvented by the use of waveform methods in which multiple time-points of the different components of the solution are computed independently. With the waveform approach, a problem is first spatially decomposed and distributed among the processors of a parallel machine. Each processor then solves its own time-dependent subsystem over the entire interval of interest using previous iterates from other processors as inputs. Synchronization and communication between processors take place infrequently, and communication consists of large packets of information - discretized functions of time (i.e., waveforms).

  11. Fast Prediction and Evaluation of Gravitational Waveforms Using Surrogate Models

    Directory of Open Access Journals (Sweden)

    Scott E. Field

    2014-07-01

    Full Text Available We propose a solution to the problem of quickly and accurately predicting gravitational waveforms within any given physical model. The method is relevant for both real-time applications and more traditional scenarios where the generation of waveforms using standard methods can be prohibitively expensive. Our approach is based on three offline steps resulting in an accurate reduced order model in both parameter and physical dimensions that can be used as a surrogate for the true or fiducial waveform family. First, a set of m parameter values is determined using a greedy algorithm from which a reduced basis representation is constructed. Second, these m parameters induce the selection of m time values for interpolating a waveform time series using an empirical interpolant that is built for the fiducial waveform family. Third, a fit in the parameter dimension is performed for the waveform’s value at each of these m times. The cost of predicting L waveform time samples for a generic parameter choice is of order O(mL+mc_{fit} online operations, where c_{fit} denotes the fitting function operation count and, typically, m≪L. The result is a compact, computationally efficient, and accurate surrogate model that retains the original physics of the fiducial waveform family while also being fast to evaluate. We generate accurate surrogate models for effective-one-body waveforms of nonspinning binary black hole coalescences with durations as long as 10^{5}M, mass ratios from 1 to 10, and for multiple spherical harmonic modes. We find that these surrogates are more than 3 orders of magnitude faster to evaluate as compared to the cost of generating effective-one-body waveforms in standard ways. Surrogate model building for other waveform families and models follows the same steps and has the same low computational online scaling cost. For expensive numerical simulations of binary black hole coalescences, we thus anticipate extremely large speedups in

  12. Positive Noise Cross Correlation in a Copper Pair Splitter.

    Science.gov (United States)

    Das, Anindya; Ronen, Yuval; Heiblum, Moty; Shtrikman, Hadas; Mahalu, Diana

    2012-02-01

    Entanglement is in heart of the Einstein-Podolsky-Rosen (EPR) paradox, in which non-locality is a fundamental property. Up to date spin entanglement of electrons had not been demonstrated. Here, we provide direct evidence of such entanglement by measuring: non-local positive current correlation and positive cross correlation among current fluctuations, both of separated electrons born by a Cooper-pair-beam-splitter. The realization of the splitter is provided by injecting current from an Al superconductor contact into two, single channel, pure InAs nanowires - each intercepted by a Coulomb blockaded quantum dot (QD). The QDs impedes strongly the flow of Cooper pairs allowing easy single electron transport. The passage of electron in one wire enables the simultaneous passage of the other in the neighboring wire. The splitting efficiency of the Cooper pairs (relative to Cooper pairs actual current) was found to be ˜ 40%. The positive cross-correlations in the currents and their fluctuations (shot noise) are fully consistent with entangled electrons produced by the beam splitter.

  13. A model-based spike sorting algorithm for removing correlation artifacts in multi-neuron recordings.

    Science.gov (United States)

    Pillow, Jonathan W; Shlens, Jonathon; Chichilnisky, E J; Simoncelli, Eero P

    2013-01-01

    We examine the problem of estimating the spike trains of multiple neurons from voltage traces recorded on one or more extracellular electrodes. Traditional spike-sorting methods rely on thresholding or clustering of recorded signals to identify spikes. While these methods can detect a large fraction of the spikes from a recording, they generally fail to identify synchronous or near-synchronous spikes: cases in which multiple spikes overlap. Here we investigate the geometry of failures in traditional sorting algorithms, and document the prevalence of such errors in multi-electrode recordings from primate retina. We then develop a method for multi-neuron spike sorting using a model that explicitly accounts for the superposition of spike waveforms. We model the recorded voltage traces as a linear combination of spike waveforms plus a stochastic background component of correlated Gaussian noise. Combining this measurement model with a Bernoulli prior over binary spike trains yields a posterior distribution for spikes given the recorded data. We introduce a greedy algorithm to maximize this posterior that we call "binary pursuit". The algorithm allows modest variability in spike waveforms and recovers spike times with higher precision than the voltage sampling rate. This method substantially corrects cross-correlation artifacts that arise with conventional methods, and substantially outperforms clustering methods on both real and simulated data. Finally, we develop diagnostic tools that can be used to assess errors in spike sorting in the absence of ground truth.

  14. An innovative scintillation process for correcting, cooling, and reducing the randomness of waveforms

    International Nuclear Information System (INIS)

    Shen, J.

    1991-01-01

    Research activities were concentrated on an innovative scintillation technique for high-energy collider detection. Heretofore, scintillation waveform data of high- energy physics events have been problematically random. This paper represents a bottleneck of data flow for the next generation of detectors for proton colliders like SSC or LHC. Prevailing problems to resolve were: additional time walk and jitter resulting from the random hitting positions of particles, increased walk and jitter caused by scintillation photon propagation dispersions, and quantum fluctuations of luminescence. However, these were manageable when the different aspects of randomness had been clarified in increased detail. For this purpose, these three were defined as pseudorandomness, quasi-randomness, and real randomness, respectively. A unique scintillation counter incorporating long scintillators with light guides, a drift chamber, and fast discriminators plus integrators was employed to resolve problems of correcting time walk and reducing the additional jitter by establishing an analytical waveform description of V(t,z) for a measured (z). Resolving problem was accomplished by reducing jitter by compressing V(t,z) with a nonlinear medium, called cooling scintillation. Resolving problem was proposed by orienting molecular and polarizing scintillation through the use of intense magnetic technology, called stabilizing the waveform

  15. Method and apparatus for resonant frequency waveform modulation

    Science.gov (United States)

    Taubman, Matthew S [Richland, WA

    2011-06-07

    A resonant modulator device and process are described that provide enhanced resonant frequency waveforms to electrical devices including, e.g., laser devices. Faster, larger, and more complex modulation waveforms are obtained than can be obtained by use of conventional current controllers alone.

  16. Frequency-domain waveform inversion using the unwrapped phase

    KAUST Repository

    Choi, Yun Seok; Alkhalifah, Tariq Ali

    2011-01-01

    Phase wrapping in the frequency-domain (or cycle skipping in the time-domain) is the major cause of the local minima problem in the waveform inversion. The unwrapped phase has the potential to provide us with a robust and reliable waveform inversion

  17. Optical rangefinding applications using communications modulation technique

    Science.gov (United States)

    Caplan, William D.; Morcom, Christopher John

    2010-10-01

    A novel range detection technique combines optical pulse modulation patterns with signal cross-correlation to produce an accurate range estimate from low power signals. The cross-correlation peak is analyzed by a post-processing algorithm such that the phase delay is proportional to the range to target. This technique produces a stable range estimate from noisy signals. The advantage is higher accuracy obtained with relatively low optical power transmitted. The technique is useful for low cost, low power and low mass sensors suitable for tactical use. The signal coding technique allows applications including IFF and battlefield identification systems.

  18. Physiological interpretation of Doppler shift waveforms: the femorodistal segment in combined disease.

    Science.gov (United States)

    Campbell, W B; Baird, R N; Cole, S E; Evans, J M; Skidmore, R; Woodcock, J P

    1983-01-01

    A new method is presented for assessing the femorodistal segment in multisegmental arterial disease, using the Laplace transform technique of Doppler waveform analysis. Blood velocity/time waveforms were obtained at femoral and ankle levels in three groups of limbs--50 without arterial disease, 12 with isolated aortoiliac stenoses, and 32 with femoropopliteal occlusions, with and without proximal disease. The waveforms were analysed for Laplace transform and pulsatility index values. The omega 0 coefficients of the Laplace transform analysis at femoral and ankle levels were compared in each subject, as the omega 0 gradient (femoral/ankle omega 0): and pulsatility index damping factor (femoral/ankle P1) was also calculated. The omega 0 gradient was shown to detect femoropopliteal occlusion in the presence of multisegmental arterial disease and to give some indication of its haemodynamic significance. The diagnostic accuracy of the omega 0 gradient was superior to that of pulsatility index damping factor. When combined with its existing ability to detect aortoiliac stenosis, this new application of the Laplace transform method offers the possibility both of a system for complete localisation of significant arterial lesions, and potential for follow-up of vascular surgical procedures in the lower limb, from two simple Doppler recordings.

  19. Scanning cross-correlator for monitoring uniform 3D ellipsoidal laser beams

    CERN Document Server

    Zelenogorskii, V V; Gacheva, E I; Gelikonov, G V; Krasilnikov, M; Mart'yanov, M A; Mironov, S Yu; Potemkin, A K; Syresin, E M; Stephan, F; Khazanov, E A

    2014-01-01

    The specific features of experimental implementation of a cross-correlator with a scan rate above 1600 cm s(-1) and a spatial delay amplitude of more than 15 mm are considered. The possibility of measuring the width of femtosecond pulses propagating in a train 300 mu s in duration with a repetition rate of 1 MHz is demonstrated. A time resolution of 300 fs for the maximum time window of 50 ps is attained.The cross-correlator is aimed at testing 3D pulses of a laser driver of an electron photo-injector.

  20. Pleasant/Unpleasant Filtering for Affective Image Retrieval Based on Cross-Correlation of EEG Features

    Directory of Open Access Journals (Sweden)

    Keranmu Xielifuguli

    2014-01-01

    Full Text Available People often make decisions based on sensitivity rather than rationality. In the field of biological information processing, methods are available for analyzing biological information directly based on electroencephalogram: EEG to determine the pleasant/unpleasant reactions of users. In this study, we propose a sensitivity filtering technique for discriminating preferences (pleasant/unpleasant for images using a sensitivity image filtering system based on EEG. Using a set of images retrieved by similarity retrieval, we perform the sensitivity-based pleasant/unpleasant classification of images based on the affective features extracted from images with the maximum entropy method: MEM. In the present study, the affective features comprised cross-correlation features obtained from EEGs produced when an individual observed an image. However, it is difficult to measure the EEG when a subject visualizes an unknown image. Thus, we propose a solution where a linear regression method based on canonical correlation is used to estimate the cross-correlation features from image features. Experiments were conducted to evaluate the validity of sensitivity filtering compared with image similarity retrieval methods based on image features. We found that sensitivity filtering using color correlograms was suitable for the classification of preferred images, while sensitivity filtering using local binary patterns was suitable for the classification of unpleasant images. Moreover, sensitivity filtering using local binary patterns for unpleasant images had a 90% success rate. Thus, we conclude that the proposed method is efficient for filtering unpleasant images.

  1. Leakage Current Waveforms and Arcing Characteristics of Epoxy Resin for Outdoor Insulators under Clean and Salt Fogs

    Directory of Open Access Journals (Sweden)

    Suwarno

    2008-05-01

    Full Text Available Ceramic outdoor insulators have been used in high voltage transmission lines since long time ago. Due to superiority in their resistance to pollution, recently, polymeric outdoor insulators are widely used. Epoxy resin is one polymer which shows good properties for outdoor insulation. During service, outdoor insulators may severe a certain degree of pollution which may reduce their surface resistance. Leakage current (LC usually increase and degradation may take place. This paper reports experimental results on the leakage current waveforms and arcing characteristics of epoxy resin under clean and salt fog. The samples used are blocks of epoxy resin with dimension of 250 x 50 x 20 mm3. The samples were put in a test chamber with dimension of 900x900x1200 mm3 with controllable humidity and pollution conditions. Clean and salt fog were generated according to IEC 60-1 and 507. The arcing experiment was done with incline plane test in accordance with IEC 587. AC voltage in the range from 5 kV to 50 kV with frequency of 50 Hz was applied. The LC waveforms up to flash over were measured. The magnitudes as well as harmonic content of the LC were analyzed. The correlation between LC waveforms and dry band arching phenomenon was elaborated. Visual observation of the arc on the sample surfaces was observed using a video camera. Experimental results indicated that LC magnitude on clean samples was slightly affected by humidity (RH. However, under salt fog, RH greatly affected the LC magnitude. The flashover voltage of clean samples under salt fog reduced significantly for fog conductivity of more than 1.2 mS/cm. Kaolin-polluted samples under salt fog showed an Ohmic behaviour. The LC magnitude was high and a large discrepancy of LC magnitude was observed for high applied voltage of larger than 25 kV. The largest LC magnitude was observed on salt-kaolin polluted samples under clean fog at high RH. LC waveforms analysis indicated that in general LC waveforms

  2. Nonlinear Analysis on Cross-Correlation of Financial Time Series by Continuum Percolation System

    Science.gov (United States)

    Niu, Hongli; Wang, Jun

    We establish a financial price process by continuum percolation system, in which we attribute price fluctuations to the investors’ attitudes towards the financial market, and consider the clusters in continuum percolation as the investors share the same investment opinion. We investigate the cross-correlations in two return time series, and analyze the multifractal behaviors in this relationship. Further, we study the corresponding behaviors for the real stock indexes of SSE and HSI as well as the liquid stocks pair of SPD and PAB by comparison. To quantify the multifractality in cross-correlation relationship, we employ multifractal detrended cross-correlation analysis method to perform an empirical research for the simulation data and the real markets data.

  3. Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter

    Science.gov (United States)

    Tröster, Tilman; Camera, Stefano; Fornasa, Mattia; Regis, Marco; van Waerbeke, Ludovic; Harnois-Déraps, Joachim; Ando, Shin'ichiro; Bilicki, Maciej; Erben, Thomas; Fornengo, Nicolao; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kuijken, Konrad; Viola, Massimo

    2017-05-01

    We measure the cross-correlation between Fermi gamma-ray photons and over 1000 deg2 of weak lensing data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the Red Cluster Sequence Lensing Survey (RCSLenS), and the Kilo Degree Survey (KiDS). We present the first measurement of tomographic weak lensing cross-correlations and the first application of spectral binning to cross-correlations between gamma rays and weak lensing. The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription. We verify the accuracy of our covariance estimate by comparing it to two internal covariance estimators. Based on the non-detection of a cross-correlation signal, we derive constraints on weakly interacting massive particle (WIMP) dark matter. We compute exclusion limits on the dark matter annihilation cross-section , decay rate Γdec and particle mass mDM. We find that in the absence of a cross-correlation signal, tomography does not significantly improve the constraining power of the analysis. Assuming a strong contribution to the gamma-ray flux due to small-scale clustering of dark matter and accounting for known astrophysical sources of gamma rays, we exclude the thermal relic cross-section for particle masses of mDM ≲ 20 GeV.

  4. Detecting Near-Earth Objects Using Cross-Correlation with a Point Spread Function

    Science.gov (United States)

    2009-03-01

    impact in the Yucatan Peninsula caused the extinction of the dinosaurs in the Cretaceous Period [Fix, 1995]. Even the Moon is pot marked by many...the atmosphere that the light traverses. For this reason , it is typically better to be at higher elevations to decrease the amount of atmosphere the...detection on average for the Rayleigh sampling with cross-correlation of a PSF than the Rayleigh sampling without cross- correlation. For this reason

  5. Spatially varying cross-correlation coefficients in the presence of nugget effects

    KAUST Repository

    Kleiber, William; Genton, Marc G.

    2012-01-01

    We derive sufficient conditions for the cross-correlation coefficient of a multivariate spatial process to vary with location when the spatial model is augmented with nugget effects. The derived class is valid for any choice of covariance functions, and yields substantial flexibility between multiple processes. The key is to identify the cross-correlation coefficient matrix with a contraction matrix, which can be either diagonal, implying a parsimonious formulation, or a fully general contraction matrix, yielding greater flexibility but added model complexity. We illustrate the approach with a bivariate minimum and maximum temperature dataset in Colorado, allowing the two variables to be positively correlated at low elevations and nearly independent at high elevations, while still yielding a positive definite covariance matrix. © 2012 Biometrika Trust.

  6. Spatially varying cross-correlation coefficients in the presence of nugget effects

    KAUST Repository

    Kleiber, William

    2012-11-29

    We derive sufficient conditions for the cross-correlation coefficient of a multivariate spatial process to vary with location when the spatial model is augmented with nugget effects. The derived class is valid for any choice of covariance functions, and yields substantial flexibility between multiple processes. The key is to identify the cross-correlation coefficient matrix with a contraction matrix, which can be either diagonal, implying a parsimonious formulation, or a fully general contraction matrix, yielding greater flexibility but added model complexity. We illustrate the approach with a bivariate minimum and maximum temperature dataset in Colorado, allowing the two variables to be positively correlated at low elevations and nearly independent at high elevations, while still yielding a positive definite covariance matrix. © 2012 Biometrika Trust.

  7. Lane marking detection based on waveform analysis and CNN

    Science.gov (United States)

    Ye, Yang Yang; Chen, Hou Jin; Hao, Xiao Li

    2017-06-01

    Lane markings detection is a very important part of the ADAS to avoid traffic accidents. In order to obtain accurate lane markings, in this work, a novel and efficient algorithm is proposed, which analyses the waveform generated from the road image after inverse perspective mapping (IPM). The algorithm includes two main stages: the first stage uses an image preprocessing including a CNN to reduce the background and enhance the lane markings. The second stage obtains the waveform of the road image and analyzes the waveform to get lanes. The contribution of this work is that we introduce local and global features of the waveform to detect the lane markings. The results indicate the proposed method is robust in detecting and fitting the lane markings.

  8. The theory and implementation of a high quality pulse width modulated waveform synthesiser applicable to voltage FED inverters

    Science.gov (United States)

    Lower, Kim Nigel

    1985-03-01

    Modulation processes associated with the digital implementation of pulse width modulation (PWM) switching strategies were examined. A software package based on a portable turnkey structure is presented. Waveform synthesizer implementation techniques are reviewed. A three phase PWM waveform synthesizer for voltage fed inverters was realized. It is based on a constant carrier frequency of 18 kHz and a regular sample, single edge, asynchronous PWM switching scheme. With high carrier frequencies, it is possible to utilize simple switching strategies and as a consequence, many advantages are highlighted, emphasizing the importance to industrial and office markets.

  9. Waveform efficiency analysis of auditory nerve fiber stimulation for cochlear implants

    International Nuclear Information System (INIS)

    Navaii, Mehdi Lotfi; Sadhedi, Hamed; Jalali, Mohsen

    2013-01-01

    Evaluation of the electrical stimulation efficiency of various stimulating waveforms is an important issue for efficient neural stimulator design. Concerning the implantable micro devices design, it is also necessary to consider the feasibility of hardware implementation of the desired waveforms. In this paper, the charge, power and energy efficiency of four waveforms (i.e. square, rising ramp, triangular and rising ramp-decaying exponential) in various durations have been simulated and evaluated based on the computational model of the auditory nerve fibers. Moreover, for a fair comparison of their feasibility, a fully integrated current generator circuit has been developed so that the desired stimulating waveforms can be generated. The simulation results show that stimulation with the square waveforms is a proper choice in short and intermediate durations while the rising ramp-decaying exponential or triangular waveforms can be employed for long durations.

  10. The Comparison of Canopy Height Profiles Extracted from Ku-band Profile Radar Waveforms and LiDAR Data

    Directory of Open Access Journals (Sweden)

    Hui Zhou

    2018-05-01

    Full Text Available An airborne Ku-band frequency-modulated continuous waveform (FM-CW profiling radar, Tomoradar, records the backscatter signal from the canopy surface and the underlying ground in the southern boreal forest zone of Finland. The recorded waveforms are transformed into canopy height profiles (CHP with a similar methodology utilized in large-footprint light detection and ranging (LiDAR. The point cloud data simultaneously collected by a Velodyne® VLP-16 LiDAR on-board the same platform represent the frequency of discrete returns, which are also applied to the extraction of the CHP by calculating the gap probability and incremental distribution. To thoroughly explore the relationships of the CHP derived from Tomoradar waveforms and LiDAR data we utilized the effective waveforms of one-stripe field measurements and comparison them with four indicators, including the correlation coefficient, the root-mean-square error (RMSE of the difference, and the coefficient of determination and the RMSE of residuals of linear regression. By setting the Tomoradar footprint as 20 degrees to contain over 95% of the transmitting energy of the main lobe, the results show that 88.17% of the CHPs derived from Tomoradar waveforms correlated well with those from the LiDAR data; 98% of the RMSEs of the difference ranged between 0.002 and 0.01; 79.89% of the coefficients of determination were larger than 0.5; and 98.89% of the RMSEs of the residuals ranged from 0.001 to 0.01. Based on the investigations, we discovered that the locations of the greatest CHP derived from the Tomoradar were obviously deeper than those from the LiDAR, which indicated that the Tomoradar microwave signal had a stronger penetration capability than the LiDAR signal. Meanwhile, there are smaller differences (the average RMSEs of differences is only 0.0042 when the total canopy closure is less than 0.5 and better linear regression results in an area with a relatively open canopy than with a denser

  11. Effects of waveform model systematics on the interpretation of GW150914

    OpenAIRE

    Abbott, B. P.; Abbott, R.; Adhikari, R. X.; Ananyeva, A.; Anderson, S. B.; Appert, S.; Arai, K.; Araya, M. C.; Barayoga, J. C.; Barish, B. C.; Berger, B. K.; Billingsley, G.; Biscans, S; Blackburn, J. K.; Bork, R.

    2017-01-01

    Parameter estimates of GW150914 were obtained using Bayesian inference, based on three semi-analytic waveform models for binary black hole coalescences. These waveform models differ from each other in their treatment of black hole spins, and all three models make some simplifying assumptions, notably to neglect sub-dominant waveform harmonic modes and orbital eccentricity. Furthermore, while the models are calibrated to agree with waveforms obtained by full numerical solutions of Einstein's e...

  12. Discriminating Induced-Microearthquakes Using New Seismic Features

    Science.gov (United States)

    Mousavi, S. M.; Horton, S.

    2016-12-01

    We studied characteristics of induced-microearthquakes on the basis of the waveforms recorded on a limited number of surface receivers using machine-learning techniques. Forty features in the time, frequency, and time-frequency domains were measured on each waveform, and several techniques such as correlation-based feature selection, Artificial Neural Networks (ANNs), Logistic Regression (LR) and X-mean were used as research tools to explore the relationship between these seismic features and source parameters. The results show that spectral features have the highest correlation to source depth. Two new measurements developed as seismic features for this study, spectral centroids and 2D cross-correlations in the time-frequency domain, performed better than the common seismic measurements. These features can be used by machine learning techniques for efficient automatic classification of low energy signals recorded at one or more seismic stations. We applied the technique to 440 microearthquakes-1.7Reference: Mousavi, S.M., S.P. Horton, C. A. Langston, B. Samei, (2016) Seismic features and automatic discrimination of deep and shallow induced-microearthquakes using neural network and logistic regression, Geophys. J. Int. doi: 10.1093/gji/ggw258.

  13. Centered Differential Waveform Inversion with Minimum Support Regularization

    KAUST Repository

    Kazei, Vladimir

    2017-05-26

    Time-lapse full-waveform inversion has two major challenges. The first one is the reconstruction of a reference model (baseline model for most of approaches). The second is inversion for the time-lapse changes in the parameters. Common model approach is utilizing the information contained in all available data sets to build a better reference model for time lapse inversion. Differential (Double-difference) waveform inversion allows to reduce the artifacts introduced into estimates of time-lapse parameter changes by imperfect inversion for the baseline-reference model. We propose centered differential waveform inversion (CDWI) which combines these two approaches in order to benefit from both of their features. We apply minimum support regularization commonly used with electromagnetic methods of geophysical exploration. We test the CDWI method on synthetic dataset with random noise and show that, with Minimum support regularization, it provides better resolution of velocity changes than with total variation and Tikhonov regularizations in time-lapse full-waveform inversion.

  14. EPG waveform library for Graphocephala atropunctata (Hemiptera: Cicadellidae): Effect of adhesive, input resistor, and voltage levels on waveform appearance and stylet probing behaviors.

    Science.gov (United States)

    Cervantes, Felix A; Backus, Elaine A

    2018-05-31

    Blue-green sharpshooter, Graphocephala atropunctata, is a native California vector of Xylella fastidiosa (Xf), a foregut-borne bacterium that is the causal agent of Pierce's disease in grapevines. A 3rd-generation, AC-DC electropenetrograph (EPG monitor) was used to record stylet probing and ingestion behaviors of adult G. atropunctata on healthy grapevines. This study presents for the first time a complete, updated waveform library for this species, as well as effects of different electropenetrograph settings and adhesives on waveform appearances. Both AC and DC applied signals were used with input resistor (Ri) levels (amplifier sensitivities) of 10 6 , 10 7 , 10 8 and 10 9  Ohms, as well as two type of adhesives, conducting silver paint and handmade silver glue. Waveform description, characterization of electrical origins (R versus emf components), and proposed biological meanings of waveforms are reported, as well as qualitative differences in waveform appearances observed with different electropenetrograph settings and adhesives. In addition, a quantitative study with AC signal, using two applied voltage levels (50 and 200 mV) and two Ri levels (10 7 and 10 9  Ohms) was performed. Intermediate Ri levels 10 7 and 10 8  Ohms provided EPG waveforms with the greatest amount of information, because both levels captured similar proportions of R and emf components, as supported by appearance, clarity, and definition of waveforms. Similarly, use of a gold wire loop plus handmade silver glue provided more definition of waveforms than a gold wire loop plus commercial conducting silver paint. Qualitative/observational evidence suggested that AC applied signal caused fewer aberrant behaviors/waveforms than DC applied signal. In the quantitative study, behavioral components of the sharpshooter X wave were the most affected by changes in Ri and voltage level. Because the X wave probably represents X. fastidiosa inoculation behavior, future studies of X. fastidiosa

  15. The dependence of Pi2 waveforms on periodic velocity enhancements within bursty bulk flows

    Directory of Open Access Journals (Sweden)

    K. R. Murphy

    2011-03-01

    Full Text Available Pi2s are a category of Ultra Low Frequency (ULF waves associated with the onset of magnetic substorms. Recent work has suggested that the deceleration of bulk plasma flows in the central plasmasheet, known as bursty bulk flows (BBFs, are able to directly-drive Pi2 oscillations. Some of these studies have further shown evidence that there is a one-to-one correlation between Pi2 magnetic waveforms observed on the ground and periodic peaks in flow velocity within the BBF, known as flow bursts. Utilising a favourable conjunction between the Geotail spacecraft and the Canadian Array for Real-time Investigations of Magnetic Activity (CARISMA magnetometer array on 31 May 1998, we examine the causality of the link between BBF flow bursts and Pi2 waveforms. Using a series of analytical tests in both the time and frequency domains, we find that while the Pi2 and BBF waveforms are very similar, the ground response for this event occurs prior to the observed flow enhancements in the magnetotail. We conclude that during this specific case study the temporal variations of the flow bursts within the BBF are not directly-driving the observed ground-based Pi2 waveforms, despite the fact that a visual inspection of both time-series might initially suggest that there is a causal relationship. We postulate that rather than there being a direct causal relation, the similar waveforms observed in both Pi2s and BBFs may result from temporal variations in a common source for both the BBFs and the Pi2s, such as magnetic reconnection in the tail, this source modulating both the Pi2 and BBF at the same frequency.

  16. Influence of crystal orientation on magnetostriction waveform in grain orientated electrical steel

    Energy Technology Data Exchange (ETDEWEB)

    Kijima, Gou, E-mail: g-kijima@jfe-steel.co.jp [Steel Research Laboratory, JFE Steel Corporation, Kawasaki, 210-0855 (Japan); Yamaguchi, Hiroi; Senda, Kunihiro; Hayakawa, Yasuyuki [Steel Research Laboratory, JFE Steel Corporation, Kurashiki, 712-8511 (Japan)

    2014-08-01

    Aiming to gain insight into the mechanisms of grain-oriented electrical steel sheet magnetostriction waveforms, we investigated the influence of crystal orientations. An increase in the β angle results in an increase in the amplitude of magnetostriction waveform, but does not affect the waveform itself. By slanting the excitation direction to simulate the change of the α angle, change in the magnetostriction waveform and a constriction–extension transition point in the steel plate was observed. The amplitude, however, was not significantly affected. We explained the nature of constriction–extension transition point in the magnetostriction waveform by considering the magnetization rotation. We speculated that the change of waveform resulting from the increase in the coating tensile stress can be attributed to the phenomenon of the magnetization rotation becoming hard to be generated due to the increase of magnetic anisotropy toward [001] axis. - Highlights: • β angle is related with the amplitude of magnetostriction waveform. • α angle is related with the magnetostriction waveform itself. • The effect of α angle can be controlled by the effect of coating tensile stress.

  17. Sinusoidal oscillators and waveform generators using modern electronic circuit building blocks

    CERN Document Server

    Senani, Raj; Singh, V K; Sharma, R K

    2016-01-01

    This book serves as a single-source reference to sinusoidal oscillators and waveform generators, using classical as well as a variety of modern electronic circuit building blocks. It provides a state-of-the-art review of a large variety of sinusoidal oscillators and waveform generators and includes a catalogue of over 600 configurations of oscillators and waveform generators, describing their relevant design details and salient performance features/limitations. The authors discuss a number of interesting, open research problems and include a comprehensive collection of over 1500 references on oscillators and non-sinusoidal waveform generators/relaxation oscillators. Offers readers a single-source reference to everything connected to sinusoidal oscillators and waveform generators, using classical as well as modern electronic circuit building blocks; Provides a state-of-the-art review of a large variety of sinusoidal oscillators and waveform generators; Includes a catalog of over 600 configurations of oscillato...

  18. Initial results with time series forecasting of TJ-II heliac waveforms

    International Nuclear Information System (INIS)

    Farias, G.; Dormido-Canto, S.; Vega, J.; Díaz, N.

    2015-01-01

    This article discusses about how to apply forecasting techniques to predict future samples of plasma signals during a discharge. One application of the forecasting could be to detect in real time anomalous behaviors in fusion waveforms. The work describes the implementation of three prediction techniques; two of them based on machine learning methods such as artificial neural networks and support vector machines for regression. The results have shown that depending on the temporal horizon, the predictions match the real samples in most cases with an error less than 5%, even more the forecasting of five samples ahead can reach accuracy over 90% in most signals analyzed.

  19. Multiparameter Elastic Full Waveform Inversion with Facies-based Constraints

    KAUST Repository

    Zhang, Zhendong; Alkhalifah, Tariq Ali; Naeini, Ehsan Zabihi; Sun, Bingbing

    2018-01-01

    Full waveform inversion (FWI) incorporates all the data characteristics to estimate the parameters described by the assumed physics of the subsurface. However, current efforts to utilize full waveform inversion beyond improved acoustic imaging, like

  20. Power-law cross-correlations estimation under heavy tails

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav

    2016-01-01

    Roč. 40, č. 1 (2016), s. 163-172 ISSN 1007-5704 R&D Projects: GA ČR(CZ) GP14-11402P Institutional support: RVO:67985556 Keywords : Power-law cross-correlations * Heavy tails * Monte Carlo study Subject RIV: AH - Economics Impact factor: 2.784, year: 2016 http://library.utia.cas.cz/separaty/2016/E/kristoufek-0472030.pdf

  1. Binary joint transform correlation using error-diffusion techniques

    Science.gov (United States)

    Inbar, Hanni; Marom, Emanuel; Konforti, Naim

    1993-08-01

    Optical pattern recognition techniques based on the optical joint transform correlator (JTC) scheme are attractive due to their simplicity. Recent improvements in spatial light modulators (SLM) increased the popularity of the JTC, providing means for real time operation. Using a binary SLM for the display of the Fourier spectrum, first requires binarization of the joint power spectrum distribution. Although hard-clipping is the simplest and most common binarization method used, we suggest to apply error-diffusion as an improved binarization technique. The performance of a binary JTC, whose input image is considered to contain additive zero-mean white Gaussian noise, is investigated. Various ways for nonlinearly modifying the joint power spectrum prior to the binarization step, which is based on either error-diffusion or hard-clipping techniques, are discussed. These nonlinear modifications aim at increasing the contrast of the interference fringes at the joint power spectrum plane, leading to better definition of the correlation signal. Mathematical analysis, computer simulations and experimental results are presented.

  2. Source-independent elastic waveform inversion using a logarithmic wavefield

    KAUST Repository

    Choi, Yun Seok; Min, Dong Joon

    2012-01-01

    The logarithmic waveform inversion has been widely developed and applied to some synthetic and real data. In most logarithmic waveform inversion algorithms, the subsurface velocities are updated along with the source estimation. To avoid estimating

  3. Waveform inversion for acoustic VTI media in frequency domain

    KAUST Repository

    Wu, Zedong; Alkhalifah, Tariq Ali

    2016-01-01

    Reflected waveform inversion (RWI) provides a method to reduce the nonlinearity of the standard full waveform inversion (FWI) by inverting for the background model using a single scattered wavefield from an inverted perturbation. However, current

  4. Principles of waveform diversity and design

    CERN Document Server

    Wicks, Michael

    2011-01-01

    This is the first book to discuss current and future applications of waveform diversity and design in subjects such as radar and sonar, communications systems, passive sensing, and many other technologies. Waveform diversity allows researchers and system designers to optimize electromagnetic and acoustic systems for sensing, communications, electronic warfare or combinations thereof. This book enables solutions to problems, explaining how each system performs its own particular function, as well as how it is affected by other systems and how those other systems may likewise be affected. It is

  5. Heeding the waveform inversion nonlinearity by unwrapping the model and data

    KAUST Repository

    Alkhalifah, Tariq Ali

    2012-01-01

    Unlike traveltime inversion, waveform inversion provides relatively higher-resolution inverted models. This feature, however, comes at the cost of introducing complex nonlinearity to the inversion operator complicating the convergence process. We use unwrapped-phase-based objective functions to reduce such nonlinearity in a domain in which the high-frequency component is given by the traveltime inversion. Such information is packaged in a frequency-dependent attribute (or traveltime) that can be easily manipulated at different frequencies. It unwraps the phase of the wavefield yielding far less nonlinearity in the objective function than those experienced with the conventional misfit objective function, and yet it still holds most of the critical waveform information in its frequency dependency. However, it suffers from nonlinearity introduced by the model (or reflectivity), as events interact with each other (something like cross talk). This stems from the sinusoidal nature of the band-limited reflectivity model. Unwrapping the phase for such a model can mitigate this nonlinearity as well. Specifically, a simple modification to the inverted domain (or model), can reduce the effect of the model-induced nonlinearity and, thus, make the inversion more convergent. Simple examples are used to highlight such features.

  6. Minimizing the trend effect on detrended cross-correlation analysis with empirical mode decomposition

    International Nuclear Information System (INIS)

    Zhao Xiaojun; Shang Pengjian; Zhao Chuang; Wang Jing; Tao Rui

    2012-01-01

    Highlights: ► Investigate the effects of linear, exponential and periodic trends on DCCA. ► Apply empirical mode decomposition to extract trend term. ► Strong and monotonic trends are successfully eliminated. ► Get the cross-correlation exponent in a persistent behavior without crossover. - Abstract: Detrended cross-correlation analysis (DCCA) is a scaling method commonly used to estimate long-range power law cross-correlation in non-stationary signals. However, the susceptibility of DCCA to trends makes the scaling results difficult to analyze due to spurious crossovers. We artificially generate long-range cross-correlated signals and systematically investigate the effect of linear, exponential and periodic trends. Specifically to the crossovers raised by trends, we apply empirical mode decomposition method which decomposes underlying signals into several intrinsic mode functions (IMF) and a residual trend. After the removal of residual term, strong and monotonic trends such as linear and exponential trends are successfully eliminated. But periodic trend cannot be separated out according to the criterion of IMF, which can be eliminated by Fourier transform. As a special case of DCCA, detrended fluctuation analysis presents similar results.

  7. Cross correlations of quantum key distribution based on single-photon sources

    International Nuclear Information System (INIS)

    Dong Shuangli; Wang Xiaobo; Zhang Guofeng; Sun Jianhu; Zhang Fang; Xiao Liantuan; Jia Suotang

    2009-01-01

    We theoretically analyze the second-order correlation function in a quantum key distribution system with real single-photon sources. Based on single-event photon statistics, the influence of the modification caused by an eavesdropper's intervention and the effects of background signals on the cross correlations between authorized partners are presented. On this basis, we have shown a secure range of correlation against the intercept-resend attacks.

  8. Weak value amplification via second-order correlated technique

    International Nuclear Information System (INIS)

    Cui Ting; Huang Jing-Zheng; Zeng Gui-Hua; Liu Xiang

    2016-01-01

    We propose a new framework combining weak measurement and second-order correlated technique. The theoretical analysis shows that weak value amplification (WVA) experiment can also be implemented by a second-order correlated system. We then build two-dimensional second-order correlated function patterns for achieving higher amplification factor and discuss the signal-to-noise ratio influence. Several advantages can be obtained by our proposal. For instance, detectors with high resolution are not necessary. Moreover, detectors with low saturation intensity are available in WVA setup. Finally, type-one technical noise can be effectively suppressed. (paper)

  9. Cosmic microwave and infrared backgrounds cross-correlation for ISW detection

    International Nuclear Information System (INIS)

    Ilić, S

    2014-01-01

    We have investigated the cross-correlation between the cosmic infrared and microwave backgrounds (CIB and CMB) anisotropies through the integrated Sachs-Wolfe effect. We have first described the CIB anisotropies using a linearly biased power spectrum, then derive the theoretical angular power spectrum of the CMB-CIB cross-correlation for different instruments and frequencies. We have discussed the detectability of the ISW signal by performing a signal-to-noise (SNR) analysis with our predicted spectra. The significances obtained range from 6σ to 7σ in an ideal case, depending on the frequency; in realistic cases which account for the presence of noise including astrophysical contaminants, the results span the range 2 – 5σ, depending strongly on the major contribution to the noise term

  10. Faithful effective-one-body waveforms of small-mass-ratio coalescing black hole binaries

    International Nuclear Information System (INIS)

    Damour, Thibault; Nagar, Alessandro

    2007-01-01

    We address the problem of constructing high-accuracy, faithful analytic waveforms describing the gravitational wave signal emitted by inspiralling and coalescing binary black holes. We work within the effective-one-body (EOB) framework and propose a methodology for improving the current (waveform) implementations of this framework based on understanding, element by element, the physics behind each feature of the waveform and on systematically comparing various EOB-based waveforms with exact waveforms obtained by numerical relativity approaches. The present paper focuses on small-mass-ratio nonspinning binary systems, which can be conveniently studied by Regge-Wheeler-Zerilli-type methods. Our results include (i) a resummed, 3 PN-accurate description of the inspiral waveform, (ii) a better description of radiation reaction during the plunge, (iii) a refined analytic expression for the plunge waveform, (iv) an improved treatment of the matching between the plunge and ring-down waveforms. This improved implementation of the EOB approach allows us to construct complete analytic waveforms which exhibit a remarkable agreement with the exact ones in modulus, frequency, and phase. In particular, the analytic and numerical waveforms stay in phase, during the whole process, within ±1.1% of a cycle. We expect that the extension of our methodology to the comparable-mass case will be able to generate comparably accurate analytic waveforms of direct use for the ground-based network of interferometric detectors of gravitational waves

  11. The development of the miniaturized waveform receiver with the function measuring Antenna Impedance in space plasmas

    Science.gov (United States)

    Ishii, H.; Kojima, H.; Fukuhara, H.; Okada, S.; Yamakawa, H.

    2012-04-01

    ) is in attention which is a technique to integrate large scale and complicated circuits. Lots of ASICs have been applied to high energy astrophysics. In this paper, we show our attempt to miniaturize the antennas impedances measurement system and Waveform Capture using the analogue ASIC. We design 8bits segment D/A converter that is implemented inside the waveform receiver ASIC chip. We improve input logic of the D/A converter to generate very weak signals accurately. The designed chip realizes the measurement of the antenna impedance as well as the waveform observation in the board size of business cards.

  12. Image-domain full waveform inversion

    KAUST Repository

    Zhang, Sanzong

    2013-08-20

    The main difficulty with the data-domain full waveform inversion (FWI) is that it tends to get stuck in the local minima associated with the waveform misfit function. This is because the waveform misfit function is highly nonlinear with respect to changes in velocity model. To reduce this nonlinearity, we define the image-domain objective function to minimize the difference of the suboffset-domain common image gathers (CIGs) obtained by migrating the observed data and the calculated data. The derivation shows that the gradient of this new objective function is the combination of the gradient of the conventional FWI and the image-domain differential semblance optimization (DSO). Compared to the conventional FWI, the imagedomain FWI is immune to cycle skipping problems by smearing the nonzero suboffset images along wavepath. It also can avoid the edge effects and the gradient artifacts that are inherent in DSO due to the falsely over-penalized focused images. This is achieved by subtracting the focused image associated with the calculated data from the unfocused image associated with the observed data in the image-domain misfit function. The numerical results of the Marmousi model show that image-domain FWI is less sensitive the initial model than the conventional FWI. © 2013 SEG.

  13. Image-domain full waveform inversion

    KAUST Repository

    Zhang, Sanzong; Schuster, Gerard T.

    2013-01-01

    The main difficulty with the data-domain full waveform inversion (FWI) is that it tends to get stuck in the local minima associated with the waveform misfit function. This is because the waveform misfit function is highly nonlinear with respect to changes in velocity model. To reduce this nonlinearity, we define the image-domain objective function to minimize the difference of the suboffset-domain common image gathers (CIGs) obtained by migrating the observed data and the calculated data. The derivation shows that the gradient of this new objective function is the combination of the gradient of the conventional FWI and the image-domain differential semblance optimization (DSO). Compared to the conventional FWI, the imagedomain FWI is immune to cycle skipping problems by smearing the nonzero suboffset images along wavepath. It also can avoid the edge effects and the gradient artifacts that are inherent in DSO due to the falsely over-penalized focused images. This is achieved by subtracting the focused image associated with the calculated data from the unfocused image associated with the observed data in the image-domain misfit function. The numerical results of the Marmousi model show that image-domain FWI is less sensitive the initial model than the conventional FWI. © 2013 SEG.

  14. A New Waveform Mosaic Algorithm in the Vectorization of Paper Seismograms

    Directory of Open Access Journals (Sweden)

    Maofa Wang

    2014-11-01

    Full Text Available History paper seismograms are very important information for earthquake monitoring and prediction, and the vectorization of paper seismograms is a very import problem to be resolved. In this paper, a new waveform mosaic algorithm in the vectorization of paper seismograms is presented. We also give out the technological process to waveform mosaic, and a waveform mosaic system used to vectorize analog seismic record has been accomplished independently. Using it, we can precisely and speedy accomplish waveform mosaic for vectorizing analog seismic records.

  15. Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse γ-ray emission

    International Nuclear Information System (INIS)

    Camera, S.; Fornasa, M.; Fornengo, N.; Regis, M.

    2015-01-01

    We recently proposed to cross-correlate the diffuse extragalactic γ-ray background with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search for annihilating or decaying particle dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in separate bins of redshift and energy significantly improves the sensitivity to a DM signal. Indeed, the technique proposed here takes advantage of the different scaling of the astrophysical and DM components with redshift and, simultaneously of their different energy spectra and different angular extensions. The sensitivity to a particle DM signal is extremely promising even when the DM-induced emission is quite faint. We first quantify the prospects of detecting DM by cross-correlating the Fermi Large Area Telescope (LAT) diffuse γ-ray background with the cosmic shear expected from the Dark Energy Survey. Under the hypothesis of a significant subhalo boost, such a measurement can deliver a 5σ detection of DM, if the DM particle is lighter than 300 GeV and has a thermal annihilation rate. We then forecast the capability of the European Space Agency Euclid satellite (whose launch is planned for 2020), in combination with an hypothetical future γ-ray detector with slightly improved specifications compared to current telescopes. We predict that the cross-correlation of their data will allow a measurement of the DM mass with an uncertainty of a factor of 1.5–2, even for moderate subhalo boosts, for DM masses up to few hundreds of GeV and thermal annihilation rates

  16. Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse γ-ray emission

    Energy Technology Data Exchange (ETDEWEB)

    Camera, S. [Jodrell Bank Centre for Astrophysics, The University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom); Fornasa, M. [School of Physics and Astronomy, University of Nottingham, University Campus, Nottingham NG7 2RD (United Kingdom); Fornengo, N.; Regis, M., E-mail: stefano.camera@manchester.ac.uk, E-mail: fornasam@gmail.com, E-mail: fornengo@to.infn.it, E-mail: regis@to.infn.it [Dipartimento di Fisica, Università di Torino, Via P. Giuria 1, 10125 Torino (Italy)

    2015-06-01

    We recently proposed to cross-correlate the diffuse extragalactic γ-ray background with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search for annihilating or decaying particle dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in separate bins of redshift and energy significantly improves the sensitivity to a DM signal. Indeed, the technique proposed here takes advantage of the different scaling of the astrophysical and DM components with redshift and, simultaneously of their different energy spectra and different angular extensions. The sensitivity to a particle DM signal is extremely promising even when the DM-induced emission is quite faint. We first quantify the prospects of detecting DM by cross-correlating the Fermi Large Area Telescope (LAT) diffuse γ-ray background with the cosmic shear expected from the Dark Energy Survey. Under the hypothesis of a significant subhalo boost, such a measurement can deliver a 5σ detection of DM, if the DM particle is lighter than 300 GeV and has a thermal annihilation rate. We then forecast the capability of the European Space Agency Euclid satellite (whose launch is planned for 2020), in combination with an hypothetical future γ-ray detector with slightly improved specifications compared to current telescopes. We predict that the cross-correlation of their data will allow a measurement of the DM mass with an uncertainty of a factor of 1.5–2, even for moderate subhalo boosts, for DM masses up to few hundreds of GeV and thermal annihilation rates.

  17. Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse γ-ray emission

    Science.gov (United States)

    Camera, S.; Fornasa, M.; Fornengo, N.; Regis, M.

    2015-06-01

    We recently proposed to cross-correlate the diffuse extragalactic γ-ray background with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search for annihilating or decaying particle dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in separate bins of redshift and energy significantly improves the sensitivity to a DM signal. Indeed, the technique proposed here takes advantage of the different scaling of the astrophysical and DM components with redshift and, simultaneously of their different energy spectra and different angular extensions. The sensitivity to a particle DM signal is extremely promising even when the DM-induced emission is quite faint. We first quantify the prospects of detecting DM by cross-correlating the Fermi Large Area Telescope (LAT) diffuse γ-ray background with the cosmic shear expected from the Dark Energy Survey. Under the hypothesis of a significant subhalo boost, such a measurement can deliver a 5σ detection of DM, if the DM particle is lighter than 300 GeV and has a thermal annihilation rate. We then forecast the capability of the European Space Agency Euclid satellite (whose launch is planned for 2020), in combination with an hypothetical future γ-ray detector with slightly improved specifications compared to current telescopes. We predict that the cross-correlation of their data will allow a measurement of the DM mass with an uncertainty of a factor of 1.5-2, even for moderate subhalo boosts, for DM masses up to few hundreds of GeV and thermal annihilation rates.

  18. A study of doppler waveform using pulsatile flow model

    International Nuclear Information System (INIS)

    Chung, Hye Won; Chung, Myung Jin; Park, Jae Hyung; Chung, Jin Wook; Lee, Dong Hyuk; Min, Byoung Goo

    1997-01-01

    Through the construction of a pulsatile flow model using an artificial heart pump and stenosis to demonstrate triphasic Doppler waveform, which simulates in vivo conditions, and to evaluate the relationship between Doppler waveform and vascular compliance. The flow model was constructed using a flowmeter, rubber tube, glass tube with stenosis, and artificial heart pump. Doppler study was carried out at the prestenotic, poststenotic, and distal segments;compliance was changed by changing the length of the rubber tube. With increasing proximal compliance, Doppler waveforms show decreasing peak velocity of the first phase and slightly delayed acceleration time, but the waveform itself did not change significantly. Distal compliance influenced the second phase, and was important for the formation of pulsus tardus and parvus, which without poststenotic vascular compliance, did not develop. The peak velocity of the first phase was inversely proportional to proximal compliance, and those of the second and third phases were directly proportional to distal compliance. After constructing this pulsatile flow model, we were able to explain the relationship between vascular compliance and Doppler waveform, and also better understand the formation of pulsus tardus and parvus

  19. A Novel wave-form command shaper for overhead cranes

    Directory of Open Access Journals (Sweden)

    KHALED ALHAZZA

    2013-12-01

    Full Text Available In this work, a novel command shaping control strategy for oscillation reduction of simple harmonic oscillators is proposed, and validated experimentally. A wave-form acceleration command shaper is derived analytically. The performance of the proposed shaper is simulated numerically, and validated experimentally on a scaled model of an overhead crane. Amplitude modulation is used to enhance the shaper performance, which results in a modulated wave-form command shaper. It is determined that the proposed wave-form and modulated wave-form command shaper profiles are capable of eliminating travel and residual oscillations. Furthermore, unlike traditional impulse and step command shapers, the proposed command shaper has piecewise smoother acceleration, velocity, and displacement profiles. Experimental results using continuous and discrete commands are presented. Experiments with discrete commands involved embedding a saturation model-based feedback in the algorithm of the command shaper.

  20. Multichannel waveform display system

    International Nuclear Information System (INIS)

    Kolvankar, V.G.

    1989-01-01

    For any multichannel data acquisition system, a multichannel paper chart recorder undoubtedly forms an essential part of the system. When deployed on-line, it instantaneously provides, for visual inspection, hard copies of the signal waveforms on common time base at any desired sensitivity and time resolution. Within the country, only a small range of these strip chart recorder s is available, and under stringent specifications imported recorders are often procured. The cost of such recorders may range from 1 to 5 lakhs of rupees in foreign exchange. A system to provide on the oscilloscope a steady display of multichannel waveforms, refreshed from the digital data stored in the memory is developed. The merits and demerits of the display system are compared with that built around a conventional paper chart recorder. Various illustrations of multichannel seismic event data acquired at Gauribidanur seismic array station are also presented. (author). 2 figs

  1. Within-footprint roughness measurements using ICESat/GLAS waveform and LVIS elevation

    International Nuclear Information System (INIS)

    Li, Xiaolu; Xu, Kai; Xu, Lijun

    2016-01-01

    The surface roughness is an important characteristic over an ice sheet or glacier, since it is an identification of boundary-layer meteorology and is an important limiter on the accuracy of surface-height measurements. In this paper, we propose a simulation method to derive the within-footprint roughness (called simulation-derived roughness) using ICESat/GLAS echo waveform, laser vegetation imaging sensor (LVIS) elevations, and laser profile array (LPA) images of ICESat/GLAS. By dividing the within-footprint surface into several elements, a simulation echo waveform can be obtained as the sum of the elementary pulses reflected from each surface element. The elevation of the surface elements, which is utilized to get the return time of the elementary pulses, is implemented based on an LVIS interpolated elevation using a radial basis function (RBF) neural network. The intensity of the elementary pulses can be obtained from the thresholded LPA images. Based on the return time and the intensity of the elementary pulses, we used the particle swarm optimization (PSO) method to approximate the simulation waveform to the ICESat/GLAS echo waveform. The full width at half maximum) (FWHM) of the elementary pulse was extracted from the simulation waveform for estimating the simulation-derived roughness. By comparing with the elevation-derived roughness (derived from the elevation) and the waveform-derived roughness (derived from the ICESat/GLAS waveform), the proposed algorithm can exclude the slope effect from waveform width broadening for describing the roughness of the surface elements. (paper)

  2. Cross-correlation analysis of pulse wave propagation in arteries: in vitro validation and in vivo feasibility.

    Science.gov (United States)

    Nauleau, Pierre; Apostolakis, Iason; McGarry, Matthew; Konofagou, Elisa

    2018-05-29

    The stiffness of the arteries is known to be an indicator of the progression of various cardiovascular diseases. Clinically, the pulse wave velocity (PWV) is used as a surrogate for arterial stiffness. Pulse wave imaging (PWI) is a non-invasive, ultrasound-based imaging technique capable of mapping the motion of the vessel walls, allowing the local assessment of arterial properties. Conventionally, a distinctive feature of the displacement wave (e.g. the 50% upstroke) is tracked across the map to estimate the PWV. However, the presence of reflections, such as those generated at the carotid bifurcation, can bias the PWV estimation. In this paper, we propose a two-step cross-correlation based method to characterize arteries using the information available in the PWI spatio-temporal map. First, the area under the cross-correlation curve is proposed as an index for locating the regions of different properties. Second, a local peak of the cross-correlation function is tracked to obtain a less biased estimate of the PWV. Three series of experiments were conducted in phantoms to evaluate the capabilities of the proposed method compared with the conventional method. In the ideal case of a homogeneous phantom, the two methods performed similarly and correctly estimated the PWV. In the presence of reflections, the proposed method provided a more accurate estimate than conventional processing: e.g. for the soft phantom, biases of  -0.27 and -0.71 m · s -1 were observed. In a third series of experiments, the correlation-based method was able to locate two regions of different properties with an error smaller than 1 mm. It also provided more accurate PWV estimates than conventional processing (biases:  -0.12 versus -0.26 m · s -1 ). Finally, the in vivo feasibility of the proposed method was demonstrated in eleven healthy subjects. The results indicate that the correlation-based method might be less precise in vivo but more accurate than the conventional method.

  3. Tabular cross section file generation and utilization techniques

    International Nuclear Information System (INIS)

    Cullen, D.E.; Ozer, O.; Weisbin, C.R.

    1975-03-01

    Criteria of importance to the generation of linear cross section tabulations are presented. Algorithms for reducing or thinning such tables within a desired accuracy criterion and the implementation of paging techniques for efficient utilization of large data tables are reviewed. (1 figure, 3 tables) (U.S.)

  4. Analytic family of post-merger template waveforms

    Science.gov (United States)

    Del Pozzo, Walter; Nagar, Alessandro

    2017-06-01

    Building on the analytical description of the post-merger (ringdown) waveform of coalescing, nonprecessing, spinning binary black holes introduced by Damour and Nagar [Phys. Rev. D 90, 024054 (2014), 10.1103/PhysRevD.90.024054], we propose an analytic, closed form, time-domain, representation of the ℓ=m =2 gravitational radiation mode emitted after merger. This expression is given as a function of the component masses and dimensionless spins (m1 ,2,χ1 ,2) of the two inspiraling objects, as well as of the mass MBH and (complex) frequency σ1 of the fundamental quasinormal mode of the remnant black hole. Our proposed template is obtained by fitting the post-merger waveform part of several publicly available numerical relativity simulations from the Simulating eXtreme Spacetimes (SXS) catalog and then suitably interpolating over (symmetric) mass ratio and spins. We show that this analytic expression accurately reproduces (˜0.01 rad ) the phasing of the post-merger data of other data sets not used in its construction. This is notably the case of the spin-aligned run SXS:BBH:0305, whose intrinsic parameters are consistent with the 90% credible intervals reported in the parameter-estimation followup of GW150914 by B.P. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016), 10.1103/PhysRevLett.116.241102]. Using SXS waveforms as "experimental" data, we further show that our template could be used on the actual GW150914 data to perform a new measure of the complex frequency of the fundamental quasinormal mode so as to exploit the complete (high signal-to-noise-ratio) post-merger waveform. We assess the usefulness of our proposed template by analyzing, in a realistic setting, SXS full inspiral-merger-ringdown waveforms and constructing posterior probability distribution functions for the central frequency damping time of the first overtone of the fundamental quasinormal mode as well as for the physical parameters of the systems. We also briefly explore the possibility

  5. Cross-correlation between EMG and center of gravity during quiet stance: theory and simulations.

    Science.gov (United States)

    Kohn, André Fabio

    2005-11-01

    Several signal processing tools have been employed in the experimental study of the postural control system in humans. Among them, the cross-correlation function has been used to analyze the time relationship between signals such as the electromyogram and the horizontal projection of the center of gravity. The common finding is that the electromyogram precedes the biomechanical signal, a result that has been interpreted in different ways, for example, the existence of feedforward control or the preponderance of a velocity feedback. It is shown here, analytically and by simulation, that the cross-correlation function is dependent in a complicated way on system parameters and on noise spectra. Results similar to those found experimentally, e.g., electromyogram preceding the biomechanical signal may be obtained in a postural control model without any feedforward control and without any velocity feedback. Therefore, correct interpretations of experimentally obtained cross-correlation functions may require additional information about the system. The results extend to other biomedical applications where two signals from a closed loop system are cross-correlated.

  6. Anisotropic wave-equation traveltime and waveform inversion

    KAUST Repository

    Feng, Shihang

    2016-09-06

    The wave-equation traveltime and waveform inversion (WTW) methodology is developed to invert for anisotropic parameters in a vertical transverse isotropic (VTI) meidum. The simultaneous inversion of anisotropic parameters v0, ε and δ is initially performed using the wave-equation traveltime inversion (WT) method. The WT tomograms are then used as starting background models for VTI full waveform inversion. Preliminary numerical tests on synthetic data demonstrate the feasibility of this method for multi-parameter inversion.

  7. Multifractal detrended cross-correlation between the Chinese domestic and international gold markets based on DCCA and DMCA methods

    Science.gov (United States)

    Cao, Guangxi; Han, Yan; Chen, Yuemeng; Yang, Chunxia

    2014-05-01

    Based on the daily price data of Shanghai and London gold spot markets, we applied detrended cross-correlation analysis (DCCA) and detrended moving average cross-correlation analysis (DMCA) methods to quantify power-law cross-correlation between domestic and international gold markets. Results show that the cross-correlations between the Chinese domestic and international gold spot markets are multifractal. Furthermore, forward DMCA and backward DMCA seems to outperform DCCA and centered DMCA for short-range gold series, which confirms the comparison results of short-range artificial data in L. Y. He and S. P. Chen [Physica A 390 (2011) 3806-3814]. Finally, we analyzed the local multifractal characteristics of the cross-correlation between Chinese domestic and international gold markets. We show that multifractal characteristics of the cross-correlation between the Chinese domestic and international gold markets are time-varying and that multifractal characteristics were strengthened by the financial crisis in 2007-2008.

  8. Full-waveform data for building roof step edge localization

    Science.gov (United States)

    Słota, Małgorzata

    2015-08-01

    Airborne laser scanning data perfectly represent flat or gently sloped areas; to date, however, accurate breakline detection is the main drawback of this technique. This issue becomes particularly important in the case of modeling buildings, where accuracy higher than the footprint size is often required. This article covers several issues related to full-waveform data registered on building step edges. First, the full-waveform data simulator was developed and presented in this paper. Second, this article provides a full description of the changes in echo amplitude, echo width and returned power caused by the presence of edges within the laser footprint. Additionally, two important properties of step edge echoes, peak shift and echo asymmetry, were noted and described. It was shown that these properties lead to incorrect echo positioning along the laser center line and can significantly reduce the edge points' accuracy. For these reasons and because all points are aligned with the center of the beam, regardless of the actual target position within the beam footprint, we can state that step edge points require geometric corrections. This article presents a novel algorithm for the refinement of step edge points. The main distinguishing advantage of the developed algorithm is the fact that none of the additional data, such as emitted signal parameters, beam divergence, approximate edge geometry or scanning settings, are required. The proposed algorithm works only on georeferenced profiles of reflected laser energy. Another major advantage is the simplicity of the calculation, allowing for very efficient data processing. Additionally, the developed method of point correction allows for the accurate determination of points lying on edges and edge point densification. For this reason, fully automatic localization of building roof step edges based on LiDAR full-waveform data with higher accuracy than the size of the lidar footprint is feasible.

  9. Closed-loop waveform control of boost inverter

    DEFF Research Database (Denmark)

    Zhu, Guo Rong; Xiao, Cheng Yuan; Wang, Haoran

    2016-01-01

    The input current of single-phase inverter typically has an AC ripple component at twice the output frequency, which causes a reduction in both the operating lifetime of its DC source and the efficiency of the system. In this paper, the closed-loop performance of a proposed waveform control method...... to eliminate such a ripple current in boost inverter is investigated. The small-signal stability and the dynamic characteristic of the inverter system for input voltage or wide range load variations under the closed-loop waveform control method are studied. It is validated that with the closedloop waveform...... control, not only was stability achieved, the reference voltage of the boost inverter capacitors can be instantaneously adjusted to match the new load, thereby achieving improved ripple mitigation for a wide load range. Furthermore, with the control and feedback mechanism, there is minimal level of ripple...

  10. Wavelet analysis of the impedance cardiogram waveforms

    Science.gov (United States)

    Podtaev, S.; Stepanov, R.; Dumler, A.; Chugainov, S.; Tziberkin, K.

    2012-12-01

    Impedance cardiography has been used for diagnosing atrial and ventricular dysfunctions, valve disorders, aortic stenosis, and vascular diseases. Almost all the applications of impedance cardiography require determination of some of the characteristic points of the ICG waveform. The ICG waveform has a set of characteristic points known as A, B, E ((dZ/dt)max) X, Y, O and Z. These points are related to distinct physiological events in the cardiac cycle. Objective of this work is an approbation of a new method of processing and interpretation of the impedance cardiogram waveforms using wavelet analysis. A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. Use of original wavelet differentiation algorithm allows combining filtration and calculation of the derivatives of rheocardiogram. The proposed approach can be used in clinical practice for early diagnostics of cardiovascular system remodelling in the course of different pathologies.

  11. Wavelet analysis of the impedance cardiogram waveforms

    International Nuclear Information System (INIS)

    Podtaev, S; Stepanov, R; Dumler, A; Chugainov, S; Tziberkin, K

    2012-01-01

    Impedance cardiography has been used for diagnosing atrial and ventricular dysfunctions, valve disorders, aortic stenosis, and vascular diseases. Almost all the applications of impedance cardiography require determination of some of the characteristic points of the ICG waveform. The ICG waveform has a set of characteristic points known as A, B, E ((dZ/dt) max ) X, Y, O and Z. These points are related to distinct physiological events in the cardiac cycle. Objective of this work is an approbation of a new method of processing and interpretation of the impedance cardiogram waveforms using wavelet analysis. A method of computer thoracic tetrapolar polyrheocardiography is used for hemodynamic registrations. Use of original wavelet differentiation algorithm allows combining filtration and calculation of the derivatives of rheocardiogram. The proposed approach can be used in clinical practice for early diagnostics of cardiovascular system remodelling in the course of different pathologies.

  12. Using convolutional neural networks to estimate time-of-flight from PET detector waveforms

    Science.gov (United States)

    Berg, Eric; Cherry, Simon R.

    2018-01-01

    Although there have been impressive strides in detector development for time-of-flight positron emission tomography, most detectors still make use of simple signal processing methods to extract the time-of-flight information from the detector signals. In most cases, the timing pick-off for each waveform is computed using leading edge discrimination or constant fraction discrimination, as these were historically easily implemented with analog pulse processing electronics. However, now with the availability of fast waveform digitizers, there is opportunity to make use of more of the timing information contained in the coincident detector waveforms with advanced signal processing techniques. Here we describe the application of deep convolutional neural networks (CNNs), a type of machine learning, to estimate time-of-flight directly from the pair of digitized detector waveforms for a coincident event. One of the key features of this approach is the simplicity in obtaining ground-truth-labeled data needed to train the CNN: the true time-of-flight is determined from the difference in path length between the positron emission and each of the coincident detectors, which can be easily controlled experimentally. The experimental setup used here made use of two photomultiplier tube-based scintillation detectors, and a point source, stepped in 5 mm increments over a 15 cm range between the two detectors. The detector waveforms were digitized at 10 GS s-1 using a bench-top oscilloscope. The results shown here demonstrate that CNN-based time-of-flight estimation improves timing resolution by 20% compared to leading edge discrimination (231 ps versus 185 ps), and 23% compared to constant fraction discrimination (242 ps versus 185 ps). By comparing several different CNN architectures, we also showed that CNN depth (number of convolutional and fully connected layers) had the largest impact on timing resolution, while the exact network parameters, such as convolutional

  13. Development of OCDMA system based on Flexible Cross Correlation (FCC) code with OFDM modulation

    Science.gov (United States)

    Aldhaibani, A. O.; Aljunid, S. A.; Anuar, M. S.; Arief, A. R.; Rashidi, C. B. M.

    2015-03-01

    The performance of the OCDMA systems is governed by numerous quantitative parameters such as the data rate, simultaneous number of users, the powers of transmitter and receiver, and the type of codes. This paper analyzes the performance of the OCDMA system using OFDM technique to enhance the channel data rate, to save power and increase the number of user of OSCDMA systems compared with previous hybrid subcarrier multiplexing/optical spectrum code division multiplexing (SCM/OSCDM) system. The average received signal to noise ratio (SNR) with the nonlinearity of subcarriers is derived. The theoretical results have been evaluated based on BER and number of users as well as amount of power saved. The proposed system gave better performance and save around -6 dBm of the power as well as increase the number of users twice compare to SCM/OCDMA system. In addition it is robust against interference and much more spectrally efficient than SCM/OCDMA system. The system was designed based on Flexible Cross Correlation (FCC) code which is easier construction, less complexity of encoder/decoder design and flexible in-phase cross-correlation for uncomplicated to implement using Fiber Bragg Gratings (FBGs) for the OCDMA systems for any number of users and weights. The OCDMA-FCC_OFDM improves the number of users (cardinality) 108% compare to SCM/ODCMA-FCC system.

  14. Computational Stimulation of the Basal Ganglia Neurons with Cost Effective Delayed Gaussian Waveforms.

    Science.gov (United States)

    Daneshzand, Mohammad; Faezipour, Miad; Barkana, Buket D

    2017-01-01

    Deep brain stimulation (DBS) has compelling results in the desynchronization of the basal ganglia neuronal activities and thus, is used in treating the motor symptoms of Parkinson's disease (PD). Accurate definition of DBS waveform parameters could avert tissue or electrode damage, increase the neuronal activity and reduce energy cost which will prolong the battery life, hence avoiding device replacement surgeries. This study considers the use of a charge balanced Gaussian waveform pattern as a method to disrupt the firing patterns of neuronal cell activity. A computational model was created to simulate ganglia cells and their interactions with thalamic neurons. From the model, we investigated the effects of modified DBS pulse shapes and proposed a delay period between the cathodic and anodic parts of the charge balanced Gaussian waveform to desynchronize the firing patterns of the GPe and GPi cells. The results of the proposed Gaussian waveform with delay outperformed that of rectangular DBS waveforms used in in-vivo experiments. The Gaussian Delay Gaussian (GDG) waveforms achieved lower number of misses in eliciting action potential while having a lower amplitude and shorter length of delay compared to numerous different pulse shapes. The amount of energy consumed in the basal ganglia network due to GDG waveforms was dropped by 22% in comparison with charge balanced Gaussian waveforms without any delay between the cathodic and anodic parts and was also 60% lower than a rectangular charged balanced pulse with a delay between the cathodic and anodic parts of the waveform. Furthermore, by defining a Synchronization Level metric, we observed that the GDG waveform was able to reduce the synchronization of GPi neurons more effectively than any other waveform. The promising results of GDG waveforms in terms of eliciting action potential, desynchronization of the basal ganglia neurons and reduction of energy consumption can potentially enhance the performance of DBS

  15. Computational Stimulation of the Basal Ganglia Neurons with Cost Effective Delayed Gaussian Waveforms

    Directory of Open Access Journals (Sweden)

    Mohammad Daneshzand

    2017-08-01

    Full Text Available Deep brain stimulation (DBS has compelling results in the desynchronization of the basal ganglia neuronal activities and thus, is used in treating the motor symptoms of Parkinson's disease (PD. Accurate definition of DBS waveform parameters could avert tissue or electrode damage, increase the neuronal activity and reduce energy cost which will prolong the battery life, hence avoiding device replacement surgeries. This study considers the use of a charge balanced Gaussian waveform pattern as a method to disrupt the firing patterns of neuronal cell activity. A computational model was created to simulate ganglia cells and their interactions with thalamic neurons. From the model, we investigated the effects of modified DBS pulse shapes and proposed a delay period between the cathodic and anodic parts of the charge balanced Gaussian waveform to desynchronize the firing patterns of the GPe and GPi cells. The results of the proposed Gaussian waveform with delay outperformed that of rectangular DBS waveforms used in in-vivo experiments. The Gaussian Delay Gaussian (GDG waveforms achieved lower number of misses in eliciting action potential while having a lower amplitude and shorter length of delay compared to numerous different pulse shapes. The amount of energy consumed in the basal ganglia network due to GDG waveforms was dropped by 22% in comparison with charge balanced Gaussian waveforms without any delay between the cathodic and anodic parts and was also 60% lower than a rectangular charged balanced pulse with a delay between the cathodic and anodic parts of the waveform. Furthermore, by defining a Synchronization Level metric, we observed that the GDG waveform was able to reduce the synchronization of GPi neurons more effectively than any other waveform. The promising results of GDG waveforms in terms of eliciting action potential, desynchronization of the basal ganglia neurons and reduction of energy consumption can potentially enhance the

  16. Enhancement of the Signal-to-Noise Ratio in Sonic Logging Waveforms by Seismic Interferometry

    KAUST Repository

    Aldawood, Ali

    2012-04-01

    Sonic logs are essential tools for reliably identifying interval velocities which, in turn, are used in many seismic processes. One problem that arises, while logging, is irregularities due to washout zones along the borehole surfaces that scatters the transmitted energy and hence weakens the signal recorded at the receivers. To alleviate this problem, I have extended the theory of super-virtual refraction interferometry to enhance the signal-to-noise ratio (SNR) sonic waveforms. Tests on synthetic and real data show noticeable signal-to-noise ratio (SNR) enhancements of refracted P-wave arrivals in the sonic waveforms. The theory of super-virtual interferometric stacking is composed of two redatuming steps followed by a stacking procedure. The first redatuming procedure is of correlation type, where traces are correlated together to get virtual traces with the sources datumed to the refractor. The second datuming step is of convolution type, where traces are convolved together to dedatum the sources back to their original positions. The stacking procedure following each step enhances the signal to noise ratio of the refracted P-wave first arrivals. Datuming with correlation and convolution of traces introduces severe artifacts denoted as correlation artifacts in super-virtual data. To overcome this problem, I replace the datuming with correlation step by datuming with deconvolution. Although the former datuming method is more robust, the latter one reduces the artifacts significantly. Moreover, deconvolution can be a noise amplifier which is why a regularization term is utilized, rendering the datuming with deconvolution more stable. Tests of datuming with deconvolution instead of correlation with synthetic and real data examples show significant reduction of these artifacts. This is especially true when compared with the conventional way of applying the super-virtual refraction interferometry method.

  17. Selection and generation of waveforms for differential mobility spectrometry.

    Science.gov (United States)

    Krylov, Evgeny V; Coy, Stephen L; Vandermey, John; Schneider, Bradley B; Covey, Thomas R; Nazarov, Erkinjon G

    2010-02-01

    Devices based on differential mobility spectrometry (DMS) are used in a number of ways, including applications as ion prefilters for API-MS systems, as detectors or selectors in hybrid instruments (GC-DMS, DMS-IMS), and in standalone systems for chemical detection and identification. DMS ion separation is based on the relative difference between high field and low field ion mobility known as the alpha dependence, and requires the application of an intense asymmetric electric field known as the DMS separation field, typically in the megahertz frequency range. DMS performance depends on the waveform and on the magnitude of this separation field. In this paper, we analyze the relationship between separation waveform and DMS resolution and consider feasible separation field generators. We examine ideal and practical DMS separation field waveforms and discuss separation field generator circuit types and their implementations. To facilitate optimization of the generator designs, we present a set of relations that connect ion alpha dependence to DMS separation fields. Using these relationships we evaluate the DMS separation power of common generator types as a function of their waveform parameters. Optimal waveforms for the major types of DMS separation generators are determined for ions with various alpha dependences. These calculations are validated by comparison with experimental data.

  18. Direct current contamination of kilohertz frequency alternating current waveforms.

    Science.gov (United States)

    Franke, Manfred; Bhadra, Niloy; Bhadra, Narendra; Kilgore, Kevin

    2014-07-30

    Kilohertz frequency alternating current (KHFAC) waveforms are being evaluated in a variety of physiological settings because of their potential to modulate neural activity uniquely when compared to frequencies in the sub-kilohertz range. However, the use of waveforms in this frequency range presents some unique challenges regarding the generator output. In this study we explored the possibility of undesirable contamination of the KHFAC waveforms by direct current (DC). We evaluated current- and voltage-controlled KHFAC waveform generators in configurations that included a capacitive coupling between generator and electrode, a resistive coupling and combinations of capacitive with inductive coupling. Our results demonstrate that both voltage- and current-controlled signal generators can unintentionally add DC-contamination to a KHFAC signal, and that capacitive coupling is not always sufficient to eliminate this contamination. We furthermore demonstrated that high value inductors, placed in parallel with the electrode, can be effective in eliminating DC-contamination irrespective of the type of stimulator, reducing the DC contamination to less than 1 μA. This study highlights the importance of carefully designing the electronic setup used in KHFAC studies and suggests specific testing that should be performed and reported in all studies that assess the neural response to KHFAC waveforms. Published by Elsevier B.V.

  19. Selection and generation of waveforms for differential mobility spectrometry

    International Nuclear Information System (INIS)

    Krylov, Evgeny V.; Coy, Stephen L.; Nazarov, Erkinjon G.; Vandermey, John; Schneider, Bradley B.; Covey, Thomas R.

    2010-01-01

    Devices based on differential mobility spectrometry (DMS) are used in a number of ways, including applications as ion prefilters for API-MS systems, as detectors or selectors in hybrid instruments (GC-DMS, DMS-IMS), and in standalone systems for chemical detection and identification. DMS ion separation is based on the relative difference between high field and low field ion mobility known as the alpha dependence, and requires the application of an intense asymmetric electric field known as the DMS separation field, typically in the megahertz frequency range. DMS performance depends on the waveform and on the magnitude of this separation field. In this paper, we analyze the relationship between separation waveform and DMS resolution and consider feasible separation field generators. We examine ideal and practical DMS separation field waveforms and discuss separation field generator circuit types and their implementations. To facilitate optimization of the generator designs, we present a set of relations that connect ion alpha dependence to DMS separation fields. Using these relationships we evaluate the DMS separation power of common generator types as a function of their waveform parameters. Optimal waveforms for the major types of DMS separation generators are determined for ions with various alpha dependences. These calculations are validated by comparison with experimental data.

  20. Average current is better than peak current as therapeutic dosage for biphasic waveforms in a ventricular fibrillation pig model of cardiac arrest.

    Science.gov (United States)

    Chen, Bihua; Yu, Tao; Ristagno, Giuseppe; Quan, Weilun; Li, Yongqin

    2014-10-01

    Defibrillation current has been shown to be a clinically more relevant dosing unit than energy. However, the effects of average and peak current in determining shock outcome are still undetermined. The aim of this study was to investigate the relationship between average current, peak current and defibrillation success when different biphasic waveforms were employed. Ventricular fibrillation (VF) was electrically induced in 22 domestic male pigs. Animals were then randomized to receive defibrillation using one of two different biphasic waveforms. A grouped up-and-down defibrillation threshold-testing protocol was used to maintain the average success rate of 50% in the neighborhood. In 14 animals (Study A), defibrillations were accomplished with either biphasic truncated exponential (BTE) or rectilinear biphasic waveforms. In eight animals (Study B), shocks were delivered using two BTE waveforms that had identical peak current but different waveform durations. Both average and peak currents were associated with defibrillation success when BTE and rectilinear waveforms were investigated. However, when pathway impedance was less than 90Ω for the BTE waveform, bivariate correlation coefficient was 0.36 (p=0.001) for the average current, but only 0.21 (p=0.06) for the peak current in Study A. In Study B, a high defibrillation success (67.9% vs. 38.8%, pcurrent (14.9±2.1A vs. 13.5±1.7A, pcurrent unchanged. In this porcine model of VF, average current was better than peak current to be an adequate parameter to describe the therapeutic dosage when biphasic defibrillation waveforms were used. The institutional protocol number: P0805. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  1. Analysis of Gradient Waveform in Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    OU-YANG Shan-mei

    2017-12-01

    Full Text Available The accuracy of gradient pulse waveform affects image quality significantly in magnetic resonance imaging (MRI. Recording and analyzing the waveform of gradient pulse helps to make rapid and accurate diagnosis of spectrometer gradient hardware and/or pulse sequence. Using the virtual instrument software LabVIEW to control the high speed data acquisition card DAQ-2005, a multi-channel acquisition scheme was designed to collect the gradient outputs from a custom-made spectrometer. The collected waveforms were post-processed (i.e., histogram statistical analysis, data filtering and difference calculation to obtain feature points containing time and amplitude information. Experiments were carried out to validate the method, which is an auxiliary test method for the development of spectrometer and pulses sequence.

  2. On detection of black hole quasinormal ringdowns: Detection efficiency and waveform parameter determination in matched filtering

    International Nuclear Information System (INIS)

    Tsunesada, Yoshiki; Tatsumi, Daisuke; Kanda, Nobuyuki; Nakano, Hiroyuki; Ando, Masaki; Sasaki, Misao; Tagoshi, Hideyuki; Takahashi, Hirotaka

    2005-01-01

    Gravitational radiation from a slightly distorted black hole with ringdown waveform is well understood in general relativity. It provides a probe for direct observation of black holes and determination of their physical parameters, masses and angular momenta (Kerr parameters). For ringdown searches using data of gravitational wave detectors, matched filtering technique is useful. In this paper, we describe studies on problems in matched filtering analysis in realistic gravitational wave searches using observational data. Above all, we focus on template constructions, matches or signal-to-noise ratios (SNRs), detection probabilities for Galactic events, and accuracies in evaluation of waveform parameters or black hole hairs. In template design for matched filtering, search parameter ranges and template separations are determined by requirements from acceptable maximum loss of SNRs, detection efficiencies, and computational costs. In realistic searches using observational data, however, effects of nonstationary noises cause decreases of SNRs, and increases of errors in waveform parameter determinations. These problems will potentially arise in any matched filtering searches for any kind of waveforms. To investigate them, we have performed matched filtering analysis for artificial ringdown signals which are generated with Monte-Carlo technique and injected into the TAMA300 observational data. We employed an efficient method to construct a bank of ringdown filters recently proposed by Nakano et al., and use a template bank generated from a criterion such that losses of SNRs of any signals do not exceed 2%. We found that this criterion is fulfilled in ringdown searches using TAMA300 data, by examining distribution of SNRs of simulated signals. It is also shown that with TAMA300 sensitivity, the detection probability for Galactic ringdown events is about 50% for black holes of masses greater than 20M · with SNR>10. The accuracies in waveform parameter estimations are

  3. The Modularized Software Package ASKI - Full Waveform Inversion Based on Waveform Sensitivity Kernels Utilizing External Seismic Wave Propagation Codes

    Science.gov (United States)

    Schumacher, F.; Friederich, W.

    2015-12-01

    We present the modularized software package ASKI which is a flexible and extendable toolbox for seismic full waveform inversion (FWI) as well as sensitivity or resolution analysis operating on the sensitivity matrix. It utilizes established wave propagation codes for solving the forward problem and offers an alternative to the monolithic, unflexible and hard-to-modify codes that have typically been written for solving inverse problems. It is available under the GPL at www.rub.de/aski. The Gauss-Newton FWI method for 3D-heterogeneous elastic earth models is based on waveform sensitivity kernels and can be applied to inverse problems at various spatial scales in both Cartesian and spherical geometries. The kernels are derived in the frequency domain from Born scattering theory as the Fréchet derivatives of linearized full waveform data functionals, quantifying the influence of elastic earth model parameters on the particular waveform data values. As an important innovation, we keep two independent spatial descriptions of the earth model - one for solving the forward problem and one representing the inverted model updates. Thereby we account for the independent needs of spatial model resolution of forward and inverse problem, respectively. Due to pre-integration of the kernels over the (in general much coarser) inversion grid, storage requirements for the sensitivity kernels are dramatically reduced.ASKI can be flexibly extended to other forward codes by providing it with specific interface routines that contain knowledge about forward code-specific file formats and auxiliary information provided by the new forward code. In order to sustain flexibility, the ASKI tools must communicate via file output/input, thus large storage capacities need to be accessible in a convenient way. Storing the complete sensitivity matrix to file, however, permits the scientist full manual control over each step in a customized procedure of sensitivity/resolution analysis and full

  4. Cross-correlated imaging of distributed mode filtering rod fiber

    DEFF Research Database (Denmark)

    Laurila, Marko; Barankov, Roman; Jørgensen, Mette Marie

    2013-01-01

    We analyze the modal properties of an 85μm core distributed mode filtering rod fiber using cross-correlated (C2) imaging. We evaluate suppression of higher-order modes (HOMs) under severely misaligned mode excitation and identify a single-mode regime where HOMs are suppressed by more than 20dB....

  5. Interferometric crosstalk suppression using polarization multiplexing technique and an SOA

    DEFF Research Database (Denmark)

    Liu, Fenghai; Xueyan, Zheng; Pedersen, Rune Johan Skullerud

    2000-01-01

    Interferometric crosstalk can be greatly suppressed at 10Gb/s and 20Gb/s by using a gain saturated SOA and a polarization multiplexing technique that eliminates impairments like waveform and extinction ratio degradation from the SOA.......Interferometric crosstalk can be greatly suppressed at 10Gb/s and 20Gb/s by using a gain saturated SOA and a polarization multiplexing technique that eliminates impairments like waveform and extinction ratio degradation from the SOA....

  6. 'Kludge' gravitational waveforms for a test-body orbiting a Kerr black hole

    International Nuclear Information System (INIS)

    Babak, Stanislav; Fang Hua; Gair, Jonathan R.; Glampedakis, Kostas; Hughes, Scott A.

    2007-01-01

    One of the most exciting potential sources of gravitational waves for low-frequency, space-based gravitational wave (GW) detectors such as the proposed Laser Interferometer Space Antenna (LISA) is the inspiral of compact objects into massive black holes in the centers of galaxies. The detection of waves from such 'extreme mass ratio inspiral' systems (EMRIs) and extraction of information from those waves require template waveforms. The systems' extreme mass ratio means that their waveforms can be determined accurately using black hole perturbation theory. Such calculations are computationally very expensive. There is a pressing need for families of approximate waveforms that may be generated cheaply and quickly but which still capture the main features of true waveforms. In this paper, we introduce a family of such kludge waveforms and describe ways to generate them. Different kinds of kludges have already been used to scope out data analysis issues for LISA. The models we study here are based on computing a particle's inspiral trajectory in Boyer-Lindquist coordinates, and subsequent identification of these coordinates with flat-space spherical polar coordinates. A gravitational waveform may then be computed from the multipole moments of the trajectory in these coordinates, using well-known solutions of the linearised gravitational perturbation equations in flat space time. We compute waveforms using a standard slow-motion quadrupole formula, a quadrupole/octupole formula, and a fast-motion, weak-field formula originally developed by Press. We assess these approximations by comparing to accurate waveforms obtained by solving the Teukolsky equation in the adiabatic limit (neglecting GW backreaction). We find that the kludge waveforms do extremely well at approximating the true gravitational waveform, having overlaps with the Teukolsky waveforms of 95% or higher over most of the parameter space for which comparisons can currently be made. Indeed, we find these

  7. Lossless compression of waveform data for efficient storage and transmission

    International Nuclear Information System (INIS)

    Stearns, S.D.; Tan, Li Zhe; Magotra, Neeraj

    1993-01-01

    Compression of waveform data is significant in many engineering and research areas since it can be used to alleviate data storage and transmission bandwidth. For example, seismic data are widely recorded and transmitted so that analysis can be performed on large amounts of data for numerous applications such as petroleum exploration, determination of the earth's core structure, seismic event detection and discrimination of underground nuclear explosions, etc. This paper describes a technique for lossless wave form data compression. The technique consists of two stages. The first stage is a modified form of linear prediction with discrete coefficients and the second stage is bi-level sequence coding. The linear predictor generates an error or residue sequence in a way such that exact reconstruction of the original data sequence can be accomplished with a simple algorithm. The residue sequence is essentially white Gaussian with seismic or other similar waveform data. Bi-level sequence coding, in which two sample sizes are chosen and the residue sequence is encoded into subsequences that alternate from one level to the other, further compresses the residue sequence. The principal feature of the two-stage data compression algorithm is that it is lossless, that is, it allows exact, bit-for-bit recovery of the original data sequence. The performance of the lossless compression algorithm at each stage is analyzed. The advantages of using bi-level sequence coding in the second stage are its simplicity of implementation, its effectiveness on data with large amplitude variations, and its near-optimal performance in encoding Gaussian sequences. Applications of the two-stage technique to typical seismic data indicates that an average number of compressed bits per sample close to the lower bound is achievable in practical situations

  8. Electrochemical sensing using comparison of voltage-current time differential values during waveform generation and detection

    Science.gov (United States)

    Woo, Leta Yar-Li; Glass, Robert Scott; Fitzpatrick, Joseph Jay; Wang, Gangqiang; Henderson, Brett Tamatea; Lourdhusamy, Anthoniraj; Steppan, James John; Allmendinger, Klaus Karl

    2018-01-02

    A device for signal processing. The device includes a signal generator, a signal detector, and a processor. The signal generator generates an original waveform. The signal detector detects an affected waveform. The processor is coupled to the signal detector. The processor receives the affected waveform from the signal detector. The processor also compares at least one portion of the affected waveform with the original waveform. The processor also determines a difference between the affected waveform and the original waveform. The processor also determines a value corresponding to a unique portion of the determined difference between the original and affected waveforms. The processor also outputs the determined value.

  9. Full waveform inversion using oriented time-domain imaging method for vertical transverse isotropic media

    KAUST Repository

    Zhang, Zhendong

    2017-07-11

    Full waveform inversion for reection events is limited by its linearized update re-quirements given by a process equivalent to migration. Unless the background velocity model is reasonably accurate, the resulting gradient can have an inaccurate update direction leading the inversion to converge what we refer to as local minima of the objective function. In our approach, we consider mild lateral variation in the model, and thus, use a gradient given by the oriented time-domain imaging method. Specifically, we apply the oriented time-domain imaging on the data residual to obtain the geometrical features of the velocity perturbation. After updating the model in the time domain, we convert the perturbation from the time domain to depth using the average velocity. Considering density is constant, we can expand the conventional 1D impedance inversion method to 2D or 3D velocity inversion within the process of full waveform inversion. This method is not only capable of inverting for velocity, but it is also capable of retrieving anisotropic parameters relying on linearized representations of the reection response. To eliminate the cross-talk artifacts between different parameters, we utilize what we consider being an optimal parametrization for this step. To do so, we extend the prestack time-domain migration image in incident angle dimension to incorporate angular dependence needed by the multiparameter inversion. For simple models, this approach provides an efficient and stable way to do full waveform inversion or modified seismic inversion and makes the anisotropic inversion more practicable. The proposed method still needs kinematically accurate initial models since it only recovers the high-wavenumber part as conventional full waveform inversion method does. Results on synthetic data of isotropic and anisotropic cases illustrate the benefits and limitations of this method.

  10. Mergers of black-hole binaries with aligned spins: Waveform characteristics

    International Nuclear Information System (INIS)

    Kelly, Bernard J.; Baker, John G.; Centrella, Joan; Boggs, William D.; McWilliams, Sean T.

    2011-01-01

    We conduct a descriptive analysis of the multipolar structure of gravitational-radiation waveforms from equal-mass aligned-spin mergers, following an approach first presented in the complementary context of nonspinning black holes of varying mass ratio [J. G. Baker et al., Phys. Rev. D 78, 044046 (2008).]. We find that, as with the nonspinning mergers, the dominant waveform mode phases evolve together in lock-step through inspiral and merger, supporting the previous waveform description in terms of an adiabatically rigid rotator driving gravitational-wave emission--an implicit rotating source. We further apply the late-time merger-ringdown model for the rotational frequency introduced in [J. G. Baker et al., Phys. Rev. D 78, 044046 (2008).], along with an improved amplitude model appropriate for the dominant (2, ±2) modes. This provides a quantitative description of the merger-ringdown waveforms, and suggests that the major features of these waveforms can be described with reference only to the intrinsic parameters associated with the state of the final black hole formed in the merger. We provide an explicit model for the merger-ringdown radiation, and demonstrate that this model agrees to fitting factors better than 95% with the original numerical waveforms for system masses above ∼150M · . This model may be directly applicable to gravitational-wave detection of intermediate-mass black-hole mergers.

  11. The Instagram: A Novel Sounding Technique for Enhanced HF Propagation Advice

    Science.gov (United States)

    2010-05-01

    precautions are necessary before such a scheme is attempted, and an ultimate aim might be to have the technique as close to subliminal as possible...Federal Communications Commission (FCC) and military rules. Figure 1. (a) Time and (b) frequency domains of an Instagram waveform Guard bands around...waveform on reception has been reduced to subliminal levels. Figure 4 PSD plot of the weighted instagram waveform as received on a

  12. MEASUREMENT OF 21 cm BRIGHTNESS FLUCTUATIONS AT z {approx} 0.8 IN CROSS-CORRELATION

    Energy Technology Data Exchange (ETDEWEB)

    Masui, K. W.; Switzer, E. R.; Calin, L.-M.; Pen, U.-L.; Shaw, J. R. [Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George St., Toronto, Ontario, M5S 3H8 (Canada); Banavar, N. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, Ontario, M5S 3H4 (Canada); Bandura, K. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec, H3A 2T8 (Canada); Blake, C. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122 (Australia); Chang, T.-C.; Liao, Y.-W. [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei, 10617, Taiwan (China); Chen, X.; Li, Y.-C. [National Astronomical Observatories, Chinese Academy of Science, 20A Datun Road, Beijing 100012 (China); Natarajan, A.; Peterson, J. B.; Voytek, T. C. [McWilliams Center for Cosmology, Carnegie Mellon University, Department of Physics, 5000 Forbes Ave., Pittsburgh, PA 15213 (United States)

    2013-01-20

    In this Letter, 21 cm intensity maps acquired at the Green Bank Telescope are cross-correlated with large-scale structure traced by galaxies in the WiggleZ Dark Energy Survey. The data span the redshift range 0.6 < z < 1 over two fields totaling {approx}41 deg. sq. and 190 hr of radio integration time. The cross-correlation constrains {Omega}{sub HI} b{sub HI} r = [0.43 {+-} 0.07(stat.) {+-} 0.04(sys.)] Multiplication-Sign 10{sup -3}, where {Omega}{sub HI} is the neutral hydrogen (H I) fraction, r is the galaxy-hydrogen correlation coefficient, and b{sub HI} is the H I bias parameter. This is the most precise constraint on neutral hydrogen density fluctuations in a challenging redshift range. Our measurement improves the previous 21 cm cross-correlation at z {approx} 0.8 both in its precision and in the range of scales probed.

  13. High resolution aquifer characterization using crosshole GPR full-waveform tomography: Comparison with direct-push and tracer test data

    Science.gov (United States)

    Gueting, Nils; Vienken, Thomas; Klotzsche, Anja; van der Kruk, Jan; Vanderborght, Jan; Caers, Jef; Vereecken, Harry; Englert, Andreas

    2017-01-01

    Limited knowledge about the spatial distribution of aquifer properties typically constrains our ability to predict subsurface flow and transport. Here we investigate the value of using high resolution full-waveform inversion of cross-borehole ground penetrating radar (GPR) data for aquifer characterization. By stitching together GPR tomograms from multiple adjacent crosshole planes, we are able to image, with a decimeter scale resolution, the dielectric permittivity and electrical conductivity of an alluvial aquifer along cross sections of 50 m length and 10 m depth. A logistic regression model is employed to predict the spatial distribution of lithological facies on the basis of the GPR results. Vertical profiles of porosity and hydraulic conductivity from direct-push, flowmeter and grain size data suggest that the GPR predicted facies classification is meaningful with regard to porosity and hydraulic conductivity, even though the distributions of individual facies show some overlap and the absolute hydraulic conductivities from the different methods (direct-push, flowmeter, grain size) differ up to approximately one order of magnitude. Comparison of the GPR predicted facies architecture with tracer test data suggests that the plume splitting observed in a tracer experiment was caused by a hydraulically low-conductive sand layer with a thickness of only a few decimeters. Because this sand layer is identified by GPR full-waveform inversion but not by conventional GPR ray-based inversion we conclude that the improvement in spatial resolution due to full-waveform inversion is crucial to detect small-scale aquifer structures that are highly relevant for solute transport.

  14. Nuclear material safeguards surveillance and accountancy by isotope correlation techniques

    International Nuclear Information System (INIS)

    Persiani, P.J.; Goleb, J.A.

    1981-01-01

    This paper presents the initial phase of the US study program and involves the computation of isotopic correlations for the LMFBR fuel cycle. The LWR fuel cycle phase of the study is currently in progress. The selection of the more safeguards effective functionals will depend not only on the level of reliability of isotope correlation technique (ICT) for verification, but also on the capability and difficulty of developing measurement methods. Performance characteristics of existing and proposed isotopic measurement techniques cover the general areas including assay and isotopic wet chemistry and NDA: (1) simultaneous multicomponent analysis techniques, (2) mass spectrometry, (3) x-ray fluorescence or densitometry with high flux monochromatic x-ray sources and high dispersion spectrometers, (4) passive and active neutron interrogation, (5) high level gamma-ray spectroscopy, (6) coulometry, and (7) potentiometry. The measurement capabilities and inherent limitations of these systems are to be evaluated in terms of total systems, operational mode, sample preparation requirements and consequent effect on dissolver solution representation, accuracy and precision estimates (if available), development status of the technique, and development requirements. The isotopic correlation technique shows considerable promise for use in verifying the initial isotopic composition and burnup of discharged assemblies based on the measured ratios of several key isotopes, obtained probably at the dissolver stage in reprocessing. This technique should, for example, easily be capable of indicating the exchange of a blanket assembly for a fuel assembly

  15. Intracellular dynamics and fate of polystyrene nanoparticles in A549 Lung epithelial cells monitored by image (cross-) correlation spectroscopy and single particle tracking.

    Science.gov (United States)

    Deville, Sarah; Penjweini, Rozhin; Smisdom, Nick; Notelaers, Kristof; Nelissen, Inge; Hooyberghs, Jef; Ameloot, Marcel

    2015-10-01

    Novel insights in nanoparticle (NP) uptake routes of cells, their intracellular trafficking and subcellular targeting can be obtained through the investigation of their temporal and spatial behavior. In this work, we present the application of image (cross-) correlation spectroscopy (IC(C)S) and single particle tracking (SPT) to monitor the intracellular dynamics of polystyrene (PS) NPs in the human lung carcinoma A549 cell line. The ensemble kinetic behavior of NPs inside the cell was characterized by temporal and spatiotemporal image correlation spectroscopy (TICS and STICS). Moreover, a more direct interpretation of the diffusion and flow detected in the NP motion was obtained by SPT by monitoring individual NPs. Both techniques demonstrate that the PS NP transport in A549 cells is mainly dependent on microtubule-assisted transport. By applying spatiotemporal image cross-correlation spectroscopy (STICCS), the correlated motions of NPs with the early endosomes, late endosomes and lysosomes are identified. PS NPs were equally distributed among the endolysosomal compartment during the time interval of the experiments. The cotransport of the NPs with the lysosomes is significantly larger compared to the other cell organelles. In the present study we show that the complementarity of ICS-based techniques and SPT enables a consistent elaborate model of the complex behavior of NPs inside biological systems. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Temporal cross-correlation asymmetry and departure from equilibrium in a bistable chemical system.

    Science.gov (United States)

    Bianca, C; Lemarchand, A

    2014-06-14

    This paper aims at determining sustained reaction fluxes in a nonlinear chemical system driven in a nonequilibrium steady state. The method relies on the computation of cross-correlation functions for the internal fluctuations of chemical species concentrations. By employing Langevin-type equations, we derive approximate analytical formulas for the cross-correlation functions associated with nonlinear dynamics. Kinetic Monte Carlo simulations of the chemical master equation are performed in order to check the validity of the Langevin equations for a bistable chemical system. The two approaches are found in excellent agreement, except for critical parameter values where the bifurcation between monostability and bistability occurs. From the theoretical point of view, the results imply that the behavior of cross-correlation functions cannot be exploited to measure sustained reaction fluxes in a specific nonlinear system without the prior knowledge of the associated chemical mechanism and the rate constants.

  17. Finite sample properties of power-law cross-correlations estimators

    Czech Academy of Sciences Publication Activity Database

    Krištoufek, Ladislav

    2015-01-01

    Roč. 419, č. 1 (2015), s. 513-525 ISSN 0378-4371 R&D Projects: GA ČR(CZ) GP14-11402P Keywords : power-law cross-correlations * long - term memory * econophysics Subject RIV: AH - Economics Impact factor: 1.785, year: 2015 http://library.utia.cas.cz/separaty/2014/E/kristoufek-0433530.pdf

  18. Groundwater travel time uncertainty analysis. Sensitivity of results to model geometry, and correlations and cross correlations among input parameters

    International Nuclear Information System (INIS)

    Clifton, P.M.

    1985-03-01

    This study examines the sensitivity of the travel time distribution predicted by a reference case model to (1) scale of representation of the model parameters, (2) size of the model domain, (3) correlation range of log-transmissivity, and (4) cross correlations between transmissivity and effective thickness. The basis for the reference model is the preliminary stochastic travel time model previously documented by the Basalt Waste Isolation Project. Results of this study show the following. The variability of the predicted travel times can be adequately represented when the ratio between the size of the zones used to represent the model parameters and the log-transmissivity correlation range is less than about one-fifth. The size of the model domain and the types of boundary conditions can have a strong impact on the distribution of travel times. Longer log-transmissivity correlation ranges cause larger variability in the predicted travel times. Positive cross correlation between transmissivity and effective thickness causes a decrease in the travel time variability. These results demonstrate the need for a sound conceptual model prior to conducting a stochastic travel time analysis

  19. Rapidly reconfigurable high-fidelity optical arbitrary waveform generation in heterogeneous photonic integrated circuits.

    Science.gov (United States)

    Feng, Shaoqi; Qin, Chuan; Shang, Kuanping; Pathak, Shibnath; Lai, Weicheng; Guan, Binbin; Clements, Matthew; Su, Tiehui; Liu, Guangyao; Lu, Hongbo; Scott, Ryan P; Ben Yoo, S J

    2017-04-17

    This paper demonstrates rapidly reconfigurable, high-fidelity optical arbitrary waveform generation (OAWG) in a heterogeneous photonic integrated circuit (PIC). The heterogeneous PIC combines advantages of high-speed indium phosphide (InP) modulators and low-loss, high-contrast silicon nitride (Si3N4) arrayed waveguide gratings (AWGs) so that high-fidelity optical waveform syntheses with rapid waveform updates are possible. The generated optical waveforms spanned a 160 GHz spectral bandwidth starting from an optical frequency comb consisting of eight comb lines separated by 20 GHz channel spacing. The Error Vector Magnitude (EVM) values of the generated waveforms were approximately 16.4%. The OAWG module can rapidly and arbitrarily reconfigure waveforms upon every pulse arriving at 2 ns repetition time. The result of this work indicates the feasibility of truly dynamic optical arbitrary waveform generation where the reconfiguration rate or the modulator bandwidth must exceed the channel spacing of the AWG and the optical frequency comb.

  20. Factors influencing the renal arterial Doppler waveform: a simulation study using an electrical circuit model (secondary publication)

    Energy Technology Data Exchange (ETDEWEB)

    Sung, Chang Kyu [Dept. of Radiology, SMG-SNU Boramae Medical Center, Seoul National University College of Medicine, Seoul (Korea, Republic of); Han, Bong Soo [Dept. of Radiological Science, College of Health Science, Yonsei University, Wonju (Korea, Republic of); Kim, Seung Hyup [Dept. of Radiology, Institute of Radiation Medicine, Seoul National University Hospital, Seoul National University College of Medicine, Seoul (Korea, Republic of)

    2016-01-15

    The goal of this study was to evaluate the effect of vascular compliance, resistance, and pulse rate on the resistive index (RI) by using an electrical circuit model to simulate renal blood flow. In order to analyze the renal arterial Doppler waveform, we modeled the renal blood-flow circuit with an equivalent simple electrical circuit containing resistance, inductance, and capacitance. The relationships among the impedance, resistance, and compliance of the circuit were derived from well-known equations, including Kirchhoff’s current law for alternating current circuits. Simulated velocity-time profiles for pulsatile flow were generated using Mathematica (Wolfram Research) and the influence of resistance, compliance, and pulse rate on waveforms and the RI was evaluated. Resistance and compliance were found to alter the waveforms independently. The impedance of the circuit increased with increasing proximal compliance, proximal resistance, and distal resistance. The impedance decreased with increasing distal compliance. The RI of the circuit decreased with increasing proximal compliance and resistance. The RI increased with increasing distal compliance and resistance. No positive correlation between impedance and the RI was found. Pulse rate was found to be an extrinsic factor that also influenced the RI. This simulation study using an electrical circuit model led to a better understanding of the renal arterial Doppler waveform and the RI, which may be useful for interpreting Doppler findings in various clinical settings.

  1. Factors influencing the renal arterial Doppler waveform: a simulation study using an electrical circuit model (secondary publication)

    International Nuclear Information System (INIS)

    Sung, Chang Kyu; Han, Bong Soo; Kim, Seung Hyup

    2016-01-01

    The goal of this study was to evaluate the effect of vascular compliance, resistance, and pulse rate on the resistive index (RI) by using an electrical circuit model to simulate renal blood flow. In order to analyze the renal arterial Doppler waveform, we modeled the renal blood-flow circuit with an equivalent simple electrical circuit containing resistance, inductance, and capacitance. The relationships among the impedance, resistance, and compliance of the circuit were derived from well-known equations, including Kirchhoff’s current law for alternating current circuits. Simulated velocity-time profiles for pulsatile flow were generated using Mathematica (Wolfram Research) and the influence of resistance, compliance, and pulse rate on waveforms and the RI was evaluated. Resistance and compliance were found to alter the waveforms independently. The impedance of the circuit increased with increasing proximal compliance, proximal resistance, and distal resistance. The impedance decreased with increasing distal compliance. The RI of the circuit decreased with increasing proximal compliance and resistance. The RI increased with increasing distal compliance and resistance. No positive correlation between impedance and the RI was found. Pulse rate was found to be an extrinsic factor that also influenced the RI. This simulation study using an electrical circuit model led to a better understanding of the renal arterial Doppler waveform and the RI, which may be useful for interpreting Doppler findings in various clinical settings

  2. Cross-correlation analysis between Chinese TF contracts and treasury ETF based on high-frequency data

    Science.gov (United States)

    Zhou, Yu; Chen, Shi

    2016-02-01

    In this paper, we investigate the high-frequency cross-correlation relationship between Chinese treasury futures contracts and treasury ETF. We analyze the logarithmic return of these two price series, from which we can conclude that both return series are not normally distributed and the futures markets have greater volatility. We find significant cross-correlation between these two series. We further confirm the relationship using the DCCA coefficient and the DMCA coefficient. We quantify the long-range cross-correlation with DCCA method, and we further show that the relationship is multifractal. An arbitrage algorithm based on DFA regression with stable return is proposed in the last part.

  3. A Waveform Archiving System for the GE Solar 8000i Bedside Monitor.

    Science.gov (United States)

    Fanelli, Andrea; Jaishankar, Rohan; Filippidis, Aristotelis; Holsapple, James; Heldt, Thomas

    2018-01-01

    Our objective was to develop, deploy, and test a data-acquisition system for the reliable and robust archiving of high-resolution physiological waveform data from a variety of bedside monitoring devices, including the GE Solar 8000i patient monitor, and for the logging of ancillary clinical and demographic information. The data-acquisition system consists of a computer-based archiving unit and a GE Tram Rac 4A that connects to the GE Solar 8000i monitor. Standard physiological front-end sensors connect directly to the Tram Rac, which serves as a port replicator for the GE monitor and provides access to these waveform signals through an analog data interface. Together with the GE monitoring data streams, we simultaneously collect the cerebral blood flow velocity envelope from a transcranial Doppler ultrasound system and a non-invasive arterial blood pressure waveform along a common time axis. All waveform signals are digitized and archived through a LabView-controlled interface that also allows for the logging of relevant meta-data such as clinical and patient demographic information. The acquisition system was certified for hospital use by the clinical engineering team at Boston Medical Center, Boston, MA, USA. Over a 12-month period, we collected 57 datasets from 11 neuro-ICU patients. The system provided reliable and failure-free waveform archiving. We measured an average temporal drift between waveforms from different monitoring devices of 1 ms every 66 min of recorded data. The waveform acquisition system allows for robust real-time data acquisition, processing, and archiving of waveforms. The temporal drift between waveforms archived from different devices is entirely negligible, even for long-term recording.

  4. Noninvasive arterial blood pressure waveforms in patients with continuous-flow left ventricular assist devices.

    Science.gov (United States)

    Martina, Jerson R; Westerhof, Berend E; de Jonge, Nicolaas; van Goudoever, Jeroen; Westers, Paul; Chamuleau, Steven; van Dijk, Diederik; Rodermans, Ben F M; de Mol, Bas A J M; Lahpor, Jaap R

    2014-01-01

    Arterial blood pressure and echocardiography may provide useful physiological information regarding cardiac support in patients with continuous-flow left ventricular assist devices (cf-LVADs). We investigated the accuracy and characteristics of noninvasive blood pressure during cf-LVAD support. Noninvasive arterial pressure waveforms were recorded with Nexfin (BMEYE, Amsterdam, The Netherlands). First, these measurements were validated simultaneously with invasive arterial pressures in 29 intensive care unit patients. Next, the association between blood pressure responses and measures derived by echocardiography, including left ventricular end-diastolic dimensions (LVEDDs), left ventricular end-systolic dimensions (LVESDs), and left ventricular shortening fraction (LVSF) were determined during pump speed change procedures in 30 outpatients. Noninvasive arterial blood pressure waveforms by the Nexfin monitor slightly underestimated invasive measures during cf-LVAD support. Differences between noninvasive and invasive measures (mean ± SD) of systolic, diastolic, mean, and pulse pressures were -7.6 ± 5.8, -7.0 ± 5.2, -6.9 ± 5.1, and -0.6 ± 4.5 mm Hg, respectively (all blood pressure responses did not correlate with LVEDD, LVESD, or LVSF, while LVSF correlated weakly with both pulse pressure (r = 0.24; p = 0.005) and (dP(art)/dt)max (r = 0.25; p = 0.004). The dicrotic notch in the pressure waveform was a better predictor of aortic valve opening (area under the curve [AUC] = 0.87) than pulse pressure (AUC = 0.64) and (dP(art)/dt)max (AUC = 0.61). Patients with partial support rather than full support at 9,000 rpm had a significant change in systolic pressure, pulse pressure, and (dP(art)/dt)max during ramp studies, while echocardiographic measures did not change. Blood pressure measurements by Nexfin were reliable and may thereby act as a compliment to the assessment of the cf-LVAD patient.

  5. On the linearity of cross-correlation delay times

    Science.gov (United States)

    Mercerat, E. D.; Nolet, G.

    2012-12-01

    We investigate the question whether a P-wave delay time Δ T estimated by locating the maximum of the cross-correlation function between data d(t) and a predicted test function s(t): γ (t) = ∫ t1t_2 s(τ ) d(τ -t) \\ {d}τ, provides an estimate of the Delta T that is (quasi-)linear with the relative velocity perturbation deltaln V_P}. Such linearity is intuitive if the data d(t) is an undeformed but delayed replica of the test signal, i.e. if d(t)=s(t-Delta T). Then the maximum of gamma (t) is shifted exactly by the delay Delta T, and linearity holds even for Delta T very large. In this case, we say that the body waves are in the ray theoretical regime and their delays, because of Fermat's Principle, depend quasi-linearly on the relative velocity (or slowness) perturbations deltaln V_P in the model. However, even if we correct for dispersion induced by the instrument response and by attenuation, body waves may show frequency dependent delay times that are caused by diffraction effects around lateral heterogeneities. It is not a-priori clear that linearity holds for Delta T, as is assumed in finite-frequency theory, if the waveforms of d(t) and s(t) differ substantially because of such dispersion. To test the linearity, we generate synthetic seismograms between two boreholes, and between the boreholes and the surface, in a 3D box of 200 × 120 × 120 m. The heterogeneity is a checkerboard with cubic anomalies of size 12 × 12 × 12 m. We test two different anomaly amplitudes: ± 2% and ± 5%, and measure Delta T using a test seismogram s(t) computed for an homogeneous medium. We also predict the delays for the 5% model from those in the 2% model by multiplying with 5/2. These predictions are in error by 10-20% of the delay, which is usually acceptable for tomography when compared with actual data errors. A slight bias in the prediction indicates that the Wielandt effect - the fact that negative delays suffer less wavefront healing than positive delays - is a

  6. Variable Rate Characteristic Waveform Interpolation Speech Coder Based on Phonetic Classification

    Institute of Scientific and Technical Information of China (English)

    WANG Jing; KUANG Jing-ming; ZHAO Sheng-hui

    2007-01-01

    A variable-bit-rate characteristic waveform interpolation (VBR-CWI) speech codec with about 1.8kbit/s average bit rate which integrates phonetic classification into characteristic waveform (CW) decomposition is proposed.Each input frame is classified into one of 4 phonetic classes.Non-speech frames are represented with Bark-band noise model.The extracted CWs become rapidly evolving waveforms (REWs) or slowly evolving waveforms (SEWs) in the cases of unvoiced or stationary voiced frames respectively, while mixed voiced frames use the same CW decomposition as that in the conventional CWI.Experimental results show that the proposed codec can eliminate most buzzy and noisy artifacts existing in the fixed-bit-rate characteristic waveform interpolation (FBR-CWI) speech codec, the average bit rate can be much lower, and its reconstructed speech quality is much better than FS 1016 CELP at 4.8kbit/s and similar to G.723.1 ACELP at 5.3kbit/s.

  7. Accuracy of Binary Black Hole waveforms for Advanced LIGO searches

    Science.gov (United States)

    Kumar, Prayush; Barkett, Kevin; Bhagwat, Swetha; Chu, Tony; Fong, Heather; Brown, Duncan; Pfeiffer, Harald; Scheel, Mark; Szilagyi, Bela

    2015-04-01

    Coalescing binaries of compact objects are flagship sources for the first direct detection of gravitational waves with LIGO-Virgo observatories. Matched-filtering based detection searches aimed at binaries of black holes will use aligned spin waveforms as filters, and their efficiency hinges on the accuracy of the underlying waveform models. A number of gravitational waveform models are available in literature, e.g. the Effective-One-Body, Phenomenological, and traditional post-Newtonian ones. While Numerical Relativity (NR) simulations provide for the most accurate modeling of gravitational radiation from compact binaries, their computational cost limits their application in large scale searches. In this talk we assess the accuracy of waveform models in two regions of parameter space, which have only been explored cursorily in the past: the high mass-ratio regime as well as the comparable mass-ratio + high spin regime.s Using the SpEC code, six q = 7 simulations with aligned-spins and lasting 60 orbits, and tens of q ∈ [1,3] simulations with high black hole spins were performed. We use them to study the accuracy and intrinsic parameter biases of different waveform families, and assess their viability for Advanced LIGO searches.

  8. Cross-correlation of instantaneous phase increments in pressure-flow fluctuations: Applications to cerebral autoregulation

    Science.gov (United States)

    Chen, Zhi; Hu, Kun; Stanley, H. Eugene; Novak, Vera; Ivanov, Plamen Ch.

    2006-03-01

    We investigate the relationship between the blood flow velocities (BFV) in the middle cerebral arteries and beat-to-beat blood pressure (BP) recorded from a finger in healthy and post-stroke subjects during the quasisteady state after perturbation for four different physiologic conditions: supine rest, head-up tilt, hyperventilation, and CO2 rebreathing in upright position. To evaluate whether instantaneous BP changes in the steady state are coupled with instantaneous changes in the BFV, we compare dynamical patterns in the instantaneous phases of these signals, obtained from the Hilbert transform, as a function of time. We find that in post-stroke subjects the instantaneous phase increments of BP and BFV exhibit well-pronounced patterns that remain stable in time for all four physiologic conditions, while in healthy subjects these patterns are different, less pronounced, and more variable. We propose an approach based on the cross-correlation of the instantaneous phase increments to quantify the coupling between BP and BFV signals. We find that the maximum correlation strength is different for the two groups and for the different conditions. For healthy subjects the amplitude of the cross-correlation between the instantaneous phase increments of BP and BFV is small and attenuates within 3-5 heartbeats. In contrast, for post-stroke subjects, this amplitude is significantly larger and cross-correlations persist up to 20 heartbeats. Further, we show that the instantaneous phase increments of BP and BFV are cross-correlated even within a single heartbeat cycle. We compare the results of our approach with three complementary methods: direct BP-BFV cross-correlation, transfer function analysis, and phase synchronization analysis. Our findings provide insight into the mechanism of cerebral vascular control in healthy subjects, suggesting that this control mechanism may involve rapid adjustments (within a heartbeat) of the cerebral vessels, so that BFV remains steady in

  9. The large-scale quasar-Lyman α forest cross-correlation from BOSS

    Energy Technology Data Exchange (ETDEWEB)

    Font-Ribera, Andreu [Institute of Theoretical Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich (Switzerland); Arnau, Eduard [Institut de Ciències del Cosmos (IEEC/UB), Martí i Franquès 1, 08028 Barcelona, Catalonia (Spain); Miralda-Escudé, Jordi, E-mail: font@physik.uzh.ch, E-mail: edu.arnau.lazaro@gmail.com, E-mail: miralda@icc.ub.edu [Institució Catalana de Recerca i Estudis Avançats, Passeig Lluís Companys 23, 08010 Barcelona, Catalonia (Spain); and others

    2013-05-01

    We measure the large-scale cross-correlation of quasars with the Lyα forest absorption in redshift space, using ∼ 60000 quasar spectra from Data Release 9 (DR9) of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is detected over a wide range of scales, up to comoving separations r of 80 h{sup −1}Mpc. For r > 15 h{sup −1}Mpc, we show that the cross-correlation is well fitted by the linear theory prediction for the mean overdensity around a quasar host halo in the standard ΛCDM model, with the redshift distortions indicative of gravitational evolution detected at high confidence. Using previous determinations of the Lyα forest bias factor obtained from the Lyα autocorrelation, we infer the quasar bias factor to be b{sub q} = 3.64{sup +0.13}{sub −0.15} at a mean redshift z = 2.38, in agreement with previous measurements from the quasar auto-correlation. We also obtain a new estimate of the Lyα forest redshift distortion factor, β{sub F} = 1.1±0.15, slightly larger than but consistent with the previous measurement from the Lyα forest autocorrelation. The simple linear model we use fails at separations r < 15h{sup −1}Mpc, and we show that this may reasonably be due to the enhanced ionization due to radiation from the quasars. We also provide the expected correction that the mass overdensity around the quasar implies for measurements of the ionizing radiation background from the line-of-sight proximity effect.

  10. The large-scale quasar-Lyman α forest cross-correlation from BOSS

    International Nuclear Information System (INIS)

    Font-Ribera, Andreu; Arnau, Eduard; Miralda-Escudé, Jordi

    2013-01-01

    We measure the large-scale cross-correlation of quasars with the Lyα forest absorption in redshift space, using ∼ 60000 quasar spectra from Data Release 9 (DR9) of the Baryon Oscillation Spectroscopic Survey (BOSS). The cross-correlation is detected over a wide range of scales, up to comoving separations r of 80 h −1 Mpc. For r > 15 h −1 Mpc, we show that the cross-correlation is well fitted by the linear theory prediction for the mean overdensity around a quasar host halo in the standard ΛCDM model, with the redshift distortions indicative of gravitational evolution detected at high confidence. Using previous determinations of the Lyα forest bias factor obtained from the Lyα autocorrelation, we infer the quasar bias factor to be b q = 3.64 +0.13 −0.15 at a mean redshift z = 2.38, in agreement with previous measurements from the quasar auto-correlation. We also obtain a new estimate of the Lyα forest redshift distortion factor, β F = 1.1±0.15, slightly larger than but consistent with the previous measurement from the Lyα forest autocorrelation. The simple linear model we use fails at separations r −1 Mpc, and we show that this may reasonably be due to the enhanced ionization due to radiation from the quasars. We also provide the expected correction that the mass overdensity around the quasar implies for measurements of the ionizing radiation background from the line-of-sight proximity effect

  11. Dynamical Analysis of Stock Market Instability by Cross-correlation Matrix

    Science.gov (United States)

    Takaishi, Tetsuya

    2016-08-01

    We study stock market instability by using cross-correlations constructed from the return time series of 366 stocks traded on the Tokyo Stock Exchange from January 5, 1998 to December 30, 2013. To investigate the dynamical evolution of the cross-correlations, crosscorrelation matrices are calculated with a rolling window of 400 days. To quantify the volatile market stages where the potential risk is high, we apply the principal components analysis and measure the cumulative risk fraction (CRF), which is the system variance associated with the first few principal components. From the CRF, we detected three volatile market stages corresponding to the bankruptcy of Lehman Brothers, the 2011 Tohoku Region Pacific Coast Earthquake, and the FRB QE3 reduction observation in the study period. We further apply the random matrix theory for the risk analysis and find that the first eigenvector is more equally de-localized when the market is volatile.

  12. Dynamical Analysis of Stock Market Instability by Cross-correlation Matrix

    International Nuclear Information System (INIS)

    Takaishi, Tetsuya

    2016-01-01

    We study stock market instability by using cross-correlations constructed from the return time series of 366 stocks traded on the Tokyo Stock Exchange from January 5, 1998 to December 30, 2013. To investigate the dynamical evolution of the cross-correlations, crosscorrelation matrices are calculated with a rolling window of 400 days. To quantify the volatile market stages where the potential risk is high, we apply the principal components analysis and measure the cumulative risk fraction (CRF), which is the system variance associated with the first few principal components. From the CRF, we detected three volatile market stages corresponding to the bankruptcy of Lehman Brothers, the 2011 Tohoku Region Pacific Coast Earthquake, and the FRB QE3 reduction observation in the study period. We further apply the random matrix theory for the risk analysis and find that the first eigenvector is more equally de-localized when the market is volatile. (paper)

  13. Ultrafast chirped optical waveform recorder using referenced heterodyning and a time microscope

    Science.gov (United States)

    Bennett, Corey Vincent [Livermore, CA

    2011-11-22

    A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

  14. Ultrafast chirped optical waveform recording using referenced heterodyning and a time microscope

    Science.gov (United States)

    Bennett, Corey Vincent

    2010-06-15

    A new technique for capturing both the amplitude and phase of an optical waveform is presented. This technique can capture signals with many THz of bandwidths in a single shot (e.g., temporal resolution of about 44 fs), or be operated repetitively at a high rate. That is, each temporal window (or frame) is captured single shot, in real time, but the process may be run repeatedly or single-shot. This invention expands upon previous work in temporal imaging by adding heterodyning, which can be self-referenced for improved precision and stability, to convert frequency chirp (the second derivative of phase with respect to time) into a time varying intensity modulation. By also including a variety of possible demultiplexing techniques, this process is scalable to recoding continuous signals.

  15. Closed form of optimal current waveform for class-F PA up to fourth ...

    Indian Academy of Sciences (India)

    PA and its dual, usually referred as inverse class-F PA, current and voltage ... voltage waveforms provides a number of advantages in the process of PA design ... RF PA design approaches with waveform theory and experimental waveform.

  16. An Overview of Radar Waveform Optimization for Target Detection

    Directory of Open Access Journals (Sweden)

    Wang Lulu

    2016-10-01

    Full Text Available An optimal waveform design method that fully employs the knowledge of the target and the environment can further improve target detection performance, thus is of vital importance to research. In this paper, methods of radar waveform optimization for target detection are reviewed and summarized and provide the basis for the research.

  17. Financial liberalization and stock market cross-correlation: MF-DCCA analysis based on Shanghai-Hong Kong Stock Connect

    Science.gov (United States)

    Ruan, Qingsong; Zhang, Shuhua; Lv, Dayong; Lu, Xinsheng

    2018-02-01

    Based on the implementation of Shanghai-Hong Kong Stock Connect in China, this paper examines the effects of financial liberalization on stock market comovement using both multifractal detrended fluctuation analysis (MF-DFA) and multifractal detrended cross-correlation analysis (MF-DCCA) methods. Results based on MF-DFA confirm the multifractality of Shanghai and Hong Kong stock markets, and the market efficiency of Shanghai stock market increased after the implementation of this connect program. Besides, analysis based on MF-DCCA has verified the existence of persistent cross-correlation between Shanghai and Hong Kong stock markets, and the cross-correlation gets stronger after the launch of this liberalization program. Finally, we find that fat-tail distribution is the main source of multifractality in the cross-correlations before the stock connect program, while long-range correlation contributes to the multifractality after this program.

  18. A nonlinear approach of elastic reflection waveform inversion

    KAUST Repository

    Guo, Qiang

    2016-09-06

    Elastic full waveform inversion (EFWI) embodies the original intention of waveform inversion at its inception as it is a better representation of the mostly solid Earth. However, compared with the acoustic P-wave assumption, EFWI for P- and S-wave velocities using multi-component data admitted mixed results. Full waveform inversion (FWI) is a highly nonlinear problem and this nonlinearity only increases under the elastic assumption. Reflection waveform inversion (RWI) can mitigate the nonlinearity by relying on transmissions from reflections focused on inverting low wavenumber components of the model. In our elastic endeavor, we split the P- and S-wave velocities into low wavenumber and perturbation components and propose a nonlinear approach to invert for both of them. The new optimization problem is built on an objective function that depends on both background and perturbation models. We utilize an equivalent stress source based on the model perturbation to generate reflection instead of demigrating from an image, which is applied in conventional RWI. Application on a slice of an ocean-bottom data shows that our method can efficiently update the low wavenumber parts of the model, but more so, obtain perturbations that can be added to the low wavenumbers for a high resolution output.

  19. A nonlinear approach of elastic reflection waveform inversion

    KAUST Repository

    Guo, Qiang; Alkhalifah, Tariq Ali

    2016-01-01

    Elastic full waveform inversion (EFWI) embodies the original intention of waveform inversion at its inception as it is a better representation of the mostly solid Earth. However, compared with the acoustic P-wave assumption, EFWI for P- and S-wave velocities using multi-component data admitted mixed results. Full waveform inversion (FWI) is a highly nonlinear problem and this nonlinearity only increases under the elastic assumption. Reflection waveform inversion (RWI) can mitigate the nonlinearity by relying on transmissions from reflections focused on inverting low wavenumber components of the model. In our elastic endeavor, we split the P- and S-wave velocities into low wavenumber and perturbation components and propose a nonlinear approach to invert for both of them. The new optimization problem is built on an objective function that depends on both background and perturbation models. We utilize an equivalent stress source based on the model perturbation to generate reflection instead of demigrating from an image, which is applied in conventional RWI. Application on a slice of an ocean-bottom data shows that our method can efficiently update the low wavenumber parts of the model, but more so, obtain perturbations that can be added to the low wavenumbers for a high resolution output.

  20. Moment tensor inversions using strong motion waveforms of Taiwan TSMIP data, 1993–2009

    Science.gov (United States)

    Chang, Kaiwen; Chi, Wu-Cheng; Gung, Yuancheng; Dreger, Douglas; Lee, William H K.; Chiu, Hung-Chie

    2011-01-01

    Earthquake source parameters are important for earthquake studies and seismic hazard assessment. Moment tensors are among the most important earthquake source parameters, and are now routinely derived using modern broadband seismic networks around the world. Similar waveform inversion techniques can also apply to other available data, including strong-motion seismograms. Strong-motion waveforms are also broadband, and recorded in many regions since the 1980s. Thus, strong-motion data can be used to augment moment tensor catalogs with a much larger dataset than that available from the high-gain, broadband seismic networks. However, a systematic comparison between the moment tensors derived from strong motion waveforms and high-gain broadband waveforms has not been available. In this study, we inverted the source mechanisms of Taiwan earthquakes between 1993 and 2009 by using the regional moment tensor inversion method using digital data from several hundred stations in the Taiwan Strong Motion Instrumentation Program (TSMIP). By testing different velocity models and filter passbands, we were able to successfully derive moment tensor solutions for 107 earthquakes of Mw >= 4.8. The solutions for large events agree well with other available moment tensor catalogs derived from local and global broadband networks. However, for Mw = 5.0 or smaller events, we consistently over estimated the moment magnitudes by 0.5 to 1.0. We have tested accelerograms, and velocity waveforms integrated from accelerograms for the inversions, and found the results are similar. In addition, we used part of the catalogs to study important seismogenic structures in the area near Meishan Taiwan which was the site of a very damaging earthquake a century ago, and found that the structures were dominated by events with complex right-lateral strike-slip faulting during the recent decade. The procedures developed from this study may be applied to other strong-motion datasets to compliment or fill

  1. Multifractal cross-correlations between crude oil and tanker freight rate

    Science.gov (United States)

    Chen, Feier; Miao, Yuqi; Tian, Kang; Ding, Xiaoxu; Li, Tingyi

    2017-05-01

    Analysis of crude oil price and tanker freight rate volatility attract more attention as the mechanism is not only the basis of industrialization but also a vital role in economics, especially after the year 2008 when financial crisis notably blew the maritime transportation. In this paper, we studied the cross-correlations between the West Texas International crude oil (WTI) and Baltic Exchange Dirty Tanker Index (BDTI) employing the Multifractal Detrended Cross-Correlation Analysis (MF-DCCA). Empirical results show that the degree of short-term cross-correlation is higher than that in the long term and that the strength of multifractality after financial crisis is larger than that before. Moreover, the components of multifractal spectrum are quantified with the finite-size effect taken into consideration and an improved method in terms of constructing the surrogated time series provided. Numerical results show that the multifractality is generated mostly from the nonlinear and the fat-tailed probability distribution (PDF) part. Also, it is apparent that the PDF part changes a lot after the financial crisis. The research is contributory to risk management by providing various instructions for participants in shipping markets. Our main contribution is that we investigated both the multifractal features and the origin of multifractality and provided confirming evidence of multifractality through numerical results while applying quantitative analysis based on MF-DCCA; furthermore, the research is contributory to risk management since it provides instructions in both economic market and stock market simultaneously. However, constructing the surrogated series in order to obtain consistence seems less convincing which requires further discussion and attempts.

  2. Exploring the use of numerical relativity waveforms in burst analysis of precessing black hole mergers

    International Nuclear Information System (INIS)

    Fischetti, Sebastian; Cadonati, Laura; Mohapatra, Satyanarayan R. P.; Healy, James; London, Lionel; Shoemaker, Deirdre

    2011-01-01

    Recent years have witnessed tremendous progress in numerical relativity and an ever improving performance of ground-based interferometric gravitational wave detectors. In preparation for the Advanced Laser Interferometer Gravitational Wave Observatory (Advanced LIGO) and a new era in gravitational wave astronomy, the numerical relativity and gravitational wave data analysis communities are collaborating to ascertain the most useful role for numerical relativity waveforms in the detection and characterization of binary black hole coalescences. In this paper, we explore the detectability of equal mass, merging black hole binaries with precessing spins and total mass M T (set-membership sign)[80,350]M · , using numerical relativity waveforms and templateless search algorithms designed for gravitational wave bursts. In particular, we present a systematic study using waveforms produced by the MayaKranc code that are added to colored, Gaussian noise and analyzed with the Omega burst search algorithm. Detection efficiency is weighed against the orientation of one of the black-hole's spin axes. We find a strong correlation between the detection efficiency and the radiated energy and angular momentum, and that the inclusion of the l=2, m=±1, 0 modes, at a minimum, is necessary to account for the full dynamics of precessing systems.

  3. Electronics via waveform analysis

    CERN Document Server

    Craig, Edwin C

    1993-01-01

    The author believes that a good basic understanding of electronics can be achieved by detailed visual analyses of the actual voltage waveforms present in selected circuits. The voltage waveforms included in this text were photographed using a 35-rrun camera in an attempt to make the book more attractive. This book is intended for the use of students with a variety of backgrounds. For this reason considerable material has been placed in the Appendix for those students who find it useful. The Appendix includes many basic electricity and electronic concepts as well as mathematical derivations that are not vital to the understanding of the circuit being discussed in the text at that time. Also some derivations might be so long that, if included in the text, it could affect the concentration of the student on the circuit being studied. The author has tried to make the book comprehensive enough so that a student could use it as a self-study course, providing one has access to adequate laboratory equipment.

  4. PBX-M waveform generator

    International Nuclear Information System (INIS)

    Feng, H.; Frank, K.T.; Kaye, S.

    1987-01-01

    The PBX-M (Princeton Beta Experiment) is an unique Tokamak experiment designed to run with a highly indented plasma. The shaping control will be accomplished through a closed-loop power supply control system. The system will make use of sixteen pre-programmed reference signals and twenty signals taken from direct measurements as input to an analog computer. Through a matrix conversion in the analog computer, these input signals will be used to generate eight control signals to control the eight power supplies. The pre-programmed reference signals will be created using a Macintosh personal computer interfaced to CAMAC (Comptuer Automated Measurement And Control) hardware for down-loading waveforms. The reference signals will be created on the Macintosh by the physics operators, utilizing the full graphics capability of the system. These waveforms are transferred to CAMAC memory, which are then strobed in real time through digital-to-analog converters and fed into the analog computer. The overall system (both hardware and software) is designed to be fail-safe. Specific features of the system, such as load inhibit and discharge inhibit, are discussed

  5. Atmospheric pollution measurement by optical cross correlation methods - A concept

    Science.gov (United States)

    Fisher, M. J.; Krause, F. R.

    1971-01-01

    Method combines standard spectroscopy with statistical cross correlation analysis of two narrow light beams for remote sensing to detect foreign matter of given particulate size and consistency. Method is applicable in studies of generation and motion of clouds, nuclear debris, ozone, and radiation belts.

  6. Full Waveform Inversion with Multisource Frequency Selection of Marine Streamer Data

    KAUST Repository

    Huang, Yunsong

    2017-10-27

    The theory and practice of multisource full waveform inversion of marine supergathers are described with a frequency-selection strategy. The key enabling property of frequency selection is that it eliminates the crosstalk among sources, thus overcoming the aperture mismatch of marine multisource inversion. Tests on multisource full waveform inversion of synthetic marine data and Gulf of Mexico data show speedups of 4× and 8×, respectively, compared to conventional full waveform inversion.

  7. Full Waveform Inversion with Multisource Frequency Selection of Marine Streamer Data

    KAUST Repository

    Huang, Yunsong; Schuster, Gerard T.

    2017-01-01

    The theory and practice of multisource full waveform inversion of marine supergathers are described with a frequency-selection strategy. The key enabling property of frequency selection is that it eliminates the crosstalk among sources, thus overcoming the aperture mismatch of marine multisource inversion. Tests on multisource full waveform inversion of synthetic marine data and Gulf of Mexico data show speedups of 4× and 8×, respectively, compared to conventional full waveform inversion.

  8. A microcomputer-based waveform generator for Moessbauer spectrometers

    International Nuclear Information System (INIS)

    Huang Jianping; Chen Xiaomei

    1995-01-01

    A waveform generator for Moessbauer spectrometers based on 8751 single chip microcomputer is described. The reference wave form with high linearity is generated with a 12 bit DAC, and its amplitude is controlled with a 8 bit DAC. Because the channel advance and synchronous signals can be delayed arbitrarily, excellent folded spectra can be acquired. This waveform generator can be controlled with DIP switches on faceplate or series interface of the IBM-PC microcomputer

  9. Golay Complementary Waveforms in Reed–Müller Sequences for Radar Detection of Nonzero Doppler Targets

    Science.gov (United States)

    Wang, Xuezhi; Huang, Xiaotao; Suvorova, Sofia; Moran, Bill

    2018-01-01

    Golay complementary waveforms can, in theory, yield radar returns of high range resolution with essentially zero sidelobes. In practice, when deployed conventionally, while high signal-to-noise ratios can be achieved for static target detection, significant range sidelobes are generated by target returns of nonzero Doppler causing unreliable detection. We consider signal processing techniques using Golay complementary waveforms to improve radar detection performance in scenarios involving multiple nonzero Doppler targets. A signal processing procedure based on an existing, so called, Binomial Design algorithm that alters the transmission order of Golay complementary waveforms and weights the returns is proposed in an attempt to achieve an enhanced illumination performance. The procedure applies one of three proposed waveform transmission ordering algorithms, followed by a pointwise nonlinear processor combining the outputs of the Binomial Design algorithm and one of the ordering algorithms. The computational complexity of the Binomial Design algorithm and the three ordering algorithms are compared, and a statistical analysis of the performance of the pointwise nonlinear processing is given. Estimation of the areas in the Delay–Doppler map occupied by significant range sidelobes for given targets are also discussed. Numerical simulations for the comparison of the performances of the Binomial Design algorithm and the three ordering algorithms are presented for both fixed and randomized target locations. The simulation results demonstrate that the proposed signal processing procedure has a better detection performance in terms of lower sidelobes and higher Doppler resolution in the presence of multiple nonzero Doppler targets compared to existing methods. PMID:29324708

  10. Extended families of 2D arrays with near optimal auto and low cross-correlation

    Science.gov (United States)

    Svalbe, I. D.; Tirkel, A. Z.

    2017-12-01

    Families of 2D arrays can be constructed where each array has perfect autocorrelation, and the cross-correlation between any pair of family members is optimally low. We exploit equivalent Hadamard matrices to construct many families of p p × p arrays, where p is any 4k-1 prime. From these families, we assemble extended families of arrays with members that exhibit perfect autocorrelation and next-to-optimally low cross-correlation. Pseudo-Hadamard matrices are used to construct extended families using p = 4k + 1 primes. An optimal family of 31 31 × 31 perfect arrays can provide copyright protection to uniquely stamp a robust, low-visibility watermark within every frame of each second of high-definition, 30 fps video. The extended families permit the embedding of many more perfect watermarks that have next-to-minimal cross-correlations.

  11. Traitement des diagraphies acoustiques. Première partie : application de techniques issues de l'intelligence artificielle au pointe des diagraphies acoustiques Full Waveform Acoustic Data Processing. Part One: an Artificial Intelligence Approach for the Picking of Waves on Full-Waveform Acoustic Data

    Directory of Open Access Journals (Sweden)

    Mari J. L.

    2006-11-01

    Full Text Available Les enregistrements des données acoustiques en champ total (fuit waveform ont conduit le géophysicien et le diagraphiste à utiliser des techniques de traitement du signal pour séparer les différentes ondes observées sur les enregistrements. L'une des tâches importantes du traitement des diagraphies acoustiques est le pointé des temps d'arrivée des différentes ondes enregistrées. Une démarche de type système expert a été utilisée pour mettre au point un algorithme multicanaux qui réalise le pointé des différentes ondes, à l'aide de règles faisant intervenir les caractéristiques ou attributs de chaque onde. Une onde est caractérisée par sa vitesse, sa fréquence, son amplitude et sa cohérence latérale. L'algorithme fournit un ensemble de logs accompagnés d'une estimation de la dispersion des mesures à chaque cote profondeur. Les logs fournis sont les logs de lenteur et les logs de fréquence. Les résultats obtenus sur un ensemble de diagraphies acoustiques enregistrées dans un puits vertical du Bassin parisien montrent que la dispersion des mesures reste faible en comparaison des pas d'échantillonnage en temps et profondeur. Les logs de dispersion peuvent aussi permettre de détecter des phénomènes physiques tels que caves, fractures, conversions d'ondes ou interférences, reliés à la lithologie. Dans une deuxième partie, nous montrerons différentes techniques de séparation d'ondes. La troisième partie illustrera, sur un cas particulier, l'utilisation des logs issus des diagraphies acoustiques pour caractériser les formations. The full waveforms recorded by an array of recievers in a borehole sonic tool contain a set of waves that can be fruitfully used to obtain detailed information about the nearborehole lithology and structure. The different waves that can be observed by full-waveform sonic data are described in this article. The main tools used in the recording of full-waveform data are then reviewed

  12. A minimax technique for time-domain design of preset digital equalizers using linear programming

    Science.gov (United States)

    Vaughn, G. L.; Houts, R. C.

    1975-01-01

    A linear programming technique is presented for the design of a preset finite-impulse response (FIR) digital filter to equalize the intersymbol interference (ISI) present in a baseband channel with known impulse response. A minimax technique is used which minimizes the maximum absolute error between the actual received waveform and a specified raised-cosine waveform. Transversal and frequency-sampling FIR digital filters are compared as to the accuracy of the approximation, the resultant ISI and the transmitted energy required. The transversal designs typically have slightly better waveform accuracy for a given distortion; however, the frequency-sampling equalizer uses fewer multipliers and requires less transmitted energy. A restricted transversal design is shown to use the least number of multipliers at the cost of a significant increase in energy and loss of waveform accuracy at the receiver.

  13. Elastic full waveform inversion based on the homogenization method: theoretical framework and 2-D numerical illustrations

    Science.gov (United States)

    Capdeville, Yann; Métivier, Ludovic

    2018-05-01

    Seismic imaging is an efficient tool to investigate the Earth interior. Many of the different imaging techniques currently used, including the so-called full waveform inversion (FWI), are based on limited frequency band data. Such data are not sensitive to the true earth model, but to a smooth version of it. This smooth version can be related to the true model by the homogenization technique. Homogenization for wave propagation in deterministic media with no scale separation, such as geological media, has been recently developed. With such an asymptotic theory, it is possible to compute an effective medium valid for a given frequency band such that effective waveforms and true waveforms are the same up to a controlled error. In this work we make the link between limited frequency band inversion, mainly FWI, and homogenization. We establish the relation between a true model and an FWI result model. This relation is important for a proper interpretation of FWI images. We numerically illustrate, in the 2-D case, that an FWI result is at best the homogenized version of the true model. Moreover, it appears that the homogenized FWI model is quite independent of the FWI parametrization, as long as it has enough degrees of freedom. In particular, inverting for the full elastic tensor is, in each of our tests, always a good choice. We show how the homogenization can help to understand FWI behaviour and help to improve its robustness and convergence by efficiently constraining the solution space of the inverse problem.

  14. Codesign of Beam Pattern and Sparse Frequency Waveforms for MIMO Radar

    Directory of Open Access Journals (Sweden)

    Chaoyun Mai

    2015-01-01

    Full Text Available Multiple-input multiple-output (MIMO radar takes the advantages of high degrees of freedom for beam pattern design and waveform optimization, because each antenna in centralized MIMO radar system can transmit different signal waveforms. When continuous band is divided into several pieces, sparse frequency radar waveforms play an important role due to the special pattern of the sparse spectrum. In this paper, we start from the covariance matrix of the transmitted waveform and extend the concept of sparse frequency design to the study of MIMO radar beam pattern. With this idea in mind, we first solve the problem of semidefinite constraint by optimization tools and get the desired covariance matrix of the ideal beam pattern. Then, we use the acquired covariance matrix and generalize the objective function by adding the constraint of both constant modulus of the signals and corresponding spectrum. Finally, we solve the objective function by the cyclic algorithm and obtain the sparse frequency MIMO radar waveforms with desired beam pattern. The simulation results verify the effectiveness of this method.

  15. Stimulator with arbitrary waveform for auditory evoked potentials

    International Nuclear Information System (INIS)

    Martins, H R; Romao, M; Placido, D; Provenzano, F; Tierra-Criollo, C J

    2007-01-01

    The technological improvement helps many medical areas. The audiometric exams involving the auditory evoked potentials can make better diagnoses of auditory disorders. This paper proposes the development of a stimulator based on Digital Signal Processor. This stimulator is the first step of an auditory evoked potential system based on the ADSP-BF533 EZ KIT LITE (Analog Devices Company - USA). The stimulator can generate arbitrary waveform like Sine Waves, Modulated Amplitude, Pulses, Bursts and Pips. The waveforms are generated through a graphical interface programmed in C++ in which the user can define the parameters of the waveform. Furthermore, the user can set the exam parameters as number of stimuli, time with stimulation (Time ON) and time without stimulus (Time OFF). In future works will be implemented another parts of the system that includes the acquirement of electroencephalogram and signal processing to estimate and analyze the evoked potential

  16. Stimulator with arbitrary waveform for auditory evoked potentials

    Energy Technology Data Exchange (ETDEWEB)

    Martins, H R; Romao, M; Placido, D; Provenzano, F; Tierra-Criollo, C J [Universidade Federal de Minas Gerais (UFMG), Departamento de Engenharia Eletrica (DEE), Nucleo de Estudos e Pesquisa em Engenharia Biomedica NEPEB, Av. Ant. Carlos, 6627, sala 2206, Pampulha, Belo Horizonte, MG, 31.270-901 (Brazil)

    2007-11-15

    The technological improvement helps many medical areas. The audiometric exams involving the auditory evoked potentials can make better diagnoses of auditory disorders. This paper proposes the development of a stimulator based on Digital Signal Processor. This stimulator is the first step of an auditory evoked potential system based on the ADSP-BF533 EZ KIT LITE (Analog Devices Company - USA). The stimulator can generate arbitrary waveform like Sine Waves, Modulated Amplitude, Pulses, Bursts and Pips. The waveforms are generated through a graphical interface programmed in C++ in which the user can define the parameters of the waveform. Furthermore, the user can set the exam parameters as number of stimuli, time with stimulation (Time ON) and time without stimulus (Time OFF). In future works will be implemented another parts of the system that includes the acquirement of electroencephalogram and signal processing to estimate and analyze the evoked potential.

  17. Source-independent time-domain waveform inversion using convolved wavefields: Application to the encoded multisource waveform inversion

    KAUST Repository

    Choi, Yun Seok; Alkhalifah, Tariq Ali

    2011-01-01

    Full waveform inversion requires a good estimation of the source wavelet to improve our chances of a successful inversion. This is especially true for an encoded multisource time-domain implementation, which, conventionally, requires separate

  18. PAPR-Constrained Pareto-Optimal Waveform Design for OFDM-STAP Radar

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Satyabrata [ORNL

    2014-01-01

    We propose a peak-to-average power ratio (PAPR) constrained Pareto-optimal waveform design approach for an orthogonal frequency division multiplexing (OFDM) radar signal to detect a target using the space-time adaptive processing (STAP) technique. The use of an OFDM signal does not only increase the frequency diversity of our system, but also enables us to adaptively design the OFDM coefficients in order to further improve the system performance. First, we develop a parametric OFDM-STAP measurement model by considering the effects of signaldependent clutter and colored noise. Then, we observe that the resulting STAP-performance can be improved by maximizing the output signal-to-interference-plus-noise ratio (SINR) with respect to the signal parameters. However, in practical scenarios, the computation of output SINR depends on the estimated values of the spatial and temporal frequencies and target scattering responses. Therefore, we formulate a PAPR-constrained multi-objective optimization (MOO) problem to design the OFDM spectral parameters by simultaneously optimizing four objective functions: maximizing the output SINR, minimizing two separate Cramer-Rao bounds (CRBs) on the normalized spatial and temporal frequencies, and minimizing the trace of CRB matrix on the target scattering coefficients estimations. We present several numerical examples to demonstrate the achieved performance improvement due to the adaptive waveform design.

  19. Lenses in the forest: cross correlation of the Lyman-alpha flux with cosmic microwave background lensing.

    Science.gov (United States)

    Vallinotto, Alberto; Das, Sudeep; Spergel, David N; Viel, Matteo

    2009-08-28

    We present a theoretical estimate for a new observable: the cross correlation between the Lyman-alpha flux fluctuations in quasar spectra and the convergence of the cosmic microwave background as measured along the same line of sight. As a first step toward the assessment of its detectability, we estimate the signal-to-noise ratio using linear theory. Although the signal-to-noise is small for a single line of sight and peaks at somewhat smaller redshifts than those probed by the Lyman-alpha forest, we estimate a total signal-to-noise of 9 for cross correlating quasar spectra of SDSS-III with Planck and 20 for cross correlating with a future polarization based cosmic microwave background experiment. The detection of this effect would be a direct measure of the neutral hydrogen-matter cross correlation and could provide important information on the growth of structures at large scales in a redshift range which is still poorly probed.

  20. Measurement of the dipole in the cross-correlation function of galaxies

    CERN Document Server

    Gaztanaga, Enrique; Hui, Lam

    2017-01-01

    It is usually assumed that in the linear regime the two-point correlation function of galaxies contains only a monopole, quadrupole and hexadecapole. Looking at cross-correlations between different populations of galaxies, this turns out not to be the case. In particular, the cross-correlations between a bright and a faint population of galaxies contain also a dipole. In this paper we present the first attempt to measure this dipole. We discuss the four types of effects that contribute to the dipole: relativistic distortions, evolution effect, wide-angle effect and large-angle effect. We show that the first three contributions are intrinsic anti-symmetric contributions that do not depend on the choice of angle used to measure the dipole. On the other hand the large-angle effect appears only if the angle chosen to extract the dipole breaks the symmetry of the problem. We show that the relativistic distortions, the evolution effect and the wide-angle effect are too small to be detected in the LOWz and CMASS sam...

  1. Fuel reprocessing data validation using the isotope correlation technique

    International Nuclear Information System (INIS)

    Persiani, P.J.; Bucher, R.G.; Pond, R.B.; Cornella, R.J.

    1990-01-01

    The Isotope Correlation Technique (ICT), in conjunction with the gravimetric (Pu/U ratio) method for mass determination, provides an independent verification of the input accountancy at the dissolver or accountancy stage of the reprocessing plant. The Isotope Correlation Technique has been applied to many classes of domestic and international reactor systems (light-water, heavy-water, and graphite reactors) operating in a variety of modes (power, research, and production reactors), and for a variety of reprocessing fuel cycle management strategies. Analysis of reprocessing operations data based on isotopic correlations derived for assemblies in a PWR environment and fuel management scheme, yielded differences between the measurement-derived and ICT-derived plutonium mass determinations of (- 0.02 ± 0.23)% for the measured U-235 and (+ 0.50 ± 0.31)% for the measured Pu-239, for a core campaign. The ICT analyses has been implemented for the plutonium isotopics in a depleted uranium assembly in a heavy-water, enriched uranium system and for the uranium isotopes in the fuel assemblies in light-water, highly-enriched systems

  2. Efficient data retrieval method for similar plasma waveforms in EAST

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ying, E-mail: liuying-ipp@szu.edu.cn [SZU-CASIPP Joint Laboratory for Applied Plasma, Shenzhen University, Shenzhen 518060 (China); Huang, Jianjun; Zhou, Huasheng; Wang, Fan [SZU-CASIPP Joint Laboratory for Applied Plasma, Shenzhen University, Shenzhen 518060 (China); Wang, Feng [Institute of Plasma Physics Chinese Academy of Sciences, Hefei 230031 (China)

    2016-11-15

    Highlights: • The proposed method is carried out by means of bounding envelope and angle distance. • It allows retrieving for whole similar waveforms of any time length. • In addition, the proposed method is also possible to retrieve subsequences. - Abstract: Fusion research relies highly on data analysis due to its massive-sized database. In the present work, we propose an efficient method for searching and retrieving similar plasma waveforms in Experimental Advanced Superconducting Tokamak (EAST). Based on Piecewise Linear Aggregate Approximation (PLAA) for extracting feature values, the searching process is accomplished in two steps. The first one is coarse searching to narrow down the search space, which is carried out by means of bounding envelope. The second step is fine searching to retrieval similar waveforms, which is implemented by the angle distance. The proposed method is tested in EAST databases and turns out to have good performance in retrieving similar waveforms.

  3. Performance Analysis of Blind Subspace-Based Signature Estimation Algorithms for DS-CDMA Systems with Unknown Correlated Noise

    Science.gov (United States)

    Zarifi, Keyvan; Gershman, Alex B.

    2006-12-01

    We analyze the performance of two popular blind subspace-based signature waveform estimation techniques proposed by Wang and Poor and Buzzi and Poor for direct-sequence code division multiple-access (DS-CDMA) systems with unknown correlated noise. Using the first-order perturbation theory, analytical expressions for the mean-square error (MSE) of these algorithms are derived. We also obtain simple high SNR approximations of the MSE expressions which explicitly clarify how the performance of these techniques depends on the environmental parameters and how it is related to that of the conventional techniques that are based on the standard white noise assumption. Numerical examples further verify the consistency of the obtained analytical results with simulation results.

  4. A new mathematical model of wrist pulse waveforms characterizes patients with cardiovascular disease - A pilot study.

    Science.gov (United States)

    He, Dianning; Wang, Lu; Fan, Xiaobing; Yao, Yang; Geng, Ning; Sun, Yingxian; Xu, Lisheng; Qian, Wei

    2017-10-01

    The purpose of this study was to analyze and compare a series of measured radial pulse waves as a function of contact pressure for young and old healthy volunteers, and old patients with cardiovascular disease. The radial pulse waves were detected with a pressure sensor and the contact pressure of the sensor was incremented by 20gf during the signal acquisition. A mathematical model of radial pulse waveform was developed by using two Gaussian functions modulated by radical functions and used to fit the pulse waveforms. Then, a ratio of area (r A ) and a ratio of peak height (r PH ) between percussion wave and dicrotic wave as a function of contact pressure were calculated based on fitted parameters. The results demonstrated that there was a maximum for waveform peak height, a minimum for r A (r A min ) and a minimum for r PH (r PH min ) appeared as contact pressure varied. On average, older patients had higher peak amplitude and a significantly smaller r A min (pmathematical model had moderate to strong positive linear correlations (r=0.66 to 0.84, pmodel. The receiver operating characteristic (ROC) analysis showed that the r A min calculated with the model and the contact pressure measured at the r A min had good diagnostic accuracy to distinguish healthy volunteers vs. diseased patients. Therefore, using the mathematical model to quantitatively analyze the radial pulse waveforms as a function of contact pressure could be useful in the diagnosis of cardiovascular diseases. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

  5. Experimental cross-correlation nitrogen Q-branch CARS thermometry in a spark ignition engine

    Science.gov (United States)

    Lockett, R. D.; Ball, D.; Robertson, G. N.

    2013-07-01

    A purely experimental technique was employed to derive temperatures from nitrogen Q-branch Coherent Anti-Stokes Raman Scattering (CARS) spectra, obtained in a high pressure, high temperature environment (spark ignition Otto engine). This was in order to obviate any errors arising from deficiencies in the spectral scaling laws which are commonly used to represent nitrogen Q-branch CARS spectra at high pressure. The spectra obtained in the engine were compared with spectra obtained in a calibrated high pressure, high temperature cell, using direct cross-correlation in place of the minimisation of sums of squares of residuals. The technique is demonstrated through the measurement of air temperature as a function of crankshaft angle inside the cylinder of a motored single-cylinder Ricardo E6 research engine, followed by the measurement of fuel-air mixture temperatures obtained during the compression stroke in a knocking Ricardo E6 engine. A standard CARS programme (SANDIA's CARSFIT) was employed to calibrate the altered non-resonant background contribution to the CARS spectra that was caused by the alteration to the mole fraction of nitrogen in the unburned fuel-air mixture. The compression temperature profiles were extrapolated in order to predict the auto-ignition temperatures.

  6. Study of complex resistivity measurement using current and potential waveform data; Denryu to den`i hakei data wo riyoshita fukusohi teiko sokutei no kento

    Energy Technology Data Exchange (ETDEWEB)

    Shima, H; Sakurai, K; Yamashita, Y [OYO Corp., Tokyo (Japan)

    1997-10-22

    This paper proposes a measurement method for complex resistivity using both current and potential waveforms. This method was applied to actual data. Especially, chargeability was discussed among complex resistivities. A method was proposed for determining the complex resistivity. At first, digital measurements of both current and potential waveforms were conducted. For the potential waveform, zero-order self-potential was canceled. Then, the FFT technique was applied to both current and potential waveforms, to determine both current and potential in the frequency domain. Hereafter, complex resistivity was determined through simple division. Since the inductive coupling was observed at higher frequencies, it was difficult to apply Cole-Cole model, simply. However, the inductive coupling could be removed using proper sampling frequency. Thus, a proper Cole-Cole dispersion curve could be obtained. Using this Cole-Cole dispersion curve, new chargeability could be defined. A linear relation between this chargeability and the ordinary time domain chargeability was made clear. 4 refs., 10 figs.

  7. Augmented kludge waveforms for detecting extreme-mass-ratio inspirals

    Science.gov (United States)

    Chua, Alvin J. K.; Moore, Christopher J.; Gair, Jonathan R.

    2017-08-01

    The extreme-mass-ratio inspirals (EMRIs) of stellar-mass compact objects into massive black holes are an important class of source for the future space-based gravitational-wave detector LISA. Detecting signals from EMRIs will require waveform models that are both accurate and computationally efficient. In this paper, we present the latest implementation of an augmented analytic kludge (AAK) model, publicly available at https://github.com/alvincjk/EMRI_Kludge_Suite as part of an EMRI waveform software suite. This version of the AAK model has improved accuracy compared to its predecessors, with two-month waveform overlaps against a more accurate fiducial model exceeding 0.97 for a generic range of sources; it also generates waveforms 5-15 times faster than the fiducial model. The AAK model is well suited for scoping out data analysis issues in the upcoming round of mock LISA data challenges. A simple analytic argument shows that it might even be viable for detecting EMRIs with LISA through a semicoherent template bank method, while the use of the original analytic kludge in the same approach will result in around 90% fewer detections.

  8. A compact, multichannel, and low noise arbitrary waveform generator.

    Science.gov (United States)

    Govorkov, S; Ivanov, B I; Il'ichev, E; Meyer, H-G

    2014-05-01

    A new type of high functionality, fast, compact, and easy programmable arbitrary waveform generator for low noise physical measurements is presented. The generator provides 7 fast differential waveform channels with a maximum bandwidth up to 200 MHz frequency. There are 6 fast pulse generators on the generator board with 78 ps time resolution in both duration and delay, 3 of them with amplitude control. The arbitrary waveform generator is additionally equipped with two auxiliary slow 16 bit analog-to-digital converters and four 16 bit digital-to-analog converters for low frequency applications. Electromagnetic shields are introduced to the power supply, digital, and analog compartments and with a proper filter design perform more than 110 dB digital noise isolation to the output signals. All the output channels of the board have 50 Ω SubMiniature version A termination. The generator board is suitable for use as a part of a high sensitive physical equipment, e.g., fast read out and manipulation of nuclear magnetic resonance or superconducting quantum systems and any other application, which requires electromagnetic interference free fast pulse and arbitrary waveform generation.

  9. A compact, multichannel, and low noise arbitrary waveform generator

    International Nuclear Information System (INIS)

    Govorkov, S.; Ivanov, B. I.; Il'ichev, E.; Meyer, H.-G.

    2014-01-01

    A new type of high functionality, fast, compact, and easy programmable arbitrary waveform generator for low noise physical measurements is presented. The generator provides 7 fast differential waveform channels with a maximum bandwidth up to 200 MHz frequency. There are 6 fast pulse generators on the generator board with 78 ps time resolution in both duration and delay, 3 of them with amplitude control. The arbitrary waveform generator is additionally equipped with two auxiliary slow 16 bit analog-to-digital converters and four 16 bit digital-to-analog converters for low frequency applications. Electromagnetic shields are introduced to the power supply, digital, and analog compartments and with a proper filter design perform more than 110 dB digital noise isolation to the output signals. All the output channels of the board have 50 Ω SubMiniature version A termination. The generator board is suitable for use as a part of a high sensitive physical equipment, e.g., fast read out and manipulation of nuclear magnetic resonance or superconducting quantum systems and any other application, which requires electromagnetic interference free fast pulse and arbitrary waveform generation

  10. Development of plasma current waveform adjusting system ZLJ for tokamak device HL-1

    International Nuclear Information System (INIS)

    Wang Shangbing; Hu Haotian; Tang Fangqun; Zhou Yongzheng; Chu Xiuzhong; Cheng Jiashun; Gao Yunxia

    1989-12-01

    The control of some typical Tokamak discharge waveforms has been achieved by using plasma current waveform adjusting system ZLJ in the ohmic heating of HL-1. The discharge waveforms include a series of regular plasma current waveforms with various slow rising rate, such as 80 kA, 450 ms long flat-topping; 100 kA, 200 ms rising; 200 ms falt-topping and 180 kA, 400 ms slow rising etc. The design principle of the system and the initial experimental results are described

  11. Foreshock search over a long duration using a method of setting appropriate criteria

    Science.gov (United States)

    Toyomoto, Y.; Kawakata, H.; Hirano, S.; Doi, I.

    2016-12-01

    Recently, small foreshocks have been detected using cross-correlation techniques (e.g., Bouchon et al., 2011) in which the foreshocks are identified when the cross-correlation coefficient (CC) exceeded a certain threshold. For some shallow intraplate earthquakes, foreshocks whose hypocenters were estimated to be adjacent to the main shock hypocenter were detected from several tens of minutes before the main shock occurrence (Doi and Kawakata, 2012; 2013). At least two problems remain in the cross-correlation techniques employed. First, previous studies on foreshocks used data whose durations are at most a month (Kato et al., 2013); this is insufficient to check if such events occurred only before the main shock occurrence or not. Second, CC is used for detection criteria without considering validity of the threshold. In this study, we search for foreshocks of an M 5.4 earthquake in central Nagano prefecture in Japan on June 30, 2011 with a vertical-component waveform at N.MWDH (Hi-net) station due to one of the cataloged foreshocks (M 1) as a template to calculate CC. We calculate CC between the template and continuous waveforms of the same component at the same station for two years before the main shock occurrence, and we try to overcome the problems mentioned above. We find that histogram of CC is well modeled with the normal distribution, which is similar to previous studies on tremors (e.g., Ohta and Ide, 2008). According to the model, the expected number of misdetection is less than 1 when CC > 0.63. Therefore, we regard that the waveform is due to a foreshock when CC > 0.63. As a result, foreshocks are detected only within thirteen hours immediately before the main shock occurrence for the two years. By setting an appropriate threshold, we conclude that foreshocks just before the main shock occurrence are not stationary events. Acknowledgments: We use continuous waveform records of NIED high sensitivity seismograph network in Japan (Hi-net) and the JMA

  12. The correlated k-distribution technique as applied to the AVHRR channels

    Science.gov (United States)

    Kratz, David P.

    1995-01-01

    Correlated k-distributions have been created to account for the molecular absorption found in the spectral ranges of the five Advanced Very High Resolution Radiometer (AVHRR) satellite channels. The production of the k-distributions was based upon an exponential-sum fitting of transmissions (ESFT) technique which was applied to reference line-by-line absorptance calculations. To account for the overlap of spectral features from different molecular species, the present routines made use of the multiplication transmissivity property which allows for considerable flexibility, especially when altering relative mixing ratios of the various molecular species. To determine the accuracy of the correlated k-distribution technique as compared to the line-by-line procedure, atmospheric flux and heating rate calculations were run for a wide variety of atmospheric conditions. For the atmospheric conditions taken into consideration, the correlated k-distribution technique has yielded results within about 0.5% for both the cases where the satellite spectral response functions were applied and where they were not. The correlated k-distribution's principal advantages is that it can be incorporated directly into multiple scattering routines that consider scattering as well as absorption by clouds and aerosol particles.

  13. 2D acoustic-elastic coupled waveform inversion in the Laplace domain

    KAUST Repository

    Bae, Hoseuk; Shin, Changsoo; Cha, Youngho; Choi, Yun Seok; Min, Dongjoo

    2010-01-01

    Although waveform inversion has been intensively studied in an effort to properly delineate the Earth's structures since the early 1980s, most of the time- and frequency-domain waveform inversion algorithms still have critical limitations

  14. Monitoring of civil engineering structures using Digital Image Correlation technique

    Science.gov (United States)

    Malesa, M.; Szczepanek, D.; Kujawińska, M.; Świercz, A.; Kołakowski, P.

    2010-06-01

    The Digital Image Correlation (DIC) technique enables full field, noncontact measurements of displacements and strains of a wide variety of objects. An adaptation of the DIC technique for monitoring of civil-engineering structures is presented in the paper. A general concept of the complex, automatic monitoring system, in which the DIC sensor plays an important role is described. Some new software features, which aim to facilitate outdoor measurements and speed up the correlation analysis, is also introduced. As an example of application, measurements of a railway bridge in Nieporet (Poland) are presented. The experimental results are compared with displacements of a FEM model of the bridge.

  15. Quantifying and modeling long-range cross correlations in multiple time series with applications to world stock indices.

    Science.gov (United States)

    Wang, Duan; Podobnik, Boris; Horvatić, Davor; Stanley, H Eugene

    2011-04-01

    We propose a modified time lag random matrix theory in order to study time-lag cross correlations in multiple time series. We apply the method to 48 world indices, one for each of 48 different countries. We find long-range power-law cross correlations in the absolute values of returns that quantify risk, and find that they decay much more slowly than cross correlations between the returns. The magnitude of the cross correlations constitutes "bad news" for international investment managers who may believe that risk is reduced by diversifying across countries. We find that when a market shock is transmitted around the world, the risk decays very slowly. We explain these time-lag cross correlations by introducing a global factor model (GFM) in which all index returns fluctuate in response to a single global factor. For each pair of individual time series of returns, the cross correlations between returns (or magnitudes) can be modeled with the autocorrelations of the global factor returns (or magnitudes). We estimate the global factor using principal component analysis, which minimizes the variance of the residuals after removing the global trend. Using random matrix theory, a significant fraction of the world index cross correlations can be explained by the global factor, which supports the utility of the GFM. We demonstrate applications of the GFM in forecasting risks at the world level, and in finding uncorrelated individual indices. We find ten indices that are practically uncorrelated with the global factor and with the remainder of the world indices, which is relevant information for world managers in reducing their portfolio risk. Finally, we argue that this general method can be applied to a wide range of phenomena in which time series are measured, ranging from seismology and physiology to atmospheric geophysics.

  16. Quantifying and modeling long-range cross correlations in multiple time series with applications to world stock indices

    Science.gov (United States)

    Wang, Duan; Podobnik, Boris; Horvatić, Davor; Stanley, H. Eugene

    2011-04-01

    We propose a modified time lag random matrix theory in order to study time-lag cross correlations in multiple time series. We apply the method to 48 world indices, one for each of 48 different countries. We find long-range power-law cross correlations in the absolute values of returns that quantify risk, and find that they decay much more slowly than cross correlations between the returns. The magnitude of the cross correlations constitutes “bad news” for international investment managers who may believe that risk is reduced by diversifying across countries. We find that when a market shock is transmitted around the world, the risk decays very slowly. We explain these time-lag cross correlations by introducing a global factor model (GFM) in which all index returns fluctuate in response to a single global factor. For each pair of individual time series of returns, the cross correlations between returns (or magnitudes) can be modeled with the autocorrelations of the global factor returns (or magnitudes). We estimate the global factor using principal component analysis, which minimizes the variance of the residuals after removing the global trend. Using random matrix theory, a significant fraction of the world index cross correlations can be explained by the global factor, which supports the utility of the GFM. We demonstrate applications of the GFM in forecasting risks at the world level, and in finding uncorrelated individual indices. We find ten indices that are practically uncorrelated with the global factor and with the remainder of the world indices, which is relevant information for world managers in reducing their portfolio risk. Finally, we argue that this general method can be applied to a wide range of phenomena in which time series are measured, ranging from seismology and physiology to atmospheric geophysics.

  17. Full waveform inversion in the frequency domain using classified time-domain residual wavefields

    Science.gov (United States)

    Son, Woohyun; Koo, Nam-Hyung; Kim, Byoung-Yeop; Lee, Ho-Young; Joo, Yonghwan

    2017-04-01

    We perform the acoustic full waveform inversion in the frequency domain using residual wavefields that have been separated in the time domain. We sort the residual wavefields in the time domain according to the order of absolute amplitudes. Then, the residual wavefields are separated into several groups in the time domain. To analyze the characteristics of the residual wavefields, we compare the residual wavefields of conventional method with those of our residual separation method. From the residual analysis, the amplitude spectrum obtained from the trace before separation appears to have little energy at the lower frequency bands. However, the amplitude spectrum obtained from our strategy is regularized by the separation process, which means that the low-frequency components are emphasized. Therefore, our method helps to emphasize low-frequency components of residual wavefields. Then, we generate the frequency-domain residual wavefields by taking the Fourier transform of the separated time-domain residual wavefields. With these wavefields, we perform the gradient-based full waveform inversion in the frequency domain using back-propagation technique. Through a comparison of gradient directions, we confirm that our separation method can better describe the sub-salt image than the conventional approach. The proposed method is tested on the SEG/EAGE salt-dome model. The inversion results show that our algorithm is better than the conventional gradient based waveform inversion in the frequency domain, especially for deeper parts of the velocity model.

  18. Computer model analysis of the radial artery pressure waveform.

    Science.gov (United States)

    Schwid, H A; Taylor, L A; Smith, N T

    1987-10-01

    Simultaneous measurements of aortic and radial artery pressures are reviewed, and a model of the cardiovascular system is presented. The model is based on resonant networks for the aorta and axillo-brachial-radial arterial system. The model chosen is a simple one, in order to make interpretation of the observed relationships clear. Despite its simplicity, the model produces realistic aortic and radial artery pressure waveforms. It demonstrates that the resonant properties of the arterial wall significantly alter the pressure waveform as it is propagated from the aorta to the radial artery. Although the mean and end-diastolic radial pressures are usually accurate estimates of the corresponding aortic pressures, the systolic pressure at the radial artery is often much higher than that of the aorta due to overshoot caused by the resonant behavior of the radial artery. The radial artery dicrotic notch is predominantly dependent on the axillo-brachial-radial arterial wall properties, rather than on the aortic valve or peripheral resistance. Hence the use of the radial artery dicrotic notch as an estimate of end systole is unreliable. The rate of systolic upstroke, dP/dt, of the radial artery waveform is a function of many factors, making it difficult to interpret. The radial artery waveform usually provides accurate estimates for mean and diastolic aortic pressures; for all other measurements it is an inadequate substitute for the aortic pressure waveform. In the presence of low forearm peripheral resistance the mean radial artery pressure may significantly underestimate the mean aortic pressure, as explained by a voltage divider model.

  19. Kinetic description of the total photoabsorption cross section: correlation effects

    International Nuclear Information System (INIS)

    Ferreira Filho, L.G.; Nemes, M.C.

    1986-02-01

    It is shown that the inclusion of correlation effects in describing the nuclear photoabsorption cross section leads to a Breit-Wigner type curve with energy dependent width. It is also shown that a very slow energy dependence is enough to reproduce the data up to ∼ 139 MeV. (Author) [pt

  20. Intracardiac impedance response during acute AF internal cardioversion using novel rectilinear and capacitor-discharge waveforms.

    Science.gov (United States)

    Rababah, A S; Walsh, S J; Manoharan, G; Walsh, P R; Escalona, O J

    2016-07-01

    Intracardiac impedance (ICI) is a major determinant of success during internal cardioversion of atrial fibrillation (AF). However, there have been few studies that have examined the dynamic behaviour of atrial impedance during internal cardioversion in relation to clinical outcome. In this study, voltage and current waveforms captured during internal cardioversion of acute AF in ovine models using novel radiofrequency (RF) generated low-tilt rectilinear and conventional capacitor-discharge based shock waveforms were retrospectively analysed using a digital signal processing algorithm to investigate the dynamic behaviour of atrial impedance during cardioversion. The algorithm was specifically designed to facilitate the simultaneous analysis of multiple impedance parameters, including: mean intracardiac impedance (Z M), intracardiac impedance variance (ICIV) and impedance amplitude spectrum area (IAMSA) for each cardioversion event. A significant reduction in ICI was observed when comparing two successive shocks of increasing energy where cardioversion outcome was successful. In addition, ICIV and IAMSA variables were found to inversely correlate to the magnitude of energy delivered; with a stronger correlation found to the former parameter. In conclusion, ICIV and IAMSA have been evidenced as two key dynamic intracardiac impedance variables that may prove useful in better understanding of the cardioversion process and that could potentially act as prognostic markers with respect to clinical outcome.

  1. Heterogeneous local order in self-assembled nanoparticle films revealed by X-ray cross-correlations

    Directory of Open Access Journals (Sweden)

    Felix Lehmkühler

    2018-05-01

    Full Text Available We report on the self-assembly of gold nanoparticles coated with a soft poly(ethylene glycol shell studied by X-ray cross-correlation analysis. Depending on the initial concentration of gold nanoparticles used, structurally heterogeneous films were formed. The films feature hot spots of dominating four- and sixfold local order with patch sizes of a few micrometres, containing 104–105 particles. The amplitude of the order parameters suggested that a minimum sample amount was necessary to form well ordered local structures. Furthermore, the increasing variation in order parameters with sample thickness demonstrated a high degree of structural heterogeneity. This wealth of information cannot be obtained by the conventional microscopy techniques that are commonly used to study nanocrystal superstructures, as illustrated by complementary scanning electron microscopy measurements.

  2. Extracting structural land cover components using small-footprint waveform LDAR data

    CSIR Research Space (South Africa)

    McGlinchy, J

    2010-07-01

    Full Text Available .e., without vertical interactions. Three measurements were taken from the waveform once this component was removed. They are defined as ?Road Ratio?, ?Leftover?, and ?Ratio Removed?. ?Road Ratio? is measured as the ratio of an amplitude scaled dirt road... sample to an original dirt road waveform sample extracted from LU8. ?Leftover? is measured as the ratio of the sum of what remains in the ground pulse to the sum of these same points in the original waveform. ?Ratio Removed? is measured simply...

  3. Multimedia-Based Integration of Cross-Layer Techniques

    Science.gov (United States)

    2014-06-01

    Wireless Commun. Mag., vol. 12, no. 4, pp. 50–58, August 2005. 11. E. Setton, T. Yoo, X. Zhu, A. Goldsmith , and B. Girod, “Cross-layer design of ad-hoc...Overview,” DARPA Presentation by Preston Marshall and Todd Martin, WAND Industry Day Workshop, Feb. 27, 2007. 17. S. Chan, “Shared spectrum access for DOD...Lavery, A. Goldsmith , and D. J. Goodman, “Throughput optimization using adaptive techniques,” IEEE Commun. Lett., pp. 1–7, 2006. 32. S. Choudhury and J

  4. Nonspinning numerical relativity waveform surrogates: assessing the model

    Science.gov (United States)

    Field, Scott; Blackman, Jonathan; Galley, Chad; Scheel, Mark; Szilagyi, Bela; Tiglio, Manuel

    2015-04-01

    Recently, multi-modal gravitational waveform surrogate models have been built directly from data numerically generated by the Spectral Einstein Code (SpEC). I will describe ways in which the surrogate model error can be quantified. This task, in turn, requires (i) characterizing differences between waveforms computed by SpEC with those predicted by the surrogate model and (ii) estimating errors associated with the SpEC waveforms from which the surrogate is built. Both pieces can have numerous sources of numerical and systematic errors. We make an attempt to study the most dominant error sources and, ultimately, the surrogate model's fidelity. These investigations yield information about the surrogate model's uncertainty as a function of time (or frequency) and parameter, and could be useful in parameter estimation studies which seek to incorporate model error. Finally, I will conclude by comparing the numerical relativity surrogate model to other inspiral-merger-ringdown models. A companion talk will cover the building of multi-modal surrogate models.

  5. CORRELATION BETWEEN UTERINE ARTERY FLOW VELOCITY ...

    African Journals Online (AJOL)

    CORRELATION BETWEEN UTERINE ARTERY FLOW VELOCITY WAVEFORMS AND ENDOMETRIAL HISTOPATHOLOGY IN WOMEN WITH PERIMENOPAUSAL AND POSTMENOPAUSAL BLEEDING. Dr. Ebtesam Saied, Dr. Ismail El Garhy(MD), Dr. Farid I. Hassan(MD), Dr. Adel-Gamil Abd-Allah, Abd El Shafy Ibrahim ...

  6. Computational nanometrology of line-edge roughness: noise effects, cross-line correlations and the role of etch transfer

    Science.gov (United States)

    Constantoudis, Vassilios; Papavieros, George; Lorusso, Gian; Rutigliani, Vito; Van Roey, Frieda; Gogolides, Evangelos

    2018-03-01

    The aim of this paper is to investigate the role of etch transfer in two challenges of LER metrology raised by recent evolutions in lithography: the effects of SEM noise and the cross-line and edge correlations. The first comes from the ongoing scaling down of linewidths, which dictates SEM imaging with less scanning frames to reduce specimen damage and hence with more noise. During the last decade, it has been shown that image noise can be an important budget of the measured LER while systematically affects and alter the PSD curve of LER at high frequencies. A recent method for unbiased LER measurement is based on the systematic Fourier or correlation analysis to decompose the effects of noise from true LER (Fourier-Correlation filtering method). The success of the method depends on the PSD and HHCF curve. Previous experimental and model works have revealed that etch transfer affects the PSD of LER reducing its high frequency values. In this work, we estimate the noise contribution to the biased LER through PSD flat floor at high frequencies and relate it with the differences between the PSDs of lithography and etched LER. Based on this comparison, we propose an improvement of the PSD/HHCF-based method for noise-free LER measurement to include the missed high frequency real LER. The second issue is related with the increased density of lithographic patterns and the special characteristics of DSA and MP lithography patterns exhibits. In a previous work, we presented an enlarged LER characterization methodology for such patterns, which includes updated versions of the old metrics along with new metrics defined and developed to capture cross-edge and cross-line correlations. The fundamental concept has been the Line Center Roughness (LCR), the edge c-factor and the line c-factor correlation function and length quantifying the line fluctuations and the extent of cross-edge and cross-line correlations. In this work, we focus on the role of etch steps on cross-edge and

  7. Isotope correlation and mass spectrometry techniques for irradiated fuel assay

    International Nuclear Information System (INIS)

    Deron, S.

    1985-01-01

    This paper outlines the methods used to account for fissionable materials in irradiated nuclear fuel elements entering reprocessing plants. Verification is accomplished at three mass balance stations in the plant. Techniques employed fall into two categories: isotopic and isotope dilution analyses by mass spectometry and isotope correlation techniques. These methods are discussed in some detail

  8. Multifractal detrended cross correlation analysis of neuro-degenerative diseases-An in depth study

    Science.gov (United States)

    Dutta, Srimonti; Ghosh, Dipak; Chatterjee, Sucharita

    2018-02-01

    This work revisits our previous study on human gait diseases, (Dutta et al., 2013) where we have studied the autocorrelation of human gait pattern in normal and diseased set. Significant difference in results was observed for normal and diseased set. However we were not able to distinguish between sets of Parkinson's and Huntington's disease. In this paper we attempt to study whether cross correlations between two feet of human gait pattern can help to distinguish between different diseased set. The results reveal that study of cross correlations can help to distinguish between Parkinson's and Huntington's disease.

  9. Full Seismic Waveform Tomography of the Japan region using Adjoint Methods

    Science.gov (United States)

    Steptoe, Hamish; Fichtner, Andreas; Rickers, Florian; Trampert, Jeannot

    2013-04-01

    We present a full-waveform tomographic model of the Japan region based on spectral-element wave propagation, adjoint techniques and seismic data from dense station networks. This model is intended to further our understanding of both the complex regional tectonics and the finite rupture processes of large earthquakes. The shallow Earth structure of the Japan region has been the subject of considerable tomographic investigation. The islands of Japan exist in an area of significant plate complexity: subduction related to the Pacific and Philippine Sea plates is responsible for the majority of seismicity and volcanism of Japan, whilst smaller micro-plates in the region, including the Okhotsk, and Okinawa and Amur, part of the larger North America and Eurasia plates respectively, contribute significant local intricacy. In response to the need to monitor and understand the motion of these plates and their associated faults, numerous seismograph networks have been established, including the 768 station high-sensitivity Hi-net network, 84 station broadband F-net and the strong-motion seismograph networks K-net and KiK-net in Japan. We also include the 55 station BATS network of Taiwan. We use this exceptional coverage to construct a high-resolution model of the Japan region from the full-waveform inversion of over 15,000 individual component seismograms from 53 events that occurred between 1997 and 2012. We model these data using spectral-element simulations of seismic wave propagation at a regional scale over an area from 120°-150°E and 20°-50°N to a depth of around 500 km. We quantify differences between observed and synthetic waveforms using time-frequency misfits allowing us to separate both phase and amplitude measurements whilst exploiting the complete waveform at periods of 15-60 seconds. Fréchet kernels for these misfits are calculated via the adjoint method and subsequently used in an iterative non-linear conjugate-gradient optimization. Finally, we employ

  10. Frequency sweep of the field scattered by an inhomogeneous structure using method of moments and asymptotic waveform evaluation

    DEFF Research Database (Denmark)

    Troelsen, Jens; Meincke, Peter; Breinbjerg, Olav

    2000-01-01

    into account. To the knowledge of the authors the AWE technique has not previously been applied to a MoM solution based on this kind of integral equation. It is the purpose of this paper to investigate the use of the AWE technique as a tool to obtain a fast frequency sweep of the field scattered......In many radar applications it is necessary to determine the scattering from an object over a wide frequency band. The asymptotic waveform evaluation (AWE), which is a moment matching (MM) technique, constitutes a method to this end. In general, MM techniques provide a reduced-order model...

  11. Cross-correlation studies between CMB temperature anisotropies and 21 cm fluctuations

    International Nuclear Information System (INIS)

    Cooray, Asantha

    2004-01-01

    During the transition from a neutral to a fully reionized universe, scattering of cosmic microwave background (CMB) photons via free electrons leads to a new anisotropy contribution to the temperature distribution. If the reionization process is inhomogeneous and patchy, the era of reionization is also visible via brightness temperature fluctuations in the redshifted 21 cm line emission from neutral hydrogen. Since regions containing electrons and neutral hydrogen are expected to trace the same underlying density field, the two are (anti)correlated and this is expected to be reflected in the anisotropy maps via a correlation between arcminute-scale CMB temperature and the 21 cm background. In terms of the angular cross-power spectrum, unfortunately, this correlation is insignificant due to a geometric cancellation associated with second-order CMB anisotropies. The same cross correlation between ionized and neutral regions, however, can be studied using a bispectrum involving large-scale velocity field of ionized regions from the Doppler effect, arcminute-scale CMB anisotropies during reionization, and the 21 cm background. While the geometric cancellation is partly avoided, the signal-to-noise ratio related to this bispectrum is reduced due to the large cosmic variance related to velocity fluctuations traced by the Doppler effect. Unless the velocity field during reionization can be independently established, it is unlikely that the correlation information related to the relative distribution of ionized electrons and regions containing neutral hydrogen can be obtained with a combined study involving CMB and 21 cm fluctuations

  12. Transcranial motor evoked potential waveform changes in corrective fusion for adolescent idiopathic scoliosis.

    Science.gov (United States)

    Kobayashi, Kazuyoshi; Imagama, Shiro; Ito, Zenya; Ando, Kei; Hida, Tetsuro; Ito, Kenyu; Tsushima, Mikito; Ishikawa, Yoshimoto; Matsumoto, Akiyuki; Nishida, Yoshihiro; Ishiguro, Naoki

    2017-01-01

    OBJECTIVE Corrective surgery for spinal deformities can lead to neurological complications. Several reports have described spinal cord monitoring in surgery for spinal deformity, but only a few have included patients younger than 20 years with adolescent idiopathic scoliosis (AIS). The goal of this study was to evaluate the characteristics of cases with intraoperative transcranial motor evoked potential (Tc-MEP) waveform deterioration during posterior corrective fusion for AIS. METHODS A prospective database was reviewed, comprising 68 patients with AIS who were treated with posterior corrective fusion in a prospective database. A total of 864 muscles in the lower extremities were chosen for monitoring, and acceptable baseline responses were obtained from 819 muscles (95%). Intraoperative Tc-MEP waveform deterioration was defined as a decrease in intraoperative amplitude of ≥ 70% of the control waveform. Age, Cobb angle, flexibility, operative time, estimated blood loss (EBL), intraoperative body temperature, blood pressure, number of levels fused, and correction rate were examined in patients with and without waveform deterioration. RESULTS The patients (3 males and 65 females) had an average age of 14.4 years (range 11-19 years). The mean Cobb angles before and after surgery were 52.9° and 11.9°, respectively, giving a correction rate of 77.4%. Fourteen patients (20%) exhibited an intraoperative waveform change, and these occurred during incision (14%), after screw fixation (7%), during the rotation maneuver (64%), during placement of the second rod after the rotation maneuver (7%), and after intervertebral compression (7%). Most waveform changes recovered after decreased correction or rest. No patient had a motor deficit postoperatively. In multivariate analysis, EBL (OR 1.001, p = 0.085) and number of levels fused (OR 1.535, p = 0.045) were associated with waveform deterioration. CONCLUSIONS Waveform deterioration commonly occurred during rotation maneuvers

  13. Evaluating a small footprint, waveform-resolving lidar over coastal vegetation communities

    Science.gov (United States)

    Nayegandhl, A.; Brock, J.C.; Wright, C.W.; O'Connell, M. J.

    2006-01-01

    NASA's Experimental Advanced Airborne Research Lidar (EAARL) is a raster-scanning, waveform-resolving, green-wavelength (532 nm) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor records the time history of the return waveform within a small footprint (20 cm diameter) for each laser pulse, enabling characterization of vegetation canopy structure and "bare earth" topography under a variety of vegetation types. A collection of individual waveforms combined within a synthesized large footprint was used to define three metrics: canopy height (CH), canopy reflection ratio (CRR), and height of median energy (HOME). Bare Earth Elevation (BEE) metric was derived using the individual small-footprint waveforms. All four metrics were tested for reproducibility, which resulted in an average of 95 percent correspondence within two standard deviations of the mean. CH and BEE values were also tested for accuracy using ground-truth data. The results presented in this paper show that combining several individual small-footprint laser pulses to define a composite "large-footprint" waveform is a possible method to depict the vertical structure of a vegetation canopy. ?? 2006 American Society for Photogrammetry and Remote Sensing.

  14. Multifractal detrended cross-correlations between crude oil market and Chinese ten sector stock markets

    Science.gov (United States)

    Yang, Liansheng; Zhu, Yingming; Wang, Yudong; Wang, Yiqi

    2016-11-01

    Based on the daily price data of spot prices of West Texas Intermediate (WTI) crude oil and ten CSI300 sector indices in China, we apply multifractal detrended cross-correlation analysis (MF-DCCA) method to investigate the cross-correlations between crude oil and Chinese sector stock markets. We find that the strength of multifractality between WTI crude oil and energy sector stock market is the highest, followed by the strength of multifractality between WTI crude oil and financial sector market, which reflects a close connection between energy and financial market. Then we do vector autoregression (VAR) analysis to capture the interdependencies among the multiple time series. By comparing the strength of multifractality for original data and residual errors of VAR model, we get a conclusion that vector auto-regression (VAR) model could not be used to describe the dynamics of the cross-correlations between WTI crude oil and the ten sector stock markets.

  15. Railway Crossing Risk Area Detection Using Linear Regression and Terrain Drop Compensation Techniques

    Science.gov (United States)

    Chen, Wen-Yuan; Wang, Mei; Fu, Zhou-Xing

    2014-01-01

    Most railway accidents happen at railway crossings. Therefore, how to detect humans or objects present in the risk area of a railway crossing and thus prevent accidents are important tasks. In this paper, three strategies are used to detect the risk area of a railway crossing: (1) we use a terrain drop compensation (TDC) technique to solve the problem of the concavity of railway crossings; (2) we use a linear regression technique to predict the position and length of an object from image processing; (3) we have developed a novel strategy called calculating local maximum Y-coordinate object points (CLMYOP) to obtain the ground points of the object. In addition, image preprocessing is also applied to filter out the noise and successfully improve the object detection. From the experimental results, it is demonstrated that our scheme is an effective and corrective method for the detection of railway crossing risk areas. PMID:24936948

  16. Railway Crossing Risk Area Detection Using Linear Regression and Terrain Drop Compensation Techniques

    Directory of Open Access Journals (Sweden)

    Wen-Yuan Chen

    2014-06-01

    Full Text Available Most railway accidents happen at railway crossings. Therefore, how to detect humans or objects present in the risk area of a railway crossing and thus prevent accidents are important tasks. In this paper, three strategies are used to detect the risk area of a railway crossing: (1 we use a terrain drop compensation (TDC technique to solve the problem of the concavity of railway crossings; (2 we use a linear regression technique to predict the position and length of an object from image processing; (3 we have developed a novel strategy called calculating local maximum Y-coordinate object points (CLMYOP to obtain the ground points of the object. In addition, image preprocessing is also applied to filter out the noise and successfully improve the object detection. From the experimental results, it is demonstrated that our scheme is an effective and corrective method for the detection of railway crossing risk areas.

  17. Variation of Pressure Waveforms in Measurements of Extracorporeal Shock Wave Lithotripter

    Science.gov (United States)

    Inose, Naoto; Ide, Masao

    1993-05-01

    In this paper, we describe measurement of variation in pressure waveforms of the acoustic field of an extra-corporeal shock-wave lithotripter (ESWL). Variations in the measured acoustic fields and pressure waveform of an underwater spark-gap-type ESWL with an exhausted spark plug electrode have been reported by researchers using crystal sensors. If the ESWL spark plugs become exhausted, patients feel pain during kidney, biliary stone disintegration. We studied the relationship between exhaustion of electrodes and the variation of pressure waveforms and shock-wave fields of the ESWL using a newly developed hydrophone.

  18. Static inverter with synchronous output waveform synthesized by time-optimal-response feedback

    Science.gov (United States)

    Kernick, A.; Stechschulte, D. L.; Shireman, D. W.

    1976-01-01

    Time-optimal-response 'bang-bang' or 'bang-hang' technique, using four feedback control loops, synthesizes static-inverter sinusoidal output waveform by self-oscillatory but yet synchronous pulse-frequency-modulation (SPFM). A single modular power stage per phase of ac output entails the minimum of circuit complexity while providing by feedback synthesis individual phase voltage regulation, phase position control and inherent compensation simultaneously for line and load disturbances. Clipped sinewave performance is described under off-limit load or input voltage conditions. Also, approaches to high power levels, 3-phase arraying and parallel modular connection are given.

  19. Predicting Electrocardiogram and Arterial Blood Pressure Waveforms with Different Echo State Network Architectures

    Science.gov (United States)

    2014-11-01

    Predicting Electrocardiogram and Arterial Blood Pressure Waveforms with Different Echo State Network Architectures Allan Fong, MS1,3, Ranjeev...the medical staff in Intensive Care Units. The ability to predict electrocardiogram and arterial blood pressure waveforms can potentially help the...type of neural network for mining, understanding, and predicting electrocardiogram and arterial blood pressure waveforms. Several network

  20. Characterization of volumetric flow rate waveforms at the carotid bifurcations of older adults

    International Nuclear Information System (INIS)

    Hoi, Yiemeng; Xie, Yuanyuan J; Steinman, David A; Wasserman, Bruce A; Najjar, Samer S; Lakatta, Edward G; Ferruci, Luigi; Gerstenblith, Gary

    2010-01-01

    While it is widely appreciated that volumetric blood flow rate (VFR) dynamics change with age, there has been no detailed characterization of the typical shape of carotid bifurcation VFR waveforms of older adults. Toward this end, retrospectively gated phase contrast magnetic resonance imaging was used to measure time-resolved VFR waveforms proximal and distal to the carotid bifurcations of 94 older adults (age 68 ± 8 years) with little or no carotid artery disease, recruited from the BLSA cohort of the VALIDATE study of factors in vascular aging. Timings and amplitudes of well-defined feature points from these waveforms were extracted automatically and averaged to produce representative common, internal and external carotid artery (CCA, ICA and ECA) waveform shapes. Relative to young adults, waveforms from older adults were found to exhibit a significantly augmented secondary peak during late systole, resulting in significantly higher resistance index (RI) and flow augmentation index (FAI). Cycle-averaged VFR at the CCA, ICA and ECA were 389 ± 74, 245 ± 61 and 125 ± 49 mL min −1 , respectively, reflecting a significant cycle-averaged outflow deficit of 5%, which peaked at around 10% during systole. A small but significant mean delay of 13 ms between arrivals of ICA versus CCA/ECA peak VFR suggested differential compliance of these vessels. Sex and age differences in waveform shape were also noted. The characteristic waveforms presented here may serve as a convenient baseline for studies of VFR waveform dynamics or as suitable boundary conditions for models of blood flow in the carotid arteries of older adults