SynchroPhasor Measurements: System Architecture and Performance Evaluation in Supporting Wide-Area Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zhenyu; Dagle, Jeffery E.

2008-07-31

The infrastructure of phasor measurements have evolved over the last two decades from isolated measurement units to networked measurement systems with footprints beyond individual utility companies. This is, to a great extent, a bottom-up self-evolving process except some local systems built by design. Given the number of phasor measurement units (PMUs) in the system is small (currently 70 each in western and eastern interconnections), current phasor network architecture works just fine. However, the architecture will become a bottleneck when large number of PMUs are installed (e.g. >1000~10000). The need for phasor architecture design has yet to be addressed. This papermore » reviews the current phasor networks and investigates future architectures, as related to the efforts undertaken by the North America SynchroPhasor Initiative (NASPI). Then it continues to present staged system tests to evaluate the performance of phasor networks, which is a common practice in the Western Electricity Coordinating Council (WECC) system. This is followed by field measurement evaluation and the implication of phasor quality issues on phasor applications.« less

A Distribution Level Wide Area Monitoring System for the Electric Power Grid–FNET/GridEye

DOE PAGES

Liu, Yong; You, Shutang; Yao, Wenxuan; ...

2017-02-09

The wide area monitoring system (WAMS) is considered a pivotal component of future electric power grids. As a pilot WAMS that has been operated for more than a decade, the frequency monitoring network FNET/GridEye makes use of hundreds of global positioning system-synchronized phasor measurement sensors to capture the increasingly complicated grid behaviors across the interconnected power systems. In this paper, the FNET/GridEye system is overviewed and its operation experiences in electric power grid wide area monitoring are presented. Particularly, the implementation of a number of data analytics applications will be discussed in details. FNET/GridEye lays a firm foundation for themore » later WAMS operation in the electric power industry.« less

GPS synchronized power system phase angle measurements

NASA Astrophysics Data System (ADS)

Wilson, Robert E.; Sterlina, Patrick S.

1994-09-01

This paper discusses the use of Global Positioning System (GPS) synchronized equipment for the measurement and analysis of key power system quantities. Two GPS synchronized phasor measurement units (PMU) were installed before testing. It was indicated that PMUs recorded the dynamic response of the power system phase angles when the northern California power grid was excited by the artificial short circuits. Power system planning engineers perform detailed computer generated simulations of the dynamic response of the power system to naturally occurring short circuits. The computer simulations use models of transmission lines, transformers, circuit breakers, and other high voltage components. This work will compare computer simulations of the same event with field measurement.

Quantifying light-dependent circadian disruption in humans and animal models.

PubMed

Rea, Mark S; Figueiro, Mariana G

2014-12-01

Although circadian disruption is an accepted term, little has been done to develop methods to quantify the degree of disruption or entrainment individual organisms actually exhibit in the field. A variety of behavioral, physiological and hormonal responses vary in amplitude over a 24-h period and the degree to which these circadian rhythms are synchronized to the daily light-dark cycle can be quantified with a technique known as phasor analysis. Several studies have been carried out using phasor analysis in an attempt to measure circadian disruption exhibited by animals and by humans. To perform these studies, species-specific light measurement and light delivery technologies had to be developed based upon a fundamental understanding of circadian phototransduction mechanisms in the different species. When both nocturnal rodents and diurnal humans, experienced different species-specific light-dark shift schedules, they showed, based upon phasor analysis of the light-dark and activity-rest patterns, similar levels of light-dependent circadian disruption. Indeed, both rodents and humans show monotonically increasing and quantitatively similar levels of light-dependent circadian disruption with increasing shift-nights per week. Thus, phasor analysis provides a method for quantifying circadian disruption in the field and in the laboratory as well as a bridge between ecological measurements of circadian entrainment in humans and parametric studies of circadian disruption in animal models, including nocturnal rodents.

Dynamic state estimation assisted power system monitoring and protection

NASA Astrophysics Data System (ADS)

Cui, Yinan

The advent of phasor measurement units (PMUs) has unlocked several novel methods to monitor, control, and protect bulk electric power systems. This thesis introduces the concept of "Dynamic State Estimation" (DSE), aided by PMUs, for wide-area monitoring and protection of power systems. Unlike traditional State Estimation where algebraic variables are estimated from system measurements, DSE refers to a process to estimate the dynamic states associated with synchronous generators. This thesis first establishes the viability of using particle filtering as a technique to perform DSE in power systems. The utility of DSE for protection and wide-area monitoring are then shown as potential novel applications. The work is presented as a collection of several journal and conference papers. In the first paper, we present a particle filtering approach to dynamically estimate the states of a synchronous generator in a multi-machine setting considering the excitation and prime mover control systems. The second paper proposes an improved out-of-step detection method for generators by means of angular difference. The generator's rotor angle is estimated with a particle filter-based dynamic state estimator and the angular separation is then calculated by combining the raw local phasor measurements with this estimate. The third paper introduces a particle filter-based dual estimation method for tracking the dynamic states of a synchronous generator. It considers the situation where the field voltage measurements are not readily available. The particle filter is modified to treat the field voltage as an unknown input which is sequentially estimated along with the other dynamic states. The fourth paper proposes a novel framework for event detection based on energy functions. The key idea is that any event in the system will leave a signature in WAMS data-sets. It is shown that signatures for four broad classes of disturbance events are buried in the components that constitute the energy function for the system. This establishes a direct correspondence (or mapping) between an event and certain component(s) of the energy function. The last paper considers the dynamic latency effect when the measurements and estimated dynamics are transmitted from remote ends to a centralized location through the networks.

GPS Spoofing Attack Characterization and Detection in Smart Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blum, Rick S.; Pradhan, Parth; Nagananda, Kyatsandra

The problem of global positioning system (GPS) spoofing attacks on smart grids endowed with phasor measurement units (PMUs) is addressed, taking into account the dynamical behavior of the states of the system. First, it is shown how GPS spoofing introduces a timing synchronization error in the phasor readings recorded by the PMUs and alters the measurement matrix of the dynamical model. Then, a generalized likelihood ratio-based hypotheses testing procedure is devised to detect changes in the measurement matrix when the system is subjected to a spoofing attack. Monte Carlo simulations are performed on the 9-bus, 3-machine test grid to demonstratemore » the implication of the spoofing attack on dynamic state estimation and to analyze the performance of the proposed hypotheses test.« less

Utilization of optical sensors for phasor measurement units

DOE PAGES

Yao, Wenxuan; Wells, David; King, Daniel; ...

2017-11-10

With the help of GPS signals for synchronization, increasingly ubiquitous phasor measurement units (PMUs) provide power grid operators unprecedented system monitoring and control opportunities. However, the performance of PMUs is limited by the inherent deficiencies in traditional transformers. To address these issues, an optical sensor is used in PMU for signal acquisition to replace the traditional transformers. This is the first time the utilization of an optical sensor in PMUs has ever been reported. The accuracy of frequency, angle, and amplitude are evaluated via experiments. Lastly, the optical sensor based PMU can achieve the accuracy of 9.03 × 10 –4more » Hz for frequency, 6.38 × 10 –3 rad for angle and 6.73 × 10 –2 V for amplitude with real power grid signal, demonstrating the practicability of optical sensors in future PMUs.« less

Initial Results in Using a Self-Coherence Method for Detecting Sustained Oscillations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Ning; Dagle, Jeffery E.

2015-01-01

This paper develops a self-coherence method for detecting sustained oscillations using phasor measurement unit (PMU) data. Sustained oscillations decrease system performance and introduce potential reliability issues. Timely detection of the oscillations at an early stage provides the opportunity for taking remedial reaction. Using high-speed time-synchronized PMU data, this paper details a self-coherence method for detecting sustained oscillation, even when the oscillation amplitude is lower than ambient noise. Simulation and field measurement data are used to evaluate the proposed method’s performance. It is shown that the proposed method can detect sustained oscillations and estimate oscillation frequencies with a low signal-to-noise ratio.more » Comparison with a power spectral density method also shows that the proposed self-coherence method performs better. Index Terms—coherence, power spectral density, phasor measurement unit (PMU), oscillations, power system dynamics« less

Development of a Laboratory Synchrophasor Network and an Application to Estimate Transmission Line Parameters in Real Time

NASA Astrophysics Data System (ADS)

Almiron Bonnin, Rubens Eduardo

The development of an experimental synchrophasors network and application of synchrophasors for real-time transmission line parameter monitoring are presented in this thesis. In the laboratory setup, a power system is simulated in a RTDS real-time digital simulator, and the simulated voltages and currents are input to hardware phasor measurement units (PMUs) through the analog outputs of the simulator. Time synchronizing signals for the PMU devices are supplied from a common GPS clock. The real time data collected from PMUs are sent to a phasor data concentrator (PDC) through Ethernet using the TCP/IP protocol. A real-time transmission line parameter monitoring application program that uses the synchrophasor data provided by the PDC is implemented and validated. The experimental synchrophasor network developed in this thesis is expected to be used in research on synchrophasor applications as well as in graduate and undergraduate teaching.

Utilization of optical sensors for phasor measurement units

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yao, Wenxuan; Wells, David; King, Daniel

With the help of GPS signals for synchronization, increasingly ubiquitous phasor measurement units (PMUs) provide power grid operators unprecedented system monitoring and control opportunities. However, the performance of PMUs is limited by the inherent deficiencies in traditional transformers. To address these issues, an optical sensor is used in PMU for signal acquisition to replace the traditional transformers. This is the first time the utilization of an optical sensor in PMUs has ever been reported. The accuracy of frequency, angle, and amplitude are evaluated via experiments. Lastly, the optical sensor based PMU can achieve the accuracy of 9.03 × 10 –4more » Hz for frequency, 6.38 × 10 –3 rad for angle and 6.73 × 10 –2 V for amplitude with real power grid signal, demonstrating the practicability of optical sensors in future PMUs.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eto, Joseph H.; Parashar, Manu; Lewis, Nancy Jo

The Real Time System Operations (RTSO) 2006-2007 project focused on two parallel technical tasks: (1) Real-Time Applications of Phasors for Monitoring, Alarming and Control; and (2) Real-Time Voltage Security Assessment (RTVSA) Prototype Tool. The overall goal of the phasor applications project was to accelerate adoption and foster greater use of new, more accurate, time-synchronized phasor measurements by conducting research and prototyping applications on California ISO's phasor platform - Real-Time Dynamics Monitoring System (RTDMS) -- that provide previously unavailable information on the dynamic stability of the grid. Feasibility assessment studies were conducted on potential application of this technology for small-signal stabilitymore » monitoring, validating/improving existing stability nomograms, conducting frequency response analysis, and obtaining real-time sensitivity information on key metrics to assess grid stress. Based on study findings, prototype applications for real-time visualization and alarming, small-signal stability monitoring, measurement based sensitivity analysis and frequency response assessment were developed, factory- and field-tested at the California ISO and at BPA. The goal of the RTVSA project was to provide California ISO with a prototype voltage security assessment tool that runs in real time within California ISO?s new reliability and congestion management system. CERTS conducted a technical assessment of appropriate algorithms, developed a prototype incorporating state-of-art algorithms (such as the continuation power flow, direct method, boundary orbiting method, and hyperplanes) into a framework most suitable for an operations environment. Based on study findings, a functional specification was prepared, which the California ISO has since used to procure a production-quality tool that is now a part of a suite of advanced computational tools that is used by California ISO for reliability and congestion management.« less

Measuring the effect of a Western diet on liver tissue architecture by FLIM autofluorescence and harmonic generation microscopy

PubMed Central

Ranjit, Suman; Dvornikov, Alexander; Dobrinskikh, Evgenia; Wang, Xiaoxin; Luo, Yuhuan; Levi, Moshe; Gratton, Enrico

2017-01-01

The phasor approach to auto-fluorescence lifetime imaging was used to identify and characterize a long lifetime species (LLS) (~7.8 ns) in livers of mice fed with a Western diet. The size of the areas containing this LLS species depends on the type of diet and the size distribution shows Western diet has much larger LLS sizes. Combination of third harmonic generation images with FLIM identified the LLS species with fat droplets and the droplet size distribution was estimated. Second harmonic generation microscopy combined with phasor FLIM shows that there is an increase in fibrosis with a Western diet. A new decomposition in three components of the phasor plot shows that a Western diet is correlated with a higher fraction of free NADH, signifying more reducing condition and more glycolytic condition. Multiparametric analysis of phasor distribution shows that from the distribution of phasor points, a Western diet fed versus a low fat diet fed samples of mice livers can be separated. The phasor approach for the analysis of FLIM images of autofluorescence in liver specimens can result in discovery of new fluorescent species and then these new fluorescent species can help assess tissue architecture. Finally integrating FLIM and second and third harmonic analysis provides a measure of the advancement of fibrosis as an effect of diet. PMID:28717559

Performance Evaluation of Phasor Measurement Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zhenyu; Kasztenny, Bogdan; Madani, Vahid

2008-07-20

After two decades of phasor network deployment, phasor measurements are now available at many major substations and power plants. The North American SynchroPhasor Initiative (NASPI), supported by both the US Department of Energy and the North American Electricity Reliability Council (NERC), provides a forum to facilitate the efforts in phasor technology in North America. Phasor applications have been explored and some are in today’s utility practice. IEEE C37.118 Standard is a milestone in standardizing phasor measurements and defining performance requirements. To comply with IEEE C37.118 and to better understand the impact of phasor quality on applications, the NASPI Performance andmore » Standards Task Team (PSTT) initiated and accomplished the development of two important documents to address characterization of PMUs and instrumentation channels, which leverage prior work (esp. in WECC) and international experience. This paper summarizes the accomplished PSTT work and presents the methods for phasor measurement evaluation.« less

A Robust State Estimation Framework Considering Measurement Correlations and Imperfect Synchronization

DOE PAGES

Zhao, Junbo; Wang, Shaobu; Mili, Lamine; ...

2018-01-08

Here, this paper develops a robust power system state estimation framework with the consideration of measurement correlations and imperfect synchronization. In the framework, correlations of SCADA and Phasor Measurements (PMUs) are calculated separately through unscented transformation and a Vector Auto-Regression (VAR) model. In particular, PMU measurements during the waiting period of two SCADA measurement scans are buffered to develop the VAR model with robustly estimated parameters using projection statistics approach. The latter takes into account the temporal and spatial correlations of PMU measurements and provides redundant measurements to suppress bad data and mitigate imperfect synchronization. In case where the SCADAmore » and PMU measurements are not time synchronized, either the forecasted PMU measurements or the prior SCADA measurements from the last estimation run are leveraged to restore system observability. Then, a robust generalized maximum-likelihood (GM)-estimator is extended to integrate measurement error correlations and to handle the outliers in the SCADA and PMU measurements. Simulation results that stem from a comprehensive comparison with other alternatives under various conditions demonstrate the benefits of the proposed framework.« less

A Robust State Estimation Framework Considering Measurement Correlations and Imperfect Synchronization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Junbo; Wang, Shaobu; Mili, Lamine

Here, this paper develops a robust power system state estimation framework with the consideration of measurement correlations and imperfect synchronization. In the framework, correlations of SCADA and Phasor Measurements (PMUs) are calculated separately through unscented transformation and a Vector Auto-Regression (VAR) model. In particular, PMU measurements during the waiting period of two SCADA measurement scans are buffered to develop the VAR model with robustly estimated parameters using projection statistics approach. The latter takes into account the temporal and spatial correlations of PMU measurements and provides redundant measurements to suppress bad data and mitigate imperfect synchronization. In case where the SCADAmore » and PMU measurements are not time synchronized, either the forecasted PMU measurements or the prior SCADA measurements from the last estimation run are leveraged to restore system observability. Then, a robust generalized maximum-likelihood (GM)-estimator is extended to integrate measurement error correlations and to handle the outliers in the SCADA and PMU measurements. Simulation results that stem from a comprehensive comparison with other alternatives under various conditions demonstrate the benefits of the proposed framework.« less

A method exploiting direct communication between phasor measurement units for power system wide-area protection and control algorithms.

PubMed

Almas, Muhammad Shoaib; Vanfretti, Luigi

2017-01-01

Synchrophasor measurements from Phasor Measurement Units (PMUs) are the primary sensors used to deploy Wide-Area Monitoring, Protection and Control (WAMPAC) systems. PMUs stream out synchrophasor measurements through the IEEE C37.118.2 protocol using TCP/IP or UDP/IP. The proposed method establishes a direct communication between two PMUs, thus eliminating the requirement of an intermediate phasor data concentrator, data mediator and/or protocol parser and thereby ensuring minimum communication latency without considering communication link delays. This method allows utilizing synchrophasor measurements internally in a PMU to deploy custom protection and control algorithms. These algorithms are deployed using protection logic equations which are supported by all the PMU vendors. Moreover, this method reduces overall equipment cost as the algorithms execute internally in a PMU and therefore does not require any additional controller for their deployment. The proposed method can be utilized for fast prototyping of wide-area measurements based protection and control applications. The proposed method is tested by coupling commercial PMUs as Hardware-in-the-Loop (HIL) with Opal-RT's eMEGAsim Real-Time Simulator (RTS). As illustrative example, anti-islanding protection application is deployed using proposed method and its performance is assessed. The essential points in the method are: •Bypassing intermediate phasor data concentrator or protocol parsers as the synchrophasors are communicated directly between the PMUs (minimizes communication delays).•Wide Area Protection and Control Algorithm is deployed using logic equations in the client PMU, therefore eliminating the requirement for an external hardware controller (cost curtailment)•Effortless means to exploit PMU measurements in an environment familiar to protection engineers.

Phasor Analysis of Binary Diffraction Gratings with Different Fill Factors

ERIC Educational Resources Information Center

Martinez, Antonio; Sanchez-Lopez, Ma del Mar; Moreno, Ignacio

2007-01-01

In this work, we present a simple analysis of binary diffraction gratings with different slit widths relative to the grating period. The analysis is based on a simple phasor technique directly derived from the Huygens principle. By introducing a slit phasor and a grating phasor, the intensity of the diffracted orders and the grating's resolving…

Development of a Phasor Diagram Creator to Visualize the Piston and Displacer Forces in an Advanced Stirling Convertor

NASA Technical Reports Server (NTRS)

Saha, Dipanjan; Lewandowski, Edward J.

2013-01-01

The steady-state, nearly sinusoidal behavior of the components in a free-piston Stirling engine allows for visualization of the forces in the system using phasor diagrams. Based on Newton's second law, F = ma, any phasor diagrams modeling a given component in a system should close if all of the acting forces have been considered. Since the Advanced Stirling Radioisotope Generator (ASRG), currently being developed for future NASA deep space missions, is made up of such nearly sinusoidally oscillating components, its phasor diagrams would also be expected to close. A graphical user interface (GUI) has been written in MATLAB (MathWorks), which takes user input data, passes it to Sage (Gedeon Associates), a one-dimensional thermodynamic modeling program used to model the Stirling convertor, runs Sage, and then automatically plots the phasor diagrams. Using this software tool, the effect of varying different Sage inputs on the phasor diagrams was determined. The parameters varied were piston amplitude, hot-end temperature, cold-end temperature, operating frequency, and displacer spring constant. These phasor diagrams offer useful insight into convertor operation and performance.

The Phasor Approach to Fluorescence Lifetime Imaging Analysis

PubMed Central

Digman, Michelle A.; Caiolfa, Valeria R.; Zamai, Moreno; Gratton, Enrico

2008-01-01

Changing the data representation from the classical time delay histogram to the phasor representation provides a global view of the fluorescence decay at each pixel of an image. In the phasor representation we can easily recognize the presence of different molecular species in a pixel or the occurrence of fluorescence resonance energy transfer. The analysis of the fluorescence lifetime imaging microscopy (FLIM) data in the phasor space is done observing clustering of pixels values in specific regions of the phasor plot rather than by fitting the fluorescence decay using exponentials. The analysis is instantaneous since is not based on calculations or nonlinear fitting. The phasor approach has the potential to simplify the way data are analyzed in FLIM, paving the way for the analysis of large data sets and, in general, making the FLIM technique accessible to the nonexpert in spectroscopy and data analysis. PMID:17981902

Development of a Phasor Diagram Creator to Visualize the Piston and Displacer Forces in an Advanced Stirling Convertor

NASA Technical Reports Server (NTRS)

Saha, Dipanjan; Lewandowski, Edward J.

2013-01-01

The steady state, nearly sinusoidal behavior of the components in a Free Piston Stirling Engine allows for visualization of the forces in the system using phasor diagrams. Based on Newton's second law, F=ma, any phasor diagrams modeling a given component in a system should close if all of the acting forces have been considered. Since the Advanced Stirling Radioisotope Generator (ASRG), currently being developed for future NASA deep space missions, is made up of such nearly sinusoidally oscillating components, its phasor diagrams would also be expected to close. A graphical user interface (GUI) has been written in MATLAB by taking user input data, passing it to Sage, a 1-D thermodynamic modeling program used to model the Stirling convertor, running Sage and then automatically plotting the phasor diagrams. Using this software tool, the effect of varying different Sage inputs on the phasor diagrams was determined. The parameters varied were piston amplitude, hot end temperature, cold end temperature, operating frequency, and displacer spring constant. By using these phasor diagrams, better insight can be gained as to why the convertor operates the way that it does.

Spectral Phasor approach for fingerprinting of photo-activatable fluorescent proteins Dronpa, Kaede and KikGR

PubMed Central

Cutrale, Francesco; Salih, Anya; Gratton, Enrico

2013-01-01

The phasor global analysis algorithm is common for fluorescence lifetime applications, but has only been recently proposed for spectral analysis. Here the phasor representation and fingerprinting is exploited in its second harmonic to determine the number and spectra of photo-activated states as well as their conversion dynamics. We follow the sequence of photo-activation of proteins over time by rapidly collecting multiple spectral images. The phasor representation of the cumulative images provides easy identification of the spectral signatures of each photo-activatable protein. PMID:24040513

A Two-Stage Kalman Filter Approach for Robust and Real-Time Power System State Estimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jinghe; Welch, Greg; Bishop, Gary

2014-04-01

As electricity demand continues to grow and renewable energy increases its penetration in the power grid, realtime state estimation becomes essential for system monitoring and control. Recent development in phasor technology makes it possible with high-speed time-synchronized data provided by Phasor Measurement Units (PMU). In this paper we present a two-stage Kalman filter approach to estimate the static state of voltage magnitudes and phase angles, as well as the dynamic state of generator rotor angles and speeds. Kalman filters achieve optimal performance only when the system noise characteristics have known statistical properties (zero-mean, Gaussian, and spectrally white). However in practicemore » the process and measurement noise models are usually difficult to obtain. Thus we have developed the Adaptive Kalman Filter with Inflatable Noise Variances (AKF with InNoVa), an algorithm that can efficiently identify and reduce the impact of incorrect system modeling and/or erroneous measurements. In stage one, we estimate the static state from raw PMU measurements using the AKF with InNoVa; then in stage two, the estimated static state is fed into an extended Kalman filter to estimate the dynamic state. Simulations demonstrate its robustness to sudden changes of system dynamics and erroneous measurements.« less

Dissemination of the Phasor Method in Electrical Engineering in China

ERIC Educational Resources Information Center

Zhang, Liangliang; Lei, Yinzhao

2014-01-01

Synchrophasors, widely used in the monitoring and analysis of power systems, evolved from the phasor method presented by Charles Proteus Steinmetz in 1893. The phasor method is a mathematical method for solving linear sinusoidal steady-state circuits and time-varying electromagnetic fields. This paper traces the history and diffusion of the phasor…

Development of a reference Phasor Measurement Unit (PMU) for the monitoring and control of grid stability and quality

NASA Astrophysics Data System (ADS)

Ndilimabaka, Hervé; Blanc, Isabelle

2014-08-01

This paper discusses the details of the development of a Phasor Measurement Unit regarding the requirements of the IEEE C37.118-2005 synchrophasor standard relative to steady-state conditions on grid monitoring and control. This phasor measurement unit is intended to be used for field tests sooner.

Synchrophasor Based Tracking Three-Phase State Estimator and It's Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phadke, A. G.; Thorp, James; Centeno, Virgilio

2013-08-31

Electric power infrastructure is one of the critical resources of the nation. Its reliability in the face of natural or man-made catastrophes is of paramount importance for the economic and public health wellbeing of a modern society. Maintaining high levels of security for the high voltage transmission back bone of the electric supply network is a task requiring access to modern monitoring tools. These tools have been made particularly effective with the advent of synchronized phasor measurement units (PMUs) which became available in late 1990s, and have now become an indispensable for optimal monitoring, protection and control of the powermore » grid. The present project was launched with an objective of demonstrating the value of the Wide Area Measurement System (WAMS) using PMUs and its applications on the Dominion Virginia Power High Voltage transmission grid. Virginia Tech is the birth place of PMUs, and was chosen to be the Principal Investigator of this project. In addition to Dominion Virginia Power, Quanta Technology of Raleigh, NC was selected to be co-Principal Investigators of this project.« less

A phasor approach analysis of multiphoton FLIM measurements of three-dimensional cell culture models

NASA Astrophysics Data System (ADS)

Lakner, P. H.; Möller, Y.; Olayioye, M. A.; Brucker, S. Y.; Schenke-Layland, K.; Monaghan, M. G.

2016-03-01

Fluorescence lifetime imaging microscopy (FLIM) is a useful approach to obtain information regarding the endogenous fluorophores present in biological samples. The concise evaluation of FLIM data requires the use of robust mathematical algorithms. In this study, we developed a user-friendly phasor approach for analyzing FLIM data and applied this method on three-dimensional (3D) Caco-2 models of polarized epithelial luminal cysts in a supporting extracellular matrix environment. These Caco-2 based models were treated with epidermal growth factor (EGF), to stimulate proliferation in order to determine if FLIM could detect such a change in cell behavior. Autofluorescence from nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) in luminal Caco-2 cysts was stimulated by 2-photon laser excitation. Using a phasor approach, the lifetimes of involved fluorophores and their contribution were calculated with fewer initial assumptions when compared to multiexponential decay fitting. The phasor approach simplified FLIM data analysis, making it an interesting tool for non-experts in numerical data analysis. We observed that an increased proliferation stimulated by EGF led to a significant shift in fluorescence lifetime and a significant alteration of the phasor data shape. Our data demonstrates that multiphoton FLIM analysis with the phasor approach is a suitable method for the non-invasive analysis of 3D in vitro cell culture models qualifying this method for monitoring basic cellular features and the effect of external factors.

Extended output phasor representation of multi-spectral fluorescence lifetime imaging microscopy

PubMed Central

Campos-Delgado, Daniel U.; Navarro, O. Gutiérrez; Arce-Santana, E. R.; Jo, Javier A.

2015-01-01

In this paper, we investigate novel low-dimensional and model-free representations for multi-spectral fluorescence lifetime imaging microscopy (m-FLIM) data. We depart from the classical definition of the phasor in the complex plane to propose the extended output phasor (EOP) and extended phasor (EP) for multi-spectral information. The frequency domain properties of the EOP and EP are analytically studied based on a multiexponential model for the impulse response of the imaged tissue. For practical implementations, the EOP is more appealing since there is no need to perform deconvolution of the instrument response from the measured m-FLIM data, as in the case of EP. Our synthetic and experimental evaluations with m-FLIM datasets of human coronary atherosclerotic plaques show that low frequency indexes have to be employed for a distinctive representation of the EOP and EP, and to reduce noise distortion. The tissue classification of the m-FLIM datasets by EOP and EP also improves with low frequency indexes, and does not present significant differences by using either phasor. PMID:26114031

The use of the phasor display in studying ionospheric radio echoes

NASA Astrophysics Data System (ADS)

From, W. R.; Whitehead, J. D.

1981-12-01

The phase and amplitude of a radio pulse reflected from the ionosphere usually vary during the pulse. It is convenient to observe these variations using the X-Y mode of an oscilloscope to display the phasor of the echo. The variations are then seen as an oval or spiral shape traced out by the end point of the phasor. These shapes provide a sensitive method of detecting the presence of more than one echo, and are useful as a measure of dispersion.

Spectral Properties and Dynamics of Gold Nanorods Revealed by EMCCD Based Spectral-Phasor Method

PubMed Central

Chen, Hongtao; Digman, Michelle A.

2015-01-01

Gold nanorods (NRs) with tunable plasmon-resonant absorption in the near-infrared region have considerable advantages over organic fluorophores as imaging agents. However, the luminescence spectral properties of NRs have not been fully explored at the single particle level in bulk due to lack of proper analytic tools. Here we present a global spectral phasor analysis method which allows investigations of NRs' spectra at single particle level with their statistic behavior and spatial information during imaging. The wide phasor distribution obtained by the spectral phasor analysis indicates spectra of NRs are different from particle to particle. NRs with different spectra can be identified graphically in corresponding spatial images with high spectral resolution. Furthermore, spectral behaviors of NRs under different imaging conditions, e.g. different excitation powers and wavelengths, were carefully examined by our laser-scanning multiphoton microscope with spectral imaging capability. Our results prove that the spectral phasor method is an easy and efficient tool in hyper-spectral imaging analysis to unravel subtle changes of the emission spectrum. Moreover, we applied this method to study the spectral dynamics of NRs during direct optical trapping and by optothermal trapping. Interestingly, spectral shifts were observed in both trapping phenomena. PMID:25684346

Monitoring tooth profile faults in epicyclic gearboxes using synchronously averaged motor currents: Mathematical modeling and experimental validation

NASA Astrophysics Data System (ADS)

Ottewill, J. R.; Ruszczyk, A.; Broda, D.

2017-02-01

Time-varying transmission paths and inaccessibility can increase the difficulty in both acquiring and processing vibration signals for the purpose of monitoring epicyclic gearboxes. Recent work has shown that the synchronous signal averaging approach may be applied to measured motor currents in order to diagnose tooth faults in parallel shaft gearboxes. In this paper we further develop the approach, so that it may also be applied to monitor tooth faults in epicyclic gearboxes. A low-degree-of-freedom model of an epicyclic gearbox which incorporates the possibility of simulating tooth faults, as well as any subsequent tooth contact loss due to these faults, is introduced. By combining this model with a simple space-phasor model of an induction motor it is possible to show that, in theory, tooth faults in epicyclic gearboxes may be identified from motor currents. Applying the synchronous averaging approach to experimentally recorded motor currents and angular displacements recorded from a shaft mounted encoder, validate this finding. Comparison between experiments and theory highlight the influence of operating conditions, backlash and shaft couplings on the transient response excited in the currents by the tooth fault. The results obtained suggest that the method may be a viable alternative or complement to more traditional methods for monitoring gearboxes. However, general observations also indicate that further investigations into the sensitivity and robustness of the method would be beneficial.

Model-free methods to study membrane environmental probes: a comparison of the spectral phasor and generalized polarization approaches

PubMed Central

Malacrida, Leonel; Gratton, Enrico; Jameson, David M

2016-01-01

In this note, we present a discussion of the advantages and scope of model-free analysis methods applied to the popular solvatochromic probe LAURDAN, which is widely used as an environmental probe to study dynamics and structure in membranes. In particular, we compare and contrast the generalized polarization approach with the spectral phasor approach. To illustrate our points we utilize several model membrane systems containing pure lipid phases and, in some cases, cholesterol or surfactants. We demonstrate that the spectral phasor method offers definitive advantages in the case of complex systems. PMID:27182438

Precise time dissemination and applications development on the Bonneville Power Administration system

NASA Technical Reports Server (NTRS)

Martin, Ken E.; Esztergalyos, J.

1992-01-01

The Bonneville Power Administration (BPA) uses IRIG-B transmitted over microwave as its primary system time dissemination. Problems with accuracy and reliability have led to ongoing research into better methods. BPA has also developed and deployed a unique fault locator which uses precise clocks synchronized by a pulse over microwaves. It automatically transmits the data to a central computer for analysis. A proposed system could combine fault location timing and time dissemination into a Global Position System (GPS) timing receiver and close the verification loop through a master station at the Dittmer Control Center. Such a system would have many advantages, including lower cost, higher reliability, and wider industry support. Test results indicate the GPS has sufficient accuracy and reliability for this and other current timing requirements including synchronous phase angle measurements. A phasor measurement system which provides phase angle has recently been tested with excellent results. Phase angle is a key parameter in power system control applications including dynamic braking, DC modulation, remedial action schemes, and system state estimation. Further research is required to determine the applications which can most effectively use real-time phase angle measurements and the best method to apply them.

Precise time dissemination and applications development on the Bonneville Power Administration system

NASA Astrophysics Data System (ADS)

Martin, Ken E.; Esztergalyos, J.

1992-07-01

The Bonneville Power Administration (BPA) uses IRIG-B transmitted over microwave as its primary system time dissemination. Problems with accuracy and reliability have led to ongoing research into better methods. BPA has also developed and deployed a unique fault locator which uses precise clocks synchronized by a pulse over microwaves. It automatically transmits the data to a central computer for analysis. A proposed system could combine fault location timing and time dissemination into a Global Position System (GPS) timing receiver and close the verification loop through a master station at the Dittmer Control Center. Such a system would have many advantages, including lower cost, higher reliability, and wider industry support. Test results indicate the GPS has sufficient accuracy and reliability for this and other current timing requirements including synchronous phase angle measurements. A phasor measurement system which provides phase angle has recently been tested with excellent results. Phase angle is a key parameter in power system control applications including dynamic braking, DC modulation, remedial action schemes, and system state estimation. Further research is required to determine the applications which can most effectively use real-time phase angle measurements and the best method to apply them.

Vibration sensing in smart machine rotors using internal MEMS accelerometers

NASA Astrophysics Data System (ADS)

Jiménez, Samuel; Cole, Matthew O. T.; Keogh, Patrick S.

2016-09-01

This paper presents a novel topology for enhanced vibration sensing in which wireless MEMS accelerometers embedded within a hollow rotor measure vibration in a synchronously rotating frame of reference. Theoretical relations between rotor-embedded accelerometer signals and the vibration of the rotor in an inertial reference frame are derived. It is thereby shown that functionality as a virtual stator-mounted displacement transducer can be achieved through appropriate signal processing. Experimental tests on a prototype rotor confirm that both magnitude and phase information of synchronous vibration can be measured directly without additional stator-mounted key-phasor sensors. Displacement amplitudes calculated from accelerometer signals will become erroneous at low rotational speeds due to accelerometer zero-g offsets, hence a corrective procedure is introduced. Impact tests are also undertaken to examine the ability of the internal accelerometers to measure transient vibration. A further capability is demonstrated, whereby the accelerometer signals are used to measure rotational speed of the rotor by analysing the signal component due to gravity. The study highlights the extended functionality afforded by internal accelerometers and demonstrates the feasibility of internal sensor topologies, which can provide improved observability of rotor vibration at externally inaccessible rotor locations.

Placement of Synchronized Measurements for Power System Observability during Cascaded Outages

NASA Astrophysics Data System (ADS)

Thirugnanasambandam, Venkatesh; Jain, Trapti

2017-11-01

Cascaded outages often result in power system islanding followed by a blackout and therefore considered as a severe disturbance. Maintaining the observability of each island may help in taking proper control actions to preserve the stability of individual islands thus, averting system collapse. With this intent, a strategy for placement of synchronized measurements, which can be obtained from phasor measurement units (PMU), has been proposed in this paper to keep the system observable during cascaded outages also. Since, all the cascaded failures may not lead to islanding situations, therefore, failures leading to islanding as well as non-islanding situations have been considered. A topology based algorithm has been developed to identify the islanding/non-islanding condition created by a particular cascaded event. Additional contingencies such as single line loss and single PMU failure have also been considered after the occurrence of cascaded events. The proposed method is further extended to incorporate the measurement redundancy, which is desirable for a reliable state estimation. The proposed scheme is tested on IEEE 14-bus, IEEE 30-bus and a practical Indian 246-bus networks. The numerical results ensure the observability of the power system under system intact as well as during cascaded islanding and non-islanding disturbances.

Bad data detection in two stage estimation using phasor measurements

NASA Astrophysics Data System (ADS)

Tarali, Aditya

The ability of the Phasor Measurement Unit (PMU) to directly measure the system state, has led to steady increase in the use of PMU in the past decade. However, in spite of its high accuracy and the ability to measure the states directly, they cannot completely replace the conventional measurement units due to high cost. Hence it is necessary for the modern estimators to use both conventional and phasor measurements together. This thesis presents an alternative method to incorporate the new PMU measurements into the existing state estimator in a systematic manner such that no major modification is necessary to the existing algorithm. It is also shown that if PMUs are placed appropriately, the phasor measurements can be used to detect and identify the bad data associated with critical measurements by using this model, which cannot be detected by conventional state estimation algorithm. The developed model is tested on IEEE 14, IEEE 30 and IEEE 118 bus under various conditions.

Phasor based single-molecule localization microscopy in 3D (pSMLM-3D): An algorithm for MHz localization rates using standard CPUs

NASA Astrophysics Data System (ADS)

Martens, Koen J. A.; Bader, Arjen N.; Baas, Sander; Rieger, Bernd; Hohlbein, Johannes

2018-03-01

We present a fast and model-free 2D and 3D single-molecule localization algorithm that allows more than 3 × 106 localizations per second to be calculated on a standard multi-core central processing unit with localization accuracies in line with the most accurate algorithms currently available. Our algorithm converts the region of interest around a point spread function to two phase vectors (phasors) by calculating the first Fourier coefficients in both the x- and y-direction. The angles of these phasors are used to localize the center of the single fluorescent emitter, and the ratio of the magnitudes of the two phasors is a measure for astigmatism, which can be used to obtain depth information (z-direction). Our approach can be used both as a stand-alone algorithm for maximizing localization speed and as a first estimator for more time consuming iterative algorithms.

Wide-Area Situational Awareness of Power Grids with Limited Phasor Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Ning; Huang, Zhenyu; Nieplocha, Jarek

Lack of situational awareness has been identified as one of root causes for the August 14, 2003 Northeast Blackout in North America. To improve situational awareness, the Department of Energy (DOE) launched several projects to deploy Wide Area Measurement Systems (WAMS) in different interconnections. Compared to the tens of thousands of buses, the number of Phasor Measurement Units (PMUs) is quite limited and not enough to achieve the observability for the whole interconnections. To utilize the limited number of PMU measurements to improve situational awareness, this paper proposes to combine PMU measurement data and power flow equations to form amore » hybrid power flow model. Technically, a model which combines the concept of observable islands and modeling of power flow conditions, is proposed. The model is called a Hybrid Power Flow Model as it has both PMU measurements and simulation assumptions, which describes prior knowledge available about whole power systems. By solving the hybrid power flow equations, the proposed method can be used to derive power system states to improve the situational awareness of a power grid.« less

Advanced EMT and Phasor-Domain Hybrid Simulation with Simulation Mode Switching Capability for Transmission and Distribution Systems

DOE PAGES

Huang, Qiuhua; Vittal, Vijay

2018-05-09

Conventional electromagnetic transient (EMT) and phasor-domain hybrid simulation approaches presently exist for trans-mission system level studies. Their simulation efficiency is generally constrained by the EMT simulation. With an increasing number of distributed energy resources and non-conventional loads being installed in distribution systems, it is imperative to extend the hybrid simulation application to include distribution systems and integrated transmission and distribution systems. Meanwhile, it is equally important to improve the simulation efficiency as the modeling scope and complexity of the detailed system in the EMT simulation increases. To meet both requirements, this paper introduces an advanced EMT and phasor-domain hybrid simulationmore » approach. This approach has two main features: 1) a comprehensive phasor-domain modeling framework which supports positive-sequence, three-sequence, three-phase and mixed three-sequence/three-phase representations and 2) a robust and flexible simulation mode switching scheme. The developed scheme enables simulation switching from hybrid simulation mode back to pure phasor-domain dynamic simulation mode to achieve significantly improved simulation efficiency. The proposed method has been tested on integrated transmission and distribution systems. In conclusion, the results show that with the developed simulation switching feature, the total computational time is significantly reduced compared to running the hybrid simulation for the whole simulation period, while maintaining good simulation accuracy.« less

Advanced EMT and Phasor-Domain Hybrid Simulation with Simulation Mode Switching Capability for Transmission and Distribution Systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Qiuhua; Vittal, Vijay

Conventional electromagnetic transient (EMT) and phasor-domain hybrid simulation approaches presently exist for trans-mission system level studies. Their simulation efficiency is generally constrained by the EMT simulation. With an increasing number of distributed energy resources and non-conventional loads being installed in distribution systems, it is imperative to extend the hybrid simulation application to include distribution systems and integrated transmission and distribution systems. Meanwhile, it is equally important to improve the simulation efficiency as the modeling scope and complexity of the detailed system in the EMT simulation increases. To meet both requirements, this paper introduces an advanced EMT and phasor-domain hybrid simulationmore » approach. This approach has two main features: 1) a comprehensive phasor-domain modeling framework which supports positive-sequence, three-sequence, three-phase and mixed three-sequence/three-phase representations and 2) a robust and flexible simulation mode switching scheme. The developed scheme enables simulation switching from hybrid simulation mode back to pure phasor-domain dynamic simulation mode to achieve significantly improved simulation efficiency. The proposed method has been tested on integrated transmission and distribution systems. In conclusion, the results show that with the developed simulation switching feature, the total computational time is significantly reduced compared to running the hybrid simulation for the whole simulation period, while maintaining good simulation accuracy.« less

Phasor imaging with a widefield photon-counting detector

PubMed Central

Siegmund, Oswald H. W.; Tremsin, Anton S.; Vallerga, John V.; Weiss, Shimon

2012-01-01

Abstract. Fluorescence lifetime can be used as a contrast mechanism to distinguish fluorophores for localization or tracking, for studying molecular interactions, binding, assembly, and aggregation, or for observing conformational changes via Förster resonance energy transfer (FRET) between donor and acceptor molecules. Fluorescence lifetime imaging microscopy (FLIM) is thus a powerful technique but its widespread use has been hampered by demanding hardware and software requirements. FLIM data is often analyzed in terms of multicomponent fluorescence lifetime decays, which requires large signals for a good signal-to-noise ratio. This confines the approach to very low frame rates and limits the number of frames which can be acquired before bleaching the sample. Recently, a computationally efficient and intuitive graphical representation, the phasor approach, has been proposed as an alternative method for FLIM data analysis at the ensemble and single-molecule level. In this article, we illustrate the advantages of combining phasor analysis with a widefield time-resolved single photon-counting detector (the H33D detector) for FLIM applications. In particular we show that phasor analysis allows real-time subsecond identification of species by their lifetimes and rapid representation of their spatial distribution, thanks to the parallel acquisition of FLIM information over a wide field of view by the H33D detector. We also discuss possible improvements of the H33D detector’s performance made possible by the simplicity of phasor analysis and its relaxed timing accuracy requirements compared to standard time-correlated single-photon counting (TCSPC) methods. PMID:22352658

Roller Bearing Health Monitoring Using CPLE Frequency Analysis Method

NASA Technical Reports Server (NTRS)

Jong, Jen-Yi; Jones, Jess H.

2007-01-01

This paper describes a unique vibration signature analysis technique Coherence Phase Line Enhancer (CPLE) Frequency Analysis - for roller bearing health monitoring. Defects of roller bearing (e.g. wear, foreign debris, crack in bearing supporting structure, etc.) can cause small bearing characteristic frequency shifts due to minor changes in bearing geometry. Such frequency shifts are often too small to detect by the conventional Power Spectral Density (PSD) due to its frequency bandwidth limitation. This Coherent Phase Line Enhancer technology has been evolving over the last few years and has culminated in the introduction of a new and novel frequency spectrum which is fully described in this paper. This CPLE technology uses a "key phasor" or speed probe as a preprocessor for this analysis. With the aid of this key phasor, this CPLE technology can develop a two dimensional frequency spectrum that preserves both amplitude and phase that is not normally obtained using conventional frequency analysis. This two-dimensional frequency transformation results in several newly defined spectral functions; i. e. CPLE-PSD, CPLE-Coherence and the CPLE-Frequency. This paper uses this CPLE frequency analysis to detect subtle, low level bearing related signals in the High Pressure Fuel Pump (HPFP) of the Space Shuttle Main Engine (SSME). For many rotating machinery applications, a key phasor is an essential measurement that is used in the detection of bearing related signatures. There are times however, when a key phasor is not available; i. e. during flight of any of the SSME turbopumps or on the SSME High Pressure Oxygen Turbopump (HPOTP) where no speed probe is present. In this case, the CPLE analysis approach can still be achieved using a novel Pseudo Key Phasor (PKP) technique to reconstruct a 1/Rev PKP signal directly from external vibration measurements. This paper develops this Pseudo Key Phasor technique and applies it to the SSME vibration data.

Intracellular pH measurements made simple by fluorescent protein probes and the phasor approach to fluorescence lifetime imaging†

PubMed Central

Digman, Michelle A.; Gratton, Enrico; Storti, Barbara; Beltram, Fabio

2013-01-01

A versatile pH-dependent fluorescent protein was applied to intracellular pH measurements by means of the phasor approach to fluorescence lifetime imaging. By this fit-less method we obtain intracellular pH maps under resting or altered physiological conditions by single-photon confocal or two-photon microscopy. PMID:22517076

Development and Integration of an Advanced Stirling Convertor Linear Alternator Model for a Tool Simulating Convertor Performance and Creating Phasor Diagrams

NASA Technical Reports Server (NTRS)

Metscher, Jonathan F.; Lewandowski, Edward J.

2013-01-01

A simple model of the Advanced Stirling Convertors (ASC) linear alternator and an AC bus controller has been developed and combined with a previously developed thermodynamic model of the convertor for a more complete simulation and analysis of the system performance. The model was developed using Sage, a 1-D thermodynamic modeling program that now includes electro-magnetic components. The convertor, consisting of a free-piston Stirling engine combined with a linear alternator, has sufficiently sinusoidal steady-state behavior to allow for phasor analysis of the forces and voltages acting in the system. A MATLAB graphical user interface (GUI) has been developed to interface with the Sage software for simplified use of the ASC model, calculation of forces, and automated creation of phasor diagrams. The GUI allows the user to vary convertor parameters while fixing different input or output parameters and observe the effect on the phasor diagrams or system performance. The new ASC model and GUI help create a better understanding of the relationship between the electrical component voltages and mechanical forces. This allows better insight into the overall convertor dynamics and performance.

Imaging Fibrosis and Separating Collagens using Second Harmonic Generation and Phasor Approach to Fluorescence Lifetime Imaging

PubMed Central

Ranjit, Suman; Dvornikov, Alexander; Stakic, Milka; Hong, Suk-Hyun; Levi, Moshe; Evans, Ronald M.; Gratton, Enrico

2015-01-01

In this paper we have used second harmonic generation (SHG) and phasor approach to auto fluorescence lifetime imaging (FLIM) to obtain fingerprints of different collagens and then used these fingerprints to observe bone marrow fibrosis in the mouse femur. This is a label free approach towards fast automatable detection of fibrosis in tissue samples. FLIM has previously been used as a method of contrast in different tissues and in this paper phasor approach to FLIM is used to separate collagen I from collagen III, the markers of fibrosis, the largest groups of disorders that are often without any effective therapy. Often characterized by an increase in collagen content of the corresponding tissue, the samples are usually visualized by histochemical staining, which is pathologist dependent and cannot be automated. PMID:26293987

Discrete-state phasor neural networks

NASA Astrophysics Data System (ADS)

Noest, André J.

1988-08-01

An associative memory network with local variables assuming one of q equidistant positions on the unit circle (q-state phasors) is introduced, and its recall behavior is solved exactly for any q when the interactions are sparse and asymmetric. Such models can describe natural or artifical networks of (neuro-)biological, chemical, or electronic limit-cycle oscillators with q-fold instead of circular symmetry, or similar optical computing devices using a phase-encoded data representation.

Application of PMU-Based Information in the Indian Power System

NASA Astrophysics Data System (ADS)

Agarwal, P. K.; Agarwal, V. K.; Rathour, Harish

2013-05-01

SCADA/EMS system has been the most commonly used tool for real-time power system operation and control throughout the world. This system has been found to be very useful in steady-state analysis of the power system. The ever-increasing dependence of human society and every country's economy on electrical energy calls for reliable power delivery. In order to meet these expectations, engineers across the globe have been exploring such new technologies that can improve upon the limitations of SCADA and provide dynamic visibility of the power system. A breakthrough has now been achieved in the form of synchrophasor technology. Synchrophasor measurements using phasor measurement units (PMUs) deployed over a wide area, facilitate dynamic state measurement and visualization of a power system, which are useful in monitoring safety and security of the grid. The Power System Operation Corporation (POSOCO) has taken initiative and implemented a pilot project wherein nine phasor measurement units (PMUs) along with one phasor data concentrator (PDC) were commissioned in the Northern Region (NR) of India. The primary objective of this pilot project was to comprehend the synchrophasor technology and its applications in power system operation. The data received and information derived from the pilot project have been found to be very useful and helped in improving the performance of the grid operation in several ways. The pilot project is operational for the last two years; in the meanwhile, many other initiatives have also been taken in other regions by POSOCO. This article details the utilization of the data collected from the pilot projects and the application of the data in the improvement of Indian power grid.

Application of phasor plot and autofluorescence correction for study of heterogeneous cell population

PubMed Central

Szmacinski, Henryk; Toshchakov, Vladimir; Lakowicz, Joseph R.

2014-01-01

Abstract. Protein-protein interactions in cells are often studied using fluorescence resonance energy transfer (FRET) phenomenon by fluorescence lifetime imaging microscopy (FLIM). Here, we demonstrate approaches to the quantitative analysis of FRET in cell population in a case complicated by a highly heterogeneous donor expression, multiexponential donor lifetime, large contribution of cell autofluorescence, and significant presence of unquenched donor molecules that do not interact with the acceptor due to low affinity of donor-acceptor binding. We applied a multifrequency phasor plot to visualize FRET FLIM data, developed a method for lifetime background correction, and performed a detailed time-resolved analysis using a biexponential model. These approaches were applied to study the interaction between the Toll Interleukin-1 receptor (TIR) domain of Toll-like receptor 4 (TLR4) and the decoy peptide 4BB. TLR4 was fused to Cerulean fluorescent protein (Cer) and 4BB peptide was labeled with Bodipy TMRX (BTX). Phasor displays for multifrequency FLIM data are presented. The analytical procedure for lifetime background correction is described and the effect of correction on FLIM data is demonstrated. The absolute FRET efficiency was determined based on the phasor plot display and multifrequency FLIM data analysis. The binding affinity between TLR4-Cer (donor) and decoy peptide 4BB-BTX (acceptor) was estimated in a heterogeneous HeLa cell population. PMID:24770662

Modeling of Transionospheric Radio Propagation

DTIC Science & Technology

1975-08-01

entitled RFMOD, contains the main elements of the scattering theory, the morphological model for ionospheric irregularity strength and other...phasor lies within an elemental area on the complex plain. To begin, we write E as the resultant of its long-term mean (E) and a zero-mean, randomly...totally defined by either of these sets of three parameters (i.e., the three real variances or the real R and the real and imaginary parts of B ). Most

Generator Dynamic Model Validation and Parameter Calibration Using Phasor Measurements at the Point of Connection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zhenyu; Du, Pengwei; Kosterev, Dmitry

2013-05-01

Disturbance data recorded by phasor measurement units (PMU) offers opportunities to improve the integrity of dynamic models. However, manually tuning parameters through play-back events demands significant efforts and engineering experiences. In this paper, a calibration method using the extended Kalman filter (EKF) technique is proposed. The formulation of EKF with parameter calibration is discussed. Case studies are presented to demonstrate its validity. The proposed calibration method is cost-effective, complementary to traditional equipment testing for improving dynamic model quality.

Prony Ringdown GUI (CERTS Prony Ringdown, part of the DSI Tool Box)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tuffner, Francis; Marinovici, PNNL Laurentiu; Hauer, PNNL John

2014-02-21

The PNNL Prony Ringdown graphical user interface is one analysis tool included in the Dynamic System Identification toolbox (DSI Toolbox). The Dynamic System Identification toolbox is a MATLAB-based collection of tools for parsing and analyzing phasor measurement unit data, especially in regards to small signal stability. It includes tools to read the data, preprocess it, and perform small signal analysis. 5. Method of Solution: The Dynamic System Identification Toolbox (DSI Toolbox) is designed to provide a research environment for examining phasor measurement unit data and performing small signal stability analysis. The software uses a series of text-driven menus to helpmore » guide users and organize the toolbox features. Methods for reading in populate phasor measurement unit data are provided, with appropriate preprocessing options for small-signal-stability analysis. The toolbox includes the Prony Ringdown GUI and basic algorithms to estimate information on oscillatory modes of the system, such as modal frequency and damping ratio.« less

Event Classification and Identification Based on the Characteristic Ellipsoid of Phasor Measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Jian; Diao, Ruisheng; Makarov, Yuri V.

2011-09-23

In this paper, a method to classify and identify power system events based on the characteristic ellipsoid of phasor measurement is presented. The decision tree technique is used to perform the event classification and identification. Event types, event locations and clearance times are identified by decision trees based on the indices of the characteristic ellipsoid. A sufficiently large number of transient events were simulated on the New England 10-machine 39-bus system based on different system configurations. Transient simulations taking into account different event types, clearance times and various locations are conducted to simulate phasor measurement. Bus voltage magnitudes and recordedmore » reactive and active power flows are used to build the characteristic ellipsoid. The volume, eccentricity, center and projection of the longest axis in the parameter space coordinates of the characteristic ellipsoids are used to classify and identify events. Results demonstrate that the characteristic ellipsoid and the decision tree are capable to detect the event type, location, and clearance time with very high accuracy.« less

Algorithm for Screening Phasor Measurement Unit Data for Power System Events and Categories and Common Characteristics for Events Seen in Phasor Measurement Unit Relative Phase-Angle Differences and Frequency Signals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, A.; Santoso, S.; Muljadi, E.

2013-08-01

A network of multiple phasor measurement units (PMU) was created, set up, and maintained at the University of Texas at Austin to obtain actual power system measurements for power system analysis. Power system analysis in this report covers a variety of time ranges, such as short- term analysis for power system disturbances and their effects on power system behavior and long- term power system behavior using modal analysis. The first objective of this report is to screen the PMU data for events. The second objective of the report is to identify and describe common characteristics extracted from power system eventsmore » as measured by PMUs. The numerical characteristics for each category and how these characteristics are used to create selection rules for the algorithm are also described. Trends in PMU data related to different levels and fluctuations in wind power output are also examined.« less

Available pressure amplitude of linear compressor based on phasor triangle model

NASA Astrophysics Data System (ADS)

Duan, C. X.; Jiang, X.; Zhi, X. Q.; You, X. K.; Qiu, L. M.

2017-12-01

The linear compressor for cryocoolers possess the advantages of long-life operation, high efficiency, low vibration and compact structure. It is significant to study the match mechanisms between the compressor and the cold finger, which determines the working efficiency of the cryocooler. However, the output characteristics of linear compressor are complicated since it is affected by many interacting parameters. The existing matching methods are simplified and mainly focus on the compressor efficiency and output acoustic power, while neglecting the important output parameter of pressure amplitude. In this study, a phasor triangle model basing on analyzing the forces of the piston is proposed. It can be used to predict not only the output acoustic power, the efficiency, but also the pressure amplitude of the linear compressor. Calculated results agree well with the measurement results of the experiment. By this phasor triangle model, the theoretical maximum output pressure amplitude of the linear compressor can be calculated simply based on a known charging pressure and operating frequency. Compared with the mechanical and electrical model of the linear compressor, the new model can provide an intuitionistic understanding on the match mechanism with faster computational process. The model can also explain the experimental phenomenon of the proportional relationship between the output pressure amplitude and the piston displacement in experiments. By further model analysis, such phenomenon is confirmed as an expression of the unmatched design of the compressor. The phasor triangle model may provide an alternative method for the compressor design and matching with the cold finger.

Ripples on spikes show increased phase-amplitude coupling in mesial temporal lobe epilepsy seizure onset zones

PubMed Central

Weiss, Shennan A; Orosz, Iren; Salamon, Noriko; Moy, Stephanie; Wei, Linqing; Van ’t Klooster, Maryse A; Knight, Robert T; Harper, Ronald M; Bragin, Anatol; Fried, Itzhak; Engel, Jerome; Staba, Richard J

2016-01-01

Objective Ripples (80–150 Hz) recorded from clinical macroelectrodes have been shown to be an accurate biomarker of epileptogenic brain tissue. We investigated coupling between epileptiform spike phase and ripple amplitude to better understand the mechanisms that generate this type of pathological ripple (pRipple) event. Methods We quantified phase amplitude coupling (PAC) between epileptiform EEG spike phase and ripple amplitude recorded from intracranial depth macroelectrodes during episodes of sleep in 12 patients with mesial temporal lobe epilepsy. PAC was determined by 1) a phasor transform that corresponds to the strength and rate of ripples coupled with spikes, and a 2) ripple-triggered average to measure the strength, morphology, and spectral frequency of the modulating and modulated signals. Coupling strength was evaluated in relation to recording sites within and outside the seizure onset zone (SOZ). Results Both the phasor transform and ripple-triggered averaging methods showed ripple amplitude was often robustly coupled with epileptiform EEG spike phase. Coupling was more regularly found inside than outside the SOZ, and coupling strength correlated with the likelihood a macroelectrode’s location was within the SOZ (p<0.01). The ratio of the rate of ripples coupled with EEG spikes inside the SOZ to rates of coupled ripples in non-SOZ was greater than the ratio of rates of ripples on spikes detected irrespective of coupling (p<0.05). Coupling strength correlated with an increase in mean normalized ripple amplitude (p<0.01), and a decrease in mean ripple spectral frequency (p<0.05). Significance Generation of low-frequency (80–150 Hz) pRipples in the SOZ involves coupling between epileptiform spike phase and ripple amplitude. The changes in excitability reflected as epileptiform spikes may also cause clusters of pathologically interconnected bursting neurons to grow and synchronize into aberrantly large neuronal assemblies. PMID:27723936

Effects of Phasor Measurement Uncertainty on Power Line Outage Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Chen; Wang, Jianhui; Zhu, Hao

2014-12-01

Phasor measurement unit (PMU) technology provides an effective tool to enhance the wide-area monitoring systems (WAMSs) in power grids. Although extensive studies have been conducted to develop several PMU applications in power systems (e.g., state estimation, oscillation detection and control, voltage stability analysis, and line outage detection), the uncertainty aspects of PMUs have not been adequately investigated. This paper focuses on quantifying the impact of PMU uncertainty on power line outage detection and identification, in which a limited number of PMUs installed at a subset of buses are utilized to detect and identify the line outage events. Specifically, the linemore » outage detection problem is formulated as a multi-hypothesis test, and a general Bayesian criterion is used for the detection procedure, in which the PMU uncertainty is analytically characterized. We further apply the minimum detection error criterion for the multi-hypothesis test and derive the expected detection error probability in terms of PMU uncertainty. The framework proposed provides fundamental guidance for quantifying the effects of PMU uncertainty on power line outage detection. Case studies are provided to validate our analysis and show how PMU uncertainty influences power line outage detection.« less

BabelFish-Tools for IEEE C37.118.2-compliant real-time synchrophasor data mediation

NASA Astrophysics Data System (ADS)

Almas, M. S.; Vanfretti, L.; Baudette, M.

BabelFish (BF) is a real-time data mediator for development and fast prototyping of synchrophasor applications. BF is compliant with the synchrophasor data transmission IEEE Std C37.118.2-2011. BF establishes a TCP/IP connection with any Phasor Measurement Unit (PMU) or Phasor Data Concentrator (PDC) stream and parses the IEEE Std C37.118.2-2011 frames in real-time to provide access to raw numerical data in the LabVIEW environment. Furthermore, BF allows the user to select "data-of-interest" and transmit it to either a local or remote application using the User Datagram Protocol (UDP) in order to support both unicast and multicast communication. In the power systems Wide Area Monitoring Protection and Control (WAMPAC) domain, BF provides the first Free/Libre and Open Source Software (FLOSS) for the purpose of giving the users tools for fast prototyping of new applications processing PMU measurements in their chosen environment, thus liberating them of time consuming synchrophasor data handling and allowing them to develop applications in a modular fashion, without a need of a large and monolithic synchrophasor software environment.

CD81 Controls Sustained T Cell Activation Signaling and Defines the Maturation Stages of Cognate Immunological Synapses

PubMed Central

Rocha-Perugini, V.; Zamai, M.; González-Granado, J. M.; Barreiro, O.; Tejera, E.; Yañez-Mó, M.; Caiolfa, V. R.

2013-01-01

In this study, we investigated the dynamics of the molecular interactions of tetraspanin CD81 in T lymphocytes, and we show that CD81 controls the organization of the immune synapse (IS) and T cell activation. Using quantitative microscopy, including fluorescence recovery after photobleaching (FRAP), phasor fluorescence lifetime imaging microscopy-Föster resonance energy transfer (phasorFLIM-FRET), and total internal reflection fluorescence microscopy (TIRFM), we demonstrate that CD81 interacts with ICAM-1 and CD3 during conjugation between T cells and antigen-presenting cells (APCs). CD81 and ICAM-1 exhibit distinct mobilities in central and peripheral areas of early and late T cell-APC contacts. Moreover, CD81–ICAM-1 and CD81-CD3 dynamic interactions increase over the time course of IS formation, as these molecules redistribute throughout the contact area. Therefore, CD81 associations unexpectedly define novel sequential steps of IS maturation. Our results indicate that CD81 controls the temporal progression of the IS and the permanence of CD3 in the membrane contact area, contributing to sustained T cell receptor (TCR)-CD3-mediated signaling. Accordingly, we find that CD81 is required for proper T cell activation, regulating CD3ζ, ZAP-70, LAT, and extracellular signal-regulated kinase (ERK) phosphorylation; CD69 surface expression; and interleukin-2 (IL-2) secretion. Our data demonstrate the important role of CD81 in the molecular organization and dynamics of the IS architecture that sets the signaling threshold in T cell activation. PMID:23858057

Transient stability enhancement of modern power grid using predictive Wide-Area Monitoring and Control

NASA Astrophysics Data System (ADS)

Yousefian, Reza

This dissertation presents a real-time Wide-Area Control (WAC) designed based on artificial intelligence for large scale modern power systems transient stability enhancement. The WAC using the measurements available from Phasor Measurement Units (PMUs) at generator buses, monitors the global oscillations in the system and optimally augments the local excitation system of the synchronous generators. The complexity of the power system stability problem along with uncertainties and nonlinearities makes the conventional modeling non-practical or inaccurate. In this work Reinforcement Learning (RL) algorithm on the benchmark of Neural Networks (NNs) is used to map the nonlinearities of the system in real-time. This method different from both the centralized and the decentralized control schemes, employs a number of semi-autonomous agents to collaborate with each other to perform optimal control theory well-suited for WAC applications. Also, to handle the delays in Wide-Area Monitoring (WAM) and adapt the RL toward the robust control design, Temporal Difference (TD) is proposed as a solver for RL problem or optimal cost function. However, the main drawback of such WAC design is that it is challenging to determine if an offline trained network is valid to assess the stability of the power system once the system is evolved to a different operating state or network topology. In order to address the generality issue of NNs, a value priority scheme is proposed in this work to design a hybrid linear and nonlinear controllers. The algorithm so-called supervised RL is based on mixture of experts, where it is initialized by linear controller and as the performance and identification of the RL controller improves in real-time switches to the other controller. This work also focuses on transient stability and develops Lyapunov energy functions for synchronous generators to monitor the stability stress of the system. Using such energies as a cost function guarantees the convergence toward optimal post-fault solutions. These energy functions are developed on inter-area oscillations of the system identified online with Prony analysis. Finally, this work investigates the impacts of renewable energy resources, in specific Doubly Fed Induction Generator (DFIG)-based wind turbines, on power system transient stability and control. As the penetration of such resources is increased in transmission power system, neglecting the impacts of them will make the WAC design non-realistic. An energy function is proposed for DFIGs based on their dynamic performance in transient disturbances. Further, this energy is augmented to synchronous generators' energy as a global cost function, which is minimized by the WAC signals. We discuss the relative advantages and bottlenecks of each architecture and methodology using dynamic simulations of several test systems including a 2-area 8 bus system, IEEE 39 bus system, and IEEE 68 bus system in EMTP and real-time simulators. Being nonlinear-based, fast, accurate, and non-model based design, the proposed WAC system shows better transient and damping response when compared to conventional control schemes and local PSSs.

Design of a two-level power system linear state estimator

NASA Astrophysics Data System (ADS)

Yang, Tao

The availability of synchro-phasor data has raised the possibility of a linear state estimator if the inputs are only complex currents and voltages and if there are enough such measurements to meet observability and redundancy requirements. Moreover, the new digital substations can perform some of the computation at the substation itself resulting in a more accurate two-level state estimator. The objective of this research is to develop a two-level linear state estimator processing synchro-phasor data and estimating the states at both the substation level and the control center level. Both the mathematical algorithms that are different from those in the present state estimation procedure and the layered architecture of databases, communications and application programs that are required to support this two-level linear state estimator are described in this dissertation. Besides, as the availability of phasor measurements at substations will increase gradually, this research also describes how the state estimator can be enhanced to handle both the traditional state estimator and the proposed linear state estimator simultaneously. This provides a way to immediately utilize the benefits in those parts of the system where such phasor measurements become available and provides a pathway to transition to the smart grid of the future. The design procedure of the two-level state estimator is applied to two study systems. The first study system is the IEEE-14 bus system. The second one is the 179 bus Western Electricity Coordinating Council (WECC) system. The static database for the substations is constructed from the power flow data of these systems and the real-time measurement database is produced by a power system dynamic simulating tool (TSAT). Time-skew problems that may be caused by communication delays are also considered and simulated. We used the Network Simulator (NS) tool to simulate a simple communication system and analyse its time delay performance. These time delays were too small to affect the results especially since the measurement data is time-stamped and the state estimator for these small systems could be run with subseconf frequency. Keywords: State Estimation, Synchro-Phasor Measurement, Distributed System, Energy Control Center, Substation, Time-skew

A Fault Location Algorithm for Two-End Series-Compensated Double-Circuit Transmission Lines Using the Distributed Parameter Line Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Ning; Gombos, Gergely; Mousavi, Mirrasoul J.

A new fault location algorithm for two-end series-compensated double-circuit transmission lines utilizing unsynchronized two-terminal current phasors and local voltage phasors is presented in this paper. The distributed parameter line model is adopted to take into account the shunt capacitance of the lines. The mutual coupling between the parallel lines in the zero-sequence network is also considered. The boundary conditions under different fault types are used to derive the fault location formulation. The developed algorithm directly uses the local voltage phasors on the line side of series compensation (SC) and metal oxide varistor (MOV). However, when potential transformers are not installedmore » on the line side of SC and MOVs for the local terminal, these measurements can be calculated from the local terminal bus voltage and currents by estimating the voltages across the SC and MOVs. MATLAB SimPowerSystems is used to generate cases under diverse fault conditions to evaluating accuracy. The simulation results show that the proposed algorithm is qualified for practical implementation.« less

Multispectral analysis tools can increase utility of RGB color images in histology

NASA Astrophysics Data System (ADS)

Fereidouni, Farzad; Griffin, Croix; Todd, Austin; Levenson, Richard

2018-04-01

Multispectral imaging (MSI) is increasingly finding application in the study and characterization of biological specimens. However, the methods typically used come with challenges on both the acquisition and the analysis front. MSI can be slow and photon-inefficient, leading to long imaging times and possible phototoxicity and photobleaching. The resulting datasets can be large and complex, prompting the development of a number of mathematical approaches for segmentation and signal unmixing. We show that under certain circumstances, just three spectral channels provided by standard color cameras, coupled with multispectral analysis tools, including a more recent spectral phasor approach, can efficiently provide useful insights. These findings are supported with a mathematical model relating spectral bandwidth and spectral channel number to achievable spectral accuracy. The utility of 3-band RGB and MSI analysis tools are demonstrated on images acquired using brightfield and fluorescence techniques, as well as a novel microscopy approach employing UV-surface excitation. Supervised linear unmixing, automated non-negative matrix factorization and phasor analysis tools all provide useful results, with phasors generating particularly helpful spectral display plots for sample exploration.

Generation and transmission of multilevel quadrature amplitude modulation formats using only one optical modulator: MATLAB Simulink simulation models

NASA Astrophysics Data System (ADS)

Binh, Le Nguyen

2009-04-01

A geometrical and phasor representation technique is presented to illustrate the modulation of the lightwave carrier to generate quadrature amplitude modulated (QAM) signals. The modulation of the amplitude and phase of the lightwave carrier is implemented using only one dual-drive Mach-Zehnder interferometric modulator (MZIM) with the assistance of phasor techniques. Any multilevel modulation scheme can be generated, but we illustrate specifically, the multilevel amplitude and differential phase shift keying (MADPSK) signals. The driving voltage levels are estimated for driving the traveling wave electrodes of the modulator. Phasor diagrams are extensively used to demonstrate the effectiveness of modulation schemes. MATLAB Simulink models are formed to generate the multilevel modulation formats, transmission, and detection in optically amplified fiber communication systems. Transmission performance is obtained for the multilevel optical signals and proven to be equivalent or better than those of binary level with equivalent bit rate. Further, the resilience to nonlinear effects is much higher for MADPSK of 50% and 33% pulse width as compared to non-return-to-zero (NRZ) pulse shaping.

PMU Data Integrity Evaluation through Analytics on a Virtual Test-Bed

DOE Office of Scientific and Technical Information (OSTI.GOV)

Olama, Mohammed M.; Shankar, Mallikarjun

Power systems are rapidly becoming populated by phasor measurement units (PMUs) in ever increasing numbers. PMUs are critical components of today s energy management systems, designed to enable near real-time wide area monitoring and control of the electric power system. They are able to measure highly accurate bus voltage phasors as well as branch current phasors incident to the buses at which PMUs are equipped. Synchrophasor data is used for applications varying from state estimation, islanding control, identifying outages, voltage stability detection and correction, disturbance recording, and others. However, PMU-measured readings may suffer from errors due to meter biases ormore » drifts, incorrect configurations, or even cyber-attacks. Furthermore, the testing of early PMUs showed a large disparity between the reported values from PMUs provided by different manufacturers, particularly when frequency was off-nominal, during dynamic events, and when harmonic/inter-harmonic content was present. Detection and identification of PMU gross measurement errors are thus crucial in maintaining highly accurate phasor readings throughout the system. In this paper, we present our work in conducting analytics to determine the trustworthiness and worth of the PMU readings collected across an electric network system. By implementing the IEEE 118 bus test case on a virtual test bed (VTB) , we are able to emulate PMU readings (bus voltage and branch current phasors in addition to bus frequencies) under normal and abnormal conditions using (virtual) PMU sensors deployed across major substations in the network. We emulate a variety of failures such as bus, line, transformer, generator, and/or load failures. Data analytics on the voltage phase angles and frequencies collected from the PMUs show that specious (or compromised) PMU device(s) can be identified through abnormal behaviour by comparing the trend of its frequency and phase angle reading with the ensemble of all other PMU readings in the network. If the reading trend of a particular PMU deviates from the weighted average of the reading trends of other PMUs at nearby substations, then it is likely that the PMU is malfunctioning. We assign a weight to each PMU denoting how electric-topology-wise close it is from where the PMU under consideration is located. The closer a PMU is, the higher the weight it has. To compute the closeness between two nodes in the power network, we employ a form of the resistance distance metric. It computes the electrical distance by taking into consideration the underlying topology as well as the physical laws that govern the electrical connections or flows between the network components. The detection accuracy of erroneous PMUs should be improved by employing this metric. We present results to validate the proposed approach. We also discuss the effectiveness of using an end-to-end VTB approach that allows us to investigate different types of failures and their responses as seen by the ensemble of PMUs. The collected data on certain types of events may be amenable to certain types of analysis (e.g., alerting for sudden changes can be done on a small window of data) and hence determine the data analytics architectures is required to evaluate the streaming PMU data.« less

Theory of post-block 2 VLBI observable extraction

NASA Technical Reports Server (NTRS)

Lowe, Stephen T.

1992-01-01

The algorithms used in the post-Block II fringe-fitting software called 'Fit' are described. The steps needed to derive the very long baseline interferometry (VLBI) charged-particle corrected group delay, phase delay rate, and phase delay (the latter without resolving cycle ambiguities) are presented beginning with the set of complex fringe phasors as a function of observation frequency and time. The set of complex phasors is obtained from the JPL/CIT Block II correlator. The output of Fit is the set of charged-particle corrected observables (along with ancillary information) in a form amenable to the software program 'Modest.'

Bonneville, Power Administration Timing System

NASA Technical Reports Server (NTRS)

Martin, Kenneth E.

1996-01-01

Time is an integral part of the Bonneville Power Administration's (BPA) operational systems. Generation and power transfers are planned in advance. Utilities coordinate with each other by making these adjustments on a timed schedule. Price varies with demand, so billing is based on time. Outages for maintenance are scheduled to assure they do not interrupt reliable power delivery. Disturbance records are aligned with recorded timetags for analysis and comparison with related information. Advanced applications like traveling wave fault location and real-time phase measurement require continuous timing with high precision. Most of BPA is served by a Central Time System (CTS) at the Dittmer Control Center near Portland, OR. This system keeps time locally and supplies time to both the control center systems and field locations via a microwave signal. It is kept synchronized to national standard time and coordinated with interconnected utilities. It is the official BPA time. Powwer system control and operation is described, followed by a description of BPA timing systems including CTS, the Fault Location Acquisition Reporter, time dissemination, and phasor measurements. References are provided for further reading.

Developing High PV Penetration Cases for Frequency Response Study of U.S. Western Interconnection: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Jin; Zhang, Yingchen; Veda, Santosh

Recent large penetrations of solar photovoltaic (PV) generation and the inertial characteristics of inverter-based generation technologies have caught the attention of those in the electric power industry in the United States. This paper presents a systematic approach to developing test cases of high penetrations of PV for the Western Interconnection. First, to examine the accuracy of the base case model, the Western Electricity Coordinating Council (WECC) model is validated by using measurement data from synchronized phasor measurement units. Based on the 2022 Light Spring case, we developed four high PV penetration cases for the WECC system that are of interestmore » to the industry: 5% PV+15 % wind, 25% PV+15% wind, 45% PV+15% wind, 65% PV+15% wind). Additionally, a method to project PV is proposed that is based on collected, realistic PV distribution information, including the current and future PV power plant locations and penetrations in the WECC system. Both the utility-scale PV plant and residential rooftop PV are included in this study.« less

Developing High PV Penetration Cases for Frequency Response Study of U.S. Western Interconnection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Jin; Zhang, Yingchen; Veda, Santosh

Recent large penetrations of solar photovoltaic (PV) generation and the inertial characteristics of inverter-based generation technologies have caught the attention of those in the electric power industry in the United States. This paper presents a systematic approach to developing test cases of high penetrations of PV for the Western Interconnection. First, to examine the accuracy of the base case model, the Western Electricity Coordinating Council (WECC) model is validated by using measurement data from synchronized phasor measurement units. Based on the 2022 Light Spring case, we developed four high PV penetration cases for the WECC system that are of interestmore » to the industry: 5% PV+15 % wind, 25% PV+15% wind, 45% PV+15% wind, 65% PV+15% wind). Additionally, a method to project PV is proposed that is based on collected, realistic PV distribution information, including the current and future PV power plant locations and penetrations in the WECC system. Both the utility-scale PV plant and residential rooftop PV are included in this study.« less

Developing High PV Penetration Cases for Frequency Response Study of U.S. Western Interconnection: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tan, Jin; Zhang, Yingchen; Veda, Santosh

2017-04-11

Recent large penetrations of solar photovoltaic (PV) generation and the inertial characteristics of inverter-based generation technologies have caught the attention of those in the electric power industry in the United States. This paper presents a systematic approach to developing test cases of high penetrations of PV for the Western Interconnection. First, to examine the accuracy of the base case model, the Western Electricity Coordinating Council (WECC) model is validated by using measurement data from synchronized phasor measurement units. Based on the 2022 Light Spring case, we developed four high PV penetration cases for the WECC system that are of interestmore » to the industry: 5% PV+15 % wind, 25% PV+15% wind, 45% PV+15% wind, 65% PV+15% wind). Additionally, a method to project PV is proposed that is based on collected, realistic PV distribution information, including the current and future PV power plant locations and penetrations in the WECC system. Both the utility-scale PV plant and residential rooftop PV are included in this study.« less

Coordinated control of wind generation and energy storage for power system frequency regulation

NASA Astrophysics Data System (ADS)

Baone, Chaitanya Ashok

Large-scale centralized synchronous generators have long been the primary actors in exercising active power and frequency control, and much of the existing grid control framework is predicated upon their dynamic terminal characteristics. Important among these characteristics is the inertia of such generators. These play key roles in determining the electromechanical stability of the electric power grid. Modern wind generator systems are partially or fully connected to the grid through power electronic interfaces, and hence do not present the same level of inertial coupling. The absence of inertial frequency response from modern wind generator systems is a topic of growing concern in power engineering practice, as the penetration of wind generation is expected to grow dramatically in the next few years. Solutions proposed in the literature have sought to address this problem by seeking to mimic the inherent inertial response characteristics of traditional synchronous generators via control loops added to wind generators. Recent literature has raised concerns regarding this approach, and the work here will further examine its shortcomings, motivating approaches that seek to optimally design for the characteristics of the equipment exercising the control, rather than forcing new technologies to mimic the characteristics of synchronous machines. In particular, this work will develop a new approach to power system frequency regulation, with features suited to distributed energy storage devices such as grid-scale batteries and wind turbine speed and blade pitch control. The dynamic characteristics of these new technologies are treated along with existing mechanisms, such as synchronous machine governor control, to develop a comprehensive multi-input control design approach. To make the method practically feasible for geographically distributed power systems, an observer-based distributed control design utilizing phasor measurement unit (PMU) signals along with local measurements is developed. In addition to the system-wide objective of frequency regulation, a local objective of reducing the wind turbine drivetrain stress is considered. Also, an algorithm is proposed to characterize the modal degrees of controllability and observability on a subspace of critical modes of the system, so that the most effective sensor and actuator locations to be used in the control design can be found.

Synchrophasor-Assisted Prediction of Stability/Instability of a Power System

NASA Astrophysics Data System (ADS)

Saha Roy, Biman Kumar; Sinha, Avinash Kumar; Pradhan, Ashok Kumar

2013-05-01

This paper presents a technique for real-time prediction of stability/instability of a power system based on synchrophasor measurements obtained from phasor measurement units (PMUs) at generator buses. For stability assessment the technique makes use of system severity indices developed using bus voltage magnitude obtained from PMUs and generator electrical power. Generator power is computed using system information and PMU information like voltage and current phasors obtained from PMU. System stability/instability is predicted when the indices exceeds a threshold value. A case study is carried out on New England 10-generator, 39-bus system to validate the performance of the technique.

Phasor Simulator for Operator Training Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyer, Jim

2016-09-14

Synchrophasor systems are being deployed in power systems throughout the North American Power Grid and there are plans to integrate this technology and its associated tools into Independent System Operator (ISO)/utility control room operations. A pre-requisite to using synchrophasor technologies in control rooms is for operators to obtain training and understand how to use this technology in real-time situations. The Phasor Simulator for Operator Training (PSOT) project objective was to develop, deploy and demonstrate a pre-commercial training simulator for operators on the use of this technology and to promote acceptance of the technology in utility and ISO/Regional Transmission Owner (RTO)more » control centers.« less

Comparing different approaches to visualizing light waves: An experimental study on teaching wave optics

NASA Astrophysics Data System (ADS)

Mešić, Vanes; Hajder, Erna; Neumann, Knut; Erceg, Nataša

2016-06-01

Research has shown that students have tremendous difficulties developing a qualitative understanding of wave optics, at all educational levels. In this study, we investigate how three different approaches to visualizing light waves affect students' understanding of wave optics. In the first, the conventional, approach light waves are represented by sinusoidal curves. The second teaching approach includes representing light waves by a series of static images, showing the oscillating electric field vectors at characteristic, subsequent instants of time. Within the third approach phasors are used for visualizing light waves. A total of N =85 secondary school students were randomly assigned to one of the three teaching approaches, each of which lasted a period of four class hours. Students who learned with phasors and students who learned from the series of static images outperformed the students learning according to the conventional approach, i.e., they showed a much better understanding of basic wave optics, as measured by a conceptual survey administered to the students one week after the treatment. Our results suggest that visualizing light waves with phasors or oscillating electric field vectors is a promising approach to developing a deeper understanding of wave optics for students enrolled in conceptual level physics courses.

Phasor-based single-molecule fluorescence lifetime imaging using a wide-field photon-counting detector

PubMed Central

Colyer, R.; Siegmund, O.; Tremsin, A.; Vallerga, J.; Weiss, S.; Michalet, X.

2011-01-01

Fluorescence lifetime imaging (FLIM) is a powerful approach to studying the immediate environment of molecules. For example, it is used in biology to study changes in the chemical environment, or to study binding processes, aggregation, and conformational changes by measuring Förster resonance energy transfer (FRET) between donor and acceptor fluorophores. FLIM can be acquired by time-domain measurements (time-correlated single-photon counting) or frequency-domain measurements (with PMT modulation or digital frequency domain acquisition) in a confocal setup, or with wide-field systems (using time-gated cameras). In the best cases, the resulting data is analyzed in terms of multicomponent fluorescence lifetime decays with demanding requirements in terms of signal level (and therefore limited frame rate). Recently, the phasor approach has been proposed as a powerful alternative for fluorescence lifetime analysis of FLIM, ensemble, and single-molecule experiments. Here we discuss the advantages of combining phasor analysis with a new type of FLIM acquisition hardware presented previously, consisting of a high temporal and spatial resolution wide-field single-photon counting device (the H33D detector). Experimental data with live cells and quantum dots will be presented as an illustration of this new approach. PMID:21625298

The phasor-FLIM fingerprints reveal shifts from OXPHOS to enhanced glycolysis in Huntington Disease

PubMed Central

Sameni, Sara; Syed, Adeela; Marsh, J. Lawrence; Digman, Michelle A.

2016-01-01

Huntington disease (HD) is an autosomal neurodegenerative disorder caused by the expansion of Polyglutamine (polyQ) in exon 1 of the Huntingtin protein. Glutamine repeats below 36 are considered normal while repeats above 40 lead to HD. Impairment in energy metabolism is a common trend in Huntington pathogenesis; however, this effect is not fully understood. Here, we used the phasor approach and Fluorescence Lifetime Imaging Microscopy (FLIM) to measure changes between free and bound fractions of NADH as a indirect measure of metabolic alteration in living cells. Using Phasor-FLIM, pixel maps of metabolic alteration in HEK293 cell lines and in transgenic Drosophila expressing expanded and unexpanded polyQ HTT exon1 in the eye disc were developed. We found a significant shift towards increased free NADH, indicating an increased glycolytic state for cells and tissues expressing the expanded polyQ compared to unexpanded control. In the nucleus, a further lifetime shift occurs towards higher free NADH suggesting a possible synergism between metabolic dysfunction and transcriptional regulation. Our results indicate that metabolic dysfunction in HD shifts to increased glycolysis leading to oxidative stress and cell death. This powerful label free method can be used to screen native HD tissue samples and for potential drug screening. PMID:27713486

Laboratory Performance Evaluation Report of SEL 421 Phasor Measurement Unit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Zhenyu; faris, Anthony J.; Martin, Kenneth E.

2007-12-01

PNNL and BPA have been in close collaboration on laboratory performance evaluation of phasor measurement units for over ten years. A series of evaluation tests are designed to confirm accuracy and determine measurement performance under a variety of conditions that may be encountered in actual use. Ultimately the testing conducted should provide parameters that can be used to adjust all measurements to a standardized basis. These tests are performed with a standard relay test set using recorded files of precisely generated test signals. The test set provides test signals at a level and in a format suitable for input tomore » a PMU that accurately reproduces the signals in both signal amplitude and timing. Test set outputs are checked to confirm the accuracy of the output signal. The recorded signals include both current and voltage waveforms and a digital timing track used to relate the PMU measured value with the test signal. Test signals include steady-state waveforms to test amplitude, phase, and frequency accuracy, modulated signals to determine measurement and rejection bands, and step tests to determine timing and response accuracy. Additional tests are included as necessary to fully describe the PMU operation. Testing is done with a BPA phasor data concentrator (PDC) which provides communication support and monitors data input for dropouts and data errors.« less

Propagation phasor approach for holographic image reconstruction

PubMed Central

Luo, Wei; Zhang, Yibo; Göröcs, Zoltán; Feizi, Alborz; Ozcan, Aydogan

2016-01-01

To achieve high-resolution and wide field-of-view, digital holographic imaging techniques need to tackle two major challenges: phase recovery and spatial undersampling. Previously, these challenges were separately addressed using phase retrieval and pixel super-resolution algorithms, which utilize the diversity of different imaging parameters. Although existing holographic imaging methods can achieve large space-bandwidth-products by performing pixel super-resolution and phase retrieval sequentially, they require large amounts of data, which might be a limitation in high-speed or cost-effective imaging applications. Here we report a propagation phasor approach, which for the first time combines phase retrieval and pixel super-resolution into a unified mathematical framework and enables the synthesis of new holographic image reconstruction methods with significantly improved data efficiency. In this approach, twin image and spatial aliasing signals, along with other digital artifacts, are interpreted as noise terms that are modulated by phasors that analytically depend on the lateral displacement between hologram and sensor planes, sample-to-sensor distance, wavelength, and the illumination angle. Compared to previous holographic reconstruction techniques, this new framework results in five- to seven-fold reduced number of raw measurements, while still achieving a competitive resolution and space-bandwidth-product. We also demonstrated the success of this approach by imaging biological specimens including Papanicolaou and blood smears. PMID:26964671

The phasor-FLIM fingerprints reveal shifts from OXPHOS to enhanced glycolysis in Huntington Disease

NASA Astrophysics Data System (ADS)

Sameni, Sara; Syed, Adeela; Marsh, J. Lawrence; Digman, Michelle A.

2016-10-01

Huntington disease (HD) is an autosomal neurodegenerative disorder caused by the expansion of Polyglutamine (polyQ) in exon 1 of the Huntingtin protein. Glutamine repeats below 36 are considered normal while repeats above 40 lead to HD. Impairment in energy metabolism is a common trend in Huntington pathogenesis; however, this effect is not fully understood. Here, we used the phasor approach and Fluorescence Lifetime Imaging Microscopy (FLIM) to measure changes between free and bound fractions of NADH as a indirect measure of metabolic alteration in living cells. Using Phasor-FLIM, pixel maps of metabolic alteration in HEK293 cell lines and in transgenic Drosophila expressing expanded and unexpanded polyQ HTT exon1 in the eye disc were developed. We found a significant shift towards increased free NADH, indicating an increased glycolytic state for cells and tissues expressing the expanded polyQ compared to unexpanded control. In the nucleus, a further lifetime shift occurs towards higher free NADH suggesting a possible synergism between metabolic dysfunction and transcriptional regulation. Our results indicate that metabolic dysfunction in HD shifts to increased glycolysis leading to oxidative stress and cell death. This powerful label free method can be used to screen native HD tissue samples and for potential drug screening.

Label-free separation of human embryonic stem cells and their differentiating progenies by phasor fluorescence lifetime microscopy

NASA Astrophysics Data System (ADS)

Stringari, Chiara; Sierra, Robert; Donovan, Peter J.; Gratton, Enrico

2012-04-01

We develop a label-free optical technique to image and discriminate undifferentiated human embryonic stem cells (hESCs) from their differentiating progenies in vitro. Using intrinsic cellular fluorophores, we perform fluorescence lifetime microscopy (FLIM) and phasor analysis to obtain hESC metabolic signatures. We identify two optical biomarkers to define the differentiation status of hESCs: Nicotinamide adenine dinucleotide (NADH) and lipid droplet-associated granules (LDAGs). These granules have a unique lifetime signature and could be formed by the interaction of reactive oxygen species and unsaturated metabolic precursor that are known to be abundant in hESC. Changes in the relative concentrations of these two intrinsic biomarkers allow for the discrimination of undifferentiated hESCs from differentiating hESCs. During early hESC differentiation we show that NADH concentrations increase, while the concentration of LDAGs decrease. These results are in agreement with a decrease in oxidative phosphorylation rate. Single-cell phasor FLIM signatures reveal an increased heterogeneity in the metabolic states of differentiating H9 and H1 hESC colonies. This technique is a promising noninvasive tool to monitor hESC metabolism during differentiation, which can have applications in high throughput analysis, drug screening, functional metabolomics and induced pluripotent stem cell generation.

Secure Hashing of Dynamic Hand Signatures Using Wavelet-Fourier Compression with BioPhasor Mixing and [InlineEquation not available: see fulltext.] Discretization

NASA Astrophysics Data System (ADS)

Wai Kuan, Yip; Teoh, Andrew B. J.; Ngo, David C. L.

2006-12-01

We introduce a novel method for secure computation of biometric hash on dynamic hand signatures using BioPhasor mixing and[InlineEquation not available: see fulltext.] discretization. The use of BioPhasor as the mixing process provides a one-way transformation that precludes exact recovery of the biometric vector from compromised hashes and stolen tokens. In addition, our user-specific[InlineEquation not available: see fulltext.] discretization acts both as an error correction step as well as a real-to-binary space converter. We also propose a new method of extracting compressed representation of dynamic hand signatures using discrete wavelet transform (DWT) and discrete fourier transform (DFT). Without the conventional use of dynamic time warping, the proposed method avoids storage of user's hand signature template. This is an important consideration for protecting the privacy of the biometric owner. Our results show that the proposed method could produce stable and distinguishable bit strings with equal error rates (EERs) of[InlineEquation not available: see fulltext.] and[InlineEquation not available: see fulltext.] for random and skilled forgeries for stolen token (worst case) scenario, and[InlineEquation not available: see fulltext.] for both forgeries in the genuine token (optimal) scenario.

Study of rabbit erythrocytes membrane solubilization by sucrose monomyristate using laurdan and phasor analysis.

PubMed

Günther, German; Herlax, Vanesa; Lillo, M Pilar; Sandoval-Altamirano, Catalina; Belmar, Libnny N; Sánchez, Susana A

2018-01-01

The study of surfactant and bio membranes interaction is particularly complex due to the diversity in lipid composition and the presence of proteins in natural membranes. Even more difficult is the study of this interaction in vivo since cellular damage may complicate the interpretation of the results, therefore for most of the studies in this field either artificial or model systems are used. One of the model system most used to study biomembranes are erythrocytes due to their relatively simple structure (they lack nuclei and organelles having only the plasma membrane), their convenient experimental manipulation and availability. In this context, we used rabbit erythrocytes as a model membrane and Laurdan (6-lauroyl-2-dimethylaminonaphthalene) as the fluorescent probe to study changes promoted in the membrane by the interaction with the sucrose monoester of myristic acid, β-d-fructofuranosyl-6-O-myristoyl-α-d-glucopyranoside (MMS). Surfactant and erythrocytes interaction was studied by measuring hemoglobin release and the changes in water content in the membrane sensed by Laurdan. Using two-photon excitation, three types of measurements were performed: Generalized Polarization (analyzed as average GP values), Fluorescence Lifetime Imaging, FLIM (analyzed using phasor plots) and Spectral imaging (analyzed using spectral phasor). Our data indicate that at sublytical concentration of surfactant (20μM MMS), there is a decrease of about 35% in erythrocytes size, without changes in Laurdan lifetime or emission spectra. We also demonstrate that as hemolysis progress, Laurdan lifetime increased due to the decrease in hemoglobin (strong quencher of Laurdan emission) content inside the erythrocytes. Under these conditions, Laurdan spectral phasor analyses can extract the information on the water content in the membrane in the presence of hemoglobin. Our results indicate an increase in membrane fluidity in presence of MMS. Copyright © 2017 Elsevier B.V. All rights reserved.

Fuzzy Inference System Approach for Locating Series, Shunt, and Simultaneous Series-Shunt Faults in Double Circuit Transmission Lines

PubMed Central

Swetapadma, Aleena; Yadav, Anamika

2015-01-01

Many schemes are reported for shunt fault location estimation, but fault location estimation of series or open conductor faults has not been dealt with so far. The existing numerical relays only detect the open conductor (series) fault and give the indication of the faulty phase(s), but they are unable to locate the series fault. The repair crew needs to patrol the complete line to find the location of series fault. In this paper fuzzy based fault detection/classification and location schemes in time domain are proposed for both series faults, shunt faults, and simultaneous series and shunt faults. The fault simulation studies and fault location algorithm have been developed using Matlab/Simulink. Synchronized phasors of voltage and current signals of both the ends of the line have been used as input to the proposed fuzzy based fault location scheme. Percentage of error in location of series fault is within 1% and shunt fault is 5% for all the tested fault cases. Validation of percentage of error in location estimation is done using Chi square test with both 1% and 5% level of significance. PMID:26413088

Sensor Transmission Power Schedule for Smart Grids

NASA Astrophysics Data System (ADS)

Gao, C.; Huang, Y. H.; Li, J.; Liu, X. D.

2017-11-01

Smart grid has attracted much attention by the requirement of new generation renewable energy. Nowadays, the real-time state estimation, with the help of phasor measurement unit, plays an important role to keep smart grid stable and efficient. However, the limitation of the communication channel is not considered by related work. Considering the familiar limited on-board batteries wireless sensor in smart grid, transmission power schedule is designed in this paper, which minimizes energy consumption with proper EKF filtering performance requirement constrain. Based on the event-triggered estimation theory, the filtering algorithm is also provided to utilize the information contained in the power schedule. Finally, its feasibility and performance is demonstrated using the standard IEEE 39-bus system with phasor measurement units (PMUs).

A POSITIONAL DATA SYSTEM

DOEpatents

Forster, G.A.

1963-09-24

between master and slave synchros is described. A threephase a-c power source is connected to the stators of the synchros and an error detector is connected to the rotors of the synchros to measure the phasor difference therebetween. A phase shift network shifts the phase of one of the rotors 90 degrees and a demodulator responsive thereto causes the phasor difference signal of the rotors to shift phase 180 degrees whenever the 90 degree phase shifted signal goes negative. The phase shifted difference signal has a waveform which, with the addition of small values of resistance and capacitance, gives a substantially pure d-c output whose amplitude and polarity is proportional to the magnitude and direction of the difference in the angular positions of the synchro's rotors. (AEC)

Applying phasor approach analysis of multiphoton FLIM measurements to probe the metabolic activity of three-dimensional in vitro cell culture models

PubMed Central

Lakner, Pirmin H.; Monaghan, Michael G.; Möller, Yvonne; Olayioye, Monilola A.; Schenke-Layland, Katja

2017-01-01

Fluorescence lifetime imaging microscopy (FLIM) can measure and discriminate endogenous fluorophores present in biological samples. This study seeks to identify FLIM as a suitable method to non-invasively detect a shift in cellular metabolic activity towards glycolysis or oxidative phosphorylation in 3D Caco-2 models of colorectal carcinoma. These models were treated with potassium cyanide or hydrogen peroxide as controls, and epidermal growth factor (EGF) as a physiologically-relevant influencer of cell metabolic behaviour. Autofluorescence, attributed to nicotinamide adenine dinucleotide (NADH), was induced by two-photon laser excitation and its lifetime decay was analysed using a standard multi-exponential decay approach and also a novel custom-written code for phasor-based analysis. While both methods enabled detection of a statistically significant shift of metabolic activity towards glycolysis using potassium cyanide, and oxidative phosphorylation using hydrogen peroxide, employing the phasor approach required fewer initial assumptions to quantify the lifetimes of contributing fluorophores. 3D Caco-2 models treated with EGF had increased glucose consumption, production of lactate, and presence of ATP. FLIM analyses of these cultures revealed a significant shift in the contribution of protein-bound NADH towards free NADH, indicating increased glycolysis-mediated metabolic activity. This data demonstrate that FLIM is suitable to interpret metabolic changes in 3D in vitro models. PMID:28211922

Applying phasor approach analysis of multiphoton FLIM measurements to probe the metabolic activity of three-dimensional in vitro cell culture models.

PubMed

Lakner, Pirmin H; Monaghan, Michael G; Möller, Yvonne; Olayioye, Monilola A; Schenke-Layland, Katja

2017-02-13

Fluorescence lifetime imaging microscopy (FLIM) can measure and discriminate endogenous fluorophores present in biological samples. This study seeks to identify FLIM as a suitable method to non-invasively detect a shift in cellular metabolic activity towards glycolysis or oxidative phosphorylation in 3D Caco-2 models of colorectal carcinoma. These models were treated with potassium cyanide or hydrogen peroxide as controls, and epidermal growth factor (EGF) as a physiologically-relevant influencer of cell metabolic behaviour. Autofluorescence, attributed to nicotinamide adenine dinucleotide (NADH), was induced by two-photon laser excitation and its lifetime decay was analysed using a standard multi-exponential decay approach and also a novel custom-written code for phasor-based analysis. While both methods enabled detection of a statistically significant shift of metabolic activity towards glycolysis using potassium cyanide, and oxidative phosphorylation using hydrogen peroxide, employing the phasor approach required fewer initial assumptions to quantify the lifetimes of contributing fluorophores. 3D Caco-2 models treated with EGF had increased glucose consumption, production of lactate, and presence of ATP. FLIM analyses of these cultures revealed a significant shift in the contribution of protein-bound NADH towards free NADH, indicating increased glycolysis-mediated metabolic activity. This data demonstrate that FLIM is suitable to interpret metabolic changes in 3D in vitro models.

Conversion and Validation of Distribution System Model from a QSTS-Based Tool to a Real-Time Dynamic Phasor Simulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chamana, Manohar; Prabakar, Kumaraguru; Palmintier, Bryan

A software process is developed to convert distribution network models from a quasi-static time-series tool (OpenDSS) to a real-time dynamic phasor simulator (ePHASORSIM). The description of this process in this paper would be helpful for researchers who intend to perform similar conversions. The converter could be utilized directly by users of real-time simulators who intend to perform software-in-the-loop or hardware-in-the-loop tests on large distribution test feeders for a range of use cases, including testing functions of advanced distribution management systems against a simulated distribution system. In the future, the developers intend to release the conversion tool as open source tomore » enable use by others.« less

Conversion and Validation of Distribution System Model from a QSTS-Based Tool to a Real-Time Dynamic Phasor Simulator: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chamana, Manohar; Prabakar, Kumaraguru; Palmintier, Bryan

A software process is developed to convert distribution network models from a quasi-static time-series tool (OpenDSS) to a real-time dynamic phasor simulator (ePHASORSIM). The description of this process in this paper would be helpful for researchers who intend to perform similar conversions. The converter could be utilized directly by users of real-time simulators who intend to perform software-in-the-loop or hardware-in-the-loop tests on large distribution test feeders for a range of use cases, including testing functions of advanced distribution management systems against a simulated distribution system. In the future, the developers intend to release the conversion tool as open source tomore » enable use by others.« less

Potential formulation of the dispersion relation for a uniform, magnetized plasma with stationary ions in terms of a vector phasor

NASA Astrophysics Data System (ADS)

Johnson, Robert W.

2012-06-01

The derivation of the helicon dispersion relation for a uniform plasma with stationary ions subject to a constant background magnetic field is reexamined in terms of the potential formulation of electrodynamics. Under the same conditions considered by the standard derivation, the nonlinear self-coupling between the perturbed electron flow and the potential it generates is addressed. The plane wave solution for general propagation vector is determined for all frequencies and expressed in terms of a vector phasor. The behavior of the solution as described in vacuum units depends upon the ratio of conductivity to the magnitude of the background field. Only at low conductivity and below, the cyclotron frequency can significant propagation occur as determined by the ratio of skin depth to wavelength.

Stability of Synchronization Clusters and Seizurability in Temporal Lobe Epilepsy

PubMed Central

Palmigiano, Agostina; Pastor, Jesús; García de Sola, Rafael; Ortega, Guillermo J.

2012-01-01

Purpose Identification of critical areas in presurgical evaluations of patients with temporal lobe epilepsy is the most important step prior to resection. According to the “epileptic focus model”, localization of seizure onset zones is the main task to be accomplished. Nevertheless, a significant minority of epileptic patients continue to experience seizures after surgery (even when the focus is correctly located), an observation that is difficult to explain under this approach. However, if attention is shifted from a specific cortical location toward the network properties themselves, then the epileptic network model does allow us to explain unsuccessful surgical outcomes. Methods The intraoperative electrocorticography records of 20 patients with temporal lobe epilepsy were analyzed in search of interictal synchronization clusters. Synchronization was analyzed, and the stability of highly synchronized areas was quantified. Surrogate data were constructed and used to statistically validate the results. Our results show the existence of highly localized and stable synchronization areas in both the lateral and the mesial areas of the temporal lobe ipsilateral to the clinical seizures. Synchronization areas seem to play a central role in the capacity of the epileptic network to generate clinical seizures. Resection of stable synchronization areas is associated with elimination of seizures; nonresection of synchronization clusters is associated with the persistence of seizures after surgery. Discussion We suggest that synchronization clusters and their stability play a central role in the epileptic network, favoring seizure onset and propagation. We further speculate that the stability distribution of these synchronization areas would differentiate normal from pathologic cases. PMID:22844524

Calibration of Reduced Dynamic Models of Power Systems using Phasor Measurement Unit (PMU) Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Ning; Lu, Shuai; Singh, Ruchi

2011-09-23

Accuracy of a power system dynamic model is essential to the secure and efficient operation of the system. Lower confidence on model accuracy usually leads to conservative operation and lowers asset usage. To improve model accuracy, identification algorithms have been developed to calibrate parameters of individual components using measurement data from staged tests. To facilitate online dynamic studies for large power system interconnections, this paper proposes a model reduction and calibration approach using phasor measurement unit (PMU) data. First, a model reduction method is used to reduce the number of dynamic components. Then, a calibration algorithm is developed to estimatemore » parameters of the reduced model. This approach will help to maintain an accurate dynamic model suitable for online dynamic studies. The performance of the proposed method is verified through simulation studies.« less

An Empirical Study of Synchrophasor Communication Delay in a Utility TCP/IP Network

NASA Astrophysics Data System (ADS)

Zhu, Kun; Chenine, Moustafa; Nordström, Lars; Holmström, Sture; Ericsson, Göran

2013-07-01

Although there is a plethora of literature dealing with Phasor Measurement Unit (PMU) communication delay, there has not been any effort made to generalize empirical delay results by identifying the distribution with the best fit. The existing studies typically assume a distribution or simply build on analogies to communication network routing delay. Specifically, this study provides insight into the characterization of the communication delay of both unprocessed PMU data and synchrophasors sorted by a Phasor Data Concentrator (PDC). The results suggest that a bi-modal distribution containing two normal distributions offers the best fit of the delay of the unprocessed data, whereas the delay profile of the sorted synchrophasors resembles a normal distribution based on these results, the possibility of evaluating the reliability of a synchrophasor application with respect to a particular choice of PDC timeout is discussed.

Potential formulation of the dispersion relation for a uniform, magnetized plasma with stationary ions in terms of a vector phasor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Robert W.

2012-06-15

The derivation of the helicon dispersion relation for a uniform plasma with stationary ions subject to a constant background magnetic field is reexamined in terms of the potential formulation of electrodynamics. Under the same conditions considered by the standard derivation, the nonlinear self-coupling between the perturbed electron flow and the potential it generates is addressed. The plane wave solution for general propagation vector is determined for all frequencies and expressed in terms of a vector phasor. The behavior of the solution as described in vacuum units depends upon the ratio of conductivity to the magnitude of the background field. Onlymore » at low conductivity and below, the cyclotron frequency can significant propagation occur as determined by the ratio of skin depth to wavelength.« less

An Introduction to Goodness of Fit for PMU Parameter Estimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riepnieks, Artis; Kirkham, Harold

2017-10-01

New results of measurements of phasor-like signals are presented based on our previous work on the topic. In this document an improved estimation method is described. The algorithm (which is realized in MATLAB software) is discussed. We examine the effect of noisy and distorted signals on the Goodness of Fit metric. The estimation method is shown to be performing very well with clean data and with a measurement window as short as a half a cycle and as few as 5 samples per cycle. The Goodness of Fit decreases predictably with added phase noise, and seems to be acceptable evenmore » with visible distortion in the signal. While the exact results we obtain are specific to our method of estimation, the Goodness of Fit method could be implemented in any phasor measurement unit.« less

Development of real-time voltage stability monitoring tool for power system transmission network using Synchrophasor data

NASA Astrophysics Data System (ADS)

Pulok, Md Kamrul Hasan

Intelligent and effective monitoring of power system stability in control centers is one of the key issues in smart grid technology to prevent unwanted power system blackouts. Voltage stability analysis is one of the most important requirements for control center operation in smart grid era. With the advent of Phasor Measurement Unit (PMU) or Synchrophasor technology, real time monitoring of voltage stability of power system is now a reality. This work utilizes real-time PMU data to derive a voltage stability index to monitor the voltage stability related contingency situation in power systems. The developed tool uses PMU data to calculate voltage stability index that indicates relative closeness of the instability by producing numerical indices. The IEEE 39 bus, New England power system was modeled and run on a Real-time Digital Simulator that stream PMU data over the Internet using IEEE C37.118 protocol. A Phasor data concentrator (PDC) is setup that receives streaming PMU data and stores them in Microsoft SQL database server. Then the developed voltage stability monitoring (VSM) tool retrieves phasor measurement data from SQL server, performs real-time state estimation of the whole network, calculate voltage stability index, perform real-time ranking of most vulnerable transmission lines, and finally shows all the results in a graphical user interface. All these actions are done in near real-time. Control centers can easily monitor the systems condition by using this tool and can take precautionary actions if needed.

Measurement-Based Investigation of Inter- and Intra-Area Effects of Wind Power Plant Integration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, Alicia J.; Singh, Mohit; Muljadi, Eduard

This paper has a two pronged objective: the first objective is to analyze the general effects of wind power plant (WPP) integration and the resulting displacement of conventional power plant (CPP) inertia on power system stability and the second is to demonstrate the efficacy of PMU data in power system stability analyses, specifically when knowledge of the network is incomplete. Traditionally modal analysis applies small signal stability analysis based on Eigenvalues and the assumption of complete knowledge of the network and all of its components. The analysis presented here differs because it is a measurement-based investigation and employs simulated measurementmore » data. Even if knowledge of the network were incomplete, this methodology would allow for monitoring and analysis of modes. This allows non-utility entities and study of power system stability. To generate inter- and intra-area modes, Kundur's well-known two-area four-generator system is modeled in PSCAD/EMTDC. A doubly-fed induction generator based WPP model, based on the Western Electricity Coordination Council (WECC) standard model, is included to analyze the effects of wind power on system modes. The two-area system and WPP are connected in various configurations with respect to WPP placement, CPP inertia and WPP penetration level. Analysis is performed on the data generated by the simulations. For each simulation run, a different configuration is chosen and a large disturbance is applied. The sampling frequency is set to resemble the sampling frequency at which data is available from phasor measurement units (PMUs). The estimate of power spectral density of these signals is made using the Yule-Walker algorithm. The resulting analysis shows that the presence of a WPP does not, of itself, lead to the introduction of new modes. The analysis also shows however that displacement of inertia may lead to introduction of new modes. The effects of location of inertia displacement (i.e. the effects on modes if WPP integration leads to displacement of inertia in its own region or in another region) and of WPP controls such as droop control and synthetic inertia are also examined. In future work, the methods presented here will be applied to real-world phasor data to examine the effects of integration of variable generation and displacement of CPP inertia on inter- and intra-area modes.« less

Automatic Implementation of Prony Analysis for Electromechanical Mode Identification from Phasor Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Ning; Huang, Zhenyu; Tuffner, Francis K.

2010-07-31

Small signal stability problems are one of the major threats to grid stability and reliability. Prony analysis has been successfully applied on ringdown data to monitor electromechanical modes of a power system using phasor measurement unit (PMU) data. To facilitate an on-line application of mode estimation, this paper developed a recursive algorithm for implementing Prony analysis and proposed an oscillation detection method to detect ringdown data in real time. By automatically detect ringdown data, the proposed method helps guarantee that Prony analysis is applied properly and timely on the ringdown data. Thus, the mode estimation results can be performed reliablymore » and timely. The proposed method is tested using Monte Carlo simulations based on a 17-machine model and is shown to be able to properly identify the oscillation data for on-line application of Prony analysis.« less

Real time test bed development for power system operation, control and cyber security

NASA Astrophysics Data System (ADS)

Reddi, Ram Mohan

The operation and control of the power system in an efficient way is important in order to keep the system secure, reliable and economical. With advancements in smart grid, several new algorithms have been developed for improved operation and control. These algorithms need to be extensively tested and validated in real time before applying to the real electric power grid. This work focuses on the development of a real time test bed for testing and validating power system control algorithms, hardware devices and cyber security vulnerability. The test bed developed utilizes several hardware components including relays, phasor measurement units, phasor data concentrator, programmable logic controllers and several software tools. Current work also integrates historian for power system monitoring and data archiving. Finally, two different power system test cases are simulated to demonstrate the applications of developed test bed. The developed test bed can also be used for power system education.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hauer, John F.; Mittelstadt, William; Martin, Kenneth E.

During 2005 and 2006 the Western Electricity Coordinating Council (WECC) performed three major tests of western system dynamics. These tests used a Wide Area Measurement System (WAMS) based primarily on Phasor Measurement Units (PMUs) to determine response to events including the insertion of the 1400-MW Chief Joseph braking resistor, probing signals, and ambient events. Test security was reinforced through real-time analysis of wide area effects, and high-quality data provided dynamic profiles for interarea modes across the entire western interconnection. The tests established that low-level optimized pseudo-random ±20-MW probing with the Pacific DC Intertie (PDCI) roughly doubles the apparent noise thatmore » is natural to the power system, providing sharp dynamic information with negligible interference to system operations. Such probing is an effective alternative to use of the 1400-MW Chief Joseph dynamic brake, and it is under consideration as a standard means for assessing dynamic security.« less

A network of networks model to study phase synchronization using structural connection matrix of human brain

NASA Astrophysics Data System (ADS)

Ferrari, F. A. S.; Viana, R. L.; Reis, A. S.; Iarosz, K. C.; Caldas, I. L.; Batista, A. M.

2018-04-01

The cerebral cortex plays a key role in complex cortical functions. It can be divided into areas according to their function (motor, sensory and association areas). In this paper, the cerebral cortex is described as a network of networks (cortex network), we consider that each cortical area is composed of a network with small-world property (cortical network). The neurons are assumed to have bursting properties with the dynamics described by the Rulkov model. We study the phase synchronization of the cortex network and the cortical networks. In our simulations, we verify that synchronization in cortex network is not homogeneous. Besides, we focus on the suppression of neural phase synchronization. Synchronization can be related to undesired and pathological abnormal rhythms in the brain. For this reason, we consider the delayed feedback control to suppress the synchronization. We show that delayed feedback control is efficient to suppress synchronous behavior in our network model when an appropriate signal intensity and time delay are defined.

The effects of visual stimulation and selective visual attention on rhythmic neuronal synchronization in macaque area V4.

PubMed

Fries, Pascal; Womelsdorf, Thilo; Oostenveld, Robert; Desimone, Robert

2008-04-30

Selective attention lends relevant sensory input priority access to higher-level brain areas and ultimately to behavior. Recent studies have suggested that those neurons in visual areas that are activated by an attended stimulus engage in enhanced gamma-band (30-70 Hz) synchronization compared with neurons activated by a distracter. Such precise synchronization could enhance the postsynaptic impact of cells carrying behaviorally relevant information. Previous studies have used the local field potential (LFP) power spectrum or spike-LFP coherence (SFC) to indirectly estimate spike synchronization. Here, we directly demonstrate zero-phase gamma-band coherence among spike trains of V4 neurons. This synchronization was particularly evident during visual stimulation and enhanced by selective attention, thus confirming the pattern inferred from LFP power and SFC. We therefore investigated the time course of LFP gamma-band power and found rapid dynamics consistent with interactions of top-down spatial and feature attention with bottom-up saliency. In addition to the modulation of synchronization during visual stimulation, selective attention significantly changed the prestimulus pattern of synchronization. Attention inside the receptive field of the recorded neuronal population enhanced gamma-band synchronization and strongly reduced alpha-band (9-11 Hz) synchronization in the prestimulus period. These results lend further support for a functional role of rhythmic neuronal synchronization in attentional stimulus selection.

Comparison of Virtual Oscillator and Droop Control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Brian B; Rodriguez, Miguel; Sinha, Mohit

Virtual oscillator control (VOC) and droop control are distinct methods to ensure synchronization and power sharing of parallel inverters in islanded systems. VOC is a control strategy where the dynamics of a nonlinear oscillator are used to derive control states to modulate the switch terminals of an inverter. Since VOC is a time-domain controller that reacts to instantaneous measurements with no additional filters or computations, it provides a rapid response during transients and stabilizes volatile dynamics. In contrast, droop control regulates the inverter voltage in response to the measured average real and reactive power output. Given that real and reactivemore » power are phasor quantities that are not well-defined in real time, droop controllers typically use multiplicative operations in conjunction with low-pass filters on the current and voltage measurements to calculate such quantities. Since these filters must suppress low frequency ac harmonics, they typically have low cutoff frequencies that ultimately impede droop controller bandwidth. Although VOC and droop control can be engineered to produce similar steady-state characteristics, their dynamic performance can differ markedly. This paper presents an analytical framework to characterize and compare the dynamic response of VOC and droop control. The analysis is experimentally validated with three 120 V inverters rated at 1kW, demonstrating that for the same design specifications VOC is roughly 8 times faster and presents almost no overshoot after a transient.« less

Comparison of free-piston Stirling engine model predictions with RE1000 engine test data

NASA Technical Reports Server (NTRS)

Tew, R. C., Jr.

1984-01-01

Predictions of a free-piston Stirling engine model are compared with RE1000 engine test data taken at NASA-Lewis Research Center. The model validation and the engine testing are being done under a joint interagency agreement between the Department of Energy's Oak Ridge National Laboratory and NASA-Lewis. A kinematic code developed at Lewis was upgraded to permit simulation of free-piston engine performance; it was further upgraded and modified at Lewis and is currently being validated. The model predicts engine performance by numerical integration of equations for each control volume in the working space. Piston motions are determined by numerical integration of the force balance on each piston or can be specified as Fourier series. In addition, the model Fourier analyzes the various piston forces to permit the construction of phasor force diagrams. The paper compares predicted and experimental values of power and efficiency and shows phasor force diagrams for the RE1000 engine displacer and piston. Further development plans for the model are also discussed.

Algorithm Summary and Evaluation: Automatic Implementation of Ringdown Analysis for Electromechanical Mode Identification from Phasor Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Ning; Huang, Zhenyu; Tuffner, Francis K.

2010-02-28

Small signal stability problems are one of the major threats to grid stability and reliability. Prony analysis has been successfully applied on ringdown data to monitor electromechanical modes of a power system using phasor measurement unit (PMU) data. To facilitate an on-line application of mode estimation, this paper develops a recursive algorithm for implementing Prony analysis and proposed an oscillation detection method to detect ringdown data in real time. By automatically detecting ringdown data, the proposed method helps guarantee that Prony analysis is applied properly and timely on the ringdown data. Thus, the mode estimation results can be performed reliablymore » and timely. The proposed method is tested using Monte Carlo simulations based on a 17-machine model and is shown to be able to properly identify the oscillation data for on-line application of Prony analysis. In addition, the proposed method is applied to field measurement data from WECC to show the performance of the proposed algorithm.« less

A method to quantify FRET stoichiometry with phasor plot analysis and acceptor lifetime ingrowth.

PubMed

Chen, WeiYue; Avezov, Edward; Schlachter, Simon C; Gielen, Fabrice; Laine, Romain F; Harding, Heather P; Hollfelder, Florian; Ron, David; Kaminski, Clemens F

2015-03-10

FRET is widely used for the study of protein-protein interactions in biological samples. However, it is difficult to quantify both the FRET efficiency (E) and the affinity (Kd) of the molecular interaction from intermolecular FRET signals in samples of unknown stoichiometry. Here, we present a method for the simultaneous quantification of the complete set of interaction parameters, including fractions of bound donors and acceptors, local protein concentrations, and dissociation constants, in each image pixel. The method makes use of fluorescence lifetime information from both donor and acceptor molecules and takes advantage of the linear properties of the phasor plot approach. We demonstrate the capability of our method in vitro in a microfluidic device and also in cells, via the determination of the binding affinity between tagged versions of glutathione and glutathione S-transferase, and via the determination of competitor concentration. The potential of the method is explored with simulations. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Mapping Diffusion in a Living Cell via the Phasor Approach

PubMed Central

Ranjit, Suman; Lanzano, Luca; Gratton, Enrico

2014-01-01

Diffusion of a fluorescent protein within a cell has been measured using either fluctuation-based techniques (fluorescence correlation spectroscopy (FCS) or raster-scan image correlation spectroscopy) or particle tracking. However, none of these methods enables us to measure the diffusion of the fluorescent particle at each pixel of the image. Measurement using conventional single-point FCS at every individual pixel results in continuous long exposure of the cell to the laser and eventual bleaching of the sample. To overcome this limitation, we have developed what we believe to be a new method of scanning with simultaneous construction of a fluorescent image of the cell. In this believed new method of modified raster scanning, as it acquires the image, the laser scans each individual line multiple times before moving to the next line. This continues until the entire area is scanned. This is different from the original raster-scan image correlation spectroscopy approach, where data are acquired by scanning each frame once and then scanning the image multiple times. The total time of data acquisition needed for this method is much shorter than the time required for traditional FCS analysis at each pixel. However, at a single pixel, the acquired intensity time sequence is short; requiring nonconventional analysis of the correlation function to extract information about the diffusion. These correlation data have been analyzed using the phasor approach, a fit-free method that was originally developed for analysis of FLIM images. Analysis using this method results in an estimation of the average diffusion coefficient of the fluorescent species at each pixel of an image, and thus, a detailed diffusion map of the cell can be created. PMID:25517145

Human Factors Evaluation of Advanced Electric Power Grid Visualization Tools

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greitzer, Frank L.; Dauenhauer, Peter M.; Wierks, Tamara G.

This report describes initial human factors evaluation of four visualization tools (Graphical Contingency Analysis, Force Directed Graphs, Phasor State Estimator and Mode Meter/ Mode Shapes) developed by PNNL, and proposed test plans that may be implemented to evaluate their utility in scenario-based experiments.

Computer-Generated Microwave Holograms.

ERIC Educational Resources Information Center

Leming, Charles W.; Hastings, Orestes Patterson, III

1980-01-01

Described is the phasor method of superposition of waves. The intensity pattern from a system of microwave sources is calculated point by point on a plane corresponding to a film emulsion, and then printed and directly converted to a hologram for 3-cm microwaves. Calculations, construction, and viewing of holograms are included. (Author/DS)

Increased phase synchronization during continuous face integration measured simultaneously with EEG and fMRI.

PubMed

Kottlow, Mara; Jann, Kay; Dierks, Thomas; Koenig, Thomas

2012-08-01

Gamma zero-lag phase synchronization has been measured in the animal brain during visual binding. Human scalp EEG studies used a phase locking factor (trial-to-trial phase-shift consistency) or gamma amplitude to measure binding but did not analyze common-phase signals so far. This study introduces a method to identify networks oscillating with near zero-lag phase synchronization in human subjects. We presented unpredictably moving face parts (NOFACE) which - during some periods - produced a complete schematic face (FACE). The amount of zero-lag phase synchronization was measured using global field synchronization (GFS). GFS provides global information on the amount of instantaneous coincidences in specific frequencies throughout the brain. Gamma GFS was increased during the FACE condition. To localize the underlying areas, we correlated gamma GFS with simultaneously recorded BOLD responses. Positive correlates comprised the bilateral middle fusiform gyrus and the left precuneus. These areas may form a network of areas transiently synchronized during face integration, including face-specific as well as binding-specific regions and regions for visual processing in general. Thus, the amount of zero-lag phase synchronization between remote regions of the human visual system can be measured with simultaneously acquired EEG/fMRI. Copyright © 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Data-Mining-Based Intelligent Differential Relaying for Transmission Lines Including UPFC and Wind Farms.

PubMed

Jena, Manas Kumar; Samantaray, Subhransu Ranjan

2016-01-01

This paper presents a data-mining-based intelligent differential relaying scheme for transmission lines, including flexible ac transmission system device, such as unified power flow controller (UPFC) and wind farms. Initially, the current and voltage signals are processed through extended Kalman filter phasor measurement unit for phasor estimation, and 21 potential features are computed at both ends of the line. Once the features are extracted at both ends, the corresponding differential features are derived. These differential features are fed to a data-mining model known as decision tree (DT) to provide the final relaying decision. The proposed technique has been extensively tested for single-circuit transmission line, including UPFC and wind farms with in-feed, double-circuit line with UPFC on one line and wind farm as one of the substations with wide variations in operating parameters. The test results obtained from simulation as well as in real-time digital simulator testing indicate that the DT-based intelligent differential relaying scheme is highly reliable and accurate with a response time of 2.25 cycles from the fault inception.

Submillimeter-Wave Phasor Beam-Pattern Measurement Based on Two-Stage Heterodyne Mixing With Unitary Harmonic Difference

NASA Astrophysics Data System (ADS)

Hwang, Yuh-Jing; Rao, Ramprasad; Christensen, Rob; Chen, Ming-Tang; Chu, Tah-Hsiung

2007-06-01

A near-field phasor beam measurement system is developed for the characterization of heterodyne receiver optics at submillimeter-wave frequencies. The system synthesizes a pair of submillimeter-wave signals as the RF and local oscillator (LO) sources from common reference sources. The synthesized harmonic numbers of the RF and LO sources are arranged with difference by one, which makes this a new configuration with a unitary harmonic difference. The coherent RF and LO signal are down-converted by the receiver under test, then mixed with the microwave-frequency common reference signal to generate the second-order IF signal around 100 MHz for amplitude and phase comparison. The amplitude and phase fluctuation of the measurement system at 683 GHz is within +-0.2 dB and +-4deg in a 1-h period, respectively. The system dynamic range at 683 and 250 GHz can be as high as 43 and 47 dB, respectively. The system is then used to measure the receiver beam patterns at 683 and 250 GHz with different RF transmitting probe antennas.

Phasor Domain Steady-State Modeling and Design of the DC–DC Modular Multilevel Converter

DOE PAGES

Yang, Heng; Qin, Jiangchao; Debnath, Suman; ...

2016-01-06

The DC-DC Modular Multilevel Converter (MMC), which originated from the AC-DC MMC, is an attractive converter topology for interconnection of medium-/high-voltage DC grids. This paper presents design considerations for the DC-DC MMC to achieve high efficiency and reduced component sizes. A steady-state mathematical model of the DC-DC MMC in the phasor-domain is developed. Based on the developed model, a design approach is proposed to size the components and to select the operating frequency of the converter to satisfy a set of design constraints while achieving high efficiency. The design approach includes sizing of the arm inductor, Sub-Module (SM) capacitor, andmore » phase filtering inductor along with the selection of AC operating frequency of the converter. The accuracy of the developed model and the effectiveness of the design approach are validated based on the simulation studies in the PSCAD/EMTDC software environment. The analysis and developments of this paper can be used as a guideline for design of the DC-DC MMC.« less

Spectral phasor analysis of LAURDAN fluorescence in live A549 lung cells to study the hydration and time evolution of intracellular lamellar body-like structures.

PubMed

Malacrida, Leonel; Astrada, Soledad; Briva, Arturo; Bollati-Fogolín, Mariela; Gratton, Enrico; Bagatolli, Luis A

2016-11-01

Using LAURDAN spectral imaging and spectral phasor analysis we concurrently studied the growth and hydration state of subcellular organelles (lamellar body-like, LB-like) from live A549 lung cancer cells at different post-confluence days. Our results reveal a time dependent two-step process governing the size and hydration of these intracellular LB-like structures. Specifically, a first step (days 1 to 7) is characterized by an increase in their size, followed by a second one (days 7 to 14) where the organelles display a decrease in their global hydration properties. Interestingly, our results also show that their hydration properties significantly differ from those observed in well-characterized artificial lamellar model membranes, challenging the notion that a pure lamellar membrane organization is present in these organelles at intracellular conditions. Finally, these LB-like structures show a significant increase in their hydration state upon secretion, suggesting a relevant role of entropy during this process. Copyright © 2016 Elsevier B.V. All rights reserved.

Managing Documents in the Wider Area: Intelligent Document Management.

ERIC Educational Resources Information Center

Bittleston, Richard

1995-01-01

Discusses techniques for managing documents in wide area networks, reviews technique limitations, and offers recommendations to database designers. Presented techniques include: increasing bandwidth, reducing data traffic, synchronizing documentation, partial synchronization, audit trials, navigation, and distribution control and security. Two…

A Comparative Study of Discovery Learning Scientific Community Laboratories and Traditional Laboratories in Physics at an Independent University, Florida, U. S

NASA Astrophysics Data System (ADS)

Reinhard, Karl E.

Electric power is fully interwoven into the fabric of American life. Its loss for extended periods has profound impacts upon public safety, health and welfare. The power system has been termed the most complex machine built by man. Not surprisingly, the measures to address the range of power system downtime causes are as diverse as the causes themselves. One important arc of effort is providing power system operators with full knowledge of the system's operating state, timely warning when changing conditions threaten system stability, and tools guiding control actions to maintain stable operations. This research is motivated, in part, by the need to explore opportunities for leveraging nascent synchrophasor data streams against known power system stability challenges. Over the past half-decade, power system operators have aggressively installed large networks of phasor measurement units (PMUs) and phasor data concentrators (PDCs) across the United States and Canada. Today, the synchrophasor data network has reached a state of maturity that opens the door to useful application. This dissertation investigates power system stability along three lines of effort. The first two efforts address steady-state power system stability--specifically methods for assessing system vulnerabilities arising from the phase angle difference between two buses connected by a transmission line. The third effort investigates the information that can be gleaned from synchrophasor measurements during a system's dynamic system response to changing system conditions. The first line of investigation extends steady-state distribution factor theory. Distribution factors are computed from a known non-linear power system load flow solution. They provide a computationally light method for estimating new system conditions under different operating circumstances. Distribution factors are extremely useful for very rapidly screening the impact of unexpected changes in power system configuration--e.g. a transmission line dropping out of service due to environmental conditions. The Line Outage Angle Factor (LOAF) developed herein provides a method for fast computation of bus voltage angle changes after a line outage. The Line Outage Generator Factor (LOGF) modifies the simulated circuit topology to include synchronous machine transient reactances, enabling rapid screening of operating states in which line opening (or re-closure) risks damaging equipment. The LOAF and LOGF provide promising results in MATLAB simulation of the Western System Coordinating Council 3-Machine, 9-Bus System. The second investigative line seeks to develop a Thevenin equivalent model to be used in tandem with synchrophasor data streams to provide real-time bus angle difference information for buses connected by a transmission line. The appeal is that real-time bus angle difference information could be computed on-site and very rapidly--and significantly, independent of other network bus measurements. The results show that developing a Thevenin equivalent that provides a useful angle difference measure often works well on paper, but is challenging using actual synchrophasor data. Efforts to develop a Thevenin equivalent using Monte Carlo methods show promise, but require further investigation. The third line of effort shifts to investigate the useful information that a PMU can produce during a power system disturbance event. A synchrophasor is defined at a specific frequency, i.e. the system steady-state operating frequency. Thus a PMU produces a data stream recording power system changes progressing slower than the nominal system frequency; consequently, this is an "off-label" synchrophasor data application. The test system is a generator with electrical and mechanical controls connected by a pair of identical transmission lines to an infinite bus. The synchronous generator is modeled as a three-damper-winding synchronous machine. A MATLAB simulation was written to simulate both the full 14 dynamic state and the reduced order 11 dynamic state system models. A Real-Time Digital Simulator (RTDS) simulation emulating the test system provides the capability to produce real-time analog generator terminal waveforms to be sampled by a commercial off-the-shelf PMU to produce synchrophasor data. We find that the RTDS generated synchrophasor data stream is similar to the MATLAB reduced order model voltage and current generator terminal data in the dqo reference frame--reflecting parallel, but distinct, filtering processes.

The synchronization of asymmetric-structured electric coupling neuronal system

NASA Astrophysics Data System (ADS)

Wang, Guanping; Jin, Wuyin; Liu, Hao; Sun, Wei

2018-02-01

Based on the Hindmarsh-Rose (HR) model, the synchronization dynamics of asymmetric-structured electric coupling two neuronal system is investigated in this paper. It is discovered that when the time-delay scope and coupling strength for the synchronization are correlated positively under unequal time delay, the time-delay difference does not make a clear distinction between the two individual inter-spike intervals (ISI) bifurcation diagrams of the two coupled neurons. Therefore, the superficial difference of the system synchronization dynamics is not obvious for the unequal time-delay feedback. In the asymmetrical current incentives under asymmetric electric coupled system, the two neurons can only be almost completely synchronized in specific area of the interval which end-pointed with two discharge modes for a single neuron under different stimuli currents before coupling, but the intervention of time-delay feedback, together with the change of the coupling strength, can make the coupled system not only almost completely synchronized within anywhere in the front area, but also outside of it.

Social Motor Synchronization: Insights for Understanding Social Behavior in Autism

ERIC Educational Resources Information Center

Fitzpatrick, Paula; Romero, Veronica; Amaral, Joseph L.; Duncan, Amie; Barnard, Holly; Richardson, Michael J.; Schmidt, R. C.

2017-01-01

Impairments in social interaction and communication are critical features of ASD but the underlying processes are poorly understood. An under-explored area is the social motor synchronization that happens when we coordinate our bodies with others. Here, we explored the relationships between dynamical measures of social motor synchronization and…

[Cardiac Synchronization Function Estimation Based on ASM Level Set Segmentation Method].

PubMed

Zhang, Yaonan; Gao, Yuan; Tang, Liang; He, Ying; Zhang, Huie

At present, there is no accurate and quantitative methods for the determination of cardiac mechanical synchronism, and quantitative determination of the synchronization function of the four cardiac cavities with medical images has a great clinical value. This paper uses the whole heart ultrasound image sequence, and segments the left & right atriums and left & right ventricles of each frame. After the segmentation, the number of pixels in each cavity and in each frame is recorded, and the areas of the four cavities of the image sequence are therefore obtained. The area change curves of the four cavities are further extracted, and the synchronous information of the four cavities is obtained. Because of the low SNR of Ultrasound images, the boundary lines of cardiac cavities are vague, so the extraction of cardiac contours is still a challenging problem. Therefore, the ASM model information is added to the traditional level set method to force the curve evolution process. According to the experimental results, the improved method improves the accuracy of the segmentation. Furthermore, based on the ventricular segmentation, the right and left ventricular systolic functions are evaluated, mainly according to the area changes. The synchronization of the four cavities of the heart is estimated based on the area changes and the volume changes.

Emotional speech synchronizes brains across listeners and engages large-scale dynamic brain networks

PubMed Central

Nummenmaa, Lauri; Saarimäki, Heini; Glerean, Enrico; Gotsopoulos, Athanasios; Jääskeläinen, Iiro P.; Hari, Riitta; Sams, Mikko

2014-01-01

Speech provides a powerful means for sharing emotions. Here we implement novel intersubject phase synchronization and whole-brain dynamic connectivity measures to show that networks of brain areas become synchronized across participants who are listening to emotional episodes in spoken narratives. Twenty participants' hemodynamic brain activity was measured with functional magnetic resonance imaging (fMRI) while they listened to 45-s narratives describing unpleasant, neutral, and pleasant events spoken in neutral voice. After scanning, participants listened to the narratives again and rated continuously their feelings of pleasantness–unpleasantness (valence) and of arousal–calmness. Instantaneous intersubject phase synchronization (ISPS) measures were computed to derive both multi-subject voxel-wise similarity measures of hemodynamic activity and inter-area functional dynamic connectivity (seed-based phase synchronization, SBPS). Valence and arousal time series were subsequently used to predict the ISPS and SBPS time series. High arousal was associated with increased ISPS in the auditory cortices and in Broca's area, and negative valence was associated with enhanced ISPS in the thalamus, anterior cingulate, lateral prefrontal, and orbitofrontal cortices. Negative valence affected functional connectivity of fronto-parietal, limbic (insula, cingulum) and fronto-opercular circuitries, and positive arousal affected the connectivity of the striatum, amygdala, thalamus, cerebellum, and dorsal frontal cortex. Positive valence and negative arousal had markedly smaller effects. We propose that high arousal synchronizes the listeners' sound-processing and speech-comprehension networks, whereas negative valence synchronizes circuitries supporting emotional and self-referential processing. PMID:25128711

Synchronous Energy Technology

NASA Technical Reports Server (NTRS)

1980-01-01

The synchronous technology requirements for large space power systems are summarized. A variety of technology areas including photovoltaics, thermal management, and energy storage, and power management are addressed.

Cell-Type and State-Dependent Synchronization among Rodent Somatosensory, Visual, Perirhinal Cortex, and Hippocampus CA1

PubMed Central

Vinck, Martin; Bos, Jeroen J.; Van Mourik-Donga, Laura A.; Oplaat, Krista T.; Klein, Gerbrand A.; Jackson, Jadin C.; Gentet, Luc J.; Pennartz, Cyriel M. A.

2016-01-01

Beta and gamma rhythms have been hypothesized to be involved in global and local coordination of neuronal activity, respectively. Here, we investigated how cells in rodent area S1BF are entrained by rhythmic fluctuations at various frequencies within the local area and in connected areas, and how this depends on behavioral state and cell type. We performed simultaneous extracellular field and unit recordings in four connected areas of the freely moving rat (S1BF, V1M, perirhinal cortex, CA1). S1BF spiking activity was strongly entrained by both beta and gamma S1BF oscillations, which were associated with deactivations and activations, respectively. We identified multiple classes of fast spiking and excitatory cells in S1BF, which showed prominent differences in rhythmic entrainment and in the extent to which phase locking was modulated by behavioral state. Using an additional dataset acquired by whole-cell recordings in head-fixed mice, these cell classes could be compared with identified phenotypes showing gamma rhythmicity in their membrane potential. We next examined how S1BF cells were entrained by rhythmic fluctuations in connected brain areas. Gamma-synchronization was detected in all four areas, however we did not detect significant gamma coherence among these areas. Instead, we only found long-range coherence in the theta-beta range among these areas. In contrast to local S1BF synchronization, we found long-range S1BF-spike to CA1–LFP synchronization to be homogeneous across inhibitory and excitatory cell types. These findings suggest distinct, cell-type contributions of low and high-frequency synchronization to intra- and inter-areal neuronal interactions. PMID:26834582

Subthalamic stimulation modulates cortical motor network activity and synchronization in Parkinson's disease.

PubMed

Weiss, Daniel; Klotz, Rosa; Govindan, Rathinaswamy B; Scholten, Marlieke; Naros, Georgios; Ramos-Murguialday, Ander; Bunjes, Friedemann; Meisner, Christoph; Plewnia, Christian; Krüger, Rejko; Gharabaghi, Alireza

2015-03-01

Dynamic modulations of large-scale network activity and synchronization are inherent to a broad spectrum of cognitive processes and are disturbed in neuropsychiatric conditions including Parkinson's disease. Here, we set out to address the motor network activity and synchronization in Parkinson's disease and its modulation with subthalamic stimulation. To this end, 20 patients with idiopathic Parkinson's disease with subthalamic nucleus stimulation were analysed on externally cued right hand finger movements with 1.5-s interstimulus interval. Simultaneous recordings were obtained from electromyography on antagonistic muscles (right flexor digitorum and extensor digitorum) together with 64-channel electroencephalography. Time-frequency event-related spectral perturbations were assessed to determine cortical and muscular activity. Next, cross-spectra in the time-frequency domain were analysed to explore the cortico-cortical synchronization. The time-frequency modulations enabled us to select a time-frequency range relevant for motor processing. On these time-frequency windows, we developed an extension of the phase synchronization index to quantify the global cortico-cortical synchronization and to obtain topographic differentiations of distinct electrode sites with respect to their contributions to the global phase synchronization index. The spectral measures were used to predict clinical and reaction time outcome using regression analysis. We found that movement-related desynchronization of cortical activity in the upper alpha and beta range was significantly facilitated with 'stimulation on' compared to 'stimulation off' on electrodes over the bilateral parietal, sensorimotor, premotor, supplementary-motor, and prefrontal areas, including the bilateral inferior prefrontal areas. These spectral modulations enabled us to predict both clinical and reaction time improvement from subthalamic stimulation. With 'stimulation on', interhemispheric cortico-cortical coherence in the beta band was significantly attenuated over the bilateral sensorimotor areas. Similarly, the global cortico-cortical phase synchronization was attenuated, and the topographic differentiation revealed stronger desynchronization over the (ipsilateral) right-hemispheric prefrontal, premotor and sensorimotor areas compared to 'stimulation off'. We further demonstrated that the cortico-cortical phase synchronization was largely dominated by genuine neuronal coupling. The clinical improvement with 'stimulation on' compared to 'stimulation off' could be predicted from this cortical decoupling with multiple regressions, and the reduction of synchronization over the right prefrontal area showed a linear univariate correlation with clinical improvement. Our study demonstrates wide-spread activity and synchronization modulations of the cortical motor network, and highlights subthalamic stimulation as a network-modulating therapy. Accordingly, subthalamic stimulation may release bilateral cortical computational resources by facilitating movement-related desynchronization. Moreover, the subthalamic nucleus is critical to balance inhibitory and facilitatory cortical players within the motor program. © The Author (2015). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Subthalamic stimulation modulates cortical motor network activity and synchronization in Parkinson’s disease

PubMed Central

Klotz, Rosa; Govindan, Rathinaswamy B.; Scholten, Marlieke; Naros, Georgios; Ramos-Murguialday, Ander; Bunjes, Friedemann; Meisner, Christoph; Plewnia, Christian; Krüger, Rejko

2015-01-01

Dynamic modulations of large-scale network activity and synchronization are inherent to a broad spectrum of cognitive processes and are disturbed in neuropsychiatric conditions including Parkinson’s disease. Here, we set out to address the motor network activity and synchronization in Parkinson’s disease and its modulation with subthalamic stimulation. To this end, 20 patients with idiopathic Parkinson’s disease with subthalamic nucleus stimulation were analysed on externally cued right hand finger movements with 1.5-s interstimulus interval. Simultaneous recordings were obtained from electromyography on antagonistic muscles (right flexor digitorum and extensor digitorum) together with 64-channel electroencephalography. Time-frequency event-related spectral perturbations were assessed to determine cortical and muscular activity. Next, cross-spectra in the time-frequency domain were analysed to explore the cortico-cortical synchronization. The time-frequency modulations enabled us to select a time-frequency range relevant for motor processing. On these time-frequency windows, we developed an extension of the phase synchronization index to quantify the global cortico-cortical synchronization and to obtain topographic differentiations of distinct electrode sites with respect to their contributions to the global phase synchronization index. The spectral measures were used to predict clinical and reaction time outcome using regression analysis. We found that movement-related desynchronization of cortical activity in the upper alpha and beta range was significantly facilitated with ‘stimulation on’ compared to ‘stimulation off’ on electrodes over the bilateral parietal, sensorimotor, premotor, supplementary-motor, and prefrontal areas, including the bilateral inferior prefrontal areas. These spectral modulations enabled us to predict both clinical and reaction time improvement from subthalamic stimulation. With ‘stimulation on’, interhemispheric cortico-cortical coherence in the beta band was significantly attenuated over the bilateral sensorimotor areas. Similarly, the global cortico-cortical phase synchronization was attenuated, and the topographic differentiation revealed stronger desynchronization over the (ipsilateral) right-hemispheric prefrontal, premotor and sensorimotor areas compared to ‘stimulation off’. We further demonstrated that the cortico-cortical phase synchronization was largely dominated by genuine neuronal coupling. The clinical improvement with ‘stimulation on’ compared to ‘stimulation off’ could be predicted from this cortical decoupling with multiple regressions, and the reduction of synchronization over the right prefrontal area showed a linear univariate correlation with clinical improvement. Our study demonstrates wide-spread activity and synchronization modulations of the cortical motor network, and highlights subthalamic stimulation as a network-modulating therapy. Accordingly, subthalamic stimulation may release bilateral cortical computational resources by facilitating movement-related desynchronization. Moreover, the subthalamic nucleus is critical to balance inhibitory and facilitatory cortical players within the motor program. PMID:25558877

Cryogenic exciter

DOEpatents

Bray, James William [Niskayuna, NY; Garces, Luis Jose [Niskayuna, NY

2012-03-13

The disclosed technology is a cryogenic static exciter. The cryogenic static exciter is connected to a synchronous electric machine that has a field winding. The synchronous electric machine is cooled via a refrigerator or cryogen like liquid nitrogen. The static exciter is in communication with the field winding and is operating at ambient temperature. The static exciter receives cooling from a refrigerator or cryogen source, which may also service the synchronous machine, to selected areas of the static exciter and the cooling selectively reduces the operating temperature of the selected areas of the static exciter.

Statistical optics

NASA Astrophysics Data System (ADS)

Goodman, J. W.

This book is based on the thesis that some training in the area of statistical optics should be included as a standard part of any advanced optics curriculum. Random variables are discussed, taking into account definitions of probability and random variables, distribution functions and density functions, an extension to two or more random variables, statistical averages, transformations of random variables, sums of real random variables, Gaussian random variables, complex-valued random variables, and random phasor sums. Other subjects examined are related to random processes, some first-order properties of light waves, the coherence of optical waves, some problems involving high-order coherence, effects of partial coherence on imaging systems, imaging in the presence of randomly inhomogeneous media, and fundamental limits in photoelectric detection of light. Attention is given to deterministic versus statistical phenomena and models, the Fourier transform, and the fourth-order moment of the spectrum of a detected speckle image.

Measuring upconversion nanoparticles photoluminescence lifetime with FastFLIM and phasor plots

NASA Astrophysics Data System (ADS)

Sun, Yuansheng; Lee, Hsien-Ming; Qiu, Hailin; Liao, Shih-Chu Jeff; Coskun, Ulas; Barbieri, Beniamino

2018-02-01

Photon upconversion is a nonlinear process in which the sequential of absorption of two or more photons leads to the anti-stoke emission. Different than the conventional multiphoton excitation process, upconversion can be efficiently performed at low excitation densities. Recent developments in lanthanide-doped upconversion nanoparticles (UCNPs) have led to a diversity of applications, including detecting and sensing of biomolecules, imaging of live cells, tissues and animals, cancer diagnostic and therapy, etc. Measuring the upconversion lifetime provides a new dimension of its imaging and opens a new window for its applications. Due to the long metastable intermediate excited state, UCNP typically has a long excited state lifetime ranging from sub-microseconds to milliseconds. Here, we present a novel development using the FastFLIM technique to measure UCNP lifetime by laser scanning confocal microscopy. FastFLIM is capable of measuring lifetime from 100 ps to 100 ms and features the high data collection efficiency (up to 140-million counts per second). Other than the traditional nonlinear least-square fitting analysis, the raw data acquired by FastFLIM can be directly processed by the model-free phasor plots approach for instant and unbiased lifetime results, providing the ideal routine for the UCNP photoluminescence lifetime microscopy imaging.

Social Motor Synchronization: Insights for Understanding Social Behavior in Autism.

PubMed

Fitzpatrick, Paula; Romero, Veronica; Amaral, Joseph L; Duncan, Amie; Barnard, Holly; Richardson, Michael J; Schmidt, R C

2017-07-01

Impairments in social interaction and communication are critical features of ASD but the underlying processes are poorly understood. An under-explored area is the social motor synchronization that happens when we coordinate our bodies with others. Here, we explored the relationships between dynamical measures of social motor synchronization and assessments of ASD traits. We found (a) spontaneous social motor synchronization was associated with responding to joint attention, cooperation, and theory of mind while intentional social motor synchronization was associated with initiating joint attention and theory of mind; and (b) social motor synchronization was associated with ASD severity but not fully explained by motor problems. Findings suggest that objective measures of social motor synchronization may provide insights into understanding ASD traits.

Self-Organized Near-Zero-Lag Synchronization Induced by Spike-Timing Dependent Plasticity in Cortical Populations

PubMed Central

Matias, Fernanda S.; Carelli, Pedro V.; Mirasso, Claudio R.; Copelli, Mauro

2015-01-01

Several cognitive tasks related to learning and memory exhibit synchronization of macroscopic cortical areas together with synaptic plasticity at neuronal level. Therefore, there is a growing effort among computational neuroscientists to understand the underlying mechanisms relating synchrony and plasticity in the brain. Here we numerically study the interplay between spike-timing dependent plasticity (STDP) and anticipated synchronization (AS). AS emerges when a dominant flux of information from one area to another is accompanied by a negative time lag (or phase). This means that the receiver region pulses before the sender does. In this paper we study the interplay between different synchronization regimes and STDP at the level of three-neuron microcircuits as well as cortical populations. We show that STDP can promote auto-organized zero-lag synchronization in unidirectionally coupled neuronal populations. We also find synchronization regimes with negative phase difference (AS) that are stable against plasticity. Finally, we show that the interplay between negative phase difference and STDP provides limited synaptic weight distribution without the need of imposing artificial boundaries. PMID:26474165

Analysis of the time structure of synchronization in multidimensional chaotic systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Makarenko, A. V., E-mail: avm.science@mail.ru

2015-05-15

A new approach is proposed to the integrated analysis of the time structure of synchronization of multidimensional chaotic systems. The method allows one to diagnose and quantitatively evaluate the intermittency characteristics during synchronization of chaotic oscillations in the T-synchronization mode. A system of two identical logistic mappings with unidirectional coupling that operate in the developed chaos regime is analyzed. It is shown that the widely used approach, in which only synchronization patterns are subjected to analysis while desynchronization areas are considered as a background signal and removed from analysis, should be regarded as methodologically incomplete.

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: A Realistic Cellular Automaton Model for Synchronized Traffic Flow

NASA Astrophysics Data System (ADS)

Zhao, Bo-Han; Hu, Mao-Bin; Jiang, Rui; Wu, Qing-Song

2009-11-01

A cellular automaton model is proposed to consider the anticipation effect in drivers' behavior. It is shown that the anticipation effect can be one of the origins of synchronized traffic flow. With anticipation effect, the congested traffic flow simulated by the model exhibits the features of synchronized flow. The spatiotemporal patterns induced by an on-ramp are also consistent with the three-phase traffic theory. Since the origin of synchronized flow is still controversial, our work can shed some light on the mechanism of synchronized flow.

Scene segmentation by spike synchronization in reciprocally connected visual areas. I. Local effects of cortical feedback.

PubMed

Knoblauch, Andreas; Palm, Günther

2002-09-01

To investigate scene segmentation in the visual system we present a model of two reciprocally connected visual areas using spiking neurons. Area P corresponds to the orientation-selective subsystem of the primary visual cortex, while the central visual area C is modeled as associative memory representing stimulus objects according to Hebbian learning. Without feedback from area C, a single stimulus results in relatively slow and irregular activity, synchronized only for neighboring patches (slow state), while in the complete model activity is faster with an enlarged synchronization range (fast state). When presenting a superposition of several stimulus objects, scene segmentation happens on a time scale of hundreds of milliseconds by alternating epochs of the slow and fast states, where neurons representing the same object are simultaneously in the fast state. Correlation analysis reveals synchronization on different time scales as found in experiments (designated as tower, castle, and hill peaks). On the fast time scale (tower peaks, gamma frequency range), recordings from two sites coding either different or the same object lead to correlograms that are either flat or exhibit oscillatory modulations with a central peak. This is in agreement with experimental findings, whereas standard phase-coding models would predict shifted peaks in the case of different objects.

Disrupted neural synchronization in toddlers with autism

PubMed Central

Dinstein, Ilan; Pierce, Karen; Eyler, Lisa; Solso, Stephanie; Malach, Rafael; Behrmann, Marlene; Courchesne, Eric

2011-01-01

Summary Autism is often described as a disorder of neural synchronization. However, it is unknown how early in development synchronization abnormalities emerge and whether they are related to the development of early autistic behavioral symptoms. Here, we show that disrupted synchronization is evident in the spontaneous cortical activity of naturally sleeping toddlers with autism, but not in toddlers with language delay or typical development. Toddlers with autism exhibited significantly weaker inter-hemispheric synchronization (i.e. weak “functional connectivity” across the two hemispheres) in putative language areas. The strength of synchronization was positively correlated with verbal ability, negatively correlated with autism severity, and enabled identification of the majority of autistic toddlers (72%) with high accuracy (84%). Disrupted cortical synchronization, therefore, appears to be a notable characteristic of autism neurophysiology that is evident at very early stages of autism development. PMID:21689606

Synchronized Drumming Enhances Activity in the Caudate and Facilitates Prosocial Commitment - If the Rhythm Comes Easily

PubMed Central

Kokal, Idil; Engel, Annerose; Kirschner, Sebastian; Keysers, Christian

2011-01-01

Why does chanting, drumming or dancing together make people feel united? Here we investigate the neural mechanisms underlying interpersonal synchrony and its subsequent effects on prosocial behavior among synchronized individuals. We hypothesized that areas of the brain associated with the processing of reward would be active when individuals experience synchrony during drumming, and that these reward signals would increase prosocial behavior toward this synchronous drum partner. 18 female non-musicians were scanned with functional magnetic resonance imaging while they drummed a rhythm, in alternating blocks, with two different experimenters: one drumming in-synchrony and the other out-of-synchrony relative to the participant. In the last scanning part, which served as the experimental manipulation for the following prosocial behavioral test, one of the experimenters drummed with one half of the participants in-synchrony and with the other out-of-synchrony. After scanning, this experimenter “accidentally” dropped eight pencils, and the number of pencils collected by the participants was used as a measure of prosocial commitment. Results revealed that participants who mastered the novel rhythm easily before scanning showed increased activity in the caudate during synchronous drumming. The same area also responded to monetary reward in a localizer task with the same participants. The activity in the caudate during experiencing synchronous drumming also predicted the number of pencils the participants later collected to help the synchronous experimenter of the manipulation run. In addition, participants collected more pencils to help the experimenter when she had drummed in-synchrony than out-of-synchrony during the manipulation run. By showing an overlap in activated areas during synchronized drumming and monetary reward, our findings suggest that interpersonal synchrony is related to the brain's reward system. PMID:22110623

Motor cortex synchronization influences the rhythm of motor performance in premanifest huntington's disease.

PubMed

Casula, Elias P; Mayer, Isabella M S; Desikan, Mahalekshmi; Tabrizi, Sarah J; Rothwell, John C; Orth, Michael

2018-03-01

In Huntington's disease there is evidence of structural damage in the motor system, but it is still unclear how to link this to the behavioral disorder of movement. One feature of choreic movement is variable timing and coordination between sequences of actions. We postulate this results from desynchronization of neural activity in cortical motor areas. The objective of this study was to explore the ability to synchronize activity in a motor network using transcranial magnetic stimulation and to relate this to timing of motor performance. We examined synchronization in oscillatory activity of cortical motor areas in response to an external input produced by a pulse of transcranial magnetic stimulation. We combined this with EEG to compare the response of 16 presymptomatic Huntington's disease participants with 16 age-matched healthy volunteers to test whether the strength of synchronization relates to the variability of motor performance at the following 2 tasks: a grip force task and a speeded-tapping task. Phase synchronization in response to M1 stimulation was lower in Huntington's disease than healthy volunteers (P < .01), resulting in a reduced cortical activity at global (P < .02) and local levels (P < .01). Participants who showed better timed motor performance also showed stronger oscillatory synchronization (r = -0.356; P < .05) and higher cortical activity (r = -0.393; P < .05). Our data may model the ability of the motor command to respond to more subtle, physiological inputs from other brain areas. This novel insight indicates that impairments of the timing accuracy of synchronization and desynchronization could be a physiological basis for some key clinical features of Huntington's disease. © 2018 International Parkinson and Movement Disorder Society. © 2018 International Parkinson and Movement Disorder Society.

Proceedings of the International Cryocooler Conference (7th) Held in Santa Fe, New Mexico on 17-19 November 1992. Part 3

DTIC Science & Technology

1993-04-01

Stirling Cryocoolers , Pulse Tube Refrigerators, Novel Concepts and Component Development, Low Temperature Regenerator Development...topics included Cryocooler Testing and Modeling, Space and Long Life Applications, Stirling Cryocoolers , Pulse Tube Refrigerators, Novel Concepts and...with bold variables. 785 PL-CP--93-1001 Phasor analysis is useful for regenerative cryocoolers , such as Stirling and pulse tube refrigerators,

Coherent emission from a bunched electron beam: superradiance and stimulated-superradiance in a uniform and tapered wiggler FEL

NASA Astrophysics Data System (ADS)

Gover, A.; Ianconescu, R.; Friedman, A.; Emma, C.; Musumeci, P.

2017-09-01

We outline fundamental coherent radiation processes from a charge particles beam: Spontaneous Superradiance (SR), Stimulated Superradiance (ST-SR), and in the context of undulator radiation: Tapering-Enhanced Superradiance (TES) and Tapering-Enhanced Stimulated Superradiance Amplification (TESSA). Both single bunch and periodic bunching (in phasor and spectral Fourier frequency formulations) are considered in a model of radiation mode expansion.

Alpha Hemolysin Induces an Increase of Erythrocytes Calcium: A FLIM 2-Photon Phasor Analysis Approach

PubMed Central

Sanchez, Susana; Bakás, Laura; Gratton, Enrico; Herlax, Vanesa

2011-01-01

α-hemolysin (HlyA) from Escherichia coli is considered as the prototype of a family of toxins called RTX (repeat in toxin), a group of proteins that share genetic and structural features. HlyA is an important virulence factor in E. coli extraintestinal infections, such as meningitis, septicemia and urinary infections. High concentrations of the toxin cause the lysis of several cells such as erythrocytes, granulocytes, monocytes, endothelial and renal epithelial cells of different species. At low concentrations it induces the production of cytokines and apoptosis. Since many of the subcytolytic effects in other cells have been reported to be triggered by the increase of intracellular calcium, we followed the calcium concentration inside the erythrocytes while incubating with sublytic concentrations of HlyA. Calcium concentration was monitored using the calcium indicator Green 1, 2-photon excitation, and fluorescence lifetime imaging microscopy (FLIM). Data were analyzed using the phasor representation. In this report, we present evidence that, at sublytic concentrations, HlyA induces an increase of calcium concentration in rabbit erythrocytes in the first 10 s. Results are discussed in relation to the difficulties of measuring calcium concentrations in erythrocytes where hemoglobin is present, the contribution of the background and the heterogeneity of the response observed in individual cells. PMID:21698153

iTesla Power Systems Library (iPSL): A Modelica library for phasor time-domain simulations

NASA Astrophysics Data System (ADS)

Vanfretti, L.; Rabuzin, T.; Baudette, M.; Murad, M.

The iTesla Power Systems Library (iPSL) is a Modelica package providing a set of power system components for phasor time-domain modeling and simulation. The Modelica language provides a systematic approach to develop models using a formal mathematical description, that uniquely specifies the physical behavior of a component or the entire system. Furthermore, the standardized specification of the Modelica language (Modelica Association [1]) enables unambiguous model exchange by allowing any Modelica-compliant tool to utilize the models for simulation and their analyses without the need of a specific model transformation tool. As the Modelica language is being developed with open specifications, any tool that implements these requirements can be utilized. This gives users the freedom of choosing an Integrated Development Environment (IDE) of their choice. Furthermore, any integration solver can be implemented within a Modelica tool to simulate Modelica models. Additionally, Modelica is an object-oriented language, enabling code factorization and model re-use to improve the readability of a library by structuring it with object-oriented hierarchy. The developed library is released under an open source license to enable a wider distribution and let the user customize it to their specific needs. This paper describes the iPSL and provides illustrative application examples.

Synchronized femtosecond laser pulse switching system based nano-patterning technology

NASA Astrophysics Data System (ADS)

Sohn, Ik-Bu; Choi, Hun-Kook; Yoo, Dongyoon; Noh, Young-Chul; Sung, Jae-Hee; Lee, Seong-Ku; Ahsan, Md. Shamim; Lee, Ho

2017-07-01

This paper demonstrates the design and development of a synchronized femtosecond laser pulse switching system and its applications in nano-patterning of transparent materials. Due to synchronization, we are able to control the location of each irradiated laser pulse in any kind of substrate. The control over the scanning speed and scanning step of the laser beam enables us to pattern periodic micro/nano-metric holes, voids, and/or lines in various materials. Using the synchronized laser system, we pattern synchronized nano-holes on the surface of and inside various transparent materials including fused silica glass and polymethyl methacrylate to replicate any image or pattern on the surface of or inside (transparent) materials. We also investigate the application areas of the proposed synchronized femtosecond laser pulse switching system in a diverse field of science and technology, especially in optical memory, color marking, and synchronized micro/nano-scale patterning of materials.

Synchronization of chaotic systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pecora, Louis M.; Carroll, Thomas L.

2015-09-15

We review some of the history and early work in the area of synchronization in chaotic systems. We start with our own discovery of the phenomenon, but go on to establish the historical timeline of this topic back to the earliest known paper. The topic of synchronization of chaotic systems has always been intriguing, since chaotic systems are known to resist synchronization because of their positive Lyapunov exponents. The convergence of the two systems to identical trajectories is a surprise. We show how people originally thought about this process and how the concept of synchronization changed over the years tomore » a more geometric view using synchronization manifolds. We also show that building synchronizing systems leads naturally to engineering more complex systems whose constituents are chaotic, but which can be tuned to output various chaotic signals. We finally end up at a topic that is still in very active exploration today and that is synchronization of dynamical systems in networks of oscillators.« less

Enhancing synchronization stability in a multi-area power grid

PubMed Central

Wang, Bing; Suzuki, Hideyuki; Aihara, Kazuyuki

2016-01-01

Maintaining a synchronous state of generators is of central importance to the normal operation of power grids, in which many networks are generally interconnected. In order to understand the condition under which the stability can be optimized, it is important to relate network stability with feedback control strategies as well as network structure. Here, we present a stability analysis on a multi-area power grid by relating it with several control strategies and topological design of network structure. We clarify the minimal feedback gain in the self-feedback control, and build the optimal communication network for the local and global control strategies. Finally, we consider relationship between the interconnection pattern and the synchronization stability; by optimizing the network interlinks, the obtained network shows better synchronization stability than the original network does, in particular, at a high power demand. Our analysis shows that interlinks between spatially distant nodes will improve the synchronization stability. The results seem unfeasible to be implemented in real systems but provide a potential guide for the design of stable power systems. PMID:27225708

Listening to a baby crying induces higher electroencephalographic synchronization among prefrontal, temporal and parietal cortices in adoptive mothers.

PubMed

Pérez-Hernández, M; Hernández-González, M; Hidalgo-Aguirre, R M; Amezcua-Gutiérrez, C; Guevara, M A

2017-05-01

Women who adopt babies show caring behaviors and respond to stimuli from their infants just as biological mothers do, but several studies have shown that the cerebral functionality of biological mothers (BM) and adoptive mothers (AM) changes in relation to the type and emotional mean of the stimuli they receive from their babies. The complex perception and processing of different stimuli with emotional content (such as those emitted by babies) require functional synchronization among different cortical and subcortical brain areas. To determine whether the degree of functional synchronization between cortices varies when they perceive such stimuli, this study characterized the degree of cortical electroencephalographic (EEG) synchronization (correlation) among prefrontal, temporal and parietal areas in BM, AM and non-mothers while listening to a recording of a baby crying. BM showed a decreased EEG synchronization between the prefrontal and temporal cortices that may indicate a decrease in the modulatory control that the former exerts on the posterior cortices, and could be associated with deeper emotional involvement and increased sensitivity to the baby crying. The AM, in contrast, had higher degree of EEG synchronization between cortical areas in both hemispheres, likely associated with a greater modulation of the affective information of the crying baby, which allowed them to perceive it as less unpleasant. These data enrich our knowledge of the neurofunctional changes involved in motherhood, and of the neural processes that allow mothers (biological and adoptive) to be sensitive to their infants' cues and respond appropriately. Copyright © 2017 Elsevier Inc. All rights reserved.

Theta-Modulated Gamma-Band Synchronization Among Activated Regions During a Verb Generation Task

PubMed Central

Doesburg, Sam M.; Vinette, Sarah A.; Cheung, Michael J.; Pang, Elizabeth W.

2012-01-01

Expressive language is complex and involves processing within a distributed network of cortical regions. Functional MRI and magnetoencephalography (MEG) have identified brain areas critical for expressive language, but how these regions communicate across the network remains poorly understood. It is thought that synchronization of oscillations between neural populations, particularly at a gamma rate (>30 Hz), underlies functional integration within cortical networks. Modulation of gamma rhythms by theta-band oscillations (4–8 Hz) has been proposed as a mechanism for the integration of local cell coalitions into large-scale networks underlying cognition and perception. The present study tested the hypothesis that these oscillatory mechanisms of functional integration were present within the expressive language network. We recorded MEG while subjects performed a covert verb generation task. We localized activated cortical regions using beamformer analysis, calculated inter-regional phase locking between activated areas, and measured modulation of inter-regional gamma synchronization by theta phase. The results show task-dependent gamma-band synchronization among regions activated during the performance of the verb generation task, and we provide evidence that these transient and periodic instances of high-frequency connectivity were modulated by the phase of cortical theta oscillations. These findings suggest that oscillatory synchronization and cross-frequency interactions are mechanisms for functional integration among distributed brain areas supporting expressive language processing. PMID:22707946

Astrocyte-Mediated Neuronal Synchronization Properties Revealed by False Gliotransmitter Release

PubMed Central

Pirttimaki, Tiina M.; Sims, Robert E.; Saunders, Gregory; Antonio, Serena A.; Codadu, Neela Krushna

2017-01-01

Astrocytes spontaneously release glutamate (Glut) as a gliotransmitter (GT), resulting in the generation of extrasynaptic NMDAR-mediated slow inward currents (SICs) in neighboring neurons, which can increase local neuronal excitability. However, there is a deficit in our knowledge of the factors that control spontaneous astrocyte GT release and the extent of its influence. We found that, in rat brain slices, increasing the supply of the physiological transmitter Glut increased the frequency and signaling charge of SICs over an extended period. This phenomenon was replicated by exogenous preexposure to the amino acid D-aspartate (D-Asp). Using D-Asp as a “false” GT, we determined the extent of local neuron excitation by GT release in ventrobasal thalamus, CA1 hippocampus, and somatosensory cortex. By analyzing synchronized neuronal NMDAR-mediated excitation, we found that the properties of the excitation were conserved in different brain areas. In the three areas, astrocyte-derived GT release synchronized groups of neurons at distances of >;200 μm. Individual neurons participated in more than one synchronized population, indicating that individual neurons can be excited by more than one astrocyte and that individual astrocytes may determine a neuron's synchronized network. The results confirm that astrocytes can act as excitatory nodes that can influence neurons over a significant range in a number of brain regions. Our findings further suggest that chronic elevation of ambient Glut levels can lead to increased GT Glut release, which may be relevant in some pathological states. SIGNIFICANCE STATEMENT Astrocytes spontaneously release glutamate (Glut) and other gliotransmitters (GTs) that can modify neuronal activity. Exposing brain slices to Glut and D-aspartate (D-Asp) before recording resulted in an increase in frequency of GT-mediated astrocyte–neuron signaling. Using D-Asp, it was possible to investigate the effects of specific GT release at neuronal NMDARs. Calcium imaging showed synchronized activity in groups of neurons in cortex, hippocampus, and thalamus. The size of these populations was similar in all areas and some neurons were involved in more than one synchronous group. The findings show that GT release is supply dependent and that the properties of the signaling and activated networks are largely conserved between different brain areas. PMID:28899919

Introduction to focus issue: Synchronization in large networks and continuous media—data, models, and supermodels

NASA Astrophysics Data System (ADS)

Duane, Gregory S.; Grabow, Carsten; Selten, Frank; Ghil, Michael

2017-12-01

The synchronization of loosely coupled chaotic systems has increasingly found applications to large networks of differential equations and to models of continuous media. These applications are at the core of the present Focus Issue. Synchronization between a system and its model, based on limited observations, gives a new perspective on data assimilation. Synchronization among different models of the same system defines a supermodel that can achieve partial consensus among models that otherwise disagree in several respects. Finally, novel methods of time series analysis permit a better description of synchronization in a system that is only observed partially and for a relatively short time. This Focus Issue discusses synchronization in extended systems or in components thereof, with particular attention to data assimilation, supermodeling, and their applications to various areas, from climate modeling to macroeconomics.

Introduction to focus issue: Synchronization in large networks and continuous media-data, models, and supermodels.

PubMed

Duane, Gregory S; Grabow, Carsten; Selten, Frank; Ghil, Michael

2017-12-01

The synchronization of loosely coupled chaotic systems has increasingly found applications to large networks of differential equations and to models of continuous media. These applications are at the core of the present Focus Issue. Synchronization between a system and its model, based on limited observations, gives a new perspective on data assimilation. Synchronization among different models of the same system defines a supermodel that can achieve partial consensus among models that otherwise disagree in several respects. Finally, novel methods of time series analysis permit a better description of synchronization in a system that is only observed partially and for a relatively short time. This Focus Issue discusses synchronization in extended systems or in components thereof, with particular attention to data assimilation, supermodeling, and their applications to various areas, from climate modeling to macroeconomics.

Determination of power system component parameters using nonlinear dead beat estimation method

NASA Astrophysics Data System (ADS)

Kolluru, Lakshmi

Power systems are considered the most complex man-made wonders in existence today. In order to effectively supply the ever increasing demands of the consumers, power systems are required to remain stable at all times. Stability and monitoring of these complex systems are achieved by strategically placed computerized control centers. State and parameter estimation is an integral part of these facilities, as they deal with identifying the unknown states and/or parameters of the systems. Advancements in measurement technologies and the introduction of phasor measurement units (PMU) provide detailed and dynamic information of all measurements. Accurate availability of dynamic measurements provides engineers the opportunity to expand and explore various possibilities in power system dynamic analysis/control. This thesis discusses the development of a parameter determination algorithm for nonlinear power systems, using dynamic data obtained from local measurements. The proposed algorithm was developed by observing the dead beat estimator used in state space estimation of linear systems. The dead beat estimator is considered to be very effective as it is capable of obtaining the required results in a fixed number of steps. The number of steps required is related to the order of the system and the number of parameters to be estimated. The proposed algorithm uses the idea of dead beat estimator and nonlinear finite difference methods to create an algorithm which is user friendly and can determine the parameters fairly accurately and effectively. The proposed algorithm is based on a deterministic approach, which uses dynamic data and mathematical models of power system components to determine the unknown parameters. The effectiveness of the algorithm is tested by implementing it to identify the unknown parameters of a synchronous machine. MATLAB environment is used to create three test cases for dynamic analysis of the system with assumed known parameters. Faults are introduced in the virtual test systems and the dynamic data obtained in each case is analyzed and recorded. Ideally, actual measurements are to be provided to the algorithm. As the measurements are not readily available the data obtained from simulations is fed into the determination algorithm as inputs. The obtained results are then compared to the original (or assumed) values of the parameters. The results obtained suggest that the algorithm is able to determine the parameters of a synchronous machine when crisp data is available.

Complex Synchronization Phenomena in Ecological Systems

NASA Astrophysics Data System (ADS)

Stone, Lewi; Olinky, Ronen; Blasius, Bernd; Huppert, Amit; Cazelles, Bernard

2002-07-01

Ecological and biological systems provide us with many striking examples of synchronization phenomena. Here we discuss a number of intriguing cases and attempt to explain them taking advantage of a modelling framework. One main focus will concern synchronized ecological end epidemiological cycles which have Uniform Phase growth associated with their regular recurrence, and Chaotic Amplitudes - a feature we term UPCA. Examples come from different areas and include decadal cycles of small mammals, recurrent viral epidemics such as childhood infections (eg., measles), and seasonally driven phytoplankton blooms observed in lakes and the oceans. A more detailed theoretical analysis of seasonally synchronized chaotic population cycles is presented.

Bridging the Capability Gap for Battle Command On-the-Move

DTIC Science & Technology

2005-06-01

FDM) and synchronous Time Division Multiplexing (TDM) network components. This advantage will become further realized once mobile satellite modem... synchronize the initial network timing . Once a NM receives this beacon, it reports the measured receive signal strength back to the NC using the NM’s...in certain areas of the world. Due to M4’s synchronous network connections, link engineering to manage required distributed network timing is often

Theta coupling between V4 and prefrontal cortex predicts visual short-term memory performance.

PubMed

Liebe, Stefanie; Hoerzer, Gregor M; Logothetis, Nikos K; Rainer, Gregor

2012-01-29

Short-term memory requires communication between multiple brain regions that collectively mediate the encoding and maintenance of sensory information. It has been suggested that oscillatory synchronization underlies intercortical communication. Yet, whether and how distant cortical areas cooperate during visual memory remains elusive. We examined neural interactions between visual area V4 and the lateral prefrontal cortex using simultaneous local field potential (LFP) recordings and single-unit activity (SUA) in monkeys performing a visual short-term memory task. During the memory period, we observed enhanced between-area phase synchronization in theta frequencies (3-9 Hz) of LFPs together with elevated phase locking of SUA to theta oscillations across regions. In addition, we found that the strength of intercortical locking was predictive of the animals' behavioral performance. This suggests that theta-band synchronization coordinates action potential communication between V4 and prefrontal cortex that may contribute to the maintenance of visual short-term memories.

Synchronization Design and Error Analysis of Near-Infrared Cameras in Surgical Navigation.

PubMed

Cai, Ken; Yang, Rongqian; Chen, Huazhou; Huang, Yizhou; Wen, Xiaoyan; Huang, Wenhua; Ou, Shanxing

2016-01-01

The accuracy of optical tracking systems is important to scientists. With the improvements reported in this regard, such systems have been applied to an increasing number of operations. To enhance the accuracy of these systems further and to reduce the effect of synchronization and visual field errors, this study introduces a field-programmable gate array (FPGA)-based synchronization control method, a method for measuring synchronous errors, and an error distribution map in field of view. Synchronization control maximizes the parallel processing capability of FPGA, and synchronous error measurement can effectively detect the errors caused by synchronization in an optical tracking system. The distribution of positioning errors can be detected in field of view through the aforementioned error distribution map. Therefore, doctors can perform surgeries in areas with few positioning errors, and the accuracy of optical tracking systems is considerably improved. The system is analyzed and validated in this study through experiments that involve the proposed methods, which can eliminate positioning errors attributed to asynchronous cameras and different fields of view.

Dynamic Control of Facts Devices to Enable Large Scale Penetration of Renewable Energy Resources

NASA Astrophysics Data System (ADS)

Chavan, Govind Sahadeo

This thesis focuses on some of the problems caused by large scale penetration of Renewable Energy Resources within EHV transmission networks, and investigates some approaches in resolving these problems. In chapter 4, a reduced-order model of the 500 kV WECC transmission system is developed by estimating its key parameters from phasor measurement unit (PMU) data. The model was then implemented in RTDS and was investigated for its accuracy with respect to the PMU data. Finally it was tested for observing the effects of various contingencies like transmission line loss, generation loss and large scale penetration of wind farms on EHV transmission systems. Chapter 5 introduces Static Series Synchronous Compensators (SSSC) which are seriesconnected converters that can control real power flow along a transmission line. A new application of SSSCs in mitigating Ferranti effect on unloaded transmission lines was demonstrated on PSCAD. A new control scheme for SSSCs based on the Cascaded H-bridge (CHB) converter configuration was proposed and was demonstrated using PSCAD and RTDS. A new centralized controller was developed for the distributed SSSCs based on some of the concepts used in the CHB-based SSSC. The controller's efficacy was demonstrated using RTDS. Finally chapter 6 introduces the problem of power oscillations induced by renewable sources in a transmission network. A power oscillation damping (POD) controller is designed using distributed SSSCs in NYPA's 345 kV three-bus AC system and its efficacy is demonstrated in PSCAD. A similar POD controller is then designed for the CHB-based SSSC in the IEEE 14 bus system in PSCAD. Both controllers were noted to have significantly damped power oscillations in the transmission networks.

Attentional modulation of cell-class specific gamma-band synchronization in awake monkey area V4

PubMed Central

Vinck, Martin; Womelsdorf, Thilo; Buffalo, Elizabeth A.; Desimone, Robert; Fries, Pascal

2013-01-01

Summary Selective visual attention is subserved by selective neuronal synchronization, entailing precise orchestration among excitatory and inhibitory cells. We tentatively identified these as broad (BS) and narrow spiking (NS) cells and analyzed their synchronization to the local field potential in two macaque monkeys performing a selective visual attention task. Across cells, gamma phases scattered widely but were unaffected by stimulation or attention. During stimulation, NS cells lagged BS cells on average by ~60° and gamma synchronized twice as strongly. Attention enhanced and reduced the gamma locking of strongly and weakly activated cells, respectively. During a pre-stimulus attentional cue period, BS cells showed weak gamma synchronization, while NS cells gamma synchronized as strongly as with visual stimulation. These analyses reveal the cell-type specific dynamics of the gamma cycle in macaque visual cortex and suggest that attention affects neurons differentially depending on cell type and activation level. PMID:24267656

Efficacy of Floor Control Protocols in Distributed Multimedia Collaboration

DTIC Science & Technology

1999-01-01

advanced consider- ably, support for such controlled group interaction, particularly for applications geared towards synchronous and wide-area groupwork ...transaction-oriented collaboration, and synchronous groupwork is limited mostly to text and chatting. The JETS system [32] is a recent example for a Java-based

Uniting functional network topology and oscillations in the fronto-parietal single unit network of behaving primates.

PubMed

Dann, Benjamin; Michaels, Jonathan A; Schaffelhofer, Stefan; Scherberger, Hansjörg

2016-08-15

The functional communication of neurons in cortical networks underlies higher cognitive processes. Yet, little is known about the organization of the single neuron network or its relationship to the synchronization processes that are essential for its formation. Here, we show that the functional single neuron network of three fronto-parietal areas during active behavior of macaque monkeys is highly complex. The network was closely connected (small-world) and consisted of functional modules spanning these areas. Surprisingly, the importance of different neurons to the network was highly heterogeneous with a small number of neurons contributing strongly to the network function (hubs), which were in turn strongly inter-connected (rich-club). Examination of the network synchronization revealed that the identified rich-club consisted of neurons that were synchronized in the beta or low frequency range, whereas other neurons were mostly non-oscillatory synchronized. Therefore, oscillatory synchrony may be a central communication mechanism for highly organized functional spiking networks.

Project to Study Soil Electromagnetic Properties

DTIC Science & Technology

2007-09-30

transmitter loops (these may be one and the same physical loop or any combinations of loops) and w is angular frequency. M is the magnetic flux that...space, and w is angular frequency used by the sensor. In this case sensor response is frequency-dependent, even if the layer variables are real and...Consider a transmitter current in a single turn coil with angular frequency wand amplitude I. This produces a receiver voltage V (a complex phasor) in the

Coupled Mode Formalism: Connecting Phasor, Matrix, and Geometrical Approaches

DTIC Science & Technology

2014-05-30

the Poincare sphere in classical optics, and was generalized to incoherent light as the Stokes and Mueller approach [4]. The Stokes description reduces...to the Poincare sphere description when one treats monochromatic light, and we restrict ourselves to this case. Background There are several...waves, cast as plane waves of the form g(z, t) = f(z − vt) = Aej(ω t −k z) , (1) namely a sinusoidal wave travelling in the positive z direction at phase

Wide area coverage radar imaging satellite for earth applications. [surveillance and mapping of ice on Great Lakes

NASA Technical Reports Server (NTRS)

Stevens, G. H.; Ramler, J. R.

1974-01-01

A preliminary study was made of a radar imaging satellite for earth applications. A side-looking synthetic-aperture radar was considered and the feasibility of obtaining a wide area coverage to reduce the time required to image a given area was investigated. Two basic approaches were examined; low altitude sun-synchronous orbits using a multibeam/multifrequency radar system and equatorial orbits up to near-synchronous altitude using a single beam system. Surveillance and mapping of ice on the Great Lakes was used as a typical application to focus the study effort.

UTC Time Transfer for High Frequency Trading Using IS-95 CDMA Base Station Transmissions and IEEE-1588 Precision Time Protocol

DTIC Science & Technology

2010-11-01

CDMA base stations are each synchronized by GPS receivers, they provide an indirect link to GPS system time and UTC time . The major stock...antenna synchronizes the Local Area Network (LAN) to within 10 microseconds of UTC using the IEEE-1588 Precision Time Protocol (PTP). This is an...activities. Understanding and measuring latency on the LAN is key to the success of HFTs. Without precise time synchronization below 1 millisecond

Astrocyte-Mediated Neuronal Synchronization Properties Revealed by False Gliotransmitter Release.

PubMed

Pirttimaki, Tiina M; Sims, Robert E; Saunders, Gregory; Antonio, Serena A; Codadu, Neela Krushna; Parri, H Rheinallt

2017-10-11

Astrocytes spontaneously release glutamate (Glut) as a gliotransmitter (GT), resulting in the generation of extrasynaptic NMDAR-mediated slow inward currents (SICs) in neighboring neurons, which can increase local neuronal excitability. However, there is a deficit in our knowledge of the factors that control spontaneous astrocyte GT release and the extent of its influence. We found that, in rat brain slices, increasing the supply of the physiological transmitter Glut increased the frequency and signaling charge of SICs over an extended period. This phenomenon was replicated by exogenous preexposure to the amino acid D-aspartate (D-Asp). Using D-Asp as a "false" GT, we determined the extent of local neuron excitation by GT release in ventrobasal thalamus, CA1 hippocampus, and somatosensory cortex. By analyzing synchronized neuronal NMDAR-mediated excitation, we found that the properties of the excitation were conserved in different brain areas. In the three areas, astrocyte-derived GT release synchronized groups of neurons at distances of >;200 μm. Individual neurons participated in more than one synchronized population, indicating that individual neurons can be excited by more than one astrocyte and that individual astrocytes may determine a neuron's synchronized network. The results confirm that astrocytes can act as excitatory nodes that can influence neurons over a significant range in a number of brain regions. Our findings further suggest that chronic elevation of ambient Glut levels can lead to increased GT Glut release, which may be relevant in some pathological states. SIGNIFICANCE STATEMENT Astrocytes spontaneously release glutamate (Glut) and other gliotransmitters (GTs) that can modify neuronal activity. Exposing brain slices to Glut and D-aspartate (D-Asp) before recording resulted in an increase in frequency of GT-mediated astrocyte-neuron signaling. Using D-Asp, it was possible to investigate the effects of specific GT release at neuronal NMDARs. Calcium imaging showed synchronized activity in groups of neurons in cortex, hippocampus, and thalamus. The size of these populations was similar in all areas and some neurons were involved in more than one synchronous group. The findings show that GT release is supply dependent and that the properties of the signaling and activated networks are largely conserved between different brain areas. Copyright © 2017 Pirttimaki, Sims et al.

Synchronization analysis of voltage-sensitive dye imaging during focal seizures in the rat neocortex

NASA Astrophysics Data System (ADS)

Takeshita, Daisuke; Bahar, Sonya

2011-12-01

Seizures are often assumed to result from an excess of synchronized neural activity. However, various recent studies have suggested that this is not necessarily the case. We investigate synchronization during focal neocortical seizures induced by injection of 4-aminopyridine (4AP) in the rat neocortex in vivo. Neocortical activity is monitored by field potential recording and by the fluorescence of the voltage-sensitive dye RH-1691. After removal of artifacts, the voltage-sensitive dye (VSD) signal is analyzed using the nonlinear dynamics-based technique of stochastic phase synchronization in order to determine the degree of synchronization within the neocortex during the development and spread of each seizure event. Results show a large, statistically significant increase in synchronization during seizure activity. Synchrony is typically greater between closer pixel pairs during a seizure event; the entire seizure region is synchronized almost exactly in phase. This study represents, to our knowledge, the first application of synchronization analysis methods to mammalian VSD imaging in vivo. Our observations indicate a clear increase in synchronization in this model of focal neocortical seizures across a large area of the neocortex; a sharp increase in synchronization during seizure events was observed in all 37 seizures imaged. The results are consistent with a recent computational study which simulates the effect of 4AP in a neocortical neuron model.

Investigating Teacher Presence in Courses Using Synchronous Videoconferencing

ERIC Educational Resources Information Center

Rehn, Nicole; Maor, Dorit; McConney, Andrew

2016-01-01

This research examines teacher presence in high school distance courses that are delivered by synchronous videoconference. In rural and remote areas, many school districts are using videoconferencing as way to reach dispersed students. This collective case study uses mixed methods to unpack the notion of presence from the perspective of teachers…

Stability of the phase motion in race-track microtrons

NASA Astrophysics Data System (ADS)

Kubyshin, Yu. A.; Larreal, O.; Ramírez-Ros, R.; Seara, T. M.

2017-06-01

We model the phase oscillations of electrons in race-track microtrons by means of an area preserving map with a fixed point at the origin, which represents the synchronous trajectory of a reference particle in the beam. We study the nonlinear stability of the origin in terms of the synchronous phase -the phase of the synchronous particle at the injection. We estimate the size and shape of the stability domain around the origin, whose main connected component is enclosed by an invariant curve. We describe the evolution of the stability domain as the synchronous phase varies. We also clarify the role of the stable and unstable invariant curves of some hyperbolic (fixed or periodic) points.

Imbalance of community structures in epilepsy

NASA Astrophysics Data System (ADS)

Ortega, G. J.; Herrera Peco, I.; García de Sola, R.; Pastor, J.

2010-09-01

Epilepsy is commonly associated with synchronous activity in the form of spikes and also in developed seizures. Desynchronised activity seems to play an important role also in the seizure process, favouring the initiation of seizures. The aim of the present work is to explore synchronization activity in the inner areas in the temporal lobe of epileptic patients by a novel approach. Two temporal lobe epilepsy (TLE) patients' records have been analyzed through a cluster analysis. Electrical activity in the inner part of the temporal has been recorded by using Foramen Ovale Electrodes (FOE), a semi-invasive technique frequently used in drug resistant epileptic patients. Instead of tracking synchronized activity, we give here special attention to desynchronized activity, mainly those areas which are not included in synchronization clusters. Our results show that electrical activity in the epileptic side behaves in a less cohesive fashion than the contra-lateral side. There exists a clear tendency in the epileptic side to be organized as isolated clusters of electrical activity as compared with the contra-lateral side, which is organized in the form of large clusters of synchronous activity. In particular, we shall give special attention to the cluster desynchronization during the seizures. As we shall show, our results can help in understand several characteristics of the seizures dynamics.

Synchronization properties of coupled chaotic neurons: The role of random shared input

NASA Astrophysics Data System (ADS)

Kumar, Rupesh; Bilal, Shakir; Ramaswamy, Ram

2016-06-01

Spike-time correlations of neighbouring neurons depend on their intrinsic firing properties as well as on the inputs they share. Studies have shown that periodically firing neurons, when subjected to random shared input, exhibit asynchronicity. Here, we study the effect of random shared input on the synchronization of weakly coupled chaotic neurons. The cases of so-called electrical and chemical coupling are both considered, and we observe a wide range of synchronization behaviour. When subjected to identical shared random input, there is a decrease in the threshold coupling strength needed for chaotic neurons to synchronize in-phase. The system also supports lag-synchronous states, and for these, we find that shared input can cause desynchronization. We carry out a master stability function analysis for a network of such neurons and show agreement with the numerical simulations. The contrasting role of shared random input for complete and lag synchronized neurons is useful in understanding spike-time correlations observed in many areas of the brain.

Synchronization properties of coupled chaotic neurons: The role of random shared input

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Rupesh; Bilal, Shakir; Ramaswamy, Ram

Spike-time correlations of neighbouring neurons depend on their intrinsic firing properties as well as on the inputs they share. Studies have shown that periodically firing neurons, when subjected to random shared input, exhibit asynchronicity. Here, we study the effect of random shared input on the synchronization of weakly coupled chaotic neurons. The cases of so-called electrical and chemical coupling are both considered, and we observe a wide range of synchronization behaviour. When subjected to identical shared random input, there is a decrease in the threshold coupling strength needed for chaotic neurons to synchronize in-phase. The system also supports lag–synchronous states,more » and for these, we find that shared input can cause desynchronization. We carry out a master stability function analysis for a network of such neurons and show agreement with the numerical simulations. The contrasting role of shared random input for complete and lag synchronized neurons is useful in understanding spike-time correlations observed in many areas of the brain.« less

Studies of Sub-Synchronous Oscillations in Large-Scale Wind Farm Integrated System

NASA Astrophysics Data System (ADS)

Yue, Liu; Hang, Mend

2018-01-01

With the rapid development and construction of large-scale wind farms and grid-connected operation, the series compensation wind power AC transmission is gradually becoming the main way of power usage and improvement of wind power availability and grid stability, but the integration of wind farm will change the SSO (Sub-Synchronous oscillation) damping characteristics of synchronous generator system. Regarding the above SSO problem caused by integration of large-scale wind farms, this paper focusing on doubly fed induction generator (DFIG) based wind farms, aim to summarize the SSO mechanism in large-scale wind power integrated system with series compensation, which can be classified as three types: sub-synchronous control interaction (SSCI), sub-synchronous torsional interaction (SSTI), sub-synchronous resonance (SSR). Then, SSO modelling and analysis methods are categorized and compared by its applicable areas. Furthermore, this paper summarizes the suppression measures of actual SSO projects based on different control objectives. Finally, the research prospect on this field is explored.

Polarimetry Studies of Ionospheric Modification by Rocket boosters.

DTIC Science & Technology

1981-05-27

Chemical Releases Polarimetry Studies Rocket Booster Effects Faraday Rotation 20. ABSTRACT (Coniros an ,Oer* e side It necessary and Identify by block...1112 InL I X (I _ Tl : YI) Rijl I ± ,2 for the radiowave whose electric field is given by E - E ,(z) exp ( w) + c.c. - i + Ej (2) 3 REILLY, |tARNISH, AND...has a simple phasor represen- ta "n through the definition F - E , +j E ,. (3) The linearly polarized radiowave is represented in terms of the

openECA Platform and Analytics Alpha Test Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robertson, Russell

The objective of the Open and Extensible Control and Analytics (openECA) Platform for Phasor Data project is to develop an open source software platform that significantly accelerates the production, use, and ongoing development of real-time decision support tools, automated control systems, and off-line planning systems that (1) incorporate high-fidelity synchrophasor data and (2) enhance system reliability while enabling the North American Electric Reliability Corporation (NERC) operating functions of reliability coordinator, transmission operator, and/or balancing authority to be executed more effectively.

openECA Platform and Analytics Beta Demonstration Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robertson, Russell

The objective of the Open and Extensible Control and Analytics (openECA) Platform for Phasor Data project is to develop an open source software platform that significantly accelerates the production, use, and ongoing development of real-time decision support tools, automated control systems, and off-line planning systems that (1) incorporate high-fidelity synchrophasor data and (2) enhance system reliability while enabling the North American Electric Reliability Corporation (NERC) operating functions of reliability coordinator, transmission operator, and/or balancing authority to be executed more effectively.

Frequency domain model for analysis of paralleled, series-output-connected Mapham inverters

NASA Technical Reports Server (NTRS)

Brush, Andrew S.; Sundberg, Richard C.; Button, Robert M.

1989-01-01

The Mapham resonant inverter is characterized as a two-port network driven by a selected periodic voltage. The two-port model is then used to model a pair of Mapham inverters connected in series and employing phasor voltage regulation. It is shown that the model is useful for predicting power output in paralleled inverter units, and for predicting harmonic current output of inverter pairs, using standard power flow techniques. Some sample results are compared to data obtained from testing hardware inverters.

Frequency domain model for analysis of paralleled, series-output-connected Mapham inverters

NASA Technical Reports Server (NTRS)

Brush, Andrew S.; Sundberg, Richard C.; Button, Robert M.

1989-01-01

The Mapham resonant inverter is characterized as a two-port network driven by a selected periodic voltage. The two-port model is then used to model a pair of Mapham inverters connected in series and employing phasor voltage regulation. It is shown that the model is useful for predicting power output in paralleled inverter units, and for predicting harmonic current output of inverter pairs, using standard power flow techniques. Some examples are compared to data obtained from testing hardware inverters.

Neurocognitive Brain Response to Transient Impairment of Wernicke's Area

PubMed Central

Mason, Robert A.; Prat, Chantel S.; Just, Marcel Adam

2014-01-01

This study examined how the brain system adapts and reconfigures its information processing capabilities to maintain cognitive performance after a key cortical center [left posterior superior temporal gyrus (LSTGp)] is temporarily impaired during the performance of a language comprehension task. By applying repetitive transcranial magnetic stimulation (rTMS) to LSTGp and concurrently assessing the brain response with functional magnetic resonance imaging, we found that adaptation consisted of 1) increased synchronization between compensating regions coupled with a decrease in synchronization within the primary language network and 2) a decrease in activation at the rTMS site as well as in distal regions, followed by their recovery. The compensatory synchronization included 3 centers: The contralateral homolog (RSTGp) of the area receiving rTMS, areas adjacent to the rTMS site, and a region involved in discourse monitoring (medial frontal gyrus). This approach reveals some principles of network-level adaptation to trauma with potential application to traumatic brain injury, stroke, and seizure. PMID:23322403

Neurocognitive brain response to transient impairment of Wernicke's area.

PubMed

Mason, Robert A; Prat, Chantel S; Just, Marcel Adam

2014-06-01

This study examined how the brain system adapts and reconfigures its information processing capabilities to maintain cognitive performance after a key cortical center [left posterior superior temporal gyrus (LSTGp)] is temporarily impaired during the performance of a language comprehension task. By applying repetitive transcranial magnetic stimulation (rTMS) to LSTGp and concurrently assessing the brain response with functional magnetic resonance imaging, we found that adaptation consisted of 1) increased synchronization between compensating regions coupled with a decrease in synchronization within the primary language network and 2) a decrease in activation at the rTMS site as well as in distal regions, followed by their recovery. The compensatory synchronization included 3 centers: The contralateral homolog (RSTGp) of the area receiving rTMS, areas adjacent to the rTMS site, and a region involved in discourse monitoring (medial frontal gyrus). This approach reveals some principles of network-level adaptation to trauma with potential application to traumatic brain injury, stroke, and seizure.

Online Synchronous Communication in the Second-Language Classroom

ERIC Educational Resources Information Center

Murphy, Elizabeth

2009-01-01

The study reported on in this paper used a framework of benefits, challenges and solutions to categorize data from a design experiment using synchronous online communication for learning French as a second language (FSL). Participants were 92 Grade 6, FSL students and four teachers from urban and rural areas of Newfoundland, Canada. Data…

Perceptions and Expectations of Online Graduate Students Regarding Synchronous Events

ERIC Educational Resources Information Center

Bailie, Jeffrey L.

2015-01-01

The purpose of this study was to gain an increased understanding of the perceptions and expectations of a group of experienced online student participants regarding synchronous events in the higher learning setting. Areas of inquiry posed to online student panelists included whether they expected live events to be included in their classes, and…

Experiences of Advanced High School Students in Synchronous Online Recitations

ERIC Educational Resources Information Center

Mayer, Greg; Lingle, Jeremy; Usselman, Marion

2017-01-01

The question of how to best design an online course that promotes student-centred learning is an area of ongoing research. This mixed-methods study focused on a section of advanced high school students, in college-level mathematics courses, that used a synchronous online environment mediated over web-conferencing software, and whether the…

Systematic Review of Two Decades (1995 to 2014) of Research on Synchronous Online Learning

ERIC Educational Resources Information Center

Martin, Florence; Ahlgrim-Delzell, Lynn; Budhrani, Kiran

2017-01-01

Systematic reviews of literature are studies that strategically search for published research on a specific topic in order to synthesize what is known about the topic. This systematic review describes 157 articles on synchronous online learning (SOL) from thirty-four different countries on instructional setting, content areas, participant…

Uniting functional network topology and oscillations in the fronto-parietal single unit network of behaving primates

PubMed Central

Dann, Benjamin; Michaels, Jonathan A; Schaffelhofer, Stefan; Scherberger, Hansjörg

2016-01-01

The functional communication of neurons in cortical networks underlies higher cognitive processes. Yet, little is known about the organization of the single neuron network or its relationship to the synchronization processes that are essential for its formation. Here, we show that the functional single neuron network of three fronto-parietal areas during active behavior of macaque monkeys is highly complex. The network was closely connected (small-world) and consisted of functional modules spanning these areas. Surprisingly, the importance of different neurons to the network was highly heterogeneous with a small number of neurons contributing strongly to the network function (hubs), which were in turn strongly inter-connected (rich-club). Examination of the network synchronization revealed that the identified rich-club consisted of neurons that were synchronized in the beta or low frequency range, whereas other neurons were mostly non-oscillatory synchronized. Therefore, oscillatory synchrony may be a central communication mechanism for highly organized functional spiking networks. DOI: http://dx.doi.org/10.7554/eLife.15719.001 PMID:27525488

Synchronization of Long Ocean Waves by Coastal Relief on the Southeast Shelf of Sakhalin Island

NASA Astrophysics Data System (ADS)

Kovalev, Dmitry P.; Kovalev, Peter D.

2017-12-01

The phenomenon of synchronization (trapping) of coming waves by the resonant water area in a coastal zone of the sea found from the observed data is considered in the paper. Edge waves with the period of about 10.7 minutes are visually observed in sea level fluctuations near the village of Okhotskoye and the cape Ostri on the southeast coast of Sakhalin Island. These waves are synchronized with the resonance water area. It becomes apparent from the unlimited increase of a phase between the bottom stations installed at distance of about 7.5km. In relation to the phenomenon found, the problem of weak and periodic impact on regular self-oscillatory system — Van der Paul’s oscillator — is considered. Good compliance between theoretical model and data of experiments is obtained.

Files synchronization from a large number of insertions and deletions

NASA Astrophysics Data System (ADS)

Ellappan, Vijayan; Kumari, Savera

2017-11-01

Synchronization between different versions of files is becoming a major issue that most of the applications are facing. To make the applications more efficient a economical algorithm is developed from the previously used algorithm of “File Loading Algorithm”. I am extending this algorithm in three ways: First, dealing with non-binary files, Second backup is generated for uploaded files and lastly each files are synchronized with insertions and deletions. User can reconstruct file from the former file with minimizing the error and also provides interactive communication by eliminating the frequency without any disturbance. The drawback of previous system is overcome by using synchronization, in which multiple copies of each file/record is created and stored in backup database and is efficiently restored in case of any unwanted deletion or loss of data. That is, to introduce a protocol that user B may use to reconstruct file X from file Y with suitably low probability of error. Synchronization algorithms find numerous areas of use, including data storage, file sharing, source code control systems, and cloud applications. For example, cloud storage services such as Drop box synchronize between local copies and cloud backups each time users make changes to local versions. Similarly, synchronization tools are necessary in mobile devices. Specialized synchronization algorithms are used for video and sound editing. Synchronization tools are also capable of performing data duplication.

A quantitative theory of gamma synchronization in macaque V1.

PubMed

Lowet, Eric; Roberts, Mark J; Peter, Alina; Gips, Bart; De Weerd, Peter

2017-08-31

Gamma-band synchronization coordinates brief periods of excitability in oscillating neuronal populations to optimize information transmission during sensation and cognition. Commonly, a stable, shared frequency over time is considered a condition for functional neural synchronization. Here, we demonstrate the opposite: instantaneous frequency modulations are critical to regulate phase relations and synchronization. In monkey visual area V1, nearby local populations driven by different visual stimulation showed different gamma frequencies. When similar enough, these frequencies continually attracted and repulsed each other, which enabled preferred phase relations to be maintained in periods of minimized frequency difference. Crucially, the precise dynamics of frequencies and phases across a wide range of stimulus conditions was predicted from a physics theory that describes how weakly coupled oscillators influence each other's phase relations. Hence, the fundamental mathematical principle of synchronization through instantaneous frequency modulations applies to gamma in V1 and is likely generalizable to other brain regions and rhythms.

Synchronization of unidirectionally coupled Mackey-Glass analog circuits with frequency bandwidth limitations.

PubMed

Kim, Min-Young; Sramek, Christopher; Uchida, Atsushi; Roy, Rajarshi

2006-07-01

Synchronization of chaotic systems has been studied extensively, and especially, the possible applications to the communication systems motivated many research areas. We demonstrate the effect of the frequency bandwidth limitations in the communication channel on the synchronization of two unidirectionally coupled Mackey-Glass (MG) analog circuits, both numerically and experimentally. MG system is known to generate high dimensional chaotic signals. The chaotic signal generated from the drive MG system is modified by a low pass filter and is then transmitted to the response MG system. Our results show that the inclusion of the dominant frequency component of the original drive signals is crucial to achieve synchronization between the drive and response circuits. The maximum cross correlation and the corresponding time shift reveal that the frequency-dependent coupling introduced by the low pass filtering effect in the communication channel change the quality of synchronization.

A quantitative theory of gamma synchronization in macaque V1

PubMed Central

Roberts, Mark J; Peter, Alina; Gips, Bart; De Weerd, Peter

2017-01-01

Gamma-band synchronization coordinates brief periods of excitability in oscillating neuronal populations to optimize information transmission during sensation and cognition. Commonly, a stable, shared frequency over time is considered a condition for functional neural synchronization. Here, we demonstrate the opposite: instantaneous frequency modulations are critical to regulate phase relations and synchronization. In monkey visual area V1, nearby local populations driven by different visual stimulation showed different gamma frequencies. When similar enough, these frequencies continually attracted and repulsed each other, which enabled preferred phase relations to be maintained in periods of minimized frequency difference. Crucially, the precise dynamics of frequencies and phases across a wide range of stimulus conditions was predicted from a physics theory that describes how weakly coupled oscillators influence each other’s phase relations. Hence, the fundamental mathematical principle of synchronization through instantaneous frequency modulations applies to gamma in V1 and is likely generalizable to other brain regions and rhythms. PMID:28857743

Assessing cortical synchronization during transcranial direct current stimulation: A graph-theoretical analysis.

PubMed

Mancini, Matteo; Brignani, Debora; Conforto, Silvia; Mauri, Piercarlo; Miniussi, Carlo; Pellicciari, Maria Concetta

2016-10-15

Transcranial direct current stimulation (tDCS) is a neuromodulation technique that can alter cortical excitability and modulate behaviour in a polarity-dependent way. Despite the widespread use of this method in the neuroscience field, its effects on ongoing local or global (network level) neuronal activity are still not foreseeable. A way to shed light on the neuronal mechanisms underlying the cortical connectivity changes induced by tDCS is provided by the combination of tDCS with electroencephalography (EEG). In this study, twelve healthy subjects underwent online tDCS-EEG recording (i.e., simultaneous), during resting-state, using 19 EEG channels. The protocol involved anodal, cathodal and sham stimulation conditions, with the active and the reference electrodes in the left frontocentral area (FC3) and on the forehead over the right eyebrow, respectively. The data were processed using a network model, based on graph theory and the synchronization likelihood. The resulting graphs were analysed for four frequency bands (theta, alpha, beta and gamma) to evaluate the presence of tDCS-induced differences in synchronization patterns and graph theory measures. The resting state network connectivity resulted altered during tDCS, in a polarity-specific manner for theta and alpha bands. Anodal tDCS weakened synchronization with respect to the baseline over the fronto-central areas in the left hemisphere, for theta band (p<0.05). In contrast, during cathodal tDCS a significant increase in inter-hemispheric synchronization connectivity was observed over the centro-parietal, centro-occipital and parieto-occipital areas for the alpha band (p<0.05). Local graph measures showed a tDCS-induced polarity-specific differences that regarded modifications of network activities rather than specific region properties. Our results show that applying tDCS during the resting state modulates local synchronization as well as network properties in slow frequency bands, in a polarity-specific manner. Copyright © 2016 Elsevier Inc. All rights reserved.

Current Trend Towards Using Soft Computing Approaches to Phase Synchronization in Communication Systems

NASA Technical Reports Server (NTRS)

Drake, Jeffrey T.; Prasad, Nadipuram R.

1999-01-01

This paper surveys recent advances in communications that utilize soft computing approaches to phase synchronization. Soft computing, as opposed to hard computing, is a collection of complementary methodologies that act in producing the most desirable control, decision, or estimation strategies. Recently, the communications area has explored the use of the principal constituents of soft computing, namely, fuzzy logic, neural networks, and genetic algorithms, for modeling, control, and most recently for the estimation of phase in phase-coherent communications. If the receiver in a digital communications system is phase-coherent, as is often the case, phase synchronization is required. Synchronization thus requires estimation and/or control at the receiver of an unknown or random phase offset.

Digital data detection and synchronization

NASA Technical Reports Server (NTRS)

Noack, T. L.; Morris, J. F.

1973-01-01

The primary accomplishments have been in the analysis and simulation of receivers and bit synchronizers. It has been discovered that tracking rate effects play, a rather fundamental role in both receiver and synchronizer performance, but that data relating to recorder time-base-error, for the proper characterization of this phenomenon, is in rather short supply. It is possible to obtain operationally useful tape recorder time-base-error data from high signal-to-noise ratio tapes using synchronizers with relatively wideband tracking loops. Low signal-to-noise ratio tapes examined in the same way would not be synchronizable. Additional areas of interest covered are receiver false lock, cycle slipping, and other unusual phenomena, which have been described to some extent in this and earlier reports and simulated during the study.

Data-Gathering Scheme Using AUVs in Large-Scale Underwater Sensor Networks: A Multihop Approach

PubMed Central

Khan, Jawaad Ullah; Cho, Ho-Shin

2016-01-01

In this paper, we propose a data-gathering scheme for hierarchical underwater sensor networks, where multiple Autonomous Underwater Vehicles (AUVs) are deployed over large-scale coverage areas. The deployed AUVs constitute an intermittently connected multihop network through inter-AUV synchronization (in this paper, synchronization means an interconnection between nodes for communication) for forwarding data to the designated sink. In such a scenario, the performance of the multihop communication depends upon the synchronization among the vehicles. The mobility parameters of the vehicles vary continuously because of the constantly changing underwater currents. The variations in the AUV mobility parameters reduce the inter-AUV synchronization frequency contributing to delays in the multihop communication. The proposed scheme improves the AUV synchronization frequency by permitting neighboring AUVs to share their status information via a pre-selected node called an agent-node at the static layer of the network. We evaluate the proposed scheme in terms of the AUV synchronization frequency, vertical delay (node→AUV), horizontal delay (AUV→AUV), end-to-end delay, and the packet loss ratio. Simulation results show that the proposed scheme significantly reduces the aforementioned delays without the synchronization time-out process employed in conventional works. PMID:27706042

Data-Gathering Scheme Using AUVs in Large-Scale Underwater Sensor Networks: A Multihop Approach.

PubMed

Khan, Jawaad Ullah; Cho, Ho-Shin

2016-09-30

In this paper, we propose a data-gathering scheme for hierarchical underwater sensor networks, where multiple Autonomous Underwater Vehicles (AUVs) are deployed over large-scale coverage areas. The deployed AUVs constitute an intermittently connected multihop network through inter-AUV synchronization (in this paper, synchronization means an interconnection between nodes for communication) for forwarding data to the designated sink. In such a scenario, the performance of the multihop communication depends upon the synchronization among the vehicles. The mobility parameters of the vehicles vary continuously because of the constantly changing underwater currents. The variations in the AUV mobility parameters reduce the inter-AUV synchronization frequency contributing to delays in the multihop communication. The proposed scheme improves the AUV synchronization frequency by permitting neighboring AUVs to share their status information via a pre-selected node called an agent-node at the static layer of the network. We evaluate the proposed scheme in terms of the AUV synchronization frequency, vertical delay (node→AUV), horizontal delay (AUV→AUV), end-to-end delay, and the packet loss ratio. Simulation results show that the proposed scheme significantly reduces the aforementioned delays without the synchronization time-out process employed in conventional works.

Mapping the Information Trace in Local Field Potentials by a Computational Method of Two-Dimensional Time-Shifting Synchronization Likelihood Based on Graphic Processing Unit Acceleration.

PubMed

Zhao, Zi-Fang; Li, Xue-Zhu; Wan, You

2017-12-01

The local field potential (LFP) is a signal reflecting the electrical activity of neurons surrounding the electrode tip. Synchronization between LFP signals provides important details about how neural networks are organized. Synchronization between two distant brain regions is hard to detect using linear synchronization algorithms like correlation and coherence. Synchronization likelihood (SL) is a non-linear synchronization-detecting algorithm widely used in studies of neural signals from two distant brain areas. One drawback of non-linear algorithms is the heavy computational burden. In the present study, we proposed a graphic processing unit (GPU)-accelerated implementation of an SL algorithm with optional 2-dimensional time-shifting. We tested the algorithm with both artificial data and raw LFP data. The results showed that this method revealed detailed information from original data with the synchronization values of two temporal axes, delay time and onset time, and thus can be used to reconstruct the temporal structure of a neural network. Our results suggest that this GPU-accelerated method can be extended to other algorithms for processing time-series signals (like EEG and fMRI) using similar recording techniques.

Rheological characterization of composites using a vertical oscillation rheometer.

PubMed

Lee, In Bog; Cho, Byeong Hoon; Son, Ho Hyun; Um, Chung Moon

2007-04-01

The purpose of this study was to investigate the viscoelastic properties related to the handling characteristics of composites. A custom-designed vertical oscillation rheometer (VOR) was used for the rheological measurements of composites. The VOR consists of three parts: (1) a measuring unit, (2) a deformation induction unit, and (3) a force-detecting unit. Two medium-viscous composites, Z100 and Z250, and two packable composites, P60 and SureFil, were tested. A dynamic oscillatory test was used to evaluate the storage modulus (E'), loss modulus (E''), and loss tangent (tan delta) of the composites as a function of frequency (omega) from 0.1 to 20Hz at 23 degrees C. The E' and E'' increased with increasing frequency and showed differences in magnitude among brands. The complex moduli E* of the composites at omega=2 Hz, normalized to that of Z100, were 2.16 (Z250), 4.80 (P60), and 25.21 (SureFil). The magnitudes and frequency characteristic of loss tangent differed significantly among brands. The relationship among the complex modulus E*, the phase angle delta, and the frequency omega was represented by the frequency domain phasor form E*(omega)e(idelta)=E*(omega) angledelta. The viscoelasticities of composites, which influence handling characteristics, are significantly different among brands. The VOR is a relatively simple device for the dynamic rheological measurement of dental composites. The loci of the frequency domain phasor plots in a complex plane are a valuable method of representing the viscoelastic properties of composites.

Phasor Fluorescence Lifetime Microscopy of Free and Protein-Bound NADH Reveals Neural Stem Cell Differentiation Potential

PubMed Central

Stringari, Chiara; Nourse, Jamison L.; Flanagan, Lisa A.; Gratton, Enrico

2012-01-01

In the stem cell field there is a lack of non invasive and fast methods to identify stem cell’s metabolic state, differentiation state and cell-lineage commitment. Here we describe a label-free method that uses NADH as an intrinsic biomarker and the Phasor approach to Fluorescence Lifetime microscopy to measure the metabolic fingerprint of cells. We show that different metabolic states are related to different cell differentiation stages and to stem cell bias to neuronal and glial fate, prior the expression of lineage markers. Our data demonstrate that the NADH FLIM signature distinguishes non-invasively neurons from undifferentiated neural progenitor and stem cells (NPSCs) at two different developmental stages (E12 and E16). NPSCs follow a metabolic trajectory from a glycolytic phenotype to an oxidative phosphorylation phenotype through different stages of differentiation. NSPCs are characterized by high free/bound NADH ratio, while differentiated neurons are characterized by low free/bound NADH ratio. We demonstrate that the metabolic signature of NPSCs correlates with their differentiation potential, showing that neuronal progenitors and glial progenitors have a different free/bound NADH ratio. Reducing conditions in NPSCs correlates with their neurogenic potential, while oxidative conditions correlate with glial potential. For the first time we show that FLIM NADH metabolic fingerprint provides a novel, and quantitative measure of stem cell potential and a label-free and non-invasive means to identify neuron- or glial- biased progenitors. PMID:23144844

Current Controller for Multi-level Front-end Converter and Its Digital Implementation Considerations on Three-level Flying Capacitor Topology

NASA Astrophysics Data System (ADS)

Tekwani, P. N.; Shah, M. T.

2017-10-01

This paper presents behaviour analysis and digital implementation of current error space phasor based hysteresis controller applied to three-phase three-level flying capacitor converter as front-end topology. The controller is self-adaptive in nature, and takes the converter from three-level to two-level mode of operation and vice versa, following various trajectories of sector change with the change in reference dc-link voltage demanded by the load. It keeps current error space phasor within the prescribed hexagonal boundary. During the contingencies, the proposed controller takes the converter in over modulation mode to meet the load demand, and once the need is satisfied, controller brings back the converter in normal operating range. Simulation results are presented to validate behaviour of controller to meet the said contingencies. Unity power factor is assured by proposed controller with low current harmonic distortion satisfying limits prescribed in IEEE 519-2014. Proposed controller is implemented using TMS320LF2407 16-bit fixed-point digital signal processor. Detailed analysis of numerical format to avoid overflow of sensed variables in processor, and per-unit model implementation in software are discussed and hardware results are presented at various stages of signal conditioning to validate the experimental setup. Control logic for the generation of reference currents is implemented in TMS320LF2407A using assembly language and experimental results are also presented for the same.

[The comparative analysis of changes of short pieces of EEG at perception of music on the basis of the event-related synchronization/desynchronization and wavelet-synchrony].

PubMed

Oknina, L B; Kuptsova, S V; Romanov, A S; Masherov, E L; Kuznetsova, O A; Sharova, E V

2012-01-01

The going of present pilot study is an analysis of features changes of EEG short pieces registered from 32 sites, at perception of musical melodies healthy examinees depending on logic (cognizance) and emotional (it was pleasant it was not pleasant) melody estimations. For this purpose changes of event-related synchronization/desynchronization, and also wavelet-synchrony of EEG-responses at 31 healthy examinees at the age from 18 till 60 years were compared. It is shown that at a logic estimation of music the melody cognizance is accompanied the event-related desynchronization in the left fronto-parietal-temporal area. At an emotional estimation of a melody the event-related synchronization in left fronto - temporal area for the pleasant melodies, desynchronization in temporal area for not pleasant and desynchronization in occipital area for the melodies which are not causing the emotional response is typical. At the analysis of wavelet-synchrony of EEG characterizing jet changes of interaction of cortical zones, it is revealed that the most distinct topographical distinctions concern type of processing of the heard music: logic (has learned-hasn't learned) or emotional (it was pleasant-it was not pleasant). If at an emotional estimation changes interhemispheric communications between associative cortical zones (central, frontal, temporal), are more expressed at logic - between inter - and intrahemispheric communications of projective zones of the acoustic analyzer (temporal area). It is supposed that the revealed event-related synchronization/desynhronization reflects, most likely, an activation component of an estimation of musical fragments whereas the wavelet-analysis provides guidance on character of processing of musical stimulus.

Intersubject synchronization of cortical activity during natural vision.

PubMed

Hasson, Uri; Nir, Yuval; Levy, Ifat; Fuhrmann, Galit; Malach, Rafael

2004-03-12

To what extent do all brains work alike during natural conditions? We explored this question by letting five subjects freely view half an hour of a popular movie while undergoing functional brain imaging. Applying an unbiased analysis in which spatiotemporal activity patterns in one brain were used to "model" activity in another brain, we found a striking level of voxel-by-voxel synchronization between individuals, not only in primary and secondary visual and auditory areas but also in association cortices. The results reveal a surprising tendency of individual brains to "tick collectively" during natural vision. The intersubject synchronization consisted of a widespread cortical activation pattern correlated with emotionally arousing scenes and regionally selective components. The characteristics of these activations were revealed with the use of an open-ended "reverse-correlation" approach, which inverts the conventional analysis by letting the brain signals themselves "pick up" the optimal stimuli for each specialized cortical area.

Transcranial magnetic stimulation-induced global propagation of transient phase resetting associated with directional information flow.

PubMed

Kawasaki, Masahiro; Uno, Yutaka; Mori, Jumpei; Kobata, Kenji; Kitajo, Keiichi

2014-01-01

Electroencephalogram (EEG) phase synchronization analyses can reveal large-scale communication between distant brain areas. However, it is not possible to identify the directional information flow between distant areas using conventional phase synchronization analyses. In the present study, we applied transcranial magnetic stimulation (TMS) to the occipital area in subjects who were resting with their eyes closed, and analyzed the spatial propagation of transient TMS-induced phase resetting by using the transfer entropy (TE), to quantify the causal and directional flow of information. The time-frequency EEG analysis indicated that the theta (5 Hz) phase locking factor (PLF) reached its highest value at the distant area (the motor area in this study), with a time lag that followed the peak of the transient PLF enhancements of the TMS-targeted area at the TMS onset. Phase-preservation index (PPI) analyses demonstrated significant phase resetting at the TMS-targeted area and distant area. Moreover, the TE from the TMS-targeted area to the distant area increased clearly during the delay that followed TMS onset. Interestingly, the time lags were almost coincident between the PLF and TE results (152 vs. 165 ms), which provides strong evidence that the emergence of the delayed PLF reflects the causal information flow. Such tendencies were observed only in the higher-intensity TMS condition, and not in the lower-intensity or sham TMS conditions. Thus, TMS may manipulate large-scale causal relationships between brain areas in an intensity-dependent manner. We demonstrated that single-pulse TMS modulated global phase dynamics and directional information flow among synchronized brain networks. Therefore, our results suggest that single-pulse TMS can manipulate both incoming and outgoing information in the TMS-targeted area associated with functional changes.

Synchronous activity in cat visual cortex encodes collinear and cocircular contours.

PubMed

Samonds, Jason M; Zhou, Zhiyi; Bernard, Melanie R; Bonds, A B

2006-04-01

We explored how contour information in primary visual cortex might be embedded in the simultaneous activity of multiple cells recorded with a 100-electrode array. Synchronous activity in cat visual cortex was more selective and predictable in discriminating between drifting grating and concentric ring stimuli than changes in firing rate. Synchrony was found even between cells with wholly different orientation preferences when their receptive fields were circularly aligned, and membership in synchronous groups was orientation and curvature dependent. The existence of synchrony between cocircular cells reinforces its role as a general mechanism for contour integration and shape detection as predicted by association field concepts. Our data suggest that cortical synchrony results from common and synchronous input from earlier visual areas and that it could serve to shape extrastriate response selectivity.

Oral Communication Skills Assessment in a Synchronous Hybrid MBA Programme: Does Attending Face-to-Face Matter for US and International Students?

ERIC Educational Resources Information Center

Butz, Nikolaus T.; Askim-Lovseth, Mary K.

2015-01-01

The ability to communicate effectively is an essential skill for graduates of Masters of Business Administration (MBA) programmes; however, as synchronous hybrid learning becomes more common, business schools may find it challenging to assess students' proficiency in this core area. An additional layer of complexity is added by the burgeoning…

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Synchronization in Complex Networks with Multiple Connections

NASA Astrophysics Data System (ADS)

Wu, Qing-Chu; Fu, Xin-Chu; Sun, Wei-Gang

2010-01-01

In this paper a class of networks with multiple connections are discussed. The multiple connections include two different types of links between nodes in complex networks. For this new model, we give a simple generating procedure. Furthermore, we investigate dynamical synchronization behavior in a delayed two-layer network, giving corresponding theoretical analysis and numerical examples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eto, Joseph H.; Stewart, Emma M.; Smith, Travis

This report addresses the potential use of phasor measurement units (PMUs) within electricity distribution systems, and was written to assess whether or not PMUs could provide significant benefit, at the national level. We analyze examples of present and emerging distribution-system issues related to reliability, integration of distributed energy resources, and the changing electrical characteristics of load. We find that PMUs offer important and irreplaceable advantages over present approaches. However, we also find that additional research and development for standards, testing and calibration, demonstration projects, and information sharing is needed to help industry capture these benefits.

Adaptive Energy Forecasting and Information Diffusion for Smart Power Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simmhan, Yogesh; Agarwal, Vaibhav; Aman, Saim

2012-05-16

Smart Power Grids exemplify an emerging class of Cyber Physical Applications that exhibit dynamic, distributed and data intensive (D3) characteristics along with an always-on paradigm to support operational needs. Smart Grids are an outcome of instrumentation, such as Phasor Measurement Units and Smart Power Meters, that is being deployed across the transmission and distribution network of electric grids. These sensors provide utilities with improved situation awareness on near-realtime electricity usage by individual consumers, and the power quality and stability of the transmission network.

Localization of synchronous cortical neural sources.

PubMed

Zerouali, Younes; Herry, Christophe L; Jemel, Boutheina; Lina, Jean-Marc

2013-03-01

Neural synchronization is a key mechanism to a wide variety of brain functions, such as cognition, perception, or memory. High temporal resolution achieved by EEG recordings allows the study of the dynamical properties of synchronous patterns of activity at a very fine temporal scale but with very low spatial resolution. Spatial resolution can be improved by retrieving the neural sources of EEG signal, thus solving the so-called inverse problem. Although many methods have been proposed to solve the inverse problem and localize brain activity, few of them target the synchronous brain regions. In this paper, we propose a novel algorithm aimed at localizing specifically synchronous brain regions and reconstructing the time course of their activity. Using multivariate wavelet ridge analysis, we extract signals capturing the synchronous events buried in the EEG and then solve the inverse problem on these signals. Using simulated data, we compare results of source reconstruction accuracy achieved by our method to a standard source reconstruction approach. We show that the proposed method performs better across a wide range of noise levels and source configurations. In addition, we applied our method on real dataset and identified successfully cortical areas involved in the functional network underlying visual face perception. We conclude that the proposed approach allows an accurate localization of synchronous brain regions and a robust estimation of their activity.

Cross-frequency synchronization connects networks of fast and slow oscillations during visual working memory maintenance.

PubMed

Siebenhühner, Felix; Wang, Sheng H; Palva, J Matias; Palva, Satu

2016-09-26

Neuronal activity in sensory and fronto-parietal (FP) areas underlies the representation and attentional control, respectively, of sensory information maintained in visual working memory (VWM). Within these regions, beta/gamma phase-synchronization supports the integration of sensory functions, while synchronization in theta/alpha bands supports the regulation of attentional functions. A key challenge is to understand which mechanisms integrate neuronal processing across these distinct frequencies and thereby the sensory and attentional functions. We investigated whether such integration could be achieved by cross-frequency phase synchrony (CFS). Using concurrent magneto- and electroencephalography, we found that CFS was load-dependently enhanced between theta and alpha-gamma and between alpha and beta-gamma oscillations during VWM maintenance among visual, FP, and dorsal attention (DA) systems. CFS also connected the hubs of within-frequency-synchronized networks and its strength predicted individual VWM capacity. We propose that CFS integrates processing among synchronized neuronal networks from theta to gamma frequencies to link sensory and attentional functions.

Finding the beat: a neural perspective across humans and non-human primates.

PubMed

Merchant, Hugo; Grahn, Jessica; Trainor, Laurel; Rohrmeier, Martin; Fitch, W Tecumseh

2015-03-19

Humans possess an ability to perceive and synchronize movements to the beat in music ('beat perception and synchronization'), and recent neuroscientific data have offered new insights into this beat-finding capacity at multiple neural levels. Here, we review and compare behavioural and neural data on temporal and sequential processing during beat perception and entrainment tasks in macaques (including direct neural recording and local field potential (LFP)) and humans (including fMRI, EEG and MEG). These abilities rest upon a distributed set of circuits that include the motor cortico-basal-ganglia-thalamo-cortical (mCBGT) circuit, where the supplementary motor cortex (SMA) and the putamen are critical cortical and subcortical nodes, respectively. In addition, a cortical loop between motor and auditory areas, connected through delta and beta oscillatory activity, is deeply involved in these behaviours, with motor regions providing the predictive timing needed for the perception of, and entrainment to, musical rhythms. The neural discharge rate and the LFP oscillatory activity in the gamma- and beta-bands in the putamen and SMA of monkeys are tuned to the duration of intervals produced during a beat synchronization-continuation task (SCT). Hence, the tempo during beat synchronization is represented by different interval-tuned cells that are activated depending on the produced interval. In addition, cells in these areas are tuned to the serial-order elements of the SCT. Thus, the underpinnings of beat synchronization are intrinsically linked to the dynamics of cell populations tuned for duration and serial order throughout the mCBGT. We suggest that a cross-species comparison of behaviours and the neural circuits supporting them sets the stage for a new generation of neurally grounded computational models for beat perception and synchronization. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Cholinergic modulation of event-related oscillations (ERO)

PubMed Central

Sanchez-Alavez, Manuel; Robledo, Patricia; Wills, Derek N.; Havstad, James; Ehlers, Cindy L.

2014-01-01

The cholinergic system in the brain modulates patterns of activity involved in general arousal, attention processing, memory and consciousness. In the present study we determined the effects of selective cholinergic lesions of the medial septum area (MS) or nucleus basalis magnocellularis (NBM) on amplitude and phase characteristics of event related oscillations (EROs). A time–frequency based representation was used to determine ERO energy, phase synchronization across trials, recorded within a structure (phase lock index, PLI), and phase synchronization across trials, recorded between brain structures (phase difference lock index, PDLI), in the frontal cortex (Fctx), dorsal hippocampus (DHPC) and central amygdala (Amyg). Lesions in MS produced: (1) decreases in ERO energy in delta, theta, alpha, beta and gamma frequencies in Amyg, (2) reductions in gamma ERO energy and PLI in Fctx, (3) decreases in PDLI between the Fctx–Amyg in the theta, alpha, beta and gamma frequencies, and (4) decreases in PDLI between the DHPC–Amyg and Fctx–DHPC in the theta frequency bands. Lesions in NBM resulted in: (1) increased ERO energy in delta and theta frequency bands in Fctx, (2) reduced gamma ERO energy in Fctx and Amyg, (3) reductions in PLI in the theta, beta and gamma frequency ranges in Fctx, (4) reductions in gamma PLI in DHPC and (5) reduced beta PLI in Amyg. These studies suggest that the MS cholinergic system can alter phase synchronization between brain areas whereas the NBM cholinergic system modifies phase synchronization/phase resetting within a brain area. PMID:24594019

The Effect of Task Planning on L2 Performance and L2 Development in Text-Based Synchronous Computer-Mediated Communication

ERIC Educational Resources Information Center

Hsu, Hsiu-Chen

2017-01-01

This study explored the effect of two planning conditions [the simultaneous use of rehearsal and careful online planning (ROP), and the careful online planning alone (OP)] on L2 production complexity and accuracy and the subsequent development of these two linguistic areas in the context of text-based synchronous computer-mediated communication.…

A Novel Group Coordination Protocol for Collaborative Multimedia Systems

DTIC Science & Technology

1998-01-01

technology have advanced considerably, ef- ficient group coordination support for applications characterized by synchronous and wide-area groupwork is...As a component within a general coordination architecture for many-to-many groupwork , floor control coexists with proto- cols for reliable ordered...multicast and media synchronization at a sub-application level. Orchestration of multiparty groupwork with fine-grained and fair floor control is an

Next generation information communication infrastructure and case studies for future power systems

NASA Astrophysics Data System (ADS)

Qiu, Bin

As power industry enters the new century, powerful driving forces, uncertainties and new functions are compelling electric utilities to make dramatic changes in their information communication infrastructure. Expanding network services such as real time measurement and monitoring are also driving the need for more bandwidth in the communication network. These needs will grow further as new remote real-time protection and control applications become more feasible and pervasive. This dissertation addresses two main issues for the future power system information infrastructure: communication network infrastructure and associated power system applications. Optical networks no doubt will become the predominant data transmission media for next generation power system communication. The rapid development of fiber optic network technology poses new challenges in the areas of topology design, network management and real time applications. Based on advanced fiber optic technologies, an all-fiber network is investigated and proposed. The study will cover the system architecture and data exchange protocol aspects. High bandwidth, robust optical networks could provide great opportunities to the power system for better service and efficient operation. In the dissertation, different applications are investigated. One of the typical applications is the SCADA information accessing system. An Internet-based application for the substation automation system will be presented. VLSI (Very Large Scale Integration) technology is also used for one-line diagrams auto-generation. High transition rate and low latency optical network is especially suitable for power system real time control. In the dissertation, a new local area network based Load Shedding Controller (LSC) for isolated power system will be presented. By using PMU (Phasor Measurement Unit) and fiber optic network, an AGE (Area Generation Error) based accurate wide area load shedding scheme will also be proposed. The objective is to shed the load in the limited area with minimum disturbance.

Increased overall cortical connectivity with syndrome specific local decreases suggested by atypical sleep-EEG synchronization in Williams syndrome.

PubMed

Gombos, Ferenc; Bódizs, Róbert; Kovács, Ilona

2017-07-21

Williams syndrome (7q11.23 microdeletion) is characterized by specific alterations in neurocognitive architecture and functioning, as well as disordered sleep. Here we analyze the region, sleep state and frequency-specific EEG synchronization of whole night sleep recordings of 21 Williams syndrome and 21 typically developing age- and gender-matched subjects by calculating weighted phase lag indexes. We found broadband increases in inter- and intrahemispheric neural connectivity for both NREM and REM sleep EEG of Williams syndrome subjects. These effects consisted of increased theta, high sigma, and beta/low gamma synchronization, whereas alpha synchronization was characterized by a peculiar Williams syndrome-specific decrease during NREM states (intra- and interhemispheric centro-temporal) and REM phases of sleep (occipital intra-area synchronization). We also found a decrease in short range, occipital connectivity of NREM sleep EEG theta activity. The striking increased overall synchronization of sleep EEG in Williams syndrome subjects is consistent with the recently reported increase in synaptic and dendritic density in stem-cell based Williams syndrome models, whereas decreased alpha and occipital connectivity might reflect and underpin the altered microarchitecture of primary visual cortex and disordered visuospatial functioning of Williams syndrome subjects.

Saccade-synchronized rapid attention shifts in macaque visual cortical area MT.

PubMed

Yao, Tao; Treue, Stefan; Krishna, B Suresh

2018-03-06

While making saccadic eye-movements to scan a visual scene, humans and monkeys are able to keep track of relevant visual stimuli by maintaining spatial attention on them. This ability requires a shift of attentional modulation from the neuronal population representing the relevant stimulus pre-saccadically to the one representing it post-saccadically. For optimal performance, this trans-saccadic attention shift should be rapid and saccade-synchronized. Whether this is so is not known. We trained two rhesus monkeys to make saccades while maintaining covert attention at a fixed spatial location. We show that the trans-saccadic attention shift in cortical visual medial temporal (MT) area is well synchronized to saccades. Attentional modulation crosses over from the pre-saccadic to the post-saccadic neuronal representation by about 50 ms after a saccade. Taking response latency into account, the trans-saccadic attention shift is well timed to maintain spatial attention on relevant stimuli, so that they can be optimally tracked and processed across saccades.

Nutrition for synchronized swimming: a review.

PubMed

Lundy, Bronwen

2011-10-01

Synchronized swimming enjoys worldwide popularity and has been part of the formal Olympic program since 1984. Despite this, relatively little research has been conducted on participant nutrition practices and requirements, and there are significant gaps in the knowledge base despite the numerous areas in which nutrition could affect performance and safety. This review aimed to summarize current findings and identify areas requiring further research. Uniform physique in team or duet events may be more important than absolute values for muscularity or body fat, but a lean and athletic appearance remains key. Synchronized swimmers appear to have an increased risk of developing eating disorders, and there is evidence of delayed menarche, menstrual dysfunction, and lower bone density relative to population norms. Dietary practices remain relatively unknown, but micronutrient status for iron and magnesium may be compromised. More research is required across all aspects of nutrition status, anthropometry, and physiology, and both sports nutrition and sports medicine support may be required to reduce risks for participants.

Target-oriented imaging of hydraulic fractures by applying the staining algorithm for downhole microseismic migration

NASA Astrophysics Data System (ADS)

Lin, Ye; Zhang, Haijiang; Jia, Xiaofeng

2018-03-01

For microseismic monitoring of hydraulic fracturing, microseismic migration can be used to image the fracture network with scattered microseismic waves. Compared with conventional microseismic location-based fracture characterization methods, microseismic migration can better constrain the stimulated reservoir volume regardless of the completeness of detected and located microseismic sources. However, the imaging results from microseismic migration may suffer from the contamination of other structures and thus the target fracture zones may not be illuminated properly. To solve this issue, in this study we propose a target-oriented staining algorithm for microseismic reverse-time migration. In the staining algorithm, the target area is first stained by constructing an imaginary velocity field and then a synchronized source wavefield only concerning the target structure is produced. As a result, a synchronized image from imaging with the synchronized source wavefield mainly contains the target structures. Synthetic tests based on a downhole microseismic monitoring system show that the target-oriented microseismic reverse-time migration method improves the illumination of target areas.

High-alpha band synchronization across frontal, parietal and visual cortex mediates behavioral and neuronal effects of visuospatial attention.

PubMed

Lobier, Muriel; Palva, J Matias; Palva, Satu

2018-01-15

Visuospatial attention prioritizes processing of attended visual stimuli. It is characterized by lateralized alpha-band (8-14 Hz) amplitude suppression in visual cortex and increased neuronal activity in a network of frontal and parietal areas. It has remained unknown what mechanisms coordinate neuronal processing among frontoparietal network and visual cortices and implement the attention-related modulations of alpha-band amplitudes and behavior. We investigated whether large-scale network synchronization could be such a mechanism. We recorded human cortical activity with magnetoencephalography (MEG) during a visuospatial attention task. We then identified the frequencies and anatomical networks of inter-areal phase synchronization from source localized MEG data. We found that visuospatial attention is associated with robust and sustained long-range synchronization of cortical oscillations exclusively in the high-alpha (10-14 Hz) frequency band. This synchronization connected frontal, parietal and visual regions and was observed concurrently with amplitude suppression of low-alpha (6-9 Hz) band oscillations in visual cortex. Furthermore, stronger high-alpha phase synchronization was associated with decreased reaction times to attended stimuli and larger suppression of alpha-band amplitudes. These results thus show that high-alpha band phase synchronization is functionally significant and could coordinate the neuronal communication underlying the implementation of visuospatial attention. Copyright © 2017 Elsevier Inc. All rights reserved.

Role of the dorsal premotor cortex in rhythmic auditory-motor entrainment: a perturbational approach by rTMS.

PubMed

Giovannelli, Fabio; Innocenti, Iglis; Rossi, Simone; Borgheresi, Alessandra; Ragazzoni, Aldo; Zaccara, Gaetano; Viggiano, Maria Pia; Cincotta, Massimo

2014-04-01

Synchronization of body movements to an external beat is a universal human ability, which has also been recently documented in nonhuman species. The neural substrates of this rhythmic motor entrainment are still under investigation. Correlational neuroimaging data suggest an involvement of the dorsal premotor cortex (dPMC) and the supplementary motor area (SMA). In 14 healthy volunteers, we more specifically investigated the neural network underlying this phenomenon using a causal approach by an established 1-Hz repetitive transcranial magnetic stimulation (rTMS) protocol, which produces a focal suppression of cortical excitability outlasting the stimulation period. Synchronization accuracy between rhythmic cues and right index finger tapping, as measured by the mean time lag (asynchrony) between motor and auditory events, was significantly affected when the right dPMC function was transiently perturbed by "off-line" focal rTMS, whereas the reproduction of the rhythmic sequence per se (inter-tap-interval) was spared. This approach affected metrical rhythms of different complexity, but not non-metrical or isochronous sequences. Conversely, no change in auditory-motor synchronization was observed with rTMS of the SMA, of the left dPMC or over a control site (midline occipital area). Our data strongly support the view that the right dPMC is crucial for rhythmic auditory-motor synchronization in humans.

Arrester Resistive Current Measuring System Based on Heterogeneous Network

NASA Astrophysics Data System (ADS)

Zhang, Yun Hua; Li, Zai Lin; Yuan, Feng; Hou Pan, Feng; Guo, Zhan Nan; Han, Yue

2018-03-01

Metal Oxide Arrester (MOA) suffers from aging and poor insulation due to long-term impulse voltage and environmental impact, and the value and variation tendency of resistive current can reflect the health conditions of MOA. The common wired MOA detection need to use long cables, which is complicated to operate, and that wireless measurement methods are facing the problems of poor data synchronization and instability. Therefore a novel synchronous measurement system of arrester current resistive based on heterogeneous network is proposed, which simplifies the calculation process and improves synchronization, accuracy and stability and of the measuring system. This system combines LoRa wireless network, high speed wireless personal area network and the process layer communication, and realizes the detection of arrester working condition. Field test data shows that the system has the characteristics of high accuracy, strong anti-interference ability and good synchronization, which plays an important role in ensuring the stable operation of the power grid.

Automatic exposure for panoramic systems in uncontrolled lighting conditions: a football stadium case study

NASA Astrophysics Data System (ADS)

Gaddam, Vamsidhar Reddy; Griwodz, Carsten; Halvorsen, Pâl.

2014-02-01

One of the most common ways of capturing wide eld-of-view scenes is by recording panoramic videos. Using an array of cameras with limited overlapping in the corresponding images, one can generate good panorama images. Using the panorama, several immersive display options can be explored. There is a two fold synchronization problem associated to such a system. One is the temporal synchronization, but this challenge can easily be handled by using a common triggering solution to control the shutters of the cameras. The other synchronization challenge is the automatic exposure synchronization which does not have a straight forward solution, especially in a wide area scenario where the light conditions are uncontrolled like in the case of an open, outdoor football stadium. In this paper, we present the challenges and approaches for creating a completely automatic real-time panoramic capture system with a particular focus on the camera settings. One of the main challenges in building such a system is that there is not one common area of the pitch that is visible to all the cameras that can be used for metering the light in order to nd appropriate camera parameters. One approach we tested is to use the green color of the eld grass. Such an approach provided us with acceptable results only in limited light conditions.A second approach was devised where the overlapping areas between adjacent cameras are exploited, thus creating pairs of perfectly matched video streams. However, there still existed some disparity between di erent pairs. We nally developed an approach where the time between two temporal frames is exploited to communicate the exposures among the cameras where we achieve a perfectly synchronized array. An analysis of the system and some experimental results are presented in this paper. In summary, a pilot-camera approach running in auto-exposure mode and then distributing the used exposure values to the other cameras seems to give best visual results.

Predictive factors of synchronous colorectal peritoneal metastases: Development of a nomogram and study of its utilities using decision curve analysis.

PubMed

Mo, Shaobo; Dai, Weixing; Xiang, Wenqiang; Li, Qingguo; Wang, Renjie; Cai, Guoxiang

2018-05-03

The objective of this study was to summarize the clinicopathological and molecular features of synchronous colorectal peritoneal metastases (CPM). We then combined clinical and pathological variables associated with synchronous CPM into a nomogram and confirmed its utilities using decision curve analysis. Synchronous metastatic colorectal cancer (mCRC) patients who received primary tumor resection and underwent KRAS, NRAS, and BRAF gene mutation detection at our center from January 2014 to September 2015 were included in this retrospective study. An analysis was performed to investigate the clinicopathological and molecular features for independent risk factors of synchronous CPM and to subsequently develop a nomogram for synchronous CPM based on multivariate logistic regression. Model performance was quantified in terms of calibration and discrimination. We studied the utility of the nomogram using decision curve analysis. In total, 226 patients were diagnosed with synchronous mCRC, of whom 50 patients (22.1%) presented with CPM. After uni- and multivariate analysis, a nomogram was built based on tumor site, histological type, age, and T4 status. The model had good discrimination with an area under the curve (AUC) at 0.777 (95% CI 0.703-0.850) and adequate calibration. By decision curve analysis, the model was shown to be relevant between thresholds of 0.10 and 0.66. Synchronous CPM is more likely to happen to patients with age ≤60, right-sided primary lesions, signet ring cell cancer or T4 stage. This is the first nomogram to predict synchronous CPM. To ensure generalizability, this model needs to be externally validated. Copyright © 2018 IJS Publishing Group Ltd. Published by Elsevier Ltd. All rights reserved.

Synchronous behaviour in network model based on human cortico-cortical connections.

PubMed

Protachevicz, Paulo Ricardo; Borges, Rafael Ribaski; Reis, Adriane da Silva; Borges, Fernando da Silva; Iarosz, Kelly Cristina; Caldas, Ibere Luiz; Lameu, Ewandson Luiz; Macau, Elbert Einstein Nehrer; Viana, Ricardo Luiz; Sokolov, Igor M; Ferrari, Fabiano A S; Kurths, Jürgen; Batista, Antonio Marcos

2018-06-22

We consider a network topology according to the cortico-cortical connec- tion network of the human brain, where each cortical area is composed of a random network of adaptive exponential integrate-and-fire neurons. Depending on the parameters, this neuron model can exhibit spike or burst patterns. As a diagnostic tool to identify spike and burst patterns we utilise the coefficient of variation of the neuronal inter-spike interval. In our neuronal network, we verify the existence of spike and burst synchronisation in different cortical areas. Our simulations show that the network arrangement, i.e., its rich-club organisation, plays an important role in the transition of the areas from desynchronous to synchronous behaviours. © 2018 Institute of Physics and Engineering in Medicine.

Memristive Mixed-Signal Neuromorphic Systems: Energy-Efficient Learning at the Circuit-Level

DOE PAGES

Chakma, Gangotree; Adnan, Md Musabbir; Wyer, Austin R.; ...

2017-11-23

Neuromorphic computing is non-von Neumann computer architecture for the post Moore’s law era of computing. Since a main focus of the post Moore’s law era is energy-efficient computing with fewer resources and less area, neuromorphic computing contributes effectively in this research. Here in this paper, we present a memristive neuromorphic system for improved power and area efficiency. Our particular mixed-signal approach implements neural networks with spiking events in a synchronous way. Moreover, the use of nano-scale memristive devices saves both area and power in the system. We also provide device-level considerations that make the system more energy-efficient. The proposed systemmore » additionally includes synchronous digital long term plasticity, an online learning methodology that helps the system train the neural networks during the operation phase and improves the efficiency in learning considering the power consumption and area overhead.« less

Memristive Mixed-Signal Neuromorphic Systems: Energy-Efficient Learning at the Circuit-Level

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakma, Gangotree; Adnan, Md Musabbir; Wyer, Austin R.

Neuromorphic computing is non-von Neumann computer architecture for the post Moore’s law era of computing. Since a main focus of the post Moore’s law era is energy-efficient computing with fewer resources and less area, neuromorphic computing contributes effectively in this research. Here in this paper, we present a memristive neuromorphic system for improved power and area efficiency. Our particular mixed-signal approach implements neural networks with spiking events in a synchronous way. Moreover, the use of nano-scale memristive devices saves both area and power in the system. We also provide device-level considerations that make the system more energy-efficient. The proposed systemmore » additionally includes synchronous digital long term plasticity, an online learning methodology that helps the system train the neural networks during the operation phase and improves the efficiency in learning considering the power consumption and area overhead.« less

Cross-frequency synchronization connects networks of fast and slow oscillations during visual working memory maintenance

PubMed Central

Siebenhühner, Felix; Wang, Sheng H; Palva, J Matias; Palva, Satu

2016-01-01

Neuronal activity in sensory and fronto-parietal (FP) areas underlies the representation and attentional control, respectively, of sensory information maintained in visual working memory (VWM). Within these regions, beta/gamma phase-synchronization supports the integration of sensory functions, while synchronization in theta/alpha bands supports the regulation of attentional functions. A key challenge is to understand which mechanisms integrate neuronal processing across these distinct frequencies and thereby the sensory and attentional functions. We investigated whether such integration could be achieved by cross-frequency phase synchrony (CFS). Using concurrent magneto- and electroencephalography, we found that CFS was load-dependently enhanced between theta and alpha–gamma and between alpha and beta-gamma oscillations during VWM maintenance among visual, FP, and dorsal attention (DA) systems. CFS also connected the hubs of within-frequency-synchronized networks and its strength predicted individual VWM capacity. We propose that CFS integrates processing among synchronized neuronal networks from theta to gamma frequencies to link sensory and attentional functions. DOI: http://dx.doi.org/10.7554/eLife.13451.001 PMID:27669146

Multiple broadly synchronous km-scale exhumation episodes on different continents: implications for controlling processes

NASA Astrophysics Data System (ADS)

Green, Paul; Duddy, Ian; Japsen, Peter

2015-04-01

Numerous low temperature thermochronology studies have defined regional cooling episodes which imply removal of several km of section over areas of several 104 km2. The origin of such events has long been the subject of debate, while their reality has sometimes been questioned because of the lack of a viable mechanism. Kilometre-scale denudation at rifted margins has traditionally been interpreted as related to rifting and breakup, magnified by the flexural response to denudation of the uplifted rift flanks. But it is now clear that at many margins the post-breakup history is more complex, with km-scale uplift and erosion commonly post-dating breakup by 10s of Myr and often affecting regions many 100s of kilometres inland of the margins (Green et al., 2013; Brown et al., 2014). Numerous examples around the world of km-scale exhumation affecting regions distant from continental margins, including cratonic regions traditionally regarded as stable over Phanerozoic time (e.g. Ault et al., 2009; Flowers & Kelley, 2011), cannot be explained by margin-related mechanisms. It has also become clear that periods of exhumation are separated by episodes of burial, defining a series of positive and negative vertical movements. Previous studies have defined a broad synchroneity of Early, Middle and Late Cenozoic exhumation events in regions from Alaska to Greenland, Norway and Svalbard (Green and Duddy, 2010). New results from SE Australia define a series of exhumation episodes ranging in time from Carboniferous to Cenozoic which are broadly synchronous with similar events previously defined in Brazil and South Africa (Green et al. 2013). While estimates of the timing of exhumation in different areas are subject to some uncertainty, data across three southern hemisphere continents show a broad synchronicity in similar fashion to the northern hemisphere examples cited above. Dynamic topography has been invoked as a possible mechanism for producing uplift, the effects of which might be magnified by the isostatic response to denudation, but until recently the vertical motions expected from this mechanism were thought to be restricted to 100s of metres while expected timescales of 100s of Myr are not consistent with observations. Braun et al. (2014) showed that movement of plates over areas of areas of mantle upwelling could produce much more rapid uplift and also much larger-scale vertical movements, but the predicted diachroneity of uplift across southern Africa differs from the apparent synchroneity across three continents described here. The processes described by Braun et al. are also specific to one location and one event. Japsen et al. (2012) suggested that broadly synchronous exhumation events on divergent continents resulted from lateral resistance to plate motion driven by forces transmitted in the asthenosphere, while Colli et al. (2014) proposed that dynamic topography caused by pressure-driven mantle flow could produce synchronous uplift (and erosion) in separate continents. Such processes appear to offer more viable mechanisms for producing broadly synchronous episodes of kilometre-scale exhumation and intervening burial in regions separated by large distances. Further geodynamic modelling is needed to develop and test likely mechanisms.

Application of Synchronous Text-Based Dialogue Systems in Mental Health Interventions: Systematic Review

PubMed Central

Milne, David N

2017-01-01

Background Synchronous written conversations (or “chats”) are becoming increasingly popular as Web-based mental health interventions. Therefore, it is of utmost importance to evaluate and summarize the quality of these interventions. Objective The aim of this study was to review the current evidence for the feasibility and effectiveness of online one-on-one mental health interventions that use text-based synchronous chat. Methods A systematic search was conducted of the databases relevant to this area of research (Medical Literature Analysis and Retrieval System Online [MEDLINE], PsycINFO, Central, Scopus, EMBASE, Web of Science, IEEE, and ACM). There were no specific selection criteria relating to the participant group. Studies were included if they reported interventions with individual text-based synchronous conversations (ie, chat or text messaging) and a psychological outcome measure. Results A total of 24 articles were included in this review. Interventions included a wide range of mental health targets (eg, anxiety, distress, depression, eating disorders, and addiction) and intervention design. Overall, compared with the waitlist (WL) condition, studies showed significant and sustained improvements in mental health outcomes following synchronous text-based intervention, and post treatment improvement equivalent but not superior to treatment as usual (TAU) (eg, face-to-face and telephone counseling). Conclusions Feasibility studies indicate substantial innovation in this area of mental health intervention with studies utilizing trained volunteers and chatbot technologies to deliver interventions. While studies of efficacy show positive post-intervention gains, further research is needed to determine whether time requirements for this mode of intervention are feasible in clinical practice. PMID:28784594

Uppermost synchronized generators of spike-wave activity are localized in limbic cortical areas in late-onset absence status epilepticus.

PubMed

Piros, Palma; Puskas, Szilvia; Emri, Miklos; Opposits, Gabor; Spisak, Tamas; Fekete, Istvan; Clemens, Bela

2014-03-01

Absence status (AS) epilepticus with generalized spike-wave pattern is frequently found in severely ill patients in whom several disease states co-exist. The cortical generators of the ictal EEG pattern and EEG functional connectivity (EEGfC) of this condition are unknown. The present study investigated the localization of the uppermost synchronized generators of spike-wave activity in AS. Seven patients with late-onset AS were investigated by EEG spectral analysis, LORETA (Low Resolution Electromagnetic Tomography) source imaging, and LSC (LORETA Source Correlation) analysis, which estimates cortico-cortical EEGfC among 23 ROIs (regions of interest) in each hemisphere. All the patients showed generalized ictal EEG activity. Maximum Z-scored spectral power was found in the 1-6 Hz and 12-14 Hz frequency bands. LORETA showed that the uppermost synchronized generators of 1-6 Hz band activity were localized in frontal and temporal cortical areas that are parts of the limbic system. For the 12-14 Hz band, abnormally synchronized generators were found in the antero-medial frontal cortex. Unlike the rather stereotyped spectral and LORETA findings, the individual EEGfC patterns were very dissimilar. The findings are discussed in the context of nonconvulsive seizure types and the role of the underlying cortical areas in late-onset AS. The diversity of the EEGfC patterns remains an enigma. Localizing the cortical generators of the EEG patterns contributes to understanding the neurophysiology of the condition. Copyright © 2013 British Epilepsy Association. Published by Elsevier Ltd. All rights reserved.

A Method for Determining Pseudo-measurement State Values for Topology Observability of State Estimation in Power Systems

NASA Astrophysics Data System (ADS)

Urano, Shoichi; Mori, Hiroyuki

This paper proposes a new technique for determining of state values in power systems. Recently, it is useful for carrying out state estimation with data of PMU (Phasor Measurement Unit). The authors have developed a method for determining state values with artificial neural network (ANN) considering topology observability in power systems. ANN has advantage to approximate nonlinear functions with high precision. The method evaluates pseudo-measurement state values of the data which are lost in power systems. The method is successfully applied to the IEEE 14-bus system.

State estimation for spacecraft power systems

NASA Technical Reports Server (NTRS)

Williamson, Susan H.; Sheble, Gerald B.

1990-01-01

A state estimator appropriate for spacecraft power systems is presented. Phasor voltage and current measurements are used to determine the system state. A weighted least squares algorithm with a multireference transmission cable model is used. Bad data are identified and resolved. Once the bad data have been identified, they are removed from the measurement set and the system state can be estimated from the remaining data. An observability analysis is performed on the remaining measurements to determine if the system state can be found from the reduced measurement set. An example of the algorithm for a sample spacecraft power system is presented.

Abnormal auditory synchronization in stuttering: A magnetoencephalographic study.

PubMed

Kikuchi, Yoshikazu; Okamoto, Tsuyoshi; Ogata, Katsuya; Hagiwara, Koichi; Umezaki, Toshiro; Kenjo, Masamutsu; Nakagawa, Takashi; Tobimatsu, Shozo

2017-02-01

In a previous magnetoencephalographic study, we showed both functional and structural reorganization of the right auditory cortex and impaired left auditory cortex function in people who stutter (PWS). In the present work, we reevaluated the same dataset to further investigate how the right and left auditory cortices interact to compensate for stuttering. We evaluated bilateral N100m latencies as well as indices of local and inter-hemispheric phase synchronization of the auditory cortices. The left N100m latency was significantly prolonged relative to the right N100m latency in PWS, while healthy control participants did not show any inter-hemispheric differences in latency. A phase-locking factor (PLF) analysis, which indicates the degree of local phase synchronization, demonstrated enhanced alpha-band synchrony in the right auditory area of PWS. A phase-locking value (PLV) analysis of inter-hemispheric synchronization demonstrated significant elevations in the beta band between the right and left auditory cortices in PWS. In addition, right PLF and PLVs were positively correlated with stuttering frequency in PWS. Taken together, our data suggest that increased right hemispheric local phase synchronization and increased inter-hemispheric phase synchronization are electrophysiological correlates of a compensatory mechanism for impaired left auditory processing in PWS. Published by Elsevier B.V.

Spontaneous, synchronous electrical activity in neonatal mouse cortical neurones

PubMed Central

Corlew, Rebekah; Bosma, Martha M; Moody, William J

2004-01-01

Spontaneous [Ca2+]i transients were measured in the mouse neocortex from embryonic day 16 (E16) to postnatal day 6 (P6). On the day of birth (P0), cortical neurones generated widespread, highly synchronous [Ca2+]i transients over large areas. On average, 52% of neurones participated in these transients, and in 20% of slices, an average of 80% participated. These transients were blocked by TTX and nifedipine, indicating that they resulted from Ca2+ influx during electrical activity, and occurred at a mean frequency of 0.91 min−1. The occurrence of this activity was highly centred at P0: at E16 and P2 an average of only 15% and 24% of neurones, respectively, participated in synchronous transients, and they occurred at much lower frequencies at both E16 and P2 than at P0. The overall frequency of [Ca2+]i transients in individual cells did not change between E16 and P2, just the degree of their synchronicity. The onset of this spontaneous, synchronous activity correlated with a large increase in Na+ current density that occurred just before P0, and its cessation with a large decrease in resting resistance that occurred just after P2. This widespread, synchronous activity may serve a variety of functions in the neonatal nervous system. PMID:15297578

A Novel Interhemispheric Interaction: Modulation of Neuronal Cooperativity in the Visual Areas

PubMed Central

Carmeli, Cristian; Lopez-Aguado, Laura; Schmidt, Kerstin E.; De Feo, Oscar; Innocenti, Giorgio M.

2007-01-01

Background The cortical representation of the visual field is split along the vertical midline, with the left and the right hemi-fields projecting to separate hemispheres. Connections between the visual areas of the two hemispheres are abundant near the representation of the visual midline. It was suggested that they re-establish the functional continuity of the visual field by controlling the dynamics of the responses in the two hemispheres. Methods/Principal Findings To understand if and how the interactions between the two hemispheres participate in processing visual stimuli, the synchronization of responses to identical or different moving gratings in the two hemi-fields were studied in anesthetized ferrets. The responses were recorded by multiple electrodes in the primary visual areas and the synchronization of local field potentials across the electrodes were analyzed with a recent method derived from dynamical system theory. Inactivating the visual areas of one hemisphere modulated the synchronization of the stimulus-driven activity in the other hemisphere. The modulation was stimulus-specific and was consistent with the fine morphology of callosal axons in particular with the spatio-temporal pattern of activity that axonal geometry can generate. Conclusions/Significance These findings describe a new kind of interaction between the cerebral hemispheres and highlight the role of axonal geometry in modulating aspects of cortical dynamics responsible for stimulus detection and/or categorization. PMID:18074012

[The treatment of cicatricial alopecia after burn with the technique of synchronously perforating and transplanting hair follicular-units].

PubMed

Wang, Ji-ping; Fan, Jin-cai; Chai, Jia-ke

2009-12-01

To study the effect of the technique of synchronously perforating and transplanting hair follicular-units in the treatment of cicatricial alopecia after burn. One hundred and sixty-six patients with 217 bald scar areas after burn were treated with above-mentioned technique from January 2002 to April 2008. Scalp strips, with conforming the necessity for grafting, were harvested from the occipital or temporal region. A series of follicular-units, each composing 1 - 3 hairs, were dissected from the strips under microscope or magnifying glass. Size-matching micro-slots were made in the scarred recipient area with 16 - 20 G needles to accept the grafts. The prepared follicular-unit was synchronously implanted into the bottom of the micro-slot as the needle being withdrawn. Patients who were not satisfactory with the density of hairs after I stage surgery underwent II stage surgery a half year later. Ten recipient areas with clear boundary in 10 patients were optionally chosen to observe the density of follicular-units and hair amount with naked eyes after I stage surgery. Survived transplanted hairs in above-mentioned 10 areas were counted to calculate hair survival rate at follow-up. Patients' postoperative satisfaction ratings were surveyed with questionnaire. In one half of the patients, treatment was finished after I stage surgery, the other one half received 2 stages of surgery. The follicular-unit density reached 15 - 25 grafts/cm(2) with 40 - 70 hairs/cm(2) after I stage surgery. All patients were followed up for over 8 months. Grafted hairs grew well in a natural way. 96.5% mean hair survival rate was observed in the 10 recipient areas. From patients who received only I stage surgery, 61 patients (73.5%) were very satisfactory and 22 patients (26.5%) satisfactory with the results. From the other half of patients, 76 patients (91.6%) were very satisfactory and 7 patients (8.4%) satisfactory with the results. The technique of perforating and transplanting follicular-unit hair synchronously is safe and effective with less surgery-induced injury and less bleeding. Hairs transplanted on cicatricial alopecia area with this technique grow well with high survival rate.

Final Technical Report: Distributed Controls for High Penetrations of Renewables

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byrne, Raymond H.; Neely, Jason C.; Rashkin, Lee J.

2015-12-01

The goal of this effort was to apply four potential control analysis/design approaches to the design of distributed grid control systems to address the impact of latency and communications uncertainty with high penetrations of photovoltaic (PV) generation. The four techniques considered were: optimal fixed structure control; Nyquist stability criterion; vector Lyapunov analysis; and Hamiltonian design methods. A reduced order model of the Western Electricity Coordinating Council (WECC) developed for the Matlab Power Systems Toolbox (PST) was employed for the study, as well as representative smaller systems (e.g., a two-area, three-area, and four-area power system). Excellent results were obtained with themore » optimal fixed structure approach, and the methodology we developed was published in a journal article. This approach is promising because it offers a method for designing optimal control systems with the feedback signals available from Phasor Measurement Unit (PMU) data as opposed to full state feedback or the design of an observer. The Nyquist approach inherently handles time delay and incorporates performance guarantees (e.g., gain and phase margin). We developed a technique that works for moderate sized systems, but the approach does not scale well to extremely large system because of computational complexity. The vector Lyapunov approach was applied to a two area model to demonstrate the utility for modeling communications uncertainty. Application to large power systems requires a method to automatically expand/contract the state space and partition the system so that communications uncertainty can be considered. The Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) design methodology was selected to investigate grid systems for energy storage requirements to support high penetration of variable or stochastic generation (such as wind and PV) and loads. This method was applied to several small system models.« less

Online support groups for young women with breast cancer: a proof-of-concept study.

PubMed

Stephen, Joanne; Rojubally, Adina; Linden, Wolfgang; Zhong, Lihong; Mackenzie, Gina; Mahmoud, Sahar; Giese-Davis, Janine

2017-07-01

This initial study examined a therapist-led, synchronous, online support group (OSG) with psycho-education (OSG + E) compared to self-help psycho-education (E). The study aims were to examine proof of concept-feasibility, acceptability, and usefulness-and to hone methods for a formal RCT. One hundred five young breast cancer survivors (<50 years) post-treatment were randomized either to OSG + E or E. OSG + E received a therapist-led 10-week synchronous online intervention. E received a self-help workbook. Assessments were at baseline, 10 weeks, and 3 months, with willing OSG + E members completing post-study interviews. Researchers used inductive analysis, generating qualitative themes for feasibility, acceptability, and usefulness. We examined trajectories for one primary and two secondary quantitative outcomes and a combined moderator to discover who preferentially benefitted from the intervention. Qualitative analyses revealed that synchronous chat was at times challenging, but minimal technical coaching, structure, set topics, and professional facilitation enabled conversations that were focused and meaningful. A combined moderator indicated that generally more women benefitted from OSG + E relative to E and particularly those women in semi-rural and rural areas. This study suggests that therapist-led synchronous OSGs are feasible, acceptable, and useful for young breast cancer survivors and that a future RCT with a larger sample size, perhaps more focused on non-urban areas, is needed to establish its effectiveness.

Effects of nuclear electromagnetic pulse (EMP) on synchronous stability of the electric power system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manweiler, R.W.

1975-11-01

The effects of a nuclear electromagnetic pulse (EMP) on the synchronous stability of the electric power transmission and distribution systems are evaluated. The various modes of coupling of EMP to the power system are briefly discussed, with particular emphasis on those perturbations affecting the synchronous stability of the transmission system. A brief review of the fundamental concepts of the stability problem is given, with a discussion of the general characteristics of transient analysis. A model is developed to represent single sets as well as repetitive sets of multiple faults on the distribution systems, as might be produced by EMP. Themore » results of many numerical stability calculations are presented to illustrate the transmission system's response from different types of perturbations. The important parameters of both multiple and repetitive faults are studied, including the dependence of the response on the size of the perturbed area, the fault density, and the effective impedance between the fault location and the transmission system. Both major load reduction and the effect of the opening of tie lines at the time of perturbation are also studied. We conclude that there is a high probability that EMP can induce perturbations on the distribution networks causing a large portion of the transmission network in the perturbed area to lose synchronism. The result would be an immediate and massive power failure. (auth)« less

Tactile stimulation and hemispheric asymmetries modulate auditory perception and neural responses in primary auditory cortex.

PubMed

Hoefer, M; Tyll, S; Kanowski, M; Brosch, M; Schoenfeld, M A; Heinze, H-J; Noesselt, T

2013-10-01

Although multisensory integration has been an important area of recent research, most studies focused on audiovisual integration. Importantly, however, the combination of audition and touch can guide our behavior as effectively which we studied here using psychophysics and functional magnetic resonance imaging (fMRI). We tested whether task-irrelevant tactile stimuli would enhance auditory detection, and whether hemispheric asymmetries would modulate these audiotactile benefits using lateralized sounds. Spatially aligned task-irrelevant tactile stimuli could occur either synchronously or asynchronously with the sounds. Auditory detection was enhanced by non-informative synchronous and asynchronous tactile stimuli, if presented on the left side. Elevated fMRI-signals to left-sided synchronous bimodal stimulation were found in primary auditory cortex (A1). Adjacent regions (planum temporale, PT) expressed enhanced BOLD-responses for synchronous and asynchronous left-sided bimodal conditions. Additional connectivity analyses seeded in right-hemispheric A1 and PT for both bimodal conditions showed enhanced connectivity with right-hemispheric thalamic, somatosensory and multisensory areas that scaled with subjects' performance. Our results indicate that functional asymmetries interact with audiotactile interplay which can be observed for left-lateralized stimulation in the right hemisphere. There, audiotactile interplay recruits a functional network of unisensory cortices, and the strength of these functional network connections is directly related to subjects' perceptual sensitivity. Copyright © 2013 Elsevier Inc. All rights reserved.

Areas V1 and V2 show microsaccade-related 3-4-Hz covariation in gamma power and frequency.

PubMed

Lowet, E; Roberts, M J; Bosman, C A; Fries, P; De Weerd, P

2016-05-01

Neuronal gamma-band synchronization (25-80 Hz) in visual cortex appears sustained and stable during prolonged visual stimulation when investigated with conventional averages across trials. However, recent studies in macaque visual cortex have used single-trial analyses to show that both power and frequency of gamma oscillations exhibit substantial moment-by-moment variation. This has raised the question of whether these apparently random variations might limit the functional role of gamma-band synchronization for neural processing. Here, we studied the moment-by-moment variation in gamma oscillation power and frequency, as well as inter-areal gamma synchronization, by simultaneously recording local field potentials in V1 and V2 of two macaque monkeys. We additionally analyzed electrocorticographic V1 data from a third monkey. Our analyses confirm that gamma-band synchronization is not stationary and sustained but undergoes moment-by-moment variations in power and frequency. However, those variations are neither random and nor a possible obstacle to neural communication. Instead, the gamma power and frequency variations are highly structured, shared between areas and shaped by a microsaccade-related 3-4-Hz theta rhythm. Our findings provide experimental support for the suggestion that cross-frequency coupling might structure and facilitate the information flow between brain regions. © 2015 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

The epidermal Ca(2+) gradient: Measurement using the phasor representation of fluorescent lifetime imaging.

PubMed

Celli, A; Sanchez, S; Behne, M; Hazlett, T; Gratton, E; Mauro, T

2010-03-03

Ionic gradients are found across a variety of tissues and organs. In this report, we apply the phasor representation of fluorescence lifetime imaging data to the quantitative study of ionic concentrations in tissues, overcoming technical problems of tissue thickness, concentration artifacts of ion-sensitive dyes, and calibration across inhomogeneous tissue. We used epidermis as a model system, as Ca(2+) gradients in this organ have been shown previously to control essential biologic processes of differentiation and formation of the epidermal permeability barrier. The approach described here allowed much better localization of Ca(2+) stores than those used in previous studies, and revealed that the bulk of free Ca(2+) measured in the epidermis comes from intracellular Ca(2+) stores such as the Golgi and the endoplasmic reticulum, with extracellular Ca(2+) making a relatively small contribution to the epidermal Ca(2+) gradient. Due to the high spatial resolution of two-photon microscopy, we were able to measure a marked heterogeneity in average calcium concentrations from cell to cell in the basal keratinocytes. This finding, not reported in previous studies, calls into question the long-held hypothesis that keratinocytes increase intracellular Ca(2+), cease proliferation, and differentiate passively in response to changes in extracellular Ca(2+). The experimental results obtained using this approach illustrate the power of the experimental and analytical techniques outlined in this report. Our approach can be used in mechanistic studies to address the formation, maintenance, and function of the epidermal Ca(2+) gradient, and it should be broadly applicable to the study of other tissues with ionic gradients. 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

All-digital duty-cycle corrector with synchronous and high accuracy output for double date rate synchronous dynamic random-access memory application

NASA Astrophysics Data System (ADS)

Tsai, Chih-Wei; Lo, Yu-Lung; Chang, Chia-Chen; Liu, Han-Ying; Yang, Wei-Bin; Cheng, Kuo-Hsing

2017-04-01

A synchronous and highly accurate all-digital duty-cycle corrector (ADDCC), which uses simplified dual-loop architecture, is presented in this paper. To explain the operational principle, a detailed circuit description and formula derivation are provided. To verify the proposed design, a chip was fabricated through the 0.18-µm standard complementary metal oxide semiconductor process with a core area of 0.091 mm2. The measurement results indicate that the proposed ADDCC can operate between 300 and 600 MHz with an input duty-cycle range of 40-60%, and that the output duty-cycle error is less than 1% with a root-mean-square jitter of 3.86 ps.

Fault Location Based on Synchronized Measurements: A Comprehensive Survey

PubMed Central

Al-Mohammed, A. H.; Abido, M. A.

2014-01-01

This paper presents a comprehensive survey on transmission and distribution fault location algorithms that utilize synchronized measurements. Algorithms based on two-end synchronized measurements and fault location algorithms on three-terminal and multiterminal lines are reviewed. Series capacitors equipped with metal oxide varistors (MOVs), when set on a transmission line, create certain problems for line fault locators and, therefore, fault location on series-compensated lines is discussed. The paper reports the work carried out on adaptive fault location algorithms aiming at achieving better fault location accuracy. Work associated with fault location on power system networks, although limited, is also summarized. Additionally, the nonstandard high-frequency-related fault location techniques based on wavelet transform are discussed. Finally, the paper highlights the area for future research. PMID:24701191

Application of Synchronous Text-Based Dialogue Systems in Mental Health Interventions: Systematic Review.

PubMed

Hoermann, Simon; McCabe, Kathryn L; Milne, David N; Calvo, Rafael A

2017-07-21

Synchronous written conversations (or "chats") are becoming increasingly popular as Web-based mental health interventions. Therefore, it is of utmost importance to evaluate and summarize the quality of these interventions. The aim of this study was to review the current evidence for the feasibility and effectiveness of online one-on-one mental health interventions that use text-based synchronous chat. A systematic search was conducted of the databases relevant to this area of research (Medical Literature Analysis and Retrieval System Online [MEDLINE], PsycINFO, Central, Scopus, EMBASE, Web of Science, IEEE, and ACM). There were no specific selection criteria relating to the participant group. Studies were included if they reported interventions with individual text-based synchronous conversations (ie, chat or text messaging) and a psychological outcome measure. A total of 24 articles were included in this review. Interventions included a wide range of mental health targets (eg, anxiety, distress, depression, eating disorders, and addiction) and intervention design. Overall, compared with the waitlist (WL) condition, studies showed significant and sustained improvements in mental health outcomes following synchronous text-based intervention, and post treatment improvement equivalent but not superior to treatment as usual (TAU) (eg, face-to-face and telephone counseling). Feasibility studies indicate substantial innovation in this area of mental health intervention with studies utilizing trained volunteers and chatbot technologies to deliver interventions. While studies of efficacy show positive post-intervention gains, further research is needed to determine whether time requirements for this mode of intervention are feasible in clinical practice. ©Simon Hoermann, Kathryn L McCabe, David N Milne, Rafael A Calvo. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 21.07.2017.

Genetic influences on functional connectivity associated with feedback processing and prediction error: Phase coupling of theta-band oscillations in twins.

PubMed

Demiral, Şükrü Barış; Golosheykin, Simon; Anokhin, Andrey P

2017-05-01

Detection and evaluation of the mismatch between the intended and actually obtained result of an action (reward prediction error) is an integral component of adaptive self-regulation of behavior. Extensive human and animal research has shown that evaluation of action outcome is supported by a distributed network of brain regions in which the anterior cingulate cortex (ACC) plays a central role, and the integration of distant brain regions into a unified feedback-processing network is enabled by long-range phase synchronization of cortical oscillations in the theta band. Neural correlates of feedback processing are associated with individual differences in normal and abnormal behavior, however, little is known about the role of genetic factors in the cerebral mechanisms of feedback processing. Here we examined genetic influences on functional cortical connectivity related to prediction error in young adult twins (age 18, n=399) using event-related EEG phase coherence analysis in a monetary gambling task. To identify prediction error-specific connectivity pattern, we compared responses to loss and gain feedback. Monetary loss produced a significant increase of theta-band synchronization between the frontal midline region and widespread areas of the scalp, particularly parietal areas, whereas gain resulted in increased synchrony primarily within the posterior regions. Genetic analyses showed significant heritability of frontoparietal theta phase synchronization (24 to 46%), suggesting that individual differences in large-scale network dynamics are under substantial genetic control. We conclude that theta-band synchronization of brain oscillations related to negative feedback reflects genetically transmitted differences in the neural mechanisms of feedback processing. To our knowledge, this is the first evidence for genetic influences on task-related functional brain connectivity assessed using direct real-time measures of neuronal synchronization. Copyright © 2016 Elsevier B.V. All rights reserved.

Fort Monmouth Technical Disclosure Bulletin. Volume 1, Number 1.

DTIC Science & Technology

1982-12-01

laser A may be placed between two plates in an evacuated area, and a space charge cloud caused by a multipactor i:.y be r.iade to niove between the...Radiation Detection Uodem Multipactor FuIP Ct] 1 AfTRACT (CAeM ree e, dl N nmeW -V md identl by block numbe) The Technical Disclosure Bulletin is...can be used with any digital signal containing regularly spaced synchronization bits or characters or else additional synchronization bits can be added

Study for incorporating time-synchronized approach control into the CH-47/VALT digital navigation system

NASA Technical Reports Server (NTRS)

Mcconnell, W. J., Jr.

1979-01-01

Techniques for obtaining time synchronized (4D) approach control in the VALT research helicopter is described. Various 4D concepts and their compatibility with the existing VALT digital computer navigation and guidance system hardware and software are examined. Modifications to various techniques were investigated in order to take advantage of the unique operating characteristics of the helicopter in the terminal area. A 4D system is proposed, combining the direct to maneuver with the existing VALT curved path generation capability.

A Clustering Based Approach for Observability and Controllability Analysis for Optimal Placement of PMU

NASA Astrophysics Data System (ADS)

Murthy, Ch; MIEEE; Mohanta, D. K.; SMIEE; Meher, Mahendra

2017-08-01

Continuous monitoring and control of the power system is essential for its healthy operation. This can be achieved by making the system observable as well as controllable. Many efforts have been made by several researchers to make the system observable by placing the Phasor Measurement Units (PMUs) at the optimal locations. But so far the idea of controllability with PMUs is not considered. This paper contributes how to check whether the system is controllable or not, if not then how make it controllable using a clustering approach. IEEE 14 bus system is considered to illustrate the concept of controllability.

OpenIPSL: Open-Instance Power System Library - Update 1.5 to "iTesla Power Systems Library (iPSL): A Modelica library for phasor time-domain simulations"

NASA Astrophysics Data System (ADS)

Baudette, Maxime; Castro, Marcelo; Rabuzin, Tin; Lavenius, Jan; Bogodorova, Tetiana; Vanfretti, Luigi

2018-01-01

This paper presents the latest improvements implemented in the Open-Instance Power System Library (OpenIPSL). The OpenIPSL is a fork from the original iTesla Power Systems Library (iPSL) by some of the original developers of the iPSL. This fork's motivation comes from the will of the authors to further develop the library with additional features tailored to research and teaching purposes. The enhancements include improvements to existing models, the addition of a new package of three phase models, and the implementation of automated tests through continuous integration.

Quick concurrent responses to global and local cognitive information underlie intuitive understanding in board-game experts

PubMed Central

Nakatani, Hironori; Yamaguchi, Yoko

2014-01-01

Experts have the superior cognitive capability of quickly understanding complex information in their domain; however, little is known about the neural processes underlying this ability. Here, using a board game named shogi (Japanese chess), we investigated the brain activity in expert players that was involved in their quick understanding of board-game patterns. The frontal area responded only to meaningful game positions, whereas the temporal area responded to both game and random positions with the same latency (200 ms). Subsequent to these quick responses, the temporal and parietal areas responded only to game positions, with a latency of 700 ms. During the responses, enhanced phase synchronization between these areas was observed. Thus, experts first responded to global cognitive information that was specific to game positions and to local cognitive information that was common to game and random positions concurrently. These types of information were integrated via neural synchronization at the posterior areas. As these properties were specific to experts, much of the experts' advantage in understanding game positions occurred within 1 s of perception. PMID:25081320

High-order synchronization of hair cell bundles

NASA Astrophysics Data System (ADS)

Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-Wook; Cheon, Jinwoo; Bozovic, Dolores

2016-12-01

Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells.

High-order synchronization of hair cell bundles

PubMed Central

Levy, Michael; Molzon, Adrian; Lee, Jae-Hyun; Kim, Ji-wook; Cheon, Jinwoo; Bozovic, Dolores

2016-01-01

Auditory and vestibular hair cell bundles exhibit active mechanical oscillations at natural frequencies that are typically lower than the detection range of the corresponding end organs. We explore how these noisy nonlinear oscillators mode-lock to frequencies higher than their internal clocks. A nanomagnetic technique is used to stimulate the bundles without an imposed mechanical load. The evoked response shows regimes of high-order mode-locking. Exploring a broad range of stimulus frequencies and intensities, we observe regions of high-order synchronization, analogous to Arnold Tongues in dynamical systems literature. Significant areas of overlap occur between synchronization regimes, with the bundle intermittently flickering between different winding numbers. We demonstrate how an ensemble of these noisy spontaneous oscillators could be entrained to efficiently detect signals significantly above the characteristic frequencies of the individual cells. PMID:27974743

Visually cued motor synchronization: modulation of fMRI activation patterns by baseline condition.

PubMed

Cerasa, Antonio; Hagberg, Gisela E; Bianciardi, Marta; Sabatini, Umberto

2005-01-03

A well-known issue in functional neuroimaging studies, regarding motor synchronization, is to design suitable control tasks able to discriminate between the brain structures involved in primary time-keeper functions and those related to other processes such as attentional effort. The aim of this work was to investigate how the predictability of stimulus onsets in the baseline condition modulates the activity in brain structures related to processes involved in time-keeper functions during the performance of a visually cued motor synchronization task (VM). The rational behind this choice derives from the notion that using different stimulus predictability can vary the subject's attention and the consequently neural activity. For this purpose, baseline levels of BOLD activity were obtained from 12 subjects during a conventional-baseline condition: maintained fixation of the visual rhythmic stimuli presented in the VM task, and a random-baseline condition: maintained fixation of visual stimuli occurring randomly. fMRI analysis demonstrated that while brain areas with a documented role in basic time processing are detected independent of the baseline condition (right cerebellum, bilateral putamen, left thalamus, left superior temporal gyrus, left sensorimotor cortex, left dorsal premotor cortex and supplementary motor area), the ventral premotor cortex, caudate nucleus, insula and inferior frontal gyrus exhibited a baseline-dependent activation. We conclude that maintained fixation of unpredictable visual stimuli can be employed in order to reduce or eliminate neural activity related to attentional components present in the synchronization task.

Application of Phasor Measurement Units for Protection of Distribution Networks with High Penetration of Photovoltaic Sources

NASA Astrophysics Data System (ADS)

Meskin, Matin

The rate of the integration of distributed generation (DG) units to the distribution level to meet the growth in demand increases as a reasonable replacement for costly network expansion. This integration brings many advantages to the consumers and power grids, as well as giving rise to more challenges in relation to protection and control. Recent research has brought to light the negative effects of DG units on short circuit currents and overcurrent (OC) protection systems in distribution networks. Change in the direction of fault current flow, increment or decrement of fault current magnitude, blindness of protection, feeder sympathy trip, nuisance trip of interrupting devices, and the disruption of coordination between protective devices are some potential impacts of DG unit integration. Among other types of DG units, the integration of renewable energy resources into the electric grid has seen a vast improvement in recent years. In particular, the interconnection of photovoltaic (PV) sources to the medium voltage (MV) distribution networks has experienced a rapid increase in the last decade. In this work, the effect of PV source on conventional OC relays in MV distribution networks is shown. It is indicated that the PV output fluctuation, due to changes in solar radiation, causes the magnitude and direction of the current to change haphazardly. These variations may result in the poor operation of OC relays as the main protective devices in the MV distribution networks. In other words, due to the bi-directional power flow characteristic and the fluctuation of current magnitude occurring in the presence of PV sources, a specific setting of OC relays is difficult to realize. Therefore, OC relays may operate in normal conditions. To improve the OC relay operation, a voltage-dependent-overcurrent protection is proposed. Although, this new method prevents the OC relay from maloperation, its ability to detect earth faults and high impedance faults is poor. Thus, a comprehensive protective system is suggested at the end of the dissertation. The proposed method is based on the application of the phasor measurement unit (PMU) and the differential protection method. All of the current magnitudes and angles are collected by PMU and are sent to the phasor data concentrator (PDC), where a differential protection algorithm is applied to these data. If any fault is detected, the trip will be sent back to the corresponding circuit breakers across the network. Higher selectivity, sensitivity, and faster operation in the differential protection are superior to those of other protection schemes. Differential protection operates as unit protection, which means that it operates only when there is a fault in the protection zone. It does not function for faults occurring out of zone. Therefore, no coordination is required between differential protections across the power system. Moreover, the misoperation of this protective scheme is less likely as compared to other protection methods.

Metastability and Inter-Band Frequency Modulation in Networks of Oscillating Spiking Neuron Populations

PubMed Central

Bhowmik, David; Shanahan, Murray

2013-01-01

Groups of neurons firing synchronously are hypothesized to underlie many cognitive functions such as attention, associative learning, memory, and sensory selection. Recent theories suggest that transient periods of synchronization and desynchronization provide a mechanism for dynamically integrating and forming coalitions of functionally related neural areas, and that at these times conditions are optimal for information transfer. Oscillating neural populations display a great amount of spectral complexity, with several rhythms temporally coexisting in different structures and interacting with each other. This paper explores inter-band frequency modulation between neural oscillators using models of quadratic integrate-and-fire neurons and Hodgkin-Huxley neurons. We vary the structural connectivity in a network of neural oscillators, assess the spectral complexity, and correlate the inter-band frequency modulation. We contrast this correlation against measures of metastable coalition entropy and synchrony. Our results show that oscillations in different neural populations modulate each other so as to change frequency, and that the interaction of these fluctuating frequencies in the network as a whole is able to drive different neural populations towards episodes of synchrony. Further to this, we locate an area in the connectivity space in which the system directs itself in this way so as to explore a large repertoire of synchronous coalitions. We suggest that such dynamics facilitate versatile exploration, integration, and communication between functionally related neural areas, and thereby supports sophisticated cognitive processing in the brain. PMID:23614040

Initiation of sleep-dependent cortical-hippocampal correlations at wakefulness-sleep transition.

PubMed

Haggerty, Daniel C; Ji, Daoyun

2014-10-01

Sleep is involved in memory consolidation. Current theories propose that sleep-dependent memory consolidation requires active communication between the hippocampus and neocortex. Indeed, it is known that neuronal activities in the hippocampus and various neocortical areas are correlated during slow-wave sleep. However, transitioning from wakefulness to slow-wave sleep is a gradual process. How the hippocampal-cortical correlation is established during the wakefulness-sleep transition is unknown. By examining local field potentials and multiunit activities in the rat hippocampus and visual cortex, we show that the wakefulness-sleep transition is characterized by sharp-wave ripple events in the hippocampus and high-voltage spike-wave events in the cortex, both of which are accompanied by highly synchronized multiunit activities in the corresponding area. Hippocampal ripple events occur earlier than the cortical high-voltage spike-wave events, and hippocampal ripple incidence is attenuated by the onset of cortical high-voltage spike waves. This attenuation leads to a temporary weak correlation in the hippocampal-cortical multiunit activities, which eventually evolves to a strong correlation as the brain enters slow-wave sleep. The results suggest that the hippocampal-cortical correlation is established through a concerted, two-step state change that first synchronizes the neuronal firing within each brain area and then couples the synchronized activities between the two regions. Copyright © 2014 the American Physiological Society.

Does Predation Influence the Seasonal and Diel Timing of Moose Calving in Central Ontario, Canada?

PubMed Central

Patterson, Brent R.; Mills, Kenneth J.; Middel, Kevin R.; Benson, John F.; Obbard, Martyn E.

2016-01-01

Birth synchrony is well documented among ungulates and is hypothesised to maximize neonate survival, either by minimizing the risk of predation through predator swamping or by synchronising birthing with increased seasonal food availability. We used encapsulated vaginal implant transmitters to locate and capture neonatal moose calves and document the seasonal and diel timing of parturition in two adjacent study areas with different predation pressure in central Ontario, Canada. We tested the hypothesis that predation promotes earlier and more synchronous birth of moose calves. Across both areas, proportionately more births occurred during the afternoon and fewer than expected occurred overnight. Mean date of calving averaged 1.5 days earlier and calving was also more synchronous in the study area with heavier predation pressure, despite average green-up date and peak Normalized Difference Vegetation Index date occurring 2 days later in this study area than in the area receiving lighter predation pressure. We encourage analysis of data on timing of parturition from additional study areas experiencing varying degrees of predation pressure to better clarify the influence of predation in driving seasonal and diel timing of parturition in temperate ungulates. PMID:27082234

Clinical assessment and management of general surgery patients via synchronous telehealth.

PubMed

Cain, Steven M; Moore, Robert; Sturm, Lauren; Mason, Travis; Fuhrman, Caitlin; Smith, Robin; Bojicic, Irfan; Carter, Brandon

2017-02-01

Objective This paper describes how a clinical team at Landstuhl Regional Medical Center (LRMC) successfully integrated synchronous telehealth (TH) into their routine clinical practice. Methods and materials Synchronous TH encounters were performed using Polycom® software on surgeons' computers with high-definition (HD) cameras on monitors at distant sites and PolyCom HDX9000® Telehealth Practitioner Carts at originating sites. Patients provided consented and were presented to general surgeons by nurses and medical technicians at Army health clinics throughout the European Theater. Results In calendar year (CY) 2014, five general surgeons and two surgical physician assistants (PAs) at Landstuhl Regional Medical Center along with registered nurses (RNs) at six originating clinic sites throughout Europe completed 130 synchronous TH encounters for 101 general surgery patients resulting in 73 completed and 16 recommended surgeries. Eighty-eight percent of patients had a completed or recommended surgery. No surgeries or procedures planned after initial TH evaluation were cancelled. Originating site clinics ranged in distance from 68 miles to 517 miles. Acceptance by providers, patients and clinic staff was high. Conclusion Synchronous TH was effective and safe in evaluating common general surgical conditions. We excluded sensitive and complex conditions requiring a nuanced physical examination. The TH efforts of the general surgery staff have resulted in high-quality, seamless and predictable TH activities that continue to expand into other surgical and medical specialties beyond general surgery. Seven surgeons and two PAs use synchronous TH regularly serving patients over a broad geographic area.

Non-conventional synchronization of weakly coupled active oscillators

NASA Astrophysics Data System (ADS)

Manevitch, L. I.; Kovaleva, M. A.; Pilipchuk, V. N.

2013-03-01

We present a new type of self-sustained vibrations in the fundamental physical model covering a broad area of applications from wave generation in radiophysics and nonlinear optics to the heart muscle contraction and eyesight disorder in biophysics. Such a diversity of applications is due to the universal physical phenomenon of synchronization. Previous studies of this phenomenon, originating from Huygens famous observation, are based mainly on the model of two weakly coupled Van der Pol oscillators and usually deal with their synchronization in the regimes close to nonlinear normal modes (NNMs). In this work, we show for the first time that, in the important case of threshold excitation, an alternative synchronization mechanism can develop when the conventional synchronization becomes impossible. We identify this mechanism as an appearance of dynamic attractor with the complete periodic energy exchange between the oscillators, which is the dissipative analogue of highly intensive beats in a conservative system. This type of motion is therefore opposite to the NNM-type synchronization with no energy exchange by definition. The analytical description of these vibrations employs the concept of Limiting Phase Trajectories (LPTs) introduced by one of the authors earlier for conservative systems. Finally, within the LPT approach, we describe the transition from the complete energy exchange between the oscillators to the energy localization mostly on one of the two oscillators. The localized mode is an attractor in the range of model parameters wherein the LPT as well as the in-phase and out-of-phase NNMs become unstable.

Beyond synchronicity: the worldview of Carl Gustav Jung and Wolfgang Pauli.

PubMed

Donati, Marialuisa

2004-11-01

While exploring the phenomena of synchronicity, Carl Gustav Jung became acquainted with the quantum physicist Wolfgang Pauli and eventually began a collaboration with him. During that collaboration Jung's study of synchronistic phenomena underwent a considerable change; prior to the collaboration, Jung had stressed mainly the phenomenological and empirical features of synchronistic phenomena, while in association with Pauli, he focused his attention upon their ontological, archetypal character. Pauli, on the other hand, became increasingly sensitive to the philosophical aspects concerning the unconscious. Jung and Pauli's common reflections went far beyond psychology and physics, entering into the realm where the two areas meet in the philosophy of nature. In fact, as a consequence of their collaboration, synchronicity was transformed from an empirical concept into a fundamental explanatory-interpretative principle, which together with causality could possibly lead to a more complete worldview. Exploring the problematic character of the synchronicity concept has a heuristic value because it leads to the reconsideration of the philosophical issues that drove Jung and Pauli to clear up the conceptual background of their thoughts. Within the philosophical worldview arising from Jung and Pauli's discussions about synchronicity, there are many symbolic aspects that go against mainstream science and that represent a sort of criticism to some of the commonly held views of present day science.

Global patterns of synchronization in human communications.

PubMed

Morales, Alfredo J; Vavilala, Vaibhav; Benito, Rosa M; Bar-Yam, Yaneer

2017-03-01

Social media are transforming global communication and coordination and provide unprecedented opportunities for studying socio-technical domains. Here we study global dynamical patterns of communication on Twitter across many scales. Underlying the observed patterns is both the diurnal rotation of the Earth, day and night, and the synchrony required for contingency of actions between individuals. We find that urban areas show a cyclic contraction and expansion that resembles heartbeats linked to social rather than natural cycles. Different urban areas have characteristic signatures of daily collective activities. We show that the differences detected are consistent with a new emergent global synchrony that couples behaviour in distant regions across the world. Although local synchrony is the major force that shapes the collective behaviour in cities, a larger-scale synchronization is beginning to occur. © 2017 The Author(s).

Global patterns of synchronization in human communications

PubMed Central

Vavilala, Vaibhav; Benito, Rosa M.; Bar-Yam, Yaneer

2017-01-01

Social media are transforming global communication and coordination and provide unprecedented opportunities for studying socio-technical domains. Here we study global dynamical patterns of communication on Twitter across many scales. Underlying the observed patterns is both the diurnal rotation of the Earth, day and night, and the synchrony required for contingency of actions between individuals. We find that urban areas show a cyclic contraction and expansion that resembles heartbeats linked to social rather than natural cycles. Different urban areas have characteristic signatures of daily collective activities. We show that the differences detected are consistent with a new emergent global synchrony that couples behaviour in distant regions across the world. Although local synchrony is the major force that shapes the collective behaviour in cities, a larger-scale synchronization is beginning to occur. PMID:28250100

Synchronous diversification of Sulawesi's iconic artiodactyls driven by recent geological events.

PubMed

Frantz, Laurent A F; Rudzinski, Anna; Nugraha, Abang Mansyursyah Surya; Evin, Allowen; Burton, James; Hulme-Beaman, Ardern; Linderholm, Anna; Barnett, Ross; Vega, Rodrigo; Irving-Pease, Evan K; Haile, James; Allen, Richard; Leus, Kristin; Shephard, Jill; Hillyer, Mia; Gillemot, Sarah; van den Hurk, Jeroen; Ogle, Sharron; Atofanei, Cristina; Thomas, Mark G; Johansson, Friederike; Mustari, Abdul Haris; Williams, John; Mohamad, Kusdiantoro; Damayanti, Chandramaya Siska; Wiryadi, Ita Djuwita; Obbles, Dagmar; Mona, Stephano; Day, Hally; Yasin, Muhammad; Meker, Stefan; McGuire, Jimmy A; Evans, Ben J; von Rintelen, Thomas; Ho, Simon Y W; Searle, Jeremy B; Kitchener, Andrew C; Macdonald, Alastair A; Shaw, Darren J; Hall, Robert; Galbusera, Peter; Larson, Greger

2018-04-11

The high degree of endemism on Sulawesi has previously been suggested to have vicariant origins, dating back to 40 Ma. Recent studies, however, suggest that much of Sulawesi's fauna assembled over the last 15 Myr. Here, we test the hypothesis that more recent uplift of previously submerged portions of land on Sulawesi promoted diversification and that much of its faunal assemblage is much younger than the island itself. To do so, we combined palaeogeographical reconstructions with genetic and morphometric datasets derived from Sulawesi's three largest mammals: the babirusa, anoa and Sulawesi warty pig. Our results indicate that although these species most likely colonized the area that is now Sulawesi at different times (14 Ma to 2-3 Ma), they experienced an almost synchronous expansion from the central part of the island. Geological reconstructions indicate that this area was above sea level for most of the last 4 Myr, unlike most parts of the island. We conclude that emergence of land on Sulawesi (approx. 1-2 Myr) may have allowed species to expand synchronously. Altogether, our results indicate that the establishment of the highly endemic faunal assemblage on Sulawesi was driven by geological events over the last few million years. © 2018 The Authors.

Synchronous diversification of Sulawesi's iconic artiodactyls driven by recent geological events

PubMed Central

Rudzinski, Anna; Nugraha, Abang Mansyursyah Surya; Burton, James; Linderholm, Anna; Barnett, Ross; Vega, Rodrigo; Irving-Pease, Evan K.; Haile, James; Allen, Richard; Leus, Kristin; Shephard, Jill; Hillyer, Mia; Gillemot, Sarah; van den Hurk, Jeroen; Ogle, Sharron; Atofanei, Cristina; Thomas, Mark G.; Johansson, Friederike; Mustari, Abdul Haris; Williams, John; Mohamad, Kusdiantoro; Damayanti, Chandramaya Siska; Wiryadi, Ita Djuwita; Obbles, Dagmar; Mona, Stephano; Day, Hally; Yasin, Muhammad; Meker, Stefan; McGuire, Jimmy A.; Evans, Ben J.; von Rintelen, Thomas; Ho, Simon Y. W.; Searle, Jeremy B.; Kitchener, Andrew C.; Macdonald, Alastair A.; Hall, Robert; Galbusera, Peter

2018-01-01

The high degree of endemism on Sulawesi has previously been suggested to have vicariant origins, dating back to 40 Ma. Recent studies, however, suggest that much of Sulawesi's fauna assembled over the last 15 Myr. Here, we test the hypothesis that more recent uplift of previously submerged portions of land on Sulawesi promoted diversification and that much of its faunal assemblage is much younger than the island itself. To do so, we combined palaeogeographical reconstructions with genetic and morphometric datasets derived from Sulawesi's three largest mammals: the babirusa, anoa and Sulawesi warty pig. Our results indicate that although these species most likely colonized the area that is now Sulawesi at different times (14 Ma to 2–3 Ma), they experienced an almost synchronous expansion from the central part of the island. Geological reconstructions indicate that this area was above sea level for most of the last 4 Myr, unlike most parts of the island. We conclude that emergence of land on Sulawesi (approx. 1–2 Myr) may have allowed species to expand synchronously. Altogether, our results indicate that the establishment of the highly endemic faunal assemblage on Sulawesi was driven by geological events over the last few million years. PMID:29643207

Laser pulse stacking method

DOEpatents

Moses, Edward I.

1992-01-01

A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter.

Laser pulse stacking method

DOEpatents

Moses, E.I.

1992-12-01

A laser pulse stacking method is disclosed. A problem with the prior art has been the generation of a series of laser beam pulses where the outer and inner regions of the beams are generated so as to form radially non-synchronous pulses. Such pulses thus have a non-uniform cross-sectional area with respect to the outer and inner edges of the pulses. The present invention provides a solution by combining the temporally non-uniform pulses in a stacking effect to thus provide a more uniform temporal synchronism over the beam diameter. 2 figs.

Air Temperature Distribution Measurement Using Asynchronous-Type Sound Probe

NASA Astrophysics Data System (ADS)

Katano, Yosuke; Wakatsuki, Naoto; Mizutani, Koichi

2009-07-01

In conventional temperature measurement using a sound probe, the operation beginnings of two acoustic sensors must be completely synchronized to measure time of flight (TOF), tf, because the precision of synchronization determines TOF measurement accuracy. A wireless local area network (LAN) is convenient for constructing a sensing grid; however, it causes a fluctuation in the delay of millisecond order. Therefore, it cannot provide sufficient precision for synchronizing acoustic sensors. In previous studies, synchronization was achieved by a trigger line using a coaxial cable; however, the cable reduces the flexibility of a wireless sensing grid especially in larger-scale measurement. In this study, an asynchronous-type sound probe is devised to compensate for the effect of the delay of millisecond order caused by the network. The validity of the probe was examined, and the air temperature distribution was measured using this means. A matrix method is employed to obtain the distribution. Similar results were observed using both asynchronous-type sound probes and thermocouples. This shows the validity of the use of a sensing grid with an asynchronous-type sound probe for temperature distribution measurement even if the trigger line is omitted.

Experiment K-6-06. Morphometric and EM analyses of tibial epiphyseal plates from Cosmos 1887 rats

NASA Technical Reports Server (NTRS)

Duke, P. J.; Montufar-Solis, D.; Durnova, G.

1990-01-01

Light and electron microscopy studies were carried out on decalcified tibial epiphyseal plates of rats flown aboard Cosmos 1887 (12.5d flight plus 53.5h recovery). Analysis of variance showed that the proliferative zone of flight animals was significantly higher than that of synchronous controls, while the hypertrophic/calcification zone was significantly reduced. Flight animals had more cells than synchronous controls in the proliferative zone, and less in the hypertrophic/calcification region. The total number of cells, however, was significantly higher in flight animals. No differences were found for perimeter or shape factor of growth plates, but area was significantly lower in flight animals in comparison to synchronous controls. Collagen fibrils in flight animals were shorter and wider than in synchronous controls. The time required for a cell to cycle through the growth plate is 2 to 3 days, so most of the cells and matrix present were formed after the animals had returned to 1 g, and probably represent stages of recovery from microgravity exposure, which in itself is an interesting question.

Enhanced phase synchrony in the electroencephalograph γ band for musicians while listening to music

NASA Astrophysics Data System (ADS)

Bhattacharya, Joydeep; Petsche, Hellmuth

2001-07-01

Multichannel electroencephalograph signals from two broad groups, 10 musicians and 10 nonmusicians, recorded in different states (in resting states or no task condition, with eyes opened and eyes closed, and with two musical tasks, listening to two different pieces of music) were studied. Degrees of phase synchrony in various frequency bands were assessed. No differences in the degree of synchronization in any frequency band were found between the two groups in resting conditions. Yet, while listening to music, significant increases of synchronization were found only in the γ-frequency range (>30 Hz) over large cortical areas for the group of musicians. This high degree of synchronization elicited by music in the group of musicians might be due to their ability to host long-term memory representations of music and mediate access to these stored representations.

Synchronization in monkey visual cortex analyzed with an information-theoretic measure

NASA Astrophysics Data System (ADS)

Manyakov, Nikolay V.; Van Hulle, Marc M.

2008-09-01

We apply an information-theoretic measure for phase synchrony to local field potentials recorded with a multi-electrode array implanted in area V4 of the monkey visual cortex during a reinforcement pairing experiment. We show for the first time that (1) the phase synchrony is significantly higher for the rewarded stimulus than the unrewarded one, after training the monkey; (2) just after the stimuli reversal, the difference in phase synchronization is due to the stimuli, not the reward; (3) the difference between reward and no reward is most clear in two disconnected time intervals between stimuli onset and the expected delivery of the reward; and (4) synchronous activity appears in waves running over the array, and their timing correlates well with the time intervals where the difference between reward and no reward is most prominent.

Synchronous ossifying fibromas of the jaws: a review.

PubMed

Akcam, Timur; Altug, Hasan Ayberk; Karakoc, Omer; Sencimen, Metin; Ozkan, Aydin; Bayar, Gurkan Rasit; Gunhan, Omer

2012-11-01

According to the World Health Organization, it is proposed that benign fibro-osseous lesions be divided into 3 categories, including fibrous dysplasia, ossifying fibroma (OF), and osseous dysplasia. OF arises from the periodontal ligament, which contains multipotential cells. These benign tumors may become large and aggressive. Slow growth and lack of symptoms are the cardinal features. OF tends to occur in the second and third decades of life, with predilection for women and for the mandibular premolar-molar area. The method of treatment used for large or rapidly expanding lesions is surgical removal (enucleation). Rarely, OFs occur multifocally. We report a 20-year-old man with synchronous OFs of his maxilla and mandible and review other synchronous cases reported. Such lesions can be properly diagnosed and treated by correlating radiographic, clinical, surgical, and histopathologic findings. Copyright © 2012 Elsevier Inc. All rights reserved.

Asynchronous Computer-Mediated Corrective Feedback and the Correct Use of Prepositions: Is It Really Effective?

ERIC Educational Resources Information Center

Hosseini, Seyyed Behrooz

2012-01-01

An area that has recently attracted increasing attention is providing feedback on learners' writing accuracy through the Internet. However, research in this area has largely focused on synchronous communication, i.e., chatting, with fewer studies assessing asynchronous technologies, i.e., e-mailing. Therefore, this study investigates the…

Power system observability and dynamic state estimation for stability monitoring using synchrophasor measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Kai; Qi, Junjian; Kang, Wei

2016-08-01

Growing penetration of intermittent resources such as renewable generations increases the risk of instability in a power grid. This paper introduces the concept of observability and its computational algorithms for a power grid monitored by the wide-area measurement system (WAMS) based on synchrophasors, e.g. phasor measurement units (PMUs). The goal is to estimate real-time states of generators, especially for potentially unstable trajectories, the information that is critical for the detection of rotor angle instability of the grid. The paper studies the number and siting of synchrophasors in a power grid so that the state of the system can be accuratelymore » estimated in the presence of instability. An unscented Kalman filter (UKF) is adopted as a tool to estimate the dynamic states that are not directly measured by synchrophasors. The theory and its computational algorithms are illustrated in detail by using a 9-bus 3-generator power system model and then tested on a 140-bus 48-generator Northeast Power Coordinating Council power grid model. Case studies on those two systems demonstrate the performance of the proposed approach using a limited number of synchrophasors for dynamic state estimation for stability assessment and its robustness against moderate inaccuracies in model parameters.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chamana, Manohar; Prabakar, Kumaraguru; Palmintier, Bryan

A software process is developed to convert distribution network models from a quasi-static time-series tool (OpenDSS) to a real-time dynamic phasor simulator (ePHASORSIM). The description of this process in this paper would be helpful for researchers who intend to perform similar conversions. The converter could be utilized directly by users of real-time simulators who intend to perform software-in-the-loop or hardware-in-the-loop tests on large distribution test feeders for a range of use cases, including testing functions of advanced distribution management systems against a simulated distribution system. In the future, the developers intend to release the conversion tool as open source tomore » enable use by others.« less

Global field synchronization in gamma range of the sleep EEG tracks sleep depth: Artifact introduced by a rectangular analysis window.

PubMed

Rusterholz, Thomas; Achermann, Peter; Dürr, Roland; Koenig, Thomas; Tarokh, Leila

2017-06-01

Investigating functional connectivity between brain networks has become an area of interest in neuroscience. Several methods for investigating connectivity have recently been developed, however, these techniques need to be applied with care. We demonstrate that global field synchronization (GFS), a global measure of phase alignment in the EEG as a function of frequency, must be applied considering signal processing principles in order to yield valid results. Multichannel EEG (27 derivations) was analyzed for GFS based on the complex spectrum derived by the fast Fourier transform (FFT). We examined the effect of window functions on GFS, in particular of non-rectangular windows. Applying a rectangular window when calculating the FFT revealed high GFS values for high frequencies (>15Hz) that were highly correlated (r=0.9) with spectral power in the lower frequency range (0.75-4.5Hz) and tracked the depth of sleep. This turned out to be spurious synchronization. With a non-rectangular window (Tukey or Hanning window) these high frequency synchronization vanished. Both, GFS and power density spectra significantly differed for rectangular and non-rectangular windows. Previous papers using GFS typically did not specify the applied window and may have used a rectangular window function. However, the demonstrated impact of the window function raises the question of the validity of some previous findings at higher frequencies. We demonstrated that it is crucial to apply an appropriate window function for determining synchronization measures based on a spectral approach to avoid spurious synchronization in the beta/gamma range. Copyright © 2017 Elsevier B.V. All rights reserved.

Verifying the interactive convergence clock synchronization algorithm using the Boyer-Moore theorem prover

NASA Technical Reports Server (NTRS)

Young, William D.

1992-01-01

The application of formal methods to the analysis of computing systems promises to provide higher and higher levels of assurance as the sophistication of our tools and techniques increases. Improvements in tools and techniques come about as we pit the current state of the art against new and challenging problems. A promising area for the application of formal methods is in real-time and distributed computing. Some of the algorithms in this area are both subtle and important. In response to this challenge and as part of an ongoing attempt to verify an implementation of the Interactive Convergence Clock Synchronization Algorithm (ICCSA), we decided to undertake a proof of the correctness of the algorithm using the Boyer-Moore theorem prover. This paper describes our approach to proving the ICCSA using the Boyer-Moore prover.

Large-scale synchronization of annual recruitment success and stock size in Wadden Sea populations of the mussel Mytilus edulis L.

NASA Astrophysics Data System (ADS)

Beukema, J. J.; Dekker, R.; van Stralen, M. R.; de Vlas, J.

2015-12-01

Simultaneous abundance or shortage of mussels over vast areas may seriously affect fishery as well as shellfish-eating birds. We studied synchrony in annual recruit numbers and stock sizes (biomass) of mussels on the base of long-term observations in various parts of the Dutch (and German) Wadden Sea, including regular monitoring on Balgzand (a 50-km2 tidal flat area) and published or unpublished records for other parts of the Wadden Sea. Annual records for 37 years of mussel seed abundance in the eastern and western half of the Dutch Wadden Sea proved to be mutually well correlated and were also significantly correlated with annually assessed numerical densities of mussel recruits on Balgzand. The scarce long-term series available on mussel biomass pointed to significantly positive correlations between stock sizes on Balgzand and those in the northern German Wadden Sea, at about 300 km distance. The incidence of severe winters, which occurrence is synchronized over areas in the order of thousands of km, is identified as the dominant causative factor behind Wadden Sea-wide recruitment synchrony. Severe winters are known to reduce abundance of predators on tiny bivalve spat, and this process may overrule local processes causing abundance variation in bivalves. As such extreme winters are infrequent (usually only one or two per decade), sensible studies on the phenomenon of synchronization in abundance of Wadden Sea bivalves should be based on data series of sufficient length, covering decades.

Cortical Gray and Adjacent White Matter Demonstrate Synchronous Maturation in Very Preterm Infants.

PubMed

Smyser, Tara A; Smyser, Christopher D; Rogers, Cynthia E; Gillespie, Sarah K; Inder, Terrie E; Neil, Jeffrey J

2016-08-01

Spatial and functional gradients of development have been described for the maturation of cerebral gray and white matter using histological and radiological approaches. We evaluated these patterns in very preterm (VPT) infants using diffusion tensor imaging. Data were obtained from 3 groups: 1) 22 VPT infants without white matter injury (WMI), of whom all had serial MRI studies during the neonatal period, 2) 19 VPT infants with WMI, of whom 3 had serial MRI studies and 3) 12 healthy, term-born infants. Regions of interest were placed in the cortical gray and adjacent white matter in primary motor, primary visual, visual association, and prefrontal regions. From the MRI data at term-equivalent postmenstrual age, differences in mean diffusivity were found in all areas between VPT infants with WMI and the other 2 groups. In contrast, minimal differences in fractional anisotropy were found between the 3 groups. These findings suggest that cortical maturation is delayed in VPT infants with WMI when compared with term control infants and VPT infants without WMI. From the serial MRI data from VPT infants, synchronous development between gray and white matter was evident in all areas and all groups, with maturation in primary motor and sensory regions preceding that of association areas. This finding highlights the regionally varying but locally synchronous nature of the development of cortical gray matter and its adjacent white matter. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Does Spike-Timing-Dependent Synaptic Plasticity Couple or Decouple Neurons Firing in Synchrony?

PubMed Central

Knoblauch, Andreas; Hauser, Florian; Gewaltig, Marc-Oliver; Körner, Edgar; Palm, Günther

2012-01-01

Spike synchronization is thought to have a constructive role for feature integration, attention, associative learning, and the formation of bidirectionally connected Hebbian cell assemblies. By contrast, theoretical studies on spike-timing-dependent plasticity (STDP) report an inherently decoupling influence of spike synchronization on synaptic connections of coactivated neurons. For example, bidirectional synaptic connections as found in cortical areas could be reproduced only by assuming realistic models of STDP and rate coding. We resolve this conflict by theoretical analysis and simulation of various simple and realistic STDP models that provide a more complete characterization of conditions when STDP leads to either coupling or decoupling of neurons firing in synchrony. In particular, we show that STDP consistently couples synchronized neurons if key model parameters are matched to physiological data: First, synaptic potentiation must be significantly stronger than synaptic depression for small (positive or negative) time lags between presynaptic and postsynaptic spikes. Second, spike synchronization must be sufficiently imprecise, for example, within a time window of 5–10 ms instead of 1 ms. Third, axonal propagation delays should not be much larger than dendritic delays. Under these assumptions synchronized neurons will be strongly coupled leading to a dominance of bidirectional synaptic connections even for simple STDP models and low mean firing rates at the level of spontaneous activity. PMID:22936909

Advances in the development of an imaging device for plaque measurement in the area of the carotid artery.

PubMed

Ličev, Lačezar; Krumnikl, Michal; Škuta, Jaromír; Babiuch, Marek; Farana, Radim

2014-03-04

This paper describes the advances in the development and subsequent testing of an imaging device for three-dimensional ultrasound measurement of atherosclerotic plaque in the carotid artery. The embolization from the atherosclerotic carotid plaque is one of the most common causes of ischemic stroke and, therefore, we consider the measurement of the plaque as extremely important. The paper describes the proposed hardware for enhancing the standard ultrasonic probe to provide a possibility of accurate probe positioning and synchronization with the cardiac activity, allowing the precise plaque measurements that were impossible with the standard equipment. The synchronization signal is derived from the output signal of the patient monitor (electrocardiogram (ECG)), processed by a microcontroller-based system, generating the control commands for the linear motion moving the probe. The controlling algorithm synchronizes the movement with the ECG waveform to obtain clear images not disturbed by the heart activity.

A Group Neighborhood Average Clock Synchronization Protocol for Wireless Sensor Networks

PubMed Central

Lin, Lin; Ma, Shiwei; Ma, Maode

2014-01-01

Clock synchronization is a very important issue for the applications of wireless sensor networks. The sensors need to keep a strict clock so that users can know exactly what happens in the monitoring area at the same time. This paper proposes a novel internal distributed clock synchronization solution using group neighborhood average. Each sensor node collects the offset and skew rate of the neighbors. Group averaging of offset and skew rate value are calculated instead of conventional point-to-point averaging method. The sensor node then returns compensated value back to the neighbors. The propagation delay is considered and compensated. The analytical analysis of offset and skew compensation is presented. Simulation results validate the effectiveness of the protocol and reveal that the protocol allows sensor networks to quickly establish a consensus clock and maintain a small deviation from the consensus clock. PMID:25120163

Theta–gamma coordination between anterior cingulate and prefrontal cortex indexes correct attention shifts

PubMed Central

Voloh, Benjamin; Valiante, Taufik A.; Everling, Stefan; Womelsdorf, Thilo

2015-01-01

Anterior cingulate and lateral prefrontal cortex (ACC/PFC) are believed to coordinate activity to flexibly prioritize the processing of goal-relevant over irrelevant information. This between-area coordination may be realized by common low-frequency excitability changes synchronizing segregated high-frequency activations. We tested this coordination hypothesis by recording in macaque ACC/PFC during the covert utilization of attention cues. We found robust increases of 5–10 Hz (theta) to 35–55 Hz (gamma) phase–amplitude correlation between ACC and PFC during successful attention shifts but not before errors. Cortical sites providing theta phases (i) showed a prominent cue-induced phase reset, (ii) were more likely in ACC than PFC, and (iii) hosted neurons with burst firing events that synchronized to distant gamma activity. These findings suggest that interareal theta–gamma correlations could follow mechanistically from a cue-triggered reactivation of rule memory that synchronizes theta across ACC/PFC. PMID:26100868

Rapid learning in visual cortical networks.

PubMed

Wang, Ye; Dragoi, Valentin

2015-08-26

Although changes in brain activity during learning have been extensively examined at the single neuron level, the coding strategies employed by cell populations remain mysterious. We examined cell populations in macaque area V4 during a rapid form of perceptual learning that emerges within tens of minutes. Multiple single units and LFP responses were recorded as monkeys improved their performance in an image discrimination task. We show that the increase in behavioral performance during learning is predicted by a tight coordination of spike timing with local population activity. More spike-LFP theta synchronization is correlated with higher learning performance, while high-frequency synchronization is unrelated with changes in performance, but these changes were absent once learning had stabilized and stimuli became familiar, or in the absence of learning. These findings reveal a novel mechanism of plasticity in visual cortex by which elevated low-frequency synchronization between individual neurons and local population activity accompanies the improvement in performance during learning.

Splenium of Corpus Callosum: Patterns of Interhemispheric Interaction in Children and Adults

PubMed Central

Knyazeva, Maria G.

2013-01-01

The splenium of the corpus callosum connects the posterior cortices with fibers varying in size from thin late-myelinating axons in the anterior part, predominantly connecting parietal and temporal areas, to thick early-myelinating fibers in the posterior part, linking primary and secondary visual areas. In the adult human brain, the function of the splenium in a given area is defined by the specialization of the area and implemented via excitation and/or suppression of the contralateral homotopic and heterotopic areas at the same or different level of visual hierarchy. These mechanisms are facilitated by interhemispheric synchronization of oscillatory activity, also supported by the splenium. In postnatal ontogenesis, structural MRI reveals a protracted formation of the splenium during the first two decades of human life. In doing so, the slow myelination of the splenium correlates with the formation of interhemispheric excitatory influences in the extrastriate areas and the EEG synchronization, while the gradual increase of inhibitory effects in the striate cortex is linked to the local inhibitory circuitry. Reshaping interactions between interhemispherically distributed networks under various perceptual contexts allows sparsification of responses to superfluous information from the visual environment, leading to a reduction of metabolic and structural redundancy in a child's brain. PMID:23577273

Hippocampal effective synchronization values are not pre-seizure indicator without considering the state of the onset channels

PubMed Central

Shayegh, Farzaneh; Sadri, Saeed; Amirfattahi, Rassoul; Ansari-Asl, Karim; Bellanger, Jean-Jacques; Senhadji, Lotfi

2014-01-01

In this paper, a model-based approach is presented to quantify the effective synchrony between hippocampal areas from depth-EEG signals. This approach is based on the parameter identification procedure of a realistic Multi-Source/Multi-Channel (MSMC) hippocampal model that simulates the function of different areas of hippocampus. In the model it is supposed that the observed signals recorded using intracranial electrodes are generated by some hidden neuronal sources, according to some parameters. An algorithm is proposed to extract the intrinsic (solely relative to one hippocampal area) and extrinsic (coupling coefficients between two areas) model parameters, simultaneously, by a Maximum Likelihood (ML) method. Coupling coefficients are considered as the measure of effective synchronization. This work can be considered as an application of Dynamic Causal Modeling (DCM) that enables us to understand effective synchronization changes during transition from inter-ictal to pre -ictal state. The algorithm is first validated by using some synthetic datasets. Then by extracting the coupling coefficients of real depth-EEG signals by the proposed approach, it is observed that the coupling values show no significant difference between ictal, pre-ictal and inter-ictal states, i.e., either the increase or decrease of coupling coefficients has been observed in all states. However, taking the value of intrinsic parameters into account, pre-seizure state can be distinguished from inter-ictal state. It is claimed that seizures start to appear when there are seizure-related physiological parameters on the onset channel, and its coupling coefficient toward other channels increases simultaneously. As a result of considering both intrinsic and extrinsic parameters as the feature vector, inter-ictal, pre-ictal and ictal activities are discriminated from each other with an accuracy of 91.33% accuracy. PMID:25061815

[4D-MRI using the synchronized sampling method (SSM)].

PubMed

Shimada, Yasuhiro; Fujimoto, Ichirou; Takemoto, Hironori; Takano, Sayoko; Masaki, Shinobu; Honda, Kiyoshi; Takeo, Kazuhiro

2002-12-01

A synchronized sampling method (SSM) was developed for the study of voluntary movements by combining the electrocardiographic (ECG) gating method with an external triggering device, and four-dimensional magnetic resonance imaging (4D-MRI) at a rate of 30 frames per second was accomplished by volumetric imaging with the SSM. This method was first applied to the motion imaging of articulatory organs during repetitions of a Japanese five-vowel sequence, and the dynamic change in vocal tract area function was demonstrated with sufficient temporal resolution. This paper describes the methodology, applicability, and limitations of 4D-MRI with the SSM.

Versatile synchronized real-time MEG hardware controller for large-scale fast data acquisition.

PubMed

Sun, Limin; Han, Menglai; Pratt, Kevin; Paulson, Douglas; Dinh, Christoph; Esch, Lorenz; Okada, Yoshio; Hämäläinen, Matti

2017-05-01

Versatile controllers for accurate, fast, and real-time synchronized acquisition of large-scale data are useful in many areas of science, engineering, and technology. Here, we describe the development of a controller software based on a technique called queued state machine for controlling the data acquisition (DAQ) hardware, continuously acquiring a large amount of data synchronized across a large number of channels (>400) at a fast rate (up to 20 kHz/channel) in real time, and interfacing with applications for real-time data analysis and display of electrophysiological data. This DAQ controller was developed specifically for a 384-channel pediatric whole-head magnetoencephalography (MEG) system, but its architecture is useful for wide applications. This controller running in a LabVIEW environment interfaces with microprocessors in the MEG sensor electronics to control their real-time operation. It also interfaces with a real-time MEG analysis software via transmission control protocol/internet protocol, to control the synchronous acquisition and transfer of the data in real time from >400 channels to acquisition and analysis workstations. The successful implementation of this controller for an MEG system with a large number of channels demonstrates the feasibility of employing the present architecture in several other applications.

Versatile synchronized real-time MEG hardware controller for large-scale fast data acquisition

NASA Astrophysics Data System (ADS)

Sun, Limin; Han, Menglai; Pratt, Kevin; Paulson, Douglas; Dinh, Christoph; Esch, Lorenz; Okada, Yoshio; Hämäläinen, Matti

2017-05-01

Versatile controllers for accurate, fast, and real-time synchronized acquisition of large-scale data are useful in many areas of science, engineering, and technology. Here, we describe the development of a controller software based on a technique called queued state machine for controlling the data acquisition (DAQ) hardware, continuously acquiring a large amount of data synchronized across a large number of channels (>400) at a fast rate (up to 20 kHz/channel) in real time, and interfacing with applications for real-time data analysis and display of electrophysiological data. This DAQ controller was developed specifically for a 384-channel pediatric whole-head magnetoencephalography (MEG) system, but its architecture is useful for wide applications. This controller running in a LabVIEW environment interfaces with microprocessors in the MEG sensor electronics to control their real-time operation. It also interfaces with a real-time MEG analysis software via transmission control protocol/internet protocol, to control the synchronous acquisition and transfer of the data in real time from >400 channels to acquisition and analysis workstations. The successful implementation of this controller for an MEG system with a large number of channels demonstrates the feasibility of employing the present architecture in several other applications.

Interaction matters: Strategies to promote engaged learning in an online introductory nutrition course.

PubMed

Banna, Jinan; Grace Lin, Meng-Fen; Stewart, Maria; Fialkowski, Marie K

2015-06-01

Fostering interaction in the online classroom is an important consideration in ensuring that students actively create their own knowledge and reach a high level of achievement in science courses. This study focuses on fostering interaction in an online introductory nutrition course offered in a public institution of higher education in Hawai'i, USA. Interactive features included synchronous discussions and polls in scheduled sessions, and social media tools for sharing of information and resources. Qualitative student feedback was solicited regarding the new course features. Findings indicated that students who attended monthly synchronous sessions valued live interaction with peers and the instructor. Issues identified included technical difficulties during synchronous sessions, lack of participation on the part of fellow students in discussion and inability to attend synchronous sessions due to scheduling conflicts. In addition, few students made use of the opportunity to interact via social media. While students indicated that the interactive components of the course were valuable, several areas in which improvement may be made remain. Future studies may explore potential solutions to issues identified with new features to further promote interaction and foster learning in the course. Recommendations for instructors who are interested in offering online science courses in higher education are provided.

A Model for the Fast Synchronous Oscillations of Firing Rate in Rat Suprachiasmatic Nucleus Neurons Cultured in a Multielectrode Array Dish

PubMed Central

Stepanyuk, Andrey R.; Belan, Pavel V.; Kononenko, Nikolai I.

2014-01-01

When dispersed and cultured in a multielectrode dish (MED), suprachiasmatic nucleus (SCN) neurons express fast oscillations of firing rate (FOFR; fast relative to the circadian cycle), with burst duration ∼10 min, and interburst interval varying from 20 to 60 min in different cells but remaining nevertheless rather regular in individual cells. In many cases, separate neurons in distant parts of the 1 mm recording area of a MED exhibited correlated FOFR. Neither the mechanism of FOFR nor the mechanism of their synchronization among neurons is known. Based on recent data implicating vasoactive intestinal polypeptide (VIP) as a key intercellular synchronizing agent, we built a model in which VIP acts as both a feedback regulator to generate FOFR in individual neurons, and a diffusible synchronizing agent to produce coherent electrical output of a neuronal network. In our model, VIP binding to its (VPAC2) receptors acts through Gs G-proteins to activate adenylyl cyclase (AC), increase intracellular cAMP, and open cyclic-nucleotide-gated (CNG) cation channels, thus depolarizing the cell and generating neuronal firing to release VIP. In parallel, slowly developing homologous desensitization and internalization of VPAC2 receptors terminates elevation of cAMP and thereby provides an interpulse silent interval. Through mathematical modeling, we show that this VIP/VPAC2/AC/cAMP/CNG-channel mechanism is sufficient for generating reliable FOFR in single neurons. When our model for FOFR is combined with a published model of synchronization of circadian rhythms based on VIP/VPAC2 and Per gene regulation synchronization of circadian rhythms is significantly accelerated. These results suggest that (a) auto/paracrine regulation by VIP/VPAC2 and intracellular AC/cAMP/CNG-channels are sufficient to provide robust FOFR and synchrony among neurons in a heterogeneous network, and (b) this system may also participate in synchronization of circadian rhythms. PMID:25192180

Transportable Manned and Robotic Digital Geophysical Mapping Tow Vehicle, Phase 1

DTIC Science & Technology

2007-08-01

by using the UX PROCESS QC/QA tools to evaluate quality. Areas evaluated included induced noise, position and track accuracy, synchronization/latency... tools . To gain additional data on productivity and the effect of alternate direction of travel we mapped an unobstructed subset of the Grid 1-4 area...independently evaluated by using the UX PROCESS QC/QA tools to evaluate quality. Areas evaluated included induced noise, position and track

Elliptical multi-sun-synchronous orbits for Mars exploration

NASA Astrophysics Data System (ADS)

Circi, Christian; Ortore, Emiliano; Bunkheila, Federico; Ulivieri, Carlo

2012-11-01

The multi-sun-synchronous orbits allow cycles of observation of the same area in which solar illumination repetitively changes according to the value of the orbit elements and returns to the initial condition after a temporal interval multiple of the repetition of observation. This paper generalizes the concept of multi-sun-synchronous orbits, whose classical sun-synchronous orbits represent particular solutions, taking into consideration the elliptical case. The feasibility of using this typology of orbits, referred to as elliptical periodic multi-sun-synchronous orbits, has been investigated for the exploration of Mars and particular solutions have been selected. Such solutions considerably reduce the manoeuvre of velocity variation at the end of the interplanetary transfer with respect to the case of a target circular orbit around Mars. They are based on the use of quasi-critical inclinations in order to minimize the apsidal line motion and thus reduce orbit maintenance costs. Moreover, in the case of high eccentricities, the argument of pericentre may be set in order to obtain, around the apocentre, a condition of quasi-synchronism with the planet (the footprint of the probe on the surface presents a small shift with respect to a fixed point on the Martian surface). The low altitude of pericentre allows observation of the planet at a higher spatial resolution, while the orbit arc around the apocentre may be used to observe Mars with a wide spatial coverage in quasi-stationary conditions. This latter characteristic is useful for analysing atmospheric and meteorological phenomena and it allows for most of the orbital period a link between a rover on the surface of Mars and a probe orbiting around the planet.

Dopamine depletion increases the power and coherence of high-voltage spindles in the globus pallidus and motor cortex of freely moving rats.

PubMed

Ge, Shunnan; Yang, Chen; Li, Min; Li, Jiang; Chang, Xiaozan; Fu, Jian; Chen, Lei; Chang, Chongwang; Wang, Xuelian; Zhu, Junling; Gao, Guodong

2012-07-17

Studies on patients with Parkinson's disease and in animal models have observed enhanced synchronization of oscillations in several frequency bands within and between the cortical-basal ganglia (BG) structures. Recent research has also shown that synchronization of high-voltage spindles (HVSs) in the cortex, striatum and substantia nigra pars reticulate is increased by dopamine depletion. However, more evidence is needed to determine whether HVS activity in the whole cortex-BG network represents homologous alteration following dopamine depletion. As the globus pallidus (GP) is in a central position to propagate and synchronize oscillations in the cortical-BG circuits, we employed local-field potentials and electrocorticogram to simultaneously record oscillations in the GP and primary (M1) and secondary (M2) motor cortices on freely moving 6-hydroxydopamine (6-OHDA) lesioned and control rats. Results showed that HVS episodes recorded from GP, and M2 and M1 cortex areas were more numerous and longer in 6-OHDA lesioned rats compared to controls. Relative power associated with HVS activity in the GP, and M2 and M1 cortices of 6-OHDA lesioned rats was significantly greater than that for control rats. Coherence values for HVS activity between the GP, and M2 and M1 cortex areas were significantly increased by dopamine depletion. Time lag between the M1 cortex HVS and GP HVS was significantly shorter for dopamine depleted than normal rats. Findings indicate a crucial rule for dopamine in the regulation of HVS activity in the whole cortical-BG circuit, and suggest a close relationship between abnormally synchronized HVS oscillations in the cortex-BG network and Parkinson's disease. Copyright © 2012 Elsevier B.V. All rights reserved.

Desynchronization of chaos in coupled logistic maps.

PubMed

Maistrenko, Y L; Maistrenko, V L; Popovych, O; Mosekilde, E

1999-09-01

When identical chaotic oscillators interact, a state of complete or partial synchronization may be attained in which the motion is restricted to an invariant manifold of lower dimension than the full phase space. Riddling of the basin of attraction arises when particular orbits embedded in the synchronized chaotic state become transversely unstable while the state remains attracting on the average. Considering a system of two coupled logistic maps, we show that the transition to riddling will be soft or hard, depending on whether the first orbit to lose its transverse stability undergoes a supercritical or subcritical bifurcation. A subcritical bifurcation can lead directly to global riddling of the basin of attraction for the synchronized chaotic state. A supercritical bifurcation, on the other hand, is associated with the formation of a so-called mixed absorbing area that stretches along the synchronized chaotic state, and from which trajectories cannot escape. This gives rise to locally riddled basins of attraction. We present three different scenarios for the onset of riddling and for the subsequent transformations of the basins of attraction. Each scenario is described by following the type and location of the relevant asynchronous cycles, and determining their stable and unstable invariant manifolds. One scenario involves a contact bifurcation between the boundary of the basin of attraction and the absorbing area. Another scenario involves a long and interesting series of bifurcations starting with the stabilization of the asynchronous cycle produced in the riddling bifurcation and ending in a boundary crisis where the stability of an asynchronous chaotic state is destroyed. Finally, a phase diagram is presented to illustrate the parameter values at which the various transitions occur.

Finding the beat: a neural perspective across humans and non-human primates

PubMed Central

Merchant, Hugo; Grahn, Jessica; Trainor, Laurel; Rohrmeier, Martin; Fitch, W. Tecumseh

2015-01-01

Humans possess an ability to perceive and synchronize movements to the beat in music (‘beat perception and synchronization’), and recent neuroscientific data have offered new insights into this beat-finding capacity at multiple neural levels. Here, we review and compare behavioural and neural data on temporal and sequential processing during beat perception and entrainment tasks in macaques (including direct neural recording and local field potential (LFP)) and humans (including fMRI, EEG and MEG). These abilities rest upon a distributed set of circuits that include the motor cortico-basal-ganglia–thalamo-cortical (mCBGT) circuit, where the supplementary motor cortex (SMA) and the putamen are critical cortical and subcortical nodes, respectively. In addition, a cortical loop between motor and auditory areas, connected through delta and beta oscillatory activity, is deeply involved in these behaviours, with motor regions providing the predictive timing needed for the perception of, and entrainment to, musical rhythms. The neural discharge rate and the LFP oscillatory activity in the gamma- and beta-bands in the putamen and SMA of monkeys are tuned to the duration of intervals produced during a beat synchronization–continuation task (SCT). Hence, the tempo during beat synchronization is represented by different interval-tuned cells that are activated depending on the produced interval. In addition, cells in these areas are tuned to the serial-order elements of the SCT. Thus, the underpinnings of beat synchronization are intrinsically linked to the dynamics of cell populations tuned for duration and serial order throughout the mCBGT. We suggest that a cross-species comparison of behaviours and the neural circuits supporting them sets the stage for a new generation of neurally grounded computational models for beat perception and synchronization. PMID:25646516

Air Coupled Acoustic Thermography (ACAT) Inspection Technique

NASA Technical Reports Server (NTRS)

Zalameda, Joseph; Winfree, William P.; Yost, William T.

2007-01-01

The scope of this effort is to determine the viability of a new heating technique using a noncontact acoustic excitation source. Because of low coupling between air and the structure, a synchronous detection method is employed. Any reduction in the out of plane stiffness improves the acoustic coupling efficiency and as a result, defective areas have an increase in temperature relative to the surrounding area. Hence a new measurement system, based on air-coupled acoustic energy and synchronous detection is presented. An analytical model of a clamped circular plate is given, experimentally tested, and verified. Repeatability confirms the technique with a measurement uncertainty of plus or minus 6.2 percent. The range of frequencies used was 800-2,000 Hertz. Acoustic excitation and consequent thermal detection of flaws in a helicopter blade is examined and results indicate that air coupled acoustic excitation enables the detection of core damage in sandwich honeycomb structures.

Spike-Timing of Orbitofrontal Neurons Is Synchronized With Breathing.

PubMed

Kőszeghy, Áron; Lasztóczi, Bálint; Forro, Thomas; Klausberger, Thomas

2018-01-01

The orbitofrontal cortex (OFC) has been implicated in a multiplicity of complex brain functions, including representations of expected outcome properties, post-decision confidence, momentary food-reward values, complex flavors and odors. As breathing rhythm has an influence on odor processing at primary olfactory areas, we tested the hypothesis that it may also influence neuronal activity in the OFC, a prefrontal area involved also in higher order processing of odors. We recorded spike timing of orbitofrontal neurons as well as local field potentials (LFPs) in awake, head-fixed mice, together with the breathing rhythm. We observed that a large majority of orbitofrontal neurons showed robust phase-coupling to breathing during immobility and running. The phase coupling of action potentials to breathing was significantly stronger in orbitofrontal neurons compared to cells in the medial prefrontal cortex. The characteristic synchronization of orbitofrontal neurons with breathing might provide a temporal framework for multi-variable processing of olfactory, gustatory and reward-value relationships.

Regional synchroneity in fire regimes of western Oregon and Washington, USA.

Treesearch

P.J. Weisberg; F.J. Swanson

2003-01-01

For much of the world's forested area, the history of fire has significant implications for understanding forest dynamics over stand to regional scales. We analyzed temporal patterns of area burned at 25-year intervals over a 600-year period, using 10 treering-based fire history studies located west of the crest of the Cascade Range in the Pacific Northwest (PNW...

Fault Identification Based on Nlpca in Complex Electrical Engineering

NASA Astrophysics Data System (ADS)

Zhang, Yagang; Wang, Zengping; Zhang, Jinfang

2012-07-01

The fault is inevitable in any complex systems engineering. Electric power system is essentially a typically nonlinear system. It is also one of the most complex artificial systems in this world. In our researches, based on the real-time measurements of phasor measurement unit, under the influence of white Gaussian noise (suppose the standard deviation is 0.01, and the mean error is 0), we used mainly nonlinear principal component analysis theory (NLPCA) to resolve fault identification problem in complex electrical engineering. The simulation results show that the fault in complex electrical engineering is usually corresponding to the variable with the maximum absolute value coefficient in the first principal component. These researches will have significant theoretical value and engineering practical significance.

Comparison of measured and calculated forces on the RE-1000 free-piston Stirling engine displacer

NASA Technical Reports Server (NTRS)

Schreiber, Jeffrey G.

1987-01-01

The NASA Lewis Research Center has tested a 1 kW free-piston Stirling engine at the NASA Lewis test facilities. The tests performed over the past several years on the RE-1000 single cylinder engine are known as the sensitivity tests. This report presents an analysis of some of the data published in the sensitivity test report. A basic investigation into the measured forces acting on the unconstrained displacer of the engine is presented. These measured forces are then correlated with the values predicted by the NASA Lewis Stirling engine computer simulation. The results of the investigation are presented in the form of phasor diagrams. Possible future work resulting from this investigation is outlined.

Label-free identification of macrophage phenotype by fluorescence lifetime imaging microscopy

NASA Astrophysics Data System (ADS)

Alfonso-García, Alba; Smith, Tim D.; Datta, Rupsa; Luu, Thuy U.; Gratton, Enrico; Potma, Eric O.; Liu, Wendy F.

2016-04-01

Macrophages adopt a variety of phenotypes that are a reflection of the many functions they perform as part of the immune system. In particular, metabolism is a phenotypic trait that differs between classically activated, proinflammatory macrophages, and alternatively activated, prohealing macrophages. Inflammatory macrophages have a metabolism based on glycolysis while alternatively activated macrophages generally rely on oxidative phosphorylation to generate chemical energy. We employ this shift in metabolism as an endogenous marker to identify the phenotype of individual macrophages via live-cell fluorescence lifetime imaging microscopy (FLIM). We demonstrate that polarized macrophages can be readily discriminated with the aid of a phasor approach to FLIM, which provides a fast and model-free method for analyzing fluorescence lifetime images.

A Probabilistic Risk Mitigation Model for Cyber-Attacks to PMU Networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mousavian, Seyedamirabbas; Valenzuela, Jorge; Wang, Jianhui

The power grid is becoming more dependent on information and communication technologies. Complex networks of advanced sensors such as phasor measurement units (PMUs) are used to collect real time data to improve the observability of the power system. Recent studies have shown that the power grid has significant cyber vulnerabilities which could increase when PMUs are used extensively. Therefore, recognizing and responding to vulnerabilities are critical to the security of the power grid. This paper proposes a risk mitigation model for optimal response to cyber-attacks to PMU networks. We model the optimal response action as a mixed integer linear programmingmore » (MILP) problem to prevent propagation of the cyber-attacks and maintain the observability of the power system.« less

Crack azimuths on Europa: The G1 lineament sequence revisited

USGS Publications Warehouse

Sarid, A.R.; Greenberg, R.; Hoppa, G.V.; Brown, D.M.; Geissler, P.

2005-01-01

The tectonic sequence in the anti-jovian area covered by regional mapping images from Galileo's orbit E15 is determined from a study of cross-cutting relationships among lineament features. The sequence is used to test earlier results from orbit G1, based on lower resolution images, which appeared to display a progressive change in azimuthal orientation over about 90?? in a clockwise sense. Such a progression is consistent with expected stress variations that would accompany plausible non-synchronous rotation. The more recent data provide a more complete record than the G1 data did. We find that to fit the sequence into a continual clockwise change of orientation would require at least 1000?? (> 5 cycles) of azimuthal rotation. If due to non-synchronous rotation of Europa, this result implies that we are seeing back further into the tectonic record than the G1 results had suggested. The three sets of orientations found by Geissler et al. now appear to have been spaced out over several cycles, not during a fraction of one cycle. While our more complete sequence of lineament formation is consistent with non-synchronous rotation, a statistical test shows that it cannot be construed as independent evidence. Other lines of evidence do support non-synchronous rotation, but azimuths of crack sequences do not show it, probably because only a couple of cracks form in a given region in any given non-synchronous rotation period. ?? 2004 Elsevier Inc. All rights reserved.

Altered long-range alpha-band synchronization during visual short-term memory retention in children born very preterm.

PubMed

Doesburg, Sam M; Ribary, Urs; Herdman, Anthony T; Miller, Steven P; Poskitt, Kenneth J; Moiseev, Alexander; Whitfield, Michael F; Synnes, Anne; Grunau, Ruth E

2011-02-01

Children born very preterm, even when intelligence is broadly normal, often experience selective difficulties in executive function and visual-spatial processing. Development of structural cortical connectivity is known to be altered in this group, and functional magnetic resonance imaging (fMRI) evidence indicates that very preterm children recruit different patterns of functional connectivity between cortical regions during cognition. Synchronization of neural oscillations across brain areas has been proposed as a mechanism for dynamically assigning functional coupling to support perceptual and cognitive processing, but little is known about what role oscillatory synchronization may play in the altered neurocognitive development of very preterm children. To investigate this, we recorded magnetoencephalographic (MEG) activity while 7-8 year old children born very preterm and age-matched full-term controls performed a visual short-term memory task. Very preterm children exhibited reduced long-range synchronization in the alpha-band during visual short-term memory retention, indicating that cortical alpha rhythms may play a critical role in altered patterns functional connectivity expressed by this population during cognitive and perceptual processing. Long-range alpha-band synchronization was also correlated with task performance and visual-perceptual ability within the very preterm group, indicating that altered alpha oscillatory mechanisms mediating transient functional integration between cortical regions may be relevant to selective problems in neurocognitive development in this vulnerable population at school age. Copyright © 2010 Elsevier Inc. All rights reserved.

Gamma oscillation maintains stimulus structure-dependent synchronization in cat visual cortex.

PubMed

Samonds, Jason M; Bonds, A B

2005-01-01

Visual cortical cells demonstrate both oscillation and synchronization, although the underlying causes and functional significance of these behaviors remain uncertain. We simultaneously recorded single-unit activity with microelectrode arrays in supragranular layers of area 17 of cats paralyzed and anesthetized with propofol and N(2)O. Rate-normalized autocorrelograms of 24 cells reveal bursting (100%) and gamma oscillation (63%). Renewal density analysis, used to explore the source of oscillation, suggests a contribution from extrinsic influences such as feedback. However, a bursting refractory period, presumably membrane-based, could also encourage oscillatory firing. When we investigated the source of synchronization for 60 cell pairs we found only moderate correlation of synchrony with bursts and oscillation. We did, nonetheless, discover a possible functional role for oscillation. In all cases of cross-correlograms that exhibited oscillation, the strength of the synchrony was maintained throughout the stimulation period. When no oscillation was apparent, 75% of the cell pairs showed decay in their synchronization. The synchrony between cells is strongly dependent on similar response onset latencies. We therefore propose that structured input, which yields tight organization of latency, is a more likely candidate for the source of synchronization than oscillation. The reliable synchrony at response onset could be driven by spatial and temporal correlation of the stimulus that is preserved through the earlier stages of the visual system. Oscillation then contributes to maintenance of the synchrony to enhance reliable transmission of the information for higher cognitive processing.

Using the virtual brain to reveal the role of oscillations and plasticity in shaping brain's dynamical landscape.

PubMed

Roy, Dipanjan; Sigala, Rodrigo; Breakspear, Michael; McIntosh, Anthony Randal; Jirsa, Viktor K; Deco, Gustavo; Ritter, Petra

2014-12-01

Spontaneous brain activity, that is, activity in the absence of controlled stimulus input or an explicit active task, is topologically organized in multiple functional networks (FNs) maintaining a high degree of coherence. These "resting state networks" are constrained by the underlying anatomical connectivity between brain areas. They are also influenced by the history of task-related activation. The precise rules that link plastic changes and ongoing dynamics of resting-state functional connectivity (rs-FC) remain unclear. Using the framework of the open source neuroinformatics platform "The Virtual Brain," we identify potential computational mechanisms that alter the dynamical landscape, leading to reconfigurations of FNs. Using a spiking neuron model, we first demonstrate that network activity in the absence of plasticity is characterized by irregular oscillations between low-amplitude asynchronous states and high-amplitude synchronous states. We then demonstrate the capability of spike-timing-dependent plasticity (STDP) combined with intrinsic alpha (8-12 Hz) oscillations to efficiently influence learning. Further, we show how alpha-state-dependent STDP alters the local area dynamics from an irregular to a highly periodic alpha-like state. This is an important finding, as the cortical input from the thalamus is at the rate of alpha. We demonstrate how resulting rhythmic cortical output in this frequency range acts as a neuronal tuner and, hence, leads to synchronization or de-synchronization between brain areas. Finally, we demonstrate that locally restricted structural connectivity changes influence local as well as global dynamics and lead to altered rs-FC.

Emotions promote social interaction by synchronizing brain activity across individuals

PubMed Central

Nummenmaa, Lauri; Glerean, Enrico; Viinikainen, Mikko; Jääskeläinen, Iiro P.; Hari, Riitta; Sams, Mikko

2012-01-01

Sharing others’ emotional states may facilitate understanding their intentions and actions. Here we show that networks of brain areas “tick together” in participants who are viewing similar emotional events in a movie. Participants’ brain activity was measured with functional MRI while they watched movies depicting unpleasant, neutral, and pleasant emotions. After scanning, participants watched the movies again and continuously rated their experience of pleasantness–unpleasantness (i.e., valence) and of arousal–calmness. Pearson’s correlation coefficient was used to derive multisubject voxelwise similarity measures [intersubject correlations (ISCs)] of functional MRI data. Valence and arousal time series were used to predict the moment-to-moment ISCs computed using a 17-s moving average. During movie viewing, participants' brain activity was synchronized in lower- and higher-order sensory areas and in corticolimbic emotion circuits. Negative valence was associated with increased ISC in the emotion-processing network (thalamus, ventral striatum, insula) and in the default-mode network (precuneus, temporoparietal junction, medial prefrontal cortex, posterior superior temporal sulcus). High arousal was associated with increased ISC in the somatosensory cortices and visual and dorsal attention networks comprising the visual cortex, bilateral intraparietal sulci, and frontal eye fields. Seed-voxel–based correlation analysis confirmed that these sets of regions constitute dissociable, functional networks. We propose that negative valence synchronizes individuals’ brain areas supporting emotional sensations and understanding of another’s actions, whereas high arousal directs individuals’ attention to similar features of the environment. By enhancing the synchrony of brain activity across individuals, emotions may promote social interaction and facilitate interpersonal understanding. PMID:22623534

A novel rat model for chemotherapy-induced alopecia.

PubMed

Wikramanayake, T C; Amini, S; Simon, J; Mauro, L M; Elgart, G; Schachner, L A; Jimenez, J J

2012-04-01

More than half of all people diagnosed with cancer receive chemotherapy, and approximately 65% of these develop chemotherapy-induced alopecia (CIA), a side-effect that can have considerable negative psychological repercussions. Currently, there are very few animal models available to study the mechanism and prevention of CIA. To develop a clinically relevant adult rat model for CIA. We first tested whether neonatal pigmented Long-Evans (LE) rats developed alopecia in response to the chemotherapeutic agents etoposide and cyclophosphamide. We then determined whether the rats developed CIA as adults. In the latter experiment, rat dorsal hair was clipped during the early telogen stage to synchronize the hair cycle, and starting 15 days later, the rats were treated with etoposide for 3 days. Neonatal LE pups developed CIA in response to etoposide and cyclophosphamide, similar to other murine models for CIA. Clipping of the hair shaft during early telogen resulted in synchronized anagen induction and subsequent alopecia after etoposide treatment in the clipped areas only. Hair follicles in the clipped areas had the typical chemotherapy-induced follicular dystrophy (dystrophic catagen). When the hair in the pigmented alopecic areas regrew, it had normal pigmentation. A novel, pigmented adult rat model has been established for CIA. By hair-shaft clipping during early telogen, synchronized anagen entry was induced, which resulted in alopecia in response to chemotherapy. This is the first clinically relevant adult rat model for CIA, and will be a useful tool to test agents for the prevention and treatment of CIA. © The Author(s). CED © 2012 British Association of Dermatologists.

Seamless Image Mosaicking via Synchronization

NASA Astrophysics Data System (ADS)

Santellani, E.; Maset, E.; Fusiello, A.

2018-05-01

This paper proposes an innovative method to create high-quality seamless planar mosaics. The developed pipeline ensures good robustness against many common mosaicking problems (e.g., misalignments, colour distortion, moving objects, parallax) and differs from other works in the literature because a global approach, known as synchronization, is used for image registration and colour correction. To better conceal the mosaic seamlines, images are cut along specific paths, computed using a Voronoi decomposition of the mosaic area and a shortest path algorithm. Results obtained on challenging real datasets show that the colour correction mitigates significantly the colour variations between the original images and the seams on the final mosaic are not evident.

Telemetering and telecommunications research

NASA Technical Reports Server (NTRS)

Osborne, William; Paz, Robert; Ross, Michael; Kopp, Brian; Ashley, Norm

1993-01-01

The New Mexico State University (NMSU) Center for Space Telemetering and Telecommunications systems is engaged in advanced communications systems research. Four areas of study that are being sponsored concern investigations into the use of trellis-coded modulation (TCM). In particular, two areas concentrate on carrier synchronization research in TCM M-ary phase shift key (MPSK) systems. A third research topic is the study of interference effects on TCM, while the fourth research area is in the field of concatenated TCM systems.

[Coupling between ecological vulnerability and economic poverty in contiguous destitute areas, China: Empirical analysis of 714 poverty-stricken counties.

PubMed

Cao, Shi Song; Wang, Yan Hui; Duan, Fu Zhou; Zhao, Wen Ji; Wang, Zhi Heng; Fang, Na

2016-08-01

Maintaining the coordinated correlation between ecological environment and economic development is one of the important strategies in the new stage of poverty alleviation and development. Taking 714 poverty-stricken counties in contiguous destitute areas as study areas, this paper designed the ecological vulnerability evaluation indicator system based on the ecological sensitivity-resilience-pressure (SRP) conceptual model, as well as the comprehensive poverty evaluation indicators from the perspective of socioeconomic development, so as to build the coupling model to reveal the coupling between ecological vulnerability and economic poverty. The results showed that Hu-Line could act as a feasible partition label to depict the spatial distribution patterns of ecological vulnerability, economic poverty, as well as their coupling degree in contiguous destitute areas, which should be fully taken into consideration the influence of Hu-Line on the east-west pattern classification of national poverty reduction. In addition, there existed a symbiotic positive correlation between ecological vulnerability and economic poverty, therefore, the strategic significance of ecological and environment protection in poverty-stricken areas should be specifically emphasized to reduce economic poverty by synchronously protecting the ecological environment. Approximately half of the counties involved in the study area were in the coordinated type of recession disorders, where the ecological environment quality and the economic development could not be synchronized.

High-Speed Optical Wide-Area Data-Communication Network

NASA Technical Reports Server (NTRS)

Monacos, Steve P.

1994-01-01

Proposed fiber-optic wide-area network (WAN) for digital communication balances input and output flows of data with its internal capacity by routing traffic via dynamically interconnected routing planes. Data transmitted optically through network by wavelength-division multiplexing in synchronous or asynchronous packets. WAN implemented with currently available technology. Network is multiple-ring cyclic shuffle exchange network ensuring traffic reaches its destination with minimum number of hops.

Timing of population peaks of Norway lemming in relation to atmospheric pressure: A hypothesis to explain the spatial synchrony.

PubMed

Selås, Vidar

2016-06-01

Herbivore cycles are often synchronized over larger areas than what could be explained by dispersal. In Norway, the 3-4 year lemming cycle usually show no more than a one-year time lag between different regions, despite distances of up to 1000 km. If important food plants are forced to reallocate defensive proteins in years with high seed production, spatially synchronized herbivore outbreaks may be due to climate-synchronized peaks in flowering. Because lemming peaks are expected to occur one year after a flowering peak, and the formation of flower buds is induced in the year before flowering, a two-year time lag between flower-inducing climate events and lemming peaks is predicted. At Hardangervidda, South Norway, the probability that a year was a population peak year of lemming during 1920-2014 increased with increasing midsummer atmospheric pressure two years earlier, even when the number of years since the previous peak was accounted for.

Oscillatory mechanisms of process binding in memory.

PubMed

Klimesch, Wolfgang; Freunberger, Roman; Sauseng, Paul

2010-06-01

A central topic in cognitive neuroscience is the question, which processes underlie large scale communication within and between different neural networks. The basic assumption is that oscillatory phase synchronization plays an important role for process binding--the transient linking of different cognitive processes--which may be considered a special type of large scale communication. We investigate this question for memory processes on the basis of different types of oscillatory synchronization mechanisms. The reviewed findings suggest that theta and alpha phase coupling (and phase reorganization) reflect control processes in two large memory systems, a working memory and a complex knowledge system that comprises semantic long-term memory. It is suggested that alpha phase synchronization may be interpreted in terms of processes that coordinate top-down control (a process guided by expectancy to focus on relevant search areas) and access to memory traces (a process leading to the activation of a memory trace). An analogous interpretation is suggested for theta oscillations and the controlled access to episodic memories. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Auditory presentation and synchronization in Adobe Flash and HTML5/JavaScript Web experiments.

PubMed

Reimers, Stian; Stewart, Neil

2016-09-01

Substantial recent research has examined the accuracy of presentation durations and response time measurements for visually presented stimuli in Web-based experiments, with a general conclusion that accuracy is acceptable for most kinds of experiments. However, many areas of behavioral research use auditory stimuli instead of, or in addition to, visual stimuli. Much less is known about auditory accuracy using standard Web-based testing procedures. We used a millisecond-accurate Black Box Toolkit to measure the actual durations of auditory stimuli and the synchronization of auditory and visual presentation onsets. We examined the distribution of timings for 100 presentations of auditory and visual stimuli across two computers with difference specs, three commonly used browsers, and code written in either Adobe Flash or JavaScript. We also examined different coding options for attempting to synchronize the auditory and visual onsets. Overall, we found that auditory durations were very consistent, but that the lags between visual and auditory onsets varied substantially across browsers and computer systems.

Experience with synchronous and asynchronous digital control systems

NASA Technical Reports Server (NTRS)

Regenie, V. A.; Chacon, C. V.; Lock, W. P.

1986-01-01

Flight control systems have undergone a revolution since the days of simple mechanical linkages; presently the most advanced systems are full-authority, full-time digital systems controlling unstable aircraft. With the use of advanced control systems, the aerodynamic design can incorporate features that allow greater performance and fuel savings, as can be seen on the new Airbus design and advanced tactical fighter concepts. These advanced aircraft will be and are relying on the flight control system to provide the stability and handling qualities required for safe flight and to allow the pilot to control the aircraft. Various design philosophies have been proposed and followed to investigate system architectures for these advanced flight control systems. One major area of discussion is whether a multichannel digital control system should be synchronous or asynchronous. This paper addressed the flight experience at the Dryden Flight Research Facility of NASA's Ames Research Center with both synchronous and asynchronous digital flight control systems. Four different flight control systems are evaluated against criteria such as software reliability, cost increases, and schedule delays.

Predator-induced synchrony in population oscillations of coexisting small mammal species.

PubMed

Korpimäki, Erkki; Norrdahl, Kai; Huitu, Otso; Klemola, Tero

2005-01-22

Comprehensive analyses of long-term (1977-2003) small-mammal abundance data from western Finland showed that populations of Microtus voles (field voles M. agrestis and sibling voles M. rossiaemeridionalis) voles, bank (Clethrionomys glareolus) and common shrews (Sorex araneus) fluctuated synchronously in 3 year population cycles. Time-series analyses indicated that interspecific synchrony is influenced strongly by density-dependent processes. Synchrony among Microtus and bank voles appeared additionally to be influenced by density-independent processes. To test whether interspecific synchronization through density-dependent processes is caused by predation, we experimentally reduced the densities of the main predators of small mammals in four large agricultural areas, and compared small mammal abundances in these to those in four control areas (2.5-3 km(2)) through a 3 year small-mammal population cycle. Predator reduction increased densities of the main prey species, Microtus voles, in all phases of the population cycle, while bank voles, the most important alternative prey of predators, responded positively only in the low and the increase phase. Manipulation also increased the autumn densities of water voles (Arvicola terrestris) in the increase phase of the cycle. No treatment effects were detected for common shrews or mice. Our results are in accordance with the alternative prey hypothesis, by which predators successively reduce the densities of both main and alternative prey species after the peak phase of small-mammal population cycles, thus inducing a synchronous low phase.

Speed synchronization control for integrated automotive motor-transmission powertrain system with random delays

NASA Astrophysics Data System (ADS)

Zhu, Xiaoyuan; Zhang, Hui; Fang, Zongde

2015-12-01

This paper presents a robust speed synchronization controller design for an integrated motor-transmission powertrain system in which the driving motor and multi-gearbox are directly coupled. As the controller area network (CAN) is commonly used in the vehicle powertrain system, the possible network-induced random delays in both feedback and forward channel are considered and modeled by using two Markov chains in the controller design process. For the application perspective, the control law adopted here is a generalized proportional-integral (PI) control. By employing the system-augmentation technique, a delay-free stochastic closed-loop system is obtained and the generalized PI controller design problem is converted to a static output feedback (SOF) controller design problem. Since there are external disturbances involved in the closed-loop system, the energy-to-peak performance is considered to guarantee the robustness of the controller. And the controlled output is chosen as the speed synchronization error. To further improve the transient response of the closed-loop system, the pole placement is also employed in the energy-to-peak performance based speed synchronization control. The mode-dependent control gains are obtained by using an iterative linear matrix inequality (LMI) algorithm. Simulation results show the effectiveness of the proposed control approach.

A Low Power and High Throughput Self Synchronous FPGA Using 65nm CMOS with Throughput Optimization by Pipeline Alignment

NASA Astrophysics Data System (ADS)

Stefan Devlin, Benjamin; Nakura, Toru; Ikeda, Makoto; Asada, Kunihiro

We detail a self synchronous field programmable gate array (SSFPGA) with dual-pipeline (DP) architecture to conceal pre-charge time for dynamic logic, and its throughput optimization by using pipeline alignment implemented on benchmark circuits. A self synchronous LUT (SSLUT) consists of a three input tree-type structure with 8bits of SRAM for programming. A self synchronous switch box (SSSB) consists of both pass transistors and buffers to route signals, with 12bits of SRAM. One common block with one SSLUT and one SSSB occupies 2.2Mλ2 area with 35bits of SRAM, and the prototype SSFPGA with 34 × 30 (1020) blocks is designed and fabricated using 65nm CMOS. Measured results show at 1.2V 430MHz and 647MHz operation for a 3bit ripple carry adder, without and with throughput optimization, respectively. We find that using the proposed pipeline alignment techniques we can perform at maximum throughput of 647MHz in various benchmarks on the SSFPGA. We demonstrate up to 56.1 times throughput improvement with our pipeline alignment techniques. The pipeline alignment is carried out within the number of logic elements in the array and pipeline buffers in the switching matrix.

Throughput analysis of the IEEE 802.4 token bus standard under heavy load

NASA Technical Reports Server (NTRS)

Pang, Joseph; Tobagi, Fouad

1987-01-01

It has become clear in the last few years that there is a trend towards integrated digital services. Parallel to the development of public Integrated Services Digital Network (ISDN) is service integration in the local area (e.g., a campus, a building, an aircraft). The types of services to be integrated depend very much on the specific local environment. However, applications tend to generate data traffic belonging to one of two classes. According to IEEE 802.4 terminology, the first major class of traffic is termed synchronous, such as packetized voice and data generated from other applications with real-time constraints, and the second class is called asynchronous which includes most computer data traffic such as file transfer or facsimile. The IEEE 802.4 token bus protocol which was designed to support both synchronous and asynchronous traffic is examined. The protocol is basically a timer-controlled token bus access scheme. By a suitable choice of the design parameters, it can be shown that access delay is bounded for synchronous traffic. As well, the bandwidth allocated to asynchronous traffic can be controlled. A throughput analysis of the protocol under heavy load with constant channel occupation of synchronous traffic and constant token-passing times is presented.

Early multisensory interactions affect the competition among multiple visual objects.

PubMed

Van der Burg, Erik; Talsma, Durk; Olivers, Christian N L; Hickey, Clayton; Theeuwes, Jan

2011-04-01

In dynamic cluttered environments, audition and vision may benefit from each other in determining what deserves further attention and what does not. We investigated the underlying neural mechanisms responsible for attentional guidance by audiovisual stimuli in such an environment. Event-related potentials (ERPs) were measured during visual search through dynamic displays consisting of line elements that randomly changed orientation. Search accuracy improved when a target orientation change was synchronized with an auditory signal as compared to when the auditory signal was absent or synchronized with a distractor orientation change. The ERP data show that behavioral benefits were related to an early multisensory interaction over left parieto-occipital cortex (50-60 ms post-stimulus onset), which was followed by an early positive modulation (80-100 ms) over occipital and temporal areas contralateral to the audiovisual event, an enhanced N2pc (210-250 ms), and a contralateral negative slow wave (CNSW). The early multisensory interaction was correlated with behavioral search benefits, indicating that participants with a strong multisensory interaction benefited the most from the synchronized auditory signal. We suggest that an auditory signal enhances the neural response to a synchronized visual event, which increases the chances of selection in a multiple object environment. Copyright © 2010 Elsevier Inc. All rights reserved.

Interaction matters: Strategies to promote engaged learning in an online introductory nutrition course

PubMed Central

Banna, Jinan; Grace Lin, Meng-Fen; Stewart, Maria; Fialkowski, Marie K.

2016-01-01

Fostering interaction in the online classroom is an important consideration in ensuring that students actively create their own knowledge and reach a high level of achievement in science courses. This study focuses on fostering interaction in an online introductory nutrition course offered in a public institution of higher education in Hawai‘i, USA. Interactive features included synchronous discussions and polls in scheduled sessions, and social media tools for sharing of information and resources. Qualitative student feedback was solicited regarding the new course features. Findings indicated that students who attended monthly synchronous sessions valued live interaction with peers and the instructor. Issues identified included technical difficulties during synchronous sessions, lack of participation on the part of fellow students in discussion and inability to attend synchronous sessions due to scheduling conflicts. In addition, few students made use of the opportunity to interact via social media. While students indicated that the interactive components of the course were valuable, several areas in which improvement may be made remain. Future studies may explore potential solutions to issues identified with new features to further promote interaction and foster learning in the course. Recommendations for instructors who are interested in offering online science courses in higher education are provided. PMID:27441032

Wideband Interferometric Sensing and Imaging Polarimetry

NASA Technical Reports Server (NTRS)

Verdi, James Salvatore; Kessler, Otto; Boerner, Wolfgang-Martin

1996-01-01

Wideband Interferometric Sensing and Imaging Polarimetry (WISIP) has become an important, indispensible tool in wide area military surveillance and global environmental monitoring of the terrestrial and planetary covers. It enables dynamic, real time optimal feature extraction of significant characteristics of desirable targets and/or target sections with simultaneous suppression of undesirable background clutter and propagation path speckle at hitherto unknown clarity and never before achieved quality. WISIP may be adopted to the detection, recognition, and identification (DRI) of any stationary, moving or vibrating targets or distributed scatterer segments versus arbitrary stationary, dynamical changing and/or moving geo-physical/ecological environments, provided the instantaneous 2x2 phasor and 4x4 power density matrices for forward propagation/backward scattering, respectively, can be measured with sufficient accuracy. For example, the DRI of stealthy, dynamically moving inhomogeneous volumetric scatter environments such as precipitation scatter, the ocean/sea/lake surface boundary layers, the littoral coastal surf zones, pack ice and snow or vegetative canopies, dry sands and soils, etc. can now be successfully realized. A comprehensive overview is presented on how these modern high resolution/precision, complete polarimetric co-registered signature sensing and imaging techniques, complemented by full integration of novel navigational electronic tools, such as DGPS, will advance electromagnetic vector wave sensing and imaging towards the limits of physical realization. Various examples utilizing the most recent image data take sets of airborne, space shuttle, and satellite imaging systems demonstrate the utility of WISIP.

Reliability analysis of a phaser measurement unit using a generalized fuzzy lambda-tau(GFLT) technique.

PubMed

Komal

2018-05-01

Nowadays power consumption is increasing day-by-day. To fulfill failure free power requirement, planning and implementation of an effective and reliable power management system is essential. Phasor measurement unit(PMU) is one of the key device in wide area measurement and control systems. The reliable performance of PMU assures failure free power supply for any power system. So, the purpose of the present study is to analyse the reliability of a PMU used for controllability and observability of power systems utilizing available uncertain data. In this paper, a generalized fuzzy lambda-tau (GFLT) technique has been proposed for this purpose. In GFLT, system components' uncertain failure and repair rates are fuzzified using fuzzy numbers having different shapes such as triangular, normal, cauchy, sharp gamma and trapezoidal. To select a suitable fuzzy number for quantifying data uncertainty, system experts' opinion have been considered. The GFLT technique applies fault tree, lambda-tau method, fuzzified data using different membership functions, alpha-cut based fuzzy arithmetic operations to compute some important reliability indices. Furthermore, in this study ranking of critical components of the system using RAM-Index and sensitivity analysis have also been performed. The developed technique may be helpful to improve system performance significantly and can be applied to analyse fuzzy reliability of other engineering systems. Copyright © 2018 ISA. Published by Elsevier Ltd. All rights reserved.

Scanner. [photography from a spin stabilized synchronous satellite

NASA Technical Reports Server (NTRS)

Hummer, R. F.; Upton, D. T. (Inventor)

1981-01-01

An aerial vehicle rotating in gyroscopic fashion about one of its axes has an optical system which scans an area below the vehicle in determined relation to vehicle rotation. A sensing device is provided to sense the physical condition of the area of scan and optical means are associated to direct the physical intelligence received from the scan area to the sensing means. Means are provided to incrementally move the optical means through a series of steps to effect sequential line scan of the area being viewed keyed to the rotational rate of the vehicle.

Concurrent tACS-fMRI Reveals Causal Influence of Power Synchronized Neural Activity on Resting State fMRI Connectivity.

PubMed

Bächinger, Marc; Zerbi, Valerio; Moisa, Marius; Polania, Rafael; Liu, Quanying; Mantini, Dante; Ruff, Christian; Wenderoth, Nicole

2017-05-03

Resting state fMRI (rs-fMRI) is commonly used to study the brain's intrinsic neural coupling, which reveals specific spatiotemporal patterns in the form of resting state networks (RSNs). It has been hypothesized that slow rs-fMRI oscillations (<0.1 Hz) are driven by underlying electrophysiological rhythms that typically occur at much faster timescales (>5 Hz); however, causal evidence for this relationship is currently lacking. Here we measured rs-fMRI in humans while applying transcranial alternating current stimulation (tACS) to entrain brain rhythms in left and right sensorimotor cortices. The two driving tACS signals were tailored to the individual's α rhythm (8-12 Hz) and fluctuated in amplitude according to a 1 Hz power envelope. We entrained the left versus right hemisphere in accordance to two different coupling modes where either α oscillations were synchronized between hemispheres (phase-synchronized tACS) or the slower oscillating power envelopes (power-synchronized tACS). Power-synchronized tACS significantly increased rs-fMRI connectivity within the stimulated RSN compared with phase-synchronized or no tACS. This effect outlasted the stimulation period and tended to be more effective in individuals who exhibited a naturally weak interhemispheric coupling. Using this novel approach, our data provide causal evidence that synchronized power fluctuations contribute to the formation of fMRI-based RSNs. Moreover, our findings demonstrate that the brain's intrinsic coupling at rest can be selectively modulated by choosing appropriate tACS signals, which could lead to new interventions for patients with altered rs-fMRI connectivity. SIGNIFICANCE STATEMENT Resting state fMRI (rs-fMRI) has become an important tool to estimate brain connectivity. However, relatively little is known about how slow hemodynamic oscillations measured with fMRI relate to electrophysiological processes. It was suggested that slowly fluctuating power envelopes of electrophysiological signals synchronize across brain areas and that the topography of this activity is spatially correlated to resting state networks derived from rs-fMRI. Here we take a novel approach to address this problem and establish a causal link between the power fluctuations of electrophysiological signals and rs-fMRI via a new neuromodulation paradigm, which exploits these power synchronization mechanisms. These novel mechanistic insights bridge different scientific domains and are of broad interest to researchers in the fields of Medical Imaging, Neuroscience, Physiology, and Psychology. Copyright © 2017 the authors 0270-6474/17/374766-12$15.00/0.

Growth synchrony between leaves and stems during twig development differs among plant functional types of subtropical rainforest woody species.

PubMed

Meng, Fengqun; Zhang, Guangfu; Li, Xincheng; Niklas, Karl J; Sun, Shucun

2015-06-01

During the development of woody twigs, the growth in leaf may or may not be proportional to the growth in stem. The presence or absence of a synchronicity between these two phenologies may reflect differences in life history adaptive strategies concerning carbon gain. We hypothesized that sun-adapted species are more likely to be less synchronous between growths in total leaf area (TLA) and stem length compared with shade-adapted species, with a bias in growth in stem length, and that shade-adapted species are more likely to be more synchronous between increases in individual leaf area (ILA) (leaf size) and leaf number (LN) during twig development compared with sun-adapted species, giving priority to growth of leaf size. We tested these two hypotheses by recording the phenologies of leaf emergence, leaf expansion and stem elongation during twig development for 19 evergreen woody species (including five shade-adapted understory species, six sun-adapted understory species and eight sun-adapted canopy species) in a subtropical evergreen broad-leaved forest in eastern China. We constructed indices to characterize the synchronicity between TLA and stem length (αLS) and between leaf size and leaf number (αSN) and we derived the α values from logistic functions taking the general form of A = A(max)/[1 + exp(β - αB)] (where A is the TLA or average ILA, B is the corresponding stem length or LN at a specific time, and A(max) is the maximum TLA or the maximum ILA of a twig; the higher the numerical value of α, the less synchronous the corresponding phenologies). Consistent with our hypotheses, sun-adapted species were higher both in α(LS) and α(SN), showing less synchronous patterns in the growths of TLA vs stem length and leaf size vs LN during twig development. Moreover, α(LS) and α(SN) were significantly positively correlated with relative growth rates of LN and leaf size across species, as indicated by both analyses of ordinary regression and phylogenetic generalized least squares. The across-species synchronies during twig development show that the temporal dynamics of the leaf size-twig size spectrum is of adaptive significance in plants. We suggest that temporal dynamics of plant functional traits should be extensively studied to characterize plant life history. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Laparoscopic resection of synchronous colorectal cancers in separate specimens.

PubMed

Inada, Ryo; Yamamoto, Seiichiro; Takawa, Masashi; Fujita, Shin; Akasu, Takayuki

2014-08-01

Laparoscopic approaches are increasingly being used in patients with colorectal cancer, but the feasibility of laparoscopic resection of synchronous colorectal cancers in separate specimens remains unknown. In such cases, it is necessary to consider the site of port placement, sequence of dissection, choice of specimen extraction sites, specimen handling, and extracorporeal anastomosis sites. Moreover, the need for complete mesenteric dissection in two areas, removal of two separate specimens containing malignancies, and two anastomoses elicit unique questions related to technical considerations. The aim of this study was to determine the feasibility of laparoscopic resection of two separate specimens containing malignancies for multiple synchronous colorectal cancers. Between June 2001 and January 2013, 1341 patients with colorectal cancer underwent laparoscopic surgery at our institution. Of them, 11 patients underwent laparoscopy-assisted combined resection of two separate colorectal specimens for multiple synchronous primary colorectal cancers. We retrospectively reviewed their surgical outcomes. All procedures were completed laparoscopically without perioperative mortality. Patients underwent right-sided colon resection for right-sided cancer and left-sided or rectal resection for left-sided colon or rectal cancer. The median duration of surgery was 296 min, and the median blood loss was 65 mL. Median time to first postoperative liquid and solid intake was 1 day and 3 days, respectively. Most patients were discharged on postoperative day 8. With regard to postoperative complications, two patients had a surgical-site infection. Laparoscopic resection of two separate colorectal specimens for multiple synchronous primary colorectal cancers is a feasible and safe procedure. © 2014 Japan Society for Endoscopic Surgery, Asia Endosurgery Task Force and Wiley Publishing Asia Pty Ltd.

Synchronous isolated splenic metastasis from colon carcinoma and concomitant splenic abscess: A case report and review of the literature

PubMed Central

Pisanu, Adolfo; Ravarino, Alberto; Nieddu, Riccardo; Uccheddu, Alessandro

2007-01-01

This study aimed to describe a case in which an isolated splenic metastasis was synchronous with the colonic primary and a concomitant splenic abscess was associated. A wide review of the literature was also performed. A 54-year-old woman with abdominal pain and fever was admitted to our department. Abdominal CT revealed two low-density areas in the spleen and wall-thickening of the left colonic flexure, which was indistinguishable from the spleen parenchyma. The patient underwent emergency celiotomy, with the presumptive diagnosis of obstructing colon carcinoma of the splenic flexure, and concomitant splenic abscess. Subtotal colectomy and splenectomy were performed. Pathological findings were consistent with mucinous colonic carcinoma, synchronous isolated splenic metastasis and concomitant splenic abscess. This paper is also a review of the existing literature on the association between colorectal cancer and splenic metastasis. Only 41 cases of isolated splenic metastasis from colon carcinoma have been reported in the literature. This report is the third described case of synchronous isolated splenic metastasis from colon carcinoma. Only one case with concomitant splenic abscess has been previously reported. When obstructing left-sided colorectal cancer is suspected, careful CT examination can allow early diagnosis of splenic involvement by the tumor. The literature review suggests that there might be a significant improvement in survival following splenectomy for a metachronous isolated splenic metastasis from colon carcinoma. Prognosis for synchronous splenic metastasis seems to be related to the advanced stage of the disease. Nevertheless, no definitive conclusions can be drawn because of the small number of cases. PMID:17907299

Scaling of movement is related to pallidal γ oscillations in patients with dystonia.

PubMed

Brücke, Christof; Huebl, Julius; Schönecker, Thomas; Neumann, Wolf-Julian; Yarrow, Kielan; Kupsch, Andreas; Blahak, Christian; Lütjens, Goetz; Brown, Peter; Krauss, Joachim K; Schneider, Gerd-Helge; Kühn, Andrea A

2012-01-18

Neuronal synchronization in the gamma (γ) band is considered important for information processing through functional integration of neuronal assemblies across different brain areas. Movement-related γ synchronization occurs in the human basal ganglia where it is centered at ~70 Hz and more pronounced contralateral to the moved hand. However, its functional significance in motor performance is not yet well understood. Here, we assessed whether event-related γ synchronization (ERS) recorded from the globus pallidus internus in patients undergoing deep brain stimulation for medically intractable primary focal and segmental dystonia might code specific motor parameters. Pallidal local field potentials were recorded in 22 patients during performance of a choice-reaction-time task. Movement amplitude of the forearm pronation-supination movements was parametrically modulated with an angular degree of 30°, 60°, and 90°. Only patients with limbs not affected by dystonia were tested. A broad contralateral γ band (35-105 Hz) ERS occurred at movement onset with a maximum reached at peak velocity of the movement. The pallidal oscillatory γ activity correlated with movement parameters: the larger and faster the movement, the stronger was the synchronization in the γ band. In contrast, the event-related decrease in beta band activity was similar for all movements. Gamma band activity did not change with movement direction and did not occur during passive movements. The stepwise increase of γ activity with movement size and velocity suggests a role of neuronal synchronization in this frequency range in basal ganglia control of the scaling of ongoing movements.

Brain functional connectivity and the pathophysiology of schizophrenia.

PubMed

Angelopoulos, E

2014-01-01

In the last decade there is extensive evidence to suggest that cognitive functions depending on coordination of distributed neuronal responses are associated with synchronized oscillatory activity in various frequency ranges suggesting a functional mechanism of neural oscillations in cortical networks. In addition to their role in normal brain functioning, there is increasing evidence that altered oscillatory activity may be associated with certain neuropsychiatric disorders, such as schizophrenia. Consequently, disturbances in neural synchronization may represent the functional relationship of disordered connectivity of cortical networks underlying the characteristic fragmentation of mind and behavior in schizophrenia. In recent studies the synchronization of oscillatory activity in the experience of characteristic symptoms such as auditory verbal hallucinations and thought blocks have been studied in patients with schizophrenia. Studies involving analysis of EEG activity obtained from individuals in resting state (in cage Faraday, isolated from external influences and with eyes closed). In patients with schizophrenia and persistent auditory verbal hallucinations (AVHs) observed a temporary increase in the synchronization phase of α and high θ oscillations of the electroencephalogram (EEG) compared with those of healthy controls and patients without AVHs . This functional hyper-connection manifested in time windows corresponding to experience AVHs, as noted by the patients during the recording of EEG and observed in speech related cortical areas. In another study an interaction of theta and gamma oscillations engages in the production and experience of AVHs. The results showed increased phase coupling between theta and gamma EEG rhythms in the left temporal cortex during AVHs experiences. A more recent study, approaches the thought blocking experience in terms of functional brain connectivity. Thought blocks (TBs) are characterized by regular interruptions of the flow of thought. Outward signs are abrupt and repeated interruptions in the flow of conversation or actions while subjective experience is that of a total and uncontrollable emptying of the mind. In the very limited bibliography regarding TB, the phenomenon is thought to be conceptualized as a disturbance of consciousness that can be attributed to stoppages of continuous information processing due to an increase in the volume of information to be processed. In an attempt to investigate potential expression of the phenomenon on the functional properties of electroencephalographic (EEG) activity, an EEG study was contacted in schizophrenic patients with persisting auditory verbal hallucinations (AVHs) who additionally exhibited TBs. Phase synchronization analyses performed on EEG segments during the experience of TBs showed that synchrony values exhibited a long-range common mode of coupling (grouped behavior) among the left temporal area and the remaining central and frontal brain areas. These common synchrony-fluctuation schemes were observed for 0.5 to 2 s and were detected in a 4-s window following the estimated initiation of the phenomenon. The observation was frequency specific and detected in the broad alpha band region (6-12 Hz). The introduction of synchrony entropy (SE) analysis applied on the cumulative synchrony distribution showed that TB states were characterized by an explicit preference of the system to be functioned at low values of synchrony, while the synchrony values are broadly distributed during the recovery state. The results indicate that during TB states, the phase locking of several brain areas were converged uniformly in a narrow band of low synchrony values and in a distinct time window, impeding thus the ability of the system to recruit and to process information during this time window. The results of this study seem to have greater importance on neuronal correlation of consciousness. The brain is a highly distributed system in which numerous operations are executed in parallel and that lacks a single coordinating center. This raises the question of how the computations occurring simultaneously in spatially segregated processing areas are coordinated and bound together to give rise to coherent percepts and actions. One of the coordinating mechanisms appears to be the synchronization of neuronal activity by phase locking of self-generated network oscillations. This led to the hypothesis that the cerebral cortex might exploit the option to synchronize the discharges of neurons with millisecond ` theoretical formulations of the binding-by-synchrony hypothesis were proposed earlier by Milner (1974), but the Singer lab in the 1990s was the first to obtain experimental evidence supporting the potential role of synchrony as a relational code. The results concerning the functional connectivity of the brain during TBs further support the hypothesis of phase synchronization as a key mechanism for neuronal assemblies underlying mental representations in the human brain.

Horizons of cybernetical physics

PubMed Central

2017-01-01

The subject and main areas of a new research field—cybernetical physics—are discussed. A brief history of cybernetical physics is outlined. The main areas of activity in cybernetical physics are briefly surveyed, such as control of oscillatory and chaotic behaviour, control of resonance and synchronization, control in thermodynamics, control of distributed systems and networks, quantum control. This article is part of the themed issue ‘Horizons of cybernetical physics’. PMID:28115620

Identification of Successive ``Unobservable'' Cyber Data Attacks in Power Systems Through Matrix Decomposition

NASA Astrophysics Data System (ADS)

Gao, Pengzhi; Wang, Meng; Chow, Joe H.; Ghiocel, Scott G.; Fardanesh, Bruce; Stefopoulos, George; Razanousky, Michael P.

2016-11-01

This paper presents a new framework of identifying a series of cyber data attacks on power system synchrophasor measurements. We focus on detecting "unobservable" cyber data attacks that cannot be detected by any existing method that purely relies on measurements received at one time instant. Leveraging the approximate low-rank property of phasor measurement unit (PMU) data, we formulate the identification problem of successive unobservable cyber attacks as a matrix decomposition problem of a low-rank matrix plus a transformed column-sparse matrix. We propose a convex-optimization-based method and provide its theoretical guarantee in the data identification. Numerical experiments on actual PMU data from the Central New York power system and synthetic data are conducted to verify the effectiveness of the proposed method.

Determination of displacements and their derivatives from 3D fringe patterns via extended monogenic phasor method

NASA Astrophysics Data System (ADS)

Sciammarella, Cesar A.; Lamberti, Luciano

2018-05-01

For 1D signals, it is necessary to resort to a 2D abstract space because the concept of phase utilized in the retrieval of fringe pattern analysis information relies on the use of a vectorial function. Fourier and Hilbert transforms provide in-quadrature signals that lead to the very important basic concept of local phase. A 3D abstract space must hence be generated in order to analyze 2D signals. A 3D vector space in a Cartesian complex space is graphically represented by a Poincare sphere. In this study, the extension of the associated spaces is extended to 3D. A 4D hypersphere is defined for that purpose. The proposed approach is illustrated by determining the deformations of the heart left ventricle.

PMU Data Event Detection: A User Guide for Power Engineers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Allen, A.; Singh, M.; Muljadi, E.

2014-10-01

This user guide is intended to accompany a software package containing a Matrix Laboratory (MATLAB) script and related functions for processing phasor measurement unit (PMU) data. This package and guide have been developed by the National Renewable Energy Laboratory and the University of Texas at Austin. The objective of this data processing exercise is to discover events in the vast quantities of data collected by PMUs. This document attempts to cover some of the theory behind processing the data to isolate events as well as the functioning of the MATLAB scripts. The report describes (1) the algorithms and mathematical backgroundmore » that the accompanying MATLAB codes use to detect events in PMU data and (2) the inputs required from the user and the outputs generated by the scripts.« less

Three-dimensional computation of laser cavity eigenmodes by the use of finite element analysis (FEA)

NASA Astrophysics Data System (ADS)

Altmann, Konrad; Pflaum, Christoph; Seider, David

2004-06-01

A new method for computing eigenmodes of a laser resonator by the use of finite element analysis (FEA) is presented. For this purpose, the scalar wave equation [Δ + k2]E(x,y,z) = 0 is transformed into a solvable 3D eigenvalue problem by separating out the propagation factor exp(-ikz) from the phasor amplitude E(x,y,z) of the time-harmonic electrical field. For standing wave resonators, the beam inside the cavity is represented by a two-wave ansatz. For cavities with parabolic optical elements the new approach has successfully been verified by the use of the Gaussian mode algorithm. For a DPSSL with a thermally lensing crystal inside the cavity the expected deviation between Gaussian approximation and numerical solution could be demonstrated clearly.

Ncl Synchronously Regulates Na+, K+, and Cl- in Soybean and Greatly Increases the Grain Yield in Saline Field Conditions.

PubMed

Do, Tuyen Duc; Chen, Huatao; Hien, Vu Thi Thu; Hamwieh, Aladdin; Yamada, Tetsuya; Sato, Tadashi; Yan, Yongliang; Cong, Hua; Shono, Mariko; Suenaga, Kazuhiro; Xu, Donghe

2016-01-08

Salt stress inhibits soybean growth and reduces gain yield. Genetic improvement of salt tolerance is essential for sustainable soybean production in saline areas. In this study, we isolated a gene (Ncl) that could synchronously regulate the transport and accumulation of Na(+), K(+), and Cl(-) from a Brazilian soybean cultivar FT-Abyara using map-based cloning strategy. Higher expression of the salt tolerance gene Ncl in the root resulted in lower accumulations of Na(+), K(+), and Cl(-) in the shoot under salt stress. Transfer of Ncl with the Agrobacterium-mediated transformation method into a soybean cultivar Kariyutaka significantly enhanced its salt tolerance. Introgression of the tolerance allele into soybean cultivar Jackson, using DNA marker-assisted selection (MAS), produced an improved salt tolerance line. Ncl could increase soybean grain yield by 3.6-5.5 times in saline field conditions. Using Ncl in soybean breeding through gene transfer or MAS would contribute to sustainable soybean production in saline-prone areas.

A novel technique for phase synchrony measurement from the complex motor imaginary potential of combined body and limb action

NASA Astrophysics Data System (ADS)

Zhou, Zhong-xing; Wan, Bai-kun; Ming, Dong; Qi, Hong-zhi

2010-08-01

In this study, we proposed and evaluated the use of the empirical mode decomposition (EMD) technique combined with phase synchronization analysis to investigate the human brain synchrony of the supplementary motor area (SMA) and primary motor area (M1) during complex motor imagination of combined body and limb action. We separated the EEG data of the SMA and M1 into intrinsic mode functions (IMFs) using the EMD method and determined the characteristic IMFs by power spectral density (PSD) analysis. Thereafter, the instantaneous phases of the characteristic IMFs were obtained by the Hilbert transformation, and the single-trial phase-locking value (PLV) features for brain synchrony measurement between the SMA and M1 were investigated separately. The classification performance suggests that the proposed approach is effective for phase synchronization analysis and is promising for the application of a brain-computer interface in motor nerve reconstruction of the lower limbs.

Synchronization and anti-synchronization of a fractional order delayed memristor-based chaotic system using active control

NASA Astrophysics Data System (ADS)

Ding, Dawei; Qian, Xin; Wang, Nian; Liang, Dong

2018-05-01

In this paper, the issue of synchronization and anti-synchronization for fractional-delayed memristor-based chaotic system is studied by using active control strategy. Firstly, some explicit conditions are proposed to guarantee the synchronization and anti-synchronization of the proposed system. Secondly, the influence of order and time delay on the synchronization (anti-synchronization) is discussed. It reveals that synchronization (anti-synchronization) is faster as the order increases or the time delay decreases. Finally, some numerical simulations are presented to verify the validity of our theoretical analysis.

Active control strategy for synchronization and anti-synchronization of a fractional chaotic financial system

NASA Astrophysics Data System (ADS)

Huang, Chengdai; Cao, Jinde

2017-05-01

This paper is concerned with the issues of synchronization and anti-synchronization for fractional chaotic financial system with market confidence by taking advantage of active control approach. Some sufficient conditions are derived to guarantee the synchronization and anti-synchronization for the proposed fractional system. Moreover, the relationship between the order and synchronization(anti-synchronization) is demonstrated numerically. It reveals that synchronization(anti-synchronization) is faster as the order increases. Finally, two illustrative examples are exploited to verify the efficiency of the obtained theoretical results.

Cortical connectivity modulation during sleep onset: A study via graph theory on EEG data.

PubMed

Vecchio, Fabrizio; Miraglia, Francesca; Gorgoni, Maurizio; Ferrara, Michele; Iberite, Francesco; Bramanti, Placido; De Gennaro, Luigi; Rossini, Paolo Maria

2017-11-01

Sleep onset is characterized by a specific and orchestrated pattern of frequency and topographical EEG changes. Conventional power analyses of electroencephalographic (EEG) and computational assessments of network dynamics have described an earlier synchronization of the centrofrontal areas rhythms and a spread of synchronizing signals from associative prefrontal to posterior areas. Here, we assess how "small world" characteristics of the brain networks, as reflected in the EEG rhythms, are modified in the wakefulness-sleep transition comparing the pre- and post-sleep onset epochs. The results show that sleep onset is characterized by a less ordered brain network (as reflected by the higher value of small world) in the sigma band for the frontal lobes indicating stronger connectivity, and a more ordered brain network in the low frequency delta and theta bands indicating disconnection on the remaining brain areas. Our results depict the timing and topography of the specific mechanisms for the maintenance of functional connectivity of frontal brain regions at the sleep onset, also providing a possible explanation for the prevalence of the frontal-to-posterior information flow directionality previously observed after sleep onset. Hum Brain Mapp 38:5456-5464, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

The role of global cloud climatologies in validating numerical models

NASA Technical Reports Server (NTRS)

HARSHVARDHAN

1993-01-01

The purpose of this work is to estimate sampling errors of area-time averaged rain rate due to temporal samplings by satellites. In particular, the sampling errors of the proposed low inclination orbit satellite of the Tropical Rainfall Measuring Mission (TRMM) (35 deg inclination and 350 km altitude), one of the sun synchronous polar orbiting satellites of NOAA series (98.89 deg inclination and 833 km altitude), and two simultaneous sun synchronous polar orbiting satellites--assumed to carry a perfect passive microwave sensor for direct rainfall measurements--will be estimated. This estimate is done by performing a study of the satellite orbits and the autocovariance function of the area-averaged rain rate time series. A model based on an exponential fit of the autocovariance function is used for actual calculations. Varying visiting intervals and total coverage of averaging area on each visit by the satellites are taken into account in the model. The data are generated by a General Circulation Model (GCM). The model has a diurnal cycle and parameterized convective processes. A special run of the GCM was made at NASA/GSFC in which the rainfall and precipitable water fields were retained globally for every hour of the run for the whole year.

The role of attention and intention in synchronization to music: effects on gait.

PubMed

Leow, Li-Ann; Waclawik, Kristina; Grahn, Jessica A

2018-01-01

Anecdotal accounts suggest that individuals spontaneously synchronize their movements to the 'beat' of background music, often without intending to, and perhaps even without attending to the music at all. However, the question of whether intention and attention are necessary to synchronize to the beat remains unclear. Here, we compared whether footsteps during overground walking were synchronized to the beat when young healthy adults were explicitly instructed to synchronize (intention to synchronize), and were not instructed to synchronize (no intention) (Experiment 1: intention). We also examined whether reducing participants' attention to the music affected synchronization, again when participants were explicitly instructed to synchronize, and when they were not (Experiment 2: attention/intention). Synchronization was much less frequent when no instructions to synchronize were given. Without explicit instructions to synchronize, there was no evidence of synchronization in 60% of the trials in Experiment 1, and 43% of the trials in Experiment 2. When instructed to synchronize, only 26% of trials in Experiment 1, and 14% of trials in Experiment 2 showed no evidence of synchronization. Because walking to music alters gait, we also examined how gait kinematics changed with or without instructions to synchronize, and attention to the music was required for synchronization to occur. Instructions to synchronize elicited slower, shorter, and more variable strides than walking in silence. Reducing attention to the music did not significantly affect synchronization of footsteps to the beat, but did elicit slower gait. Thus, during walking, intention, but not attention, appears to be necessary to synchronize footsteps to the beat, and synchronization elicits slower, shorter, and more variable strides, at least in young healthy adults.

Synchronous brain activity across individuals underlies shared psychological perspectives

PubMed Central

Lahnakoski, Juha M.; Glerean, Enrico; Jääskeläinen, Iiro P.; Hyönä, Jukka; Hari, Riitta; Sams, Mikko; Nummenmaa, Lauri

2014-01-01

For successful communication, we need to understand the external world consistently with others. This task requires sufficiently similar cognitive schemas or psychological perspectives that act as filters to guide the selection, interpretation and storage of sensory information, perceptual objects and events. Here we show that when individuals adopt a similar psychological perspective during natural viewing, their brain activity becomes synchronized in specific brain regions. We measured brain activity with functional magnetic resonance imaging (fMRI) from 33 healthy participants who viewed a 10-min movie twice, assuming once a ‘social’ (detective) and once a ‘non-social’ (interior decorator) perspective to the movie events. Pearson's correlation coefficient was used to derive multisubject voxelwise similarity measures (inter-subject correlations; ISCs) of functional MRI data. We used k-nearest-neighbor and support vector machine classifiers as well as a Mantel test on the ISC matrices to reveal brain areas wherein ISC predicted the participants' current perspective. ISC was stronger in several brain regions—most robustly in the parahippocampal gyrus, posterior parietal cortex and lateral occipital cortex—when the participants viewed the movie with similar rather than different perspectives. Synchronization was not explained by differences in visual sampling of the movies, as estimated by eye gaze. We propose that synchronous brain activity across individuals adopting similar psychological perspectives could be an important neural mechanism supporting shared understanding of the environment. PMID:24936687

Phase synchronization of oxygenation waves in the frontal areas of children with attention-deficit hyperactivity disorder detected by optical diffusion spectroscopy correlates with medication

NASA Astrophysics Data System (ADS)

Wigal, Sharon B.; Polzonetti, Chiara M.; Stehli, Annamarie; Gratton, Enrico

2012-12-01

The beneficial effects of pharmacotherapy on children with attention-deficit hyperactivity disorder (ADHD) are well documented. We use near-infrared spectroscopy (NIRS) methodology to determine reorganization of brain neurovascular properties following the medication treatment. Twenty-six children with ADHD (ages six through 12) participated in a modified laboratory school protocol to monitor treatment response with lisdexamfetamine dimesylate (LDX; Vyvanse, Shire US Inc.). All children refrained from taking medication for at least two weeks (washout period). To detect neurovascular reorganization, we measured changes in synchronization of oxy (HbO2) and deoxy (HHb) hemoglobin waves between the two frontal lobes. Participants without medication displayed average baseline HbO2 phase difference at about -7-deg. and HHb differences at about 240-deg.. This phase synchronization index changed after pharmacological intervention. Medication induced an average phase changes of HbO2 after first medication to 280-deg. and after medication optimization to 242-deg.. Instead first medication changed of the average HHb phase difference at 186-deg. and then after medication optimization to 120-deg. In agreement with findings of White et al., and Varela et al., we associated the phase synchronization differences of brain hemodynamics in children with ADHD with lobe specific hemodynamic reorganization of HbO2- and HHB oscillations following medication status.

Core strengthening and synchronized swimming: TRX® suspension training in young female athletes.

PubMed

Tinto, Amalia; Campanella, Marta; Fasano, Milena

2017-06-01

Developing muscle strength and full body stability is essential for the efficient execution of technical moves in synchronized swimming. However, many swimmers find it difficult to control body stability while executing particular figures in water. We evaluated the effects of TRX® suspension training (2 sessions weekly for 6 months on core strength and core stability in young female. Twenty synchronized swimmers (Beginners A category, mean age 10±1 years) are divided in experimental group (EG; N.=10 athletes) and control group (CG; N.=10 athletes). EG received suspension training twice weekly (each session lasting about 15 min) as dryland exercises for 6 months in addition to routine training. CG completed routine training with conventional dryland exercises. Before (T1) and after (T2) completion of the study oblique and transversus abdominis muscle force was measured using a Stabilizer Pressure Biofeedback unit, in prone and supine positions, and isotonic muscle endurance was evaluated with the McGill Test. Non-parametric statistical analysis showed a significant increase (P<0.0001) in the majority of the parameters in the experimental group. The study results provide evidence for the benefit of integrating TRX® suspension training in dryland exercises for muscle strengthening in young athletes practicing synchronized swimming, and in general reiterates the importance of strengthening the core area to ensure stability and specific adaptations, improve the quality of the movement and prevent against injury.

Comparison of connectivity analyses for resting state EEG data

NASA Astrophysics Data System (ADS)

Olejarczyk, Elzbieta; Marzetti, Laura; Pizzella, Vittorio; Zappasodi, Filippo

2017-06-01

Objective. In the present work, a nonlinear measure (transfer entropy, TE) was used in a multivariate approach for the analysis of effective connectivity in high density resting state EEG data in eyes open and eyes closed. Advantages of the multivariate approach in comparison to the bivariate one were tested. Moreover, the multivariate TE was compared to an effective linear measure, i.e. directed transfer function (DTF). Finally, the existence of a relationship between the information transfer and the level of brain synchronization as measured by phase synchronization value (PLV) was investigated. Approach. The comparison between the connectivity measures, i.e. bivariate versus multivariate TE, TE versus DTF, TE versus PLV, was performed by means of statistical analysis of indexes based on graph theory. Main results. The multivariate approach is less sensitive to false indirect connections with respect to the bivariate estimates. The multivariate TE differentiated better between eyes closed and eyes open conditions compared to DTF. Moreover, the multivariate TE evidenced non-linear phenomena in information transfer, which are not evidenced by the use of DTF. We also showed that the target of information flow, in particular the frontal region, is an area of greater brain synchronization. Significance. Comparison of different connectivity analysis methods pointed to the advantages of nonlinear methods, and indicated a relationship existing between the flow of information and the level of synchronization of the brain.

Influence of weather on the synchrony of gypsy moth (Lepidoptera: Lymantriidae) outbreaks in New England

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, D.W.; Liebhold, A.M.

1995-10-01

Outbreaks of the gypsy moth, Lymantria dispar (L.), were partially synchronous across New England states (Massachusetts, Maine, New Hampshire, and Vermont) from 1938 to 1992. To explain this synchrony, we investigated the Moran effect, a hypothesis that local population oscillations, which result form similar density-dependent mechanisms operating at time lags, may be synchronized over wide areas by exposure to common weather patterns. We also investigated the theory of climatic release, which ostulates that outbreaks are triggered by climatic factors favorable for population growth. Time series analysis revealed defoliation series in 2 states as 1st-order autoregressive processes and the other 2more » as periodic 2nd-order autoregressive processes. Defoliation residuals series computed using the autoregressive models for each state were cross correlated with series of weather variables recorded in the respective states. The weather variables significantly correlated with defoliation residuals in all 4 states were minimum temperature and precipitation in mid-December in the same gypsy moth generation and minimum temperature in mid- to late July of the previous generation. These weather variables also were correlated strongly among the 4 states. The analyses supported the predictions of the Moran effect and suggest the common weather may synchronize local populations so as to produce pest outbreaks over wide areas. We did not find convincing evidence to support the theory of climatic release. 41 refs., 7 figs., 4 tabs.« less

Sleep-related modifications of EEG connectivity in the sensory-motor networks in Huntington Disease: An eLORETA study and review of the literature.

PubMed

Piano, Carla; Imperatori, Claudio; Losurdo, Anna; Bentivoglio, Anna Rita; Cortelli, Pietro; Della Marca, Giacomo

2017-07-01

To evaluate EEG functional connectivity in the sensory-motor network, during wake and sleep, in patients with Huntington Disease (HD). 23 patients with HD and 23 age- and sex-matched healthy controls were enrolled. EEG connectivity analysis was performed by means of exact Low Resolution Electric Tomography (eLORETA). In wake, HD patients showed an increase of delta lagged phase synchronization (T=3.60; p<0.05) among Broadman's Areas (BA) 6-8 bilaterally; right BA 6-8 and right BA 1-2-3; left BA 1-2-3 and left BA 4. In NREM, HD patients showed an increase of delta lagged phase synchronization (T=3.56; p<0.05) among left BA 1-2-3 and right BA 6-8. In REM, HD patients showed an increase of lagged phase synchronization (T=3.60; p<0.05) among the BA 6-8 bilaterally (delta band); left BA 1-2-3 and right BA 1-2-3 (theta); left BA 1-2-3 and right BA 4 (theta); left BA 1-2-3 and right BA 1-2-3 (alpha). Our results may reflect an abnormal function of the motor areas or an effort to counterbalance the pathological motor output. Our results may help to understand the pathophysiology of sleep-related movement disorders in Huntington's Disease, and to define therapeutically strategies. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Contribution a l'etude des spectres composites. VI. HD 66068-9.

NASA Astrophysics Data System (ADS)

Carquillat, J. M.; Ginestet, N.; Duquennoy, A.; Pedoussaut, A.

1994-09-01

HD 66068-9 is listed by Hynek (1938) as a star having a composite spectrum. Classifications made by various authors and by us indicate that this star is, in fact, an Am one. Our radial velocity observations, carried out at the Observatoire de Haute-Provence with the spectrovelocimeter CORAVEL, show HD 66068-9 to be a double-lined spectroscopic binary with the following orbital elements: P=7.74799days; T=2447600.690JD; ω=341.1deg; e=0.418; K_1_=56.1km/s; K_2_=75.1km/s; V_0_=-21.1km/s; a_1_sini=5.43x10^6^km; a_2_sini=7.27x10^6^km; M_1_sin^3^i=0.78Msun_; M_2_sin^3^i=0.58Msun_. The system appears to be a detached one (a=~25Rsun_) without possibility of eclipses (i=~47deg); the secondary component should be an early F dwarf star. The ratio of the corelation dip areas indicates a blue magnitude difference {DELTA}m~1.6mag., and the dip area of the primary alone a metallicity [Fe/H]=~0.37dex for the Am star. Rotation-revolution synchronism is discussed: we conclude that this binary does not rotate synchronically but perhaps that pseudo-synchronization occurs near the periastron passage, according to Hut's theory. Perturbations of some radial velocities during 1983 suggest the existence of a long period third body.

Predator-induced synchrony in population oscillations of coexisting small mammal species

PubMed Central

Korpimäki, Erkki; Norrdahl, Kai; Huitu, Otso; Klemola, Tero

2005-01-01

Comprehensive analyses of long-term (1977–2003) small-mammal abundance data from western Finland showed that populations of Microtus voles (field voles M. agrestis and sibling voles M. rossiaemeridionalis) voles, bank (Clethrionomys glareolus) and common shrews (Sorex araneus) fluctuated synchronously in 3 year population cycles. Time-series analyses indicated that interspecific synchrony is influenced strongly by density-dependent processes. Synchrony among Microtus and bank voles appeared additionally to be influenced by density-independent processes. To test whether interspecific synchronization through density-dependent processes is caused by predation, we experimentally reduced the densities of the main predators of small mammals in four large agricultural areas, and compared small mammal abundances in these to those in four control areas (2.5–3 km2) through a 3 year small-mammal population cycle. Predator reduction increased densities of the main prey species, Microtus voles, in all phases of the population cycle, while bank voles, the most important alternative prey of predators, responded positively only in the low and the increase phase. Manipulation also increased the autumn densities of water voles (Arvicola terrestris) in the increase phase of the cycle. No treatment effects were detected for common shrews or mice. Our results are in accordance with the alternative prey hypothesis, by which predators successively reduce the densities of both main and alternative prey species after the peak phase of small-mammal population cycles, thus inducing a synchronous low phase. PMID:15695211

Microinjection of procaine and electrolytic lesion in the ventral tegmental area suppresses hippocampal theta rhythm in urethane-anesthetized rats.

PubMed

Orzeł-Gryglewska, Jolanta; Jurkowlaniec, Edyta; Trojniar, Weronika

2006-01-30

The midbrain ventral tegmental area (VTA), a key structure of the mesocorticolimbic system is anatomically connected with the hippocampal formation. In addition mesocortical dopamine was found to influence hippocampus-related memory and hippocampal synaptic plasticity, both being linked to the theta rhythm. Therefore, the aim of the present study was to evaluate the possible role of the VTA in the regulation of the hippocampal theta activity. The study was performed on urethane-anesthetized male Wistar rats in which theta rhythm was evoked by tail pinch. It was found that unilateral, temporal inactivation of the VTA by means of direct procaine injection resulted in bilateral suppression of the hippocampal theta which manifested as a loss of synchronization of hippocampal EEG and respective reduction of the power and also the frequency of the 3-6 Hz theta band. Depression of the power of the 3-6 Hz component of the EEG signal was also seen in spontaneous hippocampal EEG after procaine. The permanent destruction of the VTA by means of unilateral electrocoagulation evoked a long-lasting, mainly ipsilateral depression of the power of the theta with some influence on its frequency. Simultaneously, there was a substantial increase of the power in higher frequency bands indicating decrease of a synchrony of the hippocampal EEG activity. On the basis of these results indicating impairment of synchronization of the hippocampal activity the VTA may be considered as another part of the brainstem theta synchroning system.

A combined gene and cell therapy approach for restoration of conduction.

PubMed

Hofshi, Anat; Itzhaki, Ilanit; Gepstein, Amira; Arbel, Gil; Gross, Gil J; Gepstein, Lior

2011-01-01

Abnormal conduction underlies both bradyarrhythmias and re-entrant tachyarrhythmias. However, no practical way exists for restoring or improving conduction in areas of conduction slowing or block. This study sought to test the feasibility of a novel strategy for conduction repair using genetically engineered cells designed to form biological "conducting cables." An in vitro model of conduction block was established using spatially separated, spontaneously contracting, nonsynchronized human embryonic stem cell-derived cardiomyocytes clusters. Immunostaining, dye transfer, intracellular recordings, and multielectrode array (MEA) studies were performed to evaluate the ability of genetically engineered HEK293 cells, expressing the SCN5A-encoded Na(+) channel, to couple with cultured cardiomyocytes and to synchronize their electrical activity. Connexin-43 immunostaining and calcein dye-transfer experiments confirmed the formation of functional gap junctions between the engineered cells and neighboring cardiomyocytes. MEA and intracellular recordings were performed to assess the ability of the engineered cells to restore conduction in the co-cultures. Synchronization was defined by establishment of fixed local activation time differences between the cardiomyocytes clusters and convergence of their activation cycle lengths. Nontransfected control cells were able to induce synchronization between cardiomyocytes clusters separated by distances up to 300 μm (n = 21). In contrast, the Na(+) channel-expressing cells synchronized contractions between clusters separated by up to 1,050 μm, the longest distance studied (n = 23). Finally, engineered cells expressing the voltage-sensitive K(v)1.3 potassium channel prevented synchronization at any distance. Genetically engineered cells, transfected to express Na(+) channels, can form biological conducting cables bridging and coupling spatially separated cardiomyocytes. This novel cell therapy approach might be useful for the development of therapeutic strategies for both bradyarrhythmias and tachyarrhythmias. Copyright © 2011 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Mechanisms of Zero-Lag Synchronization in Cortical Motifs

PubMed Central

Gollo, Leonardo L.; Mirasso, Claudio; Sporns, Olaf; Breakspear, Michael

2014-01-01

Zero-lag synchronization between distant cortical areas has been observed in a diversity of experimental data sets and between many different regions of the brain. Several computational mechanisms have been proposed to account for such isochronous synchronization in the presence of long conduction delays: Of these, the phenomenon of “dynamical relaying” – a mechanism that relies on a specific network motif – has proven to be the most robust with respect to parameter mismatch and system noise. Surprisingly, despite a contrary belief in the community, the common driving motif is an unreliable means of establishing zero-lag synchrony. Although dynamical relaying has been validated in empirical and computational studies, the deeper dynamical mechanisms and comparison to dynamics on other motifs is lacking. By systematically comparing synchronization on a variety of small motifs, we establish that the presence of a single reciprocally connected pair – a “resonance pair” – plays a crucial role in disambiguating those motifs that foster zero-lag synchrony in the presence of conduction delays (such as dynamical relaying) from those that do not (such as the common driving triad). Remarkably, minor structural changes to the common driving motif that incorporate a reciprocal pair recover robust zero-lag synchrony. The findings are observed in computational models of spiking neurons, populations of spiking neurons and neural mass models, and arise whether the oscillatory systems are periodic, chaotic, noise-free or driven by stochastic inputs. The influence of the resonance pair is also robust to parameter mismatch and asymmetrical time delays amongst the elements of the motif. We call this manner of facilitating zero-lag synchrony resonance-induced synchronization, outline the conditions for its occurrence, and propose that it may be a general mechanism to promote zero-lag synchrony in the brain. PMID:24763382

Intracranial electroencephalography power and phase synchronization changes during monaural and binaural beat stimulation.

PubMed

Becher, Ann-Katrin; Höhne, Marlene; Axmacher, Nikolai; Chaieb, Leila; Elger, Christian E; Fell, Juergen

2015-01-01

Auditory stimulation with monaural or binaural auditory beats (i.e. sine waves with nearby frequencies presented either to both ears or to each ear separately) represents a non-invasive approach to influence electrical brain activity. It is still unclear exactly which brain sites are affected by beat stimulation. In particular, an impact of beat stimulation on mediotemporal brain areas could possibly provide new options for memory enhancement or seizure control. Therefore, we examined how electroencephalography (EEG) power and phase synchronization are modulated by auditory stimulation with beat frequencies corresponding to dominant EEG rhythms based on intracranial recordings in presurgical epilepsy patients. Monaural and binaural beat stimuli with beat frequencies of 5, 10, 40 and 80 Hz and non-superposed control signals were administered with low amplitudes (60 dB SPL) and for short durations (5 s). EEG power was intracranially recorded from mediotemporal, temporo-basal and temporo-lateral and surface sites. Evoked and total EEG power and phase synchronization during beat vs. control stimulation were compared by the use of Bonferroni-corrected non-parametric label-permutation tests. We found that power and phase synchronization were significantly modulated by beat stimulation not only at temporo-basal, temporo-lateral and surface sites, but also at mediotemporal sites. Generally, more significant decreases than increases were observed. The most prominent power increases were seen after stimulation with monaural 40-Hz beats. The most pronounced power and synchronization decreases resulted from stimulation with monaural 5-Hz and binaural 80-Hz beats. Our results suggest that beat stimulation offers a non-invasive approach for the modulation of intracranial EEG characteristics. © 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

A comprehensive methodology for the multidimensional and synchronic data collecting in soundscape.

PubMed

Kogan, Pablo; Turra, Bruno; Arenas, Jorge P; Hinalaf, María

2017-02-15

The soundscape paradigm is comprised of complex living systems where individuals interact moment-by-moment among one another and with the physical environment. The real environments provide promising conditions to reveal deep soundscape behavior, including the multiple components involved and their interrelations as a whole. However, measuring and analyzing the numerous simultaneous variables of soundscape represents a challenge that is not completely understood. This work proposes and applies a comprehensive methodology for multidimensional and synchronic data collection in soundscape. The soundscape variables were organized into three main entities: experienced environment, acoustic environment, and extra-acoustic environment, containing, in turn, subgroups of variables called components. The variables contained in these components were acquired through synchronic field techniques that include surveys, acoustic measurements, audio recordings, photography, and video. The proposed methodology was tested, optimized, and applied in diverse open environments, including squares, parks, fountains, university campuses, streets, and pedestrian areas. The systematization of this comprehensive methodology provides a framework for soundscape research, a support for urban and environment management, and a preliminary procedure for standardization in soundscape data collecting. Copyright © 2016 Elsevier B.V. All rights reserved.

Experience with synchronous and asynchronous digital control systems. [for flight

NASA Technical Reports Server (NTRS)

Regenie, Victoria A.; Chacon, Claude V.; Lock, Wilton P.

1986-01-01

Flight control systems have undergone a revolution since the days of simple mechanical linkages; presently the most advanced systems are full-authority, full-time digital systems controlling unstable aircraft. With the use of advanced control systems, the aerodynamic design can incorporate features that allow greater performance and fuel savings, as can be seen on the new Airbus design and advanced tactical fighter concepts. These advanced aircraft will be and are relying on the flight control system to provide the stability and handling qualities required for safe flight and to allow the pilot to control the aircraft. Various design philosophies have been proposed and followed to investigate system architectures for these advanced flight control systems. One major area of discussion is whether a multichannel digital control system should be synchronous or asynchronous. This paper addressed the flight experience at the Dryden Flight Research Facility of NASA's Ames Research Center with both synchronous and asynchronous digital flight control systems. Four different flight control systems are evaluated against criteria such as software reliability, cost increases, and schedule delays.

Minimally invasive surgery using the open magnetic resonance imaging system combined with video-assisted thoracoscopic surgery for synchronous hepatic and pulmonary metastases from colorectal cancer: report of four cases.

PubMed

Sonoda, Hiromichi; Shimizu, Tomoharu; Takebayashi, Katsushi; Ohta, Hiroyuki; Murakami, Koichiro; Shiomi, Hisanori; Naka, Shigeyuki; Hanaoka, Jun; Tani, Tohru

2015-05-01

Simultaneous resection of hepatic and pulmonary metastases (HPM) from colorectal cancer (CRC) has been reported to be effective, but it is also considered invasive. We report the preliminary results of performing minimally invasive surgery using the open magnetic resonance (MR) imaging system to resect synchronous HPM from CRC in four patients. All four patients were referred for thoracoscopy-assisted interventional MR-guided microwave coagulation therapy (T-IVMR-MCT) combined with video-assisted thoracoscopic surgery (VATS). The median diameters of the HPM were 18.2 and 23.2 mm, respectively. The median duration of VATS and T-IVMR-MCT was 82.5 and 139 min, respectively. All patients were discharged without any major postoperative complications. One patient was still free of disease at 24 months and the others died of disease progression 13, 36, and 47 months without evidence of recurrence in the treated area. Thus, simultaneous VATS + T-IVMR-MCT appears to be an effective option as a minimally invasive treatment for synchronous HPM from CRC.

The control gain region for synchronization in non-diffusively coupled complex networks

NASA Astrophysics Data System (ADS)

Gequn, Liu; Wenhui, Li; Huijie, Yang; Knowles, Gareth

2014-07-01

The control gain region for synchronization of non-diffusively coupled networks was studied with respect to three conditions: synchronization, synchronization in finite time, and synchronization in the minimum time. Based on cancellation control methodology and master stability function formalism, we found that a complete feasible control gain region may be bounded, unbounded, empty or a union of several bounded and unbounded regions, with a similar shape to the synchronized region. An interesting possibility emerged that a network could be synchronized by both negative and positive feedback control simultaneously. By bridging synchronizability and synchronizing response speeds with a settling time index, we have developed timed synchronized region (TSR) as a substitute for the classical synchronized region to study finite time synchronization. As for the last condition, a graphical method was developed to estimate control gain with the minimum synchronization time (CGMST). Each condition has examples provided for illustration and verification.

New type of chaos synchronization in discrete-time systems: the F-M synchronization

NASA Astrophysics Data System (ADS)

Ouannas, Adel; Grassi, Giuseppe; Karouma, Abdulrahman; Ziar, Toufik; Wang, Xiong; Pham, Viet-Thanh

2018-04-01

In this paper, a new type of synchronization for chaotic (hyperchaotic) maps with different dimensions is proposed. The novel scheme is called F - M synchronization, since it combines the inverse generalized synchronization (based on a functional relationship F) with the matrix projective synchronization (based on a matrix M). In particular, the proposed approach enables F - M synchronization with index d to be achieved between n-dimensional drive system map and m-dimensional response system map, where the synchronization index d corresponds to the dimension of the synchronization error. The technique, which exploits nonlinear controllers and Lyapunov stability theory, proves to be effective in achieving the F - M synchronization not only when the synchronization index d equals n or m, but even if the synchronization index d is larger than the map dimensions n and m. Finally, simulation results are reported, with the aim to illustrate the capabilities of the novel scheme proposed herein.

Haitian Creole: Sound-System, Form-Classes, Texts.

ERIC Educational Resources Information Center

Ferere, Gerard Alphonse

A synchronic structural description is presented of Haitian Creole as spoken in the Port-au-Prince-Jacmel area, concentrating mainly on phonoloqy and morphology. Historical information and commentary are presented on diglossia and illiteracy, two intertwining sociolinguistic problems of Haiti. A detailed analysis is presented of the Creole sound…

Learning Disabilities at Twenty-Five: The Early Adulthood of a Maturing Concept.

ERIC Educational Resources Information Center

Levine, Melvin D.

1989-01-01

The keynote speech identifies six categories of problem areas for children with learning disabilities: (1) synchronization, (2) consistency, (3) methodology, (4) cohesion, (5) saliency determination, and (6) tempo. A model of neurodevelopmental functions and performance elements to guide researchers and practitioners is offered. (DB)

Perceptions of Quality in an Online Learning Environment: A Faculty Outlook

ERIC Educational Resources Information Center

Adams, April Michele

2017-01-01

The study investigated the faculty perception of quality in online courses. The areas considered were media richness, interaction, synchronism, self-efficacy, online teaching experience, and education level. Participants included members of three online Yahoo groups that were designed for online faculty members. There were 510 total members…

The optimization of self-phased arrays for diurnal motion tracking of synchronous satellites

NASA Technical Reports Server (NTRS)

Theobold, D. M.; Hodge, D. B.

1977-01-01

The diurnal motion of a synchronous satellite necessitates mechanical tracking when a large aperture, high gain antenna is employed at the earth terminal. An alternative solution to this tracking problem is to use a self phased array consisting of a number of fixed pointed elements, each with moderate directivity. Non-mechanical tracking and adequate directive gain are achieved electronically by phase coherent summing of the element outputs. The element beamwidths provide overlapping area coverage of the satellite motion but introduce a diurnal variation into the array gain. The optimum element beamwidth and pointing direction of these elements can be obtained under the condition that the array gain is maximized simultaneously with the minimization of the diurnal variation.

Signal design study for shuttle/TDRSS Ku-band uplink

NASA Technical Reports Server (NTRS)

1976-01-01

The adequacy of the signal design approach chosen for the TDRSS/orbiter uplink was evaluated. Critical functions and/or components associated with the baseline design were identified, and design alternatives were developed for those areas considered high risk. A detailed set of RF and signal processing performance specifications for the orbiter hardware associated with the TDRSS/orbiter Ku band uplink was analyzed. Performances of a detailed design of the PN despreader, the PSK carrier synchronization loop, and the symbol synchronizer are identified. The performance of the downlink signal by means of computer simulation to obtain a realistic determination of bit error rate degradations was studied. The three channel PM downlink signal was detailed by means of analysis and computer simulation.

Cooperative synchronized assemblies enhance orientation discrimination.

PubMed

Samonds, Jason M; Allison, John D; Brown, Heather A; Bonds, A B

2004-04-27

There is no clear link between the broad tuning of single neurons and the fine behavioral capabilities of orientation discrimination. We recorded from populations of cells in the cat visual cortex (area 17) to examine whether the joint activity of cells can support finer discrimination than found in individual responses. Analysis of joint firing yields a substantial advantage (i.e., cooperation) in fine-angle discrimination. This cooperation increases to more considerable levels as the population of an assembly is increased. The cooperation in a population of six cells provides encoding of orientation with an information advantage that is at least 2-fold in terms of requiring either fewer cells or less time than independent coding. This cooperation suggests that correlated or synchronized activity can increase information.

A Mobile GPS Application: Mosque Tracking with Prayer Time Synchronization

NASA Astrophysics Data System (ADS)

Hashim, Rathiah; Ikhmatiar, Mohammad Sibghotulloh; Surip, Miswan; Karmin, Masiri; Herawan, Tutut

Global Positioning System (GPS) is a popular technology applied in many areas and embedded in many devices, facilitating end-users to navigate effectively to user's intended destination via the best calculated route. The ability of GPS to track precisely according to coordinates of specific locations can be utilized to assist a Muslim traveler visiting or passing an unfamiliar place to find the nearest mosque in order to perform his prayer. However, not many techniques have been proposed for Mosque tracking. This paper presents the development of GPS technology in tracking the nearest mosque using mobile application software embedded with the prayer time's synchronization system on a mobile application. The prototype GPS system developed has been successfully incorporated with a map and several mosque locations.

Variations of magnetic and electrostatic atmospheric parameters and dynamics of the heart rate in mHz range

NASA Astrophysics Data System (ADS)

Nagorskiy, Petr; Zenchenko, Tatiana; Breus, Tamara; Smirnov, Sergey

The objective of this work was to study the degree of synchronization of heart rate (HR) of healthy volunteers with magnetic variations and various weather conditions in mHz - frequency range. Experimental results for synchronic registration of physiological variations, atmospheric electrical and meteorological parameters with a time resolution of 0.5-1 min are presented. The experiment was conducted in a building of IMCES SB RAS (Tomsk). 15 experiments of 60 minutes each were conducted, and four volunteers of all ages in a state of rest were examined. Meteorological parameters (atmospheric pressure, relative air humidity and temperatureas well as a wind speed) were measured using standard meteorological devices located on the roof of the same building and also on the open area. Data on geomagnetic activity on the nearest magnetic station Klyichi were obtained from the site http://ottawa.intermagnet.org/apps/download/index-eng.php # view. The electric field intensity was recorded the following way: in the room (5-storey panel ferroconcrete building) by the autonomous fluxmeter CS110 at a distance of 1.5 meters from the investigated volunteers, and on the open test - area by the stationary electric fluxmeter "Field 2". Data analysis techniques were: cross-correlation analysis, spectral analysis (Fourier transform and the calculation of the coherence function) and wavelet analysis. It was found that the dependence of the heart rate variation dynamics from the X-component of the Earth magnetic field magnitude was observed in 53% of cases, from the relative humidity - in 33%, from the atmospheric pressure, the wind speed and intensity of the electric field in an open area - in 20%, from the intensity the electric field in the room of the experiment - in 7% of cases. It was found not only coincidence of observed values of oscillation periods in physiological and geophysical series lasting 5-30 minutes, but also moments of approximate synchronicity in their appearance and disappearance. The highest degree of synchronization of HR with the variations of the geomagnetic field (in all four conducted experiments in this day) was observed in the most geomagnetically quiet day - 04.10.12 (Ap = 1), while the lowest one - in the day of the geomagnetic disturbances - 01.10.12 (Ap = 32). The characteristics of the electric field variations in the time-frequency domain in the experiments conducted indoors and outdoors differ fundamentally.

Demonstration of a Novel Synchrophasor-based Situational Awareness System: Wide Area Power System Visualization, On-line Event Replay and Early Warning of Grid Problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosso, A.

Since the large North Eastern power system blackout on August 14, 2003, U.S. electric utilities have spent lot of effort on preventing power system cascading outages. Two of the main causes of the August 14, 2003 blackout were inadequate situational awareness and inadequate operator training In addition to the enhancements of the infrastructure of the interconnected power systems, more research and development of advanced power system applications are required for improving the wide-area security monitoring, operation and planning in order to prevent large- scale cascading outages of interconnected power systems. It is critically important for improving the wide-area situation awarenessmore » of the operators or operational engineers and regional reliability coordinators of large interconnected systems. With the installation of large number of phasor measurement units (PMU) and the related communication infrastructure, it will be possible to improve the operators’ situation awareness and to quickly identify the sequence of events during a large system disturbance for the post-event analysis using the real-time or historical synchrophasor data. The purpose of this project was to develop and demonstrate a novel synchrophasor-based comprehensive situational awareness system for control centers of power transmission systems. The developed system named WASA (Wide Area Situation Awareness) is intended to improve situational awareness at control centers of the power system operators and regional reliability coordinators. It consists of following main software modules: • Wide-area visualizations of real-time frequency, voltage, and phase angle measurements and their contour displays for security monitoring. • Online detection and location of a major event (location, time, size, and type, such as generator or line outage). • Near-real-time event replay (in seconds) after a major event occurs. • Early warning of potential wide-area stability problems. The system has been deployed and demonstrated at the Tennessee Valley Authority (TVA) and ISO New England system using real-time synchrophasor data from openPDC. Apart from the software product, the outcome of this project consists of a set of technical reports and papers describing the mathematical foundations and computational approaches of different tools and modules, implementation issues and considerations, lessons learned, and the results of lidation processes.« less

Fault-tolerant clock synchronization in distributed systems

NASA Technical Reports Server (NTRS)

Ramanathan, Parameswaran; Shin, Kang G.; Butler, Ricky W.

1990-01-01

Existing fault-tolerant clock synchronization algorithms are compared and contrasted. These include the following: software synchronization algorithms, such as convergence-averaging, convergence-nonaveraging, and consistency algorithms, as well as probabilistic synchronization; hardware synchronization algorithms; and hybrid synchronization. The worst-case clock skews guaranteed by representative algorithms are compared, along with other important aspects such as time, message, and cost overhead imposed by the algorithms. More recent developments such as hardware-assisted software synchronization and algorithms for synchronizing large, partially connected distributed systems are especially emphasized.

Composite synchronization of three eccentric rotors driven by induction motors in a vibrating system

NASA Astrophysics Data System (ADS)

Kong, Xiangxi; Chen, Changzheng; Wen, Bangchun

2018-03-01

This paper addresses the problem of composite synchronization of three eccentric rotors (ERs) driven by induction motors in a vibrating system. The composite synchronous motion of three ERs is composed of the controlled synchronous motion of two ERs and the self-synchronous motion of the third ER. Combining an adaptive sliding mode control (ASMC) algorithm with a modified master-slave control structure, the controllers are designed to implement controlled synchronous motion of two ERs with zero phase difference. Based on Lyapunov stability theorem and Barbalat's lemma, the stability of the designed controllers is verified. On basis of controlled synchronization of two ERs, self-synchronization of the third ER is introduced to implement composite synchronous motion of three ERs. The feasibility of the proposed composite synchronization method is analyzed by numerical method. The effects of motor and structure parameters on composite synchronous motion are discussed. Experiments on a vibrating test bench driven by three ERs are operated to validate the effectiveness of the proposed composite synchronization method, including a comparison with self-synchronization method.

A proportional integral estimator-based clock synchronization protocol for wireless sensor networks.

PubMed

Yang, Wenlun; Fu, Minyue

2017-11-01

Clock synchronization is an issue of vital importance in applications of WSNs. This paper proposes a proportional integral estimator-based protocol (EBP) to achieve clock synchronization for wireless sensor networks. As each local clock skew gradually drifts, synchronization accuracy will decline over time. Compared with existing consensus-based approaches, the proposed synchronization protocol improves synchronization accuracy under time-varying clock skews. Moreover, by restricting synchronization error of clock skew into a relative small quantity, it could reduce periodic re-synchronization frequencies. At last, a pseudo-synchronous implementation for skew compensation is introduced as synchronous protocol is unrealistic in practice. Numerical simulations are shown to illustrate the performance of the proposed protocol. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

ML Frame Synchronization for OFDM Systems Using a Known Pilot and Cyclic Prefixes

NASA Astrophysics Data System (ADS)

Huh, Heon

Orthogonal frequency-division multiplexing (OFDM) is a popular air interface technology that is adopted as a standard modulation scheme for 4G communication systems owing to its excellent spectral efficiency. For OFDM systems, synchronization problems have received much attention along with peak-to-average power ratio (PAPR) reduction. In addition to frequency offset estimation, frame synchronization is a challenging problem that must be solved to achieve optimal system performance. In this paper, we present a maximum likelihood (ML) frame synchronizer for OFDM systems. The synchronizer exploits a synchronization word and cyclic prefixes together to improve the synchronization performance. Numerical results show that the performance of the proposed frame synchronizer is better than that of conventional schemes. The proposed synchronizer can be used as a reference for evaluating the performance of other suboptimal frame synchronizers. We also modify the proposed frame synchronizer to reduce the implementation complexity and propose a near-ML synchronizer for time-varying fading channels.

Anomaly Detection Using Optimally-Placed μPMU Sensors in Distribution Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jamei, Mahdi; Scaglione, Anna; Roberts, Ciaran

IEEE As the distribution grid moves toward a tightly-monitored network, it is important to automate the analysis of the enormous amount of data produced by the sensors to increase the operators situational awareness about the system. Here, focusing on Micro-Phasor Measurement Unit (μPMU) data, we propose a hierarchical architecture for monitoring the grid and establish a set of analytics and sensor fusion primitives for the detection of abnormal behavior in the control perimeter. And due to the key role of the μPMU devices in our architecture, a source-constrained optimal μPMU placement is also described that finds the best location ofmore » the devices with respect to our rules. The effectiveness of the proposed methods are tested through the synthetic and real μPMU data.« less

Stabilizing Gyroscopic Modes in Magnetic-Bearing-Supported Flywheels by Using Cross-Axis Proportional Gains

NASA Technical Reports Server (NTRS)

Brown, Gerald V.; Kascak, Albert F.; Jansen, Ralph H.; Dever, Timothy P.; Duffy, Kirsten P.

2006-01-01

For magnetic-bearing-supported high-speed rotating machines with significant gyroscopic effects, it is necessary to stabilize forward and backward tilt whirling modes. Instability or low damping of these modes can prevent the attainment of desired shaft speed. We show analytically that both modes can be stabilized by using cross-axis proportional gains and high- and low-pass filters in the magnetic bearing controller. Furthermore, at high shaft speeds, where system phase lags degrade the stability of the forward-whirl mode, a phasor advance of the control signal can partially counteract the phase lag. In some range of high shaft speed, the derivative gain for the tilt modes (essential for stability for slowly rotating shafts) can be removed entirely. We show analytically how the tilt eigenvalues depend on shaft speed and on various controller feedback parameters.

Comparison of the hydrological excitation functions HAM of polar motion for the period 1980.0-2007.0

NASA Astrophysics Data System (ADS)

Nastula, J.; Pasnicka, M.; Kolaczek, B.

2011-10-01

In this study we compared contributions of polar motion excitation determined from hydrological models and harmonic coefficients of the Earth gravity field obtained from Gravity Recovery and Climate Experiment (GRACE). Hydrological excitation function (hydrological angular momentum - HAM) has been estimated from models of global hydrology, based on the observed distribution of surface water, snow, ice and soil moisture. All of them were compared with observed Geodetic Angular Momentum (GAM), excitations of polar motion. The spectra of these excitation functions of polar motion and residual geodetic excitation function G-A-O obtained from GAM by elimination of atmospheric and oceanic excitation functions were computed too. Phasor diagrams of the seasonal components of the polar motion excitation functions of all HAM excitation functions as well as of two GRACE solutions: CSR, CNES were determined and discussed.

A review of pulse tube refrigeration

NASA Technical Reports Server (NTRS)

Radebaugh, Ray

1990-01-01

This paper reviews the development of the three types of pulse tube refrigerators: basic, resonant, and orifice types. The principles of operation are given. It is shown that the pulse tube refrigerator is a variation of the Stirling-cycle refrigerator, where the moving displacer is substituted by a heat transfer mechanism or by an orifice to bring about the proper phase shifts between pressure and mass flow rate. A harmonic analysis with phasors is described which gives reasonable results for the refrigeration power, yet is simple enough to make clear the processes which give rise to the refrigeration. The efficiency and refrigeration power are compared with those of other refrigeration cycles. A brief review is given of the research being done at various laboratories on both one- and two-stage pulse tubes. A preliminary assessment of the role of pulse tube refrigerators is discussed.

Impact of Measurement Error on Synchrophasor Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yilu; Gracia, Jose R.; Ewing, Paul D.

2015-07-01

Phasor measurement units (PMUs), a type of synchrophasor, are powerful diagnostic tools that can help avert catastrophic failures in the power grid. Because of this, PMU measurement errors are particularly worrisome. This report examines the internal and external factors contributing to PMU phase angle and frequency measurement errors and gives a reasonable explanation for them. It also analyzes the impact of those measurement errors on several synchrophasor applications: event location detection, oscillation detection, islanding detection, and dynamic line rating. The primary finding is that dynamic line rating is more likely to be influenced by measurement error. Other findings include themore » possibility of reporting nonoscillatory activity as an oscillation as the result of error, failing to detect oscillations submerged by error, and the unlikely impact of error on event location and islanding detection.« less

Anomaly Detection Using Optimally-Placed μPMU Sensors in Distribution Grids

DOE PAGES

Jamei, Mahdi; Scaglione, Anna; Roberts, Ciaran; ...

2017-10-25

IEEE As the distribution grid moves toward a tightly-monitored network, it is important to automate the analysis of the enormous amount of data produced by the sensors to increase the operators situational awareness about the system. Here, focusing on Micro-Phasor Measurement Unit (μPMU) data, we propose a hierarchical architecture for monitoring the grid and establish a set of analytics and sensor fusion primitives for the detection of abnormal behavior in the control perimeter. And due to the key role of the μPMU devices in our architecture, a source-constrained optimal μPMU placement is also described that finds the best location ofmore » the devices with respect to our rules. The effectiveness of the proposed methods are tested through the synthetic and real μPMU data.« less

Cortical network modeling: analytical methods for firing rates and some properties of networks of LIF neurons.

PubMed

Tuckwell, Henry C

2006-01-01

The circuitry of cortical networks involves interacting populations of excitatory (E) and inhibitory (I) neurons whose relationships are now known to a large extent. Inputs to E- and I-cells may have their origins in remote or local cortical areas. We consider a rudimentary model involving E- and I-cells. One of our goals is to test an analytic approach to finding firing rates in neural networks without using a diffusion approximation and to this end we consider in detail networks of excitatory neurons with leaky integrate-and-fire (LIF) dynamics. A simple measure of synchronization, denoted by S(q), where q is between 0 and 100 is introduced. Fully connected E-networks have a large tendency to become dominated by synchronously firing groups of cells, except when inputs are relatively weak. We observed random or asynchronous firing in such networks with diverse sets of parameter values. When such firing patterns were found, the analytical approach was often able to accurately predict average neuronal firing rates. We also considered several properties of E-E networks, distinguishing several kinds of firing pattern. Included were those with silences before or after periods of intense activity or with periodic synchronization. We investigated the occurrence of synchronized firing with respect to changes in the internal excitatory postsynaptic potential (EPSP) magnitude in a network of 100 neurons with fixed values of the remaining parameters. When the internal EPSP size was less than a certain value, synchronization was absent. The amount of synchronization then increased slowly as the EPSP amplitude increased until at a particular EPSP size the amount of synchronization abruptly increased, with S(5) attaining the maximum value of 100%. We also found network frequency transfer characteristics for various network sizes and found a linear dependence of firing frequency over wide ranges of the external afferent frequency, with non-linear effects at lower input frequencies. The theory may also be applied to sparsely connected networks, whose firing behaviour was found to change abruptly as the probability of a connection passed through a critical value. The analytical method was also found to be useful for a feed-forward excitatory network and a network of excitatory and inhibitory neurons.

Quantum synchronization in an optomechanical system based on Lyapunov control.

PubMed

Li, Wenlin; Li, Chong; Song, Heshan

2016-06-01

We extend the concepts of quantum complete synchronization and phase synchronization, which were proposed in A. Mari et al., Phys. Rev. Lett. 111, 103605 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.103605, to more widespread quantum generalized synchronization. Generalized synchronization can be considered a necessary condition or a more flexible derivative of complete synchronization, and its criterion and synchronization measure are proposed and analyzed in this paper. As examples, we consider two typical generalized synchronizations in a designed optomechanical system. Unlike the effort to construct a special coupling synchronization system, we purposefully design extra control fields based on Lyapunov control theory. We find that the Lyapunov function can adapt to more flexible control objectives, which is more suitable for generalized synchronization control, and the control fields can be achieved simply with a time-variant voltage. Finally, the existence of quantum entanglement in different generalized synchronizations is also discussed.

Overview of Cell Synchronization.

PubMed

Banfalvi, Gaspar

2017-01-01

The widespread interest in cell synchronization is maintained by the studies of control mechanism involved in cell cycle regulation. During the synchronization distinct subpopulations of cells are obtained representing different stages of the cell cycle. These subpopulations are then used to study regulatory mechanisms of the cycle at the level of macromolecular biosynthesis (DNA synthesis, gene expression, protein synthesis), protein phosphorylation, development of new drugs, etc. Although several synchronization methods have been described, it is of general interest that scientists get a compilation and an updated view of these synchronization techniques. This introductory chapter summarizes: (1) the basic concepts and principal criteria of cell cycle synchronizations, (2) the most frequently used synchronization methods, such as physical fractionation (flow cytometry, dielectrophoresis, cytofluorometric purification), chemical blockade, (3) synchronization of embryonic cells, (4) synchronization at low temperature, (5) comparison of cell synchrony techniques, (6) synchronization of unicellular organisms, and (7) the effect of synchronization on transfection.

System and method to allow a synchronous motor to successfully synchronize with loads that have high inertia and/or high torque

DOEpatents

Melfi, Michael J.

2015-10-20

A mechanical soft-start type coupling is used as an interface between a line start, synchronous motor and a heavy load to enable the synchronous motor to bring the heavy load up to or near synchronous speed. The soft-start coupling effectively isolates the synchronous motor from the load for enough time to enable the synchronous motor to come up to full speed. The soft-start coupling then brings the load up to or near synchronous speed.

Characterizing Deep Brain Stimulation effects in computationally efficient neural network models.

PubMed

Latteri, Alberta; Arena, Paolo; Mazzone, Paolo

2011-04-15

Recent studies on the medical treatment of Parkinson's disease (PD) led to the introduction of the so called Deep Brain Stimulation (DBS) technique. This particular therapy allows to contrast actively the pathological activity of various Deep Brain structures, responsible for the well known PD symptoms. This technique, frequently joined to dopaminergic drugs administration, replaces the surgical interventions implemented to contrast the activity of specific brain nuclei, called Basal Ganglia (BG). This clinical protocol gave the possibility to analyse and inspect signals measured from the electrodes implanted into the deep brain regions. The analysis of these signals led to the possibility to study the PD as a specific case of dynamical synchronization in biological neural networks, with the advantage to apply the theoretical analysis developed in such scientific field to find efficient treatments to face with this important disease. Experimental results in fact show that the PD neurological diseases are characterized by a pathological signal synchronization in BG. Parkinsonian tremor, for example, is ascribed to be caused by neuron populations of the Thalamic and Striatal structures that undergo an abnormal synchronization. On the contrary, in normal conditions, the activity of the same neuron populations do not appear to be correlated and synchronized. To study in details the effect of the stimulation signal on a pathological neural medium, efficient models of these neural structures were built, which are able to show, without any external input, the intrinsic properties of a pathological neural tissue, mimicking the BG synchronized dynamics.We start considering a model already introduced in the literature to investigate the effects of electrical stimulation on pathologically synchronized clusters of neurons. This model used Morris Lecar type neurons. This neuron model, although having a high level of biological plausibility, requires a large computational effort to simulate large scale networks. For this reason we considered a reduced order model, the Izhikevich one, which is computationally much lighter. The comparison between neural lattices built using both neuron models provided comparable results, both without traditional stimulation and in presence of all the stimulation protocols. This was a first result toward the study and simulation of the large scale neural networks involved in pathological dynamics.Using the reduced order model an inspection on the activity of two neural lattices was also carried out at the aim to analyze how the stimulation in one area could affect the dynamics in another area, like the usual medical treatment protocols require.The study of population dynamics that was carried out allowed us to investigate, through simulations, the positive effects of the stimulation signals in terms of desynchronization of the neural dynamics. The results obtained constitute a significant added value to the analysis of synchronization and desynchronization effects due to neural stimulation. This work gives the opportunity to more efficiently study the effect of stimulation in large scale yet computationally efficient neural networks. Results were compared both with the other mathematical models, using Morris Lecar and Izhikevich neurons, and with simulated Local Field Potentials (LFP).

Guaranteeing synchronous message deadlines with the timed token medium access control protocol

NASA Technical Reports Server (NTRS)

Agrawal, Gopal; Chen, Baio; Zhao, Wei; Davari, Sadegh

1992-01-01

We study the problem of guaranteeing synchronous message deadlines in token ring networks where the timed token medium access control protocol is employed. Synchronous capacity, defined as the maximum time for which a node can transmit its synchronous messages every time it receives the token, is a key parameter in the control of synchronous message transmission. To ensure the transmission of synchronous messages before their deadlines, synchronous capacities must be properly allocated to individual nodes. We address the issue of appropriate allocation of the synchronous capacities. Several synchronous capacity allocation schemes are analyzed in terms of their ability to satisfy deadline constraints of synchronous messages. We show that an inappropriate allocation of the synchronous capacities could cause message deadlines to be missed even if the synchronous traffic is extremely low. We propose a scheme called the normalized proportional allocation scheme which can guarantee the synchronous message deadlines for synchronous traffic of up to 33 percent of available utilization. To date, no other synchronous capacity allocation scheme has been reported to achieve such substantial performance. Another major contribution of this paper is an extension to the previous work on the bounded token rotation time. We prove that the time elapsed between any consecutive visits to a particular node is bounded by upsilon TTRT, where TTRT is the target token rotation time set up at system initialization time. The previous result by Johnson and Sevcik is a special case where upsilon = 2. We use this result in the analysis of various synchronous allocation schemes. It can also be applied in other similar studies.

Synchronization of metronomes

NASA Astrophysics Data System (ADS)

Pantaleone, James

2002-10-01

Synchronization is a common phenomenon in physical and biological systems. We examine the synchronization of two (and more) metronomes placed on a freely moving base. The small motion of the base couples the pendulums causing synchronization. The synchronization is generally in-phase, with antiphase synchronization occurring only under special conditions. The metronome system provides a mechanical realization of the popular Kuramoto model for synchronization of biological oscillators, and is excellent for classroom demonstrations and an undergraduate physics lab.

On Synchronization Primitive Systems.

DTIC Science & Technology

The report studies the question: what synchronization primitive should be used to handle inter-process communication. A formal model is presented...between these synchronization primitives. Although only four synchronization primitives are compared, the general methods can be used to compare other... synchronization primitives. Moreover, in the definitions of these synchronization primitives, conditional branches are explicitly allowed. In addition

Mass synchronization: Occurrence and its control with possible applications to brain dynamics

NASA Astrophysics Data System (ADS)

Chandrasekar, V. K.; Sheeba, Jane H.; Lakshmanan, M.

2010-12-01

Occurrence of strong or mass synchronization of a large number of neuronal populations in the brain characterizes its pathological states. In order to establish an understanding of the mechanism underlying such pathological synchronization, we present a model of coupled populations of phase oscillators representing the interacting neuronal populations. Through numerical analysis, we discuss the occurrence of mass synchronization in the model, where a source population which gets strongly synchronized drives the target populations onto mass synchronization. We hypothesize and identify a possible cause for the occurrence of such a synchronization, which is so far unknown: Pathological synchronization is caused not just because of the increase in the strength of coupling between the populations but also because of the strength of the strong synchronization of the drive population. We propose a demand controlled method to control this pathological synchronization by providing a delayed feedback where the strength and frequency of the synchronization determine the strength and the time delay of the feedback. We provide an analytical explanation for the occurrence of pathological synchronization and its control in the thermodynamic limit.

Dynamic Systems for Individual Tracking via Heterogeneous Information Integration and Crowd Source Distributed Simulation

DTIC Science & Technology

2015-12-04

51   6.6   Power Consumption: Communications ...simulations executing on mobile computing platforms, an area not widely studied to date in the distributed simulation research community . A...simulation community . These initial studies focused on two conservative synchronization algorithms widely used in the distributed simulation field

Rationale, Design and Implementation of a Computer Vision-Based Interactive E-Learning System

ERIC Educational Resources Information Center

Xu, Richard Y. D.; Jin, Jesse S.

2007-01-01

This article presents a schematic application of computer vision technologies to e-learning that is synchronous, peer-to-peer-based, and supports an instructor's interaction with non-computer teaching equipments. The article first discusses the importance of these focused e-learning areas, where the properties include accurate bidirectional…

Spatial analysis of harmonic oscillation of gypsy moth outbreak intensity

Treesearch

Kyle J. Haynes; Andrew M. Liebhold; Derek M. Johnson

2009-01-01

Outbreaks of many forest-defoliating insects are synchronous over broad geographic areas and occur with a period of approximately 10 years. Within the range of the gypsy moth in North America, however, there is considerable geographic heterogeneity in strength of periodicity and the frequency of outbreaks. Furthermore, gypsy moth outbreaks exhibit two significant...

Planning and Second Language Development in Task-Based Synchronous Computer-Mediated Communication

ERIC Educational Resources Information Center

Hsu, Hsiu-Chen

2012-01-01

This dissertation explored the effect of two planning conditions (the multiple planning condition with rehearsal and online planning time, and the single planning condition with online planning time only) on L2 production complexity and accuracy and the subsequent development of these two linguistic areas in the context of written synchronous…

PBFA II, a 100 TW Pulsed Power Driver for the Inertial Confinement Fusion Program

DTIC Science & Technology

1985-06-01

providing a 30 MV, 15 ns output pulse,which accelerates lithium ions. The ions will focus onto a pellet containing deuterium-tritium, producing fusion ... energy . Several research areas will be reviewed: low jitter, highly reliable 370 kJ Marx generators; highly synchronized gas switching at 5 MV; efficient

Synchronic historical patterns of species diversification in seasonal aplocheiloid killifishes of the semi-arid Brazilian Caatinga

PubMed Central

Amorim, Pedro F.; Mattos, José Leonardo O.

2018-01-01

The Caatinga is the largest nucleus of seasonally dry tropical forests in South America, but little is known about the evolutionary history and biogeography of endemic organisms. Evolutionary diversification and distribution of terrestrial vertebrates endemic to the Caatinga have been explained by palaeogeographical Neogene episodes, mostly related to changes in the course of the São Francisco River, the largest river in the region. Our objective is to estimate the timing of divergence of two endemic groups of short-lived seasonal killifishes inhabiting all ecoregions of the Caatinga, testing the occurrence of synchronic events of spatial diversification in light of available data on regional palaeogeography. We performed independent time-calibrated phylogenetic molecular analyses for two clades of sympatric and geographically widespread seasonal killifishes endemic to the Caatinga, the Hypsolebias antenori group and the Cynolebias alpha-clade. Our results consistently indicate that species diversification took place synchronically in both groups, as well as it is contemporary to diversification of other organisms adapted to life in the semi-arid Caatinga, including lizards and small mammals. Both groups originated during the Miocene, but species diversification started between the Late Miocene and Early Pliocene, when global cooling probably favoured the expansion of semi-arid areas. Synchronic diversification patterns found are chronologically related to Tertiary palaeogeographical reorganizations associated to continental drift and to Quaternary climatic changes, corroborating the recent proposal that South American biodiversity has been continuously shaped between the Late Paleogene and Pleistocene. PMID:29451915

Synchronic historical patterns of species diversification in seasonal aplocheiloid killifishes of the semi-arid Brazilian Caatinga.

PubMed

Costa, Wilson J E M; Amorim, Pedro F; Mattos, José Leonardo O

2018-01-01

The Caatinga is the largest nucleus of seasonally dry tropical forests in South America, but little is known about the evolutionary history and biogeography of endemic organisms. Evolutionary diversification and distribution of terrestrial vertebrates endemic to the Caatinga have been explained by palaeogeographical Neogene episodes, mostly related to changes in the course of the São Francisco River, the largest river in the region. Our objective is to estimate the timing of divergence of two endemic groups of short-lived seasonal killifishes inhabiting all ecoregions of the Caatinga, testing the occurrence of synchronic events of spatial diversification in light of available data on regional palaeogeography. We performed independent time-calibrated phylogenetic molecular analyses for two clades of sympatric and geographically widespread seasonal killifishes endemic to the Caatinga, the Hypsolebias antenori group and the Cynolebias alpha-clade. Our results consistently indicate that species diversification took place synchronically in both groups, as well as it is contemporary to diversification of other organisms adapted to life in the semi-arid Caatinga, including lizards and small mammals. Both groups originated during the Miocene, but species diversification started between the Late Miocene and Early Pliocene, when global cooling probably favoured the expansion of semi-arid areas. Synchronic diversification patterns found are chronologically related to Tertiary palaeogeographical reorganizations associated to continental drift and to Quaternary climatic changes, corroborating the recent proposal that South American biodiversity has been continuously shaped between the Late Paleogene and Pleistocene.

Synchronous diagnosis of metastatic cancer to the thyroid is associated with poor prognosis.

PubMed

Chen, Jeng-Yeou; Chen, I-Wen; Hsueh, Chuen; Chao, Tzu-Chieh; Gao, Bing-Ru; Lin, Jen-Der

2015-03-01

The incidence and histopathological characteristics of metastatic cancers to the thyroid (MCT) are different in various geographic areas. The aim of this study was to elucidate the clinical features of MCT, including histocytological diagnosis and therapeutic outcomes. A retrospective analysis of patients with thyroid cancer treated and followed up at the Chang Gung Medical Center in Linkou was performed. Among 3957 patients with thyroid cancer, a total of 56 patients with MCT were evaluated. Of them, 47 patients (83.9 %) were diagnosed with malignancy or suspected malignancy via fine needle aspiration cytology of the thyroid. Synchronous primary cancers were diagnosed in 44 of the patients with MCT. Of the MCT, metastasis of lung cancer to the thyroid was the leading category. Other primary sites of MCT were the head and neck, gastrointestinal tract, kidneys, breast, cervix, and unknown primary site. The mean 5-, 10-, 20-, and 60-month survival rates were 46.4, 32.1, 21.4, and 7.9 % for the patients. Patients with metachronous thyroid carcinoma had significantly better survival than patients with synchronous cancer. In conclusions, the incidence of MCT in patients with thyroid cancer is low; however, the prognosis of patients with MCT is poor, especially in patients diagnosed with synchronous primary tumors. In this study, MCT commonly originated in organs located near the thyroid, such as the lungs, head, and neck. Close monitoring of these malignancies may improve the prognosis of patients with MCT in the future.

Selective Interareal Synchronization through Gamma Frequency Differences and Slower-Rhythm Gamma Phase Reset.

PubMed

Burwick, Thomas; Bouras, Alexandros

2017-03-01

The communication-through-coherence (CTC) hypothesis states that a sending group of neurons will have a particularly strong effect on a receiving group if both groups oscillate in a phase-locked ("coherent") manner (Fries, 2005 , 2015 ). Here, we consider a situation with two visual stimuli, one in the focus of attention and the other distracting, resulting in two sites of excitation at an early cortical area that project to a common site in a next area. Taking a modeler's perspective, we confirm the workings of a mechanism that was proposed by Bosman et al. ( 2012 ) in the context of providing experimental evidence for the CTC hypothesis: a slightly higher gamma frequency of the attended sending site compared to the distracting site may cause selective interareal synchronization with the receiving site if combined with a slow-rhythm gamma phase reset. We also demonstrate the relevance of a slightly lower intrinsic frequency of the receiving site for this scenario. Moreover, we discuss conditions for a transition from bottom-up to top-down driven phase locking.

ACTIVE REGION MORPHOLOGIES SELECTED FROM NEAR-SIDE HELIOSEISMIC DATA

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacDonald, G. A.; McAteer, R. T. J.; Henney, C. J.

We estimate the morphology of near-side active regions using near-side helioseismology. Active regions from two data sets, Air Force Data Assimilative Photospheric flux Transport synchronic maps and Global Oscillation Network Group near-side helioseismic maps, were matched and their morphologies compared. Our algorithm recognizes 382 helioseismic active regions between 2002 April 25 and 2005 December 31 and matches them to their corresponding magnetic active regions with 100% success. A magnetic active region occupies 30% of the area of its helioseismic signature. Recovered helioseismic tilt angles are in good agreement with magnetic tilt angles. Approximately 20% of helioseismic active regions can bemore » decomposed into leading and trailing polarity. Leading polarity components show no discernible scaling relationship, but trailing magnetic polarity components occupy approximately 25% of the area of the trailing helioseismic component. A nearside phase-magnetic calibration is in close agreement with a previous far-side helioseismic calibration and provides confidence that these morphological relationships can be used with far-side helioseismic data. Including far-side active region morphology in synchronic maps will have implications for coronal magnetic topology predictions and solar wind forecasts.« less

Wind Tunnel Measurement of Turbulent and Advective Scalar Fluxes: A Case Study on Intersection Ventilation

PubMed Central

Kukačka, Libor; Nosek, Štĕpán; Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk

2012-01-01

The objective of this study is to determine processes of pollution ventilation in the X-shaped street intersection in an idealized symmetric urban area for the changing approach flow direction. A unique experimental setup for simultaneous wind tunnel measurement of the flow velocity and the tracer gas concentration in a high temporal resolution is assembled. Advective horizontal and vertical scalar fluxes are computed from averaged measured velocity and concentration data within the street intersection. Vertical advective and turbulent scalar fluxes are computed from synchronized velocity and concentration signals measured in the plane above the intersection. All the results are obtained for five approach flow directions. The influence of the approach flow on the advective and turbulent fluxes is determined. The contribution of the advective and turbulent flux to the ventilation is discussed. Wind direction with the best dispersive conditions in the area is found. The quadrant analysis is applied to the synchronized signals of velocity and concentration fluctuation to determine events with the dominant contribution to the momentum flux and turbulent scalar flux. PMID:22649290

Atypical frontal-posterior synchronization of Theory of Mind regions in autism during mental state attribution

PubMed Central

Kana, Rajesh K.; Keller, Timothy A.; Cherkassky, Vladimir L.; Minshew, Nancy J.; Just, Marcel Adam

2011-01-01

This study used fMRI to investigate the functioning of the Theory of Mind (ToM) cortical network in autism during the viewing of animations that in some conditions entailed the attribution of a mental state to animated geometric figures. At the cortical level, mentalizing (attribution of metal states) is underpinned by the coordination and integration of the components of the ToM network, which include the medial frontal gyrus, the anterior paracingulate, and the right temporoparietal junction. The pivotal new finding was a functional underconnectivity (a lower degree of synchronization) in autism, especially in the connections between frontal and posterior areas during the attribution of mental states. In addition, the frontal Theory of Mind regions activated less in participants with autism relative to control participants. In the autism group, an independent psychometric assessment of Theory of Mind ability and the activation in the right temporoparietal junction were reliably correlated. The results together provide new evidence for the biological basis of atypical processing of Theory of Mind in autism, implicating the underconnectivity between frontal regions and more posterior areas. PMID:18633829

Wind tunnel measurement of turbulent and advective scalar fluxes: a case study on intersection ventilation.

PubMed

Kukačka, Libor; Nosek, Štĕpán; Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk

2012-01-01

The objective of this study is to determine processes of pollution ventilation in the X-shaped street intersection in an idealized symmetric urban area for the changing approach flow direction. A unique experimental setup for simultaneous wind tunnel measurement of the flow velocity and the tracer gas concentration in a high temporal resolution is assembled. Advective horizontal and vertical scalar fluxes are computed from averaged measured velocity and concentration data within the street intersection. Vertical advective and turbulent scalar fluxes are computed from synchronized velocity and concentration signals measured in the plane above the intersection. All the results are obtained for five approach flow directions. The influence of the approach flow on the advective and turbulent fluxes is determined. The contribution of the advective and turbulent flux to the ventilation is discussed. Wind direction with the best dispersive conditions in the area is found. The quadrant analysis is applied to the synchronized signals of velocity and concentration fluctuation to determine events with the dominant contribution to the momentum flux and turbulent scalar flux.

Effects of control parameters of three-point initiation on the formation of an explosively formed projectile with fins

NASA Astrophysics Data System (ADS)

Li, R.; Li, W. B.; Wang, X. M.; Li, W. B.

2018-03-01

The effects of the initiation diameter and synchronicity error on the formation of fins and stable-flight velocity of an explosively formed projectile (EFP) with three-point initiation are investigated. The pressure and area of the Mach wave acting on the metal liner at different initiation diameters are calculated employing the Whitham method. LS-DYNA software is used to investigate the asymmetric collision of detonation waves resulting from three-point initiation synchronicity error, the distortion characteristics of the liner resulting from the composite detonation waves, and the performance parameters of the EFP with fins. Results indicate that deviations of the Y-shaped high-pressure zone and central ultrahigh-pressure zone from the liner center can be attributed to the error of three-point initiation, which leads to the irregular formation of EFP fins. It is noted that the area of the Mach wave decreases, but the pressure of the Mach wave and the final speed and length-to-diameter ( L/ D) ratio of the EFP increase, benefiting the formation of the EFP fins, as the initiation diameter increases.

Beta phase synchronization in the frontal-temporal-cerebellar network during auditory-to-motor rhythm learning.

PubMed

Edagawa, Kouki; Kawasaki, Masahiro

2017-02-22

Rhythm is an essential element of dancing and music. To investigate the neural mechanisms underlying how rhythm is learned, we recorded electroencephalographic (EEG) data during a rhythm-reproducing task that asked participants to memorize an auditory stimulus and reproduce it via tapping. Based on the behavioral results, we divided the participants into Learning and No-learning groups. EEG analysis showed that error-related negativity (ERN) in the Learning group was larger than in the No-learning group. Time-frequency analysis of the EEG data showed that the beta power in right and left temporal area at the late learning stage was smaller than at the early learning stage in the Learning group. Additionally, the beta power in the temporal and cerebellar areas in the Learning group when learning to reproduce the rhythm were larger than in the No Learning group. Moreover, phase synchronization between frontal and temporal regions and between temporal and cerebellar regions at late stages of learning were larger than at early stages. These results indicate that the frontal-temporal-cerebellar beta neural circuits might be related to auditory-motor rhythm learning.

Atypical frontal-posterior synchronization of Theory of Mind regions in autism during mental state attribution.

PubMed

Kana, Rajesh K; Keller, Timothy A; Cherkassky, Vladimir L; Minshew, Nancy J; Just, Marcel Adam

2009-01-01

This study used fMRI to investigate the functioning of the Theory of Mind (ToM) cortical network in autism during the viewing of animations that in some conditions entailed the attribution of a mental state to animated geometric figures. At the cortical level, mentalizing (attribution of metal states) is underpinned by the coordination and integration of the components of the ToM network, which include the medial frontal gyrus, the anterior paracingulate, and the right temporoparietal junction. The pivotal new finding was a functional underconnectivity (a lower degree of synchronization) in autism, especially in the connections between frontal and posterior areas during the attribution of mental states. In addition, the frontal ToM regions activated less in participants with autism relative to control participants. In the autism group, an independent psychometric assessment of ToM ability and the activation in the right temporoparietal junction were reliably correlated. The results together provide new evidence for the biological basis of atypical processing of ToM in autism, implicating the underconnectivity between frontal regions and more posterior areas.

Interaction between visiting bees (Hymenoptera, Apoidea) and flowers of Ludwigia elegans (Camb.) hara (Onagraceae) during the year in two different areas in São Paulo, Brazil.

PubMed

Gimenes, M

2003-11-01

This study was designed to characterize the interactions between Ludwigia elegans flowers and visiting bees during two years in two areas 200 km apart, at the same latitude (approximately 22 masculine 48'S) but at different altitudes (Alumínio, 600 m, and Campos do Jordão, 1500 m), in the State of São Paulo, Brazil. As these flowers open simultaneously in the morning and lose their petals by sunset, interaction with bees occurs only during the photophase. Flowers of L. elegans were mainly visited by bees, the most frequent species being: Tetraglossula anthracina (Michener, 1989) (Colletidae), Rhophitulus sp. (Andrenidae), and Pseudagapostemon spp. (Halictidae), all considered specialized bees for collecting pollen and nectar from these flowers, as well as the generalist bee Apis mellifera Linnaeus, 1758 (Apidae). The specialist bees were temporally adjusted to the opening schedule of the flower, which occurs primarily in the morning, but shows a circannual variation. T. anthracina appears in both study areas, but only between December and April. The annual activity patterns of these specialist bees are synchronized to the phenology of L. elegans. Photoperiod and temperature cycles are suggested as the main synchronizers of both bees and plants.

Bifurcation behaviors of synchronized regions in logistic map networks with coupling delay

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Longkun, E-mail: tomlk@hqu.edu.cn, E-mail: xqwu@whu.edu.cn; Wu, Xiaoqun, E-mail: tomlk@hqu.edu.cn, E-mail: xqwu@whu.edu.cn; Lu, Jun-an, E-mail: jalu@whu.edu.cn

2015-03-15

Network synchronized regions play an extremely important role in network synchronization according to the master stability function framework. This paper focuses on network synchronous state stability via studying the effects of nodal dynamics, coupling delay, and coupling way on synchronized regions in Logistic map networks. Theoretical and numerical investigations show that (1) network synchronization is closely associated with its nodal dynamics. Particularly, the synchronized region bifurcation points through which the synchronized region switches from one type to another are in good agreement with those of the uncoupled node system, and chaotic nodal dynamics can greatly impede network synchronization. (2) Themore » coupling delay generally impairs the synchronizability of Logistic map networks, which is also dominated by the parity of delay for some nodal parameters. (3) A simple nonlinear coupling facilitates network synchronization more than the linear one does. The results found in this paper will help to intensify our understanding for the synchronous state stability in discrete-time networks with coupling delay.« less

Synchronous motor with soft start element formed between the motor rotor and motor output shaft to successfully synchronize loads that have high inertia and/or high torque

DOE Office of Scientific and Technical Information (OSTI.GOV)

Umans, Stephen D; Nisley, Donald L; Melfi, Michael J

A line-start synchronous motor has a housing, a rotor shaft, and an output shaft. A soft-start coupling portion is operatively coupled to the output shaft and the rotor shaft. The soft-start coupling portion is configurable to enable the synchronous motor to obtain synchronous operation and to drive, at least near synchronous speed during normal steady state operation of the motor, a load having characteristics sufficient to prevent obtaining normal synchronous operation of the motor when the motor is operatively connected to the load in the absence of the soft-start coupling. The synchronous motor is sufficiently rated to obtain synchronous operationmore » and to drive, at least near synchronous speed during normal steady state operation of the motor, a load having characteristics sufficient to prevent obtaining normal synchronous operation of the motor when the motor is operatively connected to the load in the absence of the soft-start coupling.« less

Changes in White Matter Microstructure Impact Cognition by Disrupting the Ability of Neural Assemblies to Synchronize.

PubMed

Bells, Sonya; Lefebvre, Jérémie; Prescott, Steven A; Dockstader, Colleen; Bouffet, Eric; Skocic, Jovanka; Laughlin, Suzanne; Mabbott, Donald J

2017-08-23

Cognition is compromised by white matter (WM) injury but the neurophysiological alterations linking them remain unclear. We hypothesized that reduced neural synchronization caused by disruption of neural signal propagation is involved. To test this, we evaluated group differences in: diffusion tensor WM microstructure measures within the optic radiations, primary visual area (V1), and cuneus; neural phase synchrony to a visual attention cue during visual-motor task; and reaction time to a response cue during the same task between 26 pediatric patients (17/9: male/female) treated with cranial radiation treatment for a brain tumor (12.67 ± 2.76 years), and 26 healthy children (16/10: male/female; 12.01 ± 3.9 years). We corroborated our findings using a corticocortical computational model representing perturbed signal conduction from myelin. Patients show delayed reaction time, WM compromise, and reduced phase synchrony during visual attention compared with healthy children. Notably, using partial least-squares-path modeling we found that WM insult within the optic radiations, V1, and cuneus is a strong predictor of the slower reaction times via disruption of neural synchrony in visual cortex. Observed changes in synchronization were reproduced in a computational model of WM injury. These findings provide new evidence linking cognition with WM via the reliance of neural synchronization on propagation of neural signals. SIGNIFICANCE STATEMENT By comparing brain tumor patients to healthy children, we establish that changes in the microstructure of the optic radiations and neural synchrony during visual attention predict reaction time. Furthermore, by testing the directionality of these links through statistical modeling and verifying our findings with computational modeling, we infer a causal relationship, namely that changes in white matter microstructure impact cognition in part by disturbing the ability of neural assemblies to synchronize. Together, our human imaging data and computer simulations show a fundamental connection between WM microstructure and neural synchronization that is critical for cognitive processing. Copyright © 2017 the authors 0270-6474/17/378227-12$15.00/0.

Dynamic analysis of combined photovoltaic source and synchronous generator connected to power grid

NASA Astrophysics Data System (ADS)

Mahabal, Divya

In the world of expanding economy and technology, the energy demand is likely to increase even with the global efforts of saving and increasing energy efficiency. Higher oil prices, effects of greenhouse gases, and concerns over other environmental impacts gave way to Distributed Generation (DG). With adequate awareness and support, DG's can meet these rising energy demands at lower prices compared to conventional methods. Extensive research is taking place in different areas like fuel cells, photovoltaic cells, wind turbines, and gas turbines. DG's when connected to a grid increase the overall efficiency of the power grid. It is believed that three-fifth of the world's electricity would account for renewable energy by middle of 21st century. This thesis presents the dynamic analysis of a grid connected photovoltaic (PV) system and synchronous generator. A grid is considered as an infinite bus. The photovol-taic system and synchronous generator act as small scale distributed energy resources. The output of the photovoltaic system depends on the light intensity, temperature, and irradiance levels of sun. The maximum power point tracking and DC/AC converter are also modeled for the photovoltaic system. The PV system is connected to the grid through DC/AC system. Different combinations of PV and synchronous generator are modeled with the grid to study the dynamics of the proposed system. The dynamics of the test system is analyzed by subjecting the system to several disturbances under various conditions. All modules are individually modeled and con-nected using MATLAB/Simulink software package. Results from the study show that, as the penetration of renewable energy sources like PV increases into the power system, the dynamics of the system becomes faster. When considering cases such as load switching, PV cannot deliver more power as the performance of PV depends on environmental conditions. Synchronous generator in power system can produce the required amount of power. As the main aim of this research is to use renewable sources like PV in the system, it is advantageous to use a combination of both PV and synchronous generator in the system.

Emergence of synchronization induced by the interplay between two prisoner's dilemma games with volunteering in small-world networks

NASA Astrophysics Data System (ADS)

Chen, Yong; Qin, Shao-Meng; Yu, Lianchun; Zhang, Shengli

2008-03-01

We studied synchronization between prisoner’s dilemma games with voluntary participation in two Newman-Watts small-world networks. It was found that there are three kinds of synchronization: partial phase synchronization, total phase synchronization, and complete synchronization, for varied coupling factors. Besides, two games can reach complete synchronization for the large enough coupling factor. We also discussed the effect of the coupling factor on the amplitude of oscillation of cooperator density.

Stages of chaotic synchronization.

PubMed

Tang, D. Y.; Dykstra, R.; Hamilton, M. W.; Heckenberg, N. R.

1998-09-01

In an experimental investigation of the response of a chaotic system to a chaotic driving force, we have observed synchronization of chaos of the response system in the forms of generalized synchronization, phase synchronization, and lag synchronization to the driving signal. In this paper we compare the features of these forms of synchronized chaos and study their relations and physical origins. We found that different forms of chaotic synchronization could be interpreted as different stages of nonlinear interaction between the coupled chaotic systems. (c) 1998 American Institute of Physics.

The synchronicity between the stock and the stock index via information in market

NASA Astrophysics Data System (ADS)

Gao, Hai-Ling; Li, Jiang-Cheng; Guo, Wei; Mei, Dong-Cheng

2018-02-01

The synchronicity between the stock and the stock-index in a market system is investigated. The results show that: (i) the synchronicity between the stock and the stock-index increases with the rising degree of market information capitalized into stock prices in certain range; (ii) the synchronicity decreases for large firm-specific information; (iii) the stock return synchronicity is small compared to the big noise trading, however the variance noise facilitates the synchronization within the tailored realms. These findings may be helpful in understanding the effect of market information on synchronicity, especially for the response of firm-specific information and noise trading to synchronicity.

Synchronization of distributed power grids with the external loading system

NASA Astrophysics Data System (ADS)

Wei, Duqu; Mei, Chuncao

2018-06-01

In this paper, the synchronization between spatially distributed power plants and their supported consumers is studied, where the case of Kuramoto-like model power grids connected to an external permanent magnet synchronous motor (PMSM) is taken as an example. We focus on the dependence of the synchronization on the coupling coefficient. To quantitatively study the synchronization degree, we introduce the order parameter and the frequency deviation to measure the synchronization of the coupled system. It is found that as the external coupling coefficient is increased, the distributed power grids and the loading system become more and more synchronized in space, and the complete synchronization appears at a particular value of external coupling coefficient. Our results may provide a useful tip for analyzing the synchronous ability of distributed power grids.

Sound imaging of nocturnal animal calls in their natural habitat.

PubMed

Mizumoto, Takeshi; Aihara, Ikkyu; Otsuka, Takuma; Takeda, Ryu; Aihara, Kazuyuki; Okuno, Hiroshi G

2011-09-01

We present a novel method for imaging acoustic communication between nocturnal animals. Investigating the spatio-temporal calling behavior of nocturnal animals, e.g., frogs and crickets, has been difficult because of the need to distinguish many animals' calls in noisy environments without being able to see them. Our method visualizes the spatial and temporal dynamics using dozens of sound-to-light conversion devices (called "Firefly") and an off-the-shelf video camera. The Firefly, which consists of a microphone and a light emitting diode, emits light when it captures nearby sound. Deploying dozens of Fireflies in a target area, we record calls of multiple individuals through the video camera. We conduct two experiments, one indoors and the other in the field, using Japanese tree frogs (Hyla japonica). The indoor experiment demonstrates that our method correctly visualizes Japanese tree frogs' calling behavior. It has confirmed the known behavior; two frogs call synchronously or in anti-phase synchronization. The field experiment (in a rice paddy where Japanese tree frogs live) also visualizes the same calling behavior to confirm anti-phase synchronization in the field. Experimental results confirm that our method can visualize the calling behavior of nocturnal animals in their natural habitat.

Online Epileptic Seizure Prediction Using Wavelet-Based Bi-Phase Correlation of Electrical Signals Tomography.

PubMed

Vahabi, Zahra; Amirfattahi, Rasoul; Shayegh, Farzaneh; Ghassemi, Fahimeh

2015-09-01

Considerable efforts have been made in order to predict seizures. Among these methods, the ones that quantify synchronization between brain areas, are the most important methods. However, to date, a practically acceptable result has not been reported. In this paper, we use a synchronization measurement method that is derived according to the ability of bi-spectrum in determining the nonlinear properties of a system. In this method, first, temporal variation of the bi-spectrum of different channels of electro cardiography (ECoG) signals are obtained via an extended wavelet-based time-frequency analysis method; then, to compare different channels, the bi-phase correlation measure is introduced. Since, in this way, the temporal variation of the amount of nonlinear coupling between brain regions, which have not been considered yet, are taken into account, results are more reliable than the conventional phase-synchronization measures. It is shown that, for 21 patients of FSPEEG database, bi-phase correlation can discriminate the pre-ictal and ictal states, with very low false positive rates (FPRs) (average: 0.078/h) and high sensitivity (100%). However, the proposed seizure predictor still cannot significantly overcome the random predictor for all patients.

High resolution distributed time-to-digital converter (TDC) in a White Rabbit network

NASA Astrophysics Data System (ADS)

Pan, Weibin; Gong, Guanghua; Du, Qiang; Li, Hongming; Li, Jianmin

2014-02-01

The Large High Altitude Air Shower Observatory (LHAASO) project consists of a complex detector array with over 6000 detector nodes spreading over 1.2 km2 areas. The arrival times of shower particles are captured by time-to-digital converters (TDCs) in the detectors' frontend electronics, the arrival direction of the high energy cosmic ray are then to be reconstructed from the space-time information of all detector nodes. To guarantee the angular resolution of 0.5°, a time synchronization of 500 ps (RMS) accuracy and 100 ps precision must be achieved among all TDC nodes. A technology enhancing Gigabit Ethernet, called the White Rabbit (WR), has shown the capability of delivering sub-nanosecond accuracy and picoseconds precision of synchronization over the standard data packet transfer. In this paper we demonstrate a distributed TDC prototype system combining the FPGA based TDC and the WR technology. With the time synchronization and data transfer services from a compact WR node, separate FPGA-TDC nodes can be combined to provide uniform time measurement information for correlated events. The design detail and test performance will be described in the paper.

Functional brain networks in healthy subjects under acupuncture stimulation: An EEG study based on nonlinear synchronization likelihood analysis

NASA Astrophysics Data System (ADS)

Yu, Haitao; Liu, Jing; Cai, Lihui; Wang, Jiang; Cao, Yibin; Hao, Chongqing

2017-02-01

Electroencephalogram (EEG) signal evoked by acupuncture stimulation at "Zusanli" acupoint is analyzed to investigate the modulatory effect of manual acupuncture on the functional brain activity. Power spectral density of EEG signal is first calculated based on the autoregressive Burg method. It is shown that the EEG power is significantly increased during and after acupuncture in delta and theta bands, but decreased in alpha band. Furthermore, synchronization likelihood is used to estimate the nonlinear correlation between each pairwise EEG signals. By applying a threshold to resulting synchronization matrices, functional networks for each band are reconstructed and further quantitatively analyzed to study the impact of acupuncture on network structure. Graph theoretical analysis demonstrates that the functional connectivity of the brain undergoes obvious change under different conditions: pre-acupuncture, acupuncture, and post-acupuncture. The minimum path length is largely decreased and the clustering coefficient keeps increasing during and after acupuncture in delta and theta bands. It is indicated that acupuncture can significantly modulate the functional activity of the brain, and facilitate the information transmission within different brain areas. The obtained results may facilitate our understanding of the long-lasting effect of acupuncture on the brain function.

Neuronal synchrony: Peculiarity and generality

PubMed Central

Nowotny, Thomas; Huerta, Ramon; Rabinovich, Mikhail I.

2008-01-01

Synchronization in neuronal systems is a new and intriguing application of dynamical systems theory. Why are neuronal systems different as a subject for synchronization? (1) Neurons in themselves are multidimensional nonlinear systems that are able to exhibit a wide variety of different activity patterns. Their “dynamical repertoire” includes regular or chaotic spiking, regular or chaotic bursting, multistability, and complex transient regimes. (2) Usually, neuronal oscillations are the result of the cooperative activity of many synaptically connected neurons (a neuronal circuit). Thus, it is necessary to consider synchronization between different neuronal circuits as well. (3) The synapses that implement the coupling between neurons are also dynamical elements and their intrinsic dynamics influences the process of synchronization or entrainment significantly. In this review we will focus on four new problems: (i) the synchronization in minimal neuronal networks with plastic synapses (synchronization with activity dependent coupling), (ii) synchronization of bursts that are generated by a group of nonsymmetrically coupled inhibitory neurons (heteroclinic synchronization), (iii) the coordination of activities of two coupled neuronal networks (partial synchronization of small composite structures), and (iv) coarse grained synchronization in larger systems (synchronization on a mesoscopic scale). PMID:19045493

Synchronization Analysis of Master-Slave Probabilistic Boolean Networks.

PubMed

Lu, Jianquan; Zhong, Jie; Li, Lulu; Ho, Daniel W C; Cao, Jinde

2015-08-28

In this paper, we analyze the synchronization problem of master-slave probabilistic Boolean networks (PBNs). The master Boolean network (BN) is a deterministic BN, while the slave BN is determined by a series of possible logical functions with certain probability at each discrete time point. In this paper, we firstly define the synchronization of master-slave PBNs with probability one, and then we investigate synchronization with probability one. By resorting to new approach called semi-tensor product (STP), the master-slave PBNs are expressed in equivalent algebraic forms. Based on the algebraic form, some necessary and sufficient criteria are derived to guarantee synchronization with probability one. Further, we study the synchronization of master-slave PBNs in probability. Synchronization in probability implies that for any initial states, the master BN can be synchronized by the slave BN with certain probability, while synchronization with probability one implies that master BN can be synchronized by the slave BN with probability one. Based on the equivalent algebraic form, some efficient conditions are derived to guarantee synchronization in probability. Finally, several numerical examples are presented to show the effectiveness of the main results.

Synchronization Analysis of Master-Slave Probabilistic Boolean Networks

PubMed Central

Lu, Jianquan; Zhong, Jie; Li, Lulu; Ho, Daniel W. C.; Cao, Jinde

2015-01-01

In this paper, we analyze the synchronization problem of master-slave probabilistic Boolean networks (PBNs). The master Boolean network (BN) is a deterministic BN, while the slave BN is determined by a series of possible logical functions with certain probability at each discrete time point. In this paper, we firstly define the synchronization of master-slave PBNs with probability one, and then we investigate synchronization with probability one. By resorting to new approach called semi-tensor product (STP), the master-slave PBNs are expressed in equivalent algebraic forms. Based on the algebraic form, some necessary and sufficient criteria are derived to guarantee synchronization with probability one. Further, we study the synchronization of master-slave PBNs in probability. Synchronization in probability implies that for any initial states, the master BN can be synchronized by the slave BN with certain probability, while synchronization with probability one implies that master BN can be synchronized by the slave BN with probability one. Based on the equivalent algebraic form, some efficient conditions are derived to guarantee synchronization in probability. Finally, several numerical examples are presented to show the effectiveness of the main results. PMID:26315380

Auditory over visual advantage of sensorimotor synchronization in 6- to 7-year-old children but not in 12- to 15-year-old children and adults.

PubMed

Mu, Yan; Huang, Yingyu; Ji, Chao; Gu, Li; Wu, Xiang

2018-05-01

The superiority of the auditory over visual modality in sensorimotor synchronization-a fundamental ability to coordinate movements with external rhythms-has long been established, whereas recent metronome synchronization work showed that synchronization of a visual bouncing ball was not less stable than synchronization of auditory tones in adults. The present study examined synchronization to isochronous sequences composed of auditory tones, visual flashes, or a bouncing ball in 6- to 7-year-old children, 12- to 15-year-old children, and 19- to 29-year-old adults. Consistent with previous reporting, the results showed that synchronization stability increased with age and synchronization was less stable for flashes than for tones and bouncing balls. As for the focus of the present study, the results revealed that synchronization of the bouncing ball was less stable than synchronization of tones for younger children, but not for teenagers and adults. The finding suggests the predisposition of the auditory advantage of sensorimotor synchronization in early childhood. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Measures of Quantum Synchronization in Continuous Variable Systems

NASA Astrophysics Data System (ADS)

Mari, A.; Farace, A.; Didier, N.; Giovannetti, V.; Fazio, R.

2013-09-01

We introduce and characterize two different measures which quantify the level of synchronization of coupled continuous variable quantum systems. The two measures allow us to extend to the quantum domain the notions of complete and phase synchronization. The Heisenberg principle sets a universal bound to complete synchronization. The measure of phase synchronization is, in principle, unbounded; however, in the absence of quantum resources (e.g., squeezing) the synchronization level is bounded below a certain threshold. We elucidate some interesting connections between entanglement and synchronization and, finally, discuss an application based on quantum optomechanical systems.

Measures of quantum synchronization in continuous variable systems.

PubMed

Mari, A; Farace, A; Didier, N; Giovannetti, V; Fazio, R

2013-09-06

We introduce and characterize two different measures which quantify the level of synchronization of coupled continuous variable quantum systems. The two measures allow us to extend to the quantum domain the notions of complete and phase synchronization. The Heisenberg principle sets a universal bound to complete synchronization. The measure of phase synchronization is, in principle, unbounded; however, in the absence of quantum resources (e.g., squeezing) the synchronization level is bounded below a certain threshold. We elucidate some interesting connections between entanglement and synchronization and, finally, discuss an application based on quantum optomechanical systems.

Synchronization in node of complex networks consist of complex chaotic system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, Qiang, E-mail: qiangweibeihua@163.com; Digital Images Processing Institute of Beihua University, BeiHua University, Jilin, 132011, Jilin; Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian, 116024

2014-07-15

A new synchronization method is investigated for node of complex networks consists of complex chaotic system. When complex networks realize synchronization, different component of complex state variable synchronize up to different scaling complex function by a designed complex feedback controller. This paper change synchronization scaling function from real field to complex field for synchronization in node of complex networks with complex chaotic system. Synchronization in constant delay and time-varying coupling delay complex networks are investigated, respectively. Numerical simulations are provided to show the effectiveness of the proposed method.

Multiple types of synchronization analysis for discontinuous Cohen-Grossberg neural networks with time-varying delays.

PubMed

Li, Jiarong; Jiang, Haijun; Hu, Cheng; Yu, Zhiyong

2018-03-01

This paper is devoted to the exponential synchronization, finite time synchronization, and fixed-time synchronization of Cohen-Grossberg neural networks (CGNNs) with discontinuous activations and time-varying delays. Discontinuous feedback controller and Novel adaptive feedback controller are designed to realize global exponential synchronization, finite time synchronization and fixed-time synchronization by adjusting the values of the parameters ω in the controller. Furthermore, the settling time of the fixed-time synchronization derived in this paper is less conservative and more accurate. Finally, some numerical examples are provided to show the effectiveness and flexibility of the results derived in this paper. Copyright © 2018 Elsevier Ltd. All rights reserved.

Time delay induced different synchronization patterns in repulsively coupled chaotic oscillators

NASA Astrophysics Data System (ADS)

Yao, Chenggui; Yi, Ming; Shuai, Jianwei

2013-09-01

Time delayed coupling plays a crucial role in determining the system's dynamics. We here report that the time delay induces transition from the asynchronous state to the complete synchronization (CS) state in the repulsively coupled chaotic oscillators. In particular, by changing the coupling strength or time delay, various types of synchronous patterns, including CS, antiphase CS, antiphase synchronization (ANS), and phase synchronization, can be generated. In the transition regions between different synchronous patterns, bistable synchronous oscillators can be observed. Furthermore, we show that the time-delay-induced phase flip bifurcation is of key importance for the emergence of CS. All these findings may light on our understanding of neuronal synchronization and information processing in the brain.

Determining the degree of synchronism for intermittent phase synchronization in human electroencephalography data

NASA Astrophysics Data System (ADS)

Koloskova, A. D.; Moskalenko, O. I.

2017-05-01

The phenomenon of intermittent phase synchronization during development of epileptic activity in human beings has been discovered based on EEG data. The presence of synchronous behavior phases has been detected both during spike-wave discharges and in the regions of background activity of the brain. The degree of synchronism in the intermittent phase-synchronization regime in both cases has been determined, and it has been established that spike-wave discharges are characterized by a higher degree of synchronism than exists in the regions of background activity of the brain. To determine the degree of synchronism, a modified method of evaluating zero conditional Lyapunov exponents from time series is proposed.

Time‐resolved detection of stimulus/task‐related networks, via clustering of transient intersubject synchronization

PubMed Central

Macaluso, Emiliano

2015-01-01

Abstract Several methods are available for the identification of functional networks of brain areas using functional magnetic resonance imaging (fMRI) time‐series. These typically assume a fixed relationship between the signal of the areas belonging to the same network during the entire time‐series (e.g., positive correlation between the areas belonging to the same network), or require a priori information about when this relationship may change (task‐dependent changes of connectivity). We present a fully data‐driven method that identifies transient network configurations that are triggered by the external input and that, therefore, include only regions involved in stimulus/task processing. Intersubject synchronization with short sliding time‐windows was used to identify if/when any area showed stimulus/task‐related responses. Next, a first clustering step grouped together areas that became engaged concurrently and repetitively during the time‐series (stimulus/task‐related networks). Finally, for each network, a second clustering step grouped together all the time‐windows with the same BOLD signal. The final output consists of a set of network configurations that show stimulus/task‐related activity at specific time‐points during the fMRI time‐series. We label these configurations: “brain modes” (bModes). The method was validated using simulated datasets and a real fMRI experiment with multiple tasks and conditions. Future applications include the investigation of brain functions using complex and naturalistic stimuli. Hum Brain Mapp 36:3404–3425, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. PMID:26095530

Cooperative effect of random and time-periodic coupling strength on synchronization transitions in one-way coupled neural system: mean field approach.

PubMed

Jiancheng, Shi; Min, Luo; Chusheng, Huang

2017-08-01

The cooperative effect of random coupling strength and time-periodic coupling strengh on synchronization transitions in one-way coupled neural system has been investigated by mean field approach. Results show that cooperative coupling strength (CCS) plays an active role for the enhancement of synchronization transitions. There exist an optimal frequency of CCS which makes the system display the best CCS-induced synchronization transitions, a critical frequency of CCS which can not further affect the CCS-induced synchronization transitions, and a critical amplitude of CCS which can not occur the CCS-induced synchronization transitions. Meanwhile, noise intensity plays a negative role for the CCS-induced synchronization transitions. Furthermore, it is found that the novel CCS amplitude-induced synchronization transitions and CCS frequency-induced synchronization transitions are found.

Injuries and medical issues in synchronized Olympic sports.

PubMed

Mountjoy, Margo

2009-01-01

Spectators of the Olympic Games can enjoy a wide variety of sports, including strength, team, timed, endurance, and artistic sports. In the Olympic program, there are two synchronized events: synchronized diving and synchronized swimming. The precision of the synchronization of the athlete's movements and skills is an added feature of entertainment. Synchronized athletes have additional training requirements to perfect the synchronization of their skills. The physical demands on the athlete from the repetition of training required for the perfection of synchronization result in injuries unique to these sports. Although both traumatic and overuse injuries occur, overuse injuries are more common. As these disciplines are artistic, judged sports, these athletes also are susceptible to eating disorders and the female athlete triad. This article reviews the training regimen of these athletes and outlines the injuries and health concerns that are common in the synchronized sports.

Robust synchronization control scheme of a population of nonlinear stochastic synthetic genetic oscillators under intrinsic and extrinsic molecular noise via quorum sensing.

PubMed

Chen, Bor-Sen; Hsu, Chih-Yuan

2012-10-26

Collective rhythms of gene regulatory networks have been a subject of considerable interest for biologists and theoreticians, in particular the synchronization of dynamic cells mediated by intercellular communication. Synchronization of a population of synthetic genetic oscillators is an important design in practical applications, because such a population distributed over different host cells needs to exploit molecular phenomena simultaneously in order to emerge a biological phenomenon. However, this synchronization may be corrupted by intrinsic kinetic parameter fluctuations and extrinsic environmental molecular noise. Therefore, robust synchronization is an important design topic in nonlinear stochastic coupled synthetic genetic oscillators with intrinsic kinetic parameter fluctuations and extrinsic molecular noise. Initially, the condition for robust synchronization of synthetic genetic oscillators was derived based on Hamilton Jacobi inequality (HJI). We found that if the synchronization robustness can confer enough intrinsic robustness to tolerate intrinsic parameter fluctuation and extrinsic robustness to filter the environmental noise, then robust synchronization of coupled synthetic genetic oscillators is guaranteed. If the synchronization robustness of a population of nonlinear stochastic coupled synthetic genetic oscillators distributed over different host cells could not be maintained, then robust synchronization could be enhanced by external control input through quorum sensing molecules. In order to simplify the analysis and design of robust synchronization of nonlinear stochastic synthetic genetic oscillators, the fuzzy interpolation method was employed to interpolate several local linear stochastic coupled systems to approximate the nonlinear stochastic coupled system so that the HJI-based synchronization design problem could be replaced by a simple linear matrix inequality (LMI)-based design problem, which could be solved with the help of LMI toolbox in MATLAB easily. If the synchronization robustness criterion, i.e. the synchronization robustness ≥ intrinsic robustness + extrinsic robustness, then the stochastic coupled synthetic oscillators can be robustly synchronized in spite of intrinsic parameter fluctuation and extrinsic noise. If the synchronization robustness criterion is violated, external control scheme by adding inducer can be designed to improve synchronization robustness of coupled synthetic genetic oscillators. The investigated robust synchronization criteria and proposed external control method are useful for a population of coupled synthetic networks with emergent synchronization behavior, especially for multi-cellular, engineered networks.

Robust synchronization control scheme of a population of nonlinear stochastic synthetic genetic oscillators under intrinsic and extrinsic molecular noise via quorum sensing

PubMed Central

2012-01-01

Background Collective rhythms of gene regulatory networks have been a subject of considerable interest for biologists and theoreticians, in particular the synchronization of dynamic cells mediated by intercellular communication. Synchronization of a population of synthetic genetic oscillators is an important design in practical applications, because such a population distributed over different host cells needs to exploit molecular phenomena simultaneously in order to emerge a biological phenomenon. However, this synchronization may be corrupted by intrinsic kinetic parameter fluctuations and extrinsic environmental molecular noise. Therefore, robust synchronization is an important design topic in nonlinear stochastic coupled synthetic genetic oscillators with intrinsic kinetic parameter fluctuations and extrinsic molecular noise. Results Initially, the condition for robust synchronization of synthetic genetic oscillators was derived based on Hamilton Jacobi inequality (HJI). We found that if the synchronization robustness can confer enough intrinsic robustness to tolerate intrinsic parameter fluctuation and extrinsic robustness to filter the environmental noise, then robust synchronization of coupled synthetic genetic oscillators is guaranteed. If the synchronization robustness of a population of nonlinear stochastic coupled synthetic genetic oscillators distributed over different host cells could not be maintained, then robust synchronization could be enhanced by external control input through quorum sensing molecules. In order to simplify the analysis and design of robust synchronization of nonlinear stochastic synthetic genetic oscillators, the fuzzy interpolation method was employed to interpolate several local linear stochastic coupled systems to approximate the nonlinear stochastic coupled system so that the HJI-based synchronization design problem could be replaced by a simple linear matrix inequality (LMI)-based design problem, which could be solved with the help of LMI toolbox in MATLAB easily. Conclusion If the synchronization robustness criterion, i.e. the synchronization robustness ≥ intrinsic robustness + extrinsic robustness, then the stochastic coupled synthetic oscillators can be robustly synchronized in spite of intrinsic parameter fluctuation and extrinsic noise. If the synchronization robustness criterion is violated, external control scheme by adding inducer can be designed to improve synchronization robustness of coupled synthetic genetic oscillators. The investigated robust synchronization criteria and proposed external control method are useful for a population of coupled synthetic networks with emergent synchronization behavior, especially for multi-cellular, engineered networks. PMID:23101662

Secure remote synchronization and secure key distribution in electro-optic networks revealed by symmetries

NASA Astrophysics Data System (ADS)

Xu, Mingfeng; Pan, Wei; Zhang, Liyue

2018-07-01

Despite the intuition that synchronization of different nodes in coupled oscillator networks results from information exchange between them, it has recently been shown that remote nodes could be partially synchronous even when they are separated by intermediately unsynchronized nodes. Here based on electro-optic system, we report on a more stronger form of such synchronization pattern that is termed as secure remote synchronization, in which two remotely separated nodes could have identically synchronized dynamical behaviors while the rest of the network are both statistically and information-theoretically incoherent relative to the two synchronized nodes. The generalized form of mirror symmetry in the network structure is identified to be a key mechanism allowing for secure remote synchronization. Moreover, this synchronization mode is robust against a wild range of system parameters and noise perturbing the intermediary dynamics. The lack of information about the synchronized dynamics in the rest of the network suggests that our results could potentially lead to network-based solutions for secure key distribution and secure communication.

Patterns of Cortical Synchronization in Isolated Dystonia Compared With Parkinson Disease

PubMed Central

Miocinovic, Svjetlana; de Hemptinne, Coralie; Qasim, Salman; Ostrem, Jill L.; Starr, Philip A.

2016-01-01

IMPORTANCE Isolated dystonia and Parkinson disease (PD) are disorders of the basal gangliothalamocortical network. They have largely distinct clinical profiles, but both disorders respond to deep brain stimulation (DBS) in the same subcortical targets using similar stimulation paradigms, suggesting pathophysiologic overlap. We hypothesized that, similar to PD, isolated dystonia is associated with elevated cortical neuronal synchronization. OBJECTIVE To investigate the electrophysiologic characteristics of the sensorimotor cortex arm-related area using a temporary subdural electrode strip in patients with isolated dystonia and PD undergoing DBS implantation in the awake state. DESIGN, SETTING, AND PARTICIPANTS An observational study recruited patients scheduled for DBS at the University of California, San Francisco and the San Francisco Veterans Affairs Medical Center. Data were collected from May 1, 2008, through April 1, 2015. Findings are reported for 22 patients with isolated cervical or segmental dystonia (8 with [DYST-ARM] and 14 without [DYST] arm symptoms] and 14 patients with akinetic rigid PD. Data were analyzed from November 1, 2014, through May 1, 2015. MAIN OUTCOMES AND MEASURES Cortical local field potentials, power spectral density, and phase-amplitude coupling (PAC). RESULTS Among our 3 groups that together included 36 patients, cortical PAC was present in primary motor and premotor arm-related areas for all groups, but the DYST group was less likely to exhibit increased PAC (P = .008). Similar to what has been shown for patients with PD, subthalamic DBS reversibly decreased PAC in a subset of patients with dystonia who were studied before and during intraoperative test stimulation (n = 4). At rest, broadband gamma (50–200 Hz) power in the primary motor cortex was greater in the DYST-ARM and PD groups compared with the DYST group, whereas alpha (8–13 Hz) and beta (13–30 Hz) power was comparable in all 3 groups. During movement, the DYST-ARM group had impaired beta and low gamma desynchronization in the primary motor cortex. CONCLUSIONS AND RELEVANCE Isolated dystonia and PD have physiologic overlap with respect to high levels of motor cortex synchronization and reduction of cortical synchronization by subthalamic DBS, providing an explanation for their similar therapeutic response to basal ganglia stimulation. PMID:26409266

Guide to Synchronization of Video Systems to IRIG Timing

DTIC Science & Technology

1992-07-01

and industry. 1-2 CHAPTER 2 SYNCHRONISATION Before delving into the details of synchronization , a review is needed of the reasons for synchronizing ... Synchronization of Video Systems to IRIG Timing Optical Systems Group Range Commanders Council White Sands Missile Range, NM 88002-5110 RCC Document 456-92 Range...This document addresses a broad field of video synchronization to IRIG timing with emphasis on color synchronization . This document deals with

Local and global synchronization transitions induced by time delays in small-world neuronal networks with chemical synapses.

PubMed

Yu, Haitao; Wang, Jiang; Du, Jiwei; Deng, Bin; Wei, Xile

2015-02-01

Effects of time delay on the local and global synchronization in small-world neuronal networks with chemical synapses are investigated in this paper. Numerical results show that, for both excitatory and inhibitory coupling types, the information transmission delay can always induce synchronization transitions of spiking neurons in small-world networks. In particular, regions of in-phase and out-of-phase synchronization of connected neurons emerge intermittently as the synaptic delay increases. For excitatory coupling, all transitions to spiking synchronization occur approximately at integer multiples of the firing period of individual neurons; while for inhibitory coupling, these transitions appear at the odd multiples of the half of the firing period of neurons. More importantly, the local synchronization transition is more profound than the global synchronization transition, depending on the type of coupling synapse. For excitatory synapses, the local in-phase synchronization observed for some values of the delay also occur at a global scale; while for inhibitory ones, this synchronization, observed at the local scale, disappears at a global scale. Furthermore, the small-world structure can also affect the phase synchronization of neuronal networks. It is demonstrated that increasing the rewiring probability can always improve the global synchronization of neuronal activity, but has little effect on the local synchronization of neighboring neurons.

Transition to complete synchronization and global intermittent synchronization in an array of time-delay systems.

PubMed

Suresh, R; Senthilkumar, D V; Lakshmanan, M; Kurths, J

2012-07-01

We report the nature of transitions from the nonsynchronous to a complete synchronization (CS) state in arrays of time-delay systems, where the systems are coupled with instantaneous diffusive coupling. We demonstrate that the transition to CS occurs distinctly for different coupling configurations. In particular, for unidirectional coupling, locally (microscopically) synchronization transition occurs in a very narrow range of coupling strength but for a global one (macroscopically) it occurs sequentially in a broad range of coupling strength preceded by an intermittent synchronization. On the other hand, in the case of mutual coupling, a very large value of coupling strength is required for local synchronization and, consequently, all the local subsystems synchronize immediately for the same value of the coupling strength and, hence, globally, synchronization also occurs in a narrow range of the coupling strength. In the transition regime, we observe a type of synchronization transition where long intervals of high-quality synchronization which are interrupted at irregular times by intermittent chaotic bursts simultaneously in all the systems and which we designate as global intermittent synchronization. We also relate our synchronization transition results to the above specific types using unstable periodic orbit theory. The above studies are carried out in a well-known piecewise linear time-delay system.

Does synchronization reflect a true interaction in the cardiorespiratory system?

PubMed

Toledo, E; Akselrod, S; Pinhas, I; Aravot, D

2002-01-01

Cardiorespiratory synchronization, studied within the framework of phase synchronization, has recently raised interest as one of the interactions in the cardiorespiratory system. In this work, we present a quantitative approach to the analysis of this nonlinear phenomenon. Our primary aim is to determine whether synchronization between HR and respiration rate is a real phenomenon or a random one. First, we developed an algorithm, which detects epochs of synchronization automatically and objectively. The algorithm was applied to recordings of respiration and HR obtained from 13 normal subjects and 13 heart transplant patients. Surrogate data sets were constructed from the original recordings, specifically lacking the coupling between HR and respiration. The statistical properties of synchronization in the two data sets and in their surrogates were compared. Synchronization was observed in all groups: in normal subjects, in the heart transplant patients and in the surrogates. Interestingly, synchronization was less abundant in normal subjects than in the transplant patients, indicating that the unique physiological condition of the latter promote cardiorespiratory synchronization. The duration of synchronization epochs was significantly shorter in the surrogate data of both data sets, suggesting that at least some of the synchronization epochs are real. In view of those results, cardiorespiratory synchronization, although not a major feature of cardiorespiratory interaction, seems to be a real phenomenon rather than an artifact.

Top-Down Beta Enhances Bottom-Up Gamma

PubMed Central

Thompson, William H.

2017-01-01

Several recent studies have demonstrated that the bottom-up signaling of a visual stimulus is subserved by interareal gamma-band synchronization, whereas top-down influences are mediated by alpha-beta band synchronization. These processes may implement top-down control of stimulus processing if top-down and bottom-up mediating rhythms are coupled via cross-frequency interaction. To test this possibility, we investigated Granger-causal influences among awake macaque primary visual area V1, higher visual area V4, and parietal control area 7a during attentional task performance. Top-down 7a-to-V1 beta-band influences enhanced visually driven V1-to-V4 gamma-band influences. This enhancement was spatially specific and largest when beta-band activity preceded gamma-band activity by ∼0.1 s, suggesting a causal effect of top-down processes on bottom-up processes. We propose that this cross-frequency interaction mechanistically subserves the attentional control of stimulus selection. SIGNIFICANCE STATEMENT Contemporary research indicates that the alpha-beta frequency band underlies top-down control, whereas the gamma-band mediates bottom-up stimulus processing. This arrangement inspires an attractive hypothesis, which posits that top-down beta-band influences directly modulate bottom-up gamma band influences via cross-frequency interaction. We evaluate this hypothesis determining that beta-band top-down influences from parietal area 7a to visual area V1 are correlated with bottom-up gamma frequency influences from V1 to area V4, in a spatially specific manner, and that this correlation is maximal when top-down activity precedes bottom-up activity. These results show that for top-down processes such as spatial attention, elevated top-down beta-band influences directly enhance feedforward stimulus-induced gamma-band processing, leading to enhancement of the selected stimulus. PMID:28592697

Making Culture and Language Real in a Rural Setting: The Technology Connection.

ERIC Educational Resources Information Center

Smith, Elizabeth A.

2000-01-01

Asserts that with the growth of the Internet, e-mail, synchronous chat, and videoconferencing, students in rural (and urban) areas have virtually endless access to culture and language from their school or home. Describes the utilization of technology as a means of cultural exchange between Southwest Virginia Community College and the University…

Infant Brain Development and the Impact of Breast Feeding: A Review of Literature

ERIC Educational Resources Information Center

Minkkinen, Molly H.

2007-01-01

Research in the area of infant development has endless facets of investigation. No one facet of research is more important than another, and all of the findings work in a synchronous fashion to facilitate our understanding of child development. Research on child development has proliferated across the centuries. Infant characteristics like…

LTP in Hippocampal Area CA1 Is Induced by Burst Stimulation over a Broad Frequency Range Centered around Delta

ERIC Educational Resources Information Center

Grover, Lawrence M.; Kim, Eunyoung; Cooke, Jennifer D.; Holmes, William R.

2009-01-01

Long-term potentiation (LTP) is typically studied using either continuous high-frequency stimulation or theta burst stimulation. Previous studies emphasized the physiological relevance of theta frequency; however, synchronized hippocampal activity occurs over a broader frequency range. We therefore tested burst stimulation at intervals from 100…

Windows into Teaching and Learning: Professional Growth of Classroom Teachers in an Online Environment

ERIC Educational Resources Information Center

Petty, Teresa M.; Heafner, Tina L.; Farinde, Abiola; Plaisance, Michelle

2015-01-01

The Windows into Teaching and Learning (WiTL) project was developed by researchers at one large urban institution in the southeast region of the United States as a way to facilitate online clinical experiences for content area methods students during summer coursework. Utilising both synchronous and asynchronous elements, WiTL addressed the issue…

Similar brain networks for detecting visuo-motor and visuo-proprioceptive synchrony.

PubMed

Balslev, Daniela; Nielsen, Finn A; Lund, Torben E; Law, Ian; Paulson, Olaf B

2006-05-15

The ability to recognize feedback from own movement as opposed to the movement of someone else is important for motor control and social interaction. The neural processes involved in feedback recognition are incompletely understood. Two competing hypotheses have been proposed: the stimulus is compared with either (a) the proprioceptive feedback or with (b) the motor command and if they match, then the external stimulus is identified as feedback. Hypothesis (a) predicts that the neural mechanisms or brain areas involved in distinguishing self from other during passive and active movement are similar, whereas hypothesis (b) predicts that they are different. In this fMRI study, healthy subjects saw visual cursor movement that was either synchronous or asynchronous with their active or passive finger movements. The aim was to identify the brain areas where the neural activity depended on whether the visual stimulus was feedback from own movement and to contrast the functional activation maps for active and passive movement. We found activity increases in the right temporoparietal cortex in the condition with asynchronous relative to synchronous visual feedback from both active and passive movements. However, no statistically significant difference was found between these sets of activated areas when the active and passive movement conditions were compared. With a posterior probability of 0.95, no brain voxel had a contrast effect above 0.11% of the whole-brain mean signal. These results do not support the hypothesis that recognition of visual feedback during active and passive movement relies on different brain areas.

Integration of a Self-Coherence Algorithm into DISAT for Forced Oscillation Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Follum, James D.; Tuffner, Francis K.; Amidan, Brett G.

2015-03-03

With the increasing number of phasor measurement units on the power system, behaviors typically not observable on the power system are becoming more apparent. Oscillatory behavior on the power system, notably forced oscillations, are one such behavior. However, the large amounts of data coming from the PMUs makes manually detecting and locating these oscillations difficult. To automate portions of the process, an oscillation detection routine was coded into the Data Integrity and Situational Awareness Tool (DISAT) framework. Integration into the DISAT framework allows forced oscillations to be detected and information about the event provided to operational engineers. The oscillation detectionmore » algorithm integrates with the data handling and atypical data detecting capabilities of DISAT, building off of a standard library of functions. This report details that integration with information on the algorithm, some implementation issues, and some sample results from the western United States’ power grid.« less

Towards Effective Clustering Techniques for the Analysis of Electric Power Grids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hogan, Emilie A.; Cotilla Sanchez, Jose E.; Halappanavar, Mahantesh

2013-11-30

Clustering is an important data analysis technique with numerous applications in the analysis of electric power grids. Standard clustering techniques are oblivious to the rich structural and dynamic information available for power grids. Therefore, by exploiting the inherent topological and electrical structure in the power grid data, we propose new methods for clustering with applications to model reduction, locational marginal pricing, phasor measurement unit (PMU or synchrophasor) placement, and power system protection. We focus our attention on model reduction for analysis based on time-series information from synchrophasor measurement devices, and spectral techniques for clustering. By comparing different clustering techniques onmore » two instances of realistic power grids we show that the solutions are related and therefore one could leverage that relationship for a computational advantage. Thus, by contrasting different clustering techniques we make a case for exploiting structure inherent in the data with implications for several domains including power systems.« less

A Data Quality Filter for PMU Measurements: Description, Experience, and Examples

DOE Office of Scientific and Technical Information (OSTI.GOV)

Follum, James D.; Amidan, Brett G.

Networks of phasor measurement units (PMUs) continue to grow, and along with them, the amount of data available for analysis. With so much data, it is impractical to identify and remove poor quality data manually. The data quality filter described in this paper was developed for use with the Data Integrity and Situation Awareness Tool (DISAT), which analyzes PMU data to identify anomalous system behavior. The filter operates based only on the information included in the data files, without supervisory control and data acquisition (SCADA) data, state estimator values, or system topology information. Measurements are compared to preselected thresholds tomore » determine if they are reliable. Along with the filter's description, examples of data quality issues from application of the filter to nine months of archived PMU data are provided. The paper is intended to aid the reader in recognizing and properly addressing data quality issues in PMU data.« less

An Adaptive Instability Suppression Controls Method for Aircraft Gas Turbine Engine Combustors

NASA Technical Reports Server (NTRS)

Kopasakis, George; DeLaat, John C.; Chang, Clarence T.

2008-01-01

An adaptive controls method for instability suppression in gas turbine engine combustors has been developed and successfully tested with a realistic aircraft engine combustor rig. This testing was part of a program that demonstrated, for the first time, successful active combustor instability control in an aircraft gas turbine engine-like environment. The controls method is called Adaptive Sliding Phasor Averaged Control. Testing of the control method has been conducted in an experimental rig with different configurations designed to simulate combustors with instabilities of about 530 and 315 Hz. Results demonstrate the effectiveness of this method in suppressing combustor instabilities. In addition, a dramatic improvement in suppression of the instability was achieved by focusing control on the second harmonic of the instability. This is believed to be due to a phenomena discovered and reported earlier, the so called Intra-Harmonic Coupling. These results may have implications for future research in combustor instability control.

Neural network based control of Doubly Fed Induction Generator in wind power generation

NASA Astrophysics Data System (ADS)

Barbade, Swati A.; Kasliwal, Prabha

2012-07-01

To complement the other types of pollution-free generation wind energy is a viable option. Previously wind turbines were operated at constant speed. The evolution of technology related to wind systems industry leaded to the development of a generation of variable speed wind turbines that present many advantages compared to the fixed speed wind turbines. In this paper the phasor model of DFIG is used. This paper presents a study of a doubly fed induction generator driven by a wind turbine connected to the grid, and controlled by artificial neural network ANN controller. The behaviour of the system is shown with PI control, and then as controlled by ANN. The effectiveness of the artificial neural network controller is compared to that of a PI controller. The SIMULINK/MATLAB simulation for Doubly Fed Induction Generator and corresponding results and waveforms are displayed.

Towards two-photon excited endogenous fluorescence lifetime imaging microendoscopy

PubMed Central

Hage, C. H.; Leclerc, P.; Brevier, J.; Fabert, M.; Le Nézet, C.; Kudlinski, A.; Héliot, L.; Louradour, F.

2017-01-01

In situ fluorescence lifetime imaging microscopy (FLIM) in an endoscopic configuration of the endogenous biomarker nicotinamide adenine dinucleotide (NADH) has a great potential for malignant tissue diagnosis. Moreover, two-photon nonlinear excitation provides intrinsic optical sectioning along with enhanced imaging depth. We demonstrate, for the first time to our knowledge, nonlinear endogenous FLIM in a fibered microscope with proximal detection, applied to NADH in cultured cells, as a first step to a nonlinear endomicroscope, using a double-clad microstructured fiber with convenient fiber length (> 3 m) and excitation pulse duration (≈50 fs). Fluorescence photons are collected by the fiber inner cladding and we show that its contribution to the impulse response function (IRF), which originates from its intermodal and chromatic dispersions, is small (< 600 ps) and stable for lengths up to 8 m and allows for short lifetime measurements. We use the phasor representation as a quick visualization tool adapted to the endoscopy speed requirements. PMID:29359093

Generalized synchronization in relay systems with instantaneous coupling

NASA Astrophysics Data System (ADS)

Gutiérrez, R.; Sevilla-Escoboza, R.; Piedrahita, P.; Finke, C.; Feudel, U.; Buldú, J. M.; Huerta-Cuellar, G.; Jaimes-Reátegui, R.; Moreno, Y.; Boccaletti, S.

2013-11-01

We demonstrate the existence of generalized synchronization in systems that act as mediators between two dynamical units that, in turn, show complete synchronization with each other. These are the so-called relay systems. Specifically, we analyze the Lyapunov spectrum of the full system to elucidate when complete and generalized synchronization appear. We show that once a critical coupling strength is achieved, complete synchronization emerges between the systems to be synchronized, and at the same point, generalized synchronization with the relay system also arises. Next, we use two nonlinear measures based on the distance between phase-space neighbors to quantify the generalized synchronization in discretized time series. Finally, we experimentally show the robustness of the phenomenon and of the theoretical tools here proposed to characterize it.

Damping torque analysis of VSC-based system utilizing power synchronization control

NASA Astrophysics Data System (ADS)

Fu, Q.; Du, W. J.; Zheng, K. Y.; Wang, H. F.

2017-05-01

Power synchronization control is a new control strategy of VSC-HVDC for connecting a weak power system. Different from the vector control method, this control method utilizes the internal synchronization mechanism in ac systems, in principle, similar to the operation of a synchronous machine. So that the parameters of controllers in power synchronization control will change the electromechanical oscillation modes and make an impact on the transient stability of power system. This paper present a mathematical model for small-signal stability analysis of VSC station used power synchronization control and analyse the impact of the dynamic interactions by calculating the contribution of the damping torque from the power synchronization control, besides, the parameters of controllers which correspond to damping torque and synchronous torque in the power synchronization control is defined respectively. At the end of the paper, an example power system is presented to demonstrate and validate the theoretical analysis and associated conclusions are made.

Synchronicity from synchronized chaos

DOE PAGES

Duane, Gregory

2015-04-01

The synchronization of loosely-coupled chaotic oscillators, a phenomenon investigated intensively for the last two decades, may realize the philosophical concept of “synchronicity”—the commonplace notion that related events mysteriously occur at the same time. When extended to continuous media and/or large discrete arrays, and when general (non-identical) correspondences are considered between states, intermittent synchronous relationships indeed become ubiquitous. Meaningful synchronicity follows naturally if meaningful events are identified with coherent structures, defined by internal synchronization between remote degrees of freedom; a condition that has been posited as necessary for synchronizability with an external system. The important case of synchronization between mind andmore » matter is realized if mind is analogized to a computer model, synchronizing with a sporadically observed system, as in meteorological data assimilation. Evidence for the ubiquity of synchronization is reviewed along with recent proposals that: (1) synchronization of different models of the same objective process may be an expeditious route to improved computational modeling and may also describe the functioning of conscious brains; and (2) the nonlocality in quantum phenomena implied by Bell’s theorem may be explained in a variety of deterministic (hidden variable) interpretations if the quantum world resides on a generalized synchronization “manifold”.« less

Finite-Time and Fixed-Time Cluster Synchronization With or Without Pinning Control.

PubMed

Liu, Xiwei; Chen, Tianping

2018-01-01

In this paper, the finite-time and fixed-time cluster synchronization problem for complex networks with or without pinning control are discussed. Finite-time (or fixed-time) synchronization has been a hot topic in recent years, which means that the network can achieve synchronization in finite-time, and the settling time depends on the initial values for finite-time synchronization (or the settling time is bounded by a constant for any initial values for fixed-time synchronization). To realize the finite-time and fixed-time cluster synchronization, some simple distributed protocols with or without pinning control are designed and the effectiveness is rigorously proved. Several sufficient criteria are also obtained to clarify the effects of coupling terms for finite-time and fixed-time cluster synchronization. Especially, when the cluster number is one, the cluster synchronization becomes the complete synchronization problem; when the network has only one node, the coupling term between nodes will disappear, and the synchronization problem becomes the simplest master-slave case, which also includes the stability problem for nonlinear systems like neural networks. All these cases are also discussed. Finally, numerical simulations are presented to demonstrate the correctness of obtained theoretical results.

Atypical neural synchronization to speech envelope modulations in dyslexia.

PubMed

De Vos, Astrid; Vanvooren, Sophie; Vanderauwera, Jolijn; Ghesquière, Pol; Wouters, Jan

2017-01-01

A fundamental deficit in the synchronization of neural oscillations to temporal information in speech could underlie phonological processing problems in dyslexia. In this study, the hypothesis of a neural synchronization impairment is investigated more specifically as a function of different neural oscillatory bands and temporal information rates in speech. Auditory steady-state responses to 4, 10, 20 and 40Hz modulations were recorded in normal reading and dyslexic adolescents to measure neural synchronization of theta, alpha, beta and low-gamma oscillations to syllabic and phonemic rate information. In comparison to normal readers, dyslexic readers showed reduced non-synchronized theta activity, reduced synchronized alpha activity and enhanced synchronized beta activity. Positive correlations between alpha synchronization and phonological skills were found in normal readers, but were absent in dyslexic readers. In contrast, dyslexic readers exhibited positive correlations between beta synchronization and phonological skills. Together, these results suggest that auditory neural synchronization of alpha and beta oscillations is atypical in dyslexia, indicating deviant neural processing of both syllabic and phonemic rate information. Impaired synchronization of alpha oscillations in particular demonstrated to be the most prominent neural anomaly possibly hampering speech and phonological processing in dyslexic readers. Copyright © 2016 Elsevier Inc. All rights reserved.

Synchronicity from synchronized chaos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duane, Gregory

The synchronization of loosely-coupled chaotic oscillators, a phenomenon investigated intensively for the last two decades, may realize the philosophical concept of “synchronicity”—the commonplace notion that related events mysteriously occur at the same time. When extended to continuous media and/or large discrete arrays, and when general (non-identical) correspondences are considered between states, intermittent synchronous relationships indeed become ubiquitous. Meaningful synchronicity follows naturally if meaningful events are identified with coherent structures, defined by internal synchronization between remote degrees of freedom; a condition that has been posited as necessary for synchronizability with an external system. The important case of synchronization between mind andmore » matter is realized if mind is analogized to a computer model, synchronizing with a sporadically observed system, as in meteorological data assimilation. Evidence for the ubiquity of synchronization is reviewed along with recent proposals that: (1) synchronization of different models of the same objective process may be an expeditious route to improved computational modeling and may also describe the functioning of conscious brains; and (2) the nonlocality in quantum phenomena implied by Bell’s theorem may be explained in a variety of deterministic (hidden variable) interpretations if the quantum world resides on a generalized synchronization “manifold”.« less

State-dependent spike and local field synchronization between motor cortex and substantia nigra in hemiparkinsonian rats.

PubMed

Brazhnik, Elena; Cruz, Ana V; Avila, Irene; Wahba, Marian I; Novikov, Nikolay; Ilieva, Neda M; McCoy, Alex J; Gerber, Colin; Walters, Judith R

2012-06-06

Excessive beta frequency oscillatory and synchronized activity has been reported in the basal ganglia of parkinsonian patients and animal models of the disease. To gain insight into processes underlying this activity, this study explores relationships between oscillatory activity in motor cortex and basal ganglia output in behaving rats after dopamine cell lesion. During inattentive rest, 7 d after lesion, increases in motor cortex-substantia nigra pars reticulata (SNpr) coherence emerged in the 8-25 Hz range, with significant increases in local field potential (LFP) power in SNpr but not motor cortex. In contrast, during treadmill walking, marked increases in both motor cortex and SNpr LFP power, as well as coherence, emerged in the 25-40 Hz band with a peak frequency at 30-35 Hz. Spike-triggered waveform averages showed that 77% of SNpr neurons, 77% of putative cortical interneurons, and 44% of putative pyramidal neurons were significantly phase-locked to the increased cortical LFP activity in the 25-40 Hz range. Although the mean lag between cortical and SNpr LFPs fluctuated around zero, SNpr neurons phase-locked to cortical LFP oscillations fired, on average, 17 ms after synchronized spiking in motor cortex. High coherence between LFP oscillations in cortex and SNpr supports the view that cortical activity facilitates entrainment and synchronization of activity in basal ganglia after loss of dopamine. However, the dramatic increases in cortical power and relative timing of phase-locked spiking in these areas suggest that additional processes help shape the frequency-specific tuning of the basal ganglia-thalamocortical network during ongoing motor activity.

A revised classification and terminology for stacked and amalgamated turbidites in environments dominated by (hemi)pelagic sedimentation

NASA Astrophysics Data System (ADS)

Van Daele, Maarten; Meyer, Inka; Moernaut, Jasper; De Decker, Steven; Verschuren, Dirk; De Batist, Marc

2017-07-01

Stacked or amalgamated turbidites provide an opportunity to infer the synchronous triggering of multiple slope failures, which is a criterion often used to attribute these slope failures to earthquake shaking; and such turbidites are thus a proxy for reconstructing long-term earthquake recurrence. However, other processes, such as erosion, reflecting turbidity currents and seiching, may produce similar amalgamated/stacked deposits. Here we study two turbidites from Lake Challa, a crater lake on the lower slopes of Kilimanjaro (Kenya/Tanzania). The occurrence in Lake Challa of both single slope failures and basin-wide landslide events, all accompanied by distal turbidites, provides an excellent opportunity to assess the characteristics and significance of amalgamated/stacked turbidites in an enclosed lake basin with diatomaceous sediments, reflecting hemipelagic sedimentation in offshore areas. We also compare the characteristics of amalgamated/stacked turbidites in basins other than Lake Challa to discuss potential causes of different amalgamation patterns (stacked or multi-pulsed character). The low density and elongated shape of diatom frustules increases grain-to-grain interaction and thereby damps turbulence, resulting in faster bed aggradation and a stacked character of the amalgamated turbidites. Finally, as currently both synchronously and non-synchronously triggered turbidites are in literature referred to as ;stacked turbidite;, we propose a revised terminology that differentiates an ;amalgamated turbidite; from a ;turbidite stack;. In sedimentary environments that are dominated by (hemi)pelagic sedimentation, and where turbidity currents are anomalous events, an ;amalgamated turbidite; can often be shown to be the result of synchronous triggering, while a ;turbidite stack; must always result from a succession of discrete events.

Leader emergence through interpersonal neural synchronization

PubMed Central

Jiang, Jing; Chen, Chuansheng; Dai, Bohan; Shi, Guang; Ding, Guosheng; Liu, Li; Lu, Chunming

2015-01-01

The neural mechanism of leader emergence is not well understood. This study investigated (i) whether interpersonal neural synchronization (INS) plays an important role in leader emergence, and (ii) whether INS and leader emergence are associated with the frequency or the quality of communications. Eleven three-member groups were asked to perform a leaderless group discussion (LGD) task, and their brain activities were recorded via functional near infrared spectroscopy (fNIRS)-based hyperscanning. Video recordings of the discussions were coded for leadership and communication. Results showed that the INS for the leader–follower (LF) pairs was higher than that for the follower–follower (FF) pairs in the left temporo-parietal junction (TPJ), an area important for social mentalizing. Although communication frequency was higher for the LF pairs than for the FF pairs, the frequency of leader-initiated and follower-initiated communication did not differ significantly. Moreover, INS for the LF pairs was significantly higher during leader-initiated communication than during follower-initiated communications. In addition, INS for the LF pairs during leader-initiated communication was significantly correlated with the leaders’ communication skills and competence, but not their communication frequency. Finally, leadership could be successfully predicted based on INS as well as communication frequency early during the LGD (before half a minute into the task). In sum, this study found that leader emergence was characterized by high-level neural synchronization between the leader and followers and that the quality, rather than the frequency, of communications was associated with synchronization. These results suggest that leaders emerge because they are able to say the right things at the right time. PMID:25831535

Joint transfer of time and frequency signals and multi-point synchronization via fiber network

NASA Astrophysics Data System (ADS)

Nan, Cheng; Wei, Chen; Qin, Liu; Dan, Xu; Fei, Yang; You-Zhen, Gui; Hai-Wen, Cai

2016-01-01

A system of jointly transferring time signals with a rate of 1 pulse per second (PPS) and frequency signals of 10 MHz via a dense wavelength division multiplex-based (DWDM) fiber is demonstrated in this paper. The noises of the fiber links are suppressed and compensated for by a controlled fiber delay line. A method of calibrating and characterizing time is described. The 1PPS is synchronized by feed-forward calibrating the fiber delays precisely. The system is experimentally examined via a 110 km spooled fiber in laboratory. The frequency stabilities of the user end with compensation are 1.8×10-14 at 1 s and 2.0×10-17 at 104 s average time. The calculated uncertainty of time synchronization is 13.1 ps, whereas the direct measurement of the uncertainty is 12 ps. Next, the frequency and 1PPS are transferred via a metropolitan area optical fiber network from one central site to two remote sites with distances of 14 km and 110 km. The frequency stabilities of 14 km link reach 3.0×10-14 averaged in 1 s and 1.4×10-17 in 104 s respectively; and the stabilities of 110 km link are 8.3×10-14 and 1.7×10-17, respectively. The accuracies of synchronization are estimated to be 12.3 ps for the 14 km link and 13.1 ps for the 110 km link, respectively. Project supported by the National Natural Science Foundation of China (Grant No. 61405227).

Leader emergence through interpersonal neural synchronization.

PubMed

Jiang, Jing; Chen, Chuansheng; Dai, Bohan; Shi, Guang; Ding, Guosheng; Liu, Li; Lu, Chunming

2015-04-07

The neural mechanism of leader emergence is not well understood. This study investigated (i) whether interpersonal neural synchronization (INS) plays an important role in leader emergence, and (ii) whether INS and leader emergence are associated with the frequency or the quality of communications. Eleven three-member groups were asked to perform a leaderless group discussion (LGD) task, and their brain activities were recorded via functional near infrared spectroscopy (fNIRS)-based hyperscanning. Video recordings of the discussions were coded for leadership and communication. Results showed that the INS for the leader-follower (LF) pairs was higher than that for the follower-follower (FF) pairs in the left temporo-parietal junction (TPJ), an area important for social mentalizing. Although communication frequency was higher for the LF pairs than for the FF pairs, the frequency of leader-initiated and follower-initiated communication did not differ significantly. Moreover, INS for the LF pairs was significantly higher during leader-initiated communication than during follower-initiated communications. In addition, INS for the LF pairs during leader-initiated communication was significantly correlated with the leaders' communication skills and competence, but not their communication frequency. Finally, leadership could be successfully predicted based on INS as well as communication frequency early during the LGD (before half a minute into the task). In sum, this study found that leader emergence was characterized by high-level neural synchronization between the leader and followers and that the quality, rather than the frequency, of communications was associated with synchronization. These results suggest that leaders emerge because they are able to say the right things at the right time.

FTAP: a Linux-based program for tapping and music experiments.

PubMed

Finney, S A

2001-02-01

This paper describes FTAP, a flexible data collection system for tapping and music experiments. FTAP runs on standard PC hardware with the Linux operating system and can process input keystrokes and auditory output with reliable millisecond resolution. It uses standard MIDI devices for input and output and is particularly flexible in the area of auditory feedback manipulation. FTAP can run a wide variety of experiments, including synchronization/continuation tasks (Wing & Kristofferson, 1973), synchronization tasks combined with delayed auditory feedback (Aschersleben & Prinz, 1997), continuation tasks with isolated feedback perturbations (Wing, 1977), and complex alterations of feedback in music performance (Finney, 1997). Such experiments have often been implemented with custom hardware and software systems, but with FTAP they can be specified by a simple ASCII text parameter file. FTAP is available at no cost in source-code form.

EEG patterns in theta and gamma frequency range and their probable relation to human voluntary movement organization.

PubMed

Popivanov, D; Mineva, A; Krekule, I

1999-05-21

In experiments with EEG accompanying continuous slow goal-directed voluntary movements we found abrupt short-term transients (STs) of the coefficients of EEG time-varying autoregressive (TVAR) model. The onset of STs indicated (i) a positive EEG wave related to an increase of 3-7 Hz oscillations in time period before the movement start, (ii) synchronization of 35-40 Hz prior to movement start and during the movement when the target is nearly reached. Both these phenomena are expressed predominantly over supplementary motor area, premotor and parietal cortices. These patterns were detected after averaging of EEG segments synchronized to the abrupt changes of the TVAR coefficients computed in the time course of EEG single records. The results are discussed regarding the cognitive aspect of organization of goal-directed movements.

Synchronization of a Class of Switched Neural Networks with Time-Varying Delays via Nonlinear Feedback Control.

PubMed

Wang, Leimin; Shen, Yi; Zhang, Guodong

2016-10-01

This paper is concerned with the synchronization problem for a class of switched neural networks (SNNs) with time-varying delays. First, a new crucial lemma which includes and extends the classical exponential stability theorem is constructed. Then by using the lemma, new algebraic criteria of ψ -type synchronization (synchronization with general decay rate) for SNNs are established via the designed nonlinear feedback control. The ψ -type synchronization which is in a general framework is obtained by introducing a ψ -type function. It contains exponential synchronization, polynomial synchronization, and other synchronization as its special cases. The results of this paper are general, and they also complement and extend some previous results. Finally, numerical simulations are carried out to demonstrate the effectiveness of the obtained results.

Robust fixed-time synchronization of delayed Cohen-Grossberg neural networks.

PubMed

Wan, Ying; Cao, Jinde; Wen, Guanghui; Yu, Wenwu

2016-01-01

The fixed-time master-slave synchronization of Cohen-Grossberg neural networks with parameter uncertainties and time-varying delays is investigated. Compared with finite-time synchronization where the convergence time relies on the initial synchronization errors, the settling time of fixed-time synchronization can be adjusted to desired values regardless of initial conditions. Novel synchronization control strategy for the slave neural network is proposed. By utilizing the Filippov discontinuous theory and Lyapunov stability theory, some sufficient schemes are provided for selecting the control parameters to ensure synchronization with required convergence time and in the presence of parameter uncertainties. Corresponding criteria for tuning control inputs are also derived for the finite-time synchronization. Finally, two numerical examples are given to illustrate the validity of the theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

System and method for time synchronization in a wireless network

DOEpatents

Gonia, Patrick S.; Kolavennu, Soumitri N.; Mahasenan, Arun V.; Budampati, Ramakrishna S.

2010-03-30

A system includes multiple wireless nodes forming a cluster in a wireless network, where each wireless node is configured to communicate and exchange data wirelessly based on a clock. One of the wireless nodes is configured to operate as a cluster master. Each of the other wireless nodes is configured to (i) receive time synchronization information from a parent node, (ii) adjust its clock based on the received time synchronization information, and (iii) broadcast time synchronization information based on the time synchronization information received by that wireless node. The time synchronization information received by each of the other wireless nodes is based on time synchronization information provided by the cluster master so that the other wireless nodes substantially synchronize their clocks with the clock of the cluster master.

Synchronization enhancement of indirectly coupled oscillators via periodic modulation in an optomechanical system.

PubMed

Du, Lei; Fan, Chu-Hui; Zhang, Han-Xiao; Wu, Jin-Hui

2017-11-20

We study the synchronization behaviors of two indirectly coupled mechanical oscillators of different frequencies in a doublecavity optomechanical system. It is found that quantum synchronization is roughly vanishing though classical synchronization seems rather good when each cavity mode is driven by an external field in the absence of temporal modulations. By periodically modulating cavity detunings or driving amplitudes, however, it is possible to observe greatly enhanced quantum synchronization accompanied with nearly perfect classical synchronization. The level of quantum synchronization observed here is, in particular, much higher than that for two directly coupled mechanical oscillators. Note also that the modulation on cavity detunings is more appealing than that on driving amplitudes when the robustness of quantum synchronization is examined against the bath's mean temperature or the oscillators' frequency difference.

Analysis of remote synchronization in complex networks

NASA Astrophysics Data System (ADS)

Gambuzza, Lucia Valentina; Cardillo, Alessio; Fiasconaro, Alessandro; Fortuna, Luigi; Gómez-Gardeñes, Jesus; Frasca, Mattia

2013-12-01

A novel regime of synchronization, called remote synchronization, where the peripheral nodes form a phase synchronized cluster not including the hub, was recently observed in star motifs [Bergner et al., Phys. Rev. E 85, 026208 (2012)]. We show the existence of a more general dynamical state of remote synchronization in arbitrary networks of coupled oscillators. This state is characterized by the synchronization of pairs of nodes that are not directly connected via a physical link or any sequence of synchronized nodes. This phenomenon is almost negligible in networks of phase oscillators as its underlying mechanism is the modulation of the amplitude of those intermediary nodes between the remotely synchronized units. Our findings thus show the ubiquity and robustness of these states and bridge the gap from their recent observation in simple toy graphs to complex networks.

A synchronous game for binary constraint systems

NASA Astrophysics Data System (ADS)

Kim, Se-Jin; Paulsen, Vern; Schafhauser, Christopher

2018-03-01

Recently, Slofstra proved that the set of quantum correlations is not closed. We prove that the set of synchronous quantum correlations is not closed, which implies his result, by giving an example of a synchronous game that has a perfect quantum approximate strategy but no perfect quantum strategy. We also exhibit a graph for which the quantum independence number and the quantum approximate independence number are different. We prove new characterisations of synchronous quantum approximate correlations and synchronous quantum spatial correlations. We solve the synchronous approximation problem of Dykema and the second author, which yields a new equivalence of Connes' embedding problem in terms of synchronous correlations.

A new scheme of general hybrid projective complete dislocated synchronization

NASA Astrophysics Data System (ADS)

Chu, Yan-dong; Chang, Ying-Xiang; An, Xin-lei; Yu, Jian-Ning; Zhang, Jian-Gang

2011-03-01

Based on the Lyapunov stability theorem, a new type of chaos synchronization, general hybrid projective complete dislocated synchronization (GHPCDS), is proposed under the framework of drive-response systems. The difference between the GHPCDS and complete synchronization is that every state variable of drive system does not equal the corresponding state variable, but equal other ones of response system while evolving in time. The GHPCDS includes complete dislocated synchronization, dislocated anti-synchronization and projective dislocated synchronization as its special item. As examples, the Lorenz chaotic system, Rössler chaotic system, hyperchaotic Chen system and hyperchaotic Lü system are discussed. Numerical simulations are given to show the effectiveness of these methods.

Synchronization of motor unit firings: an epiphenomenon of firing rate characteristics not common inputs

PubMed Central

Kline, Joshua C.

2015-01-01

Synchronous motor unit firing instances have been attributed to anatomical inputs shared by motoneurons. Yet, there is a lack of empirical evidence confirming the notion that common inputs elicit synchronization under voluntary conditions. We tested this notion by measuring synchronization between motor unit action potential trains (MUAPTs) as their firing rates progressed within a contraction from a relatively low force level to a higher one. On average, the degree of synchronization decreased as the force increased. The common input notion provides no empirically supported explanation for the observed synchronization behavior. Therefore, we investigated a more probable explanation for synchronization. Our data set of 17,546 paired MUAPTs revealed that the degree of synchronization varies as a function of two characteristics of the motor unit firing rate: the similarity and the slope as a function of force. Both are measures of the excitation of the motoneurons. As the force generated by the muscle increases, the firing rate slope decreases, and the synchronization correspondingly decreases. Different muscles have motor units with different firing rate characteristics and display different amounts of synchronization. Although this association is not proof of causality, it consistently explains our observations and strongly suggests further investigation. So viewed, synchronization is likely an epiphenomenon, subject to countless unknown neural interactions. As such, synchronous firing instances may not be the product of a specific design and may not serve a specific physiological purpose. Our explanation for synchronization has the advantage of being supported by empirical evidence, whereas the common input does not. PMID:26490288

Synchronization of motor unit firings: an epiphenomenon of firing rate characteristics not common inputs.

PubMed

Kline, Joshua C; De Luca, Carlo J

2016-01-01

Synchronous motor unit firing instances have been attributed to anatomical inputs shared by motoneurons. Yet, there is a lack of empirical evidence confirming the notion that common inputs elicit synchronization under voluntary conditions. We tested this notion by measuring synchronization between motor unit action potential trains (MUAPTs) as their firing rates progressed within a contraction from a relatively low force level to a higher one. On average, the degree of synchronization decreased as the force increased. The common input notion provides no empirically supported explanation for the observed synchronization behavior. Therefore, we investigated a more probable explanation for synchronization. Our data set of 17,546 paired MUAPTs revealed that the degree of synchronization varies as a function of two characteristics of the motor unit firing rate: the similarity and the slope as a function of force. Both are measures of the excitation of the motoneurons. As the force generated by the muscle increases, the firing rate slope decreases, and the synchronization correspondingly decreases. Different muscles have motor units with different firing rate characteristics and display different amounts of synchronization. Although this association is not proof of causality, it consistently explains our observations and strongly suggests further investigation. So viewed, synchronization is likely an epiphenomenon, subject to countless unknown neural interactions. As such, synchronous firing instances may not be the product of a specific design and may not serve a specific physiological purpose. Our explanation for synchronization has the advantage of being supported by empirical evidence, whereas the common input does not. Copyright © 2016 the American Physiological Society.

Biospheric feedback effects in a synchronously coupled model of human and Earth systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornton, Peter E.; Calvin, Katherine; Jones, Andrew D.

Fossil fuel combustion and land-use change are the first and second largest contributors to industrial-era increases in atmospheric carbon dioxide concentration, which is itself the largest driver of present-day climate change1. Projections of fossil fuel consumption and land-use change are thus fundamental inputs for coupled Earth system models (ESM) used to estimate the physical and biological consequences of future climate system forcing2,3. While empirical datasets are available to inform historical analyses4,5, assessments of future climate change have relied on projections of energy and land use based on energy economic models, constrained using historical and present-day data and forced with assumptionsmore » about future policy, land-use patterns, and socio-economic development trajectories6. Here we show that the influence of biospheric change – the integrated effect of climatic, ecological, and geochemical processes – on land ecosystems has a significant impact on energy, agriculture, and land-use projections for the 21st century. Such feedbacks have been ignored in previous ESM studies of future climate. We find that synchronous exposure of land ecosystem productivity in the economic system to biospheric change as it develops in an ESM results in a 10% reduction of land area used for crop cultivation; increased managed forest area and land carbon; a 15-20% decrease in global crop price; and a 17% reduction in fossil fuel emissions for a low-mid range forcing scenario7. These simulation results demonstrate that biospheric change can significantly alter primary human system forcings to the climate system. This synchronous two-way coupling approach removes inconsistencies in description of climate change between human and biosphere components of the coupled model, mitigating a major source of uncertainty identified in assessments of future climate projections8-10.« less

When Long-Range Zero-Lag Synchronization is Feasible in Cortical Networks

PubMed Central

Viriyopase, Atthaphon; Bojak, Ingo; Zeitler, Magteld; Gielen, Stan

2012-01-01

Many studies have reported long-range synchronization of neuronal activity between brain areas, in particular in the beta and gamma bands with frequencies in the range of 14–30 and 40–80 Hz, respectively. Several studies have reported synchrony with zero phase lag, which is remarkable considering the synaptic and conduction delays inherent in the connections between distant brain areas. This result has led to many speculations about the possible functional role of zero-lag synchrony, such as for neuronal communication, attention, memory, and feature binding. However, recent studies using recordings of single-unit activity and local field potentials report that neuronal synchronization may occur with non-zero phase lags. This raises the questions whether zero-lag synchrony can occur in the brain and, if so, under which conditions. We used analytical methods and computer simulations to investigate which connectivity between neuronal populations allows or prohibits zero-lag synchrony. We did so for a model where two oscillators interact via a relay oscillator. Analytical results and computer simulations were obtained for both type I Mirollo–Strogatz neurons and type II Hodgkin–Huxley neurons. We have investigated the dynamics of the model for various types of synaptic coupling and importantly considered the potential impact of Spike-Timing Dependent Plasticity (STDP) and its learning window. We confirm previous results that zero-lag synchrony can be achieved in this configuration. This is much easier to achieve with Hodgkin–Huxley neurons, which have a biphasic phase response curve, than for type I neurons. STDP facilitates zero-lag synchrony as it adjusts the synaptic strengths such that zero-lag synchrony is feasible for a much larger range of parameters than without STDP. PMID:22866034

Pulvinar thalamic nucleus allows for asynchronous spike propagation through the cortex

PubMed Central

Cortes, Nelson; van Vreeswijk, Carl

2015-01-01

We create two multilayered feedforward networks composed of excitatory and inhibitory integrate-and-fire neurons in the balanced state to investigate the role of cortico-pulvino-cortical connections. The first network consists of ten feedforward levels where a Poisson spike train with varying firing rate is applied as an input in layer one. Although the balanced state partially avoids spike synchronization during the transmission, the average firing-rate in the last layer either decays or saturates depending on the feedforward pathway gain. The last layer activity is almost independent of the input even for a carefully chosen intermediate gain. Adding connections to the feedforward pathway by a nine areas Pulvinar structure improves the firing-rate propagation to become almost linear among layers. Incoming strong pulvinar spikes balance the low feedforward gain to have a unit input-output relation in the last layer. Pulvinar neurons evoke a bimodal activity depending on the magnitude input: synchronized spike bursts between 20 and 80 Hz and an asynchronous activity for very both low and high frequency inputs. In the first regime, spikes of last feedforward layer neurons are asynchronous with weak, low frequency, oscillations in the rate. Here, the uncorrelated incoming feedforward pathway washes out the synchronized thalamic bursts. In the second regime, spikes in the whole network are asynchronous. As the number of cortical layers increases, long-range pulvinar connections can link directly two or more cortical stages avoiding their either saturation or gradual activity falling. The Pulvinar acts as a shortcut that supplies the input-output firing-rate relationship of two separated cortical areas without changing the strength of connections in the feedforward pathway. PMID:26042026

User's manual for SYNC: A FORTRAN program for merging and time-synchronizing data

NASA Technical Reports Server (NTRS)

Maine, R. E.

1981-01-01

The FORTRAN 77 computer program SYNC for merging and time synchronizing data is described. The program SYNC reads one or more input files which contain either synchronous data frames or time-tagged data points, which can be compressed. The program decompresses and time synchronizes the data, correcting for any channel time skews. Interpolation and hold last value synchronization algorithms are available. The output from SYNC is a file of time synchronized data frames at any requested sample rate.

Frequency synchronization of a frequency-hopped MFSK communication system

NASA Technical Reports Server (NTRS)

Huth, G. K.; Polydoros, A.; Simon, M. K.

1981-01-01

This paper presents the performance of fine-frequency synchronization. The performance degradation due to imperfect frequency synchronization is found in terms of the effect on bit error probability as a function of full-band or partial-band noise jamming levels and of the number of frequency hops used in the estimator. The effect of imperfect fine-time synchronization is also included in the calculation of fine-frequency synchronization performance to obtain the overall performance degradation due to synchronization errors.

Position determination systems. [using orbital antenna scan of celestial bodies

NASA Technical Reports Server (NTRS)

Shores, P. W. (Inventor)

1976-01-01

A system for an orbital antenna, operated at a synchronous altitude, to scan an area of a celestial body is disclosed. The antenna means comprises modules which are operated by a steering signal in a repetitive function for providing a scanning beam over the area. The scanning covers the entire area in a pattern and the azimuth of the scanning beam is transmitted to a control station on the celestial body simultaneous with signals from an activated ground beacon on the celestial body. The azimuth of the control station relative to the antenna is known and the location of the ground beacon is readily determined from the azimuth determinations.

Influence of stochastic perturbations on the cluster explosive synchronization of second-order Kuramoto oscillators on networks.

PubMed

Cao, Liang; Tian, Changhai; Wang, Zhenhua; Zhang, Xiyun; Liu, Zonghua

2018-02-01

Explosive synchronization in networked second-order Kuramoto oscillators has been well studied recently and it is revealed that the synchronization process is featured by cluster explosive synchronization. However, little attention has been paid to the influence of noise or perturbation. We here study this problem and discuss the influences of noise and perturbation. For the former, we interestingly find that noise has significant influence on the cluster explosive synchronization of those nodes with smaller degrees, i.e., their synchronization will change from the first-order to second-order transition and the critical points for both the forward and backward synchronization depend on the strength of noise. Especially, when the strength of noise is in an optimal range, a synchronization of the nodes with smaller degrees will be induced in the region of coupling strength where they do not display synchronization in the absence of noise. For the latter, we find that the effect of perturbation is similar to that of noise when its duration W is small. However, the perturbation will induce a change from cluster explosive synchronization to explosive synchronization when W is large. Furthermore, a brief theory is provided to explain the influence of perturbations on the critical points.

Remote synchronization of amplitudes across an experimental ring of non-linear oscillators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Minati, Ludovico, E-mail: lminati@ieee.org, E-mail: ludovico.minati@unitn.it, E-mail: lminati@istituto-besta.it

In this paper, the emergence of remote synchronization in a ring of 32 unidirectionally coupled non-linear oscillators is reported. Each oscillator consists of 3 negative voltage gain stages connected in a loop to which two integrators are superimposed and receives input from its preceding neighbour via a “mixing” stage whose gains form the main system control parameters. Collective behaviour of the network is investigated numerically and experimentally, based on a custom-designed circuit board featuring 32 field-programmable analog arrays. A diverse set of synchronization patterns is observed depending on the control parameters. While phase synchronization ensues globally, albeit imperfectly, for certainmore » control parameter values, amplitudes delineate subsets of non-adjacent but preferentially synchronized nodes; this cannot be trivially explained by synchronization paths along sequences of structurally connected nodes and is therefore interpreted as representing a form of remote synchronization. Complex topology of functional synchronization thus emerges from underlying elementary structural connectivity. In addition to the Kuramoto order parameter and cross-correlation coefficient, other synchronization measures are considered, and preliminary findings suggest that generalized synchronization may identify functional relationships across nodes otherwise not visible. Further work elucidating the mechanism underlying this observation of remote synchronization is necessary, to support which experimental data and board design materials have been made freely downloadable.« less

Remote synchronization of amplitudes across an experimental ring of non-linear oscillators.

PubMed

Minati, Ludovico

2015-12-01

In this paper, the emergence of remote synchronization in a ring of 32 unidirectionally coupled non-linear oscillators is reported. Each oscillator consists of 3 negative voltage gain stages connected in a loop to which two integrators are superimposed and receives input from its preceding neighbour via a "mixing" stage whose gains form the main system control parameters. Collective behaviour of the network is investigated numerically and experimentally, based on a custom-designed circuit board featuring 32 field-programmable analog arrays. A diverse set of synchronization patterns is observed depending on the control parameters. While phase synchronization ensues globally, albeit imperfectly, for certain control parameter values, amplitudes delineate subsets of non-adjacent but preferentially synchronized nodes; this cannot be trivially explained by synchronization paths along sequences of structurally connected nodes and is therefore interpreted as representing a form of remote synchronization. Complex topology of functional synchronization thus emerges from underlying elementary structural connectivity. In addition to the Kuramoto order parameter and cross-correlation coefficient, other synchronization measures are considered, and preliminary findings suggest that generalized synchronization may identify functional relationships across nodes otherwise not visible. Further work elucidating the mechanism underlying this observation of remote synchronization is necessary, to support which experimental data and board design materials have been made freely downloadable.

Secure Heterogeneous Multicore Platform Through Diversity and Redundancy

DTIC Science & Technology

2012-03-31

implementation detects synchronization in this way. If a programmer uses custom synchronization primitives , our approach assumes that such primitives ... synchronization primitives . Primitives such as barriers and spinlocks explicitly enforce a pre- determined ordering among threads. Therefore, the outcome of...these synchronization operations are deterministic. In the discussion, we will refer to these primitives as ordering synchronization operations. On the

Synchronization of coupled large-scale Boolean networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Fangfei, E-mail: li-fangfei@163.com

2014-03-15

This paper investigates the complete synchronization and partial synchronization of two large-scale Boolean networks. First, the aggregation algorithm towards large-scale Boolean network is reviewed. Second, the aggregation algorithm is applied to study the complete synchronization and partial synchronization of large-scale Boolean networks. Finally, an illustrative example is presented to show the efficiency of the proposed results.

Synchronization of the DOE/NASA 100-kilowatt wind turbine generator with a large utility network

NASA Technical Reports Server (NTRS)

Gilbert, L. J.

1977-01-01

The DOE/NASA 100 kilowatt wind turbine generator system was synchronized with a large utility network. The system equipments and procedures associated with the synchronization process were described. Time history traces of typical synchronizations were presented indicating that power and current transients resulting from the synchronizing procedure are limited to acceptable magnitudes.

Time delay and long-range connection induced synchronization transitions in Newman-Watts small-world neuronal networks.

PubMed

Qian, Yu

2014-01-01

The synchronization transitions in Newman-Watts small-world neuronal networks (SWNNs) induced by time delay τ and long-range connection (LRC) probability P have been investigated by synchronization parameter and space-time plots. Four distinct parameter regions, that is, asynchronous region, transition region, synchronous region, and oscillatory region have been discovered at certain LRC probability P = 1.0 as time delay is increased. Interestingly, desynchronization is observed in oscillatory region. More importantly, we consider the spatiotemporal patterns obtained in delayed Newman-Watts SWNNs are the competition results between long-range drivings (LRDs) and neighboring interactions. In addition, for moderate time delay, the synchronization of neuronal network can be enhanced remarkably by increasing LRC probability. Furthermore, lag synchronization has been found between weak synchronization and complete synchronization as LRC probability P is a little less than 1.0. Finally, the two necessary conditions, moderate time delay and large numbers of LRCs, are exposed explicitly for synchronization in delayed Newman-Watts SWNNs.