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1

The use of interstation P wave arrival time differences to account for regional path variability  

Microsoft Academic Search

The difference between arrival times from one seismic event to a pair of receivers is largely insensitive to source location error when certain geometric conditions are met. Using catalog data from a Chinese regional network, we illustrate the use of arrival time differences to control data quality and to derive a two-dimensional map of Pn velocity and relative site terms.

W. S. Phillips; C. A. Rowe; L. K. Steck

2005-01-01

2

P-wave arrival times for the 1991 racha, Georgia earthquake sequence at stations of a test, sparse network  

SciTech Connect

The following arrival information is a supplement to Myers and Schultz (2000). Myers and Schultz (2000) demonstrate the improvement in sparse-network location that can be achieved by using travel-time corrections determined with a Bayesian Kriging algorithm (Schultz et al., 1998). Precise, benchmark locations are provided by a local aftershock study of the 1991 Racha, Georgia earthquake sequence in the Caucasus Mountains (Fuenzalida et al., 1997). A test network is used to relocate the aftershocks with and without travel-time corrections. The test network is meant to represent a typical International Monitoring System configuration, with 6 stations at regional to near teleseismic distances (less then 30{sup o} from the epicenter). The following arrival-time data help to facilitate the reproduction of Myers and Schultz (2000). The arrival picks were obtained from the International Seismic Center (ISC) (openly available) and a Lawrence Livermore National Laboratory (LLNL) analyst (Flori Ryan). Table 1 lists the arrivals in epic time (time since January 1, 1970). The author of the arrival pick is listed as either ''flori'' or ''-'', where ''-'' indicates ISC. Table 2 lists the hypocenter information determined in the local aftershock study of Fuenzalida et al. (1997), and Table 3 lists the station information for the Racha test network. Fields in all tables are described in the CSS3.O database schema.

Myers, S C; Schultz, C A; Ryall, F

2000-02-02

3

A Fast Sweeping Scheme for Calculating P Wave First-Arrival Travel Times in Transversely Isotropic Media with an Irregular Surface  

NASA Astrophysics Data System (ADS)

Seismic wave propagation shows anisotropic characteristics in many sedimentary rocks. Modern seismic exploration in mountainous areas makes it important to calculate P wave travel times in anisotropic media with irregular surfaces. The challenges in this context are mainly from two aspects. First is how to tackle the irregular surface in a Cartesian coordinate system, and the other lies in solving the anisotropic eikonal equation. Since for anisotropic media the ray (group) velocity direction is not the same as the direction of the travel-time gradient, the travel-time gradient no longer serves as an indicator of the group velocity direction in extrapolating the travel-time field. Recently, a topography-dependent eikonal equation formulated in a curvilinear coordinate system has been established, which is effective for calculating first-arrival travel times in an isotropic model with an irregular surface. Here, we extend the above equation from isotropy to transverse isotropy (TI) by formulating a topography-dependent eikonal equation in TI media in the curvilinear coordinate system, and then use a fast sweeping scheme to solve the topography-dependent anisotropic eikonal equation in the curvilinear coordinate system. Numerical experiments demonstrate the feasibility and accuracy of the scheme in calculating P wave travel times in TI models with an irregular surface.

Lan, Haiqiang; Chen, Jingyi; Zhang, Zhongjie

2014-03-01

4

Detection of anomalous features in an earthen dam using inversion of P-wave first-arrival times and surface-wave dispersion curves  

NASA Astrophysics Data System (ADS)

To locate anomalous features including seepage pathways through the Daeryong earth-fill dam, P and Rayleigh waves were recorded along a 250-m profile on the crest of the dam. Seismic energy was generated using a 5-kg sledgehammer and detected by 24 4.5-Hz vertical-axis geophones installed at 3-m intervals. P-wave and apparent S-wave velocities of the reservoir dam and underlying bedrock were then inverted from first-arrival traveltimes and dispersion curves of Rayleigh waves, respectively. Apparent dynamic Poisson's ratios as high as 0.46 were obtained at the base of the dam near its north-east end, where an outlet conduit occurs, and in the clay core body near the south-west end of the profile where the dam was repeatedly grouted to abate seepage before our survey. These anomalies of higher Poisson's ratios in the upper part of clay core were also associated with effusion of grout on the downstream slope of the dam during post-survey grouting to abate leakage. Combining P-wave traveltime tomography and inversion of Rayleigh wave velocities was very effective in detecting potential pathways for seepage and previous grouted zones in this earthen dam.

Kim, K. Y.; Jeon, K. M.; Hong, M. H.; Park, Young-gyu

2011-02-01

5

Whole mantle P-wave travel time tomography  

Microsoft Academic Search

A method of tomographic inversion to obtain three-dimensional velocity perturbations in the Earth's whole mantle has been developed, and applied to more than two million P-wave arrival time data reported by International Seismology Center (ISC). The model is parameterized with 32,768 blocks; the divisions in latitude, longitude, and radius are 32, 64, and 16, respectively. Horizontal cell size is 5.6°

Hiroshi Inoue; Yoshio Fukao; Kunio Tanabe; Yosihiko Ogata

1990-01-01

6

Upper mantle structure from teleseismic P wave arrivals in Washington and northern Oregon ( USA).  

USGS Publications Warehouse

Teleseismic P wave travel time residuals are used to detect lateral velocity heterogeneities in the upper mantle beneath Washington and N Oregon. The results of an inversion for 3-D velocity variations resolves an E dipping high-velocity zone that we interpret as the subducting Juan de Fuca plate. The plate is characterized by 3-8% higher velocities than those in the surrounding upper mantle. Inversion of the travel time data and ray trace modeling indicate that the plate extends to a depth of 200- 300 km. Based on changes in the geometry and velocity structure of the subducted Juan de Fuca plate 6 of about 123oW, we propose that the subducted slab is segmented into 3 sections beneath Washington and N Oregon. -from Authors

Michaelson, C. A.; Weaver, C. S.

1986-01-01

7

Confined Quantum Time of Arrivals  

NASA Astrophysics Data System (ADS)

We show that formulating the quantum time of arrival problem in a segment of the real line suggests rephrasing the quantum time of arrival problem to finding states that evolve to unitarily collapse at a given point at a definite time. For the spatially confined particle, we show that the problem admits a solution in the form of an eigenvalue problem of a compact and self-adjoint time of arrival operator derived by a quantization of the classical time of arrival, which is canonically conjugate with the Hamiltonian in a closed subspace of the Hilbert space.

Galapon, Eric A.; Caballar, Roland F.; Ricardo, T., Jr.

2004-10-01

8

Time domain waveform inversion of short-period p-waves for nuclear explosion source time functions. Technical report  

SciTech Connect

This research investigates the estimation of the source time parameters of underground nuclear explosions from the waveforms of short-period teleseismic P-waves. In the simplest consideration, and when the source yield is unconstrained, there are only three source parameters, two that describe the source time function and one for the delay time of the (p)P phase. There are, of course, indications that the (p)P arrival may not have the same amplitude or shape as the direct P arrival, presumably due to anelastic or nonlinear effects between the shot point and the surface. Thus, we will also consider the effect on the waveforms of a decreased (p)P amplitude. Another parameter which has a significant influence upon the observed waveforms is t (t = travel time/Q(av). Accordingly, the variations in the source parameter estimates due to a varying t will also be addressed.

Ruff, L.J.

1981-01-09

9

Travel times and station corrections for P waves at teleseismic distances  

Microsoft Academic Search

Approximately 3300 shallow focus earthquakes and 1000 seismic stations have been used in a study of P wave travel times and station residuals, including azimuthal effects. The events were selected from a catalog containing 160,000 earthquakes, and those having uniform distance and azimuthal coverage were systematically relocated and used to refine P wave travel times and station corrections. Station corrections

Adam M. Dziewonski; Don L. Anderson

1983-01-01

10

Nonnegative deconvolution for time of arrival estimation  

Microsoft Academic Search

The interaural time difference (ITD) of arrival is a primary cue for acoustic sound source localization. Traditional estimation techniques for ITD based upon cross-correlation are related to maximum-likelihood estimation of a simple generative model. We generalize the time difference estimation into a deconvolution problem with nonnegativity constraints. The resulting nonnegative least squares optimization can be efficiently solved using a novel

Yuanqing Lin; Daniel D. Lee; Lawrence K. Saul

2004-01-01

11

Time of Arrival Statistics in Cellular Environments  

Microsoft Academic Search

In this paper we study the temporal statistics of cellular mobile channel. We propose a scattering model that encloses scatterers in an elliptical scattering disc. We, further, employ this model to derive the probability density function (pdf) of time of arrival (ToA) of the multipath signal for picocell, microcell, and macrocell environments. For macrocell environment, we present generic closed-form formula

Mohammed T. Simsim; Noor M. Khan; Rodica Ramer; Predrag B. Rapajic

2006-01-01

12

Travel time delays and slowness vector deviations interpretation of multiply reflected P waves  

NASA Astrophysics Data System (ADS)

From a previous study we have shown that it was possible to observe multiply reflected P waves such as PPP, PPPP, PPPPP, PPPPPP. Despite the ray theoretical prediction that at a certain distance most of their compressional energy is converted to shear waves. A 1D P-velocity model for the pacific region was also proposed. The purpose of this new study is to make measurements of travel time delay and slowness vector deviation of these waves. We used about 400 events of magnitude Mw > 6.1 recorded from the dense network of US ARRAY, which allows us to make a very large number of travel time delays and slowness vector perturbation measurements of multiply reflected P waves. These measurements show that multiply reflected P wave are of great interests when studying the Upper mantle structure.

Foundotos, M.; Nolet, G.

2013-12-01

13

Time varying velocity structures in Earth's outer core: Constraints from exotic P-waves  

NASA Astrophysics Data System (ADS)

The outer core is one of the most dynamic divisions of our planet. However, despite undergoing vigorous convection, the outer core is not necessarily a uniform, homogeneous layer of the Earth. Accumulation of light element enriched iron at the top of the outer core, below the core-mantle boundary, may lead to the formation of a stably stratified layer, corresponding to the E' layer as defined by Bullen. The E' layer would have different properties to the rest of the outer core and may be a source of scattering. The lowermost outer core, the F layer, may also have different physical properties than the rest of the outer core, either due to the crystallisation of iron or the release of light elements as the inner core grows. Time varying structure in the Earth's core has been observed in some previous studies, particularly using earthquake doublets. The vigorous convection in the outer core may lead to small-scale lateral variations in its velocity structure over time, due to the movement of fluids and slurry near to the core-mantle and inner core boundaries. We investigate the velocity and attenuation structure of the upper 1500 km of the outer core using high frequency PmKP seismic phases. PmKP waves travel as P-waves throughout the Earth, bouncing m-1 times on the underside of the core-mantle boundary. By analysing the relative arrival times and amplitudes of the PmKP waves and other seismic phases, and comparing these to synthetic waveforms, it is possible to constrain the velocity and attenuation characteristics of the upper 1500 km of the outer core. We correct for known mantle structure and explore the effects of core-mantle boundary topography. To investigate the scattering characteristics of the uppermost outer core and the sharpness of any stratified layers we search for precursors to PmKP phases, which are elusive. P4KP-PcP differential travel times suggest that the uppermost 1300 km of the outer core is up to 0.4% slower than PREM. There is some evidence for time variations in the velocity structure of Earth's outer core from P4KP-PcP differential travel times, indicating that there may be transient features in the uppermost outer core.

Day, E. A.; Irving, J. C.; Deuss, A. F.; Cormier, V. F.

2011-12-01

14

Earthquake Travel Times: Customized Listing of Recent Arrival Times  

NSDL National Science Digital Library

The US Geological Survey Earthquake Hazards Program Web site contains the Earthquake Travel Times Customized Listing of Recent Arrival Times online calculator. The tool allows visitors to generate a listing of the times that phases from recent earthquakes arrived at their particular seismic station. After inputting the latitude and longitude of their location, the distance and magnitude of earthquakes to consider, types of phases, and other parameters, the user gets a simple but informative readout. The data includes the date and time of the earthquake, phase codes, travel time in seconds, arrival time, direction of travel, and more. Any seismologist or other researchers in similar fields should thoroughly appreciate this simple and helpful resource.

15

Fast method to calculate tsunami arrival times  

NASA Astrophysics Data System (ADS)

Exact arrival time of tsunami wave at coast or/and sensor is among important parameters for tsunami risk mitigation. Among the existing methods we mention: simulation of synthetic tsunami wave propagation from the given source; permanent data check at sensor system. Both approaches require extended CPU time or data transfer. Here we suggest alternative method based only on kinematics computation. The method is based on kinematic calculation of tsunami wave front line. Precise algorithms to move the points at the front line and, in case of necessity, to add new points, have been proposed. To start with, this method was successfully tested in an area with constant depth. Then the model bathymetry with parabolic and sloping bottom relief, in which cases exact analytical solutions are available, were studied. New algorithm was proved to be precise. The method gives possibility to compute not only tsunami travel times but also the wave rays. Tsunami amplitude can be estimated by wave-ray's divergence and depth change along wave route. The wave amplitude was estimated and then compared to results of numerical tests, obtained within the shallow-water numerical modeling of tsunami propagation using the MOST software package. For the model (slope-like) bathymetry the results differs by only a few percent. The advantage of proposed method is rapidness and low computer resources requirement.

Lavrentyev, Mikhail; Romanenko, Alexey; Marchuk, Andery; Vassilyev, George

2014-05-01

16

Bus Arrival Time Prediction Using Support Vector Machines  

Microsoft Academic Search

Effective prediction of bus arrival time is central to many advanced traveler information systems. This article presents support vector machines (SVM), a new neural network algorithm, to predict bus arrival time. The objective of this paper is to examine the feasibility and applicability of SVM in vehicle travel time forecasting area. Segment, the travel time of current segment, and the

Yu Bin; Yang Zhongzhen; Yao Baozhen

2006-01-01

17

Confined quantum time of arrival for the vanishing potential  

SciTech Connect

We give full account of our recent report in E. A. Galapon, R. Caballar, and R. Bahague, Phys. Rev. Lett. 93, 180406 (2004), where it is shown that formulating the free quantum time of arrival problem in a segment of the real line suggests rephrasing the quantum time of arrival problem to finding a complete set of states that evolve to unitarily arrive at a given point at a definite time. For a spatially confined particle, here it is shown explicitly that the problem admits a solution in the form of an eigenvalue problem of a class of compact and self-adjoint time of arrival operators derived by a quantization of the classical time of arrival. The eigenfunctions of these operators are numerically demonstrated to unitarily arrive at the origin at their respective eigenvalues.

Galapon, Eric A. [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines); Theoretical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Chemical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Caballar, Roland F.; Bahague, Ricardo [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines)

2005-12-15

18

Source Localization from Quantized Time of Arrival Measurements  

Microsoft Academic Search

In this paper, we consider the localization of a source from quantized measurements of time of arrivals (TOA) or time difference of arrivals (TDOA). Applications include, as particular examples, acoustic source localization from a network of microphones under communication constraints, and the localization of a base station using a geolocalized mobile station using tuning advance measurements. We use a maximum

N. Castaneda; Maurice Charbit; Eric Moulines

2006-01-01

19

Constraints on the evolution of East Asia's mantle from P-wave travel time tomography  

NASA Astrophysics Data System (ADS)

High resolution tomographic images of the mantle structure beneath East Asia have been obtained through inversion of travel time data from global and regional seismograph stations and regional (temporary) arrays. These data resolve three-dimensional (3-D) upper mantle heterogeneity in unprecedented detail. In the west, high velocity anomalies are dominant beneath the Himalayas and the western portion of the Tibetan plateau to 300 km depth, which we interpret as the image of the northeastward subducting Indian lithospheric mantle. In contrast, P-wave tomography does not provide evidence for underthrusting of the Indian lithosphere beneath much of central and eastern Tibet. Beneath East China, slabs subducting from the Japan and Izu-Bonin trenches are deflected in the mantle transition zone. These stagnant slabs likely influence upper mantle convection beneath East Asia and might be related to volcanism in Korea and northeast China (such as the Changbai volcanic area). Low wavespeed structures in the shallow mantle beneath the Red River fault region connect to deep, slow anomalies beneath the South China Foldbelt. Tomographic imaging also reveals high wavespeed continental roots of the Precambrian Ordos block and Sichuan Basin (to 250-300 km depth) and strong heterogeneity between the latter and the Burma ranges further to the west. Together these structures may mark a transition in tectonic regime from the continental collision control in the west to control by subduction of Pacific, Philippine Sea and Indonesia plates to the east and the southeast.

Li, C.; van der Hilst, R.; Sun, R.; Burchfiel, B.; Royden, L. H.

2007-12-01

20

Predicting the arrival times of solar particles  

NASA Technical Reports Server (NTRS)

A procedure has been developed to generate a computerized time-intensity profile of the solar proton intensity expected at the earth after the occurrence of a significant solar flare on the sun. This procedure is a combination of many pieces of independent research and theoretical results. Many of the concepts used were first reported by Smart and Shea (1979) and are summarized by Smart and Shea (1985). Extracts from the general procedure that relate to predicting the expected onset time and time of maximum at the earth after the occurrence of a solar flare are presented.

Smart, D. F.

1988-01-01

21

Mobile TV's Time to Shine Has Arrived  

NASA Astrophysics Data System (ADS)

MoFilm, the first mobile film festival, achieved some legitimacy when multiple Academy Award-winning actor Kevin Spacey hosted the show in 2009. Spacey commented: "[I]n some countries, this might be the first time they [people] ever see a movie. … They won't see it on that big screen; they'll see it on a small one."1 According to a 2007 Gartner report, sales of cell phones skyrocketed for the first time to more than 1 billion.2 In 2008, the number of worldwide subscribers topped 4 billion, covering 60% of the world population.3 There are more mobile phones than TVs (there are 1.4 billion TVs worldwide4). Spacey concluded: "The quality of work and the simple ability at storytelling, the thing that ignites someone and inspires them to tell a story, can really come from anywhere."5

Kitson, Fred

22

Time-of-arrival probabilities and quantum measurements  

SciTech Connect

In this paper we study the construction of probability densities for time of arrival in quantum mechanics. Our treatment is based upon the facts that (i) time appears in quantum theory as an external parameter to the system, and (ii) propositions about the time of arrival appear naturally when one considers histories. The definition of time-of-arrival probabilities is straightforward in stochastic processes. The difficulties that arise in quantum theory are due to the fact that the time parameter of the Schroedinger's equation does not naturally define a probability density at the continuum limit, but also because the procedure one follows is sensitive on the interpretation of the reduction procedure. We consider the issue in Copenhagen quantum mechanics and in history-based schemes like consistent histories. The benefit of the latter is that it allows a proper passage to the continuous limit--there are, however, problems related to the quantum Zeno effect and decoherence. We finally employ the histories-based description to construct Positive-Operator-Valued-Measures (POVMs) for the time-of-arrival, which are valid for a general Hamiltonian. These POVMs typically depend on the resolution of the measurement device; for a free particle, however, this dependence cancels in the physically relevant regime and the POVM coincides with that of Kijowski.

Anastopoulos, Charis; Savvidou, Ntina [Department of Physics, University of Patras, 26500 Patras (Greece); Theoretical Physics Group, Imperial College, SW7 2BZ, London (United Kingdom)

2006-12-15

23

A geometrical result regarding time-of-arrival lightning location  

NASA Technical Reports Server (NTRS)

One reason for investigating Lightning Detection And Ranging (LDAR) is to validate data from the Optical Transient Detector (OTD). A Time-Of-Arrival (TOA) procedure may be used with radio wave portions of lighting signatures. An antenna is in place at KSC.

Solakiewicz, Richard

1996-01-01

24

Geolocation by time difference of arrival using hyperbolic asymptotes  

Microsoft Academic Search

The paper proposes a new simplified algorithm to estimate the location of an emitter by utilizing time difference of arrival (TDOA) measurements. This is achieved by recasting the estimation problem in prolate spheroidal coordinates. Prolate spheroidal coordinates greatly simplify the TDOA equations, producing a set of linear equations in the far field limit. The set of linear equations corresponds to

Samuel P. Drake; K. Dogancay

2004-01-01

25

Time delay based failure-robust direction of arrival estimation  

Microsoft Academic Search

There is an increasing interest in autonomous and unattended sensory systems, including applications in smart meeting rooms and surveillance of large areas. In these systems, direction of arrival (DOA) estimation has an important role. Although several time delay based algorithms have been proposed, little attention has been given to hardware failures and malfunctions. These are, however, an important consideration when

T. W. Pirinen; J. Yli-Hietanen

2004-01-01

26

Improved Seismic Event Location and Prediction of P-wave Travel Times using the LLNL_G3D Global Earth Model  

NASA Astrophysics Data System (ADS)

LLNL-G3D is a global-scale model of P-wave velocity from the surface to the core that is designed to accurately predict seismic travel times at regional and teleseismic distances. The latest version of LLNL_G3D is based on ~2.7 million P and Pn arrivals that are re-processed using our Bayesloc global multi-event locator. Bayesloc is a formulation of the joint probability distribution across multiple-event location parameters, including hypocenters, travel time corrections, pick precision, and phase labels. Modeling the whole multiple-event system results in accurate locations and an internally consistent data set that is ideal for tomography. The Bayesloc data set is input into our recently developed inversion approach (called Progressive Multi-level Tessellation Inversion or PMTI), which operates at progressively finer resolution to image regional velocity trends and fine details where data allow. Travel time and location validation tests are based on a globally distributed set of 116 explosions with known locations and earthquakes with locations constrained by a local network. Validation events are not used in the tomographic inversion. The ak135 model is used as a baseline for travel time and location accuracy. Mean P-wave travel time prediction errors are reduced from 1.35 seconds to 0.8 seconds, a 40% reduction. Based on preliminary relocation tests, epicenter errors are reduced from an average of 11 km to 6 km when regional data dominate (a 45 % reduction) and from 10 km to 7 km when teleseismic data dominate (a 30% reduction). This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Myers, S.; Simmons, N.; Johannesson, G.; Matzel, E.

2012-04-01

27

The arrival time distribution of EAS at Taro  

NASA Astrophysics Data System (ADS)

The arrival time distribution of EAS has been observed since 1995 at Taro cosmicray laboratory (200m above sea level). The EAS arrays consist of 1m2 and 0.25m2 scintillation detectors, 0.25m2 fast timing counters and ultra fast Cherenkov detectors (UFC). 169 0.25m2 scintillation detectors are arranged in alattice configuration with a unit distance of 1.5m. UFC is placed at 20m from the center of lattice array. The arrival time distribution has been analyzed with distance from EAS core (r=10-60m). One of the results shows that the radius of corvature increases as shower size (Ne), near to the EAS core.

Maeda, T.; Kuramochi, H.; Ono, S.; Sakuyama, H.; Suzuki, N.

28

Arrival Time Distribution by the New Observation System at Taro  

NASA Astrophysics Data System (ADS)

The arrival time distribution of EAS has been observed by using Ultra Fast Cherenkov detector (UFC) and oscilloscope at Taro observatory since 1995 (sea level 200m). The EAS array is arranged 169 sets of 0.25m2 scintillation detectors in the shape of a lattice at intervals of 1.5m and about 40 scintillation detectors which consists of 1m2 and 0.25m2 is arranged in the peripheral part. Then, it consists of 8 fast timing detectors. The UFC detector is installed in the palce of about 20m from the trigger center. The observation system of a UFC detector was changed from the autumn of 2000. The outline of a new observation system and EAS arrival time distribution are reported.

Sakuyama, H.; Obara, Hitoshi; Kuramochi, Hiroshi; Ono, Shunichi; Origasa, Satoru; Mochida, Akinori; Sakuyama, Hiroshi; Suzuki, Noboru

2003-07-01

29

Quantum arrival and dwell times via idealized clocks  

SciTech Connect

A number of approaches to the problem of defining arrival- and dwell-time probabilities in quantum theory makes use of idealized models of clocks. An interesting question is the extent to which the probabilities obtained in this way are related to standard semiclassical results. In this paper, we explore this question using a reasonably general clock model, solved using path-integral methods. We find that, in the weak-coupling regime, where the energy of the clock is much less than the energy of the particle it is measuring, the probability for the clock pointer can be expressed in terms of the probability current in the case of arrival times, and the dwell-time operator in the case of dwell times, the expected semiclassical results. In the regime of strong system-clock coupling, we find that the arrival-time probability is proportional to the kinetic-energy density, consistent with an earlier model involving a complex potential. We argue that, properly normalized, this may be the generically expected result in this regime. We show that these conclusions are largely independent of the form of the clock Hamiltonian.

Yearsley, J. M.; Downs, D. A.; Halliwell, J. J.; Hashagen, A. K. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

2011-08-15

30

Probability distribution of arrival times in quantum mechanics  

NASA Astrophysics Data System (ADS)

In a previous paper [V. Delgado and J. G. Muga, Phys. Rev. A 56, 3425 (1997)] we introduced a self-adjoint operator T⁁(X) whose eigenstates can be used to define consistently a probability distribution of the time of arrival at a given spatial point. In the present work we show that the probability distribution previously proposed can be well understood on classical grounds in the sense that it is given by the expectation value of a certain positive-definite operator J⁁(+)(X), which is nothing but a straightforward quantum version of the modulus of the classical current. For quantum states highly localized in momentum space about a certain momentum p0?0, the expectation value of J⁁(+)(X) becomes indistinguishable from the quantum probability current. This fact may provide a justification for the common practice of using the latter quantity as a probability distribution of arrival times.

Delgado, V.

1998-02-01

31

Arrival Time Spectra of Heavy Particles in Hydrogen Discharge  

NASA Astrophysics Data System (ADS)

Arrival time spectrum of electrons and heavy particles in Townsend discharge at very high E/N is determined by using Monte Carlo technique. Three dimensional Monte Carlo codes are used for simulation of coupled kinetics of electrons, ions and fast neutrals. The electron collisions are represented by the anisotropic cross section set with available data for energy partitioning. Heavy particle collisions are represented by latest cross section set compiled by Phelps. Trajectories of H^ +, H2^+ and H3^+ ions, fast H and fast H2 are followed up to the electrodes where arrival time is recorded. Energy relaxation of the neutral particles is followed down to the energy limit of 5 eV. These results are used to obtain the integrated particle flux data that can be compared either to experimental emission integrated data or to data obtained by current integration. The results of simulation allow us separation of different contributions and tests of models of interactions.

Stojanovic, Vladimir; Nikitovic, Zeljka; Petrovic, Zoran

2008-10-01

32

Empirical estimation of the arrival time of ICME Shocks  

NASA Astrophysics Data System (ADS)

Empirical estimation of the arrival time of ICME Shocks Mosalam Shaltout1 ,M.Youssef 1and R.Mawad2 1 National Research Institute of Astronomy and Geophysics (NRIAG) ,Helwan -Cairo-Egypt Email: mosalamshaltout@hotmail.com 2 Faculty of Science-Monifiia University-Physics Department-Shiben Al-Koum -Monifiia-Egypt We are got the Data of the SSC events from Preliminary Reports of the ISGI (Institut de Physique du Globe, France) .Also we are selected the same CME interval 1996-2005 from SOHO/LASCO/C2.We have estimated the arrival time of ICME shocks during solar cycle 23rd (1996-2005), we take the Sudden storm commencement SSC as a indicator of the arrival of CMEs at the Earth's Magnetosphere (ICME).Under our model ,we selected 203 ICME shock-SSC associated events, we got an imperial relation between CME velocity and their travel time, from which we obtained high correlation between them, R=0.75.

Shaltout, Mosalam

33

Comment on ``Arrival time in quantum mechanics'' and ``Time of arrival in quantum mechanics''  

NASA Astrophysics Data System (ADS)

Contrary to claims contained in papers by Grot, Rovelli, and Tate [Phys. Rev. A 54, 4676 1996)] and Delgado and Muga [Phys. Rev. A 56, 3425 (1997)], the ``time operator,'' which I have constructed [Rep. Math. Phys. 6, 361 (1974)] in an axiomatic way, is a self-adjoint operator existing in a usual Hilbert space of (nonrelativistic or relativistic) quantum mechanics.

Kijowski, Jerzy

1999-01-01

34

Measurement-based approach to quantum arrival times  

SciTech Connect

For a quantum-mechanically spread-out particle we investigate a method for determining its arrival time at a specific location. The procedure is based on the emission of a first photon from a two-level system moving into a laser-illuminated region. The resulting temporal distribution is explicitly calculated for the one-dimensional case and compared with axiomatically proposed expressions. As a main result we show that by means of a deconvolution one obtains the well-known quantum-mechanical probability flux of the particle at the location as a limiting distribution.

Damborenea, J.A. [Fisika Teorikoaren Saila, Euskal Herriko Unibertsitatea, 644 Posta Kutxa, 48080 Bilbao (Spain); Departamento de Quimica-Fisica, Universidad del Pais Vasco, Apartado Postal 644, 48080 Bilbao (Spain); Egusquiza, I.L. [Fisika Teorikoaren Saila, Euskal Herriko Unibertsitatea, 644 Posta Kutxa, 48080 Bilbao (Spain); Hegerfeldt, G.C. [Institut fuer Theoretische Physik, Universitaet Goettingen, Bunsenstrasse 9, P-37073 Goettingen (Germany); Muga, J.G. [Departamento de Quimica-Fisica, Universidad del Pais Vasco, Apartado Postal 644, 48080 Bilbao (Spain)

2002-11-01

35

ConcepTest: P Wave Arrival  

NSDL National Science Digital Library

Examine the seismogram below that shows a 26-minute long record of the seismic waves from the 1906 San Francisco earthquake as it was received by a seismograph station in Germany, over 14,000 km away. Which letter ...

36

Arrival-Time Detection and Ultrasonic Flow-Meter Applications  

NASA Astrophysics Data System (ADS)

The Danfoss problem on ultrasonic flow measurement has been separated into three parts each handled by a subgroup of the authors listed above. The first subgroup deals with a presentation of modelling equations describing the physics of ultrasonic flow meters employing reciprocal ultrasonic transducer systems. The mathematical model presented allows the electrical output signal to be determined corresponding to any time-dependent electrical input signal. The transducers modelled consist of a piezoceramic material layer and a passive acoustic matching layer. The second subgroup analyzes the possibility of coding the input signal so as to simplify arrival-time detection by re.nding the coded input sequence in the received signal. The narrow-band nature of the transducers makes this problem non-trivial but suggestions for improvement are proposed. The analysis given is based on traditional autoand cross-correlation techniques. The third subgroup attempts to improve existing correlation methods in determining arrival-time detection of signals. A mathematical formulation of the problem is given and the application to a set of real signals provided by Danfoss A/S is performed with good results.

Willatzen, Morten; Søndergaard, Peter; Latino, Carl; Voss, Frands; Lervad Andersen, Niels; Brokate, Martin; Bounaim, Aicha

2006-11-01

37

Walk - Run Activity: An S and P Wave Travel Time Simulation  

NSDL National Science Digital Library

In this activity, the process of finding the epicenter of an earthquake with a travel time graph is simulated. During the course of this activity students will model how earthquake waves travel through the Earth at different speeds, construct and utilize a graph to characterize the relationship between distance and time of travel of seismic waves (a travel time-curve), and use the constructed time-travel graphs to locate the epicenter of a simulated earthquake by triangulation. The site contains detailed instructions and all of the charts and graphs required. Sample data is also included.

Braile, Larry; Brtaile, Sheryl

38

Upper mantle anisotropy beneath Australia and Tahiti from P wave polarization: Implications for real-time earthquake location  

Microsoft Academic Search

We report measurements of long-period P wave polarization (Ppol) in Australia and Tahiti made by combining modeling of the polarization deviation and harmonic analysis. The analysis of the deviation of the horizontal polarization of the P wave as a function of event back azimuth may be used to obtain information about (1) sensor misorientation, (2) dipping discontinuities, (3) seismic anisotropy,

Fabrice R. Fontaine; Guilhem Barruol; Brian L. N. Kennett; Goetz H. R. Bokelmann; Dominique Reymond

2009-01-01

39

Bolus arrival time and cerebral blood flow responses to hypercarbia.  

PubMed

The purpose of this study was to evaluate how cerebral blood flow and bolus arrival time (BAT) measures derived from arterial spin labeling (ASL) MRI data change for different hypercarbic gas stimuli. Pseudocontinuous ASL (pCASL) was applied (3.0T; spatial resolution=4 × 4 × 7?mm(3); repetition time/echo time (TR/TE)=3,600/11?ms) sequentially in healthy volunteers (n=12; age=30±4 years) for separate experiments in which (i) normocarbic normoxia (i.e., room air), hypercarbic normoxia (i.e., 5% CO2/21% O2/74% N2), and hypercarbic hyperoxia (i.e., carbogen: 5% CO2/95% O2) gas was administered (12?L/minute). Cerebral blood flow and BAT changes were quantified using models that account for macrovascular signal and partial volume effects in all gray matter and regionally in cerebellar, temporal, occipital, frontal, and parietal lobes. Regional reductions in BAT of 4.6% to 7.7% and 3.3% to 6.6% were found in response to hypercarbic normoxia and hypercarbic hyperoxia, respectively. Cerebral blood flow increased by 8.2% to 27.8% and 3.5% to 19.8% for hypercarbic normoxia and hypercarbic hyperoxia, respectively. These findings indicate that changes in BAT values may bias functional ASL data and thus should be considered when choosing appropriate experimental parameters in calibrated functional magnetic resonance imaging or ASL cerebrovascular reactivity experiments that use hypercarbic gas stimuli. PMID:24780904

Donahue, Manus J; Faraco, Carlos C; Strother, Megan K; Chappell, Michael A; Rane, Swati; Dethrage, Lindsey M; Hendrikse, Jeroen; Siero, Jeroen C W

2014-07-01

40

Lightning Geo-location via Combined use of Time of Arrival, Arrival Azimuth, and VLF Dispersion Measurements of Radio Atmospherics  

NASA Astrophysics Data System (ADS)

Every lightning strike generates a strong electromagnetic pulse with a high spectral content at very low frequencies (3-30 kHz). Those strikes with a large vertical discharge component launch a Very Low Frequency (VLF) wave that efficiently propagates through the earth-ionosphere waveguide. The horizontal component of the magnetic field from this VLF radio impulse can be recorded using two orthogonally oriented magnetic loop antennas. The geographic location of the lightning strike can then be determined by comparing arrival time differences from several such recording sites. The location accuracy of this technique depends linearly on the accuracy of the time of arrival estimation of the received waveform. Due to the dispersive nature of the earth- ionosphere waveguide, arrival time determination must take into consideration the propagation distance and path from the lightning strike to the receiver. This paper discusses new techniques for determination of the time of arrival of radio pulses generated by lightning strikes, with an emphasis on the use of the dispersive nature of the propagation path.

Said, R. K.; Inan, U.

2006-12-01

41

Effects of lateral velocity heterogeneity under the Nevada Test Site on short-period P wave amplitudes and travel times  

NASA Astrophysics Data System (ADS)

Short-period teleseismic P waves from the Nevada Test Site (NTS) show systematic variations in amplitudes and travel times, with low amplitudes corresponding to fast travel times, suggesting elastic focussing-defocussing effects. Also, the azimuthal amplitude and travel time patterns for events at the Pahute Mesa subsite are systematically different from those at the Yucca Flat subsite, indicating the presence of a near-source component in both the amplitude and travel-time variations. This component is isolated by removing the mean station pattern for all of NTS from the observations. A very-near-source component in the Pahute Mesa observations is also isolated by removing subsite station means from the measurements, whereas the Yucca Flat observations exhibited no coherent very-near-source component. These anomalies are back-projected through laterally homogeneous structure to form thin lens models at various depths. Travel-time delays are predicted from the amplitude variations using the equation for wavefront curvature. The long-wavelength components of the predicted and observed time delays correlate well, at depths of 25 km for the very-near-source component under Pahute Mesa and 160 km for the regional component under NTS. The time delay surfaces predicted by the amplitudes at these depths are mapped into warped velocity discontinuities suitable for the calculation of synthetic seismograms using the Kirchhoff-Helmholtz integral formulation. Both the intersite (near-source) and intrasite (very-near-source) differences in amplitudes are qualitatively predicted very well, although the range of variation is somewhat underpredicted. This deficiency is likely due to the destructive interference of anomalies inherent in back-projection to a single layer.

Lynnes, Christopher S.; Lay, Thorne

1990-03-01

42

Semi-coherent time of arrival estimation using regression.  

PubMed

Time of arrival (ToA) estimation is essential for many types of remote sensing applications including radar, sonar, and underground exploration. The standard method for ToA estimation employs a matched filter for computing the maximum likelihood estimator (MLE) for ToA. The accuracy of the MLE decreases rapidly whenever the amount of noise in a received signal rises above a certain threshold. This well-known threshold effect is unavoidable in several important applications due to various limitations on the power and the spectrum of a narrowband source pulse. A measurement performed in the presence of the threshold effect employs a receiver which operates in the semi-coherent state. Therefore, the conventional methods assuming a coherent state receiver should be adapted to the semi-coherent case. In this paper, a biosonar-inspired method for the semi-coherent ToA estimation is described. The method abandons the exploration of an echo signal by a single matched filter in favor of the analysis by multiple phase-shifted unmatched filters. Each phase-shifted unmatched filter gives rise to a biased ToA estimator. The described method uses regression for combining these estimators into a single unbiased ToA estimator that outperform the MLE in the presence of the threshold effect. PMID:22894206

Apartsin, Alexander; Cooper, Leon N; Intrator, Nathan

2012-08-01

43

Observations of teleseismic P wave coda for underground explosions  

Microsoft Academic Search

The earlyP wave coda (5–15 sec after the first arrival) of underground explosions at the Nevada Test Site is studied in the time domain using 2082 teleseismic short-period recordings, with the intent of identifying near-source contributions to the signals in the frequency range 0.2–2.0 Hz. Smaller magnitude events tend to have relatively high coda levels in the 0.4–0.8 Hz frequency

Christopher S. Lynnes; Thorne Lay

1988-01-01

44

S-P wave travel time residuals and lateral inhomogeneity in the mantle beneath Tibet and the Himalaya  

NASA Technical Reports Server (NTRS)

S-P wave travel time residuals were measured in earthquakes in Tibet and the Himalaya in order to study lateral inhomogeneities in the earth's mantle. Average S-P residuals, measured with respect to Jeffrey-Bullen (J-B) tables for 11 earthquakes in the Himalaya are less than +1 second. Average J-B S-P from 10 of 11 earthquakes in Tibet, however, are greater than +1 second even when corrected for local crustal thickness. The largest values, ranging between 2.5 and 4.9 seconds are for five events in central and northern Tibet, and they imply that the average velocities in the crust and upper mantle in this part of Tibet are 4 to 10 percent lower than those beneath the Himalaya. On the basis of the data, it is concluded that it is unlikely that a shield structure lies beneath north central Tibet unless the S-P residuals are due to structural variations occurring deeper than 250 km.

Molnar, P.; Chen, W.-P.

1984-01-01

45

Calibration of sonobuoy compass via arrival time inversion  

Microsoft Academic Search

Onboard magnetic compasses allow sonobuoys to measure their orientation and form beams along true headings. Compass failure means true array heading is unknown and the buoy's beams cannot be used for target localization and tracking. We describe a method for recovering buoy orientation by inverting the pattern of signal arrivals at the individual hydrophones, and present results using data recorded

K. J. Delaney; J. M. Alsup; P. Sullivan

2003-01-01

46

A Fast-Time Simulation Tool for Analysis of Airport Arrival Traffic  

NASA Technical Reports Server (NTRS)

The basic objective of arrival sequencing in air traffic control automation is to match traffic demand and airport capacity while minimizing delays. The performance of an automated arrival scheduling system, such as the Traffic Management Advisor developed by NASA for the FAA, can be studied by a fast-time simulation that does not involve running expensive and time-consuming real-time simulations. The fast-time simulation models runway configurations, the characteristics of arrival traffic, deviations from predicted arrival times, as well as the arrival sequencing and scheduling algorithm. This report reviews the development of the fast-time simulation method used originally by NASA in the design of the sequencing and scheduling algorithm for the Traffic Management Advisor. The utility of this method of simulation is demonstrated by examining the effect on delays of altering arrival schedules at a hub airport.

Erzberger, Heinz; Meyn, Larry A.; Neuman, Frank

2004-01-01

47

A COMPARISON OF COLLAPSING AND PRECISE ARRIVAL-TIME MAPPING OF MICROSEISMICITY  

SciTech Connect

In this paper they compare the improvements in microseismic location images obtained using precise arrival times with that obtained by the collapsing technique. They first collapse the initial locations for a hydraulic-fracture data set from the Carthage Cotton Valley gas field, they then use the precise-arrival-time locations as measure for the effectiveness of the collapsing. Finally, they examine the changes when applying collapsing to the precise-arrival-time locations.

RUTLEDGE, JAMES T. [Los Alamos National Laboratory; JONES, ROB H. [Los Alamos National Laboratory

2007-01-05

48

P wave tomography of the mantle under the Alpine-Mediterranean area  

Microsoft Academic Search

We study the upper mantle P wave velocity structure below the Euro-Mediterranean area, down to 1000 km depth, by seismic travel time tomography. We invert summary residuals constructed with both regional and teleseismic first arrival data reported by the International Seismological Centre (ISC) (1964-1995), introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct

Claudia Piromallo; Andrea Morelli

2003-01-01

49

P wave tomography of the mantle under the Alpine-Mediterranean area  

Microsoft Academic Search

We study the upper mantle P wave velocity structure below the Euro-Mediterranean area, down to 1000 km depth, by seismic travel time tomography. We invert summary residuals constructed with both regional and teleseismic first arrival data reported by the International Seismological Centre (ISC) (1964–1995), introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct

Claudia Piromallo; Andrea Morelli

2003-01-01

50

Transition from discrete to continuous time-of-arrival distribution for a quantum particle  

SciTech Connect

We show that the Kijowski distribution for time of arrivals in the entire real line is the limiting distribution of the time-of-arrival distribution in a confining box as its length increases to infinity. The dynamics of the confined time-of-arrival eigenfunctions is also numerically investigated and demonstrated that the eigenfunctions evolve to have point supports at the arrival point at their respective eigenvalues in the limit of arbitrarily large confining lengths, giving insight into the ideal physical content of the Kijowsky distribution.

Galapon, Eric A. [Theoretical Physics Group, National Institute of Physics, University of the Philippines, Diliman, Quezon City, 1101 (Philippines); Departamento de Quimica Fisica, UPV-EHU, Apdo. 644, 48080 Bilbao (Spain); Theoretical Physics, The University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain); Delgado, F.; Muga, J. Gonzalo [Departamento de Quimica Fisica, UPV-EHU, Apdo. 644, 48080 Bilbao (Spain); Egusquiza, Inigo [Theoretical Physics, University of the Basque Country, Apdo. 644, 48080 Bilbao (Spain)

2005-10-15

51

Timing the Random and Anomalous Arrival of Particles in a Geiger Counter with GPS Devices  

ERIC Educational Resources Information Center

The properties of the arrival time distribution of particles in a detector have been studied by the use of a small Geiger counter, with a GPS device to tag the event time. The experiment is intended to check the basic properties of the random arrival time distribution between successive events and to simulate the investigations carried out by…

Blanco, F.; La Rocca, P.; Riggi, F.; Riggi, S.

2008-01-01

52

Study of cycle time caused by lot arrival distribution in a semiconductor manufacturing line  

Microsoft Academic Search

Recently, competitive semiconductor manufacturing has been indispensable to satisfy market requirements for cycle time, throughput, and cost. Specially, in a large size fab like a mega-fab, precise cycle time control of individual lots is necessary. We studied the mechanism of cycle time caused by lot arrival distribution in a large size fab and found that the lot arrival is approximated

T. Inoue; Y. Ishii; K. Igarashi; T. Muneta; K. Imaoka

2005-01-01

53

Least squares arrival time estimators for photons detected using a photomultiplier tube  

Microsoft Academic Search

The optimal arrival time estimators for single and multiple photons arriving at the surface of a photomultiplier tube (PMT) are developed. The optimal timing estimator considered is a weighted nonlinear least squares estimate of the detection time for a high-gain PMT with Gaussian statistics. The least squares estimator is constructed using the mean and covariance function of the photomultiplier output

Nicholas Petrick; N. H. Clinthorne; W. L. Rogers

1992-01-01

54

Least squares arrival time estimators for photons detected using a photomultiplier tube  

Microsoft Academic Search

The optimal arrival time estimators for single and multiple photons arriving at the surface of a photomultiplier tube (PMT) are developed. The optimal timing estimator considered is a weighted and nonlinear least squares estimate of the detection time for a high-gain PMT with Gaussian statistics. The least squares estimator is constructed using the mean and covariance function of the photomultiplier

N. Petrick; N. H. Clinthorne; W. L. Rogers

1991-01-01

55

How long to wait?: predicting bus arrival time with mobile phone based participatory sensing  

Microsoft Academic Search

The bus arrival time is primary information to most city transport travelers. Excessively long waiting time at bus stops often discourages the travelers and makes them reluctant to take buses. In this paper, we present a bus arrival time prediction system based on bus passengers' participatory sensing. With commodity mobile phones, the bus passengers' surrounding environmental context is effectively collected

Pengfei Zhou; Yuanqing Zheng; Mo Li

2012-01-01

56

Least squares arrival time estimators for photons detected using a photomultiplier tube  

SciTech Connect

In many applications employing photodetectors, the determination of the arrival time of individual photons at the surface of the detector can be used to localize the photon source. For the case where the photon intensity is extremely low, the most common type of detector used is the photomultiplier tube. The optimal arrival time estimators for single and multiple photons arriving at the surface of a photomultiplier tube are developed in this paper. The optimal timing estimator considered is a weighted non-linear least squares estimate of the detection time for a high gain PMT with gaussian statistics. The lease squares estimator is constructed using the mean and covariance function of the photomultiplier output for different arrival times. The RMS error for the leant squares arrival time estimator was calculated and compared with the performance of other common timing estimators, including the first photoelectron timing estimators, using a Burle/RCE 8850 PMT.

Petrick, N.; Hero, A.O. III; Clinthorne, N.H.; Rogers, W.L. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Electrical Engineering and Computer Science)

1992-08-01

57

Passive source localization employing intersecting spherical surfaces from time-of-arrival differences  

Microsoft Academic Search

Problems associated with the use of intersecting hyperboloids for passive source localization from time-of-arrival difference signals are discussed. A closed-form solution for source location is presented given time-of-arrival difference measurements when the distance from the source to any arbitrary reference is unknown.

H. C. SCHAU; A. Z. ROBINSON

1987-01-01

58

Measurement of X-ray photon energy and arrival time using a silicon drift detector  

NASA Astrophysics Data System (ADS)

Detecting the X-ray emission of pulsars and obtaining the photons' time of arrival are the foundational steps in autonomous navigation via X-ray pulsar measurement. The precision of a pulse's time of arrival is mainly determined by the precision of photon arrival time measurement. In this work, a silicon drift detector is used to measure photon energy and arrival time. The measurement system consists of a signal detector, a processing unit, a signal acquisition unit and a data receiving unit. This system acquires the energy resolution and arrival time information of photons. In particular, background noise with different energies disturbs pulse profile forming, the system can also achieve a high signal-to-noise ratio profile. Ground test results show that this system can be applied in autonomous navigation based on X-ray pulsar measurement.

Liu, Li; Yu, Hai; Zheng, Wei

2014-03-01

59

The effect of the descending lithosphere beneath the Tonga island arc on P-wave travel-time residuals at the Warramunga Seismic Array  

NASA Astrophysics Data System (ADS)

P-wave travel-time residuals at the Warramunga Seismic Array (WRA) in the Northern Territory, Australia, have been studied from 49 earthquakes with epicenters south of 19°S in the Fiji-Tonga region. Focal depths are between 42 and 679 km as determined from pP-P. Using the Jeffreys-Bullen and the Herrin travel-time tables the epicentral parameters have been redetermined by considering only "normal" seismic stations in the location procedure. These are those stations where P-wave travel times are probably not affected by lateral heterogeneities caused by the lithosphere descending beneath the Tonga trench. Epicenters of deep earthquakes below 300 km have been relocated by using stations at ? > 25° only. Epicenters from shallower-depth earthquakes have been recalculated without using stations between 35 < ? < 75° epicentral distance. In both cases focal depths were determined from pP-P times. The resulting pattern of P-residuals at WRA does not show any significant change with depth below 350 km. The residuals become more negative for shallower earthquakes above about 250 km. P-waves to WRA are advanced by approximately 2 s compared with those from deep earthquakes. The results do not essentially differ for the two different travel-time tables used. The observations can be interpreted by P-wave velocities that are higher in the sinking slab down to 350-400 km by 5±2% than in both the Jeffreys-Bullen and Herrin models. Without considering possible elevations of phase boundaries this estimate yields a temperature contrast of 1000±450°C between slab and normal mantle material in this depth range.

Bock, Günter

1981-06-01

60

Mobile information systems providing estimated time of arrival for public transport users  

Microsoft Academic Search

Walking out of the house on cold and wet winter morning to catch the bus knowing with confidence that arrival is imminent would be a dream for many users of public transport. With one look at the mobile phone not only it is possible to see the exact time of arrival at a user's stop but also the next departure

Omer Rashid; Paul Coulton; Reuben Edwards; Andrew Fisher; Robert Thompson

2005-01-01

61

Perturbation analysis of queueing systems with a time-varying arrival rate  

NASA Technical Reports Server (NTRS)

The authors consider an M/G/1 queuing with a time-varying arrival rate. The objective is to obtain infinitesimal perturbation analysis (IPA) gradient estimates for various performance measures of interest with respect to certain system parameters. In particular, the authors consider the mean system time over n arrivals and an arrival rate alternating between two values. By choosing a convenient sample path representation of this system, they derive an unbiased IPA gradient estimator which, however, is not consistent, and investigate the nature of this problem.

Cassandras, Christos G.; Pan, Jie

1991-01-01

62

Sex Differences in Accuracy and Precision When Judging Time to Arrival: Data from Two Internet Studies  

Microsoft Academic Search

We report two Internet studies that investigated sex differences in the accuracy and precision of judging time to arrival.\\u000a We used accuracy to mean the ability to match the actual time to arrival and precision to mean the consistency with which each participant made their judgments. Our task was presented as a computer game in which\\u000a a toy UFO moved

Geoff SandersKamila Sinclair; Kamila Sinclair

63

Arrival-time fluctuations of coherent reflections from surface gravity water waves.  

PubMed

Arrival time fluctuations of coherent reflections from surface gravity waves are examined. A two-dimensional ray model with an evolving rough sea surface is used to explain the mechanism and formation of the deterministic striation patterns due to the surface reflection. Arrival time predictions from the ray model match qualitatively well with the measurements from bidirectional acoustic transmissions in a water depth of 100?m. PMID:24815293

Badiey, Mohsen; Eickmeier, Justin; Song, Aijun

2014-05-01

64

Airborne method to minimize fuel with fixed time-of-arrival constraints  

NASA Technical Reports Server (NTRS)

A method for generating a minimum-fuel, fixed-range, fixed-time-of-arrival flight path in an on-board flight management system computer for commercial aircraft is described. It is shown that up to 6% of the fuel otherwise used can be saved by means of this capability, despite time-of-arrival delays of up to 30 min, by a medium-range, tri-jet transport aircraft.

Sorensen, J. A.; Waters, M. H.

1981-01-01

65

Velocity structure of the crust and upper mantle at the northern group of Kamchatka volcanoes (Based on the travel time of P-waves from volcanic earthquakes)  

NASA Astrophysics Data System (ADS)

The results of a calculation of the P-wave ( V P ) velocity fields are presented on the basis of the method of the reversible wave and the TAU parameter characterizing the V P / V S ratio of seismic waves from the local volcanic earthquakes that occurred at the northern group of Kamchatka volcanoes in 2005-2007. The 3D velocity cross sections were constructed along the SW-NE-trending volcanic group from the Ploskii Tolbachik volcano in the southwest up to the Shiveluch volcano in the northeast. The change of velocity field in time and depth is found. The problems of relating these changes to volcanic activity is reviewed.

Slavina, L. B.; Pivovarova, N. B.; Senyukov, S. L.

2012-12-01

66

Tsunami Arrival Time in Sri Lanka for the 2004 Sumatra-Andaman Earthquake  

NASA Astrophysics Data System (ADS)

The Indian tsunami caused by the Sumatra-Andaman Islands earthquake of 26 December 2004 severely affected Sri Lanka, approximately 1500 km far west from the tsunami source. The post tsunami surveys in Sri Lanka by a combined team of Japanese and Sri Lankan researchers were carried out twice. The first one is from 29 December 2004 to 04 January 2005, covering the East, SE and South Sri Lanka including the cities of Moratuwa, Beruwala, Bentota, Seenigama, Hikkaduwa, Galle, Thalpe, Matara, Tangalla and Hambantota, and the second one is from 10 to 18 March 2005 covering the NE, East, SE and South Sri Lanka including Trincomalee, Batticaloa, Arugam Bay, Yala National Park and Kirinda. The main objective of the surveys is to obtain eyewitness information, in particular tsunami arrival time. Many other survey teams have completed with respect to the tsunami height measurements, therefore the survey of tsunami arrival times is needed in order to understand the tsunami quantitatively. In fact, no tide gauge station in Sri Lanka exists except for Colombo, hence eyewitness accounts by the local people are possibly basic information about the tsunami. After compiling two surveys, we could obtain some data of tsunami arrival times in addition to tsunami heights at the whole coast in Sri Lanka. The first wave arrived at 08:30 to 08:45 at the east coast, followed by the largest wave at 08:50 to 09:15. At most area at the east coast, the second wave was the largest. At the south and the west coasts, on the other hand, the first wave arrived at 09:15 to 09:45, and the largest wave arrived at 09:50 to 10:30, that were the second or the third wave. Thus eyewitness accounts indicated that there were one or two waves before the arrival of the largest tsunami. In some locations it was reported that the water receded several hundred meters before the largest wave arrived.

Matsumoto, H.; Inoue, S.; Wijeyewickrema, A.; Sekiguchi, T.; Miura, H.; Gunaratna, P.; Madurapperuma, M.; Iwasaki, S.

2005-12-01

67

Does winter region affect spring arrival time and body mass of king eiders in northern Alaska?  

USGS Publications Warehouse

Events during the non-breeding season may affect the body condition of migratory birds and influence performance during the following breeding season. Migratory birds nesting in the Arctic often rely on endogenous nutrients for reproductive efforts, and are thus potentially subject to such carry-over effects. We tested whether king eider (Somateria spectabilis) arrival time and body mass upon arrival at breeding grounds in northern Alaska were affected by their choice of a winter region in the Bering Sea. We captured birds shortly after arrival on breeding grounds in early June 2002-2006 at two sites in northern Alaska and determined the region in which individuals wintered using satellite telemetry or stable isotope ratios of head feathers. We used generalized linear models to assess whether winter region explained variation in arrival body mass among individuals by accounting for sex, site, annual variation, and the date a bird was captured. We found no support for our hypothesis that either arrival time or arrival body mass of king eiders differed among winter regions. We conclude that wintering in different regions in the Bering Sea is unlikely to have reproductive consequences for king eiders in our study areas. ?? US Government 2009.

Oppel, S.; Powell, A. N.

2009-01-01

68

Multi source- multi receiver processing for arrival time optimization of microseismic borehole array data  

NASA Astrophysics Data System (ADS)

Together with a realistic velocity model and a well-designed seismic monitoring system, the quality of arrival time measurements is one of the most important factors to limit the uncertainty in the earthquake location problem. The accuracy of time picks is generally increased by exloiting the waveform similarity. This allows to calculate more precise differential arrival times which replace or improve the original arrival time picks. Typically, the waveform data are processed either event-based or receiver-based. Here, we propose to combine the receiver- oriented and the event- oriented approaches to optimize simultaneously arrival time picks for micro seismic events recorded by multi-level borehole arrays. The method extends existing concepts by cross-linking waveforms of different events in a multiplet recorded by closely spaced receivers, and the increased interconnectivity of waveforms also increases the consistency of the arrival time data. We apply the method to a hydraulic fracturing experiment, where micro seismic data were recorded by two inclined borehole arrays consisting of 30 receivers. It is shown that the picking accuracy is significantly improved compared to the original picks and also compared to the adjusted picks obtained from single receiver based processing. We also compare the improved event relocations with the original locations.

Kummerow, Joern

2013-04-01

69

Tomographic imaging of P wave velocity structure beneath the region around Beijing  

NASA Astrophysics Data System (ADS)

The three-dimension crustal and upper mantle structures in the region around Beijing were studied by seismic tomography. We used the P wave arrival times from local and teleseismic events. These events were recorded by 250 stations of the North China Seismic Array and 108 stations of the Beijing Telemetry Seismic Network. 118 869 P wave arrivals from 10 285 local events and 12 189 P wave arrivals from 107 teleseismic events were used in the inversion. We obtained the 3-D P wave velocity structure of the crust and upper mantle with the horizontal resolution of 0.3° in the studied region. The tomographic imaging shows the remarkably heterogeneous velocity variation. The velocity anomalies are in well agreement with the geological structure in the shallow crust. The different relationships between seismic activities and velocity anomalies may imply the different seismogenic structure and mechanism. Beneath the Moho under Taihangshan mountain and Yanshan mountain, we found the high velocity anomalies deep to 120 km and 200 km, respectively. The deep high velocity zone may be explained by the existence of the mountain root under Yanshan mountain. The high velocity anomalies in the upper mantle of North China basin may be the relics of the de-rooting from the former craton mantle lithosphere.

Ding, Zhifeng; Zhou, Xiaofeng; Wu, Yan; Li, Guiyin; Zhang, Hong

2009-08-01

70

Multi-Mode Lamb Wave Arrival Time Extraction for Improved Tomographic Reconstruction  

SciTech Connect

An ultrasonic signal processing technique is applied to multi-mode arrival time estimation from Lamb waveforms. The basic tool is a simplified time-scale projection called a dynamic wavelet fingerprint (DWFP) which enables direct observation of the variation of features of interest in non-stationary ultrasonic signals. The DWFP technique was used to automatically detect and evaluate each candidate through-transmitted Lamb mode. The area of the dynamic wavelet fingerprint was then used as a feature to distinguish false modes caused by noise and other interference from the true modes of interest. The set of estimated arrival times were then used as inputs for tomographic reconstruction. The Lamb wave tomography images generated with these estimated arrival times were able to indicate different defects in aluminum plates.

Hinders, Mark K.; Hou Jidong; Leonard, Kevin R. [College of William and Mary in Virginia, Applied Science Dept., Williamsburg, VA 23187 (United States)

2005-04-09

71

Continuous measurement of the arrival times of x-ray photon sequence  

SciTech Connect

In order to record x-ray pulse profile for x-ray pulsar-based navigation and timing, this paper presents a continuous, high-precision method for measuring arrival times of photon sequence with a common starting point. In this method, a high stability atomic clock is counted to measure the coarse time of arrival photon. A high resolution time-to-digital converter is used to measure the fine time of arrival photon. The coarse times and the fine times are recorded continuously and then transferred to computer memory by way of memory switch. The pulse profile is obtained by a special data processing method. A special circuit was developed and a low-level x-ray pulse profile measurement experiment system was setup. The arrival times of x-ray photon sequence can be consecutively recorded with a time resolution of 500 ps and the profile of x-ray pulse was constructed. The data also can be used for analysis by many other methods, such as statistical distribution of photon events per time interval, statistical distribution of time interval between two photon events, photon counting histogram, autocorrelation and higher order autocorrelation.

Yan Qiurong; Sheng Lizhi [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences 710119, Xi'an (China); Graduate University of Chinese Academy of Sciences, Beijing 100049 (China); Zhao Baosheng; Liu Yong'an [State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences 710119, Xi'an (China)

2011-05-15

72

Time-of-arrival-based retransmission scheduling for unslotted random access channels  

NASA Astrophysics Data System (ADS)

Time-of-arrival-based retransmission scheduling algorithms for unslotted ALOHA-type random access channels with high propagation delay are introduced and analyzed in this paper. The techniques described are motivated by the fact that collision bursts on asynchronous channels can be analyzed to create a partial time-of-arrival based ordering between the conflicting packets. Packets successfully ordered by collision burst analysis are then retransmitted in a locally synchronous, scheduled manner, thus eliminating potential further conflict between a large fraction of retransmitted messages. Collision resolution algorithms appropriate for channels with continuous signal detection, signal and collision detection, or signal and modified collision detection are described and evaluated in terms of throughput using a simple Poisson traffic model. The maximum throughput is shown to be 0.41, 0.47 and 0.509 for the three cases, thus demonstrating that the proposed time-of-arrival algorithms are competitive with the best slotted collision resolution algorithms.

Raychaudhuri, D.

1992-06-01

73

Accurate UWB indoor localization system utilizing time difference of arrival approach  

Microsoft Academic Search

An accurate ultra wideband (UWB) localization approach has been developed based on time difference of arrival (TDOA). This method provides sub-cm accuracy, which is excellent for indoor utilization when compared with frequency modulated continuous wave (FMCW) systems. The system is also in compliance with FCC UWB regulations and achieves accurate ranging measurements. The utilized time domain measurements suppress multipath signals

C. Zhang; M. Kuhn; B. Merkl; A. E. Fathy; M. Mahfouz

2006-01-01

74

Time of arrival estimation for range-based localization in UWB sensor networks  

Microsoft Academic Search

Accurate Localization has gained significant interest within sensor networks recently and positioning systems based on Ultra-Wideband (UWB) technology have been considered, because the UWB signals have a very good accuracy due to the high time resolution (large bandwidth). Time of Arrival (TOA) estimation of the first path is usually used for range-based localization in realistic environments within UWB sensor networks,

Guowei Shen; Rudolf Zetik; Honghui Yan; Ole Hirsch; Reiner S. Thomä

2010-01-01

75

A discrete-time queueing model of the shared buffer ATM switch with bursty arrivals  

Microsoft Academic Search

We model the shared buffer ATM switch as a discrete-time queueing system. The arrival process to each port of the ATM switch is assumed to be bursty and it is modelled by an interrupted Bernoulli process. The discrete-time queueing system is analyzed approximately. It is first decomposed into subsystems, and then each subsystem is analyzed separately. The results from the

S. Hong; H. G. Perros; H. Yamashita

1993-01-01

76

An ultrafast quantum random number generator with provably bounded output bias based on photon arrival time measurements  

NASA Astrophysics Data System (ADS)

We report the implementation of a quantum random number generator based on photon arrival times. Due to fast and high resolution timing we are able to generate the highest bitrate of any current generator based on photon arrival times. Bias in the raw data due to the exponential distribution of the arrival times is removed by postprocessing which is directly integrated in the field programmable logic of the timing electronics.

Wahl, Michael; Leifgen, Matthias; Berlin, Michael; Röhlicke, Tino; Rahn, Hans-Jürgen; Benson, Oliver

2011-04-01

77

New P-wave Images of the Core Mantle Boundary Region from a Bayesian Inversion of PKP, PcP, and P4KP Differential Travel Times  

NASA Astrophysics Data System (ADS)

The core-mantle boundary is the most dramatic discontinuity within the Earth. The existence of both chemical and thermal heterogeneities on a variety of scales in the D'' region has been invoked to explain seismological observations and the Earth's dynamics. Understanding these heterogeneities is important in the context of whole mantle dynamics. Moreover, we need to be able to clearly see through the core-mantle boundary to properly understand the Earth's core. For example, in order to investigate anisotropy in the inner core, it is important to quantify the contribution to seismic travel times from the Earth's mantle. Furthermore, it is impossible to reconstruct the topography of the Earth's core without a full understanding of mantle heterogeneities. Currently, P-wave velocity maps of the lowermost mantle are rare in comparison to S-wave maps, yet both are needed to properly understand the physical and chemical state of the D" region. Here we map P-wave velocity structure of the lowermost mantle from a dataset of hand-picked PKPab-df, PKPbc-df, PcP-P, and P4KP-PcP differential travel times. We use data from sources of magnitude 5.6 or greater to compile a collection of more than 1750 PKPab-df, 1050 PKPbc-df, 1500 PcP-P, and 360 P4KP-PcP travel times. The PcP-P raypath geometry helps resolve source-receiver ambiguities associated with the use of PKP waves. The inclusion of P4KP-PcP data greatly improves the D'' coverage and further reduces unwanted mapping effects in the inversion. In addition, we focus on covering gaps in spatial sampling of the lowermost mantle from PKPab-df and PcP-P of previous studies. By using differential travel times, the biases associated with event mislocation and lateral heterogeneity in the crust are minimized. Travel time residuals are individually and simultaneously inverted for a map of P-wave velocity heterogeneities using a transdimensional approach. The model is composed of Voronoi P-wave velocity cells of variable shapes and number. In this sense, the approach lets us consider the issue of model parameterization as part of the inversion process. The problem is tackled within a Bayesian framework and explicit regularization of model parameters is not required. The advantage of this type of inversion is that both the number of model parameters and the data noise are treated as unknowns in the problem. A final solution model results from the averaging of an ensemble of models, which in turn also yields uncertainty estimates. We compare our results with previous structural models and discuss newly obtained images of the lowermost mantle in the context of mantle and core dynamics.

Young, M. K.; Tkalcic, H.; Bodin, T.; Tanaka, S.; Rawlinson, N.

2011-12-01

78

Evidence for P wave velocity discontinuities at depths greater than 650 km in the mantle  

NASA Astrophysics Data System (ADS)

The arrival times of seismic P waves recorded at long lines of portable seismographs deployed on the shield region of central Australia show evidence of breaks in the travel-time curve at epicentral distances near 30, 39 and 43°. These breaks are additional to those at about 20 and 24° (associated with the 400- and 650-km discontinuities) and imply that the P wave velocity structure of the mantle does not increase smoothly in the depth range 650-1100 km, but rather consists of regions of nearly constant velocity separated by small but significant velocity increases at depths of approximately 770, 980 and 1080 km. These conclusions are in agreement with those previously inferred from first and later arrivals at the Warramunga Seismic Array.

Muirhead, K. J.; Hales, A. L.

1980-12-01

79

Real-time Upstream Monitoring System: Using ACE Data to Predict the Arrival of Interplanetary Shocks  

NASA Astrophysics Data System (ADS)

We have developed an algorithm to predict Earth arrival times for interplanetary (IP) shock events originating at the Sun. Our predictions are generated from real-time data collected by the Electron, Proton, and Alpha Monitor (EPAM) instrument on NASA's Advanced Composition Explorer (ACE) spacecraft. The high intensities of energetic ions that occur prior to and during an IP shock pose a radiation hazard to astronauts as well as to electronics in Earth orbit. The potential to predict such events is based on characteristic signatures in the Energetic Storm Particle (ESP) event ion intensities which are often associated with IP shocks. We have previously reported on the development and implementation of an algorithm to forecast the arrival of ESP events. Historical ion data from ACE/EPAM was used to train an artificial neural network which uses the signature of an approaching event to predict the time remaining until the shock arrives. Tests on the trained network have been encouraging, with an average error of 9.4 hours for predictions made 24 hours in advance, and an reduced average error of 4.9 hours when the shock is 12 hours away. The prediction engine has been integrated into a web-based system that uses real-time ACE/EPAM data provided by the NOAA Space Environment Center (http://sd-www.jhuapl.edu/UPOS/RISP/ index.html.) This system continually processes the latest ACE data, reports whether or not there is an impending shock, and predicts the time remaining until the shock arrival. Our predictions are updated every five minutes and provide significant lead-time, thereby supplying critical information that can be used by mission planners, satellite operations controllers, and scientists. We have continued to refine the prediction capabilities of this system; in addition to forecasting arrival times for shocks, we now provide confidence estimates for those predictions.

Donegan, M. M.; Wagstaff, K. L.; Ho, G. C.; Vandegriff, J.

2003-12-01

80

Real-time Upstream Monitoring System: Predicting interplanetary shock arrivals using energetic particle data from ACE  

NASA Astrophysics Data System (ADS)

We have created a system for predicting the arrival times at Earth of interplanetary (IP) shocks that originate at the Sun. Our prediction algorithm uses the real-time data stream from the Electron, Proton, and Alpha Monitor (EPAM) instrument on NASA's Advanced Composition Explorer (ACE) spacecraft. Most IP shocks are accompanied by locally accelerated energetic storm particle (ESP) events; signatures of ESP events can be used to predict the arrival of IP shocks. We have previously reported on the development and implementation of an algorithm to forecast the arrival of IP shocks. This prediction capability is combined with a web-based system that uses real-time ACE/EPAM data provided by the NOAA Space Environment Center (http://sd-www.jhuapl.edu/UPOS/RISP/index.html.) The most recent ACE data is continually processed and when an event is approaching, predictions of shock arrival time are updated every five minutes. Tests on the algorithm show an average error of ~9 hours for predictions made 24 hours before the shock arrival and ~5 hours when the shock is 12 hours away. This can provide significant lead-time and deliver critical information to mission planners, satellite operations controllers, and scientists. As of February 4, 2004, the ACE real-time stream has been switched to include data from another detector on EPAM. We are now processing the new real-time data stream and have made improvements to our neural network based on this data. In this paper, we report prediction results from this new network.

Donegan, M. M.; Vandegriff, J.; Ho, G. C.; Wagstaff, K. L.

2004-05-01

81

Electric Fields that “Arrive” before the Time Derivative of the Magnetic Field prior to Major Earthquakes  

Microsoft Academic Search

The low frequency electric signals (emitted from the focal area when the stress reaches a critical value) that precede major earthquakes, are recorded at distances ? 100 km being accompanied by magnetic field variations. The electric field ''arrives'' 1 to 2 s before the time derivative of the horizontal magnetic field. An explanation, which is still awaiting, should consider, beyond

P. A. Varotsos; N. V. Sarlis; E. S. Skordas

2003-01-01

82

Time of Arrival Data Fusion Method for Two-Dimensional Ultrawideband Breast Cancer Detection  

Microsoft Academic Search

A new microwave imaging method is given for breast tumor detection using an ultrawideband (UWB) imaging system. By combining the time of arrival (TOA) measurements from different sensors, the presence and location of small malignant lesions can be identified. At each sensor, the generalized sequence CLEAN (GS-CLEAN) algorithm is proposed to resolve the impulse response (IR) components into bins smaller

Yifan Chen; Erry Gunawan; Kay Soon Low; Shih-Chang Wang; Cheong Boon Soh; Lin Lin Thi

2007-01-01

83

Performance of time of arrival estimation based on signal eigen vectors  

Microsoft Academic Search

Multiple signal identification and classification (MUSIC) is a well known approach to time of arrival estimation of band-limited signals received through multi-path channels. MUSIC uses the eigen vectors of the correlation matrix for the received data that are associated with noise components. We compare the performance of MUSIC to an algorithm that is based on the eigen vectors associated with

Leonid Krasny; Havish Koorapaty

2000-01-01

84

New P-wave Velocity Images of the Lowermost Mantle from a Bayesian Inversion of PKP, PcP, and P4KP Differential Travel Times  

NASA Astrophysics Data System (ADS)

Determining the scale-length, magnitude, and distribution of chemical and thermal heterogeneities in the lowermost mantle is crucial to understanding whole mantle dynamics, and yet it remains a much debated and ongoing challenge in geophysics. Common shortcomings of current seismically-derived lowermost mantle models are often the result of a lack of access to and scrutiny in performing travel time measurements from waveform data, consequently incomplete raypath coverage, arbitrary model parameterization, inaccurate uncertainty estimates, and an inadequate definition of the misfit function in the optimization framework. In response, we present a new approach to global tomography where apart from improving the existing ray path coverage using only high quality cross-correlated waveform, the problem is addressed within a Bayesian framework and explicit regularization of model parameters is not required. Our results show that velocity heterogeneities exist on a variety of scales, with anomalies between 600 and 2900 km in lateral extent dominating the lowermost mantle heterogeneity pattern. This provides an important link between the very short-scale imaging achieved through scattering experiments and the long wave-length maps resulting from more traditional tomographic approaches. We also show that the power of heterogeneity in the lowermost mantle has an rms P-wave velocity variation of 0.88%, which is significantly larger than previous global-scale estimates, is fully justified by the data. Comparison of our P-wave velocity model with high-resolution S-wave velocity models refutes a purely thermal origin of mantle heterogeneity. The pattern of correlation between our model and S-wave models, combined with the characteristic scale-length and amplitude of heterogeneity revealed by this study, will help to significantly refine allowable models of thermo-chemical convection in the lowermost mantle. We obtain high resolution images of the lowermost mantle P-wave velocity structure using a hand-picked data set of PKPab-df, PKPbc-df, PcP-P, and P4KP-PcP differential traveltimes. By using differential travel times, the biases associated with event mislocation and lateral heterogeneity in the lithosphere are minimized. The inclusion of new PcP-P and P4KP-PcP data greatly improves the D'' coverage and further reduces unwanted mapping effects in the inversion. In addition, we focus on covering gaps in spatial sampling of the lowermost mantle from PKPab-df and PcP-P of previous studies. We use a probabilistic, Bayesian inversion scheme to invert for lowermost mantle structure and obtain an accurate representation of the complexity and amplitude of the P-wave velocity heterogeneity that is complete with uncertainty estimates. The advantage of such an inversion method is that the data variance along with the number, size, and distribution of spatial model parameters are treated as unknowns in the problem.

Young, M.; Tkalcic, H.; Bodin, T.; Sambridge, M.; Tanaka, S.; Rawlinson, N.

2012-12-01

85

Determination of arrival times for acoustic emission source location in composites  

SciTech Connect

The determination of the arrival time of an AE event has been studied using simulated acoustic emission (AE) signals on a Kevlar/epoxy composite. Transient recorder records were used to study the AE waveforms as well as the background electronic noise. Parameters studied include the bandpass and the relative position of the sensor with respect to the source position. The rise of the AE signal out of the background electronic noise was studied in detail by measuring the amplitude of each ''half-cycle'' of the analog signal both before the arrival of the AE event and for the first part of the AE signal. A relatively large amplitude difference was observed between the amplitude of the first half-cycle of the AE event and the peak amplitude of the AE event. Implications of the results obtained in these experiments are discussed relative to the commercial AE instrumentation approach of using penetration of the threshold to determine the arrival time of an AE event. In particular, it is shown that accurate source location in the composite depends on having a significantly large amplitude difference between the threshold and the peak amplitude for each channel in the AE source location array. Finally, an alternative approach is examined for potential use to determine the arrival time of an AE event.

Hamstad, M.A.

1986-03-26

86

Feasibility of water seepage monitoring in concrete with embedded smart aggregates by P-wave travel time measurement  

NASA Astrophysics Data System (ADS)

Water seepage in concrete threatens the safety of marine constructions and reduces the durability of concrete structures. This note presents a smart aggregate-based monitoring method to monitor the travel time evolution of a harmonic stress wave during the water infiltrating process in concrete structures. An experimental investigation, in which two plain concrete columns were examined under different water infiltration cases, verified the validity of the proposed monitoring method. The test results show that the travel time of the harmonic stress wave is sensitive to the development of water seepage in concrete and decreases with increasing water seepage depth. The proposed active monitoring method provides an innovative approach to monitor water seepage in concrete structures.

Zou, Dujian; Liu, Tiejun; Huang, Yongchao; Zhang, Fuyao; Du, Chengcheng; Li, Bo

2014-06-01

87

Monitoring molecular interactions using photon arrival-time interval distribution analysis  

DOEpatents

A method for analyzing/monitoring the properties of species that are labeled with fluorophores. A detector is used to detect photons emitted from species that are labeled with one or more fluorophores and located in a confocal detection volume. The arrival time of each of the photons is determined. The interval of time between various photon pairs is then determined to provide photon pair intervals. The number of photons that have arrival times within the photon pair intervals is also determined. The photon pair intervals are then used in combination with the corresponding counts of intervening photons to analyze properties and interactions of the molecules including brightness, concentration, coincidence and transit time. The method can be used for analyzing single photon streams and multiple photon streams.

Laurence, Ted A. (Livermore, CA); Weiss, Shimon (Los Angels, CA)

2009-10-06

88

High resolution time of arrival estimation for a cooperative sensor system  

NASA Astrophysics Data System (ADS)

Distance resolution of cooperative sensors is limited by the signal bandwidth. For the transmission mainly lower frequency bands are used which are more narrowband than classical radar frequencies. To compensate this resolution problem the combination of a pseudo-noise coded pulse compression system with superresolution time of arrival estimation is proposed. Coded pulsecompression allows secure and fast distance measurement in multi-user scenarios which can easily be adapted for data transmission purposes (Morhart and Biebl, 2009). Due to the lack of available signal bandwidth the measurement accuracy degrades especially in multipath scenarios. Superresolution time of arrival algorithms can improve this behaviour by estimating the channel impulse response out of a band-limited channel view. For the given test system the implementation of a MUSIC algorithm permitted a two times better distance resolution as the standard pulse compression.

Morhart, C.; Biebl, E. M.

2010-09-01

89

A Comparison of Center/TRACON Automation System and Airline Time of Arrival Predictions  

NASA Technical Reports Server (NTRS)

Benefits from information sharing between an air traffic service provider and a major air carrier are evaluated. Aircraft arrival time schedules generated by the NASA/FAA Center/TRACON Automation System (CTAS) were provided to the American Airlines System Operations Control Center in Fort Worth, Texas, during a field trial of a specialized CTAS display. A statistical analysis indicates that the CTAS schedules, based on aircraft trajectories predicted from real-time radar and weather data, are substantially more accurate than the traditional airline arrival time estimates, constructed from flight plans and en route crew updates. The improvement offered by CTAS is especially advantageous during periods of heavy traffic and substantial terminal area delay, allowing the airline to avoid large predictive errors with serious impact on the efficiency and profitability of flight operations.

Heere, Karen R.; Zelenka, Richard E.

2000-01-01

90

Extraction of P-wave reflections from microseisms  

NASA Astrophysics Data System (ADS)

The last few years there has been a growing number of body-wave observations in noise records. In 1973, Vinnik conjectured that P-waves would even be the dominant wavemode, at epicentral distances of about 40 degrees and onwards from an oceanic source. At arrays far from offshore storms, surface waves induced by nearby storms would not mask the body-wave signal and hence primarily P-waves would be recorded. We measured at such an array in Egypt and indeed found a large proportion of P-waves. At the same time, a new methodology is under development to characterize the lithosphere below an array of receivers, without active sources or local earthquakes. Instead, transmitted waves are used which are caused by distant sources. These sources may either be transient or more stationary. With this new methodology, called seismic interferometry, reflection responses are extracted from the coda of transmissions. Combining the two developments, it is clear that there is a large potential for obtaining reflection responses from low-frequency noise. A potential practical advantage of using noise instead of earthquake responses would be that an array only needs to be deployed for a few days or weeks instead of months, to gather enough illumination. We used a few days of continuous noise, recorded with an array in the Abu Gharadig basin, Egypt. We split up the record in three distinct frequency bands and in many small time windows. Using array techniques and taking advantage of all three-component recordings, we could unravel the dominant wavemodes arriving in each time window and in each frequency band. The recorded wavemodes, and hence the noise sources, varied significantly per frequency band, and - to a lesser extent - per time window. Primarily P-waves were detected on the vertical component for two of the three frequency bands. For these frequency bands, we only selected the time windows with a favorable illumination. By subsequently, applying seismic interferometry, we retrieved P-wave reflection responses and delineated reflectors in the crust, the Moho and possibly the Lehmann discontinuity.

Ruigrok, Elmer; Campman, Xander; Wapenaar, Kees

2011-09-01

91

Lithospheric structure of the Illinois Basin from teleseismic P-wave tomography  

NASA Astrophysics Data System (ADS)

We examine heterogeneity of the crust and upper mantle associated with a major intracratonic basin, using arrival time data from a regional EarthScope experiment extending across the western margin of the Illinois Basin. We measured 24,062 P-wave residuals associated with 399 teleseismic events recorded from January 2012 to March 2013 by 122 stations in the Illinois Basin region. We used data from the Ozark Illinois INdiana Kentucky (OIINK) Flexible Array, the permanent New Madrid Seismic Network, and a portion of the Earthscope Transportable Array. Precise relative arrival times were determined using array cross-correlation methods. We plotted the measured arrivals as residual maps to identify first order patterns of velocity heterogeneity and to fix outliers. These data were then inverted for P-wave velocity using non-linear tomography code developed by Steven Roecker. Our preliminary results indicate the upper 200 km of the mantle can be characterized by two blocks with a transition zone centered roughly parallel to the Ohio River boundary of Illinois and Kentucky. Estimated P-wave velocities are higher in Kentucky, located southeast of the transition zone compared to Missouri and Illinois, located northwest. We caution that at this stage our tomography model may be biased as we have not accounted for variations in crustal structure or applied corrections associated with the Illinois Basin. Parallel work with receiver functions by our group and the known geometry of the Illinois Basin will be used to calculate these corrections and modify the tomographic model accordingly.

Wilson, B.; Gilbert, H. J.; Hamburger, M. W.; Merrell, T.; Pavlis, G. L.; Sherrill, E.

2013-12-01

92

A combined first-arrival travel time and reflection coherency optimization approach to velocity estimation  

NASA Astrophysics Data System (ADS)

We present a nonlinear optimization method for two-dimensional velocity estimation in strongly heterogeneous media. We achieve this by designing a simulated-annealing algorithm to simultaneously maximize reflection coherency as well as minimize first-arrival travel time residuals. Relatively shallow velocity structure is constrained by first-arrival times, while coherency information from deeper reflections (if present) helps constrain deeper velocities. Prestack migration using the optimized velocities images reflections with greater continuity, compared with other velocity estimation methods. Using synthetic and real data we demonstrate that migrations through velocities obtained using our coherency criterion reconstruct basin-boundary structures more accurately than through those obtained using only first-arrival times. Images from shot gathers collected along COCORP Mojave line 5 across the Garlock fault in Cantil Valley, California show new evidence of links between Garlock fault branches and sub-horizontal structures in the upper crust. Imaging reflections and estimating velocities using coherency annealing is more effective and less expensive than picking reflection times from shot gathers recorded complex regions.

Pullammanappallil, Sathish K.; Louie, John N.

93

Testing model for prediction system of 1-AU arrival times of CME-associated interplanetary shocks  

NASA Astrophysics Data System (ADS)

We test a model to predict arrival times of interplanetary shock waves associated with coronal mass ejections (CMEs) using a three-dimensional adaptive mesh refinement (AMR) code. The model is used for the prediction system we develop, which has a Web-based user interface and aims at people who is not familiar with operation of computers and numerical simulations or is not researcher. We apply the model to interplanetary CME events. We first choose coronal parameters so that property of background solar wind observed by ACE space craft is reproduced. Then we input CME parameters observed by SOHO/LASCO. Finally we compare the predicted arrival times with observed ones. We describe results of the test and discuss tendency of the model.

Ogawa, Tomoya; den, Mitsue; Tanaka, Takashi; Sugihara, Kohta; Takei, Toshifumi; Amo, Hiroyoshi; Watari, Shinichi

94

Correlation between X-ray Lightcurve Shape and Radio Arrival Time in the Vela Pulsar  

Microsoft Academic Search

We report the results of simultaneous observations of the Vela pulsar in\\u000aX-rays and radio from the RXTE satellite and the Mount Pleasant Radio\\u000aObservatory in Tasmania. We sought correlations between the Vela's X-ray\\u000aemission and radio arrival times on a pulse by pulse basis. At a confidence\\u000alevel of 99.8% we have found significantly higher flux density in Vela's

A. Lommen; J. Donovan; C. Gwinn; Z. Arzoumanian; A. Harding; M. Strickman; R. Dodson; P. McCulloch; D. Moffett

2006-01-01

95

Multichannel deconvolution of p waves at seismic arrays and three-component stations. Annual report, 1 October 1985-1 October 1986  

SciTech Connect

The results of a new multichannel method, applied to array recordings and three-component station networks for teleseismic P waves, are presented and interpreted in terms of possible surface reflections and other arrivals from the Nevada Test Site (NTS), Novaya Zemlya, and Eastern Kazakh Test Site (EKTS) nuclear explosions. The deconvolution method utilizes the well known fact that P-wave spectra can be decomposed into source and receiver spectral factors. The source functions obtained in the deconvolution process provide a better picture of the nature of explosion source time functions and, in particular, of the presence or lack of secondary arrivals following the P wave such as pP or spall. The presence of such secondary arrivals and their effects on the first cycle of the P wave are very important in yield estimation. For most events at the eastern part of EKTS the source time functions appear to contain a pP arrival but they also show later, unexplained arrivals and other complexities. At other test sites often there are no clearly identifiable pP phases in the deconvolved traces. Joint deconvolution of central EKTS data using all AWRE arrays indicated strong azimuthal asymmetries in the body-wave radiation. Deconvolutions of NTS events were considerably degraded by the limited signal bandwidth due to strong mantle attenuation under this test site. The site functions are also complex in most cases. Site and source effects contribute about equally to the energy observed in the P codas of the events analyzed.

Der, Z.A.; Lees, A.C.; Shumway, R.H.; McElfresh, T.W.; Marshall, M.E.

1986-10-30

96

Event-Weighted Tests for Detecting Periodicity in Photon Arrival Times  

NASA Astrophysics Data System (ADS)

This paper treats the problem of detecting periodicity in a sequence of photon arrival times, which occurs, for example, in attempting to detect gamma-ray pulsars. A particular focus is on how auxiliary information, typically, source intensity, background intensity, and incident angles and energies associated with each photon arrival, should be used to maximize the detection power. We construct a class of likelihood-based tests, score tests, which give rise to event weighting in a principled and natural way, and derive expressions quantifying the power of the tests. These results can be used to compare the efficacies of different weight functions, including cuts in energy and incident angle. The test is targeted toward a template for the periodic light curve, and we quantify how deviation from that template affects the power of detection.

Bickel, Peter; Kleijn, Bas; Rice, John

2008-09-01

97

Comparing seismic tomographic images from automatically- and manually-detected arrival times  

NASA Astrophysics Data System (ADS)

In this work we compare local earthquake tomographic images obtained using arrival times detected by an automatic picking procedure and by an expert seismologist. For this purpose we select a reference dataset composed of 476 earthquakes occurred in the Trentino region (north-eastern Italy) in the period 1994-2007. Local magnitudes are comprised between 0.8 and 5.3. Original recordings are mainly from the Provincia Autonoma di Trento (PAT), and from other networks operating in the surrounding areas (Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - INOGS; Istituto Nazionale di Geofisica e Vulcanologia - INGV; others available via the European Integrated Data Archive). The automatic picking of P and S phases is performed through a picker engine based on the Akaike information criterion (AIC). In particular, the proposed automatic phase picker includes: (i) envelope calculation, (ii) band-pass filtering, (iii) Akaike information criterion (AIC) detector for both P- and S-arrivals, (iv) checking for impulsive arrivals, (v) evaluation of expected S onset on the basis of a preliminary location derived from the P-arrival times, and (vi) quality assessment. Simultaneously, careful manual inspection by expert seismologists is applied to the same waveform dataset, to obtain manually-repicked phase readings. Both automatic and manual procedures generate a comparable amount of readings (about 6000 P- and 5000 S-phases). These data are used for the determination of two similar 3-D propagation models for the Trentino region, applying the SIMULPS code. In order to quantitatively estimate the difference of these two models we measure their discrepancies in terms of velocity at all grid points. The small differences observed among tomographic results allow us to demonstrate that the automatic picking engine adopted in this test can be used for reprocessing large amount of seismic recordings with the aim of perform a local tomographic study with an accuracy comparable to the one obtainable with a complete manual data revision.

Spallarossa, Daniele; Scafidi, Davide; Turino, Chiara; Ferretti, Gabriele; Viganò, Alfio

2013-04-01

98

Fast-Time Evaluations of Airborne Merging and Spacing in Terminal Arrival Operations  

NASA Technical Reports Server (NTRS)

NASA researchers are developing new airborne technologies and procedures to increase runway throughput at capacity-constrained airports by improving the precision of inter-arrival spacing at the runway threshold. In this new operational concept, pilots of equipped aircraft are cleared to adjust aircraft speed to achieve a designated spacing interval at the runway threshold, relative to a designated lead aircraft. A new airborne toolset, prototypes of which are being developed at the NASA Langley Research Center, assists pilots in achieving this objective. The current prototype allows precision spacing operations to commence even when the aircraft and its lead are not yet in-trail, but are on merging arrival routes to the runway. A series of fast-time evaluations of the new toolset were conducted at the Langley Research Center during the summer of 2004. The study assessed toolset performance in a mixed fleet of aircraft on three merging arrival streams under a range of operating conditions. The results of the study indicate that the prototype possesses a high degree of robustness to moderate variations in operating conditions.

Krishnamurthy, Karthik; Barmore, Bryan; Bussink, Frank; Weitz, Lesley; Dahlene, Laura

2005-01-01

99

Temporal dispersion of the emergence of intelligence: an inter-arrival time analysis  

NASA Astrophysics Data System (ADS)

Many reasons for why extraterrestrial intelligences might avoid communications with our civilization have been proposed. One possible scenario is that all civilizations follow the lead of some particularly distinguished civilization. This paper will examine the impact the first successful civilization could have on all other subsequent civilizations within its sphere of influence and the ramifications of this as it relates to the Fermi Paradox. Monte Carlo simulation is used to map the inter-arrival times of early civilizations and to highlight the immense epochs of time that the earliest civilizations could have had the Galaxy to themselves.

Hair, Thomas W.

2011-02-01

100

Emergency Department Arrival Times, Treatment, and Functional Recovery in Women with Acute Ischemic Stroke  

PubMed Central

Abstract Background Sex disparities have been well documented in patients with ischemic stroke. Previous studies have suggested that female sex is a risk factor for delay in arrival time to the emergency department (ED) and may contribute to ineligibility for thrombolytic therapy. With the increase in education efforts targeting women, we investigated whether ED arrival times, rates of thrombolytic use, and functional outcomes continue to differ in men and women with acute ischemic stroke (AIS). Methods This study was a retrospective database analysis of patients with AIS (2001–2008). All AIS patients presenting within 24 hours with a known time of symptom onset and a documented admission National Institutes of Health Stroke Scale (NIHSS) were included. The Modified Barthel Index (MBI) assessed patients' functional status preadmission (historical), admission, and at 3 and 12 months poststroke. Results Included in the analysis were 480 (50.6%) women and 468 (49.4%) men. Women were significantly older than men (70.6?±?0.7 vs. 65.3 years?±?0.6, p???0.001). Mean onset-to-ED time was not significantly different between the sexes (women 265?±?283 vs. men 245?±?300 minutes), nor was prestroke MBI. Logistic regression analysis demonstrated that female sex, increasing age, higher admission NIHSS, and longer onset-to-ED times all contributed to poorer functional status. Conclusions Women arrive at the ED at equivalent speed as men after AIS. Women had greater functional impairments at 3 months and 12 months poststroke despite equivalent prestroke MBI and admission NIHSS. Female sex contributes to poorer chronic functional outcomes after AIS.

Knauft, Wesley; Chhabra, Jyoti

2010-01-01

101

From 3-Hz P Waves to 0-S-2: Real-time and deferred estimates of the moment of the Honshu event across the full frequency spectrum  

NASA Astrophysics Data System (ADS)

In the hours following the 2011 Honshu event, and as part of tsunami warning procedures at the Laboratoire de Geophysique in Papeete, Tahiti, the seismic source of the event was analyzed using a number of real-time procedures. The ultra-long period mantle magnitude algorithm suggests a static moment of 4.2E29 dyn*cm, not signifcantly different from the NEIC value obtained by W-phase inversion. The slowness parameter, THETA = -5.65, is slightly deficient, but characteristic of other large subduction events such as Nias (2005) or Peru (2001); it remains significantly larger than for slow earthquakes such as Sumatra (2004) or Mentawai (2010). Similarly, the duration of high-frequency (2-4 Hz) P waves in relation to seismic moment or estimated energy fails to document any slowness in the seismic source. These results were confirmed in the ensuing weeks by the analysis of the lowest-frequency spheroidal modes of the Earth. A dataset of 109 fits for 8 modes (including the gravest one, 0s2, and the breathing mode, 0s0) yields a remarkably flat spectrum, with an average moment of 3.5E29 dyn*cm (*/1.07). This textbook behavior of the Sendai earthquake explains the generally successful real-time modeling of its teleseismic tsunami, based on available seismic source scaling laws. On the other hand, it confirms the dichotomy, amongst mega-quakes (M sub 0 > 10 sup 29 dyn*cm) between regular events (Nias, 2005; Chile, 2010; Sendai, 2011) and slow ones (Chile, 1960; Alaska, 1964; Sumatra, 2004; and probably Rat Island, 1965), whose origin remains unexplained.

Andre, O. E.

2011-12-01

102

Time-of-arrival analysis applied to ELF/VLF wave generation experiments at HAARP  

NASA Astrophysics Data System (ADS)

Time-of-arrival (TOA) analysis is applied to observations performed during ELF/VLF wave generation experiments at the High-frequency Active Auroral Research Program (HAARP) HF transmitter in Gakona, Alaska. In 2012, a variety of ELF/VLF wave generation techniques were employed to identify the dominant source altitude for each case. Observations were performed for beat-wave modulation, AM modulation, STF modulation, ICD modulation, and cubic frequency modulation, among others. For each of these cases, we identify the dominant ELF/VLF source altitude and compare the experimental results with theoretical HF heating predictions.

Moore, R. C.; Fujimaru, S.

2012-12-01

103

Electric fields that "arrive" before the time derivative of the magnetic field prior to major earthquakes.  

PubMed

The low frequency electric signals (emitted from the focal area when the stress reaches a critical value) that precede major earthquakes, are recorded at distances approximately 100 km being accompanied by magnetic field variations. The electric field "arrives" 1 to 2 s before the time derivative of the horizontal magnetic field. An explanation, which is still awaiting, should consider, beyond criticality, the large spatial scale as well as that the transmission of the electromagnetic fields (through an inhomogeneous weakly conductive medium like the Earth) obeys diffusion type equations. PMID:14611563

Varotsos, P A; Sarlis, N V; Skordas, E S

2003-10-01

104

VLF long-range lightning location using the arrival time difference technique (ATD)  

NASA Technical Reports Server (NTRS)

A new network of VLF receiving systems is currently being developed in the USA to support NASA's Tropical Rain Measuring Mission (TRMM). The new network will be deployed in the east coast of the US, including Puerto Rico, and will be operational in late 1995. The system should give affordable, near real-time, accurate lightning locating capabilities at long ranges and with extended coverage. It is based on the Arrival Time Difference (ATD) method of Lee (1986; 1990). The ATD technique is based on the estimation of the time of arrival of sferics detected over an 18 kHz bandwith. The ground system results will be compared and complemented with satellite optical measurements gathered with the already operational Optical Transient Detector (OTD) instrument and in due course with its successor the Lightning Imaging Sensor (LIS). Lightning observations are important to understand atmospheric electrification phenomena, discharge processes, associated phenomena on earth (e.g. whistlers, explosive Spread-F) and other planets. In addition, lightning is a conspicuous indicator of atmospheric activity whose potential is just beginning to be recognized and utilized. On more prosaic grounds, lightning observations are important for protection of life, property and services.

Ierkic, H. Mario

1996-01-01

105

Comparative Study of Bunch Length And Arrival Time Measurements at FLASH  

SciTech Connect

Diagnostic devices to precisely measure the longitudinal electron beam profile and the bunch arrival time require elaborate new instrumentation techniques. At FLASH, two entirely different methods are used. The bunch profile can be determined with high precision by a transverse deflecting RF structure, but the method is disruptive and does not allow to monitor multiple bunches in a macro-pulse train. It is therefore complemented by two non-disruptive electrooptical devices, called EO and TEO. The EO setup uses a dedicated diagnostic laser synchronized to the machine RF. The longitudinal electron beam profile is encoded in the intensity profile of a chirped laser pulse and analyzed by looking at the spectral composition of the pulse. The second setup, TEO, utilizes the TiSa-based laser system used for pump-probe experiments. Here, the temporal electron shape is encoded into the spatial dimension of the laser pulse by an intersection angle between the laser and the electron beam at the EO-crystal. In this paper, we present a comparative study of bunch length and arrival time measurements performed simultaneously with all three experimental techniques.

Schlarb, H.; Azima, A.; Dusterer, S.; Huning, M.; Knabbe, E.A.; Roehrs, M.; Rybnikov, V.; Schmidt, B.; Steffen, B.; /DESY; Ross, M.C.; /SLAC; Schmueser, P.; Winter, A.; /Hamburg U.

2007-04-16

106

Acute coronary syndrome: factors affecting time to arrival in a diverse urban setting.  

PubMed

This study seeks to better understand how individuals of different cultural/ethnic backgrounds in an urban setting assess the signs and symptoms of Acute Coronary Syndrome (ACS) and the ensuing decision to take urgent action. Few studies exist which examine these differences and enhance understanding of how to address these differences and, ultimately, reduce morbidity and mortality from ACS. Face-to-face interviews were conducted with a convenience sample of urban patients of different cultural and socioeconomic backgrounds regarding their actions upon recognition of ACS signs and symptoms. Patients (423) with presumed or diagnosed ACS were interviewed within 12 h of arrival at the urban emergency rooms. Among the different cultural groups, Haitians delayed the longest (median) from symptom onset to hospital arrival (8.24 h), followed by Caribbeans (7.83 h), African Americans (6.62 h) and Hispanics (6.00 h). Although these delay intervals were not statistically significant across groups, each racial/ethnic group sought care well beyond the recommended time period of 3 h after initial recognition of ACS signs and symptoms. Among all the cultural groups, the two key factors motivating early arrival were being employed and taking positive actions. ACS symptom perception by different cultural groups appears to play an important role in the decision to seek emergency treatment. This is an area that has not been widely studied among or within different cultural/ethnic groups. As such, further research is needed to delineate these concepts and actions and to provide opportunities for appropriate education. PMID:21877106

Deshmukh, Mrualini; Joseph, Michael A; Verdecias, Niko; Malka, Edmond S; LaRosa, Judith H

2011-12-01

107

The effect of S-wave arrival times on the accuracy of hypocenter estimation  

USGS Publications Warehouse

We have examined the theoretical basis behind some of the widely accepted "rules of thumb' for obtaining accurate hypocenter estimates that pertain to the use of S phases and illustrate, in a variety of ways, why and when these "rules' are applicable. Most methods used to determine earthquake hypocenters are based on iterative, linearized, least-squares algorithms. We examine the influence of S-phase arrival time data on such algorithms by using the program HYPOINVERSE with synthetic datasets. We conclude that a correctly timed S phase recorded within about 1.4 focal depth's distance from the epicenter can be a powerful constraint on focal depth. Furthermore, we demonstrate that even a single incorrectly timed S phase can result in depth estimates and associated measures of uncertainty that are significantly incorrect. -from Authors

Gomberg, J. S.; Shedlock, K. M.; Roecker, S. W.

1990-01-01

108

The influence of ice-pressure on p-wave velocity in alpine low-porosity rocks: a modified time-average model  

NASA Astrophysics Data System (ADS)

Most polar and many mountainous regions are affected by permafrost. Seismic field and laboratory measurements represent a standard approach to investigate permafrost since the early 1970s. Laboratory research has focussed on arctic high-porosity sandstones, shales and carbonate rocks and results have been implemented in various seismic models (Carcione and Seriani, 1998). However, alpine rock walls consist of low-porosity bedrock and some authors deny the applicability of seismic approaches to these (McGinnis et al., 1973). Models developed in high-porosity rocks explain bulk p-wave velocity of bedrock due to changing velocities in the pore infill (ice/water/air) while the matrix velocity of bedrock remains constant. Here we show, that in low-porosity rocks matrix velocities change considerably while changes in pore velocities are insignificant. Hence, p-wave refraction seismics is applicable in low-porosity alpine rock walls. For this, we (1) present data of p-wave measurements of 23 different alpine rocks, (2) evaluate the influence of ice pressure on seismic velocities, (3) determine anisotropic decrease due to ice pressure and (4) extend Timur's (1968) 2-phase model for alpine rocks. The tested rocks derive from alpine locations in Switzerland, Germany, Austria, France and Svalbard, and German sub alpine locations. All samples possess effective porosities lower than 6 %. P-wave velocities were measured parallel and perpendicular to cleavage or bedding in a temperature range from +20° C to -15° C in a WEISS WK 180/40 high-accuracy climate chamber. Rock temperature was monitored continuously with two or three calibrated thermometers; p-waves were generated with a Geotron ultrasonic transducer and measured with a Fluke Scopemeter. (1) All rock samples show p-wave velocity increase dependent on lithology due to freezing. P-wave velocity increase is in the range of 7.33 (±3.73) % for Gneiss and 78.45 (±7.00) % for carbonate rocks parallel to cleavage/bedding; perpendicular measurements show an increase between 11.10 (±2.38) % for Gneiss and 166.01 (±56.93) % for carbonate rocks. The increase of p-wave velocity of carbonate rocks is independent of effective porosity. (2) Velocity increase due to freezing is not only derived through higher velocity of ice in relation to water; ice pressure induces an increase of the velocity of the rock matrix. Matrix velocity increases parallel to cleavage/bedding between 5.08 (±4.08) % for Gneiss and 59.44 (±9.33) % for carbonate rocks; perpendicular measurements indicate matrix velocity increase reaching from 8.95 (±4.51) % for mafic metamorphic rocks and 168.53 (±62.00) % for carbonate rocks. (3) Anisotropy decreases as a result of crack closure due to ice pressure in 15 of 23 rock samples. This effect is specially pronounced for schists. (4) We extend Timur's (1968) 2 phase equation with a lithology dependent variable to increase the matrix velocity responding to developing ice pressure while freezing. This study shows the general applicability of refraction seismics in low-porosity permafrost rocks. The expansion of rigid bedrock upon freezing is restricted and, thus, ice pressure will increase matrix velocity. Here, we present a modified "Timur (1968) 2 phase equation" implementing a 4-21 % change in matrix velocity dependent on lithology.

Dräbing, D.; Krautblatter, M.

2012-04-01

109

Relaxing the closure assumption in single-season occupancy models: staggered arrival and departure times  

USGS Publications Warehouse

Occupancy statistical models that account for imperfect detection have proved very useful in several areas of ecology, including species distribution and spatial dynamics, disease ecology, and ecological responses to climate change. These models are based on the collection of multiple samples at each of a number of sites within a given season, during which it is assumed the species is either absent or present and available for detection while each sample is taken. However, for some species, individuals are only present or available for detection seasonally. We present a statistical model that relaxes the closure assumption within a season by permitting staggered entry and exit times for the species of interest at each site. Based on simulation, our open model eliminates bias in occupancy estimators and in some cases increases precision. The power to detect the violation of closure is high if detection probability is reasonably high. In addition to providing more robust estimation of occupancy, this model permits comparison of phenology across sites, species, or years, by modeling variation in arrival or departure probabilities. In a comparison of four species of amphibians in Maryland we found that two toad species arrived at breeding sites later in the season than a salamander and frog species, and departed from sites earlier.

Kendall, William L.; Hines, James E.; Nichols, James D.; Grant, Evan H. Campbell

2013-01-01

110

Real-time Upstream Monitoring System (RUMS): Forecasting arrival times of interplanetary shocks using energetic particle data from ACE  

NASA Astrophysics Data System (ADS)

We have created a system for predicting the arrival times at Earth of interplanetary (IP) shocks that originate at the Sun. This system is currently available on the web (http://sd-www.jhuapl.edu/UPOS/RISP/index.html) and runs in real-time. Input data to our prediction algorithm is energetic particle data from the Electron, Proton, and Alpha Monitor (EPAM) instrument on NASA's Advanced Composition Explorer (ACE) spacecraft. Real-time EPAM data is obtained from the National Oceanic and Atmospheric Administration (NOAA) Space Environment Center (SEC). Our algorithm operates in two stages. First it watches for a velocity dispersion signature (energetic ions show flux enhancement followed by subsequent enhancements in lower energies), which is commonly seen upstream of a large IP shock. Once a precursor signature has been detected, a pattern recognition algorithm is used to analyze the time series profile of the particle data and generate an estimate for the shock arrival time. Tests on the algorithm show an average error of roughly 9 hours for predictions made 24 hours before the shock arrival and roughly 5 hours when the shock is 12 hours away. This can provide significant lead-time and deliver critical information to mission planners, satellite operations controllers, and scientists. As of February 4, 2004, the ACE real-time stream has been switched to include data from another detector on EPAM. We are now processing the new real-time data stream and have made improvements to our algorithm based on this data. In this paper, we report prediction results from the updated algorithm.

Ho, G.; Donegan, M.; Vandegriff, J.; Wagstaff, K.

111

Fine Scale P-wave Structure of the Upper Mantle Discontinuities Beneath Northern Australia  

NASA Astrophysics Data System (ADS)

P-wave triplications arise from rapid increases in upper mantle seismic velocity with depth. Waveform analyses of the triplicated wavefield are powerful for detailed characterization of the upper mantle phase transitions, owing to their sensitivity to the size and depth of the discontinuities, as well as the under- and overlying velocity gradients. However, P-wave triplication studies are inherently more difficult than for S-waves, and hence much less common, since P-wave arrivals are typically much closer in time near the triplication crossovers than for S-waves, e.g., <1-2 sec. Here we study the P-wave field at relatively high frequency (~ 1 Hz), using the Warramunga seismic array (WRA) in Australia. WRA has an aperture of about 20 kilometers and is equipped with 20 short- period vertical instruments. We collected 1863 events between 1990 to 1994 from surrounding trenches recorded by WRA, which have an epicentral distance range roughly between 12 and 25 deg. These data mainly sample the upper mantle beneath northern Australia. We employ Nth-root stacking and fk analyses to study the triplicated waves. For each event, a master trace was computed from the 4th-root vespagram, using a sliding window that collects maximum amplitude and associated slowness information. While some master traces exhibit considerable complexity, many show clear evidence for distinctly separate upper mantle triplication phases, and provide evidence for lateral variability in upper mantle discontinuity structure, as well as heterogeneities, beneath northern Australia.

Lin, P. P.; Garnero, E. J.; Rost, S.

2007-12-01

112

Sex differences in accuracy and precision when judging time to arrival: data from two Internet studies.  

PubMed

We report two Internet studies that investigated sex differences in the accuracy and precision of judging time to arrival. We used accuracy to mean the ability to match the actual time to arrival and precision to mean the consistency with which each participant made their judgments. Our task was presented as a computer game in which a toy UFO moved obliquely towards the participant through a virtual three-dimensional space on route to a docking station. The UFO disappeared before docking and participants pressed their space bar at the precise moment they thought the UFO would have docked. Study 1 showed it was possible to conduct quantitative studies of spatiotemporal judgments in virtual reality via the Internet and confirmed reports that men are more accurate because women underestimate, but found no difference in precision measured as intra-participant variation. Study 2 repeated Study 1 with five additional presentations of one condition to provide a better measure of precision. Again, men were more accurate than women but there were no sex differences in precision. However, within the coincidence-anticipation timing (CAT) literature, of those studies that report sex differences, a majority found that males are both more accurate and more precise than females. Noting that many CAT studies report no sex differences, we discuss appropriate interpretations of such null findings. While acknowledging that CAT performance may be influenced by experience we suggest that the sex difference may have originated among our ancestors with the evolutionary selection of men for hunting and women for gathering. PMID:21125324

Sanders, Geoff; Sinclair, Kamila

2011-12-01

113

Test bolus measurement: effects of the respiratory position on bolus arrival time and signal-intensity-time curve quality  

Microsoft Academic Search

Object The aim of our study is to determine if the respiratory position (free breathing, end expiration) influences bolus arrival\\u000a time (BAT) or the quality of the SI-time curve in the test bolus measurement.\\u000a \\u000a \\u000a Materials and methods We examined 150 consecutive patients in free breathing and end expiration with 1 mL contrast media (CM) and a flow of 3 mL\\/s\\u000a with MRI.

Rolf Janka; Rudy Marius; Lell Michael; Uder Michael; Bautz Werner; Wenkel Evelyn

2007-01-01

114

Expected Time of Arrival Model for School Bus Transit Using Real-Time Global Positioning System-Based Automatic Vehicle Location Data  

Microsoft Academic Search

The school bus is a major transportation mode for students in Canada. Unexpected delay of a school bus may be a major source of inconvenience for students and their parents. Accordingly, the provision of timely and reliable information on the expected arrivals of school buses would be of great benefit to them. This study develops an expected time of arrival

Eui-Hwan Chung; Amer Shalaby

2007-01-01

115

The Advantage of Arriving First: Characteristic Times in Finite Size Populations of Error-Prone Replicators  

PubMed Central

We study the evolution of a finite size population formed by mutationally isolated lineages of error-prone replicators in a two-peak fitness landscape. Computer simulations are performed to gain a stochastic description of the system dynamics. More specifically, for different population sizes, we compute the probability of each lineage being selected in terms of their mutation rates and the amplification factors of the fittest phenotypes. We interpret the results as the compromise between the characteristic time a lineage takes to reach its fittest phenotype by crossing the neutral valley and the selective value of the sequences that form the lineages. A main conclusion is drawn: for finite population sizes, the survival probability of the lineage that arrives first to the fittest phenotype rises significantly.

Marin, Arturo; Tejero, Hector; Nuno, Juan Carlos; Montero, Francisco

2013-01-01

116

3D P-wave velocity structure beneath the Abitibi-Grenville region, eastern Canadian Shield  

NASA Astrophysics Data System (ADS)

Seismic studies of the upper mantle of the Canadian Shield have indicated a low-velocity anomaly within the cratonic lithosphere near the Ontario-Québec border, in the Abitibi-Grenville region. The lack of seismograph station coverage on the Québec side of the border previously prevented definition of the 3D geometry of this anomaly. New stations installed in the province of Québec allow us to carry out new studies of the P-wave velocity structure of the lithosphere surrounding that low-velocity anomaly, in order to better understand the complexity of the region and the interaction of the lithosphere with possible thermal anomalies in the underlying mantle. Over a hundred events have been analysed since autumn 2007. To do so, we used teleseismic P and PKP arrivals recorded at 31 stations deployed across the region, 5 belonging to UQAM’s network and 26 others belonging to the POLARIS project and the Canadian National Seismograph Network (CNSN). The relative arrival times of teleseismic P waves across the array were measured using the cross-correlation method of VanDecar & Crosson (1990). We have also calculated maps of relative arrival time residuals across the array for earthquakes coming from different back-azimuths, in order to examine systematic patterns of travel-time anomalies resulting from mantle heterogeneity. We invert the travel time data to estimate the 3D P-wave velocity structure beneath the region, using the least-squares tomographic inversion code of VanDecar (1991). Regularization and resolution tests are carried out, and we present a set of preliminary 3D upper mantle models. Depth slices and cross-sections are used to constrain the geometry of the low-velocity anomaly and surrounding upper mantle structures.

Villemaire, M.; Darbyshire, F. A.

2009-12-01

117

Factors influencing emergency department arrival time and in-hospital management of patients with acute myocardial infarction.  

PubMed

Reperfusion of the infarct-related artery in the very first hour ("golden hour") of acute myocardial infarction (AMI) significantly reduces mortality rates. Several factors may delay the initiation of reperfusion therapy (ie, thrombolytic therapy or primary percutaneous transluminal coronary angioplasty [PCTA]), most of which are related to patients. A total of 520 patients with suspected AMI were evaluated in the emergency department of Dokuz Eylül University Hospital between March 1996 and October 1999. After inclusion criteria were applied, the study consisted of 178 patients with a history of AMI. Analyzed data that affected patients' arrival to the hospital were obtained from responses to a questionnaire. The Statistical Package for the Social Sciences (SPSS; SPSS Inc., Chicago, Ill), version 11.0, was used for all statistical analyses. The mean "symptom onset-hospital arrival time" was 188+/-325 min for the entire study group. The median delay was 110 min (approximately 2 h). Only 39 (22%) patients arrived to the hospital within the first hour. The mean time needed for late responders (n=109, 74%) (hospital arrival later than 1 h after symptom onset) to arrive was 245-/+363 min. According to the results of this study, many patients with AMI who may be eligible for reperfusion therapy miss the "golden hour" because of late hospital arrival. Some groups of patients (ie, elderly, women, those with diabetes) were especially late in arriving. To reduce such delays, training programs may be advised to focus on these groups of patients. Arrival times to the hospital during AMI can be greatly improved by efficient public education programs targeted to these groups. PMID:16751157

Ayrik, Cuneyt; Ergene, Ulku; Kinay, Ozan; Nazli, Cem; Unal, Belgin; Ergene, Oktay

2006-01-01

118

On the Retrieval of Lightning Radio Sources from Time-of-Arrival Data  

NASA Technical Reports Server (NTRS)

We examine the problem of retrieving three-dimensional lightning locations from radio frequency Time-Of-Arrival (TOA) measurements. Arbitrary antenna locations are considered. By judiciously differencing measurements that are related to the location of the antennas and their excitation times, the problem is converted from the initial spherical nonlinear form to a system of linear equations. In the linear formalism, the source location and time-of-occurrence is viewed geometrically as an intersection of hyperplanes in the four-dimensional Minkowski space (x,y,z,t). The linear equations are solved to obtain explicit analytic expressions for the location and time variables. Retrieval errors are not interpreted with conventional Geometrical Dilution of Precision (GDOP) arguments as discussed by Holmes and Reedy (1951), but with more recent inversion analyses considered by Twomey (1977). Measurement errors are propagated analytically so that the specific effect of these errors on the solution is clarified. The sensitivity of the solution on the number of antennas used, antenna network geometry, source position, and measurement differencing schemes are discussed in terms of the eigenvalues of the linear system.

Koshak, William J.; Solakiewicz, Richard J.

1996-01-01

119

Fine-Scale P-wave Structure in the Upper Mantle North of Australia  

NASA Astrophysics Data System (ADS)

We study the P-wave field recorded by the high frequency (centering near 1 Hz) Warramunga seismic array (WRA) in Australia. WRA has an aperture of about 20 kilometers and is equipped with 20 short-period vertical component instruments. Nearly 2000 earthquakes at all source depths are studied, which span an epicentral distance range of roughly 12 to 25 degrees. Our initial work focused on array methods to identify relatively weak but coherent P-wave triplication arrivals due to the upper discontinuities near 410 and 660 km depth. However, significant waveform complexities and additional unpredicted seismic arrivals are commonly present, suggesting small scale structural complexities either associated with the discontinuities, or heterogeneity along the path. The additional energy does not appear source related, nor clearly attributable to any particular wave path geometry or region. Here we explore back-projection schemes to map arrivals to possible scattering or reflection locations. A challenge with this approach is confident identification of a reference phase; thus, we proceed using only the highest quality data. Nth-root stacking and fk-analysis are used to determine slowness, delay time, and back azimuth, which are used to estimate reflection locations. Results will be presented in the context of the tectonically complex region, replete with past and present subduction, and hence potentially the presence of associated chemical heterogeneity.

Lin, P. P.; Garnero, E. J.; Rost, S.

2008-12-01

120

YO-A Time-of-Arrival Receiver for Removal of Femtosecond Helicity-Correlated Beam Effects.  

National Technical Information Service (NTIS)

The G0 parity violation experiment at Jefferson Lab is based on time-of-flight measurements, and is sensitive to timing effects between the two electron helicity states of the beam. Photon counters triggered by time-of-arrival at the target mandate that t...

J. Musson T. Allison A. Freyberger J. Kuhn B. Quinn

2004-01-01

121

Joint Inversion of Body-Wave Arrival Times and Surface-Wave Dispersion for Three-Dimensional Seismic Structure Around SAFOD  

NASA Astrophysics Data System (ADS)

We incorporate body-wave arrival time and surface-wave dispersion data into a joint inversion for three-dimensional P-wave and S-wave velocity structure of the crust surrounding the site of the San Andreas Fault Observatory at Depth. The contributions of the two data types to the inversion are controlled by the relative weighting of the respective equations. We find that the trade-off between fitting the two data types, controlled by the weighting, defines a clear optimal solution. Varying the weighting away from the optimal point leads to sharp increases in misfit for one data type with only modest reduction in misfit for the other data type. All the acceptable solutions yield structures with similar primary features, but the smaller-scale features change substantially. When there is a lower relative weight on the surface-wave data, it appears that the solution over-fits the body-wave data, leading to a relatively rough V s model, whereas for the optimal weighting, we obtain a relatively smooth model that is able to fit both the body-wave and surface-wave observations adequately.

Zhang, Haijiang; Maceira, Monica; Roux, Philippe; Thurber, Clifford

2014-03-01

122

Ultra-Wideband Time-Difference-of-Arrival High Resolution 3D Proximity Tracking System  

NASA Technical Reports Server (NTRS)

This paper describes a research and development effort for a prototype ultra-wideband (UWB) tracking system that is currently under development at NASA Johnson Space Center (JSC). The system is being studied for use in tracking of lunar./Mars rovers and astronauts during early exploration missions when satellite navigation systems are not available. U IATB impulse radio (UWB-IR) technology is exploited in the design and implementation of the prototype location and tracking system. A three-dimensional (3D) proximity tracking prototype design using commercially available UWB products is proposed to implement the Time-Difference- Of-Arrival (TDOA) tracking methodology in this research effort. The TDOA tracking algorithm is utilized for location estimation in the prototype system, not only to exploit the precise time resolution possible with UWB signals, but also to eliminate the need for synchronization between the transmitter and the receiver. Simulations show that the TDOA algorithm can achieve the fine tracking resolution with low noise TDOA estimates for close-in tracking. Field tests demonstrated that this prototype UWB TDOA High Resolution 3D Proximity Tracking System is feasible for providing positioning-awareness information in a 3D space to a robotic control system. This 3D tracking system is developed for a robotic control system in a facility called "Moonyard" at Honeywell Defense & System in Arizona under a Space Act Agreement.

Ni, Jianjun; Arndt, Dickey; Ngo, Phong; Phan, Chau; Dekome, Kent; Dusl, John

2010-01-01

123

Improvement in lightning geolocation by time-of-arrival method using global ELF network data  

NASA Astrophysics Data System (ADS)

The global observation of cloud-to-ground (CG) discharges based on ELF measurements provides essential information, including vertical charge moment (Qdl) for investigations of global-scale thunderstorm activity. However, the geolocating method by direction finding of sferics in the frequency range of 1-100 Hz has a rather large error, on the order of 1000 km, even for the CGs with relatively large Qdl (>1000 C-km). Here we improve the methods for geolocation and estimation of Qdl, which are applicable to smaller CGs with Qdl down to 470 C-km, making use of the time-of-arrival method and the high correlation between Qdl and the peak amplitude of ELF sferics. The evaluated average error in geolocation, comparing with World Wide Lightning Location Network data, is 680 km. By this improved method, CGs with Qdl of <470 C-km can be detected at any location in the world. In the preliminary analysis for the year of 2004, the number of CGs whose location and Qdl are determined is about a million events per month, roughly 10-30 times compared to previous studies by ELF measurement, enabling an investigation of the day-to-day variations of the global CG distribution with transferred charge amount. The combination of accurate geolocation and the uniformity of detection show active regions in the three main areas: Africa, South America, and the Maritime Continent. In addition, minor thunderstorm areas in Japan, the Mediterranean Sea, and the Pacific Ocean can be monitored.

Yamashita, Kozo; Takahashi, Yukihiro; Sato, Mitsuteru; Kase, Hiromi

2011-02-01

124

Estimating permeability from quasi-static deformation: Temporal variations and arrival time inversion  

SciTech Connect

Transient pressure variations within a reservoir can be treated as a propagating front and analyzed using an asymptotic formulation. From this perspective one can define a pressure 'arrival time' and formulate solutions along trajectories, in the manner of ray theory. We combine this methodology and a technique for mapping overburden deformation into reservoir volume change as a means to estimate reservoir flow properties, such as permeability. Given the entire 'travel time' or phase field, obtained from the deformation data, we can construct the trajectories directly, there-by linearizing the inverse problem. A numerical study indicates that, using this approach, we can infer large-scale variations in flow properties. In an application to Interferometric Synthetic Aperture (InSAR) observations associated with a CO{sub 2} injection at the Krechba field, Algeria, we image pressure propagation to the northwest. An inversion for flow properties indicates a linear trend of high permeability. The high permeability correlates with a northwest trending fault on the flank of the anticline which defines the field.

Vasco, D.W.; Ferretti, Alessandro; Novali, Fabrizio

2008-05-01

125

Joint microseismic location and anisotropic tomography using differential arrival times and differential backazimuths  

NASA Astrophysics Data System (ADS)

We develop a new method to locate microseismic events induced by hydraulic fracturing with simultaneous anisotropic tomography, using differential arrival times and differential backazimuths. Compared to the existing double-difference method, our method incorporates backazimuth information to better constrain microseismic locations in the case of downhole linear seismic arrays used for monitoring induced seismicity. The tomography is constrained to a 1-D layered VTI (transversely isotropic structure with a vertical symmetry axis) structure to improve inversion stability given the limited passive seismic data. We derive analytical sensitivities for the elastic moduli (Cij) and layer thickness L, and verify the analytical results with numerical calculations. The forward modelled traveltimes and sensitivities are all calculated analytically without weak anisotropy assumption. By incorporating the relative information among events, the extended double-difference method can provide better relative locations for events and, therefore, can characterize the fractures with higher accuracy. In the two tests with synthetic data, our method provides more accurate relative locations than the traditional methods, which only use absolute information. With fast speed and high accuracy, our inversion scheme is suitable for real-time microseismic monitoring of hydraulic fracturing.

Li, Junlun; Zhang, Haijiang; Rodi, William L.; Toksoz, M. Nafi

2013-12-01

126

Evaluation of Operational Procedures for Using a Time-Based Airborne Inter-arrival Spacing Tool  

NASA Technical Reports Server (NTRS)

An airborne tool has been developed based on the concept of an aircraft maintaining a time-based spacing interval from the preceding aircraft. The Advanced Terminal Area Approach Spacing (ATAAS) tool uses Automatic Dependent Surveillance-Broadcast (ADS-B) aircraft state data to compute a speed command for the ATAAS-equipped aircraft to obtain a required time interval behind another aircraft. The tool and candidate operational procedures were tested in a high-fidelity, full mission simulator with active airline subject pilots flying an arrival scenario using three different modes for speed control. The objectives of this study were to validate the results of a prior Monte Carlo analysis of the ATAAS algorithm and to evaluate the concept from the standpoint of pilot acceptability and workload. Results showed that the aircraft was able to consistently achieve the target spacing interval within one second (the equivalent of approximately 220 ft at a final approach speed of 130 kt) when the ATAAS speed guidance was autothrottle-coupled, and a slightly greater (4-5 seconds), but consistent interval with the pilot-controlled speed modes. The subject pilots generally rated the workload level with the ATAAS procedure as similar to that with standard procedures, and also rated most aspects of the procedure high in terms of acceptability. Although pilots indicated that the head-down time was higher with ATAAS, the acceptability of head-down time was rated high. Oculometer data indicated slight changes in instrument scan patterns, but no significant change in the amount of time spent looking out the window between the ATAAS procedure versus standard procedures.

Oseguera-Lohr, Rosa M.; Lohr, Gary W.; Abbott, Terence S.; Eischeid, Todd M.

2002-01-01

127

Time-of-Arrival Mapping at Three-dimensional Time-resolved Contrast-enhanced MR Angiography1  

PubMed Central

This study was HIPAA compliant and institutional review board approved, and informed consent was obtained from all volunteers. The authors describe a method for generating a time-of-arrival (TOA) map of intravenously administered contrast material, as observed in a time series of three-dimensional (3D) contrast material–enhanced magnetic resonance (MR) angiograms. The method may enable visualization and interpretation, on one 3D image, of the temporal enhancement patterns that occur in the vasculature. Colorization of TOA values may further aid interpretation. The quality of the results depends not only on the adequacy of the frame rate, spatial resolution, and signal-to-noise ratio of the MR image acquisition method but also on the accuracy and clarity with which the leading edge of the contrast material bolus is depicted. The criteria for optimizing these parameters are described. The TOA mapping technique is demonstrated by using vascular studies of the hands, brain, and lower leg regions. © RSNA, 2009

Riederer, Stephen J.; Haider, Clifton R.; Borisch, Eric A.

2009-01-01

128

Arrival Time Correction for Dynamic Susceptibility Contrast MR Permeability Imaging in Stroke Patients  

PubMed Central

Purpose To determine if applying an arrival time correction (ATC) to dynamic susceptibility contrast (DSC) based permeability imaging will improve its ability to identify contrast leakage in stroke patients for whom the shape of the measured curve may be very different due to hypoperfusion. Materials and Methods A technique described in brain tumor patients was adapted to incorporate a correction for delayed contrast delivery due to perfusion deficits. This technique was applied to the MRIs of 9 stroke patients known to have blood-brain barrier (BBB) disruption on T1 post contrast imaging. Regions of BBB damage were compared with normal tissue from the contralateral hemisphere. Receiver operating characteristic (ROC) analysis was performed to compare the detection of BBB damage before and after ATC. Results ATC improved the area under the curve (AUC) of the ROC from 0.53 to 0.70. The sensitivity improved from 0.51 to 0.67 and the specificity improved from 0.57 to 0.66. Visual inspection of the ROC curve revealed that the performance of the uncorrected analysis was worse than random guess at some thresholds. Conclusions The ability of DSC permeability imaging to identify contrast enhancing tissue in stroke patients improved considerably when an ATC was applied. Using DSC permeability imaging in stroke patients without an ATC may lead to false identification of BBB disruption.

Leigh, Richard; Jen, Shyian S.; Varma, Daniel D.; Hillis, Argye E.; Barker, Peter B.

2012-01-01

129

Resolution for a local earthquake arrival time and ambient seismic noise tomography around the Eyjafjallajökull volcano  

NASA Astrophysics Data System (ADS)

The explosive summit eruption of Eyjafjallajökull volcano from 14 April to end of May 2010 was preceded by an effusive flank eruption of the volcano (at Fimmvörðuháls) March 20th - April 12th. These eruptions culminated 18 years of recurrent volcanic unrest in the area, with extensive seismicity and high deformation rates since beginning of January 2010. A national network of seismic stations in Iceland (the SIL network), operated by he Icelandic Meteorological Office, monitored the precursors and development of the eruptions, in real time. We analyse a seismic dataset available from SIL stations in the vicinity of the eruption area, as well as data from additional portable stations that were deployed during a period of unrest in 1999 and just before and during the eruptions in 2010. The SIL system detected and located 2328 events between early March and late May 2010 in the area around Eyjafjallajökull. Here we present a preliminary evaluation of resolution for a local earthquake arrival time tomography. Adding the portable stations to the pre-existing SIL data set is crucial in order to identify more seismic events and improve the data coverage for tomography. We also present a resolution analysis for Ambient Seismic Noise Tomography (ASNT) in the area. In this method ambient seismic noise, recorded at two seismic stations, is cross-correlated. This band-limited approximation of the Green's function between two stations is used to estimate surface wave velocities. The fundamental assumptions underlying this method is that the noise is constructed from a randomly distributed wavefield, but this may be violated by volcanic tremor during the eruptions. We evaluate the robustness of inter-station correlograms as a function of time during the unrest period as well as their frequency content for evaluation of depth resolution. The results can be compared to constraints on magma movements inside the volcano based on interpretation of crustal deformation and geochemical analyses.

Benediktsdóttir, Á.; Gudmundsson, Ö.; Tryggvason, A.; Bödvarsson, R.; Brandsdóttir, B.; Vogfjörd; K.; Sigmundsson, F.

2012-04-01

130

Design and Performance Evaluation on Ultra-Wideband Time-Of-Arrival 3D Tracking System  

NASA Technical Reports Server (NTRS)

A three-dimensional (3D) Ultra-Wideband (UWB) Time--of-Arrival (TOA) tracking system has been studied at NASA Johnson Space Center (JSC) to provide the tracking capability inside the International Space Station (ISS) modules for various applications. One of applications is to locate and report the location where crew experienced possible high level of carbon-dioxide and felt upset. In order to accurately locate those places in a multipath intensive environment like ISS modules, it requires a robust real-time location system (RTLS) which can provide the required accuracy and update rate. A 3D UWB TOA tracking system with two-way ranging has been proposed and studied. The designed system will be tested in the Wireless Habitat Testbed which simulates the ISS module environment. In this presentation, we discuss the 3D TOA tracking algorithm and the performance evaluation based on different tracking baseline configurations. The simulation results show that two configurations of the tracking baseline are feasible. With 100 picoseconds standard deviation (STD) of TOA estimates, the average tracking error 0.2392 feet (about 7 centimeters) can be achieved for configuration Twisted Rectangle while the average tracking error 0.9183 feet (about 28 centimeters) can be achieved for configuration Slightly-Twisted Top Rectangle . The tracking accuracy can be further improved with the improvement of the STD of TOA estimates. With 10 picoseconds STD of TOA estimates, the average tracking error 0.0239 feet (less than 1 centimeter) can be achieved for configuration "Twisted Rectangle".

Ni, Jianjun; Arndt, Dickey; Ngo, Phong; Dusl, John

2012-01-01

131

Correlation between X-Ray Light-Curve Shape and Radio Arrival Time in the Vela Pulsar  

NASA Astrophysics Data System (ADS)

We report the results of simultaneous observations of the Vela pulsar in X-rays and radio from the RXTE satellite and the Mount Pleasant Radio Observatory in Tasmania. We sought correlations between Vela's X-ray emission and radio arrival times on a pulse-by-pulse basis. At a confidence level of 99.8% we have found significantly higher flux density in Vela's main X-ray peak during radio pulses that arrived early. This excess flux shifts to the ``trough'' following the second X-ray peak during radio pulses that arrive later. Our results suggest that the mechanism producing the radio pulses is intimately connected to the mechanism producing X-rays. Current models using resonant absorption of radio emission in the outer magnetosphere as a cause of the X-ray emission are explored as a possible explanation for the correlation.

Lommen, A.; Donovan, J.; Gwinn, C.; Arzoumanian, Z.; Harding, A.; Strickman, M.; Dodson, R.; McCulloch, P.; Moffett, D.

2007-03-01

132

Combining Analyst and Waveform-Correlation-Based Arrival Time Measurements in the Bayesloc Multiple-Event Location Algorithm  

NASA Astrophysics Data System (ADS)

We implement an efficient waveform-correlation method to determine relative arrival times and we add relative arrival-time measurements to the Bayesloc multiple-event location algorithm. Because the arrival time of seismic phases is a powerful indicator of phase type, we use Bayesloc to probabilistically determine the phase labels for the correlation picks during simultaneous multiple-event location. Bayesloc is a formulation of joint probability over event locations, travel time corrections, phase labels, and arrival-time measurement errors. The Bayesloc formulation is hierarchical with distinct statistical models for each component of the multiple-event system, including prior constraints for any of the parameters. Bayes' Theorem allows calculation of the joint probability for hypothesized configurations of Bayesloc parameters, which facilitates using the Markov-Chain Monte Carlo (MCMC) method to draw samples from the joint probability function. The marginal posteriori distribution for each parameter or covariance between parameters is inferred from MCMC samples. Correlation-based picks are integrated into the Bayesloc formulation by including a new category of arrival time measurement that is derived from correlation of empirical waveforms. Because relative picks are derived from correlation between two waveforms and absolute-time picks are made by analysis of a single waveform - typically an analyst - error processes for relative and absolute arrival time measurements are modeled independently. Relative pick precision is formulated as a function of correlation coefficient and the time-bandwidth product of the correlated waveforms, and absolute arrival times precision - as described in previous work - is formulated as a function phase type, the station, and the individual event. We adopt widely used methodologies for computing differential times based on waveform cross correlation. We first collect all waveforms for a given station and event cluster. A user-specified, phase-specific bandpass filter is applied to each waveform and the phase window is cut from the seismogram based on either analyst picks or a theoretical arrival time. We then compute and save the Fourier transform of each phase-windowed seismogram. Complex multiplication in the frequency domain is used to compute auto correlation and cross correlation spectra. Cross correlation spectra are inverse transformed and normalized based on the average of the autocorrelation amplitudes to produce a normalized, time-domain correlation function. The correlation coefficient is the peak of the correlation function and the time shift is the offset of the peak from the center of the correlation function. The time shift and the correlation coefficient are refined by fitting a parabolic function to the sample points in the neighborhood of the peak in the time-domain correlation function, which allows sub-sample precision for the correlation pick. The difference in time between the arrivals is computed by differencing the start time of the phase windows and adding the correlation-based time shift. Prepared by LLNL under Contract DE-AC52-07NA27344. LLNL-CONF-490688.

Myers, S. C.; Johannesson, G.; Dodge, D. A.; Simmons, N. A.

2011-12-01

133

The influence of photon peak arrival in the timing of plastic scintillators by means of pulsed laser and optical fibers  

Microsoft Academic Search

The influence of photon peak arrival in the laser-optical fibers timing system of a large array of plastic scintillators has been studied for different types of photomultipliers. The obtained results, helpful in properly designing the system are presented and discussed.

Pietro Benetti; Massimo Genoni; Alessandra Tomaselli

1988-01-01

134

The Development of a General Associative Learning Account of Skill Acquisition in a Relative Arrival-Time Judgment Task  

ERIC Educational Resources Information Center

Current theory assumes that individuals only use information from the immediate environment to perform relative arrival-time judgment tasks. This article presents a theoretical analysis of the memory requirements of this task. The authors present an analysis of the inputs to the memory system and the processes that map those inputs onto outputs.…

Loft, Shayne; Neal, Andrew; Humphreys, Michael S.

2007-01-01

135

Annual variation in arrival and departure times of carrion insects at carcasses: implications for succession studies in forensic entomology  

Microsoft Academic Search

A succession of insect species associate with decaying bodies, and because of the relatively predictable arrival and departure times of many species, this process is routinely used to estimate minimum post-mortem interval. Corpse fauna are compared with baseline data on succession rates, which are usually taken from decomposing animal carcasses. Baseline data are traditionally collected over a single year only;

M. S. Archer

2003-01-01

136

Development of the town data base: Estimates of exposure rates and times of fallout arrival near the Nevada Test Site.  

National Technical Information Service (NTIS)

As part of the U.S. Department of Energy's Off-Site Radiation Exposure Review Project, the time of fallout arrival and the H+12 exposure rate were estimated for populated locations in Arizona, California, Nevada, and Utah that were affected by fallout fro...

C. B. Thompson R. D. McArthur S. W. Hutchinson

1994-01-01

137

Practical solutions to the aircraft minimum fuel, fixed-range, fixed time-of-arrival trajectory optimization problem  

NASA Technical Reports Server (NTRS)

A practical scheme is presented for generating fixed range, minimum fuel vertical flight profiles that also satisfy time-of-arrival constraints. The resulting algorithm is suitable for incorporation into an on-board flight management system. Example results show that such a capability can save up to 6% of fuel burned in flights subject to delays because of terminal area congestion.

Sorensen, J. A.; Waters, M. H.

1980-01-01

138

`Inter-Arrival Time' Inspired Algorithm and its Application in Clustering and Molecular Phylogeny  

NASA Astrophysics Data System (ADS)

Bioinformatics, being multidisciplinary field, involves applications of various methods from allied areas of Science for data mining using computational approaches. Clustering and molecular phylogeny is one of the key areas in Bioinformatics, which help in study of classification and evolution of organisms. Molecular phylogeny algorithms can be divided into distance based and character based methods. But most of these methods are dependent on pre-alignment of sequences and become computationally intensive with increase in size of data and hence demand alternative efficient approaches. `Inter arrival time distribution' (IATD) is a popular concept in the theory of stochastic system modeling but its potential in molecular data analysis has not been fully explored. The present study reports application of IATD in Bioinformatics for clustering and molecular phylogeny. The proposed method provides IATDs of nucleotides in genomic sequences. The distance function based on statistical parameters of IATDs is proposed and distance matrix thus obtained is used for the purpose of clustering and molecular phylogeny. The method is applied on a dataset of 3' non-coding region sequences (NCR) of Dengue virus type 3 (DENV-3), subtype III, reported in 2008. The phylogram thus obtained revealed the geographical distribution of DENV-3 isolates. Sri Lankan DENV-3 isolates were further observed to be clustered in two sub-clades corresponding to pre and post Dengue hemorrhagic fever emergence groups. These results are consistent with those reported earlier, which are obtained using pre-aligned sequence data as an input. These findings encourage applications of the IATD based method in molecular phylogenetic analysis in particular and data mining in general.

Kolekar, Pandurang S.; Kale, Mohan M.; Kulkarni-Kale, Urmila

2010-10-01

139

Influence and timing of arrival of murine neural crest on pancreatic beta cell development and maturation  

PubMed Central

Interactions between cells from the ectoderm and mesoderm influence development of the endodermally-derived pancreas. While much is known about how mesoderm regulates pancreatic development, relatively little is understood about how and when the ectodermally-derived neural crest regulates pancreatic development and specifically, beta cell maturation. A previous study demonstrated that signals from the neural crest regulate beta cell proliferation and ultimately, beta cell mass. Here, we expand on that work to describe timing of neural crest arrival at the developing pancreatic bud and extend our knowledge of the non-cell autonomous role for neural crest derivatives in the process of beta cell maturation. We demonstrated that murine neural crest entered the pancreatic mesenchyme between the 26 and 27 somite stages (approximately 10.0 dpc) and became intermingled with pancreatic progenitors as the epithelium branched into the surrounding mesenchyme. Using a neural crest-specific deletion of the Forkhead transcription factor Foxd3, we ablated neural crest cells that migrate to the pancreatic primordium. Consistent with previous data, in the absence of Foxd3, and therefore the absence of neural crest cells, proliferation of Insulin-expressing cells and Insulin-positive area are increased. Analysis of endocrine cell gene expression in the absence of neural crest demonstrated that, although the number of Insulin-expressing cells was increased, beta cell maturation was significantly impaired. Decreased MafA and Pdx1 expression illustrated the defect in beta cell maturation; we discovered that without neural crest, there was a reduction in the percentage of Insulin-positive cells that co-expressed Glut2 and Pdx1 compared to controls. In addition, transmission electron microscopy analyses revealed decreased numbers of characteristic Insulin granules and the presence of abnormal granules in Insulin-expressing cells from mutant embryos. Together, these data demonstrate that the neural crest is a critical regulator of beta cell development on two levels: by negatively regulating beta cell proliferation and by promoting beta cell maturation.

Plank, Jennifer L.; Mundell, Nathan A.; Frist, Audrey Y.; LeGrone, Alison W.; Kim, Thomas; Musser, Melissa A.; Walter, Teagan J.; Labosky, Patricia A.

2010-01-01

140

Time difference of arrival to blast localization of potential chemical/biological event on the move  

NASA Astrophysics Data System (ADS)

Integrating a sensor suite with ability to discriminate potential Chemical/Biological (CB) events from high-explosive (HE) events employing a standalone acoustic sensor with a Time Difference of Arrival (TDOA) algorithm we developed a cueing mechanism for more power intensive and range limited sensing techniques. Enabling the event detection algorithm to locate to a blast event using TDOA we then provide further information of the event as either Launch/Impact and if CB/HE. The added information is provided to a range limited chemical sensing system that exploits spectroscopy to determine the contents of the chemical event. The main innovation within this sensor suite is the system will provide this information on the move while the chemical sensor will have adequate time to determine the contents of the event from a safe stand-off distance. The CB/HE discrimination algorithm exploits acoustic sensors to provide early detection and identification of CB attacks. Distinct characteristics arise within the different airburst signatures because HE warheads emphasize concussive and shrapnel effects, while CB warheads are designed to disperse their contents over large areas, therefore employing a slower burning, less intense explosive to mix and spread their contents. Differences characterized by variations in the corresponding peak pressure and rise time of the blast, differences in the ratio of positive pressure amplitude to the negative amplitude, and variations in the overall duration of the resulting waveform. The discrete wavelet transform (DWT) is used to extract the predominant components of these characteristics from air burst signatures at ranges exceeding 3km. Highly reliable discrimination is achieved with a feed-forward neural network classifier trained on a feature space derived from the distribution of wavelet coefficients and higher frequency details found within different levels of the multiresolution decomposition. The development of an adaptive noise floor to provide early event detection assists in minimizing the false alarm rate and increasing the confidence whether the event is blast event or back ground noise. The integration of these algorithms with the TDOA algorithm provides a complex suite of algorithms that can give early warning detection and highly reliable look direction from a great stand-off distance for a moving vehicle to determine if a candidate blast event is CB and if CB what is the composition of the resulting cloud.

Morcos, Amir; Desai, Sachi; Peltzer, Brian; Hohil, Myron E.

2007-10-01

141

Probability distributions of travel time and intensity of the earliest arrivals of a short pulse backscattered by a rough surface  

NASA Astrophysics Data System (ADS)

Precise measurements of the travel times of backscattered waves, and especially the travel times of the first (i.e., earliest) arrivals, underlie a number of geophysical remote sensing techniques. In this paper, statistical properties of the travel time and intensity of pulses backscattered by a two-dimensional rough surface are investigated within the geometric optics approximation by adopting a method originally developed in the theory of excursions of a stochastic process. We assume a wave source located sufficiently far from a rough surface with Gaussian statistics, and show that the probability distribution functions of the normalized deviation of the travel time of the first and second backscattered pulses from the travel time in the absence of roughness, are functions of a single dimensionless parameter, T = ggr20H/(2pgrsgr), where sgr2 and ggr20 are the variances of the rough surface elevation and slope, and H is the source altitude. Signals from the rough surface return to the source location earlier than from the mean plane by O(2sgr/c), where c is the velocity of wave propagation. On average, the travel times of the first and second arrivals decrease as parameter T increases, with the travel time shift being proportional to \\sqrt{\\ln T} . The time delay between the first and the second arrivals is inversely proportional to \\sqrt{\\ln T} . The joint probability density functions (PDF) of the travel times and the intensities of the first two backscattered pulses are derived. This allows us to obtain the travel time PDF for signals exceeding the given intensity threshold. It is shown that the travel time and the intensity are strongly correlated: on average, earlier arrivals have smaller amplitudes.

Fuks, Iosif M.; Godin, Oleg A.

2004-10-01

142

A three-dimensional P wave velocity model for the Charlevoix seismic zone, Quebec, Canada  

NASA Astrophysics Data System (ADS)

A three-dimensional P wave velocity model has been developed for the Charlevoix seismic zone (CSZ). The CSZ is located along the St. Lawrence River ˜100 km northeast of Quebec City, Canada, and is one of the most active seismic zones in eastern North America. Five earthquakes with magnitudes equal to or exceeding 6.0 have occurred in the CSZ in historic time, and around 200 earthquakes occur annually. Hypocenters are located in Precambrian basement rocks. Basement rocks have been affected by numerous tectonic events including Grenvillian collision, Iapetan rifting, and meteor impact. We performed a sequential, tomographic inversion for P wave velocity structure based upon 3093 P wave arrivals from 489 earthquakes recorded by 12 stations. High velocity is associated with the center of the impact crater. The region of high velocity is surrounded by low velocities interpreted to be highly disrupted rocks. An elongated, high-velocity region is present at midcrustal depths that trends parallel to the St. Lawrence River. Earthquakes avoid the high-velocity body and separate into two bands, one on either side of the feature. Larger earthquakes (magnitude ? 4) have occurred along the northern edges of the high-velocity region.

Vlahovic, Gordana; Powell, Christine; Lamontagne, Maurice

2003-09-01

143

YO!-A Time-of-Arrival Receiver for Removal of Femtosecond Helicity-Correlated Beam Effects  

SciTech Connect

The G0 parity violation experiment at Jefferson Lab is based on time-of-flight measurements, and is sensitive to timing effects between the two electron helicity states of the beam. Photon counters triggered by time-of-arrival at the target mandate that timing must be independent of delays associated with different orbits taken by the two helicity states. In addition, the standard 499 MHz beam structure is altered such that 1 of every 16 microbunches are filled, resulting in an arrival frequency of 31.1875 (31) MHz, and an average current of 40 {micro}A. Helicity correction involves identifying and tracking the 31 MHz subharmonic, applying a fast/fine phase correction, and finally producing a clean 31 MHz trigger and a 499 MHz clock train. These signals are phase-matched to the beam arrival at the target on the order of femtoseconds. The 10 kHz output bandwidth is sufficiently greater than the 30 Hz helicity flip settling time (500 {micro}s). This permits the system to correct each helicity bin for any orbit-induced timing inequalities. A sampling phase detection scheme is used in order to eliminate the unavoidable 2n/n phase shifts associated with frequency dividers. Conventional receiver architecture and DSP techniques are combined for maximum sensitivity, bandwidth, and flexibility. Results of bench tests, commissioning and production data will be presented.

John Musson; Trent Allison; Arne Freyberger; Joachim Kuhn; Brian Quinn

2004-05-02

144

YO{exclamation_point} - A Time-of-Arrival Receiver for Removal of Femtosecond Helicity-Correlated Beam Effects  

SciTech Connect

The G0 parity violation experiment at Jefferson Lab is based on time-of-flight measurements, and is sensitive to timing effects between the two electron helicity states of the beam. Photon counters triggered by time-of-arrival at the target mandate that timing must be independent of delays associated with different orbits taken by the two helicity states. In addition, the standard 499 MHz beam structure is altered such that 1 of every 16 microbunches are filled, resulting in an arrival frequency of 31.1875 (31) MHz, and an average current of 40 {mu}A. Helicity correction involves identifying and tracking the 31 MHz sub-harmonic, applying a fast/fine phase correction, and finally producing a clean 31 MHz trigger and a 499 MHz clock train. These signals are phase-matched to the beam arrival at the target on the order of femtoseconds. The 10 kHz output bandwidth is sufficiently greater than the 30 Hz helicity flip settling time (500 {mu}s). This permits the system to correct each helicity bin for any orbit-induced timing inequalities. A sampling phase detection scheme is used in order to eliminate the unavoidable 2n/n phase shifts associated with frequency dividers. Conventional receiver architecture and DSP techniques are combined for maximum sensitivity, bandwidth, and flexibility. Results of bench tests, commissioning and production data will be presented.

Musson, J.; Allison, T.; Freyberger, A. [TJNAF, Newport News, VA 23606 (United States); Kuhn, J.; Quinn, B. [Carnegie-Mellon University, Pittsburgh, PA 15213 (United States)

2004-11-10

145

Seismic imaging of the entire arc of Tohoku and Hokkaido in Japan using P-wave, S-wave and sP depth-phase data  

Microsoft Academic Search

In order to better understand seismic structure and seismotectonics of the entire arc of Tohoku and Hokkaido in Japan, we combined arrival time data from earthquakes beneath Tohoku and Hokkaido land areas, and beneath the Pacific Ocean to determine the three-dimensional (3D) velocity structures (Vp and Vs) under the entire Northeast (NE) Japan–Kuril arc. We adopted 176,431 P-wave and 110,953

Zhi Wang; Dapeng Zhao

2005-01-01

146

Operational warning of interplanetary shock arrivals using energetic particle data from ACE: Real-time Upstream Monitoring System  

NASA Astrophysics Data System (ADS)

We report on an operational system which provides advance warning and predictions of arrival times at Earth of interplanetary (IP) shocks that originate at the Sun. The data stream used in our prediction algorithm is real-time and comes from the Electron, Proton, and Alpha Monitor (EPAM) instrument on NASA's Advanced Composition Explorer (ACE) spacecraft. Since locally accelerated energetic storm particle (ESP) events accompany most IP shocks, their arrival can be predicted using ESP event signatures. We have previously reported on the development and implementation of an algorithm which recognizes the upstream particle signature of approaching IP shocks and provides estimated countdown predictions. A web-based system (see (http://sd-www.jhuapl.edu/UPOS/RISP/index.html) combines this prediction capability with real-time ACE/EPAM data provided by the NOAA Space Environment Center. The most recent ACE data is continually processed and predictions of shock arrival time are updated every five minutes when an event is impending. An operational display is provided to indicate advisories and countdowns for the event. Running the algorithm on a test set of historical events, we obtain a median error of about 10 hours for predictions made 24-36 hours before actual shock arrival and about 6 hours when the shock is 6-12 hours away. This system can provide critical information to mission planners, satellite operations controllers, and scientists by providing significant lead-time for approaching events. Recently, we have made improvements to the triggering mechanism as well as re-training the neural network, and here we report prediction results from the latest system.

Donegan, M.; Vandegriff, J.; Ho, G. C.; Julia, S. J.

2004-12-01

147

Timepix, a 65k programmable pixel readout chip for arrival time, energy and/or photon counting measurements  

NASA Astrophysics Data System (ADS)

A novel approach for the readout of a TPC at the future linear collider is to use a CMOS pixel detector combined with some kind of gas gain grid. A first test using the photon counting chip Medipix2 with GEM or Micromegas demonstrated the feasibility of such an approach. Although this experiment demonstrated that single primary electrons could be detected the chip did not provide information on the arrival time of the electron in the sensitive gas volume nor did it give any indication of the quantity of charge detected. The Timepix chip uses an external clock with a frequency of up to 100 MHz as a time reference. Each pixel contains a preamplifier, a discriminator with hysteresis and 4-bit DAC for threshold adjustment, synchronization logic and a 14-bit counter with overflow control. Moreover, each pixel can be independently configured in one of four different modes: masked mode: pixel is off, counting mode: 1-count for each signal over threshold, TOT mode: the counter is incremented continuously as long as the signal is above threshold, and arrival time mode: the counter is incremented continuously from the time the first hit arrives until the end of the shutter. The chip resembles very much the Medipix2 chip physically and can be readout using slightly modified versions of the various existing systems. This paper presents the main features of the new design, electrical measurements and some first images.

Llopart, X.; Ballabriga, R.; Campbell, M.; Tlustos, L.; Wong, W.

2007-10-01

148

Search for Coincidences in Time and Arrival Direction of Auger Data with Astrophysical Transients  

SciTech Connect

The data collected by the Pierre Auger Observatory are analyzed to search for coincidences between the arrival directions of high-energy cosmic rays and the positions in the sky of astrophysical transients. Special attention is directed towards gamma ray observations recorded by NASA's Swift mission, which have an angular resolution similar to that of the Auger surface detectors. In particular, we check our data for evidence of a signal associated with the giant flare that came from the soft gamma repeater 1806-20 on December 27, 2004.

Anchordoqui, Luis; Collaboration, for the Pierre Auger

2007-06-01

149

Fast computation algorithm of ray-paths and their travel times including later arrivals for a multi layered earth model  

Microsoft Academic Search

Seismic tomography techniques have been rapidly developed to interpret crustal seismic refraction data. Forward modeling approaches, however, are also necessary to examine an initial model for inversion and\\/or later phases. Ray-paths and travel times of later phases, as well as fastest arrivals, such as reflection, later refraction and P-SV converted waves, provide indispensable information for seismic crustal structure analyses. Although

R. Kubota; E. Nishiyama; K. Murase; J. Kasahara

2005-01-01

150

Correlation between X-Ray Light-Curve Shape and Radio Arrival Time in the Vela Pulsar  

Microsoft Academic Search

We report the results of simultaneous observations of the Vela pulsar in X-rays and radio from the RXTE satellite and the Mount Pleasant Radio Observatory in Tasmania. We sought correlations between Vela's X-ray emission and radio arrival times on a pulse-by-pulse basis. At a confidence level of 99.8% we have found significantly higher flux density in Vela's main X-ray peak

A. Lommen; J. Donovan; C. Gwinn; Z. Arzoumanian; A. Harding; M. Strickman; R. Dodson; P. McCulloch; D. Moffett

2007-01-01

151

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?  

Code of Federal Regulations, 2013 CFR

...Property Management 4 2013-07-01 2012-07-01 true Am I required to record departure/arrival dates and times on my...EXPENSES 11-PER DIEM EXPENSES General Rules § 301-11.10 Am I required to record departure/arrival dates and times on...

2013-07-01

152

The Initial Busy Cycle of a Discrete-Time GI/G/1 Queue in which the Inter-Arrival Times are not Necessarily Identically Distributed.  

National Technical Information Service (NTIS)

This paper studies a generalization of the discrete-time GI/G/1 queueing system. Here, the inter-arrival times are not necessarily identically distributed. A recursive scheme is derived to obtain the joint distribution of the duration of the initial busy ...

D. L. Minh

1979-01-01

153

Using soft X-ray observations to help the prediction of flare related interplanetary shocks arrival times at the Earth  

NASA Astrophysics Data System (ADS)

It is very important to predict the shock arrival times (SATs) at Earth for space weather practice. In this paper we use the energy of soft X-ray during solar flare events to help predict the SATs at Earth. We combine the soft X-ray energy and SAT prediction models previously developed by researchers to obtain two new methods. By testing the methods with the total of 585 solar flare events following the generation of a metric type II radio burst during the Solar Cycle 23 from September 1997 to December 2006, we find that the predictions of SATs at Earth could be improved by significantly increasing PODn, the proportion of events without shock detection that were correctly forecast. PODn represents a method's ability in forecasting the solar flare events without shocks arriving at the Earth, which is important for operational predictions.

Liu, H.-L.; Qin, G.

2012-04-01

154

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles  

DOEpatents

An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Benjamin, R.F.

1983-10-18

155

Optical pin apparatus for measuring the arrival time and velocity of shock waves and particles  

DOEpatents

An apparatus for the detection of the arrival and for the determination of the velocity of disturbances such as shock-wave fronts and/or projectiles. Optical pins using fluid-filled microballoons as the light source and an optical fiber as a link to a photodetector have been used to investigate shock-waves and projectiles. A microballoon filled with a noble gas is affixed to one end of a fiber-optic cable, and the other end of the cable is attached to a high-speed streak camera. As the shock-front or projectile compresses the microballoon, the gas inside is heated and compressed producing a bright flash of light. The flash of light is transmitted via the optic cable to the streak camera where it is recorded. One image-converter streak camera is capable of recording information from more than 100 microballoon-cable combinations simultaneously.

Benjamin, Robert F. (315 Rover Blvd., Los Alamos, NM 87544)

1987-01-01

156

Connecting Speeds, Directions and Arrival Times of 22 Coronal Mass Ejections from the Sun to 1 AU  

NASA Astrophysics Data System (ADS)

Forecasting the in situ properties of coronal mass ejections (CMEs) from remote images is expected to strongly enhance predictions of space weather and is of general interest for studying the interaction of CMEs with planetary environments. We study the feasibility of using a single heliospheric imager (HI) instrument, imaging the solar wind density from the Sun to 1 AU, for connecting remote images to in situ observations of CMEs. We compare the predictions of speed and arrival time for 22 CMEs (in 2008-2012) to the corresponding interplanetary coronal mass ejection (ICME) parameters at in situ observatories (STEREO PLASTIC/IMPACT, Wind SWE/MFI). The list consists of front- and backsided, slow and fast CMEs (up to 2700 km s-1). We track the CMEs to 34.9 ± 7.1 deg elongation from the Sun with J maps constructed using the SATPLOT tool, resulting in prediction lead times of -26.4 ± 15.3 hr. The geometrical models we use assume different CME front shapes (fixed-?, harmonic mean, self-similar expansion) and constant CME speed and direction. We find no significant superiority in the predictive capability of any of the three methods. The absolute difference between predicted and observed ICME arrival times is 8.1 ± 6.3 hr (rms value of 10.9 hr). Speeds are consistent to within 284 ± 288 km s-1. Empirical corrections to the predictions enhance their performance for the arrival times to 6.1 ± 5.0 hr (rms value of 7.9 hr), and for the speeds to 53 ± 50 km s-1. These results are important for Solar Orbiter and a space weather mission positioned away from the Sun-Earth line.

Möstl, C.; Amla, K.; Hall, J. R.; Liewer, P. C.; De Jong, E. M.; Colaninno, R. C.; Veronig, A. M.; Rollett, T.; Temmer, M.; Peinhart, V.; Davies, J. A.; Lugaz, N.; Liu, Y. D.; Farrugia, C. J.; Luhmann, J. G.; Vršnak, B.; Harrison, R. A.; Galvin, A. B.

2014-06-01

157

Near-surface seismic imaging using first arrival time inversion with pre-stack depth migration  

NASA Astrophysics Data System (ADS)

This paper presents a hybrid acquisition strategy for imaging near surface stratigraphy. Shallow seismic depth imaging studies typically involve data processing followed by velocity estimation and migration. Most researchers apply the commonly used conventional processing (stacking velocity analysis) for velocity model building that in turn is used in migration. However, we find that when it comes to shallow imaging, the conventional processing lacks accuracy in velocity model estimation, which consequently leads to poor quality in depth image. To improve the velocity model reliability, we followed an unconventional procedure: first arrival inversion combined with prestack Kirchhoff depth migration. We demonstrate the imaging application for an ultra shallow (<15m) geological target, which is a set of paleo-channels in the Bull Creek, Beaver County, Oklahoma. To demonstrate the concept two coincident profiles were acquired - one targeted towards inversion and the other towards migration. Besides migrating data with the inversion model, we also migrate the data with velocity model developed though conventional processing. We compare the results to illustrate that significant improvements can be made in imaging of the shallow subsurface by using velocity models created by traveltime inversion.

Woldearegay, Ammanuel Fesseha

158

Connecting speeds, directions and arrival times of 22 coronal mass ejections from the Sun to 1 AU  

NASA Astrophysics Data System (ADS)

Forecasting in situ properties of coronal mass ejections (CMEs) from remote images is expected to strongly enhance predictions of space weather, and is of general interest for studying the interaction of the solar wind with planetary environments. We study the feasibility of using a heliospheric imager (HI) instrument, which is able to image the solar wind density along the full Sun to 1 AU distance, for connecting remote images to in situ observations of CMEs. Such an instrument is currently in operation on each of the two STEREO spacecraft. We compare the predictions for speed and arrival time for 22 different CME events (between 2008-2012), each observed remotely by one STEREO spacecraft, to the interplanetary coronal mass ejection (ICME) speed and arrival time observed at in situ observatories (STEREO PLASTIC/IMPACT, Wind SWE/MFI). We use croissant modeling for STEREO/COR2, and with a single-spacecraft STEREO/HI instrument, we track each CME to 34.9 ± 7.1 degree elongation from the Sun with J-maps constructed with the SATPLOT tool. We then fit geometrical models to each track, assuming different CME front shapes (Fixed-?, Harmonic Mean, Self-Similar Expansion), and constant CME speed and direction. We find no significant preference in the predictive capability for any of the three geometrical modeling methods used on the full event list, consisting of front- and backsided, slow and fast CMEs (up to 2700 km s-1). The absolute difference between predicted and observed ICME arrival times is 8.1 ± 6.4 hours (rms value of 10.9h), and speeds are consistent within 284 ± 291 km s-1, including the geometric effects of CME apex or flank encounters. We derive new empirical corrections to the imaging results, enhancing the performance of the arrival time predictions to 6.1 ± 5.0 hours (rms value of 7.9h), and the speed predictions to 53 ± 50 km s-1, for this particular set of events. The prediction lead time is around 1 day (-26.4 ± 15.3h). CME directions given by the HI methods differ considerably, and biases are found on the order of 30-50 degree in heliospheric longitude, consistent with theoretical expectations. These results are of interest concerning future missions such as Solar Orbiter or a dedicated space weather mission positioned remotely from the Earth.

Möstl, Christian; Amla, Keshav; Hall, Jeff R.; Liewer, Paulett C.; DeJong, Eric M.; Colaninno, Robin C.; Veronig, Astrid M.; Rollett, Tanja; Temmer, Manuela; Peinhart, Vanessa; Davies, Jackie A.; Lugaz, Noé; Liu, Ying; Farrugia, Charles J.; Luhmann, Janet G.; Vrsnak, Bojan; Harrison, Richard A.; Galvin, Antoinette B.

2014-05-01

159

Alignment of leading-edge and peak-picking time of arrival methods to obtain accurate source locations  

SciTech Connect

The location of a radiating source can be determined by time-tagging the arrival of the radiated signal at a network of spatially distributed sensors. The accuracy of this approach depends strongly on the particular time-tagging algorithm employed at each of the sensors. If different techniques are used across the network, then the time tags must be referenced to a common fiducial for maximum location accuracy. In this report we derive the time corrections needed to temporally align leading-edge, time-tagging techniques with peak-picking algorithms. We focus on broadband radio frequency (RF) sources, an ionospheric propagation channel, and narrowband receivers, but the final results can be generalized to apply to any source, propagation environment, and sensor. Our analytic results are checked against numerical simulations for a number of representative cases and agree with the specific leading-edge algorithm studied independently by Kim and Eng (1995) and Pongratz (2005 and 2007).

Roussel-Dupre, R.; Symbalisty, E.; Fox, C.; and Vanderlinde, O.

2009-08-01

160

A New Version of the Shock Propagation Model (SPM2) for Predicting the Arrival Time of Interplanetary Shocks  

NASA Astrophysics Data System (ADS)

Forecasting the arrival time at the near Earth space of interplanetary (IP) shocks following the solar disturbances is one of the important ingredients of space weather prediction. Shock Propagation Model (SPM), based on the analytic solution of the blast wave theory, is one of the models to predict the shock arrival time (SAT). The input parameters of SPM include the initial shock speed, the duration time of the X-ray flare, and the background solar wind speed. Considering the fact that the measurement errors exist in the input parameters as well as the shortage of the theoretical model in real applications, a new version of SPM, called SPM2 is presented with the aim of overcome these shortages. Firstly, SPM is used to train the input data, and an empirical relationship is established to correct for the error in the initial shock speed (computed from the type II burst drafting speed). And the corrected shock speed is used is the SPM2 model. Secondly, a large number of data set during solar cycle 23 are adopted to train the model, and an additional acceleration/deceleration relation is added in SPM2. Thirdly, the propagating direction is introduced as one of the contributing factors to the shock's arrival at Earth, which overcomes the shortage of the isotropy of the blast wave theory in the practice of real prediction. Finally, SPM2 adopts an equivalent Mach number of the shock at 1 AU in order to judge whether or not the shock could reach the Earth. 584 flare-type II related shock events during Solar Cycle 23 are used to test the prediction capability of the SPM2 model. Several standard meteorological forecast skill scores of SPM2 are also computed. The corresponding success rates of SPM2 for both shock and non-shock events at Earth are above 60%, and the application of a x2 test demonstrates that the predictions of the model are statistically significant. As for the predicting accuracy in shock arrival time, the root-mean-square err of ?T of SPM2 is less than 12 hours, and its mean-absolute err is below 10 hours.

Zhao, X.; Feng, X.

2012-12-01

161

Numerical simulation of the propagation of P waves in fractured media  

NASA Astrophysics Data System (ADS)

We study the propagation of P waves through media containing open fractures by performing numerical simulations. The important parameter in such problems is the ratio between crack length and incident wavelength. When the wavelength of the incident wavefield is close to or shorter than the crack length, the scattered waves are efficiently excited and the attenuation of the primary waves can be observed on synthetic seismograms. On the other hand, when the incident wavelength is greater than the crack length, we can simulate the anisotropic behaviour of fractured media resulting from the scattering of seismic waves by the cracks through the time delay of the arrival of the transmitted wave. The method of calculation used is a boundary element method in which the Green's functions are computed by the discrete wavenumber method. For simplicity, the 2-D elastodynamic diffraction problem is considered. The rock matrix is supposed to be elastic, isotropic and homogeneous, while the cracks are all empty and have the same length and strike direction. An iterative method of calculation of the diffracted wavefield is developed in the case where a large number of cracks are present in order to reduce the computation time. The attenuation factor Q^-1 of the direct waves passing through a fractured zone is measured in several frequency bands. We observe that the attenuation factor Q^-1 of the direct P wave peaks around kd=2, where k is the incident wavenumber and d the crack length, and decreases proportionally to (kd)^-1 in the high-wavenumber range. In the long-wavelength domain, the velocity of the direct P wave measured for two different crack realizations is very close to the value predicted by Hudson's theory on the overall elastic properties of fractured materials.

Kelner, Sylvie; Bouchon, Michel; Coutant, Olivier

1999-04-01

162

Time of arrival of gravid Culex pipiens fatigans at an oviposition site, the oviposition cycle and the relationship between time of feeding and time of oviposition*  

PubMed Central

One of the most important activities in a female mosquito's life is the flight to the breeding place and the subsequent deposition of eggs. During this phase, motivated by endogenous and exogenous stimuli, the female is particularly exposed and susceptible to attack. It is therefore important to investigate these episodes in the gravid female's life. The work reported in this paper shows that gravid Culex pipiens fatigans females are easily trapped over breeding-water; there are two peaks in the arrival at a breeding site, one just after sunset and the other at sunrise. The oviposition cycle is biphasic, the two peaks coinciding, in calm weather, with the two arrival peaks; wind and rain cause marked disturbances in the oviposition cycle. The mean duration of the gonotrophic cycle depends on the time of feeding; this finding is of practical importance since the length of the cycle is often used to calculate the daily survival rate of adult mosquitos. It appears that oviposition is stimulated by a change in light: from light to dark for mosquitos ovipositing in the evening and from dark to light for those ovipositing in the morning. Apart from revealing some hitherto unknown behaviour patterns, the techniques evolved could also be used in the assessment of mosquito populations and hence the effects of control measures.

de Meillon, Botha; Sebastian, Anthony; Khan, Z. H.

1967-01-01

163

First arrival time tomography for a near vertical reflection seismic profile in the Kaokoland region in Northern Namibia - first results  

NASA Astrophysics Data System (ADS)

Within the LISPWAL project (part of the SAMPLE SPP), in 2012 a Near Vertical Reflection (NVR) Seismic profile was generated in the Kaokoland region in Northern Namibia. 150 (25kg) controlled source shots at ~1350 m spacing were conducted along a 200 km North-South profile. A spread of 300 seismic stations, spaced 100 m apart, was moved in a roll-along style, to collect data suitable for standard reflection seismic processing and first arrival time tomography. Travel time data of seismic phases are used as input data to derive shallow velocity models of compressional waves (P), shear waves (S) and the Vp/Vs ratio. Using First Arrival Seismic Tomography (FAST) software, we derive shallow tomographic models for the upper 1 to 1.5 km. All three models are characterized by significant differences between the northern and the southern part. In the south P- and S-velocities are higher and Vp/Vs ratios lower while in the north the P- and S-velocities are lower while the Vp/Vs ratios show higher values.

Braeuer, Benjamin; Ryberg, Trond; Haberland, Christian; Bauer, Klaus; Weber, Michael

2014-05-01

164

Three-dimensional P-wave velocity structure of Mt. Etna, Italy  

USGS Publications Warehouse

The three-dimensional P-wave velocity structure of Mt. Etna is determined to depths of 15 km by tomographic inversion of first arrival times from local earthquakes recorded by a network of 29 permanent and temporary seismographs. Results show a near-vertical low-velocity zone that extends from beneath the central craters to a depth of 10 km. This low-velocity region is coincident with a band of steeply-dipping seismicity, suggesting a magmatic conduit that feeds the summit eruptions. The most prominent structure is an approximately 8-km-diameter high-velocity body located between 2 and 12 km depth below the southeast flank of the volcano. This high-velocity body is interpreted as a remnant mafic intrusion that is an important structural feature influencing both volcanism and east flank slope stability and faulting.

Villasenor, A.; Benz, H. M.; Filippi, L.; De Luca, G.; Scarpa, R.; Patane, G.; Vinciguerra, S.

1998-01-01

165

On the possibility to discriminate the mass of the primary cosmic ray using the muon arrival times from extensive air showers: Application for Pierre Auger Observatory  

NASA Astrophysics Data System (ADS)

In this paper we study the possibility to discriminate the mass of the primary cosmic ray by observing the muon arrival times in ground detectors. We analyzed extensive air showers (EAS) induced by proton and iron nuclei with the same energy 8×1017 eV simulated with CORSIKA, and analyzed the muon arrival times at ground measured by the infill array detectors of the Pierre Auger Observatory (PAO). From the arrival times of the core and of the muons the atmospheric depth of muon generation locus is evaluated. The results suggest a potential mass discrimination on the basis of muon arrival times and of the reconstructed atmospheric depth of muon production. An analysis of a larger set of CORSIKA simulations carried out for primary energies above 1018 eV is in progress.

Arsene, N.; Rebel, H.; Sima, O.

2012-11-01

166

On the possibility to discriminate the mass of the primary cosmic ray using the muon arrival times from extensive air showers: Application for Pierre Auger Observatory  

SciTech Connect

In this paper we study the possibility to discriminate the mass of the primary cosmic ray by observing the muon arrival times in ground detectors. We analyzed extensive air showers (EAS) induced by proton and iron nuclei with the same energy 8 Multiplication-Sign 10{sup 17} eV simulated with CORSIKA, and analyzed the muon arrival times at ground measured by the infill array detectors of the Pierre Auger Observatory (PAO). From the arrival times of the core and of the muons the atmospheric depth of muon generation locus is evaluated. The results suggest a potential mass discrimination on the basis of muon arrival times and of the reconstructed atmospheric depth of muon production. An analysis of a larger set of CORSIKA simulations carried out for primary energies above 10{sup 18} eV is in progress.

Arsene, N.; Rebel, H.; Sima, O. [Institute of Space Science (ISS), Bucharest-Magurele, P.O. Box MG-23 (Romania) and Physics Department, University of Bucharest, Bucharest-Magurele (Romania); Karlsruhe Institute of Technology, Karlsruhe (Germany); Physics Department, University of Bucharest, Bucharest-Magurele (Romania)

2012-11-20

167

Post-Newtonian arrival-time analysis for a pulsar in a binary system  

NASA Astrophysics Data System (ADS)

The post-Newtonian timing model for a binary pulsar that was used by Weisberg and Taylor (1984) to make the first observations of post-Newtonian timing effects in PSR 1913 + 16 is presented. The analysis corrects problems with the earlier model of Epstein (1977), which prevented consistent fittings to binary pulsar timing data. Detection of post-Newtonian timing effects in PSR 1913 + 16 consistent with the relativistic two-point-mass model of the system provides powerful, independent evidence that the observed decrease of the pulsar's orbital period is due to the emission of gravitational radiation.

Haugan, M. P.

1985-09-01

168

The gravity dual of a p-wave superconductor  

NASA Astrophysics Data System (ADS)

We construct black hole solutions to the Yang-Mills equations in an AdS4-Schwarzschild background which exhibit superconductivity. What makes these backgrounds p-wave superconductors is that the order parameter is a vector, and the conductivities are strongly anisotropic in a manner that is suggestive of a gap with nodes. The low-lying excitations of the normal state have a relaxation time which grows rapidly as the temperature decreases, consistent with the absence of impurity scattering. A numerical exploration of quasinormal modes close to the transition temperature suggests that p-wave backgrounds are stable against perturbations analogous to turning on a p+ip gap, whereas p+ip-wave configurations are unstable against turning into pure p-wave backgrounds.

Gubser, Steven S.; Pufu, Silviu S.

2008-11-01

169

Mapping P-wave azimuthal anisotropy in the crust and upper mantle beneath the United States  

NASA Astrophysics Data System (ADS)

Much progress has been made on revealing seismic structure and mantle dynamics beneath the United States (US) with the EarthScope/USArray project. Seismic anisotropy revealed by shear-wave splitting studies provides important constraints on constructing geodynamic models with regard to the seismic images, but the shear-wave splitting observations have poor vertical resolution and so their interpretations are often not unique. In this work we used a large number of arrival-time data from local and distant earthquakes recorded by the USArray to determine the first P-wave azimuthal anisotropy tomography of the crust and upper mantle beneath the US. Our results show that fast velocity directions (FVDs) in the lithosphere under the tectonically active areas correlate well with the surface tectonic features, suggesting that the P-wave anisotropy mainly reflects the present deformation. A circular pattern of the FVDs centered in the Great Basin is revealed, which is well consistent with the specific circular shear-wave splitting observations there, suggesting that the anisotropy occurs in the crust and uppermost mantle. In contrast, beneath the stable cratonic region, the FVDs revealed by this study differ from the shear-wave splitting observations but consistent with the features of gravity and magnetic anomalies, indicating that the P-wave FVDs mainly reflect the fossil anisotropy in the lithosphere, whereas the S-wave splitting observations mainly reflect the significant anisotropy in the asthenosphere. The present results shed new light on the seismic anisotropy in the crust and upper mantle and provide new constraints on constructing geodynamic models beneath the US.

Huang, Zhouchuan; Zhao, Dapeng

2013-12-01

170

ESTIMATING THE ARRIVAL TIME OF EARTH-DIRECTED CORONAL MASS EJECTIONS AT IN SITU SPACECRAFT USING COR AND HI OBSERVATIONS FROM STEREO  

SciTech Connect

Predicting the arrival time and transit speed of coronal mass ejections (CMEs) near the Earth is critical to understanding the solar-terrestrial relationship. Even though STEREO observations now provide multiple views of CMEs in the heliosphere, the true speeds derived from stereoscopic reconstruction of SECCHI coronagraph data are not quite sufficient for accurate forecasting of the arrival time at Earth of a majority of CMEs. This uncertainty is due to many factors that change CME kinematics, such as the interaction of two or more CMEs or the interaction of CMEs with the pervading solar wind. In order to understand the propagation of CMEs, we have used the three-dimensional triangulation method on SECCHI coronagraph (COR2) images and geometric triangulation on the J-maps constructed from Heliospheric Imagers HI1 and HI2 data for eight Earth-directed CMEs observed during 2008-2010. Based on the reconstruction, and implementing the drag-based model for the distance where the CMEs could not be tracked unambiguously in the interplanetary (IP) medium, the arrival time of these CMEs have been estimated. These arrival times have also been compared with the actual arrival times as observed by in situ instruments. The analysis reveals the importance of heliospheric imaging for improved forecasting of the arrival time and direction of propagation of CMEs in the IP medium.

Mishra, Wageesh; Srivastava, Nandita, E-mail: wageesh@prl.res.in [Udaipur Solar Observatory, Physical Research Laboratory, P.O. Box 198, Badi Road, Udaipur 313 001 (India)

2013-07-20

171

Smolt Condition and Timing of Arrival at Lower Granite Reservoir, 1988 Annual Report.  

SciTech Connect

This project monitored the daily passage of smelts during the 1988 spring outmigration at two migrant traps; one each on the Snake and Clear-water rivers. Due to the low runoff year, chinook salmon catch at the Snake River trap was very low. Steelhead trout catch was higher than normal, probably due to trap modifications and because the trap was moved to the east side of the river. Chinook salmon and steelhead trout catch at the Clearwater River trap was similar to 1987. Total cumulative recovery of PIT tagged fish at the three dams, with PIT tag detection systems was: 55% for chinook salmon, 73% for hatchery steelhead trout, and 75% for wild steelhead trout. Travel time through Lower Granite Reservoir for PIT tagged chinook salmon and steelhead trout, marked at the head of the reservoir, was affected by discharge. Statistical analysis showed that as discharge increased from 40 kcfs to 80 kcfs, chinook salmon travel time decreased three fold, and steelhead trout travel time decreased two fold. There was a statistical difference between estimates of travel time through Lower Granite Reservoir for PIT tagged and freeze branded steelhead trout, but not for chinook salmon. These differences may be related to the estimation techniques used for PIT tagged and freeze branded groups, rather than real differences in travel time.

Buettner, Edwin W.; Nelson, William R.

1989-10-01

172

Development of the town data base: Estimates of exposure rates and times of fallout arrival near the Nevada Test Site  

SciTech Connect

As part of the U.S. Department of Energy`s Off-Site Radiation Exposure Review Project, the time of fallout arrival and the H+12 exposure rate were estimated for populated locations in Arizona, California, Nevada, and Utah that were affected by fallout from one or more nuclear tests at the Nevada Test Site. Estimates of exposure rate were derived from measured values recorded before and after each test by fallout monitors in the field. The estimate for a given location was obtained by retrieving from a data base all measurements made in the vicinity, decay-correcting them to H+12, and calculating an average. Estimates were also derived from maps produced after most events that show isopleths of exposure rate and time of fallout arrival. Both sets of isopleths on these maps were digitized, and kriging was used to interpolate values at the nodes of a 10-km grid covering the pattern. The values at any location within the grid were then estimated from the values at the surrounding grid nodes. Estimates of dispersion (standard deviation) were also calculated. The Town Data Base contains the estimates for all combinations of location and nuclear event for which the estimated mean H+12 exposure rate was greater than three times background. A listing of the data base is included as an appendix. The information was used by other project task groups to estimate the radiation dose that off-site populations and individuals may have received as a result of exposure to fallout from Nevada nuclear tests.

Thompson, C.B.; McArthur, R.D. [Univ. and Community College System of Nevada, Las Vegas, NV (United States); Hutchinson, S.W. [Mead Johnson Nutritional Group, Evansville, IN (United States)

1994-09-01

173

Analyzing Word Frequencies in Large Text Corpora Using Inter-arrival Times and Bootstrapping  

Microsoft Academic Search

\\u000a Comparing frequency counts over texts or corpora is an important task in many applications and scientific disciplines. Given\\u000a a text corpus, we want to test a hypothesis, such as “word X is frequent”, “word X has become more frequent over time”, or\\u000a “word X is more frequent in male than in female speech”. For this purpose we need a null

Jefrey Lijffijt; Panagiotis Papapetrou; Kai Puolamäki; Heikki Mannila

174

Random number generation based on the time of arrival of single photons  

NASA Astrophysics Data System (ADS)

We report the demonstration of a new type of true random number generator based on the random distribution of the time interval between photons from a single-photon-like source. The experimental setup is simple and robust against mechanical and temperature disturbances. With improved detector resolution and efficiency, the random number bit rate could be increased by more than an order of magnitude to satisfy practical requirements.

Ma, Hai-Qiang; Xie, Yuejian; Wu, Ling-An

2005-12-01

175

A study of the importance of nonlinearity in the inversion of earthquake arrival time data for velocity structure  

NASA Astrophysics Data System (ADS)

All techniques that currently exist to invert arrival time data from earthquake sources for velocity structure rest on a local linearization of the nonlinear equations relating these data to the velocity model. We have studied the limitations imposed by this approximation using synthetic data in which a one dimensional velocity model is the only variable. We have found that this problem is sufficiently nonlinear that some iterative scheme is generally required to obtain results that are quantitatively correct. On the other hand, convergence studies using the algorithm recently developed by Pavlis (1982) suggest that this problem is somewhat better behaved than one might think. Convergence to a solution linearly close to the truth is fairly readily achieved whenever the resolution of the data is sufficient to resolve the structure of the true velocity model. Convergence to solutions that are not linearly close where found to occur, however, when the true velocity model contained significant unresolvable structure.

Pavlis, Gary L.; Booker, John R.

1983-06-01

176

Automated seismic event location by arrival time stacking: Applications to local and micro-seismicity  

NASA Astrophysics Data System (ADS)

Locating seismic events is one of the oldest problem in seismology. In microseismicity application, when the number of event is very large, it is not possible to locate earthquake manually and automated location procedures must be established. Automated seismic event location at different scales is very important in different application areas, including mining monitoring, reservoir geophysics and early warning systems. Location is needed to start rescue operations rapidly. Locating and mapping microearthquakes or acoustic emission sources in mining environments is important for monitoring of mines stability. Mapping fractures through microseimicity distribution inside hydrocarbon reservoirs is needed to find areas with an higher permeability and enhance oil production. In the last 20 years a large number of picking algorithm was developed in order to locate seismic events automatically. While P onsets can now be accurately picked using automatic routines, the automatic picking of later seismic phases (including S onset) is still problematic , thus limiting the location performance. In this work we present a picking free location method based on the use of the Short-Term-Average/Long-Term-Average (STA/LTA) traces at different stations as observed data. For different locations and origin times, observed STA/LTA are stacked along the travel time surface corresponding to the selected hypocentre. Iterating this procedure on a three-dimensional grid we retrieve a multidimensional matrix whose absolute maximum corresponds to the spatio-temporal coordinates of the seismic event. We tested our methodology on synthetic data, simulating different environments and network geometries. Finally, we apply our method to real datasets related to microseismic activity in mines and earthquake swarms in Italy. This work has been funded by the German BMBF "Geotechnologien" project MINE (BMBF03G0737A).

Grigoli, F.; Cesca, S.; Braun, T.; Philipp, J.; Dahm, T.

2012-04-01

177

Non-volcanic tremor triggered by P-wave and surface waves from the 2011 Tohoku-oki earthquake  

NASA Astrophysics Data System (ADS)

The Mw9.0 2011 Tohoku-oki earthquake increased the seismicity over the Japanese Island, which includes triggering of non-volcanic tremor (NVT) in western Shikoku at distance of ~960 km. The NVT was correlated with incoming large surface waves with large amplitude, as has been previously observed [Miyazawa and Mori, 2006; Miyazawa and Brodsky, 2008; Miyazawa et al., 2008]. The NVT in western Shikoku has been mainly triggered by Rayleigh waves via dynamic Coulomb failure function changes, which cause volumetric stress changes, thus the fluid dehydrated from the subduction zone is thought to play an important role for its excitation. P-waves are also compression waves which have the potential to trigger NVT. I examined the P-wave triggering from the Tohoku earthquake. Because the P-wave arrivals caused high-frequency transient stress changes, it is difficult to identify a local event by using a high-pass filtering technique used for surface wave triggering, especially if the embedded event is small. To detect the high-frequency triggering, I use a reference spectrum method, where I looked at the difference from of the spectral content from a reference event. The reference event was the Mw6.0 earthquake on March 10, which was an event in the sequence of foreshocks that started on March 9 and occurred close to the hypocenter of the mainshock. Using the first 25 s time-window after the onset of P-wave, I calculated the spectral ratio of the mainshock to the reference event at 692 borehole stations. Two regions with high values are found in Tohoku and western Shikoku. The values at Tohoku are mainly due to a directivity effect of the fault rupture, which is not observed for the reference earthquake. The high value for western Shikoku is observed at multiple stations and corresponds to the region of NVT activity which was triggered during arrival of surface waves. This result indicates that the NVT activity was also triggered by the P wave, and is consistent with the fluid related source process of NVT inferred from previous studies.

Miyazawa, M.

2011-12-01

178

Arrival-time judgments on multiple-lane streets: The failure to ignore irrelevant traffic.  

PubMed

How do road users decide whether or not they have enough time to cross a multiple-lane street with multiple approaching vehicles? Temporal judgments have been investigated for single cars approaching an intersection; however, close to nothing is known about how street crossing decisions are being made when several vehicles are simultaneously approaching in two adjacent lanes. This task is relatively common in urban environments. We report two simulator experiments in which drivers had to judge whether it would be safe to initiate street crossing in such cases. Matching traffic gaps (i.e., the temporal separation between two consecutive vehicles) were presented either with cars approaching on a single lane or with cars approaching on two adjacent lanes, either from the same side (Experiment 1) or from the opposite sides (Experiment 2). The stimuli were designed such that only the shortest gap was decision-relevant. The results showed that when the two gaps were in sight simultaneously (Experiment 1), street-crossing decisions were also influenced by the decision-irrelevant longer gap. Observers were more willing to cross the street when they had access to information about the irrelevant gap. However, when the two gaps could not be seen simultaneously but only sequentially (Experiment 2), only the shorter and relevant gap influenced the street-crossing decisions. The results are discussed within the framework of perceptual averaging processes, and practical implications for road safety are presented. PMID:24445138

Baurès, Robin; Oberfeld, Daniel; Tournier, Isabelle; Hecht, Heiko; Cavallo, Viola

2014-04-01

179

Simulation-based validation and arrival-time correction for Patlak analyses of Perfusion-CT scans  

NASA Astrophysics Data System (ADS)

Blood-brain-barrier (BBB) breakdown is a hypothesized mechanism for hemorrhagic transformation in acute stroke. The Patlak analysis of a Perfusion Computed Tomography (PCT) scan measures the BBB permeability, but the method yields higher estimates when applied to the first pass of the contrast bolus compared to a delayed phase. We present a numerical phantom that simulates vascular and parenchymal time-attenuation curves to determine the validity of permeability measurements obtained with different acquisition protocols. A network of tubes represents the major cerebral arteries ipsi- and contralateral to an ischemic event. These tubes branch off into smaller segments that represent capillary beds. Blood flow in the phantom is freely defined and simulated as non-Newtonian tubular flow. Diffusion of contrast in the vessels and permeation through vessel walls is part of the simulation. The phantom allows us to compare the results of a permeability measurement to the simulated vessel wall status. A Patlak analysis reliably detects areas with BBB breakdown for acquisitions of 240s duration, whereas results obtained from the first pass are biased in areas of reduced blood flow. Compensating for differences in contrast arrival times reduces this bias and gives good estimates of BBB permeability for PCT acquisitions of 90-150s duration.

Bredno, Jörg; Hom, Jason; Schneider, Thomas; Wintermark, Max

2009-02-01

180

Joint inversion of gravity and arrival time data from Parkfield: New constraints on structure and hypocenter locations near the SAFOD drill site  

USGS Publications Warehouse

Taking advantage of large datasets of both gravity and elastic wave arrival time observations available for the Parkfield, California region, we generated an image consistent with both types of data. Among a variety of strategies, the best result was obtained from a simultaneous inversion with a stability requirement that encouraged the perturbed model to remain close to a starting model consisting of a best fit to the arrival time data. The preferred model looks essentially the same as the best-fit arrival time model in areas where ray coverage is dense, with differences being greatest at shallow depths and near the edges of the model where ray paths are few. Earthquake locations change by no more than about 100 m, the general effect being migration of the seismic zone to the northeast, closer to the surface trace of the San Andreas Fault. Copyright 2004 by the American Geophysical Union.

Roecker, S.; Thurber, C.; McPhee, D.

2004-01-01

181

ARRIVAL TIME CALCULATION FOR INTERPLANETARY CORONAL MASS EJECTIONS WITH CIRCULAR FRONTS AND APPLICATION TO STEREO OBSERVATIONS OF THE 2009 FEBRUARY 13 ERUPTION  

SciTech Connect

One of the goals of the NASA Solar TErestrial RElations Observatory (STEREO) mission is to study the feasibility of forecasting the direction, arrival time, and internal structure of solar coronal mass ejections (CMEs) from a vantage point outside the Sun-Earth line. Through a case study, we discuss the arrival time calculation of interplanetary CMEs (ICMEs) in the ecliptic plane using data from STEREO/SECCHI at large elongations from the Sun in combination with different geometric assumptions about the ICME front shape [fixed-{Phi} (FP): a point and harmonic mean (HM): a circle]. These forecasting techniques use single-spacecraft imaging data and are based on the assumption of constant velocity and direction. We show that for the slow (350 km s{sup -1}) ICME on 2009 February 13-18, observed at quadrature by the two STEREO spacecraft, the results for the arrival time given by the HM approximation are more accurate by 12 hr than those for FP in comparison to in situ observations of solar wind plasma and magnetic field parameters by STEREO/IMPACT/PLASTIC, and by 6 hr for the arrival time at Venus Express (MAG). We propose that the improvement is directly related to the ICME front shape being more accurately described by HM for an ICME with a low inclination of its symmetry axis to the ecliptic. In this case, the ICME has to be tracked to >30{sup 0} elongation to obtain arrival time errors < {+-} 5 hr. A newly derived formula for calculating arrival times with the HM method is also useful for a triangulation technique assuming the same geometry.

Moestl, C.; Rollett, T.; Temmer, M.; Veronig, A. M.; Biernat, H. K. [Institute of Physics, University of Graz, Graz A-8010 (Austria); Lugaz, N. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Farrugia, C. J.; Galvin, A. B. [Space Science Center and Department of Physics, University of New Hampshire, Durham, NH 03824 (United States); Davies, J. A.; Harrison, R. A.; Crothers, S. [RAL Space, Harwell Oxford, Didcot OX11 0QX (United Kingdom); Luhmann, J. G. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Zhang, T. L.; Baumjohann, W., E-mail: christian.moestl@uni-graz.at [Space Research Institute, Austrian Academy of Sciences, Graz A-8042 (Austria)

2011-11-01

182

Gamma-Ray Burst Arrival Time Localizations: Simultaneous Observations by Pioneer Venus Orbiter, Compton Gamma-Ray Observatory, and ULYSSES  

NASA Astrophysics Data System (ADS)

Between the Compton Gamma Ray Observatory (CGRO) launch in 1991 April and the Pioneer Venus Orbiter (PVO) demise in 1992 October, concurrent coverage by CGRO, PVO, and Ulysses was obtained for several hundred gamma-ray bursts (GRBs). Although most of these were below the PVO and Ulysses thresholds, 37 were positively detected by all three spacecraft, with data quality adequate for quantitative localization analysis. All were localized independently to ~2° accuracy by the CGRO Burst and Transient Source Experiment (BATSE), and three were also localized by COMPTEL. We computed arrival-time error boxes, whose larger dimensions range from about 2' to several degrees and whose smaller dimensions are in the arcminute range. Twelve have areas less than 10 arcmin2, and only four have areas greater than 1 deg2. The area of the smallest box is 0.44 arcmin2. We find that the overall BATSE localization accuracy for these events is consistent with the most recent stated uncertainties. This work indicates that the ROSAT soft X-ray source found within a preliminary IPN error box for GB920501 (Trig 1576) (Hurley et al.) is less likely to be the GRB counterpart than previously reported.

Laros, J. G.; Hurley, K. C.; Fenimore, E. E.; Klebesadel, R. W.; Briggs, M. S.; Kouveliotou, C.; McCollough, M. L.; Fishman, G. J.; Meegan, C. A.; Cline, T. L.; Boer, M.; Niel, M.

1998-10-01

183

Anisotropy of p-wave Josephson junction  

NASA Astrophysics Data System (ADS)

The anisotropy of the dc Josephson current in the superconducting junctions of the p-wave equal spin pairing symmetry is theoretically investigated by the Furusaki-Tsukada-like formula. The current phase relations exhibit different oscillation periods and different phase shifts for the current along different directions, respectively.

Wang, Zhen-Yan; Shen, Rui

2010-08-01

184

The energy radiated by the 26 December 2004 Sumatra-Andaman earthquake estimated from 10-minute P-wave windows  

USGS Publications Warehouse

The rupture process of the Mw 9.1 Sumatra-Andaman earthquake lasted for approximately 500 sec, nearly twice as long as the teleseismic time windows between the P and PP arrival times generally used to compute radiated energy. In order to measure the P waves radiated by the entire earthquake, we analyze records that extend from the P-wave to the S-wave arrival times from stations at distances ?? >60??. These 8- to 10-min windows contain the PP, PPP, and ScP arrivals, along with other multiply reflected phases. To gauge the effect of including these additional phases, we form the spectral ratio of the source spectrum estimated from extended windows (between TP and TS) to the source spectrum estimated from normal windows (between TP and TPP). The extended windows are analyzed as though they contained only the P-pP-sP wave group. We analyze four smaller earthquakes that occurred in the vicinity of the Mw 9.1 mainshock, with similar depths and focal mechanisms. These smaller events range in magnitude from an Mw 6.0 aftershock of 9 January 2005 to the Mw 8.6 Nias earthquake that occurred to the south of the Sumatra-Andaman earthquake on 28 March 2005. We average the spectral ratios for these four events to obtain a frequency-dependent operator for the extended windows. We then correct the source spectrum estimated from the extended records of the 26 December 2004 mainshock to obtain a complete or corrected source spectrum for the entire rupture process (???600 sec) of the great Sumatra-Andaman earthquake. Our estimate of the total seismic energy radiated by this earthquake is 1.4 ?? 1017 J. When we compare the corrected source spectrum for the entire earthquake to the source spectrum from the first ???250 sec of the rupture process (obtained from normal teleseismic windows), we find that the mainshock radiated much more seismic energy in the first half of the rupture process than in the second half, especially over the period range from 3 sec to 40 sec.

Choy, G. L.; Boatwright, J.

2007-01-01

185

P-wave and surface wave survey for permafrost analysis in alpine regions  

NASA Astrophysics Data System (ADS)

In various high mountain environments the estimate of mechanical properties of slope and sediments are relevant for the link of the geo-mechanical properties with the climate change effects. Two different locations were selected to perform seismic and georadar surveying, the Tsanteleina glacier (Gran Paradiso) and the Blue Lake in Val d'Ayas in the massif of Monterosa. The analysis of the seismic and GPR lines allowed to characterize the silty soil (top layer) and underlying bedrock. We applied seismic survey in time lapse mode to check the presence of "active" layer and estimate the mechanical properties of the moraines material and their sensitivity to the permafrost changes. Mechanical properties of sediments and moraines in glacial areas are related to the grain-size, the compaction of the material subjected to the past glacial activity, the presence of frozen materials and the reactivity of the permafrost to the climate changes. The test site of Tsanteleina has been equipped with sensors to monitor the temperature of soil and air and with time domain reflectometry to estimate the soil moisture and the frozen and thawing cycle of the uppermost material. Seismic reflections from the top of the permafrost layer are difficult to identify as they are embedded in the source-generated noise. Therefore we estimate seismic velocities from the analysis of traveltime refraction tomography and the analysis of surface wave. This approach provides information on compressional and shear waves using a single acquisition layout and a hammer acts as source. This reduces the acquisition time in complex logistical condition especially in winter period. The seismic survey was performed using 48 vertical geophones with 2 m spacing. The survey has been repeated in two different periods: summer 2011 and winter 2011. Common offset reflection lines with a 200 MHz GPR system (in summer) permitted to investigate the sediments and obtain information on the subsoil layering. The processing of seismic data involved the tomographic interpretation of traveltime P-wave first arrivals by considering the continuous refraction of the ray-paths. Several surface-wave dispersion curves were extracted in f-k domain along the seismic line and then inverted through a laterally constrained inversion algorithm to obtain a pseudo-2D section of S-wave velocity. Georadar investigation (about 2 km of georadar lines in the first site) confirmed the presence both of fine and coarse sediments in the uppermost layer; the seismic data allowed the moraines to be characterized down to 20-25 meters of depth. At the elevation of 2700 m asl, we observed a general decrease of the P-wave traveltimes collected in November, when the near surface layer was in frozen condition, respect to the data acquired in June. The frozen layer is responsible of the inversion of P-wave velocity with depth; the higher velocity layer (frozen) cannot be detected in the tomographic interpretation of refraction tomographic of the P-wave arrivals. Compressional wave velocity ranges from 700 m/s on the uppermost part, to 2000-2500 m/s in the internal part of the sediments reaching values higher than 5000 m/s at depth about 20 m. The analysis of surface wave permitted to estimate a slight increase from summer to winter of the S-wave velocity, in the depth range between 0 to 5 m.

Godio, A.; Socco, L. V.; Garofalo, F.; Arato, A.; Théodule, A.

2012-04-01

186

BGPR_Reconstruct: A MATLAB ® ray-tracing program for nonlinear inversion of first arrival travel time data from zero-offset borehole radar  

Microsoft Academic Search

A MATLAB program was developed to invert first arrival travel time picks from zero offset profiling borehole ground penetrating radar traces to obtain the electromagnetic wave propagation velocities in soil. Zero-offset profiling refers to a mode of operation wherein the centers of the bistatic antennae being lowered to the same depth below ground for each measurement. The inversion uses a

Dale F. Rucker; Ty P. A. Ferre

2004-01-01

187

Three-dimensional inversion of regional P and S arrival times in the East Aleutians and sources of subduction zone gravity highs  

Microsoft Academic Search

Free-air gravity highs over forearcs represent a large fraction of the power in the Earth`s anomalous field, yet their origin remains uncertain. Seismic velocities, as indicators of density, are estimated here as a means to compare the relative importance of upper plate sources for the gravity high with sources in the downgoing plate. P and S arrival times for local

Geoffrey A. Abers

1994-01-01

188

Seismicity, arrival time delays of the seismic phases and slowness characteristics study in Abu Dabbab area, Egypt  

NASA Astrophysics Data System (ADS)

The temporal variations of seismicity from the Abu Dabbab area, 25 km west of the Red Sea coast, are collected from the Egyptian national seismic network (ENSN), which has magnified the detection capability in that area to ML < 1 earthquakes. These data show a sequence of the micro earthquake swarm during 2003-2011. This area has experienced larger shocks up to M = 6 during the 20th century and its seismicity is concentrated in a narrow spatial volume. We analyze the digital waveform data of about 1000 seismograms, recorded by portable network of 10 vertical component seismographs that are employed in a temporary survey experiment in the Abu Dabbab area in 2004, and the results indicate: firstly, there are similar waveform seismograms, which are classified into three groups. In each group a master event is identified. Then, the arrival time delays of the P and S phases (?tp and ?ts, respectively) are measured between the master event and its slave events. ?tp and ?ts range between -0.01 and 0.02 s, respectively. These values are used to relocate the studied events. Secondly, the slowness vector (?s) in 3-dimensional pattern, which is estimated using the genetic algorithms, is found ?sx = 0.0153, ?sy = 0.00093 and ?sz = 0.2086 s/km in the three spatial coordinates (X, Y and Z), respectively. These analyses demonstrate the inhomogeneities within the upper crust of the study area. Also, ?s shows little dependence of lateral distances and reasonably high slowness along the depth extent, which is consistent with the seismic velocity structure variations.

Sami, Mahmoud; Hassoup, Awad; Hosny, Ahmed; Mohamed, Gadelkarem A.

2013-12-01

189

Nuclear explosion locations at the Balapan, Kazakhstan, nuclear test site: the effects of high-precision arrival times and three-dimensional structure  

Microsoft Academic Search

We have investigated the potential contributions of improved arrival times (using waveform cross-correlation) and the use of three-dimensional (3-D) velocity models for seismic event location capability. Our analyses are applied to a dataset of nuclear explosions at Balapan, Kazakhstan, for which ground-truth locations and some absolute origin times are available. This ground-truth information allows us to determine excellent origin time

Clifford Thurber; Chad Trabant; Florian Haslinger; Renate Hartog

2001-01-01

190

The analyses of P-wave velocity structures in the Manila subduction system  

NASA Astrophysics Data System (ADS)

During the TAIGER project in 2009, we deployed 260 OBSs around offshore Taiwan, and recorded the refracted wave from the deep crust. The seismic source was provided by a 6000 cu-in airgun array from R/V Langseth. During leg 1 and 4 of TAIGER experiment, 3 OBS lines, T1 (consists of MGL0908_05 and MGL0908_07), T2 (consists of MGL0908_01 and MGL0908_09), and MGL0905_27, were shot in the Manila subduction system. We picked OBS first arrivals and inversed the P-wave velocity model to demonstrate the major feactures such as the Manila subduction zone, Luzon arc and part of West Philippine Basin. In the results, the oceanic crust thickness of the northeast part of the South China Sea was identified which is about 10-12 km thick in west of the LRTPB (Luzon-Ryukyu Transform Plate Boundary). But the thickness of the crust thins across the LRTPB to Manila Trench (6-8km), and start to subduct into the Philippine Sea Plate beneath the Manila Trench. Both sides of the Gagua Ridge are the oceanic crust, and their thickness is about 8 km. Even the P-wave velocity model cannot demonstrates the subducting angle very well along Manila Trench, but the depth of the Moho can be showed about 16 km at west of the Manila Trench, and about 25 km deep beneath the accretionary prism. In addition, we also used the earthquake data from CWB, IRIS, and Philippine. The subduction zone of the Benioff zone can be extended up to 100 km. Several splay faults and out-of-sequence thrusts (OOST) are also detected from multi-beam echo sounder and multi-channel seismic data. The stress of the splay faults and the OOST increases from collision and compression. If the stress accumulates for a long time, the mega earthquake and tsunami probably may be occurred.

Liang, C.; Chen, H.; Wu, H.; Lee, C.

2011-12-01

191

P-wave Cooper pair splitting.  

PubMed

Background: Splitting of Cooper pairs has recently been realized experimentally for s-wave Cooper pairs. A split Cooper pair represents an entangled two-electron pair state, which has possible application in on-chip quantum computation. Likewise the spin-activity of interfaces in nanoscale tunnel junctions has been investigated theoretically and experimentally in recent years. However, the possible implications of spin-active interfaces in Cooper pair splitters so far have not been investigated.Results: We analyze the current and the cross correlation of currents in a superconductor-ferromagnet beam splitter, including spin-active scattering. Using the Hamiltonian formalism, we calculate the cumulant-generating function of charge transfer. As a first step, we discuss characteristics of the conductance for crossed Andreev reflection in superconductor-ferromagnet beam splitters with s-wave and p-wave superconductors and no spin-active scattering. In a second step, we consider spin-active scattering and show how to realize p-wave splitting using only an s-wave superconductor, through the process of spin-flipped crossed Andreev reflection. We present results for the conductance and cross correlations.Conclusion: Spin-activity of interfaces in Cooper pair splitters allows for new features in ordinary s-wave Cooper pair splitters, that can otherwise only be realized by using p-wave superconductors. In particular, it provides access to Bell states that are different from the typical spin singlet state. PMID:23019543

Soller, Henning; Komnik, Andreas

2012-01-01

192

3-D P-wave Velocity Structure in Western Greece Determined from Tomography Using Earthquake Data Recorded at the University of Patras Seismic Network (PATNET)  

NASA Astrophysics Data System (ADS)

The 3-D P-wave velocity structure of the upper crust in the region of western Greece is investigated by inversion of about 1500 residuals of P-wave arrival times from local earthquake data recorded in the year 1996 by the newly established University of Patras Seismic Network (PATNET). The resulting velocity structure shows strong horizontal variations due to the complicated structure and the variation of crustal thickness. Relatively low-velocity contours are observed in the area defined by Cephallonia-Zakynthos Islands and northwestern Peloponnesos. This is in addition to some well localized peaks of relatively higher values of P-wave velocity may be related to the zone of Triassic evaporites in the region and correspond to diapirism that breaks through to the uppermost layer. Finally, a low P-velocity `deeping' zone extending from Zakynthos to the Gulf of Patras is correlated with Bouguer anomaly map and onshore and offshore borehole drillings which indicate that thick sediments overly the evaporites which exist there at depth greater than 2 km.

Melis, N. S.; Tselentis, G.-A.

193

Typical CME-IP shock events during the ascending phase of Solar Cycle 24 and their arrival time predictions at Earth  

NASA Astrophysics Data System (ADS)

Predicting arrival times of interplanetary (IP) shocks at the near Earth space is an important ingredient of space weather forecasting because the passage of an IP shock at Earth will compress the magnetosphere and produce corresponding space weather effects. We have developed a new shock arrival time prediction model, called SPM2, based on 551 solar disturbance events during Solar Cycle 23. Here new shock events in Solar Cycle 24 will be used to check the predicting performance of SPM2. 35 typical CME-IP shock events during the ascending phase of Solar Cycle 24 (2009-2013) with near-simultaneous coronagraph observations of CMEs and metric type II radio bursts are adopted as the sample events. Comparisons between the initial shock speed calculated from the type II burst drifting rate and the CME speed derived from coronagraph observations are investigated. It is found that the multi-spacecraft coronagraph observations combined with appropriate CME leading edge fitting model can give a more reliable CME radial speed than the type II burst shock speed. Then, SPM2 and an empirical model, which input the type II shock speed and CME speed respectively, are used to give the arrival time prediction of the associated IP shocks at the Earth orbit. The predicting precision of the empirical model would become better if the CME is tracked to a larger helio-distance. The prediction of SPM2 gives a similar predicting accuracy even its input parameters contain larger uncertainties. On this sense, the potential capability of the SPM2 model is also discussed in terms of real-time shock arrival time forecasts.

Zhao, X.; Feng, X.

2013-12-01

194

Computer program modifications of Open-file report 82-1065; a comprehensive system for interpreting seismic-refraction and arrival-time data using interactive computer methods  

USGS Publications Warehouse

The computer programs published in Open-File Report 82-1065, A comprehensive system for interpreting seismic-refraction arrival-time data using interactive computer methods (Ackermann, Pankratz, and Dansereau, 1982), have been modified to run on a mini-computer. The new version uses approximately 1/10 of the memory of the initial version, is more efficient and gives the same results.

Ackermann, Hans D.; Pankratz, Leroy W.; Dansereau, Danny A.

1983-01-01

195

Reactivation and mantle dynamics of North China Craton: insight from P-wave anisotropy tomography  

NASA Astrophysics Data System (ADS)

We determined the first 3-D P-wave anisotropic tomography beneath the North China Craton (NCC) using a large number of high-quality arrival-time data from local earthquakes and teleseismic events, which reveals depth-dependent azimuthal anisotropy in the crust and upper mantle down to 600 km depth. In the NCC western block, the fast velocity direction (FVD) varies from east-west in the southern part to northeast-southwest in the northern part, which may reflect either the interaction between the Yangtze block and NCC or fossil lithospheric fabrics in the craton. Under the NCC eastern block, a uniform northwest-southeast FVD is revealed in the lower part of the upper mantle (300-410 km depths) and the mantle transition zone (410-660 km depths), which may reflect horizontal and upwelling flows in the big mantle wedge (BMW) above the stagnant Pacific slab in the mantle transition zone. The NCC central block exhibits a northeast-southwest FVD, consistent with the surface tectonic orientation there, suggesting that the cold and thick (>300 km) cratonic root of the NCC western block may obstruct the northwest-southeast trending mantle flow induced by the Pacific Plate subduction, resulting in a northeast-southwest trending mantle flow under the central block. Our present results indicate that the corner flow in the BMW associated with the deep subduction of the Pacific Plate is the main cause of NCC reactivation and mantle dynamics under East China.

Tian, You; Zhao, Dapeng

2013-12-01

196

Nonlinear inversion of the P-wave P-wave reflection coefficient data  

SciTech Connect

Surface seismic data are used to estimate lithologic parameters at an interface. The four unknown independent parameters at an interface are the ratio of the P-wave velocities and the ratio of the densities of upper and lower media, and the P-wave/S-wave velocity ratios in the upper and lower media respectively. The forward problem is solved by a reparameterized form of the full Zoeppritz equation for PP reflections. The inversion model is fitted to the data using a two part inversion scheme. The near offset (near normal incidence) data is initially inverted using a linearized Zoeppritz normal incidence equation to obtain estimates of the P-wave ratio and density ratio. The estimates of these two parameters are then used as initial guesses in a nonlinear full Zoeppritz inversion by a Levenberg Marquardt procedure. Partial derivatives of the reparameterized Zoeppritz equation for the Jacobian matrix are calculated analytically at each iteration. All parameters are successfully estimated from synthetic data. Poisson`s ratio of the upper and lower media can be calculated from inversion estimates of P-wave/S-wave velocity ratio. Lithologic parameters are estimated for several CDP gathers from a 3D survey of the Rabbit Hills Field in North Central Montana. A sensitivity analysis for the different parameters is performed.

Pate, A.J. [Univ. of Montana, Butte, MT (United States)

1996-06-01

197

P Wave Dispersion and Maximum P Wave Duration Are Associated with Renal Outcomes in Chronic Kidney Disease  

PubMed Central

P wave parameters measured by 12-lead electrocardiogram (ECG) are commonly used as a noninvasive tool to evaluate left atrial enlargement. This study was designed to assess whether P wave parameters were associated with renal outcomes in chronic kidney disease (CKD) patients. This longitudinal study enrolled 439 patients with CKD stages 3–5. Renal end points were defined as the commencement of dialysis or death. Change in renal function was measured using the estimated glomerular filtration rate (eGFR) slope. We measured two ECG P wave parameters corrected for heart rate, i.e., corrected P wave dispersion and corrected maximum P wave duration. The values of P wave dispersion and maximum P wave duration were 88.8±21.7 ms and 153.3±21.7 ms, respectively. During the follow-up period (mean, 25.2 months), 95 patients (21.6%) started hemodialysis and 30 deaths (6.8%) were recorded. Multivariate Cox regression analysis identified that increased P wave dispersion [hazard ratio (HR), 1.020; 95% confidence interval (CI), 1.009–1.032; P<0.001] and maximum P wave duration (HR, 1.013; 95% CI, 1.003–1.024; P?=?0.012) were associated with progression to renal end points. Furthermore, increased P wave dispersion (unstandardized coefficient ??=?–0.016; P?=?0.037) and maximum P wave duration (unstandardized coefficient ??=?–0.014; P?=?0.040) were negatively associated with the eGFR slope. We demonstrated that increased P wave dispersion and maximum P wave duration were associated with progression to the renal end points of dialysis or death and faster renal function decline in CKD patients. Screening CKD patients on the basis of P wave dispersion and maximum P wave duration may help identify patients at high risk for worse renal outcomes.

Huang, Jiun-Chi; Wei, Shu-Yi; Chen, Szu-Chia; Chang, Jer-Ming; Hung, Chi-Chih; Su, Ho-Ming; Hwang, Shang-Jyh; Chen, Hung-Chun

2014-01-01

198

Teleseismic P wave attenuation and nuclear explosion source functions inferred from Yellowknife Array data  

NASA Astrophysics Data System (ADS)

We report here the results of a comprehensive seismic attenuation investigation along the paths connecting Canada's Yellowknife seismic array (YKA) with seven active nuclear explosion testing areas. The data consist of more than 600 explosion-generated teleseismic P wave records. A dual time-frequency averaging technique is used to take advantage of the array recording characteristics without the drawback of the conventional beam-forming, excessive annihilation of high-frequency signal energies. The dual averaging technique, deployed in conjunction with a multiwindow spectral analysis method, yields smooth amplitude spectra whose falloff at high frequencies suffers little from spectral leakage due to the familiar presence of a prominent low-frequency plateau. Measured in terms of t*, the highest attenuation (0.66 s) is found along the path which originates from the Tuamotu test area; somewhat less attenuating are the two paths which depart from the Pahute Mesa (0.59 s) and Yucca Flat (0.50 s) nuclear test areas, both located within the U.S. Nevada Test Site. We find t* for these three paths to be substantially (up to 0.21 s) higher than recently published estimates (e.g., Der et al., 1985). We attribute these disparities largely to differences in spectral leakage control capability between the conventional single window and the improved multiwindow spectral analysis methods. The least attenuating paths all originate from the Soviet test areas: Novaya Zemlya (NZ), west Kazakhstan, Degelen Mountain (DM), and Shagan River (SR). The last two of these test areas, DM and SR, are both located in east Kazakhstan. The P wave signatures of the Soviet explosions are rich in high-frequency (>4.5 Hz) energies, and the YKA data (0.5-8.0 Hz) support a frequency-dependent t* whose value at high frequencies (>4.5 Hz) is as small as 0.17 s. To gain a grasp of the ramifications of the t* disparity between the multiple-window and the single-window results, we have compared explosion source time functions obtained by the multichannel deconvolution technique of Shumway and Der (1985) in order to assess their sensitivity to the input t* value. In our example involving the deconvolved source functions of five French Tuamotu explosions, we find that a 0.1-s t* difference is large enough to cause clearly discernible signature differences, in terms of the signal frequency content as well as the extractability of a secondary arrival some 0.4 s behind the first P arrival. This secondary arrival is believed to be the depth phase pP, a seismic signature of importance in both yield estimation and earthquake/explosion source discrimination. The absorption band modeling (Minster, 1978a, b) of the French Tuamotu explosion data yields 1.08±0.05 and 0.079±0.008 s for t*0 and ?m, respectively. The corresponding parameter estimates derived from the U.S. explosion data are somewhat smaller. The t*0 and ?m estimates are the smallest along the paths which depart from the four Soviet test areas. For the NZ-YKA path the t*0 and ?m estimates are 0.56±0.08 and 0.061±0.013 s, respectively. Plagued by a strong trade-off between the two model parameters, these estimates are not tightly constrained, however.

Chun, Kin-Yip; Zhu, Tianfei; West, Gordon F.

1991-07-01

199

3D P-wave velocity structure of the deep Galicia rifted margin: A first analysis of the Galicia 3D wide-angle seismic dataset  

NASA Astrophysics Data System (ADS)

Galicia 3D, a reflection-refraction and long offset seismic experiment was carried out from May through September 2013, at the Galicia rifted margin (in the northeast Atlantic Ocean, west of Spain) as a collaboration between US, UK, German and Spanish groups. The 3D multichannel seismic acquisition conducted by R/V Marcus Langseth covered a 64 km by 20 km (1280 km2) zone where the main geological features are the Peridotite Ridge (PR), composed of serpentinized peridotite and thought be upper mantle exhumed to the seafloor during rifting, and the S reflector which has been interpreted to be a low angle detachment fault overlain by fault bounded, rotated, continental crustal blocks. In the 3D box, two airgun arrays of 3300 cu.in. were fired alternately (in flip-flop configuration) every 37.5 m. All shots are recorded by 44 short period four component ocean bottom seismometers (OBS) and 26 ocean bottom hydrophones (OBH) deployed and recovered by R/V Poseidon, as well as four 6 km hydrophone streamers with 12.5 m channel spacing towed by R/V Marcus Langseth. We present the preliminary results of the first arrival time tomography study which is carried out with a subset of the wide-angle dataset, in order to generate a 3D P-wave velocity volume for the entire depth sampled by the reflection data. After the relocation of OBSs and OBHs, an automatic first-arrival time picking approach is applied to a subset of the dataset, which comprises more than 5.5 million source-receiver pairs. Then, the first-arrival times are checked visually, in 3-dimensions. The a priori model used for the first-arrival time tomography is built up using information from previous seismic surveys carried out at the Galicia margin (e.g. ISE, 1997). The FAST algorithm of Zelt and Barton (1998) is used for the first-arrival time inversion. The 3D P-wave velocity volume can be used in interpreting the reflection dataset, as a starting point for migration, to quantify the thinning of the crustal layers, and to determine the degree of the serpentinization of the uppermost mantle.

Bayrakci, Gaye; Minshull, Timothy A.; Davy, Richard G.; Karplus, Marianne S.; Kaeschen, Dirk; Papenberg, Cord; Krabbenhoeft, Anne; Sawyer, Dale; Reston, Timothy J.; Shillington, Donna J.; Ranero, César R.

2014-05-01

200

The effect of the Earth's oblate spheroid shape on the accuracy of a time-of-arrival lightning ground strike locating system  

NASA Technical Reports Server (NTRS)

The algorithm used in previous technology time-of-arrival lightning mapping systems was based on the assumption that the earth is a perfect spheroid. These systems yield highly-accurate lightning locations, which is their major strength. However, extensive analysis of tower strike data has revealed occasionally significant (one to two kilometer) systematic offset errors which are not explained by the usual error sources. It was determined that these systematic errors reduce dramatically (in some cases) when the oblate shape of the earth is taken into account. The oblate spheroid correction algorithm and a case example is presented.

Casper, Paul W.; Bent, Rodney B.

1991-01-01

201

Pseudo 3D - P-wave refraction seismic monitoring of permafrost in steep bedrock: laboratory calibration, error assessment and field techniques  

NASA Astrophysics Data System (ADS)

Degrading permafrost in rock walls can cause instabilities due to changes in rock- and ice-mechanical as well as hydraulic properties. For the first time, we used seismic refraction tomography (SRT) to evaluate the degradation of permafrost in solid rock walls. Five parallel NE-SW transects were installed across a crestline on the Steintälli, Matter Valley, Switzerland, at 3070-3150 m a.s.l.. P-wave velocities were measured repeatedly during the summer 2006 and 2007, first arrivals were picked manually and traveltimes were compared and analysed. P-wave velocity was calibrated in the laboratory. Two cuboid water-saturated samples were cooled from 20° to -5° C. P-wave velocity was measured parallel and perpendicular to the direction of cleavage. Parallel to the cleavage, P-wave velocities respond to freezing with a sudden increase from 5228±25 m/s (sample S1) and 5239±19 m/s (S4) to values of 5774±21 m/s (S1) and 5895±27 m/s (S4). Perpendicular to the cleavage direction, p-wave velocity increases from 1953±15 m/s (S1) and 1667±14 m/s (S4) to values of 4331±12 m/s (S1) and 4404±36 m/s (S4) respectively. Supercooled conditions were possibly observed between 0° C an 0.25±0.15° C (S4). Traveltime analysis provides P-wave velocities in the range of the laboratory results and indicates permafrost existence. Initial P-Wave velocities of 3500 - 4000 m/s yielded best model fits, in terms of total absolute time difference. For all five transects and recorded time steps the total absolute time difference was 1.1-1.5 ms. Raytracing and ray density provide insight into the distribution of P-wave ray paths in the subsurface. Large ray densities up to 100 and more rays delimit the upper boundary between unfrozen and frozen bedrock and thus facilitate an accurate positioning of the upper limits of frozen rock (i.e. permafrost). SRT was used to monitor monthly alterations of the thawing front in August and September 2006, as well as annual changes in August 2007. SR tomographies display permafrost close to the north face and below ice-filled fractures at the crestline mostly in depths of 4-8 m. Due to remaining snow cover or glacier ice contact, perennially frozen bedrock persisted close to the surface especially in 2007. In contrast to ERT, SRT provides a geometrically more accurate detection of the upper bedrock permafrost boundary and a novel independent tool for the validation of permafrost fluctuations in steep bedrock throughout time.

Krautblatter, Michael; Draebing, Daniel

2010-05-01

202

Crosswell seismic studies in gas hydrate-bearing sediments: P wave velocity and attenuation tomography  

NASA Astrophysics Data System (ADS)

We present crosswell seismic data from the Mallik 2002 Production Research Well Program, an international research project on Gas Hydrates in the Northwest Territories of Canada. The program participants include 8 partners; The Geological Survey of Canada (GSC), The Japan National Oil Corporation (JNOC), GeoForschungsZentrum Potsdam (GFZ), United States Geological Survey (USGS), United States Department of the Energy (USDOE), India Ministry of Petroleum and Natural Gas (MOPNG)/Gas Authority of India (GAIL) and the Chevron-BP-Burlington joint venture group. The crosswell seismic measurements were carried out by making use of two 1160 m deep observation wells (Mallik 3L-38 and 4L-38) both 45 m from and co-planar with the 1188 m deep production research well (5L-38). A high power piezo-ceramic source was used to generate sweeped signals with frequencies between 100 and 2000 Hz recorded with arrays of 8 hydrophones per depth level. A depth range between 800 and 1150 m was covered, with shot and receiver spacings of 0.75 m. High quality data could be collected during the survey which allow for application of a wide range of crosswell seismic methods. The initial data analysis included suppression of tube wave energy and picking of first arrivals. A damped least-squares algorithm was used to derive P-wave velocities from the travel time data. Next, t* values were derived from the decay of the amplitude spectra, which served as input parameters for a damped least-squares attenuation tomography. The initial results of the P-wave velocity and attenuation tomography reveal significant features reflecting the stratigraphic environment and allow for detection and eventually quantification of gas hydrate bearing sediments. A prominent correlation between P velocity and attenuation was found for the gas hydrate layers. This contradicts to the apparently more meaningful inverse correlation as it was determined for the gas hydrates at the Blake Ridge but supports the results from the Mallik 2L-38 sonic log data. The P velocities and attenuation values, if combined with other information can be important for the quantitative evaluation of the gas hydrate saturation, and may further constrain petrophysical models of the hydrate bearing sediment formation.

Bauer, K.; Haberland, Ch.; Pratt, R. G.; Ryberg, T.; Weber, M. H.; Mallik Working Group

2003-04-01

203

Comparison of the CME-associated shock arrival times at the earth using the WSA-ENLIL model with three cone models  

NASA Astrophysics Data System (ADS)

We have made a comparison of CME-associated shock arrival times at the earth based on the WSA-ENLIL model with three cone models using 29 halo CMEs from 2001 to 2002. These halo CMEs have cone model parameters from Michalek et al. (2007) as well as their associated interplanetary (IP) shocks. For this study we consider three different cone models (an asymmetric cone model, an ice-cream cone model and an elliptical cone model) to determine CME cone parameters (radial velocity, angular width and source location), which are used for input parameters of the WSA-ENLIL model. The mean absolute error (MAE) of the arrival times for the elliptical cone model is 10 hours, which is about 2 hours smaller than those of the other models. However, this value is still larger than that (8.7 hours) of an empirical model by Kim et al. (2007). We are investigating several possibilities on relatively large errors of the WSA-ENLIL cone model, which may be caused by CME-CME interaction, background solar wind speed, and/or CME density enhancement.

Jang, S.; Moon, Y.; Na, H.

2012-12-01

204

Investigation of inhomogeneities and anisotropy in the crust and upper mantle of central Europe by means of teleseismic P waves  

NASA Astrophysics Data System (ADS)

Travel-time residuals from global samples as well as azimuth and slowness deviations of teleseismic P-wave arrivals have been analysed both at the individual seismic stations BRG, CLL, MOX, and PRU, and using the G.D.R. station network. The main results of the analysis are as follows. (1) Azimuth and incidence-angle deviations of short-period P waves have been observed at individual stations by means of three-component measurements. Their transformations into the slowness space reveal a mislocation pattern at all stations, which suggests the superimposition of regional and strong local effects on wave propagation. (2) The mean station residuals, as well as the azimuth dependence of the residuals with a period of 2?, indicate a rising of the upper mantle discontinuities to the north of central Europe to the east European platform. (3) This general trend is confirmed by the mislocation patterns observed at various subnetworks of the telemetric system of seismic stations of the G.D.R. The refined model assumes a dipping of flat discontinuities or isotachs in the upper mantle down to the 20° discontinuity, with a dip angle of about 11° ± 2° north of the network centre and a zero dip south of it. The dip direction is 192° ± 5°. (4) Fourier analysis of the azimuth dependence of travel-time residuals revealed almost the same phase of the second azimuthal term at all individual stations. This fact could be interpreted in terms of an anisotropic layer of some 200 km thickness in the upper mantle assuming a coefficient of anisotropy of 6%. The azimuth of maximum velocity is 10° (+180°) and agrees well with the results derived by Bamford (1977) from Pn-wave measurements.

Wylegalla, K.; Bormann, P.; Baumbach, M.

1988-06-01

205

Estimating the value of containment strategies in delaying the arrival time of an influenza pandemic: A case study of travel restriction and patient isolation  

NASA Astrophysics Data System (ADS)

With a simple phenomenological metapopulation model, which characterizes the invasion process of an influenza pandemic from a source to a subpopulation at risk, we compare the efficiency of inter- and intrapopulation interventions in delaying the arrival of an influenza pandemic. We take travel restriction and patient isolation as examples, since in reality they are typical control measures implemented at the inter- and intrapopulation levels, respectively. We find that the intrapopulation interventions, e.g., patient isolation, perform better than the interpopulation strategies such as travel restriction if the response time is small. However, intrapopulation strategies are sensitive to the increase of the response time, which might be inevitable due to socioeconomic reasons in practice and will largely discount the efficiency.

Wang, Lin; Zhang, Yan; Huang, Tianyi; Li, Xiang

2012-09-01

206

P-wave velocity structure of the crust and uppermost mantle beneath Iceland from local earthquake tomography  

Microsoft Academic Search

The structure of the crust and uppermost mantle beneath Iceland, the keys to understanding the magma plumbing system of the hotspot and hotspot–ridge interaction, was poorly constrained in previous seismological investigations. Here we develop a three-dimensional P-wave velocity model of the Icelandic crust and uppermost mantle from tomographic inversion of over 3500 first-arrivals from local earthquakes recorded in Iceland. The

Ting Yang; Yang Shen

2005-01-01

207

Physiological correlates of coastal arrival and river entry timing in late summer Fraser River sockeye salmon (Oncorhynchus nerka)  

Microsoft Academic Search

Animal migrations typically occur within a predictable time frame and sequence, but little is known about the triggers that initiate migration, despite their importance in animal ecology and for resource management. The migration of adult sockeye salmon (Oncorhynchus nerka) in the Fraser River, British Columbia, Canada, is an excellent model to study such triggers because for nearly a decade a

Steven J. Cooke; Scott G. Hinch; Glenn T. Crossin; David A. Patterson; Karl K. English; Michael C. Healey; J. Steve Macdonald; J. Mark Shrimpton; Jeffrey L. Young; Andrea Lister; Glen Van Der Kraak; A. P. Farrell

2008-01-01

208

P-wave tomography of the Calabrian Arc region (South Italy) using a new 'a priori  

NASA Astrophysics Data System (ADS)

A recently published tomographic investigation of the Calabrian Arc, South Italy (Neri et al., SRL, 2009) has shown that the Ionian subducting slab appears in-depth continuous only beneath the central part of the Arc (southern Calabria), while it has already undergone detachment at the edges of the arcuate structure (northern Calabria and northeastern Sicily). Starting from this result we tried to better define the features of the slab by performing a new tomographic inversion of crust and upper lithosphere in the Calabrian Arc region. The starting velocity model was derived from the integration of a new crustal velocity model obtained applying the method proposed by Waldhauser et al. (GJI, 1998 and 2002) and a deep model used by Neri et al. (SRL, 2009). We merged these two models into an averaged regional one, ranging between the surface and 300km depth. Then we used it to perform a new P-wave tomographic inversion of shallow and deep earthquakes occurred between 1981 and 2008 in Southern Italy. We selected all the events with a minimum of 12P+S and 8 P+S readings for shallow and deep earthquakes respectively. The quality of the readings was, in the majority of cases, checked directly on the recordings. The final inversion dataset consists of 75141 P and 40118 S arrival times relative to 7050 earthquakes recorded at a total of 591 stations. All the data available from the national and local networks, including the CAT-SCAN and UniCal network, have been used for inversion. This new model reduced significantly the RMS parameter and allowed us to enlarge the inversion zone. The investigation, together with a detailed analysis of seismicity, allows us to propose an improved and more complete view of the subduction system with respect to the previous works, including Neri et al. (SRL, 2009).

Orecchio, Barbara; Presti, Debora; Totaro, Cristina; Guerra, Ignazio; Neri, Giancarlo

2010-05-01

209

P wave crustal velocity structure in the greater Mount Rainier area from local earthquake tomography  

USGS Publications Warehouse

We present results from a local earthquake tomographic imaging experiment in the greater Mount Rainier area. We inverted P wave arrival times from local earthquakes recorded at permanent and temporary Pacific Northwest Seismograph Network seismographs between 1980 and 1996. We used a method similar to that described by Lees and Crosson [1989], modified to incorporate the parameter separation method for decoupling the hypocenter and velocity problems. In the upper 7 km of the resulting model there is good correlation between velocity anomalies and surface geology. Many focal mechanisms within the St. Helens seismic zone have nodal planes parallel to the epicentral trend as well as to a north-south trending low-velocity trough, leading us to speculate that the trough represents a zone of structural weakness in which a moderate (M 6.5-7.0) earthquake could occur. In contrast, the western Rainier seismic zone does not correlate in any simple way with anomaly patterns or focal mechanism fault planes, leading us to infer that it is less likely to experience a moderate earthquake. A ???10 km-wide low-velocity anomaly occurs 5 to 18 km beneath the summit of Mount Rainier, which we interpret to be a signal of a region composed of hot, fractured rock with possible small amounts of melt or fluid. No systematic velocity pattern is observed in association with the southern Washington Cascades conductor. A midcrustal anomaly parallels the Olympic-Wallowa lineament as well as several other geophysical trends, indicating that it may play an important role in regional tectonics. Copyright 1999 by the American Geophysical Union.

Moran, S. C.; Lees, J. M.; Malone, S. D.

1999-01-01

210

Efficient sampling of early signal arrival for estimation of perfusion and transit time in whole-brain arterial spin labeling.  

PubMed

Arterial spin labeling can be used to measure both cerebral perfusion and arterial transit time. However, accurate estimation of these parameters requires adequate temporal sampling of the arterial spin labeling difference signal. In whole-brain multislice acquisitions, two factors reduce the accuracy of the parameter estimates: saturation of labeled blood in transit and inadequate sampling of early difference signal in superior slices. Label saturation arises when slices are acquired inferior-to-superior such that slice selection in proximal slices spoils the label for a distal slice. Inadequate sampling arises when the time spent acquiring inferior slices is too long to allow early sampling of the difference signal in superior slices. A novel approach to multislice imaging is proposed to address these two issues. In round-robin arterial spin labeling, slices are acquired in a different order after every pair of control-label acquisitions. Round-robin arterial spin labeling enables the acquisitions of all slices across the same range of postlabel delays in a descending superior-to-inferior order. This eliminates the temporal sampling problem and greatly reduces label saturation. Arterial transit time estimates obtained for the whole brain with round-robin arterial spin labeling show better agreement with a single-slice acquisition than do conventional multislice acquisitions. PMID:22189961

Lee, Wayne; Janik, Rafal; Scouten, Amy; Stefanovic, Bojana; Sled, John G

2012-07-01

211

Wavelet-based automatic determination of the P- and S-wave arrivals  

NASA Astrophysics Data System (ADS)

The detection of P- and S-wave arrivals is important for a variety of seismological applications including earthquake detection and characterization, and seismic tomography problems such as imaging of hydrocarbon reservoirs. For many years, dedicated human-analysts manually selected the arrival times of P and S waves. However, with the rapid expansion of seismic instrumentation, automatic techniques that can process a large number of seismic traces are becoming essential in tomographic applications, and for earthquake early-warning systems. In this work, we present a pair of algorithms for efficient picking of P and S onset times. The algorithms are based on the continuous wavelet transform of the seismic waveform that allows examination of a signal in both time and frequency domains. Unlike Fourier transform, the basis functions are localized in time and frequency, therefore, wavelet decomposition is suitable for analysis of non-stationary signals. For detecting the P-wave arrival, the wavelet coefficients are calculated using the vertical component of the seismogram, and the onset time of the wave is identified. In the case of the S-wave arrival, we take advantage of the polarization of the shear waves, and cross-examine the wavelet coefficients from the two horizontal components. In addition to the onset times, the automatic picking program provides estimates of uncertainty, which are important for subsequent applications. The algorithms are tested with synthetic data that are generated to include sudden changes in amplitude, frequency, and phase. The performance of the wavelet approach is further evaluated using real data by comparing the automatic picks with manual picks. Our results suggest that the proposed algorithms provide robust measurements that are comparable to manual picks for both P- and S-wave arrivals.

Bogiatzis, P.; Ishii, M.

2013-12-01

212

Position surveillance using one active ranging satellite and time-of-arrival of a signal from an independent satellite  

NASA Technical Reports Server (NTRS)

A satellite-aided mobile communication service was tested for position surveillance, with an automatic responder circuit connected between the vehicle receiver and transmitter, and a receiver coded for signals from another satellite. Using the ATS-6 and GOES satellites, a tone-code ranging transponder was connected between the receiver and transmitter, and a 468 MHz receiver was connected to the responder unit for passive reception of the 100 bit per second timing and data signal. Results showed lines of position derived from the active ranging through ATS-6 to be accurate to approximately 0.1 nautical mile, while the NOAA-GOES signals were accurate to about 1.6 miles. The active ranging bandwidth was 2.44 kHz, and the integration time was 0.1 second, while the limitation on accuracy was the 100 Hz bandwidth. This technique of position surveillance was concluded to be feasible and simple to operate, providing needed, good quality communications to the inland waterways industry.

Anderson, R. E.; Frey, R. L.; Lewis, J. R.

1981-01-01

213

Understanding complex teleseismic wave propagation in the Sierra Nevada through vertical-component P-wave receiver functions  

NASA Astrophysics Data System (ADS)

Past seismic studies attempting to image the lithosphere underneath the Sierra Nevada and to constrain the geometry of the upper mantle Isabella anomaly, a high wave-speed body underneath the western foothills of the range, have observed complex behavior in teleseismic and regional waveforms recorded at stations within the range. Notably, a 1993 teleseismic mini-array recorded multipath P-wave arrivals, topographic reflections, and scattered energy ~25 km west of the Sierran crest. These effects suggest wave propagation through strongly heterogeneous lithosphere complicated by near-surface phenomena. Multipathing and other complex wave propagation are indicative of strong variations in wavespeed, which in turn reflect structural complexity important in understanding the genesis of the Isabella anomaly. However, determining the extent of such propagative behavior in and underneath the Sierra Nevada has not been studied. We investigate the behavior of teleseismic P-waves using vertical-component receiver functions in an effort to better understand the extent of complex waveforms as a first tool in better constraining the geographic region(s) where sufficiently complex lithospheric structure exists. We expect that the presence of sufficiently high velocity gradients should result in P-wave multipath arrivals from events that skirt the perimeter of the Isabella anomaly from certain backazimuths. We deconvolve regionally beamed vertical P-waveforms from individual vertical component P-waves. This effectively recovers variability in the P waveforms that is normally lost in typical single-station radial- and transverse-component receiver function analyses. Vertical P-wave beams are constructed using dbxcor, a waveform correlation algorithm developed by G. Pavlis. Seismic data for the northern and central Sierra Nevada are from the 2005-2007 Sierra Nevada Earthscope Project (SNEP) and further supplemented by many permanent and temporary stations including the Earthscope Transportable Array. Data for the southern Sierra Nevada comes from the 1997 Sierran Paradox Experiment (SPE).

Bernardino, M. J.; Jones, C. H.

2013-12-01

214

p-wave holographic insulator/superconductor phase transition  

SciTech Connect

Using a five-dimensional anti-de Sitter (AdS) soliton in an Einstein-Yang-Mills theory with SU(2) gauge group, we study p-wave holographic insulator/superconductor phase transition. To explore the phase structure of the model, we consider the system in the probe limit as well as fully back-reacted solutions. We will also study the zero temperature limit of the p-wave holographic superconductor in four dimensions.

Akhavan, Amin [School of physics, Institute for Research in Fundamental Sciences (IPM) P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Department of Physics, Sharif University of Technology P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Alishahiha, Mohsen [School of physics, Institute for Research in Fundamental Sciences (IPM) P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

2011-04-15

215

Collisional Properties of p-Wave Feshbach Molecules  

SciTech Connect

We have observed p-wave Feshbach molecules for all three combinations of the two lowest hyperfine spin states of {sup 6}Li. By creating a pure molecular sample in an optical trap, we measured the inelastic collision rates of p-wave molecules. We have also measured the elastic collision rate from the thermalization rate of a breathing mode which was excited spontaneously upon molecular formation.

Inada, Yasuhisa; Kuwata-Gonokami, Makoto [ERATO Macroscopic Quantum Control Project, JST, Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Department of Applied Physics, University of Tokyo, Hongo, Bunkyo-Ku, Tokyo 113-8656 (Japan); Horikoshi, Munekazu; Mukaiyama, Takashi [ERATO Macroscopic Quantum Control Project, JST, Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Nakajima, Shuta; Ueda, Masahito [ERATO Macroscopic Quantum Control Project, JST, Yayoi, Bunkyo-Ku, Tokyo 113-8656 (Japan); Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2008-09-05

216

Simultaneous travel time inversion for earthquake location and subduction zone structure in the central Aleutian Islands  

Microsoft Academic Search

A combined location and velocity inversion technique is applied to travel time data from 151 well-recorded central Aleutian earthquakes. The data include P and S wave arrivals at stations of a local network and P, pP, and sP wave arrivals at teleseismic stations. After correction for crustal structure at the reflection points, the depth phases pP and sP provide important

E. R. Engdahl; D. Gubbins

1987-01-01

217

Evaluation of the real-time earthquake information system in Japan  

NASA Astrophysics Data System (ADS)

The real-time earthquake information system (REIS) of the Japanese seismic network is developed for automatically determining earthquake parameters within a few seconds after the P-waves arrive at the closest stations using both the P-wave arrival times and the timing data that P-waves have not yet arrived at other stations. REIS results play a fundamental role in the real-time information for earthquake early warning in Japan. We show the rapidity and accuracy of REIS from the analysis of 4,050 earthquakes in three years since 2005; 44 percent of the first reports are issued within 5 seconds after the first P-wave arrival and 80 percent of the events have a difference in epicenter distance less than 20 km relative to manually determined locations. We compared the formal catalog to the estimated magnitude from the real-time analysis and found that 94 percent of the events had a magnitude difference of +/-1.0 unit.

Nakamura, Hiromitsu; Horiuchi, Shigeki; Wu, Changjiang; Yamamoto, Shunroku; Rydelek, Paul A.

2009-01-01

218

P-wave and S-wave traveltime residuals in Caledonian and adjacent units of Northern Europe and Greenland  

NASA Astrophysics Data System (ADS)

This work combines P-wave and S-wave travel time residuals from in total 477 temporary and 56 permanent stations deployed across Caledonian and adjacent units in Northern Europe and Greenland (Tor, Gregersen et al. 2002; SVEKALAPKO, Sandoval et al., 2003; CALAS, Medhus et al, 2012a; MAGNUS, Weidle et al. 2010; SCANLIPS south, England & Ebbing 2012; SCANLIPS north, Hejrani et al. 2012; JULS Hejrani et al. 2013; plus permanent stations in the region). We picked data from 2002 to 2012 (1221 events) using a cross correlation technique on all waveforms recorded for each event. In this way we achieve maximum consistency of relative residuals over the whole region (Medhus et al. 2012b). On the European side 18362 P-wave travel time residuals was delivered. In East Greenland 1735 P-wave residuals were recovered at the Central Fjord array (13 stations) and 2294 residuals from the sparse GLISN-array (23 stations). Likewise, we picked a total of 6034 residuals of the SV phase (For the Tor and SVEKALAPKO projects we used data from Amaru et al. 2008). Relative residuals within the region are mainly due to sub-crustal uppermost mantle velocity anomalies. A dominant subvertical boundary was detected by Medhus et al. (2012), running along the Tornquist zone, east of the Oslo Graben and crossing under high topography of the southern Scandes. We delineated this boundary in more detail, tracking it towards the Atlantic margin north of Trondheim. Further north (Scanlips north), a similar subvertical upper mantle boundary seems to be present close to the coast, coinciding with the edge of the stretched crust. The North German Caledonides were probed by the new JULS (JUtland Lower Saxony) profile which closes the gap between Tor and CALAS arrays. Mantle structure found by the Tor project was confirmed, and modelling was extended to the eastern edge of the North Sea. References: Amaru, M. L., Spakman, W., Villaseñor, A., Sandoval, S., Kissling, E., 2008, A new absolute arrival time data set for Europe.Geophysical Journal International, 173, 465-472. England, R. W.; Ebbing, J., 2012, Crustal structure of central Norway and Sweden from integrated modelling of teleseismic receiver functions and the gravity anomaly.GEOPHYSICAL JOURNAL INTERNATIONAL, 191, 1-11. Gregersen S., Voss P., TOR Working Group, 2002. Summary of project TOR: delineation of a stepwise, sharp, deep lithosphere transition across Germany-Denmark-Sweden, Tectonophysics, 360, 61-73. Hejrani, B., Jacobsen, B. H., Balling,N. and England, R. W.. 2012, A seismic tomography study of lithospheric structure under the Norwegian Caledonides.Geophysical Research Abstracts, 14, 4334. Hejrani, B.; Jacobsen, B.H.; Balling, N.;Tilmann, F.; Kind, R., 2013, Upper-mantle velocity structure beneathJutland, Denmark and northern Germany:Preliminary results. Joint Assembly Gothenburg Abstract S401S2.01, Medhus, A. B., Balling, N., Jacobsen, B. H., Weidle, C., England, R. W., Kind, R., Thybo, H., Voss, P. (2012a): Upper-mantle structure beneath the Southern Scandes Mountains and the Northern Tornquist Zone revealed by P-wave traveltime tomography. Geophysical Journal International, 189, 3, 1315-1334. Medhus, Jacobsen, B. H.,A. B., Balling, N., 2012b, Bias Problems in Existing Teleseismic Travel Time Databases: Ignore or Repair? Seismological Research Letters, 83, 1030-1037. Sandoval, S., Kissling, E. &Ansorge, J., 2003.High-resolution body wave tomography beneath the SVEKALAPKO array: I. A priori three-dimensional crustal model and associated traveltime effects on teleseismic wave fronts, Geophys. J. Int., 153, 75-87. Weidle, C., Maupin, V., Ritter, J.,Kværna, T., Schweitzer J., Balling, N.,Thybo, H.,Faleide, J. I.,and,Wenzel, F., 2010, MAGNUS-A Seismological Broadband Experiment to Resolve Crustal and Upper Mantle Structure beneath the Southern Scandes Mountains in Norway. SEISMOLOGICAL RESEARCH LETTERS, 81, 76-84.

Hejrani, Babak; Balling, Niels; Holm Jacobsen, Bo; Kind, Rainer; Tilmann, Frederik; England, Richard; Bom Nielsen, Søren

2014-05-01

219

Evidence for the subducting lithosphere under Southern Vancouver Island and Western Oregon from teleseismic P wave conversions  

SciTech Connect

Long-period teleseismic P waves recorded at VIC (Victoria, British Columbia) and COR (Corvallis, Orgeon) show anomalously large Ps conversions and later arriving P-to-S reverberations not observed from typical continental crustal sections or from previously proposed structures for these stations determined from refraction surveys. The timing and large amplitude of the Ps phase, relative to direct P, suggests a high velocity-contrast interface at 45 to 50 km depth under VIC and COR forming the base of a distinct low velocity zone. This interface is proposed to be the oceanic Moho which is being subducted under North America. Off azimuth Ps recorded at COR is consistent with a 20/sup 0/ eastward dip for the interface. Horizontal particle motion at both sites show evidence for lateral heterogeneity in local crustal structure. The distinct low velocity zone and its negative gradient with depth has important consequences for refraction interpretation in the region since the usual assumption of increasing velocity with depth is violated. Crustal thicknesses derived from such misinterpretation may be overestimated. In principle, this type of structure suggests a solution for the Vancouver Island crustal thickness problem in which the observed positive Bouguer gravity anomaly is inconsistent with the 50 km thick crustal thickness derived from previous refraction work.

Langston, C.A.

1981-05-10

220

Analysis of near-source contributions to early P-wave coda for underground explosions. II. Frequency dependence  

SciTech Connect

Analysis of dispersion in more than 1600 teleseismic short-period P waves from 46 underground explosions has established that near-source effects are responsible for systematic frequency-dependent variations observed in the first 15 sec of the P signals. Explosions from the Nevada, Amchitka, and Novaya Zemlya test sites exhibit a common magnitude dependence of the dispersive behavior, with smaller events having relatively enriched low-frequency (0.4 to 0.8 Hz) energy in the coda. For the Nevada and Amchitka sites, the larger events have relatively enhanced high-frequency (0.8 to 1.1 hz) energy in the coda as well, which may be a consequence of diminished high-frequency content of the direct arrivals. The dispersive behavior also correlates well with known source depths for the Nevada Test Site and Amchitka events, and with estimated pP delay times for the Novaya Zemlya events, indicating that burial depth and/or explosion size are important factors. Pahute Mesa tests show a secondary dependence on position in the site, with centrally located events having stronger dispersion, as well as more pronounced slowly varying azimuthal patterns in frequency dependence. Stations at azimuths NNE from the Mesa have particularly strong dispersion for centrally located events. Spatial and azimuthal variations for Pahute Mesa events do not appear to be the result of aftershock radiation but instead are associated with frequency-dependent defocusing and scattering from a high-velocity structure beneath the test site.

Lay, T.

1987-08-01

221

Three-dimensional inversion of regional P and S arrival times in the East Aleutians and sources of subduction zone gravity highs  

SciTech Connect

Free-air gravity highs over forearcs represent a large fraction of the power in the Earth`s anomalous field, yet their origin remains uncertain. Seismic velocities, as indicators of density, are estimated here as a means to compare the relative importance of upper plate sources for the gravity high with sources in the downgoing plate. P and S arrival times for local earthquakes, recorded by a seismic network in the eastern Aleutians, are inverted for three-dimensional velocity structure between the volcanic arc and the downgoing plate. A three-dimensional ray tracing scheme is used to invert the 7974 P and 6764 S arrivals for seismic velocities and hypocenters of 635 events. One-dimensional inversions show that station P residuals are systematically 0.25 - 0.5 s positive at stations 0-30 km north of the Aleutian volcanic arc, indicating slow material, while residuals at stations 10-30 km south of the arc are 0.1-0.25 s negative. Both features are explained in three-dimensional inversions by velocity variations at depths less than 25-35 km. Tests using a one-dimensional or a two-dimensional slab starting model show that below 100 km depth, velocities are poorly determined and trade off almost completely with hypocenters for earthquakes at these depths. The locations of forearc velocity highs, in the crust of the upper plate, correspond to the location of the gravity high between the trench and volcanic arc. Free-air anomalies, calculated from the three-dimensional velocity inversion result, match observed gravity for a linear density-velocity relationship between 0.1 and 0.3 (Mg m{sup {minus}3})/(km s{sup {minus}1}), when a 50-km-thick slab is included with a density of 0.055{+-}0.005 Mg m{sup {minus}3}. Values outside these ranges do not match the observed gravity. The slab alone contributes one third to one half of the total 75-150 mGal amplitude of the gravity high but predicts a high that is much broader than is observed.

Abers, G.A. [Columbia Univ., Palisades, NY (United States)] [Columbia Univ., Palisades, NY (United States)

1994-03-10

222

Supercurrent in a p-wave holographic superconductor  

SciTech Connect

The p-wave and p+ip-wave holographic superconductors with fixed DC supercurrent are studied by introducing a nonvanishing vector potential. We find that close to the critical temperature T{sub c} of zero current, the numerical results of both the p-wave model and the p+ip model are the same as those of Ginzburg-Landau (GL) theory; for example, the critical current is j{sub c}{approx}(T{sub c}-T){sup 3/2} and the phase transition in the presence of a DC current is a first-order transition. Beside the similar results between both models, the p+ip superconductor shows isotropic behavior for the supercurrent, while the p-wave superconductor shows anisotropic behavior for the supercurrent.

Zeng Huabi [Department of Physics, Nanjing University, Nanjing 210093 (China); Sun Weimin; Zong Hongshi [Department of Physics, Nanjing University, Nanjing 210093 (China); Joint Center for Particle, Nuclear Physics and Cosmology, Nanjing 210093 (China)

2011-02-15

223

Mantle P-wave velocity structure beneath the Hawaiian hotspot  

NASA Astrophysics Data System (ADS)

Three-dimensional images of P-wave velocity structure beneath the Hawaiian Islands, obtained from a network of seafloor and land seismometers, show an upper-mantle low-velocity anomaly that is elongated in the direction of the island chain and surrounded by a high-velocity anomaly in the shallow upper mantle that is parabolic in map view. Low velocities continue downward to the mantle transition zone between 410 and 660 km depth and extend into the topmost lower mantle, although the resolution of lower mantle structure from this data set is limited. Comparisons of inversions with separate data sets at different frequencies suggest that contamination by water reverberations is not markedly biasing the P-wave imaging of mantle structure. Many aspects of the P-wave images are consistent with independent tomographic images of S-wave velocity in the region, but there are some differences in upper mantle structure between P-wave and S-wave velocities. Inversions without station terms show a southwestward shift in the location of lowest P-wave velocities in the uppermost mantle relative to the pattern for shear waves, and inversions with station terms show differences between P-wave and S-wave velocity heterogeneity in the shallow upper mantle beneath and immediately east of the island of Hawaii. Nonetheless, the combined data sets are in general agreement with the hypothesis that the Hawaiian hotspot is the result of an upwelling, high-temperature plume. The broad upper-mantle low-velocity region beneath the Hawaiian Islands may reflect the diverging "pancake" at the top of the upwelling zone; the surrounding region of high velocities could represent a downwelling curtain; and the low-velocity anomalies southeast of Hawaii in the transition zone and topmost lower mantle are consistent with predictions of plume tilt.

Wolfe, Cecily J.; Solomon, Sean C.; Laske, Gabi; Collins, John A.; Detrick, Robert S.; Orcutt, John A.; Bercovici, David; Hauri, Erik H.

2011-03-01

224

Discretized versus continuous models of p-wave interacting fermions in one dimension  

SciTech Connect

We present a general mapping between continuous and lattice models of Bose and Fermi gases in one dimension, interacting via local two-body interactions. For s-wave interacting bosons we arrive at the Bose-Hubbard model in the weakly interacting, low-density regime. The dual problem of p-wave interacting fermions is mapped to the spin-1/2 XXZ model close to the critical point in the highly polarized regime. The mappings are shown to be optimal in the sense that they produce the least error possible for a given discretization length. As an application we examine the ground state of an interacting Fermi gas in a harmonic trap, calculating numerically real-space and momentum-space distributions as well as two-particle correlations. In the analytically known limits the convergence of the results of the lattice model with the continuous one is shown.

Muth, Dominik; Fleischhauer, Michael; Schmidt, Bernd [Fachbereich Physik und Forschungszentrum OPTIMAS, Technische Universitaet Kaiserslautern, D-67663 Kaiserslautern (Germany); Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet Frankfurt, D-60438 Frankfurt am Main (Germany)

2010-07-15

225

Global P-wave tomography of mantle plumes and subducting slabs  

NASA Astrophysics Data System (ADS)

There are many volcanoes on the Earth which can be generally classified into 3 categories: island arc volcanoes, mid-ocean ridge volcanoes, and hotspot volcanoes. Hotspot volcanoes denote intraplate volcanoes like Hawaii, or anomalously large mid-ocean ridge volcanoes like Iceland. So far many researchers have studied the origin of hotspot volcanoes and have used mantle plume hypothesis to explain them. However, we still have little knowledge about mantle plumes yet. In this study, we determined a new model of whole mantle P-wave tomography to understand the origin of hotspot volcanoes. We used the global tomography method of Zhao (2001, 2004). A 3-D grid net was set up in the mantle, and velocity perturbations at every grid nodes were taken as unknown parameters. The iasp91 velocity model (Kennett and Engdahl, 1991) was taken as the 1-D initial model. We selected 9106 earthquakes from the events occurred in the last forty years from the ISC catalog. About 1.6 million arrival-time data of five-type P phases (P, pP, PP, PcP, and Pdiff) were used to conduct the tomographic inversion. In our previous model (Zhao, 2004), the grid interval in the E-W direction is too small in the polar regions. In this study, in order to remedy this problem, we use a flexible-grid approach to make the lateral grid intervals in the polar regions nearly the same as the other portions of the mantle. As a result, the tomographic images in the polar regions are remarkably improved. Our new tomographic model shows huge low-velocity (low-V) zones in the entire mantle under Tahiti and Lake Victoria, which reflect the Pacific and African superplumes, being consistent with the previous studies. A clear low-V zone is revealed under Mt. Erebus volcano in Antarctica. Other major hotspots also exhibit significant low-V zones in the mantle under their surface locations. Beneath Bering Sea, we found that the Pacific slab is subducting from the Aleutian trench and it is stagnant in the mantle transition zone. In Bering Sea, there are several intraplate volcanoes such as St. Paul island. Given the existence of the stagnant Pacific slab and very low-V mantle wedge above the slab, we think that the origin of the intraplate volcanoes in Bering Sea is most likely related to the deep subduction of the Pacific slab and its stagnancy in the mantle transition zone, similar to the Changbai and Wudalianchi volcanoes in Northeast Asia (Zhao, 2004). Zhao, D. (2001) Earth Planet. Sci. Lett. 192, 251-265. Zhao, D. (2004) Phys. Earth Planet. Inter. 146, 3-34.

Yamamoto, Y.; Zhao, D.

2008-12-01

226

[Pseudonecrosis waves: simulation of myocardial necrosis by retrograde P wave].  

PubMed

The Authors describe a case of a patient showing, during an episode of chest pain, an ecg-pattern of wide and tall "Q" wave simulating inferior myocardial infarction. In fact, a further ecg recorded during sinus rhythm denotes that the "Q" wave was a retrograde P wave generated by a nodal rhythm. The other known causes of "pseudonecrosis" are discussed. PMID:1808540

Cento, D; Migliorato, A; Cavalli, G; Arrigo, F

1991-11-01

227

Laboratory monitoring of P-waves in partially saturated sand  

NASA Astrophysics Data System (ADS)

Seismic data depends on a variety of hydrogeological properties of the prospected porous media such as porosity, permeability and fluid saturation. We have performed a laboratory experiment in the kiloHertz range in order to analyze the role of partial saturation on direct propagating P-waves phase velocity and attenuation. The experiment consists of a sand-filled tank 107 cm x 34 cm x 35cm equipped with accelerometers and water capacitance probes. The P-waves seismic propagation is generated by hitting a steel ball on a granite plate on the one lateral side of the container. Several imbibition/drainage cycles are performed between the water residual saturation and the gas residual saturation. The laboratory seismic data are processed by two Continuous Wavelet Transforms using one real mother wavelet (Mexican hat) and one complex (Morlet) to recover velocity and attenuation as a function of frequency. Phase velocity of direct P-wave decreases with an increase of water content and is quite consistent with the low frequency limit of the Biot's theory both for imbibition and drainage. The interpretation of the P-waves attenuation needs to go beyond the macroscopic fluid flow of Biot's theory and to introduce a viscoelastic contribution linked to the grain to grain overall losses which are described by a constant Q-model. A strong hysteresis between imbibition and drainage is observed and explained by introducing an effective permeability depending on water and gas relative permeabilities (Van Genuchten model).

Barrière, J.; Bordes, C.; Brito, D.; Sénéchal, P.; Perroud, H.

2011-12-01

228

GPS/Loran-C interoperability for time and frequency applications: A survey of the times of arrival of Loran-C transmissions via GPS common mode/common view satellite observations  

NASA Technical Reports Server (NTRS)

The results from this survey clearly indicate that the Global Positioning System (GPS) time transfer capability is superior to that of the Loran-C system for absolute timing accuracy, and that even with the most careful calibration of the Loran-C receiver delay and propagation path, inexplicable time of arrival (TOA) biases remain which are larger than the variations across all of the transmitters. Much more data covering years would be needed to show that these biases were stable enough to be removed with a one time site calibration. The synchronization of the transmissions is excellent, all showing low parts in 10(exp 13) offsets versus the United States Naval Observatory (USNO) master clock. With the exception of the Searchlight transmitter, all of the transmissions exhibit timing stabilities over the entire period of less than 300 ns RMS which is at the observed levels of GPS under selective availability (SA). The Loran-C phase instabilities take place over a much greater time interval than those being forced onto the GPS signals under SA, providing for better medium to short term frequency stability. Data show that all but the most distant transmitters offer better than three parts in 10(exp 11) stability at this averaging time. It is in the frequency control area where GPS/Loran-C interoperation will offer some synergistic advantages over GPS alone under SA.

Penrod, Bruce; Funderburk, Richard; Dana, Peter

1990-01-01

229

Observation and modelling of P-wave polarization for teleseismic events  

NASA Astrophysics Data System (ADS)

P-wave polarization may yield valuable information on lateral heterogeneity and anisotropy of the crust and uppermost mantle. Using 20 years of the Gräfenberg (GRF) array data we show that stable measurements of P-wave polarization attributes - azimuthal deviation and incidence angle - may be obtained by automated data processing. The P-wave polarization at the GRF array is frequency dependent and a function of backazimuth. By applying harmonic analysis, properties of the 180° and 360° periodicities of azimuthal deviation and incidence angle as a function of backazimuth are quantified. The observations point to the presence of azimuthal anisotropy and lateral heterogenetiy in the crust and uppermost mantle in the vicinity of the stations. The fast propagation direction of P-waves and lateral velocity gradients of P-wave velocity may be estimated based on results of the harmonic analysis. For the GRF array the fast direction of P-wave propagation is found to be about 20° in the frequency range from 0.03 to 0.1Hz that is mainly sensitive to the lower crust and the uppermost mantle. At higher frequencies from 0.1 to 0.5 Hz, mainly related to the upper crust, the variability is larger with a predominant direction of fast P-wave propagation of about 100°. In order to investigate the sensitivity of P-wave polarization to azimuthal anisotropy quantitatively, full waveform forward modellings are performed using 3D Elastic Ray-Born Modelling. Ray and ray-Born techniques have proven their importance in seismology as all travel time tomography is based on ray tracing and all finite frequency travel time and amplitude kernels are based on ray-Born theory. Moreover ray and ray-Born methods are relatively fast and specifically valid at high frequencies. Thus these methods complement the finite-difference and spectral-element full waveform modelling methods . The actual implementation is done using an isotropic background medium with an anisotropic medium perturbation characterized by the 3 Thomsen parameters (which were originally developed for use in hydrocarbon exploration). The ray tracing through the background model is done using 4th order Runge-Kutta and the background model maybe 1D or 3D. Kinematic ray tracing is used for the computation of the travel times and dynamic ray tracing is used for the computation of the amplitudes. In our numerical examples we use a velocity model with a horizontal size 2000 km and depth 1000 km. The background model is a smoothed version of PREM. The 3D anisotropic perturbation has a Gaussian shape and is placed 30 km below the receiver. The modelling is done for earthquakes located within an annulus around the receiver. The inner radius of the annulus is 1400 km and its outer radius is 1900 km. All three components of the seismograms have been computed and are shown. These seismograms are used to perform a synthetic polarization analysis of the P-phase. The effects of the strength, depth and horizontal location of the anisotropic perturbation are investigated. Finally, we compute and show sensitivity attributes for the polarization parameters.

Cristiano, Luigia; Minakov, Alexander; Meier, Thomas; Keers, Henk

2014-05-01

230

Holographic p-wave superconductors from Gauss-Bonnet gravity  

SciTech Connect

We study the holographic p-wave superconductors in a five-dimensional Gauss-Bonnet gravity with an SU(2) Yang-Mills gauge field. In the probe approximation, we find that when the Gauss-Bonnet coefficient grows, the condensation of the vector field becomes harder, both the perpendicular and parallel components, with respect to the direction of the condensation, of the anisotropic conductivity decrease. We also study the mass of the quasiparticle excitations, the gap frequency and the DC conductivities of the p-wave superconductor. All of them depend on the Gauss-Bonnet coefficient. In addition, we observe a strange behavior for the condensation and the relation between the gap frequency and the mass of quasiparticles when the Gauss-Bonnet coefficient is larger than 9/100, which is the upper bound for the Gauss-Bonnet coefficient from the causality of the dual field theory.

Cai Ronggen; Nie Zhangyu; Zhang Haiqing [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China)

2010-09-15

231

P-wave baryons in the quark model  

Microsoft Academic Search

We discuss the spectrum and mixing angles of negative-parity baryons in a quark-model framework inspired by quantum chromodynamics. We take into account in zero order the removal of the degeneracy between the two P-wave states of the three-quark system in the S=-1 sector, as well as the hyperfine interaction between quarks, but neglect spin-orbit coupling. We find good agreement with

Nathan Isgur; Gabriel Karl

1978-01-01

232

Models of the upper mantle beneath the central North Island, New Zealand, from speeds and anisotropy of subhorizontal P waves (Pn)  

NASA Astrophysics Data System (ADS)

The central North Island of New Zealand shows significant variations in Pn wave speeds over small distances, ranging from 8.5 ± 0.2 km/s to 7.4 ± 0.1 km/s over a distance of 150 km. A combination of national network seismometers, local volcanic seismic monitoring networks, and temporary deployments are used to collect arrival times from local events, during the period of 1990-2006. The data set consists of approximately 11,200 Pn observations from 3000 local earthquakes at 91 seismograph sites. We have created a method that allows us to model the predominant wavelength features of P wave speeds in the uppermost mantle, as well as estimating values of mantle anisotropy and irregularities in the crust beneath stations, using least squares collocation. The resulting model shows distinct variations in uppermost mantle Pn velocities. Velocities of less than 7.5 km/s are found beneath the back-arc extension region of the Central Volcanic Region, and under the Taranaki Volcanic Region, indicating the presence of water and partial melt. The region to the east shows extremely high velocities of 8.3-8.5 km/s, where the P waves are traveling within the subducting Pacific slab. Slightly lower than normal mantle velocities of 7.8-8.1 km/s are found in the western North Island, suggesting a soft mantle. Pn anisotropy estimates throughout the North Island show predominately trench-parallel fast directions, ceasing to nulls in the west. Anisotropy measurements indicate the strain history of the mantle. Null anisotropy measurements suggest an undisturbed mantle, suggesting that mantle beneath the western North Island is young.

Seward, A. M.; Henderson, C. M.; Smith, E. G. C.

2009-01-01

233

Renormalization group approach to a p-wave superconducting model  

NASA Astrophysics Data System (ADS)

We present in this work an exact renormalization group (RG) treatment of a one-dimensional p-wave superconductor. The model proposed by Kitaev consists of a chain of spinless fermions with a p-wave gap. It is a paradigmatic model of great actual interest since it presents a weak pairing superconducting phase that has Majorana fermions at the ends of the chain. Those are predicted to be useful for quantum computation. The RG allows to obtain the phase diagram of the model and to study the quantum phase transition from the weak to the strong pairing phase. It yields the attractors of these phases and the critical exponents of the weak to strong pairing transition. We show that the weak pairing phase of the model is governed by a chaotic attractor being non-trivial from both its topological and RG properties. In the strong pairing phase the RG flow is towards a conventional strong coupling fixed point. Finally, we propose an alternative way for obtaining p-wave superconductivity in a one-dimensional system without spin–orbit interaction.

Continentino, Mucio A.; Deus, Fernanda; Caldas, Heron

2014-04-01

234

Paired fermionic superfluids with s- and p-wave interactions  

NASA Astrophysics Data System (ADS)

This thesis presents theoretical work in s- and p-wave resonantly paired Fermi gases at zero temperature. In the BEC regime of the wide-resonance s-wave BCS-BEC crossover, the chemical potential, speed of sound, condensate depletion, and ground state energy are computed. The quantities are calculated in a low density approximation. The bosonic scattering length is computed diagrammatically to be approximately 0.60a with a the fermionic scattering length, confirming a well-known result. The perturbative approach breaks down in the intermediate BCS-BEC crossover regime which is not investigated. Quantum corrections are computed in the low density expansion, and the mass-imbalanced two-species Fermi gas is investigated. For identical fermions, it is discussed how p-wave Feshbach resonances naturally fall into two classes of "weak" and "strong", depending on the short-distance physics. It is shown how bound fermionic trimers appear in the strongly-resonant superfluid. The appearance of the trimer under the strengthening of the resonance is investigated, and the lifetime of p-wave diatomic molecules due to collisional relaxation into trimers is estimated.

Levinsen, Jesper

2008-07-01

235

Crust and upper mantle P wave velocity structure beneath Valles caldera, New Mexico: Results from the Jemez teleseismic tomography experiment  

SciTech Connect

New results are presented from the teleseismic component of the Jemez Tomography Experiment conducted across Valles caldera in northern New Mexico. We invert 4872 relative {ital P} wave arrival times recorded on 50 portable stations to determine velocity structure to depths of 40 km. The three principle features of our model for Valles caldera are: (1) near-surface low velocities of {minus}17{percent} beneath the Toledo embayment and the Valle Grande, (2) midcrustal low velocities of {minus}23{percent} in an ellipsoidal volume underneath the northwest quadrant of the caldera, and (3) a broad zone of low velocities ({minus}15{percent}) in the lower crust or upper mantle. Crust shallower than 20 km is generally fast to the northwest of the caldera and slow to the southeast. Near-surface low velocities are interpreted as thick deposits of Bandelier tuff and postcaldera volcaniclastic rocks. Lateral variation in the thickness of these deposits supports increased caldera collapse to the southeast, beneath the Valle Grande. We interpret the midcrustal low-velocity zone to contain a minimum melt fraction of 10{percent}. While we cannot rule out the possibility that this zone is the remnant 1.2 Ma Bandelier magma chamber, the eruption history and geochemistry of the volcanic rocks erupted in Valles caldera following the Bandelier tuff make it more likely that magma results from a new pulse of intrusion, indicating that melt flux into the upper crust beneath Valles caldera continues. The low-velocity zone near the crust-mantle boundary is consistent with either partial melt in the lower crust or mafic rocks without partial melt in the upper mantle. In either case, this low-velocity anomaly indicates that underplating by mantle-derived melts has occurred. {copyright} 1998 American Geophysical Union

Steck, Lee K.; Fehler, Michael C.; Roberts, Peter M.; Baldridge, W. Scott; Stafford, Darrik G. [Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Lutter, William J.; Sessions, Robert [Department of Geology and Geophysics, University of Wisconsin-Madison (United States)] [Department of Geology and Geophysics, University of Wisconsin-Madison (United States)

1998-10-01

236

P-wave anisotropic tomography in Southeast Tibet: New insight into the lower crustal flow and seismotectonics  

NASA Astrophysics Data System (ADS)

We determined the first 3-D P-wave anisotropy tomography beneath Southeast Tibet and adjacent regions using 63,773 P-wave arrivals from 2866 local earthquakes and 55,457 arrivals from 2802 teleseismic events. A remarkable low-velocity layer with a thickness of about 20 km is revealed in the lower crust, which may reflect a mechanically weak zone capable of flow on a geological timescale. Our seismic anisotropy results suggest that the flow direction changes when it encounters the mechanically strong Sichuan basin. Most of the large earthquakes including the 2008 Wenchuan earthquake (M 8.0) and the 2013 Lushan earthquake (M 7.0) occurred at the margin of the ductile flow in the lower crust, suggesting that the seismogenesis is controlled by the deep dynamic processes. In the upper mantle, the subducting Indian plate is imaged clearly as a high-velocity zone which has reached near the Jinsha River suture. In addition, our results show significant variations of seismic anisotropy with depth, implying that the upper crust and the lithospheric mantle deform separately beneath most parts of the study region.

Wei, Wei; Zhao, Dapeng; Xu, Jiandong

2013-09-01

237

Regional P wave velocity structure of the Northern Cascadia Subduction Zone  

USGS Publications Warehouse

This paper presents the first regional three-dimensional, P wave velocity model for the Northern Cascadia Subduction. Zone (SW British Columbia and NW Washington State) constructed through tomographic inversion of first-arrival traveltime data from active source experiments together with earthquake traveltime data recorded at permanent stations. The velocity model images the structure of the subducting Juan de Fuca plate, megathrust, and the fore-arc crust and upper mantle. Beneath southern Vancouver Island the megathrust above the Juan de Fuca plate is characterized by a broad zone (25-35 km depth) having relatively low velocities of 6.4-6.6 km/s. This relative low velocity zone coincides with the location of most of the episodic tremors recently mapped beneath Vancouver Island, and its low velocity may also partially reflect the presence of trapped fluids and sheared lower crustal rocks. The rocks of the Olympic Subduction Complex are inferred to deform aseismically as evidenced by the lack of earthquakes withi the low-velocity rocks. The fore-arc upper mantle beneath the Strait of Georgia and Puget Sound is characterized by velocities of 7.2-7.6 km/s. Such low velocities represent regional serpentinization of the upper fore-arc mantle and provide evidence for slab dewatering and densification. Tertiary sedimentary basins in the Strait of Georgia and Puget Lowland imaged by the velocity model lie above the inferred region of slab dewatering and densification and may therefore partly result from a higher rate of slab sinking. In contrast, sedimentary basins in the Strait of Juan de Fuca lie in a synclinal depression in the Crescent Terrane. The correlation of in-slab earthquake hypocenters M>4 with P wave velocities greater than 7.8 km/s at the hypocenters suggests that they originate near the oceanic Moho of the subducting Juan de Fuca plate. Copyright 2006 by the American Geophysical Union.

Ramachandran, K.; Hyndman, R. D.; Brocher, T. M.

2006-01-01

238

Laboratory monitoring of P waves in partially saturated sand  

NASA Astrophysics Data System (ADS)

Energy dissipation is observed on seismic data when a wave propagates through a porous medium, involving different frequency regimes depending on the nature of rock and fluid types. We focus here on the role of partial fluid saturation in unconsolidated porous media, looking in particular at P-wave phase velocity and attenuation. The study consists in running an experiment in a sand-filled tank partially saturated with water. Seismic propagation in the tank is generated in the kHz range by hitting a steel ball on a granite plate. Seismic data are recorded by buried accelerometers and injecting or extracting water controls the partial saturation. Several imbibition/drainage cycles were performed between the water and gas residual saturations. A Continuous Wavelet Transform applied on seismic records allowed us to extract the direct P wave at each receiver. We observe an hysteresis in phase velocities and inverse quality factors between imbibition and drainage. Phase velocities and inverse quality factors are then jointly inverted to get a final poro-viscoelastic model of the partially saturated sand that satisfactorily reproduces the data. The model formulation consists in generalizing the Biot theory to effective properties of the fluid and medium (permeability and bulk modulus) to properly explain the phase velocity variation as a function of the saturation. The strong level of attenuation measured experimentally is further explained by an anelastic effect due to grain to grain sliding, adding to Biot's losses. This study shows that fluid distribution at microscopic scale has strong influence on the attenuation of direct P waves at macroscopic scale and confirms that seismic prospection may be a powerful tool for the characterization of transport phenomena in porous media.

Barrière, Julien; Bordes, Clarisse; Brito, Daniel; Sénéchal, Pascale; Perroud, Hervé

2012-12-01

239

Endstates in multichannel spinless p-wave superconducting wires  

NASA Astrophysics Data System (ADS)

Multimode spinless p-wave superconducting wires with a width W much smaller than the superconducting coherence length ? are known to have multiple low-energy subgap states localized near the wire's ends. Here we compare the typical energies of such endstates for various terminations of the wire: A superconducting wire coupled to a normal-metal stub, a weakly disordered superconductor wire and a wire with smooth confinement. Depending on the termination, we find that the energies of the subgap states can be higher or lower than for the case of a rectangular wire with hard-wall boundaries.

Rieder, M.-T.; Kells, G.; Duckheim, M.; Meidan, D.; Brouwer, P. W.

2012-09-01

240

Impact of Phase Transitions on P Wave Velocities  

SciTech Connect

In regions where a high pressure phase is in equilibrium with a low pressure phase, the bulk modulus defined by the P-V relationship is greatly reduced. Here we evaluate the effect of such transitions on the P wave velocity. A model, where cation diffusion is the rate limiting factor, is used to project laboratory data to the conditions of a seismic wave propagating in the two-phase region. We demonstrate that for the minimum expected effect there is a significant reduction of the seismic velocity, as large as 10% over a narrow depth range.

D Weidner; L Li

2011-12-31

241

P Wave Indices: Current Status and Future Directions in Epidemiology, Clinical and Research Applications  

PubMed Central

Indices of P wave duration and dispersion are accessible from the surface electrocardiogram. Their prolongation reflects inhomogeneous atrial depolarization secondary to insults such as chronically elevated atrial pressure, ischemia, or metabolic stress. In turn, these insults promote atrial structural remodeling and provide a substrate for atrial fibrillation (AF). P wave indices have been examined in cardiac and non-cardiac disease states. Prolonged P wave indices have been associated with hypertension, obesity and diabetes, all of which are risk factors for AF. Similarly, prolonged P wave duration and dispersion have been associated with AF recurrence in patients with paroxysmal AF and following cardioversion, and with incident AF following cardiothoracic surgeries. Our review describes the current field of P wave indices. We report the methodology for determining P wave indices. We also describe the strengths and limitations of the current literature on the clinical correlates and prognosis of P wave indices. We suggest future clinical and research directions for P wave indices.

Magnani, Jared W.; Williamson, MaryAnn; Ellinor, Patrick T.; Monahan, Kevin M.; Benjamin, Emelia J.

2009-01-01

242

P wave velocity structure in the Yucca Mountain, Nevada, region  

NASA Astrophysics Data System (ADS)

We have performed a crustal tomographic inversion using over 250,000 P arrival times from local earthquake sources and surface explosions in the Yucca Mountain, Nevada, region. Within the shallowest 2-3 km, topographic features tend to dominate the structure with high velocities imaged under Bare Mountain, the Funeral Mountains, and higher terrain to the east of Yucca Mountain and low velocities imaged under Crater Flat, Jackass Flat, the Amargosa Desert, and the caldera complexes. Imaged shallow velocities also show correlation with several known gravity and aeromagnetic anomalies. Below the basins (˜2-3 km depth), velocities vary between 5.5 and 6.5 km/s and lose many of the correlations seen in the shallowest layers; however, a few major structures, such as the Bare Mountain block, can be traced to at least 10 km depth. Additionally, we image structures that may be associated with the Wahmonie intrusion and pre-Tertiary structural trends. Yucca Mountain itself is underlain by a high-velocity upper crustal-scale structure similar to other structures in the region such as Bare Mountain and may represent a Basin and Range style back-tilted block, which may provide a structural explanation for Yucca Mountain's topographic expression. Additionally, the imaged, relatively low velocity basement under Crater Flat may provide a preferred conduit for magma intrusion into Crater Flat compared to Yucca Mountain, accounting for the lack of post-Miocene volcanism observed at the mountain proper. We explore our tomographic results in the context of four major tectonic models that have been proposed for the Yucca Mountain region.

Preston, Leiph; Smith, Ken; von Seggern, David

2007-11-01

243

Connecting the African Superplume to the Anomalous Upper Mantle beneath East Africa and Western Arabia: Results from Adaptively Parameterized P-wave Tomography  

NASA Astrophysics Data System (ADS)

A variety of different plume models have been proposed to explain the pattern of uplift, rifting, and volcanism observed throughout East Africa and western Arabia. Some studies advocate for a single, lower-mantle-originating plume impinging on the lithosphere beneath either southern Ethiopia or Afar. Other studies support multiple upwellings beneath this region, which may originate in the upper or lower mantle. A third proposed explanation is that the rifting and volcanism in East Africa and Arabia are connected to the African Superplume, a large low-velocity anomaly originating near the core-mantle boundary beneath southern Africa. We assess the competing plume models by combining P-wave arrival time data from many new permanent and temporary seismic stations throughout Africa with reprocessed data from the International Seismological Centre. These data are inverted using a global, adaptively parameterized tomography approach that provides improved resolution, especially at mid-mantle depths. We find that neither the single nor multiple lower mantle plume models match our observations, as there is no evidence for any low-velocity plume tails extending into the lower mantle beneath East Africa or Arabia. Additionally, the horizontal resolution of our model is sufficient to distinguish between individual upper mantle plumes, but we do not observe such features. Instead, our results support the African Superplume model and strongly indicate a wide connection (>500 km) between the lower mantle structure beneath southern Africa and the upper mantle structure beneath East Africa and Arabia.

Hansen, S. E.; Nyblade, A.; Benoit, M. H.; Burdick, S. A.; van der Hilst, R. D.

2010-12-01

244

Tomographic imaging of local earthquake delay times for three-dimensional velocity variation in Western Washington  

Microsoft Academic Search

Tomographic inversion is applied to delay times from local earthquakes to image three dimensional velocity variations in the Puget Sound region of Western Washington. The 37,500 square km region is represented by nearly cubic blocks of 5 km per side. P-wave arrival time observations from 4,387 crustal earthquakes, with depths of 0 to 40 km, were used as sources producing

Jonathan M. Lees; Roberts S. Crosson

1990-01-01

245

Holographic droplets in p-wave insulator/superconductor transition  

NASA Astrophysics Data System (ADS)

In the present paper, based on the notion of marginally stable modes of vector perturbations in the AdS soliton back ground we investigate the magnetic field effect on holographic p-wave insulator/superconductor transition in the probe limit. We perform explicit analytic calculations considering both Schwarzschild AdS soliton and Gauss Bonnet AdS soliton back grounds and obtain a unique relation between the chemical potential and the magnetic field near the critical point. We also extend our analysis for p + ip-wave back ground in the presence of external magnetic field. In both the cases it is observed that the non abelian model exhibit droplet solutions. Moreover it is also found that the increase in the value of the external magnetic field essentially reduces the size of the droplet and thereby makes the condensation harder.

Roychowdhury, Dibakar

2013-05-01

246

Surface states, edge currents, and the angular momentum of chiral p-wave superfluids  

NASA Astrophysics Data System (ADS)

The spectra of fermionic excitations, pairing correlations, and edge currents confined near the boundary of a chiral p-wave superfluid are calculated to leading order in ?/pf?. Results for the energy- and momentum-resolved spectral functions, including the spectral current density, of a chiral p-wave superfluid near a confining boundary are reported. The spectral functions reveal the subtle role of the chiral edge states in relation to the edge current and the angular momentum of a chiral p-wave superfluid, including the rapid suppression of Lz(T) for 0?T?Tc in the fully gapped two-dimensional chiral superfluid. The edge current and ground-state angular momentum are shown to be sensitive to boundary conditions, and as a consequence the topology and geometry of the confining boundaries. For perfect specular boundaries, the edge current accounts for the ground-state angular momentum, Lz=(N/2)?, of a cylindrical disk of a chiral superfluid with N/2 fermion pairs. Nonspecular scattering can dramatically suppress the edge current. In the limit of perfect retroreflection, the edge states form a flat band of zero modes that are nonchiral and generate no edge current. For a chiral superfluid film confined in a cylindrical toroidal geometry, the ground-state angular momentum is, in general, nonextensive, and can have a value ranging from Lz>(N/2)? to Lz<-(N/2)? depending on the ratio of the inner and outer radii and the degree of backscattering on the inner and outer surfaces. Nonextensive scaling of Lz, and the reversal of the ground-state angular momentum for a toroidal geometry, would provide a signature of broken time-reversal symmetry of the ground state of superfluid 3He-A, as well as direct observation of chiral edge currents.

Sauls, J. A.

2011-12-01

247

P Wave Indices to Predict Atrial Fibrillation Recurrences Post Pulmonary Vein Isolation  

PubMed Central

Background P-wave indices are appealing markers for predicting atrial fibrillation (AF) recurrences post ablation. Objective This study evaluates the value of P wave indices to predict recurrences post pulmonary vein isolation (PVI) in patients with paroxysmal AF. Methods We selected 198 patients (57 ± 8 years, 150 males) with symptomatic drug-refractory paroxysmal AF undergoing PVI in our hospital. A 12-lead electrocardiogram was used to measure P wave duration in lead II, P wave terminal force (PWTF) in lead V1, P wave axis and dispersion. Results During a follow-up of 9 ± 3 months, recurrences occurred in 60 (30.3%) patients. The patients that had AF recurrence had longer mean P wave duration (122.9 ± 10.3 vs 104.3 ± 14.2 ms, p < 0.001), larger P wave dispersion (40.7 ± 1.7 ms vs 36.6 ± 3.2 ms, p < 0.001). P wave duration ? 125 ms has 60% sensitivity, 90% specificity, positive predictive value (PPV) of 72% and negative predictive value (NPV) of 83.7%, whereas P wave dispersion ? 40 ms has 78% sensitivity, 67% specificity, PPV of 51% and NPV of 87.6% 48/66 (72.7%) patients with PWTF ? - 0.04 mm/second vs 12/132(9%) with PWTF > -0.04 mm/second showed recurrence of AF (p < 0.001). P wave axis was not different between two groups. On multivariate analysis, P wave indices were not independent from left atrial size and age. Conclusions P wave duration ? 125 ms, P wave dispersion ? 40 ms and PWTF in V1 ? - 0.04 mm/sec are good clinical predictors of AF recurrences post PVI in patients with paroxysmal atrial fibrillation; however they were not independent from left atrial size and age.

Salah, Ahmed; Zhou, Shenghua; Liu, Qiming; Yan, Hui

2013-01-01

248

New insights on the structure of La Soufriere dome from joint inversion of P-wave velocity and density  

NASA Astrophysics Data System (ADS)

One objective of the french project Domoscan (2009-2013) was to obtain better constraints on the geological structure of La Soufriere hydrothermal system, that is the dome inner structure but also its basement that has not yet been imaged, while it may play an essential role in potential flank destabilization. In this framework, we performed a 3D gravity and P-wave travel time joint inversion to obtain density and P-wave velocity images of La Soufriere hydrothermal system (Coutant et al., 2012). The joint inversion approach was proposed to overcome the lack of resolution of the two methods taken separately. In this study, the coupling between P-wave velocity and density relies on a relationship derived from laboratory measurements on 58 samples from La Soufriere and Mt Pelee deposits. The laboratory data cover a large range of porosity (1-73%) with P wave velocity ranging from 2 to 5.4 km/s and density from 1.5 to 2.8 g/cm3 in water saturated samples. The joint inversion results show that P wave velocity model benefits from density resolution at the volcano summit, while density resolution improves at depth. The improved images allow new insights on La Soufriere structures. As an example the resistive zones that have been so far only seen by electromagnetic surveys may not be due only to argilization but may also be explained by the presence of dense massive zones, that we interpret as andesite spines resulting from 3100 B.P. or 1530 A.D eruptions. These dense bodies may have implication on the stability of the edifice and then the destabilization risks at La Soufriere of Guadeloupe. This work also shows that laboratory studies on physical properties of volcanic rocks and their relationships can be useful in the interpretation of geophysical observations on structurally complex areas such as volcano or geothermal system.

Bernard, Marie-Lise; Coutant, Olivier; Beauducel, Francois

2014-05-01

249

Value of the signal-averaged P wave analysis in predicting atrial fibrillation after cardiac surgery.  

PubMed

Atrial fibrillation (AF) is the most common sustained arrhythmia occurring after cardiac surgery. Beside important implications regarding patient recovery, AF has been shown to substantially lengthen hospital stay--our recent study found a 3-day prolongation after adjusting for all other significant factors. Identification of those at highest risk of AF by clinical or noninvasive characteristics may be a useful strategy for targeted prophylactic therapy. Our data have shown that prolonged atrial conduction as assessed by analysis of the P wave duration from the signal-averaged electrocardiogram (SAECG) imparts a four fold increase in risk for postoperative AF, independently of other measured variables. In addition, abnormal conduction was present on the preoperative P wave ECG (P-SAECG), implying a preexisting substrate that is triggered by surgery. The use of combination abnormal noninvasive variables (eg, abnormal P-SAECG and low left ventricular ejection fraction) can identify groups with a 50% risk of AF, which is nine times as high as when both tests are normal. Thus, the P-SAECG is a useful and accurate predictor of AF after cardiac surgery. PMID:9535479

Tamis, J E; Steinberg, J S

1998-01-01

250

High resolution teleseismic P-wave tomography for SE Romania  

NASA Astrophysics Data System (ADS)

The Vrancea earthquake region in SE Romania is characterized by strong intermediate depth seismicity in a very limited and well defined hypocentral region. Previous studies recognized a high velocity body as locus of the intermediate depth seismicity. Present models interpret this body as a remnant of subducted lithosphere that has been detached along the Carpathian arc, now representing the final stage of slab break-off in the upper mantle. For our new results we used the teleseismic dataset of the CALIXTO'99 tomography experiment for a nonlinear inversion of teleseismic P-wave traveltimes. The dataset consists of more than 12 000 traveltime readings from 196 events leading to a good ray coverage within the model. In previous results the influence of the poorly resolved crust caused uncontrolled smearing into the upper mantle. To overcome this limitation traveltimes were calculated through a realistic crustal model for this region and through the IASP'91 model with a 3D-FD raytracing algorithm. Therefore the effect of the traveltime anomalies within the crust could be eliminated from the tomographic inversion. We will present the high resolution image of the high velocity body and the surroundings in the upper mantle as the results of the nonlinear tomography and discuss it in terms of structure, resolution capability and solution reliability to outline the boundary conditions for the geodynamic model of this region.

Martin, M.; Calixto Working Group

2003-04-01

251

Seismic Tomography of the Sacramento -- San Joaquin River Delta: Joint P-wave/Gravity and Ambient Noise Methods  

NASA Astrophysics Data System (ADS)

The Sacramento -- San Joaquin River Delta (SSJRD) is an area that has been identified as having high seismic hazard but has resolution gaps in the seismic velocity models of the area due to a scarcity of local seismic stations and earthquakes. I present new three-dimensional (3D) P-wave velocity (Vp) and S-wave velocity (Vs) models for the SSJRD which fill in the sampling gaps of previous studies. I have created a new 3D seismic velocity model for the SSJRD, addressing an identified need for higher resolution velocity models in the region, using a new joint gravity/body-wave tomography algorithm. I am able to fit gravity and arrival-time residuals jointly using an empirical density-velocity relationship to take advantage of existing gravity data in the region to help fill in the resolution gaps of previous velocity models in the area. I find that the method enhances the ability to resolve the relief of basin structure relative to seismic-only tomography at this location. I find the depth to the basement to be the greatest in the northwest portion of the SSJRD and that there is a plateau in the basement structure beneath the southeast portion of the SSJRD. From my findings I infer that the SSJRD may be prone to focusing effects and basin amplification of ground motion. A 3D, Vs model for the SSJRD and surrounding area was created using ambient noise tomography. The empirical Green's functions are in good agreement with published cross-correlations and match earthquake waveforms sharing similar paths. The group velocity and shear velocity maps are in good agreement with published regional scale models. The new model maps velocity values on a local scale and successfully recovers the basin structure beneath the Delta. From this Vs model I find the maximum depth of the basin to reach approximately 15 km with the Great Valley Ophiolite body rising to a depth of 10 km east of the SSJRD. We consider our basement-depth estimates from the Vp model to be more robust than from the Vs model.

Teel, Alexander C.

252

Analysis of changes in the beat-to-beat P-wave morphology using clustering techniques  

Microsoft Academic Search

Several pathologies related to the atrial electrical activity can be detected in the electrocardiogram P-wave. A protocol for analyzing P-wave morphology changes has been developed in this article. By using this protocol a study on the beat-to-beat P-wave morphology changes of 89 ECG signals is performed. An algorithm based on the embedding space techniques has been used to extract the

Alberto Herreros; Enrique Baeyens; Rolf Johansson; Jonas Carlson; José R. Perán; Bertil Olsson

2009-01-01

253

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?  

Code of Federal Regulations, 2010 CFR

...your per diem allowance or other travel expenses. You also should show...times, but you must annotate your travel claim when your travel is more than 12 hours but not exceeding 24 hours to reflect that...

2009-07-01

254

41 CFR 301-11.10 - Am I required to record departure/arrival dates and times on my travel claim?  

Code of Federal Regulations, 2010 CFR

...your per diem allowance or other travel expenses. You also should show...times, but you must annotate your travel claim when your travel is more than 12 hours but not exceeding 24 hours to reflect that...

2010-07-01

255

Electric car arrives - again  

SciTech Connect

The first mass-produced electric cars in modern times are here, although they are expensive, limited in capability and unfamiliar to most prospective consumers. This article presents a brief history of the reintroduction of the modern electric car as well as discussions of the limitations of development, alternative routes to both producing and selling electric cars or some modified version of electric cars, economic incentives and governmental policies, and finally a snapshot description of the future for electric cars. 6 refs., 1 tab.

Dunn, S.

1997-03-01

256

Finite frequency whole mantle P wave tomography: Improvement of subducted slab images  

NASA Astrophysics Data System (ADS)

present a new whole mantle P wave tomographic model GAP_P4. We used two data groups; short-period data of more than 10 million picked-up onset times and long-period data of more than 20 thousand differential travel times measured by waveform cross correlation. Finite frequency kernels were calculated at the corresponding frequency bands for both long- and short-period data. With respect to an earlier model GAP_P2, we find important improvements especially in the transition zone and uppermost lower mantle beneath the South China Sea and the southern Philippine Sea owing to broadband ocean bottom seismometers (BBOBSs) deployed in the western Pacific Ocean where station coverage is poor. This new model is different from a model in which the full data set is interpreted with classical ray theory. BBOBS observations should be more useful to sharpen images of subducted slabs than expected from simple raypath coverage arguments.

Obayashi, Masayuki; Yoshimitsu, Junko; Nolet, Guust; Fukao, Yoshio; Shiobara, Hajime; Sugioka, Hiroko; Miyamachi, Hiroki; Gao, Yuan

2013-11-01

257

Data rate selection in WBSS-based IEEE 802.11p\\/WAVE vehicular ad hoc networks  

Microsoft Academic Search

The upcoming IEEE 802.11p\\/WAVE (Wireless Access for Vehicular Environment) standard is intended to deliver both safety and non-safety applications to vehicles on the roads. Despite the massive research effort related to the design of reliable and timely schemes for dissemination of safety messages, only a few works have investigated on-the-road delivery of non-safety applications, such as comfort and entertainment (e.g.,

Claudia Campolo; Antonella Molinaro

2010-01-01

258

An efficient hybrid pseudospectral/finite-difference scheme for solving the TTI pure P-wave equation  

NASA Astrophysics Data System (ADS)

The pure P-wave equation for modelling and migration in tilted transversely isotropic (TTI) media has attracted more and more attention in imaging seismic data with anisotropy. The desirable feature is that it is absolutely free of shear-wave artefacts and the consequent alleviation of numerical instabilities generally suffered by some systems of coupled equations. However, due to several forward-backward Fourier transforms in wavefield updating at each time step, the computational cost is significant, and thereby hampers its prevalence. We propose to use a hybrid pseudospectral (PS) and finite-difference (FD) scheme to solve the pure P-wave equation. In the hybrid solution, most of the cost-consuming wavenumber terms in the equation are replaced by inexpensive FD operators, which in turn accelerates the computation and reduces the computational cost. To demonstrate the benefit in cost saving of the new scheme, 2D and 3D reverse-time migration (RTM) examples using the hybrid solution to the pure P-wave equation are carried out, and respective runtimes are listed and compared. Numerical results show that the hybrid strategy demands less computation time and is faster than using the PS method alone. Furthermore, this new TTI RTM algorithm with the hybrid method is computationally less expensive than that with the FD solution to conventional TTI coupled equations.

Zhan, Ge; Pestana, Reynam C.; Stoffa, Paul L.

2013-04-01

259

Model input and output files for the simulation of time of arrival of landfill leachate at the water table, Municipal Solid Waste Landfill Facility, U.S. Army Air Defense Artillery Center and Fort Bliss, El Paso County, Texas  

USGS Publications Warehouse

This report contains listings of model input and output files for the simulation of the time of arrival of landfill leachate at the water table from the Municipal Solid Waste Landfill Facility (MSWLF), about 10 miles northeast of downtown El Paso, Texas. This simulation was done by the U.S. Geological Survey in cooperation with the U.S. Department of the Army, U.S. Army Air Defense Artillery Center and Fort Bliss, El Paso, Texas. The U.S. Environmental Protection Agency-developed Hydrologic Evaluation of Landfill Performance (HELP) and Multimedia Exposure Assessment (MULTIMED) computer models were used to simulate the production of leachate by a landfill and transport of landfill leachate to the water table. Model input data files used with and output files generated by the HELP and MULTIMED models are provided in ASCII format on a 3.5-inch 1.44-megabyte IBM-PC compatible floppy disk.

Abeyta, Cynthia G.; Frenzel, Peter F.

1999-01-01

260

A Powerful Twin Arrives  

NASA Astrophysics Data System (ADS)

First Images from FORS2 at VLT KUEYEN on Paranal The first, major astronomical instrument to be installed at the ESO Very Large Telescope (VLT) was FORS1 ( FO cal R educer and S pectrograph) in September 1998. Immediately after being attached to the Cassegrain focus of the first 8.2-m Unit Telescope, ANTU , it produced a series of spectacular images, cf. ESO PR 14/98. Many important observations have since been made with this outstanding facility. Now FORS2 , its powerful twin, has been installed at the second VLT Unit Telescope, KUEYEN . It is the fourth major instrument at the VLT after FORS1 , ISAAC and UVES.. The FORS2 Commissioning Team that is busy installing and testing this large and complex instrument reports that "First Light" was successfully achieved already on October 29, 1999, only two days after FORS2 was first mounted at the Cassegrain focus. Since then, various observation modes have been carefully tested, including normal and high-resolution imaging, echelle and multi-object spectroscopy, as well as fast photometry with millisecond time resolution. A number of fine images were obtained during this work, some of which are made available with the present Press Release. The FORS instruments ESO PR Photo 40a/99 ESO PR Photo 40a/99 [Preview - JPEG: 400 x 345 pix - 203k] [Normal - JPEG: 800 x 689 pix - 563kb] [Full-Res - JPEG: 1280 x 1103 pix - 666kb] Caption to PR Photo 40a/99: This digital photo shows the twin instruments, FORS2 at KUEYEN (in the foreground) and FORS1 at ANTU, seen in the background through the open ventilation doors in the two telescope enclosures. Although they look alike, the two instruments have specific functions, as described in the text. FORS1 and FORS2 are the products of one of the most thorough and advanced technological studies ever made of a ground-based astronomical instrument. They have been specifically designed to investigate the faintest and most remote objects in the universe. They are "multi-mode instruments" that may be used in several different observation modes. FORS2 is largely identical to FORS1 , but there are a number of important differences. For example, it contains a Mask Exchange Unit (MXU) for laser-cut star-plates [1] that may be inserted at the focus, allowing a large number of spectra of different objects, in practice up to about 70, to be taken simultaneously. Highly sophisticated software assigns slits to individual objects in an optimal way, ensuring a great degree of observing efficiency. Instead of the polarimetry optics found in FORS1 , FORS2 has new grisms that allow the use of higher spectral resolutions. The FORS project was carried out under ESO contract by a consortium of three German astronomical institutes, the Heidelberg State Observatory and the University Observatories of Göttingen and Munich. The participating institutes have invested a total of about 180 man-years of work in this unique programme. The photos below demonstrate some of the impressive possibilities with this new instrument. They are based on observations with the FORS2 standard resolution collimator (field size 6.8 x 6.8 armin = 2048 x 2048 pixels; 1 pixel = 0.20 arcsec). In addition, observations of the Crab pulsar demonstrate a new observing mode, high-speed photometry. Protostar HH-34 in Orion ESO PR Photo 40b/99 ESO PR Photo 40b/99 [Preview - JPEG: 400 x 444 pix - 220kb] [Normal - JPEG: 800 x 887 pix - 806kb] [Full-Res - JPEG: 2000 x 2217 pix - 3.6Mb] The Area around HH-34 in Orion ESO PR Photo 40c/99 ESO PR Photo 40c/99 [Preview - JPEG: 400 x 494 pix - 262kb] [Full-Res - JPEG: 802 x 991 pix - 760 kb] The HH-34 Superjet in Orion (centre) PR Photo 40b/99 shows a three-colour composite of the young object Herbig-Haro 34 (HH-34) , now in the protostar stage of evolution. It is based on CCD frames obtained with the FORS2 instrument in imaging mode, on November 2 and 6, 1999. This object has a remarkable, very complicated appearance that includes two opposite jets that ram into the surrounding interstellar matter. This structure is produced by a machine-gu

1999-11-01

261

A finite-frequency P-wave tomographic model: images of subducted slabs stagnant above, penetrating through and trapped below the 660-km discontinuity  

NASA Astrophysics Data System (ADS)

We constructed a new P-wave tomographic model of the mantle using more than ten millions of travel time data. The finite frequency effect of seismic ray was taken into account by calculating banana-donut kernels at 2 Hz for all the first arrival data and at 0.1 Hz for the broadband differential travel time data. Based on this model, a systematic survey was made for subducted slab images around the circum Pacific including Kurile, Honshu, Izu-Bonin, Mariana, Java, Tonga-Kermadec, southern and northern South America, and Central America. This survey clarified a progressive lateral variation of slab configuration along the arc or through the arc to arc, where a subducted slab is in general in one or two of the following four stages: I. slab stagnant above the 660, II. slab penetrating the 660, III. slab trapped in the uppermost lower mantle (660 to ?1000 km in depth), and IV. slab descending well into the deep lower mantle. The majority of the slab images are either at stage I or III. We interpret I to IV as the successive stages of slab subduction through the transition region with the 660 at the middle, where I and III are relatively stable or neutral stages and II and IV are relatively unstable, transient stages. In particular, we emphasize III as a distinct stage of slab subduction, through which the slab once softened by the phase transition may progressively recover its hardness. Alternatively, the mantle viscosity may not increase stepwise across the 660 but increase gradually throughout the uppermost lower mantle. Plots of hypocentral distribution on tomographic slab images show that deep shocks at depths greater than ?620 km are a good measure of slab penetration at stage either II or III.

Fukao, Y.; Obayashi, M.

2012-12-01

262

P-wave tomography reveals a westward dipping low velocity zone beneath the Kenya Rift  

NASA Astrophysics Data System (ADS)

Three teleseismic P-wave travel time data sets (KRISP 1985, 1989-1990 Kenya Broadband Seismic Experiment) have been inverted to obtain a new tomographic model of the upper mantle beneath the Kenya Rift. The model shows a 0.5-1.5% low velocity anomaly below the rift extending to about 150 km depth. Below ~150 km depth, the anomaly broadens to the west toward the Tanzania Craton, suggesting a westward dip to the structure. Tomographic images to the south in Tanzania and to the north in Ethiopia also show westward dipping low velocity anomalies below depths of ~150-200 km. The presence of westward dipping low velocity structures along much of the East African rift (Ethiopia, Kenya and Tanzania) is difficult to explain with a plume model and is consistent with some models of the African Superplume showing anomalous lower and upper mantle structure connecting at mid-mantle depths under the western side of East Africa.

Park, Yongcheol; Nyblade, Andrew A.

2006-04-01

263

P wave dispersion is prolonged in patients with Wilson’s disease  

Microsoft Academic Search

AIM: To investigate the P wave dispersion as a non- invasive marker of intra-atrial conduction disturbances in patients with Wilson's disease. METHODS: We compared Wilson's disease patients (n = 18) with age matched healthy subjects (n = 15) as controls. The diagnosis was based on clinical symptoms, laboratory tests (ceruloplasmin, urinary and hepatic copper concentrations). P wave dispersion, a measurement

Nurcan Arat; Sabite Kacar; Zehra Golbasi; Meral Akdogan; Yeliz Sokmen; Sedef Kuran; Ramazan Idilman; Türkiye Yüksek

2008-01-01

264

Laboratory velocities and attenuation of P-waves in limestones during freeze-thaw cycles  

Microsoft Academic Search

The velocity and the attenuation of compressional P-waves, measured in the laboratory at ultrasonic frequencies during a series of freezing and thawing cycles, are used as a method for predicting frost damage in a bedded limestone. Pulse transmission and spectral ratio techniques are used to determine the P-wave velocities and the attenuation values relative to an aluminum reference samples with

Jean-Michel Remy; M. Bellanger; F. Homand-Etienne

1994-01-01

265

On the resolution of ECG acquisition systems for the reliable analysis of the P-wave  

Microsoft Academic Search

The analysis of the P-wave on surface ECG is widely used to assess the risk of atrial arrhythmias. In order to provide reliable results, the automatic analysis of the P-wave must be precise and reliable and must take into account technical aspects, one of those being the resolution of the acquisition system. The aim of this note is to investigate

Federica Censi; Giovanni Calcagnini; Ivan Corazza; Eugenio Mattei; Michele Triventi; Pietro Bartolini; Giuseppe Boriani

2012-01-01

266

On the resolution of ECG acquisition systems for the reliable analysis of the P-wave.  

PubMed

The analysis of the P-wave on surface ECG is widely used to assess the risk of atrial arrhythmias. In order to provide reliable results, the automatic analysis of the P-wave must be precise and reliable and must take into account technical aspects, one of those being the resolution of the acquisition system. The aim of this note is to investigate the effects of the amplitude resolution of ECG acquisition systems on the P-wave analysis. Starting from ECG recorded by an acquisition system with a less significant bit (LSB) of 31 nV (24 bit on an input range of 524 mVpp), we reproduced an ECG signal as acquired by systems with lower resolution (16, 15, 14, 13 and 12 bit). We found that, when the LSB is of the order of 128 µV (12 bit), a single P-wave is not recognizable on ECG. However, when averaging is applied, a P-wave template can be extracted, apparently suitable for the P-wave analysis. Results obtained in terms of P-wave duration and morphology revealed that the analysis of ECG at lowest resolutions (from 12 to 14 bit, LSB higher than 30 µV) could lead to misleading results. However, the resolution used nowadays in modern electrocardiographs (15 and 16 bit, LSB <10 µV) is sufficient for the reliable analysis of the P-wave. PMID:22274002

Censi, Federica; Calcagnini, Giovanni; Corazza, Ivan; Mattei, Eugenio; Triventi, Michele; Bartolini, Pietro; Boriani, Giuseppe

2012-02-01

267

Medically treated anorexia nervosa is associated with normal P wave parameters.  

PubMed

Anorexia nervosa (AN) is an increasingly common medical condition. Some studies have demonstrated an increased prevalence of atrial premature contractions and anatomical changes in AN patients. Our aim was to investigate P wave parameters and P wave dispersion, an electrocardiographic marker for supraventricular arrhythmias, and its effect on AN. The study group included 48 patients with AN, most hospitalized for a few weeks, and a matched control group. All participants underwent 12-lead electrocardiography (ECG) under strict standards. P wave length and P wave dispersion in each patient were computed from a randomly selected beat and an averaged beat, constructed from 7 to 12 beats, included in a 10-s ECG. There were no statistically significant differences found between the groups for minimal, maximal, average P wave duration and P wave dispersion, calculated either from a random beat or averaged beats. In conclusion, medically treated AN patients who have gained weight have normal P wave parameters, and therefore do not appear to have an increased electrocardiographic risk for atrial fibrillation compared with healthy controls. Further studies are required to evaluate the influence of different disease stages, electrolyte imbalance and other medical complications on P wave parameters and risk for supraventricular arrhythmias in AN patients. PMID:22421068

Nussinovitch, Moshe; Gur, Eitan; Nussinovitch, Naomi; Kaminer, Keren; Volovitz, Benjamin; Nussinovitch, Udi

2012-07-30

268

Inferences on Crustal Velocities and Densities from P Wave Delays and Gravity Anomalies  

Microsoft Academic Search

A correlation is demonstrated between P wave delays and Bouguer gravity anomalies. For California data it is given approximately by (Ag> _-- --355PD where (Ag> is the Bouguer (slab equivalent) gravity change in milligals and PD is the delay in seconds. The increases in P wave delays and negative gravity anomalies associated with topographic highs are manifestations of isostatic adjustment.

SHAWN BIEI-ILER

1964-01-01

269

Finite-fault source inversion using teleseismic P waves: simple parameterization and rapid analysis  

USGS Publications Warehouse

We examine the ability of teleseismic P waves to provide a timely image of the rupture history for large earthquakes using a simple, 2D finite?fault source parameterization. We analyze the broadband displacement waveforms recorded for the 2010 Mw~7 Darfield (New Zealand) and El Mayor?Cucapah (Baja California) earthquakes using a single planar fault with a fixed rake. Both of these earthquakes were observed to have complicated fault geometries following detailed source studies conducted by other investigators using various data types. Our kinematic, finite?fault analysis of the events yields rupture models that similarly identify the principal areas of large coseismic slip along the fault. The results also indicate that the amount of stabilization required to spatially smooth the slip across the fault and minimize the seismic moment is related to the amplitudes of the observed P waveforms and can be estimated from the absolute values of the elements of the coefficient matrix. This empirical relationship persists for earthquakes of different magnitudes and is consistent with the stabilization constraint obtained from the L?curve in Tikhonov regularization. We use the relation to estimate the smoothing parameters for the 2011 Mw 7.1 East Turkey, 2012 Mw 8.6 Northern Sumatra, and 2011 Mw 9.0 Tohoku, Japan, earthquakes and invert the teleseismic P waves in a single step to recover timely, preliminary slip models that identify the principal source features observed in finite?fault solutions obtained by the U.S. Geological Survey National Earthquake Information Center (USGS/NEIC) from the analysis of body? and surface?wave data. These results indicate that smoothing constraints can be estimated a priori to derive a preliminary, first?order image of the coseismic slip using teleseismic records.

Mendoza, C.; Hartzell, S.

2013-01-01

270

Global P-wave Tomography Using Finite-Frequency Modeling and Finite-Frequency Data  

NASA Astrophysics Data System (ADS)

We use our matched-filtering measurements of finite-frequency, teleseismic body-wave traveltimes and amplitudes as input data for global-scale "banana-doughnut" tomography. We present a new mantle model of Vp anomalies obtained from joint inversion of P-wave traveltimes and amplitudes. A Qs model is also obtained since amplitudes are inverted simultaneously for focusing and attenuation. In accordance with their definition in the Born approximation, traveltimes and amplitudes were measured by cross-correlating observed and predicted seismograms. Observables are consistent across frequency bands since for any source-receiver path, finite-frequency measurements are derived by filtering a single broadband seismogram into distinct sub-bands. Our bandpass filters have central frequencies between 0.03 and 1~Hz. In this range, predicted waveforms depend heavily on accurate estimates of source time functions, a challenge explicitly addressed by our method. Frechet kernels are computed using the exact frequency responses of the bandpass filters used. Our data set comprises teleseismic P-wave data from 1999-2007, available from IRIS DMC. We have processed all events for which mb ? 6.0, and most events for which 5.7 ? mb < 6.0, for a total of >1,500 earthquakes. We have thus far concentrated on the inversion of teleseismic P-wave data observed in North America. The obtained models predict traveltime dispersion due to diffraction effects on the order of 0.1-0.5 sec, consistent with what we observe in the data. Amplitude dispersion is on the order of 20%. Our models explain roughly half of the variance associated with the amplitude data. For North America, we observe a close correspondence of upper mantle Vp patterns with known surface tectonics. Thanks to the excellent USArray data, features on the order of 200~km can be resolved in large parts of the upper mantle under the Western U.S. Deeper down and further east, the presumed fragments of the subducting Farallon plate are clearly visible. We expect to include the full data set with global source-receiver coverage and to present preliminary results for a global inversion in addition to the North American tomography.

Sigloch, K.; Nolet, G.

2007-12-01

271

Scheduling and Sequencing Arrivals to a Stochastic Service System.  

National Technical Information Service (NTIS)

Optimization of scheduled arrival times to an appointment system is approached from the perspectives of both queueing and scheduling theory. The appointment system is modeled as a one-server, first-come-first-served, transient queue with independent, dist...

P. M. Bosch

1997-01-01

272

NASA's SOFIA Arrives in Christchurch, New Zealand, July 14, 2013  

NASA Video Gallery

NASA's Stratospheric Observatory for Infrared Astronomy airborne observatory arrived at Christchurch International Airport, New Zealand, July 14 at 12:14 p.m. (New Zealand Standard Time) to investi...

273

Scheduling and Separating Departures Crossing Arrival Flows in Shared Airspace  

NASA Technical Reports Server (NTRS)

Flight efficiency and reduction of flight delays are among the primary goals of NextGen. In this paper, we propose a concept of shared airspace where departures fly across arrival flows, provided gaps are available in these flows. We have explored solutions to separate departures temporally from arrival traffic and pre-arranged procedures to support controllers' decisions. We conducted a Human-in-the-Loop simulation and assessed the efficiency and safety of 96 departures from the San Jose airport (SJC) climbing across the arrival airspace of the Oakland and San Francisco arrival flows. In our simulation, the SJC tower had a tool to schedule departures to fly across predicted gaps in the arrival flow. When departures were mistimed and separation could not be ensured, a safe but less efficient route was provided to the departures to fly under the arrival flows. A coordination using a point-out procedure allowed the arrival controller to control the SJC departures right after takeoff. We manipulated the accuracy of departure time (accurate vs. inaccurate) as well as which sector took control of the departures after takeoff (departure vs. arrival sector) in a 2x2 full factorial plan. Results show that coordination time decreased and climb efficiency increased when the arrival sector controlled the aircraft right after takeoff. Also, climb efficiency increased when the departure times were more accurate. Coordination was shown to be a critical component of tactical operations in shared airspace. Although workload, coordination, and safety were judged by controllers as acceptable in the simulation, it appears that in the field, controllers would need improved tools and coordination procedures to support this procedure.

Chevalley, Eric; Parke, Bonny K.; Lee, Paul; Omar, Faisal; Lee, Hwasoo; Beinert, Nancy; Kraut, Joshua M.; Palmer, Everett

2013-01-01

274

Geohydrology of the unsaturated zone and simulated time of arrival of landfill leachate at the water table, municipal solid waste landfill facility, US Army Air Defense Artillery Center and Fort Bliss, El Paso County, Texas  

USGS Publications Warehouse

The U.S. Air Defense Artillery Center and Fort Bliss Municipal Solid Waste Landfill Facility (MSWLF) is located about 10 miles northeast of downtown El Paso, Texas. The landfill is built on the Hueco Bolson, a deposit that yields water to five public-supply wells within 1.1 miles of the landfill boundary on all sides. The bolson deposits consist of lenses and mixtures of sand, clay, silt, gravel, and caliche. The unsaturated zone at the landfill is about 300 feet thick. The Hydrologic Evaluation of Landfill Performance (HELP) and the Multimedia Exposure Assessment Model for Evaluating the Land Disposal of Wastes (MULTIMED) computer models were used to simulate the time of first arrival of landfill leachate at the water table. Site-specific data were collected for model input. At five sites on the landfill cover, hydraulic conductivity was measured by an in situ method; in addition, laboratory values were obtained for porosity, moisture content at field capacity, and moisture content at wilting point. Twenty-seven sediment samples were collected from two adjacent boreholes drilled near the southwest corner of the landfill. Of these, 23 samples were assumed to represent the unsaturated zone beneath the landfill. The core samples were analyzed in the laboratory for various characteristics required for the HELP and MULTIMED models: initial moisture content, dry bulk density, porosity, saturated hydraulic conductivity, moisture retention percentages at various suction values, total organic carbon, and pH. Parameters were calculated for the van Genuchten and Brooks-Corey equations that relate hydraulic conductivity to saturation. A reported recharge value of 0.008 inch per year was estimated on the basis of soil- water chloride concentration. The HELP model was implemented using input values that were based mostly on site-specific data or assumed in a conservative manner. Exceptions were the default values used for waste characteristics. Flow through the landfill was assumed to be at steady state. The HELP-estimated landfill leakage rate was 101.6 millimeters per year, approximately 500 times the estimated recharge rate for the area near the landfill. The MULTIMED model was implemented using input values that were based mainly on site-specific data and some conservatively assumed values. Landfill leakage was assumed to begin when the landfill was established and to continue at a steady-state rate of 101.6 millimeters per year as estimated by the HELP model. By using an assumed solute concentration in the leachate of 1 milligram per liter and assuming no delay or decay of solute, the solute serves as a tracer to indicate the first arrival of landfill leachate. The simulated first arrival of leachate at the water table was 204 to 210 years after the establishment of the landfill.

Frenzel, Peter F.; Abeyta, Cynthia G.

1999-01-01

275

Collaborative Arrival Planning: Data Sharing and User Preference Tools  

NASA Technical Reports Server (NTRS)

Air traffic growth and air carrier economic pressures have motivated efforts to increase the flexibility of the air traffic management process and change the relationship between the air traffic control service provider and the system user. One of the most visible of these efforts is the U.S. government/industry "free flight" initiative, in which the service provider concentrates on safety and cross-airline fairness, and the user on their business objectives and operating preferences, including selecting their own path and speed in real-time. In the terminal arrival phase of flight, severe restrictions and rigid control are currently placed on system users, typically without regard for individual user operational preferences. Airborne delays applied to arriving aircraft into capacity constrained airports are imposed on a first-come, first-serve basis, and thus do not allow the system user to plan for or prioritize late arrivals, or to economically optimize their arrival sequence. A central tenant of the free-flight operating paradigm is collaboration between service providers and users in reaching air traffic management decisions. Such collaboration would be particularly beneficial to an airline's "hub" operation, where off-schedule arrival aircraft are a consistent problem, as they cause serious air-port ramp difficulties, rippling airline scheduling effects, and result in large economic inefficiencies. Greater collaboration can also lead to increased airport capacity and decrease the severity of over-capacity rush periods. In the NASA Collaborative Arrival Planning (CAP) project, both independent exchange of real-time data between the service provider and system user and collaborative decision support tools are addressed. Data exchange of real-time arrival scheduling, airspace management, and air carrier fleet data between the FAA service provider and an air carrier is being conducted and evaluated. Collaborative arrival decision support tools to allow intra-airline arrival preferences are being developed and simulated. The CAP project is part of and leveraged from the NASA/FAA Center TRACON Automation System (CTAS), a fielded set of decision support tools that provide computer generated advisories for both enroute and terminal area controllers to manage and control arrival traffic more efficiently. In this paper, the NASA Collaborative Arrival Planning project is outlined and recent results detailed, including the real-time use of CTAS arrival scheduling data by a major air carrier and simulations of tactical and strategic user preference decision support tools.

Zelenka, Richard E.; Edwards, Thomas A. (Technical Monitor)

1998-01-01

276

A Bayesian approach to the detection of temporal changes in P wave velocity  

NASA Astrophysics Data System (ADS)

On the basis of Akaike's Bayesian information criterion (ABIC), a new method is proposed for detecting a temporal change in a seismic velocity in a source region. The method of joint hypocenter determination was modified in order to determine a seismic velocity in a source layer as a function of time together with hypocenters and station corrections. Arrival times of initial waves of shallow earthquakes in a small area are analyzed in this method. The smoothness of the estimated temporal variation in the velocity is guaranteed by the introduction of a prior distribution of the parameter. The hyperparameter of the prior distribution of the velocity, the reading error of arrival times, and the initial velocity in the source layer are chosen to minimize ABIC. This procedure was applied to the 1983 eastern Yamanashi M = 6.0 earthquake in central Japan. We analyzed P arrival times of 374 earthquakes observed at 12 stations in the network of the National Research Center for Disaster Prevention by dividing the whole period (from October 1981 to May 1987) into 12 six-month subperiods. Calculating ABICs for different combinations of the three parameters above, we searched for the minimum value of ABIC and found two minima. The first one corresponds to a model of a constant velocity in time, and the other corresponds to a model of a variable velocity with 5% velocity change at maximum. However, since ABIC in the former is 10 smaller than that in the latter, the former constant velocity model is statistically more suitable than the latter. Furthermore, generating artificial data with the same reading errors as the actual data, we used computer simulation to examine the lower limit of the velocity change detectable for this data set. In conclusion, the velocity in the source region is 6.24±0.18 km/s, and the velocity change exceeding 6-7% at maximum did not exist during the 6 years before and after the M = 6.0 earthquake.

Hurukawa, Nobuo; Imoto, Masajiro

1989-02-01

277

The effects of spall on teleseismic P-waves: An investigation with theoretical seismograms  

NASA Astrophysics Data System (ADS)

The effects of spall on teleseismic P-wave seismograms are investigated using theoretical seismograms calculated with an extended reflectivity method. The equivalent point-source used to model the spall process has been derived following the work of Day et al. [1983] with the modification of a spall rise-time which is introduced to account for the time necessary to bring the total spalled mass into ballistic flight. The effect of spall is studied by the superposition of synthetic seismograms for a pure explosion source with synthetic seismograms for a pure spall source. The source signal for the pure explosion is the von Seggern-Blandford reduced displacement potential. The model parameters for explosion and spall sources used are representative for the Pahute Mesa (NTS) nuclear explosion HARZER and have been determined from close-in (distance 2-7 km) and regional seismograms [Johnson, 1988; Patton, 1988]. Additionally, spall model parameters calculated from scaling relations which have been derived independently of the HARZER event are used. The result of this part of the study is that spall can contribute significantly to the waveforms of teleseismic P-waves. This conclusion still holds if certain ranges for the parameters of both the explosion and spall models are introduced. The effect of spall is to increase the peak-to-peak amplitudes and to enhance the higher frequencies compared to the predictions for the explosion without spall. However, the interference pattern in the composite explosion/spall seismograms is generally complicated and depends critically on the kinematic spall characteristics like the spall dwell- and rise-time. For the spall scaling relations considered here Sobel'ls [1978] and Patton's [1989, 1990] relations predict essential contributions of spall to teleseismic P-waveforms; only that of Viecelli [1973] predicts a minor effect on teleseismic P-waveforms. Finally, a comparison of the theoretical seismograms with observations of HARZER at teleseismic distances (SRO stations MAJO and GRFO) is made. From this comparison it is found that an explosion source without spall explains reasonably well both the maximum peak-to-peak amplitudes and the general frequency content of the data if an earth model with a dissipation time t* of 0.75 s is assumed. Therefore it is argued that the spall-model parameters momentum and spall mass used for the HARZER calculations might be up to an order of magnitude too large.

Schlittenhardt, Jörg

278

[High resolution electrocardiography of P-wave signals in clinical cardiology].  

PubMed

Signal-averaged electrocardiography of the QRS complex detects presence of late potentials which represent significant arrhythmogenic marker responsible for increased risk of life-threatening ventricular arrhythmias especially in post myocardial infarction patients. The P wave signal-averaged electrocardiography has been designed to predict development of atrial fibrillation in different populations of patients. Many P wave signal-averaging methodological procedures have been developed. However their common disadvantages remain lack of standardization, relatively low specificity and sensitivity, low positive predictive value as well as limited number of larger prospective clinical trials. Recent software and technological improvements of the P wave high resolution techniques as well as some new reports about the influence of antiarrhythmic drugs on the parameters of the P wave signal-averaged electrocardiography are creating new possibilities not only for the diagnosis of paroxysmal atrial fibrillation but also for the prediction of antiarrhythmic drug efficiency. PMID:11048540

Kucinský, R; Gonsorcík, J; Franko, J; Rajnic, A; Olexa, P

2000-02-01

279

Spin density wave fluctuations and p-wave pairing in Sr2RuO4.  

PubMed

Recently, a debate has arisen over which of the two distinct parts of the Fermi surface of Sr(2)RuO(4) is the active part for the chiral p-wave superconductivity exhibited. Early theories proposed p-wave pairing on the two-dimensional ? band, whereas a recent proposal focuses on the one-dimensional (?, ?) bands whose nesting pockets are the source of the strong incommensurate spin density wave (SDW) fluctuations. We apply a renormalization group theory to study quasi-one-dimensional repulsive Hubbard chains and explain the form of SDW fluctuations, reconciling the absence of long-range order with their nesting Fermi surface. The mutual exclusion of p-wave pairing and SDW fluctuations in repulsive Hubbard chains favors the assignment of the two-dimensional ? band as the source of p-wave pairing. PMID:23679633

Huo, Jia-Wei; Rice, T M; Zhang, Fu-Chun

2013-04-19

280

P Wave Area for Quantitative Electrocardiographic Assessment of Left Atrial Remodeling  

PubMed Central

Background Left atrial (LA) dilation provides a substrate for mitral regurgitation (MR) and atrial arrhythmias. ECG can screen for LA dilation but standard approaches do not assess LA geometry as a continuum, as does non-invasive imaging. This study tested ECG-quantified P wave area as an index of LA geometry. Methods and Results 342 patients with CAD underwent ECG and CMR within 7 (0.1±1.4) days. LA area on CMR correlated best with P wave area in ECG lead V1 (r?=?0.42, p<0.001), with lesser correlations for P wave amplitude and duration. P wave area increased stepwise in relation to CMR-evidenced MR severity (p<0.001), with similar results for MR on echocardiography (performed in 86% of patients). Pulmonary arterial (PA) pressure on echo was increased by 50% among patients in the highest (45±14 mmHg) vs. the lowest (31±9 mmHg) P wave area quartile of the population. In multivariate regression, CMR and echo-specific models demonstrated P wave area to be independently associated with LA size after controlling for MR, as well as echo-evidenced PA pressure. Clinical follow-up (mean 2.4±1.9 years) demonstrated ECG and CMR to yield similar results for stratification of arrhythmic risk, with a 2.6-fold increase in risk for atrial fibrillation/flutter among patients in the top P wave area quartile of the population (CI 1.1–5.9, p?=?0.02), and a 3.2-fold increase among patients in the top LA area quartile (CI 1.4–7.0, p?=?0.005). Conclusions ECG-quantified P wave area provides an index of LA remodeling that parallels CMR-evidenced LA chamber geometry, and provides similar predictive value for stratification of atrial arrhythmic risk.

Weinsaft, Jonathan W.; Kochav, Jonathan D.; Kim, Jiwon; Gurevich, Sergey; Volo, Samuel C.; Afroz, Anika; Petashnick, Maya; Kim, Agnes; Devereux, Richard B.; Okin, Peter M.

2014-01-01

281

Upper mantle P wave velocity structure of the northern part of China and Mongolia  

Microsoft Academic Search

The average upper mantle P wave velocity structure and lateral heterogeneity in the northern part of China and Mongolia are\\u000a investigated by waveform inversion of broadband body waveform data recorded by CDSN and digital stations around China. The\\u000a average model has a low P wave velocity lid (about 7.8–8.0 km·s?1) with thickness about 60 km, and two discontinuities with velocity

Jian-Ping Wu; Rong-Sheng Zeng; Yue-Hong Ming

1998-01-01

282

Transverse isotropy versus lateral heterogeneity in the inversion of P-wave reflection traveltimes  

Microsoft Academic Search

Nonelliptic transverse isotropy may cause pronounced nonhyperbolic moveout of long-spread P-wave reflection data. Lateral heterogeneity may alter the moveout in much the same way, and one can expect that a given P-wave reflection moveout may be interpreted equally well in terms of parameters of homogeneous transversely isotropic (TI) or laterally heterogeneous (LH) isotropic models. Here, the common-midpoint (CMP) moveout of

Vladimir Y. Grechka

1998-01-01

283

When Did the First Americans Arrive?  

NSDL National Science Digital Library

Who were the first Americans, when did they arrive, and from where did they come? With limited evidence, scientists have long proposed a hypothesis that linked the migration route and the timing of the migration of these ancient people to the end of the last ice age. This video segment, adapted from a NOVA television broadcast, describes how archaeologists have uncovered new evidence suggesting that the first Americans may have been able to migrate down the coast of North America, rather than waiting for an ice-free corridor to develop, implying that migration could have occurred earlier than previously thought. The segment is five minutes forty seconds in length.

284

When Did the First Americans Arrive?  

NSDL National Science Digital Library

Who were the first Americans, when did they arrive, and from where did they come? With limited evidence, scientists have long proposed a hypothesis that linked the migration route and the timing of the migration of these ancient people to the end of the last ice age. This video segment, adapted from a NOVA television broadcast, describes how archaeologists have uncovered new evidence suggesting that the first Americans may have been able to migrate down the coast of North America, rather than waiting for an ice-free corridor to develop, implying that migration could have occurred earlier than previously thought. The segment is five minutes forty seconds in length.

2010-09-15

285

Upper critical field of p-wave superconductors with orthorhombic symmetry  

NASA Astrophysics Data System (ADS)

Recent experiments on exotic ferromagnetic superconducting materials such as UCoGe and topological superconductors such as CuxBi2Se3, have spawned renewed interest in p-wave superconductivity. We present an extension of the Scharnberg-Klemm theory of Hc2 in p-wave superconductors to cases of partially broken symmetry in an orthorhombic crystal. Using a uniaxial anisotropic pairing interaction as is appropriate for the low-field regime of UCoGe, we have shown that a field induced crossover from one p-wave state to another can lead to kinks in Hc2(T), which can mimic upward curvature in all three crystal axis directions. Reasonably good fits to the low-field UCoGe data are obtained. We have also investigated the angular dependence of the axial p-wave state, which might prove useful in identifying the p-wave state present in certain materials, and possibly suggest new experiments on well known p-wave superconductors.

Lörscher, Christopher; Klemm, Richard

2012-02-01

286

Estimating Controller Intervention Probabilities for Optimized Profile Descent Arrivals  

NASA Technical Reports Server (NTRS)

Simulations of arrival traffic at Dallas/Fort-Worth and Denver airports were conducted to evaluate incorporating scheduling and separation constraints into advisories that define continuous descent approaches. The goal was to reduce the number of controller interventions required to ensure flights maintain minimum separation distances of 5 nmi horizontally and 1000 ft vertically. It was shown that simply incorporating arrival meter fix crossing-time constraints into the advisory generation could eliminate over half of the all predicted separation violations and more than 80% of the predicted violations between two arrival flights. Predicted separation violations between arrivals and non-arrivals were 32% of all predicted separation violations at Denver and 41% at Dallas/Fort-Worth. A probabilistic analysis of meter fix crossing-time errors is included which shows that some controller interventions will still be required even when the predicted crossing-times of the advisories are set to add a 1 or 2 nmi buffer above the minimum in-trail separation of 5 nmi. The 2 nmi buffer was shown to increase average flight delays by up to 30 sec when compared to the 1 nmi buffer, but it only resulted in a maximum decrease in average arrival throughput of one flight per hour.

Meyn, Larry A.; Erzberger, Heinz; Huynh, Phu V.

2011-01-01

287

Scattering of teleseismic P-waves by the Japan Trench: A significant effect of reverberation in the seawater column  

NASA Astrophysics Data System (ADS)

We detected a scattered wave train in data from the high-sensitivity seismograph network in Japan (Hi-net) following the arrival of the near-vertically incident P-wave generated by the 2009 earthquake (Mw 7.8) off the South Island of New Zealand. The scattered wave train represented predominantly vertical ground motion at a period of 20 to 50 s and with an apparent velocity of 3.5 km/s; it propagated cylindrically westward through the Kanto area of central Japan. Array analysis showed that the scattered wave train developed beneath the Pacific Ocean near the Boso triple junction, southeast of the Kanto area. A 3D finite-difference simulation of seismic wave propagation using a high-resolution model incorporating subsurface structure, topography, and bathymetry revealed that the strong scattered waves that were generated along the Japan Trench and propagated normal to the trench axis represented multiple reverberations of seismic waves between the seafloor and the Pacific plate boundary. In addition, strong reverberation of acoustic waves in the seawater column above the Boso triple junction causes elongated scattered waves, which reasonably explains our observations.

Maeda, Takuto; Furumura, Takashi; Obara, Kazushige

2014-07-01

288

Location, size and shape of ocean sources for Rayleigh and compressional (P) waves contained in microseisms.  

NASA Astrophysics Data System (ADS)

The analysis of microseisms, also called seismic noise, has been used for long as an indirect method to describe ocean sea-states. More recently, it has also raised much interest for tomographic purpose. The dominant seismic noise, with periods 3 to 10s, is generated by non linear ocean wave-wave interactions (double frequency microseisms, or DFM) as described theoretically [Longuet-Higgins, 1950; Hasselmann, 1963] and modeled numerically [Kedar et al., 2008; Ardhuin et al., 2011; Stutzmann et al, 2012]. The magnitude of the noise source is conditioned by the directional spectra of the swells and wind seas and the bathymetry. Seismic noise has been continuously recorded by stations spread all over the Globe for decades, which offers great perspectives for climate studies and 4D seismic tomography. Nevertheless, the efficiency of noise analysis is still limited by the poor knowledge of the location and geometry of noise sources. Here we use seismic records and numerical modeling to characterize the distribution of the DFM sources in time and space. Our numerical approach combines a numerical wave model based on the WAVEWATCH III® framework. We compute the second-order pressure fluctuation that generates Rayleigh and compressional (P) waves. The coastal reflection of ocean waves is accounted for. We inspect noise records to detect anomalously high levels of seismic noise (peaks up to a few micrometers for the standard deviation of the vertical ground displacement) recorded simultaneously at several broadband stations. For events (peaks) well modeled, we validate the source centroid position using an independent estimate from seismic data. Sources for Raleigh waves that dominate the DFM spectra are located by performing a polarization analysis of the three-axes ground displacement recorded at a set of three or more seismic stations [Schimmel et al., G3. 2011]. When P waves are also detected, the source location is estimated using beam-forming analysis at dense seismic arrays. Once validated, the computed sources are described and discussed. Our preliminary results show that the strongest sources are not localized only close to the coasts where they are promoted by incoming- and reflected-swell interactions, but rather in deep water where reflection is absent. Our analysis also suggests that most sources span large areas, with a gaussian width at half maximum around 1000 km. Only a few sources, in particular at the lowest frequencies, are more localized (500 km wide).

Obrebski, M.; Ardhuin, F.; Schimmel, M.; Stutzmann, E.

2012-04-01

289

Scattering amplitude of ultracold atoms near the p-wave magnetic Feshbach resonance  

SciTech Connect

Most of the current theories on the p-wave superfluid in cold atomic gases are based on the effective-range theory for the two-body scattering, where the low-energy p-wave scattering amplitude f{sub 1}(k) is given by f{sub 1}(k)=-1/[ik+1/(Vk{sup 2})+1/R]. Here k is the incident momentum, V and R are the k-independent scattering volume and effective range, respectively. However, due to the long-range nature of the van der Waals interaction between two colliding ultracold atoms, the p-wave scattering amplitude of the two atoms is not described by the effective-range theory [J. Math. Phys. 4, 54 (1963); Phys. Rev. A 58, 4222 (1998)]. In this paper we provide an explicit calculation for the p-wave scattering of two ultracold atoms near the p-wave magnetic Feshbach resonance. We show that in this case the low-energy p-wave scattering amplitude f{sub 1}(k)=-1/[ik+1/(V{sup eff}k{sup 2})+1/(S{sup eff}k)+1/R{sup eff}] where V{sup eff}, S{sup eff}, and R{sup eff} are k-dependent parameters. Based on this result, we identify sufficient conditions for the effective-range theory to be a good approximation of the exact scattering amplitude. Using these conditions we show that the effective-range theory is a good approximation for the p-wave scattering in the ultracold gases of {sup 6}Li and {sup 40}K when the scattering volume is enhanced by the resonance.

Zhang Peng [Exploratory Research for Advanced Technology, Macroscopic Quantum Project, Japan Science and Technology, Tokyo 113-8656 (Japan); Department of Physics, Renmin University of China, Beijing 100872 (China); Naidon, Pascal [Exploratory Research for Advanced Technology, Macroscopic Quantum Project, Japan Science and Technology, Tokyo 113-8656 (Japan); Ueda, Masahito [Exploratory Research for Advanced Technology, Macroscopic Quantum Project, Japan Science and Technology, Tokyo 113-8656 (Japan); Department of Physics, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033 (Japan)

2010-12-15

290

Imaging the Juan de Fuca plate beneath southern Oregon using teleseismic P wave residuals  

USGS Publications Warehouse

Images the Juan de Fuca plate in southern Oregon using seismic tomography. P wave travel time residuals from a 366-km-long seismic array operated in southern Oregon in 1982 are inverted. The southeast striking array extended from the Coast ranges to the Modoc Plateau and crossed the High Cascades at Crater Lake, Oregon. Three features under the array were imaged: one high-velocity zone and two low-velocity zones. The high-velocity zone is 3-4% faster than the surrounding upper mantle. It dips steeply at 65?? to the east beneath the Cascade Range and extends down to at least 200 km. It is proposed that this high-velocity feature is subducted Juan de Fuca plate. Two low-velocity zones were also imaged, both of which are 3-4% slower than the surrounding earth structure. The southeastern low-velocity zone may be caused by partially molten crust underlying the Crater Lake volcano region. -from Authors

Harris, R. A.; Iyer, H. M.; Dawson, P. B.

1991-01-01

291

Investigation of Semileptonic {ital B} Meson Decays to {ital p} -Wave Charm Mesons  

SciTech Connect

We have studied semileptonic B meson decays with a p -wave charm meson in the final state using 3.29{times}10{sup 6} B{ovr B} events collected with the CLEOII detector at the Cornell Electron-Positron Storage Ring. We find a value for the exclusive semileptonic product branching fraction B(B{sup {minus}}{r_arrow}D{sup 0}{sub 1} {ell}{sup {minus}}{ovr {nu}}{sub {ell}}) B(D{sup 0}{sub 1}{r_arrow}D{sup {asterisk}+} {pi}{sup {minus}})=(0.373{plus_minus}0.085{plus_minus} 0.052{plus_minus}0.024){percent} and an upper limit for B(B{sup {minus}}{r_arrow}D{sup {asterisk}0}{sub 2} {ell}{sup {minus}}{ovr {nu}}{sub {ell}}) B(D{sup {asterisk}0}{sub 2}{r_arrow}D{sup {asterisk}+ }{pi}{sup {minus}}){lt}0.16{percent} (90{percent} C.L.). Furthermore, we present the first measurement of the q{sup 2} spectrum for B{sup {minus}}{r_arrow}D{sup 0}{sub 1}{ell}{sup {minus}} {ovr {nu}}{sub {ell}} . {copyright} {ital 1998} {ital The American Physical Society}

Anastassov, A.; Duboscq, J.E.; Fujino, D.; Gan, K.K.; Hart, T.; Honscheid, K.; Kagan, H.; Kass, R.; Lee, J.; Spencer, M.B.; Sung, M.; Undrus, A.; Wanke, R.; Wolf, A.; Zoeller, M.M. [Ohio State University, Columbus, Ohio 43210 (United States)] [Ohio State University, Columbus, Ohio 43210 (United States); Nemati, B.; Richichi, S.J.; Ross, W.R.; Skubic, P. [University of Oklahoma, Norman, Oklahoma 73019 (United States)] [University of Oklahoma, Norman, Oklahoma 73019 (United States); Bishai, M.; Fast, J.; Hinson, J.W.; Menon, N.; Miller, D.H.; Shibata, E.I.; Shipsey, I.P.; Yurko, M. [Purdue University, West Lafayette, Indiana 47907 (United States)] [Purdue University, West Lafayette, Indiana 47907 (United States); Glenn, S.; Johnson, S.D.; Kwon, Y.; Roberts, S.; Thorndike, E.H. [University of Rochester, Rochester, New York 14627 (United States)] [University of Rochester, Rochester, New York 14627 (United States); Jessop, C.P.; Lingel, K.; Marsiske, H.; Perl, M.L.; Savinov, V.; Ugolini, D.; Wang, R.; Zhou, X. [Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States)] [Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States); Coan, T.E.; Fadeyev, V.; Korolkov, I.; Maravin, Y.; Narsky, I.; Shelkov, V.; Staeck, J.; Stroynowski, R.; Volobouev, I.; Ye, J. [Southern Methodist University, Dallas, Texas 75275 (United States)] [Southern Methodist University, Dallas, Texas 75275 (United States); Artuso, M.; Efimov, A.; Goldberg, M.; He, D.; Kopp, S.; Moneti, G.C.; Mountain, R.; Schuh, S.; Skwarnicki, T.; Stone, S.; Viehhauser, G.; Xing, X. [Syracuse University, Syracuse, New York 13244 (United States)] [Syracuse University, Syracuse, New York 13244 (United States); Bartelt, J.; Csorna, S.E.; Jain, V.; McLean, K.W.; Marka, S. [Vanderbilt University, Nashville, Tennessee 37235 (United States)] [Vanderbilt University, Nashville, Tennessee 37235 (United States); Godang, R.; Kinoshita, K.; Lai, I.C.; Pomianowski, P.; Schrenk, S. [Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (United States)] [Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (United States); Bonvicini, G.; Cinabro, D.; Greene, R.; Perera, L.P.; Zhou, G.J. [Wayne State University, Detroit, Michigan 48202 (United States)] [Wayne State University, Detroit, Michigan 48202 (United States); Barish, B.; Chadha, M.; Chan, S.; Eigen, G.; Miller, J.S.; OGrady, C.; Schmidtler, M.; Urheim, J.; Weinstein, A.J.; Wuerthwein, F. [California Institute of Technology, Pasadena, California 91125 (United States)] [California Institute of Technology, Pasadena, California 91125 (United States); Bliss, D.W.; Masek, G.; Paar, H.P.; Prell, S.; Sharma, V. and others

1998-05-01

292

Inversion of Source Parameters for Moderate Earthquakes Using Short-Period Teleseismic P Waves  

NASA Astrophysics Data System (ADS)

In this paper, we introduce a new method for estimating the source parameters of moderate earthquakes (M w ~5.0) by modeling short-period teleseismic waveforms. This method uses a grid-search algorithm to minimize misfits between observed data and synthetic seismograms in depth, magnitude, and mechanism domain in a relative high-frequency range of 0.8-2.0 Hz, similar to the traditional cut-and-paste method used in regional modeling (uc(Zhu) and uc(Helmberger,) Bull Sesimol Soc Am 86:1634-1641, 1996). In this frequency range, a significant challenge is determining the initial P-wave polarity because of a low signal-to-noise ratio (SNR). Therefore we first determine source properties for a master earthquake with a relative strong SNR. Both the travel time and amplitude corrections are developed relative to the reference 1D model along each path used in inverting the master event. We then applied these corrections to other earthquakes clustered in the same area to constrain the initial P polarities. Thus the focal mechanisms can be determined reasonably well. We inverted focal mechanisms for a small set of events beneath Qeshm Island in southern Iran and demonstrate the importance of radiation pattern at short periods.

Chu, Risheng; Ni, Sidao; Pitarka, Arben; Helmberger, Don V.

2013-10-01

293

Isolated vortex and vortex lattice in a holographic p-wave superconductor  

NASA Astrophysics Data System (ADS)

Using the holographic gauge-gravity duality, we find a solution for an isolated vortex and a vortex lattice in a 2+1-dimensional p-wave superconductor, which is described by the boundary theory dual to an SU(2) gauge theory in 3+1-dimensional anti-de Sitter space. Both px+ipy and px-ipy components of the superconducting order parameter, as well as the effects of a magnetic field on these components, are considered. The isolated vortex solution is studied, and it is found that the two order parameter components have different amplitudes due to the time-reversal symmetry breaking. The vortex lattice for large magnetic fields is also studied, where it is argued that only one order parameter component will be nonzero sufficiently close to the upper critical field. The upper critical field exhibits a characteristic upward curvature, reflecting the effects of field-induced correlations captured by the holographic theory. The free energy is calculated perturbatively in this region of the phase diagram, and it is shown that the triangular vortex lattice is the thermodynamically preferred solution.

Murray, James M.; Tešanovi?, Zlatko

2011-06-01

294

Increased QT dispersion and P wave dispersion in major depressive disorder  

PubMed Central

BACKGROUND: QT and P wave dispersion parameters can indicate abnormalities in autonomic nervous system and cardiac functioning. OBJECTIVES: To determine QT and P wave dispersion in patients with major depressive disorder compared with healthy volunteers. METHODS: Fifty newly diagnosed patients with major depressive disorder and 50 age- and sex-matched healthy volunteers underwent 12-lead electrocardiography. QT interval, QT dispersion, heart rate-corrected QT dispersion and P wave dispersions were calculated manually by a blinded specialist. RESULTS: Groups were comparable in terms of age, sex, body mass index, smoking status, metabolic diseases and left ventricular ejection fraction. The major depressive disorder group had significantly higher QT dispersion (58.5±9.9 versus 41.7±3.8; P<0.001), heart rate-corrected QT dispersion (62.5±10.0 versus 45.2±4.3; P<0.001) and P wave dispersion (46.9±4.8 versus 41.5±5.1; P<0.001). CONCLUSION: Increased QT dispersion, heart-rate corrected QT dispersion and P wave dispersion in major depressive disorder patients may be indicative of autonomic imbalance and increased risk of cardiac morbidity and mortality.

Tosu, Aydin Rodi; Demir, Serafettin; Kaya, Yuksel; Selcuk, Murat; Asker, Muntecep; Ozdemir, Mahmut; Tenekecioglu, Erhan

2013-01-01

295

First-order P-wave ray synthetic seismograms in inhomogeneous, weakly anisotropic, layered media  

NASA Astrophysics Data System (ADS)

The calculation of first-order P-wave ray synthetic seismograms based on first-order ray tracing (FORT) and dynamic ray tracing (FODRT) for P-waves propagating in inhomogeneous, weakly anisotropic media is extended from smooth to layered media. All the basic formulae necessary to calculate the P-wave FORT and FODRT quantities inside layers and to transform them at the points of reflection/transmission are given. The proposed formulae are applicable in subcritical as well as overcritical regions. The accuracy of the results is tested by comparing the approximate (FORT) results with the results obtained from a standard ray tracer for anisotropic media. The tests indicate that, except for critical regions, where the ray theory provides incorrect results anyway, the accuracy of FORT and FODRT in layered media is comparable with the accuracy in smooth media.

Pšen?ík, Ivan; Farra, Véronique

2014-07-01

296

First-order P-wave ray synthetic seismograms in inhomogeneous, weakly anisotropic, layered media  

NASA Astrophysics Data System (ADS)

The calculation of first-order P-wave ray synthetic seismograms based on first-order ray tracing (FORT) and dynamic ray tracing (FODRT) for P-waves propagating in inhomogeneous, weakly anisotropic media is extended from smooth to layered media. All the basic formulae necessary to calculate the P-wave FORT and FODRT quantities inside layers and to transform them at the points of reflection/transmission are given. The proposed formulae are applicable in subcritical as well as overcritical regions. The accuracy of the results is tested by comparing the approximate (FORT) results with the results obtained from a standard ray tracer for anisotropic media. The tests indicate that, except for critical regions, where the ray theory provides incorrect results anyway, the accuracy of FORT and FODRT in layered media is comparable with the accuracy in smooth media.

Pšen?ík, Ivan; Farra, Véronique

2014-05-01

297

Structure of the upper mantle beneath POLENET/LAPNET array, northern Fennoscandian Shield, revealed by high-resolution teleseismic P-wave traveltime tomography  

NASA Astrophysics Data System (ADS)

POLENET/LAPNET project is a passive seismic array experiment in northern Fennoscandia with stations in northern Finland, Sweden, Norway and Russia with the study area extending between 18 - 31 degrees E and 64 - 70 degrees N. One of the major targets of POLENET/LAPNET temporary seismic array research during the International Polar Year 2007-2009 was to obtain a 3D seismic model of the upper mantle in the northern part of the Precambrian Fennoscandian shield. To reach this aim we use a high-resolution teleseismic traveltime tomography. 3167 arrivals of P-waves from 97 teleseismic events with epicentral distances of 30 - 90 degrees were manually picked and inverted using TELINV code. As the crustal thickness in the study area varies from 40 km to almost 60 km, the traveltimes of P-waves were corrected for the effect of the crust using the crustal velocity model compiled from previous results of controlled-source seismic profiling, P-wave receiver function studies, and seismic noise tomography in the area. The resolution analysis demonstrated that resolution of POLENET/LAPNET data is reasonably good between depths of 75 km and 300 km. The structure of the upper mantle in the northern Fennoscandian Shield revealed in our study is generally different from the structure of the southeastern part of the Fennoscandian Shield revealed by the previous SVEKALAPKO experiment, where a high-velocity lithospheric "keel" was located stretching down to the depth of 300 km. The structure of the upper mantle beneath POLENET/LAPNET array appears to be heterogeneous down to at least 300 km, with a number of positive and negative anomalies relative to the IASP91 standard velocity model.

Silvennoinen, Hanna; Kozlovskaya, Elena; Kissling, Eduard

2013-04-01

298

p-wave superconductivity in the N-type infinite layered cuprates  

NASA Astrophysics Data System (ADS)

Recently the quasiparticle density of states(DOS) in the N-type infinite layered cuprate(NILC) Sr_0.9La_0.1CuO2 is determined through STM. The DOS doesn't look like s-wave or d-wave superconductivity. On the other hand N(E) ˜ (fracE?)^2 for E/? <1 is well described by triplet p-wave superconductivity(ABM state) same as the one in superfluid ^3He. We shall discuss the specific heat, the superfluid density for NILC within the p-wave model.

Won, Hyekyung; Maki, Kazumi

2004-03-01

299

Anomalous quantum mass flow of atoms in p-wave resonance  

SciTech Connect

I analyze an atomic Fermi gas with a planar p-wave interaction, motivated by the experimentally observed anisotropy in p-wave Feshbach resonances. An axial superfluid state is verified. A domain wall object is discovered to be a new topological defect of this superfluid and an explicit solution has been found. Gapless quasiparticles appear as bound states on the wall, dispersing in the continuum of reduced dimensions. They are chiral, deeply related to fermion zero modes in quantum chromodynamics. The chirality of the superfluid is manifested by a persistent anomalous mass current of atoms in the ground state. This quantum phenomenon is a prediction for future experiments.

Liu, W. Vincent [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

2005-11-15

300

Travel-time tomography of the Abitibi-Grenville region, eastern Canada  

NASA Astrophysics Data System (ADS)

Seismic studies of the Canadian Shield have indicated certain structural anomalies within the cratonic lithosphere. A low-velocity anomaly has been imaged near the Ontario-Québec border, in the Abitibi-Grenville province, but its 3D geometry was poorly-defined due to a lack of seismograph station coverage on the Québec side of the border. With the help of the 5 new seismograph stations installed in western Québec in 2007, 26 others belonging to the POLARIS project and the Canadian National Seismograph Network (CNSN), and a data set of travel time picks from the ABI-96 teleseismic experiment (Rondenay et al., 2000), we analyse the P-wave velocity structure of the lithosphere in order to better understand the complexity of the region and the interaction of the lithosphere with thermal anomalies in the underlying mantle. Several analysis steps have been carried out. We first measured the relative arrival times of teleseismic P waves across the array, using the cross-correlation method of VanDecar & Crosson (1990). We present the results of an analysis of azimuthal variations of these arrival times for representative stations across the array. We have also calculated maps of relative arrival time residuals across the array for earthquakes coming from different back- azimuths, in order to examine systematic patterns of travel-time anomalies resulting from mantle heterogeneity. Finally, we have inverted the travel time data to estimate a preliminary model of the 3D P-wave velocity structure beneath the region, using a standard tomographic inversion technique.

Villemaire, M.; Darbyshire, F. A.

2009-05-01

301

Travel-time Tomography of the Abitibi-Grenville Region, Eastern Canada  

NASA Astrophysics Data System (ADS)

Seismic studies of the Canadian Shield have indicated certain structural anomalies within the cratonic lithosphere. A low-velocity anomaly has been imaged near the Ontario-Quebec border, in the Abitibi- Grenville province, but its 3D geometry was poorly-defined due to a lack of seismograph station coverage on the Quebec side of the border. With the help of the 5 new seismograph stations installed in western Quebec in 2007, 26 others belonging to the POLARIS project and the Canadian National Seismograph Network (CNSN), and a data set of travel time picks from the ABI-96 teleseismic experiment (Rondenay et al., 2000), we analyse the P-wave velocity structure of the lithosphere in order to better understand the complexity of the region and the interaction of the lithosphere with thermal anomalies in the underlying mantle. Several analysis steps have been carried out. We first measured the relative arrival times of teleseismic P waves across the array, using the cross-correlation method of VanDecar & Crosson (1990). We present the results of an analysis of azimuthal variations of these arrival times for representative stations across the array. We have also calculated maps of relative arrival time residuals across the array for earthquakes coming from different back-azimuths, in order to examine systematic patterns of travel-time anomalies resulting from mantle heterogeneity. Finally, we have inverted the travel time data to estimate a preliminary model of the 3D P-wave velocity structure beneath the region, using a standard tomographic inversion technique.

Villemaire, M.; Darbyshire, F. A.

2008-12-01

302

Rupture imaging of the Mw 7.9 12 May 2008 Wenchuan earthquake from back projection of teleseismic P waves  

NASA Astrophysics Data System (ADS)

The Mw 7.9 Wenchuan earthquake of 12 May 2008 was the most destructive Chinese earthquake since the 1976 Tangshan event. Tens of thousands of people were killed, hundreds of thousands were injured, and millions were left homeless. Here we infer the detailed rupture process of the Wenchuan earthquake by back-projecting teleseismic P energy from several arrays of seismometers. This technique has only recently become feasible and is potentially faster than traditional finite-fault inversion of teleseismic body waves; therefore, it may reduce the notification time to emergency response agencies. Using the IRIS DMC, we collected 255 vertical component broadband P waves at 30-95° from the epicenter. We found that at periods of 5 s and greater, nearly all of these P waves were coherent enough to be used in a global array. We applied a simple down-sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function (ARF). We also considered three regional subarrays of seismometers in Alaska, Australia, and Europe that had apertures less than 30° and P waves that were coherent to periods as short as 1 s. Individual ARFs for these subarrays were skewed toward the subarrays; however, the linear sum of the regional subarray beams at 1 s produced a symmetric ARF, similar to that of the groomed global subarray at 5 s. For both configurations we obtained the same rupture direction, rupture length, and rupture time. We found that the Wenchuan earthquake had three distinct pulses of high beam power at 0, 23, and 57 s after the origin time, with the pulse at 23 s being highest, and that it ruptured unilaterally to the northeast for about 300 km and 110 s, with an average speed of 2.8 km/s. It is possible that similar results can be determined for future large dip-slip earthquakes within 20-30 min of the origin time using relatively sparse global networks of seismometers such as those the USGS uses to locate earthquakes in near-real time.

Xu, Yan; Koper, Keith D.; Sufri, Oner; Zhu, Lupei; Hutko, Alexander R.

2009-04-01

303

Rupture imaging of the Mw 7.9 12 May 2008 Wenchuan earthquake from back projection of teleseismic P waves  

USGS Publications Warehouse

[1] The Mw 7.9 Wenchuan earthquake of 12 May 2008 was the most destructive Chinese earthquake since the 1976 Tangshan event. Tens of thousands of people were killed, hundreds of thousands were injured, and millions were left homeless. Here we infer the detailed rupture process of the Wenchuan earthquake by back-projecting teleseismic P energy from several arrays of seismometers. This technique has only recently become feasible and is potentially faster than traditional finite-fault inversion of teleseismic body waves; therefore, it may reduce the notification time to emergency response agencies. Using the IRIS DMC, we collected 255 vertical component broadband P waves at 30-95?? from the epicenter. We found that at periods of 5 s and greater, nearly all of these P waves were coherent enough to be used in a global array. We applied a simple down-sampling heuristic to define a global subarray of 70 stations that reduced the asymmetry and sidelobes of the array response function (ARF). We also considered three regional subarrays of seismometers in Alaska, Australia, and Europe that had apertures less than 30?? and P waves that were coherent to periods as short as 1 s. Individual ARFs for these subarrays were skewed toward the subarrays; however, the linear sum of the regional subarray beams at 1 s produced a symmetric ARF, similar to that of the groomed global subarray at 5 s. For both configurations we obtained the same rupture direction, rupture length, and rupture time. We found that the Wenchuan earthquake had three distinct pulses of high beam power at 0, 23, and 57 s after the origin time, with the pulse at 23 s being highest, and that it ruptured unilaterally to the northeast for about 300 km and 110 s, with an average speed of 2.8 km/s. It is possible that similar results can be determined for future large dip-slip earthquakes within 20-30 min of the origin time using relatively sparse global networks of seismometers such as those the USGS uses to locate earthquakes in near-real time. Copyright 2009 by the American Geophysical Union.

Xu, Y.; Koper, K. D.; Sufri, O.; Zhu, L.; Hutko, A. R.

2009-01-01

304

ECG Segmentation and P-Wave Feature Extraction: Application to Patients Prone to Atrial Fibrillation.  

National Technical Information Service (NTIS)

This paper presents an automatic analysis method of the P-wave, based on lead II of a 12 lead standard ECG, which will be applied to the detection of patients prone to atrial fibrillation (AF), one of the most frequent arrhythmias. It focuses first on the...

R. Lepage J. Boucher J. Blanc J. Cornilly

2001-01-01

305

Confinement-induced p-wave resonances from s-wave interactions  

SciTech Connect

We show that a purely s-wave interaction in three dimensions (3D) can induce higher partial-wave resonances in mixed dimensions. We develop two-body scattering theories in all three cases of 0D-3D, 1D-3D, and 2D-3D mixtures and determine the positions of higher partial-wave resonances in terms of the 3D s-wave scattering length assuming a harmonic confinement potential. We also compute the low-energy scattering parameters in the p-wave channel (scattering volume and effective momentum) that are necessary for the low-energy effective theory of the p-wave resonance. We point out that some of the resonances observed in the Florence group experiment [Phys. Rev. Lett. 104, 153202 (2010)] can be interpreted as the p-wave resonances in the 2D-3D mixed dimensions. Our study paves the way for a variety of physics, such as Anderson localization of matter waves under p-wave resonant scatterers.

Nishida, Yusuke [Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Tan, Shina [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2010-12-15

306

Laboratory velocities and attenuation of p-waves in limestones during freeze-thaw cycles  

SciTech Connect

The velocity and the attenuation of compressional P-waves, measured in the laboratory at ultrasonic frequencies during a series of freezing and thawing cycles, are used as a method for predicting frost damage in a bedded limestone. Pulse transmission and spectral ratio techniques are used to determine the P-wave velocities and the attenuation values relative to an aluminum reference samples with very low attenuation. Limestone samples were water saturated under vacuum conditions, jacketed with rubber sleeves, and immersed in an antifreeze bath (50 percent methanol solution). They were submitted to repeated 24-hour freezing and thawing cycles simulating natural environment conditions. During the freeze/thaw cycles, P-wave velocities and quality factor Q diminished rapidly in thawed rock samples, indicating modification of the pore space. Measurements of crack porosity were conducted by hydrostatic compression tests on cubic rock samples that had been submitted to these freeze/thaw cycles. These measurements are used as an index of crack formation. The hydrostatic compression tests confirmed the phases of rock damage that were shown by changes in the value of Q. Furthermore, comparison between Q values and crack porosity demonstrate that the variations of P-wave attenuation are caused by the creation of new cracks and not by the enlargement of pre-existing cracks.

Remy, J.M.; Bellanger, M.; Homand-Etienne, F. (Lab. de Geomecanique de Nancy, Vandoeuvre-les-Nancy (France))

1994-02-01

307

Relationship between P-Wave Dispersion and Effective Hemodialysis in Chronic Hemodialysis Patients  

Microsoft Academic Search

Objective: To investigate whether or not P-wave dispersion (PWD) can be used as a good indicator of effective hemodialysis. Subjects andMethods: The study included 35 patients (20 males, 15 females, mean age 61 ± 10 years) who regularly received hemodialysis treatment for chronic renal failure. Following hemodialysis, the patients whose hemodynamic parameters were preserved and who reached dry body weight

Namik Ozmen; Beker Sitki Cebeci; Ejder Kardesoglu; Enes Murat Atasoyu; Suat Unver; Turgay Celik; Mustafa Aparci; Mehmet Dincturk

2007-01-01

308

High-precision earthquake location and three-dimensional P wave velocity determination at Redoubt Volcano, Alaska  

Microsoft Academic Search

Redoubt Volcano, Alaska poses significant volcanic hazard to the Cook Inlet region and overlying flight paths. During and following the most recent eruption in 1989–1990 the Alaska Volcano Observatory deployed up to 10 seismometers to improve real-time monitoring capabilities at Redoubt and continues to produce an annual earthquake catalog with associated arrival times for this volcano. We compute a three-dimensional

Heather R. DeShon; Clifford H. Thurber; Charlotte Rowe

2007-01-01

309

P-wave Local Earthquake Tomography in the Central Alborz Mountains, Iran  

NASA Astrophysics Data System (ADS)

The Alborz Mountain ranges in the southern margin of the Caspian Sea, as a part of the Alpine- Himalayan orogenic belt is an arc of parallel synclines and anticlines. Among the major tectonic and geological features of the Alborz Mountains are the Damavand quaternary volcano, and active and seismic faults like the Mosha, and North Tehran faults. In this study, the first 3D P-wave velocity model of the upper crust in the Central Alborz Mountains is obtained using a local travel-time earthquake tomography method. A data set of 895 earthquakes recorded on a local 19 station short-period network between 1996 and 2006 provided by the Iranian Seismological Centre (ISC) is used in this inversion. The result of tomography shows considerable velocity anomalies in this region. These anomalies show remarkable features in the vicinity of the Mosha and North Tehran faults, as well as in the Damavand volcanic area. In depth of 15 kilometer a low velocity region is observed parallel to the above two mentioned faults. This can be caused by the crushed rocks along these two faults. In the place of splitting North Tehran fault from the Mosha fault, a very noticeable low velocity anomaly represents intense fracturing in rocks. In the Damavand volcanic area and in the northern side of the summit an anomalous high velocity body found to the depth of 20 kilometer. According to its considerable correlation with the position of the old Damavand cone, it is related to the older and crystallized magma chamber of the Damavand volcano. A low velocity anomaly exactly beneath the present cone to the depth of seven kilometer, with another low velocity anomaly in depth of 10 to 20 kilometer constitutes the present magma chamber of the Damavand volcano.

Mostafanejad, A.; Hosein Shomali, Z.

2010-12-01

310

Analysis of the Mantle Transition Zone beneath West Antarctica using P-wave receiver functions  

NASA Astrophysics Data System (ADS)

Several exposed, sub-glacial, and submarine volcanoes exist throughout West Antarctica in the vicinity of the West Antarctic Rift System; prior work has suggested that a mantle plume beneath the region influences the observed rifting and volcanism. However the existence of a mantle plume has not been verified, because models from recent seismic tomography results are not well resolved at mantle transition zone depths. We use P-wave receiver functions (PRFs) from all Antarctic seismic stations installed at sites above less than 1 km of ice, including recent 2007-2012 Antarctic POLENET, permanent GSN, and the 2000-2003 TAMSEIS seismographs to explore the depth to and the thickness of the mantle transition zone beneath West Antarctica. We calculate PRFs for all earthquakes occurring at 30-90° with Mb>5.5 using a time-domain iterative deconvolution method filtered using a Gaussian-width factor of 0.5, corresponding to frequencies less than ~0.24 Hz. Using this method, we check stability of the deconvolution by convolving the vertical component with the final radial receiver function, rejecting all receiver functions that did not recover at least 80% of the original trace. Maps showing Ps pierce-points cover most of West Antarctica and the Transantarctic Mountains, with particularly good coverage beneath Marie Byrd Land and the region around Ross Island. Preliminary results for P receiver functions stacked by station and migrated to depth using the ak135 1-d velocity model indicate a depressed 410' discontinuity beneath West Antarctica; beneath the Transantarctic and East Antarctic sites, the 410' is not depressed. However, no clear depth patterns are observed for the 660' discontinuity throughout West Antarctica; at several West Antarctic sites, the 660' may even be depressed slightly. Additional work using common conversion point (CCP) stacking will enable us to more clearly map the depth of the 410' and 660' and to identify spatial variations in mantle transition zone thickness.

Emry, E.; Nyblade, A.; Julia, J.; Anandakrishnan, S.; Aster, R. C.; Wiens, D. A.; Huerta, A. D.; Wilson, T. J.

2013-12-01

311

P-wave and QT interval dispersion analysis in children with Eisenmenger syndrome.  

PubMed

Objectives: P-wave and QT dispersion are increased and associated with atrial and ventricular arrhythmia and an increase in sudden death in a variety of diseases. This study aimed to investigate P-wave and QT dispersion in children with Eisenmenger syndrome (ES). Study design: The study group included 27 children (15 females, 12 males) with both congenital heart disease (CHD) and ES. The control group consisted of 30 children with CHD without pulmonary arterial hypertension. Electrocardiographic records were used to determine P-wave, QT, and corrected QT (QTc) dispersions. 24-hour (h) rhythm Holter was fitted in all patients. Atrial volumes, ventricular dimensions and tricuspid annular plane systolic excursion (TAPSE) were measured by echocardiography. Results: There was no difference between groups with regard to age, sex, weight, and body surface area (p>0.05). Right atrial volume was significantly larger in the ES group than in the control group. P-wave, QT and QTc dispersions were higher in the patients with ES (50.10±11.12 vs. 26.32±8.90, p<0.001; 57.40±24.21 vs. 38.20±8.92 ms, p<0.001; and 78.20±16.02 vs. 56.52±13.92 ms, p<0.001, respectively). Ventricular and supraventricular ectopy were significantly more frequent in the ES group. Four patients (14.8%) in the study group had tachyarrhythmias during 24-h Holter monitoring. Conclusion: In our study, P-wave and QT dispersion were found to be greater in children with ES than in the healthy control subjects. PMID:24643147

Ece, Ibrahim; Uner, Abdurrahman; Ball?, Sevket; Oflaz, Mehmet Burhan; Kibar, Ay?e Esin; Sal, Ertan

2014-03-01

312

Body waves separation in the time-frequency domain  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

313

Determining surface wave arrival angle anomalies  

NASA Astrophysics Data System (ADS)

A new method for measuring arrival angles of teleseismic Love and Rayleigh waves is developed. The new method utilizes estimates of surface wave dispersion to create a phase-matched filter to isolate the Love or Rayleigh wave in three-component recordings. The polarization of the filtered wave group is determined in the time domain by application of a variation of the complex polarization method of Vidale [1986]. Orientation, linearity, and ellipticity of particle motion are estimated in several frequency bands to determine the frequency-dependent polarization. The method employs an iterative scheme, by which a predicted Love wave, based on the estimated dispersion and polarization, is subtracted from the three-component data prior to the estimation of Rayleigh wave polarization, and vice versa. The method is applied to an extensive set of Global Seismographic Network data covering the years 1989-1998. Between 4244 and 15,075 measurements are collected for fundamental mode Love and Rayleigh waves at nine different periods (37 to 150 s). Measurement uncertainties are estimated using the statistics of observations for pairwise similar paths and are generally of the order of 15-50% of the total signal, depending on the period and the wave type. Large and azimuthally invariant angle anomalies are documented for several stations and are consistent with misorientation of the horizontal seismometers. Two schemes are employed to determine the misorientations: (1) an azimuthally weighted average at each station, and (2) a joint inversion for seismometer misorientation and globally heterogeneous phase velocities. The determined corrections are robust and correlate well with those reported in earlier studies. Azimuthally varying arrival angle anomalies are shown to agree qualitatively with predictions of wave refraction calculated for recent phase velocity maps, which explain up to 30% of the variance in the new measurements.

Larson, Erik W. F.; Ekström, Göran

2002-06-01

314

Three-dimensional modeling of the Nevada Test Site and vicinity from teleseismic P-wave residuals  

USGS Publications Warehouse

A teleseismic P-wave travel-time residual study is described which reveals the regional compressional-velocity structure of southern Nevada and neighboring parts of California to a depth of 280 km. During 1980, 98 teleseismic events were recorded at as many as 53 sites in this area. P-wave residuals were calculated relative to a network-wide average residual for each event and are displayed on maps of the stations for each of four event-azimuth quadrants. Fluctuations in these map-patterns of residuals with approach azimuth combined with results of linear, three-dimensional inversions of some 2887 residuals indicate the following characteristics of the velocity structure of the southern Nevada region: 1) a low-velocity body exists in the upper crust 50 km northeast of Beatty, Nevada, near the Miocene Timber Mountain-Silent Canyon caldera complex. Another highly-localized low-velocity anomaly occurs near the southwest corner of the Nevada Test Site (NTS). These two anomalies seem to be part of a low-velocity trough extending from Death Valley, California, to about 50 km north of NTS. 2) There is a high-velocity body in the mantle between 81 and 131 km deep centered about i0 km north of the edge of the Timber Mountain caldera, 3) a broad low-velocity body is delineated between 81 and 131 km deep centered about 30 km north of Las Vegas, 4) there is a monotonic increase in travel-time delays from west to east across the region, probably indicating an eastward decrease in velocity, and lower than average velocities in southeastern Nevada below 31 km, and 5) considerable complexity in three-dimensional velocity structure exists in this part of the southern Great Basin. Inversions of teleseismic P-wave travel-time residuals were also performed on data from 12 seismometers in the immediate vicinity of the Nevada Test Site to make good use of the closer station spacing i in that area. Results of these inversions show more details of the velocity structure but generally the same features as those found in the regional study.

Monfort, Mary E.; Evans, John R.

1982-01-01

315

Design Considerations for a New Terminal Area Arrival Scheduler  

NASA Technical Reports Server (NTRS)

Design of a terminal area arrival scheduler depends on the interrelationship between throughput, delay and controller intervention. The main contribution of this paper is an analysis of the above interdependence for several stochastic behaviors of expected system performance distributions in the aircraft s time of arrival at the meter fix and runway. Results of this analysis serve to guide the scheduler design choices for key control variables. Two types of variables are analyzed, separation buffers and terminal delay margins. The choice for these decision variables was tested using sensitivity analysis. Analysis suggests that it is best to set the separation buffer at the meter fix to its minimum and adjust the runway buffer to attain the desired system performance. Delay margin was found to have the least effect. These results help characterize the variables most influential in the scheduling operations of terminal area arrivals.

Thipphavong, Jane; Mulfinger, Daniel

2010-01-01

316

First-arrival traveltime tomography using second generation wavelets  

Microsoft Academic Search

Wavelet decomposition of the slowness model allows a multiscale description of the seismic first-arrival time tomography. We propose the introduction of the so-called second generation wavelets that could be used for any mesh structure and do not re- quire a number of samples, such as the power of two in each direction for fast wavelet transform. A linearized procedure for

Matthieu Delost; Jean Virieux; Stéphane Operto

2008-01-01

317

Optimal arrival tra c spacing via dynamic programming  

Microsoft Academic Search

We present the application of dynamic programming to a combinatorial optimization problem to achieve proper arrival runway spacing, which appears in the process of assign-ing speed during the transition to approach and approach phases of flight. We apply the algorithm to data from a fast-time simulation developed under NASA's Advanced Air Transportation Technologies Project for investigating new air tra c

Alexandre M. Bayen; Todd Callantine; Claire J. Tomlin; Yinyu Ye; Jiawei Zhang

318

Anchorage Arrival Scheduling Under Off-Nominal Weather Conditions  

NASA Technical Reports Server (NTRS)

Weather can cause flight diversions, passenger delays, additional fuel consumption and schedule disruptions at any high volume airport. The impacts are particularly acute at the Ted Stevens Anchorage International Airport in Anchorage, Alaska due to its importance as a major international portal. To minimize the impacts due to weather, a multi-stage scheduling process is employed that is iteratively executed, as updated aircraft demand and/or airport capacity data become available. The strategic scheduling algorithm assigns speed adjustments for flights that originate outside of Anchorage Center to achieve the proper demand and capacity balance. Similarly, an internal departure-scheduling algorithm assigns ground holds for pre-departure flights that originate from within Anchorage Center. Tactical flight controls in the form of airborne holding are employed to reactively account for system uncertainties. Real-world scenarios that were derived from the January 16, 2012 Anchorage visibility observations and the January 12, 2012 Anchorage arrival schedule were used to test the initial implementation of the scheduling algorithm in fast-time simulation experiments. Although over 90% of the flights in the scenarios arrived at Anchorage without requiring any delay, pre-departure scheduling was the dominant form of control for Anchorage arrivals. Additionally, tactical scheduling was used extensively in conjunction with the pre-departure scheduling to reactively compensate for uncertainties in the arrival demand. For long-haul flights, the strategic scheduling algorithm performed best when the scheduling horizon was greater than 1,000 nmi. With these long scheduling horizons, it was possible to absorb between ten and 12 minutes of delay through speed control alone. Unfortunately, the use of tactical scheduling, which resulted in airborne holding, was found to increase as the strategic scheduling horizon increased because of the additional uncertainty in the arrival times of the aircraft. Findings from these initial experiments indicate that it is possible to schedule arrivals into Anchorage with minimal delays under low-visibility conditions with less disruption to high-cost, international flights.

Grabbe, Shon; Chan, William N.; Mukherjee, Avijit

2012-01-01

319

Interatrial conduction disturbance in postoperative atrial fibrillation: a comparative study of P-wave dispersion and Doppler myocardial imaging in cardiac surgery  

PubMed Central

Objective Disturbances of interatrial conduction have been proposed as one of the contributing mechanisms of postoperative atrial fibrillation (AF). P-wave dispersion has been recognized as a sensitive tool for detecting interatrial conduction disturbances. Doppler myocardial imaging (DMI) has been validated as a non-invasive tool to indirectly reflect electrical atrial activation and therefore is used in this study to detect possible interatrial electromechanical disturbances after cardiac surgery. Methods 30 patients (23 men, age 62?±?1 years) admitted for coronary bypass surgery with no prior history of AF were included in this investigation. Echocardiography and electrocardiograms (ECG) were obtained on the day before and after surgery. In addition to standard echocardiography, DMI-loops were acquired from the apical window. The following time intervals were derived off-line from the free right atrial (RA), left atrial (LA) lateral and LA posterior wall: onset P-wave to start (P to A’start), to peak (P to A’peak) and to end of atrial deformation (total electromechanical activity). These intervals were compared to each other and to P-wave dispersion derived from the recorded ECGs. Results All patients were in sinus rhythm during their postoperative assessment, but 11 patients presented episodes of AF within the first three postoperative days. Atrial electromechanical activation was earliest in the RA and latest in the lateral LA. In patients with AF, P-wave dispersion was significantly prolonged postoperatively (mean: +18.6 ms; 95% confidence interval (CI): 12.1–25.2 ms; p?P-wave dispersion. Equally effective to P-wave dispersion, this simple and reproducible tool might help to early identify the risk for postoperative AF, thus extending the informative value of routine postoperative echocardiography.

2014-01-01

320

Electron-He(+) P-wave Elastic Scattering and Photoabsorption in Two-electron Systems  

NASA Technical Reports Server (NTRS)

In a previous paper [Bhatia, Phys. Rev. A 69,032714 (2004)], electron-hydrogen P-wave scattering phase shifts were calculated using the optical potential approach based on the Feshbach projection operator formalism. This method is now extended to the singlet and triplet electron-He(+) P-wave scattering in the elastic region. Phase shifts are calculated using Hylleraas-type correlation functions with up to 220 terms. Results are rigorous lower bounds to the exact phase shifts and they are compared to phase shifts obtained from the method of polarized orbitals and close-coupling calculations. The continuum functions calculated here are used to calculate photoabsorption cross sections. Photoionization cross sections of He and photodetachment cross sections of H(-) are calculated in the elastic region, i.e. leaving He(+) and H in their respective ground states, and compared with previous calculations. Radiative attachment rates are also calculated.

Bhatia, A. K.

2006-01-01

321

Observation of a p-Wave One-Neutron Halo Configuration in Mg37  

NASA Astrophysics Data System (ADS)

Cross sections of 1n-removal reactions from the neutron-rich nucleus Mg37 on C and Pb targets and the parallel momentum distributions of the Mg37 residues from the C target have been measured at 240 MeV /nucleon. A combined analysis of these distinct nuclear- and Coulomb-dominated reaction data shows that the Mg37 ground state has a small 1n separation energy of 0.22-0.09+0.12 MeV and an appreciable p-wave neutron single-particle strength. These results confirm that Mg37 lies near the edge of the "island of inversion" and has a sizable p-wave neutron halo component, the heaviest such system identified to date.

Kobayashi, N.; Nakamura, T.; Kondo, Y.; Tostevin, J. A.; Utsuno, Y.; Aoi, N.; Baba, H.; Barthelemy, R.; Famiano, M. A.; Fukuda, N.; Inabe, N.; Ishihara, M.; Kanungo, R.; Kim, S.; Kubo, T.; Lee, G. S.; Lee, H. S.; Matsushita, M.; Motobayashi, T.; Ohnishi, T.; Orr, N. A.; Otsu, H.; Otsuka, T.; Sako, T.; Sakurai, H.; Satou, Y.; Sumikama, T.; Takeda, H.; Takeuchi, S.; Tanaka, R.; Togano, Y.; Yoneda, K.

2014-06-01

322

Observation of a p-Wave One-Neutron Halo Configuration in ^{37}Mg.  

PubMed

Cross sections of 1n-removal reactions from the neutron-rich nucleus ^{37}Mg on C and Pb targets and the parallel momentum distributions of the ^{37}Mg residues from the C target have been measured at 240??MeV/nucleon. A combined analysis of these distinct nuclear- and Coulomb-dominated reaction data shows that the ^{37}Mg ground state has a small 1n separation energy of 0.22_{-0.09}^{+0.12}??MeV and an appreciable p-wave neutron single-particle strength. These results confirm that ^{37}Mg lies near the edge of the "island of inversion" and has a sizable p-wave neutron halo component, the heaviest such system identified to date. PMID:24996084

Kobayashi, N; Nakamura, T; Kondo, Y; Tostevin, J A; Utsuno, Y; Aoi, N; Baba, H; Barthelemy, R; Famiano, M A; Fukuda, N; Inabe, N; Ishihara, M; Kanungo, R; Kim, S; Kubo, T; Lee, G S; Lee, H S; Matsushita, M; Motobayashi, T; Ohnishi, T; Orr, N A; Otsu, H; Otsuka, T; Sako, T; Sakurai, H; Satou, Y; Sumikama, T; Takeda, H; Takeuchi, S; Tanaka, R; Togano, Y; Yoneda, K

2014-06-20

323

Transverse spin current in the s-wave/p-wave Josephson junction.  

PubMed

We report a theoretical study on spin transport in the hybrid Josephson junction composed of singlet s-wave and triplet p-wave superconductor. The node of the triplet pair potential is considered perpendicular to the interface of the junction. Based on a symmetry analysis, we predict that there is no net spin density at the interface of the junction but instead a transverse mode-resolved spin density can exist and a nonzero spin current can flow transversely along the interface of the junction. The predictions are numerically demonstrated by means of the lattice Matsubara Green's function method. It is also shown that, when a normal metal is sandwiched in between two superconductors, both spin current and transverse mode-resolved spin density are only residing at two interfaces due to the smearing effect of the multimode transport. Our findings are useful for identifying the pairing symmetry of the p-wave superconductor and generating spin current. PMID:21952523

Zhang, Huan; Chan, K S; Lin, Zijing; Wang, J

2011-10-19

324

MAC Channel Congestion Control Mechanism in IEEE 802.11p\\/WAVE Vehicle Networks  

Microsoft Academic Search

IEEE 802.11p\\/WAVE (Wireless Access in Vehicular Environments) is an emerging family of standards intended to support wireless access in Vehicular Ad Hoc Networks (VANETs). Broadcasting of data and control packets is expected to be crucial in this environment. Both safety-related and non-safety applications rely on broadcasting for the exchange of data or status and advertisement messages. Most of the broadcasting

Chih-Wei Hsu; Chung-Hsien Hsu; Huei-Ru Tseng

2011-01-01

325

Cooperative service channel reservation to improve performances of IEEE 802.11p\\/WAVE networks  

Microsoft Academic Search

The upcoming IEEE802.11p\\/WAVE (wireless access for vehicular environment) standard is intended to deliver both safety and non-safety applications to vehicles on the roads. Despite huge research on safety traffic, only a few works have investigated non-safety comfort and entertainment applications (e.g., multimedia, web browsing, e-maps) when considering the WAVE standard features and capabilities. In this paper, we focus on the

Claudia Campolo; Alessandro Cortese; Antonella Molinaro

2009-01-01

326

Effect of tectonic stress release on explosion P-wave signatures  

Microsoft Academic Search

The influence of induced tectonic stress release on the short-period teleseismic P-wave signature of underground nuclear explosions is studied. Primary attention is directed to the first few cycles of the record from which body-wave magnitude (m\\/sub b\\/) is determined. Computational models for both the explosion and the superimposed tectonic release double couple are employed and theoretical seismograms are computed. Interest

Bache

1976-01-01

327

Permeability and P-wave velocity change in granitic rocks under freeze–thaw cycles  

Microsoft Academic Search

An extensive experimental investigation of microstructural changes in granites under freeze–thaw cycles using permeability and P-wave velocity measurements is described. Two types of natural granite rocks are considered and tested under dry and saturated conditions. The specimens were subjected to 200 heating–cooling cycles (??20°C\\/?+?20°C); each cycle had a duration of 24 h. The results indicate that the ageing process decreases the

M. Takarli; W. Prince

2007-01-01

328

Estimation of uniaxial compressive strength from point load strength, Schmidt hardness and P-wave velocity  

Microsoft Academic Search

Uniaxial compressive strength is considered one of the most important parameters in the characterization of rock material\\u000a in rock engineering practice. The study investigated correlations between uniaxial compressive strength and point load index,\\u000a P-wave velocity and Schmidt hardness rebound number together with the effects of core diameter size. A total of 150 core samples\\u000a at five different diameters (54, 48,

?brahim Çobano?lu; Sefer Beran Çelik

2008-01-01

329

Upper critical field of p-wave ferromagnetic superconductors with orthorhombic symmetry  

NASA Astrophysics Data System (ADS)

We extended the Scharnberg-Klemm theory of Hc2(T) in p-wave superconductors with broken symmetry to cases of partially broken symmetry in an orthorhombic crystal, as is appropriate for the more exotic ferromagnetic superconductor UCoGe in strong magnetic fields. For some partially broken symmetry cases, Hc2(T) can mimic upward curvature in two crystal axis directions, and reasonably good fits to some of the UCoGe data are obtained.

Klemm, Richard A.; Lörscher, Christopher; Zhang, Jingchuan; Gu, Qiang

2012-12-01

330

Simulation Results for Airborne Precision Spacing along Continuous Descent Arrivals  

NASA Technical Reports Server (NTRS)

This paper describes the results of a fast-time simulation experiment and a high-fidelity simulator validation with merging streams of aircraft flying Continuous Descent Arrivals through generic airspace to a runway at Dallas-Ft Worth. Aircraft made small speed adjustments based on an airborne-based spacing algorithm, so as to arrive at the threshold exactly at the assigned time interval behind their Traffic-To-Follow. The 40 aircraft were initialized at different altitudes and speeds on one of four different routes, and then merged at different points and altitudes while flying Continuous Descent Arrivals. This merging and spacing using flight deck equipment and procedures to augment or implement Air Traffic Management directives is called Flight Deck-based Merging and Spacing, an important subset of a larger Airborne Precision Spacing functionality. This research indicates that Flight Deck-based Merging and Spacing initiated while at cruise altitude and well prior to the Terminal Radar Approach Control entry can significantly contribute to the delivery of aircraft at a specified interval to the runway threshold with a high degree of accuracy and at a reduced pilot workload. Furthermore, previously documented work has shown that using a Continuous Descent Arrival instead of a traditional step-down descent can save fuel, reduce noise, and reduce emissions. Research into Flight Deck-based Merging and Spacing is a cooperative effort between government and industry partners.

Barmore, Bryan E.; Abbott, Terence S.; Capron, William R.; Baxley, Brian T.

2008-01-01

331

Majorana modes and p-wave superfluids for fermionic atoms in optical lattices.  

PubMed

The quest for realization of non-Abelian phases of matter, driven by their possible use in fault-tolerant topological quantum computing, has been spearheaded by recent developments in p-wave superconductors. The chiral px+ipy-wave superconductor in two-dimensions exhibiting Majorana modes provides the simplest phase supporting non-Abelian quasiparticles and can be seen as the blueprint of fractional topological order. Alternatively, Kitaev's Majorana wire has emerged as an ideal toy model to understand Majorana modes. Here we present a way to make the transition from Kitaev's Majorana wires to two-dimensional p-wave superconductors in a system with cold atomic gases in an optical lattice. The main idea is based on an approach to generate p-wave interactions by coupling orbital degrees of freedom with strong s-wave interactions. We demonstrate how this design can induce Majorana modes at edge dislocations in the optical lattice, and we provide an experimentally feasible protocol for the observation of the non-Abelian statistics. PMID:25060143

Bühler, A; Lang, N; Kraus, C V; Möller, G; Huber, S D; Büchler, H P

2014-01-01

332

Suppression of surface p-wave superconductivity in disordered topological insulators  

NASA Astrophysics Data System (ADS)

The paper proposes a self-consistent Green function description of the induced surface superconductivity in a disordered three-dimensional topological insulator (TI) coupled to an s-wave superconductor. We recover earlier results regarding the induced spin-triplet p-wave pairing, showing that a mixture of p- and s-wave pair correlations appears as a result of broken spin-rotation symmetry on the helical surface of the TI. Unlike the s-wave pairing, the p-wave component is found to be suppressed in dirty TIs in which the elastic mean-free path is much smaller than the superconducting coherence length. The suppression is due to the generic nonlocality of the spin-triplet correlations, which makes them strongly dependent on the mean-free path in a disordered system. In dirty TIs the induced superconductivity is predicted to be predominantly s-wave like. In cleaner TIs, however, the p-wave component may reach a magnitude comparable to (but not larger than) the s-wave pairing.

Tkachov, G.

2013-06-01

333

Preliminary result of Taiwan 3-D stress field estimated using P wave polarity data  

NASA Astrophysics Data System (ADS)

We apply the composite focal mechanism method and use more than half million P wave polarity data to invert for the 3-D stress field in Taiwan region. At a given location, earthquake focal mechanism is estimated using all the P wave polarity data originated from its neighborhood, and the data are weighted using a Gaussian distance weighting function. This method has the advantage of allowing maximum amount of data input in the solution, including polarity data from small earthquakes whose focal mechanisms are undeterminable with too few observation data available. Comparing to traditional focal mechanism estimation methods, this method produces focal mechanism estimates covering a broader area, and provides better averages of local focal mechanism solutions. We present the focal mechanism result in a 0.25 degree x 0.25 degree x 2.5 km grid in Taiwan and its adjacent areas. The preliminary result shows that the P and T axis directions change markedly across moho discontinuity, suggesting certain amount of mechanical decoupling between the crust and mantle. The P and T axis directions at the 15-45 km depth range also correlate with P wave velocity perturbations and delineate the northwestward subduction of the Philippine Sea plate in northeast Taiwan and the eastward subduction of the Eurasia plate in southern Taiwan, respectively. This 3-D stress field result may provide new constraints on geodynamics process in Taiwan region.

Wan, Y.; Wu, Y.; Sheng, S.; Shen, Z.

2010-12-01

334

Spectral modulation effect in teleseismic P-waves from DPRK nuclear tests recorded at different azimuths  

NASA Astrophysics Data System (ADS)

Two underground nuclear explosions conducted by North Korea in 2009 and 2013 were recorded by the Israel Seismic Network. Pronounced coherent minima (spectral nulls) at 1.2-1.3 Hz were revealed in the spectra of teleseismic P-waves. For a ground-truth explosion with a shallow source depth (relatively to an earthquake), this phenomenon can be interpreted in terms of the interference between the down-going P-wave and the pP phase reflected from the Earth's surface. A similar effect was observed at ISN stations for the Pakistan nuclear explosion at a different frequency 1.7 Hz indicating a source and not site-effect. Similar spectral minima with about the same frequency were observed in teleseismic P-waves of all three North Korea explosions (including the 2006 test) recorded at network stations and arrays in Kazakhstan (KURK), Norway (NORESS, ARCESS), Australia (Alice Springs, Warramunga) and Canada (Yellowknife), covering a broad azimuthal range. Data of the 2013 test at Warramunga array showed harmonic spectral modulation with several minima, evidencing a clear interference effect. These observations support the above-mentioned interpretation. Based on the null frequency dependency on the near-surface acoustic velocity and the source depth, the depth of the North Korea tests was estimated as ~2 km (different from the value ~1 km reported by USGS for the third test). This unusual depth estimation needs an additional validation based on more stations and verification by other methods.

Gitterman, Yefim; Kim, So Gu; Hofstetter, Abraham

2014-05-01

335

P-wave velocity structure of the uppermost mantle beneath Hawaii from traveltime tomography  

USGS Publications Warehouse

We examine the P-wave velocity structure beneath the island of Hawaii using P-wave residuals from teleseismic earthquakes recorded by the Hawaiian Volcano Observatory seismic network. The station geometry and distribution of events makes it possible to image the velocity structure between ~ 40 and 100 km depth with a lateral resolution of ~ 15 km and a vertical resolution of ~ 30 km. For depths between 40 and 80 km, P-wave velocities are up to 5 per cent slower in a broad elongated region trending SE-NW that underlies the island between the two lines defined by the volcanic loci. No direct correlation between the magnitude of the lithospheric anomaly and the current level of volcanic activity is apparent, but the slow region is broadened at ~ 19.8??N and narrow beneath Kilauea. In the case of the occanic lithosphere beneath Hawaii, slow seismic velocities are likely to be related to magma transport from the top of the melting zone at the base of the lithosphere to the surface. Thermal modelling shows that the broad elongated low-velocity zone cannot be explained in terms of conductive heating by one primary conduit per volcano but that more complicated melt pathways must exist.

Tilmann, F. J.; Benz, H. M.; Priestley, K. F.; Okubo, P. G.

2001-01-01

336

QT and P wave dispersion and heart rate variability in patients with Dravet syndrome.  

PubMed

SCN1A mutations are found in up to 80 % of patients with Dravet syndrome (DS), and the sudden unexpected death in epilepsy (SUDEP) rate is higher in DS than in most forms of severe epilepsy. The aim of this study is to examine the autonomic cardiac function and the risk of arrhythmia in DS patients by evaluating QT and P wave dispersion and heart rate variability (HRV) using standard electrocardiography (ECG) and 24-h ECG. The study group consisted of 15 patients (9 boys and 6 girls aged 3.5-17 years) who were genetically diagnosed with DS. The control group comprised 20 healthy subjects, 13 boys and 7 girls aged 4-17 years. P wave dispersion (44.6 ± 3.5 ms), QT dispersion (58.8 ± 7.5 ms) and QTc dispersion (70.8 ± 7.4 ms) were significantly higher in DS patients as compared to the control group (p < 0.001 for all values). However, there was no significant difference in PR, QT or QTc length between the groups. 24-h Holter ECG showed that all HRV parameters were significantly lower in patients with DS. The decreased HRV and increased P wave and QT dispersion seen in DS patients are important signs of autonomic dysfunction with increased adrenergic tone. To determine whether autonomic dysfunction is correlated with SUDEP in DS, long-term electrocardiographic monitoring and wider prospective studies are necessary. PMID:23065439

Ergul, Yakup; Ekici, Baris; Tatli, Burak; Nisli, Kemal; Ozmen, Meral

2013-06-01

337

8 CFR 232.3 - Arriving aliens.  

Code of Federal Regulations, 2010 CFR

8 Aliens and Nationality 1 2010-01-01 2010-01-01 false Arriving aliens. 232.3 Section 232.3 Aliens and Nationality DEPARTMENT OF HOMELAND SECURITY IMMIGRATION REGULATIONS DETENTION OF ALIENS FOR PHYSICAL...

2010-01-01

338

New Expedition 32 Trio Arrives at Station  

NASA Video Gallery

Expedition 32 Flight Engineers Suni Williams, Yuri Malenchenko and Aki Hoshide have arrived at the International Space Station after two days in orbit. The new trio docked its Soyuz TMA-05M spacecr...

339

Has biomimetics arrived in architecture?  

Microsoft Academic Search

Architecture and construction are highly interdisciplinary fields, integrating many professions and many disciplines on different levels of scale and complexity. Studies of natural systems have at all times been inspirational for design. Investigating the overlaps between biology and architecture we find that a biological paradigm inspires the current frontier of research and innovation in many sectors. Using biology's categories to

Petra Gruber; George Jeronimidis

2012-01-01

340

Does Pet Arrival Trigger Prosocial Behaviors in Individuals with Autism?  

PubMed Central

Alteration of social interactions especially prosocial behaviors – an important aspect of development – is one of the characteristics of autistic disorders. Numerous strategies or therapies are used to improve communication skills or at least to reduce social impairments. Animal-assisted therapies are used widely but their relevant benefits have never been scientifically evaluated. In the present study, we evaluated the association between the presence or the arrival of pets in families with an individual with autism and the changes in his or her prosocial behaviors. Of 260 individuals with autism - on the basis of presence or absence of pets - two groups of 12 individuals and two groups of 8 individuals were assigned to: study 1 (pet arrival after age of 5 versus no pet) and study 2 (pet versus no pet), respectively. Evaluation of social impairment was assessed at two time periods using the 36-items ADI-R algorithm and a parental questionnaire about their child-pet relationships. The results showed that 2 of the 36 items changed positively between the age of 4 to 5 (t0) and time of assessment (t1) in the pet arrival group (study 1): “offering to share” and “offering comfort”. Interestingly, these two items reflect prosocial behaviors. There seemed to be no significant changes in any item for the three other groups. The interactions between individuals with autism and their pets were more – qualitatively and quantitatively - reported in the situation of pet arrival than pet presence since birth. These findings open further lines of research on the impact of pet’s presence or arrival in families with an individual with autism. Given the potential ability of individuals with autism to develop prosocial behaviors, related studies are needed to better understand the mechanisms involved in the development of such child-pet relationship.

Grandgeorge, Marine; Tordjman, Sylvie; Lazartigues, Alain; Lemonnier, Eric; Deleau, Michel; Hausberger, Martine

2012-01-01

341

Does pet arrival trigger prosocial behaviors in individuals with autism?  

PubMed

Alteration of social interactions especially prosocial behaviors--an important aspect of development--is one of the characteristics of autistic disorders. Numerous strategies or therapies are used to improve communication skills or at least to reduce social impairments. Animal-assisted therapies are used widely but their relevant benefits have never been scientifically evaluated. In the present study, we evaluated the association between the presence or the arrival of pets in families with an individual with autism and the changes in his or her prosocial behaviors. Of 260 individuals with autism--on the basis of presence or absence of pets--two groups of 12 individuals and two groups of 8 individuals were assigned to: study 1 (pet arrival after age of 5 versus no pet) and study 2 (pet versus no pet), respectively. Evaluation of social impairment was assessed at two time periods using the 36-items ADI-R algorithm and a parental questionnaire about their child-pet relationships. The results showed that 2 of the 36 items changed positively between the age of 4 to 5 (t(0)) and time of assessment (t(1)) in the pet arrival group (study 1): "offering to share" and "offering comfort". Interestingly, these two items reflect prosocial behaviors. There seemed to be no significant changes in any item for the three other groups. The interactions between individuals with autism and their pets were more--qualitatively and quantitatively--reported in the situation of pet arrival than pet presence since birth. These findings open further lines of research on the impact of pet's presence or arrival in families with an individual with autism. Given the potential ability of individuals with autism to develop prosocial behaviors, related studies are needed to better understand the mechanisms involved in the development of such child-pet relationship. PMID:22870246

Grandgeorge, Marine; Tordjman, Sylvie; Lazartigues, Alain; Lemonnier, Eric; Deleau, Michel; Hausberger, Martine

2012-01-01

342

33 CFR 146.405 - Safety and Security notice of arrival for vessels arriving at a place on the OCS.  

Code of Federal Regulations, 2013 CFR

...Safety and Security notice of arrival for vessels arriving at a place on the OCS. 146...CONTINENTAL SHELF ACTIVITIES OPERATIONS Vessels-Safety and Security Notice of Arrival...Safety and Security notice of arrival for vessels arriving at a place on the OCS....

2013-07-01

343

Stochastic Scheduling Games with Markov Decision Arrival Processes.  

National Technical Information Service (NTIS)

The dependent arrival processes MDAP (Markov Decision Arrival Processes) were introduced by Hordijk and Koole to model special arrival processes into controlled queueing networks. These were applied to solve control problems with several controllers havin...

E. Altman G. Koole

1992-01-01

344

8 CFR 251.1 - Arrival manifests and lists.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Arrival manifests and lists. 251.1 Section...SECURITY IMMIGRATION REGULATIONS ARRIVAL AND DEPARTURE MANIFESTS AND LISTS: SUPPORTING DOCUMENTS § 251.1 Arrival manifests and lists. (a)...

2009-01-01

345

8 CFR 251.1 - Arrival manifests and lists.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Arrival manifests and lists. 251.1 Section...SECURITY IMMIGRATION REGULATIONS ARRIVAL AND DEPARTURE MANIFESTS AND LISTS: SUPPORTING DOCUMENTS § 251.1 Arrival manifests and lists. (a)...

2010-01-01

346

Experimental studies of electrical conductivities and P-wave velocities of gabbro at high pressures and high temperatures  

Microsoft Academic Search

The P-wave velocities and electrical conductivities of gabbro were measured using ultrasonic transmission method and impedance\\u000a spectroscopy from room temperature to 1100°C at 1–2 GPa, and the factors controlling the P-wave velocity and the microscopic\\u000a conductance mechanisms of the rock were analyzed. The experimental results show that the P-wave velocities of gabbro drop\\u000a abruptly at temperatures of 800-850°C and under

Liping Bai; Jianguo Du; Wei Liu; Wenge Zhou

2003-01-01

347

Improvement to Airport Throughput Using Intelligent Arrival Scheduling and an Expanded Planning Horizon  

NASA Technical Reports Server (NTRS)

The first phase of this study investigated the amount of time a flight can be delayed or expedited within the Terminal Airspace using only speed changes. The Arrival Capacity Calculator analysis tool was used to predict the time adjustment envelope for standard descent arrivals and then for CDA arrivals. Results ranged from 0.77 to 5.38 minutes. STAR routes were configured for the ACES simulation, and a validation of the ACC results was conducted comparing the maximum predicted time adjustments to those seen in ACES. The final phase investigated full runway-to-runway trajectories using ACES. The radial distance used by the arrival scheduler was incrementally increased from 50 to 150 nautical miles (nmi). The increased Planning Horizon radii allowed the arrival scheduler to arrange, path stretch, and speed-adjust flights to more fully load the arrival stream. The average throughput for the high volume portion of the day increased from 30 aircraft per runway for the 50 nmi radius to 40 aircraft per runway for the 150 nmi radius for a traffic set representative of high volume 2018. The recommended radius for the arrival scheduler s Planning Horizon was found to be 130 nmi, which allowed more than 95% loading of the arrival stream.

Glaab, Patricia C.

2012-01-01

348

Research Of Airborne Precision Spacing to Improve Airport Arrival Operations  

NASA Technical Reports Server (NTRS)

In September 2004, the European Organization for the Safety of Air Navigation (EUROCONTROL) and the United States Federal Aviation Administration (FAA) signed a Memorandum of Cooperation to mutually develop, modify, test, and evaluate systems, procedures, facilities, and devices to meet the need for safe and efficient air navigation and air traffic control in the future. In the United States and Europe, these efforts are defined within the architectures of the Next Generation Air Transportation System (NextGen) Program and Single European Sky Air Traffic Management Research (SESAR) Program respectively. Both programs have identified Airborne Spacing as a critical component, with Automatic Dependent Surveillance Broadcast (ADS-B) as a key enabler. Increased interest in reducing airport community noise and the escalating cost of aviation fuel has led to the use of Continuous Descent Arrival (CDA) procedures to reduce noise, emissions, and fuel usage compared to current procedures. To provide these operational enhancements, arrival flight paths into terminal areas are planned around continuous vertical descents that are closer to an optimum trajectory than those in use today. The profiles are designed to be near-idle descents from cruise altitude to the Final Approach Fix (FAF) and are typically without any level segments. By staying higher and faster than conventional arrivals, CDAs also save flight time for the aircraft operator. The drawback is that the variation of optimized trajectories for different types and weights of aircraft requires the Air Traffic Controller to provide more airspace around an aircraft on a CDA than on a conventional arrival procedure. This additional space decreases the throughput rate of the destination airport. Airborne self-spacing concepts have been developed to increase the throughput at high-demand airports by managing the inter-arrival spacing to be more precise and consistent using on-board guidance. It has been proposed that the additional space needed around an aircraft performing a CDA could be reduced or eliminated when using airborne spacing techniques.

Barmore, Bryan E.; Baxley, Brian T.; Murdoch, Jennifer L.

2011-01-01

349

Multi-object filtering with Poisson arrival-rate measurements  

NASA Astrophysics Data System (ADS)

Recent interest in multi-object filtering has focussed on the problem of discrete-time filtering, where sets of measurements are collected at regular intervals from the sensor. Many sensors do not provide multiple measurements at regular intervals but instead provide single-measurement reports at irregular time-steps. In this paper we study the multi-object filtering problem for estimation from measurements where the target and clutter processes provide measurements with Poisson arrival rates. In particular, we show that the Probability Hypothesis Density (PHD) filter can be adapted to Poisson arrival rate measurements by modelling the probability of detection with an exponential distribution. We demonstrate the approach in simulated scenarios.

Clark, Daniel; Nagappa, Sharad

2011-05-01

350

S- and P-wave kaon-pion phase shifts from chiral perturbation theory  

SciTech Connect

We fit, by adjusting the parameters L{sub 1}{sup r}, L{sub 2}{sup r} and L{sub 3} of chiral perturbation theory (ChPT) amplitude, the low energy kaon-pion S- and P-wave experimental phase-shifts. We get the K* resonance, positive and large isospin 1/2 S-wave and a negative and small 3/2 S-wave phase shifts, compatible with experimental data. We propose the present method as the best way to fix ChPT parameters. The unitarization program of current algebra is also discussed.

Borges, J. sa; Barbosa, J. Soares; Oguri, V. [Instituto de Fisica, Universidade do Estado do Rio de Janeiro, Rua Sao Francisco Xavier 524, Maracana, Rio de Janeiro (Brazil)

1997-03-15

351

P-wave pentaquark and its decay in the quark model with instanton induced interaction  

SciTech Connect

P-wave pentaquarks with strangeness +1, I=0, and J{sup P}=1/2{sup +} are studied in the nonrelativistic quark model with instanton induced interaction (III). We present their mass splittings and orbital-spin-isospin-color structures. It is found that decompositions of the wave functions are sensitive to III, while the mass splittings are insensitive. The decay of the lowest energy pentaquark, {theta}{sup +}, is found to be suppressed when the contribution of III is increased. Spin structure of the dominant components of the wave function is studied.

Shinozaki, Tetsuya; Oka, Makoto [Department of Physics, H-27, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Takeuchi, Sachiko [Japan College of Social Work, Kiyose 204-8555 (Japan)

2006-09-01

352

A Split of Direction of Propagation and Attenuation of P Waves in the Po Valley  

NASA Astrophysics Data System (ADS)

On July 17, 2011 a ML 4.8 earthquake occurred in the PO valley at a 48 km epicentral distance from a seismic station located at Palazzo Te (Mantova). The station is situated on deep quaternary sediments: the uppermost layers are mainly composed of clay and silty clay with interbedded sands; the Robertson index is 1.4P wave particle motion, that appears rather difficult to explain if we assume the homogeneity of the P waves (that means attenuation is scalar). Note that the degree of nonlinearity is very low given that the maximum strain can be roughly estimated as 10-5 on the basis of maximum ground velocity of the P wave train considered and the Vp. On the contrary we show that P wave particle motion can be fully (and easily) described by a Homogeneous Isotropic Linear Viscoelastic model (HILV). HILV, as in the 2009 Borcherdt formulation adopted here, allows two different directions of propagation and attenuation; in other words attenuation becomes a vector that is not necessarily parallel to the propagation vector. The results evidence that the incidence angle and the inhomogeneity angle (it is the angle between propagation and attenuation vectors and it is closely related to Q factor) are in good agreement with the geological conditions of the site. Finally, we observed that these results are very similar to the ones obtained when we analyzed two explosions recorded by a seismic station in Milano, also situated in the Po valley at some 140 km from Mantova (Marcellini & Tento, 2011). Borcherdt, R.D. (2009) 'Viscoelastic Waves in Layered Media', Cambridge University Press, Cambridge, United Kingdom, 305 pp. Marcellini, A. and A. Tento (2011) ' Explosive Sources Prove the Validity of Homogeneous Isotropic Linear Viscoelastic Models', BSSA, Vol. 101, No. 4, pp. 1576-1583.

Daminelli, R.; Tento, A.; Marcellini, A.

2013-12-01

353

Transport coefficients of the superfluid Fermi gas in p-wave state at low temperatures  

NASA Astrophysics Data System (ADS)

In this paper, we obtain the shear viscosity and diffusive thermal conductivity of the superfluid p-wave Fermi gas with weak interaction by using the quasi-particle relaxation rate ?P-1, and the Boltzmann equation approach at low temperatures. We show that ?P-1 is proportional to T4. The shear viscosity components, ?xx, ?yy, ?xy are proportional to T-2, whereas ?xz, ?yz and ?zz are proportional to T-4 and T-6, respectively. The components of the diffusive thermal conductivity Kxx and Kyy are proportional to T-1, whereas Kzz is proportional to T-3.

Nasirimoghadam, S.; Nabipoor, F.; Khademi-Dehkordi, M.; Shahzamanian, M. A.

2012-12-01

354

Tomographic imaging of the P-wave velocity structure beneath the Kamchatka peninsula  

NASA Astrophysics Data System (ADS)

A total of 5270 shallow and intermediate-depth earthquakes recorded by the 32 stations of the regional seismic network of the Geophysical Service of Russia are used to assess the P-wave velocity structure beneath the Kamchatka peninsula in the Western Pacific. The tomographic inversion is carried out in three steps. First, a 1-D tomographic problem is solved in order to obtain an initial velocity model. Based on the 1-D velocity model, 3-D tomographic inversions with homogeneous and heterogeneous starting models are obtained. The Conrad (15 km depth) and Moho (35 km depth) discontinuities determined from the 1-D tomographic inversion, and the upper boundary of the subducting slab are taken into account in the heterogeneous starting model for the traveltimes and ray-path determinations. Both velocity structure and hypocentral locations are determined simultaneously in the inversion. The spacing of the grid nodes is a half-degree in the horizontal direction and 20-50 km in the vertical direction. A detailed P-wave tomographic image is determined down to a depth of 200 km. The resulting tomographic image has a prominent low-velocity anomaly that shows a maximum decrease in P-wave velocity of approximately 6 per cent at 30 km depth beneath a chain of active volcanoes. At depth, low-velocity anomalies are also observed in the mantle wedge extending down to a depth of approximately 150 km. These anomalies are apparently associated with the volcanic activity. The sedimentary basin of the Central Kamchatsky graben, to the west of the volcanic front, and the accretionary prism at the trench correlate with shallow low-velocity anomalies. High-velocity anomalies observed at a depth of 10 km may be associated with the location of metamorphic basements in the Ganalsky-Valaginskoe uplift and upper crust of Shipunsky cape. The results also suggest that the subducted Pacific plate has P-wave velocities approximately 2-7 per cent higher than those of the surrounding mantle and a thickness of approximately 70 km.

Gorbatov, A.; Domínguez, J.; Suárez, G.; Kostoglodov, V.; Zhao, D.; Gordeev, E.

1999-05-01

355

Optimal Arrival Flight Sequencing and Scheduling Using Discrete Airborne Delays  

Microsoft Academic Search

An algorithm for optimal arrival flight sequencing and spacing in a near-terminal area is proposed. The optimization problem and algorithm proposed in this paper are developed for a decision-support tool for air-traffic control, which uses discrete delay times as optimization variables. The algorithm is applicable to various scenarios with situational and operational constraints such as maximum position shift (MPS) constraints

Yeonju Eun; Inseok Hwang; Hyochoong Bang

2010-01-01

356

Analysis of sequencing and scheduling methods for arrival traffic  

NASA Technical Reports Server (NTRS)

The air traffic control subsystem that performs scheduling is discussed. The function of the scheduling algorithms is to plan automatically the most efficient landing order and to assign optimally spaced landing times to all arrivals. Several important scheduling algorithms are described and the statistical performance of the scheduling algorithms is examined. Scheduling brings order to an arrival sequence for aircraft. First-come-first-served scheduling (FCFS) establishes a fair order, based on estimated times of arrival, and determines proper separations. Because of the randomness of the traffic, gaps will remain in the scheduled sequence of aircraft. These gaps are filled, or partially filled, by time-advancing the leading aircraft after a gap while still preserving the FCFS order. Tightly scheduled groups of aircraft remain with a mix of heavy and large aircraft. Separation requirements differ for different types of aircraft trailing each other. Advantage is taken of this fact through mild reordering of the traffic, thus shortening the groups and reducing average delays. Actual delays for different samples with the same statistical parameters vary widely, especially for heavy traffic.

Neuman, Frank; Erzberger, Heinz

1990-01-01

357

Illuminating the near-sonic rupture velocities of the intracontinental Kokoxili Mw 7.8 and Denali fault Mw 7.9 strike-slip earthquakes with global P wave back projection imaging  

Microsoft Academic Search

The Denali and Kokoxili strike-slip earthquakes are two of the longest recent intracontinental ruptures. Previous studies report a range of rupture velocities. Here we image these earthquakes by reverse time migration of the intermediate-frequency P wave train recorded by global broadband seismometers. This technique permits a relatively direct measure of rupture velocity (speed and direction) as constrained by the radiated

Kristoffer T. Walker; Peter M. Shearer

2009-01-01

358

Cardiopulmonary arrest on arrival due to penetrating trauma  

PubMed Central

INTRODUCTION The aim of this study was to clarify the outcome of patients with cardiopulmonary arrest on arrival due to penetrating trauma (PT-CPA) and to establish the treatment strategy. PATIENTS AND METHODS The clinical course of 29 patients with PT-CPA over the past 10 years was examined. We have taken three approaches to these patients: (i) an aggressive treatment strategy; (ii) an in-hospital system supporting this aggressive resuscitation; and (iii) the pre-hospital emergency medical service (EMS) system in our city. RESULTS Although the return of spontaneous circulation (ROSC) was established in 59% of patients, only 17% survived for 7 days, 14% were discharged, and 7% were neurologically intact. Of 10 patients showing pulseless electrical activity (PEA) on the scene, ROSC was established in 100% and 30% were discharged; however, of 12 patients showing asystole, ROSC was established in 33% and no patient could be discharged. There was no difference in the time interval from the arrival at the emergency department to ROSC between discharged patients and patients who died. The time interval from collapse to arrival at the emergency department in discharged patients and patients who went to the intensive care unit was shorter than that of patients who died in the emergency department with and without ROSC. CONCLUSIONS We cannot decide to give up and terminate resuscitation in any PT-CPA patients and cannot define salvageable patients. However, our data show that 30-min resuscitation is thought to be relevant and that we should not give up on resuscitation because of the time interval without ROSC after arrival at the hospital.

Moriwaki, Yoshihiro; Sugiyama, Mitsugi; Toyoda, Hiroshi; Kosuge, Takayuki; Tahara, Yoshio; Suzuki, Noriyuki

2010-01-01

359

Joint Tomographic Inversion of Body-Wave Arrivals and Gravity Data at the Sacramento-San Joaquin River Delta  

NASA Astrophysics Data System (ADS)

The Sacramento-San Joaquin River Delta (SSJRD) occurs at the confluence of the Sacramento and San Joaquin rivers in the Central Valley of California. The Central Valley is a sedimentary basin that divides the granitic Sierra Nevada range on the east from the heterogeneous Franciscan formation to the west. It is home to a series of levees that control about half of California's annual stream flow, and more than half of Californians get their drinking water from the SSJRD area. Previous studies show that ground motion from magnitude 6.0 earthquakes, which have recurrence intervals of about 100 years in the area, are capable of causing levee failure. While the highest risk for levee failure is in the western SSJRD, since it is near at least five major faults, a medium to high risk of catastrophic levee failure also exists for most of the central SSJRD. These assessments incorporate qualitative estimates of parameters such as basin amplification based on individual knowledge and experience, since geotechnical information is limited in the area. Likewise, two fault models are used in the study, which differ primarily in the assumed presence or absence of a blind thrust fault under the northwest corner of the SSJRD. To improve hazard assessment, particularly in regards to basin amplification of strong ground motion, local tomographic imaging is necessary to determine the shape of the Central Valley at depth and to help evaluate the presence of faults. We will present a new local P-wave velocity model for the SSJRD, determined from joint inversion of seismic arrival times and gravity measurements. For the purposes of this study, gravity data primarily complement body-wave data by providing information on shallow density structure and are more effective at delineating lateral density variations. Seismic waves provide better depth resolution but are limited by the spatial distribution of earthquake and receiver locations. Our datasets comprise over 213,000 (regional and local) arrival times and approximately 5000 local Bouguer-corrected gravity readings. We are developing a version of the seismic tomography code tomoDD, modified to incorporate gravity data. Published empirical relationships between density and seismic velocity will be used to connect the two data types. Current density-velocity relationships are based on rocks from different geologic settings and can not account for non-uniqueness in density and velocity for different rock types. We will strive to implement these density-velocity relationships with depth dependence in order to model them more realistically.

Teel, A.; Thurber, C. H.; Bennington, N. L.; Zhang, H.

2011-12-01

360

S and P-wave velocity structure beneath the Hawaiian hotspot from the PLUME deployments of ocean-bottom and land seismometers  

NASA Astrophysics Data System (ADS)

Seismological studies can provide key constraints on the existence and characteristics of mantle plumes. Remotely located oceanic hotspots pose challenges for mantle seismic imaging with land stations because of the limited areal extent of oceanic islands and thus are excellent targets for dedicated marine experiments. The PLUME project at Hawaii successfully deployed two networks of ~35 ocean-bottom seismometers and a concurrent set of portable land seismometers, providing unprecedented, dense seismic coverage around Hawaii across an ~1,000-km-wide aperture. Three-dimensional finite-frequency body-wave tomographic images of S- and P-wave velocity structure beneath the Hawaiian Islands show an upper-mantle low-velocity anomaly that is elongated in the direction of the island chain and surrounded by a high-velocity anomaly in the shallow upper mantle that is parabolic in map view. Low velocities continue downward to the mantle transition zone between 410 and 660 km depth and extend into the topmost lower mantle. For P-waves, comparisons of inversions with separate data sets at different frequencies suggest that contamination by water reverberations is not markedly biasing the imaging. Many aspects of the S- and P-wave images are consistent with each other and support the hypothesis that the Hawaiian hotspot is the result of an upwelling, high-temperature plume. The broad upper-mantle low-velocity region beneath the Hawaiian Islands may reflect the "diverging pancake" at the top of the upwelling zone; the surrounding region of high velocities could represent a downwelling curtain; and the low-velocity anomalies southeast of Hawaii in the transition zone and topmost lower mantle are consistent with predictions of a tilted plume conduit. However, there are some differences in upper mantle structure between P-wave and S-wave velocity. Inversions without station terms show a southwestward shift in the location of lowest P-wave velocities in the uppermost mantle relative to the pattern for shear waves, and inversions with station terms show differences between P-wave and S-wave velocity heterogeneity in the shallow upper mantle beneath and immediately east of the island of Hawaii. Upper mantle structure from both S and P waves is asymmetric, with lower velocities just southwest of Hawaii and higher velocities to the east. Independent Rayleigh-wave tomography of the lower lithosphere and asthenosphere reveals a similarly asymmetric upper mantle structure. Much work has been performed (e.g., examination of delay time patterns, examination of wave path coverage, resolution tests, squeezing tests, inversions with subsets of data, assessment of the possible contaminating effects of outside structure) to ascertain that the body wave inversions, and our interpretations, are well constrained.

Wolfe, C. J.; Laske, G.; Solomon, S. C.; Collins, J. A.; Detrick, R. S.; Orcutt, J. A.; Bercovici, D.; Hauri, E. H.

2011-12-01

361

Electron transport in p-wave superconductor-normal metal junctions  

NASA Astrophysics Data System (ADS)

We study low-temperature electron transport in p-wave superconductor-insulator-normal metal junctions. In diffusive metals, the p-wave component of the order parameter is strongly suppressed at distances greater than the mean free path l. At the superconductor-normal metal boundary, due to spin-orbit interaction, there is a triplet to singlet conversion of the superconducting order parameter. The singlet component survives at distances much larger than l from the boundary. It is this component that controls the low-temperature resistance of the junctions. As a result, the resistance of the system strongly depends on the angle between the insulating boundary and the d vector characterizing the spin structure of the triplet superconducting order parameter. We also analyze the spatial dependence of the electric potential in the presence of the current and show that the electric field is suppressed in the insulating boundary as well as in the normal metal at distances of order of the coherence length away from the boundary. This is very different from the case of the normal metal-insulator-normal metal junctions, where the voltage drop takes place predominantly at the insulator.

Keles, A.; Andreev, A. V.; Spivak, B. Z.

2014-01-01

362

The effect of diabetic autonomic neuropathy on P-wave duration, dispersion and atrial fibrillation  

PubMed Central

Introduction Atrial fibrillation (AF) is the most common sustained arrhythmia. Diabetic autonomic neuropathy (DAN) is a frequent complication of diabetes mellitus and has a negative impact on the cardiovascular system. There are no data about the occurrence of paroxysmal atrial fibrillation (PAF) in the population with DAN. Material and methods We analysed the data of 100 patients with PAF. The study population was divided into three groups: group I: 28 patients with diabetes mellitus (DM) and DAN, group II: 34 patients with DM without DAN, and group III: 38 patients without DM. P-wave duration (FPD) and dispersion (PWD) were measured during sinus rhythm and AF episodes were counted during 12 months of follow-up. Results Recurrence of PAF was higher in group I (47 episodes/year) compared to groups II and III (26 and 22 episodes/year) – p<0.01. The FPD was longer in group I (137.4 ±12.0 ms vs. 126 ±23.0 ms in II group and 129 ±18.3 ms in group III; p<0.001). The PWD was longer in patients with DAN (53 ±19 ms vs. 36 ±18 ms and 34 ± 20 ms, p<0.001). Conclusions The results showed that the presence of DAN caused a significant increase in P-wave duration and dispersion, which might be responsible for the recurrence of AF.

Bissinger, Andrzej; Grycewicz, Tomasz; Grabowicz, Wlodzimierz; Lubinski, Andrzej

2011-01-01

363

Preliminary Results for Crustal Structure in Southeastern Africa from P-wave Receiver Functions  

NASA Astrophysics Data System (ADS)

The crustal structure of southeastern Africa is investigated by modeling P-wave receiver functions using H-k stacking and joint inversion methods. P-wave receiver functions are analyzed for 29 broadband seismic stations in Zambia, Malawi and Mozambique. Estimates for the Moho depth and Poisson's ratio are determined from H-k stacking, and estimates for the shear wave velocity are determined by the joint inversion of receiver functions and surface wave dispersion. Preliminary results show that Moho depths beneath southeastern Africa range from 32 km to 51 km. Thicker crust is found in Proterozoic terrains, such as the Irumide Belt, while thinner crust is found in reworked Archean terrains, such as the Bangweulu Block. These results are consistent with previous studies and global averages for Precambrian terrains. The preliminary results also show a range of Poisson's ratios from 0.2 to 0.3. These new results for southeastern Africa are being combined with similar results from elsewhere in eastern and southern Africa to improve our understanding of African crustal structure.

Kachingwe, M.; Nyblade, A.; Mulibo, G.; Mulowezi, A.; Kunkuta, E.; De Magalhães, V.; Wysession, M. E.; Wiens, D. A.; Julia, J.

2012-12-01

364

Preliminary Results for Crustal Structure in Southeastern Africa from P-wave Receiver Functions  

NASA Astrophysics Data System (ADS)

The crustal structure of southeastern Africa is investigated by modeling P-wave receiver functions using H-k stacking and joint inversion methods. P-wave receiver functions are analyzed for 29 broadband seismic stations in Zambia, Malawi and Mozambique. Estimates for the Moho depth and Poisson's ratio are determined from H-k stacking, and estimates for the shear wave velocity are determined by the joint inversion of receiver functions and surface wave dispersion. Preliminary results show that Moho depths beneath southeastern Africa range from 32 km to 51 km. Thicker crust is found in Proterozoic terrains, such as the Irumide Belt, while thinner crust is found in reworked Archean terrains, such as the Bangweulu Block. These results are consistent with previous studies and global averages for Precambrian terrains. The preliminary results also show a range of Poisson's ratios from 0.2 to 0.3. These new results for southeastern Africa are being combined with similar results from elsewhere in eastern and southern Africa to improve our understanding of African crustal structure.

Kachingwe, M.; Nyblade, A.; Mulibo, G. D.; Mulowezi, A.; Kunkuta, E.; De Magalhães, V.; Wiens, D. A.; Wysession, M. E.; Julia, J.

2013-12-01

365

Component azimuths of the CEArray stations estimated from P-wave particle motion  

NASA Astrophysics Data System (ADS)

The recently built China Digital Seismic Network consists of the China National Digital Seismic Network (CNDSN), 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850+ broadband stations. It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth's deep interior besides its routine task of seismic monitoring. Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different types of seismic waves. Knowledge of the orientations of the two horizontal components thus is important to perform a correction rotation. We analyzed particle motions of teleseismic P waves recorded by the network and used them to estimate the north-component azimuth of each station. An SNR-weighted-multi-event method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station. The method provides robust estimates including a measurement error calculated from background noise levels. We found that about one third of the stations have some sort of problems, including misorientation of the two horizontal components, mislabeling and polarity reversal in one or more components. These problems need to be taken into account for any rotation based seismic studies.

Niu, Fenglin; Li, Juan

2011-02-01

366

The S3 truss arrives at KSC  

NASA Technical Reports Server (NTRS)

A Super Guppy aircraft arrives at the KSC Shuttle Landing Facility with its cargo of Integrated Truss Structure S3, built by The Boeing Co. After offloading, the S3 will be transported to the Operations and Checkout Building. The second starboard truss segment of the International Space Station, the S3 truss is scheduled to be added to the Station in April 2003.

2000-01-01

367

New Accessions Arriving at Field Records  

USGS Multimedia Gallery

Materials arrive from across the country to be accessioned and processed at the Denver Library, Field Records Collection. Geologic Discipline scientists are encouraged to deposit their project materials and with the Field Records Collection. Materials in the collection are managed as Federal records...

2009-04-09

368

STS-93 Mission Specialist Coleman arrives at SLF for launch.  

NASA Technical Reports Server (NTRS)

STS-93 Mission Specialist Catherine G. 'Cady' Coleman (Ph.D.) smiles upon her arrival at KSC's Shuttle Landing Facility aboard a T-38 jet aircraft. She and other crew members Commander Eileen Collins, Pilot Jeffrey S. Ashby, and Mission Specialists Steven A. Hawley (Ph.D.) and Michel Tognini of France, with the Centre National d'Etudes Spatiales (CNES), are arriving for pre-launch activities. Coleman is making her second Shuttle flight. The primary mission of STS-93 is the release of the Chandra X-ray Observatory, which will allow scientists from around the world to study some of the most distant, powerful and dynamic objects in the universe. The new telescope is 20 to 50 times more sensitive than any previous X-ray telescope and is expected to unlock the secrets of supernovae, quasars and black holes.

1999-01-01

369

STS-93 Mission Specialist Coleman arrives at SLF for launch  

NASA Technical Reports Server (NTRS)

STS-93 Mission Specialist Catherine G. 'Cady' Coleman (Ph.D.) shows her sense of humor upon arriving at KSC's Shuttle Landing Facility aboard a T-38 jet aircraft. She and other crew members Commander Eileen Collins, Pilot Jeffrey S. Ashby, and Mission Specialists Steven A. Hawley (Ph.D.) and Michel Tognini of France, with the Centre National d'Etudes Spatiales (CNES), are arriving for pre-launch activities. Coleman is making her second Shuttle flight. The primary mission of STS-93 is the release of the Chandra X-ray Observatory, which will allow scientists from around the world to study some of the most distant, powerful and dynamic objects in the universe. The new telescope is 20 to 50 times more sensitive than any previous X-ray telescope and is expected to unlock the secrets of supernovae, quasars and black holes.

1999-01-01

370

Effect of cracks on the pressure dependence of P wave velocities in crystalline rocks  

NASA Astrophysics Data System (ADS)

To test the "bed of nails" model, we have made detailed measurements of P wave velocities in five low-porosity, crystalline rocks at effective pressures to 500 MPa and fit two equations based on the model to the laboratory data. The first equation, V(P) = V0(1 + P/ Pi)(1 - m)/2, applies at relatively low pressures because it assumes that the grain modulus is very much larger than the crack modulus. It can be fit to four of the five data sets. The fit to the data for a monomineralic epidote yields values for V0, Piand m of 8.02±0.02 km/s, 1.2±0.5 MPa, and 0.9845±0.0004, respectively, with a rms error of 6.28 m/s. The second equation, 1/V2 (P) = (1/Vc2 - Vg2)/(1 + P/Pi)1 - m + 1/Vg2 assigns a constant velocity to the grains and applies when the modulus of the cracks is of the order of the grain modulus at high pressures. This equation can be fit to three of the data sets; the fit to data for a diopside pyroxenite yields values of Vc, Vg, Pi, and m of 6.20±0.04 km/s, 8.28±0.02 km/s, 7±1 MPa, and 0.20±0.05, with a rms error of 17.9 m/s. For all seven fits to the laboratory data the rms errors range from 0.1 to 0.3% and are of the order of the limits of precision of the measurements. The "bed of nails" model explains the pressure dependence of P wave velocities in the samples remarkably well, as evidenced by the small rms errors. The variation with pressure of P wave velocities in these rocks clearly reflects the increasing stiffness of cracks. The fact that the first equation fits four of five data sets is one of several indications that cracks significantly affect the mechanical properties of the rocks even at 500 MPa. Finally, we note that different kinds of cracks have markedly different mechanical properties; the best fitting model parameters reflect the nature of the cracks which populate the samples.

Carlson, Richard L.; Gangi, Anthony F.

1985-09-01

371

NASA's ATM Technology Demonstration-1: Integrated Concept of Arrival Operations  

NASA Technical Reports Server (NTRS)

This paper describes operations and procedures envisioned for NASA s Air Traffic Management (ATM) Technology Demonstration #1 (ATD-1). The ATD-1 Concept of Operations (ConOps) demonstration will integrate three NASA technologies to achieve high throughput, fuel-efficient arrival operations into busy terminal airspace. They are Traffic Management Advisor with Terminal Metering (TMA-TM) for precise time-based schedules to the runway and points within the terminal area, Controller-Managed Spacing (CMS) decision support tools for terminal controllers to better manage aircraft delay using speed control, and Flight deck Interval Management (FIM) avionics and flight crew procedures to conduct airborne spacing operations. The ATD-1 concept provides de-conflicted and efficient operations of multiple arrival streams of aircraft, passing through multiple merge points, from top-of-descent (TOD) to touchdown. It also enables aircraft to conduct Optimized Profile Descents (OPDs) from en route altitude to the runway, using primarily speed control to maintain separation and schedule. The ATD-1 project is currently addressing the challenges of integrating the three technologies, and implantation into an operational environment. Goals of the ATD-1 demonstration include increasing the throughput of high-density airports, reducing controller workload, increasing efficiency of arrival operations and the frequency of trajectory-based operations, and promoting aircraft ADS-B equipage.

Baxley, Brian T.; Swenson, Harry N.; Prevot, Thomas; Callantine, Todd J.

2012-01-01

372

Deformation-Driven p-Wave Halos at the Drip Line: Ne31.  

PubMed

The halo structure of Ne31 is studied using 1n-removal reactions on C and Pb targets at 230??MeV/nucleon. A combined analysis of the cross sections of these nuclear and Coulomb dominated reactions that feed directly the Ne30 ground-state reveals Ne31 to have a small neutron separation energy, 0.15-0.10+0.16??MeV, and spin-parity 3/2-. Consistency of the data with reaction and large-scale shell-model calculations identifies Ne31 as deformed and having a significant p-wave halo component, suggesting that halos are more frequent occurrences at the neutron drip line. PMID:24765946

Nakamura, T; Kobayashi, N; Kondo, Y; Satou, Y; Tostevin, J A; Utsuno, Y; Aoi, N; Baba, H; Fukuda, N; Gibelin, J; Inabe, N; Ishihara, M; Kameda, D; Kubo, T; Motobayashi, T; Ohnishi, T; Orr, N A; Otsu, H; Otsuka, T; Sakurai, H; Sumikama, T; Takeda, H; Takeshita, E; Takechi, M; Takeuchi, S; Togano, Y; Yoneda, K

2014-04-11

373

Engineering p-wave interactions in ultracold atoms using nanoplasmonic traps  

NASA Astrophysics Data System (ADS)

Engineering strong p-wave interactions between fermions is one of the challenges in modern quantum physics. Such interactions are responsible for a plethora of fascinating quantum phenomena, such as topological quantum liquids and exotic superconductors. Here we propose a method to generate these fermionic interactions by combining recent developments in nanoplasmonics with progress in realizing laser-induced gauge fields. Nanoplasmonics allows for strong confinement, leading to a geometric resonance in the atom-atom scattering. In combination with the laser coupling of the atomic states, this is shown to result in the desired interaction. We illustrate how this scheme can be used for the stabilization of strongly correlated fractional quantum Hall states in ultracold fermionic gases.

Juliá-Díaz, B.; Graß, T.; Dutta, O.; Chang, D. E.; Lewenstein, M.

2013-07-01

374

Hyperfine structure of S- and P-wave states in muonic-helium ion  

SciTech Connect

Corrections of order {alpha}{sup 5} and {alpha}{sup 6} to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, -1334.73 meV (1S), -166.64 meV (2S), -58 712.90 {mu}eV (2P{sub 1/2}), and -24 290.69 {mu}eV (2P{sub 3/2}), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of {Delta}{sub 12} = 8{Delta}E{sup hfs}(2S) - {Delta}E{sup hfs}(1S) = 1.59 meV can be used to test QED predictions.

Martynenko, A. P., E-mail: mart@ssu.samara.ru; Elekina, E. N. [Samara State University (Russian Federation)

2010-12-15

375

Doubly excited P-wave resonance states of H{sup ?} in Debye plasmas  

SciTech Connect

We investigate the doubly excited P-wave resonance states of H{sup ?} system in Debye plasmas modeled by static screened Coulomb potentials. The screening effects of the plasma environment on resonance parameters (energy and width) are investigated by employing the complex-scaling method with Hylleraas-type wave functions for both the shape and Feshbach resonances associated with the H(N = 2 to 6) thresholds. Under the screening conditions, the H(N) threshold states are no longer l degenerate, and all the H{sup ?} resonance energy levels are shifted away from their unscreened values toward the continuum. The influence of Debye plasmas on resonance widths has also been investigated. The shape resonance widths are broadened with increasing plasma screening strength, whereas the Feshbach resonance widths would generally decrease. Our results associated with the H(N = 2) and H(N = 3) thresholds are compared with others in the literature.

Jiao, L. G.; Ho, Y. K. [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan (China)] [Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan (China)

2013-08-15

376

Three-Body Bound States in Atomic Mixtures With Resonant p-Wave Interaction  

NASA Astrophysics Data System (ADS)

We employ the Born-Oppenheimer approximation to find the effective potential in a three-body system consisting of a light particle and two heavy ones when the heavy-light short-range interaction potential has a resonance corresponding to a nonzero orbital angular momentum. In the case of an exact resonance in the p-wave scattering amplitude, the effective potential is attractive and long range; namely, it decreases as the third power of the interatomic distance. Moreover, we show that the range and power of the potential, as well as the number of bound states, are determined by the mass ratio of the particles and the parameters of the heavy-light short-range potential.

Efremov, Maxim A.; Plimak, Lev; Ivanov, Misha Yu.; Schleich, Wolfgang P.

2013-09-01

377

Holographic phase transitions of p-wave superconductors in Gauss-Bonnet gravity with backreaction  

SciTech Connect

We investigate the phase transitions of holographic p-wave superconductors in (4+1)-dimensional Einstein-Yang-Mills-Gauss-Bonnet theories, in a grand canonical ensemble. Turning on the backreaction of the Yang-Mills field, it is found that the condensations of vector order parameter become harder if the Gauss-Bonnet coefficient grows up or the backreaction becomes stronger. In particular, the vector order parameter exhibits the features of first order and second order phase transitions, while only the second order phase transition is observed in the probe limit. We discuss the roles that the Gauss-Bonnet term and the backreaction play in changing the order of phase transition.

Cai Ronggen; Nie Zhangyu; Zhang Haiqing [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, P.O. Box 2735, Beijing 100190 (China)

2011-03-15

378

Upper mantle P-wave speed variations beneath Ethiopia and the origin of the Afar hotspot  

NASA Astrophysics Data System (ADS)

The Afar hotspot has long been attributed to one or more thermal upwellings in the mantle, in particular starting thermal plumes characterized by a head that spreads laterally beneath the lithosphere, and a tail. New P-wave tomography images of the upper mantle beneath Ethiopia reveal an elongated low wave speed region that is deep (>400 km) and wide (>500 km). The location of the low wave speed anomaly aligns with the Afar Depression and Main Ethiopian Rift in the uppermost mantle, but the center of the anomaly shifts to the west with depth. The shape, depth extent, and location of the low wave speed anomaly is not consistent with a starting thermal plume presently beneath the hotspot. Instead, the anomaly suggests that the hotspot may be the surface manifestation of a broad mantle upwelling connected to the African Superplume in the lower mantle beneath southern Africa.

Benoit, Margaret H.; Nyblade, Andrew A.; Vandecar, John C.

2006-05-01

379

Deformation-Driven p-Wave Halos at the Drip Line: Ne31  

NASA Astrophysics Data System (ADS)

The halo structure of Ne31 is studied using 1n-removal reactions on C and Pb targets at 230 MeV /nucleon. A combined analysis of the cross sections of these nuclear and Coulomb dominated reactions that feed directly the Ne30 ground-state reveals Ne31 to have a small neutron separation energy, 0.15-0.10+0.16 MeV, and spin-parity 3/2-. Consistency of the data with reaction and large-scale shell-model calculations identifies Ne31 as deformed and having a significant p-wave halo component, suggesting that halos are more frequent occurrences at the neutron drip line.

Nakamura, T.; Kobayashi, N.; Kondo, Y.; Satou, Y.; Tostevin, J. A.; Utsuno, Y.; Aoi, N.; Baba, H.; Fukuda, N.; Gibelin, J.; Inabe, N.; Ishihara, M.; Kameda, D.; Kubo, T.; Motobayashi, T.; Ohnishi, T.; Orr, N. A.; Otsu, H.; Otsuka, T.; Sakurai, H.; Sumikama, T.; Takeda, H.; Takeshita, E.; Takechi, M.; Takeuchi, S.; Togano, Y.; Yoneda, K.

2014-04-01

380

Regional difference in small-scale heterogeneities in the crust and upper mantle in Japan derived by the analysis of high-frequency P-wave  

NASA Astrophysics Data System (ADS)

In order to understand distribution properties of small-scale heterogeneities in the crust and upper mantle structure, we analyze three-component seismograms recorded by Hi-net in Japan. We examined relative strength of the P-wave in the transverse (T) component and its change as a function of frequency and propagation distances, which is strongly relating to the strength of seismic wave scattering in the lithosphere. We analyzed 53,220 Hi-net record from 310 shallow (h<30km) crustal earthquakes with MJMA =2.0-5.3. The three-component seismograms are firstly applied by band-pass filter with pass band frequency of f=1-2, 2-4, 4-8, 8-16, 16-32 Hz and then the Hilbert transform is used to synthesize envelope of each component. Then, the energy partition (EP) of P wave in the T component relative to total P-wave energy is evaluated around the P wave in 3-sec time window. The estimated EP value is almost constant 0.2 in high-frequencies (8-16 Hz) at shorter distance, while it is 0.07 in low-frequencies (1-2 Hz). We found clearly frequency-change property of EP value. But at larger distance over 150 km, EP values gradually increase with increasing distance. In high-frequencies (8-16, 16-32 Hz), especially EP values asymptotically reach from 0.2 to 0.33, equi-partitioning of P-wave energy into three components. This may because Pn-phase dominates in larger hypocentral distances. In order to examine difference in the EP in each area of Japan which would be relating to the strength of crustal heterogeneities in each area we divided the area of Japan into three regions, fore-arc side of Tohoku, back-arc side of Tohoku and Chugoku-Shikoku area. The difference in EP value in each area is clearly found in the high-frequency (4-8 Hz) band, where larger EP (0.2) was obtained at back-arc side of Tohoku relative to smaller EP (0.1) at fore-arc side of Tohoku and Chugoku-Shikoku. This is consistent with the results of Carcole and Sato (2009) who estimated the strength of crustal heterogeneities based on the multi lapse time-window analysis. In order to clarify the cause of such regional difference of EP, we conduct 3-D FDM simulations using stochastic random media. The model covers a zone 204.8 km by 204.8 km by 64.0 km descretized with 0.1 km in horizontal direction and 0.05 km in vertical direction. The small-scale heterogeneity in the lithosphere is constructed by velocity fluctuation from average velocity. The fluctuation is characterized by von Karman-type ACF with the correlation length a, the rms value e and decay order k. We assume average background velocities of P-wave and S-wave are VP = 5.8 km and VS = 3.36 km, respectively. We employ an explosive point source into the model. The FDM simulations were conducted on the Earth Simulator at JAMSTEC. We conducted a number of FDM simulation using different model parameters of stochastic random media for different e (= 0.03, 0.05, 0.07, 0.09) and fixed a and k (a = 5km, k = 0.5). The simulation results confirm EP value increases linearly with increasing e. We also found that larger EP obtained in the back-arc side of Tohoku can be explained by 4% larger e relative to those of other regions.

Takemura, S.; Furumura, T.

2010-12-01

381

Crustal P-wave velocity structure from Altyn Tagh to Longmen mountains along the Taiwan-Altay geoscience transect  

USGS Publications Warehouse

Based upon the seismic experiments along Geoscience Transect from the Altyn Tagh to the Longmen Mountains, the crustal P-wave velocity structure was derived to outline the characteristics of the crustal structure. The section shows a few significant features. The crustal thickness varies dramatically, and is consistent with tectonic settings. The Moho boundary abruptly drops to 73km depth beneath the southern Altyn Tagh from 50km below the Tarim basin, then rises again to about 58km depth beneath the Qaidam basin. Finally, the Moho drops again to about 70km underneath the Songpan-Garze Terrane and rises to 60km near the Longmen Mountains with a step-shape. Further southeast, the crust thins to 52km beneath the Sichuan basin in the southeast of the Longmen Mountains. In the north of the Kunlun fault, a low-velocity zone, which may be a layer of melted rocks due to high temperature and pressure at depth, exists in the the bottom of the middle crust. The two depressions of the Moho correlate with the Qilian and Songpan-Garze terranes, implying that these two mountains have thick roots. According to our results, it is deduced that the thick crust of the northeastern Tibetan Plateau probably is a result of east-west and northwest-southeast crustal shortening since Mesozoic time during the collision between the Asian and Indian plates.

Wang, Y. -X.; Mooney, W. D.; Han, G. -H.; Yuan, X. -C.; Jiang, M.

2005-01-01

382

Dependence of P-wave dispersion on mean arterial pressure as an independent hemodynamic variable in school children  

PubMed Central

Introduction: The relationship between diastolic dysfunction and P-wave dispersion (PWD) in the electrocardiogram has been studied for some time. In this regard, echocardiography is emerging as a diagnostic tool to improve risk stratification for mild hypertension. Objective: To determine the dependence of PWD on the electrocardiogram and on echocardiographic variables in a pediatric population. Methods: 515 children from three elementary schools were studied from a total of 565 children. Those whose parents did not want them to take part in the study, as well as those with known congenital diseases, were excluded. Tests including 12-lead surface ECGs and 4 blood pressure (BP) measurements were performed. Maximum and minimum P-values were measured, and the PWD on the electrocardiogram was calculated. Echocardiography for structural measurements and the pulsed Doppler of mitral flow were also performed. Results: A significant correlation in statistical variables was found between PWD and mean BP for pre-hypertensive and hypertensive children, i.e., r = 0.32, p <0.01 and r = 0.33, p <0.01, respectively. There was a significant correlation found between PWD and the left atrial area (r = 0.45 and p <0.01). Conclusions: We highlight the dependency between PWD, the electrocardiogram and mean blood pressure. We also draw attention to the dependence of PWD on the duration of the mitral inflow A-wave. This result provides an explanation for earlier changes in atrial electrophysiological and hemodynamic characteristics in pediatric patients.

Gonzalez, Emilio F.; Llanes, Maria del Carmen; Llanes, Merlin Gari; Garcia, Yosvany

2013-01-01

383

Formation and propagation of Love waves from a P-wave source  

NASA Astrophysics Data System (ADS)

The objective of this research is to experimentally investigate and support, by finite element calculations, the formation and propagation of Love waves from a P-wave source due to scattering at material heterogeneities. A series of experiments were conducted where surface strains were measured parallel and perpendicular to a planar granite scattering surface. The granite wall that is cast in a surface layer waveguide of a low-impedance grout and then cast on a granite base provided the interface for generating horizontally polarized (SH) waves in the surface layer. The in-plane shear waves are the Love waves we measured at the surface. The P-wave source was a 1-cm-diameter spherical explosive of PETN diluted with microballoons to provide a charge density of 0.45 g/cm cast in a styrofoam sphere to further attenuate the peak pressure. We successfully measured the strains at three locations parallel to the wall and two locations perpendicular to the wall, and the test repeatability was good. Good agreement was also observed between the measured and calculated strain at all locations. The code calculations also showed that in-plane shear strains form along the surface layer/granite interface, and these shear strains propagate with little reduction in amplitude but transform relatively high-frequency oscillations to low-frequency wave packets. The experimental configuration used to generate and measure Love waves, an evaluation of the source used in the surface layer experiments, and results from finite element code calculations of the experiment are presented.

Florence, A. L.; Miller, S. A.; Kirkpatrick, S. W.

1992-01-01

384

P-wave dispersion: an indicator of cardiac autonomic dysfunction in children with neurocardiogenic syncope.  

PubMed

Neurocardiogenic syncope is the most frequent cause of fainting in childhood and adolescence. Although head-up tilt table testing (HUTT) was previously considered as the reference standard in the diagnosis of syncope, in children with a typical history of reflex syncope, normal physical examination, and electrocardiogram (ECG) are sufficient to cease investigation; however, according to recent reports, TT is indicated in patients in whom this diagnosis cannot be proven by initial evaluation. The hypothesis of this study is that P-wave dispersion (PWD) can be a useful electrocardiographic predictor of cardiac autonomic dysfunction in children with vasovagal syncope (VVS). The study was designed prospectively and included 50 children with positive and 50 children with negative HUTT who presented with at least two previous unexplained episodes of syncope as well as 50 sex- and age-matched healthy children as the control group. All standard 12-lead ECGs were obtained in patients and controls, and the difference between maximum and minimum durations of the P wave was defined as the PWD. A total of 100 children with VVS and 50 healthy controls were evaluated for the study. The P maximum values of HUTT-positive (HUTT[+]) patients were significantly greater than those in the HUTT-negative (HUTT[-]) and control groups(p < 0.05). In addition, mean PWD values were 50.2 ± 18.5, 39.6 ± 11.2 and 32.0 ± 11.2 ms in the HUTT(+), HUTT(-), and control groups, respectively. The difference between groups was statistically significant (p < 0.05). We suggest that PWD is an early sign of cardiac autonomic dysfunction in children with neurally mediated syncope and can be used as a noninvasive electrocardiographic test to evaluate orthostatic intolerance syndromes. PMID:24633236

Köse, Melis Demir; Ba?, Özlem; Güven, Bar??; Me?e, Timur; Öztürk, Aysel; Tavl?, Vedide

2014-04-01

385

Experimental study of P-wave attenuation in partially frozen brine  

NASA Astrophysics Data System (ADS)

In order to estimate the amount of methane hydrates (MHs) which form in marine sediments at water depths greater than a few hundred meters, using not only velocity information but also attenuation information can provide much more information about MH-bearing sediments. While the presence of MH increases seismic velocity in the host sediment, recent works on sonic logging data show that sonic waveforms are also significantly affected by the presence of MH. These studies also showed a strong correlation of attenuation with velocity in the MH-bearing sediments. However, the increase of attenuation with increasing velocity is somewhat unintuitive. Thus, it is important elucidate the rock physical mechanism responsible for these phenomena. In this study, we conducted laboratory measurements to explain partially the reason for the physically unrealizable phenomenon. The ice generated from brine was assumed to be methane hydrate, namely, partially frozen brine was considered to be as an analogue for a mixture of methane hydrate and water present in the pore space of hydrate bearing sediments. We observed the variations of a transmitted wave with frequency content of 150-V1000 kHz through a liquid system to a solid-liquid coexistence system, changing its temperature from 20 ,aC to -20 ,aC. As a result, P-wave speed increases with changing in a solid-liquid coexistence system from a liquid system, while P-wave attenuation increases with changing in a solid-liquid coexistence system from a liquid system. Our observations indicate that the interaction in a micro scale of the solid and liquid causes the dissipation of transmitted wave energy.

Suzuki, M.; Matsushima, J.; Kato, Y.; Rokugawa, S.

2005-12-01

386

STS-76 crew after arrival at SLF  

NASA Technical Reports Server (NTRS)

STS-76 Mission Commander Kevin P. Chilton (left); Mission Specialists Linda M. Godwin and Shannon W. Lucid; Pilot Richard A. Searfoss and Mission Specialist Michael 'Rich' Clifford chat shortly after their arrival at KSC's Shuttle Landing Facility. Not shown is Payload Commander Ronald M. Sega. The astronauts' late-night arrival allows them to maintain the shift in their waking and sleeping hours, altered in preparation for their upcoming spaceflight. The Space Shuttle Atlantis is scheduled to lift off on STS-76 around 3:35 a.m. EST, March 21, with one of the primary mission objectives being the third docking between the U.S. Shuttle and the Russian Space Station Mir.

1996-01-01

387

STS-76 crew after arrival at SLF  

NASA Technical Reports Server (NTRS)

STS-76 Mission Commander Kevin P. Chilton (second from left) chats with Mission Specialist Shannon W. Lucid (left); Pilot Richard A. Searfoss and Mission Specialist Michael 'Rich' Clifford shortly after their arrival at KSC's Shuttle Landing Facility. The Space Shuttle Atlantis is scheduled to lift off on STS-76 around 3:35 a.m. EST, March 21, with one of the primary mission objectives being the third docking between the U.S. Shuttle and the Russian Space Station Mir.

1996-01-01

388

Semiautomated Management Of Arriving Air Traffic  

NASA Technical Reports Server (NTRS)

System of computers, graphical workstations, and computer programs developed for semiautomated management of approach and arrival of numerous aircraft at airport. System comprises three subsystems: traffic-management advisor, used for controlling traffic into terminal area; descent advisor generates information integrated into plan-view display of traffic on monitor; and final-approach-spacing tool used to merge traffic converging on final approach path while making sure aircraft are properly spaced. Not intended to restrict decisions of air-traffic controllers.

Erzberger, Heinz; Nedell, William

1992-01-01

389

Application of P-wave Hybrid Theory to the Scattering of Electrons from He+ and Resonances in He and H ion  

NASA Technical Reports Server (NTRS)

The P-wave hybrid theory of electron-hydrogen elastic scattering [Phys. Rev. A 85, 052708 (2012)] is applied to the P-wave scattering from He ion. In this method, both short-range and long-range correlations are included in the Schroedinger equation at the same time, by using a combination of a modified method of polarized orbitals and the optical potential formalism. The short-correlation functions are of Hylleraas type. It is found that the phase shifts are not significantly affected by the modification of the target function by a method similar to the method of polarized orbitals and they are close to the phase shifts calculated earlier by Bhatia [Phys. Rev. A 69, 032714 (2004)]. This indicates that the correlation function is general enough to include the target distortion (polarization) in the presence of the incident electron. The important fact is that in the present calculation, to obtain similar results only a 20-term correlation function is needed in the wave function compared to the 220- term wave function required in the above-mentioned calculation. Results for the phase shifts, obtained in the present hybrid formalism, are rigorous lower bounds to the exact phase shifts. The lowest P-wave resonances in He atom and hydrogen ion have been calculated and compared with the results obtained using the Feshbach projection operator formalism [Phys. Rev. A, 11, 2018 (1975)]. It is concluded that accurate resonance parameters can be obtained by the present method, which has the advantage of including corrections due to neighboring resonances, bound states and the continuum in which these resonance are embedded.

Bhatia, A. K.

2012-01-01

390

P-wave Tomographic Image Across the Central Transverse Ranges Region From Inversion of Local Earthquake and Active Source Data, Southern California  

NASA Astrophysics Data System (ADS)

The central Transverse Ranges region is considered as a place that has documented significant evidence of tectonic history of southern California. To investigate such a region associated with extensive Cenozoic tectonic activities, we apply a new deformable-layer tomography approach to determine layers of varying thickness as a direct product of tomographic imaging. 1,546 P-wave first arrival data from local earthquakes and 10,869 from active shots of Los Angles Regional Seismic Experiment (LARSE) I have been used together to invert the velocity structure along a northeastern trending 2-D profile across the Central Transverse Ranges region. The combined data result in highly dense ray path distribution, especially within the upper crust. In addition, Moho depths from previous study have been incorporated into the inversion to improve solving the model in the deep and sparsely sampled areas. The tomographic inversion procedure implemented in this study is as follows: first, a long wavelength model is constructed by inverting local earthquake arrivals only with sparse Moho constraints; second, this tomographic model is refined by adding surface seismic arrivals and introducing lateral velocity variations within layers. Along the profile, our tomographic image shows high resolution, detailed near-surface geological features besides those long-wavelength features resolved in the previous studies. The existence of the San Andreas Fault is clearly evidenced, which is characterized by a vertical low-velocity zone to at least 20-km depth. The sedimentary basin boundaries are observed unconformably lying above the high velocity basement. Near the northern edge of t